Hybrid vehicle

Abstract

The present invention is a hybrid vehicle, comprising a hybrid control unit 20 that allows selection of a series mode and a parallel mode and switches the travel mode of the vehicle by operational control of an engine clutch 16 on the basis of the travel velocity of the vehicle and the charging rate of a drive battery 11. When the vehicle is in decelerating travel, a first prescribed duration ta required to reach an engine stop vehicle velocity in the parallel mode and a second prescribed duration required to switch from the parallel mode to the series mode by interrupting the engine clutch 16 on the basis of engine torque are computed; a switching vehicle velocity Vps at which the first prescribed duration will be equal to or greater than the second prescribed duration is set; and when the vehicle velocity V has reached the switching vehicle velocity Vps or below, the switch from the parallel mode to the series mode is started.

Description

Hybrid vehicles

[0001] The present invention relates to a driving mode switching control technique for a hybrid vehicle.

[0002] Hybrid vehicles developed in recent years are known to have a driving mode that can be switched between an EV mode in which the vehicle is driven by a drive motor (electric motor) using power from a drive battery without operating the engine, a series mode in which the vehicle is driven by the drive motor while the engine drives a generator to generate electricity, and a parallel mode in which the vehicle can be driven by both the engine and the drive motor.

[0003] In a hybrid vehicle capable of parallel mode, power can be transmitted from the engine to the driving shaft via a transmission (reduction gear) and a clutch. In parallel mode, the clutch is connected and power is transmitted from the engine to the driving wheels via the transmission.

[0004] For example, Patent Document 1 discloses a hybrid vehicle that automatically switches the driving mode between EV mode, series mode, and parallel mode based on the charging rate of the drive battery and the driving speed of the vehicle.

[0005] JP 2014-121962 A

[0006] However, in a hybrid vehicle that automatically switches between driving modes as described above, when switching from the parallel mode to another mode during sudden deceleration, the switching speed is set with a margin of error so that the engine does not stop due to a decrease in engine speed caused by a decrease in vehicle speed in the parallel mode. Therefore, if the switching speed is set with a margin of error in this way, in a vehicle that switches between driving modes based on vehicle speed and the battery charge rate as in Patent Document 1, the frequency of switching between driving modes may increase due to fluctuations in vehicle speed.

[0007] The present embodiment aims to provide a hybrid vehicle that can appropriately set the vehicle speed at which the parallel mode and the series mode are switched, thereby reducing the frequency of switching between the driving modes.

[0008] In order to achieve the above object, a hybrid vehicle according to claim 1 comprises an engine mounted on the vehicle, a generator driven by the engine to generate electricity, a drive battery that can be charged by receiving power from the generator, an electric drive motor connected to a traveling drive shaft of the vehicle and receiving power from the drive battery to drive the traveling drive shaft, a clutch disposed between the engine and the traveling drive shaft, and a charge rate detection unit that detects the charge rate of the drive battery, and the vehicle is in a driving mode in which the clutch is disengaged and the generator is driven by the engine to generate electricity and the drive battery is charged. The hybrid vehicle has a series mode in which the drive motor is driven to drive the driving drive shaft, and a parallel mode in which the clutch is connected and the driving drive shaft is driven by both the engine and the drive motor, and is equipped with a driving mode switching control unit that switches the driving mode of the vehicle based on the vehicle's driving speed and the charging rate, and is characterized in that it also has an engine torque acquisition unit that acquires engine torque output by the engine, and the driving mode switching control unit sets a switching vehicle speed of the vehicle at which the parallel mode and the series mode are switched based on the engine torque.

[0009] This allows the switching vehicle speed between parallel mode and series mode to be appropriately set in response to the change in the time required for the clutch to operate depending on the engine torque in a hybrid vehicle that switches between driving modes based on the vehicle's driving speed and the charge rate of the drive battery.

