Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1999-05-28
2001-09-18
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S116100, C303S115400, C303S901000, C060S585000
Reexamination Certificate
active
06290306
ABSTRACT:
PRIOR ART
The invention is based on a hydraulic vehicle brake system as set forth hereinafter.
One such hydraulic vehicle brake system is already known (WO A 92/17357), in which a valve assembly is provided in a line between the first pressure chamber of the master cylinder and the supply container: The valve assembly comprises a 2/2-way valve with a parallel-connected pressure limiting valve. The multiway valve upon spring actuation assumes its open position and upon electromagnetic actuation assumes its blocking position. It is switched into the blocking position by the control unit of the brake system when the pump is put into operation for automatic braking. The pressure generated by the pump is operative in the first pressure chamber of the master cylinder and causes the second piston to be displaced, so that the pressure in the second pressure chamber of the master cylinder is increased. Consequently, without pedal actuation, an increased pressure is available in both brake circuits of the brake system; this pressure can be modulated by means of the valve assemblies for brake pressure modulation and fed into at least one wheel brake cylinder. The pressure limiting valve disposed parallel to the multiway valve limits the pump pressure. A disadvantage, however, is the increased complexity of control for the electrical triggering of the 2/2-way valve, and the engineering expense for the multiway valve and pressure limiting valve.
Also in a hydraulic motor vehicle brake system in accordance with German Patent Disclosure DE-A 4 000 836, a valve means is used which in a brake circuit is located between a master cylinder connection and valve assemblies for brake pressure modulation in wheel brake cylinders of driven vehicle wheels. In both its spring-actuated position and its position reinforced by the pressure in the master cylinder, the valve means allows an unhindered flow of pressure fluid. The valve means can be switched by the pressure of a pump, for the sake of automatic braking, into a second position in which the valve means blocks off the flow. The pressure of the pump can then be fed in controlled fashion into the wheel brake cylinders by means of the valve assemblies. To protect the pump, the valve means functions in the second position as a pressure limiting valve.
ADVANTAGES OF THE INVENTION
The hydraulic vehicle brake system has the advantage over the prior art that the valve means can be switched as a function of the level of the pressure generated during pump operation. The control unit of the brake system can therefore be embodied at less effort and expense than in the known state of the art. Finally, the valve means protects the pump against an overload.
By the provisions recited herein, advantageous refinements of and improvements to the hydraulic vehicle brake system are possible.
With the embodiment of the invention defined here in after the hydraulic brake system is further developed into a brake system in which the pump connected to the supply container need merely furnish charge pressure at a low level, in order to supply the high-pressure pumps with pressure fluid so that the high pressure pumps can furnish high pressure to the brake circuits sufficiently quickly in automatic braking operation. This demand made of the pump is advantageous in the sense that an economical embodiment of low capacity can be used for the pump. It is advantageous that the pump, operated at a relatively low pressure level in comparison with the high-pressure pumps, puts only little strain on the master cylinder; that is, for the communication between the master cylinder and the supply container, the usual plug-type connection at the first and third connections of the master cylinder can be used.
Further, versions of the valve means are disclosed, which comprises only a few, easily manufactured components, and then as a component unit can be checked and quickly installed.
REFERENCES:
patent: 4329846 (1982-05-01), Gaiser
patent: 4373333 (1983-02-01), Coleman
patent: 4640098 (1987-02-01), Brademeyer et al.
patent: 5362140 (1994-11-01), Burgdorf
patent: 5501514 (1996-03-01), Resch et al.
patent: 5927824 (1999-07-01), Pahl et al.
Greigg Edwin E.
Greigg Ronald E.
Oberleitner Robert J.
Robert & Bosch GmbH
Sy Mariano
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