Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1993-11-24
1995-05-23
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303900, B60T 13138
Patent
active
054174848
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a hydraulic change-over valve having a prolonged closing time.
BACKGROUND OF THE INVENTION
In a brake system disclosed by German patent DE-38 31 426 A1, a brake line leads to a wheel brake of a driven wheel from a master brake cylinder through a hydraulically controlled three-way/two-position valve, which simultaneously serves as a change-over valve and as a cut-off valve, and through an electromagnetic inlet valve, open in its de-energized state. When an anti-lock control operation is performed, pressure fluid is discharged into a low-pressure accumulator through an electromagnetic outlet valve closed in its de-energized state. A return pump supplies the fluid out of this accumulator into the brake line between the hydraulic three-way/two-position directional control valve and the inlet valve again. For a traction slip control operation, the suction side of the pump is connected to the master cylinder through the third port of the three-way/two-position directional control valve so that it can take in fluid out of the pressure fluid reservoir via the master cylinder. When the brake is not applied, the connection is established from the master brake cylinder to the suction side of the pump, while the brake line is closed. As soon as pressure is built up by the master brake cylinder, the three-way/two-position directional control valve will assume its second switch position in which the connection is established from the master brake cylinder to the wheel brake.
Hydraulic change-over valves are advantageous in economizing electric lines. It is a disadvantage, however, that a certain fluid volume for switching is required on each brake application to change the valve over, which impairs the pedal feeling at the brake pedal, since the fluid volume intake takes place abruptly when the valve closes.
OBJECTS OF THE INVENTION
Therefore, it is an object of the present invention to provide a hydraulic change-over valve which avoids impairments during the pedal application.
It is another object of the present invention to provide for continuous intake of the fluid volume for switching by slowing the switching time so that the driver does not feel any effects on the brake pedal.
It is yet another object of the present invention to employ a diaphragm as an operating device that avoids "stick-slip effect" and that avoids abrupt start-up as is the case with a piston having a rubber seal and that permits variation of its effective surface, depending on the switching stroke.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other objects of the present invention will be explained in more detail by way of the specification with reference to the accompanying drawings, in which:
FIG. 1 is a representative cross-sectional view of a first embodiment of a change-over valve in accordance with the present invention;
FIG. 2 is a representative cross-sectional view of a second embodiment of a change-over valve in accordance with the present invention;
FIG. 3 is a representative cross-sectional view of a third embodiment of a change-over valve; and
FIG. 4 is a representative cross-sectional view of a fourth embodiment of a change-over valve in accordance with the present invention.
FIG. 5 is a block diagram of the brake system having the change-over valve of the present invention.
DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS
The change-over valve 1 illustrated in FIG. 1 is arranged in the housing 2 and is fixed by the screw member 3 which is screwed into the housing 2 in sealed relationship thereto. Instead of a screw coupling, a closure member can also be caulked or coupled by plug-in engagement. Further possibilities of fixation consist of attaching a circular clip, such as a lock ring, which will be referred to herein as a "circlip," to the housing. As a still further possibility, a self-clinching device may be used. In the latter possibility, a closure member would be chosen which is more rigid than the housing receiving it. When the closure member, screw 3, is
REFERENCES:
patent: 4919495 (1990-04-01), Kircher et al.
patent: 5007687 (1991-04-01), Kircher et al.
Beck Erhard
Reinartz Hans-Dieter
Risch Stefan
ITT Automotive Europe GmbH
Muratori Alfred
Oberleitner Robert J.
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