Internal combustion engine misfire determination device

Abstract

To provide a misfire determination device for an internal combustion engine capable of suppressing deterioration of misfire determination accuracy.SOLUTION: When rotating speed of a rotating shaft 60a of a motor generator 60 is low, a PU 72 engages a clutch 50 and then, starts combustion control of an internal combustion engine 10 to start the internal combustion engine 10. When the rotating speed of the rotating shaft 60a is high, the PU 72 engages the clutch 50 to apply initial rotation to a crank shaft 28, and then, releases the clutch 50. Then, the PU 72 starts the combustion control of the internal combustion engine 10. Compared to the former start processing, in the latter start processing, the PU 72 increases a delay time from start of the combustion control to start of misfire determination processing.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a misfire determination device for an internal combustion engine.

Background Art

[0002] For example, Patent Document 1 below describes a device for determining the presence or absence of misfire in an internal combustion engine in a hybrid vehicle.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The inventor considered a device including the following two processes as a start-up process for shifting an internal combustion engine from a stopped state to an operating state in a hybrid vehicle. The first process is a process of starting the internal combustion engine by increasing the engine rotation speed, which is the rotation speed of the crankshaft of the internal combustion engine, by combustion control of the internal combustion engine. The second process is a process of starting combustion control in a state where the engine rotation speed has been increased to a certain extent. In that case, when starting the misfire determination process at the same timing uniformly from the start of combustion control, the determination process is started at a lower rotation speed in the first process. However, when the engine rotation speed is excessively low, the misfire determination accuracy tends to be low.

Means for Solving the Problems

[0005] Hereinafter, means for solving the above problems and their effects will be described. Note that the correspondence between the numbers assigned to the means for solving the problems described below and the claims in the claims of the patent is as follows. Claim 1 in the claims of the patent corresponds to the corrected version of means 2 below. Claim 2 in the claims of the patent corresponds to means 3 below. 1. An internal combustion engine misfire determination device applied to a vehicle equipped with an internal combustion engine and a rotating electric machine, configured to execute a start process, a misfire determination process, and a variable process, wherein the start process is a process of starting combustion control of the internal combustion engine to shift the internal combustion engine from a stopped state to an operating state, the misfire determination process is a process of determining the presence or absence of misfire in the internal combustion engine, and the variable process is a process of making the delay amount of the start timing of the misfire determination process with respect to the start timing of the combustion control shorter when the engine rotation speed at the start of the combustion control by the start process is equal to or higher than a predetermined rotation speed than when it is lower than the predetermined rotation speed, and the engine rotation speed is the rotation speed of the crankshaft of the internal combustion engine.

[0006] In the above configuration, the delay amount of the start timing of the misfire determination process with respect to the start timing of the combustion control is made longer when the engine rotation speed at the start of the combustion control is lower than the predetermined rotation speed. Thereby, it is possible to suppress the misfire determination process from starting when the engine rotation speed is excessively low. Therefore, it is possible to suppress a decrease in the determination accuracy of misfire.

[0007] 2. The crankshaft is mechanically connectable to the rotating shaft of the rotating electric machine and the drive wheels of the vehicle via a clutch, the start process includes a first start process and a second start process, the first start process is a process of increasing the engine rotation speed by combustion control of the internal combustion engine in a released state of the clutch and including a process of starting the combustion control when the engine rotation speed is lower than the predetermined rotation speed, the second start process is a process of starting the combustion control in a engaged state of the clutch, a start determination process is executed to determine whether or not the engine rotation speed is equal to or higher than a start determination value by the first start process, the start determination value is a value equal to or higher than the predetermined rotation speed, and the variable process includes a process of starting the misfire determination process after it is determined to be equal to or higher than the start determination value by the start determination process when the internal combustion engine is started by the first start process, which is the internal combustion engine misfire determination device according to the above 1.

[0008] The first starting process is a process that starts combustion control when the rotational speed is less than a predetermined rotational speed. However, in the above configuration, when the internal combustion engine is started by the first starting process, misfire determination is started after the engine rotational speed is determined to be equal to or higher than the starting determination value. Therefore, even when the internal combustion engine is started by the first starting process, it is possible to suppress the start of misfire determination processing when the engine rotational speed is excessively low.

