Control Method for Hybrid Vehicle

Abstract

To provide a control method of a hybrid vehicle configured so that an EV travelling area can be enlarged.SOLUTION: A control method of a hybrid vehicle comprises: a step of calculating basic maximum motor torque MTb that is determined by a rotation speed of a rotary electric machine and an input voltage from an inverter that drives the rotary electric machine; a step of calculating temporary increase torque MTup at which maximum motor torque MTmax of the rotary electric machine can be increased temporarily, before an engine is cranked; a step of setting motor torque in which the temporary increase torque MTup is added to the basic maximum motor torque MTb to maximum motor torque MTmax1 when the engine is cranked; and a step of calculating engine-start-up determination torque MTst that is used for determining start-up of the engine, on the basis of the maximum motor torque MTmax1 set when the engine is cranked.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control method for a hybrid vehicle, and particularly to a control method for a hybrid vehicle including an engine and a rotating electric machine.

Background Art

[0002] There is known a hybrid vehicle that stops or starts the engine during traveling and travels. In such a hybrid vehicle, when there is a start request for the engine, start control may be performed to crank the engine by engaging a clutch provided in the drive system and driving the rotating electric machine.

[0003] Patent Document 1 discloses a hybrid vehicle in which a clutch is provided between an engine and a motor, and a clutch fastening pressure is supplied from a control valve provided in a line pressure circuit in which a mechanical pump discharges a working fluid. When there is an engine start request during EV traveling by driving the motor, a start control unit that executes start control to start the engine by engaging the first clutch and inputting torque from the motor to the engine, and included in the start control unit, calculates a transmission input torque that is an input torque to the automatic transmission, and when this transmission input torque exceeds a preset set input torque based on the working fluid pressure, a start determination unit that executes start control is provided. A start control device for a hybrid vehicle is disclosed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the control of a hybrid vehicle, it is desired to expand the EV driving range in which the vehicle can travel with only the rotating electric machine as the driving force source while the engine is stopped. For example, in the case of EV driving, the maximum motor torque may be set so that the torque output from the rotating electric machine can further output torque sufficient to start the stopped engine. However, in the technique described in Patent Document 1, once the maximum motor torque and the cranking torque required for cranking the engine are determined, the engine start determination torque (EV driving range) is uniquely determined. Therefore, there is a problem that the EV driving range becomes narrow depending on the setting of the maximum motor torque.

[0006] The present invention has been made to solve such problems, and an object thereof is to provide a control method for a hybrid vehicle capable of expanding the EV driving range.

Means for Solving the Problems

[0007] A control method for a hybrid vehicle according to an embodiment is a control method for a hybrid vehicle including an engine and a rotating electric machine, the method including: calculating a basic maximum motor torque determined by the rotational speed of the rotating electric machine and the input voltage of an inverter that drives the rotating electric machine; calculating a temporary up-torque that can temporarily increase the maximum motor torque of the rotating electric machine before cranking of the engine; setting a motor torque obtained by adding the temporary up-torque to the basic maximum motor torque as the maximum motor torque at the time of cranking of the engine; and calculating an engine start determination torque used for determining engine start based on the set maximum motor torque at the time of cranking.

Effects of the Invention

[0008] According to the present invention, it is possible to provide a control method for a hybrid vehicle capable of expanding the EV driving range.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

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Figure 8

Modes for Carrying Out the Invention

[0010] Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. Also, for clarity of explanation, the following description and drawings are appropriately simplified. What is shown in the drawings is a part of the whole, and many other configurations not shown are actually included. Furthermore, in the following description, the same or equivalent elements are denoted by the same reference numerals, and duplicate descriptions are omitted.

[0011] First, referring to FIG. 1, the system configuration of the hybrid vehicle 100 according to the present embodiment will be described. FIG. 1 is a configuration diagram showing a hybrid vehicle according to Embodiment 1. FIG. 1 shows a schematic configuration of the main part of the hybrid vehicle 100, showing the state during EV driving on the left side and the state during engine start processing (cranking) when shifting from EV driving to HEV driving on the right side. Note that the engine start process is the process from when a start request for the engine 1 is made until the start of the engine 1 is completed.

