JP7694358B2 - Hybrid vehicle control device - Google Patents

Description

The present invention relates to a control device for a hybrid vehicle.

There is a known control device for a hybrid vehicle that has a clutch, motor, and transmission, which are arranged in that order on the power transmission path from the engine to the wheels. When the motor is running and the clutch is in a disengaged state and there is a request to start the engine, this control device transitions the clutch to an engaged state, thereby cranking the engine using the motor to start the engine (see, for example, Patent Document 1).

JP 2020-111276 A

When starting the engine in this way, it is conceivable that the engine throttle opening is controlled to a starting throttle opening, and after the engine starts, the throttle opening is controlled to an idle maintenance throttle opening that maintains the engine speed at the target idle speed. However, depending on the timing at which the throttle opening is switched from the starting throttle opening to the idle maintenance throttle opening, there is a risk that the engine torque will increase, causing a shock to the vehicle.

The present invention aims to provide a control device for a hybrid vehicle that suppresses the occurrence of shocks.

The object of the present invention is to provide a control device for a hybrid vehicle in which a clutch, a motor, and a transmission are provided in this order on a power transmission path from an engine to wheels, comprising: a start control unit which, when the motor is being driven and the clutch is in a released state and there is a request to start the engine, cranks the engine using the motor by transitioning the clutch to an engaged state while controlling a throttle opening of the engine to a start opening; a torque control unit which, after the engine has been started and the clutch is in an engaged state , controls the torque of the motor and the engine so that a share of the load of the transmission that the motor shares is increased while a share of the load of the transmission that the engine shares is decreased; and, when the share of the load of the engine is equal to or less than a threshold value, controls the throttle opening of the engine to the start opening, and when the share of the load of the engine exceeds the threshold value, controls the throttle opening to the start opening. and a throttle control unit that controls an engine speed to an idle maintenance opening that maintains a target idle speed , wherein the idle maintenance opening is greater than the start-up opening, and the start-up opening is an opening that is set taking into consideration the load of the engine when the engine's throttle opening is 0%, and the threshold value is the engine's torque share corresponding to the amount of torque of the engine that can be increased by adjusting parameters related to the engine torque other than the engine's throttle opening when the engine's throttle opening is maintained at the start-up opening, and is set to a value greater than 0% and less than 50%, and when the engine's throttle opening is equal to or less than the threshold value, the torque control unit controls the engine torque so as to increase the engine's torque share by adjusting the parameters while the engine's throttle opening is maintained at the start-up opening .

The present invention provides a control device for a hybrid vehicle that suppresses the occurrence of shocks.

FIG. 1 is a schematic diagram of a hybrid vehicle. FIG. 2 is a schematic diagram of the engine. FIG. 3 is a timing chart showing an example of switching control from the motor mode to the hybrid mode. FIG. 4 is a flowchart showing an example of a switching control from the motor mode to the hybrid mode executed by the ECU.

[General configuration of hybrid vehicle]
FIG. 1 is a schematic diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, and a transmission 18 are provided in this order in a power transmission path from an engine 10 to wheels 13. The engine 10 and the motor 15 are mounted as a driving source for running the hybrid vehicle 1. The engine 10 is, for example, a V-type 6-cylinder gasoline engine, but the number of cylinders is not limited thereto, and may be an in-line gasoline engine or a diesel engine. The K0 clutch 14, the motor 15, and the transmission 18 are provided in a gear change unit 11. The gear change unit 11 and the left and right wheels 13 are drive-coupled via a differential 12. The transmission 18 includes a torque converter 19 and a gearbox 20.

The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 receives hydraulic pressure from a released state, changes to a slip state, and then to an engaged state, connecting the power transmission between the engine 10 and the motor 15. When the hydraulic pressure supply is stopped, the K0 clutch 14 changes to a released state, cutting off the power transmission between the engine 10 and the motor 15. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor 15 have the same rotation speed. The slip state is a state in which both engagement elements of the K0 clutch 14 are slipping with a predetermined rotation speed difference. The released state is a state in which both engagement elements of the K0 clutch 14 are separated.

The motor 15 is connected to the battery 16 via the inverter 17. The motor 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16, and also functions as a generator that generates power to charge the battery 16 in response to power transmission from the engine 10 and the wheels 13. The power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

The inverter 17 is controlled by the ECU 100 described below, and converts the DC voltage from the battery 16 to an AC voltage, or converts the AC voltage from the motor 15 to a DC voltage. In the case of power running in which the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 to an AC voltage and adjusts the power supplied to the motor 15. In the case of regenerative running in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 to a DC voltage and adjusts the power supplied to the battery 16.

