JP6264746B2 - Control device and control method for internal combustion engine - Google Patents

Description

  The present invention relates to a control device and a control method for an internal combustion engine that use both a port injection fuel injection valve that injects fuel into an intake port and an in-cylinder injection fuel injection valve that injects fuel into a combustion chamber.

  A port injection fuel injection valve that injects fuel into the intake port and an in-cylinder injection fuel injection valve that directly injects fuel into the combustion chamber are used in combination, and the two are switched appropriately according to engine operating conditions. An internal combustion engine provided with a fuel injection device is described in Patent Document 1. In Patent Document 1, in the operation region where fresh air (air mixture) is blown from the intake passage to the exhaust passage during the valve overlap period in which the intake valve and the exhaust valve are simultaneously opened, the blow-off of fuel is avoided. On the other hand, if it is determined that a blow-through has occurred, port injection is prohibited, and in-cylinder injection is performed after the exhaust valve is closed.

JP 2005-133632 A

  As the share ratio of in-cylinder injection increases, the risk of deterioration of the engine operating state and environmental conditions increases due to the in-cylinder injection. Specifically, when the ratio of in-cylinder injection to port injection increases, the degree of risk that the fuel droplets adhering to the cylinder wall surface mix with the oil and the oil is diluted increases. Exhaust particulates contained in the exhaust due to droplets interfering with oil existing near the cylinder wall surface, increasing the risk of abnormal combustion before the ignition timing, so-called super knock, or decreasing the homogenization of the mixture The degree of risk that emissions will increase.

Therefore, if the port injection is simply prohibited in the operation region where the blow-through occurs as in the technique described in Patent Document 1, the original merit of using the in-cylinder injection and the port injection cannot be obtained, and the in-cylinder injection is not performed. There exists a problem that the said risk level resulting from becomes high.

Therefore, in the present invention, a port injection fuel injection valve that injects fuel into the intake port and an in-cylinder injection fuel injection valve that injects fuel into the combustion chamber are used in combination, and each of the port injection and the in-cylinder injection is shared. In the operating range where fresh air blows out into the exhaust passage during the valve overlap period when the intake valve and exhaust valve open simultaneously, from the completion timing of the blow-through to the closing timing of the intake valve by performing limited to the period port injection, to reduce the share of the cylinder injection Rutotomoni, as the risk potential of the engine operating condition or environmental condition by in-cylinder injector is deteriorated becomes the predetermined value or less The ratio of port injection is controlled according to the degree of risk .

  In other words, even in the operating region where blow-through occurs, by making it possible to set port injection only during the period from the completion timing of blow-through to the closing timing of the intake valve, the fuel injected into the intake port is fresh air. At the same time, while suppressing and avoiding blow-through to the exhaust passage, the share ratio of in-cylinder injection is suppressed from becoming excessively high (100%), and the engine operating state and environmental conditions deteriorate due to in-cylinder injection. It is possible to suppress the risk level from becoming excessively high.

  According to the present invention, even in an operation region in which fresh air blow-through occurs during the valve overlap period, while suppressing blow-through of fuel, the share ratio of in-cylinder injection is suppressed, and engine operation resulting from in-cylinder injection is performed. It is possible to suppress an excessive increase in the risk level of deterioration of the state (oil dilution amount / abnormal combustion) and environmental conditions (exhaust amount of exhaust particulates).

BRIEF DESCRIPTION OF THE DRAWINGS Structure explanatory drawing which shows the system structure of the control apparatus which concerns on one Example of this invention. The flowchart which shows the flow of the setting of the share rate of cylinder injection and port injection of the said Example, and injection timing. Explanatory drawing which shows the relationship between the share rate of in-cylinder injection (GDI), and a risk degree. The timing chart which shows the share rate and the injection timing of cylinder injection and port injection in the driving | running | working area | region which produces a fresh air blow-off in a valve timing mechanism.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a system configuration of an automotive internal combustion engine 1 to which an embodiment of the present invention is applied. This internal combustion engine 1 is a spark ignition internal combustion engine with a turbocharger of a 4-stroke cycle equipped with a variable compression ratio mechanism 2 using, for example, a multi-link type piston crank mechanism. The intake valve 4 and a pair of exhaust valves 5 are disposed, and a spark plug 6 is disposed in a central portion surrounded by the intake valves 4 and the exhaust valves 5.

