JP2019065800A - Internal combustion engine control device - Google Patents

Abstract

To provide an internal combustion engine control device capable of continuing a dither control after self-ignition.SOLUTION: A CPU 32 executes a dither control for making one of cylinders #1 to #4 to a rich combustion cylinder whose air-fuel ratio is richer than a stoichiometric air-fuel ratio, and others of the cylinders to lean combustion cylinders whose air-fuel ratio is leaner than the stoichiometric air-fuel ratio, under a condition that a temperature rise request occurs to a three-way catalyst 24. The CPU 32 exceptionally increases an injection amount of a cylinder in which self-ignition occurs in its combustion cycle without stopping the dither control, when the self-ignition occurs.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a control device for an internal combustion engine that controls an internal combustion engine including an exhaust gas purification device that purifies exhaust gas discharged from a plurality of cylinders, and a fuel injection valve provided for each of the plurality of cylinders.

  For example, in Patent Document 1, when there is a temperature increase request of a catalyst device (catalyst), some cylinders are rich combustion cylinders whose air fuel ratio becomes richer than the theoretical air fuel ratio, and the remaining cylinders are empty A control device is described which executes dither control to make a lean combustion cylinder in which the fuel ratio is leaner than the stoichiometric air fuel ratio.

Unexamined-Japanese-Patent No. 2004-218541

  By the way, in the temperature range in the combustion chamber of the internal combustion engine, there is a range in which the phenomenon that the air-fuel mixture self-ignites easily occurs prior to the spark discharge of the igniter. When self-ignition occurs, the temperature in the combustion chamber rises, so self-ignition tends to occur continuously, and when self-ignition occurs continuously, the dither control itself has to be stopped, and as a result, The temperature rise effect by dither control is reduced.

  In order to solve the above problems, a control device for an internal combustion engine controls an internal combustion engine including an exhaust gas purification device for purifying exhaust gas discharged from a plurality of cylinders, and a fuel injection valve provided for each of the plurality of cylinders. The target is that some of the plurality of cylinders are rich combustion cylinders whose air fuel ratio is richer than the theoretical air fuel ratio, and cylinders other than the some cylinders of the plurality of cylinders are used. A dither control process for operating the fuel injection valve so as to make the air-fuel ratio leaner than the stoichiometric air-fuel ratio, and a detection process for detecting self-ignition when the dither control process is being performed; When self-ignition is detected by the detection processing, an increase processing is performed to increase the injection amount of the cylinder in which self-ignition has occurred with respect to the amount required by the dither control processing.

  In the above configuration, when self-ignition occurs during dither control, the amount of injection of the cylinder where self-ignition occurs is increased by the increase processing to cool the cylinder where self-ignition has occurred. As a result, it is possible to suppress the occurrence of continuous self-ignition in the cylinder. Therefore, dither control can be continued even after self-ignition occurs.

FIG. 1 shows a control device and an internal combustion engine according to one embodiment. The flowchart which shows the procedure of the process which the control apparatus concerning the embodiment performs.

Hereinafter, an embodiment according to a control device for an internal combustion engine will be described with reference to the drawings.
In the internal combustion engine 10 shown in FIG. 1, air taken in from the intake passage 12 flows into the combustion chamber 16 of each cylinder via the supercharger 14. The combustion chamber 16 is provided with a fuel injection valve 18 for injecting fuel and an igniter 20 for generating spark discharge. In the combustion chamber 16, the mixture of air and fuel is subjected to combustion, and the mixture supplied to combustion is discharged to the exhaust passage 22 as exhaust gas. A three-way catalyst 24 having an oxygen storage capacity is provided downstream of the turbocharger 14 in the exhaust passage 22.

