Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1990-03-28
1992-03-17
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303114PN, 303119R, 60568, b60t 844
Patent
active
050962680
DESCRIPTION:
BRIEF SUMMARY
A brake system is described in German published patent application 33 17 629, the master brake cylinder of which is force-applied by a pedal-actuated booster. This booster comprises a valve which, in dependence upon the pedal force, develops an amount of pressure in the booster which loads the master brake cylinder in addition to the pedal force. Under the effect of the introduced pressure, a wall in the booster moves towards the master brake cylinder and thereby causes a decrease of the working chambers of the master brake cylinder. Further, the above published patent application describes the possibility of realising brake slip control, that means of avoiding locking of the wheels by reducing the pressure in the wheel brakes. This is effected in that a counterpressure is built up in the booster which results in unloading the master brake cylinder because it acts upon the wall in opposition to the pedal force. Valves are inserted into the brake lines which are open only when the pressure is to be reduced in the associated wheel brake cylinders. When the pressure has been reduced, the wheel can re-accelerate so that renewed braking pressure build-up becomes necessary after a while. To this end, the counterforce is `withdrawn` from the booster, i.e. reduced, so that renewed build-up of pressure takes place in the master cylinder which is supplied further to the wheel brakes. Previously, the wheels had been able to sufficiently re-accelerate, and now they have to slow down again. The wall of the booster is constantly moving to and fro during a like control action and entrains the control valve. Since the pedal is coupled directly with the valve in previously known designs, the pedal performs a movement to and fro during the brake slip control action. This may even be desirable to a certain degree, since thus there is the possibility of informing the driver that a brake slip control action is performed. However, it has shown that these movements are too vigorous under certain circumstances and are felt as disturbing by the driver. From this derives the object to devise the coupling between the actuator, which actuates the master brake cylinder, and the pedal in such a fashion that the movements of the booster wall (of the actuator) are not transmitted onto the brake pedal. Moreover, the possibility must be afforded that the driver can influence the pressure in the wheel brakes by reducing the pedal force. This object is achieved by virtue of a hydraulic coupling as is described in claim 1.
The design becomes particularly simple when the pistons are guided in one common housing bore.
In a favourable manner, the pedal piston has a portion of smaller cross-section which extends through a wall in a sealed relationship thereto and which can be accommodated in an axial bore of the compensating piston for the purpose of guiding.
The wall isolates two chambers from each other which are interconnected for the hydraulic coupling. The chambers are filled with incompressible liquid so that, caused by the movement of the pedal piston, pressure fluid is displaced out of the blocking chamber into the compensating chamber and urges the actuator piston to advance.
For decoupling the pedal piston and the actuator piston, the blocking chamber is shut off hydraulically so that the pedal piston is no more actuatable in the actuating direction, and the compensating chamber is connected to a receiving chamber so that the actuator piston is freely movable.
The said receiving chamber can be a simple open supply reservoir, or a closed accumulator having a piston which is movable in opposition to a spring. The spring force generates a pressure in the accumulator which acts upon the actuator instead of the pedal force.
To this end, the accumulator piston is biassed by a spring against stops so that the spring force does not convert into a hydraulic pressure at first. When now pressure fluid is pressed out of the compensating chamber into the accumulator, the piston lifts from its stops, and the spring generates a pressure in the accumul
REFERENCES:
patent: 4702531 (1987-10-01), Kircher et al.
patent: 4703978 (1987-11-01), Belart et al.
patent: 4750789 (1988-06-01), Belart et al.
patent: 4815793 (1989-03-01), Reinartz et al.
Beilfuss Hans-Juergen
Jakobi Ralf
Luetteke Harald
Rueffer Manfred
Schiel Lothar
Alfred Teves GmbH
Ballato Josie A.
Lewis J. Gordon
Oberleitner Robert J.
Seitter Robert P.
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