Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1996-07-01
1998-10-27
Poon, Peter M.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031162, 3031132, B60T 836
Patent
active
058269525
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a brake system for automotive vehicles including a pedal-operable pressure generator connected to wheel brake cylinders of wheel brakes associated with the individual wheels, at least two actuator units actuatable independently of the pressure generator and arranged in hydraulic connections between pressure generator and wheel brake cylinders to permit shutting off the hydraulic connections, each of the actuator units including one cylinder-and-piston assembly and one actuator, and an electronic controller whose control signals serve to actuate the actuator units, wherein, on simultaneous actuation of the pressure generator and at least one actuator unit, the force resulting from the pressure build-up in the pressure generator is added to the external actuating force generated by the actuator and applied to the piston of the cylinder-and-piston assembly.
European patent application EP 0 395 262 A2, for example, discloses a brake system of this type. In the prior art brake system, the actuator unit is a hydraulic cylinder having a piston with a gear profile. The gear profile is engaged by a rotary pinion driven by an electric motor, and the rotary movement of the pinion is converted into a translational movement of the piston. A disadvantage of the prior art brake system is the unfavorable efficiency of the actuator which is due to the complicated way of conversion of the electrical energy, that is to be conducted to the electric motor, into the displacing movement of the hydraulic piston. In addition, major problems during the assembly or mounting of the known actuator unit can be caused by the positioning of the electric motor vertically relative to the longitudinal axis of the cylinder and by the comparatively high weight.
Therefore, an object of the present invention is to propose a brake system of the previously mentioned type which permits accomplishing an increased efficiency of the actuator. In addition, small dimensions and a low weight of the actuator units shall be provided.
SUMMARY OF THE INVENTION
According to a first solution of the object to be achieved by the present invention, the actuator is an electromagnet whose armature is the piston of the cylinder-and-piston assembly.
In another preferred aspect of the present invention, the stroke operation of the electromagnet is optimally utilized because the electromagnet is a stroke magnet whose action of force is controlled irrespective of stroke in response to output signals of a magnetic flux sensor. Alternatively, the action of force of the stroke magnet can be controlled in response to output signals of a differential pressure sensor sensing the pressure differential between the pressure generated by the pressure generator and the output pressure of the cylinder-and-piston assembly.
In an embodiment of the present invention which is compact and inexpensive to manufacture, the cylinder-and-piston assembly and the actuator are accommodated in one housing.
It is favorable in a pressure-tight design of the housing that the piston is a hollow piston which is sealedly guided on a cylindrical port and defines a hydraulic annular chamber in the housing to which the hydraulic pressure of the pressure generator can be applied.
In non-pressure-tight housing designs, the piston is a stepped hollow piston which is sealedly guided on a cylindrical port and defines in the housing a pneumatic annular chamber which is connected to the end surface of the large-diameter step remote from the annular chamber, and the small-diameter step is sealed in the housing and can be acted upon by the hydraulic pressure of the pressure generator.
A filter element can precede the small-diameter step, serving additionally as a stop for the valve member of a central valve which shuts off the hydraulic connection between pressure generator and wheel brakes.
According to a second solution of the object to be achieved by the present invention, wherein the actuator of the cylinder-and-piston assembly is a hydraulic a
REFERENCES:
patent: 3877760 (1975-04-01), Cole et al.
patent: 4844559 (1989-07-01), Harrison
patent: 5332304 (1994-07-01), Maas
Feigel Hans-Jorg
Neumann Ulrich
Schiel Lothar
ITT Automotive Europe GmbH
Lewis J. Gordon
Poon Peter M.
Twomey Thomas N.
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