Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Patent
1997-01-14
1998-08-18
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
30312212, B60T 804, B60T 800
Patent
active
057950393
DESCRIPTION:
BRIEF SUMMARY
This application is the U.S. national-phase application of PCT International Application No. PCT/EP95/01467.
FIELD OF THE INVENTION
The present invention relates to a circuit for a brake system with electronic control of the brake force distribution to the wheel brakes of the front and rear axles, hereinbelow referred to as EBV, and with electronic anti-lock control and/or traction slip control systems, hereinbelow referred to as ABS and/or TCS. This circuit includes (a) electrically controllable hydraulic valves in the pressure fluid conduits leading to the wheel brakes and in the return conduits, by which pressure fluid is discharged in the pressure reduction periods, (b) wheel sensors to determine the rotational behavior of the individual wheels, (c) electric circuits to evaluate the sensor signals to produce a vehicle reference speed and to generate the braking-pressure control signals or valve control signals, and (d) circuits to monitor the brake system and to partially or completely disconnect or change the control over in response to defects or malfunctions and/or in response to the respective control situation or driving situation.
German Patent No. 33 23 402 discloses an anti-lock brake system including electrically operable hydraulic valves which are used for anti-lock control and for the control of the brake force distribution to the front axle and the rear axle for an adaption to the static and dynamic load of the vehicle axles. The data about the rotational behavior of the individual wheels, produced by wheel sensors, are evaluated for the electronic control of the brake force distribution in partial braking operations, (i.e. in the absence of anti-lock control). The brake slip of the rear wheels is limited to a defined value or percentage of the brake slip on the front wheels by operation of the rear-wheel hydraulic valves. Because the hydraulic valves in the connecting lines of the rear-wheel brakes and the wheel sensors and the electric circuits for evaluating the sensor signals are already required for anti-lock control operations, only very limited additional structure is needed for the extension to the electronic brake force distribution control system. However, it should be ensured that overbraking of the rear wheels is prevented even upon failure of the current supply or malfunction of the electronic control. Typically, a conventional mechanical or hydraulic braking-pressure reducing valve or brake force control valve is additionally required for safety reasons in spite of the electronic control of the brake force distribution.
A number of suggestions and measures are known to monitor the electronic and hydraulic components of electronically controlled brake systems. In general, the objective of these monitoring operations is to disconnect the control immediately, or after termination of the instantaneous control operation or the jeopardized control situation, upon the occurrence of defects or malfunctions to ensure at least the conventional, (i.e. the uncontrolled), function of the brake system. For example, German published Patent Application No. 27 12 693 discloses measures to monitor the wheel sensors of an anti-lock control system (ABS). In this publication, the dependency of the control on the spurious signal is eliminated after the disturbance of a wheel sensor has been detected. Instead, anti-lock control is taken over by the intact wheel sensor and the associated control channel. Further, the pressure reduction periods and the pressure maintaining periods for both wheel brakes are extended in this case of error. The development of great yawing torques, which are caused by locking of a wheel or by an unpressurized wheel brake, are prevented by changing from the individual control to the parallel control of the braking pressure.
German Patent Application No. 40 37 175 discloses an anti-lock brake system including a failure-signaling circuit. A connection by way of a main relay and, in parallel thereto, by way of a decoupling diode and a warning lamp, which permits only a lim
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Ehmer Norbert
Fennel Helmut
Kolbe Alexander
Proger Thomas
Schmidt Robert
Graham Matthew C.
ITT Automotive Europe GmbH
Lewis J. Gordon
Twomey Thomas N.
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