JP6179441B2 - Engine control device - Google Patents

Description

  The present disclosure relates to an engine control device.

  In recent years, in an engine for a vehicle using a lean region in which the value of air-fuel ratio (A / F) exceeds 30 at low load, the value of A / F at which the amount of nitrogen oxide (NOx) generated increases during acceleration. In some cases, for example, the region λ ≦ 1 is used while avoiding the region of about 1 <λ <2, where λ is the excess air ratio. λ = 1 corresponds to A / F = 14.7 (theoretical air-fuel ratio).

  In such an engine, there is a concern that smoke (soot) increases because the amount of fresh air taken into the combustion chamber during the transition period after acceleration increases and the amount of fuel increases.

  In Patent Document 1 below, the maximum value of the fuel injection amount that does not cause exhaust smoke is set according to the amount of fresh air sucked into the engine and the engine speed, and the fuel injection amount is limited by this maximum value. Describes a diesel engine in which the fuel injection amount is set in a range in which smoke does not occur with respect to the actual intake air amount. As a result, the amount of fuel injected into the engine is set in a range in which smoke does not occur with respect to the actual intake air amount. Therefore, the smoke caused by exhaust gas recirculation (EGR) operation delay during transient operation such as acceleration, etc. Is prevented from occurring.

Japanese Patent Laid-Open No. 11-036962

  However, in the technique described in Patent Document 1, since the fuel injection amount is set in a range in which smoke does not occur during transient operation such as acceleration, predetermined fuel is not injected and engine torque is insufficient. As a result, there is a problem that the responsiveness of acceleration is lowered.

  The technology of the present disclosure has been made in view of the above points, and the purpose of the technology is to eliminate smoke and improve low emission performance even in a high load region such as during acceleration, and to accelerate performance. Is to improve.

In order to solve the above problems, the present invention increases the amount of fuel by a predetermined amount when accelerating the engine from a low load to a high load, and adds ozone (O ₃ ) before and during combustion of the fuel. It is characterized by that.

  Specifically, the present invention is directed to an engine control device and has taken the following solutions.

That is, the first invention includes an engine body and a controller configured to operate the engine body. The controller supplies fuel to the combustion chamber after the second half of the compression stroke in the engine body, and From the low load region where the excess air ratio λ is relatively larger than 2, the EGR rate (ratio of the amount of exhaust gas recirculation to the total gas amount in the cylinder) is relatively high, and the fresh air amount is relatively During acceleration to a high load region where the excess air ratio λ is less than 1.05, the fuel is increased to a predetermined amount in the acceleration transition period before the new air amount is reduced to the new air amount in the high load region. In addition , ozone is added so that fresh air is activated before and during combustion, and in a low load region where the excess air ratio λ is greater than 2, the mixture layer locally rich in the combustion chamber It burns after the second half of the compression stroke so that fresh air is located in the vicinity. And it supplies the fuel to the chamber.

  According to this, a local rich state is generated in the air-fuel mixture due to the non-uniformity of the air-fuel mixture density due to fuel injection after the latter half of the compression stroke, and smoke is generated. In the present disclosure, fresh air located in the vicinity of a locally rich state (fresh air in the lean region) is activated by ozone, and further, combustion is continued in the expansion stroke, thereby burning the generated smoke. Can be made. As a result, the amount of fuel can be increased, so that low emission performance and acceleration performance can be improved.

  According to a second aspect, in the first aspect, the predetermined amount of fuel in the acceleration transition period is an amount at which the excess air ratio λ is 1.

  According to this, since the excess air ratio λ is 1, high flammability and low emission performance are ensured by the three-way catalyst widely installed in any engine, and the acceleration performance can be reliably improved. it can. In the high load region, it becomes difficult to set the excess air ratio λ to 2.5 or more as the load on the engine body increases. That is, as the fuel injection amount increases, a large amount of air However, since the set EGR rate is high and the amount of air is insufficient, the excess air ratio λ is set to an intermediate air-fuel ratio that is 2.5 or less and greater than 1.05. It is preferable to set it to 1 instead of.

  According to a third invention, in the first invention, an exhaust gas recirculation (EGR) means is provided so as to recirculate a part of the exhaust gas in a cylinder provided in the engine body. In the high load region, the exhaust gas recirculation rate by the exhaust gas recirculation (EGR) means is set to be relatively high and higher than the exhaust gas recirculation (EGR) rate in the low load region.