  A cylinder injection fuel injection valve 8 that directly injects fuel into the combustion chamber 3 is disposed below the intake port 7 that is opened and closed by the intake valve 4. The intake port 7 is provided with a port injection fuel injection valve 41 that injects fuel into the intake port 7. These in-cylinder injection fuel injection valve 8 and port injection fuel injection valve 41 are both electromagnetic or piezoelectric injection valves that are opened when a drive pulse signal is applied. An amount of fuel that is substantially proportional to the pulse width is injected.

  An electronically controlled throttle valve 19 whose opening is controlled by a control signal from the engine controller 9 is interposed upstream of the collector portion 18a of the intake passage 18 connected to the intake port 7. A turbocharger compressor 20 is disposed on the upstream side. An air flow meter 10 that detects the intake air amount is disposed upstream of the compressor 20.

  In addition, a catalyst device 13 made of a three-way catalyst is interposed in the exhaust passage 12 connected to the exhaust port 11, and an air-fuel ratio sensor 14 for detecting the air-fuel ratio is disposed upstream thereof.

  In addition to the air flow meter 10 and the air-fuel ratio sensor 14, the engine controller 9 includes a crank angle sensor 15 for detecting the engine speed, a water temperature sensor 16 for detecting the coolant temperature, and an accelerator pedal operated by the driver. Detection signals of sensors such as an accelerator opening sensor 17 that detects the amount of depression of the vehicle are input. Based on these detection signals, the engine controller 9 optimally controls the fuel injection amount and injection timing by the fuel injection valves 8 and 41, the ignition timing by the spark plug 6, the opening of the throttle valve 19, and the like.

  On the other hand, the variable compression ratio mechanism 2 uses a known multi-link type piston crank mechanism, and includes a lower link 22 rotatably supported by a crank pin 21 a of the crankshaft 21 and one end of the lower link 22. An upper link 25 for connecting the upper pin 23 of the part and the piston pin 24a of the piston 24, a control link 27 having one end connected to the control pin 26 at the other end of the lower link 22, and the other end of the control link 27 And a control shaft 28 that supports the shaft in a swingable manner. The crankshaft 21 and the control shaft 28 are rotatably supported in a crankcase below the cylinder block 29 via a bearing structure (not shown). The control shaft 28 has an eccentric shaft portion 28a whose position changes with the rotation of the control shaft 28. Specifically, the end portion of the control link 27 is rotatably fitted to the eccentric shaft portion 28a. Match. In the variable compression ratio mechanism 2 described above, the top dead center position of the piston 24 is displaced up and down with the rotation of the control shaft 28, so that the mechanical compression ratio changes.

  As a drive mechanism for variably controlling the compression ratio of the variable compression ratio mechanism 2, an electric motor 31 having a rotation center axis parallel to the crankshaft 21 is disposed below the cylinder block 29. A reduction gear 32 is connected so as to be arranged in series in the direction. As the speed reducer 32, for example, a wave gear mechanism having a large speed reduction ratio is used, and the speed reducer output shaft 32 a is positioned coaxially with the output shaft (not shown) of the electric motor 31. Accordingly, the speed reducer output shaft 32a and the control shaft 28 are positioned in parallel with each other, and the first arm 33 and the control shaft 28 fixed to the speed reducer output shaft 32a are connected to each other so that both of them rotate in conjunction with each other. The fixed second arm 34 is connected to each other by an intermediate link 35.

  That is, when the electric motor 31 rotates, the angle of the speed reducer output shaft 32a changes in a form greatly decelerated by the speed reducer 32. The rotation of the speed reducer output shaft 32a is transmitted from the first arm 33 to the second arm 34 via the intermediate link 35, and the control shaft 28 rotates. Thereby, as mentioned above, the mechanical compression ratio of the internal combustion engine 1 changes. In the illustrated example, the first arm 33 and the second arm 34 extend in the same direction. Therefore, for example, when the speed reducer output shaft 32a rotates in the clockwise direction, the control shaft 28 also rotates in the clockwise direction. Although it is related, the link mechanism can also be configured to rotate in the opposite direction.