  The control device 30 controls the internal combustion engine 10, and operates the operation part of the internal combustion engine 10 such as the fuel injection valve 18 and the ignition device 20 in order to control the control amount (torque, exhaust component, etc.). At this time, the controller 30 controls the air-fuel ratio Af detected by the air-fuel ratio sensor 40 upstream of the three-way catalyst 24, the output signal Scr of the crank angle sensor 44, the intake air amount Ga detected by the air flow meter 46, The output signal Sn of the knocking sensor 48 is referred to. The control device 30 includes a CPU 32, a ROM 34, and a RAM 36. The CPU 32 executes a program stored in the ROM 34 to control the control amount.

  FIG. 2 shows one of the processes performed by the control device 30. The process shown in FIG. 2 is realized by the CPU 32 repeatedly executing the program stored in the ROM 34 at a predetermined cycle, for example.

  In the series of processes shown in FIG. 2, the CPU 32 first determines whether there is a temperature increase request for the three-way catalyst 24 by dither control (S10). In the present embodiment, the temperature increase request by dither control is performed when the logical sum of the request for warm-up of the three-way catalyst 24 and the request for execution of the sulfur poisoning recovery processing is true. It is determined that there is Here, the warm-up requirement of the three-way catalyst 24 is the condition (i) that the integrated value InGa of the intake air amount Ga from the start of the internal combustion engine 10 is greater than or equal to the first specified value Inth1; (2) It occurs when the logical product with the condition (i) that the specified value Inth2 or less is true is true. Here, the second predetermined value Inth2 is larger than the first predetermined value Inth1. Condition (a) is a condition determined that the temperature of the upstream end of the three-way catalyst 24 is the activation temperature. Condition (i) is a condition under which it is determined that the entire three-way catalyst 24 has not yet been activated. On the other hand, the execution request of the sulfur poisoning recovery process is generated when the sulfur poisoning amount is equal to or more than a predetermined amount. Here, the CPU 32 calculates the sulfur poisoning amount based on the integrated value of the injection amount of the fuel injection valve 18 in a process different from that of FIG. 2.

  When determining that there is a temperature increase request (S10: YES), the CPU 32 multiplies the base injection amount Qb by the feedback operation amount KAF to calculate the required injection amount Qd (S12). Here, the base injection amount Qb is an open loop operation amount that is an operation amount for open loop control of the air fuel ratio of the air fuel mixture in the combustion chamber 16 to the target air fuel ratio, and the CPU 32 outputs an output signal of the crank angle sensor 44 It is calculated based on the rotational speed NE calculated based on Scr and the intake air amount Ga. On the other hand, the feedback operation amount KAF is an operation amount for performing feedback control of the air-fuel ratio Af, which is a feedback control amount, to the target value Af *. In this embodiment, the sum of the output values of the proportional element, the integral element, and the differential element, which receives the difference between the target value Af * and the air-fuel ratio Af, is taken as the correction ratio δ of the base injection amount Qb. Let KAF be “1 + δ”.

  Next, the CPU 32 sets the air-fuel ratio of the air-fuel mixture to be burned by all the cylinders # 1 to # 4 as the component of the entire exhaust discharged from each of the cylinders # 1 to # 4 of the internal combustion engine 10 to the target air-fuel ratio The correction required value (the injection amount correction required value α) of the required injection amount Qd is calculated and output by the dither control in which the air fuel ratio of the mixture to be combusted is made different among the cylinders while being equivalent to the case S14). Here, in the dither control according to the present embodiment, a rich combustion cylinder in which one of the first cylinder # 1 to the fourth cylinder # 4 is made richer in air-fuel ratio of air-fuel mixture than stoichiometric air-fuel ratio Let the remaining three cylinders be lean-burning cylinders in which the air-fuel ratio of the mixture is leaner than the stoichiometric air-fuel ratio. Then, the injection amount in the rich combustion cylinder is made “1 + α” times the required injection amount Qd, and the injection amount in the lean combustion cylinder is made “1− (α / 3)” times the required injection amount Qd. According to the setting of the injection amount of the lean combustion cylinder and the rich combustion cylinder, if the amount of air charged in each of the cylinders # 1 to # 4 is the same, from each cylinder # 1 to # 4 of the internal combustion engine 10 The component of the entire exhaust gas to be discharged can be made equal to the case where the air-fuel ratio of the mixture to be burned in all the cylinders # 1 to # 4 is made the target air-fuel ratio. Note that according to the setting of the injection amount, if the amount of air charged in each of the cylinders # 1 to # 4 is the same, the reciprocal of the average value of the fuel / air ratio of the mixture to be burned in each cylinder Becomes the target air-fuel ratio. The fuel-air ratio is the reciprocal of the air-fuel ratio.

