Hybrid vehicle driving mode transition controller

Abstract

A driving mode transition controller is provided for a hybrid vehicle equipped with engine, motor-generator, and clutch installed between the engine and the motor-generator, wherein the engine is started by engaging the clutch and using the motor-generator as a starter motor for the engine when making a mode transition from an “EV mode” which utilizes only motor-generator MG as the power source to an “HEV mode” which includes the engine E as part of the power source. The controller uses an acceleration intention determination module to control the controls the maximum torque capacity of the clutch at the time of clutch engagement such that the weaker a driver's intention to accelerate is determined to be, the lower the rate of engine rpm rise becomes when making the mode transition from EV mode to HEV mode.

Description

BRIEF DESCRIPTION OF THE FIGURES

The description herein makes reference to the accompanying drawings wherein like reference numerals refer to like modules throughout the several views, and wherein:

FIG. 1 is a system-level block diagram showing a rear-wheel-drive hybrid vehicle equipped with a hybrid vehicle driving mode transition controller in accordance with a first embodiment.

FIG. 2 is a control block diagram showing an arithmetic processing program in the integration controller of FIG. 1.

FIG. 3 is a graph showing an example of a target driving force map used for target driving force computation in the target driving force computation part of FIG. 2.

FIG. 4 is a graph showing an example of an engine start/stop selection map used for selecting a target mode in the mode selection part of FIG. 2.

FIG. 5 is a graph showing an example of a target charge/discharge amount map used for target charge/discharge power computation in the target charge/discharge computation part of FIG. 2.

FIG. 6 is a flow chart showing the driving mode selection processing executed by the integration controller of FIG. 1.

FIG. 7 is a flow chart showing the control executed while in EV mode by the integration controller of FIG. 1.

FIG. 8 is a flow chart showing the control executed while in HEV mode by the integration controller of FIG. 1.

FIG. 9 is a flow chart showing engine start mode processing executed by the integration controller of FIG. 1 when making a transition from EV mode to HEV mode.

FIG. 10 is a graph showing an example of an engine start/stop selection map which shows an engine start request line when the driver's intention to accelerate is strong and when the driver's intention to accelerate is weak.

FIG. 11 is a time chart showing the characteristics in terms of transmission input rpm, motor-generator rpm, engine rpm, motor-generator torque, and first clutch torque capacity when a transition is made from “EV mode” to “HEV mode” (a) when a determination is made that driver's intention to accelerate is strong and (b) when a determination is made that driver's intention to accelerate is weak.

FIG. 12 is a diagram showing an outline of the drive system of another example of a rear-wheel-drive hybrid vehicle.

FIG. 13 is a chart showing the portion of the maximum usable torque of the motor-generator which can be used to start the engine (a) when a determination is made that driver's intention to accelerate is strong and (b) when a determination is made that driver's intention to accelerate is weak.

Claims

1. An apparatus for controlling the mode transition in a hybrid vehicle having an engine, a motor-generator, and a clutch installed between the engine and the motor-generator to start the engine using the motor-generator, comprising: a controller adapted to determine the driver's intention to accelerate based on at least one driving condition; and to engage the clutch to start the engine so that the rate of change in the rpm of the engine when starting is relatively faster when the driver's intention to accelerate is strong than when the driver's intention to accelerate is weak.

2. The apparatus of claim 1, wherein the controller is further adapted to engage the clutch at a maximum torque capacity; and to set the maximum torque capacity higher when the driver's intention to accelerate is strong than when the driver's intention to accelerate is weak.

3. The apparatus of claim 1, wherein the controller is further adapted to determine a travel-enabling torque, wherein the travel-enabling torque is set to a relatively lower torque value when the driver's intention to accelerate is strong then when the driver's intention to accelerate is weak.

4. The apparatus of claim 3, where in the controller is further adapted to engage the clutch at a maximum torque capacity; and to set the maximum torque capacity as a function of the difference between the maximum torque of the motor-generator and the travel-enabling torque.

5. The apparatus of claim 3, wherein the controller is further adapted to detect the torque required by the vehicle, and to engage the clutch when the torque required by the vehicle exceeds the travel-enabling torque.

6. The apparatus of claim 2, wherein the controller is operatively connected to a second clutch installed between the transmission and one of the motor-generator and the engine, and wherein the controller is adapted to transition the second clutch to a slip-engagement state and to set the maximum torque capacity of the first clutch while the second clutch is in the slip-engagement state.

7. The apparatus of claim 1, where in the controller is further adapted to detect an accelerator pedal opening and an accelerator pedal opening rate of change; and to determine that the driver's intention to accelerate is strong when at least one of: the accelerator pedal opening is equal to or greater than a prescribed accelerator pedal opening threshold value, and the accelerator pedal opening rate of change is equal to or greater than a prescribed accelerator pedal opening rate of change threshold value.

8. The apparatus of claim 1, wherein the controller is further adapted to detect average value of the torque required by the vehicle during a prescribed time period; and to determine that the driver's intention to accelerate is strong when the average value of the torque required by the vehicle is equal to or greater than a prescribed acceleration intention determining threshold value.

9. The apparatus of claim 1, wherein the controller is further adapted to detect the average value of the torque required by the vehicle during a prescribed time period and the value of the torque required by the vehicle; and to determine that the driver's intention to accelerate is strong when the difference between the current torque required by the vehicle and the average value of the torque required by the vehicle is equal to or greater than a prescribed value.