[0012] The hybrid vehicle 100 shown in Fig. 1 is a parallel hybrid vehicle equipped with an engine 1 and a rotary electric machine 2 as driving power sources. The hybrid vehicle 100 includes an engine 1, a first clutch K0, a rotary electric machine 2, a second clutch WSC, a transmission 3, and drive wheels 4. The engine 1 is connected to the rotary electric machine 2, the second clutch WSC, the transmission 3, and the drive wheels 4 via the first clutch K0. Also, the rotary electric machine 2 is connected to the transmission 3 and the drive wheels 4 via the second clutch WSC.

[0013] That is, the rotary electric machine 2 is arranged closer to the drive wheels 4 than the engine 1. The first clutch K0 can connect and disconnect the engine 1 and the rotary electric machine 2, and the second clutch WSC can connect and disconnect the rotary electric machine 2 and the transmission 3.

[0014] The engine 1 is composed of an internal combustion engine such as a gasoline engine or a diesel engine. The engine 1 converts the combustion energy of fuel into the rotational motion of the crankshaft 1a and outputs it. The engine torque, which is the output torque of the engine 1, is transmitted to the drive wheels 4 via the first clutch K0, the rotary electric machine 2, the second clutch WSC, the transmission 3, and the drive shaft 4a.

[0015] The first clutch K0 is a clutch interposed between the crankshaft 1a of the engine 1 and the rotary shaft 2a of the rotary electric machine 2. The first clutch K0 is, for example, a wet multi-plate clutch, which connects the engine 1 and the rotary electric machine 2 in the engaged state and disconnects the engine 1 and the rotary electric machine 2 in the released state.

[0016] The rotating electrical machine 2 has a function as a motor (electric motor) and a function as a generator. The rotating electrical machine 2 is connected to a battery provided in the hybrid vehicle 100 via an inverter provided in the hybrid vehicle 100. The rotating electrical machine 2 generates driving power by electric power supplied from the battery via an inverter that drives the rotating electrical machine 2, instead of or in addition to the engine 1. The rotating electrical machine 2 converts the power of the engine 1 or the driven power input from the drive wheel 4 side into electric power by regeneration, and accumulates the electric power in the battery via the inverter. In the present embodiment, the rotating electrical machine 2 is a synchronous motor generator in which permanent magnets are embedded in the rotor and stator coils are wound around the stator.

[0017] The second clutch WSC is a clutch interposed between the rotating electrical machine 2 and the drive wheel 4. The second clutch WSC shown in FIG. 1 is provided on the input shaft 3a of the transmission 3 and is interposed between the rotating electrical machine 2 and the transmission 3. The second clutch WSC is a wet multi-plate clutch that also functions as a launch clutch, for example, and connects the rotating electrical machine 2 and the transmission 3 in the engaged state and disconnects the rotating electrical machine 2 and the transmission 3 in the released state.

[0018] The transmission 3 is an automatic transmission, for example, a stepped automatic transmission (A / T). However, the transmission 3 is not limited to this, and may be a continuously variable transmission (CVT) or the like. The output shaft 3b of the transmission 3 is connected to the drive wheel 4 via the drive shaft 4a. It is preferable that a differential mechanism is provided between the output shaft 3b of the transmission 3 and the drive shaft 4a.

[0019] The hybrid vehicle 100 is equipped with an electronic control unit (ECU) capable of executing the control method of the hybrid vehicle according to the present embodiment. The ECU is configured to include, for example, a so-called microcomputer having a CPU (Central Processing Unit), a storage device, an input / output interface, and the like. The storage device includes a RAM (Random Access Memory) as a working memory and a ROM (Read Only Memory) as a storage storage. The storage storage may be a rewritable non-volatile memory or the like. The CPU reads the program stored in the ROM, expands it in the RAM, and executes various controls performed by the ECU by executing various processes according to the expanded program.

