Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Patent
1998-01-21
2000-10-03
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
303170, 303186, B60T 888, B60T 874, B60T 862
Patent
active
061262501
DESCRIPTION:
BRIEF SUMMARY
STATE OF THE ART
The invention pertains to a brake system for a motor vehicle according to the introductory clause of claim 1.
A brake system of this type is known from DE 4 12 388 A1 (U.S. Pat. No. 5,281,012). The brake system described in that document has an electronic control unit, which at least adjusts the braking force distribution between a front axle and a rear axle. The braking force distribution between the front axle and the rear axle should be as close as possible to the ideal braking force distribution with respect to deceleration and stability of the vehicle. This is achieved by means of an automatic controller, in which the difference between the slowest rear wheel and the fastest front wheel is compared with a predetermined difference value; the braking pressure is then adjusted in the rear axle brakes in such a way that the predetermined value is at least not exceeded. The electronic controller limits the pressure in the rear axle and prevents the rear axle wheels from locking before the front axle wheels. In the known automatic controller, it is assumed that the rotational speeds of the wheels of the vehicle are determined correctly. No measures for dealing with the occurrence of a defect are presented.
It is therefore the task of the invention to provide measures which ensure that the braking force distribution controller remains functional and that the rear wheels will not lock before the front wheels do even when there is a defect in one of the rotational speed sensors.
This is achieved by means of the characterizing features of claim 1.
Many different measures for testing the functionality of rotational speed sensors or for detecting defects in such sensors are known (see, for example, DE 34 18 235 C2).
ADVANTAGES OF THE INVENTION
By means of the procedure according to the invention, the advantageous effects of an electronic braking force distribution controller are obtained even when one of the rotational speed sensors fails.
It is especially advantageous that the advantageous effects are obtained when a rotational speed sensor at a front wheel fails and also when a rotational speed sensor at a rear wheel fails.
The functionality of the braking force distribution controller is maintained advantageously in such cases, and as a result the rear wheels are prevented from locking before the front wheels during a braking process. It is particularly advantageous, furthermore, that the stability of the vehicle is improved in vehicles with an overbraked rear axle.
By means of supplemental measures, the stability of the vehicle is improved when it is braked while traveling around a curve both in the event of the failure of a rotational speed sensor on a front wheel and also in the event of the failure of a rotational speed sensor on a rear wheel.
Additional advantages can be derived from the following description of exemplary embodiments and from the dependent claims.
DRAWING
The invention is explained in greater detail below on the basis of the embodiments illustrated in the drawing.
FIG. 1 shows an overall block circuit diagram of a brake system with electronic braking force distribution control, in which the measures according to the invention are used in the event of a defect.
FIGS. 2 and 3 show flow charts, which sketch the procedure according to the invention which is implemented when a rotational speed sensor fails at a front wheel and at a rear wheel, respectively.
DESCRIPTION OF THE EXEMPLARY EMBODIMENTS
FIG. 1 shows an electronic control unit 10, which consists of at least one microcomputer (not shown). With reference to the control of the braking force distribution between the front and rear axles, control unit 10 or the microcomputer here comprises essentially an appropriate automatic controller 12. Output line 14 of control unit 10, i,.e., of automatic controller 12, leads to valves 16, which affect the braking pressure in the rear wheel brakes. Over a line 18, a measure of the deviation between the nominal and the actual values of the difference between the fastest fro
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patent: 4834466 (1989-05-01), Arikawa
patent: 5172959 (1992-12-01), Eickhoff et al.
patent: 5277482 (1994-01-01), Beyer et al.
Gutoehrlein Bernd
Meier Thomas
Oberleitner Robert J.
Robert & Bosch GmbH
Woller Jeffrey
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