[0010] Preferably, the driving mode switching control unit calculates, when the vehicle is decelerating, a first predetermined time required for the vehicle to reach an engine stop vehicle speed at which the engine stops in the parallel mode, and a second predetermined time required for the clutch disengagement control to be initiated and the vehicle to switch from the parallel mode to the series mode, sets the switching vehicle speed so that the first predetermined time is within a range equal to or greater than the second predetermined time, and initiates switching from the parallel mode to the series mode when the vehicle's driving speed reaches or exceeds the switching vehicle speed.

[0011] This allows the first predetermined time and the second predetermined time to be calculated when the vehicle is decelerating, and the switching vehicle speed to be calculated so that the first predetermined time is within a range equal to or greater than the second predetermined time, so that the switching vehicle speed can be set low within a range that does not reach the engine stop vehicle speed.

[0012] Preferably, the second predetermined time includes a clutch torque difference resolution time required to make the torque difference before and after the clutch a torque difference that allows disengagement, and a clutch disengagement time required from the start to the completion of disengagement of the clutch, thereby enabling accurate calculation of the second predetermined time required from the start of clutch disengagement control to the completion of disengagement.

[0013] Preferably, the traveling mode switching control unit is capable of clutch torque difference absorption power generation in which the generator absorbs the rotational torque of the engine to generate power when the torque difference before and after the clutch is reduced to a torque difference that allows the clutch to be disconnected. By performing clutch torque difference absorption power generation, the clutch torque difference cancellation time can be shortened and the switching vehicle speed can be set low.

[0014] Preferably, the vehicle has a regenerative power generation control unit that regenerates power using the drive motor and charges the drive battery when the vehicle is decelerating, and a chargeable amount acquisition unit that acquires the amount of power that can be charged to the drive battery, wherein the driving mode switching control unit calculates, when the vehicle is decelerating, a first charge amount to be charged to the drive battery by the regenerative power generation control unit before the engine stops, and a second charge amount to be charged to the drive battery by the clutch torque difference absorption power generation, and when the vehicle is decelerating, if the chargeable amount of the drive battery is less than the sum of the first charge amount and the second charge amount.

[0015] This prevents overcharging of the drive battery by restricting clutch torque difference absorption power generation when the drive battery cannot be charged with power generated by regeneration and clutch torque difference absorption power generation during deceleration of the vehicle. Also, when the drive battery can be charged, the clutch torque difference absorption power generation is executed, allowing the switching vehicle speed to be set low.

[0016] Preferably, the vehicle control system further includes a weight acquisition unit that acquires a weight of the vehicle, and the driving mode switching control unit calculates the first predetermined time based on the weight of the vehicle and the deceleration of the vehicle, thereby enabling accurate calculation of the first predetermined time until the engine stop vehicle speed is reached based on the vehicle weight.

[0017] Preferably, a speed reducer capable of switching the speed reduction ratio is provided between the engine and the traveling drive shaft, and the traveling mode switching control unit calculates the first predetermined time based on the speed reduction ratio of the speed reducer. This makes it possible to accurately calculate the first predetermined time until the vehicle speed reaches the engine stop speed based on the speed reduction ratio of the speed reducer.

[0018] Preferably, the vehicle has a regenerative braking force selection operation unit that selects the braking force of the vehicle generated by the regenerative power generation, and the driving mode switching control unit calculates the first charge amount based on the braking force selected by the regenerative braking force selection operation unit.

[0019] This makes it possible to select the vehicle braking force generated by regenerative power generation, and calculates the first charge amount to the drive battery by regenerative power generation according to the selected braking force, thereby appropriately regulating clutch torque difference absorption power generation.

[0020] In the hybrid vehicle of the present invention, by setting the switching speed between parallel mode and series mode based on engine torque, the switching speed can be appropriately set in response to the time from when the vehicle reaches the switching speed to when the switching between parallel mode and series mode is completed, which changes depending on the engine torque, and the frequency of switching between parallel mode and series mode can be reduced.