[0020] The ECU is connected to the engine 1, the first clutch K0, the rotating electric machine 2, the second clutch WSC, the transmission 3, etc., and can control them. For example, the ECU is adapted to execute output control of the engine 1, drive control of the rotating electric machine 2, shift control of the transmission 3, torque capacity control (engagement and release control) of the first clutch K0 and the second clutch WSC, and the like.

[0021] The above hybrid vehicle 100 can selectively switch between EV running, HEV running, and WSC (Wet Start Clutch) running with different driving modes. The EV running mode (electric vehicle running mode) is a running mode in which the hybrid vehicle 100 is run using only the power of the rotating electric machine 2 with the first clutch K0 in the released state as the driving power source. The HEV running mode (engine usage running mode) is a running mode in which the hybrid vehicle 100 is run while including the engine 1 as the driving power source with the first clutch K0 in the engaged state. The WSC running mode (engine usage slip running mode) is a running mode in which the second clutch WSC is in a semi-engaged state with the first clutch K0 in the engaged state, and the hybrid vehicle 100 is run while including the engine 1 as the driving power source.

[0022] Furthermore, HEV driving includes driving using only the engine 1 as a driving force source, driving using both the engine 1 and the rotary electric machine 2 as driving force sources, and driving using the engine 1 as a driving force source while generating a reaction force by regenerative control in the rotary electric machine 2.

[0023] When the first clutch K0 and the second clutch WSC each have a hydraulic actuator, the ECU controls the engagement degree (torque capacity) for each of the first clutch K0 and the second clutch WSC by adjusting the supply hydraulic pressure. That is, by changing the torque capacity of each of the first clutch K0 and the second clutch WSC, each of the first clutch K0 and the second clutch WSC can be controlled to be in an engaged state, a semi-engaged state (slip state), or an open state.

[0024] During EV driving, the ECU controls to open the first clutch K0 and engage the second clutch WSC, and in this state, controls the rotary electric machine 2 to output the motor torque required for EV driving. During HEV driving, the ECU controls the first clutch K0 and the second clutch WSC to be in an engaged state, and controls the engine torque of the engine 1 and the motor torque of the rotary electric machine 2 to output the engine torque and the motor torque.

[0025] When shifting from EV driving to HEV driving, the ECU performs start control of the engine 1. In the start control of the engine 1, the ECU performs a process of controlling the inverter so that the rotary electric machine 2 outputs a cranking torque MTcr for cranking the engine 1 via the first clutch K0. Then, when the rotational speed of the engine 1 (engine rotational speed) reaches a predetermined rotational speed by cranking via the first clutch K0, the ECU performs a process of starting fuel injection control and ignition control of the engine 1. Thereby, the start of the engine 1 is completed. When shifting from EV driving to HEV driving, the first clutch K0 is set in a semi-engaged state to transmit the cranking torque MTcr to the engine 1, and the engine rotational speed is gradually increased to start the engine 1.

[0026] In the control method of the hybrid vehicle according to this embodiment, when starting the engine 1 (during cranking), the maximum motor torque MTmax that can be output from the rotating electrical machine 2 is temporarily increased. Thereby, it is possible to expand the EV driving range.

[0027] Further, in the control method of the hybrid vehicle according to this embodiment, when it is assumed that the estimated temperature of the target component that may enter a heat generation state exceeds the upper limit temperature of the preset target component when the maximum motor torque MTmax is temporarily increased as the engine 1 starts, the temporary increase in the maximum motor torque MTmax is prohibited. Thereby, damage to the component that may be caused by overheating of the component (target component) can be suppressed, and the component can be protected.

[0028] Therefore, FIG. 2 is a flowchart showing the control method of the hybrid vehicle according to Embodiment 1. As shown in FIG. 2, the processes of steps S10 to S80 in the control method of the hybrid vehicle according to this embodiment are executed by the ECU.

[0029] First, in step S10, the ECU calculates a basic maximum motor torque MTb determined by the rotational speed of the rotating electrical machine 2 (motor rotational speed) and the input voltage of the inverter that drives the rotating electrical machine 2. The basic maximum motor torque MTb can be calculated from the motor rotational speed and the input voltage with reference to a preset MTb calculation map.

