Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1996-12-16
2000-03-07
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031162, 303155, B60T 712
Patent
active
06033035&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method of operation of an electronically controllable brake actuation system for anti-lock automotive vehicle brake systems, including a master brake cylinder operable by an actuating pedal, braking pressure generators which are electromechanically operable by an electronic control unit, which braking pressure generators are directly connected to wheel brakes of a vehicle and are connectable to the master brake cylinder by way of hydraulic connections closable by valves that are electromagnetically operable by the electronic control unit, at least one sensor device for identification of the driver wish for deceleration, and at least one simulator chamber interacting with the master brake cylinder.
BACKGROUND OF THE INVENTION
A known brake actuation system has hydraulic connections between the braking pressure generators and the master brake cylinder which are closed by operation of the solenoid operated separating valves, the closing of which are delayed with respect to pedal actuation. Low-pressure accumulators which are connected to the wheel brakes in the release position of the braking pressure generators, are connected to the pressure chambers of the braking pressure generators. In particular in the event of quick actuation, the response time is shortened and the dynamic behavior of the system is enhanced.
A disadvantage of this known brake actuation system is that due to different actuation speeds, the fluid volume which is furnished for rapid prefilling of the wheel brakes from the master brake cylinder through the separating valves, is not exactly defined after the time-controlled closing of the separating valves, on the one hand. Thus, the fluid volume supplied by the braking pressure generators does not provide an indication of the pressure prevailing in the wheel brakes. On the other hand, the separating valves remain open for the predetermined period even at slow actuation speeds. This is detrimental to the pedal feeling. Further, providing the low-pressure accumulators necessitates great structural efforts.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method of operation of a brake actuation system of the type referred to in the description of the field of the invention which eliminates the above-mentioned drawbacks so that the initial condition of the wheel brakes after closing of the separating valves is known, and the unnecessarily long opening of the separating valves is prevented during slow actuation.
According to the present invention, this object is achieved in that on commencement of a braking operation, a signal representative of the position of the master brake cylinder piston and a signal representative of the actuating speed occurring on the actuating pedal is produced, and in that the length of the time delay, after which the valves are closed upon commencement of the braking operation, is determined by at least one of the signals.
The position of the master brake cylinder piston is preferably determined by sensing the actuating travel at the actuating pedal.
To produce the signal representative of the actuating speed occurring on the actuating pedal, the signal representative of the actuating travel is subjected to a time derivative processing operation.
The delayed or retarded closing of the separating valves involves the mentioned advantage that the fluid volume taken from the master cylinder assists the pressure increase in the wheel brakes. However, the retarded valve closure is disadvantageous with respect to the pedal feeling because the pedal travel is undesirably increased. The objective is that the braking pressure generators prefill the wheel brakes on commencement of the braking operation providing a jump-in function. If the separating valves remained open during slow actuation, there would even be the risk that fluid volume from the brake system is conducted by the braking pressure generators through the breathering bores into the supply reservoir. Therefore, a principal o
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Feigel Hans-Jorg
Klein Andreas
Neumann Ulrich
Schiel Lothar
Graham Matthew C.
ITT Manufacturing Enterprises Inc.
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