[0021] For example, the frequency of switching between the parallel mode and the series mode can be reduced by delaying the timing of switching from the parallel mode to the series mode while avoiding engine stall during deceleration.

[0022] 1 is a schematic configuration diagram of a hybrid vehicle according to an embodiment of the present invention; 2 is a block diagram showing the configuration of a driving mode switching system according to the present embodiment; 3 is a flowchart showing a control procedure for driving mode switching control according to the present embodiment; 4 is an explanatory diagram showing an image of setting a transition time from parallel mode to series mode according to the present embodiment; 5 is a time chart showing an example of changes in various torques when engine torque absorption power generation is being performed; and 6 is a time chart showing an example of changes in various torques when engine torque absorption power generation is not being performed.

[0023] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. Fig. 1 is a schematic diagram of a hybrid vehicle (hereinafter referred to as vehicle 1) according to an embodiment of the present invention.

[0024] The vehicle 1 of this embodiment is a vehicle such as a plug-in hybrid vehicle (PHEV) or hybrid vehicle that can run by driving the front wheels 3 with the output of the engine 2 and is equipped with an electric front motor 4 (driving motor) that drives the front wheels 3, and is also capable of external charging and external power supply.

[0025] The engine 2 is capable of driving a drive shaft 8 (traveling drive shaft) of the front wheels 3 via a reduction gear 7, and is also capable of driving a motor generator 9 (electric generator) via the reduction gear 7 to generate electricity. The reduction gear 7 is capable of switching the reduction ratio.

[0026] The front motor 4 is powered by high-voltage power supplied from a drive battery 11 and a motor generator 9 mounted on the vehicle 1 via a front inverter 10, and drives a drive shaft 8 of the front wheels 3 via a reduction gear 7. The reduction gear 7 has a built-in engine clutch 16 that can switch between connecting and disconnecting the transmission of power between the output shaft of the engine 2 and the drive shaft 8 of the front wheels 3. The engine clutch 16 is drive-controlled by a hybrid control unit 20 (described later) via an engine clutch control unit 40 (engine clutch ECU).

[0027] The drive battery 11 is composed of a secondary battery such as a lithium-ion battery, and has a battery module (not shown) configured by a group of multiple battery cells. The battery ECU 11a (battery ECU) 11a (charge rate detection unit, chargeable amount acquisition unit) monitors the temperature and state of charge (SOC) of the battery module. The battery monitoring unit 11a also has a function to calculate the amount of power W that can be charged to the drive battery 11 based on the temperature, state of charge, usage status (integrated values ​​of input and output current), etc. The chargeable amount W is the amount of power that can be input to the drive battery 11 for charging, and is a value based on the state of charge SOC. However, this value decreases at low temperatures and also decreases due to deterioration over time.

[0028] The front inverter 10 has a front motor control unit 10a and a generator control unit (generator ECU) 10b (regenerative power generation control unit). The front motor control unit 10a controls the output of the front motor 4 based on a control signal from a hybrid control unit 20 (driving mode switching control unit). The generator control unit 10b has a function of controlling the amount of power generated by the motor generator 9 based on a control signal from the hybrid control unit 20.

[0029] The hybrid control unit 20 is a control device for performing overall control of the vehicle 1, and is composed of input / output devices, memory devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), a timer, etc.

[0030] The input side of the hybrid control unit 20 is connected to various sensors, such as a battery monitoring unit 11a of the drive battery 11, a front motor control unit 10a and a generator control unit 10b of the front inverter 10, an engine control unit (engine ECU) 22 (engine torque acquisition unit) that controls the drive of the engine 2, and an accelerator position sensor that detects the amount of accelerator operation, and detection and operation information from these devices is input.

[0031] On the other hand, the output side of the hybrid control unit 20 is connected to the front motor control unit 10 a and generator control unit 10 b of the front inverter 10 , the reducer 7 (engine clutch 16 ), and the engine control unit 22 .