  The target compression ratio of the variable compression ratio mechanism 2 is set in the engine controller 9 based on engine operating conditions (for example, required load and engine speed), and the electric motor 31 is driven so as to realize this target compression ratio. Be controlled.

  In the present invention, the variable compression ratio mechanism 2 is not essential, and may be a fixed compression ratio internal combustion engine.

  Further, an intake variable valve timing mechanism 51 capable of changing the valve timing of the intake valve 4 and an exhaust variable valve timing mechanism 53 capable of changing the valve timing of the exhaust valve 5 are provided. These valve timing mechanisms 51 and 53 can apply known configurations. For example, by changing the phases of the intake camshaft 50 and the exhaust camshaft 52 with respect to the crankshaft 21, the intake and exhaust valves are opened and closed. The valve timing can be changed continuously. These variable valve timing mechanisms 51 and 53 are also driven and controlled by the engine controller 9 based on the engine operating state.

  FIG. 2 is a flowchart showing the flow of control according to this embodiment, and this routine is repeatedly executed by the engine controller 9 every predetermined period (every predetermined time or every predetermined crank angle). In the following description, the in-cylinder injection by the in-cylinder injection fuel injection valve 8 is also referred to as “DGI”, and the port injection by the port injection fuel injection valve 41 is also referred to as “MPI”.

  In step S11, detection signals of sensors representing the engine operating state such as the air flow meter 10, the air-fuel ratio sensor 14, the crank angle sensor 15, the water temperature sensor 16, and the accelerator opening sensor 17 are read.

  In step S12, a sharing ratio between in-cylinder injection (DGI) and port injection (MPI) is set. Here, in this embodiment, the in-cylinder fuel injection valve 8 is mainly used for the purpose of improving the fuel efficiency, and the required fuel amount is large (in other words, the air amount per unit time is large). When the required fuel amount cannot be supplied only by the in-cylinder injection fuel injection valve 8 as in the load region, port injection (MPI) by the port injection fuel injection valve 41 is performed.

  More specifically, the degree of risk that the engine operating state or the environmental condition due to in-cylinder injection deteriorates is obtained, and the injection period of in-cylinder injection is set within a range in which this degree of risk is below a predetermined level. Then, the share ratio of the port injection is set so as to make up for the shortage with respect to the required fuel injection amount only by the in-cylinder injection.

The above “risk degree” is, for example, a risk degree of occurrence of abnormal combustion also called dilution amount of oil mixed in oil, emission amount of particulate matter contained in exhaust gas (exhaust particle number) PMPN, and super knock. is there. As shown in FIG. 3, the risk of oil dilution, PMPN, and super knock increases as the share of in-cylinder injection increases. Explaining the degree of individual risk, the risk of increased oil dilution due to fuel droplets adhering to the cylinder wall and mixing into the oil, especially when the engine is not warmed up, as the ratio of in-cylinder injection to port injection increases. The degree becomes higher. In addition, when the share ratio of in-cylinder injection increases, the fuel in the cylinder is not sufficiently homogenized and vaporized, especially when the engine is not warmed up, and the amount of unburned fuel increases, causing particulate matter contained in the exhaust. The risk of increased (PM) emissions increases. In this embodiment, the number of discharged particles PMPN is used as an index of the amount of particulate matter (PM) discharged. The super over knock, a specific abnormal combustion caused by in-cylinder injection, mutually mixed with the oil in the vicinity of the cylinder wall by the fuel spray scraped when not warmed up with fuel and ignited before the spark timing It is a phenomenon that causes abnormal combustion. Then, as shown in FIG. 3, the in-cylinder injection sharing ratio is set so that the risk levels of oil dilution, super knock and PMPN are less than or equal to a predetermined value sL.

