JP3750293B2 - Engine control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an engine control device, and more particularly, to an engine control device including an NOx purification catalyst in an exhaust system.
[0002]
[Prior art]
  Conventionally, in an engine such as an automobile, a catalyst is provided in an exhaust system to purify exhaust gas after combustion. A three-way catalyst is often used as such an exhaust gas purifying catalyst. The three-way catalyst is excellent for three components that adversely affect the environment among harmful components contained in the exhaust gas, that is, carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx). Demonstrates purification properties.
[0003]
  However, in a diesel engine, combustion is performed in an oxygen-excess state than the stoichiometric air-fuel ratio (air / fuel = 14.7), so the composition of the exhaust gas after combustion also reflects the air-fuel ratio at the time of combustion. Excessive state. However, the conventional three-way catalyst has a problem in that NOx cannot be effectively removed because the purification performance against NOx is extremely lowered under an oxygen-excess atmosphere (lean atmosphere). Therefore, for diesel engines, NOx is reduced to N by, for example, NOx and HC.₂Catalysts exhibiting excellent NOx purification characteristics even in lean atmosphere (hereinafter referred to as NOx purification catalysts) have come to be used, such as metal-supported zeolite that is decomposed and purified.
[0004]
  By the way, in recent years, regarding this type of NOx purification catalyst, it has been known that the NOx purification rate is improved by adding an HC component. An attempt has been made to improve the characteristics of the NOx purification catalyst by using this characteristic and adding and supplying fuel to the exhaust gas.
[0005]
  For example, Japanese Utility Model Publication No. 3-68516 discloses a diesel engine in which a zeolite-based catalyst is provided in an exhaust system, and a fuel component (HC component) is added to the exhaust gas after combustion using an injector for fuel supply. ing.
[0006]
  On the other hand, an EGR (Exhaust Gas Recirculation) system is known as another means for reducing NOx in exhaust gas. The EGR system performs a recirculation operation in which a communication path is provided between an exhaust system and an intake system, and a part of the exhaust gas is returned to the intake system through this communication path. The amount of exhaust gas returned to the intake system is adjusted by a control valve (EGR valve) provided in the communication path. Such exhaust gas recirculation reduces the maximum temperature during combustion and reduces the amount of NOx produced.
[0007]
[Problems to be solved by the invention]
  However, for the following reasons, the system for supplying unburned fuel to the NOx purification catalyst and the EGR system have not been provided in the same engine.
[0008]
  That is, when unburned fuel is supplied to the exhaust system so as to improve the purification performance of the NOx purification catalyst, a part of the unburned fuel is returned to the intake system through the communication path together with the exhaust gas. At this time, the exhaust gas passes through the EGR valve, but unburned fuel in the exhaust gas may adhere to the EGR valve. If a considerable amount of fuel adheres to the EGR valve, the smooth operation of the valve is hindered, and as a result, the control of the valve may be disabled.
[0009]
  Therefore, it has been considered difficult to coexist the system for supplying unburned fuel and the EGR system.
[0010]
  The present invention has been made in view of such points, and an object of the present invention is to provide an engine that includes a system for supplying unburned fuel to a NOx purification catalyst and an EGR system, and that effectively utilizes both systems. It is to provide a control device.
[0011]
[Means for Solving the Problems]
  In order to achieve the above object, the present invention has decided to suppress the supply of unburned fuel during the EGR operation.
[0012]
  Specifically, the invention described in claim 1Fuel injection means facing the combustion chamber of the diesel engine;An exhaust gas recirculation means comprising an exhaust gas recirculation passage for communicating an exhaust system and an intake system and returning a part of the exhaust gas to the intake system, an exhaust gas recirculation valve for opening and closing the exhaust gas recirculation passage, and the exhaust system NOx purification catalyst provided downstream of the inlet of the exhaust gas recirculation passage inNormal injection means for injecting fuel from the fuel injection means at the end of the compression stroke to cause combustion in the combustion chamber;Supply unburned fuel to NOx purification catalystTherefore, an exhaust stroke injection unit that causes the fuel injection unit to perform fuel injection during an exhaust stroke, and an intake stroke injection that causes the fuel injection unit to perform fuel injection during an intake stroke when the exhaust gas recirculation valve is open. Means,When the exhaust gas recirculation valve is open,Prohibit exhaust stroke injection by exhaust stroke injection meansWith suppression meansAnd a cold time determination means for determining the cold time, and when the cold stroke determination means determines that the cold stroke determination means is cold, the intake stroke injection means is at the initial stage of the intake stroke. For causing the fuel injection means to perform fuel injectionIt is what.
