Hybrid vehicle control device

Abstract

To compatibly secure stability of combustion at a restart of an engine and complete the restart of the engine early.SOLUTION: An execution device 51 of a controller 50 executes, when an engine 11 is requested to be restarted with the engine rotating speed lower than a second determination rotating speed, first restart processing in which the engine 11 is cranked by a motor generator 13 while a clutch 12 is engaged to couple the motor generator 13 to a crank shaft 22 and fuel injection and ignition of the engine 11 are started once combustion start conditions are met in this state. The execution device 51 executes, when the engine 11 is requested to be restarted with the engine rotating speed equal to or higher than the second determination rotating speed, second restart processing in which the fuel injection and ignition of the engine 11 are started and the clutch 12 is engaged after the engine 11 starts to couple the motor generator 13 to the crank shaft 22.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a control device for a hybrid vehicle. [Background technology]

[0002] Patent Document 1 discloses a hybrid vehicle that includes an engine, a motor generator, and a clutch that is disposed between the crankshaft of the engine and the motor generator. In such a hybrid vehicle, when the clutch is engaged, the crankshaft and the motor generator are connected. On the other hand, when the clutch is released, the connection between the crankshaft and the motor generator is released.

[0003] A control device applied to such a hybrid vehicle cranks the engine by driving the motor generator with the clutch engaged, and when a predetermined combustion start condition is met while the crankshaft is being rotated by cranking, the control device starts fuel injection control and ignition control of the engine, thereby starting the engine. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-54165 Summary of the Invention [Problem to be solved by the invention]

[0005] In a hybrid vehicle, there are cases where the engine is required to be restarted while the engine speed is dropping due to the fuel cut-off, and it is desirable to ensure both stable combustion during the engine restart and to complete the engine restart as quickly as possible. [Means for solving the problem]

[0006] A hybrid vehicle control device for solving the above problems is applied to a hybrid vehicle including an engine having a crankshaft, a motor generator, and a clutch disposed between the crankshaft and the motor generator. The hybrid vehicle control device includes an execution device that executes a restart process to restart the engine when a restart of the engine is requested under a condition in which combustion in the engine is interrupted. When a restart of the engine is requested under a situation in which the engine speed has dropped because combustion in the engine has been interrupted and the engine speed is lower than a reference speed, the execution device executes a first restart process as the restart process, in which the engine is cranked by engaging the clutch and driving the motor generator while the motor generator is connected to the crankshaft, and when a combustion start condition is satisfied while the cranking is being performed, the execution device executes a second restart process as the restart process, in which the engine is started by starting fuel injection and ignition, and after the engine has been started, the execution device engages the clutch and connects the motor generator to the crankshaft.

[0007] In a hybrid vehicle, the combustion in the engine may be interrupted while the crankshaft is rotating, and the restart of the engine may be requested while the engine speed is decreasing. In the above configuration, when the restart of the engine is requested under the condition that the engine speed is decreasing and the engine speed is lower than the judgment speed, the first restart process is executed. In the first restart process, the motor generator is connected to the crankshaft by the clutch, and cranking is performed by driving the motor generator. In this way, when the combustion start condition is satisfied under the condition that the engine speed is adjusted by driving the motor generator, fuel injection and ignition are started in the engine. That is, when the engine is restarted under the condition that the engine speed is relatively low, the engine speed is increased by cranking and then the engine is restarted. Therefore, the engine can be restarted while ensuring the stability of the combustion.

[0008] On the other hand, when the engine is restarted under a condition where the engine speed is lowered and is equal to or higher than the reference speed, the second restart process is executed instead of the first restart process. In the second restart process, the engine is restarted before the motor generator is connected to the crankshaft by the clutch. That is, fuel injection and ignition in the engine are started regardless of whether the combustion start condition is satisfied. Therefore, the engine restart can be completed earlier than when the first restart process is executed.

[0009] Therefore, the above-described control device for a hybrid vehicle can ensure the stability of combustion when the engine is restarted, while also quickly completing the restart of the engine. In a hybrid vehicle to which the hybrid vehicle control device is applied, the engine has cylinders and pistons that reciprocate in the cylinders in synchronization with the rotation of the crankshaft, and in the hybrid vehicle control device, the combustion start condition is that the number of the cylinders whose pistons have passed top dead center of compression after the start of the cranking by driving the motor generator reaches a predetermined number.

