Electric device control method and electric device control device

Abstract

An electric device control method for controlling an electric device provided with an internal combustion engine and a first electric motor connected to the internal combustion engine, wherein: when there is demand for power generation, a controller assesses whether the electric device is in a power generation transition state for transitioning from a first state in which the internal combustion engine is in a non-combustion mode and the first electric motor is performing motoring to turn the internal combustion engine to a second state in which the internal combustion engine is in a combustion mode and the first electric motor is driven by the internal combustion engine to generate electricity; in cases in which the electric device is in the power generation transition state, the controller determines, before the internal combustion engine begins combustion, whether to implement torque limitation for reducing the torque generated by the internal combustion engine below the torque required for the internal combustion engine in the combustion mode; and once the internal combustion engine begins combustion, the controller reduces the speed of the internal combustion engine to a speed within a prescribed speed range by operating the first electric motor as a power generator while implementing the torque limitation.

Description

Electric device control method and electric device control device

[0001] The present invention relates to an electric device control method and an electric device control device.

[0002] There is known an electric device that can switch between motoring control, which uses a motor that rotates with regenerative electric power generated during vehicle deceleration, to forcibly rotate an internal combustion engine whose fuel supply is cut off, thereby consuming regenerative electric power, and firing control, which supplies fuel to the internal combustion engine to rotate the internal combustion engine. Such an electric device has a problem in that, when an engine speed that has increased during motoring control is transitioned from motoring control to firing control and an attempt is made to reduce the engine speed to a predetermined speed by the torque of the motor, an abnormal noise is generated from the intake system of the internal combustion engine.

[0003] To solve the above problem, WO 2019 / 116559A discloses control that limits the torque of an internal combustion engine from the start of firing control until the engine speed drops to a predetermined speed. In this control, the need for torque limiting is determined after transitioning to firing control. However, in torque control of an internal combustion engine, there is a delay time between changing the torque command value and the actual torque change. Therefore, if the decision to implement torque limiting is made after transitioning to firing control and the torque command value is changed to the limit value, as in the control described in the above document, the torque will not be limited during the delay time, which may prevent abnormal noise from being suppressed.

[0004] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for controlling an electric device that suppresses abnormal noise from the intake system of an internal combustion engine even if there is a delay time between when the torque command value is changed and when the actual torque changes.

[0005] According to one aspect of the present invention, there is provided a method for controlling an electric device including an internal combustion engine and a first electric motor connected to the internal combustion engine. In this method, when a request for power generation is made, a controller determines whether the state is in a power generation transition state, which is a state in which the internal combustion engine transitions from a first state in which the internal combustion engine is in a non-combustion mode and the first electric motor is motoring the internal combustion engine to a second state in which the internal combustion engine is in a combustion mode and the first electric motor is driven by the internal combustion engine to generate power. If the state is in the power generation transition state, the controller determines before combustion starts in the internal combustion engine whether to implement torque limiting to reduce the torque generated by the internal combustion engine below the torque required for the internal combustion engine in the combustion mode, and once combustion starts in the internal combustion engine, the controller operates the first electric motor as a generator while implementing torque limiting, thereby reducing the rotational speed of the internal combustion engine to a predetermined rotational speed range.

[0006] Fig. 1 is a schematic diagram of a hybrid car. Fig. 2 is a block diagram showing functional components of a vehicle controller. Fig. 3 is a flowchart showing the processing procedure for torque limitation according to the control method of this embodiment. Fig. 4 is a timing chart when the control method of this embodiment is executed.

[0007] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0008] 1 is a schematic diagram of a hybrid car (hereinafter also simply referred to as "vehicle") including an electric power device according to an embodiment of the present invention. The hybrid car of this embodiment includes an engine 1 (internal combustion engine), a generator 2 (first electric motor), a battery 3, a drive motor 4, and wheels 6. The vehicle is a so-called series hybrid car in which the wheels 6 are driven by the drive motor 4 using electric power from the battery 3, rather than by the engine 1.

[0009] The engine 1 is mechanically connected to a generator 2. The generator 2 is connected to a battery 3 so as to be able to transmit and receive power. The generator 2 and a drive motor 4, and the battery 3 and a drive motor 4, are also connected so as to be able to transmit and receive power. The drive motor 4 is mechanically connected to an axle via a gear 5, and the axle is mechanically connected to wheels 6.

