Anti-skid control apparatus for a vehicle braking system

• US 5,118,168 A
• Filed: 12/12/1989
• Issued: 06/02/1992
• Est. Priority Date: 02/09/1987
• Status: Expired due to Fees

• Current Assignee: Bosch Braking Systems Corporation (Robert Bosch GmbH)
• Original Assignee: Nippon ABS Ltd.
• Inventors: Arikawa, Tetsuro
• Primary Examiner(s): Graham, Matthew C.
• Application Number:
  US07/453,145
• Time in Patent Office: 903 Days
• Field of Search: 308/95, 308/96, 308/97, 308/100, 308/103, 308/105, 308/106, 308/109, 308/110, 308/111, 364/426.1, 364/426.2, 188/181 A, 188/181 R, 188/181 C
• US Class Current: 303/148
• CPC Class Codes: B60T 8/1764 Regulation during travel on surface with different coefficients of friction, e.g. between left and right sides, mu-split or between front and rear
• CPC Class Codes: B60T 8/4275 Pump-back systems
• CPC Class Codes: Y10S 303/06 Axle differential control

Abstract

An anti-skid control apparatus for a vehicle includes fluid pressure control valve devices arranged between fluid pressure generating chambers of a tandem master cylinder and the wheel cylinders of the front wheels, respectively, and a control unit receiving outputs of wheel speed sensors for measuring or judging the skid conditions of the front and rear wheels and for generating instructions for controlling the fluid pressure control valve devices. The control unit discriminates the frictionally lower side of the road on which the wheels are running, on the basis of the measuring or judging results of the skid conditions of the rear and/or front wheels, combines logically the measuring or judging result of the skid condition of the one rear wheel running on the low side of the road or the measuring or judging results of the skid conditions of the rear wheels, with that of the one front wheel running on the low side, for generating the instruction for controlling the first or second fluid pressure control valve device for the corresponding front wheel, and generates the instruction for controlling the second or first fluid pressure control valve device for the other front wheel, on the basis of the measuring or judging result of the skid condition of the measuring or judging result of the skid condition of the other front wheel running on the high side independently of those of the rear wheels. The low side can be changed over in accordance with the measuring or judging result. Or the control unit will reset the low side.

Claims

1. In an anti-skid control apparatus for a vehicle braking system including:

(A) a pair of front wheels, and a pair of rear wheels;

(B) wheel speed sensors associated with each of said wheels;

(C) a first fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of one of said front wheels, arranged between a first fluid pressure generating chamber of a tandem master cylinder and said wheel cylinder of the one front wheel;

(D) a second fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of another of said front wheels, arranged between a second fluid pressure generating chamber of said tandem master cylinder and said wheel cylinder of the other front wheel; and

(E) a control unit receiving outputs of said wheel speed sensors for judging the skid conditions of said front and rear wheels and for generating instructions for controlling said first and second fluid pressure control valve devices, the improvements in said control unit comprising;

(i) a judging circuit for judging the skid conditions of said rear and front wheels on the basis of the outputs of said wheel speed sensors and thereby producing judging, results;

(ii) a low-side discrimination circuit for discriminating which side of the road on which said wheels are running is frictionally lower from the judging results of said judging circuit with the road side determined to be frictionally lower designated as the "low side";

(iii) a low side change-over means for changing the road side designated the "low side" over in accordance with said judging results at any time;

(iv) a combining means for logically combining the judging results of skid conditions of said rear wheels; and

(v) a logic control circuit for combining logically the output of said combining means with the judging result of the skid condition of the one front wheel running on the low side for generating the instruction for controlling said first or second fluid pressure control valve device for the corresponding front wheel, and for generating the instruction for controlling said second or first fluid pressure control valve device for the other front wheel on the basis of the judging result of the skid condition of the other front wheel running on the high side independently from the skid conditions of said rear wheels.

2. An anti-skid control apparatus according to claim 1, in which said judging results of the skid conditions from said judging circuit include a brake increasing signal, a brake holding signal, and a brake relieving signal, and wherein said low side discrimination circuit further comprises means for determining the road side having the one front or rear wheel which generates said brake maintaining signal sooner than the other front or rear wheel to be the "low side", the determination being made before any of said front and rear wheels generates said brake relieving signal.

3. An anti-skid control apparatus according to claim 1, wherein the judging results of the skid conditions from said judging circuit include a brake increasing signal, a brake holding signal, and a brake relieving signal, and wherein said low side discrimination circuit further comprises means for determining the road side having the one front or rear wheel which generates said brake relieving signal sooner than the other front or rear wheel to be the "low side".