[0032] Then, based on the above-mentioned various detection and operation information, the hybrid control unit 20 calculates the required output power P required to drive the vehicle 1, and sends control signals to the engine control unit 22, the front motor control unit 10a, the generator control unit 10b, and the reducer 7 to switch the driving mode (EV mode (electric vehicle mode), series mode, parallel mode), control the output of the engine 2 and the front motor 4, the amount of power generated by the motor generator 9, and the reduction ratio of the reducer 7.

[0033] In EV mode, the engine 2 is stopped, and the front motor 4 is driven by electric power supplied from the drive battery 11 to drive the vehicle. In series mode, the engine clutch 16 is disengaged, and the motor generator 9 is operated by the engine 2. The front motor 4 is then driven by electric power generated by the motor generator 9 and electric power supplied from the drive battery 11 to drive the vehicle. Also, in series mode, the rotational speed of the engine 2 is maintained within a highly efficient range, i.e., a range with good fuel economy, and electric power generated by surplus output is supplied to the drive battery 11 to charge it.

[0034] In the parallel mode, the engine clutch 16 is connected, and power is mechanically transmitted from the engine 2 via the reduction gear 7 to drive the front wheels 3. The front motor 4 is driven by the electric power generated by the engine 2 operating the motor generator 9 and the electric power supplied from the drive battery 11, causing the vehicle to travel.

[0035] The hybrid control unit 20 switches the driving mode based on the state of charge SOC of the drive battery 11, the required output P, ​​the vehicle speed V (the running speed of the vehicle 1), and the chargeable energy W. For example, the EV mode is selected when the required output P is low and the state of charge SOC is high.

[0036] Switching between parallel mode and series mode is performed based on the vehicle speed V, the state of charge SOC of the drive battery 11, the chargeable energy amount W, etc. In more detail, when the required output P is high or the state of charge SOC is low, the parallel mode is selected when the vehicle speed V is higher than the switching vehicle speed Vps, and the series mode is selected when the vehicle speed V is equal to or lower than the switching vehicle speed Vps.

[0037] 2 is a block diagram showing the configuration of the driving mode switching system 25. The driving mode switching system 25 has a vehicle information control unit 30 and a driving mode control unit 31 provided in the hybrid control unit 20.

[0038] The vehicle 1 is provided with a regenerative level selector 32 (regenerative braking force selection operation unit) that allows the driver to set the regenerative braking force. The regenerative level selector 32 is provided, for example, near the driver's seat of the vehicle 1, and can selectively set the regenerative braking force to one of five levels, from B5, which indicates a high regenerative braking force, to B1, which indicates a low regenerative braking force, and B0, which indicates that no regenerative braking force is applied, for a total of six levels.

[0039] The vehicle 1 is also equipped with a weight sensor 33 (weight acquisition unit) that detects the vehicle weight or a value related to the vehicle weight, and a vehicle speed sensor 34 that detects the driving speed, and these operation information and detection information are input to the hybrid control unit 20.

[0040] The vehicle information control unit 30 provided in the hybrid control unit 20 has a regeneration level determination unit 35 and a vehicle weight estimation unit 36. The driving mode control unit 31 also has a parallel driving possible vehicle speed control unit 37 and an engine clutch engagement determination unit 38.

[0041] The regeneration level determination unit 35 determines the regeneration level (regenerative braking force) based on the operation information of the regeneration level selector 32, and assigns one of the six levels to the regeneration level. The vehicle weight estimation unit 36 ​​estimates the vehicle weight based on the detection information of the weight sensor 33. The vehicle weight is a value including the weight of the vehicle itself and the weight of any passengers and passengers on or mounted on the vehicle.

[0042] The parallel running speed control unit 37 calculates a parallel running lower limit vehicle speed at which parallel running is possible, and sets a switching vehicle speed Vps. The engine clutch engagement determination unit 38 determines whether the engine clutch 16 is engaged or disengaged.

