Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-04-29
1994-03-29
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031154, 3031131, 303901, B60T 848, B60T 832
Patent
active
052978621
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
A brake system of the type with which the present invention is concerned is described in German Patent application No. P 40 00 837.1 and copending U.S. patent application Ser. No. 07/638,927, filed on Jan. 9, 1991. The pump is located in the brake conduit connecting the master cylinder and wheel cylinder and separated from the master cylinder upon commencement of a slip control operation. The separation is performed by an electromagnetically actuated separating valve.
If the separating valve were not activated, this would result in the master brake cylinder being evacuated during a control operation. Switching of the separating valve hence, is thus absolutely necessary prior to a control operation. Accordingly, it is readily apparent that the switch-over operation of the separating valve must be monitored.
It is, therefore an object of the invention to provide an improved brake system of this type in which the need for an electromagnetically actuated separating valve is eliminated while insuring a reliably operating system.
SUMMARY OF THE INVENTION
This object is achieved by providing a switch over valve operated by development of a predetermined master cylinder pressure to block flow from the master cylinder to the pump chamber. A pressure opened valve is in a secondary conduit bypassing the pump, which valve opens at a lesser pressure than that necessary to operate the switch over valve.
By arrangement, the pump is scavenged only upon commencement of a braking operation, which is adequate to avoid the formation of air bubbles within the pump. Once a predetermined pressure level, for example 5 bar, has been reached, the brake conduit is closed and the further supply of brake fluid to the wheel brakes takes place through the secondary conduit by opening of the pressure operated valve.
During an antislip control process, the pump, through a separate intake nozzle, will take in pressure fluid from a reservoir.
DESCRIPTION OF THE DRAWING
The FIGURE is a schematic diagram of a hydraulic brake system according to the present invention.
DETAILED DESCRIPTION
The principle of the invention will now be described in greater detail with reference to one embodiment shown in the FIGURE. The brake system comprises a master cylinder 1, to which are connected, through a brake conduit 2, one or more wheel brakes 3, each including a wheel cylinder. A pump 4, described hereinafter in greater detail, is installed in series in the brake conduit 2, with a connection A, through a first brake conduit section 5, being in fluid communication with the master brake cylinder 1. The pressure side D thereof, through a second brake conduit section 6, is in fluid communication with the cylinder of the wheel brake 3.
The second brake conduit section 6 has installed therein an inlet valve 7, which is electromagnetically actuated. In a basic position thereof, inlet valve 7 keeps open the conduit 6, and in a switching position, it blocks the conduit 6.
The cylinder of the wheel brake 3, through a return conduit 9, is in fluid communication with a pressure fluid collector, with an electromagnetically operated outlet valve 8 installed in the return conduit 9. Outlet valve 8 in a basic condition thereof, blocks the return conduit 9 and, in a switching position thereof opens the return conduit 9.
A pressure fluid reservoir 25 and master brake cylinder 1 are in pressure fluid communication whenever the pedal is not depressed. The reservoir 25, through a suction valve 22, is also in communication with the pump chamber 21.
The wheel brake cylinder, through a direct conduit 13, is in direct communication with the master brake cylinder 1. The direct conduit 13 is provided with a check valve 14, opening toward the master brake cylinder 1.
The pump 4 according to the embodiment shown in the FIGURE, is in the form of a piston pump, the piston 19 of which is actuated through a motor-driven eccentric 20. The pump chamber 21, defined forward of the pump piston 19, through respective check valves 22 and 23, with the inta
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patent: 5002345 (1991-03-01), Becker
patent: 5058961 (1991-10-01), Mergenthaler et al.
Reinartz Hans D.
Steffes Helmut
Alfred Teves GmbH
Lewis J. Gordon
Oberleitner Robert J.
Poon Peter M.
Seitter Robert P.
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