[0010] In the above configuration, when the number of cylinders whose pistons have passed the compression top dead center reaches a predetermined number, it is determined that the engine speed has increased to a certain degree due to cranking driven by the motor generator. Therefore, it is determined that the combustion start condition is satisfied, and fuel injection and ignition are started in the engine. This ensures stable combustion when the engine is restarted. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a hybrid vehicle including a control device which is an embodiment of a control device for a hybrid vehicle, and a drive system controlled by the control device. [Diagram 2] FIG. 2 is a schematic diagram showing the engine of the drive system. [Diagram 3] FIG. 3 is a flowchart illustrating a processing routine executed by the control device when starting the engine. [Figure 4] FIG. 4 is a flowchart illustrating the first restart process. [Diagram 5] FIG. 5 is a flowchart illustrating the second restart process. [Figure 6] In FIG. 6, (A) is a time chart showing the transition of engine speed, (B) is a diagram showing the start processing selected by the control device, (C) is a diagram showing whether or not cranking is performed when the engine is started, and (D) is a diagram showing whether or not a combustion start determination is made prior to starting the engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, one embodiment of a control device for a hybrid vehicle will be described with reference to Figs. 1 shows a schematic configuration of a hybrid vehicle 10. The hybrid vehicle 10 includes a drive system of the hybrid vehicle 10 and a control device 50 that controls the drive system. In this embodiment, the control device 50 corresponds to a "hybrid vehicle control device."

[0013] <Hybrid vehicle 10 drive system> The drive system of the hybrid vehicle 10 includes an engine 11, a clutch 12, a motor generator 13, a transmission 14, and drive wheels 15. The clutch 12 is disposed between the engine 11 and the motor generator 13 in the power transmission path. In addition, the transmission 14 is disposed between the motor generator 13 and the drive wheels 15 in the power transmission path.

[0014] As shown in Figures 1 and 2, the engine 11 has a plurality of cylinders 21 and a crankshaft 22. A piston 23 is accommodated in each cylinder 21. A combustion chamber 24 is defined in each cylinder 21 by the piston 23. The piston 23 reciprocates in a direction to expand the volume of the combustion chamber 24 and a direction to reduce the volume. The plurality of pistons 23 are connected to the crankshaft 22 via a connecting rod 25. The reciprocating motion of the plurality of pistons 23 causes the crankshaft 22 to rotate. That is, the pistons 23 reciprocate in the cylinders 21 in synchronization with the rotation of the crankshaft 22.

[0015] The engine 11 has an intake passage 26 and an exhaust passage 28. The intake passage 26 is a passage through which intake air flows to be introduced into the combustion chambers 24 of the multiple cylinders 21. The amount of intake air flowing through the intake passage 26 can be adjusted by the opening degree of a throttle valve 27. The exhaust passage 28 is a passage through which gas exhausted from the combustion chambers 24 of the multiple cylinders 21 flows.

[0016] The engine 11 has a plurality of spark plugs 29 and a plurality of fuel injection valves. In the example shown in FIG. 1, one spark plug 29 is provided for each of the cylinders 21. In addition, in the example shown in FIG. 1, a port injection valve 30 that injects fuel into the intake passage 26 and an in-cylinder injection valve 31 that injects fuel into the cylinder 21 are provided as fuel injection valves. That is, one port injection valve 30 and one in-cylinder injection valve 31 are provided for each cylinder 21. In the combustion chamber 24, a mixture containing fuel injected from at least one of the port injection valve 30 and the in-cylinder injection valve 31 and intake air introduced into the combustion chamber 24 from the intake passage 26 is burned by spark discharge of the spark plug 29. The piston 23 reciprocates in the cylinder 21 due to the power generated by the combustion of the mixture, and the crankshaft 22 rotates. Note that exhaust gas generated by the combustion of the mixture is discharged from the combustion chamber 24 to the exhaust passage 28.

[0017] The clutch 12 connects the crankshaft 22 to the motor generator 13. The clutch 12 is operated under the control of the control device 50. The clutch 12 may be, for example, a hydraulically driven clutch or an electromagnetically driven clutch. When the clutch 12 is engaged, the motor generator 13 is connected to the crankshaft 22. Therefore, when the clutch 12 is engaged, the crankshaft 22 can be rotated by the drive of the motor generator 13. On the other hand, when the clutch 12 is disengaged, the connection between the crankshaft 22 and the motor generator 13 is released.

