CN106351770B

CN106351770B - Method for improving blowby gas and EGR via separating exhaust gases

Info

Publication number: CN106351770B
Application number: CN201610552198.3A
Authority: CN
Inventors: D·P·麦迪逊; J·N·尤瑞; B·A·博伊尔
Original assignee: Ford Global Technologies LLC
Current assignee: Ford Global Technologies LLC
Priority date: 2015-07-13
Filing date: 2016-07-13
Publication date: 2020-06-19
Anticipated expiration: 2036-07-13
Also published as: CN106351770A; DE102016111686A1

Abstract

The invention relates to a method of improving blowby gas and EGR via separating exhaust gases. Methods and systems are provided for a boosted engine with a separate exhaust system. In one example, the method includes directing exhaust gas from the first cylinder group to one or more of a forward compressor location, an aft compressor location, and an exhaust turbine, and directing exhaust gas from the second cylinder group to one or more of the forward compressor location and the exhaust turbine. By directing exhaust to different locations based on engine operating conditions, engine efficiency and knock control may be enhanced.

Description

Method for improving blowby gas and EGR via separating exhaust gases

Cross Reference to Related Applications

This application is a continuation-in-part application entitled "method of improving blowby VIA separated venting" (U.S. patent application No.14/157,167, filed on 16.1.2014, which is hereby incorporated by reference in its entirety for all purposes.

Technical Field

The present application relates to split exhaust in an exhaust system of a boosted internal combustion engine.

Background

Engines may use a boosting device, such as a turbocharger, to increase engine power density. However, engine knock may occur due to the increased combustion temperature. Engine knock can be addressed by retarding spark timing; however, significant spark retard can reduce fuel economy and limit torque capacity. Knocking is particularly problematic under boosted conditions due to the high charge temperature.

One method of reducing charge temperature and thus knock is via blow-by during the positive valve overlap phase, where boosted intake air is blown through the combustion chamber to the exhaust.

Another method of suppressing knock is by diluting the intake air with cooled Exhaust Gas Recirculation (EGR). Roth (US 8495992) shows an example method of controlling the flow of exhaust gas for EGR, where a separate exhaust system separates the exhaust gas exiting the combustion chambers during the blowdown (blowdown) and scavenging (scavenging) phases. The exhaust gas from the blowdown phase is distributed to a turbine in a turbocharger system or to an EGR system that directs cooled EGR gas upstream of a compressor in an intake manifold or turbocharger. Similarly, exhaust gas from the scavenging stage is delivered to an emission control device or EGR system that delivers cooled gas upstream of the intake manifold or compressor. Intake and exhaust valve timing are controlled to adjust the amount of exhaust gas flowing to the turbocharger and/or EGR based on engine operating conditions.

The inventors herein have identified potential problems, including the problem of addressing knock limits with the above-described methods. For example, an EGR throttle may be placed in the intake device, upstream of the compressor, to enhance EGR flow at low back pressures, which can make the turbocharger more sensitive to surge (surge) and increase pumping losses. Further, in examples where blow-by technology is used to reduce knock, additional fuel injected to bring the exhaust to stoichiometry can cause overheating of the catalyst and affect emissions, while increasing fuel consumption. Further, engine efficiency may deteriorate at lower engine loads, and EGR may contribute to combustion instability.

Disclosure of Invention

The inventors herein have recognized the above-mentioned problems, and identified methods that at least partially address the problems. In one example method, a method for an engine includes directing exhaust gas from a first cylinder group to one or more of a forward compressor location, an aft compressor location, and an exhaust turbine, and directing exhaust gas from a second cylinder group to one or more of the forward compressor location and the exhaust turbine. In this way, exhaust gas can be recirculated to different locations by separating cylinder banks for improved performance and efficiency.

For example, a boost engine may include a first cylinder group and a second cylinder group, where the first cylinder group includes cylinders that are different from the second cylinder group. Exhaust gas from the first cylinder bank may be directed to one or more of three separate destinations, including a first location upstream of the compressor (forward compressor), a second location downstream of the compressor (aft compressor), and a third location directly upstream of the exhaust gas turbine. The second location downstream of the compressor may include a location downstream of the intake throttle and upstream of the intake manifold. Exhaust gas from the second cylinder bank may be directed to one or more of a first location upstream of the compressor and a third location directly upstream of the exhaust turbine. Thus, based on engine conditions, exhaust gas may be directed to one or more of the locations described above. Exhaust gas from the first cylinder group may be directed to the second location during intermediate engine loads and lower engine loads while exhaust gas from the second cylinder group is simultaneously directed to the exhaust turbine. During higher engine loads, a greater proportion of exhaust gas may be directed to the exhaust turbine from both the first and second cylinder groups, while a lesser proportion of exhaust gas is directed to a location upstream of the compressor. Herein, by adjusting the valve timing, a smaller proportion of exhaust gas may be blown through the cylinders upstream of the compressor along with fresh intake air, thereby allowing positive valve overlap between at least one intake valve and one exhaust valve of each of the first and second cylinder groups.

In this way, knock can be reduced during different engine conditions while engine efficiency is improved. Recirculating exhaust gas from the first cylinder group to a location downstream of the compressor may allow for a reduction in pumping losses and heat loss during specific engine conditions (e.g., low and medium engine loads). At the same time, by directing exhaust from the second cylinder group to the exhaust turbine, a desired engine power may be provided. Thus, reduced pumping losses and heat losses may improve engine efficiency. Further, during higher engine loads, allowing fresh intake air to blow through any residual hot exhaust gases in the cylinder can reduce the temperature within the combustion chamber. Furthermore, because the blow-by air is not directed to the emission control device, the stoichiometric ratio in the exhaust gas is maintained without the need for injection of additional fuel.

It should be appreciated that the summary above is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. It is not intended to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 depicts a schematic diagram of a turbocharged engine system having a separate exhaust manifold.

FIG. 2 shows a partial engine view.

FIG. 3 depicts example cylinder intake and exhaust valve timings for one of the engine cylinders of FIG. 1.

FIG. 4 is an example flowchart illustrating a routine for activating a compressor inlet valve based on various engine operating conditions.

FIG. 5 depicts example valve operations based on various engine conditions and subsequent exhaust flow through three passages of one cylinder of the engine of FIG. 1.

FIG. 6 schematically depicts the second embodiment of the turbocharged engine system of FIG. 1.

FIG. 7 sets forth a schematic depiction of a second embodiment of a turbocharged engine including a cam profile shifting system.

FIG. 8 shows an example map of engine operating conditions that may be used to determine the operating mode of the second embodiment of the turbocharged engine.

9A, 9B, and 9C depict example exhaust valve timing for a cylinder of a second embodiment of a turbocharged engine.

FIG. 10 is an example flowchart illustrating a routine for adjusting exhaust valves of a plurality of cylinders of a second embodiment of a turbocharged engine based on engine operating conditions.

FIG. 11 sets forth an example flow chart describing a routine for transitioning between different operating modes of the plurality of cylinders of the second embodiment of the turbocharged engine in response to changes in engine operating conditions.

FIG. 12 shows a table listing various modes of operation of a plurality of cylinders of the second embodiment of the turbocharged engine.

Detailed Description

The following description relates to systems and methods for controlling knock in an engine (such as the engine systems of fig. 1-2) by exhausting engine cylinders through three different passages. Specifically, during one combustion cycle, a first or bleed portion of the exhaust gas may be directed to a turbine of the turbocharger via a first passage, a second or purge portion of the exhaust gas may be directed to an emission control device via a second passage, and a third portion of the exhaust gas mixed with the blow-by air toward the end of the exhaust stroke may be directed to an inlet of a compressor in the turbocharger via a third passage. Thus, each cylinder of the engine may include five valves: two intake valves, two exhaust valves and one compressor inlet valve. The engine controller may be configured to execute a control routine (such as the routine of fig. 4) to operate the compressor inlet valve based on various engine operating conditions, such as shown in fig. 5. The compressor inlet valve timing may be coordinated with the timing of the exhaust valves and intake valves to allow for Exhaust Gas Recirculation (EGR) and blowby gases (fig. 3). In the second embodiment shown in FIG. 6, engine efficiency may be improved during low to medium engine loads. Herein, the cam profile shifting system may be coupled to each of the two exhaust valves and the compressor inlet valve (FIG. 7) of each engine cylinder. Further, a fourth passage may be included in the second embodiment that fluidly couples each of the compressor inlet valves of each engine cylinder with the intake manifold of the engine downstream of the compressor. By adjusting the valve timing of the exhaust valve and compressor inlet valve of each engine cylinder (fig. 9A, 9B, and 9C), the engine can be operated in three different modes (fig. 10). Different operating modes may be selected based on existing engine operating conditions (FIG. 11) including existing engine load and engine speed (FIG. 8). In this way, during a single engine cycle, exhaust gas from different durations of the exhaust stroke within each engine cylinder may be directed to different locations in the engine system (FIG. 12), thereby providing knock control via EGR and cylinder cooling via blow-by gases. Further, by changing the location where exhaust gas is recirculated, engine efficiency may be improved.

In the following description, the valves being operable or activated indicates that the valves are opened and/or closed according to a determined timing during a combustion cycle for a given set of conditions. Likewise, the valve being disabled or inoperable indicates that the valve is being held closed unless otherwise specified. A deactivated valve, when held closed, may block fluid flow (including gas) therethrough.

FIG. 1 shows a schematic diagram of a multi-cylinder internal combustion engine 10 that may be included in a propulsion system of an automobile. Engine 10 may include a plurality of combustion chambers (also referred to as cylinders), the top of which may cover a cylinder head (not shown). In the example shown in FIG. 1, engine 10 includes

combustion chambers

20, 22, 24, and 26 arranged in an inline four-cylinder configuration. It should be appreciated, however, that although FIG. 1 illustrates four cylinders, engine 10 may include any number of cylinders in any configuration (e.g., V-6, I-6, V-12, opposed 4, etc.).

Each combustion chamber may receive intake air from an intake manifold 27 via an air intake passage 28. Intake manifold 27 may be coupled to the combustion chambers via intake ports. For example, intake manifold 27 is shown in FIG. 1 as being coupled to

cylinders

20, 22, 24, and 26 via

intake ports

152, 154, 156, and 158, respectively. Each intake port may supply air and/or fuel to the cylinder to which it is coupled for combustion. Each cylinder intake port can be in selective communication with the cylinder via one or more intake valves.

Cylinders

20, 22, 24, and 26 are shown in FIG. 1 as having two intake valves each. For example, cylinder 20 has two

intake valves

32 and 34, cylinder 22 has two

intake valves

36 and 38, cylinder 24 has two

intake valves

40 and 42, and cylinder 26 has two

intake valves

44 and 46. In one example, an intake passage may be formed by selective communication of an intake manifold 27 with each intake valve. In other embodiments, the intake passage for a single cylinder may split near the cylinder into two adjacent paths with a wall in between, each split path of the passage communicating with a single intake valve. In another example, at a particular engine speed, each of the two intake valves may be controlled to open, and thus may communicate with the intake manifold via a common intake passage.

Each combustion chamber may exhaust combustion gases via one or more exhaust passages coupled thereto.

Cylinders

20, 22, 24, and 26 are shown in FIG. 1 as each being coupled to two exhaust passages for directing a blowdown portion and a scavenge portion, respectively, of combustion gases. For example,

exhaust ports

33 and 35 are coupled to cylinder 22,

exhaust ports

39 and 41 are coupled to cylinder 22, exhaust ports 45 and 47 are coupled to cylinder 24, and exhaust ports 51 and 53 are coupled to cylinder 26. Each exhaust passage may be selectively communicable via a cylinder to which the exhaust valve is coupled. For example,

exhaust passages

33, 35, 39, 41, 45, 47, 51, and 53 communicate with their respective cylinders via their

respective exhaust valves

122, 132, 124, 134, 126, 136, 128, and 138.

This is a separate manifold system, and

exhaust ports

33, 39, 45, and 51 may lead into exhaust manifold 55, while

exhaust ports

35, 41, 47, and 53 may be combined into exhaust manifold 57. The exhaust manifold in the system may be configured to exhaust products of combustion from the

cylinders

20, 22, 24, and 26.

Engine 10 may include a turbocharger 190. The turbocharger 190 may include the exhaust turbine 92 and the intake compressor 94 coupled on the common shaft 96. A wastegate 127 may be coupled across the turbine 92. Specifically, a wastegate 127 may be included in a bypass 166 coupled between the inlet and outlet of the exhaust turbine to control the amount of boost provided by the turbine.

The exhaust manifold may be designed to separately direct the bleed and scavenge portions of the exhaust gas. Exhaust manifold 55 may direct bleed pulses of exhaust gas to turbine 92 of turbocharger 190 via conduit 160, while exhaust manifold 57 may direct purge portions of exhaust gas downstream of turbine 92 and upstream of emission control device 72 (also referred to as an exhaust emission device, an exhaust catalyst, an emission catalyst, etc.) via conduit 162. For example, exhaust valves 122, 124, 126, and 128 direct a bleed portion of the exhaust gas to the turbine through exhaust manifold 55 and line 160, while

exhaust valves

132, 134, 136, and 138 direct a purge portion of the exhaust gas to emission control device 72 through exhaust manifold 57 via line 162.

Exhaust gas exiting turbine 92 may also pass through emission control device 72. In one example, emission control device 72 can include a plurality of bricks. In another example, multiple emission control devices, each having multiple bricks, can be used. In some examples, emission control device 72 may be a three-way type catalyst. In other examples, emission control device 72 may include one or more Diesel Oxidation Catalysts (DOCs) and selective catalytic reduction catalysts (SCRs). After passing through emission control device 72, the exhaust may be directed out to tailpipe 58.

In addition to two intake valves and two exhaust valves as shown in FIG. 1, each cylinder of engine 10 may also include a fifth valve, referred to as a "compressor inlet valve". The fifth valve can also be referred to as a third exhaust valve. For example,

cylinders

20, 22, 24, and 26 include

compressor inlet valves

112, 114, 116, and 118, respectively, coupled to their

respective ports

31, 37, 43, and 49. Further, each of the ports in communication with the compressor inlet valve may be combined into a different manifold 59, which may be connected to the intake 28 upstream of the compressor 94 and downstream of the air filter 70 via a conduit 164. For example, the compressor inlet valve 112 may be opened in the cylinder 20 toward the end of the exhaust stroke, thereby allowing residual exhaust gas flow to the inlet of the compressor 94. Further, the compressor inlet valve 112 may remain open past the Top Dead Center (TDC) position of the piston to overlap the intake valves 32 and/or 34 of the cylinder 20, allowing fresh intake air to leak out of the combustion chamber and discharging any remaining exhaust gas to the compressor 94. A valve 125 may be included in line 164 to control the flow of EGR and leak air into the compressor inlet. The valve 125 may be referred to as a first exhaust gas recirculation valve (ERV) 125. Further, valve 125 may also be referred to as a forward compressor ERV because valve 125 may regulate the flow of exhaust gas and leak air to a location upstream of the compressor. As such, the valve 125 may be a binary valve (e.g., a two-way valve) that may be controlled to be fully open or fully closed (closed). The fully open position of the binary valve is a position in which the valve does not impose a flow restriction, while the fully closed position of the binary valve is a position in which the valve restricts all flow so that no flow can pass through the valve. In an alternative embodiment, the valve 125 may be a continuously variable valve capable of assuming positions between fully closed and fully open.

In one example, the amount of blow-by air and EGR supplied to the compressor inlet may be controlled by varying the timing, lift, and/or duration of one or more of the

compressor inlet valves

112, 114, 116, and 118. In another example, valve 125 in line 164 may be operated to control the amount of blow-by air and EGR delivered to compressor 94, and the compressor inlet valve(s) may be operated at fixed timing, lift, and duration.

Thus, the combustion gases exiting the cylinders may be divided into three portions via three different passages, including two exhaust passages formed by separate exhaust manifolds and one passage connecting the compressor inlet valve upstream of the turbocompressor. For example, during one combustion cycle, the first exhaust valve 122 of the cylinder 20 may direct a first portion of the exhaust (i.e., the bleed portion) to the turbine 92 via a first passage (line 160). The second exhaust valve 132 of the same cylinder 20 may direct a second portion of the exhaust gas after the bleed portion to the emission control device 72 via a second passage (line 162). The second portion of the exhaust gas exiting via the second exhaust valve 132 may be primarily a scavenging portion of the exhaust gas. Towards the end of the exhaust stroke, the remaining exhaust gas may be purged from the clearance volume of the same cylinder 20 by fresh intake air from the blow-by gas and diverted to the inlet of the turbine compressor 94 via the compressor inlet valve 112 and the third passage (line 164). Specifically, the second portion of the exhaust gas comprises primarily exhaust gas without any fresh air content, while the compressor inlet valve 112 and line 164 primarily deliver fresh blow-by air with a smaller exhaust gas content.