The torque converter 19 is a fluid coupling with a torque amplification function. The transmission 20 is a stepped automatic transmission that switches the gear ratio in multiple stages by switching the gear stage, but is not limited to this and may be a continuously variable automatic transmission. The transmission 20 is provided between the motor 15 and the wheels 13 on the power transmission path. The motor 15 and the transmission 20 are connected via the torque converter 19. The torque converter 19 is provided with a lock-up clutch 19a that receives a supply of hydraulic pressure and enters an engaged state to directly connect the motor 15 and the transmission 20. Note that the torque converter 19 is not necessarily required and may not be provided.

The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 19, the transmission 20, and the lock-up clutch 19a via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for the K0 clutch 14, the torque converter 19, the transmission 20, and the lock-up clutch 19a, as well as various hydraulic control valves for controlling the operating hydraulic pressures thereof.

The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 as a control device for the vehicle. The ECU 100 is an electronic control unit that includes a calculation processing circuit that performs various calculation processes related to the vehicle's driving control, and a memory that stores control programs and data. The ECU 100 is an example of a control device for a hybrid vehicle, and functionally realizes a starting control unit, a torque control unit, and a throttle control unit, which will be described in detail later.

The ECU 100 controls the operation of the engine 10 and the motor 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the torque and rotation speed of the motor 15 by controlling the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16. The ECU 100 also controls the operation of the K0 clutch 14, the lock-up clutch 19a, and the transmission 20 through the control of the hydraulic control mechanism 22.

Signals are input to the ECU 100 from an ignition switch 71, a crank angle sensor 72, a motor revolution speed sensor 73, an accelerator opening sensor 74, and an airflow meter 75. The crank angle sensor 72 detects the rotation speed of the crankshaft of the engine 10, i.e., the engine revolution speed. The motor revolution speed sensor 73 detects the rotation speed of the output shaft of the motor 15, i.e., the motor revolution speed. The accelerator opening sensor 74 detects the accelerator pedal opening, which is the amount of depression of the accelerator pedal by the driver. The airflow meter 75 detects the amount of intake air to the engine 10.

The ECU 100 runs the hybrid vehicle in either the motor mode or the hybrid mode. In the motor mode, the ECU 100 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. The hybrid mode includes a mode in which the vehicle runs using only the power of the engine 10, and a mode in which the motor 15 is powered and the vehicle runs using both the engine 10 and the motor 15 as power sources.

The driving mode is switched based on the vehicle's required driving force calculated from the vehicle speed and accelerator opening, and the state of charge of the battery 16. For example, when the required driving force is relatively small and the SOC (State of Charge), which indicates the charge level of the battery 16, is relatively high, the motor mode in which the engine 10 is stopped is selected to improve fuel efficiency. When the required driving force is relatively large or the SOC of the battery 16 is relatively low, the hybrid mode in which the engine 10 is driven is selected.

[General configuration of engine]
Fig. 2 is a schematic diagram of the engine 10. The engine 10 has cylinders 30, pistons 31, connecting rods 32, a crankshaft 33, an intake passage 35, an intake valve 36, an exhaust passage 37, and an exhaust valve 38. Only one of the multiple cylinders 30 of the engine 10 is shown in Fig. 2. An air-fuel mixture is burned in the cylinder 30. A piston 31 is accommodated in each cylinder 30 so as to be capable of reciprocating, and is connected to a crankshaft 33, which is an output shaft of the engine 10, via a connecting rod 32. The connecting rod 32 converts the reciprocating motion of the piston 31 into the rotational motion of the crankshaft 33.

The intake passage 35 is connected to the intake port 35p of each cylinder 30 via an intake valve 36. The exhaust passage 37 is connected to the exhaust port 37p of each cylinder 30 via an exhaust valve 38. The intake passage 35 is provided with the air flow meter 75 described above and a throttle valve 40 that adjusts the amount of intake air. The exhaust passage 37 is provided with a catalyst 43 for purifying exhaust gas.

Each cylinder 30 is provided with an in-cylinder injection valve 41. The in-cylinder injection valve 41 injects fuel directly into the cylinder 30. Note that instead of or in addition to the in-cylinder injection valve 41, a port injection valve that injects fuel toward the intake port 35p may be provided. Each cylinder 30 is provided with an ignition device 42 that ignites a mixture of intake air introduced through the intake passage 35 and fuel injected by the in-cylinder injection valve 41 by spark discharge.

[Switching control from motor mode to hybrid mode]
There may be a case where the driving mode is required to be switched from the motor mode to the hybrid mode. In this case, the engine 10 is required to be started with the motor 15 being driven. The ECU 100 transitions the K0 clutch 14 from a released state to an engaged state, thereby cranking the engine 10 with the motor 15 to start the engine 10. In this way, the engine 10 can be started while the vehicle is traveling with the motor 15, and the driving mode can be switched from the motor mode to the hybrid mode.

