JP2023139771A - Controller of internal combustion engine - Google Patents

Abstract

To suppress deterioration in determination accuracy for accidental fire.SOLUTION: A CPU 72 executes: an injection amount reduction process of more reducing a fuel injection amount of some cylinders among a plurality of cylinders than a fuel injection amount of the other cylinders; and a determination process of determining the presence or absence of accidental fire in a determination cylinder based on the difference between an instantaneous speed variable, which is an index value of a rotational speed of a crankshaft of the determination cylinder that determines the presence or absence of accidental fire, and an average value of the instantaneous speed variables of the plurality of cylinders that are in the combustion stroke before the determination cylinder. Then, the CPU 72 executes a process of calculating an average value by excluding the instantaneous speed variables of some cylinders that have executed the injection amount reduction process.SELECTED DRAWING: Figure 1

Description

The present invention relates to a control device for an internal combustion engine.

For example, the control device for an internal combustion engine described in Patent Document 1 determines the presence or absence of a misfire based on the difference between the rotational speed fluctuation of a judgment cylinder and the rotational speed fluctuation of a cylinder that entered the combustion stroke before the judgment cylinder. Determine whether or not there is a misfire in the determination cylinder.

Japanese Patent Application Publication No. 2009-138663

Incidentally, in an internal combustion engine, an injection amount reduction process is sometimes executed to reduce the fuel injection amount of some cylinders among a plurality of cylinders compared to the fuel injection amount of other cylinders. When this injection amount reduction process is executed, the combustion state of the air-fuel mixture becomes different from the normal state. Therefore, the above-mentioned difference changes due to the execution of the injection amount reduction process, which may reduce the accuracy of misfire determination.

A control device for an internal combustion engine that solves the above problems is applied to an internal combustion engine having a plurality of cylinders. This control device performs an injection amount reduction process that reduces the fuel injection amount of some of the plurality of cylinders compared to the fuel injection amount of other cylinders, and controls the crankshaft of the judgment cylinder to determine the presence or absence of a misfire. The presence or absence of a misfire in the judgment cylinder is determined based on the difference between an instantaneous speed variable that is an index value of the rotational speed and an average value of the instantaneous speed variables of a plurality of cylinders that entered a combustion stroke before the judgment cylinder. Execute the determination process. Then, the control device executes a process of calculating the average value by excluding the instantaneous speed variables of the some of the cylinders that have undergone the injection amount reduction process.

According to this configuration, the instantaneous speed variable of the cylinder that has undergone the injection amount reduction process is not reflected in the average value. Therefore, the adverse effect of the injection amount reduction process on the average value is suppressed, so that it is possible to suppress a decrease in misfire determination accuracy.

1 is a diagram showing the configuration of a drive system and a control device of a vehicle according to an embodiment. 5 is a flowchart showing the procedure of a misfire determination process executed by the control device of the embodiment. It is a time chart which shows the calculation aspect of the average time in the same embodiment.

Hereinafter, one embodiment of a control device for an internal combustion engine will be described with reference to the drawings.
<Vehicle configuration>
As shown in FIG. 1, an internal combustion engine 10 mounted on a vehicle includes four cylinders, cylinder #1 to cylinder #4. A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10 . An intake port 12a, which is a downstream portion of the intake passage 12, is provided with a port injection valve 16 that injects fuel into the intake port 12a. Air taken into the intake passage 12 and fuel injected from the port injection valve 16 flow into the combustion chamber 20 as the intake valve 18 opens. Fuel is injected into the combustion chamber 20 from an in-cylinder injection valve 22 . Furthermore, the mixture of air and fuel within the combustion chamber 20 is subjected to combustion as a result of spark discharge from the ignition plug 24. The combustion energy generated at that time is converted into rotational energy of the crankshaft 26.

The air-fuel mixture subjected to combustion in the combustion chamber 20 is discharged into the exhaust passage 30 as exhaust gas when the exhaust valve 28 is opened. The exhaust passage 30 is provided with a three-way catalyst 32 having an oxygen storage capacity and a gasoline particulate filter (GPF 34). In this embodiment, it is assumed that the GPF 34 is a filter that collects PM and supports a three-way catalyst.