  According to this, low temperature combustion (low temperature combustion of 1500 K or less) and slow combustion can be realized in the high load region, so that NOx generation due to the combustion temperature and the maximum pressure (Pmax) in the combustion chamber accompanying rapid combustion is achieved. Since the increase can be suppressed, low emission performance can be improved and noise during combustion can be suppressed. Further, by using EGR, it becomes easy to set the excess air ratio λ to 1. On the other hand, in the low load region, in the case of a compression ignition engine, ignition is suppressed by EGR. Further, stratified ignition can be realized, and NOx can be reduced.

  In a fourth aspect based on the third aspect, the exhaust gas recirculation means is provided with a cooling mechanism for cooling the exhaust gas.

  According to this, since the temperature of the gas introduced into the cylinder can be lowered and high-density air can be introduced, it is possible to suppress a decrease in intake charging efficiency, realize low-temperature combustion, and suppress the generation of NOx. it can.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the present invention, the fuel is supplied to the combustion chamber after the latter half of the compression stroke by retarded injection performed in the expansion stroke following the compression stroke.

  According to this, since a rapid change (dp / dt) in pressure during combustion can be suppressed, noise can be reduced.

  As described above, according to the engine control apparatus, smoke can be eliminated to improve low emission performance and acceleration performance even in a high load region such as during acceleration.

FIG. 1 is a schematic configuration diagram illustrating an engine according to an embodiment. FIG. 2 is a block diagram showing a configuration of engine control according to an embodiment. FIG. 3A is a map related to engine operation control according to an embodiment. FIG. 3B is a schematic graph showing the relationship between the engine load and the in-cylinder gas amount. FIG. 3C is a schematic graph showing a time chart of the fuel injection amount in the transition period from the low load region to the high load region of the engine control apparatus according to the embodiment. FIG. 4 is a schematic cross-sectional view showing how the ozone of the engine according to the embodiment is added. FIG. 5 is a schematic diagram illustrating an example of a control pattern in the engine control apparatus according to the embodiment.

  Hereinafter, an embodiment of an engine control device will be described with reference to the drawings. The following description is exemplary.

(Overall configuration of engine system)
1 and 2 show the configuration of the engine system 1 according to the present embodiment. The engine system 1 is a system mounted on a vehicle. The engine system 1 includes an engine main body (hereinafter simply referred to as “engine”) 10, various actuators associated with the engine 10, various sensors, and a PCM (Powertrain Control Module: PCM) that controls the actuators based on signals from the sensors. Controller) 100.

  Although not shown, the output shaft of the engine 10 is connected to drive wheels via a transmission. The vehicle is propelled by the output of the engine 10 being transmitted to the drive wheels. The engine 10 includes a cylinder block 12 and a cylinder head 13 placed thereon, and a plurality of cylinders 11 are formed inside the cylinder block 12 (only one is shown in FIG. 1). .) A water jacket (not shown) through which cooling water flows is formed inside the cylinder block 12 and the cylinder head 13.

  A piston 15 is slidably inserted in each cylinder 11, and the piston 15 defines a combustion chamber together with the cylinder 11 and the cylinder head 13. In the present embodiment, the combustion chamber is a so-called pent roof type, and the ceiling surface (the lower surface of the cylinder head 13) has a triangular roof shape composed of two inclined surfaces on the intake side and the exhaust side. The crown surface of the piston 15 has a convex shape corresponding to the ceiling surface, and a concave cavity 15a is formed at the center of the crown surface. The shape of the ceiling surface and the crown surface of the piston 15 may be any shape as long as a high geometric compression ratio described later is possible. For example, the ceiling surface and the crown surface of the piston 15 (cavity) Both of the portions excluding 15a may be formed of a surface perpendicular to the central axis of the cylinder 11, and the ceiling surface forms a triangular roof as described above, while the crown surface of the piston 15 (cavity 15a). May be formed of a surface perpendicular to the central axis of the cylinder 11.

  The cylinder head 13 is formed with two intake ports 18 for each cylinder 11 and each communicates with the combustion chamber by opening on the lower surface of the cylinder head 13 (the inclined surface on the intake side of the ceiling surface of the combustion chamber). Yes. Similarly, two exhaust ports 19 are formed in the cylinder head 13 for each cylinder 11, and each of the exhaust ports 19 opens to the lower surface of the cylinder head 13 (the inclined surface on the exhaust side of the ceiling surface of the combustion chamber). Communicate.

