Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1998-12-02
2001-04-17
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S119100, C303SDIG003
Reexamination Certificate
active
06217132
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to an improved hydraulic brake system for use in a vehicle, and in particular to an anti-lock braking system.
Vehicle braking systems generally include a driver operated brake pedal which is connected to a master cylinder. The master cylinder is in fluid communication with brakes at associated wheels of the vehicle. Operation of the brake pedal generates pressure within the master cylinder which is supplied to the brakes, thereby decelerating the vehicle or preventing the vehicle from moving from a stopped position. A booster may also be provided between the brake pedal and the master cylinder to assist the pedal effort by the driver of the vehicle.
Typical anti-lock braking systems (ABS systems) further include a separate hydraulic control unit (HCU) in fluid communication between the master cylinder and selected brakes. The HCU incorporates a plurality of solenoid operated valves to selectively control the application of hydraulic fluid pressure to the selected brakes to prevent locking of the associated wheels. Generally, the valves cyclically relieve and reapply pressure to the associated brakes to limit wheel slippage to a safe level while continuing to produce adequate brake torque to decelerate the vehicle as desired by the driver.
ABS systems can be configured to independently control the application of fluid to all four brakes associated with a four wheeled vehicle. Alternatively, an ABS system can be configured to control the application of fluid to the brakes associated with the rear wheels of the vehicle, such as the ABS system disclosed in U.S. Pat. No. 4,828,335 to Fuller et al.
Typically, the HCU of an ABS system includes a fluid accumulator for the storage of fluid which is diverted from the wheel brakes during an ABS function. A conventional accumulator includes a variable volume fluid reservoir which is maintained at a slightly elevated pressure by a slidable piston disposed therein. The accumulator includes a spring which biases the piston. Fluid enters the reservoir of the accumulator causing the piston to move against the biasing of the spring, thereby increasing the size of the reservoir to store fluid. If one or more of the solenoid valves for selectively controlling the application of pressure to the brakes is faulty such that fluid leaks therethrough, the accumulator will generally fill up, thereby preventing further loss of fluid from the controlled brake circuit. Due to the size of the accumulator and the solenoid valves, the HCU is generally located remotely from the master cylinder and is in fluid communication therewith by a series of brake fluid conduits and connections. However, the accumulator adds weight and cost to the brake system.
BRIEF SUMMARY OF THE INVENTION
This invention relates in general to an improved brake system for use in vehicles, and in particular to an anti-lock brake system. The vehicle brake system generally includes a wheel brake, a master cylinder, a reservoir, an isolation valve, a dump valve, and a cut-off valve which are preferably disposed in a single housing. The master cylinder is operable to provide pressurized fluid to the wheel brake by actuation of a brake pedal operatively connected to the master cylinder. The master cylinder includes a housing having a bore formed therein, and further including a piston slidably disposed in the bore. The fluid reservoir is in selective fluid communication with the bore of the master cylinder which defines a fluid chamber. The isolation valve is movable between an open position, wherein fluid is permitted to flow between the master cylinder and the wheel brake, and a closed position, wherein fluid is restricted from flowing between the master cylinder and the wheel brake. The dump valve is movable between a closed position, wherein fluid is prevented from flowing between the wheel brake and the reservoir, and an open position, wherein fluid is permitted to flow between the wheel brake and the reservoir. The a cut-off valve is movable between an open position, wherein fluid is permitted to flow between the dump valve and the reservoir, and a closed position, wherein fluid is restricted from flowing between the dump valve and the reservoir.
In a specific embodiment of the invention, the piston of the master cylinder includes a ramped surface defined by a frustoconical portion formed about the piston. The ramped surface cooperates with a contact member of the cut-off valve to engage and disengage a valve member against a valve seat caused by the movement of the piston of the master cylinder.
Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings.
REFERENCES:
patent: 3827242 (1974-08-01), Belart
patent: 3980345 (1976-09-01), Doerfler
patent: 4440454 (1984-04-01), Belart et al.
patent: 4603918 (1986-08-01), Leiber et al.
patent: 4828333 (1989-05-01), Reinartz et al.
patent: 4828335 (1989-05-01), Fuller et al.
patent: 5000525 (1991-03-01), Reinartz et al.
patent: 5332303 (1994-07-01), Wupper
patent: 5390987 (1995-02-01), Willi et al.
Avenel Serge G.
Gualdoni Glenn R.
Hool Patrick H.
Lubischer Frank P.
Sternal Norbert
Butler Douglas C.
Kelsey-Hayes Company
MacMillan Sobanski & Todd LLC
LandOfFree
Hydraulic control unit having a master cylinder and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Hydraulic control unit having a master cylinder and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Hydraulic control unit having a master cylinder and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2500345