4. An anti-skid control apparatus according to claim 1, wherein a valve apparatus for generating a fluid pressure in accordance with the lower one of the brake fluid pressures of said front wheels controlled with said first and second fluid pressure control valve devices is arranged between said wheel cylinders of the front wheels and those of the rear wheels.

5. In an anti-skid control apparatus for a vehicle braking system including:

(A) a pair of front wheels, and a pair of rear wheels;

(B) wheel speed sensors associated with each of said wheels;

(C) a first fluid pressure control valve device for controlling the bake fluid pressure of the wheel cylinder of one of said front wheels, arranged between a first fluid pressure generating chamber of a tandem master cylinder and said wheel cylinder of the one front wheel;

(D) a second fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of another of said front wheels, arranged between a second fluid pressure generating chamber of said tandem master cylinder and said wheel cylinder of the other front wheel; and

(E) a control unit receiving outputs of said wheel speed sensors for judging the skid conditions of said front and rear wheels and for generating instructions for controlling said first and second fluid pressure control valve devices, the improvements in said control unit comprising;

(i) a judging circuit for judging the skid conditions of said rear ad front wheels on the basis of the outputs of said wheel speed sensors and thereby producing judging results;

(ii) a low-side discrimination circuit for discriminating which side of the road on which said wheels are running is frictionally lower from the judging results of said judging circuit with the road side determined to be frictionally lower designated as the "low side;

"

(iii) means for resetting the discrimination of which road side is the "low side" upon the fulfillment of a reset condition based on said judging results; and

,

(iv) a logic control circuit for combining logically the judging result of the skid condition of the one rear wheel running on the low side of the road with that of the one front wheel also running on the low side for generating the instruction for controlling said first or second fluid pressure control valve device for the corresponding front wheel, and for generating the instruction for controlling said second or first fluid pressure control valve device for the front wheel running on the high side on the basis of the judging result of the skid condition of the front wheel running on the high side independently from said rear wheels.

6. An anti-skid control apparatus according to claim 5, wherein said low-side discrimination circuit further comprises means, after being reset, for determining the side of the one front or rear wheel which generates said brake maintaining signal sooner than the other front or rear wheel to be the "low side", the determination being made before any one of front wheels or rear wheels generates said brake relieving signal.

7. An anti-skid control apparatus according to claim 5, wherein said low-side discrimination circuit further comprises means, after being reset, for determining the side of the one front or rear wheel which generates said brake relieving signal sooner than the other front or rear wheel to be "low side".

8. An anti-skid control apparatus according to claim 5, wherein said low-side discrimination circuit further comprises a reset circuit for resetting the determination of said "low side" in a predetermined time after a reset condition is fulfilled.

11. An anti-skid control apparatus according to claim 5 or 9, further comprising means for resetting the discrimination of which road side is the "low side" in the case that at least one of said front and rear wheels on the low side is rapidly accelerated beyond a predetermined acceleration threshold.

12. An anti-skid control apparatus according to claim 5, or 9, further comprising means for resetting the determination of which road side is the "low side" in the case that at least one of said front and rear wheels on the low side is rotating in the stable region of the μ

-slip characteristics.

13. An anti-skid control apparatus according to claim 12, wherein said low-side discrimination circuit further comprises a reset circuit for resetting the determination of said "low-side" in the case that a reset condition is fulfilled and both of the rear wheels and the front wheel on the low side are not being accelerated.

14. An anti-skid control apparatus according to claim 12, wherein said low-side discrimination circuit further comprises a reset circuit for resetting the determination of said "low side" in the case that at least one of said reset conditions is fulfilled, and the accelerations of both of the rear wheels and of the front wheel on the low side are lower than a predetermined acceleration threshold value.

15. An anti-skid control apparatus according to claim 5 or 9, further comprising means for resetting the discrimination of which road side is the "low side" in the case that at least one of said front and rear wheels on the low side has rotated continuously in the stable region of the μ

-slip characteristics for a predetermined time.

16. An anti-skid control apparatus according to claim 15 further comprising means for changing said predetermined time in accordance with the continuation time of said brake relieving signal of at least one of said front and rear wheels on the low side in the last control cycle.

17. An anti-skid control apparatus according to claim 16, wherein said low side discrimination circuit further comprises means for determining, after said reset, the side of the one front or rear wheel which generates said brake maintaining signal sooner than the other front or rear wheel to be the "low side" before any one of the front wheels or rear wheels generates said brake relieving signal.

