Braking/driving force control apparatus for vehicle

• US 8,328,690 B2
• Filed: 06/25/2009
• Issued: 12/11/2012
• Est. Priority Date: 07/10/2008
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohtsu, Nobuyuki
• Primary Examiner(s): Holmes, Justin
• Assistant Examiner(s): Hlavka, David J
• Application Number:
  US12/491,625
• Publication Number:
  US 20100009808A1
• Time in Patent Office: 1,265 Days
• Field of Search: 477/182, 477/183, 477/184, 477/185, 477/186, 477/187, 477/203, 701/82, 701/70, 701/71, 701/73, 701/74, 701/75, 701/79, 701/80, 701/81, 701/84, 701/89, 303/139, 303/15, 303/20, 303/141, 303148-150, 303/155, 303/160, 303/165, 303/171, 303/183, 303/185
• US Class Current: 477/185
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60W 10/06 including control of combustion engines
• CPC Class Codes: B60W 10/184 with wheel brakes
• CPC Class Codes: B60W 30/18136 Engine braking

Abstract

A braking/driving force control apparatus for a vehicle includes a drive wheel configured to be driven by an output of a drive source; a brake unit configured to control a braking force to be applied to the drive wheel, in accordance with a state of the vehicle; and a brake control unit configured to control the brake unit, and configured to reduce a brake torque of the drive source when the brake unit actually applies a braking force to at least the drive wheel of the vehicle.

Claims

1. A braking/driving force control apparatus for a vehicle, comprising:

a drive wheel configured to be driven by an output of a drive source;

a brake unit configured to control a braking force to be applied to the drive wheel, in accordance with a state of the vehicle; and

a brake control unit configured to control the brake unit, and configured to reduce a brake torque of the drive source irrespective of a slip ratio of the drive wheel when the brake unit actually applies the braking force to at least the drive wheel of the vehicle.

2. The braking/driving force control apparatus as claimed in claim 1, wherein

the drive source is an engine;

the braking/driving force control apparatus further comprises an engine control unit configured to control an output of the engine;

the brake control unit is further configured to calculate a value of an optimum engine-brake torque as an optimum engine-brake torque value, and to output the optimum engine-brake torque value to the engine control unit; and

the engine control unit is further configured to control the engine to attain the optimum engine-brake torque value.

3. The braking/driving force control apparatus as claimed in claim 2, wherein

the optimum engine-brake torque value is equal to 0 when the brake unit applies the braking force to at least the drive wheel.

4. The braking/driving force control apparatus as claimed in claim 2, wherein

the braking/driving force control apparatus further comprises a road friction-coefficient calculating section configured to calculate a friction coefficient of a road surface as a calculated friction coefficient;

and

the engine control unit is further configured to cause the engine to output an engine torque for accelerating the vehicle, when the calculated friction coefficient varies from a high friction-coefficient value to a low friction-coefficient value.

5. The braking/driving force control apparatus as claimed in claim 2, wherein

the braking/driving force control apparatus further comprises a slip-state calculating section configured to calculate a slip state of the drive wheel as a calculated slip state;

and

the brake control unit is further configured to control an engine-brake torque in accordance with the calculated slip state, so as to set the optimum engine-brake torque value at a first engine-brake torque value when the slip ratio is greater than a first slip ratio value, and set the optimum engine-brake torque value at a second engine-brake torque value when the slip ratio is smaller than the first slip ratio value, the second engine-brake torque value being greater than the first engine-brake torque value.

6. The braking/driving force control apparatus as claimed in claim 5, wherein

the first engine-brake torque value is an accelerating engine torque, and the second engine-brake torque value is a decelerating engine torque.

7. The braking/driving force control apparatus as claimed in claim 2, wherein

the braking/driving force control apparatus further comprises a wheel-acceleration calculating section configured to calculate an acceleration of the drive wheel as a calculated wheel acceleration;

and

the optimum engine-brake torque value is set as an accelerating engine torque when the calculated wheel acceleration has a tendency to decrease a speed of the drive wheel, and is set as a decelerating engine torque when the calculated wheel acceleration has a tendency to increase the speed of the drive wheel.

8. The braking/driving force control apparatus as claimed in claim 1, wherein

the brake control unit is further configured to reduce the brake torque by means of at least one of a shift to neutral position of a transmission, a change of speed ratio of the transmission and a disengagement control of a clutch.