[0009] 3. Execute a selection process for selecting a process used for starting the internal combustion engine from among the two processes of the first starting process and the second starting process. The selection process includes a process of setting the motor rotational speed when selecting the first starting process to a value larger than the motor rotational speed when selecting the second starting process. The motor rotational speed is the rotational speed of the rotating shaft of the rotating electrical machine. The misfire determination device for an internal combustion engine according to the above item 2.

[0010] When the second starting process is executed when the engine rotational speed is high, it is necessary to significantly increase the engine rotational speed by the power of the rotating electrical machine. Therefore, the workload of the rotating electrical machine increases. In addition, since the time required to increase the engine rotational speed becomes long, the time until the power of the internal combustion engine is transmitted to the drive wheels becomes long. Therefore, in the above configuration, when the motor rotational speed is high, the first starting process is selected. This makes it possible to reduce the workload that the rotating electrical machine does on the internal combustion engine and to rapidly increase the rotational speed of the crankshaft.

[0011] 4. The fuel pump that adjusts the injection pressure of the fuel of the internal combustion engine is an engine-driven pump. The selection process includes a process of selecting the first starting process when the pressure of the fuel of the internal combustion engine is high and selecting the second starting process when the pressure is low when the motor rotational speed is the specified rotational speed. The misfire determination device for an internal combustion engine according to the above item 3.

[0012] An engine-driven pump stops when the internal combustion engine stops. Therefore, when the internal combustion engine is stopped, the fuel pressure may gradually decrease. When starting the internal combustion engine with a low fuel pressure, there is a risk that fuel injection cannot be properly executed. Therefore, in the above configuration, the second starting process is prioritized when the fuel pressure is low. Since the second starting process is executed in the engaged state of the clutch, the starting process is executed with the crankshaft being driven by the rotating electric machine. Therefore, the starting process is executed with the pump being driven by the rotating electric machine. Therefore, it is possible to prevent the fuel pressure from becoming excessively low when the starting process is executed.

[0013] 5. The second starting process is a process of starting the combustion control without switching the clutch to the disengaged state after increasing the engine rotation speed by shifting the clutch from the disengaged state to the engaged state, and the selection process is a process of selecting the first starting process when the required torque for the vehicle is large and the second starting process when the required torque is small when the motor rotation speed is a specific rotation speed. The misfire determination device for an internal combustion engine according to any one of 3 or 4 above.

[0014] When the required torque is large, the motor rotation speed is more likely to increase than when it is small. When the second starting process is adopted when the motor rotation speed increases, the amount of work required for the rotating electric machine to increase the rotation speed of the crankshaft increases. Also, the time required to increase the rotation speed of the crankshaft to the motor rotation speed becomes longer. Therefore, in the above configuration, when the required torque is large, the first starting process is preferentially adopted. Thereby, the rotation speed of the crankshaft can be increased by the combustion control of the internal combustion engine in the disengaged state of the clutch. Therefore, it is possible to reduce the amount of work done by the rotating electric machine on the internal combustion engine and to quickly increase the rotation speed of the crankshaft.

[0015] 6. The first starting process includes a process of starting the combustion control after applying an initial rotation to the crankshaft by the rotational power of the rotating shaft of the rotary electric machine with the clutch in the engaged state and then setting the clutch in the disengaged state. The misfire determination device for an internal combustion engine according to any one of 2 to 5 above.

[0016] According to the above configuration, by setting the clutch in the engaged state, an initial rotation can be applied to the crankshaft.

Brief Description of the Drawings

[0017]

Figure 1

Figure 2

Figure 3

Figure 4

Modes for Carrying Out the Invention

[0018] Hereinafter, an embodiment will be described with reference to the drawings. A throttle valve 14 is provided in an intake passage 12 of an internal combustion engine 10 shown in FIG. 1. The air inhaled into the intake passage 12 is inhaled into a combustion chamber 22 partitioned by a cylinder 18 and a piston 20 as the intake valve 16 opens. Fuel is injected into the combustion chamber 22 from a fuel injection valve 24. In the combustion chamber 22, an air-fuel mixture is subjected to combustion with a spark discharge by an ignition device 26. The energy generated by the combustion is converted into rotational energy of a crankshaft 28 via a piston 20. The air-fuel mixture subjected to combustion is discharged into an exhaust passage 32 as exhaust as the exhaust valve 30 opens. Fuel supplied to the fuel injection valve 24 is supplied from a fuel pump 40 that sucks fuel from a fuel tank 42.