  In the subsequent step S13, during the valve overlap period in which both the intake valve and the exhaust valve are opened simultaneously, for example, in a scavenging (scavenging) region in which the exhaust amount is increased and in-cylinder cooling is performed in the low rotation range, It is determined whether or not it is an operating region in which fresh air is blown from the passage to the exhaust passage. This determination can be obtained, for example, in a feedforward manner based on the target values of the variable valve timing mechanisms 51 and 53, or can be detected and estimated in a feedback manner from a detection signal of the crank angle sensor 15 or the like.

  When it is determined that the operation region is in which the blow-through occurs, the process proceeds to step S14 and step S15, and the completion timing of the blow-through and the closing timing of the intake valve are obtained. Since the blow-off completion timing is almost the exhaust valve closing timing, the exhaust valve closing timing is simply obtained from the target values of the variable valve timing mechanisms 51 and 53 set according to the engine operating state, It can be obtained in a feedforward manner from the closing timing of the exhaust valve. Alternatively, the completion timing of the blow-through may be detected or estimated in a feedback manner from the detection signal of the crank angle sensor 15 or the like. Alternatively, by combining these, detection of the completion timing of the blow-through detected and estimated in feedback from the basic value of the blow-through completion timing obtained in a feed-forward manner according to the engine operating state and the detection signal of the crank angle sensor 15, etc. You may make it obtain | require blow-through completion time together using a value (estimated value). In this case, since only the variation with respect to the basic value is corrected in a feedback manner, the calculation load is reduced as compared with the case where only the feedback method is used.

  As with the completion timing of the blow-by, the intake valve closing timing is also determined in a feedforward manner using the target value, or is set in a feedback manner based on the detected / estimated value, or a combination of both.

  In step S16, the injection timing of each of in-cylinder injection (GDI) and port injection (MPI) is set. Here, in the present embodiment, in the operation region where the blow-through occurs, the port injection is performed only during the period from the completion timing of the blow-through to the closing timing of the intake valve, so that the port is in the operation region where the blow-through occurs. It is possible to perform injection and to reduce the share ratio of in-cylinder injection. Thereby, while performing the port injection while suppressing the fuel blow-through while being in the operation region in which the blow-through occurs, the share ratio of the in-cylinder injection is reduced, and the oil dilution amount, PMPN, And it can suppress that the risk degree of a super knock becomes high too much.

  FIG. 4 is a timing chart in an operating state in which a blow-through occurs when the control of this embodiment is applied. As shown in the figure, in the valve overlap period in which the intake valve and the exhaust valve are simultaneously opened at time t1-t2, unburned fuel is discharged into the exhaust passage together with the fresh air because blowout of fresh air occurs. In order to prevent this, both in-cylinder injection (GDI) and port injection (MPI) are prohibited. Specifically, the GDI ejection possible period (C) and the port injection (MPI) ejection possible period (D) are set to a value “No” indicating prohibition.

  At the completion timing t2 of the fresh air blow-off, both in-cylinder injection (GDI) and port injection (MPI) are permitted, that is, the GDI ejectable period (C) and MPI ejectable period (D) flags are permitted. The value to represent is “possible”. Port injection (MPI) is permitted until the closing timing t3 of the intake valve. Therefore, the period from the completion timing t2 of the fresh air blow-out to the closing timing t3 of the intake valve is set as the MPI ejection possible period.

  For example, when the risk of oil dilution, PMPN, and super knock resulting from in-cylinder injection (GDI) is low, most of the required fuel injection amount is in-cylinder injection (GDI) as in Case 1 (E). Therefore, the port injection (MPI) share ratio is set so as to compensate for the shortage with respect to the required fuel injection amount only by the in-cylinder injection.

  On the other hand, when the risk of oil dilution, PMPN, and super knock caused by in-cylinder injection (GDI) is high, port injection (MPI) is possible as much as possible within the MPI jettable period as in Case 2 (F). By performing this, it is possible to suppress an increase in the risk of oil dilution, PMPN, and super knock.

  Case 3 (G) shows a case where the risk level is intermediate between Case 1 and Case 2. In this case, the risk level is limited to a predetermined level sL (see FIG. 3) or less as much as possible. The share of in-cylinder injection (GDI) is increased. The port injection (MPI) sharing ratio is set so that the remaining amount obtained by subtracting the in-cylinder injection amount from the required fuel injection amount is covered by the port injection (MPI).

