Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1997-05-01
1998-11-17
Young, Lee W.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031134, 303DIG11, B60T 842
Patent
active
058366598
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to an electronically controllable brake actuation system for automotive vehicles, including a master brake cylinder operable by an actuating pedal, braking pressure generators actuatable by an electronic control unit and having pressure chambers which are connected to the wheel brakes of the vehicle, the braking pressure generators being connectable to the master brake cylinder by way of hydraulic connections closable by valve assemblies, at least one sensor device to identify the driver's wish for deceleration, and at least one simulator chamber which interacts with the master brake cylinder.
German patent application No. 34 24 912, for example, discloses a brake actuation system of this type. The hydraulic connections between the braking pressure generators and the master brake cylinder in the prior art brake actuation system are closed by bores (breathering bores) which are provided in the hydraulic cylinders of the braking pressure generators and are overridden by sealing sleeves arranged on pistons of the braking pressure generators upon actuation of the braking pressure generators.
The prior art brake actuation system is little appropriate for use in anti-lock brake systems. Thus, the closable hydraulic connections do not permit the reduction of the hydraulic pressure prevailing in the wheel brakes close to zero bar during anti-lock control operations. This is because the above-mentioned bore, to which the comparatively high pressure generated by the driver is applied, would be opened during the entire restoring movement of the braking pressure generator piston required in the control operation.
Another disadvantage with respect to anti-lock control operations must be seen in the chambers provided in the hydraulic cylinders of the braking pressure generators. The pressure fluid volume is conducted to the chambers by the driver of the vehicle to maintain the pedal feel which is normal to the driver during actuation. In any case, the drive units of the braking pressure generators must actively ensure the restoring movement of the pressure generator pistons so that high costs are incurred for a four-quadrant actuating electronics and a maximum actuating force rating is required. Further, pedal resetting occurs without damping against the driver's foot.
Finally, the direct actuation of the valve assembly provided by the combination of bore (breathering bore) and sealing sleeve is effected by the electric drive due to the mass inertias (which should not be left out of account) with a time delay. The time delay, in turn, causes inflow of a considerable pressure fluid volume so that pressure reduction to values close to zero bar is not possible. Especially control operations at low .mu.-values are thereby impaired.
Further, German patent application No. 42 29 041 discloses an electronically controllable fail-safe brake actuation system wherein the master brake cylinder and the electrically actuatable braking pressure generators, each furnished with a separate pressure fluid supply reservoir, are connectable to the wheel brakes by way of an electromagnetically operable three-way/two-position directional control valve. In a first switch position of the three-way/two-position directional control valve, there is a hydraulic connection between the master brake cylinder or the pressure generator and the wheel brake, and the connection between the pressure generator or the master brake cylinder and the wheel brake is closed. In a second switch position, the three-way/two-position directional control valve establishes a hydraulic connection between the pressure generator or the master brake cylinder and the wheel brake, and the connection between the master brake cylinder or the pressure generator and the wheel brake is closed. When the system is intact, the driver is separated from the wheel brake and senses a firm pedal in consequence of the mentioned measures. Due to the fact that the braking pressure generators have pressure fluid supply reservoirs on t
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patent: 5302008 (1994-04-01), Miyake et al.
patent: 5312172 (1994-05-01), Takeuchi
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Feigel Hans-Jorg
Klein Andreas
Neumann Ulrich
Schiel Lothar
ITT Manufacturing Enterprises Inc.
Lewis J. Gordon
Twomey Thomas N.
Young Lee W.
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