Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-07-08
1994-07-26
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031192, 60582, 60589, B60T 844, B60T 1314
Patent
active
053323025
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is related to a brake pressure control device for a hydraulic vehicle brake unit with a valve arrangement being actuatable by a brake pedal by means of which a hydraulic fluid outlet for the connection of a brake circuit is connectible alternately either to a reservoir or to a pressure source.
An example of brake pressure control device of this type is shown in U.S. Pat. No. 4,705,324. Such brake pressure control devices supply pressurized hydraulic fluid from a pressure source, such as a pump or pressure accumulator in a controlled manner to one or more brake circuits, depending on an actuating force exerted on a brake pedal in order to generate a braking effect at the brakes of a vehicle which is proportional to the actuating force. Brake pressure control devices of this kind are frequently employed in brake units which are equipped with a brake slip control by which the locking of the vehicle wheels during a braking action is prevented. In the prior-art brake pressure control devices, solenoid valves are provided for achieving a brake slip control which are actuated by an electronic anti-locking device in order to separate the brake circuit from the hydraulic fluid outlet and to connect it to the reservoir and in this way to attain a pressure reduction in the brake circuit. By switching the solenoid valves back into the starting position, the brake circuit is connected again to the hydraulic fluid outlet of the brake pressure control valve for a pressure build-up.
It is the object of the present invention to create a brake pressure control device of the type described which affords a control of the brake pressure by an electronic control device without the necessity of additional solenoid valves.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved in that, independently of the actuating position of the brake pedal, a low and high pressure combination valve is operable by an electromagnetic actuator shifting a valve piston into a position in which the hydraulic fluid connection is connected to the reservoir. In the inventive brake pressure control device, the pressure reduction in the brake circuit is attained by an actuation of the valve combination notwithstanding the brake pedal position, and being brought about by energization of an electromagnet controlled by an electronic brake slip control. No additional control valve is therefore required. This affords a considerable simplification and reduction of the manufacturing cost of the brake unit. Moreover, the safety of the unit is increased since an additional valve sealing point in the brake circuit is eliminated.
In the preferred embodiment of the invention, it is envisaged that between the valve combination and the brake pedal a spring is positioned for the normal transmission of a brake pedal actuating force, but the spring is compressible by the electromagnetic actuator to reverse the operation of the valve combination despite the continued exertion of the brake pedal actuating force. This arrangement simplifies the brake pressure control system because in case of an electromagnetic actuation of the valve arrangement, the force of the brake pedal applied to the valve combination need not be interrupted.
According to the invention, the brake pedal is connected to an actuating piston which projects out of the housing of the brake pressure control device and which contains in a bore formed therein, a valve piston drivingly engaged by the actuating piston through an interposed compression spring so as to be movable with the actuation piston. The actuating piston is surrounded by an electromagnet by which the valve piston is movable in a reverse direction, compressing the spring. The actuating piston also provides an alternate means for creating a hydraulic pressure in addition to the actuation of the valve combination, by which means an emergency actuation of the brake circuit in the event of a failure of the fluid pressure supply is possible.
This feature is provided in that the a
REFERENCES:
patent: 3473850 (1969-10-01), Lawrie
patent: 4489555 (1984-12-01), Leiber
patent: 4620750 (1986-11-01), Leiber
patent: 4705324 (1987-11-01), Kervagoret
patent: 4793660 (1988-12-01), Becker et al.
patent: 5172964 (1992-12-01), Levrai et al.
Alfred Teves GmbH
Ballato Josie A.
Lewis J. Gordon
Oberleitner Robert J.
Seitter Robert P.
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