  The cylinder head 13 is provided with an intake valve 21 and an exhaust valve 22 so that the intake port 18 and the exhaust port 19 can be shut off (closed) from the combustion chamber, respectively. The intake valve 21 is driven by an intake valve drive mechanism, and the exhaust valve 22 is driven by an exhaust valve drive mechanism. The intake valve 21 and the exhaust valve 22 reciprocate at a predetermined timing to open and close the intake port 18 and the exhaust port 19, respectively, and exchange gas in the cylinder 11. Although not shown, the intake valve drive mechanism and the exhaust valve drive mechanism each have an intake camshaft and an exhaust camshaft that are drivingly connected to the crankshaft. These camshafts rotate in synchronization with the rotation of the crankshaft. In this example, the intake valve driving mechanism and the exhaust valve driving mechanism are a hydraulic or electric variable phase mechanism (Variable Valve Timing: VVT) capable of continuously changing the phase of the intake camshaft within a predetermined angle range. 23 at least (see FIG. 2). In addition, you may make it provide the lift variable mechanism which can change valve lift amount with VVT23. The lift variable mechanism may be a CVVL (Continuous Variable Valve Lift) capable of continuously changing the lift amount.

  The intake port 18 of each cylinder 11 communicates with the intake passage 30 via an intake manifold not explicitly shown in FIG. Similarly, the exhaust port 19 of each cylinder 11 communicates with the exhaust passage 40 via an exhaust manifold that is not clearly shown.

  In the intake passage 30, an air cleaner 31 and a throttle valve 33 that adjusts the amount of intake air to each cylinder 11 are sequentially arranged from upstream to downstream.

  In the exhaust passage 40, a direct catalyst 41 and an underfoot catalyst 42 are sequentially arranged from the upstream side to the downstream side as exhaust purification devices for purifying harmful components in the exhaust gas. Each of the direct catalyst 41 and the underfoot catalyst 42 includes a cylindrical case and a three-way catalyst disposed in a flow path in the case.

  The downstream portion of the throttle valve 33 in the intake passage 30 and the upstream portion of the direct catalyst 41 in the exhaust passage 40 are connected by a high pressure EGR passage 510 for returning a part of the exhaust gas to the intake passage 30. Yes. The high pressure EGR passage 510 is provided with a high pressure EGR valve 511 for adjusting the recirculation amount of the exhaust gas to the intake passage 30 and a water-cooled EGR cooler 512 for cooling the exhaust gas. A high pressure EGR system 51 (exhaust gas recirculation means) is configured including the high pressure EGR passage 510, the high pressure EGR valve 511, and the EGR cooler 512.

  In the engine 10, an injector 34 that directly injects fuel into the cylinder (combustion chamber) is disposed on the central axis of the cylinder 11 in the cylinder head 13. The injector 34 is attached and fixed to the cylinder head 13 with a known structure such as using a bracket. The tip of the injector 34 faces the center of the ceiling of the combustion chamber.

  In the present embodiment, the injector 34 is an externally open type injector. That is, although detailed illustration of the configuration is omitted, the cylinder 11 has an outer opening valve that opens and closes a nozzle port for injecting fuel, and the outer opening valve lifts to the cylinder 11 side to open the nozzle port. . At this time, the fuel is injected into the cylinder 11 from the nozzle opening in a cone shape (specifically, a hollow cone shape) centering on the central axis of the cylinder 11. As the lift amount of the outer valve increases, the opening of the nozzle opening increases, and the penetration of fuel spray injected from the nozzle opening into the cylinder 11 increases (becomes longer). Furthermore, the amount of fuel injected per unit time increases and the particle size of the fuel spray increases. The injector 34 is not limited to the external valve opening type, and may be a multi-hole injector.

  The fuel supply system 35 includes an electric circuit for driving the outer valve and a fuel supply system for supplying fuel to the injector 34. The PCM 100 outputs an injection signal having a voltage corresponding to the lift amount to an electric circuit at a predetermined timing, thereby operating the outer valve via the electric circuit, and supplying a desired amount of fuel into the cylinder 11. Let spray. When the injection signal is not output (when the voltage of the injection signal is 0), the nozzle opening is closed by the outer valve. In this way, the PCM 100 controls the operation of the outer valve to control the fuel injection from the nozzle opening of the injector 34 and the lift amount at the time of the fuel injection.