  Next, characteristic structures and operational effects of the present embodiment will be listed below.

  [1] When setting the respective ratios of port injection and in-cylinder injection by the engine controller 9, an operation in which fresh air is blown into the exhaust passage during a valve overlap period in which the intake valve and the exhaust valve are simultaneously opened. In the region, in particular, when the entire amount of fuel cannot be covered only by in-cylinder injection, port injection is performed only during the MPI injection possible period from the blow-through completion timing to the intake valve closing timing. As a result, the port injection makes it possible to reduce the share ratio of in-cylinder injection and reduce oil dilution due to in-cylinder injection (GDI), PMPN, super knock, etc. An excessive increase in the risk level can be suppressed.

  [2] In setting the MPI injection possible period, the completion timing of the blow-through and the closing timing of the intake valve are, for example, simply set using a map adapted to the engine operating state such as the engine load and the cooling water temperature. It can be obtained in a feed-forward manner using a target value such as a valve timing mechanism.

  [3] Further, when setting the MPI injection possible period, the actual new air blow-out completion timing and intake valve closing timing are determined using the engine operating state such as valve timing, exhaust temperature, turbo rotation speed, etc. detected by various sensors. May be detected or estimated, and using this value, the fresh air blowout completion timing and the intake valve closing timing may be set in a feedback manner. In this case, the setting accuracy can be improved as compared with the case where the feed-forward setting is performed.

  [4] Furthermore, the above settings [2] and [3] may be used together as the setting of the MPI injection possible period. In other words, the value obtained in the feedforward of [2] may be used as a basic value, and this basic value may be corrected and increased / decreased in a feedback manner as in [3].

  [5] In setting the sharing ratio of both injection valves including the valve overlap period in which fresh air blow-through occurs, in-cylinder injection that is advantageous in terms of fuel consumption is performed as much as possible, and fuel injection amount (heat generation amount) The port injection (MPI) share ratio is set so as to compensate for the shortage of). Here, in the setting of the share ratio of in-cylinder injection, for example, the degree of risk of oil dilution, PMPN, super knock, etc. caused by in-cylinder injection from the spray of the in-cylinder injection valve, mainly from the particle size / angle and penetration. The ratio of in-cylinder injection and the injection period are set so as to be within a predetermined value (allowable value) or less. As a result, the intake port injection valve shares the amount of heat generated by the in-cylinder injection valve alone.

  [6] The risk level of oil dilution, PMPN, super knock, etc. due to in-cylinder injection is directly detected using a sensor or the like, or estimated from the engine operating state, and the risk level is below a predetermined value. As such, the share ratio of port injection may be controlled in a feedback manner according to the detected and estimated risk level. That is, when the risk level of a predetermined level is exceeded, the share ratio of port injection may be increased in a feedback manner.

  [7] When setting the sharing rate, the feed forward setting of [5] and the feedback setting of [6] may coexist.

  [8] In the case of the configuration including the variable compression ratio mechanism 2 that makes the mechanical compression ratio variable by changing the relative positional relationship between the piston 24 and the cylinder, the above-described in-cylinder injection is also performed by setting the compression ratio. Risk levels such as oil dilution, PMPN, and super knock change. Therefore, at the time of valve overlap that causes blow-through, the compression ratio and the share ratio of in-cylinder injection / port injection are controlled in a coordinated manner so that the risk of oil dilution in cylinder injection, PMPN, super knock, etc. is below a predetermined level. It is desirable to do.

  [9] Further, it is preferable to control the ignition timing to be retarded or advanced in accordance with the compression ratio and the sharing ratio so as not to cause a torque step due to the increase / decrease in the sharing ratio and the compression ratio described above. . The ignition timing at this time may be set in a feed-forward manner using a map set in advance, or may be controlled in a feedback manner according to the water temperature, intake air temperature, knock level, or the like.