[0043] In this embodiment, the hybrid control unit 20 acquires the above-mentioned regeneration level, vehicle weight, and other vehicle information (vehicle speed V, required output P, ​​state of charge (SOC) of the drive battery 11, and chargeable electric energy W) in the vehicle information control unit 30, sets the switching vehicle speed Vps in the parallel running vehicle speed control unit 37 of the driving mode control unit 31, and controls the operation of the engine clutch 16 based on the switching vehicle speed Vps and the vehicle speed V in the engine clutch engagement determination unit 38.

[0044] 3 is a flowchart showing a control procedure for setting the switching vehicle speed Vps and determining whether parallel running (parallel mode) is possible in the hybrid control unit 20. This routine is repeatedly executed at predetermined time intervals when the power supply to the vehicle 1 is ON.

[0045] First, in step S10, the current engine torque is obtained from the engine control unit 22, and the regeneration level is obtained from the regeneration level determination unit 35, and the amount of charge to the drive battery 11 when the vehicle is suddenly decelerated from the current vehicle speed V to a stop is calculated. The amount of charge to the drive battery 11 may be calculated using, for example, a pre-stored map. Note that the higher the engine torque, the greater the amount of charge to the drive battery 11, and the higher the regeneration level (greater the regenerative braking force), the greater the amount of charge to the drive battery 11.

[0046] Furthermore, the vehicle weight input from the weight sensor 33 and the engine gear ratio (reduction ratio) planned to be used in the reducer 7 are acquired, and a first predetermined time ta required for the vehicle speed V to decrease to the engine stall vehicle speed Ves is calculated. The engine stall vehicle speed Ves (engine stop vehicle speed) is the upper limit of the vehicle speed at which the engine 2 stops in parallel mode. Note that the heavier the vehicle weight, the longer the first predetermined time ta required for the vehicle speed V to decrease to the engine stall vehicle speed Ves, and the higher the engine gear ratio, the longer the first predetermined time ta required for the vehicle speed V to decrease to the engine stall vehicle speed Ves. Then, the process proceeds to step S20.

[0047] In step S20, the chargeable power amount W of the drive battery 11 is input from the battery monitoring unit 11a, and a determination is made as to whether the gear disengagement time by the motor generator 9 can be shortened.

[0048] Whether or not the gear disengagement time by the motor generator 9 can be shortened can be determined by calculating the amount of electricity generated when the motor generator 9 is caused to generate electricity to offset the current engine torque and the amount of charge to the drive battery 11 when deceleration is performed based on the regeneration level, and determining whether the sum of these values ​​is less than or equal to the chargeable power amount W of the drive battery 11. If the gear disengagement time can be shortened, that is, if the amount of regenerated electricity and the amount of electricity generated to offset the engine torque can be charged, proceed to step S30. If the gear disengagement time cannot be shortened, that is, if the amount of regenerated electricity and the amount of electricity generated to offset the engine torque cannot be charged, proceed to step S50.

[0049] In step S30, the time required for the clutch torque of the engine clutch 16 to be reduced to a threshold value or less (the front and rear torque difference at which the clutch can be disengaged) (clutch torque difference elimination time tca) is set as t1. Time t1 is the time when the motor generator 9 is caused to generate electricity so as to cancel out the engine torque as described above. The motor generator 9 is controlled so as to add a negative torque equal to the engine torque. Time t1 becomes a value corresponding to the engine torque. Then, the process proceeds to step S40.

[0050] In step S40, the parallel traveling lower limit vehicle speed Va is set to V1. The parallel traveling lower limit vehicle speed Va is set on the condition that the engagement and disengagement of the engine clutch 16 is completed before the first predetermined time ta, which is required for the parallel traveling vehicle speed to decrease to the engine stall vehicle speed Ves, has elapsed. The time required to engage and disengage the engine clutch 16 is the sum of the clutch torque difference elimination time tca (= t1) calculated in step S30 and the time required for the engine clutch 16 to disengage by operation of the clutch actuator (clutch disengagement time tcb). Note that the clutch disengagement time tcb is a constant value. Then, the process proceeds to step S70.

