Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1990-11-26
1992-08-04
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303DIG5, 303DIG6, B60T 862
Patent
active
051352923
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is based on a drive slip control system as known, for example, from product catalog "Hydraulik fur Fahrzeuge" HB49l09DA. The known ASR and the one in accordance with the invention are not to be considered a user-friendly ASR but rather as a starter aid to prevent slipping of the wheels and to maintain the rotational speeds at approximately the same level as is done by a locking differential.
Depending on the design of the brake circuit, the system includes two rotational speed sensors at the two driven wheels, one or two pressure generators, two or three magnetic valves and an electronic unit. If, during departure and travel, the rotational speed of one of the driven wheels exceeds the speed of the other driven wheel by a certain amount, a blocking of the brake line between pressure generator and main brake cylinder as well as the action of a pressure generator make the faster rotating and faster slipping wheel slow down until a difference in the rotational speeds falls below a certain threshold.
SUMMARY OF THE INVENTION
The ASR with the features of the invention ensures that brake pressure can be built up and reduced by using the main brake cylinder even in case of a system failure, namely when the valve sticks or in case of an erroneous activation which causes the brake line to remain open despite braking action. This applies in particular when the pressure generator is not equipped with a fail-safe-function which is the case, for example, in a pressure generator where an electromotor drives an actuating piston via a self-locking threaded spindle. Moreover, the ASR in accordance with the invention can be upgraded.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a first example of an ASR in accordance with the invention,
FIG. 2 is a possible design for the valve arrangement and
FIG. 3 is an integrated design of the valve arrangement.
In FIG. 1, the main brake cylinder 1 of a vehicle is connected to a wheel brake cylinder 3 of a driven wheel via brake line 2a, 2b . A valve arrangement 4 is interposed in the brake line between segments 2a and 2b. A pressure generator 5 is connected to the brake line segment 2b between the valve arrangement 4 and the wheel brake cylinder 3. When activated, it continuously supplies pressure to the segment 2b. It includes, for example, an activating piston driven by an electromotor via a threaded spindle.
The signals of the sensors 7 and 8 which depend upon the speed of the driven wheels are supplied to an evaluation circuit 6 which, in case the rotational speeds greatly deviate, supplies via an AND-gate 9 a signal to the magnetic coil 4a of the valve arrangement. The brake line 2a/2b is then interrupted. An output signal of the evaluation circuit 6 is at the same time supplied to the pressure generator 5. The latter then continuously increases the pressure in the segment 2b until the rotational speeds are balanced. The valve arrangement 4 remains closed until the drive slip control procedures are completed. An arrangement 10 for the other driven wheel which corresponds to the arrangement of the components 3, 4, 5 and is connected to the main brake cylinder (so called black-white brake circuit arrangement).
When the main brake cylinder is activated a signal is generated which interrupts the signal to the valve arrangement 4 and the brake line 2a/2b is reopened.
If the valve 4 were not released or if the signal of the AND-gate 9 were erroneously not terminated, it would not be possible to build up or reduce pressure at the wheel. In order to avoid this disadvantage, the valve arrangement 4 includes a pressure dependent component which is put into action via a selector valve 11 when pressure is built up in the main brake cylinder 1. The valve arrangement 4 is then open. The pressure built up for this purpose in the valve arrangement can be reduced only very slowly via a throttle 12 when the brake pressure is reduced so that it remains dominant, for example, over the still present actuation signal of the magnetic coil 4a. The valve arr
REFERENCES:
patent: 4462642 (1984-07-01), Leiber
patent: 4620750 (1986-11-01), Leiber
patent: 4861116 (1989-08-01), Bernhardt et al.
patent: 5002345 (1991-03-01), Becker
patent: 5039176 (1991-08-01), Hellmann et al.
Muratori Alfred
Oberleitner Robert J.
Robert & Bosch GmbH
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