Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-10-15
1999-07-06
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
188276, B60T 842
Patent
active
059189495
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a brake system according to the preamble of claim 1.
European patent application No. 0 460 408 discloses a brake system of this type, for example. The charging pump disclosed therein has a very high pilot pressure. Therefore, the publication discloses an additional charging valve which is switched to its open position only if the control valve device is switched to pressure increase.
An additional valve of this type not only renders the system more expensive but also causes additional noises during operation of the system caused by switching of the valve.
Therefore, an object of the present invention is to simplify a system by reducing the number and complexity of the valves to thereby minimize switching noise during operation of the system.
SUMMARY OF THE INVENTION
To this end, the present invention discloses designing the charging pump so that it generates a pilot pressure which is only slightly in excess of the prestress condition of the low-pressure accumulator in the low-pressure range of the brake system.
The advantage is an almost constant operation of the pump in a control phase, i.e. in phases of controlled pressure increase and controlled pressure decrease in the wheel brakes. At most, it may be necessary to provide a safety device which prevents the low-pressure accumulator from being entirely filled by the charging pump.
However, the need for such a device may be obviated when operation of the system is appropriately adapted.
A joint drive of the return pump and charging pump can be provided because the charging pump and the return pump shall be operated together. It has been found that hydrodynamic pumps, for example rotary pumps, are appropriate as charging pumps. The advantage of hydrodynamic pumps is that the pressure at the pump outlet rises if no pressure fluid is removed.
For example, pressure fluid is not discharged when the return pump performs a delivery stroke. The suction valve is closed then, and pressure fluid can develop at the pressure side of the charging pump, with the result that the suction valve is opened early during the suction stroke of the delivery pump. Simultaneously, the starting pressure decline causes increase of the rate of flow of the rotary pump, so that a major charging effect is achieved. Thus, a rotary pump would be optimally adapted to requirements. A corresponding characteristic curve for a reciprocating pump is difficult to achieve.
A further advantage of a rotary pump is that there is no need for an additional pressure relief valve which exactly adjusts the charging pressure.
A pressure relief valve can be provided in case that a hydrostatic pump, e.g., a piston pump, is intended to be used as a charging pump. Advantageously, the opening pressure of the pressure relief valve is temperature-responsive. More particularly, the opening pressure is desired to increase at low temperatures, e.g., at temperatures below -10/C.
The present invention will be explained in detail by way of five Figures.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings,
FIGS. 1 to 3 are views of various wiring diagrams.
FIG. 4 is a view of a pressure accumulator connected downstream of a charging pump.
FIG. 5 is a cross-sectional view of a valve controlled by a low-pressure accumulator.
DETAILED DESCRIPTION OF THE DRAWINGS
FIGS. 1 to 3 show hydraulic brake systems wherein pressure can be produced in the wheel brakes by pedal application or independently of pedal application.
The basic structure of the brake system includes a master cylinder 1 which is operated by a pedal 2.
Normally, the master cylinder 1 has two working chambers 3, 4 to which wheel brakes 7, 8, 9, 10 are connected by way of brake lines 5, 6. Application of the pedal causes pressure fluid from the working chambers 31 4 to hie conducted to the wheel brakes 7, 8, 9, 10 by way of brake lines 5, 6, with the result that braking pressure may develop.
Further, the working chambers 3, 4 are connected to a supply reservoir 13 by way of central valves 11, 12
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patent: 5180216 (1993-01-01), Kirestein
patent: 5188433 (1993-02-01), Reinartz et al.
patent: 5207485 (1993-05-01), Troster
patent: 5261730 (1993-11-01), Steiner et al.
patent: 5486040 (1996-01-01), Beck et al.
Linhoff Paul
Volz Peter
Zaviska Dalibor
ITT Manufacturing Enterprises Inc.
Oberleitner Robert J.
Siconolfi Robert A.
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