Anti-skid control apparatus for a vehicle braking system

• US 4,836,620 A
• Filed: 06/05/1987
• Issued: 06/06/1989
• Est. Priority Date: 06/11/1986
• Status: Expired due to Term

• Current Assignee: Bosch Braking Systems Co Ltd (Robert Bosch GmbH)
• Original Assignee: Nippon ABS Ltd.
• Inventors: Arikawa, Tetsuro
• Primary Examiner(s): Reger, Duane A.
• Application Number:
  US07/058,548
• Time in Patent Office: 732 Days
• Field of Search: 188/181 A, 303/92, 303/100, 303/102, 303/103, 303/105, 303/106, 303/109, 303/110, 303/111, 303/113, 303/116
• US Class Current: 303/186
• CPC Class Codes: B60T 8/26 characterised by producing differential braking between front and rear wheels using electrical circuitry or regulation means B60T8/17
• CPC Class Codes: B60T 8/346 2 Channel systems B60T8/345 takes precedence
• CPC Class Codes: B60T 8/4275 Pump-back systems

Abstract

Anti-skid control apparatus includes wheel speed sensors for front and rear wheels. First and second fluid pressure control valve devices control brake fluid pressures of wheel cylinders of the front and rear wheels, arranged between fluid pressure generating chambers of a tandem master cylinder and the wheel cylinders respectively. A control unit receives outputs of the sensors for measuring or judging the skid conditions of the wheels and for generating instructions for controlling the valve devices. A valve apparatus generates fluid pressure in accordance with the lower one of the brake fluid pressures of the front wheels controlled with the valve devices arranged between the wheel cylinders of the front wheels and those of the rear wheels. When the wheel speed difference between the front and rear wheels on the same side of the road becomes larger than a predetermined value, or when the deceleration of the one rear wheel becomes larger than a predetermined deceleration for the one rear wheel which is smaller than a second predetermined deceleration for the one front wheel running on the same side as the one rear wheel, before the one front or rear wheel on the same side first generates a brake relieving signal, the control unit generates the instruction which controls the first or second fluid pressure control valve device for the same side so as to maintain the pressure constant, or to reduce the rising gradient of the pressure.

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 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, the improvement comprising;

a control unit receiving outputs of said wheel speed sensors for measuring of judging the skid conditions of said front and rear wheels and for generating instruction for controlling said first and second fluid pressure control valve devices, said control unit including wheel speed signal generators receiving the outputs of said wheel speed sensors and calculating rotational speeds of said wheels, the control unit including

a substractor receiving the outputs of the corresponding ones of said wheel speed signal generators for the front and rear wheels on the same side of the road, and calculating the rotational speed difference between said front and rear wheels on the same side,

a first comparator comparing said rotational speed difference with a reference value and generating output when said rotational speed difference becomes larger than said reference value,

wheel deceleration signal generators receiving the outputs of said wheel speed signal generators and calculating decelerations of said wheels,

a second comparator receiving the output of the rear wheel decelerator signal generator of said wheel deceleration signal generators, comparing the rear wheel deceleration as said output with a reference deceleration value which is smaller than another reference deceleration value for the front wheel, and generating output when said rear wheel deceleration becomes higher than said reference deceleration value; and

a logic part generating the instruction which controls said first or second fluid pressure control valve device for said same side so as the maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, on the basis of the output of said first or second comparator, before said one front or rear wheel one said same side first generates a brake relieving signal as the measuring or judging result of the skid condition; 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.

2. An anti-skid control apparatus according to claim 1 in which pressure-reducing proportioning valves are arranged between said valve apparatus and said rear wheels, respectively.

3. An anti-skid control apparatus according to claim 1 or 2 in which said logic part is connected to said first or second fluid pressure control valve device so as to maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, during the generation of the output of said first or second comparator.

4. An anti-skid control apparatus according to claim 1 or 2 in which said logic part is connected to one of said first and second fluid pressure control valve devices to maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, during the generation of the output of said first or second comparator, and continuously for a predetermined time after said output disappears.

5. An anti-skid control apparatus according to claim 1 or 2 in which said logic part is connected to one of said first and second fluid pressure control valve devices to maintain the brake fluid pressure to the wheel cylinder at constant during the generation of the output of said first comparator, and to reduce the rising gradient of the brake fluid pressure to the wheel cylinder continuously for a predetermined time after the output of said first comparator disappears.

6. An anti-skid control apparatus according to claim 1 or 2 in which an instruction from said logic part is coupled to said first or second fluid pressure control valve device so as to maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, during the generation of the output of said first or second comparator, and continuously for a predetermined time after said output disappears, and to reduce the rising gradient of the brake pressure continuously for a second predetermined time.

7. An anti-skid control apparatus according to claim 1 or 2 in which before said one front or rear wheel on said same side first generates a brake relieving signal as the measuring or judging result of the skid condition, said logic part generates the instruction which controls said first or second fluid pressure control valve device for the one side of the road on which the rotational speed difference between the one front and rear wheels becomes larger than said reference value, sooner than one the other side of the road, or on which the one rear wheel deceleration become higher than said reference deceleration value, sooner than on the other side of the road, so as the maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, and said lock part generates no instruction which controls said second or first fluid pressure control valve device for the other side on which the rotational speed deference between the other front and rear wheels become larger than said reference value, later than on the one side of the road, or on which the other rear wheel deceleration becomes higher than said reference deceleration value, later than on the one side of the road.

8. An anti-skid control apparatus according to claim 7 in which said logic part generates the instruction which controls said first or second fluid pressure control valve device so as to maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, during the generation of the output of said first or second comparator.

9. An anti-skid control apparatus according to claim 7 in which said logic part generates the instruction which controls said first or second fluid pressure control valve device so as to maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, during the generation of the output of said first or second comparator, and continuously for a predetermined time after said output disappears.

10. An anti-skid control apparatus according to claim 7 in which said logic part generates the instruction which controls said first or second fluid pressure control valve device so as to maintain the brake fluid pressure to the wheel cylinder at constant during the generation of the output of said first comparator, and to reduce the rising gradient of the brake fluid pressure to the wheel cylinder continuously for a predetermined time after the output of said first comparator disappears.

11. An anti-skid control apparatus according to claim 7 in which said logic part generates the instruction which controls said first or second fluid pressure control valve device so as to maintain the brake fluid pressure to the wheel cylinder at constant or to reduce the rising gradient of the brake fluid pressure to the wheel cylinder, during the generation of the output of said first or second comparator, and continuously for a predetermined time after said output disappears, and to reduce the rising gradient of the brake pressure continuously for a second predetermined time.