JP2005090457A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of carrying out reliable burning of deposits with no fluctuation in the output of an engine. <P>SOLUTION: The internal combustion engine has an cylinder injector 11 for injecting fuel into a cylinder and an intake port injector 12 for injecting fuel into an intake port. When deposits on the cylinder injector 11 should be burnt down, the intake port injector 12 is controlled to perform injecting operation and engine is controlled to perform an operation with reduced number of cylinders. In the intermittent cylinder, an intake valve 65 and an exhaust valve 66 both remain closed right after final burning. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a control device for an internal combustion engine, and more particularly, includes a so-called in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into an intake port. The present invention relates to a control device for a dual injection internal combustion engine.

  Generally, an in-cylinder injector for injecting fuel into a cylinder and an intake port injector for injecting fuel into an intake port are provided, and these injectors are selected according to the operating state of the engine. There is known a so-called dual injection type internal combustion engine that realizes stratified combustion in a low load operation region and homogeneous combustion in a high load operation region by improving the fuel consumption characteristics and output characteristics. .

  By the way, in such a dual injection type internal combustion engine, when this low load operation region continues for a long time, there is a problem that carbon adheres as a deposit around the gap portion of the spark plug and the injection nozzle. In order to solve the problem, for example, a technique described in Patent Document 1 has been proposed.

  In this case, when the stratified combustion of the air-fuel mixture by the in-cylinder injector continues for a predetermined time or longer, the operation of the in-cylinder injector is prohibited and the intake port injection injector is forced to operate for a set time. Switching means is provided.

JP 63-138120 A

  However, in the technique described in Patent Document 1, although the intake port injection injector is forcibly operated for a set time, the combustion temperature is not so high because it is in a low load operation region. It was not enough to burn off deposits adhering to plugs and injectors. In order to cope with this, it is conceivable to increase the amount of fuel itself for combustion, but if this is done, the engine output will change and a new problem will arise.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a control device for an internal combustion engine that can reliably burn out deposits without causing fluctuations in engine output.

  An internal combustion engine control apparatus according to one aspect of the present invention that achieves the above object includes an in-cylinder injector that injects fuel into a cylinder, an intake port injector that injects fuel into an intake port, and When the deposit deposited on the in-cylinder injector is to be burnt down, the intake port injection injector performs injection and the reduced-cylinder operation is performed.

  Here, when shifting to the reduced-cylinder operation, in the cylinder to be deactivated, it is preferable that both the intake valve and the exhaust valve are kept closed immediately after the last combustion.

  In addition, a control device for an internal combustion engine according to another embodiment of the present invention that achieves the above object includes an in-cylinder injector that injects fuel into a cylinder and an intake port injection that injects fuel into an intake port. In an internal combustion engine equipped with a fuel injector, when the deposit deposited on the in-cylinder injector is to be burned out, the intake port injector performs injection, increases the amount of fuel, and opens the exhaust valve. The feature is that the timing is advanced.

  Furthermore, the control device for an internal combustion engine according to still another embodiment of the present invention that achieves the above object includes an in-cylinder injector that injects fuel into a cylinder and an intake port that injects fuel into the intake port. In an internal combustion engine equipped with an injector for injection, when the deposit deposited on the in-cylinder injector is to be burned off, the intake port injector causes the injector to perform injection and the exhaust valve closing timing to increase the EGR amount It is characterized by that it was made to speed up.

  Furthermore, an internal combustion engine control device according to another aspect of the present invention that achieves the above object includes an in-cylinder injector that injects fuel inward and an intake port injection that injects fuel into an intake port. In an internal combustion engine equipped with an injector, when the deposit deposited on the in-cylinder injector is to be burned off, the intake port injection injector performs injection, the fuel amount is increased, and all cylinders are injected. It is characterized in that it is performed intermittently every other cycle.

  According to the control apparatus for an internal combustion engine according to one aspect of the present invention, the internal combustion engine includes an in-cylinder injector that injects fuel into the cylinder and an intake port injector that injects fuel into the intake port. In this case, when the deposit deposited on the in-cylinder injector is to be burned out, injection is performed by the intake port injection injector and the reduced-cylinder operation is performed, so that the load is increased and the fuel amount is increased for the operating cylinder. The Therefore, the combustion temperature is raised while the output of the engine is kept constant, and the deposit deposited on the in-cylinder injector is surely burned out.