The first exhaust valve may open earlier than the second exhaust valve and the compressor inlet valve to capture the bleed pulse, and may be closed at an earlier timing than the second exhaust valve and the compressor inlet valve. The second exhaust valve may be opened later than the first exhaust valve but earlier than the compressor inlet valve to capture the purged portion of the exhaust gas. The first exhaust valve may be closed before the compressor inlet valve is opened, but the second exhaust valve may be closed after the compressor inlet valve is opened. The second exhaust valve may be closed long before the intake stroke begins and the intake valve is opened, however, the compressor inlet valve may be closed just after the intake stroke begins. The intake valve may be opened just prior to the end of the exhaust stroke at the piston's TDC position, and may be closed just past the compressor stroke, e.g., at the piston's Bottom Dead Center (BDC) position. Effectively, the compressor inlet valve may direct residual exhaust gas toward the end of the exhaust stroke, and may also direct blow-by and EGR by overlapping with one or more intake valves.

Intake passage 28 may include an intake throttle 62 (also referred to as throttle 62) downstream of charge air cooler 90. The position of throttle 62 is adjustable by control system 15 via a throttle actuator (not shown) communicatively coupled to controller 12. By modulating the intake throttle 62 while operating the compressor 94, an amount of fresh air may be introduced into the engine 10 from the atmosphere, cooled by the charge air cooler 90, and delivered to the engine cylinders via the intake manifold 27 at compressor (or boost) pressure. To reduce compressor surge, at least a portion of the air charge compressed by the compressor 94 may be recirculated to the compressor inlet. A compressor recirculation passage 168 may be provided for recirculating cooled compressed air from a compressor outlet downstream of charge air cooler 90 to a compressor inlet. A compressor recirculation valve 120 may be provided for adjusting the amount of cooled recirculation flow recirculated to the compressor inlet.

In FIG. 1, for example, a fuel injector is shown directly coupled to the combustion chamber for injecting fuel directly into the combustion chamber in proportion to the pulse width of signal FPW received from controller 12 by the electronic driver. Each cylinder is shown coupled with two injectors per cylinder at each intake valve. For example, fuel injectors 74 and 76 are coupled to cylinders 20, 78, and 80 are coupled to cylinder 24, cylinders 22, 82, and 84, while fuel injectors 86 and 88 are coupled to cylinder 26, as shown in FIG. 1. In this way, the fuel injector provides a so-called direct injection of fuel into the combustion chamber. For example, each respective fuel injector may be mounted to the side of the respective combustion chamber, or at the top of the respective combustion chamber. In some examples, one or more fuel injectors may be disposed in intake manifold 27, the configuration providing so-called port injection of fuel into the intake port upstream of the respective combustion chamber. Although not shown in fig. 1, fuel may be delivered to the fuel injectors by a fuel system including a fuel tank, a fuel pump, a fuel line, and a fuel rail.

In some examples, a distributorless ignition system (not shown) may provide an ignition spark to a spark plug coupled to the combustion chamber in response to controller 12. For example, spark plugs 50, 52, 54, and 56 are shown in FIG. 1 coupled to

cylinders

20, 22, 24, and 26, respectively.

Engine 10 may be controlled, at least in part, by a control system 15 including controller 12 and by input from a vehicle operator via an input device (not shown). The control system 15 is shown receiving information from a plurality of sensors 16 (various examples of which are described herein) and sending control signals to a plurality of actuators 81. As one example, sensors 16 may include turbo compressor inlet pressure and temperature sensors, and a Manifold Air Pressure (MAP) sensor located within the intake passage. Other sensors may include a Throttle Inlet Pressure (TIP) sensor for estimating Throttle Inlet Pressure (TIP), and/or a throttle inlet temperature sensor coupled downstream of the throttle in the intake passage for estimating throttle air temperature (TCT). Additional system sensors and actuators are set forth in detail below with reference to fig. 2. As another example, actuators 81 may include fuel injectors,

valves

120, 125, and 127, and throttle 62. The controller 12, corresponding to one or more programs, based on instructions or code programmed therein, may receive input data from various sensors, process the input data, and trigger actuators in response to the processed input data. An example control routine is described herein in FIG. 4.

Referring to FIG. 2, a partial view 200 of a single cylinder of internal combustion engine 10 is depicted. Thus, the components previously described in fig. 1 are denoted by the same reference numerals, and are not re-described.

Engine 10 is depicted as having combustion chambers (cylinders) 230, coolant jackets 214, and cylinder walls 232 with pistons 236 positioned therein and connected to crankshaft 240. Combustion chamber 230 is shown communicating with intake passage 146 and exhaust passage 148 via respective intake valve 252 and exhaust valve 256. As previously described in FIG. 1, each cylinder of engine 10 may exhaust products of combustion along three conduits. In the illustrated view 200, exhaust passage 148 represents a first exhaust passage leading from the cylinder to the turbine (such as exhaust passage 33 of FIG. 1), but the second exhaust conduit and the conduit leading to the compressor inlet are not visible in this view.

Also, as previously elaborated in FIG. 1, each cylinder of engine 10 may include two (or more) intake valves and two (or more) exhaust valves in addition to the compressor inlet valve. In the illustrated view 200, the intake valve 252 and the exhaust valve 256 are located in an upper region of the combustion chamber 230. Intake valve 252 and exhaust valve 256 may be controlled by controller 12 using respective cam actuation systems that include one or more cams. Cam actuation systems may utilize one or more of Cam Profile Switching (CPS), Variable Cam Timing (VCT), Variable Valve Timing (VVT) and/or Variable Valve Lift (VVL) systems to vary valve operation. In the illustrated example, each intake valve 252 is controlled by an intake cam 251, and each exhaust valve 256 is controlled by an exhaust cam 253. The position of intake valve 252 and exhaust valve 256 may be determined by

valve position sensors

255 and 257, respectively.

In alternative embodiments, the intake and/or exhaust valves may be controlled by electric valve actuation. For example, cylinder 230 may alternatively include an intake valve controlled via electric valve actuation and an exhaust valve controlled via cam actuation including CPS and/or VCT systems. In still other embodiments, the intake and exhaust valves may be controlled by a common valve actuator or actuation system, or a variable valve timing actuator or actuation system. Note that the compressor inlet valve may be similarly controlled.

In one example, intake cam 251 includes separate and distinct cam lobes that provide different valve profiles (e.g., valve timing, valve lift, duration, etc.) for each of the two intake valves of combustion chamber 230. Likewise, the exhaust cam 253 may include separate and distinct cam lobes that provide different valve profiles (e.g., valve timing, valve lift, duration, etc.) for each of the two exhaust valves of the combustion chamber 230. Similarly, the compressor inlet valves (not shown in FIG. 2) may be controlled by a camshaft that includes separate and distinct cam lobes that provide various valve profiles. In another example, intake cam 251 may include a common lobe, or similar lobes, that provides a substantially similar valve profile for each of the two intake valves.

In addition, different cam profiles for different exhaust valves can be used to separate exhaust gases discharged at low cylinder pressures from exhaust gases discharged at exhaust pressures. For example, the first exhaust cam profile can open the first exhaust valve from a closed position just before BDC (bottom dead center) of a power stroke of the combustion chamber 230 and close the same exhaust valve just before Top Dead Center (TDC) to selectively exhaust the blowdown gases from the combustion chamber. Further, the second exhaust cam profile can be positioned to open the second exhaust valve from closing near a midpoint of the exhaust stroke and close it before TDC to selectively exhaust a scavenging portion of the exhaust gas. Further, the compressor inlet cam profile can be set to open the compressor inlet valve from the closed position toward the end of the exhaust stroke. Just after TDC after the beginning of the intake stroke, the compressor inlet valve may be closed, allowing for overlap between the compressor inlet valve and one or more of the intake valves, which may be opened during the intake stroke.

The compressor inlet valve may be activated or deactivated based on intake manifold air pressure. Specifically, when the intake manifold air pressure is higher than the compressor inlet pressure, the exhaust gas within the cylinder may be drawn to the low pressure compressor inlet along with the blow-by gas, thereby reducing pumping losses. Conversely, when the manifold air pressure is lower than the compressor inlet pressure, for example, under throttling conditions, the compressor inlet valve operation may be deactivated during the entire engine cycle to prevent reverse flow of air from the compressor inlet into the intake manifold via the cylinder and the compressor inlet valve. In this example, exhaust gas may be diverted completely to the turbine and emission control device through both exhaust valves, without any blow-by gases.

Thus, the timing of the first and second exhaust valves can isolate the cylinder bleed gas from the purged portion of the exhaust gas, while any residual exhaust gas in the clearance volume of the cylinder can be purged out by the fresh intake air blowby during the positive valve overlap between the intake valve and the compressor inlet valve. By flowing a first portion of the exhaust gas (e.g., higher pressure exhaust gas) through the turbine and the higher pressure exhaust passage, and flowing a second portion of the exhaust gas (e.g., lower pressure exhaust gas) through the catalytic device and the lower pressure exhaust passage, when a third portion of the low pressure exhaust gas and a third portion of the blow-by air are circulated to the compressor inlet, the combustion temperature can be reduced while improving the operating efficiency of the turbine and engine torque.

With continued reference to FIG. 2, exhaust gas sensor 226 is shown coupled to exhaust passage 148. Sensor 226 may be positioned in the exhaust passage upstream of one or more emission control devices, such as device 72 of FIG. 1. Sensor 226 may be selected from a variety of suitable sensors for providing an indication of exhaust gas air/fuel ratio, such as a linear oxygen sensor or UEGO (universal or wide-range exhaust gas oxygen), a two-state oxygen sensor or EGO (as shown), a HEGO (heated EGO), a NOx, HC, or CO sensor, for example. The downstream emission control devices may include one or more of a Three Way Catalyst (TWC), NOx trap, various other emission control devices, or combinations thereof.

Exhaust gas temperature may be estimated by one or more temperature sensors (not shown) located in exhaust passage 148. Alternatively, the exhaust temperature may be inferred based on engine operating conditions such as speed, load, air-fuel ratio (AFR), spark timing, etc.

The cylinder 230 can have a compression ratio, which is the ratio of the volume of the piston 236 at bottom dead center to top dead center. Conventionally, the compression ratio is in the range of 9: 1 to 10: 1. However, in some examples where different fuels are used, the compression ratio may be increased. This may occur, for example, when higher octane fuels or fuels with higher latent enthalpy of vaporization are used. If direct injection is used, the compression ratio may also be increased due to its effect on engine knock.

In some embodiments, each cylinder of engine 10 may include a spark plug 91 for initiating combustion. Ignition system 288 is capable of providing an ignition spark to combustion chamber 230 via spark plug 91 in response to spark advance signal SA from controller 12, under select operating modes. However, in some embodiments, spark plug 91 may be omitted, such as where engine 10 may initiate combustion by self-ignition or by injection of fuel, as is the case with some diesel engines.

In some embodiments, each cylinder of engine 10 may be configured with one or more fuel injectors for providing fuel thereto. As a non-limiting example, cylinder 230 is shown including one fuel injector 66. Fuel injector 66 is shown coupled directly to combustion chamber 230 for injecting fuel directly into the combustion chamber in proportion to the pulse width of signal FPW received from controller 12 via electronic driver 268. In this manner, fuel injector 66 provides what is known as direct injection (hereinafter also referred to as "DI") of fuel into combustion cylinder 230. Although FIG. 2 shows injector 66 as a side injector, it may also be located at a top position of the piston, such as near spark plug 91. This location may improve mixing and combustion when operating an engine with an alcohol-based fuel due to the lower volatility of some alcohol-based fuels. Alternatively, the injector may be located at the top and near the intake valve, thereby improving mixing. In an alternative embodiment, injector 66 may be a port injector that provides fuel into the intake port upstream of cylinder 230.

Fuel may be delivered to fuel injector 66 from high pressure fuel system 8, including a fuel tank, fuel pumps, and a fuel rail. Alternatively, fuel may be delivered at a lower pressure by a single stage fuel pump, in which case the timing of direct fuel injection may be more limited during the compression stroke than if a high pressure fuel system were used. Further, although not shown, the fuel tank may have a pressure transducer that provides a signal to controller 12. The fuel tanks in fuel system 8 may contain fuels of different fuel qualities, such as different fuel compositions. These differences may include different alcohol content, different octane numbers, different heat of vaporization, different fuel blends, and/or combinations thereof, and the like. In some embodiments, fuel system 8 may be coupled to a fuel vapor recovery system that includes a canister for storing the refill fuel and diurnal fuel vapors. When the purging condition is satisfied, fuel vapors may be purged from the canister to the engine cylinders during engine operation. For example, the purge vapor may be naturally drawn into the cylinder at or below atmospheric pressure via the first intake passage.

The controller 12 is shown in fig. 2 as a microcomputer, which includes: a microprocessor unit (CPU)102, input/output ports (I/O)104, an electronic storage medium for executable programs and calibration values, which in this particular example is shown as Read Only Memory (ROM)106, Random Access Memory (RAM)108, Keep Alive Memory (KAM)110 and a data bus. Storage medium read-only memory 106 can be programmed with computer readable data representing instructions executable by microprocessor 102 for performing the methods and programs described below as well as other variations that are contemplated but not specifically listed. In addition to those signals previously discussed, controller 12 may receive various signals from sensors coupled to engine 10, including: a measure of the incoming Mass Air Flow (MAF) from a mass air flow sensor 48; engine Coolant Temperature (ECT) from temperature sensor 212 coupled to cooling sleeve 214; a surface ignition pickup signal (PIP) from Hall effect sensor 220 (or other type) coupled to crankshaft 240; a Throttle Position (TP) from a throttle position sensor; absolute manifold pressure signal (MAP) from sensor 98; cylinder AFR from EGR sensor 226; and abnormal combustion from the knock sensor and the crank acceleration sensor. Engine speed signal, RPM, may be generated by controller 12 from signal PIP. Manifold pressure signal MAP from a manifold pressure sensor may be used to provide an indication of vacuum or pressure in the intake manifold.

Based on input from one or more of the above-described sensors, controller 12 may adjust one or more actuators, such as fuel injector 66, throttle 62, spark plug 91, compressor inlet valves, intake/exhaust valves, cams, and so forth. The controller, corresponding to one or more programs, based on instructions or code programmed therein, may receive input data from the various sensors, process the input data, and trigger the actuators in response to the processed input data. An example control routine will be described later with reference to fig. 4.

Turning now to FIG. 3, a map 300 depicts example valve timing relative to piston position for an engine cylinder including 5 valves: two intake valves, two exhaust valves, and a compressor inlet valve, such as described in fig. 1-2. The example of fig. 3 is essentially to scale even though each point is not labeled with a numerical value. Thus, relative differences in timing can be estimated by drawing size. However, other relative timings may be used, if desired.

With continued reference to fig. 3, the cylinder is configured to receive intake air via two intake valves and to exhaust a first bleed portion to the turbine inlet via a first exhaust valve, a second purge portion to an emission control device via a second exhaust valve, and to flow a combination of low pressure exhaust gas and fresh leakage air to the inlet of the turbine compressor via a compressor inlet valve. By adjusting the timing of the opening and/or closing of the compressor inlet valves by means of the timing of the opening and/or closing of the two exhaust valves and the two intake valves, residual exhaust gas in the cylinder clearance volume can be purged out and recirculated as EGR together with fresh intake blow-by gas.

Map 300 shows engine position along the x-axis at Crank Angle Degrees (CAD). Curve 302 illustrates piston position (along the y-axis) with reference to their position from Top Dead Center (TDC) and/or Bottom Dead Center (BDC), and further with reference to their position within the four strokes of the engine cycle (intake, compression, power, and exhaust).

During engine operation, each cylinder typically undergoes a four-stroke cycle that includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. Generally, during the intake stroke, the exhaust valve is closed and the intake valve is opened. Air is introduced into the cylinder via the corresponding intake passage, and the cylinder piston moves to the bottom of the cylinder so as to increase the volume inside the cylinder. The position of the piston near the bottom of the cylinder and at the end of its stroke (e.g., when the combustion chamber is at its largest volume) is typically referred to by those skilled in the art as Bottom Dead Center (BDC). During the compression stroke, the intake and exhaust valves are closed. The piston moves toward the cylinder head to compress air within the combustion chamber. The point at which the piston is at the end of its stroke and closest to the cylinder head (e.g., when the combustion chamber is at its smallest volume) is commonly referred to by those skilled in the art as Top Dead Center (TDC). In a process referred to herein as injection, fuel is introduced into the combustion chamber. In a process referred to herein as ignition, the injected fuel is ignited by a known ignition device, such as a spark plug, resulting in combustion. During the expansion stroke, the expanding gases push the piston back to BDC. The crankshaft converts the piston movement into a rotational torque of the rotating shaft. During the exhaust stroke, in conventional designs, the exhaust valve is opened to release the residual combusted air-fuel mixture to the corresponding exhaust passage, and the piston returns to TDC. In this specification, the compressor inlet valve may be opened towards the end of the exhaust stroke, while the exhaust valve is closed, thereby expelling the remaining exhaust gas by means of the leakage air.

