Internal Combustion Engine Misfire Detection Device and Method

Abstract

The present invention provides a misfire detection device and method for an internal combustion engine. The CPU calculates a rotational momentum change (ΔT30) of a determination object by subtracting a value of a cylinder that had the previous compression top dead center from a value of a cylinder that is a determination object for misfire of a time (T30) required for the crankshaft to rotate 30° CA from the compression top dead center. When the rotational momentum change (ΔT30) is for a cylinder in which combustion control is stopped, the rotational momentum change (ΔT30) is set as a reference value (ΔT30ref). In contrast, in the case of a cylinder in which combustion control is being executed, when the absolute value of the difference between the rotational momentum change (ΔT30) and the reference value (ΔT30ref) is equal to or less than a determination value (Δth), it is determined that misfire has occurred.

Description

Technical Field

[0001] The present invention relates to an in-cylinder misfire detection device and method for an internal combustion engine. Background Art

[0002] In Japanese Unexamined Patent Application Publication No. 2009-138663, a device for determining the presence or absence of misfire based on the rotational momentum of a crankshaft is described. In this device, the rotational momentum is defined by the difference between the rotational speed of the crankshaft during the combustion stroke of the cylinder to be determined and the rotational speed of the crankshaft during the previous combustion stroke. Further, in this device, when the difference between the rotational momentum related to the cylinder to be determined and the rotational momentum 360°CA before exceeds a threshold value, it is determined that misfire has occurred.

[0003] The inventors conducted the following research: When the shaft torque of an internal combustion engine is not zero, in order to perform the regeneration process of an exhaust after-treatment device, only the combustion control of a part of the cylinders is stopped, the air-fuel ratio of the remaining cylinders is made richer than the stoichiometric air-fuel ratio, and unburned fuel and oxygen are supplied to the exhaust. In this case, it is conceivable to calculate the rotational momentum 360°CA before based on the rotational speed of the cylinders in which a part of the combustion control is stopped. This may lead to a false determination of misfire. Summary of the Invention

[0004] In order to solve the above problems, according to a first aspect of the present invention, there is provided an in-cylinder misfire detection device for an internal combustion engine. The internal combustion engine has a plurality of cylinders. The misfire detection device performs the following processes: a stop process for stopping the combustion control of the air-fuel mixture in a part of the plurality of cylinders; a combustion variable acquisition process for acquiring a value of a combustion variable, which is a variable representing the combustion state in each of the plurality of cylinders and is determined based on the detection value of a sensor that detects a physical quantity corresponding to the combustion state of the air-fuel mixture in each of the plurality of cylinders; and a determination process for, when the stop process is executed, using the cylinders in which the combustion control has been performed as the cylinders to be determined for the presence or absence of misfire, and determining that misfire has occurred in the determination target cylinders when the deviation degree of the value of the combustion variable in the determination target cylinders with respect to the value of the combustion variable in the cylinders that are the targets of the stop process is equal to or less than a predetermined degree.

[0005] The value of the combustion variable of the cylinders in which the stop process has been executed is equal to the value of the combustion variable of the cylinders in which misfire has occurred despite the execution of the combustion control. Therefore, in the above structure, the value of the combustion variable of the cylinders that are the targets of the stop process is used as a reference value. Further, when the deviation degree of the value of the combustion variable of the cylinders related to the determination target with respect to the reference value is small, it is determined that misfire has occurred. Thus, even when the stop process is executed, the determination process for the presence or absence of misfire can be appropriately performed.

[0006] Preferably, in the above-described misfire detection device, the sensor is a crank angle sensor, the combustion variable is the rotational momentum of the crankshaft of the internal combustion engine, the rotational momentum is a variable related to the difference in magnitude of a plurality of instantaneous speed variables, the instantaneous speed variable is a variable representing the rotational speed of the crankshaft in a predetermined angular interval equal to or less than the occurrence interval of the top dead center of compression of the internal combustion engine, and among the plurality of instantaneous speed variables corresponding to the rotational momentum of a specific cylinder among the plurality of cylinders, the instantaneous speed variable during the period between the top dead center of compression of the specific cylinder and the next top dead center of compression is included.

[0007] The rotational motion of the crankshaft during the period between the top dead center of compression of a specific cylinder and the next top dead center of compression has a strong correlation with the presence or absence of misfire in the specific cylinder. Therefore, by using the instantaneous speed variable related to this period to form the rotational momentum related to the specific cylinder, the rotational momentum can be set to a quantity that accurately represents the presence or absence of misfire in the specific cylinder.

[0008] In the above-described misfire detection device, preferably, the determination process is as follows: when the deviation amount of the rotational momentum of the cylinder to be determined with respect to the rotational momentum of the cylinder that is the object of the stop process is equal to or less than a predetermined specified amount, it is determined that misfire has occurred in the cylinder to be determined, and the specified amount is a fixed value.

[0009] The rotational momentum corresponding to the presence or absence of misfire varies according to the rotational speed of the crankshaft and the load of the internal combustion engine. On the other hand, the rotational momentum in the cylinder that is the object of the stop process is a quantity corresponding to the rotational speed of the crankshaft and the load of the internal combustion engine. Therefore, in the above structure, the rotational momentum in the cylinder that is the object of the stop process is used as a reference value, and when the deviation amount between the rotational momentum of the cylinder executing combustion control and the reference value is equal to or less than the specified amount that is a fixed value, it is determined that misfire has occurred. Thereby, the man-hours suitable for the determination process of the presence or absence of misfire can be reduced.

[0010] In the above-described misfire detection device, preferably, the misfire detection device is configured to execute the stop process on the condition that the rotational speed of the crankshaft of the internal combustion engine is equal to or higher than a specified speed.

[0011] The rotational energy of the crankshaft is proportional to the square of the rotational speed. Therefore, when the rotational speed is low, the change ratio of the rotational speed with respect to the energy supplied to the crankshaft becomes larger compared to the case of high rotational speed. Thus, in the low rotational region, if misfire occurs in the cylinder where the compression top dead center appears after the cylinder to be subjected to the stop process, the decrease in rotational speed may be greater than that of the cylinder to be subjected to the stop process. In contrast, in the above structure, the stop process is executed on the condition that the rotational speed is equal to or higher than a specified speed. Thereby, the difference that may occur in the rotational momentum becomes smaller between the cylinder to be subjected to the stop process and the cylinder where combustion control is executed. Therefore, even if the specified amount in the above structure is set to a fixed value, it is possible to accurately determine the presence or absence of misfire.

[0012] In the above misfire detection device, it is preferable that the misfire detection device is configured to execute the stop process on the condition that the torque of the internal combustion engine is equal to or higher than a specified value.

[0013] When the torque of the internal combustion engine is large, the decrease in the determination accuracy of misfire caused by the tolerance of the crank angle sensor becomes smaller compared to the case of small torque. In this regard, according to the present invention, the stop process is executed when the torque is equal to or higher than a specified value. In this case, even when the influence of the tolerance is different between the rotational momentum of the cylinder to be subjected to the stop process and the rotational momentum of the cylinder for determining the presence or absence of misfire, the difference also becomes smaller. Therefore, it is possible to accurately determine the presence or absence of misfire.