[0030] Here, FIG. 3 is a diagram for explaining the MTb calculation map. The MTb calculation map shown in FIG. 3 illustrates three types of MTb curves corresponding to the input voltage of the inverter. The solid line shown in FIG. 3 is an MTb curve showing the relationship between the motor rotational speed and the basic maximum motor torque MTb when the input voltage is V1. The one-dot chain line shown in FIG. 3 is an MTb curve showing the relationship between the motor rotational speed and the basic maximum motor torque MTb when the input voltage is V2. The two-dot chain line shown in FIG. 3 is an MTb curve showing the relationship between the motor rotational speed and the basic maximum motor torque MTb when the input voltage is V3. Note that the input voltages V1, V2, and V3 satisfy V1 < V2 < V3.

[0031] The MTb calculation map is created in advance by experiments, analysis, etc. In the MTb calculation map, the relationship between the motor speed and the basic maximum motor torque MTb is set for each arbitrary input voltage. The basic maximum motor torque MTb included in the MTb calculation map preferably sets the motor torque that the rotating electrical machine 2 can continuously output over a certain period of time (for example, approximately 5 minutes or more).

[0032] The MTb calculation map is stored in a storage means such as the ROM of the ECU. In step S10, when a start request for the engine 1 is made, the ECU refers to the MTb calculation map and performs a process of deriving the corresponding basic maximum motor torque MTb from the current motor speed and the current input voltage.

[0033] In step S20, the ECU determines whether the maximum motor torque MTmax can be temporarily increased by comparing the estimated temperature of the target part that may become overheated due to engine cranking with the preset upper limit temperature of the target part during cranking. Here, with reference to FIG. 4, the estimated temperature and the upper limit temperature will be described. FIG. 4 is a graph for explaining the estimated temperature and the upper limit temperature of the target part.

[0034] In the present embodiment, the case where the target parts are the inverter that drives the rotating electrical machine 2 and the rotating electrical machine 2 will be described as an example. Here, as the estimated temperature and the upper limit temperature of the inverter, for example, the estimated temperature Twat0 and the upper limit temperature Twat1 of the inverter cooling water temperature Twat, and the estimated temperature Tinv0 and the upper limit temperature Tinv1 of the temperature of the inverter element (inverter element temperature Tinv) included in the inverter can be used. As the estimated temperature and the upper limit temperature of the rotating electrical machine 2, for example, the estimated temperature Tco0 and the upper limit temperature Tco1 of the temperature of the stator coil (stator coil temperature Tco) can be used.

[0035] The upper graph in FIG. 4 shows an example of temperature rise data, predicting the change over time of the inverter element temperature Tinv during engine start-up processing. Also, the lower graph in FIG. 4 shows a prediction of the change over time of the motor torque during engine start-up processing.

[0036] The solid line in the graph showing the change over time of the inverter element temperature Tinv is the measured temperature during EV driving, and the dotted line is the estimated temperature Tinv0 after the start of engine start-up processing. The solid line in the graph showing the change over time of the motor torque is the measured motor torque during EV driving, and the dotted line shows the transition of the motor torque when it is assumed that the maximum motor torque MTmax is temporarily increased during engine start-up.

[0037] When the time required for starting engine 1 (the start-up time from the start of engine start-up processing until the start of engine 1 is completed) is known, assuming that the maximum motor torque MTmax is temporarily increased during engine start-up, the transition of the inverter element temperature Tinv after the start of engine start-up processing (during engine start-up and HEV driving) can be predicted from the measured temperature of the inverter element temperature Tinv and the inverter cooling water temperature Twat during EV driving.

[0038] FIG. 4 shows an example in which the inverter element temperature Tinv rises from point P1, which is the start time of engine start-up processing, and the estimated temperature Tinv0 reaches the upper limit temperature Tinv1 at point P2 when switching to HEV driving as the start of engine 1 is completed.

[0039] Similarly, when the time required for starting engine 1 is known, assuming that the maximum motor torque MTmax is temporarily increased during engine start-up, the transition of the stator coil temperature Tco after the start of engine start-up processing can be predicted from the measured temperature of the stator coil temperature Tco during EV driving, and the transition of the inverter cooling water temperature Twat after the start of engine start-up processing can be predicted from the measured temperature of the inverter cooling water temperature Twat during EV driving.