Curve 304 depicts a first intake valve timing, lift, and duration for a first intake valve (Int _1), while curve 306 depicts a second intake valve timing, lift, and duration for a second intake valve (Int _2) coupled to an intake passage of an engine cylinder. Curve 308 depicts an example exhaust valve timing, lift, and duration for a first exhaust valve (Exh _1) coupled to a first exhaust passage of an engine cylinder, while

curves

310a and 310b show an example exhaust valve timing, lift, and duration for a second exhaust valve (Exh _2) coupled to a second exhaust passage of an engine cylinder. As previously elaborated, a first exhaust passage connects the first exhaust valve to an inlet of a turbine in the turbocharger, and a second exhaust passage connects the second exhaust valve downstream of the turbine and upstream of the emission control device. Curve 312 shows example valve timing, lift, and duration for a Compressor Inlet Valve (CIV) coupled to a third passageway connecting the CIV to an inlet of the turbo compressor. The first and second exhaust passages and the third passage for flowing EGR and blowby air may be separated from each other.

In the illustrated example, the first and second intake valves are fully opened from a closed position at a common timing (curves 304 and 306) just prior to CAD2 (e.g., at or just before intake stroke TDC) to begin substantially closer to intake stroke TDC, and are closed just after the subsequent compression stroke has begun to pass through CAD3 (e.g., at or just after BDC). Additionally, when fully open, both intake valves may be opened by the same amount as the valve lift L1 for the same duration of D1. In other examples, the two valves may be operated with different timings by adjusting phasing, lift, or duration based on engine conditions.

Turning now to the exhaust valves, the timing of the first and second exhaust valves are staggered with the timing of the Compressor Inlet Valve (CIV). Specifically, the first exhaust valve is opened from a closed position at a first timing (curve 308) that is earlier in the engine cycle than the timing at which the second exhaust valve is opened from closing (

curves

310a, 310b), and that is earlier than the timing at which the CIV is opened from closing (curve 312). Specifically, just prior to CAD1 (e.g., at or just before exhaust stroke BDC), the first timing for the first exhaust valve is closer to exhaust stroke BDC, while after CAD1, but before CAD2, the timing for opening the second exhaust valve and the CIV are retarded from exhaust stroke BDC. Prior to the end of the exhaust stroke, the first exhaust valve (curve 308) and the second exhaust valve (curve 310a) may be closed, while the CIV is held open past TDC, so as to be in positive overlap with the intake valve, when the intake stroke has begun. For example, the CIV may be closed prior to the midpoint of the intake stroke.

To elaborate, at or before the beginning of the exhaust stroke (e.g., within 10 degrees before BDC), the first exhaust valve may be fully opened from closing, it may be held fully open through the first portion of the exhaust stroke, and it may be fully closed before the end of the exhaust stroke (e.g., within 45 degrees before TDC), to collect the bleed portion of the exhaust pulse. The second exhaust valve (curve 310a) may be fully opened from a closed position near a midpoint of the exhaust stroke (e.g., between 60 and 90 degrees past BDC), it may be held open through a second portion of the exhaust stroke, and it may be fully closed to exhaust a purged portion of the exhaust before the end of the exhaust stroke (e.g., within 20 degrees before TDC). The CIV may be fully opened from closing toward the end of the exhaust stroke (e.g., within 25 degrees before TDC), it may be held fully opened at least until the subsequent intake stroke has begun, and it may be fully closed just after exhaust stroke TDC (e.g., within 30 degrees past TDC). Just before the end of the exhaust stroke (e.g., within 10 degrees before TDC), the intake valve may be fully opened, it is held open through the intake stroke, and at the beginning of the compression stroke, or just past the beginning of the compression stroke (e.g., within 10 degrees past BDC), it may be fully closed. Thus, as shown in FIG. 3, the CIV and intake valve may have positive overlap periods (e.g., from within 10 degrees before TDC to 30 degrees past TDC) to allow for blow-by via EGR. Based on engine operating conditions, the cycle may repeat itself with all five valves operable.

Further, the first exhaust valve may be fully closed and remain closed just before the CIV is fully opened, while the second exhaust valve may be fully closed just after the CIV is opened. Further, the first and second exhaust valves may overlap each other, the second exhaust valve and the CIV may minimally overlap each other, but the first exhaust valve may not overlap the CIV.

As previously mentioned, the CIV may be operable when the MAP is above the compressor inlet pressure. However, when MAP is below compressor inlet pressure, the CIV may be deactivated and remain closed until MAP is above the pressure at the compressor inlet. Specifically, if open, the CIV may be closed, or remain closed, to prevent reverse airflow from the engine intake into the intake manifold via the cylinders. Herein, the timing of the first exhaust valve may be the same as the first timing shown in curve 308 of fig. 3: open just before BDC when the exhaust stroke begins, and close just before the end of TDC of the exhaust stroke. However, near halfway through the exhaust stroke, the second exhaust valve may be opened and may remain open (curve 310b) until just after the end of the exhaust stroke (e.g., past TDC10 degrees) to expel its exhaust gas from the cylinder. At the end of the exhaust stroke, or just after the end of the exhaust stroke, the second exhaust valve may be fully closed and positive valve overlap may not occur between the second exhaust valve and the intake valve to avoid blow-by.

Basically, the timing of the second exhaust valve may be changed based on the activation or deactivation of the CIV. When MAP is above compressor inlet pressure and the CIV is operable through the combustion cycle, the second exhaust valve may be opened near halfway through the exhaust stroke and closed just before the end of the exhaust stroke (curve 310 a). In one example, the second exhaust valve may be opened approximately 80 degrees through BDC and closed within 20 degrees before TDC. When MAP is below compressor inlet pressure and CIV is deactivated and remains closed, the second exhaust valve may be opened near halfway through the exhaust stroke and fully closed when the end of the exhaust stroke is at or just past TDC (curve 310 b). For example, the second exhaust valve may be opened approximately 90 degrees through BDC and closed within 10 degrees through TDC. In the example shown in FIG. 3 for the second exhaust valve, curves 310a and 310b may have the same duration D3. In other examples, the duration may be changed along with the phasing of the second exhaust valve.

In addition, the first exhaust valve may be opened at the first timing with a first amount of valve lift L2, while the second exhaust valve may be opened with a second amount of valve lift L3 (curve 310a), and the CIV may be opened with a third amount of valve lift L5. Further, the first exhaust valve may be opened at the first timing for a duration of D2, while the second exhaust valve may be opened for a duration of D3, and the CIV may be opened for a duration of D5. It should be appreciated that in alternative embodiments, both exhaust valves may have the same amount of valve lift and/or the same duration of opening, while opening at different phase timings.

In this way, by using staggered valve timing, engine efficiency and power can be improved by separating exhaust gases released at higher pressures (e.g., expanding blowdown exhaust gases in the cylinder) from residual exhaust gases at lower pressures (e.g., remaining in the cylinder after blowdown) into different passages. By delivering low pressure residual exhaust gas as EGR to the compressor inlet along with blow-by air, the combustion chamber temperature can be reduced, thus reducing knock and spark retard from torque capacity. Furthermore, because the exhaust gas at the end of the stroke is directed downstream of the turbine or upstream of the compressor, both at lower pressures, exhaust pumping losses can be minimized to improve engine efficiency.

Thus, the exhaust gas can be used more efficiently than simply directing all of the exhaust gas from the cylinders through a single, common exhaust passage to the turbocharger turbine. Thus, several advantages are achieved. For example, by dividing the bleed pulse and directing it into the turbine inlet, the average exhaust temperature supplied to the turbocharger can be increased, thereby increasing turbocharger output. Additionally, because the blow-by air is not routed to the catalyst, but instead is directed to the compressor inlet, fuel economy may be improved, and, as a result, excess fuel may not be injected into the exhaust gas to maintain a stoichiometric ratio.

Turning now to FIG. 4, an example routine 400 for operating a Compressor Inlet Valve (CIV) and two exhaust valves based on engine conditions is shown. Specifically, the routine may determine different valve positions based on engine operating conditions including combustion stability, engine limitations, and transients among other conditions. Further, as explained below, the valve is operated for the duration of a particular engine condition through one or more combustion cycles.

At 402, engine operating conditions may be estimated and/or measured. These may include, for example, ambient temperature and pressure, engine temperature, engine speed, crankshaft speed, battery state of charge, fuel availability, catalyst temperature, driver demanded torque, and the like. At 404, based on the estimated engine operating conditions, the operation and operation of all valves may be determined. For example, under steady state conditions, the CIV may be operated during an engine combustion cycle, allowing for blow-by, reducing exhaust pumping losses, and improving torque.

At 406, it may be determined whether an engine start condition exists. Engine starting may include cranking the engine from rest via a motor (such as a starter motor). If an engine start condition exists, at 408, the CIV and first exhaust valve are deactivated and remain closed while the entire exhaust portion is delivered to the emission control device via the second exhaust valve. To elaborate, during a burn cycle, under engine starting conditions, just prior to the beginning of the exhaust stroke, the second exhaust valve may be fully open, and at the beginning of the intake stroke, the second exhaust valve may be fully closed. During a cold start, the hot exhaust gas may help bring the emission control device to a light-off temperature. During a hot start, the initial emissions may be purged by the emission control device having reached the light-off temperature.

At 410, it may be determined whether tip-in is desired. To speed up the exhaust turbine to increase power in a turbocharged system in preparation for tip-in, the first exhaust valve may be activated in addition to the second exhaust valve to direct a bleed portion of the exhaust gas to the turbine. Specifically, the first exhaust valve may be opened just as the exhaust stroke begins and closed just prior to the end of the exhaust stroke, thereby directing (target) a bleed pulse to the turbine. The second exhaust valve may be opened near halfway through the exhaust stroke and closed just before the end of the exhaust stroke, thereby directing a purge portion of exhaust gas to the emission control device.

If tip-in is identified, the routine may determine whether the Manifold Air Pressure (MAP) is greater than the turbocompressor inlet pressure at 412. If it is determined that the MAP is high, the CIV may be activated to open toward the end of the exhaust stroke at 414, allowing EGR and blow-by air to be diverted to the compressor inlet.

If MAP is below compressor inlet pressure, the CIV may be or remain closed and deactivated to prevent reverse airflow. For example, under throttled conditions, intake air may need to flow from upstream of the compressor to the intake manifold via the combustion chambers. To prevent this reverse flow, the CIV may be deactivated and closed, while the second exhaust valve may be opened near halfway through the exhaust stroke and closed at or just past the beginning of the intake stroke.

At 418, it may be determined whether there is any indication of engine knock. If engine knock is determined to be present, at 420, the routine includes operating the CIV to enable EGR and blow-by gases that can cool the combustion chamber temperature. Specifically, the CIV may be opened toward the end of the exhaust stroke and closed just past the beginning of the exhaust stroke. As previously described, two exhaust valves may be operated to direct bleed and purge portions to the turbine and the emission control device, respectively. Engine knock may be due to an abnormal combustion event occurring in the cylinder after a spark ignition event of the cylinder. To promote combustion stability, additional fuel may be injected into the blow-by air to enrich the EGR gas. By injecting fuel to enrich EGR, engine knock may be mitigated without using spark retard, thereby improving engine torque.

Next, at 422, it may be determined whether a deceleration fuel cutoff (DFSO) or tip-out condition is satisfied. The DFSO event may be in response to the torque demand being below a threshold, such as during tip-out. Wherein cylinder fuel injection may be selectively stopped. If the DFSO or tip-out pedal is asserted, at 424, the CIV may be deactivated or closed, or remain closed, thereby reducing the amount of residuals delivered to the engine intake during deceleration. Specifically, the CIV is closed and/or remains closed for as long as the DFSO or accelerator pedal is released during the entire combustion cycle. Further, the exhaust gas may be directed into two parts: via an earlier bleed portion of the first exhaust valve and via a second purge portion of the second exhaust valve. After exiting from the DFSO, the engine settings may be adjusted to maximize the engine torque response. For example, the throttle may be positioned to allow for optimal transient response to tip-in.

If the engine conditions are not present, the valves may be operated based on steady state conditions at 426. In one example, during steady state conditions, if MAP is above compressor inlet pressure, the CIV may be activated and opened toward the end of the exhaust stroke and closed just after the beginning of the intake stroke similar to step 414. In another example, if the MAP is below the compressor inlet pressure, the CIV may be deactivated and held closed, as at step 416. As previously described, two exhaust valves may be operated: if the CIV is operable during a combustion cycle, both exhaust valves close just before the end of the exhaust stroke. If the CIV is not operable, the bleed portion of the exhaust gas continues to be delivered to the turbine via the first exhaust, while the second exhaust valve exhausts the remaining exhaust gas to an emission control device. Herein, the blowby gas and the EGR may not be directed to the compressor inlet. In another example, in an unsteady state condition, valve operation may be modified and adapted to existing conditions.

Various examples of engine conditions and resulting valve adjustments will now be described in detail with reference to FIG. 5. Specifically, table 500 lists example combinations of exhaust gases exiting a cylinder along three different passages, including a first exhaust passage that leads to an exhaust turbine inlet through a first exhaust valve, a second passage that leads to an emission control device through a second exhaust valve, and a third passage that leads from a compressor inlet valve to upstream of a turbo compressor. Thus, as previously elaborated with reference to FIG. 3, three portions of exhaust gas may be separately exhausted and at different times within the same engine combustion cycle. Further, during all of the conditions described below, the intake valve is operable, as described with reference to FIG. 3. Both intake valves may be fully opened at the beginning of the intake stroke (e.g., at or just before the TDC exhaust stroke) and fully closed at the end of the intake stroke (e.g., at or just after the BDC intake stroke).

During an engine start condition, the CIV and the first exhaust valve may be deactivated and remain closed, while the second exhaust valve is operable and opens through the entire exhaust stroke (e.g., from just before the end of power stroke BDC to just after the end of exhaust stroke TDC), whereby all exhaust gas is directed to the exhaust control device. Thus, when the engine is started from rest or shut-down, neither the turbine nor the compressor inlet receives any portion of the exhaust gas. Both exhaust valves may be activated and operated during tip-in. The bleed portion of the exhaust gas may be directed to the turbine by opening the first exhaust valve just prior to the end of the power stroke BDC and closing the first exhaust valve prior to the end of the exhaust stroke BDC. By opening the second exhaust valve near the middle of the exhaust stroke, a second portion of the exhaust gas after the bleed may be delivered to the emission control device. Both exhaust valves may be closed prior to the end of exhaust stroke TDC. During the intake stroke, a final portion of low pressure exhaust gas (LP-EGR) combined with fresh leakage air may be delivered to the turbine compressor inlet by operating the CIV to open toward the end of the exhaust stroke, and by maintaining positive valve overlap with one or more intake valves. The CIV may be closed just after the beginning of the intake stroke, e.g., just past TDC. Thus, with energy recovered from the bleed pulses of exhaust gas, the exhaust turbine may increase power for tip-in, while knock and other combustion instabilities may be reduced by recirculating LP-EGR and blow-by gases via the compressor inlet. Operation of the CIV may depend on the MAP. The CIV may be opened during a combustion cycle only when the manifold air pressure is higher than the compressor inlet pressure to allow fresh intake air to flow through the cylinders and the CIV, thereby diverting residual low pressure exhaust gas to the compressor inlet.

When the engine is operating in a throttled condition, the manifold air pressure may be lower than the compressor inlet pressure. Thus, the CIV may be deactivated and remain closed during a cycle while the two exhaust valves are operable to exhaust combusted gases from the cylinder. The bleed pulses from the exhaust gas may be directed to a turbine of the turbocharger, and the purged portion of the exhaust gas may be delivered to an emission control device. The first exhaust valve may be opened just prior to the beginning of the exhaust stroke and may be closed just prior to the end of the exhaust stroke. The second exhaust valve may be opened near halfway through the exhaust stroke and closed at TDC or just after the end of the exhaust stroke past TDC.