[0018] <Control device 50> The control device 50 includes an execution device 51. The execution device 51 includes a CPU 52, a ROM 53, and a RAM 54. The ROM 53 stores a control program executed by the CPU 52. The RAM 54 stores the results of calculations performed by the CPU 52.

[0019] The control device 50 receives detection signals from a plurality of types of sensors provided in the hybrid vehicle 10. For example, detection signals from an accelerator opening sensor 61 and a crank angle sensor 62 are input to the control device 50. The accelerator opening sensor 61 detects an accelerator opening AC, which is the opening of the accelerator pedal, and outputs the detection result as a detection signal. The crank angle sensor 62 outputs a detection signal corresponding to the engine speed Ne, which is the rotation speed of the crankshaft 22. The control device 50 then controls the engine 11, the clutch 12, the motor generator 13, and the transmission 14 based on the detection signals from the plurality of types of sensors.

[0020] Hybrid driving control and electric driving control are provided as driving controls for the hybrid vehicle 10. The hybrid driving control is a control in which both the engine 11 and the motor generator 13 are driven to drive the hybrid vehicle 10. The electric driving control is a control in which only the motor generator 13 of the engine 11 and the motor generator 13 is driven to drive the hybrid vehicle 10.

[0021] In the hybrid driving control, the operation of the engine 11 may be intermittently stopped even while the hybrid vehicle 10 is traveling. Stopping the operation of the engine 11 during the hybrid driving control means interrupting combustion in the engine 11. That is, the execution device 51 may interrupt combustion in the engine 11 even while the hybrid vehicle 10 is traveling by stopping fuel injection from the fuel injection valves 30, 31 and ignition from the spark plug 29 by implementing a fuel cut.

[0022] In the hybrid driving control, fuel cut may be performed while the crankshaft 22 is rotating. If the clutch 12 is disengaged when fuel cut is performed, the engine speed Ne decreases due to reasons such as the driving force of the motor generator 13 not being transmitted to the crankshaft 22. While the engine speed Ne is decreasing in this manner, or when the rotation of the crankshaft 22 is stopped, a request to restart the engine 11 may be made by increasing the accelerator opening AC. In addition, when the hybrid vehicle 10 is traveling in an automatic driving mode, an acceleration request may be input to the control device 50 from another control device that manages the automatic driving, and a request to restart the engine 11 may be made.

[0023] <Process to restart engine 11> 3 to 5, a description will be given of a processing routine executed by the execution unit 51 when restarting the engine 11. The processing routine shown in Fig. 3 is executed by the execution unit 51 when a request to restart the engine 11 is made.

[0024] In step S11 of the processing routine shown in Fig. 3, the execution unit 51 determines whether the engine speed Ne is higher than a first judgment speed Neth1. The first judgment speed Neth1 is a criterion for determining whether to execute a restart process or a fuel cut recovery process, which will be described later. If the engine speed Ne is higher than the first judgment speed Neth1 (S11: YES), the execution unit 51 shifts the processing to step S13.

[0025] In step S13, the execution unit 51 executes a fuel cut recovery process. In the fuel cut recovery process, the execution unit 51 starts fuel injection and ignition of the engine 11. For example, the execution unit 51 performs stratified combustion in the cylinder 21 by injecting fuel from the in-cylinder injection valve 31 during the compression stroke. At this time, the execution unit 51 does not perform cranking of the engine 11 by driving the motor generator 13. When the engine 11 is restarted by the fuel cut recovery process, the execution unit 51 ends this processing routine.

[0026] On the other hand, if the engine speed Ne is equal to or lower than the first judgment speed Neth1 in step S11 (NO), the execution unit 51 shifts the process to step S15. In step S15, the execution unit 51 determines whether the engine speed Ne is higher than the second judgment speed Neth2. An engine speed lower than the first judgment speed Neth1 is set as the second judgment speed Neth2. The second judgment speed Neth2 is a criterion for determining whether it is necessary to increase the engine speed Ne by cranking when restarting the engine 11. If the engine speed Ne is higher than the second judgment speed Neth2 (S15: YES), the execution unit 51 shifts the process to step S17.