A crank rotor 40 provided with teeth 42 is coupled to the crankshaft 26 . The tooth portion 42 indicates each of a plurality of rotation angles of the crankshaft 26. Although the crank rotor 40 is basically provided with tooth portions 42 at intervals of 10° CA, there is one missing tooth portion 44 where the interval between adjacent tooth portions 42 is 30° CA. It is provided. This is to indicate the reference rotation angle of the crankshaft 26.

The crankshaft 26 is mechanically connected to a carrier C of a planetary gear mechanism 50 that constitutes a power split device. A rotating shaft 52a of a first motor generator 52 is mechanically connected to the sun gear S of the planetary gear mechanism 50. Further, the ring gear R of the planetary gear mechanism 50 is mechanically connected to the rotation shaft 54a of the second motor generator 54 and the drive wheel 60. An alternating current voltage is applied to the terminals of the first motor generator 52 by an inverter 56 . Furthermore, an AC voltage is applied to the terminals of the second motor generator 54 by an inverter 58 .

The control device 70 controls the internal combustion engine 10, and controls the throttle valve 14, the port injection valve 16, the in-cylinder injection valve 22, the spark plug 24, etc. in order to control the internal combustion engine 10, such as torque and exhaust component ratio as control variables. The operator operates the operating section of the internal combustion engine 10 of the engine. Further, the control device 70 controls the first motor generator 52, and operates the inverter 56 to control the rotational speed, which is a control amount of the first motor generator 52. Further, the control device 70 controls the second motor generator 54 and operates the inverter 58 to control the torque that is the control amount of the second motor generator 54 . FIG. 1 shows operation signals MS1 to MS6 for the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, spark plug 24, and inverters 56 and 58, respectively.

In order to control the control amount of the internal combustion engine 10, the control device 70 refers to the intake air amount Ga detected by the air flow meter 80 and the output signal Scr of the crank angle sensor 82. Further, in order to control the control amount of the internal combustion engine 10, the control device 70 refers to the water temperature THW detected by the water temperature sensor 86 and the pressure Pex of the exhaust gas flowing into the GPF 34 detected by the exhaust pressure sensor 88. Furthermore, in order to control the control amount of the first motor generator 52, the control device 70 refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor generator 52. Furthermore, in order to control the control amount of the second motor generator 54, the control device 70 refers to the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54.

The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and a peripheral circuit 76, which can communicate with each other via a communication line 78. Here, the peripheral circuit 76 includes a circuit that generates a clock signal that defines internal operations, a power supply circuit, a reset circuit, and the like. The control device 70 controls the control amount by having the CPU 72 execute a program stored in the ROM 74 .

<Injection amount reduction process>
As part of the process of controlling the internal combustion engine 10, the control device 70 executes an injection amount reduction process that reduces the fuel injection amount of some of the plurality of cylinders compared to the fuel injection amount of other cylinders. In this embodiment, as the injection amount reduction process, an injection stop process is performed in which fuel injection is stopped in one of the four cylinders #1 to #4, and fuel injection is continued in the remaining three cylinders. In the following description, the fuel cut cylinder, which is the cylinder in which fuel injection is stopped in the injection stop process, will be referred to as an FC cylinder. Further, a cylinder in which fuel injection is continued during the injection stop processing is referred to as a combustion cylinder. When the injection stop process is executed, fresh air is discharged from the FC cylinder and burnt gas is discharged from the combustion cylinder to the exhaust passage 30. Then, oxygen in the fresh air and unburned fuel components in the burnt gas are supplied to the three-way catalyst 32. Therefore, when the injection stop process is performed, an oxidation reaction between oxygen and unburned fuel components occurs in the three-way catalyst 32, and the temperature of the three-way catalyst 32 increases due to the heat generated by the reaction. When the temperature of the three-way catalyst 32 is raised in this way, the temperature of the gas passing through the three-way catalyst 32 increases, and therefore the temperature of the GPF 34 increases.