[0010] The driving force of the engine 1 is transmitted to the generator 2, which rotates and generates electricity using the driving force of the engine 1. When the electric power generated by the generator 2 flows to the battery 3, the electric power is consumed to charge the battery 3. When the electric power generated by the generator 2 flows to the drive motor 4, the electric power is consumed to drive the drive motor 4.

[0011] The drive motor 4 receives power from either the generator 2 or the battery 3, or both, and consumes the power to generate drive force. The drive force of the drive motor 4 is transmitted to wheels 6 via gears 5 and axles. The drive force of the drive motor 4 rotates the wheels 6, causing the vehicle to move.

[0012] Furthermore, when the vehicle decelerates or goes down a slope, torque is input from the wheels 6 via the axles and gears 5 to the drive motor 4, and when the input torque rotates the drive motor 4, the drive motor 4 operates as a generator and generates regenerative power. When regenerative power is generated in the drive motor 4, a regenerative braking force is generated in the wheels 6 via the gears 5 and axles due to the reaction of the torque input to the drive motor 4.

[0013] When the regenerative power generated by the drive motor 4 flows to the battery 3, the regenerative power is consumed to charge the battery 3. When the regenerative power generated by the drive motor 4 flows to the generator 2, the regenerative power is consumed to drive the engine 1 and the generator 2 against the resistance of the engine 1 (engine brake).

[0014] The battery 3 has the function of charging and discharging. When the battery 3 is being charged, the battery 3 stores the energy of the electric power supplied from the generator 2 or the drive motor 4. When the battery 3 is being discharged, the battery 3 supplies the stored energy to the drive motor 4 as electric power.

[0015] The flow of power between the generator 2, battery 3, and drive motor 4 can change depending on the respective states of the battery 3 and drive motor 4, the driving situation of the vehicle, and the power supply and demand situation of the entire vehicle including auxiliary devices installed in the vehicle (air conditioner, car stereo, navigation system, etc.) The flow of power between the generator 2, battery 3, and drive motor 4 is determined by the control of a vehicle controller 11, which will be described later.

[0016] For example, when the drive motor 4 needs to generate drive force, power may be supplied from the battery 3 to the drive motor 4. When the battery 3 cannot supply sufficient power to the drive motor 4, the engine 1 may be driven to generate power with the generator 2, and the power from the generator 2 in addition to the power from the battery 3 may be supplied to the drive motor 4.

[0017] Furthermore, when charging of the battery 3 is not complete, regenerative power generated by the drive motor 4 when the vehicle decelerates or when the vehicle goes down a slope may be supplied from the drive motor 4 to the battery 3. Furthermore, when charging of the battery 3 is not complete, the engine 1 may be driven to generate power using the generator 2, and the power from the generator 2 may be supplied to the battery 3.

[0018] Furthermore, when the state of charge (SOC) of the battery 3 is high, the regenerative power generated by the drive motor 4 when the vehicle decelerates or goes downhill may be supplied to the generator 2. In this case, the regenerative power supplied from the drive motor 4 to the generator 2 is consumed by the generator 2 to perform work against the engine brake of the engine 1, and as a result, the regenerative power supplied from the drive motor 4 to the generator 2 is forcibly discharged.

[0019] The vehicle further includes a mode switch 12 (mode SW) for alternatively selecting one of a plurality of driving modes, a selector lever 13 operated by the driver, a brake sensor 14 for detecting braking force, an accelerator position sensor 15 (APS) for detecting accelerator opening, an engine state sensor 16 for detecting the state of the engine, a generator state sensor 17 for detecting the state of the generator 2, and a vehicle controller 11 for controlling the entire hybrid car. The vehicle controller 11 functions as a control circuit for controlling the electric device according to the embodiment.

[0020] The vehicle controller 11 is electrically connected to each of the mode switch 12, select lever 13, brake sensor 14, accelerator position sensor 15, engine state sensor 16, and generator state sensor 17. The vehicle controller 11 receives a signal indicating the selected driving mode from the mode switch 12, a signal indicating the selected range from the select lever 13, a signal indicating the brake oil pressure from the brake sensor 14, and a signal indicating the accelerator opening degree Ac of the accelerator pedal (input device) from the accelerator position sensor 15.

[0021] The vehicle controller 11 receives a signal indicating the state of the engine 1 from the engine state sensor 16. Here, the signal indicating the state of the engine 1 includes a signal indicating whether or not fuel is being supplied to the engine 1, and a signal indicating the engine rotation speed Nr.