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Variable compression ratio mechanism 6 ... Spark plug 8 ... Fuel injection valve for in-cylinder injection 9 ... Engine controller 14 ... Air fuel ratio sensor 20 ... Compressor 41 ... Fuel injection valve for port injection 51, 53 ... Variable valve timing mechanism

Claims (9)

In a control device for an internal combustion engine, comprising: a port injection fuel injection valve that injects fuel into an intake port; and a cylinder injection fuel injection valve that injects fuel into a combustion chamber.
Sharing rate setting means for setting each sharing rate of port injection and in-cylinder injection ;
Means for detecting or estimating the risk of deterioration of the engine operating state or environmental conditions due to the in-cylinder injection ,
In the operation region in which fresh air is blown into the exhaust passage during the valve overlap period in which the intake valve and the exhaust valve are simultaneously opened, the share ratio setting means is from the completion timing of the blow-through to the closing timing of the intake valve. by performing limited to port injection period of Rutotomoni reduce the share of the cylinder injection, as described above risk potential is equal to or less than a predetermined value, controls the distribution ratio of the port injection in accordance with the risk potential A control device for an internal combustion engine.   2. The control apparatus for an internal combustion engine according to claim 1, wherein the completion timing of the blow-by is determined according to an engine operating state including an engine load.   2. The control apparatus for an internal combustion engine according to claim 1, further comprising a blow-through completion time acquisition means for detecting or estimating the blow-through completion time.   The completion time of the blow-through is obtained based on a basic value obtained according to an engine operating state including an engine load and a value detected or estimated by the blow-through completion time acquisition means. Item 4. The control device for an internal combustion engine according to Item 3.   The above-mentioned share ratio setting means sets the injection period of the in-cylinder injection according to the degree of risk that the engine operating state or the environmental condition due to the in-cylinder is deteriorated, and the in-cylinder injection alone is insufficient for the required fuel injection amount. The control device for an internal combustion engine according to any one of claims 1 to 4, wherein a share ratio of port injection is set so as to compensate for the amount to be compensated. The degree of risk that the engine operating state or the environmental condition due to in-cylinder injection deteriorates includes at least one of a degree of risk of oil dilution, exhaust particulate emission, or abnormal combustion. The control device for an internal combustion engine according to claim 1 . In a control device for an internal combustion engine, comprising: a port injection fuel injection valve that injects fuel into an intake port; and a cylinder injection fuel injection valve that injects fuel into a combustion chamber.
Sharing rate setting means for setting each sharing rate of port injection and in-cylinder injection;
A variable compression ratio mechanism that makes the mechanical compression ratio variable by changing the relative positional relationship between the piston and the cylinder;
Means for detecting or estimating the risk of deterioration of the engine operating state or environmental conditions due to the in-cylinder injection,
In the operation region in which fresh air is blown into the exhaust passage during the valve overlap period in which the intake valve and the exhaust valve are simultaneously opened, the share ratio setting means is from the completion timing of the blow-through to the closing timing of the intake valve. By performing port injection only during this period, the ratio of in-cylinder injection is reduced, and the degree of risk that engine operating conditions or environmental conditions due to in-cylinder injection are deteriorated is less than or equal to a predetermined value. An internal combustion engine control apparatus that controls a compression ratio and a share ratio. 8. The control apparatus for an internal combustion engine according to claim 7 , further comprising ignition timing control means for controlling the ignition timing in accordance with the compression ratio and the sharing ratio set by the sharing ratio setting means. In a control method for an internal combustion engine, comprising: a port injection fuel injection valve that injects fuel into an intake port; and a cylinder injection fuel injection valve that injects fuel into a combustion chamber.
In an operating region where fresh air is blown into the exhaust passage during the overlap period when the intake valve and the exhaust valve open simultaneously, and when the required fuel injection amount cannot be in-cylinder injection. The port injection is performed only during the period from the completion timing of the blow-through to the closing timing of the intake valve, thereby reducing the share ratio of the in- cylinder injection and the engine operating state or the environmental condition by the in-cylinder injection. A control method for an internal combustion engine, wherein a share ratio of port injection is controlled in accordance with the risk level so that the risk level of deterioration of the fuel becomes less than a predetermined value .

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