[0019] The internal combustion engine 10 has four cylinders #1 to #4. A motor generator 60 and a transmission 52 can be mechanically connected to the crankshaft 28 via a clutch 50. Specifically, the rotation shaft 60a of the motor generator 60 can be mechanically connected to the crankshaft 28 via the clutch 50. The transmission 52 can be connected to the rotation shaft 60a.

[0020] The transmission 52 includes a stepped transmission 52a. The stepped transmission 52a includes a planetary gear mechanism and friction engagement elements including clutches and brakes. The stepped transmission 52a is a device capable of changing the gear ratio, which is the ratio of the rotational speed of the output shaft to the rotational speed of the input shaft. The input shaft of the stepped transmission 52a is mechanically connected to the rotation shaft 60a via a torque converter 52b. The torque converter 52b includes a lock-up clutch 52c. Further, the output shaft of the stepped transmission 52a is mechanically connected to the drive wheels 56 via a differential 54.

[0021] The control device 70 operates operation units such as the throttle valve 14, the fuel injection valve 24, and the ignition device 26 in order to control the torque and the exhaust component ratio, which are the control amounts of the internal combustion engine 10 as the control target. Further, the control device 70 operates the inverter 62 in order to control the torque, which is the control amount of the motor generator 60 as the control target. The inverter 62 applies an AC voltage to the terminals of the motor generator 60. The control device 70 also operates the clutch 50, the lock-up clutch 52c, and the stepped transmission 52a. An operation signal MS is shown in FIG. 1.

[0022] When controlling various control quantities, the control device 70 refers to the output signal Scr of the crank angle sensor 80 and the pressure P of the fuel supplied to the fuel injection valve 24 detected by the pressure sensor 82. Further, the control device 70 refers to the accelerator operation amount ACCP which is the depression amount of the accelerator pedal 84 detected by the accelerator sensor 86. Further, the control device 70 refers to the output signal Sm of the rotation angle sensor 88 that senses the rotation angle of the rotation shaft 60a of the motor generator 60.

[0023] The control device 70 includes a PU 72, a storage device 74, and a peripheral circuit 76. The PU 72 is a software processing device including at least one of a CPU, a GPU, a TPU, and the like. The peripheral circuit 76 includes a circuit that generates a clock signal that defines the internal operation, a power supply circuit, a reset circuit, and the like. The control device 70 controls the control quantity by the PU 72 executing the program stored in the storage device 74.

[0024] Under predetermined conditions, the control device 70 runs the vehicle only with the power of the motor generator 60 with the clutch 50 in the released state. That is, it is an EV mode in which the internal combustion engine 10 is in a stopped state. On the other hand, for example, when the output of the motor generator 60 is insufficient such that the accelerator operation amount ACCP is equal to or greater than a predetermined value, the control device 70 engages the clutch 50. Then, the control device 70 runs the vehicle using both the power of the internal combustion engine 10 and the power of the motor generator 60. This is the EHV mode. Hereinafter, the processes executed by the control device 70 will be described in the order of "starting process of the internal combustion engine 10", "process related to detection of misfire", and "process related to start of misfire determination".

[0025] "Starting process of the internal combustion engine 10" Fig. 2 shows the procedure of the starting process of the internal combustion engine 10 for the transition from the EV mode to the EHV mode. The process shown in Fig. 2 is realized by the PU72 repeatedly executing the program stored in the storage device 74 each time a predetermined condition is satisfied. Here, the predetermined condition is a condition indicating that a switching request from the EV mode to the EHV mode has occurred. In the following, the step numbers of each process are represented by numbers preceded by "S".

[0026] In the series of processes shown in Fig. 2, the PU72 first acquires the required torque Trq*, the pressure P, and the motor rotational speed Nm which is the rotational speed of the rotating shaft 60a of the internal combustion engine 10 (S10). The motor rotational speed Nm is calculated by the PU72 based on the output signal Sm. Next, the PU72 determines whether the logical product of the following conditions (A) and (B) is true (S12).