[0014] In the above misfire detection device, it is preferable that the misfire detection device is configured to execute the following learning process: learning the difference between the rotational momentum when the combustion control of the internal combustion engine is stopped for a cylinder whose appearance interval of the compression top dead center with respect to the cylinder to be subjected to the stop process is not an integer multiple of one cycle and the rotational momentum of the cylinder to be subjected to the stop process, and the determination process is the following process: when the deviation amount of the rotational momentum of the cylinder to be determined with respect to the rotational momentum of the cylinder to be subjected to the stop process becomes equal to or less than a predetermined specified amount, it is determined that misfire has occurred in the cylinder to be determined, and the determination process includes the following correction process: determining the specified amount when the cylinder whose appearance interval is not an integer multiple of one cycle is determined as the cylinder to be determined based on the difference learned through the learning process.

[0015] The rotational momentum includes the influence of the tolerance of the signal that is the input for the calculation process of the rotational momentum. Here, the influence of the tolerance on the rotational momentum of the cylinder with a compression top dead center having an angular interval that is an integer multiple of one revolution away from the compression top dead center of the cylinder that is the object of the stop process is equal to the influence of the tolerance on the rotational momentum of the cylinder that is the object of the stop process. In contrast, the influence of the tolerance on the rotational momentum of the cylinder with a compression top dead center having an angular interval different from an integer multiple of one revolution away from the cylinder that is the object of the stop process may be significantly different from the influence of the tolerance on the rotational momentum related to the cylinder that is the object of the stop process.

[0016] Therefore, in the above structure, a learning process is executed, and a specified amount is determined based on the difference learned through the learning process when determining a cylinder that is not an integer multiple of one revolution as an object of misfire determination. Thereby, it is possible to suppress a decrease in the misfire determination accuracy due to the influence of the tolerance.

[0017] In the above misfire detection device, it is preferable that the sensor is a sensor provided in the combustion chamber of each of the plurality of cylinders to detect the combustion state of the air-fuel mixture in the combustion chamber, and the combustion variable related to each of the plurality of cylinders is quantified based on the detection value of the sensor between the compression top dead center and the next occurring compression top dead center in the cylinder.

[0018] The combustion stroke of a specific cylinder is the period from the compression top dead center of the specific cylinder to the next compression top dead center. Therefore, by using the detection value of the sensor during this period, the combustion state during the combustion stroke can be quantified. Therefore, according to the above structure, the combustion variable can be set to a quantity that accurately represents the presence or absence of misfire in a specific cylinder.

[0019] In the above misfire detection device, it is preferable that the sensor is a sensor that detects the pressure in the combustion chamber.

[0020] The pressure in the combustion chamber rises when the air-fuel mixture burns during the combustion stroke compared to when the air-fuel mixture does not burn. Therefore, the pressure in the combustion chamber is an appropriate variable representing the combustion state of the air-fuel mixture in the combustion chamber. Therefore, in the above structure, by using the pressure in the combustion chamber to quantify the combustion variable, the combustion variable can be set to a quantity that accurately represents the presence or absence of misfire in a specific cylinder.

[0021] In order to solve the above problems, according to a second aspect of the present invention, there is provided a misfire detection method for an internal combustion engine. The internal combustion engine has a plurality of cylinders. The misfire detection method includes: stopping the combustion control of the air-fuel mixture in a part of the plurality of cylinders; obtaining a value of a combustion variable, which is a variable representing the combustion state in each cylinder of the plurality of cylinders and is determined based on the detection value of a sensor that detects a physical quantity corresponding to the combustion state of the air-fuel mixture in each cylinder of the plurality of cylinders; and when performing the stop process, using the cylinders that have undergone the combustion control as the cylinders to be determined for the presence or absence of misfire. When the deviation degree of the value of the combustion variable in the determined cylinders with respect to the value of the combustion variable in the cylinders that are the objects of the stop process is equal to or less than a predetermined degree, it is determined that a misfire has occurred in the determined cylinders. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 FIG. is a diagram showing the structure of a drive system and a control device according to the first embodiment.

[0023] Figure 2 FIG. is a flowchart showing the steps of the process executed by the control device.

[0024] Figure 3 FIG. is a flowchart showing the steps of the process executed by the control device.

[0025] Figure 4 FIG. is a timing chart illustrating misfire determination.

[0026] Figure 5 FIG. is a timing chart showing the order of occurrence of top dead center compression in the second embodiment.

[0027] Figure 6 FIG. is a flowchart showing the steps of the process executed by the control device.

[0028] Figure 7 FIG. is a flowchart showing the steps of the process executed by the control device.

[0029] Figure 8 FIG. is a diagram illustrating the correction process of the deviation amount.

[0030] Figure 9 FIG. is a flowchart showing the steps of the process executed by the control device. DETAILED DESCRIPTION OF THE INVENTION

[0031] <FIRST EMBODIMENT>

[0032] Hereinafter, the first embodiment will be described with reference to the drawings.

[0033] As Figure 1As shown, the internal combustion engine 10 has four cylinders #1 to #4. A throttle valve 14 is provided in the intake passage 12 of the internal combustion engine 10. The downstream part of the intake passage 12 is the intake port 12a. An intake port injection valve 16 for injecting fuel into the intake port 12a is provided at the intake port 12a. The air sucked into the intake passage 12 and the fuel injected from the intake 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 the in-cylinder injection valve 22. In addition, the air-fuel mixture in the combustion chamber 20 burns with the spark discharge of the spark plug 24. The combustion energy generated at this time is converted into the rotational energy of the crankshaft 26.

[0034] The air-fuel mixture burned in the combustion chamber 20 is discharged as exhaust gas into the exhaust passage 30 as the exhaust valve 28 opens. A three-way catalyst 32 having an oxygen storage capacity and a gasoline particulate filter (GPF 34) are provided in the exhaust passage 30. In the GPF 34, a three-way catalyst is supported on the filter that traps particulate matter (PM).

[0035] A crankshaft rotor 40 having a tooth portion 42 is coupled to the crankshaft 26. The tooth portion 42 represents a plurality of rotational angles of the crankshaft 26. On the crankshaft rotor 40, the tooth portions 42 are provided at substantially 10° CA intervals. In addition, on the crankshaft rotor 40, a toothless portion 44 is provided at a position where the interval between adjacent tooth portions 42 is 30° CA. The toothless portion 44 is used to represent the rotational angle that serves as a reference for the crankshaft 26.

[0036] 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 electric 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 electric generator 54 and the drive wheel 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 electric generator 52 through the inverter 56. In addition, an AC voltage is applied to the terminals of the second electric generator 54 through the inverter 58.

[0037] The control device 70 takes the internal combustion engine 10 as the control object, and in order to control the torque, exhaust gas component ratio, etc. as its control quantities, operates the operating parts of the internal combustion engine 10 such as the throttle valve 14, the intake port injection valve 16, the in-cylinder injection valve 22, and the spark plug 24. In addition, the control device 70 takes the first electric generator 52 as the control object, and in order to control the rotational speed as its control quantity, operates the inverter 56. In addition, the control device 70 takes the second electric generator 54 as the control object, and in order to control the torque as its control quantity, operates the inverter 58. In Figure 1It describes the operation signals MS1 to MS6 of the throttle valve 14, the intake port injection valve 16, the in-cylinder injection valve 22, the spark plug 24, and the converters 56 and 58 respectively. To control the control quantity of the internal combustion engine 10, the control device 70 refers to the intake air quantity Ga detected by the air flow meter 80, the output signal Scr of the crank angle sensor 82, 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. In addition, the control device 70 refers to the in-cylinder pressure Pc detected by the in-cylinder pressure sensors 89 respectively provided in the combustion chambers 20 of cylinders #1 to #4. In addition, to control the control quantities of the first motor generator 52 and the second motor generator 54, 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 and the output signal Sm2 of the second rotation angle sensor 92 that detects the rotation angle of the second motor generator 54.