  Here, when shifting to the reduced-cylinder operation, in the cylinder that is deactivated, immediately after the last combustion, the intake valve and the exhaust valve are both kept closed. Since the high-temperature combustion gas is confined, the deposit deposited on the in-cylinder injector is expected to be burned out.

  Further, according to the control device for an internal combustion engine according to another aspect of the present invention, an in-cylinder injector that injects fuel into the cylinder, an intake port injector that injects fuel into the intake port, and In an internal combustion engine equipped with an in-cylinder engine, when the deposit deposited on the in-cylinder injector is to be burned out, the injection is performed by the intake port injector, the fuel amount is increased, and the opening timing of the exhaust valve is advanced. The combustion temperature becomes high, but there is no increase in output. Therefore, the deposit deposited on the in-cylinder injector is surely burned out by increasing the combustion temperature while maintaining the engine output constant.

  Furthermore, according to the control device for an internal combustion engine according to still another aspect of the present invention, an in-cylinder injector that injects fuel into the cylinder and an intake port injector that injects fuel into the intake port In the internal combustion engine provided with the above, when the deposit deposited on the in-cylinder injector is to be burned out, the injection is performed by the intake port injector, and the closing timing of the exhaust valve is advanced to increase the EGR amount. As a result of the intake air being heated and ignited by EGR remaining at a high temperature, self-ignition occurs due to an increase in pressure during the combustion process, and a higher combustion temperature is reached. Therefore, the deposit deposited on the in-cylinder injector is surely burned out by increasing the combustion temperature while the output of the engine is kept constant by increasing the EGR amount.

  Furthermore, according to the control apparatus for an internal combustion engine according to another aspect of the present invention, an in-cylinder injector that injects fuel into the cylinder, an intake port injector that injects fuel into the intake port, When the deposit deposited on the in-cylinder injector is to be burned out, the intake port injection injector performs injection, the fuel amount is increased, and all cylinders are injected every other cycle. In the operation cycle, the load increases and the amount of fuel increases. Further, since the residual gas is scavenged in the pause cycle, the combustion temperature also rises. Therefore, the combustion temperature is raised while the output of the engine is kept constant, and the deposit deposited on the in-cylinder injector is surely burned out.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
First, referring to FIG. 1 showing a schematic configuration diagram of a control apparatus for a dual injection internal combustion engine according to the present invention, the entire engine 1 includes four cylinders 1a. Each cylinder 1 a is connected to a common surge tank 3 via a corresponding intake branch pipe 2. The surge tank 3 is connected to an air flow meter 4 a through an intake duct 4, and the air flow meter 4 a is connected to an air cleaner 5. A throttle valve 7 driven by a step motor 6 is disposed in the intake duct 4. The throttle valve 7 is closed to some extent only when the engine load is extremely low, and is kept fully open when the engine load is slightly increased. On the other hand, each cylinder 1 a is connected to a common exhaust manifold 8, and this exhaust manifold 8 is connected to a three-way catalytic converter 9.

  Each cylinder 1a is provided with an in-cylinder injector 11 for injecting fuel into the cylinder and an intake port injector 12 for injecting fuel into the intake port. These injectors 11 and 12 are controlled based on the output signal of the electronic control unit 30. Further, each in-cylinder injector 11 is connected to a common fuel distribution pipe 13, and this fuel distribution pipe 13 is connected to a fuel distribution pipe 13 through a check valve 14, and is driven by an engine drive type. It is connected to the high pressure pump 15.

  As shown in FIG. 1, the discharge side of the high-pressure pump 15 is connected to the suction side of the high-pressure pump 15 via the electromagnetic valve 15a. When the amount of fuel supplied into the pipe 13 is increased and the solenoid valve 15a is fully opened, the fuel supply from the high-pressure pump 15 to the fuel distribution pipe 13 is stopped. The electromagnetic valve 15a is controlled based on the output signal of the electronic control unit 30.