  The fuel supply system is provided with a high-pressure fuel pump and a common rail (not shown). The high-pressure fuel pump pumps fuel supplied from the fuel tank via the low-pressure fuel pump to the common rail. Is stored at a predetermined fuel pressure. Thereafter, when the injector 34 is operated, the fuel stored in the common rail is injected from the nozzle opening.

  Here, the fuel of the engine 10 is gasoline in the present embodiment, but may be gasoline containing bioethanol or the like, and any fuel as long as it is a fuel (liquid fuel) containing at least gasoline. Also good.

An ozone generator 36 is disposed in the combustion chamber of the engine 10. The ozone generator 36 is fixed to the cylinder head 13 by a known structure such as a screw. The tip of the ozone generator 36 faces the ceiling of the combustion chamber. The tip of the ozone generator 36 is located in the vicinity of the nozzle opening of the injector 34. The ozone generator 36 has one electrode (positive electrode) disposed in an insulated manner. The ozone generator 36 is driven by an ozone generation system 37. The ozone generation system 37 has an ozone generation circuit. The ozone generation system 37 receives a control signal from the PCM 100 and outputs a high-frequency high-frequency voltage to the ozone generator 36. When a high frequency voltage is applied, the ozone generator 36 generates ozone (O ₃ ) between the electrode and the cylinder block 12 or the cylinder head 13. The ozone concentration can be adjusted by changing the high-frequency voltage value or frequency applied to the ozone generator 36. The arrangement and configuration of the ozone generator 36 are not limited to the above configuration.

  The PCM 100 is a controller based on a well-known microcomputer, and includes a central processing unit (CPU) that executes a program, a memory that includes, for example, a RAM and a ROM and stores a program and data, and an electric signal input. And an input / output (I / O) bus for outputting.

  Connected to the PCM 100 are a vehicle speed sensor 71 that detects the vehicle speed, an accelerator opening sensor 72 that detects the accelerator opening, and an engine rotation speed sensor 73 that detects the rotation speed of the engine 10.

  An air flow sensor 74 that detects the flow rate (and temperature) of fresh air flowing through the intake passage 30 is disposed in the intake passage 30. The air flow sensor 74 outputs the detected flow rate and outside air temperature to the PCM 100.

  An intake pressure sensor 75 that detects the pressure of the air supplied to the combustion chamber is attached to the surge tank 38, and an exhaust pressure sensor 76 that detects the pressure of the exhaust is disposed in the exhaust passage 40. Each sensor 75 and 76 is connected to the PCM 100 and outputs the detected value to the PCM 100.

  The PCM 100 determines the operating state of the engine 10 based on the signals from the sensors described above, and sets the control parameters of the engine 10 corresponding thereto. The PCM 100 outputs a signal corresponding to each control parameter to the throttle valve 33, the fuel supply system 35, the VVT 23, the high pressure EGR valve 511, the ozone generation system 37, and the like.

  As a modification of the present embodiment, the engine body 10 is equipped with a turbocharger having a turbocharger in which a compressor is disposed in the intake passage 30 and a turbine coaxial with the compressor is disposed in the exhaust passage 40. It may be an engine. Further, the turbocharger may be a VGT (Variable Geometry Turbo) having a variable nozzle.

  In the case of an engine with a supercharger, a part of the exhaust gas is passed between the downstream portion of the air cleaner 31 in the intake passage 30 and the downstream portion of the direct catalyst 41 in the exhaust passage 40. A low pressure EGR system for refluxing to 30 may be provided.

(Engine structure)
Next, the configuration of the engine body 10 will be described in more detail. The geometric compression ratio ε of the engine 10 is set to 20 or more and 40 or less. The geometric compression ratio ε is particularly preferably 25 or more and 35 or less. Since the engine 10 is configured such that the compression ratio = expansion ratio, it is also an engine 10 having a relatively high expansion ratio as well as a high compression ratio. In addition, you may employ | adopt the structure (for example, Atkinson cycle and a mirror cycle) used as compression ratio <= expansion ratio. When the intake valve is closed late, the effective compression ratio of the engine 10 is set to 12 or more. Preferably, the effective compression ratio of the engine 10 is set to 18 or more.

