JP7655265B2 - Control device for internal combustion engine - Google Patents

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 whether or not a misfire has occurred in a judged cylinder based on the difference between the rotational speed fluctuation of the judged cylinder that is used to judge whether or not a misfire has occurred and the rotational speed fluctuation of a reference cylinder that entered the combustion stroke before the judged cylinder.

JP 2009-138663 A

However, when the operating conditions of the internal combustion engine change, the rotational speed fluctuation of the reference cylinder also changes. Therefore, the above-mentioned difference may change due to such differences in operating conditions, which may reduce the accuracy of misfire determination.

The control device for an internal combustion engine that solves the above problem is applied to an internal combustion engine having multiple cylinders. This control device executes a determination process that determines whether or not a misfire has occurred in a determination cylinder based on the difference between an instantaneous speed variable, which is an index value of the rotation speed of the crankshaft of a determination cylinder for determining whether or not a misfire has occurred, and an average value of the instantaneous speed variables of multiple cylinders that entered the combustion stroke before the determination cylinder, and a variation process that changes the number of samples of the instantaneous speed variable when calculating the average value between a case where a predetermined default operating state is present and a case where the default operating state is not present.

According to this configuration, the average value is calculated to obtain a value that smooths out the fluctuations in the instantaneous speed variables of the multiple cylinders that entered the combustion stroke before the determined cylinder. Here, in an operating state where the combustion state becomes unstable, the number of samples taken when calculating the average value is increased, so that the effect of temporary changes in the instantaneous speed variables due to the instability of the combustion state on the average value can be suppressed, improving the accuracy of misfire determination. In addition, during transient operation, the number of samples taken when calculating the average value is reduced, so that the most recent instantaneous speed variables of the multiple cylinders that entered the combustion stroke before the determined cylinder are reflected in the average value, improving the accuracy of misfire determination.

In this configuration, the variable process is executed to vary the number of samples of the instantaneous speed variable when calculating the average value, depending on the operating state of the internal combustion engine. Therefore, an appropriate value depending on the operating state of the internal combustion engine is set as the average value. This makes it possible to prevent the accuracy of misfire determination from decreasing due to changes in the operating state of the internal combustion engine.

1 is a diagram showing a configuration of a drive system and a control device for a vehicle according to an embodiment; 4 is a flowchart showing the procedure of a misfire determination process executed by the control device of the embodiment. 4 is a time chart showing a calculation mode of an average time in the embodiment. 11 is a table showing how the number of samples is set in the embodiment;

Hereinafter, an 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 has a plurality of cylinders. For example, the internal combustion engine 10 has four cylinders, namely, cylinder #1 to cylinder #4. A throttle valve 14 is provided in an intake passage 12 of the internal combustion engine 10. A port injection valve 16 that injects fuel into the intake port 12a is provided in an intake port 12a, which is a downstream portion of the intake passage 12. Air taken into the intake passage 12 and fuel injected from the port injection valve 16 flow into a combustion chamber 20 when an intake valve 18 opens. Fuel is injected into the combustion chamber 20 from an in-cylinder injection valve 22. The mixture of air and fuel in the combustion chamber 20 is combusted in response to a spark discharge from an ignition plug 24. The combustion energy generated at that time is converted into the rotational energy of a crankshaft 26.

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

A crank rotor 40 having teeth 42 is connected to the crankshaft 26. The teeth 42 indicate each of the multiple rotation angles of the crankshaft 26. The crank rotor 40 has teeth 42 basically spaced at intervals of 10° CA, but has one missing tooth portion 44 where the interval between adjacent teeth 42 is 30° CA. This is to indicate the reference rotation angle of the crankshaft 26.

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

The control device 70 controls the internal combustion engine 10, and operates the operating parts of the internal combustion engine 10, such as the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, and spark plug 24, to control the torque and exhaust component ratio as the controlled variables. The control device 70 also controls the first motor generator 52, and operates the inverter 56 to control the rotation speed, which is the controlled variable. The control device 70 also controls the second motor generator 54, and operates the inverter 58 to control the torque, which is the controlled variable. Figure 1 shows the operation signals MS1 to MS6 of the throttle valve 14, port injection valve 16, in-cylinder injection valve 22, spark plug 24, and inverters 56 and 58.