  On the other hand, each intake port injector 12 is connected to a common fuel distribution pipe 16, and the fuel distribution pipe 16 and the high pressure pump 15 are connected to a low pressure pump 18 via a common fuel pressure regulator 17. Further, the low pressure pump 18 is connected to the fuel tank 20 via the fuel filter 19. The fuel pressure regulator 17 is configured to return a part of the fuel discharged from the low pressure pump 18 to the fuel tank 20 when the fuel pressure of the fuel discharged from the low pressure pump 18 becomes higher than a predetermined set fuel pressure. Therefore, the fuel pressure supplied to the intake port injector 12 and the fuel pressure supplied to the high-pressure pump 15 are prevented from becoming higher than the set fuel pressure. Further, as shown in FIG. 1, a flow valve 21 is provided between the high pressure pump 15 and the fuel pressure regulator 17. The flow valve 21 is normally opened. When the flow valve 21 is closed, the fuel supply from the low pressure pump 18 to the high pressure pump 15 is stopped. The opening / closing of the flow valve 21 is controlled based on the output signal of the electronic control unit 30.

  The electronic control unit 30 is composed of a digital computer and includes a ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, and an input port which are connected to each other via a bidirectional bus 31. 35 and an output port 36. The air flow meter 4 a generates an output voltage proportional to the amount of intake air, and the output voltage of the air flow meter 4 a is input to the input port 35 via the AD converter 37. A fuel amount sensor 38 that generates an output voltage proportional to the amount of fuel in the fuel tank is attached to the fuel tank 20, and the output voltage of the fuel amount sensor 38 is input to the input port 35 via the AD converter 39. . A fuel pressure sensor 40 that generates an output voltage proportional to the fuel pressure in the fuel distribution pipe 13 is attached to the fuel distribution pipe 13, and the output voltage of the fuel pressure sensor 40 is supplied to the input port 35 via the AD converter 41. Entered. An oxygen concentration sensor 42 that generates an output voltage proportional to the oxygen concentration in the exhaust gas is attached to the exhaust manifold 8 upstream of the catalyst 9. The output voltage of the oxygen concentration sensor 42 is input to an input port 35 via an AD converter 43. Is input. The accelerator pedal 10 is connected to a load sensor 44 that generates an output voltage proportional to the depression amount of the accelerator pedal 10, and the output voltage of the load sensor 44 is input to the input port 35 via the AD converter 45. The input port 35 is connected to a rotational speed sensor 46 that generates an output pulse representing the engine rotational speed. In the ROM 32 of the electronic control unit 30, the value of the fuel injection amount set corresponding to the operating state based on the engine load and the engine speed obtained by the load sensor 44 and the engine speed sensor 46 is previously mapped. Has been remembered.

  Furthermore, FIG. 2 shows a side sectional view of the cylinder 1a. Referring to FIG. 2, 61 is a cylinder block, 62 is a piston having a recess 62a formed on the top surface, 63 is a cylinder head secured on the cylinder block 61, and 64 is between the piston 62 and the cylinder head 63. The formed combustion chamber, 65 is an intake valve, 66 is an exhaust valve, 67 is an intake port, 68 is an exhaust port, and 69 is an ignition plug. The intake port 67 is formed so that the air flowing into the combustion chamber 64 generates a swirling flow around the cylinder axis. The recess 62 a extends from the peripheral edge of the piston 62 located on the in-cylinder injector 11 side toward the center of the piston 62 and extends upward below the spark plug 69.

  The intake valve 65 and the exhaust valve 66 are linked to an intake valve drive mechanism 70 and an exhaust valve drive mechanism 71, respectively. The intake valve drive mechanism 70 and the exhaust valve drive mechanism 71 are configured by electromagnetic drive mechanisms that drive the intake valve 65 and the exhaust valve 66 forward and backward, respectively, using electromagnetic force generated when an excitation current is applied. Based on the signal of the electronic control unit 30, the opening / closing timing and the lift amount can be arbitrarily controlled. Therefore, for example, when the intake valve drive mechanism 70 and / or the exhaust valve drive mechanism 71 are operated based on a signal from the electronic control unit 30, the opening / closing timing of the intake valve 65 and / or the intake valve 65, and thus the open period. Is variably controlled to be long or short.

