Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1991-06-12
1993-05-25
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031162, 3031191, 303901, B60T 832, B60T 848, B60T 842
Patent
active
052133990
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an anti-lock hydraulic brake system.
BACKGROUND OF THE INVENTION
A like brake system is described in DE-OS 36 03 533. The separating valve is operated hydraulically, a first surface of the valve member being loaded by the pressure in the accumulator, while a second surface of the valve member is acted upon by the pressure in the wheel brake. A weak resetting spring keeps the valve in abutment on a stop, the valve passage being open.
During a braking pressure control action, the pump delivers fluid into the high-pressure accumulator, the pressure of which accumulator moves the valve member in opposition to the effect of the weak spring to bear against a valve seat, whereby the brake line is closed. After a pressure control action, the accumulator pressure is reduced so that the valve member will be reset by the action of the weak spring.
The separating valve serves to accomplish hydraulic isolation of the master cylinder during a control action, thereby preventing the brake pedal from being depressed any further, not even when increased pedal force is applied. Furthermore, no pressure fluctuations due to control may occur in the master brake cylinder which would cause vibrating of the pedal. However, for obtaining such a "quiet" pedal one has to put up with the shortcoming that there is the risk that the separating valve will not switch over after a braking pressure control action and that the brake line remains closed as a result. The consequence of this would be that the vehicle can no longer be slowed down sufficiently. Yet the resetting spring in the brake system according to the cited publication cannot be strengthened to any desired extent, because then it be assured that the separating valve will close during a control action.
SUMMARY OF THE INVENTION
Therefore, the present invention is directed to the object of improving a brake system according to the cited publication such as to ensure reliable re-opening of the separating valve after a control action.
This object is achieved by the separating valve being opened mechanically by the accumulator piston which is applied by a strong biassed spring. The great spring force ensures in any case that even in the event of impeded motion of the accumulator piston the latter will always re-assume its initial position after a control action, whereby the separating valve will be opened reliably. Hereinbelow, the present invention shall be explained in more detail by way of two embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 illustrates a first embodiment of an anti-lock hydraulic brake system constructed in accordance with the present invention.
FIG. 2 illustrates a second embodiment of an anti-lock hydraulic brake system constructed in accordance with the present invention.
DETAILED DESCRIPTION OF THE INVENTION
Referring to the drawings, a brake system, constructed in accordance with the present invention, is composed of a tandem master brake cylinder 1 with two working chambers 2 and 3 which are isolated from each other by means of a floating piston. The working chambers 2 and 3 are pressurized by operation of the symbolically illustrated pedal. Allocated to each working chamber 2 and 3 is a brake circuit I, II, brake circuit I comprising the wheel brakes of the front wheels 4, 5 (VL for the front left wheel and VR for the front right wheel) and brake circuit II comprising the wheel brakes 6, 7 of the rear wheels (HL for the rear left wheel and HR for the rear right wheel). Wheel brakes 4, 5 are in communication with the working chamber 3 via a branching brake line 8 (branch lines 8', 8''). Wheel brakes 6, 7 are in communication with the working chamber 2 via a branching brake line 9 (branch lines 9', 9''). Inserted into each branch line 8', 8'' is an electromagnetic inlet valve 11 which is open in its initial position. Another inlet valve 11 is interposed into the brake line 9. Associated with each brake circuit is a low-pressure accumulator 13 which is in communication with the wheel brakes
REFERENCES:
patent: 3532391 (1970-10-01), Klein
patent: 4453782 (1984-06-01), Arikawa et al.
patent: 4618189 (1986-10-01), Nakanishi et al.
patent: 4703979 (1987-11-01), Nakanishi et al.
patent: 5094511 (1992-03-01), Becker et al.
Burgdorf Jochen
Haselwanter Eugen
Butler Douglas C.
Lewis J. Gordon
Seitter Robert P.
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