Fluid-pressure and analogous brake systems – Pulsation neutralizers
Reexamination Certificate
1998-10-19
2001-03-20
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Pulsation neutralizers
C303S119100, C303SDIG001, C138S031000
Reexamination Certificate
active
06203117
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates in general to electronically-controlled vehicular brake systems, and in particular is concerned with a compensator assembly mounted in a hydraulic control unit to accommodate travel of a master cylinder piston.
Electronically-controlled hydraulic brake systems for vehicles are well known. Such systems typically include a hydraulic control unit (HCU) hydraulically connected between a master cylinder and wheel brakes. The master cylinder generates hydraulic forces in the brake circuit by pressurizing brake fluid when the driver steps on the brake pedal. A piston in the master cylinder travels in response to the brake pedal. The pressurized fluid travels through the fluid conduit in the circuit to actuate brake cylinders at the wheel brakes and slow the vehicle.
The hydraulic control unit contains control valves and other components such as a pump. Through an electronic controller, the control valves and other components selectively control pressure to the wheel brake assemblies to provide a desired braking response of the vehicle, such as anti-lock braking, traction control, and vehicle stability control.
The master cylinder includes a piston having at least one annular seal. Preferably, this seal is formed as a one-way seal commonly known as a lip seal. During a braking event, this seal can rest adjacent a comp port of the master cylinder. Fluid from the comp port tends to flap the seal back and forth, which can result in deterioration of the seal and premature failure. Known braking systems can provide additional displacement of the master cylinder piston to move the seal away from the comp port, but such systems add extra pedal stroke to every braking event, i.e., normal (base) braking as well as anti-lock braking. Additional pedal stroke is generally not desired in many braking systems.
SUMMARY OF THE INVENTION
This invention relates to a compensator assembly mounted in a hydraulic control unit of electronically-controlled vehicular brake systems. The compensator assembly permits additional displacement of a master cylinder piston during electronically-activated braking events (such as anti-lock braking) only. The additional displacement moves a seal mounted on the master cylinder piston away from a comp port, thereby preventing repeated flapping of the seal which can cause premature seal failure. An advantage this compensator assembly is that additional pedal stroke is not present during normal base braking, since this compensator assembly has no effect during normal braking. The compensator assembly is mounted in a hydraulic control unit and can be used with many electronically-controlled brake systems.
In a preferred embodiment, a hydraulic control unit of an electronically-controlled vehicular brake system includes a housing having a bore. The bore is in fluid communication with a first fluid passage leading to an outlet of a pump. The bore is also in fluid communication with a second fluid passage leading to a master cylinder. A retainer cap is mounted in the bore. A piston is slidably received in the retainer cap. The piston includes a fluid channel providing fluid communication between the first and second fluid passages. A spring is positioned between the retainer cap and the piston to urge the piston from the retainer cap. A check valve assembly is mounted in the fluid channel of the piston that permits only one-way fluid flow from the first fluid passage to the second fluid passage. The compensator assembly provides a controlled amount of additional displacement of a master cylinder piston when the brake system is operating in an electronically activated mode only.
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.
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Sorenson Ronald L.
Starr Joseph A.
Kelsey-Hayes Corporation
King Bradley
MacMillan Sobanski & Todd LLC
Oberleitner Robert J.
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