Brake force control apparatus for vehicle and brake force control method for vehicle

Patent metadata

Field	Value
Publication number	US-9333956-B2
Application number	US-201113884782-A
Country	US
Kind code	B2
Filing date	Nov 24, 2011
Priority date	Nov 25, 2010
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

A brake force control apparatus includes a diagonal two-system brake device and performs front-rear wheel distribution control of brake force by individually controlling the brake pressure of the left and right rear wheels so as to obtain a target relationship between a wheel speed of the left and right rear wheels and the front wheels during braking. It is determined whether or not a difference in wheel speed between one wheel of one system and one wheel of the other system or a difference in wheel speed between the other wheel of the one system and the other wheel of the other system exceeds a threshold. When the threshold is exceeded, the reduction of brake pressure by the front-rear wheel distribution control of brake force is not performed with respect to a rear wheel with a lower wheel speed from among the left and right rear wheels.

First claim

The invention claimed is:

1. A brake force control apparatus for a vehicle that has a brake device provided with a brake pressure control system for a left front wheel and a right rear wheel and a brake pressure control system for a right front wheel and a left rear wheel, and performs front-rear wheel distribution control of brake force by individually controlling the brake pressure of the left and right rear wheels so as to obtain a target relationship between a slip degree index value of the left and right rear wheels and a slip degree index value of the front wheels during braking, the brake force control apparatus comprising:
a controller configured to, detect a failure in one of the brake pressure control systems when either of a difference in slip degree index value between one wheel of one of the systems and one wheel of the other of the systems and a difference in slip degree index value between the other wheel of the one system and the other wheel of the other system exceeds a threshold for the difference, determine a system without the failure that includes a wheel with a lower wheel speed from among the two wheels for which the difference in slip degree index value exceeds the threshold for the difference, and inhibit a reduction of brake pressure by the front-rear wheel distribution control of brake force to maintain a brake pressure of a rear wheel of the system without the failure.

2. The brake force control apparatus for a vehicle according to claim 1 , wherein
the wheel speed is a wheel speed from which an effect of turning radius has been excluded.

3. The brake force control apparatus for a vehicle according to claim 1 , wherein
the difference in slip degree index value between the one wheel of the one system and the one wheel of the other system is a difference in slip degree index value between the left front and rear wheels, and
the difference in slip degree index value between the other wheel of the other system and the other wheel of the one system is a difference in slip degree index value between the right front and rear wheels.

4. The brake force control apparatus for a vehicle according to claim 1 , wherein
the difference in slip degree index value between the one wheel of the one system and the one wheel of the other system is a difference in slip degree index value between the left and right front wheels; and
the difference in slip degree index value between the other wheel of the other system and the other wheel of the one system is a difference in slip degree index value between the left and right rear wheels.

5. The brake force control apparatus for a vehicle according to claim 4 , wherein:
the controller corrects the difference in slip degree index value on the basis of a parameter relating to a turning radius of the vehicle.

6. The brake force control apparatus for a vehicle according to claim 1 , wherein
the controller increases a brake pressure by the front-rear wheel distribution control of brake force with respect to the rear wheel on a side opposite, in a left-right direction, to the rear wheel for which the reduction of brake pressure by the front-rear wheel distribution control of brake force is inhibited.

7. The brake force control apparatus for a vehicle according to claim 1 , wherein
the controller interrupts the front-rear wheel distribution control of brake force when the reduction of brake pressure by the front-rear wheel distribution control of brake force is continuously inhibited for a time equal to or longer than a reference time.

8. The brake force control apparatus for a vehicle according to claim 1 , wherein
the controller prohibits the reduction of brake pressure by the front-rear wheel distribution control of brake force.

9. The brake force control apparatus for a vehicle according to claim 1 ,
the threshold for the difference is set to change according to at least one of a vehicle speed, a vehicle deceleration, and a variation rate of vehicle deceleration.

10. The brake force control apparatus for a vehicle according to claim 1 , wherein:
the controller determines that either of the one system and the other system has failed when the reduction of brake pressure by the front-rear wheel distribution control of brake force is inhibited.

11. The brake force control apparatus for a vehicle according to claim 1 , wherein:
the controller determines that the system including a wheel with a higher wheel speed, from among the two wheels for which the threshold for the difference in slip degree index value is exceeded, has failed when the reduction of brake pressure by the front-rear wheel distribution control of brake force is inhibited.

12. The brake force control apparatus for a vehicle according to claim 1 , wherein:
the controller determines that the system including a wheel with a higher wheel speed, from among the left and right rear wheels, has failed when the reduction of brake pressure by the front-rear wheel distribution control of brake force is inhibited.

13. The brake force control apparatus for a vehicle according to claim 1 , wherein the controller is configured to determine that a master cylinder pressure is equal to or higher than a control start determination reference value before detecting the failure in one of the brake pressure control systems.

14. The brake force control apparatus for a vehicle according to claim 1 , wherein the controller is configured to perform the detection of the failure in one of the brake pressure control systems and the inhibition of the reduction of brake pressure by the front-rear wheel distribution control of brake force in a control routine, and to repeatedly execute the control routine with a predetermined period until a master cylinder pressure is equal to or less than a control end determination reference value.

15. A brake force control method for a vehicle that uses a brake device provided with a brake pressure control system for a left front wheel and a right rear wheel and a brake pressure control system for a right front wheel and a left rear wheel to perform front-rear wheel distribution control of brake force by individually controlling the brake pressure of the left and right rear wheels so as to obtain a target relationship between a slip degree index value of the left and right rear wheels and a slip degree index value of the front wheels during braking, comprising:
detecting a failure in one of the brake pressure control systems when if either of a difference in slip degree index value between one wheel of one of the systems and one wheel of the other of the systems and a difference in slip degree index value between the other wheel of the one system and the other wheel of the other system exceeds a threshold for the difference, determining a system without the failure that includes a wheel with a lower wheel speed from among the two wheels for which the difference in slip degree index value exceeds the threshold for the difference, and inhibiting a reduction of brake pressure by the front-rear wheel distribution control of brake force with respect to maintain a brake pressure of a rear wheel of the system without the failure.

16. The brake force control method for a vehicle according to claim 15 , further comprising detecting that a master cylinder pressure is equal to or higher than a control start determination reference value before the detecting the failure in one of the brake pressure control systems.

17. The brake force control method for a vehicle according to claim 15 , further comprising performing the detection of the failure in one of the br

Assignees

• Watanabe Yoshinori
• Toyota Motor Co Ltd

Inventors

• Watanabe Yoshinori

Classifications

• B60T8/92

  automatically taking corrective action · CPC title

• B60T8/4872

  pump-back systems · CPC title

• B60T8/268

  using the valves of an ABS, ASR or ESP system · CPC title

• B60T8/885

  using electrical circuitry · CPC title

• B60T17/221

  Procedure or apparatus for checking or keeping in a correct functioning condition of brake systems (hydraulic pressure systems in general F15B19/00, F15B21/04; testing structures or apparatus G01M) · CPC title