Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1998-05-18
1999-12-28
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031164, 303DIG11, B60T 842
Patent
active
060071613
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an electronically controllable brake actuation system of the type as it is disclosed in German patent application No. 31 24 755. The pressure source of the prior art brake actuation system includes a pump, a hydraulic accumulator and a pressure fluid supply reservoir. The function of the separating valves and the inlet and outlet valves is performed by multi-position valves or four-way/four-position directional control valves having inlet ports that are connected to the pressure side of the pump or the accumulator, the pressure fluid supply reservoir and each one pressure chamber of the dual-circuit master brake cylinder. The wheel brakes are connected to the outlet ports. During independent braking or pressure increase, the four-way/four-position directional control valve is switched to its first operating position where the wheel brakes are separated from the master brake cylinder and connected to the pressure source. A phase where the pressure is maintained constant is achieved in a second operating position where the wheel brakes are isolated from the master brake cylinder and from the pressure source. Pressure decrease is effected in a third operating position where a connection is provided between the wheel brakes and the unpressurized pressure fluid supply reservoir.
Apart from the comparatively high costs incurred by the use of the sophisticated pressure source, the meterability of braking pressure in the prior art brake actuation system is a disadvantage, especially in the low-pressure range, which is due to the use of the four-way/four-position directional control valves.
Therefore, an object of the present invention is to improve upon an electronically controllable brake actuation system of the above-mentioned type to such effect as to virtually eliminate the shortcomings mentioned with respect to ABS control. More particularly, the objective is to considerably improve the meterability of braking pressure in the low-pressure range and to additionally reduce the total effort and structure.
SUMMARY OF THE INVENTION
According to the present invention, this object is achieved because the pressure source is configured as at least one continuously adjustable piston-and-cylinder assembly having a pressure chamber to which the wheel brakes are connected by the intermediary of the inlet valves. It is achieved by these provisions that normal braking operations are carried out similarly by way of the piston-and-cylinder assembly, and an increase in the speed of braking pressure reduction can be achieved by an operation of the separating valves.
The present invention will be explained in detail in the following description of an embodiment, making reference to the accompanying drawing.
BRIEF DESCRIPTION OF THE DRAWING
In the drawing, the only FIGURE shows a simplified wiring diagram of the brake actuation system of the present invention.
The electronically controllable brake actuation system of the present invention shown in the drawing is intended for use in a front-wheel driven vehicle. The system includes a dual-circuit master brake cylinder or tandem master cylinder 2 operable by an actuating pedal 1. The tandem master cylinder 2 has pressure chambers 5, 6 separated from each other, confined by two pistons 3, 4 and being in connection to an unpressurized pressure fluid supply reservoir 53. The first pressure chamber (primary pressure chamber) 5 is connected to a hydraulic wheel brake 7 associated with the driven front axle of the vehicle by way of a closable first hydraulic line 11. On the other hand, wheel brake 7 is connected to a first one-circuit piston-and-cylinder assembly 20 by way of an electromagnetically operable, preferably normally closed (NC) inlet valve 12. A first low-pressure accumulator 23 is connected to a second line portion 21 between the first piston-and-cylinder assembly 20 and the wheel brake 7, wherein a first non-return valve 22 that opens towards the piston-and-cylinder assembly 20 and an electromagnetically op
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ITT Manufacturing Enterprises Inc.
Oberleitner Robert J.
Williams Thomas J.
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