Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Reexamination Certificate
1998-07-08
2001-06-12
Butler, Douglas C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
C303S122130, C303S191000, C303SDIG004, C303S166000, C303S155000, C303S116100, C303S115100
Reexamination Certificate
active
06244672
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for controlling a brake system, specifically to guarantee the operation of an electrically controlled brake system even if the reservoir pressure detection system fails.
BACKGROUND INFORMATION
An electro-hydraulic brake system is described in SAE Paper 96/0991, where a braking request by the driver is derived from brake pedal activation by the driver. This braking request is converted into reference brake pressures for the individual wheel brakes, taking into consideration other operating variables. The reference brake pressures are established by pressure control circuits for each wheel, on the basis of the pre-determined reference brake pressure as well as the actual brake pressure measured in the area of the wheel brake. In such a hydraulic brake system, a reservoir is provided, which is charged by an electrically controlled pump for the pressure supply. In this connection, the pump is activated to charge the reservoir if the pressure in the reservoir goes below a certain value. For this purpose, a reservoir pressure sensor is provided, which detects the pressure in the pressure supply reservoir of the brake system. The reservoir pressure is also evaluated in connection with other functions of the brake system, for example, the pressure control circuits. If the reservoir pressure sensor fails, the system does not have a measurement value available for the reservoir pressure. The functions dependent on the reservoir pressure can therefore not be performed, or can only be performed in a greatly restricted manner.
SUMMARY OF THE INVENTION
The present invention provides a method and an apparatus to guarantee operation of an electrically controlled brake system even if the reservoir pressure detection system fails, thereby improving the availability of the brake system. According to the present invention, it is not necessary to shut the electrical brake system off, but rather control of the brake system can be carried out on the basis of an approximate, estimated reservoir pressure.
According to the present invention, the pump control continues to operate and the full brake effect continues to be available in an electrically controlled manner.
According to the present invention, the determination of the reservoir pressure by approximation can be checked in the non-braking state, by activating the pump, and corrected if necessary.
An improvement in estimating the reservoir pressure results if the temperature of the brake system, particularly of the hydraulic unit, is also evaluated.
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Butler Douglas C.
Kenyon & Kenyon
Robert & Bosch GmbH
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