JP7690899B2 - Hybrid vehicle control device - Google Patents

Description

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

Some hybrid vehicles are equipped with an internal combustion engine, a motor installed in the power transmission path between the engine and the wheels, and a clutch installed in the power transmission path between the engine and the motor. When a request is made to start the engine, the clutch is slipped and the motor cranks the engine, engaging the clutch and starting the engine (for example, see Patent Document 1).

JP 2013-208970 A

The clutch may be temporarily released to reduce shock when the engine is started. If proper combustion is not occurring in the engine, the engine speed may drop after the clutch is released, causing the engine to stall. Therefore, the objective of this invention is to provide a control device for a hybrid vehicle that is capable of determining whether the internal combustion engine has stalled.

The above object can be achieved by a control device for a hybrid vehicle having an internal combustion engine, a motor, and a clutch provided between the internal combustion engine and the motor, the control device comprising: a cranking control unit that controls cranking of the internal combustion engine by the motor; a clutch control unit that controls an engagement pressure of the clutch; and a judgment unit that, after the cranking is performed and after the engagement pressure of the clutch is reduced, judges whether the internal combustion engine has stalled based on the rotation speed of the internal combustion engine, wherein the judgment unit obtains a first difference that is a difference obtained by subtracting the rotation speed of the internal combustion engine after the engagement pressure has been reduced from the peak rotation speed during the cranking , and a second difference that is a difference obtained by subtracting the rotation speed of the internal combustion engine after the engagement pressure has been reduced from the rotation speed of the motor, and if the first difference is less than a first threshold value or the second difference is less than a second threshold value, the judgment unit judges that combustion in the internal combustion engine is normal, and if the first difference is equal to or greater than the first threshold value and the second difference is equal to or greater than the second threshold value, the judgment unit judges that the internal combustion engine has stalled.

It is possible to provide a control device for a hybrid vehicle that can determine whether or not the internal combustion engine has stalled.

FIG. 1 is a schematic diagram illustrating a hybrid vehicle. FIG. 2 is a flowchart illustrating the process executed by the ECU. FIG. 3 is a time chart illustrating the rotation speed and the oil pressure.

(Hybrid vehicle)
FIG. 1 is a schematic diagram illustrating a hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 (internal combustion engine) and a motor 15 as drive sources. In the hybrid vehicle 1, a K0 clutch 14, a motor 15, a torque converter 18, and an automatic transmission 19 are provided in this order in a power transmission path from the engine 10 to wheels 13. The engine 10 is, for example, a V-type six-cylinder engine having six cylinders #1 to #6. The engine 10 may be, for example, a V-type engine or an in-line engine. The engine 10 may be a gasoline engine or a diesel engine. The number of cylinders in the engine 10 may be multiple, such as four or six, or may be one. The K0 clutch 14, the motor 15, the torque converter 18, and the automatic transmission 19 are provided in a transmission unit 11. The transmission unit 11 and the left and right wheels 13 are drive-coupled via a differential gear 12.

The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 is switched between a released state, a slip state, and an engaged state depending on the supply of hydraulic pressure. In detail, when the K0 clutch 14 is in a released state, the hydraulic pressure supply causes the clutch 14 to enter a slip state or an engaged state, and the power transmission between the engine 10 and the motor 15 is connected. In addition, the K0 clutch 14 enters a released state in response to the stop of the hydraulic pressure supply, and the power transmission between the engine 10 and the motor 15 is interrupted. The slip state is a state in which the engagement element of the K0 clutch 14 on the engine 10 side and the engagement element on the motor 15 side are in sliding contact with each other with a predetermined difference in rotation speed. 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 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 50 described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor 15 into a DC voltage. In the case of powering operation in which the motor 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor 15. In the case of regenerative operation in which the motor 15 generates power, the inverter 17 converts the AC voltage from the motor 15 into a DC voltage and adjusts the power supplied to the battery 16.

The torque converter 18 is a fluid coupling with a torque amplification function. The automatic transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by changing the gear stage. The automatic transmission 19 is provided between the motor 15 and the wheels 13 on the power transmission path. The motor 15 and the automatic transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that receives a supply of hydraulic pressure, enters an engaged state, and directly connects the motor 15 and the automatic transmission 19.

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 18, the automatic transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lock-up clutch 20, 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) 50 as a control device. The ECU 50 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 50 is an example of a control device for a hybrid vehicle, and functions as a cranking control unit, a clutch control unit, and a determination unit.

