MODE CHANGE CONTROL SYSTEM FOR HYBRID VEHCILE

• US 20080091314A1
• Filed: 10/10/2007
• Published: 04/17/2008
• Est. Priority Date: 10/12/2006
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Ueno, Munetoshi, Hayashi, Nobuki
• Granted Patent: US 7,826,941 B2
• Time in Patent Office: Days
• US Class Current: 701/22
• CPC Class Codes: B60K 6/48 Parallel type
• CPC Class Codes: B60L 15/20 for control of the vehicle or its driving motor to achieve a desired performance, e.g. speed, torque, programmed variation of speed
• CPC Class Codes: B60L 15/2009 for braking
• CPC Class Codes: B60L 2210/40 DC to AC converters
• CPC Class Codes: B60L 2220/14 Synchronous machines
• CPC Class Codes: B60L 2240/12 Speed
• CPC Class Codes: B60L 2240/423 Torque
• CPC Class Codes: B60L 2240/443 Torque
• CPC Class Codes: B60L 2240/507 Operating parameters
• CPC Class Codes: B60L 2250/26 by pedal actuation
• CPC Class Codes: B60L 2260/26 Transition between different drive modes
• CPC Class Codes: B60L 50/16 with provision for separate direct mechanical propulsion
• CPC Class Codes: B60L 58/15 Preventing overcharging
• CPC Class Codes: B60L 58/16 responding to battery ageing, e.g. to the number of charging cycles or the state of health [SoH]
• CPC Class Codes: B60L 7/14 for vehicles propelled by ac motors
• CPC Class Codes: B60W 10/02 including control of driveline clutches
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/08 including control of electric propulsion units, e.g. motors or generators
• CPC Class Codes: B60W 10/26 for electrical energy, e.g. batteries or capacitors
• CPC Class Codes: B60W 20/00 Control systems specially adapted for hybrid vehicles hybrid vehicle design, B60K6/00; electric vehicles B60L
• CPC Class Codes: B60W 20/13 : in order to stay within battery power input or output limits; in order to prevent overcharging or battery depletion
• CPC Class Codes: B60W 2540/10 : Accelerator pedal position
• CPC Class Codes: Y02T 10/62 : Hybrid vehicles
• CPC Class Codes: Y02T 10/64 : Electric machine technologies in electromobility
• CPC Class Codes: Y02T 10/70 : Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y02T 10/7072 : Electromobility specific charging systems or methods for batteries, ultracapacitors, supercapacitors or double-layer capacitors
• CPC Class Codes: Y02T 10/72 : Electric energy management in electromobility
• CPC Class Codes: Y02T 10/92 : Energy efficient charging or discharging systems for batteries, ultracapacitors, supercapacitors or double-layer capacitors specially adapted for vehicles
• CPC Class Codes: Y10S 903/907 : Electricity storage, e.g. battery, capacitor
• CPC Class Codes: Y10S 903/947 : Characterized by control of braking, e.g. blending of regeneration, friction braking

Abstract

During vehicle drive under an EV mode, a battery charge state SOC becomes smaller than a SOC(L) at time t0. As a result, EV→HEV mode change is carried out. After time t1, deceleration is desired, and an accelerator opening APO is kept at 0. At time t3, the SOC increases and becomes greater than or equal to a SOC(H) by the HEV mode. In this case, after time t1 of release of an accelerator pedal, the SOC(H) is cleared at time t2 at which a vehicle operating condition is judged to be a low load drive condition in which a motor/generator performs regenerative braking. By making a judgment of HEV→EV mode change based on the SOC(L) instead of the SOC(H), the HEV→EV mode change is carried out before time t3. A regenerative braking time Δt with the engine dragged is therefore shortened, and a regenerative braking time with no-engine drag can be correspondingly lengthened, improving an energy recovery performance.

Claims

1. A control system of a hybrid vehicle including an engine, a motor/generator, a battery operable to provide the motor/generator with electric power and to receive and store electric power regenerated by the motor/generator, a first clutch disposed between the engine and the motor/generator, and at least one driving wheel, the control system comprising:

a controller configured to;

select a drive mode wherein the drive mode comprises at least one of an electric drive mode, in which the first clutch is released and power transmission is made only between the motor/generator and the at least one driving wheel, and a hybrid drive mode, in which the first clutch is engaged and power transmission is made between at least the engine and the motor/generator and the at least one driving wheels;

decide to make a mode change from the electric drive mode to the hybrid drive mode when a battery charge state of the battery becomes lower than a first set battery charge state;

decide to make a mode change from the hybrid drive mode to the electric drive mode when the battery charge state becomes higher than or equal to a second set battery charge state, wherein an initial value of the second set battery charge state is higher than the first set battery charge state; and

change the second set battery charge state to a lower value than the initial value when a vehicle driving condition is judged to be a low load drive condition in which a regenerative braking is carried out under the battery charge state where the hybrid drive mode is selected such that the mode change to the electric drive mode from the hybrid drive mode is permitted.

2. The control system according to claim 1 wherein the lower value is a same value as the first set battery charge state;

and wherein the controller is further configured to decide to make the mode change from the hybrid drive mode to the electric drive mode based on the first set battery charge state during the low load drive condition of the vehicle.

