JP2019085947A - Control device of internal combustion engine - Google Patents

Abstract

To provide a control device of an internal combustion engine capable of minimizing degradation of drivability while protecting parts of an internal combustion engine and suppressing degradation of exhaust components.SOLUTION: A CPU 32 executes dither control to apply one of cylinders #1-#4 as a rich combustion cylinder richer than a theoretical air-fuel ratio, and apply the remaining cylinders as lean combustion cylinders leaner than the theoretical air-fuel ratio under a condition that temperature rise of a three-way catalyst 24 is requested. The CPU 32 limits an absolute value of difference between an air-fuel ratio of the rich combustion cylinder and an air-fuel ratio of the lean combustion cylinder to protect components of an internal combustion engine 10, when occurrence of abnormality not less than a prescribed value in control of controlled variable of the internal combustion engine 10, is determined while executing the dither control. Further the CPU 32 limits the absolute value within a range to keep exhaust components within an allowable range when rotational fluctuation is increased although the abnormality of not less than a prescribed value is not confirmed.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 the exhaust purification catalyst (exhaust purification device), some cylinders are rich combustion cylinders whose air fuel ratio is richer than the theoretical air fuel ratio, and the remaining cylinders are: A control device is described which performs dither control processing to make a lean combustion cylinder in which the air-fuel ratio is leaner than the stoichiometric air-fuel ratio.

JP, 2016-169665, A

  The temperature raising performance of the exhaust gas purification apparatus by dither control increases as the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder increases. On the other hand, the larger the absolute value, the greater the rotational fluctuation. For this reason, in the dither control, the above-described absolute value necessary to secure the temperature rising performance is set in a range in which the rotational fluctuation does not cause a decrease in drivability. However, due to, for example, the deterioration with age of the fuel injection valve, the individual difference of the compression ratio of the internal combustion engine, etc., the rotational fluctuation becomes larger than expected, which may result in the deterioration of the drivability. However, when the absolute value is reduced to improve the drivability, the temperature rise performance may be lowered, which may lead to a decrease in the purification capacity of the exhaust gas purification apparatus.

  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. It is determined that the dither control processing for operating the fuel injection valve and the control amount of the internal combustion engine have a predetermined abnormality or more so that the air-fuel ratio is lean combustion cylinder leaner than the theoretical air-fuel ratio. Component protection processing for reducing the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder as compared with the case where it is determined that the abnormality has not occurred; Determined that no abnormality occurred If it is determined that the rotational fluctuation of the crankshaft of the internal combustion engine is equal to or greater than a predetermined value, vibration suppression is performed to reduce the absolute value of the difference between the air fuel ratio of the rich combustion cylinder and the air fuel ratio of the lean combustion cylinder. Processing is performed, and in the component protection processing, the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder is made smaller than in the vibration suppression processing.

  In dither control, it is difficult to control the combustion state of all the cylinders to the most stable state because the air-fuel ratios of the rich combustion cylinder and the lean combustion cylinder are made different by dither control, and the combustion tends to deteriorate. Have. On the other hand, when the control of the control amount of the internal combustion engine has a predetermined abnormality or more, there is a high possibility that the combustion control has an abnormality. Therefore, when the above abnormality occurs, a tendency that the combustion by the dither control is likely to deteriorate becomes apparent, and there is a possibility that deterioration of parts of the internal combustion engine is promoted. Therefore, in the above configuration, the component protection process protects the component by reducing the absolute value of the difference between the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder. On the other hand, in the case where it is determined that a predetermined or more abnormality has not occurred and the rotation fluctuation is equal to or more than a predetermined value, the absolute value of the difference between the air fuel ratio of the rich combustion cylinder and the air fuel ratio of the lean combustion cylinder is reduced. However, the value should be larger than during part protection processing. Thereby, the deterioration of drivability can be improved as much as possible while suppressing the deterioration of exhaust components.

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.
An internal combustion engine 10 shown in FIG. 1 is mounted on a vehicle. In the internal combustion engine 10, the 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, and the intake air amount Ga detected by the air flow meter 46. refer. 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 following, the step number is represented by a number to which "S" is added at the beginning.

  In the series of processes shown in FIG. 2, the CPU 32 calculates a required injection amount Qd which is an injection amount to be injected by the fuel injection valve 18 in order to control the air fuel ratio to the target air fuel ratio (S10). Specifically, the CPU 32 first calculates the base injection amount Qb based on the rotational speed NE and the intake air amount Ga. 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. Next, the CPU 32 calculates a feedback operation amount KAF, which 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 *. Specifically, the CPU 32 sets the sum of the output values of the proportional element, the integral element, and the differential element, which receives the difference Δ between the target value Af * and the air-fuel ratio Af, as the correction ratio δ of the base injection amount Qb. Let the quantity KAF be "1 + δ". Then, the CPU 32 substitutes a value obtained by multiplying the base injection amount Qb by the feedback operation amount KAF into the required injection amount Qd. The rotational speed NE is calculated by the CPU 32 based on the output signal Scr of the crank angle sensor 44 by a process different from the process shown in FIG.