[Transmission load sharing rate after engine start]
After the engine 10 is started in this manner, the T/M load share is handed over. The T/M load is the load on the transmission 18 that acts as a resistance to the rotation of the engine 10 and the motor 15. When the driving mode is the motor mode, the K0 clutch 14 is disengaged and the engine 10 is also stopped. Therefore, the T/M load share by the motor 15 (hereinafter referred to as the motor share) is 100%, and the T/M load share by the engine 10 (hereinafter referred to as the engine share) is 0%. In the hybrid mode after the engine is started, a share handover control is performed to hand over the motor share to the engine share.

In the share rate transfer control, the engine share rate and the motor share rate are calculated so that the sum of the engine share rate and the motor share rate is always kept at 100%, while the motor share rate is gradually decreased to 0% and gradually increased to 100%. The ECU 100 controls the torque of the engine 10 and the motor 15 according to the engine share rate and the motor share rate. The ECU 100 controls the engine torque by controlling the ignition timing and throttle opening of the engine 10. The ECU 100 also controls the motor torque by controlling the inverter 17 to control the amount of electricity supplied to the motor 15 from the battery 16. In the hybrid mode, the engine 10, which has a higher output torque than the motor 15, ultimately bears all of the T/M load, improving fuel efficiency.

[Switching control from motor mode to hybrid mode]
Next, the switching control from the motor mode to the hybrid mode will be described. Fig. 3 is a timing chart showing an example of the switching control from the motor mode to the hybrid mode. Fig. 3 shows the presence or absence of an engine start request, the state of the K0 clutch 14, the T/M load sharing rate (motor sharing rate, engine sharing rate) [%], the motor torque [N·m], the engine torque [N·m], the throttle opening [deg], the motor rotation speed [rpm], and the engine rotation speed [rpm]. The motor sharing rate and the motor rotation speed are shown by dotted lines, and the others are shown by solid lines.

When the engine speed is 0 at time t1, the K0 clutch 14 is in the released state, and there is a request to start the engine 10, the throttle opening is controlled to the starting opening α, the K0 clutch 14 is controlled to a slip state, and cranking by the motor 15 is started. The starting opening α is the throttle opening set at engine start, and is a fixed value. Here, since the K0 clutch 14 is in the released state, the engine share is 0%. The starting opening α is an opening set in consideration of the load on the engine 10 when the engine share is 0%, and is an opening that limits the amount of intake air so that the engine speed does not increase more than necessary. The starting opening α is determined by experiment and analysis so that the startability of the engine 10 can be ensured when the K0 clutch 14 is in the released state.

After cranking starts, the motor torque increases by the amount consumed for cranking, and the engine torque and engine speed also increase. At time t2, combustion starts in the engine 10, self-sustaining operation begins, the engine torque becomes constant, and the amount of motor torque consumed for cranking decreases. At time t3, when the engine speed has increased further, the engine speed matches the motor speed and the K0 clutch 14 is engaged.

When the share rate transfer control is started at time t4, the amount of electricity supplied to the motor 15 decreases, the motor torque gradually decreases, and the ignition timing of the engine 10 is corrected to the advanced side, so that the engine torque gradually increases. As a result, the motor share rate gradually decreases and the engine share rate gradually increases.

When the engine share exceeds the threshold value β at time t5, the throttle opening is switched from the starting opening α to an idle maintenance opening for maintaining the engine speed at the target idle speed. The idle maintenance opening is a throttle opening that is feedback controlled according to the deviation between the two engine speeds so as to maintain the engine speed at the target idle speed. Specifically, when the engine speed falls below the target idle speed, the throttle opening is controlled to increase according to the deviation, which is the amount of decrease in the engine speed. When the engine speed rises above the target idle speed, the throttle opening is controlled to decrease according to the deviation, which is the amount of increase in the engine speed.

After time t5, the motor torque continues to decrease, and the engine speed temporarily drops below the target idle speed, but the throttle opening immediately increases due to the feedback control described above. As a result, the engine speed maintains the target idle speed, while the motor torque decreases, the throttle opening increases, and the engine torque increases. When the motor share rate reaches 0% and the engine share rate reaches 100% at time t6, the share rate handover control ends and the throttle opening becomes an approximately constant value.

For example, it is possible to switch the throttle opening from the starting opening α to the idle maintenance opening between time t3 and time t4 when the engine power ratio after the engine 10 starts and the K0 clutch is engaged is 0%. When the throttle opening is switched from the starting opening α to the idle maintenance opening when the engine power ratio is 0%, the engine torque may increase. Vibrations caused by this increase in engine torque may be transmitted from the engine 10 to the wheels 13, causing a shock to the hybrid vehicle 1.