The control device 70 executes the injection stop processing in the catalyst early activation control executed when the internal combustion engine 10 is cold started. Further, the control device 70 also performs the injection stop processing in filter regeneration control for purifying PM accumulated in the GPF 34.

<Missfire determination process when executing injection stop process>
During execution of the injection stop process described above, the combustion state is different between the FC cylinder and the combustion cylinder. Therefore, during execution of the injection stop process, the control device 70 executes the misfire determination process shown in FIG. 2.

FIG. 2 shows the procedure of misfire determination processing executed by the control device 70 according to this embodiment. The process shown in FIG. 2 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example, at a predetermined period. Note that in the following, the step number of each process is expressed by a number prefixed with "S".

In the series of processes shown in FIG. 2, the CPU 72 first determines whether the current rotation angle of the crankshaft 26 is 30° CA ATDC with respect to the compression top dead center of any of the cylinders #1 to #4. Determination is made (S30).

When the CPU 72 determines that the ATDC is 30° CA (S30: YES), the CPU 72 determines whether or not injection stop processing has been executed in the cylinder for which the ATDC is determined to be 30° CA (S32). That is, it is determined whether the cylinder determined to be ATDC 30° CA is an FC cylinder.

When determining that the injection stop process is not being executed (S32: YES), the CPU 72 executes the process of S34. In the process of S34, the CPU 72 selects the cylinder determined to be ATDC 30° CA as the determination cylinder for determining the presence or absence of a misfire, and calculates the time T30[ required for the crankshaft 26 to rotate 30° CA from compression top dead center. 0]. This time T30[0] is an instantaneous speed variable that is an index value of the rotational speed of the crankshaft 26 of the cylinder to be judged for determining the presence or absence of a misfire.

Next, the CPU 72 obtains the average time T30 [AVE] (S36). This average time T30[AVE] is the average value of each time T30[0] in a plurality of cylinders that entered the combustion stroke before the above-described determined cylinder, and is calculated by the CPU 72.

FIG. 3 shows how the average time T30 [AVE] is calculated. Note that the Y axis shown in FIG. 3 is the angular velocity of the crankshaft 26, and the larger the value of the angular velocity, the smaller the value of the above-mentioned time T30[0].

In FIG. 3, the time T30[0] of the currently determined cylinder (in the example of FIG. 3, cylinder #1 indicated by a black circle) is defined as the determined cylinder T30(n). In addition, each cylinder that is a plurality of cylinders that entered the combustion stroke before the determination cylinder and whose time T30[0] is obtained when calculating the average time T30[AVE] is referred to as a reference cylinder. Then, the time T30[0] of each reference cylinder is expressed as reference cylinder T30 (nm). Here, "m" is "m=1, 2, 3, ..., S", where S is the number of reference cylinders acquired when calculating the average time T30 [AVE] (10 in the example of FIG. 3). The larger the value of m, the more the cylinder has been burned in the past. Here, the CPU 72 excludes the FC cylinder from the reference cylinders (in the example of FIG. 3, cylinder #3 indicated by a black square). That is, the CPU 72 excludes the FC cylinder time T30[0] when calculating the average time T30[AVE]. Then, the CPU 72 calculates an average value for the top L cylinders with the smallest time T30[0] among the plurality of reference cylinders T30 (nm) obtained. For example, as shown in Figure 3, T30(n-9), T30(n-8), T30(n-6), T30(n-5), and T30(n-1) are respectively indicated by black triangles. The average value for the five pieces is calculated. Then, the calculated value is substituted for the average time T30 [AVE].

Next, the CPU 72 executes the process of S38 shown in FIG. In this S38, the CPU 72 executes a process of subtracting the average time T30[AVE] obtained in S36 from the time T30[90] obtained in the process in S34, and assigning it to the rotational fluctuation amount ΔT30. If no misfire has occurred in the determined cylinder, time T30[0] has a value close to average time T30[AVE]. On the other hand, when a misfire occurs in the determined cylinder, time T30[0] takes a value larger than average time T30[AVE]. Therefore, the rotational fluctuation amount ΔT30 takes a value close to 0 when no misfire occurs in the cylinder to be determined as to whether or not there is a misfire, and takes a positive value when a misfire occurs.