[0038] The control device 70 includes a CPU 72, a ROM 74, a storage device 75, and a peripheral circuit 76, which can communicate through a communication line 78. Here, the peripheral circuit 76 includes a circuit that generates a clock signal for operating within a specified range, a power supply circuit, a reset circuit, and the like. The control device 70 controls the control quantity by the CPU 72 executing the program stored in the ROM 74.

[0039] Figure 2 It shows the steps of the processing executed by the control device 70 of the first embodiment. Figure 2 The processing shown is realized by the CPU 72 repeating the program stored in the ROM 74 at a predetermined cycle. Hereinafter, the step numbers of each processing are represented by numbers preceded by "S".

[0040] In Figure 2 In the series of processing shown, the CPU 72 first obtains the rotational speed NE, the filling efficiency η, and the water temperature THW (S10). The rotational speed NE is calculated by the CPU 72 based on the output signal Scr. In addition, the filling efficiency η is calculated by the CPU 72 based on the intake air quantity Ga and the rotational speed NE. Next, the CPU 72 calculates the update amount ΔDPM of the accumulation amount DPM, which is the amount of PM captured by the GPF 34, based on the rotational speed NE, the filling efficiency η, and the water temperature THW (S12). Here, first, the CPU 72 calculates the amount of PM in the exhaust gas discharged to the exhaust passage 30 based on the rotational speed NE, the filling efficiency η, and the water temperature THW. In addition, the CPU 72 calculates the temperature of the GPF 34 based on the rotational speed NE and the filling efficiency η. Moreover, the CPU 72 calculates the update amount ΔDPM based on the amount of PM in the exhaust gas and the temperature of the GPF 34.

[0041] The CPU 72 updates the accumulation amount DPM according to the update amount ΔDPM (S14). Next, the CPU 72 determines whether the flag F is "1" (S16). The flag F is "1" when the regeneration process for burning and removing the PM of the GPF 34 is executed, and is "0" when the regeneration process is not executed. When the flag F is "0" (S16: No), the CPU 72 determines whether the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18). The regeneration execution value DPMH is set to a value indicating that the amount of PM trapped by the GPF 34 has increased and it is desired to remove the PM. When the accumulation amount DPM is equal to or greater than the regeneration execution value DPMH (S18: Yes), the CPU 72 determines whether the logical product of the following conditions (1) and (2) is true (S20). This process is to determine whether to allow the execution of the regeneration process.

[0042] Condition (1): This is a condition meaning that the required torque of the internal combustion engine 10, i.e., the internal combustion engine required torque Te*, is equal to or greater than the specified value Teth.

[0043] Condition (2): This is a condition meaning that the rotational speed NE is equal to or greater than the specified speed NEth.

[0044] When the logical product is true (S20: Yes), the CPU 72 executes the regeneration process and substitutes "1" into the flag F (S22). That is, the CPU 72 stops the injection of fuel from the intake port injection valve 16 and the in-cylinder injection valve 22 of cylinder #1, and makes the air-fuel ratio of the air-fuel mixture in the combustion chambers 20 of cylinders #2 to #4 richer than the stoichiometric air-fuel ratio. Through this process, oxygen and unburned fuel are discharged into the exhaust passage 30, the temperature of the GPF 34 rises, and the PM trapped by the GPF 34 is burned and removed. That is, by discharging oxygen and unburned fuel into the exhaust passage 30, the unburned fuel burns in the three-way catalyst 32 or the like, and the temperature of the exhaust gas rises, thereby increasing the temperature of the GPF. In addition, by supplying oxygen to the GPF 34, the PM trapped by the GPF 34 is burned and removed.

[0045] On the other hand, when the flag F is "1" (S16: Yes), the CPU 72 determines whether the accumulation amount DPM is equal to or less than the stop threshold DPML (S24). The stop threshold DPML is set to a value indicating that the amount of PM trapped on the GPF 34 has become sufficiently small and the regeneration process can be stopped. When the accumulation amount DPM exceeds the stop threshold DPML (S24: No), the CPU 72 transfers to the process of S22. On the other hand, when the accumulation amount DPM is equal to or less than the stop threshold DPML (S24: Yes), the CPU 72 stops the regeneration process and substitutes "0" into the flag F (S26).

[0046] When the processes of S22 and S26 are completed, or when a negative determination is made in the processes of S18 and S20, the CPU 72 temporarily ends.Figure 2 A series of processes shown below.

[0047] In Figure 3 It represents the steps of other processes executed by the control device 70. Figure 3 The processes shown below are implemented by the CPU 72 repeating the program stored in the ROM 74 at a predetermined cycle.

[0048] In Figure 3 In the series of processes shown below, the CPU 72 first determines whether the flag F is "1" (S30). When the flag F is "1" (S30: Yes), the CPU 72 obtains the time T30 required for the crankshaft 26 to rotate 30°CA (S32). That is, the CPU 72 calculates the time T30 by measuring the time when the tooth part 42 of the crankshaft rotor 40 detected by the crank angle sensor 82 moves to the tooth part 42 that is 30°CA away. Then, the CPU 72 substitutes the time T30[m] into the time T30[m + 1] as "m = 0, 1, 2, 3,...", and substitutes the newly obtained time T30 in the process of S32 into the time T30[0] (S34). Through this process, the variable in the parentheses after the time T30 increases numerically as the past obtained time T30. In addition, through this process, when the value of the variable in the parentheses is 1 greater, it becomes the time T30 30°CA before.

[0049] Next, the CPU 72 determines whether the current rotation angle of the crankshaft 26 is ATDC 30°CA based on the compression top dead center of any one of cylinders #1 to #4 (S36). When the current rotation angle is ATDC 30°CA (S36: Yes), the CPU 72 substitutes the value obtained by subtracting the time T30[0] from the time T30[6] into the rotational momentum change ΔT30 (S38). The rotational momentum change ΔT30 is a value that becomes around zero when there is no misfire in the cylinder that is the determination object of whether there is a misfire, and is a variable that becomes a positive value when there is a misfire. Here, the cylinder that is the object of whether there is a misfire means the cylinder whose compression top dead center has passed 30° through the process of S36. However, the case where this cylinder is cylinder #1 is excluded.

[0050] Next, the CPU 72 determines whether the rotational momentum change ΔT30 calculated through the process of S38 is the rotational momentum change ΔT30 of cylinder #1 (S40). And when the rotational momentum change ΔT30 calculated through the process of S38 is the rotational momentum change ΔT30 of cylinder #1 (S40: Yes), the CPU 72 substitutes the rotational momentum change ΔT30 into the reference value ΔT30ref (S42). Here, since the combustion control is stopped in cylinder #1, the rotational momentum change ΔT30 is a quantity equal to that when there is a misfire.