[0051] In step S50, the clutch torque difference cancellation time tca is set to t2. The time t2 here is the value when the motor generator 9 is not generating electricity as described above, and is longer than the time t1. Then, the process proceeds to step S60.

[0052] In step S60, the parallel driving lower limit vehicle speed Va is set to V2. The parallel driving lower limit vehicle speed Va is calculated in the same manner as in step S40, but in this step, t2 calculated in step S50 is used as the clutch torque difference cancellation time tca. Therefore, in this step, the parallel driving lower limit vehicle speed Va (= V2) becomes a value equal to or greater than V1 calculated in step S40. Then, the process proceeds to step S70.

[0053] In step S70, a switching vehicle speed Vps is set. The switching vehicle speed Vps is set by providing hysteresis to the parallel running lower limit vehicle speed Va (= V1 or V2) set in step S40 or step S60. For example, when switching from parallel mode to series mode, Vps = Va - α, and when switching from series mode to parallel mode, Vps + α, where α is a positive value set appropriately.

[0054] If the engine clutch 16 is operated by hydraulic pressure generated by the engine-driven pump, the parallel driving lower limit vehicle speed Va is set to a vehicle speed equal to or higher than the vehicle speed at which hydraulic pressure is obtained that allows the clutch to operate, and the switching vehicle speed Vps also becomes a value corresponding to the parallel driving lower limit vehicle speed Va. Then, the process proceeds to step S80.

[0055] In step S80, the current vehicle speed V is input and it is determined whether or not the vehicle speed V is greater than the switching vehicle speed Vps. If the vehicle speed V is greater than the switching vehicle speed Vps, the process proceeds to step S90. If the vehicle speed V is equal to or less than the switching vehicle speed Vps, the process proceeds to step S100.

[0056] In step S90, parallel running is permitted, and the routine returns. In step S100, parallel running is prohibited, which means that switching from parallel mode to series mode is initiated, and the routine returns.

[0057] As described above, the vehicle 1 of this embodiment is a hybrid vehicle that automatically switches between a series mode in which the engine clutch 16 is disconnected and the engine 2 is not connected to the front wheels 3, which are the driving wheels, and a parallel mode in which the engine clutch 16 is connected and the engine 2 is connected to the front wheels 3, and when decelerating from the parallel mode, the vehicle automatically switches to the series mode when it reaches the switching vehicle speed Vps before the engine stops.

[0058] 4, this embodiment calculates a first predetermined time ta required for the vehicle speed to reach the engine stall vehicle speed Ves, which is the lower limit vehicle speed in the parallel mode, when the vehicle 1 is decelerating, and also calculates a second predetermined time tb required for switching from the parallel mode to the series mode, and calculates a switching vehicle speed Vps so that the first predetermined time ta is equal to or greater than the second predetermined time tb. Since the first predetermined time ta is calculated based on the running conditions of the vehicle 1 (vehicle weight, engine gear ratio), the first predetermined time ta can be calculated with high accuracy.

[0059] Furthermore, since the second predetermined time tb required to switch from parallel mode to series mode varies based on engine torque, the switching vehicle speed Vps can be set accurately by setting the switching vehicle speed Vps based on engine torque.

[0060] This makes it possible to avoid engine stall during deceleration while delaying the timing of switching from the parallel mode to the series mode, thereby reducing the frequency of switching between the parallel mode and the series mode.

[0061] The second predetermined time tb required to switch from parallel mode to series mode is calculated by calculating the clutch torque difference elimination time tca required to reduce the clutch torque of the engine clutch 16 to a threshold value or less (reducing the torque difference before and after the engine clutch 16 so that it can be disconnected), and the clutch disengagement time tcb required from the start of operation of the engine clutch 16 until it is disconnected, and the sum of these is set to the second predetermined time tb.