The ECU 50 controls the operation of the engine 10 and the motor 15. For example, the ECU 50 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 50 also controls the operation of the K0 clutch 14, the lock-up clutch 20, and the automatic transmission 19 through control of the hydraulic control mechanism 22. The ECU 50 controls the hydraulic pressure applied to the K0 clutch 14 using the hydraulic control mechanism 22, and changes the state of the K0 clutch 14 to control the cranking torque transmitted from the motor 15 to the engine 10.

The ECU 50 controls the inverter 17 to adjust the amount of power exchanged between the motor 15 and the battery 16, thereby controlling the rotation speed and torque of the motor 15. As will be described in more detail later, the ECU 50 also controls the power supplied by the inverter 17 from the motor 15 to the battery 16 so that the motor braking torque during regenerative operation reaches a target value.

Signals are input to the ECU 50 from an ignition switch 71, a crank angle sensor 72, a motor revolution speed sensor 73, an airflow meter 74, and an accelerator opening sensor 75. The crank angle sensor 72 detects the rotation speed of the crankshaft of the engine 10. The motor revolution speed sensor 73 detects the rotation speed of the output shaft of the motor 15. The airflow meter 74 detects the amount of intake air of the engine 10. The accelerator opening sensor 75 detects the accelerator pedal opening, which is the amount of depression of the accelerator pedal by the driver.

The ECU 50 runs the hybrid vehicle in either the motor mode or the hybrid mode. In the motor mode, the ECU 50 releases the K0 clutch 14 and runs the vehicle using the power of the motor 15. In the hybrid mode, the ECU 50 engages the K0 clutch 14 and runs the vehicle using at least the power of the engine 10. Note that 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) indicating the remaining charge 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 at least the engine 10 is operating is selected.

In the hybrid mode, the ECU 50 executes intermittent operation control to automatically stop the engine 10 when a predetermined stop condition is met, and to restart the automatically stopped engine 10 when a predetermined restart condition is met. For example, in the hybrid mode, when the accelerator opening becomes zero, the ECU 50 determines that the automatic stop condition is met and automatically stops the engine 10. In addition, when the accelerator opening becomes greater than zero, the ECU 50 determines that the restart condition is met and automatically restarts the engine 10. When automatically stopping the engine 10, the ECU 50 releases the K0 clutch 14 to stop fuel injection. When automatically restarting the engine 10, the ECU 50 cranks the engine 10 by the motor 15 via the K0 clutch 14 to start fuel injection and ignition.

After the engine starts, the K0 clutch 14 is engaged and the engine 10 speed becomes equal to the motor 15 speed (synchronous). The engine 10 speed increases during startup, which may cause a shock. To suppress the shock, the oil pressure of the K0 clutch 14 is reduced after cranking, for example, the K0 clutch 14 is temporarily released. However, if combustion is not occurring properly in the engine 10, the engine 10 speed will decrease after the K0 clutch 14 is released. There is also a risk that the engine 10 will stall and fail to start.

Figure 2 is a flowchart illustrating the process executed by the ECU 50. The ECU 50 performs cranking using the motor 15 (step S10). After cranking is performed, the ECU 50 determines whether the K0 clutch 14 is temporarily released (step S12). If the determination is negative (No), the process ends.

If the determination is positive (Yes), the ECU 50 determines whether the difference Nep-Ne between the peak engine speed Nep and the engine speed Ne of the engine 10 is less than a predetermined amount ΔNeth1 (step S14). If the determination is negative , the ECU 50 determines whether the difference Nem-Ne between the engine speed Ne of the engine 10 and the motor speed Nem of the motor 15 is less than a predetermined amount ΔNeth2 (step S16). If the determination is negative in step S16, the ECU 50 determines that combustion is not occurring properly in the engine 10 and that the engine has stalled (step S18). If the determination is positive in either step S14 or S16, the ECU 50 determines that combustion is occurring normally in the engine 10 (step S20).

Figure 3 is a time chart illustrating the rotation speed and oil pressure. The horizontal axis represents time. The upper part represents the rotation speed of the engine 10 (engine rotation speed) and the rotation speed of the motor 15 (motor rotation speed). The lower part represents the oil pressure of the K0 clutch 14.