[0013]
  By the above invention specific matters,First,When the exhaust gas recirculation valve is open, the supply of unburned fuel is suppressed, so that a large amount of fuel is prevented from adhering to the exhaust gas recirculation valve. As a result, exhaust gas recirculation operation is performed smoothly..
[0014]
AlsoWhen the exhaust gas recirculation valve is open, fuel injection is executed during the intake stroke. The fuel injected during the intake stroke burns with the fuel injected at the end of the compression stroke and is generated.BakedThe gas contains a lot of HC components. Therefore, since no unburned fuel is supplied, fuel does not adhere to the exhaust gas recirculation valve, while an HC component is supplied to the NOx purification catalyst, improving the purification performance of the NOx purification catalyst.
[0015]
  further,engineWhen cold, fuel injection is performed at the beginning of the intake stroke to increase the HC component contained in the combustion gas. The HC component contained in the combustion gas is adsorbed on the NOx purification catalyst. As a result, even when the NOx purification catalyst is not fully activated, the amount of NOx discharged outside the system is reduced.
[0016]
  In addition, in the above configuration, since the unburned fuel can be supplied by the fuel injection means facing the combustion chamber, a special fuel supply means for supplying unburned fuel to the NOx purification catalyst becomes unnecessary.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
  Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0018]
  <Reference example>
  First,Reference example for explaining the basic configuration of an engine control device according to the present inventionexplain. Engine 1 is a diesel engineTheAs shown in FIG. 1, the engine body 2 of the engine 1 has four cylinders 5 arranged in a row. These cylinders 5 are respectively connected to four independent intake pipes 4 branched from the surge tank 3, and are configured such that fresh air is introduced through these intake pipes 4.
[0019]
  A so-called common rail 6 is provided for the engine body 2. The common rail 6 is a type of fuel injection device that stores high-pressure fuel and injects fuel into the combustion chamber of each cylinder 5 based on a control signal from a control unit (ECU) 40.
[0020]
  Each cylinder 5 is provided with an injector 7 for injecting fuel when a needle valve is operated by a solenoid in response to a control signal. These injectors 7 serving as fuel injection means are connected to a common rail 6.
[0021]
  The common rail 6 is connected to a fuel pump 9 via a fuel passage 8, and this fuel pump 9 is connected to a fuel tank (not shown). Therefore, the fuel pumped from the fuel pump 9 is supplied to each injector 7 through the common rail 6. A pressure regulating valve 10 is provided in the fuel passage 8. The pressure regulating valve 10 is a pressure adjusting means for adjusting the injection pressure of the injector 7 by adjusting the pressure of the fuel sent to the common rail 6. Therefore, the injection pressure is adjusted by the operation of the pressure regulating valve 10 according to the control signal. A pressure sensor 11 is provided on the common rail 6, and an injection pressure is detected by the pressure sensor 11.
[0022]
  The exhaust system of the engine 1 is provided with an exhaust manifold 12 that collects exhaust gas discharged from each cylinder 5 and an exhaust pipe 13 connected to the exhaust manifold 12.
[0023]
  In the middle of the exhaust pipe 13, a catalytic converter 14 having a NOx purification catalyst made of metal-supported zeolite is installed. As the metal-supported zeolite, for example, a zeolite that supports a noble metal such as Pt, Rh, or Ir and an active metal such as a transition metal Cu on a zeolite such as Y-type, β-type, mesopore, and MFI is used.
[0024]
  The exhaust manifold 12 and the surge tank 3 are communicated with each other by an EGR passage 60 provided with an EGR valve 61 that is an exhaust gas recirculation valve. The EGR passage 60 is an exhaust gas recirculation passage for returning a part of the exhaust gas to the surge tank 3, and the amount of exhaust gas returned to the surge tank 3 is adjusted by controlling the opening degree of the EGR valve 61. It has come to be.