[0027] In step S17, the execution unit 51 executes a second restart process as the restart process. The details of the second restart process will be described later. When the engine 11 is restarted by the second restart process, the execution unit 51 ends this processing routine.

[0028] On the other hand, if the engine speed Ne is equal to or lower than the second judgment speed Neth2 in step S15 (NO), the execution device 51 shifts the process to step S19. In step S19, the execution device 51 judges whether the rotation of the crankshaft 22 has stopped. Specifically, if the engine speed Ne is equal to or lower than the stop judgment speed for a predetermined time or more, the execution device 51 judges that the rotation of the crankshaft 22 has stopped. The stop judgment speed is set to a speed lower than the first judgment speed Neth1. For example, the stop judgment speed is 0 (zero). If it is judged that the rotation of the crankshaft 22 has not stopped (S19: NO), the execution device 51 shifts the process to step S21. In step S21, the execution device 51 executes a first restart process as the restart process. The contents of the first restart process will be described later. When the engine 11 is started by the first restart process, the execution device 51 ends this processing routine.

[0029] On the other hand, if it is determined in step S19 that the rotation of the crankshaft 22 has stopped (YES), the execution unit 51 proceeds to step S23. In step S23, the execution unit 51 executes a stop-time restart process as the restart process. The details of the stop-time restart process will be described later. When the execution unit 51 starts the engine 11 by the stop-time restart process, it ends this processing routine.

[0030] <First restart process> Next, the first restart processing will be described with reference to Fig. 4. The processing routine shown in Fig. 4 shows the flow of the first restart processing.

[0031] In this processing routine, in step S31, the execution unit 51 determines whether or not the clutch 12 is released. If it is determined that the clutch 12 is released (S31: YES), the execution unit 51 shifts the processing to step S33. On the other hand, if it is determined that the clutch 12 is not released (S31: NO), the clutch 12 is engaged, so the execution unit 51 shifts the processing to step S35.

[0032] In step S33, the execution unit 51 executes an engagement process to engage the clutch 12. When the clutch 12 is engaged by executing the engagement process, the motor generator 13 is connected to the crankshaft 22, and therefore the execution unit 51 transitions to step S35.

[0033] When the engine speed Ne becomes equal to or lower than the second determination speed Neth2, the clutch 12 may be engaged. If the clutch 12 is already engaged before the first restart process is executed, this process routine may omit steps S31 and S33.

[0034] In step S35, the execution unit 51 cranks the engine 11 by driving the motor generator 13. That is, the execution unit 51 drives the motor generator 13 to increase the engine speed Ne.

[0035] Then, in step S37, the execution device 51 determines whether or not a predetermined combustion start condition is satisfied. The lower the engine speed Ne, the smaller the force that continues the rotation of the crankshaft 22. Therefore, when restarting the engine 11 in a state where the engine speed Ne is relatively low, it is preferable to start combustion after increasing the engine speed Ne to a certain extent in order to ensure the stability of combustion at the time of restart. By restarting the engine 11 after increasing the force for continuing the rotation of the crankshaft 22 by cranking to a certain extent, it is easy to ensure the stability of combustion at the time of restarting the engine 11. Therefore, the combustion start condition is set in order to determine whether the stability of combustion at the time of restarting the engine 11 has been ensured.

[0036] In this embodiment, the combustion start condition includes the following conditions. That is, the combustion start condition includes that the number of cylinders 21 whose pistons 23 have passed the compression top dead center after cranking is started by driving the motor generator 13 reaches a predetermined number Xth. A value that is equal to or less than the number of cylinders 21 of the engine 11 and is greater than 1 is set as the predetermined number Xth. In the example shown in FIG. 1, since the number of cylinders 21 is four, for example, the predetermined number Xth is set to any one of 2, 3, and 4.

[0037] Since the execution device 51 grasps the positions of the multiple pistons 23 individually based on the detection signal of the crank angle sensor 62, it can determine whether the pistons 23 have reached the compression top dead center. Therefore, when any of the multiple pistons 23 reaches the compression top dead center, the execution device 51 increments the counter value by 1. Furthermore, when a piston 23 other than the piston 23 that has passed the compression top dead center reaches the compression top dead center, the execution device 51 further increments the counter value by 1. When cranking starts, the execution device 51 starts updating the counter value, and when the counter value reaches a predetermined number Xth, it determines that the number of cylinders 21 whose pistons 23 have passed the compression top dead center after the start of cranking has reached the predetermined number Xth. In other words, the execution device 51 determines that the combustion start condition is established.