[0051] On the other hand, when the rotational momentum ΔT30 calculated by the process of S38 is the rotational momentum ΔT30 of any one of cylinders #2 to #4 (S40: No), the CPU 72 determines whether the absolute value of the difference between the rotational momentum ΔT30 and the reference value ΔT30ref is equal to or less than the determination value Δth (S44). Through this process, it is determined whether an engine misfire has occurred in the cylinder that is the determination target for the presence or absence of misfire. That is, the reference value ΔT30ref is the rotational momentum ΔT30 equal to that at the time of misfire. Thus, when the deviation degree between the rotational momentum ΔT30 and the reference value ΔT30ref is small, the CPU 72 determines that an engine misfire has occurred in the cylinder that is the determination target. The determination value Δth is a fixed value determined in advance.

[0052] When the absolute value of the difference between the rotational momentum ΔT30 and the reference value ΔT30ref is equal to or less than the determination value Δth (S44: Yes), the CPU 72 increments the counter C (S46). When the process of S46 is completed or when a negative determination is made in the process of S44, the CPU 72 determines whether a predetermined period has elapsed since a timing that is delayed from either the timing of first executing the process of S44 or the execution timing of the process of S54 described later (S48). Moreover, when the predetermined period has elapsed (S48: Yes), the CPU 72 determines whether the counter C is equal to or greater than the threshold value Cth (S50). The threshold value Cth is set according to the number of engine misfires that occur within the predetermined period when engine misfires occur at a non-negligible frequency. When the counter C is equal to or greater than the threshold value Cth (S50: Yes), the CPU 72 determines that engine misfires have occurred at a non-negligible frequency. Then, the CPU 72 Figure 1 performs a notification process of notifying the user of this situation by operating the warning lamp 100 shown (S52).

[0053] In contrast, when the counter C is less than the threshold value Cth (S50: No), the CPU 72 initializes the counter C (S54).

[0054] When the processes of S42, S52, and S54 are completed or when negative determinations are made in the processes of S30, S36, and S48, the CPU 72 temporarily ends Figure 3 the series of processes shown.

[0055] Here, the operation and effects of the first embodiment will be described.

[0056] When the accumulation amount DPM is equal to or greater than the threshold value DPMH, the CPU 72 executes the regeneration process of the GPF 34. As a result, the air inhaled during the intake stroke of cylinder #1 is not consumed by combustion and flows out into the exhaust passage during the exhaust stroke of cylinder #1. In addition, the air-fuel ratios of cylinders #2 to #4 are richer than the stoichiometric air-fuel ratio. As a result, a large amount of unburned fuel is contained in the exhaust gas discharged from cylinders #2 to #4 into the exhaust passage 30. Therefore, when the oxygen and unburned fuel in the exhaust gas burn in the three-way catalyst 32 or the like, the temperature of the GPF 34 rises. In addition, the oxygen in the air in the exhaust gas oxidizes the PM accumulated on the GPF 34. As a result, the PM burns and is removed.

[0057] On the other hand, when executing the regeneration process, the CPU 72 substitutes the rotational momentum ΔT30 of cylinder #1 into the reference value ΔT30ref. Then, when the absolute value of the difference between the rotational momenta ΔT30 of cylinders #2 to #4 and the reference value ΔT30ref is equal to or less than the determination value Δth, the CPU 72 determines that a misfire has occurred.

[0058] Figure 4 Examples of the transition of the rotational momenta ΔT30 of cylinders #1 to #4 are shown.

[0059] In Figure 4 In the example shown, since the absolute value of the difference between the rotational momentum ΔT30 of cylinder #4 and the reference value ΔT30ref is equal to or less than the determination value Δth, the CPU 72 determines that a misfire has occurred in cylinder #4. On the other hand, since the rotational momenta ΔT30 of cylinder #3 and cylinder #2 deviate from the reference value ΔT30ref by more than the determination value Δth, the CPU 72 determines that misfires have not occurred in cylinders #2 and #3.

[0060] According to the first embodiment, the following functions and effects can also be obtained.

[0061] (1) The determination value Δth is set to a fixed value. The magnitude of the rotational momentum ΔT30 in the cylinder for determining the presence or absence of misfire varies according to the load and rotational speed NE of the internal combustion engine 10. On the other hand, the rotational momentum ΔT30 in the cylinder that becomes the stop object of combustion control is a quantity corresponding to the load and rotational speed NE of the internal combustion engine 10. Therefore, the reference value ΔT30ref is a quantity corresponding to the load and rotational speed NE of the internal combustion engine 10. Therefore, according to the first embodiment, when the deviation amount between the rotational momentum ΔT30 of the cylinder executing combustion control and the reference value ΔT30ref is equal to or less than the determination value Δth, it is determined that a misfire has occurred. Thus, even if the determination value Δth is set to a fixed value, the presence or absence of misfire can be determined with high accuracy. Therefore, the man-hours suitable for the determination process of the presence or absence of misfire can be reduced.

[0062] (2) The rotational energy of the crankshaft 26 is proportional to the square of the rotational speed NE. Therefore, when the rotational speed NE is low, the ratio of the change in the rotational speed NE with respect to the change in the energy supplied to the crankshaft 26 is larger than when the rotational speed NE is high. Thus, in the low rotational region, if misfire occurs in cylinder #3 where the compression top dead center appears after cylinder #1 which is the stop object of combustion control, the decrease in the rotational speed Ne may be larger than that in cylinder #1 which is the stop object of combustion control. In contrast, in the first embodiment, the regeneration process is executed on the condition that the rotational speed NE is equal to or higher than a specified speed NEth. Thereby, the difference in the rotational momentum ΔT30 that may occur between the cylinder that is the stop object of combustion control and the cylinder that executes combustion control becomes smaller. Therefore, even if the determination value Δth is set to a fixed value, the presence or absence of misfire can be determined with high accuracy.

[0063] (3) The CPU 72 executes the regeneration process on the condition that the required torque Te* of the internal combustion engine is equal to or higher than a specified value Teth. When the torque of the internal combustion engine 10 is large, the decrease in the determination accuracy of misfire caused by the influence of the tolerance of the crankshaft rotor 40 is smaller than when the torque is small. In contrast, in the first embodiment, the regeneration process is executed when the required torque Te* of the internal combustion engine is equal to or higher than the specified value Teth. In this case, even if the tooth portions 42 used for calculating the rotational momentum ΔT30 are different between the cylinder that is the stop object of combustion control and the cylinder that is the determination object of misfire, the decrease in the determination accuracy of the presence or absence of misfire caused by the influence of the tolerance becomes smaller. Therefore, even when the tooth portions 42 used for calculating the rotational momentum ΔT30 are different between the cylinder that is the stop object of combustion control and the cylinder that is the determination object of misfire, the presence or absence of misfire can be determined with high accuracy.

[0064] <Second Embodiment>

[0065] Hereinafter, the second embodiment will be described with reference to the drawings, centering on the differences from the first embodiment.