[0022] The vehicle controller 11 receives a signal indicating the state of the generator 2 from the generator state sensor 17. Here, the signal indicating the state of the generator 2 includes a signal indicating whether or not it is operating as a generator and a signal indicating whether or not it is operating as an electric motor.

[0023] The ranges selectable by the selector lever 13 include, for example, a drive range (D), a brake range (B), a reverse range (R), a neutral range (N), and a parking range (P).

[0024] The vehicle controller 11 is electrically connected via signal lines to the engine 1, the generator 2, and the drive motor 4. The vehicle controller 11 controls the engine 1, the generator 2, and the drive motor 4 to cause the drive motor 4 to generate a required torque Tm (vehicle driving force FD) corresponding to the accelerator opening Ac. In particular, the vehicle controller 11 transmits a command torque Tc to the engine 1.

[0025] The expression "transmitting the command torque Tc" includes controlling the engine 1 so that the torque output by the engine 1 becomes the command torque Tc. For example, this includes controlling the engine 1 so that the torque output by the engine 1 becomes the command torque Tc by changing the throttle opening of the engine 1, changing the air-fuel ratio, or changing the amount of fuel supplied to the engine 1.

[0026] The vehicle controller 11 controls the driving states of the engine 1, generator 2, and drive motor 4, and also determines the states of other auxiliary equipment (not shown), thereby determining the flow of power between the generator 2, battery 3, and drive motor 4.

[0027] The vehicle controller 11 can be realized, for example, by a general-purpose microcomputer including a CPU (Central Processing Unit), memory, and input / output units. A computer program (control program) for causing the microcomputer to function as the vehicle controller 11 is installed in the microcomputer and executed. In this way, the general-purpose microcomputer functions as the vehicle controller 11.

[0028] In this embodiment, the vehicle controller 11 is implemented by software, but it is also possible to configure the vehicle controller 11 by providing dedicated hardware for executing the information processing described below. Furthermore, the multiple units (23, 25, 27, 31, 33) included in the vehicle controller 11 may be configured by individual hardware. Furthermore, the vehicle controller 11 may also serve as an electronic control unit (ECU) used for other vehicle-related control.

[0029] 2, the functional components of the vehicle controller 11 will be described. The vehicle controller 11 includes, as functional components, an engine operating point calculation unit 20, an engine operation request determination unit 21, a target rotation speed determination unit 22, an abnormal noise countermeasure determination / upper limit torque calculation unit 23, a rotation speed change rate setting unit 24, a torque command value determination unit 25, and a power generation state determination unit 26.

[0030] The engine operating point calculation unit (ENG operating point calculation unit) 20 calculates the operating point (engine torque and engine speed) of the engine 1 based on the power required to drive the drive motor 4 and the power that can be output from the battery 3. Specifically, it calculates the required torque Tm to be generated by the drive motor 4 based on the accelerator opening degree received from the accelerator position sensor, and sets the power required for the generator 2 to be equal to the power required for the drive motor 4 to generate the required torque Tm minus the power Pb that can be output from the battery 3. However, if the power Pb that can be supplied from the battery 3 to the drive motor 4 is greater than the power required for the drive motor 4 to generate the required torque Tm, the required power Pd is set to 0. Therefore, the required power Pd for the generator 2 is equal to or greater than 0.

[0031] The engine operating point calculation unit 20 then sets the torque required for the generator 2 to generate the required electric power Pd as the required torque Ttg (predetermined torque threshold) for the engine 1 .

[0032] The engine operating point calculation unit 20 also sets a target engine speed Ntg of the engine 1 in a combustion mode, which will be described later. The target engine speed Ntg is a value included in a predetermined rotation range of the combustion mode.

[0033] The engine operation requirement determination unit 21 determines the operation requirement of the engine 1, i.e., the required operation mode, based on signals indicating the state of the engine 1 (a signal indicating whether fuel is being supplied to the engine 1 and a signal indicating the engine speed Nr) received from the engine state sensor 16. The engine 1 can be in two modes: a non-combustion mode and a combustion mode.

[0034] The non-combustion mode is a mode in which fuel and air are not supplied to the engine 1. The combustion mode is a mode in which fuel and air are supplied to the engine 1 and the engine speed Nr is within a predetermined range. Here, the predetermined range of the combustion mode is a range of the engine speed Nr that is determined taking into consideration the characteristics of the engine 1 when firing. For example, the range of the engine speed Nr that provides good fuel economy for the engine 1 is determined as the predetermined range.

