Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Patent
1996-10-09
2000-07-25
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
303 3, B60T 888
Patent
active
060928794
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention pertains to a brake system for a motor vehicle wherein the ABS and/or the EBV are deactivated when defects in the electronic control system are detected.
Modern brake systems for motor vehicles include not only conventional hydraulic or pneumatic brakes but also supplemental electronic functions such as antilock protection (ABS) and/or electronic braking force distribution (EBV) between the front and rear axles. These supplemental functions assist the driver during the braking process and improve the stability and steerability of the vehicle in braking situations. For safety reasons, measures must be taken to check out the functionality of the electronic control unit which carries out the supplemental functions and also to check out the mechanical and electrical components.
For a hydraulic brake system, for example, it is known from SAE Paper 890970, "Electronic Control Unit of the Sumitomo Electronic Antilock System", that, to find a defect, it is possible to check not only the electronic control unit itself but also the shutdown path, especially the valve relay, as well as the speed sensors, the pressure control valves, and the return pump to see if they are in working order. When a defect is identified, a warning lamp is turned on to inform the driver, and the antilock controller is turned off no later than the end of the current braking process.
A brake system with ABS and EBV is known from WO 94/12377, in which, when a defective condition is recognized, the voltage supply of the individual control valves is turned off by way of a relay. Both the ABS and also the EBV controllers are thus turned off. The rear axle cannot be overbraked, however, because the valves of the rear wheel brakes continue to be supplied with current via separate circuits, and the pressure in the rear axle brakes is limited.
A controller for the distribution of the braking force between the front and rear axles of a motor vehicle is known from DE-OS 41 12 388 (U.S. Pat. No. 5,281,012). In this controller, the rear axle brake pressure is adjusted in such a way that the difference between the speed of the slowest rear wheel and that of the fastest front wheel does not fall below a predetermined value. As a result, an overbraking of the rear axle in the partial braking range is avoided. In addition to the braking force distribution controller, an antilock controller is also provided. No measures to be taken in the event of defects in the electrical or mechanical components are specified.
As a result of the measures indicated above for shutting down the control function of the ABS and EBV controllers in most cases when a defect occurs, unwanted situations can occur during braking operations, because, without the control function, large slip values can occur at the wheels. At large slip values, the wheels are no longer able to transfer lateral guide forces. As a result, the steerability and the stability of the vehicle are lost during these high-slip phases. In addition, locking wheels can be permanently damaged by the intense abrasion which occurs during braking.
It is therefore the task of the invention to provide measures for an antilock controller and/or a braking force distribution controller which avoid the disadvantages mentioned above.
SUMMARY OF THE INVENTION
The method according to the invention increases the availability of the antilock controller and/or of the braking force distribution controller.
It is especially advantageous that, in the presence of nearly any defect outside the control unit, the braking force distribution controller remains active, so that, even in this operating condition, the overbraking of the rear axle is avoided and the stability of the vehicle remains ensured during braking.
In the case of vehicles with hydraulic brake systems, it is therefore possible and advantageous to eliminate hydraulic components such as pressure reducers and/or measures for additional voltage supply to the rear axle brake valves in the event of defects.
The method according to the inventi
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Gottwick Ulrich
Kornhaas Robert
Graham Matthew C.
Krame Devon
Robert & Bosch GmbH
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