18. An anti-skid control apparatus according to claim 16, further comprising means for changing said predetermined time in accordance with the continuation time of said brake relieving signal of at least one of said front and rear wheels on the low side in the last control cycle.

19. An anti-skid control apparatus according to claim 16, further comprising means for changing said predetermined time in accordance with the continuation time of said brake relieving signal obtained from the result of the select-low calculation of said rear wheels.

20. An anti-skid control apparatus according to claim 5 or 9, further comprising means for resetting the discrimination of which road side is the low side in the case that the brake relieving signal of at least one of said front and rear wheels on the low side has disappeared continuously for a predetermined time.

21. An anti-skid control apparatus according to claim 5 or 9, wherein the judging results of the skid conditions from said judging circuit further includes a brake stepwisely increasing signal, and further comprising means for resetting the discrimination of which road side is the "low side" when the number of the steps of said brake stepwisely increasing signal for at least one of said front or rear wheels on the low side has reached a predetermined value.

22. An anti-skid control apparatus according to claim 5 or 9, wherein the judging results of the skid conditions from said judging circuit further includes a brake stepwisely increasing signal, and further comprising means for resetting the discrimination of which road side is the "low side" when the total of the brake increasing time of said brake stepwisely increasing signal for at least one of said front and rear wheels on the low side has reached a predetermined value.

23. An anti-skid control apparatus according to claim 5 or 9, further comprising means for resetting the discrimination of which road side is the "low side" when at least one of said one front and/or rear wheels on the low side generates continuously the brake increasing signal for a predetermined time.

24. An anti-skid control apparatus according to claim 5 or 9, further comprising a lateral acceleration detector for detecting the lateral acceleration of the vehicle body, and means for resetting the discrimination of which road side is the "low-side" in the case that the lateral acceleration is reversed during the time when at least one of said front and rear wheels on the low side is rotating on the stable region of the μ

-slip characteristics.

25. An anti-skid control apparatus according to claim 5 or 9, further comprising a lateral acceleration detector for detecting the lateral acceleration of the vehicle body, and also further comprising means for resetting the discrimination of which road side is the "low side" in the case that the lateral acceleration is reversed, and becomes higher than a predetermined value during the time when at least one of said front and rear wheels on the low side is rotating in the stable region of the μ

-slip characteristics.

9. In an anti-skid control apparatus for a vehicle braking system including:

(A) a pair front wheels, and a pair of rear wheels;

(B) wheel speed sensors associated with each of said wheels;

(C) a first fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of one of said front wheels, arranged between a first fluid pressure generating chamber of a tandem master cylinder and said wheel cylinder of the one front wheel;

(D) a second fluid pressure control valve device for controlling the brake fluid pressure of the wheel cylinder of another of said front wheels, arranged between a second fluid pressure generating chamber of said tandem master cylinder and said wheel cylinder of the other front wheel; and

(E) a control unit receiving outputs of said wheel speed sensors for judging the skid conditions of said front and rear wheels and for generating instructions for controlling said first and second fluid pressure control valve devices, the improvements in said control unit comprising;

(i) a judging circuit for judging the skid conditions of said rear and front wheels on the basis of the outputs of said wheel speed sensors to thereby produce judging results;

(ii) a low-side discrimination circuit for discriminating which side of the road on which said wheels are running is frictionally lower from the judging results of said judging circuit with the road side determined to be frictionally lower designated as the "low side;

"

(iii) means for resetting the discrimination of which road side is the "low side" upon the fulfillment of a reset condition based on said judging results;

(iv) a combining means for logically combining the judging results of skid conditions of said rear wheels; and

(v) a logic control circuit for combining logically the output of said combining means with the judging result of the skid condition of the one front wheel running on the low side for generating the instruction for controlling said first or second fluid pressure control valve device for the corresponding front wheel, and for generating the instruction for controlling said second or first fluid pressure control valve device for the other front wheel on the basis of the judging result of the skid condition of the other front wheel running on the high side independently from the skid conditions of said rear wheels.

10. An anti-skid control apparatus according to claim 9, further comprising a valve apparatus for generating a fluid pressure in accordance with the lower one of the brake fluid pressures of said front wheels controlled with said first and second fluid pressure control valve devices, the valve apparatus being arranged between said wheel cylinders of the front wheels and said wheel cylinders of the rear wheels.