[0066] Figure 5 The appearance intervals of the compression top dead centers of the respective cylinders in the second embodiment are shown. As Figure 5As shown, in the second embodiment, the compression top dead centers occur at 180° CA intervals in the order of cylinder #1, cylinder #3, cylinder #4, and cylinder #2. Therefore, the compression top dead center of cylinder #1 is offset by 360° CA from the compression top dead center of cylinder #4. This means that the tooth portion 42 of the crankshaft rotor 40 used for calculating the rotational momentum ΔT30 in cylinder #1 is the same as the tooth portion 42 of the crankshaft rotor 40 used for calculating the rotational momentum ΔT30 in cylinder #4. Therefore, even if there are tolerances in the intervals between the tooth portions 42, the influence of the tolerances on the rotational momentum ΔT30 in cylinder #4 is equal to the influence of the tolerances on the rotational momentum ΔT30 in cylinder #1.

[0067] In contrast, the tooth portion 42 used for calculating the rotational momentum ΔT30 in cylinder #2 and the tooth portion 42 used for calculating the rotational momentum ΔT30 in cylinder #3 are both different from the tooth portion 42 used for calculating the rotational momentum ΔT30 in cylinder #1. Therefore, when comparing the rotational momentum ΔT30 in the case of misfire occurring in cylinder #2 and the rotational momentum ΔT30 in cylinder #1, for example, the difference between the two becomes the difference in the influence of the tolerances.

[0068] Therefore, in the second embodiment, the offset amount caused by the difference in tolerances between the rotational momentum ΔT30 in cylinders #2 and #3 and the rotational momentum ΔT30 in cylinder #1 is learned.

[0069] Figure 6 The steps of the process related to the above learning are shown. Figure 6 The process shown is implemented by the CPU 72 repeating the program stored in the ROM 74.

[0070] In Figure 6 In the series of processes shown, first, the CPU 72 determines whether it is a drag when the combustion control stops in all cylinders of the internal combustion engine 10 and the crankshaft 26 rotates by the rotational power of the gear rack C (S60). When the internal combustion engine 10 is in a drag state (S60: yes), the CPU 72 determines whether the absolute value of the change amount ΔNE* per unit time of the command value of the rotational speed NE, that is, the internal combustion engine speed command value NE*, is equal to or less than a specified amount ΔNEth (S62). The specified amount ΔNEth is set based on the change amount of the rotational speed NE when the low-frequency component having a period longer than one cycle in the rotational frequency of the crankshaft 26 is sufficiently small.

[0071] When the absolute value of the change amount ΔNE* is equal to or less than the specified amount ΔNEth (S62: yes), the CPU 72 executes the process related to Figure 3The processing from S32 to S40 is the same. Moreover, when the rotational momentum ΔT30 calculated by the processing of S38 is the rotational momentum ΔT30 of cylinder #1 (S40: Yes), the CPU 72 substitutes the rotational momentum ΔT30 into the first rotational momentum ΔT30f (S62).

[0072] On the other hand, when the rotational momentum ΔT30 calculated by the processing of S38 is the rotational momentum ΔT30 of any one of cylinders #2 to #4 (S40: No), the CPU 72 determines whether it is the rotational momentum ΔT30 of cylinder #2 (S64). Moreover, when it is the rotational momentum ΔT30 of cylinder #2 (S64: Yes), the CPU 72 substitutes the rotational momentum ΔT30 into the second rotational momentum ΔT30s (S66). Then, the CPU 72 calculates the second learning value ΔLs through an exponential moving average process of the value obtained by subtracting the first rotational momentum ΔT30f from the second rotational momentum ΔT30s (S68). That is, the CPU 72 substitutes the sum of the value obtained by multiplying the second learning value ΔLs by a coefficient α greater than "0" and less than "1" and the value obtained by multiplying the value obtained by subtracting the first rotational momentum ΔT30f from the second rotational momentum ΔT30s by "1 - α" into the second learning value ΔLs. Then, the CPU 72 stores the second learning value ΔLs in the storage device 75 (S70).

[0073] On the other hand, when the rotational momentum ΔT30 calculated by the processing of S38 is the rotational momentum ΔT30 of either cylinder #3 or cylinder #4 (S64: No), the CPU 72 determines whether it is the rotational momentum ΔT30 of cylinder #3 (S72). Moreover, when it is the rotational momentum ΔT30 of cylinder #3 (S72: Yes), the CPU 72 substitutes the rotational momentum ΔT30 into the third rotational momentum ΔT30t (S74). Then, the CPU 72 calculates the third learning value ΔLt through an exponential moving average process of the value obtained by subtracting the first rotational momentum ΔT30f from the third rotational momentum ΔT30t (S76). That is, the CPU 72 substitutes the sum of the value obtained by multiplying the third learning value ΔLt by a coefficient α greater than "0" and less than "1" and the value obtained by multiplying the value obtained by subtracting the first rotational momentum ΔT30f from the third rotational momentum ΔT30t by "1 - α" into the third learning value ΔLt. Then, the CPU 72 stores the third learning value ΔLt in the storage device 75 (S78).

[0074] When the processing of S62, S70, and S78 is completed, or when a negative determination is made in the processing of S60, S62, S36, and S72, the CPU 72 temporarily ends Figure 6 the series of processing shown

[0075] Figure 7 Steps for processing related to determination of presence or absence of misfire in the second embodiment are shown. Figure 7 The processing shown is implemented by the CPU 72 repeating the program stored in the ROM 74 at a predetermined cycle. In Figure 7 For convenience, the same step numbers are assigned to the processing corresponding to the Figure 3 processing shown.

[0076] In Figure 7 the series of processing shown, when a negative determination is made in the processing of S40, the CPU 72 determines whether the rotational momentum ΔT30 calculated by the processing of S38 is the rotational momentum ΔT30 of cylinder #2 (S80). When it is the rotational momentum ΔT30 of cylinder #2 (S80: Yes), the CPU 72 updates the rotational momentum ΔT30 by subtracting the value of the second learning value ΔLs from the rotational momentum ΔT30 (S82).

[0077] On the other hand, when it is not the rotational momentum ΔT30 of cylinder #2 (S80: No), the CPU 72 determines whether the rotational momentum ΔT30 calculated by the processing of S38 is the rotational momentum ΔT30 of cylinder #3 (S84). When it is the rotational momentum ΔT30 of cylinder #3 (S84: Yes), the CPU 72 updates the rotational momentum ΔT30 by subtracting the value of the third learning value ΔLt from the rotational momentum ΔT30 (S86).

[0078] When the processing of S82 and S86 is completed or when a negative determination is made in the processing of S84, the CPU 72 transfers to the processing of S44.

[0079] Thus, according to the second embodiment, when cylinder #2 or cylinder #3 is the determination object for misfire, the upper limit value of the deviation degree when determining misfire of the reference value ΔT30ref and the rotational momentum ΔT30 of the determination object is changed.

[0080] Figure 8 Regions of the rotational momentum ΔT30 for determining misfire of cylinders #2 to #4 are shown.

[0081] As Figure 8As shown, for cylinder #4, the region where the difference from the reference value ΔT30ref is less than or equal to the determination value Δth is the region determined as misfire. In contrast, for cylinder #2, an example where the second learning value ΔLs is positive is shown. In this case, the region where the amount exceeding the reference value ΔT30ref is less than or equal to "Δth + ΔLs" and the amount below the reference value ΔT30ref is less than or equal to "-Δth + ΔLs" becomes the region determined as misfire. In other words, it is the region where the difference from the corrected value ΔT30refc obtained by increasing the reference value ΔT30ref by the second learning value ΔLs is less than or equal to the determination value Δth.

