Vehicle anti-lock brake system

• US 4,865,399 A
• Filed: 12/13/1988
• Issued: 09/12/1989
• Est. Priority Date: 08/09/1985
• Status: Expired due to Term

• Current Assignee: Kelsey-Hayes Co. (Zeppelin - Stiftung der Stadt Friedrichshafen)
• Original Assignee: Kelsey Hayes Company
• Inventors: Every, Peter, Fuller, Edward N., Atkins, Thomas M., Tuck, Brian C.
• Primary Examiner(s): Butler, Douglas C.
• Application Number:
  US07/283,689
• Time in Patent Office: 273 Days
• Field of Search: 303/116, 303/110, 303/119, 303/61, 303/109, 303/97, 303/106, 303/100, 303/6.01, 303/9.62, 303/9.71, 303/10, 188/181 A, 188/349, 364/426.02, 180/197, 180/244
• US Class Current: 303/116.2
• CPC Class Codes: B60T 11/34 Pressure reducing or limiting valves for arrangements for adjusting wheel-braking force responsive to vehicle weight or load B60T8/1831
• CPC Class Codes: B60T 8/17616 Microprocessor-based systems
• CPC Class Codes: B60T 8/17636 Microprocessor-based systems
• CPC Class Codes: B60T 8/32 responsive to a speed condition, e.g. acceleration or deceleration using electrical circuitry or regulation means B60T8/17 ; B60T8/28 takes precedence; electric devices on electrically propelled vehicles indicating the wheel slip B60L3/10; measuring linear or angular speed per se G01P3/00
• CPC Class Codes: B60T 8/341 Systems characterised by their valves B60T8/36, B60T8/38 take precedence
• CPC Class Codes: B60T 8/344 Hydraulic systems
• CPC Class Codes: B60T 8/347 3 Channel systems B60T8/345 takes precedence
• CPC Class Codes: B60T 8/36 including a pilot valve responding to an electromagnetic force
• CPC Class Codes: B60T 8/363 in hydraulic systems B60T8/3655, B60T8/3675 and B60T8/369 take precedence
• CPC Class Codes: B60T 8/3635 switching between more than two connections, e.g. 3/2-valves B60T8/364, B60T8/3645 and B60T8/365 take precedence
• CPC Class Codes: B60T 8/3675 integrated in modulator units
• CPC Class Codes: B60T 8/4054 involving the delivery pressure control B60T8/4072 takes precedence
• CPC Class Codes: B60T 8/42 having expanding chambers for controlling pressure , i.e. closed systems
• CPC Class Codes: B60T 8/4291 having means to reduce or eliminate pedal kick-back
• CPC Class Codes: B60T 8/50 having means for controlling the rate at which pressure is reapplied to or released from the brake
• CPC Class Codes: B60T 8/5025 in hydraulic brake systems
• CPC Class Codes: B60T 8/94 on a fluid pressure regulator
• CPC Class Codes: Y10S 303/08 Antichatter
• CPC Class Codes: Y10S 303/11 Accumulator

Abstract

A vehicle braking system such as an anti-lock brake system and/or a traction control utilizes a separate solenoid-actuated, two position, three-way valve in each controlled channel of the brake system for controlling the application of pressure to the respective wheel brake circuit. The valve includes a first port connected to the controlled wheel brake(s), a second port connected to an outlet of a hydraulic pump, and a third port connected to the inlet of the hydraulic pump. The valve is only moveable between a first position wherein the outlet of the pump is connected to the wheel brake to increase pressure to the wheel brake, and a second position wherein the wheel brake is connected to the inlet of the pump to decrease pressure to the wheel brake. An electronic control is provided for operating the valve to control the application of pressure to the selected wheel brakes. The control cyclically moves the valve between the first and second positions during a predetermined time period to alternately increase and decrease pressure to the wheel brake. More specifically, the control generates a pulse-width-modulated signal to modulate the time periods during which the valve is maintained in either the first or second positions to control the effective pressure to the wheel brake to obtain a net increase, decrease, or constant pressure to the wheel brake during the predetermined time period.