At time t1, the oil pressure of the K0 clutch 14 is increased, and the K0 clutch 14 is engaged. Cranking is performed by the motor 15, and the rotation speed of the engine 10 begins to increase. The rotation speed Ne of the engine 10 reaches a peak value Nep. At time t2, the oil pressure of the K0 clutch 14 is decreased, and the K0 clutch 14 is temporarily released (step S12 in FIG. 2). The rotation speed Ne of the engine 10 decreases from Nep.

The dotted line in Figure 3 is an example where the engine 10 stalls. The engine speed Ne continues to decrease and moves away from the motor speed Nem. The difference Nep-Ne between the peak value Nep and the engine speed Ne, and the difference Nem-Ne between the motor speed Nem and the engine speed Ne, become large. When Nep-Ne is equal to or greater than Neth1 and Nem-Ne is equal to or greater than Neth2, the ECU 50 determines that the engine 10 has stalled (step S18 in Figure 2).

The solid line in Figure 3 is an example of normal combustion in the engine 10. The engine speed Ne temporarily drops in response to the release of the K0 clutch 14. As combustion occurs in the engine 10, the engine speed Ne rises again and synchronizes with the motor speed Nem. The difference Nep-Ne between the peak value Nep and the engine speed Ne, and the difference Nem-Ne between the motor speed Nem and the engine speed Ne, become smaller. When Nep-Ne is less than Neth1 or Nem-Ne is less than Neth2, the ECU 50 determines that combustion in the engine 10 is normal (step S20 in Figure 2).

According to this embodiment, after cranking of the engine 10, the engagement pressure of the K0 clutch 14 decreases, and for example, the K0 clutch 14 is released. The ECU 50 determines whether the engine 10 has stalled based on the engine speed Ne.

If the difference Nep-Ne between the engine speed Ne and the peak speed Nep after cranking and release of the K0 clutch 14 is equal to or greater than ΔNeth1, and the difference Nem-Ne between the engine speed Ne and the motor speed Nem is equal to or greater than ΔNeth2, the ECU 50 determines that the engine has stalled (step S18 in FIG. 2). It can be detected that combustion is not occurring properly, the engine speed Ne has decreased due to the release of the K0 clutch 14, and the engine 10 has stalled.

If Nep-Ne is less than ΔNeth1 or Nem-Ne is less than ΔNeth2, the ECU 50 determines that combustion is occurring normally in the engine 10 (step S20). The engine speed Ne is synchronized with the motor speed Nem. The K0 clutch 14 is temporarily released after cranking, so shocks caused by starting the engine can be suppressed.

In the above example, the hybrid vehicle 1 is controlled by a single ECU 50. The embodiment is not limited to this, and the above 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 preferred embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment, and various modifications and variations are possible within the scope of the gist of the present invention described in the claims.

REFERENCE SIGNS LIST 1 Hybrid vehicle 10 Engine 11 Transmission unit 12 Differential gear 13 Wheels 14 K0 clutch 15 Motor 16 Battery 17 Inverter 18 Torque converter 19 Automatic transmission 20 Lock-up clutch 21 Oil pump 22 Hydraulic control mechanism 50 ECU
71 Ignition switch 72 Crank angle sensor 73 Motor revolution sensor 74 Air flow meter 75 Accelerator opening sensor

Claims (1)

A control device for a hybrid vehicle having an internal combustion engine, a motor, and a clutch provided between the internal combustion engine and the motor,
a cranking control unit that controls cranking of the internal combustion engine by the motor;
A clutch control unit that controls an engagement pressure of the clutch;
and a determination unit that determines whether or not the internal combustion engine has stalled based on a rotation speed of the internal combustion engine after the cranking is performed and the engagement pressure of the clutch is reduced,
The determination unit obtains a first difference which is a difference obtained by subtracting a rotation speed of the internal combustion engine after the engagement pressure has been reduced from a peak rotation speed during the cranking, and a second difference which is a difference obtained by subtracting a rotation speed of the internal combustion engine after the engagement pressure has been reduced from a rotation speed of the motor ,
When the first difference is less than a first threshold value or the second difference is less than a second threshold value, the determination unit determines that combustion in the internal combustion engine is normal;
A control device for a hybrid vehicle, wherein the determination unit determines that the internal combustion engine has stalled when the first difference is equal to or greater than a first threshold value and the second difference is equal to or greater than a second threshold value.

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