In this embodiment, as described above, when the engine share exceeds the threshold value β, the throttle opening is switched from the starting opening α to the idle maintenance opening. Therefore, the increase in engine torque due to the switching of the throttle opening is used for the engine share of the T/M load, so shock to the hybrid vehicle 1 can be suppressed.

As described above, when the engine share is equal to or less than the threshold value β, the throttle opening is maintained at the starting opening α, and the ignition timing is corrected to the advanced side to increase the engine torque. Therefore, the threshold value β may be a share corresponding to the amount of engine torque that can be increased by adjusting the parameters related to the engine torque other than the throttle opening when the throttle opening is maintained at the starting opening α. Adjustment of the parameters related to the engine torque other than the throttle opening includes the above-mentioned correction of the ignition timing to the advanced side and the increase correction of the fuel injection amount. For example, the threshold value β is preferably set to a value greater than 0% and less than 50%. When the engine share becomes higher than the threshold value β, it is preferable to control the throttle opening to the idle maintenance opening and also control the ignition timing and fuel injection amount to be suitable for idle operation.

Figure 4 is a flow chart showing an example of switching control from motor mode to hybrid mode executed by ECU 100. This control is executed repeatedly at a predetermined cycle with the ignition on. When the driving mode is motor mode, in other words, when the motor 15 is driving and the K0 clutch 14 is in a disengaged state, ECU 100 determines whether or not there is a request to start the engine, i.e., whether or not there is a request to switch to hybrid mode (step S1). If the answer is No in step S1, this control ends.

If the answer is Yes in step S1, the ECU 100 executes engine start control (step S2). Specifically, while controlling the throttle opening to the starting opening α, the K0 clutch 14 transitions from a released state to an engaged state, and the motor 15 cranks and starts the engine 10. Step S2 is an example of the control executed by the start control unit.

Next, the ECU 100 starts the above-mentioned share rate transfer control (step S3). Therefore, the ECU 100 calculates the engine share rate and the motor share rate, and controls the engine torque and the motor torque according to the share rates. Step S3 is an example of a process executed by the torque control unit.

Next, the ECU 100 determines whether the engine share rate is equal to or less than the threshold value β (step S4). If the answer is Yes in step S4, the ECU 100 maintains the throttle opening at the starting throttle opening α (step S5) and executes the process of step S4 again. If the answer is No in step S4, the ECU 100 controls the throttle opening to the idle maintenance throttle opening (step S6). Steps S4 to S6 are an example of control executed by the throttle control unit. As described above, by switching the throttle opening from the starting throttle opening α to the idle maintenance throttle opening when the engine share rate exceeds the threshold value β, it is possible to prevent shock from occurring in the hybrid vehicle 1.

In the above embodiment, the starting opening degree α is a fixed value, but it is not limited to this and may be a variable value that changes depending on a parameter other than the engine speed, for example, the coolant temperature of the engine 10.

In the above embodiment, a hybrid vehicle is controlled by a single ECU 100, but this is not limited to the above. For example, the above-mentioned control may be performed by multiple ECUs, such as an engine ECU that controls the engine 10, a motor ECU that controls the motor 15, and a clutch ECU that controls the K0 clutch 14.

Although the embodiments of the present invention have been described in detail above, the present invention is not limited to these specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as described in the claims.

10 Engine 14 K0 clutch 15 Motor 18 Transmission 40 Throttle valve 100 ECU (start control unit, torque control unit, throttle control unit)

Claims (1)

A control device for a hybrid vehicle in which a clutch, a motor, and a transmission are provided in this order on a power transmission path from an engine to wheels,
a start control unit that, when the motor is being driven and the clutch is in a released state and there is a request to start the engine, cranks the engine using the motor by transitioning the clutch to an engaged state while controlling a throttle opening of the engine to a starting opening, thereby starting the engine;
a torque control unit that controls torques of the motor and the engine so that a load ratio of the motor to the load of the transmission is increased while a load ratio of the engine to the load is decreased after the engine is started and the clutch is engaged;
a throttle control unit that controls a throttle opening of the engine to the starting throttle opening when the engine's share rate is equal to or less than a threshold value, and controls the throttle opening to an idle maintenance throttle opening at which the engine speed maintains a target idle speed when the engine's share rate exceeds the threshold value ,
The idle maintenance opening is greater than the starting opening,
The starting opening degree is an opening degree set in consideration of the load of the engine when the engine load ratio is 0%,
the threshold value is a torque share of the engine that can be increased by adjusting a parameter related to the torque of the engine other than the throttle opening of the engine while the throttle opening of the engine is maintained at the starting opening, and is set to a value greater than 0% and less than 50%;
A control device for a hybrid vehicle, wherein when the engine's share ratio is equal to or lower than the threshold value, the torque control unit controls the torque of the engine so as to increase the engine's share ratio by adjusting the parameters while maintaining the throttle opening of the engine at the starting opening .

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