[0035] When the engine 1 is in the non-combustion mode, no fuel is supplied to the engine 1, and torque must be applied from the outside to rotate the output shaft of the driving force of the engine 1. By rotating the output shaft of the engine 1 in the non-combustion mode by the generator 2, which is driven by the regenerative power generated by the drive motor 4, the regenerative power generated by the drive motor 4 can be forcibly discharged.

[0036] Rotating the output shaft of the engine 1 using an electric motor in this way is called motoring control. On the other hand, supplying fuel to the engine 1 and outputting torque from the output shaft of the engine 1 is called firing control. The period of the non-combustion mode and the period of motoring control do not necessarily coincide.

[0037] The target rotation speed determination unit 22 determines the target engine rotation speed Ntg based on the calculation result from the engine operating point calculation unit 20 and the determination result from the engine operation request determination unit 21 .

[0038] The abnormal noise countermeasure determination / upper limit torque calculation unit 23 determines whether abnormal noise countermeasures are necessary based on the target engine speed Ntg, the operation requirements of the engine 1, etc., and sets a torque limit value Tmax (normal value Tn, limit value Tcr) that is the upper limit of the command torque Tc to the engine 1 for abnormal noise countermeasures. Note that the normal value Tn is a limit value that is set in consideration of a safety factor, etc., for safe operation of the engine 1. Furthermore, the limit value Tcr is a value smaller than the normal value Tn.

[0039] The rotation speed change rate setting unit 24 sets the rotation speed decrease rate Rdown (normal value Rn, limit value Rcr) of the engine rotation speed Nr based on the requested engine mode, the engine rotation speed Nr received from the engine state sensor 16, and the target engine rotation speed Ntg. The set rotation speed decrease rate Rdown is output to the power generation state determination unit 26 and is also fed back to the abnormal noise countermeasure determination / upper limit torque calculation unit 23. The limit value Rcr set for the rotation speed decrease rate Rdown is a value different from the normal value Rn. If necessary, the limit value Rcr may be a value larger than the normal value Rn, or the limit value Rcr may be a value smaller than the normal value Rn.

[0040] The torque command value determination unit 25 compares the torque limit value Tmax with the required torque Ttg and determines the smaller one as the command torque for the engine 1. Therefore, the command torque Tc is a value that does not exceed the onshore limit value Tmax. This command torque Tc is output to the power generation state determination unit 26 and is also fed back to the abnormal noise countermeasure determination / upper limit torque calculation unit 23.

[0041] The power generation state determination unit 26 determines the power generation state of the generator 2 based on whether fuel is being supplied to the engine 1, the engine water temperature, and the rotational speed and generator torque of the generator 2 received from the generator state sensor 17. The determination result is output to the power generation state determination unit 26 and is also fed back to the abnormal noise countermeasure determination / upper limit torque calculation unit 23. The power generation state determination unit 26 also determines a command rotational speed Nc for the engine 1 based on the engine rotational speed Nr, the target engine rotational speed Ntg, and the rotational speed decrease rate Rdown. Specifically, in a situation where the engine rotational speed Nr is to be decreased toward the target engine rotational speed Ntg, the command rotational speed Nc is determined so that the magnitude of the rotational speed decrease per unit time of the engine rotational speed Nr is equal to the rotational speed decrease rate rdown.

[0042] The vehicle controller 11 controls the engine 1 based on the command torque Tc and command rotation speed Nc for the engine 1 determined as described above.

[0043] Next, the torque limiting process performed by the method for controlling an electric device according to this embodiment will be described with reference to the flowchart of FIG.

[0044] The torque limiting process shown in FIG. 3 is started when the starter switch of the vehicle is turned on, and is repeatedly executed until the starter switch is turned off.

[0045] In step S100, the vehicle controller 11 determines whether the engine 1 is either in combustion or in a power generation transition state, and if either is true, executes the processing of step S110, and if neither is true, executes the processing of step S160.

[0046] The determination of whether the engine 1 is in combustion or not is made by determining whether the engine 1 is in a non-combustion mode or a combustion mode.

[0047] The power generation transition state is a state from when a request to start the engine 1 occurs during motoring control until the engine 1 starts and begins to generate power.

