Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1998-11-09
2001-02-20
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C137S509000
Reexamination Certificate
active
06189984
ABSTRACT:
PRIOR ART
The invention relates to a hydraulically actuated cutoff valve and a hydraulic brake system for a vehicle, which can be equipped with such a cutoff valve.
One such valve is known from European Patent Disclosure EP 0 606 840 B1. The known valve has a valve housing with a partition on which a valve seat is formed. Disposed on one side of the partition is a piston as an actuating element, which is pressed by a valve opening spring in the direction of the partition and can be displaced away from the partition by imposition of pressure. Located on the other side of the partition is a valve ball acting as a valve closing body, which is lifted from the valve seat by the piston and is pressed in the direction of the valve seat by a valve closing spring which is weaker than the valve opening spring. The known valve is open in its basic position and is closed by imposition of a pressure that is above a closing pressure.
The known valve has the disadvantage of being expensive to produce. In particular, the valve housing has to be machined on both sides of the valve seat. It is large, and it requires two springs, which must be tuned to one another to established desired switching pressures. Using two springs operating contrary to one another presents a high risk that the switching pressures will vary over the course of valve use.
This valve is a component of a hydraulic vehicle brake system which is arranged to limit drive slip by automatically braking driven wheels and to that end has at least one self-aspirating feed pump, which is supplied with brake fluid through the open valve and through a master cylinder from its supply container. The hydraulic vehicle brake system also includes a pressure buildup valve and pressure reduction valve assemblies connected to wheel brake cylinders, by means of the assemblies, for instance in the traction control mode, brake fluid fed by the feed pump to generate brake pressure can be carried to at least one wheel brake cylinder.
ADVANTAGES OF THE INVENTION
The cutoff valve of the invention has only three moving parts, namely the valve closing body, the actuating element, and a rocker element, which transmits a motion of the actuating element to the valve closing body. These parts are simple in geometry and can therefore be produced inexpensively. They can be accommodated in a cylindrical bore, which can have a cone on an annular shoulder acting as its valve seat. The cutoff valve of the invention can be produced economically at little effort, is maintenance-free, and suffers only slight wear, so that it has a long useful life.
The cutoff valve of the invention is intended in particular for use as an intake valve for a hydraulic vehicle brake system that has a pump, that is, as an example for a vehicle brake system with antilock, traction control, or driving dynamics control and/or an external force vehicle brake system. The cutoff valve is disposed between a master cylinder and an intake side of the pump; it is preferably open in its basic position, and it has a large flow cross section, so that when the master cylinder is not actuated and the pump is not on, it will throttle a stream of brake fluid aspirated from a supply container through the master cylinder as little as possible, thereby assuring a rapid pressure buildup. The pressure buildup upon actuation of the master cylinder closes the cutoff valve, so that the intake side of the pump is hydraulically disconnected from the master cylinder, and brake fluid can flow unhindered out of the wheel brake cylinders through a brake pressure reduction valve during an anti-lock control mode or the like.
A hydraulic vehicle brake system of the above generic type, offers the advantage that in automatic braking, two open valve cross sections in a parallel circuit are available between the master cylinder and an inlet of a feed pump, so that the self-aspirating feed pump can become well filled and accordingly is capable of pumping well.
The definite characteristics set forth result in an exemplary embodiment in which one of the intake valves is electrically controllable and accordingly makes the hydraulic vehicle brake system capable of driving dynamics control operation and/or external force braking operation when the brake pedal is actuated.
The definitive characteristics set forth herein result in an exemplary embodiment that in the traction control mode, by automatic braking, by means of the hydraulically controllable intake valve, furnishes a large valve cross section in an economical and space-saving way.
The definitive characteristics found herein result in an exemplary embodiment that is more advantageous for driving dynamics control operation and/or external force braking operation.
REFERENCES:
patent: 3880476 (1975-04-01), Belart et al.
patent: 5026126 (1991-06-01), Umasankar et al.
patent: 5906219 (1999-05-01), Lavery
patent: 320485 (1957-05-01), None
patent: 762028 (1996-09-01), None
Alaze Norbert
Hohl Guenther
Hummel Rolf
Maier Martin
Michl Thomas
Greigg Edwin E.
Greigg Ronald E.
Kramer Devon
Oberleitner Robert J.
Robert & Bosch GmbH
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