[0062] Therefore, the switching vehicle speed Vps is set so that the sum of the clutch torque difference elimination time tca and the clutch disengagement time tcb does not exceed the first predetermined time ta, which is the time it takes for the vehicle 1 to reach the engine stall vehicle speed Ves after the switching control (series transition) from the parallel mode to the series mode is started, and the transition to the series mode begins when the vehicle speed V reaches or exceeds the switching vehicle speed Vps.

[0063] In this way, the first predetermined time ta, which is the time it takes for the vehicle 1 to reach the engine stall speed Ves after the start of switching control from parallel mode to series mode (series transition), is set based on the vehicle weight and the gear ratio of the reducer. Furthermore, since the switching speed Vps is set by calculating the time (tca + tcb) required to switch from parallel mode to series mode, it is possible to keep the switching speed Vps lower than if it were simply set to a constant value. This delays the timing of switching from parallel mode to series mode while avoiding engine stall during deceleration, thereby reducing the frequency of switching between parallel mode and series mode.

[0064] Furthermore, the time required to switch from parallel mode to series mode is calculated by calculating the clutch torque difference resolution time tca required to make the torque difference before and after engine clutch 16 a torque difference that allows disengagement, and the clutch disengagement time tcb required from the start to completion of disengagement of engine clutch 16, and using this total value as the time required to switch from parallel mode to series mode, so it is possible to accurately calculate the time required to switch from parallel mode to series mode. In particular, the clutch torque difference resolution time tca required to make the torque difference before and after engine clutch 16 a torque difference that allows disengagement varies based on engine torque, so the switching vehicle speed Vps can be accurately set.

[0065] Furthermore, the clutch torque difference elimination time tca can be shortened by absorbing the engine torque with the motor generator 9. For example, as shown in Figure 5, the clutch torque Tc is rapidly reduced by absorbing the drive torque Tg of the motor generator 9 from the engine torque Te. Therefore, the clutch torque difference elimination time tca, which is the time from the start of deceleration until the clutch torque Tc becomes approximately 0, can be shortened, and the switching vehicle speed Vps can be set low.

[0066] The motor generator 9 generates electricity by absorbing the rotational torque of the engine 2, and this generated electricity is supplied to and charged in the drive battery 11. When the vehicle is decelerating, the electric power obtained by regenerative power generation by the front motor 4 also charges the drive battery 11.

[0067] When the drive battery 11 is nearly fully charged, the motor generator 9 cannot absorb the rotational torque of the engine 2, so as shown in Figure 6, the clutch torque difference elimination time tca becomes longer, and therefore the switching vehicle speed Vps is set higher than when the motor generator 9 absorbs the rotational torque of the engine 2.

[0068] In this embodiment, the first charge amount C1 to be charged to the drive battery 11 by regenerative power generation and the second charge amount C2 to be charged to the drive battery 11 by clutch torque difference absorption power generation are calculated before the parallel driving lower limit vehicle speed Va (engine stall vehicle speed Ves), which is the lower limit vehicle speed in parallel mode, and a determination is made as to whether the sum of the first charge amount C1 and the second charge amount C2 can be used to charge the drive battery 11. If charge is not possible, clutch torque difference elimination control is not executed, thereby preventing overcharging of the drive battery 11.

[0069] The vehicle 1 is also provided with a regeneration level selector 32 that selects the regenerative braking force, i.e., the amount of regenerative power generation. The first charge amount C1 described above can be calculated based on the braking force selected by the regeneration level selector 32. This allows the first charge amount C1 to be accurately calculated for the drive battery 11 through regenerative power generation in accordance with the selected braking force, and allows appropriate regulation of clutch torque difference absorption power generation.

[0070] The present invention is not limited to the above-described embodiment. For example, the detailed control of the above-described embodiment may be modified as appropriate. In the present invention, the switching speed for switching between parallel mode and series mode may be set based on at least the engine torque and the charging rate. The present invention is widely applicable to hybrid vehicles that can switch between series mode and parallel mode.