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 in order to control the control amount of the internal combustion engine 10. The control device 70 also refers to the water temperature THW detected by the water temperature sensor 86 and the exhaust pressure Pex flowing into the GPF 34 detected by the exhaust pressure sensor 88 in order to control the control amount of the internal combustion engine 10. The control device 70 also refers to the output signal Sm1 of the first rotation angle sensor 90 that detects the rotation angle of the first motor generator 52 in order to control the control amount of the first motor generator 52. The control device 70 also refers to the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54 in order to control the control amount of the second motor generator 54. The control device 70 calculates the engine rotation speed Ne based on the output signal Scr of the crank angle sensor 82. The control device 70 also calculates the engine load rate KL based on the engine rotation speed Ne and the intake air amount Ga. The engine load ratio KL is the ratio of the current cylinder inflow air amount to the cylinder inflow air amount when the internal combustion engine 10 is operated steadily with the throttle valve 14 fully open at the current engine speed Ne. The cylinder inflow air amount is the amount of air that flows into each cylinder during the intake stroke.

The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and peripheral circuits 76, which are capable of communicating with each other via a communication line 78. Here, the peripheral circuits 76 include a circuit that generates a clock signal that regulates the internal operation, a power supply circuit, a reset circuit, etc. The control device 70 controls the control amount by the CPU 72 executing 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 cylinders from the fuel injection amount of the other cylinders. In this embodiment, as the injection amount reduction process, fuel injection is stopped in one of the four cylinders #1 to #4, and an injection stop process is executed in which fuel injection is continued in the remaining three cylinders. In the following description, a fuel cut cylinder that is a cylinder in which fuel injection is stopped in the injection stop process is referred to as an FC cylinder. Also, a cylinder in which fuel injection is continued in the injection stop process is referred to as a combustion cylinder. When the injection stop process is executed, fresh air is discharged from the FC cylinder and burned gas is discharged from the combustion cylinder into the exhaust passage 30. Then, oxygen in the fresh air and unburned fuel components in the burned gas are supplied to the three-way catalyst 32. Therefore, when the injection stop process is executed, an oxidation reaction between oxygen and unburned fuel components occurs in the three-way catalyst 32, and the heat generated by the reaction raises the temperature of the three-way catalyst 32. When the temperature of the three-way catalyst 32 is raised in this manner, the temperature of the gas passing through the three-way catalyst 32 also rises, so that the temperature of the GPF 34 also rises.

The control device 70 performs the above-mentioned injection stop process in the catalyst early activation control executed during a cold start of the internal combustion engine 10. The control device 70 also performs the above-mentioned injection stop process in the filter regeneration control for purifying PM accumulated in the GPF 34.

<Rapid warm-up control>
The control device 70 executes rapid warm-up control when there is a request for rapid warm-up to rapidly increase the temperature of the three-way catalyst 32. As this rapid warm-up control, the control device 70 executes, for example, a large amount of ignition timing retardation to a degree that is not executed during steady operation.

<Misfire Detection Processing>
The control device 70 executes a misfire determination process shown in FIG.

Figure 2 shows the procedure for the misfire determination process executed by the control device 70 according to this embodiment. The process shown in Figure 2 is realized by the CPU 72 repeatedly executing a program stored in the ROM 74, for example at a predetermined interval. In the following, the step number of each process is represented by a number preceded by "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 ATDC 30° CA with respect to the compression top dead center of any of the cylinders #1 to #4 (S30).

When the CPU 72 determines that the cylinder is ATDC 30° CA (S30: YES), it executes the process of S34. In the process of S34, the CPU 72 determines the cylinder determined to be ATDC 30° CA as the determination cylinder for determining the presence or absence of misfire, and acquires the time T30[0] required for the crankshaft 26 to rotate 30° CA from the compression top dead center. This time T30[0] is an instantaneous speed variable that is an index value of the rotational speed of the crankshaft 26 of the determination cylinder for determining the presence or absence of misfire.

Next, the CPU 72 obtains the average time T30 [AVE] (S36). This average time T30 [AVE] is the average value of the times T30 [0] for the multiple cylinders that entered the combustion stroke before the above-mentioned determined cylinder, and is calculated by the CPU 72.

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

In FIG. 3, the time T30[0] of the current judged cylinder (cylinder #1 shown by a black circle in the example of FIG. 3) is designated as judged cylinder T30(n). In the following, each of the cylinders that entered the combustion stroke before the judged cylinder and from which the time T30[0] is obtained when calculating the average time T30[AVE] is referred to as a reference cylinder. The time T30[0] of each reference cylinder is represented as reference cylinder T30(n-m). Here, the number of reference cylinders obtained when calculating the average time T30[AVE] is the sampling number S, and "m" is a value given as "m=1, 2, 3, ..., S", and the larger the value of m, the earlier the combustion cylinder is.

