Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1995-11-08
1997-05-27
Poon, Peter M.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303155, 303166, 303DIG4, B60T 834
Patent
active
056325312
DESCRIPTION:
BRIEF SUMMARY
This application is the U.S. national-phase application of PCT International Application No. PCT/EP94/00153.
BACKGROUND OF THE INVENTION
The present invention relates to a method for determining the pedal force as a control quantity during braking with anti-lock control for a brake system with anti-lock control which includes as electromotively driven hydraulic pump. The electromotively driven hydraulic pump serves as a return of pressure fluid discharged from the wheel brakes during braking pressure control or for the generation of auxiliary pressure. The present invention also relates to a circuit configuration for implementing the method, and includes sensors for determining the wheel rotational behavior and an electronic controller for: (a) evaluating the sensor signals, (b) generating braking pressure control signals, and (c) actuating the electromotively driven hydraulic pump which serves for the return of pressure fluid or the generation of auxiliary pressure.
It is difficult to determine the pedal force and the resulting supply pressure in anti-lock brake systems. Of course, it would, in principle, be possible to determine the pedal force by way of force sensors, for example, by known wire strain gages. However, the complexity of such measuring apparatus would be great, in particular, because monitoring devices would be required in addition. As a result, such measuring apparatus is avoided for cost reasons, although the supply pressure takes major effect on braking pressure control. Therefore, it would be important for the control quantity and control comfort to have data about the supply pressure.
Japanese patent application JP-A-0 3096469 teaches monitoring the voltage variation directly after deactivation of the drive motor of a hydraulic pump, which pump is included in an anti-lock system, in order to detect defects or pressure fluid leakages. Either the steep or the gradual decline of the drive motor voltage is evaluated as a criterion.
Further, it is disclosed in DE-A-38 19 490 to monitor the electromotively driven hydraulic pump of an anti-lock brake system by means of sensors which determine and evaluate measured values indicative of the actual operating condition of the electric motor from time to time or continuously during operation of the hydraulic pump. This way, the operability of the hydraulics is monitored without direct measurement of the pressure.
SUMMARY OF THE INVENTION
An object of the present invention is to determine the force applied to the brake pedal during braking with anti-lock control and to thereby determine the supply pressure caused by this force for taking the supply pressure into account in the control operation. It is evident that a possible increased expenditure in manufacturing the brake system should be as low as possible.
It has been discovered that this object can be achieved by a method of the previously mentioned type, the special features being that, during braking with anti-lock control, the drive motor of the hydraulic pump is deactivated or switched over to generator operation for a predetermined time for measuring the supply pressure, and the magnitude of the generator voltage and the variation or fade-out behavior of the generator voltage is assessed to determine the approximate supply pressure as a function of the pedal force.
Thus, the present invention is based on the knowledge that information about the so-called supply pressure or the instantaneous brake pedal force can be acquired from a very short interruption in the actuation of the pump drive motor, which interruption does not disturb the function, or a short-time switch-over to generator operation. As will be seen in the following description of an embodiment of the present invention, the generator voltage, after the deactivation and its fade-out behavior, is influenced considerably by power requirements which, in turn, depend on the supply pressure or the pedal force, respectively.
In a favorable aspect of the method according to the present invention, the intervals for measuring the
REFERENCES:
patent: 4057301 (1977-11-01), Foster
patent: 4768841 (1988-09-01), Watanabe
patent: 5230549 (1993-07-01), Osada et al.
Batistic Ivica
Christen Axel
ITT Automotive Europe GmbH
Lewis J. Gordon
Poon Peter M.
Twomey Thomas N.
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