[0038] The execution unit 51 repeatedly executes the determination in step S37 until the combustion start condition is satisfied. Then, when the combustion start condition is satisfied (S37: YES), the execution unit 51 shifts the process to step S39.

[0039] In step S39, the execution unit 51 starts combustion in the engine 11. For example, the execution unit 51 performs stratified charge combustion in the cylinder 21 by injecting fuel from the in-cylinder injection valve 31 during the compression stroke. After starting fuel injection and ignition in this manner, the execution unit 51 transitions the process to step S41.

[0040] In step S41, the execution unit 51 judges whether or not the restart of the engine 11 has been completed. For example, if the engine 11 has completely exploded, the restart of the engine 11 can be considered to have been completed, whereas if the engine 11 has not completely exploded, the restart of the engine 11 can be considered to have not been completed. If it is determined that the restart of the engine 11 has not been completed (S41: NO), the execution unit 51 repeatedly executes the judgment of step S41 until it can be determined that the restart of the engine 11 has been completed. If it is determined that the restart of the engine 11 has been completed (S41: YES), the execution unit 51 ends this processing routine. That is, the execution unit 51 ends the first restart processing.

[0041] <Restart process when stopped> The contents of the stop-time restart process are the same as the contents of the first restart process shown in Fig. 4, except for the contents of the combustion start condition. The stop-time restart process and the first restart process have different predetermined numbers Xth. For example, the predetermined number Xth in the stop-time restart process is smaller than the predetermined number Xth in the first restart process.

[0042] <Second restart process> The second restart process will be described with reference to Fig. 5. The processing routine shown in Fig. 5 shows the flow of the second restart process. In this embodiment, when the engine speed Ne is higher than the second determination speed Neth2 in a situation where a fuel cut is being performed, the clutch 12 is released.

[0043] In step S55 of this processing routine, the execution unit 51 starts combustion in the engine 11. For example, the execution unit 51 performs stratified combustion in the cylinder 21 by injecting fuel from the in-cylinder injection valve 31 during the compression stroke. After starting fuel injection and ignition in this manner, the execution unit 51 transitions the processing to step S57.

[0044] In step S57, the execution unit 51 determines whether or not the restart of the engine 11 has been completed, similarly to step S41. If it is determined that the restart of the engine 11 has not been completed (S57: NO), the execution unit 51 repeatedly executes the determination of step S57 until it can determine that the restart of the engine 11 has been completed. Then, if it is determined that the restart of the engine 11 has been completed (S57: YES), the execution unit 51 transitions the process to step S59.

[0045] In step S59, the execution unit 51 executes an engagement process to engage the clutch 12. When the clutch 12 is engaged by executing the engagement process, the motor generator 13 is connected to the crankshaft 22, and the execution unit 51 ends this processing routine. That is, the execution unit 51 ends the second restart process. Note that in the second restart process, the engine 11 is restarted regardless of whether or not the combustion start condition is satisfied before the clutch 12 is engaged.

[0046] <Actions and Effects of the Present Embodiment> The operation and effects of this embodiment will be described with reference to FIG. In the example shown in Fig. 6(A), fuel cut is initiated at timing t11 while the engine 11 is operating, and so the engine speed Ne begins to decrease. The solid line shown in Fig. 6(A) represents the transition of the engine speed Ne when the engine 11 is not restarted. When the engine 11 is not restarted, the engine speed Ne falls below the first judgment speed Neth1 at timing t12. Furthermore, the engine speed Ne falls below the second judgment speed Neth2 at timing t13. Then, the engine speed Ne becomes 0 (zero) at timing t14. That is, the rotation of the crankshaft 22 stops.

[0047] (1) When performing fuel cut recovery processing In a situation where combustion in the engine 11 is interrupted by a fuel cut, restart of the engine 11 may be requested in a state where the engine speed Ne is higher than the first judgment speed Neth1. In this case, the execution device 51 executes a fuel cut recovery process as shown in Fig. 6(B). In the fuel cut recovery process, the execution device 51 does not perform cranking as shown in Fig. 6(C), and does not determine whether or not the combustion start condition is satisfied as shown in Fig. 6(D). In the following description, the determination whether or not the combustion start condition is satisfied is referred to as a "combustion start determination."