[0040] On the one hand, the upper limit temperature of the target component may be set to a temperature at which the target component does not overheat during engine startup, even if the maximum motor torque MTmax is temporarily increased, for example, considering the heat resistance temperature when the target component is mounted. In this embodiment, taking the case of setting the upper limit temperatures Twat1, Tinv1, and Tco1 for the inverter cooling water temperature Twat, the inverter element temperature Tinv, and the stator coil temperature Tco respectively and comparing them with the corresponding estimated temperatures Twat0, Tinv0, and Tco0 as an example, the processing flow of the temporary increase approval determination will be described.

[0041] Therefore, FIG. 5 is a flowchart for explaining in detail the process of the temporary increase approval determination (step S20). As shown in FIG. 5, in step S20, the ECU executes the processes of steps S21 to S25.

[0042] In step S21, the estimated temperature Twat0 of the inverter cooling water temperature Twat is compared with the upper limit temperature Twat1 of the inverter cooling water temperature Twat to determine whether the estimated temperature Twat0 is less than or equal to the upper limit temperature Twat1. If the estimated temperature Twat0 is less than or equal to the upper limit temperature Twat1 (Twat0 ≦ Twat1) (step S21; YES), the process proceeds to step S22. If the estimated temperature Twat0 exceeds the upper limit temperature Twat1 (Twat0 > Twat1) (step S21; NO), the process proceeds to step S25.

[0043] In step S22, the estimated temperature Tinv0 of the inverter element temperature Tinv is compared with the upper limit temperature Tinv1 of the inverter element temperature Tinv to determine whether the estimated temperature Tinv0 is less than or equal to the upper limit temperature Tinv1. If the estimated temperature Tinv0 is less than or equal to the upper limit temperature Tinv1 (Tinv0 ≦ Tinv1) (step S22; YES), the process proceeds to step S23. If the estimated temperature Tinv0 exceeds the upper limit temperature Tinv1 (Tinv0 > Tinv1) (step S22; NO), the process proceeds to step S25.

[0044] In step S23, the estimated temperature Tco0 of the stator coil temperature Tco is compared with the upper limit temperature Tco1 of the stator coil temperature Tco, and it is determined whether the estimated temperature Tco0 is less than or equal to the upper limit temperature Tco1. If the estimated temperature Tco0 is less than or equal to the upper limit temperature Tco1 (Tco0 ≦ Tco1) (step S23; YES), the process proceeds to step S24. If the estimated temperature Tco0 exceeds the upper limit temperature Tco1 (Tco0 > Tco1) (step S23; NO), the process proceeds to step S25.

[0045] In steps S21 to S23, when it is confirmed that the estimated temperature of each target part is less than or equal to its respective upper limit temperature, in step S24, it is determined that the maximum motor torque MTmax can be temporarily increased, and the process proceeds to step S30. On the other hand, in steps S21 to S23, when it is confirmed that the estimated temperature of at least one target part exceeds its upper limit temperature, in step S25, it is determined that the maximum motor torque MTmax cannot be temporarily increased, and the process proceeds to step S30.

[0046] Subsequently, in step S30, if the ECU determines that the maximum motor torque MTmax can be temporarily increased (step S30; YES), the process proceeds to step S40. If it determines that the maximum motor torque MTmax cannot be temporarily increased (step S30; NO), the process proceeds to step S60.

[0047] In step S40, the ECU calculates a temporary up-torque MTup that can temporarily increase the maximum motor torque MTmax of the rotating electrical machine 2 before cranking of the engine 1. The temporary up-torque MTup can be calculated from the temperature of at least one target part with reference to a predetermined MTup calculation table.

[0048] For example, the case of calculating the temporary up-torque MTup from the inverter coolant temperature Twat will be described as an example. FIG. 6 is a diagram for explaining the MTup calculation table. The MTup calculation table is created in advance by experiments, analysis, etc. In the MTup calculation table, the relationship between an arbitrary inverter coolant temperature Twat and the temporary up-torque MTup is set. The temporary up-torque MTup included in the MTup calculation table preferably sets the motor torque that the rotating electric machine 2 can output only for a short time (for example, about 1 minute) while the engine start process is being executed.