[0027] Condition (A): This is a condition that the motor rotation speed Nm is equal to or higher than the specified rotation speed Nth. The specified rotation speed Nth is set by the PU72 according to the required torque Trq*. Here, the PU72 sets the specified rotation speed Nth when the required torque Trq* is large to be equal to or lower than the specified rotation speed Nth when the required torque Trq* is small. This process can be realized, for example, by storing map data in the storage device 74 and performing a map operation on the specified rotation speed Nth by the PU72. Here, the map data is data with the required torque Trq* as the input variable and the specified rotation speed Nth as the output variable. Note that the map data is paired data of discrete values of the input variable and the values of the output variable corresponding to each value of the input variable. Also, the map operation may be a process in which when the value of the input variable matches any of the values of the input variable of the map data, the value of the output variable of the corresponding map data is taken as the operation result. Also, the map operation may be a process in which when the value of the input variable does not match any of the values of the input variable of the map data, the value obtained by interpolation of the values of a plurality of output variables included in the map data is taken as the operation result. Also, alternatively, the map operation may be a process in which when the value of the input variable does not match any of the values of the input variable of the map data, the value of the output variable of the map data corresponding to the closest value among the values of a plurality of output variables included in the map data is taken as the operation result.

[0028] Condition (B): This is a condition that the pressure is equal to or higher than the specified value Pth. The specified value Pth is set to a value that can maintain the controllability of the fuel injected by the fuel injection valve 24 at a predetermined level or higher.

[0029] When determining that the logical product is true (S12: YES), PU72 switches the clutch 50 to the engaged state (S14). Here, the "engaged state" shall mean a state where the power of the motor generator 60 can be transmitted to the crankshaft 28 via the clutch 50. That is, it shall include a so-called semi-clutch state where the rotational speed of the crankshaft 28 does not match the motor rotational speed Nm of the rotary shaft 60a. And PU72 waits until it can apply an initial rotation to the crankshaft 28 (S16: NO). Here, PU72 determines that it can apply an initial rotation when the crankshaft 28 has rotated by a predetermined rotation angle. The predetermined rotation angle may be smaller than one rotation of the crankshaft 28.

[0030] When determining that it can apply an initial rotation (S16: YES), PU72 releases the clutch 50 (S18). And PU72 starts the combustion control of the internal combustion engine 10 (S20). That is, PU72 starts the control of burning the air-fuel mixture by injecting fuel from the fuel injection valve 24 and operating the ignition device 26. Note that when performing the process of S20, PU72 reclutches the clutch 50 when the engine rotational speed, which is the rotational speed of the crankshaft 28, rises to about the motor rotational speed Nm.

[0031] On the other hand, when determining that the above logical product is false (S12: NO), PU72 engages the clutch 50 (S22). And PU72 starts the combustion control in the engaged state of the clutch 50 (S24).

[0032] Note that when completing the processes of S20 and S24, PU72 temporarily ends the series of processes shown in FIG. 2. "Process Regarding Detection of Misfire" FIG. 3 shows the procedure of the process regarding the detection of misfire. The process shown in FIG. 3 is realized by PU72 repeatedly executing the program stored in the storage device 74 at a predetermined crank angle period.

[0033] In the series of processes shown in FIG. 3, the PU 72 first obtains the time T30 required for the crankshaft 28 to rotate 30° CA (S30). The time T30 is calculated by the PU 72 based on the output signal Scr. Next, with "m = 0, 1, 2, 3,...", the PU 72 executes a process of substituting the time T30[m] into the time T30[m + 1] and a process of substituting the time T30 newly obtained in the process of S30 into the time T30[0] (S32). These processes are for making the variables in the parentheses after the time T30 have larger numbers as they are older. By these processes, when the value of the variable in the parentheses is one larger, it becomes the time T30 30° CA earlier.