[0025]
  Next, a specific configuration of the engine 1 will be described. As shown in FIGS. 2 and 3, a piston 23 is inserted into the cylinder formed by the cylinder block 21 so as to be slidable up and down. A combustion chamber 25 is defined by the lower surface of the cylinder head 24 attached to the upper part of the cylinder block 21, the inner peripheral surface (cylinder wall surface) of the cylinder block 21, and the upper surface of the piston 23.
[0026]
  The cylinder head 24 is provided with two air supply ports 26 that respectively communicate with the combustion chamber 25 from one side surface, and two exhaust ports 27 that respectively communicate with the combustion chamber 25 from the other side surface. As shown in FIG. 3, the openings 26a, 27a of the ports 26, 27 to the combustion chamber 25 are arranged in a square shape on the lower surface of the cylinder head. Each of the ports 26 and 27 is provided with on / off valves 28 and 29. That is, an intake valve 28 that opens and closes the opening 26 a of each air supply port 26 and an exhaust valve 29 that opens and closes the opening 27 a of each exhaust port 27 are provided. The valve shaft portions 28 a and 29 a of the intake valve 28 and the exhaust valve 29 pass through the cylinder head 24 and protrude upward. Umbrella portions 28b and 29b connected to the valve shaft portions 28a and 29a are in close contact with and separated from the valve seats 30 fitted into the openings 26a and 27a of the ports 26 and 27, respectively. .
[0027]
  Further, the cylinder head 24 is provided with a stepped injector insertion hole 31 that opens at the center position of the combustion chamber 25 in the vertical direction. An injector 7 is attached to the injector insertion hole 31. That is, the injector 7 is inserted into the injector insertion hole 31 with the fuel injection portion 7a at the tip thereof exposed in the combustion chamber 25. In other words, the fuel injection part 7 a is provided at a position facing the upper surface of the piston 23. Then, the two mounting bolts 32 pass through the fixed plate 33 supported by the upper surface of the flange portion 7b at the intermediate portion of the injector 7 and are screwed into the cylinder head 24, whereby the injector 7 and the cylinder head 24 are connected. It is integrated.
[0028]
  As shown in FIG. 4, a nozzle 102 is integrally provided at the lower portion of the injector main body 101, and the fuel injection portion 7 a is expanded downward. In the fuel injection portion 7a, as shown in an enlarged view in FIG. 5, four injection holes 106 having one end opened to the sack 105 are arranged in a cross shape in plan view. An oil chamber 104 for temporarily storing fuel is provided around a needle valve 103 slidably inserted into the nozzle 102.
[0029]
  A flange portion 7b provided at an intermediate portion of the injector main body 101 is provided with a fuel inlet 107 for introducing fuel supplied through the fuel supply pipe 15, and the fuel introduced from the fuel inlet 107 is supplied to the fuel supply passage. The oil chamber 104 is supplied via 108. A plunger (not shown) organically coupled to the needle valve 103 is slidably inserted in an intermediate portion of the injector body 101, and the plunger is slid based on a control signal from the ECU 40 described later. By moving in the vertical direction, the opening and closing of the needle valve 103 is controlled.
[0030]
  As shown in FIG. 1, the engine 1 includes a control unit (ECU) 40. The ECU 40 receives a signal from a crank angle sensor 41 that detects the crank angle of the engine, a signal from an engine load sensor 42 that detects the engine load, and a signal from an accelerator opening sensor 49 that detects the amount of depression of the accelerator pedal. And a signal from the water temperature sensor 43 for detecting the engine water temperature, a signal from the intake air temperature sensor 49b for detecting the intake air temperature, and the temperature of the exhaust gas immediately after being exhausted from the combustion chamber 25 after being installed in the exhaust manifold 12. A signal from the first exhaust temperature sensor 44 to be detected, a signal from the second exhaust temperature sensor 45 to detect the temperature of the exhaust gas immediately upstream of the catalytic converter 14, and the temperature of the exhaust gas immediately downstream of the catalytic converter 14 are detected. Signals from the third exhaust temperature sensor 46 to be detected are input, and based on these signals, the fuel pump 9, the pressure regulating valve 10, By controlling Njekuta 7 operation of each, so as to perform the normal injection, the exhaust stroke injection or intake stroke injection will be described later.