Then, the CPU 72 calculates the arithmetic mean of all the times T30[0] of the multiple reference cylinders T30(n-m) that have been acquired, and substitutes the calculated value for the average time T30[AVE].
<Variable processing>
Here, the CPU 72 executes a variable process when calculating the average time T30 [AVE]. This variable process is a process for making the number of samplings S of the time T30 [0] when calculating the average time T30 [AVE] different between a case where the driving state is a predetermined default driving state and a case where the driving state is not the default driving state. More specifically, a first driving state, a second driving state, a third driving state, and a fourth driving state are defined in advance. The number of samplings S is set for each driving state.

FIG. 4 shows the number of samples S for each operating state.
In this embodiment, three sampling numbers S1, S2, and S3 are preset as the sampling number S. The magnitude relationship between these three sampling numbers S is "S1>S2>S3".

The first operating state is an operating state in which the combustion state of the internal combustion engine 10 becomes extremely unstable. For example, when the engine is started at a low temperature where the water temperature THW is equal to or lower than the predetermined threshold value THWref, and at least one of the above-mentioned injection amount reduction process or rapid warm-up control is being performed, the CPU 72 determines that the current engine operating state is the first operating state. When determining that the engine is in the first operating state, the CPU 72 sets the sampling number S to "S1".

The second operating state is an operating state in which the combustion state of the internal combustion engine 10 becomes unstable. The CPU 72 determines that the current engine operating state is the second operating state when, for example, at least one of the above-mentioned injection amount reduction processing or rapid warm-up control is being performed. When it is determined that the engine is in the second operating state, the CPU 72 sets the sampling number S to "S2".

The third operating state is an operating state in which the internal combustion engine 10 is in a transient operating state. The CPU 72 determines that the current engine operating state is the third operating state, for example, when the rate of change of the engine speed Ne or the rate of change of the engine load factor KL is equal to or greater than a predetermined threshold value. When determining that the engine is in the third operating state, the CPU 72 sets the sampling number S to "S3".

The fourth operating state is an operating state in which the combustion state of the internal combustion engine 10 is stable. The CPU 72 determines that the current engine operating state is the fourth operating state, for example, when the internal combustion engine 10 has completed warming up and the above-mentioned injection amount reduction process is not being executed. In this fourth operating state, the difference in time T30[0] between each cylinder is small, so the effect of the sampling number S on the average time T30[AVE] is small. Therefore, when determining that the fourth operating state is present, the CPU 72 sets the sampling number S to the smallest value, "S3."

Next, the CPU 72 executes the process of S38 shown in FIG. 2. 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 of S34, and assigning the result to the rotation fluctuation amount ΔT30. If there is no misfire in the judged cylinder, the time T30 [0] will be a value close to the average time T30 [AVE]. On the other hand, if there is a misfire in the judged cylinder, the time T30 [0] will be a value greater than the average time T30 [AVE]. Therefore, the rotation fluctuation amount ΔT30 will be a value close to 0 if there is no misfire in the cylinder to be judged for the presence or absence of misfire, and will be a positive value if there is a misfire.

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

When the CPU 72 has completed the process of S42 or when a negative determination is made in each of the processes of S30 and S40, the CPU 72 temporarily ends the series of processes shown in FIG.
<Action and Effects>
The operation and effects of this embodiment will be described.

When determining whether a misfire has occurred, the average time T30 [AVE] is calculated to obtain a value that smooths out the fluctuations in the time T30 [0] of the multiple cylinders that entered the combustion stroke before the determined cylinder. Here, in an operating state in which the combustion state becomes unstable, the number of samples S used to calculate the average time T30 [AVE] is increased to reduce the effect on the average time T30 [AVE] of temporary changes in the time T30 [0] due to the destabilization of the combustion state. This improves the accuracy of misfire determination.

In addition, during transient operation, the number of samples S used to calculate the average time T30 [AVE] is reduced, so that the most recent times T30 [0] for multiple cylinders that entered the combustion stroke before the judged cylinder are reflected in the average time T30 [AVE]. This improves the accuracy of misfire judgement.

On the other hand, during transient operation, the time T30[0] changes over time with changes in the engine speed Ne and the engine load factor KL. Therefore, during such transient operation, it is preferable to calculate the average time T30[AVE] based on the time T30[0] of the most recent cylinder that entered the combustion stroke before the judgment cylinder, thereby bringing the average time T30[AVE] closer to the most recent time T30[0]. Therefore, during transient operation, by reducing the number of samples S used to calculate the average time T30[AVE], the most recent time T30[0] is reflected in the average time T30[AVE] for multiple cylinders that entered the combustion stroke before the judgment cylinder. This improves the accuracy of misfire judgment.