Next, the CPU 72 determines whether the rotational variation amount ΔT30 is greater than or equal to the determination value Δth (S40). The determination value Δth is set to a value that the rotational fluctuation amount ΔT30 can take when a misfire occurs.

If the CPU 72 determines that the rotational fluctuation amount ΔT30 is greater than or equal to the determination value Δth (S40: YES), the CPU 72 determines that there is a misfire (S42). Note that if it is determined in the process of S42 that there is a misfire, the CPU 72 performs a process such as incrementing the misfire counter Cmf.

When the CPU 72 completes the process of S42, makes a negative determination in each of S30 and S40, or makes an affirmative determination in the process of S32, the CPU 72 temporarily ends the series of processes shown in FIG.

<Action and effect>
The operation and effects of this embodiment will be explained.
The time T30[0] of the FC cylinder is longer than the time T30[0] of the combustion cylinder. Therefore, if the time T30[0] of the FC cylinder is included when calculating the average time T30[AVE] described above, the average time T30[AVE] becomes large. As the average time T30[AVE] increases, the difference from the time T30[0] becomes smaller, that is, the rotational fluctuation amount ΔT30 becomes smaller, so there is a possibility that the rotational fluctuation amount ΔT30 is determined to be less than the above-described determination value Δth. It gets expensive. Therefore, even if the cylinder to be determined is misfiring, the misfire cannot be detected, and there is a risk that the misfire determination accuracy may be reduced.

On the other hand, if the above-mentioned judgment value Δth is made small in advance in anticipation that the rotational fluctuation amount ΔT30 will become smaller as the average time T30 [AVE] increases in this way, the above-mentioned decrease in judgment accuracy can be suppressed. It is possible. However, in this case, there is a high possibility that the rotational fluctuation amount ΔT30 calculated when the determined cylinder has not misfired is determined to be equal to or greater than the determined value Δth. Therefore, even though there is no misfire in the cylinder to be determined, it may be erroneously determined that there is a misfire, and in this case as well, there is a risk that the misfire determination accuracy may be reduced.

In this regard, in the present embodiment, the time T30[0] of the FC cylinder in which the injection stop process was executed is not reflected in the average time T30[AVE]. Therefore, the above-mentioned adverse effect that the injection stop process has on the average time T30 [AVE] is suppressed, so that it is possible to suppress a decrease in misfire determination accuracy due to execution of the injection stop process.

<Example of change>
Note that the above embodiment can be modified and implemented as follows. The above embodiment and the following modification examples can be implemented in combination with each other within a technically consistent range.

- When calculating the average time T30 [AVE], the same cylinder as the determined cylinder may be used as a reference cylinder among a plurality of cylinders that have entered the combustion stroke before the determined cylinder. In this case, the influence of a steady difference in output torque between cylinders on the average time T30 [AVE] can be suppressed, so that the misfire determination accuracy increases.

- When calculating the average time T30[AVE], the average value was calculated for the top L cylinders with the smallest time T30[0] among the plurality of reference cylinders T30 (nm) obtained. Alternatively, an average value whose numerator is the sum of all the values of the plurality of reference cylinders T30 (nm) obtained may be calculated and the calculated value may be substituted for the average time T30 [AVE].

- In the above embodiment, the crank angle range that defines the instantaneous speed variable, which is a variable indicating the rotational speed of the crankshaft 26, is set to 30° CA, but it is not limited to this. In short, the variable may be any variable that indicates the rotational speed of the crankshaft 26 in a crank angle range that is equal to or less than the interval between compression top dead centers, and may be, for example, 10° CA. Alternatively, it may be, for example, the interval itself between compression top dead centers.

- The instantaneous velocity variable is not limited to a quantity having a time dimension, but may be a quantity having a velocity dimension, for example.
- In the above embodiment, the rotational fluctuation amount ΔT30 is the difference between the instantaneous speed variables, but it is not limited to this. For example, it may be a difference between instantaneous speed variables.