  Here, the output port 36 of the electronic control unit 30 is connected via a corresponding drive circuit 47 to the step motor 6, each in-cylinder injector 11, each intake port injection injector 12, the electromagnetic valve 15a, the flow valve 21, and the intake air. The valve driving mechanism 70 and the exhaust valve driving mechanism 71 are connected.

Next, the control of the first embodiment of the present invention having the above configuration will be described below.
First, when the control is started, the operating state of the engine is determined based on the engine load and the engine speed described above. If it is determined that the vehicle is in the low load operation region, fuel is injected by the in-cylinder injector 11 toward the in-cylinder combustion chamber 64 to perform stratified combustion operation. Accordingly, it is determined whether or not the deposit deposited on the in-cylinder injector 11 should be burned out in the stratified combustion operation state. This determination can be made based on the magnitude of the air-fuel ratio correction feedback amount based on the detection of the oxygen concentration sensor 42. That is, when the air-fuel ratio correction feedback amount is larger than a predetermined value, the fuel injection amount corresponding to the above-described operation state is injected by the in-cylinder injector 11 due to the deposit adhering to the periphery of the injection port. It is because it is judged that it is not.

  Therefore, if it is determined that the air-fuel ratio correction feedback amount is larger than the predetermined value and the deposit deposited on the in-cylinder injector 11 is to be burned out, the electronic control unit 30 starts from the in-cylinder injector 11. Is switched so that the injection at the intake port injection injector 12 is performed, and the reduced cylinder operation is controlled. A state when shifting to the reduced-cylinder operation will be described with reference to FIG. In the normal operation in the low load operation region shown in FIG. 3A, no fuel is injected from the intake port injector 12 and a predetermined amount Q of fuel per cylinder is supplied from the in-cylinder injector 11 to all cylinders. The stratified charge combustion operation is performed by being injected. Therefore, in order to perform the reduced-cylinder operation from this state, the electronic control unit 30 switches from the full cylinder injection from the in-cylinder injector 11 to the partial cylinder injection at the intake port injector 12, and at the same time, the partial cylinder Considering the amount of fuel injected for injection approximately twice the above-mentioned predetermined amount Q, that is, the injection characteristics of the intake port injector 12 and the in-cylinder injector 11, the characteristics of stratified combustion and homogeneous combustion, etc. Therefore, the amount is set so as not to fluctuate the engine output. In the example shown in FIG. 3B, all fuel injection into the # 1 and # 3 cylinders is stopped, and the increased amount of fuel is injected from the intake port injector 12 into the # 2 and # 4 cylinders. ing. Thus, in the # 2 cylinder and the # 4 cylinder, since the operation at a higher load is performed as compared with the normal operation by all the cylinders described above, the combustion temperature becomes high while the engine output remains constant, and the in-cylinder injector 11 The deposit deposited on is burned out.

  As shown in FIG. 4, in the cylinders that are deactivated when shifting from the normal operation to the reduced-cylinder operation, in the above example, the # 1 cylinder and the # 3 cylinder, immediately after the last combustion before the transition, as shown in FIG. The intake valve drive mechanism 70 and the exhaust valve drive mechanism 71 are controlled so that the intake valve 65 and the exhaust valve 68 are both kept closed. In this way, high temperature combustion gas is confined as residual gas even in the idle cylinders of the # 1 cylinder and the # 3 cylinder, so that the deposit deposited on the in-cylinder injector 11 is expected to be burned out.

  However, in order to increase the certainty, in the present embodiment, the idle cylinder and the active cylinder are switched after a lapse of a predetermined time (for example, 1 minute) after the shift to the reduced cylinder operation. That is, in this embodiment, the # 2 cylinder and the # 4 cylinder, which were the active cylinders shown in FIG. 3B, are deactivated after the predetermined time has elapsed, and instead, the # 1 cylinder and the # 3 cylinder are replaced. It is made to operate. If the above-mentioned elapse of the predetermined time is not satisfied due to fluctuations in the operating state, for example, if the operating state has changed before the elapse of the predetermined time, the reduced-cylinder operation is continued for the predetermined time or the cylinder is temporarily reduced. The operation may be stopped. In any case, in order to cause the deposits to be burned out evenly in all cylinders, it is preferable to perform the reduced-cylinder operation when the transition to the reduced-cylinder operation is performed next time, with the cylinder that was the previously deactivated cylinder as the active cylinder. .