[0071] REFERENCE SIGNS LIST 1 vehicle 2 engine 4 front motor (driving motor) 7 reduction gear 9 motor generator (generator) 10b generator control unit (regenerative power generation control unit) 11 driving battery 11a battery monitoring unit (charging rate detection unit, chargeable amount acquisition unit) 16 engine clutch 20 hybrid control unit (driving mode switching control unit) 22 engine control unit (engine torque acquisition unit) 32 regeneration level selector (regenerative braking force selection operation unit) 33 weight sensor (weight acquisition unit)

Claims

1. An engine mounted on a vehicle, a generator driven by the engine to generate electricity, a driving battery that can be charged by receiving power from the generator, an electric driving motor connected to the traveling drive shaft of the vehicle and driven by receiving power from the driving battery to drive the traveling drive shaft, a clutch disposed between the engine and the traveling drive shaft, and a charging rate detection unit that detects the charging rate of the driving battery, As the traveling modes of the vehicle, there are a series mode in which the clutch is disengaged and the generator is driven by the engine to generate electricity, and the driving motor is driven by the generated electricity to drive the traveling drive shaft, and a parallel mode in which the clutch is engaged and both the engine and the driving motor drive the traveling drive shaft, A hybrid vehicle provided with a traveling mode switching control unit that switches the traveling mode of the vehicle based on the traveling speed and the charging rate of the vehicle, Comprising an engine torque acquisition unit that acquires the engine torque output by the engine, The traveling mode switching control unit, During decelerated traveling in the parallel mode of the vehicle, it calculates a first predetermined time required to reach an engine stop vehicle speed at which the engine stops in the parallel mode, and based on the engine torque, starts the disengagement control of the clutch and calculates a second predetermined time required to switch from the parallel mode to the series mode. A hybrid vehicle is characterized in that a switching vehicle speed for switching between the parallel mode and the series mode is set so that the first predetermined time is within a range equal to or greater than the second predetermined time, and when the traveling speed reaches a value equal to or lower than the switching vehicle speed, the switching from the parallel mode to the series mode is started.

2. (Deleted)

3. The second predetermined time, Is the clutch torque difference elimination time that makes the torque difference before and after the clutch a torque difference that can be cut, And has a clutch disengagement time required from the start to the completion of the disengagement of the clutch The hybrid vehicle according to claim 1, characterized in that.

4. When making the torque difference before and after the clutch a torque difference that can be cut, clutch torque difference absorption power generation capable of absorbing the engine torque by the generator to generate electricity is possible The hybrid vehicle according to claim 3, characterized in that.

5. A regenerative power generation control unit that performs regenerative power generation by the drive motor and charges the drive battery during decelerated travel of the vehicle; A chargeable amount acquisition unit that acquires the amount of electric power that can be charged to the drive battery, and The travel mode switching control unit During decelerated travel of the vehicle, a first charge amount that charges the drive battery by the regenerative power generation control unit before reaching the engine stop vehicle speed, and A second charge amount that charges the drive battery by clutch torque difference absorption power generation are calculated, and During decelerated travel of the vehicle, when the chargeable amount of the drive battery is less than the total value of the first charge amount and the second charge amount, the clutch torque difference absorption power generation is restricted The hybrid vehicle according to claim 4, characterized in that.

6. Having a weight acquisition unit that acquires the weight of the vehicle, and The travel mode switching control unit calculates the first predetermined time based on the weight of the vehicle The hybrid vehicle according to claim 1, characterized in that.

7. A speed reducer having a speed reduction ratio that can be switched is provided between the engine and the travel drive shaft, and The travel mode switching control unit calculates the first predetermined time based on the speed reduction ratio in the speed reducer The hybrid vehicle according to claim 1, characterized in that.

8. Having a regenerative braking force selection operation unit that selects the braking force of the vehicle by regenerative power generation, and The travel mode switching control unit calculates the first charge amount based on the braking force selected by the regenerative braking force selection operation unit The hybrid vehicle according to claim 5, characterized in that.