[0048] In step S160, the vehicle controller 11 sets the torque limit value Tmax to the normal value Tn since torque limitation is not performed, and sets the rotation speed decrease rate Rdown to the normal value Rn.

[0049] In step S110, the vehicle controller 11 determines whether the engine speed Nr is equal to or less than the value obtained by adding a predetermined value ΔNe to the target engine speed Ntg. The predetermined value ΔNe is a positive number. If the determination result is yes, the vehicle controller 11 executes the process of step S160, and if the determination result is no, the vehicle controller 11 executes the process of step S120.

[0050] In step S120, the vehicle controller 11 determines whether the engine speed Nr is equal to or greater than the value obtained by adding a predetermined value ΔNs to the target engine speed Ntg. The predetermined value ΔNs is a positive number. If the determination result is yes, the vehicle controller 11 executes the process of step S130, and if the determination result is no, the vehicle controller 11 executes the process of step S140.

[0051] In step S130, the vehicle controller 11 sets a limit value Tcr to the torque limit value Tmax and a limit value Rcr to the rotation speed decrease rate Rdown in order to limit the torque.

[0052] In step S140, the vehicle controller 11 determines whether the required torque Ttg for the engine 1 is greater than the previous torque limit value Tmz. The previous torque limit value Tmz is the value of the previous torque limit value Tmax when the torque limit process shown in Fig. 3 is repeatedly executed. If the determination result is yes, the vehicle controller 11 executes the process of step S150, and if the determination result is no, the vehicle controller 11 executes the process of step S160.

[0053] In step S150, the vehicle controller 11 adds a predetermined value ΔTcr to the previous torque limit value Tmz. As a result, the torque limit value Tmax increases by the predetermined value ΔTcr each time the torque limiting process of FIG. 3 is repeatedly executed. In other words, the torque limit value Tmax increases by the predetermined value ΔTcr per unit step.

[0054] The processes of steps S140 and S150 are not essential, and the process of step S160 may be executed if the determination result of step S120 is no.

[0055] Next, an example of torque limitation by control of the electric device according to this embodiment will be described with reference to the timing chart of FIG. 4. In the chart of torque limitation determination and engine command torque in FIG. 4, the solid line indicates the case where the control according to this embodiment is executed, and the dashed line indicates the case where control according to a comparative example is executed. The control according to the comparative example here refers to a case where the only determination factor in step S100 is the state of the engine 1, that is, a control where the determination is made solely on whether or not the engine 1 is in combustion. Note that the timing chart of FIG. 4 corresponds to a case where the determination in step S140 of FIG. 3 is no, and the torque limitation is terminated.

[0056] At timing T1, when the mode is switched from the non-combustion request mode to the combustion request mode, the engine 1 has not yet started, so the vehicle controller 11 determines that the mode is the power generation transition mode (step S100: yes). At this time, the engine speed Nr is greater than the value obtained by adding the target engine speed Ntg and the predetermined value ΔNe, and is equal to or greater than the value obtained by adding the target engine speed Ntg and the predetermined value ΔNs (step S110: no, step S120: yes), so the vehicle controller 11 limits the torque of the engine 1 (step S130).

[0057] After timing T2, the engine speed Nr decreases toward the target engine speed Ntg due to the torque limitation. At this time, the engine speed decrease rate Rdown is equal to the limit value Rcr.

[0058] If, at timing T3, the engine speed Nr becomes smaller than the value obtained by adding a predetermined value ΔNs to the target engine speed Ntg (step S120 is no), the vehicle controller 11 returns the speed decrease rate Rdown to the normal value Rn and relaxes the torque limit value Tmax at a predetermined rate (steps S140 to S150).

[0059] Then, at timing T4, when the torque limit value Tmax is reduced to the required torque Ttg, the torque limit is terminated.

[0060] In the above driving scenario, the control according to the comparative example determines to limit torque after power generation has started, i.e., after the engine 1 has started combustion. Therefore, there is a delay between the decision to limit torque and the actual torque limiting, potentially resulting in a period immediately after power generation has started during which torque limiting cannot be performed (area A in FIG. 4 ). In contrast, the control according to this embodiment determines to limit torque during the power generation transition state, enabling torque limiting immediately after power generation has started. Note that, depending on the magnitudes of the engine speed Nr, the predetermined value ΔTcr, and the speed decrease rate Rdown at the time of torque limiting initiation, the determination result in step S110 may become "yes" and torque limiting may be terminated before the determination result in step S140 in FIG. 3 becomes "no."