[0082] In addition, for cylinder #3, an example where the third learning value ΔLt is negative is shown. In this case, the region where the amount exceeding the reference value ΔT30ref is less than or equal to "Δth - |ΔLs|", and the amount below the reference value ΔT30ref is less than or equal to "-Δth - |ΔLs|" is the region determined as misfire. In other words, it is the region where the difference from the corrected value ΔT30refc obtained by decreasing the reference value ΔT30ref by the absolute value of the third learning value ΔLt is less than or equal to the determination value Δth.

[0083] Thus, compared with the determination accuracy of misfire in cylinder #4, it is possible to suppress the reduction in the determination accuracy of misfire in cylinders #2 and #3 caused by tolerances.

[0084] <Third Embodiment>

[0085] Hereinafter, centering on the differences from the first embodiment, the third embodiment will be described with reference to the accompanying drawings.

[0086] In the third embodiment, instead of setting the rotational momentum ΔT30, the combustion variable for misfire detection is quantified by the in-cylinder pressure Pc.

[0087] Figure 9 shows the steps of the process related to the determination of misfire in the third embodiment. Figure 9 The process shown is implemented by the CPU72 repeating the program stored in the ROM74 at a predetermined cycle. In Figure 9 For convenience, the same step numbers are assigned to the processes corresponding to the process shown in Figure 3 shown.

[0088] In Figure 9In the series of processes shown, first, the CPU 72 determines whether the flag is "1" (S90). When the flag is "1" (S90: Yes), the CPU 72 determines whether the current rotational angle of the crankshaft 26 is at the compression top dead center of any one of cylinders #1 to #4 (S92). When the current rotational angle of the crankshaft 26 is at the compression top dead center of any one of cylinders #1 to #4 (S92: Yes), the CPU 72 acquires the in-cylinder pressure Pc (S94). Then, the CPU 72 updates the in-cylinder pressure cumulative value InPc by adding the in-cylinder pressure Pc to the in-cylinder pressure cumulative value InPc (S96). The CPU 72 continues the processes of S94 and S96 at an angular interval of 120°CA (S98: No).

[0089] When the current rotational angle of the crankshaft 26 is at ATDC 120°CA (S98: Yes), the CPU 72 determines whether the in-cylinder pressure cumulative value InPc is the amount of cylinder #1 (S40a). When the in-cylinder pressure cumulative value InPc is the amount of cylinder #1 (S40a: Yes), the CPU 72 substitutes the in-cylinder pressure cumulative value InPc into the reference value InPcref (S42a).

[0090] On the other hand, when the calculated in-cylinder pressure cumulative value InPc is the amount of cylinders #2 to #4 (S40a: No), the CPU 72 determines whether the absolute value of the difference between the in-cylinder pressure cumulative value InPc and the reference value InPcref is equal to or less than the determination value Δth (S44a). Here, since the reference value InPcref is the cumulative value of the in-cylinder pressure Pc at the time of combustion control stop, it becomes a small value corresponding to the amount without combustion energy generation. Moreover, the reference value InPcref is a value equal to the in-cylinder pressure cumulative value InPc at the time of misfire occurrence. Therefore, when the absolute value of the difference between the in-cylinder pressure cumulative value InPc and the reference value InPcref is equal to or less than the determination value Δth (S44a: Yes), the CPU 72 determines that misfire has occurred in the cylinder to be determined and transfers to the process of S46. On the other hand, when the absolute value of the difference between the in-cylinder pressure cumulative value InPc and the reference value InPcref exceeds the determination value Δth (S44a: No), the CPU 72 transfers to the process of S48.

[0091] The determination value Δth is a fixed value determined in advance. That is, both the in-cylinder pressure cumulative value InPc at the time of misfire occurrence and the in-cylinder pressure cumulative value InPc at the time of no misfire occurrence vary according to the rotational speed NE and the filling efficiency η. However, the amount of this variation is reflected in the reference value InPcref. Thus, by determining the presence or absence of misfire based on the degree of deviation from the reference value InPcref, the man-hours for determining the value can be reduced.

[0092] <Correspondence>

[0093] The correspondence between the matters in the above-described embodiments and the matters described in the column of "Technical Solution for Solving the Problem" above is as follows. Hereinafter, for each number of the technical solutions in the scope of protection claimed, the correspondence is indicated. [1] The stop process corresponds to the process of S22. The combustion variable corresponds to the rotational momentum change amount ΔT30 in Figure 3 and Figure 7 corresponds to the in-cylinder pressure cumulative value InPc in Figure 9 . The combustion variable acquisition process corresponds to the processes of S38 and S96. The determination process corresponds to the processes of S44 and S44a. [2] The instantaneous speed variable corresponds to the time T30. [3] The specified amount corresponds to Figure 3 and Figure 9 the determination values Δth in and Figure 7 "Δth + ΔLs, Δth - ΔLs, Δth + ΔLt, Δth - ΔLt" in

[0094] <Other Embodiments>

[0095] The above-described embodiments can be implemented with the following modifications. The above-described embodiments and the following modification examples can be implemented in combination with each other within a technically non-contradictory range.

[0096] "Regarding the rotational momentum change amount"

[0097] As the rotational momentum change amount ΔT30, it is not limited to the value obtained by subtracting the time T30 required for rotation in the interval of TDC to 30 ATDC of the cylinder that is the determination target of misfire from the time T30 required for rotation in the interval of TDC to 30 ATDC of the cylinder that was the previous compression top dead center. For example, it may also be the value obtained by subtracting the time T30 required for rotation in the interval of 90 ATDC to 120 ATDC of the cylinder that is the determination target of misfire from the time T30 required for rotation in the interval of TDC to 30 ATDC of that cylinder.

[0098] In the above-described embodiment, the rotational momentum change amount, which is the change amount of the rotational speed of the crankshaft 26 in the rotational angle interval below the appearance interval of the compression top dead center, is quantified by the difference between the times required for rotation in this rotational angle interval, but it is not limited to this, and it may also be quantified according to a ratio.

[0099] The instantaneous speed variable, which is a variable representing the rotational speed of the crankshaft 26 in a rotational angle interval equal to or less than the occurrence interval of the compression top dead center for determining the rotational momentum, is not limited to a variable representing the rotational speed of the crankshaft 26 in an interval of 30° CA. For example, it may also be a variable representing the rotational speed of the crankshaft 26 in an interval of 180° CA.

[0100] In the above-described embodiment, the instantaneous speed variable, which is a variable representing the rotational speed of the crankshaft 26 in a rotational angle interval equal to or less than the occurrence interval of the compression top dead center for determining the rotational momentum, is quantified by the time required for rotation in this rotational angle interval, but is not limited thereto, and may also be quantified by speed.

[0101] "Regarding the execution conditions of the regeneration process"

[0102] The execution conditions of the regeneration process do not necessarily include both of the above conditions (1) and (2). For example, regarding the two conditions of condition (1) and condition (2), it may also include only any one of them. Of course, it may also not include both of these two conditions.