- The control for executing the injection stop process is not limited to the example described above. For example, the process may include stopping fuel supply to some cylinders in order to adjust the output of the internal combustion engine 10. Alternatively, for example, when an abnormality occurs in some cylinders, the fuel supply to the cylinders may be stopped. Also, for example, if the oxygen storage amount of the three-way catalyst 32 is below a specified value, control is executed to stop fuel supply to only some cylinders and set the air-fuel ratio of the air-fuel mixture in the remaining cylinders to the stoichiometric air-fuel ratio. It may also be a process of

・The number of cylinders for which fuel injection is stopped when executing the injection stop process described above was "1", but the number of cylinders for which fuel injection is stopped may be changed as appropriate with the maximum value being "number of cylinders - 1". Can be done. Further, it is not essential to fix the cylinder in which fuel injection is to be stopped to a predetermined cylinder. For example, the cylinder in which fuel injection is stopped may be changed every combustion cycle.

- The injection amount reduction process is not limited to the injection stop process described above. For example, by reducing the fuel injection amount in some of the cylinders compared to the fuel injection amount in the other cylinders, the air-fuel ratio of the air-fuel mixture in the certain cylinders can be made leaner than the stoichiometric air-fuel ratio. do. For the remaining cylinders, dither control may be performed to make the air-fuel ratio of the air-fuel mixture the stoichiometric air-fuel ratio or richer than the stoichiometric air-fuel ratio.

- The GPF 34 is not limited to a filter carrying a three-way catalyst, and may be a filter alone. Further, the GPF 34 is not limited to one provided downstream of the three-way catalyst 32 in the exhaust passage 30. Moreover, it is not essential to provide the GPF 34 as an exhaust purification device. For example, even if the exhaust purification device consists of only the three-way catalyst 32, by stopping the fuel supply to some cylinders, the oxygen storage capacity of the three-way catalyst 32 whose oxygen storage amount is below the specified value can be increased. When supplying the data, it is effective to execute the processes exemplified in the above embodiments and modified examples.

- The control device is not limited to one that includes a CPU 72 and a ROM 74 and executes software processing. For example, a dedicated hardware circuit such as an ASIC may be provided to process at least a part of what was processed by software in the above embodiments by hardware. That is, the control device may have any of the following configurations (a) to (c). (a) It includes a processing device that executes all of the above processing according to a program, and a program storage device such as a ROM that stores the program. (b) It includes a processing device and a program storage device that execute part of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) A dedicated hardware circuit is provided to execute all of the above processing. Here, there may be a plurality of software execution devices including a processing device and a program storage device, and a plurality of dedicated hardware circuits.

- The vehicle is not limited to a series/parallel hybrid vehicle, but may be a parallel hybrid vehicle or a series hybrid vehicle, for example. However, the present invention is not limited to a hybrid vehicle, and may be a vehicle in which the power generation device of the vehicle is only the internal combustion engine 10, for example.

10... Internal combustion engine 12... Intake passage 12a... Intake port 14... Throttle valve 16... Port injection valve 18... Intake valve 20... Combustion chamber 22... In-cylinder injection valve 24... Spark plug 26... Crankshaft 28... Exhaust valve 30... Exhaust Passage 32...Three-way catalyst 34...GPF
40... Crank rotor 50... Planetary gear mechanism 52... First motor generator 54... Second motor generator 60... Drive wheel 70... Control device 72... CPU
74...ROM
80... Air flow meter 82... Crank angle sensor 86... Water temperature sensor 90... First rotation angle sensor 92... Second rotation angle sensor

Claims (1)

Applied to internal combustion engines with multiple cylinders,
an injection amount reduction process that reduces the fuel injection amount of some cylinders among the plurality of cylinders than the fuel injection amount of other cylinders;
The difference between the instantaneous speed variable, which is an index value of the rotational speed of the crankshaft of the judgment cylinder for determining the presence or absence of misfire, and the average value of the instantaneous speed variables of the plurality of cylinders that entered the combustion stroke before the judgment cylinder. a determination process for determining whether or not there is a misfire in the determination cylinder based on the determination;
A control device for an internal combustion engine that executes a process of calculating the average value by excluding the instantaneous speed variables of the some of the cylinders in which the injection amount reduction process has been performed.

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