  Next, the CPU 32 determines whether there is a temperature increase request for the three-way catalyst 24 (S12). In the present embodiment, if the logical sum of the requirement for warm-up of the three-way catalyst 24 and the requirement for execution of the sulfur poisoning recovery processing is true, the requirement for temperature increase is present. judge. 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 required injection amount Qd in a process different from that of FIG.

  When determining that the temperature increase request is not made (S12: NO), the CPU 32 substitutes the required injection amount Qd for the injection amount command value Q * (S14). 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 (S16).

  On the other hand, when determining that there is a temperature increase request (S12: YES), the CPU 32 calculates a base value (base request value α0) of the correction request value (injection amount correction request value α) of the request injection amount Qd. (S18). The injection amount correction request value α targets the air-fuel ratio of the air-fuel mixture that is to be burned in all the cylinders # 1 to # 4 with the components of the entire exhaust discharged from each of the cylinders # 1 to # 4 of the internal combustion engine 10 This is the correction amount of the required injection amount Qd required by the dither control in which the air-fuel ratio of the mixture to be burned is made different among the cylinders while being made equal to the air-fuel ratio. 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 base required value α0 based on the rotational speed NE and the load factor KL that define the operating point of the internal combustion engine 10. In the present embodiment, the operating point at which the base required value α0 becomes larger than zero differs between the sulfur poisoning recovery process and the catalyst warm-up process. 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, the CPU 32 determines whether the base request value α0 is larger than zero (S20). When the CPU 32 determines that it is zero (S20: NO), the CPU 32 proceeds to the process of S14. On the other hand, when it is determined that the CPU 32 is larger than zero (S20: YES), the CPU 32 determines whether there is a request for protecting the components of the internal combustion engine 10 (S22). This process is a process of determining whether or not a predetermined abnormality or more has occurred in the control of the control amount of the internal combustion engine 10. That is, when the control of the control amount of the internal combustion engine 10 has a predetermined abnormality or more, the assumed control is not properly performed, and therefore, there is a possibility that the parts of the internal combustion engine 10 may be deteriorated. It is determined that there is Specifically, for example, when it is detected that the absolute value of the rotational fluctuation amount Δω of the crankshaft, which is grasped based on the output signal Scr of the crank angle sensor 44, becomes the specified value ΔthH or more, When the absolute value of the output value of the integral element subjected to feedback control continues to be in a predetermined state or more, it is determined that the control amount control has an abnormality equal to or more than the predetermined value. The rotational fluctuation amount Δω is a parameter for quantifying the degree of deterioration of the combustion, and the rotational speed (instant rotational speed ω) of a predetermined angular interval including only one compression top dead center is the timing at which the compression top dead center appears. Is a value obtained by subtracting the value in the cylinder in which the compression top dead center appears from the value in the cylinder in which the compression top dead center appears earlier in the pair of cylinders adjacent in time series. When the combustion is deteriorated and the torque is reduced, the rotational fluctuation amount Δω is negative and has a large absolute value.

  When it is determined that the component protection request is not made (S22: NO), the CPU 32 determines whether the absolute value of the rotational fluctuation amount Δω of the crankshaft is equal to or greater than a predetermined value ΔthL smaller than the prescribed value ΔthH (S24) ). In this process, although the control amount control does not have a predetermined abnormality or more, it is determined whether or not to cause deterioration in drivability. The base requirement value α0 is adapted to a value for keeping the drivability within the allowable range. However, there is a case where the base required value α0 is out of the allowable range of drivability due to the individual difference of the fuel injection valve 18, the aged deterioration, the aged difference caused by the individual difference of the compression ratio of the internal combustion engine 10, the deposit adhesion, etc. As may occur, the process of S24 is a process of detecting this situation.

  When it is determined that the CPU 32 is less than the predetermined value ΔthL (S24: NO), the CPU 32 substitutes the base request value α0 into the injection amount correction request value α (S26). Then, the CPU 32 determines whether the cylinder targeted for fuel injection is a rich combustion cylinder (S28). When determining that the cylinder is a rich combustion cylinder (S28: YES), the CPU 32 substitutes “Qd · (1 + α)” for the injection amount command value Q * (S30), and shifts to the process of S16. On the other hand, when determining that the cylinder is a lean combustion cylinder (S28: NO), the CPU 32 substitutes “Qd · {1- (α / 3)}” for the injection amount command value Q * (S32), It shifts to the processing of S16.