[0034] Next, the PU 72 determines whether the current rotation angle of the crankshaft 28 is 120° CA ATDC with respect to the compression top dead center of any one of cylinders #1 to #4 (S34). When the PU 72 determines that it is 120° CA ATDC (S34: YES), it substitutes the rotational fluctuation amount ΔT30[m] into the rotational fluctuation amount ΔT30[m + 1], and substitutes the value obtained by subtracting the time T30[4] from the time T30[0] into the rotational fluctuation amount ΔT30[0] (S36). The rotational fluctuation amount ΔT30 is a variable that becomes a negative value when no misfire occurs in the cylinder to be determined for the presence or absence of misfire, and becomes a positive value when a misfire occurs. Here, the cylinder to be determined for the presence or absence of misfire is the cylinder determined to have passed 120° past the compression top dead center by the process of S34.

[0035] Next, the PU 72 determines whether the start flag F is "1" (S38). The start flag F becomes "1" when starting the determination of misfire. When the start flag F is "0", it indicates a state where the start of the misfire determination is not permitted.

[0036] When the PU 72 determines that the start flag F is "1" (S38: YES), it determines whether the value obtained by subtracting the rotational fluctuation amount ΔT30[4] from the rotational fluctuation amount ΔT30[0] is equal to or greater than the threshold value ΔTth (S40).

[0037] This process is to determine whether misfire has occurred in the cylinder to be determined. That is, when misfire has not occurred, the rotational fluctuation amounts ΔT30[0] and ΔT30[2] are of the same order of magnitude, so the difference between them has a small absolute value. On the other hand, when misfire has occurred in the cylinder to be determined, the rotational fluctuation amount ΔT30[0] becomes a positive value. On the contrary, when misfire has not occurred in the cylinder that reached top dead center of compression 360°CA before the cylinder to be determined, the rotational fluctuation amount ΔT30[2] becomes a negative value. Therefore, when misfire has occurred in the cylinder to be determined, the value obtained by subtracting the rotational fluctuation amount ΔT30[2] from the rotational fluctuation amount ΔT30[0] is positive and has a large absolute value.

[0038] Note that, instead of comparing the magnitude of the rotational fluctuation amount ΔT30[0] with a threshold value, comparing the magnitude of the value obtained by subtracting the rotational fluctuation amount ΔT30[4] from the rotational fluctuation amount ΔT30[0] with the threshold value ΔTth is aimed at improving the accuracy. That is, due to the tolerance of the location detected by the crank angle sensor 80, an error occurs in the detected rotational angle. However, the rotational fluctuation amounts ΔT30 that are separated by an integer multiple of one rotation of the crankshaft 28 are amounts based on the same rotational angle of the crankshaft 28. Therefore, by using the difference between the rotational fluctuation amounts ΔT30 that are separated by an integer multiple of one rotation of the crankshaft 28, the influence of the error of the crank angle sensor 80 can be offset. Furthermore, the rotational fluctuation amounts ΔT30 that are separated by an integer multiple of two rotations of the crankshaft 28 are amounts in the same cylinder. Therefore, by using the difference between the rotational fluctuation amounts ΔT30 that are separated by an integer multiple of two rotations of the crankshaft 28, the influence of individual differences between cylinders and the like can be offset. Therefore, according to the difference between the rotational fluctuation amount ΔT30[0] and the rotational fluctuation amount ΔT30[4], the influence of the error of the crank angle sensor 80 and the influence of individual differences between cylinders and the like can be offset.

[0039] When PU72 determines that it is equal to or greater than the threshold value ΔTth (S40: YES), it makes a provisional determination that misfire has occurred (S42). Then, PU72 increments a counter Cn that counts the number of provisional determinations (S44).

[0040] When PU72 completes the process of S44 or makes a negative determination in the process of S40, it determines whether a predetermined period has elapsed (S46). Here, the starting point of the predetermined period is the later timing of the timing when the process of S40 is first executed and the timing when the process of S54 described later is last executed. When PU72 determines that the predetermined period has elapsed (S46: YES), it determines whether the counter Cn is equal to or greater than the threshold value Cth (S48). The threshold value Cth is set according to the lower limit value of the fire occurrence rate when a fire occurs at a fire occurrence rate that cannot be overlooked within the predetermined period. That is, the length of the predetermined period and the threshold value Cth are predetermined according to the above lower limit value.

