Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1999-04-07
2000-09-26
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303900, 303901, B60T 840
Patent
active
06123396&
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention relates to a slip-controlled brake system for a vehicle.
One such brake system is already known for the front axle of a vehicle (German Patent Disclosure DE 43 42 918 A1). The wheels of the rear axle are braked electromechanically. With this brake system, anti-lock operation is possible. The hydraulic portion of the brake system for the slip control is designed very simply; it makes do with one magnet valve and one pump per wheel brake. The brake system, which can be manufactured economically, is especially suitable for small vehicles with front wheel drive.
From European Patent Disclosure EP 0 253 157 A1, a slip-controlled vehicle brake system is known that aside from the shutoff valve is equivalent to the generic type in question here and also has a pump with a reversible direction of rotation. Instead of the shutoff valve, this brake system has a hydraulically or electrically switchable flow limiter. With 20 a brake system equipped in this way.
A vehicle brake system is also known (German Patent Disclosure DE 39 09 167 A1) in which a pump with reversible direction of rotation is disposed in the brake circuit of the driven vehicle wheels and can be connected to brake lines via 3/3-way valves in order to make anti-lock and traction control modes possible.
ADVANTAGES OF THE INVENTION
The vehicle brake system according to the invention as defined by the characteristics of the body of claim 1 has the advantage over the prior art that with the intended pump type, both anti-lock and traction control modes are possible with otherwise simple valve outfitting; that is, only one shutoff valve per wheel brake cylinder is necessary.
By means of the provisions recited in the dependent claims, advantageous refinements of and improvements to the vehicle brake system defined by claim 1 are possible.
With the design of the vehicle brake system defined by claim 2, on the one hand in the anti-lock mode a reduction in pulsation of the feed flow of the pump and on the other in the traction control mode an unthrottled aspiration of pressure fluid by the pump are obtained. In the anti-lock mode, noise abatement is attained, while in the traction control mode an improvement to control dynamics is attained.
These advantages are also attained, but at reduced expense, in the refinement of the vehicle brake system defined.
With the improvement disclosed herein, a reduction in the pulsation of the feed flow of the pump is also attained in the traction control mode, while in the anti-lock mode an unthrottled pressure reduction from the wheel brake cylinder is attained.
The provisions set forth avoid the development of negative pressure in the wheel brake cylinder while the pump is pumping in the anti-lock mode.
With the refinement of the vehicle brake system set forth, in the anti-lock mode upon pressure reduction in the wheel brake cylinder by closure of the only slightly spring-loaded or non-spring-loaded check valve, it is attained that the pressure retention valve acting to avert negative pressure in the wheel brake cylinder becomes operative. Conversely, in the traction control mode, only a slight pressure drop becomes operative at the check valve, which is advantageous.
The embodiment of the vehicle brake system defined by claim 7 makes it possible in a simple way to influence the speed of pressure buildup or reduction in the wheel brake cylinder.
BRIEF DESCRIPTION OF THE DRAWINGS
Two exemplary embodiments of the invention are shown in simplified form in the drawing and described in further detail in the ensuing description.
FIG. 1 shows a circuit diagram for a vehicle brake system including pumps with two flow directions, and
FIG. 2 shows a circuit diagram for a vehicle brake system that is simplified compared with FIG. 1.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
The first exemplary embodiment, shown in FIG. 1, of a slip-controlled vehicle brake system 10 has a dual-circuit master cylinder 13 that is actuatable with a brake pedal 11 via a brake booster 12 and that has a pressure fluid reservoi
REFERENCES:
patent: 4927213 (1990-05-01), Burgdore
patent: 5048899 (1991-09-01), Schmitt et al.
patent: 5529388 (1996-06-01), Yasui
Greigg Edwin E.
Greigg Ronald E.
Kramer Devon
Oberleitner Robert J.
Robert & Bosch GmbH
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