9. The braking/driving force control apparatus as claimed in claim 1, wherein

the brake unit is further configured to be applied to a constant-speed running system for performing an automatic braking at a time of hill-descent running of the vehicle.

10. A braking/driving force control apparatus for a vehicle, comprising:

a brake unit configured to control a braking force to be applied to wheels of the vehicle, in accordance with a state of the vehicle;

a brake control unit configured to control the brake unit; and

an engine control unit configured to control a state of an engine so as to reduce an engine-brake torque or so as to increase a rotational speed of the engine in accordance with an output signal of the brake control unit irrespective of a slip ratio of at least a drive wheel among the wheels, when the brake unit actuates the drive wheel.

11. The braking/driving force control apparatus as claimed in claim 10, wherein

the brake control unit is configured to calculate a value of an optimum engine-brake torque as an optimum engine-brake torque value, and configured to output a signal of the optimum engine-brake torque value;

and

the engine control unit is further configured to control the engine so as to attain the optimum engine-brake torque value.

12. The braking/driving force control apparatus as claimed in claim 11, wherein

the brake control unit is further configured to function as an antiskid brake control unit, and comprises a road friction-coefficient calculating section configured to calculate a friction coefficient of a road surface as a calculated friction coefficient;

the engine control unit is further configured to cause the engine to output an engine torque for accelerating the vehicle, when the calculated friction coefficient has varied from a high friction-coefficient value to a low friction-coefficient value.

13. The braking/driving force control apparatus as claimed in claim 12, wherein

the brake control unit comprises a slip-state calculating section configured to calculate a slip state of the drive wheel as a calculated slip state;

and

the engine control unit is further configured to control the engine-brake torque in accordance with the calculated slip state , so as to set the optimum engine-brake torque value at a first engine-brake torque value when the slip ratio is greater than a first slip ratio value, and set the optimum engine-brake torque value at a second engine-brake torque value when the slip ratio is smaller than the first slip ratio value, the second engine-brake torque value being greater than the first engine-brake torque value.

14. The braking/driving force control apparatus as claimed in claim 13, wherein

the first engine-brake torque value is an accelerating engine torque level, and the second engine-brake torque value is a decelerating engine torque level.

15. The braking/driving force control apparatus as claimed in claim 13, wherein

the brake control unit comprises a wheel-acceleration calculating section configured to calculate an acceleration of the drive wheel as a calculated wheel acceleration;

and

the optimum engine-brake torque value is set as an accelerating engine torque when the calculated wheel acceleration has a tendency to decrease a speed of the drive wheel, and is set as a decelerating engine torque when the calculated wheel acceleration has a tendency to increase the speed of the drive wheel.

16. The braking/driving force control apparatus as claimed in claim 11, wherein

the optimum engine-brake torque value is equal to 0 when the brake unit is actuating the drive wheel.

17. The braking/driving force control apparatus as claimed in claim 11, wherein

the brake unit is further configured to be applied to a constant-speed running system for performing an automatic braking at a time of hill-descent running of the vehicle.

18. A braking/driving force control apparatus for a vehicle, comprising:

an antiskid brake control unit configured to perform an antiskid brake control for increasing or decreasing wheel-cylinder fluid pressures of wheels of the vehicle in accordance with a slip state of the wheels; and

an engine control unit configured to control an output of an engine, so as to adjust an engine-brake torque in accordance with an accelerating/decelerating state of the wheels, when the antiskid brake control is acting on at least a drive wheel of the wheels.

19. The braking/driving force control apparatus as claimed in claim 18, wherein

the engine control unit is further configured

to set an optimum engine-brake torque value at a first engine-brake torque value when a slip ratio of the drive wheel is greater than a first slip ratio value, and set the optimum engine-brake torque value at a second engine-brake torque value when the slip ratio is smaller than the first slip ratio value, the second engine-brake torque value being greater than the first engine-brake torque value, or

to set the optimum engine-brake torque value at an accelerating-side engine torque level when the slip ratio is greater than the first slip ratio value, and set the optimum engine-brake torque value at a decelerating-side engine torque level when the slip ratio is smaller than the first slip ratio value.

20. The braking/driving force control apparatus as claimed in claim 18, wherein

the engine control unit is further configured to set an optimum engine-brake torque value as an accelerating engine torque when a calculated wheel acceleration has a tendency to decrease a rotational speed of the drive wheel, and set the optimum engine-brake torque value as a decelerating engine torque when the calculated wheel acceleration has a tendency to increase the rotational speed of the drive wheel.