  Specifically, the CPU 32 variably sets the injection amount correction request value α based on the rotational speed NE and the load factor KL that define the operating point of the internal combustion engine 10. Here, the load factor KL is a parameter indicating the amount of air charged into the combustion chamber 16, and is calculated by the CPU 32 based on the amount of intake air Ga. The load factor KL is a ratio of the amount of inflowing air per one combustion cycle of one cylinder to the reference amount of inflowing air. Incidentally, the reference inflow air amount may be an amount variably set according to the rotational speed NE.

  Next, based on the output signal Sn of the knocking sensor 48, the CPU 32 determines whether combustion of air-fuel mixture occurs in the combustion chamber 16 before the timing (ignition timing) at which spark discharge of the ignition device 20 occurs. It is determined whether self-ignition has occurred (S16). This process is a process of determining whether or not the knocking sensor 48 detects a vibration associated with the combustion before the ignition timing.

  When it is determined that the self-ignition has not occurred (S16: NO), the CPU 32 determines whether the cylinder targeted for fuel injection is a rich combustion cylinder (S18). Then, when determining that the cylinder is a rich combustion cylinder (S18: YES), the CPU 32 substitutes “Qd · (1 + α)” for the injection amount command value Q * (S20). On the other hand, when determining that the cylinder is a lean combustion cylinder (S18: NO), the CPU 32 substitutes “Qd · {1- (α / 3)}” for the injection amount command value Q * (S22). Then, the CPU 32 outputs an operation signal MS2 to the fuel injection valve 18 in order to inject fuel of an amount according to the injection amount command value Q * from the fuel injection valve 18 (S24).

  On the other hand, when detecting self-ignition (S16: YES), the CPU 32 calculates the increase coefficient K of the required injection amount Qd (S26). Here, the CPU 32 calculates the increase coefficient K to a larger value as the rotation speed NE increases, and calculates the increase coefficient K to a larger value as the load factor KL increases. Here, “K · Qd> Qd · (1 + α)”. Next, the CPU 32 substitutes a value obtained by multiplying the required injection amount Qd by the increase coefficient K into the injection amount command value Q * (S28). Then, the CPU 32 shifts to the processing of S24.

When the process of S24 is completed or when the determination of step S10 is negative, the CPU 32 temporarily ends the series of processes shown in FIG.
Here, the operation of the present embodiment will be described.

  When the CPU 32 detects self-ignition, the injection amount “K · Qd increased exceptionally over the injection amount by the dither control during the combustion cycle for the cylinder where self-ignition occurred, without stopping the dither control itself. By injecting fuel, the cylinder in which self-ignition has occurred is cooled. As a result, it is possible to suppress the occurrence of self-ignition continuously, and thereafter, it is possible to inject fuel as required for dither control. Therefore, the temperature increase effect of the three-way catalyst 24 by the dither control can be maintained high.

According to the embodiment described above, the following effects can be obtained.
(1) Since the lean combustion cylinder has a small amount of original injection, there is a possibility that the self-ignition suppressing effect becomes low when the original amount of injection is increased. Therefore, regardless of whether the self-ignitioned cylinder is a rich-burning cylinder or a lean-burning cylinder, the injection suppression effect of the self-ignition is secured by injecting the fuel of the injection amount “K · Qd”.