[0031]
  Next, the configuration of the engine control system 50 formed by the ECU 40 will be described with reference to the block diagram of FIG.
[0032]
  The control system 50 includes normal injection control means 51 that executes normal injection control, exhaust stroke injection control means 52 that executes exhaust stroke injection control, and intake stroke injection control means 53 that executes intake stroke injection control. The EGR zone determination means 54 for determining whether or not the operation state is in a predetermined EGR zone set in advance, the EGR suppression means 55 for prohibiting the EGR operation when the operation state is not in the EGR zone, and the operation state is EGR Exhaust stroke injection prohibiting means 56 for prohibiting exhaust stroke injection when in the zone is provided. Each of these means 51 to 56 receives a signal from each sensor such as the crank angle sensor 41, the accelerator opening sensor 49, the water temperature sensor 43, etc., and based on a predetermined algorithm described later, the injector 7, the pressure regulating valve 10, and the EGR valve 61. Each control is executed by adjusting the above.
[0033]
  Next, an operation of engine fuel injection control performed by the control system 50 will be described.
[0034]
  The control system 50 performs fuel injection by appropriately combining normal injection control, exhaust stroke injection control, and intake stroke injection control according to the operating state. First, each injection control will be described.
[0035]
  (Normal injection control)
  In the normal injection control, when the piston 23 is in the vicinity of the compression top dead center, that is, at the end of the compression stroke, fuel is injected from the injector 7 into the combustion chamber 25 to cause combustion in the combustion chamber 25 to generate torque. Fuel injection to be performed.
[0036]
  The normal injection control is performed by the normal injection control means 51. The normal injection control means 51 calculates the engine speed based on the signal from the crank angle sensor 41, detects the engine load from the engine load sensor 42, and performs basic fuel injection based on the engine speed and the engine load. Set the amount. Then, after correcting this basic fuel injection amount by the accelerator opening, the engine water temperature, etc., the final injection amount, injection pressure, injection timing, etc. are determined. When the predetermined injection timing, that is, the crank angle indicates a crank angle within a predetermined range set near the compression top dead center, a drive signal is output to the injector 7 for a time corresponding to the set injection amount. As a result, a predetermined amount of fuel is injected from the fuel injection portion 7a of the injector 7.
[0037]
  The crank angle, accelerator opening, and engine water temperature are detected by a crank angle sensor 41, an accelerator opening sensor 49, and a water temperature sensor 43, respectively.
[0038]
  (Exhaust stroke injection control)
  The exhaust stroke injection is fuel injection performed during the exhaust stroke for the purpose of adding and supplying a fuel component to the NOx purification catalyst of the catalytic converter 14.
[0039]
  The exhaust stroke injection control is performed by the exhaust stroke injection control means 52. The control method is basically the same as the normal injection control. That is, the exhaust stroke injection control means 52 receives a signal from the crank angle sensor 41 or the like, and sets the injection pressure, the injection timing, and the injection amount. Then, in response to signals from these sensors, a drive signal is output so that a predetermined amount of fuel is injected at a predetermined time to the injectors 7 of each cylinder.
[0040]
  (Intake stroke injection control)
  The intake stroke injection is fuel injection performed during the intake stroke.
[0041]
  As disclosed on page 83 of the Automotive Engineering Society Annual Lecture Preprint 963 (1996-5), in general, when the injection timing is advanced from the top dead center, NOx in the combustion gas is first introduced. The component increases while the HC component decreases. However, when the injection timing is further advanced, the NOx component decreases, whereas the HC component increases. This is thought to be due to the fact that the earlier the injection timing, the easier the fuel spreads throughout the combustion chamber, the combustion tends to occur simultaneously throughout the combustion chamber, and the temperature of the combustion field is low.
[0042]
  Therefore, the fuel injected during the intake stroke burns together with the fuel injected during normal injection, but the burned gas contains a lot of HC components. Therefore, the combustion gas discharged from the combustion chamber 25 contains a large amount of HC components, and a large amount of HC components is supplied to the NOx purification catalyst of the catalytic converter 14. That is, the intake stroke injection is fuel injection performed for the purpose of supplying a large amount of HC components to the NOx purification catalyst.