[0049] The MTup calculation table is stored in a storage means such as the ROM of the ECU. In step S40, the ECU refers to the MTup calculation table and performs a process of deriving the corresponding temporary up-torque MTup from the current inverter coolant temperature Twat.

[0050] In step S50, the ECU sets, as the maximum motor torque MTmax1 at cranking (the temporarily increased maximum motor torque MTmax for calculating the engine start determination torque MTst), the motor torque obtained by adding the temporary up-torque MTup to the basic maximum motor torque MTb, as shown in the following formula (1). MTmax1←MTb + MTup ··· Formula (1) Then, it proceeds to step S70.

[0051] On the other hand, in step S60, the ECU sets, as the maximum motor torque MTmax1 at cranking (the maximum motor torque MTmax that has not been temporarily increased for calculating the engine start determination torque MTst), the basic maximum motor torque MTb, as shown in the following formula (2). MTmax1←MTb ··· Formula (2) Then, it proceeds to step S70.

[0052] Note that the maximum motor torque MTmax1 set in steps S50 and S60 is the maximum motor torque MTmax when assuming that the current time is during engine startup, regardless of whether the current time is actually during engine startup. Then, in step S70, the ECU calculates an engine startup determination torque MTst for use in determining the startup of engine 1 based on the maximum motor torque MTmax1 set in step S50 or step S60.

[0053] Here, the engine startup determination torque MTst is a threshold value for determining the transition from EV driving to HEV driving. Also, the engine startup determination torque MTst can be calculated by subtracting the cranking torque MTcr and the margin torque MTmar from the maximum motor torque MTmax1, as shown in the following formula (3). Note that the margin torque MTmar is appropriately set according to the amount of change in the driving force assumed during engine startup. MTst←MTmax1 - MTcr - MTmar ··· Formula (3) By determining the engine startup determination torque MTst in this way, it is possible to suppress the drop in driving force that may occur during engine startup.

[0054] In step S80, the ECU calculates the actual maximum motor torque MTmax. FIG. 7 is a flowchart for explaining in detail the process of calculating the actual maximum motor torque MTmax (step S80). As shown in FIG. 7, in step S80, the ECU executes the processes of steps S81 to S84.

[0055] In step S81, it is checked whether it is during engine startup. If it is during engine startup (step S81; YES), the process proceeds to step S82. If it is not during engine startup (step S81; NO), the process proceeds to step S84.

[0056] In step S82, it is checked whether the maximum motor torque MTmax can be temporarily increased. If the maximum motor torque MTmax can be temporarily increased (step S82; YES), the process proceeds to step S83. If the maximum motor torque MTmax cannot be temporarily increased (step S82; NO), the process proceeds to step S84.

[0057] In step S83, the motor torque obtained by adding the temporary up-torque MTup to the basic maximum motor torque MTb is determined as the actual maximum motor torque MTmax (the actually temporarily increased maximum motor torque MTmax). On the other hand, in step S84, the basic maximum motor torque MTb is determined as the actual maximum motor torque MTmax (the actually maximum motor torque MTmax that has not been temporarily increased).

[0058] Through the above flow of steps S10 to S80, it is possible to determine whether the maximum motor torque MTmax can be temporarily increased before cranking the engine 1, and set an appropriate maximum motor torque MTmax during cranking according to the situation of the hybrid vehicle 100.

[0059] Furthermore, when the required torque to be output to the drive shaft 4a based on the accelerator opening and the vehicle speed becomes equal to or greater than the engine start determination torque MTst, the ECU determines to start the engine 1, and shifts to HEV running including the rotating electric machine 2 as a driving power source in the engaged state of the first clutch K0.