During unstable combustion conditions when engine knock may be present, the CIV may be activated and opened toward the end of the exhaust stroke and may be fully closed just after the intake stroke is initiated to allow for EGR and blowby gases. Additionally, additional fuel may be injected into the blow-by air, thereby making EGR richer and improving combustion stability. Thus, the CIV may transfer a mixture of unburned fuel, low-pressure exhaust gas (as LP-EGR), and blow-by air to the compressor inlet for recirculation to the cylinders. Similar to that described for the tip-in condition, two exhaust valves are operated and may be opened during a portion of the exhaust stroke and closed just prior to the end of the exhaust stroke.

During a tip-out condition, when the engine is disabled, the CIV may be deactivated and held closed to prevent any EGR flow through the engine. The two exhaust valves are operable whereby a first portion of the exhaust gas is discharged to the turbine through the first exhaust valve and a remaining portion of the exhaust gas is discharged to the emission control device through the second exhaust valve. At or just before the end of the power stroke, the first exhaust valve is opened and closed just before the end of the exhaust stroke. The second exhaust valve is opened halfway through the exhaust stroke and is closed just after the intake stroke starts.

Turning now to FIG. 6, another exemplary embodiment of the engine 10 of FIG. 1 is shown. Thus, FIG. 6 depicts a second exemplary embodiment 600 of engine 10. Furthermore, various components of the engine 10 described in the second example embodiment 600 of FIG. 6 may be the same as those shown in FIG. 1. Accordingly, these components are numbered identically and will not be re-introduced.

Thus, the engine 10 of FIG. 6 may be identical to the engine 10 of FIG. I, except that the second example embodiment 600 includes an aft compressor conduit 664 (or passage 664). In other words, a fourth exhaust passage (i.e., an aft compressor conduit 664) may be included in the second example embodiment 600 (as compared to the engine embodiment of FIG. 1) in addition to the three different exhaust passages previously described. Specifically, aft compressor conduit 664 fluidly couples manifold 59 to a location downstream of each of compressor 94 and intake throttle 62 via a second exhaust gas recirculation valve 625. Thus, the aft compressor conduit 664 couples the manifold 59 to a location that is an aft compressor.

For example, the passage 664 may fluidly couple the manifold 59 directly upstream of the intake manifold 27. As shown in FIG. 6, an aft compressor conduit 664 may be coupled to the intake passage 28 downstream of the intake throttle 62 at the mixer 626. Alternative embodiments may include fluidly coupling aft compressor conduit 664 downstream of compressor 94, but upstream of intake throttle 62. Mixer 626 may provide uniform mixing between the air received from manifold 59 via aft compressor conduit 664 and the fresh intake air received from intake throttle 62 via intake passage 28. In other words, spatial and temporal mixing of the exhaust gas, the blow-by air, and the fresh intake air may occur within mixer 626. An EGR cooler 690 is also included within the aft compressor conduit 664 to cool the exhaust gas received from the manifold 59.

Second exhaust gas recirculation valve 625 (or second ERV625) may be a binary (e.g., open/closed) valve that is modulated between one of fully closed and fully open. When the second ERV625 is fully closed, gas from the manifold 59 may not flow through the second ERV625 toward the mixer 626. When fully open, the second ERV625 allows fluid to flow therethrough. As described in further detail below, during a particular mode of operation, exhaust gas from cylinders 20 of engine 10 may flow along aft compressor conduit 664 via second ERV625 through compressor inlet valve 112 to manifold 59, through EGR cooler 690, and into mixer 626. Further, exhaust gas from cylinders 20 of engine 10 may be mixed with fresh intake air received from intake throttle 62 in mixer 626, and the entire mixture may enter manifold 27 and then flow into each cylinder of engine 10. In an alternative embodiment, the second ERV625 may be a continuously variable valve capable of assuming positions between fully closed and fully open.

Thus, combustion gases exiting the cylinders of the second example embodiment 600 of the engine 10 may be directed to one or more of four different locations via four separate passages, including two exhaust passages formed by separate exhaust manifolds, one passage connecting the compressor inlet valve upstream of the turbocompressor, and an after-compressor conduit (or fourth exhaust passage) coupling the compressor inlet valve downstream of the turbocompressor. To elaborate, exhaust gas from the plurality of

cylinders

20, 22, 24, and 26 may be directed to one or more of at least three locations, including an inlet directly to emission control device 72 (via conduit 162), directly to turbine 92 (via conduit 160), and directly to compressor 94 via conduit 164 and ERV 125. In addition to the three positions described above, combustion gases from (only) cylinder 20 may be directed via aft compressor conduit 664 to a fourth position (using cam profile switching and second ERV625) downstream of compressor 94 and downstream of intake throttle 62. As will be further described below with reference to FIG. 8, exhaust gas may be directed to specific locations based on engine operating conditions. Thus, based on the operating mode and the resulting desired target position for EGR, the states of the first and

second ERVs

125, 625 may also change. When EGR is desired at a location upstream of the compressor 92, the first ERV125 may be opened and the second ERV625 may be fully closed. If EGR is desired at the post-compressor position (e.g., mixer 626), the first ERV125 may be fully closed while the second ERV625 may be fully opened (from closing).

Herein, exhaust gas exiting the plurality of cylinders of engine 10 of FIG. 6 may be directed to a desired location using a variable valve timing and cam profile switching system, such as a variable cam timing. FIG. 7 shows a more detailed view 700 of an example Variable Cam Timing (VCT) system 702 and Cam Profile Switching (CPS) system 704 operatively coupled to the second example embodiment of engine 10 of FIG. 6. It should be appreciated that the engine system components described in FIG. 1 (as well as FIG. 6) are similarly numbered and will not be described again. It should also be appreciated that various components of engine 10 are not shown in FIG. 7 for simplicity and clarity of illustration. Additionally, it should be noted that, although not shown, the intake valve of each cylinder of engine 10 may be actuatable via an intake camshaft operatively coupled to VCT system 702 and CPS system 704. However, the operation of the intake valve of each cylinder of engine 10 is not described herein, and the description focuses on operating the exhaust valve and the compressor inlet valve of each cylinder.

Each exhaust valve and compressor inlet valve of each cylinder of engine 10 are actuatable between an open position that allows exhaust gas to be removed from the respective cylinder and a closed position that substantially retains gas within the respective cylinder. FIG. 7 shows the

exhaust valves

38, 128, 136, 126, 134, 124, 132, and 122 and the

compressor inlet valves

118, 116, 114, and 112 actuated by a common exhaust camshaft 714. The exhaust camshaft 714 includes a plurality of exhaust cams configured to control opening and closing of the exhaust valves. Each exhaust valve may be controlled by one or more exhaust cams, which will be described further below. In some embodiments, one or more additional exhaust cams may be included to control the exhaust valves. Further, an exhaust actuator system may allow control of the exhaust valve.

The exhaust valve actuator system may further include pushrods, rocker arms, lifters, and the like. These devices and features may control actuation of the intake and exhaust valves by translating rotational motion of the cam into translational motion of the valve. In other examples, valves may be actuated by additional cam lobe profiles on the camshaft, where the cam lobe profiles between different valves provide varying cam lift heights, cam actuation, and/or cam timing. However, alternative camshaft (top and/or push rod) arrangements may be used if desired. In other examples, the exhaust and intake valves may be actuated by a common camshaft. However, in alternative embodiments, at least one of the intake and/or exhaust valves may be actuated by its own independent camshaft or other device.

The engine 10 of the second example embodiment 600 may include a controller, such as the controller 12 described with reference to FIG. 1, that controls a subset of the plurality of cylinders in a manner different from the remaining number of the plurality of cylinders. Herein, the subset of the plurality of cylinders includes a number of cylinders that is less than a total number of the plurality of cylinders. For example, the cylinders 20 (subset) may be controlled differently relative to controlling the remaining

cylinders

22, 24, and 26 of the plurality of

cylinders

20, 22, 24, and 26. Specifically, the exhaust valves 132, 122 and the compressor inlet valve 112 of the cylinder 20 may be actuated differently relative to the

exhaust valves

138, 128, 136, 126, 134, and 124 and the

compressor inlet valves

118, 116, and 114 of the remaining

cylinders

22, 24, and 26. Thus, the exhaust valves 132, 122 and the compressor inlet valve 112 of the cylinder 20 may be operated by cams having a different and different profile than the cams that actuate the

exhaust valves

138, 128, 136, 126, 134, and 124 and the

compressor inlet valves

118, 116, and 114.

Exhaust valves

134, 136, and 138, which are fluidly coupled to exhaust manifold 57 via conduit 162, and which are immediately thereafter coupled to emission control device 72, may be actuated by first and second exhaust cams 716 and 718 disposed on a common exhaust camshaft 714. The first exhaust cam 716 may have a first cam lobe profile that provides a first exhaust duration and lift. In the example of FIG. 7, the first exhaust cams 716 of the

cylinders

22, 24, and 26 may have similar first cam lobe profiles that open the respective exhaust valves for a given duration and lift. The second exhaust cam 718 may have a second cam lobe profile that provides a second exhaust duration and lift. In the example of FIG. 7, the second exhaust cams 718 of the

cylinders

22, 24, and 26 may have similar second cam lobe profiles that open the respective exhaust valves for a given duration and lift. Thus, the first exhaust cam 716 may have a distinct and different cam profile relative to the cam profile of the second exhaust cam 718. For example, the second exhaust cam 718 may open the respective exhaust valve for a longer duration than the duration of opening provided by the first exhaust cam 716.

The exhaust valves 124, 126, and 128 that direct the bleed portion of the exhaust gas through the exhaust manifold 55 and the conduit 160 to the turbine 92 may be actuated by each of the third exhaust cam 720, the fourth exhaust cam 722, and the fifth exhaust cam 724. The third exhaust cam 720 may have a third cam lobe profile that provides a third exhaust duration and lift. In the example of FIG. 7, the third exhaust cams 720 of the

cylinders

22, 24, and 26 may have similar third cam lobe profiles that open the respective exhaust valves for a given duration and lift. The fourth exhaust cam 722 may have a fourth cam lobe profile that provides a fourth exhaust duration and lift. In the example of FIG. 7, the fourth exhaust cam 722 of the

cylinders

22, 24, and 26 may have a similar fourth cam lobe profile that opens the respective exhaust valve for a given duration and lift. Thus, the third exhaust cam 720 may have a distinct and different cam profile relative to the cam profile of the fourth exhaust cam. For example, the fourth exhaust cam 722 may open the respective exhaust valve for a longer duration than the duration of opening provided by the third exhaust cam 720. Further, the third exhaust cam 720 may have a distinct and different cam profile relative to the cam profiles of the first and second exhaust cams 716, 718. Similarly, the fourth exhaust cam 722 may have a distinct and different cam profile relative to the cam profiles of the first and second exhaust cams 716, 718.

The fifth cam 724 is depicted as a zero cam lobe that may have a profile to maintain their respective exhaust valves 124, 126, and 128 in a fully closed (e.g., deactivated) position through one or more engine cycles. Thus, during certain modes, a zero cam lobe may facilitate deactivating the corresponding exhaust valves 124, 126, and 128 in the

respective cylinders

22, 24, and 26.

Only the

compressor inlet valves

114, 116, and 118 fluidly coupled to the

cylinders

22, 24, and 26 of the exhaust manifold 59 may be actuated by each of the sixth and

seventh exhaust cams

726 and 728. The sixth exhaust cam 726 may have a sixth cam lobe profile that provides a sixth exhaust duration and lift. In the example of FIG. 7, the sixth exhaust cams 726 of the

cylinders

22, 24, and 26 may have similar sixth cam lobe profiles that open the respective exhaust valves for a given duration and lift. The sixth exhaust cam 726 may have a distinct and different cam profile relative to the cam profile of the exhaust cam previously described. The seventh exhaust cam 728 may be a zero cam lobe that holds the

compressor inlet valves

114, 116, and 118 fully closed when desired. Thus, during certain engine conditions, the compressor inlet valves in the

cylinders

22, 24, and 26 may be deactivated.

The exhaust valves 132 and 122 of the cylinders 20 may be controlled individually by a single set of cams. Specifically, the exhaust valve 132 in communication with the exhaust manifold 57 may be actuated by an eighth exhaust cam 730, a ninth exhaust cam 732, and a zero exhaust cam 733. The eighth exhaust cam 730 may have an eighth cam lobe profile that provides an eighth exhaust duration and lift. The ninth exhaust cam 732 may have a ninth cam lobe profile that provides a ninth exhaust duration and lift. The eighth exhaust cam 730 may have a distinct and different cam profile relative to the cam profiles of the previously described cams and the ninth exhaust cam 732. Further, zero exhaust cam 733 may have a profile that maintains exhaust valve 132 in its fully closed position (e.g., deactivated) when desired.

Similarly, an exhaust valve 122 fluidly coupled with the exhaust manifold 55 may be actuated by a tenth exhaust cam 734, an eleventh exhaust cam 736, and a zero exhaust cam 738. The tenth exhaust cam 734 may have a tenth cam lobe profile that provides a tenth exhaust duration and lift. The eleventh exhaust cam 736 may have an eleventh cam lobe profile that provides an eleventh exhaust duration and lift. The eleventh exhaust cam 736 may have a distinct and different cam profile relative to the previously described cam profiles of the cams and the tenth exhaust cam 734. Further, zero exhaust cam 738 may have a profile that maintains exhaust valve 122 in its fully closed position (e.g., deactivated) when desired.

The compressor inlet valve 112 of the cylinder 20 may be actuated by a twelfth exhaust cam 740, a thirteenth exhaust cam 742, and a zero exhaust cam 744. The twelfth exhaust cam 740 may have a twelfth cam lobe profile that provides a twelfth exhaust duration and lift. The thirteenth exhaust cam 742 may have a thirteenth cam lobe profile that provides a thirteenth exhaust duration and lift. The twelfth exhaust cam 740 may have a distinct and different cam profile relative to the previously described cams and the cam profile of the thirteenth exhaust cam 742. Further, zero exhaust cam 744 may have a profile that holds compressor inlet valve 112 in its fully closed position (e.g., deactivated) when desired.

Other embodiments may include different mechanisms known in the art for deactivating exhaust valves and compressor inlet valves in the cylinders. These embodiments may not utilize a zero cam lobe for deactivation. For example, these mechanisms may include a switching tappet, a switching rocker arm, or a switching hydraulic roller finger follower.

Thus, each of the

exhaust valves

138, 136, and 134 coupled to the manifold 57 may be actuated by one of two exhaust cams. However, the exhaust valves 128, 126, and 124 may be actuated by one of three different exhaust cams, while the

compressor inlet valves

118, 116, and 114 may be actuated by one of two different exhaust cams. Further, during certain engine conditions, each of exhaust valves 128, 126, and 124 and each of

compressor inlet valves

118, 116, and 114 may be deactivated by at least one zero exhaust cam. The exhaust valves 132 and 122 of the cylinders 20 and the compressor inlet valve 112 may each be actuated by one of three different exhaust cams. Further, each of the exhaust valves 132 and 122 of the cylinders 20 and the compressor inlet valve 112 may be deactivated via a respective zero exhaust cam when desired.

Each of the exhaust valve and the compressor inlet valve may be actuated by a respective actuator system operatively coupled to controller 12. Thus, the

exhaust valves

138, 128 of the cylinder 26 and the compressor inlet valve 118 may be actuated by the actuator system 706. Similarly, the exhaust valves 136, 126 and the compressor inlet valve 116 of the cylinder 24 may be actuated by an actuator system 708. Further, the exhaust valves 134, 124 and the compressor inlet valve 114 of the cylinder 22 may be actuated by the actuator system 710. Further, the exhaust valves 132, 122 and the compressor inlet valve 112 of the cylinder 20 may be actuated by an actuator system 712.

Other embodiments may include reduced actuator systems or different combinations of actuator systems without departing from the scope of the present disclosure. For example, the intake and exhaust valves of each cylinder may be actuated by a single actuator.

CPS system 704 may be configured to longitudinally translate specific portions of exhaust cam 714, thereby causing operation of the exhaust valve and compressor inlet valve of each cylinder, thereby changing between the different exhaust cams detailed previously. For example, depending on whether the third exhaust cam 720, the fourth exhaust cam 722, or the fifth exhaust cam 724 is selected, the operation of the exhaust valves 128, 126, and 124 may change. Likewise, the operation of the compressor inlet valve 112 of the cylinder 20 may vary depending on which of the twelfth exhaust cam 740, the thirteenth exhaust cam 742, or the zero exhaust cam 744 actuates the compressor inlet valve 112.

