JP7632259B2 - Hybrid vehicle control device - Google Patents

Description

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

Hybrid vehicles are known that include an engine, a motor installed in the power transmission path between the engine and the wheels, a clutch installed in the power transmission path between the engine and the motor, a battery, and an inverter that transfers power between the motor and the battery. In addition, a technology is known for shutting down the inverter in the event of a vehicle collision to ensure safety in such vehicles (see, for example, Patent Document 1).

JP 2014-100959 A

To improve engine fuel efficiency, it is possible to shut down the inverter even when the vehicle is not in a collision. When the inverter is shut down, the motor cannot be operated in powered mode, reducing power consumption from the battery, and the frequency of subsequent regenerative operation of the motor by the engine is also reduced, reducing the load on the engine. In addition, when the inverter is shut down, the motor cannot be operated in regenerative mode, which also reduces the load on the engine. However, if the motor cannot be operated in powered mode, there may be a shortage of driving force. Furthermore, if the motor cannot be operated in regenerative mode, this may affect the charge and discharge balance of the battery.

The present invention aims to provide a control device for a hybrid vehicle that ensures driving force and reduces the impact on the battery charge/discharge balance while improving engine fuel efficiency.

The above object can be achieved by a control device for a hybrid vehicle having an engine, a motor provided in a power transmission path between the engine and the wheels, a clutch provided in a portion of the power transmission path between the engine and the motor, a battery, and an inverter that transfers power between the motor and the battery, the control device for a hybrid vehicle having a condition determination unit that determines whether or not all of the following are satisfied: the clutch is engaged, the engine is running, a torque request value for the motor is equal to or less than a predetermined value, the rotation speed of the motor is equal to or less than a predetermined value, and a charge/discharge request for the battery is equal to or less than a predetermined value, and an inverter control unit that shuts down the inverter when the condition determination unit makes a positive determination.

The present invention provides a control device for a hybrid vehicle that ensures driving force and reduces the impact on the battery charge/discharge balance while improving engine fuel efficiency.

FIG. 1 is a schematic diagram of a hybrid vehicle. FIG. 2 is a flowchart showing an example of inverter shutdown control executed by the ECU.

[General configuration of hybrid vehicle]
1 is a schematic diagram of a hybrid vehicle 1. 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 an engine 10 to wheels 13. The engine 10 and the motor 15 are mounted on the hybrid vehicle 1 as a driving source for traveling. 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 engine or a diesel engine. 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 drivingly connected via a differential 12 and a drive shaft 12a.

The K0 clutch 14 is provided between the engine 10 and the motor 15 on the power transmission path. The K0 clutch 14 is engaged when hydraulic pressure is applied, connecting the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is released when the hydraulic pressure supply is stopped, cutting off the power transmission between the engine 10 and the motor 15.

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 40 described later, and converts the DC voltage from the battery 16 to AC voltage, or converts the AC voltage from the motor 15 to 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 to AC voltage and adjusts the amount of discharge from the battery 16 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 to DC voltage and adjusts the amount of charge from the motor 15 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) 40 as a control device for the vehicle. The ECU 40 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 40 is an example of a control device for a hybrid vehicle, and functionally realizes a condition determination unit and an inverter control unit, which will be described in detail later.

The ECU 40 receives signals from an ignition switch 31, a crank angle sensor 32, a motor rotation speed sensor 33, and an SOC sensor 34. The crank angle sensor 32 detects the rotation speed of the crankshaft of the engine 10, i.e., the engine rotation speed. The motor rotation speed sensor 33 detects the rotation speed of the output shaft of the motor 15, i.e., the motor rotation speed. The SOC sensor 34 detects the SOC (State Of Charge), which indicates the charge level of the battery 16.

The ECU 40 controls the operation of the engine 10 and the motor 15. For example, the ECU 40 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 40 also controls the operation of the K0 clutch 14, the lock-up clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22.

The ECU 40 runs the hybrid vehicle in either the motor mode or the hybrid mode. In the motor mode, the K0 clutch 14 is released and the vehicle runs on the power of the motor 15. In the hybrid mode, the K0 clutch 14 is engaged and the vehicle runs on at least the power of the engine 10. The hybrid mode includes a case where the vehicle runs on the power of the engine 10 only, a case where the motor 15 is operated in regenerative mode and the vehicle runs on the power of the engine 10, and a case where the motor 15 is operated in power running and the vehicle runs on the power of both the engine 10 and the motor 15.

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 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.

The ECU 40 also executes vibration suppression control to suppress vibrations caused by twisting of the drive shaft 12a while the K0 clutch 14 is engaged and the engine 10 is running. The vibration suppression control suppresses vibrations by generating a vibration suppression torque from the motor 15 that is in the opposite phase to the torque phase of the engine 10. Such vibrations caused by twisting of the drive shaft 12a are likely to occur when there is a sudden change in driving force or when driving at the resonant frequency of the drive system. Therefore, the ECU 40 determines whether the above vibrations will occur based on the rate of change of the accelerator opening and the engine speed, and executes vibration suppression control if it determines that vibrations may occur.

[Inverter shutdown control]
The ECU 40 controls the inverter 17 according to the charge/discharge requirement of the battery 16 to adjust the amount of power exchanged between the motor 15 and the battery 16. Here, when a condition described later is satisfied, the ECU 40 shuts down the inverter 17 by turning off all of the transistors provided in the inverter 17. This puts the motor 15 in a state in which power running or regenerative operation is not possible. By putting the motor 15 in a state in which power running is not possible, the power consumption of the battery 16 is reduced, and the frequency of regenerative operation thereafter is reduced. Furthermore, by putting the motor 15 in a state in which regenerative operation is not possible, the load on the engine 10 is reduced. In this way, the fuel efficiency of the engine 10 is improved.