10. A hybrid vehicle, comprising: an engine;a motor-generator;a clutch installed between the engine and the motor-generator to permit the motor-generator to start the engine; anda controller operatively coupled to the clutch and adapted to engage the clutch when a hybrid car mode of vehicle operation is selected; to determine the driver's intention to accelerate based; and to set the maximum torque capacity of the clutch as a function of the driver's intention to accelerate; whereby the weaker the driver's intention to accelerate is, the smaller is the proportion of torque used to start the engine relative to the maximum torque that can be generated by the motor-generator.

11. A hybrid vehicle, comprising: an engine;a motor-generator;a first clutch installed between the engine and the motor-generator to permit the motor-generator to start the engine; anda controller adapted to determine the driver's intention to accelerate based on at least one driving condition; and to engage the first clutch to start the engine when the vehicle transitions from an electric car mode to a hybrid car mode, wherein the controller sets the maximum torque capacity of the first clutch in response to the driver's intention to accelerate so that the rate of change in the rpm of the engine when starting is relatively slower when the driver's intention to accelerate is weak than when the driver's intention to accelerate is strong.

12. The vehicle of claim 11 wherein the controller is further adapted to determine a travel-enabling torque, wherein the travel-enabling torque is set to a relatively lower torque value when the driver's intention to accelerate is strong then when the driver's intention to accelerate is weak; and wherein the controller is further adapted to set the maximum torque capacity of the first clutch as a function of the difference between the maximum torque of the motor-generator and the travel-enabling torque.

13. The vehicle of claim 12 wherein the controller is further adapted to detect the torque required by the vehicle, and to engage the first clutch to start the engine when the torque required by the vehicle exceeds the travel-enabling torque.

14. The vehicle of claim 11, where in the controller is further adapted to detect an accelerator pedal opening and an accelerator pedal opening rate of change; and to determine that the driver's intention to accelerate is weak when at least one of: the accelerator pedal opening is less than a prescribed accelerator pedal opening threshold value, and the accelerator pedal opening rate of change is less than a prescribed accelerator pedal opening rate of change threshold value.

15. The vehicle of claim 11, wherein the controller is further adapted to detect average value of the torque required by the vehicle during a prescribed time period; and to determine that the driver's intention to accelerate is weak when the average value of the torque required by the vehicle is less than a prescribed acceleration intention determining threshold value.

16. The vehicle of claim 11, wherein the controller is further adapted to detect the average value of the torque required by the vehicle during a prescribed time period and the value of the torque required by the vehicle; and to determine that the driver's intention to accelerate is weak when the difference between the current torque required by the vehicle and the average value of the torque required by the vehicle is less than a prescribed value.

17. The vehicle of claim 11, further comprising a transmission and a second clutch installed between the transmission and one of the motor-generator and the engine, wherein the controller is operatively coupled to the second clutch and is adapted to transition the second clutch to a slip-engagement state; and to set the maximum torque capacity of the first clutch while the second clutch is in the slip-engagement state.

18. A method for controlling the mode transition in a hybrid vehicle having an engine, a motor-generator, and a clutch installed between the engine and the motor-generator to start the engine using the motor-generator, comprising: determining the driver's intention to accelerate based on at least one vehicle condition; andtransmitting torque from the motor-generator to the engine via the clutch to start the engine, wherein the amount of torque transmitted from the motor-generator to the engine, relative to the maximum torque of the motor-generator, is set as a function of the driver's intention to accelerate.

19. The method of claim 18, further comprising: setting the maximum torque capacity of the clutch relatively higher when the driver's intention to accelerate is strong than when the driver's intention to accelerate is weak.

20. The method of claim 18, wherein determining the driver's intention to accelerate further comprises: detecting an accelerator pedal opening and an accelerator pedal opening rate of change; anddetermining that the driver's intention to accelerate is strong when at least one of: the accelerator pedal opening is equal to or greater than a prescribed accelerator pedal opening threshold value, and the accelerator pedal opening rate of change is equal to or greater than a prescribed accelerator pedal opening rate of change threshold value.

21. The method of claim 18, wherein determining the driver's intention to accelerate further comprises: detecting the average value of the torque required by the vehicle during a prescribed time period; anddetermining that the driver's intention to accelerate is strong when the average value of the torque required by the vehicle is equal to or greater than a prescribed acceleration intention determining threshold value.

22. The method of claim 18, wherein determining the strength of the driver's intention to accelerate further comprises: detecting the average value of the torque required by the vehicle during a prescribed time period and the value of the current torque required by the vehicle, anddetermining that the driver's intention to accelerate is strong when the difference between the current actual torque required by the vehicle and the average value of the actual torque required by the vehicle is equal to or greater than a prescribed value.

23. The method of claim 18, further comprising: detecting the torque required by the vehicle;setting a travel-enabling torque as a function of the driver's intention to accelerate; wherein the travel-enabling torque is set lower when the driver's intention to accelerate is strong than when the driver's intention to accelerate is weak; andcommencing the transmission of torque from the motor-generator to the engine to start the engine when the actual torque required by the vehicle exceeds the travel-enabling torque.

24. The method of claim 18, further comprising: detecting the actual torque required by the vehicle;setting a travel-enabling torque as a function of the driver's intention to accelerate; andsetting the maximum capacity of the clutch as a function of the difference of the maximum torque of the motor-generator less the target torque.