The VCT system 702 includes an exhaust camshaft phaser 765 for varying valve timing. An intake camshaft phaser (although not expressly shown) may be included without departing from the scope of the present disclosure. VCT system 702 may be configured to advance or retard valve timing (example engine operating parameters) by advancing or retarding cam timing, and may be controlled via controller 12. VCT system 702 may be configured to vary the timing of valve opening and closing events by varying the relationship between crankshaft position and camshaft position. For example, the VCT system 702 may be configured to rotate the exhaust camshaft 714 independently of the crankshaft to cause the valve timing to be advanced or retarded. In some embodiments, VCT system 702 may be a cam torque actuated device configured to rapidly change cam timing. In some embodiments, valve timing, such as Intake Valve Closing (IVC) and Exhaust Valve Closing (EVC), may be varied by a Continuously Variable Valve Lift (CVVL) apparatus.

The valve/cam control apparatus and systems described above may be hydraulically powered, or electrically actuated, or a combination thereof.

In an alternative embodiment (dashed lines) where

actuator systems

706, 708, 710, and 712 include rocker arms to actuate different exhaust cams coupled to a common exhaust camshaft 714, CPS system 704 is operatively coupled to solenoid S1 and solenoid S2, which in turn is operatively coupled to the actuator system. Herein, the rocker arm may be actuated by electrical or hydraulic means via solenoids S1 and S2 to follow the selected exhaust cam for each exhaust valve and compressor inlet valve. As shown, solenoid S1 is operatively and communicatively coupled to actuator system 712 only (via dashed line 760) and is not operatively (or communicatively) coupled to

actuator systems

706, 708, and 710. Likewise, solenoid S2 is operatively and communicatively coupled to actuator systems 706 (via 772), 708 (via 774), and 710 (via 776), and is not operatively (or communicatively) coupled to actuator system 712.

To elaborate, solenoid S1 is operatively and communicatively coupled to cylinder 20 only actuator system 712, but not to actuator

systems

706, 708, and 710, which are coupled to

cylinders

26, 24, and 22, respectively. Further, solenoid S2 is operatively and communicatively coupled to 706, 708, and 710, but not to 712. In this context, the rocker arm may be actuated by electrical or hydraulic means to follow one of the previously described cams for each exhaust valve.

In this manner, the CPS system 704 may transition between cams for opening the corresponding exhaust valve for a particular duration and/or lift and/or timing. CPS system 704 may receive signals from controller 12 to transition between different cam profiles for different cylinders in engine 10 based on engine operating conditions.

FIG. 8 illustrates an example map 800 that characterizes an engine load-engine speed curve. Specifically, the map depicts different speed-load regions when different modes of operating the exhaust valves and the compressor inlet valves of different cylinders of engine 10 may be employed. Map 800 represents engine speed plotted along the x-axis, and engine load (or mean effective brake pressure (BMEP)) plotted along the y-axis. Line 802 represents the highest load that a given engine can operate at a given speed. Map 800 also includes three regions of different engine load and engine speed combinations in which the cylinders of engine 10 may be operated in different ways, thereby providing lower pumping losses and higher engine efficiency.

Region 808 defined by very low engine loads may include engine operating conditions such as engine cold start, engine idle, etc. As a non-limiting example, these very light engine loads may include BMEP in the range of 0-2 bar. Herein, the engine torque demand may be significantly low. During these very low engine load conditions, the cylinders may be operated to direct a significant portion, e.g., as much as 100%, of their exhaust gases to an exhaust catalyst, e.g., emission control device 72.

Accordingly, the cam profiles may be switched by the CPS system 704 of FIG. 7 to actuate the

exhaust valves

138, 136, and 134 via the second exhaust cam 718. Specifically, the second exhaust cam 718 may actuate the corresponding exhaust valve to open the entire duration of the respective exhaust stroke in the

cylinders

26, 24, and 22. Meanwhile, the exhaust valve 132 of the cylinder 20 may be actuated by a ninth exhaust cam 732. Herein, the exhaust valve 132 may be held open for the entire duration of the exhaust stroke in the cylinder 20. At the same time, the exhaust valves 128, 126, 124, 122 and

compressor inlet valves

118, 116, 114, and 112 of the

respective cylinders

26, 24, 22, and 20 may be held fully closed. Specifically, by actuating these exhaust valves 128, 126, and 124 via their respective zero exhaust cams, e.g., fifth exhaust cam 724, the exhaust valves 128, 126, and 124 may be held closed (e.g., deactivated), while the

compressor inlet valves

118, 116, and 114 are held closed via their respective zero cams (e.g., seventh exhaust cam 728). At the same time, by actuating the zero cam 738, the exhaust valves 122 of the cylinders 20 may be held closed, while the compressor inlet valves 112 of the cylinders 20 may be held fully closed via the zero cam 744.

Alternatively, a smaller portion of the exhaust gas, e.g., a portion of the bleed pulses, may be directed from all of the

cylinders

20, 22, 24, and 26 to the exhaust turbine, while a larger portion of the exhaust gas from all of the cylinders may be directed to the emission control device 72.

Region 806 may represent a low to medium engine load, such as 2-10 bar BMEP. Herein, the desired engine power may be low, for example, during cruising, although higher relative to the desired power in region 808. In other words, although the engine load in region 806 in the present disclosure may be classified as lower to medium load, region 806 represents a higher engine load than in region 808 (and a lower engine load than in region 804).

When the engine is operating in region 806, exhaust gas from a subset of the plurality of cylinders may be recirculated to engine 10. For example, during low to medium engine loads, the CPS system 704 may communicate with the actuator 712 to switch between the various cams coupled to the exhaust valves 132, 122 and the compressor inlet valve 112 of the cylinder 20. Specifically, compressor inlet valve 112 may be held open for the entire duration of the exhaust stroke, thereby directing all exhaust gas from cylinders 20 to manifold 59. Thus, each of the exhaust valves 132 and 122 may be held closed by actuation by their respective zero

cams

733 and 738. Further, by closing the first ERV125 and opening the second ERV625, exhaust gas from the cylinder 20 received in the manifold 59 may be directed to the mixer 626 downstream of the compressor 94 via the aft compressor conduit 664.

Simultaneously and during a first engine cycle, while the compressor inlet valve 112 of cylinder 20 is held open for the entire duration of the exhaust stroke, exhaust gas from the remaining cylinders (e.g., cylinders 26, 24, and 22) is directed to each of the turbine and the emission control device during the same first engine cycle. Specifically, the exhaust valves 128, 126, and 124 may be opened to direct a first portion of the exhaust (i.e., the bleed portion) to the turbine 92 via a first passage (line 160). At the same time, the

exhaust valves

138, 136, and 134 may direct only a second portion of the exhaust gas after the bleed portion to the emission control device 72 via a second passage (line 162). The second portion of the exhaust gas may be a purge portion of the exhaust gas that includes a small portion of the residual exhaust gas. Likewise, exhaust valves 128, 126, and 124 may be open during portions prior to an exhaust stroke, while

exhaust valves

138, 136, and 134 may be open during portions subsequent to the same exhaust stroke. Specifically, during engine operation in region 806, the

compressor inlet valves

118, 116, and 114 of the

respective cylinders

26, 24, and 22 may be deactivated and closed.

Region 804 includes high engine loads (e.g., greater than 10 bar BMEP) with the engine operating to achieve high torque demands. As an example, a high engine load condition may include a tip-in event, the vehicle traveling up a slope, and so forth. Further, the engine load in region 804 may be higher than the engine load in each of region 806 and region 808. Thus, region 804 may include a significantly higher engine load.

When the engine is operating in region 804, a significant portion of the exhaust gas may be delivered to the turbine of the turbocharger to generate the desired higher torque demand. Furthermore, to reduce knock, cooling of the combustion chamber may be achieved by providing a leak of fresh intake air. Thus, during a tip-in condition, the engine (including multiple cylinders) may operate as described with reference to FIG. 5. Specifically, by opening the first exhaust valves (e.g., exhaust valves 128, 126, 124, and 122) just prior to the end of the power stroke BDC and closing the first exhaust valves prior to the end of the exhaust stroke, the bleed portion of exhaust gas may be directed to the turbine. Near the middle of the exhaust stroke, a second portion of the exhaust gas after the bleed may be directed to the emission control device by opening a second exhaust valve (e.g.,

exhaust valves

138, 136, 134, and 132). Both exhaust valves may be closed prior to the end of exhaust stroke TDC. During the intake stroke, a final portion of low pressure exhaust gas (LP-EGR) combined with fresh leakage air may be delivered to the turbine compressor inlet by operating the CIV (e.g.,

compressor inlet valves

118, 116, 114, and 112) to open toward the end of the exhaust stroke, and by maintaining positive valve overlap with one or more intake valves.

It should be noted that when the relative load is indicated as high or low, the indication refers to the relative load compared to the range of variable loads. Thus, low engine loads may be lower relative to each of medium and higher engine loads. The high engine load may be higher relative to each of the medium (moderate) and lower engine loads. Medium or moderate engine loads may be lower relative to high or very high engine loads. Further, moderate or moderate engine loads may be higher relative to low engine loads. Further, very low engine loads may include engine loads below low engine loads and below medium and high engine loads.

Turning now to fig. 9A, 9B, and 9C, which include

maps

940, 960, and 980, respectively, which depict example valve timings relative to piston position for one or more engine cylinders, each of which includes 5 valves: two intake valves, two exhaust valves, and one compressor inlet valve, such as the cylinders depicted in fig. 1, 6, and 7. CPS systems, such as CPS system 704, may vary the timing of the opening and closing of the 5 valves, as well as vary the duration for which the 5 valves are held open. The example maps in FIGS. 9A, 9B, and 9C may be similar to the example of FIG. 3 in that they describe valve timing relative to piston position and crankshaft rotation. Thus, maps 940, 960, and 980 retain similar numbering from FIG. 3 for the curves for piston position (curve 302) and intake valve timing (curves 304 and 306).

Each of the

maps

940, 960, and 980 shows engine position in Crank Angle Degrees (CAD) along the x-axis. Curve 302 illustrates piston position (along the y-axis) with reference to their position from Top Dead Center (TDC) and/or Bottom Dead Center (BDC), and further with reference to their position within the four strokes of the engine cycle (intake, compression, power, and exhaust).

Curve 304 of each of

maps

940, 960, and 980 depicts a first intake valve timing, lift, and duration for a first intake valve (Int _1), while curve 306 shows a second intake valve timing, lift, and duration for a second intake valve (Int _2) coupled to an intake passage of an engine cylinder. In the illustrated example, the first and second intake valves are fully opened from a closed position at a common timing (curves 304 and 306) just prior to CAD2 (e.g., at or just before intake stroke TDC) to begin substantially closer to intake stroke TDC, and are closed just after the subsequent compression stroke has begun to pass through CAD3 (e.g., at or just after BDC). In addition, when fully open, both intake valves may be opened for the same duration of D1 with the same amount of valve lift L1. In other examples, the two valves may be operated at different timings by adjusting phasing, lift, or duration based on engine conditions.

It should be appreciated that each of the intake valves, each of the exhaust valves, and each of the compressor inlet valves are actuated independently of each other via associated CPS and VCT systems.

Referring now to map 940 of FIG. 9A, exemplary valve timings for all cylinders in engine 10 of FIGS. 6 and 7 when the engine is operating in region 808 of map 800 are described. Specifically, map 940 includes example exhaust valve timings for engine operation during very low engine loads (e.g., 0-2 bar BMEP). As described with reference to fig. 8, during engine operation at very low loads, the compressor inlet valves of each of the plurality of cylinders may be held closed by actuating the compressor inlet valves via their respective zero cams. Thus, curve 913 depicts the CIV having no valve lift (e.g., zero valve lift) duration D7 (e.g., from before BDC to just after TDC). In other words, when the engine is operating at very low or very light loads, the CIVs of all cylinders are completely closed for the entire duration of the exhaust stroke.

Further, when the engine is operating in region 808 of map 800, the first exhaust valves (e.g., exhaust valves 128, 126, 124, and 122) may also be fully closed for the entire duration of the exhaust stroke. In other words, the exhaust valves 128, 126, 124, and 122 may be actuated by their respective zero cams and may be deactivated. Thus, curve 911 shows that the first exhaust valve of all cylinders (Exh _1) has no valve lift (e.g., zero valve lift) duration D7 (e.g., from before BDC to just after TDC).

Curve 912 depicts example exhaust valve timing, lift, and duration for the second exhaust valve (Exh _2) of the engine cylinder coupled to the second exhaust passage (e.g., conduit 162) and manifold 57. The second exhaust valve may include

valves

138, 136, 134, and 132 in communication with manifold 57. As shown in map 940, when the engine is operating at a relatively light load, the second exhaust valve may be fully opened (from fully closed) for the entire duration of the exhaust stroke (e.g., from before CAD1 to just after CAD 2). Thus, the exhaust valve number two of the cylinders of engine 10 may be held open for duration D7, as shown. Specifically, the second exhaust valve may be opened before the exhaust stroke begins (e.g., within 10 degrees before BDC of the power stroke), held fully open for the duration of the exhaust stroke, and may be fully closed (from opening) just after the end of the exhaust stroke (e.g., within 10 degrees after TDC in the exhaust stroke).

Thus, when the engine is operating at very low engine loads, exhaust gas from all cylinders of engine 10 may be directed to the emission catalyst. Herein, all of the exhaust gas may include a bleed portion, a purge portion, and residual exhaust gas. For example, the second exhaust valves of the

cylinders

26, 24, and 22 may be actuated by their respective second exhaust cams 718. Likewise, the exhaust valves 132 may be actuated by a ninth exhaust cam 732. Further, each of the second exhaust valves may be opened with a valve lift L3 of a second amount. For example, the second amount of valve lift L3 may be the maximum opening of the second exhaust valve.

It should be appreciated that a positive valve overlap between the second exhaust valve and the corresponding intake valve may exist when the subsequent intake stroke begins after the TCD of CAD 2. Herein, exhaust gas toward the end of the exhaust stroke may be drawn into the intake manifold 27 in the opposite direction from the respective combustion chambers. Specifically, during very low engine loads, intake manifold 27 may be at a lower pressure relative to the pressure in the exhaust manifold (e.g., manifold 57 and/or manifold 55). Thus, low pressure exhaust gas remaining in the cylinder at the end of the exhaust stroke may flow from the cylinder into the intake manifold 27. This flow of exhaust gas from the combustion chamber into the intake manifold may be referred to as a "reverse" flow as opposed to a "forward" flow, wherein exhaust gas from the combustion chamber flows into the exhaust manifold. In the reverse flow mode, exhaust gas that has entered the intake manifold 27 may later be blown into the engine cylinders through the open intake valves in a subsequent intake stroke along with fresh intake air. Thus, these low pressure exhaust gases flowing into the engine cylinders during the intake stroke may function as internal EGR. Note that fresh blow-by intake air may not flow into the exhaust manifold because the intake manifold is at a reduced pressure compared to the exhaust manifold during very low engine loads.

It should also be appreciated that during low load operation, such as during an engine cold start, the emission control device may quickly reach the light-off temperature by flowing all of the exhaust gas to the emission control device (and by not diverting a portion of the exhaust gas to the turbine, the forward compressor position, or the aft compressor position).

Optionally, when the exhaust catalyst has reached the light-off temperature and the engine is operating at a very low load, a small portion of the bleed pulse may be diverted toward the turbine via the first exhaust valve by opening the first exhaust valve at the beginning of the exhaust stroke, as shown by dashed curve 908. Dashed curve 908 depicts an example valve timing, lift, and duration for the first exhaust valve to collect a portion of the bleed portion of the exhaust pulse. As shown, the first exhaust valve of all cylinders may be open for a first amount of valve lift L2 duration D6. Herein, the first exhaust valve may be opened (from closing) just before TDC or just before CAD1, and may be closed before the midpoint of the exhaust stroke between CAD1 and CAD2 (e.g., within 90CAD of the exhaust stroke).

The second exhaust valve may be opened for the same valve timing, lift, and duration during the same exhaust stroke, as shown by curve 912. Alternatively, the second exhaust valve may be opened for a shorter duration than D7, as shown by dashed curve 909. Dashed curve 909 shows an example valve timing, lift, and duration for the second exhaust valve, collecting the remainder of the exhaust pulse (e.g., the portion of exhaust gas remaining in the cylinder after the first exhaust valve closes, as shown by dashed curve 908). As shown in the example of dashed curve 909, the second exhaust valve may be opened from closing just before the first exhaust valve closes (e.g., between 45CAD and 90CAD of the exhaust stroke) and may remain open just after TDC of the exhaust stroke (e.g., just after CAD2, near 10CAD after CAD 2). Further, the second exhaust valve may be open for a duration D8, where D8 is shorter than the duration D7 of curve 912. Herein, the first exhaust valve(s) may be opened earlier in the cylinder cycle than the timing at which the second exhaust valve is opened from closing.