Figure 2 is a flowchart showing an example of inverter shutdown control executed by the ECU 40. This control is repeatedly executed at a predetermined period with the ignition on. The ECU 40 determines whether or not an execution condition for shutting down the inverter 17 is met (step S1). Step S1 is an example of processing executed by the condition determination unit.

The execution conditions include the following conditions (A) to (F).
(A) The K0 clutch 14 is engaged. (B) The engine 10 is running. (C) The torque requirement value of the motor 15 is equal to or less than a predetermined value. (D) The rotation speed of the motor 15 is equal to or less than a predetermined value. (E) The charge/discharge requirement amount of the battery 16 is equal to or less than a predetermined amount. (F) Vibration damping control is stopped.

The reason why condition (A) is included in the execution conditions is that if the inverter 17 is shut down while the K0 clutch 14 is in the released state, the driving force for traveling cannot be secured. For example, the ECU 40 determines that condition (A) is satisfied when the engine speed and the motor speed match, and determines that condition (A) is not satisfied when the engine speed and the motor speed do not match. The engine speed and the motor speed are detected by the crank angle sensor 32 and the motor speed sensor 33, respectively.

The reason why condition (B) is included in the execution conditions is that if the inverter 17 is shut down while the engine 10 is stopped, the driving force for driving cannot be secured. The ECU 40 determines whether or not condition (B) is satisfied based on, for example, whether the engine driving flag is on. Note that conditions (A) and (B) are satisfied when the driving mode is the hybrid mode. Therefore, the ECU 40 may determine that conditions (A) and (B) are satisfied when the driving mode is the hybrid mode.

The reason why condition (C) is included in the execution conditions is that if the inverter 17 is shut down when the torque requirement value of the motor 15 is greater than a predetermined value, there is a risk of a shortage of driving force. Therefore, the predetermined value in condition (C) is set to a required torque that has little effect on the driving force even if the output torque of the motor 15 becomes zero. Therefore, a case where condition (C) is satisfied is, for example, a case where the engine 10 provides most of the driving force.

The reason why condition (D) is included in the execution conditions is that if the inverter 17 is shut down when the rotation speed of the motor 15 is high, the back electromotive force of the motor 15 increases and acts as a resistance to the rotation of the engine 10, which may result in a shortage of driving force. Therefore, the predetermined value in condition (D) is set to a rotation speed at which the effect on the driving force is small even if a back electromotive force is generated in the motor 15. A case where condition (D) is satisfied is, for example, when the required driving force of the hybrid vehicle 1 is small and the vehicle is traveling steadily with a small accelerator opening on a flat road, etc.

The reason why condition (E) is included in the execution conditions is that if the inverter 17 is shut down when the charge/discharge request amount for the battery 16 is large, the battery 16 cannot be charged or discharged, and this has a large impact on the charge/discharge balance. Therefore, the predetermined amount in this condition is set to a charge/discharge amount that has a small impact on the charge/discharge balance. The charge/discharge request amount is calculated by the ECU 40 based on the deviation between the SOC detected by the SOC sensor 34 and the target SOC. Note that the charge/discharge request amount means the charge request amount when there is a charge request, and means the discharge request amount when there is a discharge request. Also, the predetermined amount for the charge request amount and the predetermined amount for the discharge request amount are the same amount, but are not limited to this and may be different amounts.

The reason why condition (F) is included in the execution conditions is that if the inverter 17 is shut down while vibration damping control is being performed, the motor 15 will not be able to output vibration damping torque, and vibrations in the hybrid vehicle 1 will increase. The ECU 40 determines that condition (F) is met when the vibration damping control request flag is off, and determines that condition (F) is not met when the vibration damping control request flag is on.

If all of conditions (A) to (F) are met, step S1 is determined as Yes, and the ECU 40 shuts down the inverter 17 (step S2). This improves fuel efficiency. Step S2 is an example of a process executed by the inverter control unit.

If at least one of the conditions (A) to (F) is not satisfied, the result in step S1 is No, and the ECU 40 continues to drive the inverter 17 (step S3). This ensures sufficient driving force for traveling.

If, after shutting down the inverter 17, the determination in step S1 is that at least one of the conditions (A) to (F) is not satisfied again, the ECU 40 turns on at least one of the transistors provided in the inverter 17 to drive the inverter 17 (step S3).

Condition (F) does not necessarily have to be included in the execution conditions. By excluding condition (F) from the execution conditions, it is possible to prioritize improving fuel efficiency over suppressing vibration.

In the above embodiment, a hybrid vehicle is controlled by a single ECU 40, 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, a clutch ECU that controls the K0 clutch 14, and an inverter ECU that controls the inverter 17.

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 16 Battery 17 Inverter 40 ECU (condition determination unit, inverter control unit)

Claims (1)

A control device for a hybrid vehicle including an engine, a motor provided in a power transmission path between the engine and wheels, a clutch provided in a portion of the power transmission path between the engine and the motor, a battery, and an inverter for transmitting and receiving electric power between the motor and the battery,
a condition determination unit that determines whether or not all of the following are satisfied: the clutch is engaged, the engine is running, a torque request value for the motor is equal to or less than a predetermined value, the rotation speed of the motor is equal to or less than a predetermined value, and a charge/discharge request for the battery is equal to or less than a predetermined value;
an inverter control unit that shuts down the inverter when a positive determination is made by the condition determination unit.

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