Fluid-pressure and analogous brake systems – Speed-controlled – With failure responsive means
Reexamination Certificate
1998-07-30
2001-03-27
Mar, Michael (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
With failure responsive means
C303SDIG009, C701S076000
Reexamination Certificate
active
06206488
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and an apparatus for controlling a braking system.
BACKGROUND INFORMATION
A system for controlling a braking system is known, for example, from SAE Paper 960991, “Electrohydraulic Brake System—The First Approach to Brake-by-Wire Technology”, which describes an electrohydraulic braking system in which an electronic control unit is added onto a hydraulic unit that comprises the hydraulic control components of the braking system. This electronic unit performs control actions on the pressures in the individual wheel brakes as a function of setpoints, and reads measured variables which are related to the wheel brakes, such as wheel brake pressure, wheel speeds, etc. This added-on control unit is connected via a communication system to a second control unit in which the vehicle-specific functions are calculated. These are understood to be, primarily, determination of the setpoints for control actions on the individual wheel brakes, e.g. pressure setpoints, reference braking forces, or torque setpoints. These setpoints are calculated from the driver's braking input, taking into consideration a predefined braking force distribution between the front and rear axles of the vehicle, and optionally taking into consideration wheel- and vehicle-related functions such as braking force distribution as a function of transverse force, antilock braking control, automatic slip control, vehicle dynamics control, etc. If this second control unit, or the communication system between the two control units by means of which setpoints and measured values are exchanged, should fail, satisfactory functioning of the braking system can no longer be maintained in all operating situations.
International Published Patent Application No. WO 95/13946 describes a control system for a braking system which has a central module as well as brake modules associated with braking circuits or wheel groups. The brake modules sense the wheel-specific variables such as wheel speed and braking pressure. One of the brake modules, preferably the one for the front axle, furthermore senses an indicator for the driver's pedal actuation. The sensed values are conveyed via a communication system to the central module, which determines, at least from the operating variables that are delivered, setpoints for the individual wheel brakes. These setpoints are delivered by the communication system to the brake modules for implementation. If the central module fails, the brake module which reads in the actuation signal takes over the determination of setpoints for the wheel brakes in the context of an emergency mode, and adjusts the brakes associated with it accordingly and transmits the setpoints to further brake modules via the communication system. No description is given of a concrete embodiment of the emergency mode, or of a control system for all wheel brakes in the event of failure of the communication system.
German Published Patent Application No. 41 12 388 (corresponding to U.S. Pat. No. 5,281,012) describes a controller for braking force distribution between the front and rear axles. In this system, the braking force distribution is implemented, on the basis of the wheel speed signals, in such a way that the speed difference between the front and rear wheels does not exceed a predetermined threshold value.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to indicate measures which maintain satisfactory operation of the braking system even in the event of failure of the second control unit or of the communication system between the two control units.
Advantageously, in the case of a control system of a braking system which comprises at least two control units, a satisfactory emergency mode is made available in the event of failure of the higher-level control unit and/or of the communication system between that higher-level control unit and the control unit performing the actual brake regulation.
It is particularly advantageous that even in the event of a fault, braking force distribution between the front and rear axles is guaranteed, effectively preventing overbraking of the rear wheels, i.e. locking of the rear wheels, without locking the front wheels.
It is particularly advantageous that the vehicle stability for vehicles in emergency mode corresponds to that of vehicles without an antilock braking system.
It is furthermore advantageous that the availability of the braking control system is considerably increased; even in the emergency mode, additional hydraulic components (such as braking pressure reducers) can be dispensed with, since braking force distribution is regulated electronically.
REFERENCES:
patent: 4740778 (1988-04-01), Harding et al.
patent: 5281012 (1994-01-01), Binder et al.
patent: 5493495 (1996-02-01), Naito et al.
patent: 5588719 (1996-12-01), Bailleux
patent: 5735583 (1998-04-01), Katayama et al.
patent: 5757641 (1998-05-01), Minto
patent: 5899540 (1999-05-01), Burgdorf et al.
patent: 5954407 (1999-09-01), Schramm et al.
patent: WO 95/13946 (1995-05-01), None
Wolf-Dieter Jonner, et al., “Electrohydraulic Brake System—The First Approach To Brake-By-Wire Technology”, SAE Paper 960991.
Binder Juergen
Gottwick Ulrich
Hachtel Juergen
Schunck Eberhardt
Kenyon & Kenyon
Mar Michael
Nguyen Xuan Lan
Robert & Bosch GmbH
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