In this manner, when the engine is operating at very low loads, such as within region 808 of map 800, all of the exhaust gas in the exhaust stroke of each cylinder may exit the cylinder into manifold 57 via the second exhaust valve (e.g.,

valves

138, 136, 134, and 132) and immediately thereafter toward emission control device 72. Optionally, a small portion of the blowdown pulses in each cylinder may be directed through the manifold 55 toward the exhaust turbine 92 via the first exhaust valve (e.g., valves 128, 126, 124, and 122). Herein, the remainder of the exhaust pulse may flow into the manifold 57 via the second exhaust valve and immediately thereafter towards the emission control device 72.

Referring now to map 960 of FIG. 9B, exemplary valve timings for all cylinders in engine 10 of FIGS. 6 and 7 are described when the engine is operating in region 806 of map 800. Specifically, map 960 includes example exhaust valve timings for engine operation during low to medium engine loads (e.g., 2-10 bar BMEP). As described with reference to FIG. 8, during engine operation at low to medium loads, a subset of the plurality of cylinders of engine 10 may be operated differently than the remaining number of cylinders of the plurality of cylinders. Specifically, a number of cylinders less than the total number of the plurality of cylinders may be operated differently from the remaining number of cylinders of the plurality of cylinders.

In the depicted example of engine 10 of FIGS. 6 and 7, a subset of the plurality of cylinders includes cylinder 20, where the plurality of cylinders includes

cylinders

20, 22, 24, and 26. Thus, when the engine is operating in region 806 of map 800, a subset of cylinders (e.g., cylinder 20) are operated differently relative to the remaining cylinders, e.g.,

cylinders

22, 24, and 26. To elaborate, all exhaust gas from the cylinder 20 (including bleed pulses, purge pulses and small amounts of residual gas) is directed to the post-compressor position. At the same time, exhaust gas from the remaining cylinders is not directed to the post-compressor location. Instead, exhaust gas from the remaining cylinders is directed to each of the turbine and the emission control device.

Dashed curve 918 represents example exhaust valve timing, lift, and duration for a Compressor Inlet Valve (CIV) for cylinder 20 only. Herein, the CIV of cylinder 20 may be fully opened for the entire duration of the exhaust stroke (e.g., from before CAD1 to just after CAD 2). As shown, in map 960, CIV 112 for cylinder 20 may be open for a duration D7. Specifically, the CIV of cylinder 20 may be opened (from being closed) before the beginning of the exhaust stroke (e.g., within 10 degrees before BDC of the power stroke), held fully open for the duration of the exhaust stroke, and may be fully closed (from being open) just after the end of the exhaust stroke (e.g., within 10 degrees after TDC). In this way, a small amount of positive overlap may occur between the CIV and the intake valve of cylinder 20 when the subsequent intake stroke begins. Thus, when the engine is operating at low to intermediate loads, substantially all exhaust gas (e.g., at least 95% of all exhaust gas) from the cylinders 20 (e.g., a subset of the cylinders) of the engine 10 may be directed to a location downstream of the compressor (also referred to as an after-compressor). This position may also be downstream of the intake throttle, as shown in FIG. 6. Dashed

gray curves

911 and 915 represent the first and second exhaust valves of cylinder 20, respectively. As shown by the dashed

gray curves

911 and 915, each of the first and second exhaust valves of cylinder 20 may be held fully closed during the exhaust stroke (duration D7). Each of the first and second exhaust valves 122, 132 may have no valve lift. Thus, the valves 122 and 132 may be actuated by their respective zero cams.

The solid curve 914 of the map 960 depicts example valve timing, lift, and duration for the first exhaust valve of the remaining cylinders (e.g., cylinders 22, 24, and 26). Further, solid curves 916 show example valve timing, lift, and duration for the second exhaust valve of the remaining cylinders (e.g., cylinders 22, 24, and 26). Further, solid lines 917 show example valve timing, lift, and duration for CIV for the remaining cylinders (e.g., cylinders 22, 24, and 26). Specifically, the first exhaust valve(s) is opened from a closed position at a first timing (solid curve 914) that is earlier in the engine cycle than the timing at which the second exhaust valve is opened from closing (solid curve 916). Specifically, just before power stroke BDC, just before CAD1 (e.g., at power stroke BDC, or just before power stroke BDC), the first timing for the first exhaust valve occurs, while, for example, after CAD1, but before CAD2, the timing for opening the second exhaust valve is retarded from power stroke BDC. As shown, the second exhaust valve may be opened at or near the midpoint of the exhaust stroke (e.g., midway between CAD1 and CAD 2). The first exhaust valve may be closed before the end of the exhaust stroke, e.g., before TDC, while the second exhaust valve is held open until just past TDC of the exhaust stroke (e.g., until just after CAD 2). As an example, the first exhaust valve may close around 45CAD before exhaust stroke TDC of CAD 2. Further, the first exhaust valve of the remaining cylinders may be held open for a duration D2.

The second exhaust valve may overlap the intake valve for a short duration. Because the engine operates under low to medium load conditions, the intake manifold may be at a lower pressure relative to the exhaust pressure in the exhaust manifold 55 or exhaust manifold 57. Thus, during positive valve overlap, internal EGR may be provided as low pressure exhaust gas towards the rear of the exhaust stroke, which is drawn into the intake manifold. During the subsequent intake stroke, the same low pressure exhaust gas may later flow into the cylinder with fresh intake air as internal EGR. Further, when the exhaust manifold is at a higher pressure than the intake manifold, fresh intake blow-by air may not flow into the cylinder during positive valve overlap and through it into the exhaust manifold.

Further, the second exhaust valve may be open for a duration D3 (as in fig. 3), which duration D3 includes a duration from at or near a midpoint of the exhaust stroke until just past the beginning of the subsequent intake stroke (e.g., from near halfway between CAD1 and CAD2 until just past CAD 2). The CIV of the remaining cylinders may be closed for the entire duration of the exhaust stroke, e.g., from CAD1 through CAD2, as shown by the flat line of curve 917.

Thus, during engine operation at low to intermediate loads, exhaust gas from the remaining cylinders may be directed to both the turbine and the exhaust catalyst. Specifically, a first portion of the exhaust gas may be delivered to the turbine, while a second, remaining portion of the exhaust gas is directed to an emission control device. In other words, the bleed portion of the exhaust gas (at a higher pressure) is directed to the turbine, thereby delivering the desired engine power, while the purge portion of the exhaust gas at a relatively lower pressure is delivered to the emission catalyst. Thus, the two portions of exhaust gas may be separately exhausted and at different times within the same engine combustion cycle, as shown in map 960.

By closing the CIV of the remaining cylinders, leakage of fresh air and flow of LP-EGR may not occur from the remaining cylinders. However, by providing all of the exhaust from the cylinders 20 (e.g., a subset of the cylinders) to the engine within the same engine cycle, a higher proportion of the exhaust may be recirculated for EGR when the exhaust from the remaining cylinders is directed to the turbine and the exhaust catalyst. In this manner, the subset of cylinders may provide rich EGR (e.g., by enriching EGR from cylinders 20), which facilitates combustion stability and combustion rate. Further, by directing exhaust gas from a subset of cylinders to the intake manifold (after-compressor), improved engine efficiency may be achieved by reducing pumping losses and heat losses during low to medium load operation.

Turning now to map 980 of fig. 9C, it describes example valve timings for all cylinders in engine 10 of fig. 6 and 7 when the engine is operating in region 804 of map 800. Specifically, map 980 includes example exhaust valve timings for engine operation during high engine loads (e.g., more than 10 bar BMEP). As described with reference to fig. 8, during engine operation at high loads, a significant portion of the exhaust gas from all cylinders of the engine may be delivered to the turbine of the turbocharger to produce the desired higher torque demand. Furthermore, to reduce knock, cooling of all combustion chambers may be achieved by providing a leak of fresh intake air via positive valve overlap.

As shown by curve 920 (similar to curve 308 of fig. 3), at or before the beginning of the exhaust stroke (e.g., within 10 degrees before BDC of the power stroke), the first exhaust valve of the plurality of cylinders (e.g., valves 122, 124, 126, and 128) may be fully opened from a closed position, held fully open through a first portion of the exhaust stroke, and fully closed before the end of the exhaust stroke (e.g., within 45 degrees before TDC of the exhaust stroke) to collect a bleed portion of the exhaust pulse. The second exhaust valve of the plurality of cylinders (curve 922) may be fully opened from a closed position near a midpoint of the exhaust stroke (e.g., between 60 and 90 degrees at BDC or CAD1 through the power stroke), held open through a second portion of the exhaust stroke, and may be fully closed before the end of the exhaust stroke (e.g., within 20 degrees before TDC of the exhaust stroke) to exhaust the purged portion of the exhaust gas.

The CIVs (curve 924) for the multiple cylinders may be fully opened from the closed position toward the end of the exhaust stroke (e.g., within 25 degrees before TDC of the exhaust stroke), may be held fully opened at least until a subsequent intake stroke has begun and may be fully closed just after TDC of the exhaust stroke (e.g., within 30 degrees past TDC). Just before the end of the exhaust stroke (e.g., within 10 degrees before TDC), the intake valve may be fully opened from closing, held open through the intake stroke, and may be fully closed at or just past the beginning of the compression stroke (e.g., within 10 degrees of BDC through the intake stroke). Thus, as shown in FIG. 9C, the CIV and intake valve may have a positive valve overlap period (e.g., from within 10 degrees before TDC to 30 degrees past TDC) to allow fresh intake air to leak via EGR to a previous compressor location (e.g., into the compressor inlet).

Thus, during high engine loads, each cylinder of the engine may be exhausted via at least three different passages, including a first exhaust passage that leads through a first exhaust valve to an exhaust turbine inlet, a second passage that leads through a second exhaust valve to an emission control device, and a third passage from a compressor inlet valve to upstream of a turbocompressor. In this way, as depicted in the map 980, the three portions of exhaust gas may be separately exhausted and at different times within the same engine combustion cycle.

In addition, the first exhaust valve may be opened at the first timing with a first amount of valve lift L2, while the second exhaust valve may be opened with a second amount of valve lift L3, and the CIV may be opened with a third amount of valve lift L5. Further, the first exhaust valve may be opened at the first timing for a duration of D2, while the second exhaust valve may be opened for a duration of D3, and the CIV may be opened for a duration of D5. It should be appreciated that in alternative embodiments, both exhaust valves may have the same amount of valve lift and/or the same duration of opening, while opening at different phase timings.

In this manner, by adjusting valve timing, lift, and duration, the engine may be operated with less pumping loss and greater efficiency at different load conditions. Rich EGR reduces combustion instability during low to medium load. During high engine loads, blow-by and low pressure EGR may provide temperature reduction while improving turbocharger performance. Herein, by separating various portions of the exhaust, engine performance may be improved while knock is reduced.

Turning now to FIG. 10, an example routine 1000 is shown for adjusting exhaust valves and compressor inlet valves of a multi-cylinder engine to change the delivery location of exhaust gases including EGR based on engine operating conditions. The method allows exhaust gas to be delivered to a turbine and an exhaust catalyst, and recirculated to each of the forward compressor and the aft compressor locations based on existing engine conditions. Thus, the routine 1000 will be described with reference to the engine system shown in fig. 6 and 7, but it should be understood that similar routines may be used with other systems without departing from the scope of the present disclosure. The instructions included herein for executing the routine 1000 may be executed by a controller (such as the controller 12 of fig. 6 and 7) based on instructions stored on a memory of the controller and in conjunction with signals received from sensors of the engine system (such as the sensors described above with reference to fig. 6). The controller may employ engine actuators of the engine system, such as the actuators of fig. 6 and 7, to adjust engine operation according to a routine described below.

At 1002, routine 1000 includes estimating and/or measuring engine operating conditions, such as engine speed, torque demand, engine load, boost, MAP, intake air flow, ambient conditions (e.g., ambient pressure, temperature, humidity), exhaust catalyst temperature, and the like. At 1004, a mode of cylinder operation is selected based on engine conditions, such as adjusting first and second exhaust valves and a compressor inlet valve. For example, the engine operating load may determine the mode in which the cylinder is operating. Next, at 1006, the positions of the first ERV (e.g., the first ERV125 of FIG. 6) and the second ERV (e.g., the second ERV625 of FIG. 6) may be based on engine operating conditions, as will be described below.

At 1008, it may be determined whether the first mode has been selected. In one example, the controller may operate the engine cylinders in a first mode in response to one or more of a very low engine load and an engine cold start condition. If the first mode is identified, routine 1000 continues to 1010 to adjust a CPS device coupled to the exhaust valves of the engine cylinders to selectively open the second exhaust valves of all cylinders and deliver hot exhaust gas to an emission control device. Specifically, the controller may send a signal to the CPS system, which in turn may be in communication with an actuator system operatively coupled to the exhaust camshaft. The exhaust camshaft may be switched to select a particular combination of cam lobes for operating the exhaust valves of the cylinders.

With the second exhaust valve open and each of the first exhaust valve and the compressor inlet valve (also referred to as a third exhaust valve) closed, the controller may operate the engine cylinders in the first mode to direct all of the exhaust gas to the catalyst. Thus, each of the first ERV and the second ERV may be maintained fully closed. Herein, the controller may transmit a signal to an electromechanical actuator coupled to the corresponding ERV. In addition, the electromechanical actuator of each respective ERV may maintain each ERV in its fully closed position. Thus, the exhaust gas may not be delivered to either the forward compressor location (e.g., at the inlet of compressor 94 via conduit 164) or the aft compressor location (e.g., at mixer 626 via aft compressor conduit 664).

Optionally, at 1012, during the beginning of the exhaust stroke, the CPS system may adjust the first exhaust valve to open for a short duration (as shown by dashed curve 908 in FIG. 9A), thereby directing a small portion of the exhaust gas to the turbine, while the remaining exhaust gas is delivered to the emission control device via the second exhaust valve (as shown by dashed curve 909 in FIG. 9A). This option may be utilized when the catalyst has reached a light-off temperature. Routine 1000 then proceeds to 1030, which will be described further below.

If at 1008 it is determined that the first mode has not been selected, then the routine 1000 continues to 1014 where it is determined whether the second mode has been selected at 1014. In one example, in response to engine operation at low to intermediate loads, such as in region 806 of map 800, the controller may operate the cylinder in the second mode. If the second mode is confirmed, process 1000 proceeds to 1016 where multiple actions may be actuated simultaneously at 1016.

At 1018, a subset of the plurality of engine cylinders can be operated in a different manner relative to the remaining plurality of engine cylinders. Herein, a subset of cylinders are operated such that all exhaust gas from the subset of cylinders is directed to a post-compressor position downstream of an intake throttle for a given engine cycle. Thus, at 1018, the CPS system may switch the cam lobe coupled to a subset of cylinders (such as cylinder 20 in engine 10) to actuate the compressor inlet valve(s) of the subset of cylinders to fully open the entire duration of the exhaust stroke. At the same time, and within the same given engine cycle, the first and second exhaust valves of the subset of cylinders are held fully closed for the entire exhaust stroke. Next, at 1020, CPS simultaneously adjusts the first exhaust valve of the remaining cylinders to open during the first portion of the exhaust stroke to deliver a bleed pulse of the exhaust stroke to the turbine of the turbocharger for the same given engine cycle. Further, the second exhaust valve is opened in the same engine cycle near the middle of the exhaust stroke, thereby directing the purge portion of the exhaust stroke to the exhaust catalyst. In addition, the CPS system keeps the compressor inlet valves of the remaining cylinders completely closed. Thus, all of the above adjustments for the remaining cylinders may occur during the same exhaust stroke in a given engine cycle.

At 1022, the second ERV625 (also referred to as the aft compressor ERV) is adjusted to be fully open, allowing exhaust gas from the cylinders 20 to flow into the intake manifold via the mixer 626. Specifically, the compressor may command a signal to an electromechanical (or hydraulic, etc.) actuator coupled to the second ERV625 to adjust the second ERV to a fully open position. Further, the first ERV125 (also referred to as the forward compressor ERV) may be held fully closed to block any exhaust gas flow to the forward compressor position. Routine 1000 then proceeds to 1030.

Returning to 1014, if the second mode is not selected, routine 1000 continues to 1024 to determine if a third mode of cylinder operation has been selected. In one example, in response to engine operation at high engine loads, such as in region 804 of map 800, the controller may operate the cylinder in the third mode. If a third mode of cylinder operation is identified, routine 1000 proceeds to 1026 where all cylinders are operated to deliver a first portion of the exhaust gas to the turbine, a second portion of the exhaust gas to the catalyst, and a residual exhaust gas to the compressor inlet (within the same combustion cycle) along with the leaked fresh air.