  On the other hand, when it is determined that the CPU 32 is the predetermined value ΔthL or more (S24: YES), the base request value α0 is more than a value obtained by subtracting the predetermined amount Δα from the previous injection amount correction request value α (n-1). It is determined whether it is large (S34). When it is determined that the value is equal to or less than the value obtained by the subtraction (S34: NO), the CPU 32 shifts to the processing of S26. On the other hand, when it is determined that the CPU 32 is larger than the subtracted value (S34: YES), the injection amount correction request value α is a value obtained by subtracting the predetermined amount Δα from the previous injection amount correction request value α (n-1). (S36). Next, the CPU 32 determines whether the injection amount correction request value α is smaller than the normal time lower limit value αthH (S38). Here, the CPU 32 sets the normal time lower limit value αthH separately for each of the catalyst warm-up processing and the sulfur poisoning recovery processing. In the catalyst warm-up process, the normal time lower limit value αthH is a lower limit value that can suppress the deterioration of the exhaust component to a predetermined value or less. Further, at the time of the sulfur poisoning recovery process, the normal time lower limit value αthH is set to the lower limit value at which the sulfur poisoning recovery process can be performed. Then, when it is determined that the CPU 32 is smaller than the normal time lower limit value αthH (S38: YES), the normal time lower limit value αthH is substituted for the injection amount correction request value α (S40).

  On the other hand, when determining that there is a component protection request (S22: YES), the CPU 32 determines whether the base request value α0 is larger than the failsafe upper limit value αthL (S42). The fail-safe upper limit value αthL is a value smaller than the normal time lower limit value αthH, and is an upper limit value of the injection amount correction request value α for protecting the component. Then, when it is determined that the CPU 32 is larger than the failsafe upper limit value αthL (S42: YES), the failsafe upper limit value αthL is substituted for the injection amount correction request value α (S44). On the other hand, when it is determined that the CPU 32 is equal to or less than the fail-safe upper limit value αthL (S42: NO), the CPU 32 substitutes the base request value α0 for the injection amount correction request value α (S46).

  When the processes of S26, S40, S44, and S46 are completed, or when the determination of step S38 is negative, the CPU 32 proceeds to the process of S28. When the process of S16 is completed, the CPU 32 temporarily ends the series of processes shown in FIG.

Hereinafter, the operation and effect of the present embodiment will be described.
If the CPU 32 determines that the absolute value of the rotational fluctuation amount Δω does not reach the specified value ΔthH or more when performing dither control, it improves the drivability if the CPU 32 determines that the absolute value exceeds the predetermined value ΔthL. Under the conditions described above, the injection amount correction request value α is decreased and corrected. Thereby, the drivability can be improved as much as possible while suppressing the deterioration of the exhaust components downstream of the three-way catalyst 24.

  On the other hand, when a component protection request occurs, the CPU 32 sets the injection amount correction request value α to a failsafe upper limit value αthL or less. That is, when the control of the control amount of the internal combustion engine 10 has a predetermined abnormality or more, the air-fuel ratio of the rich combustion cylinder and the air-fuel ratio of the lean combustion cylinder by dither control deviate from the theoretical air-fuel ratio The tendency becomes apparent, and there is a possibility that the deterioration of parts such as the fuel injection valve 18 of the internal combustion engine 10, the ignition device 20, and the three-way catalyst 24 may be promoted. Therefore, in order to protect those parts, the injection amount correction request value α is limited to a smaller value than when the absolute value of the rotational fluctuation amount Δω is equal to or greater than the predetermined value ΔthL.

<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 dither control processing corresponds to the processing of S18, S26 to S32, S16, the component protection processing corresponds to the processing of S42 to S46, and the vibration suppression processing corresponds to the processing of S24, S34 to S40.

<Other Embodiments>
The present embodiment can be modified as follows. The present embodiment and the following modifications can be implemented in combination with one another as long as there is no technical contradiction.

  The process of determining whether or not a predetermined abnormality or more has occurred in the control of the internal combustion engine 10 is not limited to that illustrated in the above embodiment. For example, when the exhaust gas temperature is equal to or higher than a predetermined temperature, it may be determined that a predetermined abnormality or more has occurred.

  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.

  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.

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;
When it is determined that the control of the control amount of the internal combustion engine has a predetermined abnormality or more, the air-fuel ratio of the rich combustion cylinder and the air of the lean combustion cylinder are compared with the case where it is determined that the abnormality does not occur. Component protection processing to reduce the absolute value of the difference with the fuel ratio,
The air-fuel ratio of the rich-burning cylinder and the air-fuel ratio of the lean-burning cylinder are determined when it is determined that the abnormality above the predetermined level does not occur and the rotational fluctuation of the crankshaft of the internal combustion engine is greater than the predetermined level. Execute vibration suppression processing to reduce the absolute value of the difference from the fuel ratio;
In the component protection process, a control device of an internal combustion engine which reduces an absolute value of a difference between an air-fuel ratio of the rich combustion cylinder and an air-fuel ratio of the lean combustion cylinder than the vibration suppression process.