Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-08-22
1999-08-10
Poon, Peter M.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031162, 303155, B60T 836
Patent
active
059347678
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a hydraulic motor vehicle power brake system with at least one valve that can be electrically controlled.
The document U.S. Pat. No. 3,802,745 has disclosed a hydraulic motor vehicle power brake system having a reservoir, a pump, a pump pressure regulating valve, and at least one external energy reservoir that can be filled by the pump. The reservoir is embodied as a hydraulic accumulator equipped with a dividing membrane and is provided with a buffer gas filling, and a valve device between the external energy reservoir valve device which valve device can be electrically controlled and is for connecting at least one wheel brake to the external energy reservoir. A wheel brake pressure sensor is associated with the at least one wheel brake, and a brake pedal have a potentiometer as a set-point transmitter for a wheel brake pressure in which the potentiometer can be adjusted by means of the brake pedal. A control device is connected to the set-point transmitter and the wheel brake pressure sensor and is equipped to control the valve device in such a way that by connecting the at least one wheel brake to the external energy source, it is possible to increase the wheel brake pressure until the set point is attained and by connecting the wheel brake to the reservoir, it is possible to reduce the wheel brake pressure when the brake pedal is released. This valve device, which is of a type that is known per se and is therefore not described, has three connections. For example, it is possible to provide a number of these valve devices so that for example, each wheel brake of each individual wheel of the vehicle has its own valve device. By disposing wheel rotation sensors and modifying the control device, it is possible to adjust brake pressures toward a set-point predetermined by the brake pedal so that a locking of vehicle wheels is prevented. The technical expenditure for the pump pressure regulator valve, which conducts excess supplied pressure fluid to the reservoir when the pump is driven, the hydraulic accumulator is fully charged, and the brake pedal is not being actuated, can be seen as disadvantageous.
A hydraulic motor vehicle power brake system disclosed by DE 19 61 039 A1 differs from the hydraulic motor vehicle power brake system according to U.S. Pat. No. 3,802,745, which is mentioned above, by the elimination of a pump pressure limiting valve and the installation in its place, of a pressure switch for turning off an electromotor, which drives the pump, when the external energy reservoir is sufficiently charged. The disposition of the pressure switch and the electromotor has on the one hand the advantage that the pump only operates until the external energy reservoir is sufficiently filled. On the other hand, though, the disposition of this kind of pressure switch has the disadvantage that when a possibly inevitable welding of contact elements occurs, the electromotor can no longer be switched off, which results in the overloading or complete destruction of the electromotor, the pump, or other components of the motor vehicle power brake system. Aside from the use of valves with three connections between the external energy source, a wheel brake cylinder, and the reservoir, DE 19 61 039 A1 also discloses the disposition of an electromagnetically controllable directional control valve between the external energy source and the wheel brake cylinder, which valve is provided with two connections and can be adjusted for two positions, and also discloses the disposition of a second 2-connection-2-position directional control valve between this wheel brake cylinder and the reservoir. Both 2-connection valves are equipped with closing springs and are closed in their normal positions.
In a vehicular brake system that can be operated with external energy, DE 40 29 793 A1 has disclosed the embodiment of necessary 2/2-way valves, which are designated for adjusting wheel brake pressures with the aid of wheel brake pressure sensors, as seat valves in order to prevent leakage flow
REFERENCES:
patent: 3877760 (1975-04-01), Cole et al.
patent: 4526203 (1985-07-01), Leiber
patent: 5609401 (1997-03-01), Johnston et al.
Gaillard Alain
Schmidt Guenther
Winner Hermann
Greigg Edwin E.
Greigg Ronald E.
Poon Peter M.
Robert & Bosch GmbH
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