[0041] When PU72 determines that it is equal to or greater than the threshold value Cth (S48: YES), it determines that a fire has occurred (S50). Then, PU72 executes a notification process of notifying the user that the fire occurrence rate has occurred at a level that cannot be overlooked by operating the warning lamp 90 shown in FIG. 1 (S52). On the other hand, when PU72 determines that the counter Cn is less than the threshold value Cth (S48: NO), it initializes the counter Cn (S54).

[0042] Note that when the processes of S52 and S54 are completed or when a negative determination is made in the processes of S34, S38, and S46, PU72 temporarily ends the series of processes shown in FIG. 3. "Processing related to the start of fire determination" FIG. 4 shows the procedure of the processing related to the start of fire determination. The processing shown in FIG. 4 is realized by PU72 repeatedly executing the program stored in the storage device 74 at a predetermined crank angle cycle.

[0043] In the series of processes shown in FIG. 4, PU72 first determines whether combustion control has started (S60). When PU72 determines that combustion control has started (S60: YES), it determines whether the engine rotation speed NE is equal to or higher than a predetermined rotation speed NthL (S62). The predetermined rotation speed NthL is set to a value larger than the engine rotation speed NE at the start of combustion control by the process of S20. Note that the engine rotation speed NE is calculated by PU72 based on the output signal Scr.

[0044] When PU72 determines that the speed is equal to or higher than the predetermined rotation speed NthL (S62: YES), after the start of combustion control, it waits until the crankshaft 28 rotates twice (S64: NO). When PU72 determines that it has rotated twice (S64: YES), it substitutes "1" into the start flag F (S66). On the other hand, when PU72 determines that the speed is less than the predetermined rotation speed NthL (S62: NO), it waits until the engine rotation speed NE becomes equal to or higher than the start determination value NthH (S68: NO). The start determination value NthH is a value for determining whether the internal combustion engine 10 has reached a start completion state where it can continue independent operation. The start determination value NthH is set to a value larger than the predetermined rotation speed NthL. When PU72 determines that the value is equal to or higher than the start determination value NthH (S68: YES), it waits until the crankshaft 28 rotates twice (S64: NO). When PU72 determines that it has rotated twice (S64: YES), it substitutes "1" into the start flag F (S66).

[0045] Note that when PU72 completes the process of S66, it temporarily ends the series of processes shown in FIG. 4. Here, the operations and effects of this embodiment will be described.

[0046] PU52 determines the presence or absence of misfire based on the rotational fluctuation amount ΔT30 separated by two rotations of the crankshaft 28. Also, when switching from the EV mode to the EHV mode, the PU52 starts the internal combustion engine 10. Here, when the motor rotation speed Nm is low, the PU52 starts the combustion control of the internal combustion engine 10 in the engaged state of the clutch 50. On the other hand, when the motor rotation speed Nm is high, the PU52 temporarily engages the clutch 50 to impart an initial rotation to the crankshaft 28, and then releases the clutch 50. Then, the PU52 starts the combustion control of the internal combustion engine 10. As a result, the engine rotation speed NE increases.

[0047] When the PU52 starts the combustion control in the engaged state of the clutch 50, the PU52 starts the determination of misfire when the crankshaft 28 rotates twice. Thereby, the PU52 can determine the presence or absence of misfire by the process of S40.

[0048] On the other hand, when the PU52 starts the combustion control in the state where the clutch 50 is released, after the start determination, the PU52 starts the determination of misfire when the crankshaft 28 rotates twice. Before the start determination, the rotational behavior of the crankshaft 28 is unstable, and the determination accuracy of misfire tends to be low. Therefore, by starting the determination of misfire after the start determination, the determination accuracy of misfire can be maintained high.

[0049] According to the present embodiment described above, the following operations and effects can be obtained. (1) When the motor rotation speed Nm is equal to or higher than the predetermined speed Nth, the PU52 starts the internal combustion engine 10 by the processes of S14 to S20. When the motor rotation speed Nm is high, the time required to increase the rotation speed of the crankshaft 28 by engaging the clutch 50 becomes long. Also, the work amount done by the motor generator 60 on the crankshaft 28 until the rotation speed of the crankshaft 28 is increased becomes large, which leads to a decrease in the charging rate of the battery. In contrast, by starting the internal combustion engine 10 by the processes of S14 to S20, it is possible to reduce the work amount done by the motor generator 60 on the crankshaft 28 and to rapidly increase the engine rotation speed NE.

