Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1993-09-09
1994-09-20
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031161, B60T 832
Patent
active
053483812
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a hydraulic brake unit with an anti-lock and traction control system for motor vehicles.
Such a brake unit is already known (DE-OS 38 16 073, FIG. 3), U.S. Pat. No. 4,900,102; in which the suction line starts in a brake circuit from a storage vessel for the pressure medium. This is therefore a so-called open brake circuit, in which the pressure medium volume between the master brake cylinder and the wheel brake is subjected to fluctuations, which necessitate additional design measures on the master brake cylinder. Moreover, the suction line, which on the master brake cylinder side takes the form of a hose, is of relatively great length. A hose is more susceptible to assembly faults and risk of damage than is a pipeline. There is moreover the risk that with a leaking check valve or a valve which closes after a delay in the suction line, pressure media will enter into the storage chamber via the return line and reduce its storage volume, in which event during anti-lock or traction control operation, pressure media has to be taken from the wheel brake.
ADVANTAGES OF THE INVENTION
In contrast, the hydraulic brake unit in accordance with the invention has the advantage that the brake circuit is a closed circuit which has a suction line starting from the brake line and an overflow line terminating in the brake line. The suction line can therefore be relatively short and designed as a pipeline or as an integral port. However, the particular advantage is provided by the protection given by the prevention of any pressure media entering into the storage chamber from the suction line side, which is achieved at minor cost. This improves the reliability of the brake unit function and its control behaviour in the anti-lock and traction control operation.
DRAWING
An embodiment example of the invention is shown simplified by means of a schematic diagram for a hydraulic brake unit and is more fully explained in the description which follows.
DESCRIPTION OF THE EMBODIMENT EXAMPLE
The hydraulic brake unit 1 shown in the drawing is intended for use in motor vehicles.
The brake unit 1 has a pedal operated, dual-circuit master brake cylinder 2 with a pressure medium storage tank 3. In a first brake circuit I of the brake unit 1, a brake line 4 extends between the master brake cylinder 2 and a first wheel brake 5. From the brake line 4, a brake line 6 branches off to a second wheel brake 7 of the brake circuit I. The wheel brakes 5 and 7 are assigned to the non-driven front axle of the vehicle. In a second brake circuit II of the brake unit 1, the master brake cylinder 2 is connected with a first wheel brake 9 by means of a brake line 8. A second wheel brake 11 is connected to a brake line 10, which branches off from the brake line 8, of the brake circuit II. The two wheel brakes 9 and 11 of this brake circuit II are assigned to the driven rear axle of the vehicle. The brake circuit II, which has a relationship with the solution provided in accordance with the invention, is described more fully as follows:
A valve arrangement 13 for the brake pressure modulation of the wheel brake 9 is located in the brake line 8 on the wheel brake side. The valve arrangement 13 is designed as a 3/3-way valve and has three connections: A first connection 13.1 is coupled to the section 8.1 of the brake line 8 on the master brake cylinder side, coupled to the second connection 13.2 is the section 8.2 of the brake line 8 on the wheel brake side, while a return line 14 for pressure media taken from the wheel brake 9 starts from a third connection 13.3. The valve arrangement 13 has a first, spring actuated position 13a, in which the two connections 13.1 and 13.2 are linked with each other. In a second position 13b, which is electromagnetically switchable, all three connections 13.1, 13.2, 13.3 are blocked. In a third position 13c, which is also electromagnetically switchable, the second connection 13.2 and the third connection 13.3 are linked with each other.
The return line 14 which starts from the valve
REFERENCES:
patent: 5156449 (1992-10-01), Wetzel
patent: 5207485 (1993-05-01), Troster
Bernhardt Wolfgang
Schmidt Guenther
Greigg Edwin E.
Greigg Ronald E.
Oberleitner Robert J.
Poon Peter M.
Robert & Bosch GmbH
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