[0061] As described above, this embodiment provides an electric device control method for controlling an electric device including the engine 1 and the generator 2 connected to the engine 1. When a power generation request is issued, the vehicle controller 11 determines whether the vehicle is in a power generation transition state (timing T1 to T2 in FIG. 4 ) from a first state (timing 0 to T1 in FIG. 4 ) in which the engine 1 is in a non-combustion mode and the generator 2 is rotating the engine 1 to a second state (timing T2 and thereafter in FIG. 4 ) in which the engine 1 is in a combustion mode and the generator 2 is driven by the engine 1 to generate power. If the vehicle is in the power generation transition state, the vehicle controller 11 determines whether to implement torque limiting, which reduces the torque generated by the engine 1 below the torque required for the engine 1 in the combustion mode, before the engine 1 starts combustion. Once the engine 1 starts combustion, the vehicle controller 11 operates the generator 2 as a generator while implementing torque limiting, thereby reducing the engine 1 rotation speed to a predetermined rotation speed range. This allows the vehicle controller 11 to accurately detect a situation in which torque limiting of the engine 1 is required and to start torque limiting without delay, thereby suppressing abnormal noise from the intake system of the internal combustion engine that accompanies a change in the torque command value.

[0062] In this embodiment, when the difference between the actual engine speed (engine speed Nr) and the target engine speed Nrg in a predetermined rotation range falls below a predetermined value ΔNs, the torque limit is released and the torque generated by the engine 1 is increased to the required torque Ttg. This makes it possible to both suppress the abnormal noise and suppress torque fluctuations that accompany the release of the torque limit.

[0063] In this embodiment, after the torque limit is released, the torque increase rate when increasing the torque generated by the engine 1 is limited to a magnitude that does not exceed a predetermined limit value, thereby suppressing abrupt torque fluctuations after the torque limit is applied.

[0064] Although the embodiments of the present invention have been described above, the above embodiments merely illustrate some of the application examples of the present invention, and it is not intended that the technical scope of the present invention be limited to the specific configurations of the above embodiments.

Claims

1. An electric device control method for controlling an electric device comprising an internal combustion engine and a first electric motor connected to the internal combustion engine, wherein, when a request for power generation occurs, a controller determines whether the state is in a power generation transition state, which is a state in which the internal combustion engine transitions from a first state in which the internal combustion engine is in a non-combustion mode and the first electric motor is motoring to rotate the internal combustion engine, to a second state in which the internal combustion engine is in a combustion mode and the first electric motor is driven by the internal combustion engine to generate power; if the state is in the power generation transition state, a controller determines before combustion begins in the internal combustion engine whether to implement torque limitation to reduce the torque generated by the internal combustion engine below the torque required for the internal combustion engine in the combustion mode; and, once combustion begins in the internal combustion engine, a method for controlling an electric device, wherein the controller implements the torque limitation while operating the first electric motor as a generator, thereby reducing the rotational speed of the internal combustion engine to a rotational speed within a predetermined rotational speed range.

2. A method for controlling an electric device according to claim 1, wherein, when the difference between the actual rotation speed of the internal combustion engine and a target rotation speed in the predetermined rotation range falls below a predetermined value, the torque limit is released and the torque generated by the internal combustion engine is increased to the required torque.

3. A method for controlling an electric device according to claim 2, wherein after the torque limit is released, the rate at which the torque generated by the internal combustion engine is increased is limited to a magnitude that does not exceed a predetermined limit value.

4. An electric device control device that controls an electric device including an internal combustion engine and a first electric motor connected to the internal combustion engine, wherein a controller comprises: a state determination unit that, when a request for power generation is made, determines whether the state is in a power generation transition state, which is a state in which the internal combustion engine is in a non-combustion mode and the first electric motor is motoring to rotate the internal combustion engine, to a second state in which the internal combustion engine is in a combustion mode and the first electric motor is driven by the internal combustion engine to generate power; a restriction necessity determination unit that, when the state is in the power generation transition state, determines before combustion begins in the internal combustion engine whether to implement torque limitation to reduce the torque generated by the internal combustion engine below the torque required for the internal combustion engine in the combustion mode; and a rotation speed control unit that, once combustion begins in the internal combustion engine, operates the first electric motor as a generator while implementing the torque limitation, thereby reducing the rotation speed of the internal combustion engine to a rotation speed within a predetermined rotation speed range.

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