Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1992-04-13
1994-01-25
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
303 10, B60T 1318, B60T 1320
Patent
active
052810143
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an electrohydraulic control apparatus for use in an anti-lock vehicle braking system of the type which is described in GB-A-22 197 402. An improvement upon the apparatus of GB-A-22 197 402 is illustrated in U.S. Pat. No. 4,892,364. FR-A-26 20 991 is also considered as state of the art.
BACKGROUND OF THE INVENTION
It is described in the first-mentioned publication that during a control action the power piston of the master cylinder is brought into a defined position which guarantees that a sufficient volume of pressure fluid remains in the master cylinder so that the vehicle still can be braked to a sufficient extent in the event of failure of the pumps. The defined position is referred to by "B" in the publication. In the course of a control action, the power piston, and hence the pedal, are brought into a defined position which is independent of the pedal effort being brought to bear by the driver. The relation between the pedal travel and the brake pressure and, respectively, master cylinder pressure during a non-controlled braking action which is known to the driver is, thus, lost.
U.S. Pat. No. 4,892,364 suggests accomplishing the pedal positioning by variation of the delivery volume of the pump, and particularly to change the drive power of the pump motor. It is known from the French specification to vary the effective output of a pump in an anti lock system in that, with the drive power of the pump motor remaining constant, a by-pass between the pressure side and the suction side of the pump is opened so that the pump delivers in a circuit, and effective fluid delivery into the brake circuit does not take place.
SUMMARY OF THE INVENTION
The present invention has as an object to adapt the position of the power piston and, respectively, of the pedal to be adjusted to the master cylinder pressure also during a control operation.
It is a further object of the present invention to put at disposal appropriate means for monitoring the power piston travel. The known applications provide for a switch which is actuated directly by the power piston. This arrangement is cumbersome to mount and difficult to adjust. It is therefore proposed to arrange a flowmeter in the brake line, with the quantity of pressure fluid entering into or exiting from the power chamber of the master cylinder being sensed, whereby direct conclusions can be drawn in regard to the position of the piston.
Further details of the invention will be explained by the following description of one embodiment.
BRIEF DESCRIPTION OF THE DRAWING
The FIGURE shows an anti-locking control apparatus according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
The apparatus is comprised of the following units: a vacuum brake power booster 9 which is actuated by the brake pedal 1, a tandem master cylinder 16, a modulator 2 for the pressure control during the anti-locking control mode, an electronic controller 5 for the processing of sensor signals, and a hydraulic pump 7, 8 which is driven by an electric motor 6.
In the FIGURE, the system is shown with the brake pedal in the release position. The pressure chambers 10, 15 of the master cylinder are connected in a known manner to the hydraulic fluid reservoir 3 through open central valves, connecting ducts in the interior of the pistons, and annular chambers 13, 14 in the power pistons 11, 12 , bores and hydraulic lines 19, 20.
The two pressure circuits 21, 22 of the master cylinder are connected to the wheel brakes 27, 28, 29, 30 through electromagnetically actuatable inlet valves 23, 24, 25, 26 switched to open in the basic position when de-energized ("SO valves").
The wheel brakes 27, 28 and 29, 30, switched in parallel, respectively, are associated with the diagonally arranged pressure circuits (brake circuits) 21, 22. The following designations are selected to denote the arrangement of the vehicle wheels corresponding to the aforementioned brakes: "VL" for front left, "HR" for rear right, "VR" for front right, "HL" for rear left.
REFERENCES:
patent: 4826255 (1989-05-01), Volz
patent: 4840435 (1989-06-01), Steffes
patent: 4892364 (1990-01-01), Burgdorf
patent: 5000525 (1991-03-01), Reinartz et al.
patent: 5013097 (1991-05-01), Gutzeit et al.
Lewis J. Gordon
Muratori Alfred
Oberleitner Robert J.
Seitter Robert P.
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