[0060] As described above, the control method for a hybrid vehicle according to the present embodiment is a control method for a hybrid vehicle including an engine 1 and a rotary electric machine 2, and includes a step of calculating a basic maximum motor torque MTb determined by the rotational speed of the rotary electric machine 2 and the input voltage of an inverter that drives the rotary electric machine 2; a step of calculating a temporary up-torque MTup that can temporarily increase the maximum motor torque MTmax of the rotary electric machine 2 before cranking of the engine 1; a step of setting the motor torque obtained by adding the temporary up-torque MTup to the basic maximum motor torque MTb as the maximum motor torque MTmax1 at the time of cranking of the engine 1; and a step of calculating an engine start determination torque MTst used for determining the start of the engine 1 based on the set maximum motor torque MTmax1 at the time of cranking.

[0061] According to the present embodiment, at the time of cranking, the maximum motor torque MTmax is temporarily increased, and the engine start determination torque MTst is determined based on the temporarily increased maximum motor torque MTmax. Therefore, compared with the case where the engine start determination torque MTst is determined without temporarily increasing the maximum motor torque MTmax, the start of the engine 1 can be delayed. Therefore, it is possible to expand the EV driving range in which the engine 1 is stopped.

[0062] Further, the control method for a hybrid vehicle according to the present embodiment includes, before the step of calculating the temporary up-torque MTup, a step of determining whether the maximum motor torque MTmax can be temporarily increased by comparing the estimated temperature of a target component that may become overheated due to cranking of the engine 1 with a preset upper limit temperature of the target component during cranking of the engine 1. When the estimated temperature exceeds the upper limit temperature, it is determined that the maximum motor torque cannot be temporarily increased, and the basic maximum motor torque is set as the maximum motor torque MTmax1 at the time of cranking of the engine, and the engine start determination torque MTst is calculated based on the set maximum motor torque MTmax1 at the time of cranking.

[0063] According to this embodiment, since the setting of the maximum motor torque MTmax is determined based on the prediction of the temperature of the target component during cranking, damage to the component that may occur due to overheating of the component can be suppressed, and the component can be appropriately protected.

[0064] Note that the present invention is not limited to the above-described embodiment, and can be appropriately modified without departing from the spirit thereof. For example, in the above embodiment, the case where the second clutch WSC is provided on the input shaft 3a of the transmission 3 has been described as an example, but the present invention is not limited thereto. As shown in FIG. 8, the hybrid vehicle 100 may be in a form in which the second clutch WSC is omitted. FIG. 8 is a configuration diagram showing another form of the hybrid vehicle. In the case of the hybrid vehicle 100 shown in FIG. 8, EV travel and HEV travel can be selectively switched.

Explanation of Reference Numerals

[0065] 1 Engine 1a Crankshaft 2 Rotating electric machine 2a Rotating shaft 3 Transmission 3a Input shaft 3b Output shaft 4 Drive wheel 4a Drive shaft 100 Hybrid vehicle K0 First clutch MTb Basic maximum motor torque MTcr Cranking torque MTmar Margin torque MTmax Maximum motor torque MTst Engine start determination torque Mtup Temporary up torque WSC Second clutch

Claims

【Claim 1】 A control method for a hybrid vehicle including an engine and a rotating electric machine, the method comprising: calculating a basic maximum motor torque determined by the rotational speed of the rotating electric machine and the input voltage of an inverter that drives the rotating electric machine; calculating a temporary up-torque that can temporarily increase the maximum motor torque of the rotating electric machine before cranking of the engine; setting, as the maximum motor torque during cranking of the engine, a motor torque obtained by adding the temporary up-torque to the basic maximum motor torque; calculating an engine start determination torque used for determining engine start based on the set maximum motor torque during cranking; wherein before the step of calculating the temporary up-torque, for a target component that may become overheated due to cranking of the engine, determining whether the maximum motor torque can be temporarily increased by comparing an estimated temperature of the target component during cranking of the engine with a preset upper limit temperature of the target component; when the estimated temperature exceeds the upper limit temperature, determining that the maximum motor torque cannot be temporarily increased, and setting the basic maximum motor torque as the maximum motor torque during cranking of the engine; calculating an engine start determination torque based on the set maximum motor torque during cranking; A control method for a hybrid vehicle.

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