  The combustion chamber is defined by the wall surface of the cylinder 11, the crown surface of the piston 15, the lower surface (ceiling surface) of the cylinder head 13, and the valve head surfaces of the intake valve 21 and the exhaust valve 22. Furthermore, in order to reduce cooling loss, the combustion chamber is thermally insulated by providing a heat insulating layer on each of these surfaces. A heat insulation layer may be provided in all of these section screens, and may be provided in a part of these section screens. Further, a heat insulating layer may be provided on the port wall surface in the vicinity of the opening on the ceiling surface side of the combustion chamber in the intake port 18 and the exhaust port 19, although it is not the wall surface that directly partitions the combustion chamber.

  Specifically, the PCM 100 has a compression stroke so that a gas layer containing fresh air is formed in the inner periphery of the cylinder 11 (combustion chamber) of the engine 10 and an air-fuel mixture layer is formed in the center. In the second half and thereafter, an injection signal is output to the electric circuit of the fuel supply system 35 in order to inject fuel into the cylinder 11 from the nozzle opening of the injector 34. That is, in the latter half of the compression stroke, the fuel is injected into the cylinder 11 by the injector 34, and the penetration of the fuel spray is such a size (length) that the fuel spray does not reach the inner periphery of the cylinder 11. Keep it down. As a result, stratification is realized in which an air-fuel mixture layer is formed at the center of the cylinder 11 and a gas layer containing fresh air is formed around the air-fuel mixture layer. This gas layer may be only fresh air, and may contain burned gas (EGR gas) in addition to fresh air. It should be noted that there is no problem even if a small amount of fuel is mixed in the gas layer, and the fuel layer may be leaner than the gas mixture layer so that the gas layer can serve as a heat insulating layer.

  If the fuel self-ignites with the gas layer and the mixture layer formed as described above, the gas layer between the mixture layer and the wall surface of the cylinder 11 causes the flame of the mixture layer to become the wall surface of the cylinder 11. The gas layer serves as a heat insulating layer without being in contact with the gas, and the release of heat from the wall surface of the cylinder 11 can be suppressed. As a result, the cooling loss can be greatly reduced.

  It should be noted that reducing the cooling loss only converts the reduced cooling loss into an exhaust loss and does not contribute much to the improvement in the illustrated thermal efficiency. However, in the engine 10, the higher expansion ratio is accompanied by the higher compression ratio. The combustion gas energy corresponding to the reduced cooling loss is efficiently converted into mechanical work. That is, the engine 10 can greatly improve the illustrated thermal efficiency by adopting a configuration that reduces both cooling loss and exhaust loss.

In the present embodiment, the engine 10 starts from a low load region where the fresh air amount is relatively large and the excess air ratio λ is greater than 2, and the fresh air amount is relatively small and the excess air ratio λ is 1.05. When accelerating to a high load region of less than, during the transition period of acceleration before the new air amount is reduced to the new air amount in the high load region, the fuel is increased to a predetermined amount, and before and during combustion Add ozone (O ₃ ).

  The above contents are schematically explained. As shown in the map relating to engine control shown in FIG. 3A and the relationship between the load and the in-cylinder gas amount shown in FIG. When accelerating from a low load region A where λ> 2 is relatively large to a high load region B where λ <1.05 is relatively small, the new air amount is new in the high load region B. In the acceleration transition period before the reduction to the air volume, the fuel is increased to a predetermined amount, for example, λ = 1, and ozone is added before and during combustion.

  In general, when accelerating from a low load region of λ> 2 to a high load region of λ ≦ 1, the mixture is locally rich due to non-uniformity in the mixture density due to fuel injection after the second half of the compression stroke. Arise.

  Therefore, in the present embodiment, the fresh air in the lean region located in the vicinity of the locally rich state is activated by ozone, and further, combustion is continued in the expansion stroke, thereby burning the generated smoke. be able to. As a result, as shown in FIG. 3C, the amount of fuel can be increased instead of being reduced (F / C), so that the amount of fuel reduced in smoke can be added to the increase in acceleration. . As a result, both low emission performance and acceleration performance can be achieved. Further, since λ = 1 is set in the high load region B, combustion stabilization can be obtained, so that low emission performance and acceleration performance can be reliably improved.