At 1026, the CPS system may adjust the cam lobe to actuate the first exhaust valve of all cylinders to open during the first (initial) duration of the exhaust stroke (curve 920 of fig. 9C) to deliver a bleed pulse to the exhaust turbine. Specifically, the first exhaust valve may be opened just at the beginning of an exhaust stroke in the corresponding cylinder and closed just before the end of the exhaust stroke. The second exhaust valve may be opened near halfway through an exhaust stroke in the corresponding cylinder and closed before the end of the exhaust stroke, thereby directing a purge portion of exhaust gas to the emission control device. Further, the CIV may be activated to open toward the end of the exhaust stroke in the corresponding cylinder and close just after the beginning of the intake stroke after the exhaust stroke, allowing low pressure EGR and blow-by air to be diverted to the compressor inlet.

Thus, during a common engine cycle, combustion gases from the exhaust stroke within each cylinder of the engine may be separated into three portions as described above. Specifically, a first portion (e.g., a blowdown portion) of each exhaust stroke from each cylinder may be delivered to the exhaust turbine during a common engine cycle, and a second portion (e.g., a purge portion) of each exhaust stroke from each cylinder may be directed to the exhaust catalyst during the common engine cycle. Further, residual exhaust gas in the clearance volume of the plurality of cylinders during a common engine cycle and blow-by air from each cylinder from a third portion of each exhaust stroke (and the initial duration of the following intake stroke) are recirculated upstream of the compressor within the same common engine cycle.

At 1028, the front compressor ERV may also be opened to allow low-pressure EGR and fresh blow-by air to be diverted to the intake passage upstream of the compressor. Specifically, when the cylinder is operated in the third mode, an electromechanical actuator coupled to the first ERV may actuate the first ERV to a fully open position based on a signal from the compressor. However, the rear compressor ERV may be maintained at a full shut-off to block any EGR and blow-by air from entering the rear compressor position.

Routine 1000 then proceeds to 1030 to determine if there is a change in operating conditions that may cause a change in the operating mode of the cylinder. If so, routine 1000 continues to 1032 to adjust the CPS system to make the desired changes to cylinder operation for operating in the desired mode based on existing engine conditions. For example, if the engine is initially operated at a high engine load and is now transitioning to operate at a medium engine load, engine operation may be transitioned from the third mode to the second mode. In response to this change in the mode of cylinder operation, the CPS system may shift the cam lobes, allowing a subset of cylinders to deliver all exhaust to the post-compressor position, while the remaining cylinders supply their exhaust to the turbine and exhaust catalyst. In another example, engine operation may transition from operation at idle (e.g., very low load) to high load. In response to the transition, the controller may transition operation of the engine cylinder from the first mode to a third mode. Routine 1000 then ends. If instead at 1030 it is determined that there is no change in engine operating conditions, routine 1000 ends.

Accordingly, an example method for an engine may include, during a first condition, recirculating a combination of residual exhaust gas and blowby air from a plurality of cylinders of the engine upstream of a compressor in a first engine cycle, and during a second condition, recirculating all exhaust gas from only a subset of the plurality of cylinders downstream of the compressor in a second engine cycle, and delivering exhaust gas from remaining cylinders to an exhaust turbine. The first condition may include a high engine load condition and the second condition includes a medium engine load condition. The second condition may also include a low engine load. As an example, the second condition may include region 806 of map 800, while the first condition may include region 804 of map 800 of fig. 8. The method may further include, during a first condition, delivering a first bleed portion of the exhaust gas to an exhaust turbine and delivering a second purge portion of the exhaust gas from the plurality of cylinders to an emission control device. Herein, a first bleed portion of the exhaust gas may be delivered to the exhaust turbine via a first exhaust valve of each of the plurality of cylinders, and a second purge portion of the exhaust gas may be delivered to the emission control device via a second exhaust valve of each of the plurality of cylinders. The combination of residual exhaust gas and blow-by air may be delivered to a location upstream of the compressor via a third exhaust valve of each of the plurality of cylinders. The method may also include, during a second condition, delivering a first bleed portion of the exhaust gas to the exhaust turbine and delivering a second purge portion of the exhaust gas from the remaining cylinders to the emission control device.

FIG. 11 presents an example routine 1100 for selecting an operating mode and transitioning between operating modes for cylinders of a multi-cylinder engine in response to engine operating conditions. Thus, the routine 1100 will be described with reference to the engine system shown in fig. 6 and 7, but it should be understood that similar routines may be used with other systems without departing from the scope of the present disclosure. The instructions included herein for carrying out the routine 1100 may be executed by a controller (such as the controller 12 of fig. 6 and 7) based on instructions stored on a memory of the controller in conjunction with signals received from sensors of the engine system (such as the sensors described above with reference to fig. 6 (and fig. 1)). The controller may employ engine actuators of the engine system, such as the actuators of fig. 6 and 7, to adjust engine operation according to a routine described below.

At 1102, engine operating conditions are estimated and/or measured, as at 1002 of routine 1000. At 1104, routine 1100 determines whether an engine cold start condition exists. In one example, an engine cold start is confirmed if the exhaust catalyst temperature is below a threshold, such as below a light-off temperature. In another example, an engine cold start may be confirmed if the engine temperature is below a threshold temperature. Thus, the engine load during an engine cold start may be very low.

If an engine cold start condition is identified, routine 1100 proceeds to 1106 to operate the cylinders of the engine in the first mode with the exhaust valves second of all the cylinders of the engine fully open to deliver all the exhaust gas to the exhaust catalyst while bypassing the exhaust turbine. Further, exhaust gas recirculation may not occur during the first mode of operation. Herein, each of the first and third exhaust valves (or CIVs) may be closed simultaneously during the exhaust stroke. Thus, the exhaust second valves of all cylinders may be open for the entire duration of the exhaust stroke, while the exhaust first valves and the CIV of all cylinders are fully closed for the entire duration of the exhaust stroke. Specifically, all exhaust gases from all cylinders of the engine may be directed to the emission control device during a common engine cycle.

Routine 1100 then continues to 1108. Thus, if a cold engine start is not confirmed at 1104, routine 1100 proceeds to 1108 where it is confirmed whether a tip-in event to a higher load has occurred. For example, there may be a sudden increase in torque demand indicative of a tip-in, where the commanded torque request increases beyond a threshold and the boost pressure is above the threshold. Thus, the engine can now be operated at high load. Further, a rapid increase in power of the turbine of the turbocharger may be desired. In another example, the engine may be operated at high load if the vehicle is traveling diagonally upward. If a tip-in event is not determined to a higher engine load, routine 1100 continues to 1112. However, if a high engine load condition is identified at 1108 (e.g., during a tip-in event), routine 1100 continues to 1110, operating (or transitioning) the cylinders of the engine in the third mode.

Operating in the third mode includes delivering a bleed portion of exhaust gas from all cylinders to the exhaust turbine during a common engine cycle, thereby enabling the turbocharger to rapidly increase power. Further, a purge portion of exhaust gas from all cylinders is directed to an exhaust catalyst within a common engine cycle. Further, a combination of residual exhaust gas and fresh leaked intake air in the clearance volumes of all cylinders is delivered to the compressor inlet via the first ERV towards the end of the exhaust stroke and the beginning of the following intake stroke in the common engine cycle. Thus, the third mode includes opening the first exhaust valve, the second exhaust valve, and the CIV of each of the plurality of cylinders during at least a portion of each exhaust stroke. In addition, the first ERV is opened during the third mode to allow residual exhaust gas and fresh blow-by air to flow into the compressor inlet. The second ERV may be closed during the third mode.

Routine 1100 then proceeds to 1112 to determine whether the engine conditions have changed to those at low to medium engine loads. For example, the vehicle can now cruise at a steady speed. If so, routine 1100 advances to 1114, transitioning and/or operating cylinders of the engine in the second mode. Thus, all exhaust gas from a subset of the plurality of cylinders, such as cylinder 20 of engine 10 in fig. 6 and 7, is recirculated to a location downstream of the compressor (and downstream of the intake throttle) and upstream of the intake manifold. Thus, the second ERV may be opened to allow exhaust flow from a subset of cylinders to the post-compressor position while the first ERV is held fully closed. Meanwhile, within the same engine cycle, where exhaust gas from a subset of the plurality of cylinders is delivered to the intake manifold as EGR, exhaust gas from the remaining cylinders of the plurality of cylinders is directed to each of an exhaust turbine and an exhaust catalyst. In this way, sufficient high pressure exhaust gas to rotate the turbine of the turbocharger provides the desired torque while increasing engine efficiency by delivering rich exhaust gas to the intake manifold. Process 1100 continues to 1116.

If it is determined at 1112 that the engine conditions are not at low to intermediate load, routine 1100 proceeds to 1116 to determine whether the engine is idling or whether the engine is operating again at a very low load, even though the exhaust catalyst is at or above light-off temperature. Thus, the engine may be operated at very low loads while the emission control devices are sufficiently warmed up. If so, routine 1100 moves to 1118, transitioning operation of the cylinders of the engine to the first mode. Specifically, by adjusting the second exhaust valves of all cylinders to open the full duration of the respective exhaust strokes within a common engine cycle, all exhaust gases from the cylinders may be delivered to the exhaust catalyst. The first exhaust valve and the CIV of all cylinders may be held closed for the entire duration of the exhaust stroke at the same time within a common engine cycle. Optionally, during a first initial duration of the respective exhaust stroke, the first exhaust valves of all cylinders may be opened to divert a portion of the bleed pulse to the exhaust turbine. Further, during the same respective exhaust stroke, the second exhaust valves may be opened during a remaining portion of the respective exhaust stroke to deliver residual exhaust gas to the emission control device. Routine 1100 then proceeds to 1120 to adjust the exhaust valves and CIV of each cylinder to maintain desired (e.g., existing) engine operation, and then ends.

Thus, an example system may include an engine having an intake manifold and an exhaust manifold, an exhaust manifold fluidly coupled to an emission control device, an intake throttle coupled in an intake passage upstream of the intake manifold, a turbocharger driven by the exhaust turbine including an intake compressor, a plurality of cylinders each including a first exhaust valve, a second exhaust valve, and a third exhaust valve (also referred to as a compressor inlet valve), a first exhaust passage fluidly coupling the first exhaust valve directly to only a turbine of the turbocharger, a second exhaust passage fluidly coupling the second exhaust valve directly to only the emission control device, and a third passage fluidly coupling the third exhaust valve directly to only an inlet of the intake compressor (e.g., line 164 of fig. 6), and a fourth passage fluidly coupling the third exhaust valve directly to only the intake passage (e.g., an aft compressor conduit 664 of FIG. 6) downstream of the intake compressor, downstream of the intake throttle, and upstream of the intake manifold, a first exhaust gas recirculation valve (e.g., valve 125 of FIG. 6) positioned in a third passage, a second exhaust gas recirculation valve (e.g., second ERV625 of FIG. 4) positioned in a fourth passage, and a cam profile conversion system coupled to each of the first, second, and third exhaust valves of each of the plurality of cylinders.

The system may also include a controller having computer readable instructions stored in non-transitory memory for operating the plurality of cylinders in a first mode with the second exhaust valve open and each of the first and third exhaust valves closed to recirculate all exhaust gas to an emission control device, operating the plurality of cylinders in a second mode, wherein a subset of the plurality of cylinders (e.g., cylinder 20 of engine 10 in fig. 6 and 7) is operated with the third exhaust valve open and each of the first and second exhaust valves closed to recirculate all exhaust gas to an intake manifold downstream of an intake compressor, and operating remaining cylinders of the plurality of cylinders (e.g.,

cylinders

22, 24, and 26 of engine 10) with each of the first and second exhaust valves open and the third exhaust valve closed to deliver a portion of the exhaust gas to an exhaust turbine and emission control device, and operating the plurality of cylinders in a third mode in which each of the first, second, and third exhaust valves are open to divert a portion of the exhaust gas to each of an inlet of the intake compressor, the emission control device, and the exhaust turbine. The controller may include further instructions for closing each of the first and second exhaust gas recirculation valves when the plurality of cylinders are operating in the first mode, closing the first exhaust gas recirculation valve when the plurality of cylinders are operating in the second mode, and opening the second exhaust gas recirculation valve; and opening the first exhaust gas recirculation valve and closing the second exhaust gas recirculation valve when the plurality of cylinders are operating in the third mode.

Referring now to FIG. 12, a table 1200 is depicted depicting example valve states and/or valve timings for each of the exhaust valves and the CIV of the plurality of cylinders, as well as the ERV based on the operating mode of the plurality of cylinders of engine 10 of FIGS. 6 and 7. Table 1200 also indicates target locations for portions of exhaust gas during different modes of cylinder operation. As previously mentioned, table 1200 will be described with reference to engine 10 of fig. 6 and 7. Further, the states of the exhaust valves, ERV, and CIV for a common engine cycle in each of the different modes of operation are shown.

Note that cylinder 20 is listed separately from

cylinders

22, 24, and 26. Thus, cylinder 20 may be a subset of the plurality of

cylinders

20, 22, 24, and 26 of engine 10. Further, the

cylinders

22, 24, and 26 may be the remaining cylinders of the plurality of cylinders. In alternative embodiments including engines with a greater number of cylinders (e.g., 6, 8, 10 cylinders), the subset of cylinders may include more than one cylinder.

During a first mode of operation (e.g., mode 1) that occurs during very low engine loads, the first exhaust valve (Exh _1) and CIV (Exh _3) of each cylinder are held closed through the entire exhaust stroke within the same common engine cycle. Specifically, during the first mode of operation, Exh _1 and Exh _3 of the

cylinders

20, 22, 24, 26 are turned off. During the same common engine cycle, the second exhaust valves (Exh _2) of all cylinders of engine 10 are opened for the entire duration of the exhaust stroke. To elaborate, Exh _2 for

cylinders

20, 22, 24, and 26 is opened toward the end of the power stroke (from the closed position) just prior to the BDC position of the corresponding piston, is held open as the piston rises to TDC of the subsequent exhaust stroke, and is closed just after reaching the TDC position of the exhaust stroke. Further, there is a small degree of positive overlap between the second exhaust valve and the intake valve on the following intake stroke to allow internal EGR. In an alternative embodiment, positive valve overlap may not occur.

The first mode of operation during very low engine loads may additionally or optionally include opening the first exhaust valve of each cylinder (from a closed position) just prior to the TDC position of the corresponding piston at the end of the power stroke (as shown in dashed curve 908 of fig. 9A). For example, the optional mode of operation may be employed during very low engine loads after the emission control device has reached a light-off temperature. The first exhaust valve may be held open until near halfway through the exhaust stroke (e.g., 90CAD after BDC in the exhaust stroke), and may be closed near the midpoint of the exhaust stroke. Thus, a first portion of the exhaust pulse may be delivered to the exhaust turbine. Further, the second exhaust valve of each cylinder may be opened (from closed) to deliver the remaining exhaust gas to an emission control device. In one example, the second exhaust valve may be held open for the entire duration of the exhaust stroke (e.g., from BDC to TDC of the exhaust stroke). Herein, the second exhaust valve may overlap the first exhaust valve from BDC to a midpoint of the exhaust stroke. In another example (as shown in dashed curve 909 of FIG. 9A), the second exhaust valve may be opened just before the first exhaust valve is closed. Specifically, the second exhaust valve may be opened just prior to the midpoint of the exhaust stroke, and it may be closed just after the end of the exhaust stroke (e.g., just after the TDC position of the corresponding piston at the end of the exhaust stroke).

During the first mode of operation, each of the first ERV (or forward compressor ERV) and the second ERV (or aft compressor ERV) is held closed. Further, during the first mode of operation, all exhaust gases from all cylinders of the engine are directed to the emission control device. In some embodiments, the first mode of operation may additionally include delivering a small portion of the bleed pulse of exhaust gas to a turbine of the turbocharger. Herein, during an initial portion of the exhaust stroke, a first exhaust valve of each cylinder (e.g.,

cylinders

20, 22, 24, and 26) may be opened while a second exhaust valve is opened for the remaining duration of the same exhaust stroke.

During a second mode of operation (e.g., mode 2) that occurs when the engine is operating at low to intermediate loads, Exh _3 in the

cylinders

22, 24, and 26 is held closed for the entire duration of the respective exhaust stroke within a given engine cycle. However, just prior to the BDC position of the respective piston, the first exhaust valve in the

cylinders

22, 24, and 26 is opened (from closing) toward the end of the power stroke in a given engine cycle, and is held open as the piston rises to TDC of the subsequent exhaust stroke. Finally, the first exhaust valve is closed (from open) just prior to the TDC position (e.g., near 45CAD before TDC) of the respective piston in the exhaust stroke within the same given engine cycle. Meanwhile, the second exhaust valves (Exh _2) of the

cylinders

22, 24, and 26 are opened from closed in the same given cycle when the corresponding first exhaust valve in the respective cylinder is at its maximum lift near the midpoint of the respective exhaust stroke. Further, just after TDC of the respective exhaust strokes, the second exhaust valves of the

cylinders

22, 24, and 26 are closed for the same given engine cycle.

