Data processing: vehicles – navigation – and relative location – Vehicle control – guidance – operation – or indication – Indication or control of braking – acceleration – or deceleration
Patent
1998-11-12
1999-12-28
Cuchlinski, Jr., William A.
Data processing: vehicles, navigation, and relative location
Vehicle control, guidance, operation, or indication
Indication or control of braking, acceleration, or deceleration
701 79, 701 74, 701 70, 303186, 303187, 303188, 303121, 303122, 180197, B60T 800
Patent
active
060093668
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of monitoring a brake system which is equipped with anti-lock control (ABS) and a system for electronic control of brake force distribution (EBV) and includes two hydraulically isolated brake circuits to which the wheel brakes of the wheels of one vehicle axle are respectively connected. The method involves that the EBV function is deactivated or the commencement of EBV control is prevented upon failure of the front-axle brake circuit.
Anti-lock systems (ABS) are presently considered already as standard equipment in high or medium price category vehicles. This applies increasingly also to small-size or low-cost passenger cars. Usually, the vehicles employ hydraulic brake systems having brake lines in which electrically operable hydraulic valves, i.e. pairs of inlet/outlet valves are inserted. The inlet valves permit closing or interrupting the pressure fluid conduit which leads from the master cylinder of the brake system to a wheel brake. In contrast thereto, the associated outlet valve which is closed in its inactive position permits a pressure fluid discharge from the wheel brake and, thus, pressure reduction. The most important input quantity of the control system (ABS) is the rotational behavior of the individual wheels which is typically sensed by way of a rotational speed sensor on each individual wheel. The braking pressure in the wheel brakes of the controlled wheels is controlled and modulated as a function of the rotational behavior of the individual wheels.
As is known, it is necessary to vary the brake force distribution to the wheel brakes of the front wheels in relation to the brake force conducted to the wheel brakes of the rear wheels in order to compensate for static and dynamic axle load shifts. Mechanical, invariably adjusted pressure reducing valves or load and/or deceleration-responsive brake force controllers, which are on the market in a great number of variations, have always been used for this purpose. It is now advisable to employ hydraulic valves of the above-mentioned type for controlling or adjusting the brake force distribution and to evaluate to this end the data about the rotational behavior of the individual wheels produced by wheel sensors. This applies in particular to vehicles with ABS in which hydraulic valves of the above-mentioned type, wheel sensors and electronic controllers are already provided.
An electronically controlled brake force distribution (EBV) is principally based on determining or calculating the slip difference, i.e., the difference between the brake slip of the front wheels and the brake slip of the rear wheels. With an optimal brake force distribution, the amount of slip on the front axle is somewhat higher than the slip on the rear axle so that, on the one hand, a relatively great contribution of the front wheels to the braking operation and, on the other hand, a high amount of driving stability is ensured. As is known, the rear wheels are able to generate high amounts of cornering force only at a relatively low slip.
In an electronic control of brake force distribution in conjunction with brake systems wherein the wheels of one axle are connected to a joint hydraulic brake circuit (this is the so-called black and white brake circuit split-up), early detection of a front-axle brake circuit failure is especially important for safety reasons. This is because the brake system must allow a minimum deceleration of the vehicle, as mandated by law, even in the event of such a brake circuit failure. Because the brake slip on the rear wheels is responsive to the slip of the front wheels when the EBV system is in operation, the braking pressure limitation by the EBV control would set in prematurely in the event of front-axle brake circuit failure and the consequence of the front wheels rotating in a `slip-free` manner or at an extremely low slip. The stopping distance would become too long.
To increase the reliability in operation of a brake system with EBV, German patent application No. 42 24 971 (P 7363) discloses
REFERENCES:
patent: 5887957 (1999-03-01), Buttner et al.
English translation of the International Preliminary Examination Report for PCT/EP96/04529.
Burkhard Dieter
Ehmer Norbert
Fennel Helmut
Kunz Gerhard
Proger Thomas
Beaulieu Yonel
Cuchlinski Jr. William A.
ITT Manufacturing Enterprises Inc.
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