  The mechanism of reducing the smoke by adding ozone to the fuel injected into the cylinder 11 is that the combustion itself is activated by the low-temperature oxidation reaction induced by the added ozone, and the smoke is not easily generated. This is because the combustion conditions shift to a high temperature and high pressure field.

(Control of ozone addition)
First, in the in-cylinder discharge, streamer discharge is generated in the initial region until the applied voltage reaches a predetermined high voltage, and arc discharge is generated in the latter region where the voltage drop and the current increase rapidly occur. This is not possible with streamer discharges where little current flows. Therefore, by applying a high voltage with an extremely short pulse width that does not exceed the streamer discharge generation region, ozone can be stably generated without interposing a dielectric between the electrodes, and the ozone generation efficiency is improved. Can be achieved.

  In the engine 10 according to this embodiment, this ultrashort pulse discharge is applied. This makes it possible to stably generate streamer discharge without causing sparks or the like inside the cylinder 11 and to directly generate ozone from the intake air inside the cylinder 11.

  For example, FIG. 4 schematically shows a state in which the piston 15 has reached top dead center (TDC) during the compression stroke. In this state, the air-fuel mixture containing gasoline and intake air is highly compressed to a high temperature and high pressure. Therefore, the air-fuel mixture is self-ignited in the compression stroke and burns thereby (CI combustion).

  As described above, the ozone generator 36 is held by the cylinder head 13, and the tip of the ozone generator 36 projects into the combustion chamber from a portion adjacent to the injection port 34 a on the upper surface of the combustion chamber. A rod-like electrode 36b whose periphery is electrically insulated by an insulator 36a is disposed at the tip of the discharge plug. Thus, the electrode 36b protrudes into the combustion chamber in a state where it is electrically insulated from the cylinder head 13 and the cylinder block 12.

  Since the cylinder head 13 and the cylinder block 12 forming the cylinder 11 are grounded, when a short pulse high voltage is applied to the electrode 36b, the inner surface of the cylinder 11 (specifically, the inner surface of the combustion chamber). ) And the electrode 36b constitute a cathode and an anode, respectively, and discharge occurs between them.

  Furthermore, the engine 10 according to the present embodiment is set with a control pattern in which the injector 34 injects fuel during the compression stroke (compression stroke injection). When the compression stroke injection is performed, the ozone generation system 37 is operated in the compression stroke and the expansion stroke so that the CI combustion can be stably performed.

  In the engine 10, a control pattern for controlling the opening degree of the injection port 34 a of the injector 34 is set in the fuel supply system 35 so that the air-fuel mixture is unevenly distributed in the central portion of the combustion chamber during the compression stroke injection. May be. This suppresses adhesion of smoke or the like to the inner surface of the combustion chamber, and an air layer is formed between the air-fuel mixture and the inner surface of the combustion chamber. When an air layer is interposed between the air-fuel mixture and the inner surface of the combustion chamber, the air heat can prevent the combustion heat of the air-fuel mixture from being radiated to the cylinder block 12 or the like (air layer heat insulation). Therefore, energy efficiency can be improved.

  Further, in the high load region, the fuel injection amount at the time of the compression stroke injection is relatively large, so a control pattern for directly generating ozone in the combustion chamber of the compression stroke may be set. That is, since the engine 10 can generate ozone only by applying a voltage to the electrode 36b, ozone can be generated in the sealed combustion chamber of the compression stroke only by changing the control pattern.

  Specifically, the ozone generator 36 operates during fuel injection in the compression stroke. As a result, even in a sealed combustion chamber, intake air flows due to the momentum of the injected fuel, and ozone and intake air are interchanged in the discharge space. As a result, ozone can be generated while maintaining high ozone generation efficiency.

(Engine fuel injection control)
In the present embodiment, the engine 10 self-ignites and burns the fuel injected into the cylinder by the injector 34 in the entire operation region.

  In the present embodiment, at least one of pre-injection (pilot injection) preceding the main fuel injection and retard injection that delays the main injection timing from a predetermined timing may be performed as fuel injection control. Good.

  The pre-stage injection can be performed at a time of, for example, about 20 ° CA before the compression top dead center. The amount of fuel injected into the cylinder 11 by the pre-injection is relatively small enough to cause an oxidation reaction without reaching a hot flame reaction. The fuel injected by this pre-stage injection undergoes an oxidation reaction without reaching a hot flame reaction, that is, the temperature in the cylinder 11 at the compression top dead center is adjusted by a partial oxidation reaction. The compression end temperature increases as the injection amount of the upstream injection increases. Therefore, an amount of fuel such that the compression end temperature becomes a desired temperature is injected into the cylinder 11 by the pre-injection.