[0043]
  The intake stroke injection is performed by the intake stroke injection control means 53, and the control method is basically the same as the normal injection control. That is, the intake stroke injection control means 53 receives a signal from the crank angle sensor 41 or the like, and sets the injection pressure, the injection timing, and the injection amount. Then, in response to signals from these sensors, a drive signal is output so that a predetermined amount of fuel is injected at a predetermined time to the injectors 7 of each cylinder.
[0044]
  (Fuel injection control)
  The fuel injection control by the control system 50 will be described with reference to the flowchart of FIG.
[0045]
  First, in step ST1, the engine speed is detected based on a signal from the crank angle sensor 41. Next, in step ST2, the accelerator opening is detected based on the signal from the accelerator opening sensor 49. In step ST3, the engine water temperature is detected based on the signal from the water temperature sensor 43.
[0046]
  In step ST4, the normal injection control means 51 sets the injection pressure, the injection timing, and the injection amount of normal injection according to the operating state.
[0047]
  Thereafter, the process proceeds to step ST5, where it is determined by the EGR zone determination means 54 whether or not the operating state is in a predetermined EGR zone set in advance. In the present embodiment, the EGR zone is determined based on the engine water temperature. That is, if the engine water temperature is equal to or higher than the predetermined value T1, it is determined that the operating state is in the EGR zone.
[0048]
  When it is determined that the operating state is in the EGR zone, the process proceeds to step ST6, the opening of the EGR valve 61 is adjusted according to the operating state, and the EGR operation is performed. In step ST7, the exhaust stroke injection prohibiting unit 56 prohibits the exhaust stroke injection. Thereafter, the process proceeds to step ST8, where the intake stroke injection control means 53 sets the injection pressure, the injection timing, and the injection amount of the intake stroke injection according to the operating state.
[0049]
  On the other hand, when it is determined in step ST5 that the operating state is not in the EGR zone, the process proceeds to step ST9, where the EGR suppression means 55 closes the EGR valve 61. That is, EGR operation is prohibited. Thereafter, the process proceeds to step ST10, where the exhaust stroke injection control means 52 sets the injection pressure, the injection timing, and the injection amount of the exhaust stroke injection according to the operating state.
[0050]
  Then, after the intake stroke injection is set in step ST8 or the exhaust stroke injection is set in step ST10, the routine proceeds to step ST11, where each fuel injection is executed.
[0051]
  By performing the control as described above, as shown in FIG. 8, during the EGR operation, fuel is once injected in the intake stroke and fuel is injected at the end of the compression stroke. The fuel injected in the intake stroke spreads throughout the combustion chamber 25 at the end of the compression stroke, and burns together with the fuel injected at the end of the compression stroke. As a result, combustion gas containing a large amount of HC components is generated after combustion. A part of the combustion gas is returned to the surge tank 3 through the EGR passage 60 and introduced into the combustion chamber 25 in the intake stroke.
[0052]
  On the other hand, when EGR operation is not performed, that is, during non-EGR operation, fuel injection is performed at the end of the compression stroke, and this fuel burns in the combustion chamber 25 to become combustion gas. Thereafter, fuel injection is performed in the first half of the exhaust stroke, and this injected fuel is discharged from the combustion chamber 25 together with the fuel gas. Since the EGR passage 60 is closed, the exhausted combustion gas and unburned fuel flow through the exhaust pipe 13 as they are and pass through the catalytic converter 14. At this time, the HC component of the unburned fuel is adsorbed by the NOx purification catalyst, and the purification performance of the NOx purification catalyst is improved.
[0053]
  As described above, according to the fuel injection control by the control system 50, the intake stroke injection is executed during the EGR operation while the exhaust stroke injection is prohibited, so that unburned fuel adheres to the EGR valve 61. Can be prevented. Therefore, it is possible to prevent a situation in which the EGR control is disabled.
[0054]
  At this time, combustion gas containing a large amount of HC component is generated by the fuel injected during the intake stroke, and this combustion gas improves the purification performance of the NOx purification catalyst in the catalytic converter 14. Therefore, combined with the effect of NOx reduction by EGR and the effect of NOx reduction by improving the purification performance of the NOx purification catalyst, it is possible to further reduce NOx discharged outside the system.