[0050] (2) Even when the motor rotation speed Nm is equal to the specified rotation speed Nth, if the pressure P is less than the specified value Pth, the internal combustion engine 10 is started by the processes of S22 and S24. As a result, when the pressure P is low, combustion control can be executed while the crankshaft 28 is rotating at about the motor rotation speed Nm. Therefore, combustion control can be started in a state where the pressure P is rapidly increased by the engine-driven fuel pump 40.

[0051] (3) When the required torque Trq* is large, the motor rotation speed Nm is more likely to increase than when it is small. And when starting the internal combustion engine 10 by the processes of S22 and S24 when the motor rotation speed Nm increases, the amount of work required for the motor generator 60 to increase the rotation speed of the crankshaft 28 becomes large. Also, the time required to increase the engine rotation speed NE to the motor rotation speed Nm becomes long. Therefore, even when the motor rotation speed Nm is the same, when the required torque Trq* is large, the internal combustion engine 10 is started by the processes of S14 to S20, while when the required torque Trq* is small, the internal combustion engine 10 is started by the processes of S22 and S24. As a result, when the motor rotation speed Nm increases, the engine rotation speed NE can be increased by the combustion control of the internal combustion engine 10 in the released state of the clutch 50. Therefore, it becomes possible to reduce the amount of work done by the motor generator 60 on the internal combustion engine 10 and to rapidly increase the engine rotation speed NE.

[0052] <Corresponding relationship> The correspondence between the matters in the above embodiment and the matters described in the column of "Means for Solving the Problems" is as follows. Below, the correspondence is shown for each number of the solving means described in the column of "Means for Solving the Problems". [1] The start-up process corresponds to the process shown in FIG. 2. The misfire determination process corresponds to the process of S40. The variable process corresponds to the process shown in FIG. 4. The predetermined rotational speed corresponds to the predetermined rotational speed NthL. [2] The clutch corresponds to the clutch 50. The first start-up process corresponds to the processes of S14 to S20. The second start-up process corresponds to the processes of S22 and S24. The start determination process corresponds to the process of S68. [3] The selection process corresponds to the process of S12. [4] Corresponds to the condition (B) in the process of S12. The specified rotational speed corresponds to the specified rotational speed Nth. [5] In the process of S12, it corresponds to the fact that the specified rotational speed Nth is variably set according to the required torque Trq*. [6] Corresponds to the processes of S14 to S20.

[0053] <Other Embodiments> Note that this embodiment can be implemented with the following modifications. This embodiment and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0054] "Regarding the First Start-up Process" · The first start-up process is not limited to the process of imparting an initial rotation to the crankshaft 28 by the rotational power of the rotating shaft 60a of the motor generator 60. For example, a starter motor, which is a dedicated motor for imparting an initial rotation to the crankshaft 28 separately from the motor generator 60, may be provided, and the initial rotation may be imparted by the starter motor.

[0055] · It is not essential for the first start-up process to include the process of imparting an initial rotation to the crankshaft 28 by the rotational power of the rotating shaft of the rotating electrical machine that imparts the initial rotation. For example, by executing a process of controlling the crank angle at the time of stopping of the internal combustion engine 10, a process of shifting from the stopped state to the operating state only by the combustion control of the internal combustion engine 10 may be used.

[0056] "Regarding Starting Process and Variable Process" · It is not essential that the starting process includes a first starting process and a second starting process. For example, after starting the operation of the clutch 50 to shift the clutch 50 from the released state to the engaged state, only the process of starting the combustion control may be performed. Even in such a case, if the delay amount of the starting timing of the misfire determination process with respect to the starting timing of the combustion control is increased when the engine rotational speed NE at the start of the combustion control by the starting process is low, it is sufficient.

[0057] "Regarding Selection Process" · The input for the process of variably setting the specified rotational speed Nth is not limited to the required torque Trq*. For example, it may be the accelerator operation amount ACCP. In that case, the PU72 may set the specified rotational speed Nth to a smaller value when the accelerator operation amount ACCP is large than when it is small. Also by this, the specified rotational speed Nth is set to a smaller value when the required torque Trq* is large than when it is small.