3. The control system according to claim 2, wherein the controller is further configured to set the second set battery charge state a second time when changing the drive mode from the electric drive mode to the hybrid drive mode and to decide to make the mode change from the hybrid drive mode to the electric drive mode based on the second set battery charge state set the second time.

4. The control system according to claim 1 wherein the low load drive condition is a drive condition in which an average accelerator opening for a predetermined period from a time at which an accelerator opening of the engine becomes 0 is smaller than a set opening and in which a vehicle deceleration during the predetermined period is greater than or equal to a set deceleration.

5. The control system according to claim 4 wherein the controller is further configured to conclude the low load drive condition exists when the accelerator opening is 0 over a set time.

6. The control system according to claim 5 wherein the controller is further configured to set the set time such that the set time is lengthened as the average accelerator opening increases.

7. The control system according to claim 5 wherein the controller is further configured to set the set time such that the set time is shortened as the vehicle deceleration increases.

8. The control system according to claim 1 wherein the controller is further configured to permit selection of the electric drive mode even when a vehicle speed is a low speed that is smaller than a set vehicle speed.

9. The control system according to claim 1 wherein the hybrid vehicle further includes a second clutch disposed between the motor/generator and the at least one driving wheel;

and wherein the controller of the control system is further configured to start the engine by engaging the first clutch and transmitting a torque of the motor/generator to the engine when the mode change from the electric drive mode to the hybrid drive mode is made.

10. A controller for a hybrid vehicle including an engine, a motor/generator, a battery operable to provide the motor/generator with electric power and to receive and store electric power regenerated by the motor/generator, a first clutch disposed between the engine and the motor/generator, and at least one driving wheel, the controller comprising:

means for selecting a drive mode wherein the drive mode comprises at least one of an electric drive mode, in which the first clutch is released and power transmission is made only between the motor/generator and the at least one driving wheel, and a hybrid drive mode, in which the first clutch is engaged and power transmission is made between at least the engine and the motor/generator and the at least one driving wheels;

means for deciding to make a mode change from the electric drive mode to the hybrid drive mode when a battery charge state of the battery becomes lower than a first set battery charge state;

means for deciding to make a mode change from the hybrid drive mode to the electric drive mode when the battery charge state becomes higher than or equal to a second set battery charge state, wherein an initial value of the second set battery charge state is higher than the first set battery charge state; and

means for changing the second set battery charge state to a lower value than the initial value when a vehicle driving condition is judged to be a low load drive condition in which a regenerative braking is carried out under the battery charge state where the hybrid drive mode is selected such that the mode change to the electric drive mode from the hybrid drive mode is permitted.

11. A control method of a hybrid vehicle including an engine, a motor/generator, a battery operable to provide the motor/generator with electric power and to receive and store electric power regenerated by the motor/generator, a first clutch disposed between the engine and the motor/generator, and at least one driving wheel, the control system comprising:

selecting a drive mode wherein the drive mode comprises at least one of an electric drive mode, in which the first clutch is released and power transmission is made only between the motor/generator and the at least one driving wheel, and a hybrid drive mode, in which the first clutch is engaged and power transmission is made between at least the engine and the motor/generator and the at least one driving wheels;

deciding to make a mode change from the electric drive mode to the hybrid drive mode when a battery charge state of the battery becomes lower than a first set battery charge state;

deciding to make a mode change from the hybrid drive mode to the electric drive mode when the battery charge state becomes higher than or equal to a second set battery charge state, wherein an initial value of the second set battery charge state is higher than the first set battery charge state; and

changing the second set battery charge state to a lower value than the initial value when a vehicle driving condition is judged to be a low load drive condition in which a regenerative braking is carried out under the battery charge state where the hybrid drive mode is selected such that the mode change to the electric drive mode from the hybrid drive mode is permitted.

12. The control method according to claim 11 wherein the lower value is a same value as the first set battery charge state, the method further comprising:

deciding to make the mode change from the hybrid drive mode to the electric drive mode based on the first set battery charge state during the low load drive condition of the vehicle.

13. The control method according to claim 11, further comprising:

setting the second set battery charge state a second time when changing the drive mode from the electric drive mode to the hybrid drive mode; and

deciding to make the mode change from the hybrid drive mode to the electric drive mode based on the second set battery charge state set the second time.

14. The control method according to claim 11 wherein the low load drive condition is a drive condition in which an average accelerator opening for a predetermined period from a time at which an accelerator opening of the engine becomes 0 is smaller than a set opening and in which a vehicle deceleration during the predetermined period is greater than or equal to a set deceleration.

15. The control method according to claim 14, further comprising:

concluding the low load drive condition exists when the accelerator opening is 0 over a set time.

16. The control method according to claim 15, further comprising:

lengthening the set time as the average accelerator opening increases.

17. The control method according to claim 15, further comprising:

shortening the set time as the vehicle deceleration increases.

18. The control method according to claim 11, further comprising:

permitting selection of the electric drive mode even when a vehicle speed is a low speed that is smaller than a set vehicle speed.