Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1991-12-10
1994-09-27
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303900, B60T 1318
Patent
active
053502264
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an anti-lock hydraulic brake system using a throttling valve which normally is open but which restricts flow to the brake line upon initiation of antilock control.
A like brake system is known from U.S. patent specification 3,829,166.
Herein an electromagnetically actuated valve operated by means of a control electronics is provided as a throttle valve. The valve is open in its initial position and releases the brake line. In the energized position, the cross-section of the brake line will be restricted so that the pressure fluid flow is throttled.
GB 21 01 245 A describes a brake system of the same type wherein the throttle valve is operated hydraulically. The pressure in the pressure fluid collecting means acts as switching pressure, the collecting means being designed as a low-pressure accumulator in this system.
It is the shortcoming of the brake system disclosed in the above U.S. patent that the electronic unit necessitates an expensive solenoid valve and additional drive modules.
The brake system according to the GB application inheres the disadvantage that the hydraulic valve is operated with delay only. Hence it is not safeguarded that rapid pressure reduction may take place.
The present invention has for its object to provide an anti-lock hydraulic brake system which is furnished with only a small number of electromagnetically actuated valves and which, in addition, safeguards a rapid pressure reduction.
SUMMARY OF THE INVENTION
This object is achieved by the means associated with the throttle valve to cause a switching to the restricted flow condition in response to development of a pressure increase in the wheel brake.
This feature effects that the pressure at the outlet of the pump switches the throttle valve over, the master brake cylinder being closed vis-a-vis the control line through a non-return valve.
To be able in case of need to quickly decrease the pressure in the wheel brake irrespective of throttling by the throttle valve, a non-return valve is connected in parallel to the throttle valve and opens towards the master cylinder. When the pressure in the master cylinder is decreased, the pressure reduction is supplied further to the wheel brake via the non-return valve past the throttle valve.
In a simple manner, the inventive idea can be combined with a so-called open loop brake system. `Open` brake system implies that the pressure-fluid collecting means is a supply reservoir which is open to the atmosphere and which communicates with the working chamber of the master brake cylinder in the master brake cylinder's non-actuated condition.
A permanent coupling between the pump piston and its eccentric permits pressure fluid to be supplied instantaneously upon the commencement of a brake slip control operation, without the need to first exhaust pressure fluid from a wheel brake.
Furthermore, the present invention can be extended easily so as to be able to also limit traction slip by virtue of the proposed brake system. To this end, the brake lines must be closable so that the pressure fluid supplied by the pumps during a traction slip control operation cannot escape via the master brake cylinder.
In a dual-circuit brake system, wherein in one circuit both the brakes of driven and non-driven wheels are comprised, the branch line of the brake line leading to the driven wheels must branch off upstream of the closing valve.
It is particularly expedient to provide for a switching member comprising an actuating rod on which a first separating piston is designed. The latter separates the housing into two chambers, with a pressure in the switching chamber switching the throttle valve into a second switch position, while a pressure in the resetting chamber causes the throttle valve to assume the first switch position.
In the event that the resetting chamber communicates with the wheel brake in an unthrottled fashion and the switching chamber connects to the wheel brake via a throttle, the following effect will result:
When the pressure
REFERENCES:
patent: 3767271 (1973-10-01), Grosseau
patent: 3829166 (1974-08-01), von Loewis et al.
patent: 3837712 (1974-09-01), Grosseau
patent: 4099793 (1978-07-01), Iio
patent: 4919495 (1990-04-01), Kircher et al.
patent: 5002344 (1991-03-01), Hashida
patent: 5002345 (1991-03-01), Becker
patent: 5176432 (1993-01-01), Burgdorf et al.
Beck Erhard
Bleckmann Hans-Wilhelm
Burgdorf Jochen
Dinkel Dieter
Fennel Helmut
Alfred Teves GmbH
Lewis J. Gordon
Muratori Alfred
Oberleitner Robert J.
Seitter Robert P.
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