[0048] When combustion in the engine 11 is resumed by the fuel cut recovery process in this manner, the engine speed Ne changes as shown by the dashed line L1 in FIG. 6(A). (2) When performing the second restart process In a situation where combustion in the engine 11 is interrupted by a fuel cut, restart of the engine 11 may be requested when the engine speed Ne is equal to or lower than the first judgment speed Neth1 and higher than the second judgment speed Neth2. In this case, the execution unit 51 executes a second restart process as shown in Fig. 6(B). In the second restart process, the execution unit 51 does not perform cranking as shown in Fig. 6(C), and does not perform a combustion start determination as shown in Fig. 6(D).

[0049] That is, in the second restart process, fuel injection and ignition in the engine 11 are started without performing a combustion start determination before the motor generator 13 is connected to the crankshaft 22 by the clutch 12. Therefore, the restart of the engine 11 can be completed earlier than when the first restart process is executed. When the engine 11 is restarted by the second restart process, the engine speed Ne changes as shown by the dashed line L2 in Fig. 6(A). Then, the clutch 12 is engaged after the engine 11 is restarted.

[0050] When the second restart process is executed instead of the first restart process, the engine speed Ne is relatively high. That is, the engine 11 is restarted in a state where the force that tries to continue the rotation of the crankshaft 22 is relatively large. In this case, it is easy to ensure the stability of combustion when the engine 11 is restarted, even if the engine 11 is not cranked by the motor generator 13. Therefore, by executing the second restart process when the engine 11 is restarted in a state where the engine speed Ne is equal to or less than the first judgment speed Neth1 and higher than the second judgment speed Neth2, it is possible to complete the restart of the engine 11 early while ensuring the stability of combustion when the engine 11 is restarted.

[0051] Here, consider a case where the engine 11 is restarted by the first restart process in a state where the engine speed Ne is higher than the second judgment speed Neth2. In this case, the engine 11 is restarted in a state where the engine 11 is cranked by the motor generator 13. In this case, since both the driving force of the motor generator 13 and the power generated by combustion are transmitted to the crankshaft 22, there is a risk that the engine speed Ne will rise sharply when the engine 11 is restarted.

[0052] In this embodiment, when the engine speed Ne is higher than the second determination speed Neth2, the second restart process is executed as the restart process instead of the first restart process, so that a sudden increase in the engine speed Ne when the engine 11 is restarted can be suppressed.

[0053] (3) When executing the first restart process In a situation where combustion in the engine 11 is interrupted by a fuel cut, the rotation of the crankshaft 22 is not stopped, and the engine speed Ne is equal to or lower than the second judgment speed Neth2, restart of the engine 11 may be requested. In this case, the execution unit 51 executes a first restart process as shown in Fig. 6(B). In the first restart process, the execution unit 51 causes cranking to be performed as shown in Fig. 6(C) and performs a combustion start judgment as shown in Fig. 6(D). Then, when the combustion start condition is satisfied, the execution unit 51 causes fuel injection and ignition in the engine 11 to be started.

[0054] That is, in the first restart process, the engine 11 is cranked by driving the motor generator 13 with the clutch 12 engaged and the motor generator 13 connected to the crankshaft 22. Then, when the combustion start condition is satisfied while the engine 11 is being cranked, fuel injection and ignition of the engine 11 are started. That is, when the engine 11 is restarted under a condition where the engine speed Ne is relatively low, the engine speed Ne is increased by cranking before the engine 11 is restarted. Therefore, the engine 11 can be restarted while ensuring the stability of combustion in the engine 11. When the engine 11 is restarted by the first restart process in this manner, the engine speed Ne changes as shown by the dashed line L3 in FIG. 6(A).

[0055] (3) When restart processing is performed after a stop In a situation where the combustion in the engine 11 is interrupted by a fuel cut, if the rotation of the crankshaft 22 is stopped, restart of the engine 11 may be requested. In this case, the execution unit 51 executes a stop-time restart process as shown in FIG. 6(B). In the stop-time restart process, the execution unit 51 performs cranking as shown in FIG. 6(C) and performs a combustion start determination as shown in FIG. 6(D). Then, when the combustion start condition is satisfied, the execution unit 51 starts fuel injection and ignition in the engine 11. Therefore, the engine 11 can be restarted while ensuring the stability of combustion in the engine 11. When the engine 11 is restarted by the stop-time restart process in this way, the engine speed Ne changes as shown by the dashed line L4 in FIG. 6(A).