During the second mode of operation, the cylinder 20 is operated differently relative to the operation of the remaining

cylinders

22, 24, and 26. The first and second exhaust valves of cylinder 20 are held closed for the entire duration of the exhaust stroke in the same given engine cycle. Further, the third exhaust valves of cylinders 20 are held open for the entire duration of the respective exhaust strokes in the same given engine cycle. Specifically, just prior to the BDC position of the corresponding piston, the CIV of cylinder 20 is opened (from closing) toward the end of the power stroke, remains open as the piston rises to TDC of the subsequent exhaust stroke, and is closed just after reaching the TDC position of the exhaust stroke. Further, there may be a positive overlap between the CIV and intake valves of the cylinder 20 in the latter intake stroke. Alternatively, positive valve overlap may not occur.

Further, the second ERV (or the aft compressor ERV) may be open during the second mode of operation for recirculating the entire exhaust content from the cylinders 20 (e.g., a subset of the cylinders) to the aft compressor location via the aft compressor conduit 664. Further, the first ERV (or the forward compressor ERV) may be kept closed. During the second mode of operation, all exhaust gas from the cylinders 20 may be recirculated to a location downstream of the compressor, which is intermediate upstream of the intake manifold and downstream of the intake throttle. Thus, during the second mode, exhaust gas from the cylinders 20 may not be supplied to the turbine, the forward compressor position (when the first ERV is closed), or the exhaust catalyst. During the same given engine cycle, exhaust gas from the remaining cylinders (e.g., cylinders 22, 24, and 26) is directed to each of the turbine and the emission control device. Specifically, at higher pressures, a first portion of the exhaust gas including the bleed pulse may be directed to the turbine, while a second portion of the exhaust gas including the purge portion of the exhaust gas may be directed to the emission control device. Thus, exhaust gas from the remaining cylinders may not be supplied to the compressor inlet or the post compressor position when the third exhaust valves of the remaining cylinders are held closed for the entire duration of the exhaust stroke during the second mode of operation.

During a third mode of operation (e.g., mode 3) that occurs during high engine loads, each of the first exhaust valve, the second exhaust valve, and the CIV of each cylinder may be opened for a particular duration and portion of the respective exhaust stroke within a different common engine cycle. The first exhaust valve in all cylinders of engine 10 is opened (from closing) toward the end of the exhaust stroke just prior to the BDC position of the respective piston, and is held open as the piston rises to TDC of the subsequent exhaust stroke. Finally, the first exhaust valve is closed (from open) just prior to the TDC position of the respective piston (e.g., near 45CAD before TDC) in the exhaust stroke in a different common engine cycle.

The second exhaust valves of all cylinders of engine 10 are opened from a closed state when the corresponding first exhaust valves in the respective cylinders are at their maximum lift near a midpoint of the respective exhaust strokes in a different common engine cycle. Further, the second exhaust valves of all of the cylinders are closed within a different, common engine cycle before TDC of the respective exhaust strokes (e.g., within 20 degrees of TDC). Finally, just prior to the respective piston TDC position in the exhaust stroke, the CIV's for all cylinders may be opened (from closed) and may be held open until about 30 degrees after TDC in the subsequent intake stroke. Specifically, the CIV may be closed just after the TDC position of the respective piston, thereby allowing positive valve overlap between the respective CIV and the intake valve within the same cylinder. When the engine is operating under heavy load, the intake manifold 27 may be at a higher pressure than the exhaust manifold 59. Herein, fresh charge-air blow-by may be forced into the cylinder and then through the open CIV. It should be appreciated that at the end of the exhaust stroke, internal EGR may not occur due to the reverse flow of low pressure exhaust gas into the intake manifold (when the intake manifold is at a lower pressure than the exhaust gas pressure in the exhaust manifold, as previously described).

Further, the first ERV may be opened during a third mode of operation to allow exhaust gas residuals to flow toward the compressor inlet along with fresh leakage air from all cylinders. Thus, during the third mode of operation, the first bleed-off portion of the exhaust gas is delivered to the turbine, the second, purge portion of the exhaust gas is supplied to the exhaust catalyst, and the combination of blow-by air and low pressure EGR is recirculated to the forward compressor location via the conduit 164 and the first ERV 125.

It should be appreciated that during any mode of operation, exhaust gas from the

cylinders

22, 24, and 26 may not be supplied to the aft compressor position. Thus, during the second mode of operation, only exhaust gas from a subset of cylinders (e.g., cylinder 20) is supplied to the post-compressor position.

In this manner, an example method for an engine may include directing exhaust gas from a first cylinder group (e.g., cylinder 20 of engine 10) to one or more of a forward compressor position, an aft compressor position, and an exhaust turbine, and directing exhaust gas from a second cylinder group (e.g.,

cylinders

22, 24, and 26 of engine 10) to one or more of a forward compressor position and an exhaust turbine. The first and second cylinder groups may be mutually exclusive and include different cylinders. For example, referring to FIG. 6, a first cylinder group of engine 10 may include cylinder 20, and a second cylinder group may include

cylinders

22, 24, and 26. Thus, each cylinder group may have a different and separate cylinder, where the cylinders included in the first cylinder group are not part of the second cylinder group. Thus, exhaust gas from the first cylinder bank is directed to the rear compressor position during intermediate engine load conditions. The method further includes not directing exhaust gas from the first cylinder group to the forward compressor position or the exhaust turbine during the intermediate engine load condition. During medium loads, exhaust gas from the second cylinder bank may be directed to the exhaust turbine and not to the forward compressor position. Herein, the aft compressor position may include a position downstream of the intake throttle and upstream of the intake manifold.

It should be appreciated that exhaust gas from the first cylinder bank may be directed to each of the forward compressor location and the exhaust gas turbine during high engine load conditions, and at the same time in the common engine cycle, exhaust gas from the second cylinder bank is directed to each of the forward compressor location and the exhaust gas turbine during high engine load conditions. Directing exhaust gas to the forward compressor position may include directing a combination of blowby intake air and residual exhaust gas upstream of the compressor toward an end of an exhaust stroke of each of the first and second cylinder groups. Further, directing the combination of blow-by intake air and residual exhaust gas toward an end of an exhaust stroke in each of the first and second cylinder groups may also include providing a positive valve overlap between at least one intake valve and one corresponding exhaust valve of each cylinder in each of the first and second cylinder groups. The method may also include not directing exhaust gas from the first cylinder group or the second cylinder group to the rear compressor position during high engine load conditions. Thus, directing exhaust gases may include selectively opening one or more exhaust valves of each of the first and second cylinder groups, and wherein selectively opening includes actuating a cam profile shifting device including a cam lobe coupled to each of the one or more exhaust valves to vary a timing and duration of opening of each of the one or more exhaust valves.

In this way, an engine with a separate exhaust manifold may be operated with improved efficiency and reduced knock. By modifying exhaust valve operation based on engine conditions to direct exhaust to different locations, a greater amount of EGR may be supplied to the engine when the engine has a lower torque demand. When the engine is operating at higher torque demand, blow-by air is used along with low pressure EGR to reduce combustion temperatures and thereby mitigate knock. Overall, engine performance may be improved.

While the above example may include two exhaust valves and a third compressor inlet valve per cylinder to exhaust gas from the cylinders, another representation may include a system with exactly one exhaust valve and one Compressor Inlet Valve (CIV) per cylinder, at least for some and possibly all cylinders. The CIV may be referred to as "exhaust second valve" in this representation. The configuration may use the various methods and components described herein, with the exhaust valve coupled to the inlet of the turbine via a first passage, and the CIV coupled to the compressor inlet via a second passage, and the CIV coupled to the intake passage at an aft compressor location via a third passage.

Referring to FIG. 1, and as one example, cylinder 20 may include a first exhaust valve 122 connected to an inlet of turbine 92 of turbocharger 190 via manifold 55 and line 160, and a compressor inlet valve 112 connected to an inlet of compressor 94 via manifold 59 and line 164. Further, the compressor inlet valve 112 may also be fluidly coupled to the intake passage 28 via an aft compressor conduit 664 and a second ERV625, the intake passage 28 being downstream of the intake throttle, upstream of the intake manifold, and downstream of the compressor 94. Further, the cylinder 20 may not include the exhaust valve 132. In some examples, other cylinders of engine 10 may also include two exhaust valves: a first exhaust valve and a compressor inlet valve.

Cylinder operation during the previously described modes of operation may be similar. For example, during a first mode of cylinder operation, a first exhaust valve of each cylinder of engine 10 may be opened throughout an exhaust stroke to deliver full combustion content (e.g., all exhaust gases) to an exhaust catalyst. During the second mode of operation, the CIV 112 of the cylinder 20 may be held open for the entire duration of the exhaust stroke in the cylinder 20, thereby diverting all exhaust from the cylinder to the aft compressor position via the aft compressor conduit 664 and the second ERV 625. Further, the first exhaust valve of the cylinder 20 may be kept closed. Meanwhile, the first exhaust valves of the remaining cylinders (e.g., cylinders 22, 24, and 26) may be opened through the entire duration of the respective exhaust strokes, delivering all of the combustion contents of these remaining cylinders to the exhaust turbine, and immediately thereafter to the exhaust catalyst, within the same engine cycle. Further, the CIVs of the remaining cylinders may be held fully closed throughout the corresponding exhaust strokes of the same engine cycle. During the third mode of operation, all of the exhaust gas may be expelled from the cylinder 20 via the exhaust valve 122 and the compressor inlet valve 112, with a larger portion of the exhaust gas exiting through the exhaust valve 122 and a smaller portion of the exhaust gas exiting through the compressor inlet valve 112. Exhaust gas exiting the cylinders 20 via the compressor inlet valve 112 may be combined with fresh blow-by air from the intake manifold 27 and may be delivered to the forward compressor position via the line 164 and the first ERV 125. During the third mode, other cylinders of the engine may also be operated in the same manner.

Note that the example control and estimation routines included herein can be used with various engine and/or vehicle system configurations. The control methods and programs disclosed herein may be stored as executable instructions in non-transitory memory and executed by a control system, including a controller, in combination with various sensors, actuators, and other engine hardware. The specific routines described herein may represent any number of processing strategies such as one or more of event-driven, interrupt-driven, multi-tasking, multi-threading, and the like. As such, various acts, operations, and/or functions illustrated may be performed in the sequence illustrated, in parallel, or in some cases omitted. Thus, the order of processing is not necessarily required to achieve the features and advantages of the example embodiments described herein, but is provided for ease of illustration and description. One or more of the illustrated acts, operations, and/or functions may be repeatedly performed depending on the particular strategy being used. Further, the described acts, operations, and/or functions may be represented graphically in code programmed into the non-transitory memory of the computer readable storage medium in an engine control system, where the acts are performed by executing instructions in a system that includes various engine hardware components in combination with an electronic controller.

It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. For example, the above techniques may be applied to V-6, I-4, I-6, V-12, opposed 4, and other engine types. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an" element or "a first" element or the equivalent thereof. It is to be understood that such claims are intended to cover combinations of one or more of such elements, neither requiring nor excluding two or more of such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

Claims

1. A method for an engine, comprising:

directing exhaust gas from the first cylinder group to a forward compressor position during a first condition;

directing exhaust gas from the second cylinder group to an exhaust turbine; and is

During a second condition, exhaust gas from the first cylinder group is directed to a rear compressor position.

2. The method of claim 1, wherein the first and second cylinder groups are mutually exclusive and comprise different cylinders.

3. The method of claim 1, wherein the second condition comprises a medium engine load condition.

4. The method of claim 3, further comprising not directing exhaust gas from the first cylinder group to the forward compressor location or the exhaust gas turbine.

5. The method of claim 4, wherein exhaust gas from the second cylinder group is directed to the exhaust turbine and not directed to the forward compressor position.

6. The method of claim 3, wherein the aft compressor position comprises a position downstream of an intake throttle and upstream of an intake manifold.

7. The method of claim 1, wherein the first condition comprises a high engine load condition.

8. The method of claim 7, wherein directing exhaust gas to the forward compressor position comprises directing a combination of blowby intake air and residual exhaust gas toward an end of an exhaust stroke in each of the first and second cylinder groups.

9. The method of claim 8, wherein directing the combination of blow-by intake air and residual exhaust gas toward the end of the exhaust stroke in each of the first and second cylinder groups comprises providing positive valve overlap between at least one intake valve and one corresponding exhaust valve of each cylinder in each of the first and second cylinder groups.

10. The method of claim 7, further comprising not directing exhaust gas from the first cylinder group or the second cylinder group to the post-compressor position.

11. The method of claim 1, wherein directing exhaust gases comprises selectively opening one or more exhaust valves of each of the first and second cylinder groups, and wherein selectively opening comprises actuating a cam profile shifting device comprising a cam lobe coupled to each of the one or more exhaust valves to vary a timing and duration of opening of each of the one or more exhaust valves.

12. A method for an engine, comprising:

during a first condition, recirculating a combination of residual exhaust gas and blow-by air from a plurality of cylinders of the engine upstream of a compressor in a first engine cycle; and is

During a second condition, in a second engine cycle, all exhaust gas from only a subset of the plurality of cylinders is recirculated downstream of the compressor and exhaust gas from the remaining cylinders is delivered to an exhaust turbine.

13. The method of claim 12, wherein the first condition comprises a high engine load condition and the second condition comprises a medium engine load condition.

14. The method of claim 12, further comprising, during the first condition, delivering a first bleed portion of exhaust gas to an exhaust turbine and delivering a second purge portion of exhaust gas from the plurality of cylinders to an emission control device.

15. The method of claim 14, wherein the first bleed portion of exhaust gas is delivered to the exhaust turbine via a first exhaust valve of each of the plurality of cylinders, and wherein the second purge portion of exhaust gas is delivered to the emission control device via a second exhaust valve of each of the plurality of cylinders.

16. The method of claim 15, wherein the combination of residual exhaust gas and blow-by air is delivered to a location upstream of the compressor via a third exhaust valve of each of the plurality of cylinders.

17. The method of claim 16, further comprising, during the second condition, delivering a first bleed portion of exhaust gas to the exhaust turbine and a second purge portion of exhaust gas from the remaining cylinders to an emission control device.

18. A system for an engine, comprising:

an engine having an intake manifold and an exhaust manifold, the exhaust manifold fluidly coupled to an emission control device;

an intake throttle positioned in an intake passage coupled upstream of the intake manifold;

a turbocharger including an intake air compressor driven by an exhaust gas turbine;

a plurality of cylinders, each of the plurality of cylinders including a first exhaust valve, a second exhaust valve, and a third exhaust valve;

a first exhaust passage fluidly coupling the first exhaust valve directly to only a turbine of the turbocharger;

a second exhaust passage fluidly coupling the second exhaust valve directly to an emission-only control device;

a third passage fluidly coupling the third exhaust valve directly to an inlet of only the intake compressor;

a fourth passage fluidly coupling the third exhaust valve directly to the intake passage downstream of the intake compressor, downstream of the intake throttle, and upstream of the intake manifold;

a first exhaust gas recirculation valve positioned within the third passageway;

a second exhaust gas recirculation valve positioned within the fourth passageway; and

a cam profile shifting system coupled to each of the first, second, and third exhaust valves of each of the plurality of cylinders.

19. The system for an engine of claim 18, further comprising a controller having computer readable instructions stored in non-transitory memory for:

operating the plurality of cylinders in a first mode in which the second exhaust valve is open and each of the first and third exhaust valves is closed to recirculate all exhaust gas to the emission control device;

operating the plurality of cylinders in a second mode, wherein a subset of the plurality of cylinders are operated with the third exhaust valve open and each of the first and second exhaust valves closed to recirculate all exhaust gas to the intake manifold downstream of the intake compressor, and remaining cylinders of the plurality of cylinders are operated with each of the first and second exhaust valves open and the third exhaust valve closed to deliver a portion of exhaust gas to the exhaust turbine and the emission control device; and

operating the plurality of cylinders in a third mode in which each of the first, second, and third exhaust valves are open to divert a portion of exhaust gas to each of the inlet of the intake compressor, the emission control device, and the exhaust turbine.

20. The system for an engine of claim 19, wherein the controller includes further instructions for:

closing each of the first and second exhaust gas recirculation valves when the plurality of cylinders are operating in the first mode;

closing the first exhaust gas recirculation valve and opening the second exhaust gas recirculation valve when the plurality of cylinders are operating in the second mode; and

opening the first exhaust gas recirculation valve and closing the second exhaust gas recirculation valve when the plurality of cylinders are operating in the third mode.