  (2) The amount of increase of the injection amount at the time of self-ignition is variably set according to the operating point of the internal combustion engine 10. As a result, it is possible to suppress an excessive increase in the amount of increase, so it is possible to suppress the disturbance of the air-fuel ratio as much as possible.

<Correspondence relationship>
Correspondence between the matters in the above-mentioned embodiment and the matters described in the above-mentioned "means for solving the problem" is as follows. The exhaust gas purification apparatus corresponds to the three-way catalyst 24, the dither control processing corresponds to the processing of S18 to S24, the detection processing corresponds to the processing of S16, and the increase processing corresponds to the processing of S26 and S28. .

<Other Embodiments>
In addition, you may change at least one of each matter of the said embodiment as follows.
-Although self-ignition was detected based on output signal Sn of knocking sensor 48 in the above-mentioned embodiment, it does not restrict to this. For example, self-ignition may be detected based on an output signal of a sensor that detects the pressure in the combustion chamber 16 (in-cylinder pressure), when the in-cylinder pressure is largely increased prior to the ignition timing.

  In the above embodiment, the increasing coefficient K is variably set based on the load factor KL. However, the load of the internal combustion engine 10 is not limited to the load factor KL, and may be, for example, the base injection amount Qb. It may be an operation amount or the like.

  The parameters for variably setting the increasing coefficient K are not limited to the rotational speed NE and the load. For example, the parameter may indicate the temperature of the internal combustion engine 10, such as the temperature of the cooling water of the internal combustion engine 10. In this case, the increase coefficient K may be calculated to be a larger value when the temperature of the internal combustion engine 10 is high than when the temperature is low. Further, for example, in the internal combustion engine 10 in which the valve closing timing of the intake valve can be variably set, the increase coefficient K may be variably set according to the valve closing timing.

It is not essential to variably set the increase coefficient K.
In the above embodiment, when self-ignition occurs, the injection amount is increased in the cylinder where self-ignition occurred in the combustion cycle, but when the increase in injection amount is not in time, auto-ignition occurred in the next combustion cycle The injection amount of the cylinder may be increased.

  The internal combustion engine is not limited to a four-cylinder internal combustion engine. Further, the fuel injection valve is not limited to one injecting fuel into the combustion chamber 16, but may be one injecting fuel into the intake passage 12. However, in this case, when self-ignition occurs, it seems that the injection amount can not be increased in the cylinder where self-ignition occurred in that combustion cycle, so the injection amount of the cylinder where self-ignition occurred in the next combustion cycle is increased .

  DESCRIPTION OF SYMBOLS 10 ... Internal combustion engine, 12 ... Intake passage, 14 ... Turbocharger, 16 ... Combustion chamber, 18 ... Fuel injection valve, 20 ... Ignition device, 22 ... Exhaust passage, 24 ... Three-way catalyst, 30 ... Control device, 32 ... CPU, 34: ROM, 36: RAM, 40: Air-fuel ratio sensor, 44: Crank angle sensor, 46: Air flow meter, 48: Knocking sensor.

Claims (1)

An internal combustion engine including an exhaust gas purification device for purifying exhaust gas discharged from a plurality of cylinders, and a fuel injection valve provided for each of the plurality of cylinders as a control target,
A part of the plurality of cylinders is a rich combustion cylinder whose air-fuel ratio is richer than the stoichiometric air-fuel ratio, and a cylinder other than the part of the plurality of cylinders is an air-fuel ratio Dither control processing for operating the fuel injection valve so as to make the lean combustion cylinder leaner than the stoichiometric air fuel ratio;
Detection processing for detecting self-ignition when the dither control processing is being performed;
A control device for an internal combustion engine that executes an increase processing to increase the injection amount of a cylinder in which self-ignition has occurred with respect to the amount required by the dither control processing when self-ignition is detected by the detection processing.