Fluid-pressure and analogous brake systems – Electric control
Patent
1996-04-08
1998-05-19
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Electric control
3031134, 30312203, 364424045, B60T 1366
Patent
active
057527482
DESCRIPTION:
BRIEF SUMMARY
STATE-OF-THE-ART
An electronic brake system is known from DE 40 22 671 A1, to which U.S. Pat. No. 5,255,962 corresponds.
ADVANTAGES OF THE INVENTION
The invention leads to an electronic brake system with a favorable emergency operating strategy.
DESCRIPTION OF THE FIGURES
FIG. 1 shows an overall block circuit diagram of a preferred embodiment of the electronic brake system,
FIG. 2 is a flow chart illustrating the procedure for detecting defects, and
FIG. 3 is a flow chart illustrating the emergency measures when defects are detected.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1 shows a decentralized electronic brake system, which has a central module 1 and brake modules 2a, 2b. The central module has the task of carrying out ABS-ASR calculations, is responsible for the distribution of the braking force, and determines the wheel-specific nominal braking force values p.sub.w1 -p.sub.w4. It is also possible for this module to carry out a central monitoring function. Central module 1 can be, for example, a microcomputer with a bus interface. It is not connected directly to sensors or actuators. In a preferred exemplary embodiment, the central module is designed in redundant fashion.
The connection between central module 1 and brake modules 2a, 2b is preferably realized as a serial bus system 3, (e.g. CAN). When central module 1 is designed with redundancy, then bus system 3 will also be realized in redundant fashion.
Brake module 2b is an autonomous unit, which regulates the wheel-specific brake values of an axle, preferably the rear axle, or of a brake circuit. The wheel velocities n.sub.3 and n.sub.4 of the associated wheels are received at module 2b and are transmitted from there to the central module. In addition, it is also the task of this module to regulate the brake pressures specific to each wheel. For this purpose, the actual brake pressure values p.sub.x are determined. Signals p.sub.w3, p.sub.w4 control corresponding actuators 4c and 4d in such a way that the nominal brake pressures are produced by the brakes. Instead of the brake pressure, it is also possible to determine some other variable which determines the brake pressure (e.g., electric current, speed, or rotational angle of a motor driving the actuator). Brake module 2b is an intelligent unit with an interface to the communications system based on a microcomputer of preferably redundant design. In a redundant realization, each of the partial functions required for the braking of a wheel are preferably separated so that each has its own channel in the computer system, and the channels are set up so that they can monitor each other.
The power electronics for driving the electrically actuated actuators connected to them are also present in module 2b.
Brake module 2a carries out the same functions as brake module 2b. It is assigned to the front axle. In addition, it is also connected to a pedal sensor 5, which detects the driver's commands in redundant fashion (distance h.sub.p traveled by pedal 7 and pressure p.sub.z generated by it in cylinder 6). It is also conceivable that the force exerted on the pedal could be measured.
Module 2a is also an intelligent unit based on a microcomputer preferably of redundant design. In a redundant realization, the functions required for the braking of the wheels are separated into two channels, and each channel monitors the other. If the central module fails, module 2a can also perform certain diagnostic functions.
The pressure p generated by actuators 4a, 4b is transmitted to the wheel brakes by separate switching units 8a, 8b, respectively. Under normal operating conditions, the switching units are driven in such a way that a connection exists between actuators 4 and the wheel brakes.
The brake circuit to which module 2a is assigned is also provided with a hydraulic backup. Brake pedal 7 is connected to a master brake cylinder 6. If switching units 8a, 8b should fail, pressure can be transmitted to the wheel brake cylinders by the master cylinder. Normally, wheel speeds n.sub.1 -n.sub.
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Bantle et al., "Der Porsche Typ 959-GruppeB-ein besonderes Automobil-Teil 3" A.T.Z. vol. 88, No. 7/8 (Aug. 1986) pp. 407-413.
Aupperle Bernd
Binder Juergen
Blessing Peter
Heinsohn Rainer
Holl Eberhard
Lipka Pamela J.
Oberleitner Robert J.
Robert & Bosch GmbH
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