[0103] "Regarding the specified amount as the upper limit value of the deviation amount for determining misfire"

[0104] In the above-described embodiment, the determination value Δth for determining the specified amount is set to a fixed value, but is not limited thereto. In particular, for example, as described in the column of "Regarding the execution conditions of the regeneration process", when the execution conditions of the regeneration process do not include condition (2) and the regeneration process is executed at a low rotational speed, in the case where misfire occurs in the cylinder that becomes the compression top dead center after cylinder #1 where combustion control has been stopped, etc., there is a tendency for the rotational momentum ΔT30 to be larger than the rotational momentum ΔT30 related to cylinder #1. Therefore, the determination value Δth can be made variable according to the rotational speed NE.

[0105] "Regarding the learning process"

[0106] In the above-described embodiment, the second learning value ΔLs and the third learning value ΔLt are calculated by the exponential moving average process of the rotational momentum ΔT30, but are not limited thereto. For example, the simple moving average process value may also be set as the second learning value ΔLs and the third learning value ΔLt. Of course, it is not essential to perform the moving average process. For example, the latest second rotational momentum ΔT30s and third rotational momentum ΔT30t calculated by the processes of S66 and S74 may be set as the second learning value ΔLs and the third learning value ΔLt, respectively.

[0107] "Regarding the correction of the deviation amount between the reference value and the rotational momentum related to the determination object"

[0108] In the processes of S82 and S84, the second learned value ΔLs or the third learned value ΔLt is subtracted from the rotational momentum ΔT30 related to the cylinder to be determined, but it is not limited thereto. For example, the second learned value ΔLs or the third learned value ΔLt may also be added to the reference value ΔT30ref.

[0109] In the above "Regarding the specified quantity" column, an example of variably setting the determination value Δth according to the rotational speed in the low rotation region is shown, but it is not limited thereto. For example, the reference value ΔT30ref may also be corrected in the low rotation region.

[0110] "Regarding the sensor provided in the combustion chamber and detecting the combustion state"

[0111] In the above embodiment, as the sensor for detecting the combustion state, an in-cylinder pressure sensor is exemplified, but it is not limited thereto. For example, it may also be a sensor for detecting the ion current. Even in this case, due to the influence of noise, etc., the threshold value for misfire also varies according to the operating state of the internal combustion engine. Therefore, it is effective to use the detected value of the ion current in the cylinder where the combustion control has stopped as the reference value. Of course, it is not limited to the ion current sensor. For example, it may also be a sensor that senses light in order to detect the combustion state of the combustion chamber using light.

[0112] "Regarding the combustion variable"

[0113] As the combustion variable calculated by using the output signal Scr of the crank angle sensor 82 as the input, it is not limited to the rotational momentum. For example, it may also be the average value of the shaft torque of the internal combustion engine 10 during a predetermined period. This can be calculated, for example, according to the following formula (c1).

[0114] Te = Ie·dωe + (1 + ρ) / {ρ·(Ig1·dωm1 - Tr)}…(c1)

[0115] The change rate dωe of the instantaneous speed ωe of the internal combustion engine 10, the inertia moment Ie of the internal combustion engine 10, the inertia moment Ig1 of the first motor generator 52, the angular acceleration dωm1 of the first motor generator 52, the reaction torque Tr of the first motor generator 52, and the planetary gear ratio ρ of the planetary gear mechanism 50 are used, which are calculated based on the shaft torque Te, the reciprocal of the time T30, etc. In addition, the above-mentioned predetermined period is a period less than the occurrence interval of the compression top dead center.

[0116] In Figure 9 the process of, as the combustion variable calculated by using the detected value of the in-cylinder pressure sensor 89, the in-cylinder pressure cumulative value InPc is exemplified, but it is not limited thereto. For example, it may also be the maximum value of the in-cylinder pressure Pc, and in addition, for example, it may also be the combustion energy.

[0117] As described in the column of "Sensor disposed in the combustion chamber and detecting the combustion state", when an ion current sensor is used as the sensor, the combustion variable can also be constituted by the integrated value of the ion current or the like.

[0118] "Regarding the stop process"

[0119] As the stop process, it is not limited to the regeneration process. For example, it may be a process of stopping the supply of fuel in a part of the cylinders in order to adjust the output of the internal combustion engine 10. Additionally, for example, it may be a process of stopping the combustion control in a cylinder when an abnormality occurs in a part of the cylinders. Additionally, for example, it may be the following process: when the oxygen storage amount of the three-way catalyst 32 is below a specified value, in order to supply oxygen to the three-way catalyst 32, only the combustion control of a part of the cylinders is stopped, and the control of making the air-fuel ratio of the air-fuel mixture in the remaining cylinders the stoichiometric air-fuel ratio is executed.

[0120] "Regarding the reflection of the misfire determination result"

[0121] In the above-described embodiment, when it is determined that a misfire has occurred, the notification process using the warning lamp 100 is executed, but as the notification process, it is not limited to the process that uses the device that outputs visual information as the operation target. For example, it may also be a process that uses the device that outputs auditory information as the operation target.

[0122] It is not essential to use the misfire determination result for the notification process itself. For example, when a misfire occurs, a process of operating the operation unit of the internal combustion engine 10 in order to change the control of the internal combustion engine 10 to an operating state less likely to cause a misfire may also be executed. That is, as the hardware unit that becomes the operation target in order to respond to the misfire determination result, not only the notification device but also the operation unit of the internal combustion engine 10 or the like may be used.

[0123] "Regarding the estimation of the accumulation amount"

[0124] As the estimation process of the accumulation amount DPM, it is not limited to Figure 2 the processes exemplified in. For example, the accumulation amount DPM may be estimated based on the pressure difference between the upstream side and the downstream side of the GPF 34 and the intake air amount Ga. Specifically, as long as the accumulation amount DPM is estimated to be a larger value in the case of a larger pressure difference than in the case of a smaller pressure difference, and even if the pressure difference is the same, the accumulation amount DPM is estimated to be a larger value in the case of a smaller intake air amount Ga than in the case of a larger intake air amount Ga. Here, when the pressure on the downstream side of the GPF 34 is regarded as a constant value, the above-described pressure Pex may be used instead of the differential pressure.

[0125] "Regarding the post-treatment device"

[0126] As the GPF 34, it is not limited to a filter carrying a three-way catalyst, and it can also be just a filter. Additionally, as the GPF 34, it is not limited to being downstream of the three-way catalyst 32 provided in the exhaust passage 30. Moreover, it is not essential for the aftertreatment device to include the GPF 34 itself. For example, even when the aftertreatment device consists only of the three-way catalyst 32, as described in the "Regarding Stopping Process" section above, when combustion control is stopped in some cylinders and oxygen is supplied to the three-way catalyst 32, it is effective to perform the processes exemplified in the above-described embodiments and their modified examples as the misfire detection process.

[0127] "Regarding the control device"

[0128] As the control device, it includes a CPU 72 and a ROM 74, but it is not limited to performing software processing. For example, it may include a dedicated hardware circuit such as an ASIC that performs hardware processing on at least a part of the components that performed software processing in the above-described embodiments. That is, the control device may have any of the following structures (a) to (c). (a) It includes a processing device that executes all of the above processes 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 a part of the above processes according to a program and a dedicated hardware circuit that executes the remaining processes. (c) It includes a dedicated hardware circuit that executes all of the above processes. Here, the software execution device including the processing device and the program storage device and the dedicated hardware circuit may be multiple.

