Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-05-04
2001-06-19
Schwartz, Christopher P. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
Reexamination Certificate
active
06247766
ABSTRACT:
TECHNICAL FIELD
This invention relates to brake control systems in wheeled vehicles and more particularly to brake control systems having a valve mechanism for establishing the maximum system pressure during self-apply operation.
BACKGROUND OF THE INVENTION
In many currently produced automotive vehicles, the brake systems are both manually applied, with power assist, and self applied during anti-lock operation and in some vehicles during traction control of the driving wheels. During manual brake application, the operator depresses the brake pedal to determine the amount of braking pressure that will develop in the system at the braking wheels. During self-apply braking, the system pressure is established by a system regulator valve.
The regulator valve sets the maximum system pressure at a fixed value regardless of the system requirements. The excess fluid flow is exhausted through the regulator valve resulting in noise and vibration from the hydraulic system which is discernable by the operator. While this occurrence is not detrimental to the braking system or the vehicle, it can be disconcerting to the operator when it occurs unexpectedly.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide an improved brake control system having an isolation valve for establishing the maximum system pressure during self-apply operation.
In one aspect of the present invention, a brake control system has a manually operable master cylinder to supply fluid to establish normal braking and a positive displacement hydraulic pump to supply fluid during self-apply braking. In another aspect of the present invention, an isolation valve is disposed in fluid flow relation between the output of the master cylinder and the output of the pump to control the pressure output of the pump during self-apply operation. In yet another aspect of the present invention, the isolation valve is a normally open valve to permit the master cylinder to supply fluid to all of the vehicle brakes during normal brake operation.
In still another aspect of the present invention, the isolation valve controls the pump output to at least some of the vehicle brakes during a self-apply traction control operation. In yet still another aspect of the present invention, the isolation valve has a damping chamber comprised of a cylindrical body, a annular restriction and an annular chamber.
In a further aspect of the present invention, the isolation valve has a body with a stepped diameter bore with long central small diameter portion and a short large diameter portion and a valve spool having a long rod portion disposed in the central small diameter, a land portion slidably disposed in the large diameter and a valve member cooperating with a valve seat. In yet a further aspect of the present invention, the land portion and the large diameter portion cooperate to provide the annular restriction.
REFERENCES:
patent: 5246280 (1993-09-01), Sigl
patent: 5588718 (1996-12-01), Winner et al.
patent: 5645325 (1997-07-01), Mueller et al.
patent: 5649748 (1997-07-01), Oehler et al.
patent: 5669675 (1997-09-01), Mueller et al.
patent: 5879060 (1999-03-01), Megerle et al.
Cornwell William Dale
Lloyd Earl Wayne
Patel Sanjay Manilal
Reuter David Fredrick
Subramanian Viswanathan
Delphi Technologies Inc.
Dobrowitsky Margaret A.
Schwartz Christopher P.
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