Anti-skid control apparatus for a vehicle braking system

• US 4,740,040 A
• Filed: 06/03/1987
• Issued: 04/26/1988
• Est. Priority Date: 06/09/1986
• Status: Expired due to Term

• Current Assignee: Bosch Braking Systems Corporation (Robert Bosch GmbH)
• Original Assignee: Nippon ABS Ltd.
• Inventors: Arikawa, Tetsuro
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US07/057,802
• Time in Patent Office: 328 Days
• Field of Search: 303/111, 303/100, 303/113-119, 303/92, 303/96, 303/97, 303/98, 303/99, 303/102, 303/103, 303/105, 303/107-110, 303/DIG. 5, 303/3-4, 303/106, 188/181 A, 188/181 C, 364/426
• US Class Current: 303/159
• 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 8/58 responsive to speed and another condition or to plural speed conditions

Abstract

An anti-skid control vehicle braking apparatus with pairs of front and rear wheels; wheel speed sensors associated with the wheels; first and second fluid pressure control valve devices for respectively controlling the brake fluid pressure of the wheel cylinders of the front wheels; a control unit receiving outputs of the 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; and a valve apparatus for generating a fluid pressure in accordance with the lower one of the brake fluid pressures of the front wheels controlled with the control valve devices, being arranged between the front wheel cylinders and rear wheel cylinders the control unit discriminates the frictionally lower one of the sides of the road on which the wheels are running, on the basis of the measuring or judging results of the skid conditions of rear wheels, combines logically the measuring or judging results of the skid conditions of the rear wheels with the measuring or judging result of the skid condition of one front wheel running on the lower side for generating the instruction for controlling one of fluid pressure control valve devices, and generates the instruction for controlling the other control valve device, on the basis of the measuring or judging result of the skid condition of the other front wheel running on the frictionally higher side independently of those of the rear wheels.

Claims

1. 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 said wheels, respectively;

(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;

(E) a control unit receiving outputs of said wheel speed sensors for measuring or 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; and

(F) 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, being arranged between said wheel cylinders of the front wheels and those of the rear wheels;

the improvements in which said control unit discriminates the frictionally lower one (designated as "low side") of the sides of the road on which said wheels are running, on the basis of the measuring or judging results of the skid conditions of said rear wheels, combines logically the measuring or judging results of the skid conditions of said rear wheels with the measuring or 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, and generates the instruction for controlling said second or first fluid pressure control valve device, on the basis of the measuring or judging result of the skid condition of the other front wheel running on the high side (frictionally higher side) independently of those of said rear wheels.

2. An anti-skid control apparatus according to claim 1, in which said measuring or judging results of the skid conditions include a brake increasing signal, a brake maintaining or holding signal and a brake relieving signal, and the side of the one rear wheel which generates said brake maintaining signal sooner than the other rear wheel, is made "low side", before anyone of said rear wheels generates said brake relieving signal.

3. An anti-skid control apparatus according to claim 1, in which said measuring or judging results of the skid conditions include a brake increasing signal, a brake maintaining or holding signal and a brake relieving signal, and the side of the one rear wheel which generates said brake relieving signal sooner than the other rear wheel, is made "low side".

4. An anti-skid control apparatus according to claim 3, in which said "low side" is changed over in the case that said one rear wheel on the low side is rapidly accelerated beyond a predetermined acceleration threshold during the time when said other rear wheel on the high side generates said brake relieving signal.

5. An anti-skid control apparatus according to claim 3, in which said "low side" is changed over in the case that said other rear wheel on the high side generates continuously said brake relieving signal for a longer time than a predetermined time during the time when said one rear wheel on the low side is rotating in the stable region of the μ

(frictional coefficient) - slip characteristics.

6. An anti-skid control apparatus according to claim 3, in which said "low side" is changed over in the case that said other rear wheel on the high side generates continuously said brake relieving signal for a longer time than a predetermined time during the time when said brake relieving signal of the one rear wheel on the low side disappears.

7. An anti-skid control apparatus according to claim 6, in which said predetermined time is changed in accordance with the continuation time of said brake relieving signal of the one rear wheel on the low side in the last control cycle, or of the brake relieving signal obtained from the result of the select-low calculation of both said rear wheels.

8. An anti-skid control apparatus according to claim 2, in which, when said one rear wheel on the low side has rotated continuously in the stable region of the μ

-slip characteristics for a longer time than a predetermined time, the side of the one rear wheel which generates said brake maintaining signal sooner than the other rear wheel, is newly made "low side", before anyone of said rear wheels generates said brake relieving signal.

9. An anti-skid control apparatus according to claim 3, in which, when said one rear wheel on the low side has rotated continuously in the stable region of the μ

-slip characteristics for a longer time than a predetermined time, the side of the one rear wheel which generates said brake relieving signal sooner than the other rear wheel, is newly made "low side".

10. An anti-skid control apparatus according to claim 2, in which said measuring or judging results of the skid conditions further includes a brake step-wisely increasing signal, and when the number of the steps of said brake step-wisely increasing signal for said one rear wheel on the low side has reached a predetermined value, the side of the one rear wheel which generates said brake maintaining signal sooner than the other rear wheel, is newly made "low side", before anyone of said rear wheels generates said brake relieving signal.

11. An anti-skid control apparatus according to claim 3, in which said measuring or judging results of the skid conditions further includes a brake step-wisely increasing signal, and when the number of the steps of said brake step-wisely increasing signal for said one rear wheel on the low side has reached a predetermined value, the side of the one rear wheel which generates said brake relieving signal sooner than the other rear wheel, is newly made "low side".

12. An anti-skid control apparatus according to claim 2, in which, when said one rear wheel on the low side generates continuously said brake increasing signal for a longer time than a predetermined time, the side of the one rear wheel which generates said brake maintaining signal sooner that the other rear wheel, is newly made "low side", before anyone of said rear wheels generates said brake relieving signal.

13. An anti-skid control apparatus according to claim 3, in which, when said one rear wheel on the low side generates continuously said brake increasing signal for a longer time than a predetermined time, the side of the one rear wheel which generates said brake relieving signal sooner that the other area wheel, is newly made "low side".

14. An anti-skid control apparatus according to claim 3, in which said "low side" is changed over in the case that said other rear wheel on the high side generates said brake relieving signal during the time when both of said front and rear wheels on the low side is rotating in the stable region of the μ

-slip characteristics.

15. An anti-skid control apparatus according to claim 1, in which, while any one of said rear wheels is rapidly accelerated beyond a predetermined acceleration threshold, the braking force to said low side is rapidly increased.

16. An anti-skid control apparatus according to claim 1, in which said control unit forms a first select-low control signal on the basis of the measuring or judging results of the skid conditions of both said rear wheels and a second select-low control signal on the basis of said first select-low control signal and measuring or judging result of the one front wheel on said low side, and, on the basis of said second select-low control signal, generates the instruction for controlling said first or second fluid pressure control valve device, and generates the instruction for controlling said second or first fluid pressure control valve device, on the basis of the measuring or judging result of the skid condition of the other front wheel running on the high side (frictionally higher side) independently of those of said rear wheels.