[0055]
  On the other hand, during the non-EGR operation, the intake stroke injection is not executed but the exhaust stroke injection is performed. Accordingly, the unburned fuel is adsorbed on the NOx purification catalyst of the catalytic converter 14 without flowing through the EGR passage 60. As a result, the purification performance of the NOx purification catalyst is improved, and NOx discharged outside the system can be reduced.
[0056]
  Thus, according to the present control system 50, the system for supplying unburned fuel to the NOx purification catalyst and the EGR system can coexist and both systems can be effectively used as appropriate.
[0057]
  <Implementation formState>
  Of the present inventionThe control system 50a according to the embodiment includes:Reference example aboveThe intake stroke injection is executed in consideration of whether or not it is cold.
[0058]
  As shown in FIG. 9, in the present control system 50a,Reference exampleIn addition to the configuration of the control system 50, a cold time determining means 57 for determining the cold time is provided.
[0059]
  When it is not cold, the catalyst in the catalytic converter 14 is often activated. In such a case, NOx can be sufficiently reduced only by EGR without particularly performing the intake stroke injection. On the other hand, when cold, the catalyst is not sufficiently activated and the NOx purification rate is low, so it is desirable to actively add the HC component.
[0060]
  Therefore, as shown in FIG. 10, in the fuel injection control by the control system 50a, during the EGR operation, after the exhaust stroke injection is prohibited in step ST7, the cold determination is performed in step ST12.
[0061]
  The cold determination is made based on whether or not the engine water temperature is in a predetermined cold zone set in advance. In the present embodiment, as shown in FIG. 11, when the engine water temperature is not less than a predetermined value T1 and not more than a predetermined value T2, it is determined that it is cold.
[0062]
  In step ST12, when the cold time determination means 57 determines that it is cold, the process proceeds to step ST8, where the intake stroke injection is set. In this embodiment, in particular, the injection timing of the intake stroke injection is set to the initial stage of the intake stroke. When the setting of the intake stroke injection is completed in step ST8, the process proceeds to step ST11 and each injection is executed.
[0063]
  On the other hand, if it is determined in step ST12 that the cold time determination means 57 is not cold, the routine proceeds to step ST11 and only normal injection is performed without setting the intake stroke injection.
[0064]
  Therefore, the injection control is simplified by not performing the intake stroke injection when it is not cold, while the intake stroke injection includes more lower HC components by utilizing the rise in intake temperature due to EGR when cold. Generate combustion gas. And HC component is made to adsorb | suck to a NOx purification catalyst, and the purification performance is improved. As a result, the NOx purification catalyst performs a sufficient purification action even in a state where it is not activated so much, so that NOx discharged outside the system can be sufficiently reduced.
[0065]
  In particular, since the intake stroke injection is performed at an early stage of the intake stroke, the generated combustion gas contains more HC components. Therefore, the purification performance of the NOx purification catalyst can be further improved.
[0066]
  <Other embodiments>
  In the above embodiment, the determination of the EGR zone is performed based on the engine water temperature, but the determination method of the EGR zone may be another method. For example, the EGR zone may be determined based on the relationship between the engine speed and the torque.
[0067]
  In the above embodiment, the EGR valve 61 is closed when the operating state is not in the EGR zone. However, the EGR valve 61 may not be completely closed during the EGR operation, but the opening degree may be set small. That is, when performing the exhaust stroke injection, the EGR operation may not be completely prohibited, but the amount of gas passing through the EGR passage 60 may be reduced to the extent that fuel does not adhere to the EGR valve 61. In other words, EGR may be suppressed.
[0068]
  ImplementationStateIn this case, the intake stroke injection may be performed even when it is not cold. In this case, a difference is set in the set value between the intake stroke injection when cold and the intake stroke injection when not cold. For example, the injection amount during cold is made larger than the injection amount during non-cold.
[0069]
  Note that, in a high load range where the exhaust gas is considered to be high temperature, the EGR valve 61 may be closed to stop the EGR operation, and the exhaust stroke injection may be executed. In this case, the temperature increase of the exhaust gas is suppressed by stopping the EGR operation, while the temperature of the exhaust gas is lowered by the fuel injected by the exhaust stroke injection, so that it is possible to protect against the high temperature deterioration of the NOx purification catalyst. Become.