[0058] · It is not essential to variably set the specified rotational speed Nth according to the required torque Trq*. · It is not essential to select the first starting process when the condition (B) that the pressure P of the fuel is equal to or higher than the specified value Pth is satisfied. For example, when the fuel pump that supplies fuel to the fuel injection valve 24 is an electric pump, the condition (B) may be deleted.

[0059] "Regarding Misfire Determination Process" · It is not limited to the process of comparing the difference between a pair of rotational fluctuation amounts ΔT30[0], ΔT30[4] separated by two rotations with a threshold value. For example, it may be a process of comparing the difference between a pair of rotational fluctuation amounts ΔT30[0], ΔT30[2] separated by one rotation with a threshold value. Also for example, it may be a process of comparing the rotational fluctuation amount ΔT30[0] with a threshold value. In those cases, instead of the process of S64, rotation with a rotation angle shorter than two rotations may be used as a condition.

[0060] "Regarding Control Device" ·The control device is not limited to one that includes the PU72 and the storage device 74 and executes software processing. For example, at least a part of what was software-processed in the above embodiment may be provided with a dedicated hardware circuit such as an ASIC that performs hardware processing. 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 storage device that stores the program. (b) It includes a processing device and a program storage device that execute a part 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 a plurality of software execution devices including a processing device and a program storage device, and dedicated hardware circuits.

[0061] "Regarding the vehicle" ·The vehicle is not limited to a parallel hybrid vehicle. For example, it may be a series-parallel hybrid vehicle. In that case, for example, the crankshaft 28, the rotation axis of the first rotating body, and the rotation axis of the second rotating body may be mechanically connected to the carrier, sun gear, and ring gear of the planetary gear mechanism, respectively. Here, it is desirable to provide a clutch between the carrier and the crankshaft 28.

Explanation of reference numerals

[0062] 10... Internal combustion engine 12... Intake passage 14... Throttle valve 16... Intake valve 18... Cylinder 20... Piston 22... Combustion chamber 24... Fuel injection valve 26... Ignition device 28... Crankshaft 30... Exhaust valve 32... Exhaust passage 40... Fuel pump 42... Fuel tank 50... Clutch 52… Transmission device 52a… Step transmission device 52b… Torque converter 52c… Lock-up clutch 54… Differential 56… Driving wheel 60… Motor generator 60a… Rotating shaft 62… Inverter 70… Control device

Claims

1. Applied to a vehicle equipped with an internal combustion engine and a rotating electric machine, The crankshaft of the internal combustion engine can be mechanically connected to the rotating shaft of the rotating electric machine and the drive wheels of the vehicle via a clutch, It is configured to execute a first starting process, a second starting process, a starting determination process, and a misfire determination process, The first starting process and the second starting process are processes that start the combustion control of the internal combustion engine and shift the internal combustion engine from a stopped state to an operating state, The first starting process is a process of increasing the engine rotational speed by the combustion control of the internal combustion engine in the released state of the clutch, The second starting process is a process of starting the combustion control in the engaged state of the clutch, The starting determination process is a process of determining whether the engine rotational speed has increased to a starting determination value or more by the first starting process, The misfire determination process is a process of determining the presence or absence of misfire in the internal combustion engine, The engine rotational speed is the rotational speed of the crankshaft, When the internal combustion engine is started by the first starting process, after it is determined by the starting determination process that the engine rotational speed has increased to the starting determination value or more, by starting the misfire determination process, the delay amount of the starting timing of the misfire determination process with respect to the starting timing of the combustion control is made larger when the internal combustion engine is started by the first starting process than when the combustion control is started when the engine rotational speed is a predetermined rotational speed or more by the second starting process. A misfire determination device for an internal combustion engine.

2. Execute a selection process for selecting a process used for starting the internal combustion engine from among the two processes of the first starting process and the second starting process, The selection process includes a process of setting the motor rotational speed when the first starting process is selected to a value larger than the motor rotational speed when the second starting process is selected, The misfire determination device for an internal combustion engine according to claim 1, wherein the motor rotational speed is the rotational speed of the rotating shaft of the rotating electric machine.

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