Therefore, in this embodiment, the above-mentioned variable process is performed to change the number of samples S of time T30[0] when calculating the average time T30[AVE] depending on the operating state of the internal combustion engine 10.

More specifically, in the second operating state where the combustion state of the internal combustion engine 10 becomes unstable, the sampling number S is set to "S2", which is a larger number of samples than "S1". In the first operating state where the combustion state of the internal combustion engine 10 becomes extremely unstable, the sampling number S is set to "S1", which is a larger number of samples than "S2". In the third operating state where the internal combustion engine 10 is in a transient operating state, the sampling number S is set to "S3", which is a smaller number of samples than "S2".

By making the sampling number S variable in this way, an appropriate value is set for the average time T30 [AVE] according to the operating state of the internal combustion engine 10. Therefore, it is possible to prevent the accuracy of misfire determination from decreasing due to changes in the operating state of the internal combustion engine 10.

<Example of change>
The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

Although four operating states are defined as the operating states for which the sampling number S is variably set, the number of operating states defined may be changed as appropriate.
Although the above description includes the cases where the combustion state of the internal combustion engine 10 becomes unstable during the injection amount reduction process and the rapid warm-up control, the operating state may be unstable during other engine control.

The sampling number S set in the third operating state and the fourth operating state was the same, "S3." Alternatively, the sampling number S set in the third operating state and the fourth operating state may be different values that are smaller than "S2."

- Of the multiple reference cylinders T30(n-m) obtained, the top L cylinders with the shortest times T30[0] are selected. The arithmetic mean of the selected L times T30[0] may then be set as the average time T30[AVE].

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

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

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

- The number of cylinders for which fuel injection is stopped when the injection stop process described above is executed is "1", but the number of cylinders for which fuel injection is stopped can be changed as appropriate, with the maximum value being "number of cylinders - 1". Also, it is not essential to fix the cylinders for which fuel injection is stopped to a predetermined cylinder. For example, the cylinders for 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, the fuel injection amount of some of the cylinders among the multiple cylinders may be reduced more than the fuel injection amount of the other cylinders, so that the air-fuel ratio of the mixture in those cylinders is made leaner than the stoichiometric air-fuel ratio. Then, for the remaining cylinders, dither control may be used to make the air-fuel ratio of the 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. Furthermore, the GPF 34 is not limited to being provided downstream of the three-way catalyst 32 in the exhaust passage 30. Furthermore, it is not essential to have a GPF 34 as an exhaust purification device. For example, even if the exhaust purification device is composed of only a three-way catalyst 32, it is effective to execute the process exemplified in the above embodiment and modified example when supplying oxygen to a three-way catalyst 32 whose oxygen storage amount is below a specified value by stopping the fuel supply to some cylinders.

The control device is not limited to a device equipped with a CPU 72 and a ROM 74 and executing software processing. For example, it may be equipped with a dedicated hardware circuit such as an ASIC that performs hardware processing of at least a portion of what was processed by software in the above embodiment. 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 program storage device that executes a portion of the above processing according to a program, and a dedicated hardware circuit that executes the remaining processing. (c) It includes a dedicated hardware circuit that executes all of the above processing. Here, there may be multiple software execution devices equipped with a processing device and program storage device, and multiple dedicated hardware circuits.

The vehicle is not limited to a series-parallel hybrid vehicle, but may be, for example, a parallel hybrid vehicle or a series hybrid vehicle. However, the vehicle is not limited to a hybrid vehicle, and may be, for example, a vehicle whose power generating device is only an internal combustion engine 10.

Reference Signs List 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
Reference Signs List 40: crank rotor 50: planetary gear mechanism 52: first motor generator 54: second motor generator 60: driving 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)

It is applied to an internal combustion engine having multiple cylinders,
a determination process for determining whether or not a misfire has occurred in a determination cylinder based on a difference between an instantaneous speed variable, which is an index value of the rotation speed of a crankshaft of a determination cylinder for which the presence or absence of a misfire has been determined, and an average value of the instantaneous speed variables of a plurality of cylinders which have entered a combustion stroke prior to the determination cylinder;
a varying process for varying the number of samples of the instantaneous speed variable when calculating the average value between a case where a predetermined operating state is in progress and a case where the operating state is not in progress.

Images