[0070]
  In the above embodiment, the fuel is injected in the first half of the intake stroke, but the fuel may be injected in the second half of the intake stroke.
[0071]
【The invention's effect】
  As described above, according to the present invention, the following effects are exhibited.
[0072]
  According to the first aspect of the present invention, when the exhaust gas recirculation valve is in the open state, the supply of unburned fuel is suppressed, so that a large amount of fuel can be prevented from adhering to the exhaust gas recirculation valve. As a result, malfunction of the exhaust gas recirculation valve can be prevented, and exhaust gas recirculation operation can be performed smoothly. Therefore, the system for supplying unburned fuel and the exhaust gas recirculation system can coexist and can be effectively used as appropriate.
[0073]
  Also,Unburned fuel can be supplied by the fuel injection means used for normal injection, and a special fuel supply means for supplying unburned fuel to the NOx purification catalyst becomes unnecessary. Therefore, the control device can be simplified and can be configured at low cost.
[0074]
  Also,When the exhaust gas recirculation valve is open, fuel injection is performed during the intake stroke, and the fuel gas contains a large amount of HC components. Therefore, since no unburned fuel is supplied, fuel does not adhere to the exhaust gas recirculation valve, while an HC component is supplied to the NOx purification catalyst, improving the purification performance of the NOx purification catalyst.
[0075]
  further,When the exhaust gas recirculation operation is cold, fuel injection is performed at the beginning of the intake stroke, so that the HC component contained in the combustion gas can be increased. Therefore, even when the NOx purification catalyst is not fully activated, the purification performance of the NOx purification catalyst is improved, so that the amount of NOx discharged outside the system can be reduced..
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of an engine control system.
FIG. 2 is an enlarged sectional view of a part of the engine.
FIG. 3 is a cross-sectional view taken along line AA in FIG.
FIG. 4 is a partially cutaway longitudinal sectional view of an injector.
5 is a cross-sectional view taken along line BB in FIG.
[Fig. 6]Reference exampleIt is a block block diagram of the control system concerning.
[Fig. 7]Reference exampleIt is a flowchart of the fuel injection control which concerns on.
FIG. 8 is a time chart of fuel injection control.
FIG. 9 Implementation formStateIt is a block block diagram of the control system which concerns.
FIG. 10 EmbodimentStateIt is a flowchart of the fuel injection control concerned.
FIG. 11 is a diagram showing an EGR zone and a cold zone.
[Explanation of symbols]
  1 engine
  3 Surge tank
  6 Common rail
  7 Injector
  9 Fuel pump
  10 Pressure regulating valve
  12 Exhaust manifold
  13 Exhaust pipe
  14 Catalytic converter
  40 ECU
  41 Crank angle sensor
  50 Control system
  60 EGR passage
  61 EGR valve

Claims (1)

Fuel injection means facing the combustion chamber of the diesel engine;
An exhaust gas recirculation means comprising an exhaust gas recirculation passage that connects the exhaust system and the intake system to return part of the exhaust gas to the intake system, and an exhaust gas recirculation valve that opens and closes the exhaust gas recirculation passage;
A NOx purification catalyst provided downstream of the inlet of the exhaust gas recirculation passage in the exhaust system;
Normal injection means for injecting fuel from the fuel injection means at the end of the compression stroke to cause combustion in the combustion chamber;
To supply the unburned fuel in the upper Symbol NOx purifying catalyst and an exhaust stroke injection means for executing the fuel injection in the fuel injection means during the exhaust stroke,
An intake stroke injection means for causing the fuel injection means to perform fuel injection in an intake stroke when the exhaust gas recirculation valve is in an open state;
Rutotomoni a suppressing means the exhaust gas recirculation valve to prohibit the exhaust stroke injection by the exhaust stroke injection means when in the open state,
Furthermore, it has a cold time determination means for determining the cold time,
The intake stroke injection means causes the fuel injection means to perform fuel injection at the initial stage of the intake stroke when the cold time determination means determines that the time is cold. Engine control device .

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