[0129] "Regarding the vehicle"

[0130] As the vehicle, it is not limited to series-parallel hybrid vehicles. For example, it can be a parallel hybrid vehicle or a series hybrid vehicle. Of course, it is not limited to hybrid vehicles. For example, it can also be a vehicle in which the power generation device is only the internal combustion engine 10.

Claims

1. An apparatus for detecting misfire in an internal combustion engine, The internal combustion engine has a plurality of cylinders, The misfire detection apparatus is configured to perform the following processes: A stop process for stopping the combustion control of the air-fuel mixture in a part of the plurality of cylinders; A combustion variable acquisition process for acquiring a value of a combustion variable, which is a variable representing the combustion state in each of the plurality of cylinders and is determined based on a detection value of a sensor that detects a physical quantity corresponding to the combustion state of the air-fuel mixture in each of the plurality of cylinders; and A determination process for, when the stop process is executed, using the cylinders that have undergone the combustion control as the cylinders to be determined for misfire. When the degree of deviation of the value of the combustion variable in the cylinders to be determined from the value of the combustion variable in the cylinders that are the objects of the stop process is equal to or less than a predetermined degree, it is determined that misfire has occurred in the cylinders to be determined. The sensor is a crank angle sensor, The combustion variable is the rotational momentum of the crankshaft of the internal combustion engine, The rotational momentum is a variable related to the difference in the magnitudes of a plurality of instantaneous speed variables, The instantaneous speed variable is a variable representing the rotational speed of the crankshaft at a predetermined angular interval equal to or less than the interval between the occurrences of the top dead center of compression of the internal combustion engine, Among the plurality of instantaneous speed variables corresponding to the rotational momentum of a specific cylinder among the plurality of cylinders, the instantaneous speed variables during the period between the top dead center of compression of the specific cylinder and the next top dead center of compression are included.

2. The apparatus for detecting misfire in an internal combustion engine according to claim 1, wherein, The determination process is as follows: when the deviation amount of the rotational momentum of the cylinder to be determined with respect to the rotational momentum of the cylinder that is the object of the stop process is equal to or less than a predetermined specified amount, it is determined that misfire has occurred in the cylinder to be determined. The specified amount is a fixed value.

3. The apparatus for detecting misfire in an internal combustion engine according to claim 2, wherein, The misfire detection device is configured to execute the stop process on the condition that the rotational speed of the crankshaft of the internal combustion engine is equal to or higher than a specified speed.

4. The apparatus for detecting misfire in an internal combustion engine according to claim 2 or 3, wherein, The misfire detection device is configured to execute the stop process on the condition that the torque of the internal combustion engine is equal to or higher than a specified value.

5. The apparatus for detecting misfire in an internal combustion engine according to claim 1, wherein, The misfire detection device is configured to execute the following learning process: learning the difference between the rotational momentum when the combustion control of the internal combustion engine is stopped for a cylinder whose appearance interval of the compression top dead center with respect to the cylinder that is the object of the stop process is not an integer multiple of one cycle and the rotational momentum of the cylinder that is the object of the stop process. The determination process is as follows: when the deviation amount of the rotational momentum of the cylinder to be determined with respect to the rotational momentum of the cylinder that is the object of the stop process is equal to or less than a predetermined specified amount, it is determined that misfire has occurred in the cylinder to be determined, and the determination process includes the following correction process: determining the specified amount when determining the cylinder that is not an integer multiple of one cycle as the cylinder to be determined according to the difference learned through the learning process.

6. An apparatus for detecting misfire in an internal combustion engine, The internal combustion engine has a plurality of cylinders, The fire detection device is configured to perform the following processes: A stop process that stops the combustion control of the air-fuel mixture in some of the plurality of cylinders; A combustion variable acquisition process that acquires a value of a combustion variable, which is a variable representing the combustion state in each of the plurality of cylinders and is determined based on a detection value of a sensor that detects a physical quantity corresponding to the combustion state of the air-fuel mixture in each of the plurality of cylinders; and A determination process that, when the stop process is executed, designates the cylinders that have undergone the combustion control as cylinders to be determined for the presence or absence of misfire, and determines that misfire has occurred in the designated cylinders when the degree of deviation of the value of the combustion variable in the designated cylinders from the value of the combustion variable in the cylinders that are the target of the stop process is equal to or less than a predetermined degree. The sensor is a sensor that is provided in the combustion chamber of each of the plurality of cylinders and detects the combustion state of the air-fuel mixture in the combustion chamber. The combustion variable related to each of the plurality of cylinders is quantified based on the detection value of the sensor between the top dead center of compression and the next top dead center of compression in the cylinder.

7. The misfire detection device for an internal combustion engine according to claim 6, wherein The sensor is a sensor that detects the pressure in the combustion chamber.

8. A misfire detection method for an internal combustion engine, The internal combustion engine has a plurality of cylinders, The misfire detection method includes: Execute a stop process for stopping the combustion control of the air-fuel mixture in some of the plurality of cylinders; Obtain a value of a combustion variable, which is a variable representing the combustion state in each of the plurality of cylinders, determined based on the detection value of a sensor that detects a physical quantity corresponding to the combustion state of the air-fuel mixture in each of the plurality of cylinders; and When executing the stop process, use the cylinders for which the combustion control has been executed as the cylinders to be determined for the presence or absence of misfire. When the degree of deviation of the value of the combustion variable of the cylinder to be determined with respect to the value of the combustion variable of the cylinder that is the object of the stop process is equal to or less than a predetermined degree, it is determined that misfire has occurred in the cylinder to be determined. The sensor is a crank angle sensor. The combustion variable is the rotational momentum of the crankshaft of the internal combustion engine. The rotational momentum is a variable related to the difference in the magnitudes of a plurality of instantaneous speed variables. The instantaneous speed variable is a variable representing the rotational speed of the crankshaft in a predetermined angular interval equal to or less than the appearance interval of the compression top dead center of the internal combustion engine. Among the plurality of instantaneous speed variables corresponding to the rotational momentum of a specific cylinder among the plurality of cylinders, the instantaneous speed variable during the period between the compression top dead center of the specific cylinder and the next compression top dead center is included.

9. A misfire detection method for an internal combustion engine, The internal combustion engine has a plurality of cylinders, The misfire detection method includes: Execute a stop process for stopping the combustion control of the air-fuel mixture in some of the plurality of cylinders; Obtain the value of a combustion variable, which is a variable representing the combustion state in each of the plurality of cylinders and is determined based on the detection value of a sensor that detects a physical quantity corresponding to the combustion state of the air-fuel mixture in each cylinder of the plurality of cylinders; and When performing the stop process, use the cylinder that has undergone the combustion control as the cylinder to be determined for misfire. When the deviation degree of the value of the combustion variable of the cylinder to be determined from the value of the combustion variable of the cylinder that is the object of the stop process is equal to or less than a predetermined degree, it is determined that misfire has occurred in the cylinder to be determined. The sensor is a sensor that is provided in the combustion chamber of each cylinder of the plurality of cylinders and detects the combustion state of the air-fuel mixture in the combustion chamber. The combustion variable related to each cylinder of the plurality of cylinders is quantified based on the detection value of the sensor between the top dead center of compression and the next top dead center of compression in the cylinder.

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