  In addition, the retarded injection can be executed as the main injection after the above-mentioned pre-injection and after the compression top dead center (TDC). Thereby, since the rapid change of the pressure at the time of combustion can be suppressed, noise can be reduced.

  In addition, the addition of ozone makes it possible not only to reduce smoke, but also to extend the retard period when retarding self-ignition combustion. The concentration of ozone to be added can be about 10 ppm to 30 ppm. Further, the ozone concentration may be set higher as the load of the engine 10 is higher.

(Engine EGR control)
Next, EGR control (intake charge amount control) of the engine 10 will be described.

  As shown in FIGS. 3A and 3B, first, in the low load region A in the lean region, the exhaust gas is recirculated at a relatively small ratio by the high pressure EGR system 51. EGR in a lean region with an A / F of about 50, for example, can perform stratified ignition, and can suppress ignition and reduce NOx.

  On the other hand, in the high load region B, the exhaust gas is recirculated at a higher rate than in the low load region A. EGR in the high load region B can reduce the fresh air amount to lower the combustion temperature and prevent lower layer combustion. Thereby, low emission performance can be improved and noise during combustion can be suppressed. As described above, since the high pressure EGR system 51 includes the EGR cooler 512, the exhaust gas recirculated through the high pressure EGR system 51 is cooled.

  In the present embodiment, a heat insulating structure is adopted for the combustion chamber and the intake port 18 and a heat insulating layer is formed by a gas layer in the cylinder 11 (combustion chamber). The present technology can also be applied to an engine that does not employ a heat insulating structure or an engine that does not form a heat insulating layer by a gas layer.

  In the present embodiment, the combustion system of the engine 10 is the compression ignition (CI) system, but the present technology is not limited to the CI system and can be applied to a spark ignition (SI) system.

1 Engine system 10 Engine (engine body)
11 Cylinder 12 Cylinder block 13 Cylinder head 15 Piston 15a Cavity 18 Intake port 19 Exhaust port 21 Intake valve 22 Exhaust valve 30 Intake passage 31 Air cleaner 33 Throttle valve 34 Injector (fuel injection valve)
36 ozone generator 36a insulator 36b electrode 38 surge tank 40 exhaust passage 41 direct catalyst 42 underfoot catalyst 51 high pressure EGR system (exhaust recirculation means)
74 Airflow sensor 75 Intake pressure sensor 76 Exhaust pressure sensor 100 PCM (controller)

Claims (5)

The engine body,
A controller configured to operate the engine body,
The controller is
Supplying fuel to the combustion chamber after the latter half of the compression stroke in the engine body,
When accelerating from a low load area where the excess air ratio λ with a relatively large amount of fresh air is greater than 2 to a high load area where the excess air ratio λ with a relatively small amount of fresh air is less than 1.05, In the acceleration transition period before the air volume is reduced to the fresh air volume in the high load region, the fuel is increased to a predetermined amount, and ozone is added so that the fresh air is activated before and during the combustion ,
In the low load region where the excess air ratio λ is greater than 2, the fresh air is placed in the combustion chamber after the latter half of the compression stroke so that fresh air is located around the air-fuel mixture layer that is locally rich in the combustion chamber. the engine control system to supply fuel. The engine control device according to claim 1,
The predetermined amount of fuel in the acceleration transition period is an engine control device in which the excess air ratio λ is 1. The engine control device according to claim 1,
Exhaust recirculation means provided so as to recirculate part of the exhaust gas in a cylinder provided in the engine body,
The controller is
An engine control device that sets an exhaust gas recirculation rate by the exhaust gas recirculation means relatively high in the high load region and that is set higher than an exhaust gas recirculation rate in the low load region. The engine control device according to claim 3,
An engine control device in which the exhaust gas recirculation means is provided with a cooling mechanism for cooling the exhaust gas. In the engine control device according to any one of claims 1 to 4,
The engine control apparatus, wherein the fuel supply to the combustion chamber after the latter half of the compression stroke is retarded injection performed in an expansion stroke following the compression stroke.

Images