[0056] As described above, when the engine 11 is restarted in a state where the engine speed Ne is not low, the engine 11 is restarted before the motor generator 13 is connected to the crankshaft 22 by the clutch 12. On the other hand, when the engine 11 is restarted in a state where the engine speed Ne is low, the motor generator 13 is connected to the crankshaft 22 by the clutch 12, and the engine 11 is restarted in a state where the engine 11 is being cranked by the motor generator 13. Therefore, in this embodiment, it is possible to ensure both the stability of combustion when the engine 11 is restarted and the early completion of the restart of the engine 11.

[0057] <Example of change> The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0058] The combustion start condition of the first restart process may be a condition different from the condition described in the above embodiment. For example, the combustion start condition may be that a predetermined time has elapsed since the start of cranking of the engine 11 by driving the motor generator 13. Also, for example, the combustion start condition may be that the increase in the engine speed Ne from the start of cranking of the engine 11 by driving the motor generator 13 is equal to or greater than a predetermined increase.

[0059] If the clutch 12 is disengaged when the fuel cut is performed, the determination process of step S31 in the processing routine shown in FIG. 4 may be omitted.

[0060] A control configuration may be adopted in which the clutch 12 is not disengaged even when fuel cut is performed. In this case, when the engine 11 is restarted by the second restart process, it may be determined whether or not the clutch 12 is engaged before combustion starts in the engine 11. If the clutch 12 is engaged, the second restart process may be executed after a process for disengaging the clutch 12 is executed. On the other hand, if the clutch 12 is not engaged, combustion in the engine 11 may be started promptly by the second restart process.

[0061] The execution device 51 is not limited to a device that includes a CPU 52 and a ROM 53 and executes software processing. In other words, the execution device 51 may have any one of the following configurations (a) to (c). (a) The execution device 51 includes one or more processors that execute various processes according to a computer program. The processor includes a CPU and memory such as RAM and ROM. The memory stores program codes or instructions that are configured to cause the CPU to execute processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or special-purpose computer. (b) The execution device 51 includes one or more dedicated hardware circuits for executing various processes. Examples of the dedicated hardware circuits include application specific integrated circuits, i.e., ASIC and FPGA. ASIC is an abbreviation for "Application Specific Integrated Circuit" and "FPGA" is an abbreviation for "Field Programmable Gate Array." (c) The execution device 51 includes a processor that executes some of the various processes in accordance with a computer program, and a dedicated hardware circuit that executes the remaining processes among the various processes. [Explanation of symbols]

[0062] 10. Hybrid vehicle 11…Engine 12…Clutch 13...Motor generator 21…Cylinder 22…Crankshaft 23…Piston 50...Control device 51...Execution device

Claims

[Claim 1] The present invention is applied to a hybrid vehicle including an engine having a crankshaft, a motor generator, and a clutch disposed between the crankshaft and the motor generator, the engine having a plurality of cylinders and a plurality of pistons that reciprocate within the cylinders in synchronization with rotation of the crankshaft, a restart execution device that executes a restart process to restart the engine when a restart of the engine is requested under a condition in which combustion in the engine is interrupted; The execution device is when a restart of the engine is requested under a condition in which the engine speed is lower than a reference speed due to the interruption of combustion in the engine, a first restart process is executed as the restart process, in which the engine is cranked by driving the motor generator in a state in which the clutch is engaged and the motor generator is connected to the crankshaft, and when a combustion start condition is satisfied while the cranking is being performed, fuel injection and ignition of the engine are started; when a restart of the engine is requested under a condition in which the engine speed is lowered due to the interruption of combustion in the engine and the engine speed is equal to or higher than the reference speed, a second restart process is executed as the restart process, in which fuel injection and ignition of the engine are started, and after the engine is started, the clutch is engaged to couple the motor generator to the crankshaft; The combustion start condition is that the number of the cylinders in which the pistons have passed top dead center of compression after the start of the cranking by driving the motor generator reaches a predetermined number that is set as a value equal to or less than the number of the cylinders and greater than 1. Hybrid vehicle control device.

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