Claims

1. A braking system for controlling a wheel brake of at least one wheel of a wheeled vehicle comprising:

a fluid pump having an inlet and an outlet;

a two position, three-way valve having a first port connected to the wheel brake, a second port connected to said outlet of said pump, and a third port connected to said inlet of said pump;

said valve only moveable between a first position wherein said first port is connected to said second port to increase pressure to the wheel brake, and a second position wherein said first port is connected to said third port to decrease pressure to the wheel brake;

control means for operating said valve to control the application of pressure to the wheel brake, said control means including means for cyclically moving said valve between said first and second positions during a predetermined time period to alternately increase and decrease pressure to the wheel brake, said control means operable to modulate the time periods during which said valve is maintained in said first and second positions to control the effective pressure to the wheel brake to obtain a net increase, decrease, or constant pressure to the wheel brake during said predetermined time period.

2. The braking system according to claim 1 wherein said three-way valve is solenoid-activated and said control means generates a pulse-width-modulated signal to operate said valve.

3. The braking system according to claim 2 wherein said pulse-width-modulated signal is generated at a frequency having a period less than said predetermined time period.

4. The braking system according to claim 3 wherein said frequency is 50 Hertz.

5. The braking system according to claim 1 wherein said braking system is an anti-lock braking system.

6. An anti-lock braking system for a wheeled vehicle having at least one wheel provided with a wheel brake, a brake pedal operable by the vehicle driver, and a master cylinder actuated by the brake pedal and having an outlet connected to supply pressurized brake fluid to actuate the wheel brake, said system comprising:

a fluid pump having an inlet and an outlet;

a two position, three-way valve having a first port connected to said wheel brake, a second port connected to both said outlet of said pump and the outlet of the master cylinder, and a third port connected to said inlet of said pump;

said valve only moveable between a first position wherein said first port is connected to said second port to increase pressure to the wheel brake and a second position wherein said first port is connected to said third port to decrease pressure to said wheel brake;

control means for operating said valve to control the application of pressure to said wheel brake, said control means including means for cyclically moving said valve between said first and second positions during a predetermined time period to alternately increase and decrease pressure to said wheel brake, said control means operable to modulate the time periods during which said valve is maintained in said first and second positions to control the effective pressure to said wheel brake to obtain a net increase, decrease, or constant pressure to said wheel brake during said predetermined time period to prevent lock-up of the associated wheel.

7. The anti-lock braking system according to claim 6 wherein said three-way valve is solenoid-activated and said control means generates a pulse-width-modulated signal to operate said valve.

8. The anti-lock braking system according to claim 6 including a solenoid actuated, normally open isolation valve connected between the outlet of the master cylinder and said second port of said valve.

9. The anti-lock braking system according to claim 8 including a reset switch connected to monitor the differential pressure between fluid at the output of the master cylinder and fluid supplied to said wheel brake.

10. The anti-lock braking system according to claim 8 including a check valve connected between the outlet of the master cylinder and said outlet of said pump for preventing fluid flow from the master cylinder to said outlet of said pump.

11. The anti-lock braking system according to claim 8 including a low pressure accumulator connected to said inlet of said pump.

12. The anti-lock braking system according to claim 11 including a high pressure accumulator connected to said outlet of said pump.

13. The anti-lock braking system according to claim 12 including a high pressure by-pass valve connected between said outlet and said inlet of said pump.

14. An anti-lock brake system for a wheeled vehicle having a pair of front wheel brakes and at least one pair of rear wheel brakes, a brake pedal operable by the vehicle driver, and a master cylinder actuated by the brake pedal for supplying pressurized brake fluid to actuate the front and rear wheel brakes, said system comprising:

a first anti-lock control circuit connected between the master cylinder and the front wheel brakes and including a pump for providing a supply of pressurized brake fluid, said first control circuit operable in an impending front lock-up condition to control the application of fluid pressure to the front wheel brakes by cyclically relieving and reapplying pressure to maintain the front wheels in a predetermined wheel slip range throughout the remainder of the stop; and

a second anti-lock pumpless control circuit connected between the master cylinder and the rear wheel brakes, said second control circuit operable in an impending rear lock-up condition to control the application of fluid pressure to the rear wheel brakes by selectively relieving pressure to correct the rear lock-up condition and to maintain the rear pressure at a relatively constant level throughout the remainder of the stop.