  Next, the control of the second embodiment of the control apparatus for an internal combustion engine of the present invention will be described below. In the present embodiment, in the same manner as in the previous embodiment, when it is determined when the deposit deposited on the in-cylinder injector 11 should be burned out, the electronic control unit 30 starts from the in-cylinder injector 11. The exhaust valve drive mechanism 71 is controlled so that the injection at the intake port injection injector 12 is performed from this injection, the amount of fuel injected is increased, and the opening timing of the exhaust valve 66 is advanced. In this case, the opening timing of the exhaust valve 66 during normal operation is 140 to 150 ° after the top dead center, whereas during the burn-out treatment operation of this deposited deposit, the opening is about 20 to 30 °. Try to advance the timing. The increase amount of the injected fuel is increased by several percent with respect to the reference fuel amount during normal operation, but the increase in the output corresponding to the increase amount of the fuel and the opening timing of the exhaust valve 66 are advanced. The respective appropriate values are selected so that the decrease in the output due to this cancels out and the engine output is kept constant. Thus, the deposit deposited on the in-cylinder injector 11 is surely burned down by increasing the combustion temperature while the output of the engine is kept constant.

  Furthermore, a third embodiment of the control device for an internal combustion engine of the present invention will be described. In the present embodiment, in the same manner as in the previous embodiment, when it is determined when the deposit deposited on the in-cylinder injector 11 should be burned out, the electronic control unit 30 starts from the in-cylinder injector 11. The exhaust valve drive mechanism 71 is controlled so as to advance the closing timing of the exhaust valve 66 in order to increase the EGR amount while performing the injection from the first injection to the intake port injection injector 12. In this case, the closing timing of the exhaust valve 66 during normal operation is 10 to 15 ° after the top dead center, while the adhesion deposit is burned out by 20 to 30 °. Try to advance the timing. As a result, the exhaust valve 66 is closed at 20 to 5 ° before the top dead center.

  In the present embodiment, the intake air introduced from the intake port 67 in the intake stroke is heated by the EGR remaining at a high temperature. Then, at the end of the compression stroke, the ignition plug 69 ignites and combustion starts. The state of heat generation by this combustion will be described with reference to FIG. FIG. 5 (A) shows the state of heat generation in the present embodiment during normal combustion, and FIG. 5 (A) shows the state of heat generation in this embodiment. During normal combustion, combustion starts by ignition at the point of arrow S, and only combustion by flame propagation is performed, and the heat generation curve is a symmetrical curve with a peak at the compression top dead center (TDC). expressed.

  On the other hand, in the present embodiment, combustion is started by ignition at the time of the arrow S and flame is propagated by the start of combustion, which is the same as in normal combustion. It is represented by a heat generation curve having a higher peak when it self-ignites with an increase in temperature and pressure and passes the compression top dead center. This is because the intake air is heated by the EGR remaining at a high temperature in advance, and as a result, the air-fuel mixture temperature at the unreached portion of the flame rises, resulting in self-ignition. In the case of self-ignition, the combustion speed is high unlike normal combustion by flame propagation, so that a higher combustion temperature is reached. Accordingly, the deposit deposited on the in-cylinder injector 11 is surely burned out by increasing the combustion temperature while the output of the engine is kept constant by increasing the EGR amount.

  Furthermore, a fourth embodiment of the control device for an internal combustion engine of the present invention will be described. In the present embodiment, in the same manner as in the previous embodiment, when it is determined when the deposit deposited on the in-cylinder injector 11 is to be burned out, the electronic control unit 30 performs the in-cylinder injector 11. The injection is performed from the injection at the intake port injection injector 12, the fuel amount is increased, and all cylinders are controlled to be intermittently injected every other cycle.

  The state when shifting to the intermittent injection operation every other cycle will be described with reference to FIG. 3 again. In the normal operation in the low load operation region shown in FIG. 3A, the predetermined amount Q of fuel per cylinder is injected from the in-cylinder injector 11 to all cylinders without being injected from the intake port injector 12. Thus, stratified combustion operation is performed. Therefore, in order to perform the intermittent injection operation from this state, the electronic control unit 30 switches from all cylinder injection from the in-cylinder injector 11 to all cylinder injection at the intake port injector 12, and at the same time, The amount of fuel injected by the cylinder injection is approximately twice the predetermined amount Q described above. Then, increased fuel is injected from each intake port injector 12 into each of # 1 cylinder to # 4 cylinder for the first cycle. Further, in the next cycle, the fuel injection for each of the # 1 cylinder to the # 4 cylinder is stopped, and thereafter, the operation cycle in which the fuel is injected and the pause cycle in which the fuel injection is stopped are repeated. In this operation cycle, the opening degree of the throttle valve 7 is increased so as to ensure an air amount commensurate with the increased fuel. On the other hand, the fuel injection is stopped in the pause cycle, but the intake valve drive mechanism 70 and the exhaust valve drive mechanism 71 are controlled so that the intake valve 65 and the exhaust valve 66 are opened and closed in the same manner as during normal operation. Introducing and discharging only air.

Thus, also in the present embodiment, the injection of all cylinders is intermittently performed every other cycle, and the load increases and the fuel amount increases in the operation cycle. Further, since the residual gas is scavenged in the rest cycle, there is no inert residual gas in the next operation cycle, and the combustion temperature rises. Therefore, the combustion temperature is increased while the output of the engine is kept constant, and the deposit deposited on the in-cylinder injector 11 is surely burned out.
Needless to say, the control according to the present invention is not limited to a four-cylinder engine, and can be performed by a multi-cylinder engine having more cylinders.

1 is a schematic diagram showing a schematic configuration diagram of a control device for a dual injection internal combustion engine according to the present invention. It is a sectional side view of the engine shown in FIG. In one Embodiment of this invention, it is a diagram explaining a mode when it transfers to a reduced cylinder driving | operation, (A) shows at the time of normal operation, (B) shows at the time of reduced cylinder operation. In one Embodiment of this invention, it is a figure explaining a mode that both an intake valve and an exhaust valve are maintained closed, when shifting to a reduced cylinder driving | operation. In one Embodiment of this invention, it is a graph explaining the mode of heat generation, (A) is at the time of normal combustion, (B) is at the time of self-ignition.

Explanation of symbols

11 In-Cylinder Injector 12 Intake Port Injection Injector 30 Electronic Control Unit 42 Oxygen Concentration Sensor 44 Load Sensor 46 Rotational Speed Sensor 65 Intake Valve 66 Exhaust Valve 70 Intake Valve Drive Mechanism 71 Exhaust Valve Drive Mechanism

Claims (5)

In an internal combustion engine comprising an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into the intake port,
A control apparatus for an internal combustion engine, characterized in that when the deposit deposited on the in-cylinder injector is to be burned out, the intake port injection injector performs an injection and a reduced-cylinder operation.   2. The internal combustion engine according to claim 1, wherein when the transition to the reduced-cylinder operation is performed, the intake valve and the exhaust valve are both kept closed immediately after the last combustion in the cylinder to be deactivated. Control device. In an internal combustion engine comprising an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into the intake port,
When the deposit deposited on the in-cylinder injector is to be burned off, the intake port injector performs injection, increases the amount of fuel, and accelerates the opening timing of the exhaust valve. A control device for an internal combustion engine. In an internal combustion engine comprising an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into the intake port,
When the deposit deposited on the in-cylinder injector is to be burned out, the intake port injection injector performs injection, and the exhaust valve closing timing is advanced so as to increase the EGR amount. Control device for internal combustion engine. In an internal combustion engine comprising an in-cylinder injector that injects fuel into a cylinder and an intake port injector that injects fuel into the intake port,
When the deposit deposited on the in-cylinder injector is to be burned out, the intake port injection injector performs injection, the fuel amount is increased, and all cylinders are injected intermittently every other cycle. A control device for an internal combustion engine, characterized in that

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