Fluid-pressure and analogous brake systems – Multiple systems – Fluid pressure and electric
Patent
1995-07-14
1996-10-22
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Multiple systems
Fluid pressure and electric
188358, 3031134, 3031141, 303155, 303DIG3, 303DIG4, B60T 1314, B60T 840, B60T 706, B60T 1366
Patent
active
055670210
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a power-assisted brake system. Such a brake system is known from the publication DE 23 27 508 A1.
Such a power-assisted brake system has an electric desired value transmitter for electrically controlling the power-assisted braking in order to be able to set the brake pressures in the wheel brake cylinders as a function of the selected force of the driver's foot. No pedal travel is actually required when absorbing the selected force of the foot on the pedal. However, for ergonomic reasons it is-- as is customary in conventional brake systems-- very advantageous if the driver senses the pedal travel as a function of the force exerted on the pedal by his foot when he activates the brake. Therefore, a travel simulator is used in this power-assisted brake system.
In the known, electrically controllable power-assisted brake system, the travel simulator which contains a compressible simulator spring is arranged between the pedal and an emergency brake cylinder. Every time the pedal is activated, the simulator spring is compressed and the electric desired value transmitter, to which an electronic control unit is connected, is adjusted. The hydraulic power assistance being applied and the brakes being actuated by means of the said electronic control unit with the aid of solenoid valves. In the event of the hydraulic power assistance or the control unit failing, the pedal must be depressed still further in order to produce emergency brake pressure by displacing emergency braking pistons in the emergency brake cylinder and ultimately in the wheel brake cylinders.
In another dual-circuit power-assisted brake system known from GB-PS 20 84 275, a travel simulator with a simulator cylinder, with a simulator spring and with a piston is provided on a dual-circuit emergency brake cylinder, which piston is displaced by a hydraulic pressure starting from the emergency brake cylinder when the pedal is moved, i.e. the pistons in the emergency brake cylinder must first experience travel in order to produce an activation pressure for the travel simulator. Moreover, the travel simulator includes a nonreturn valve which normally closes off an opening in the simulator cylinder and can be opened under the control of pressure from the power-assistance source so that the simulator spring can only be compressed in power-assistance operation. If the power assistance fails, pressure fluid enclosed in the simulator cylinder prevents the simulator spring being compressed so that one pedal stroke in all is available to displace the emergency brake cylinder pistons for pump work producing the brake pressure. It is an advantage in terms of production technology that the simulator cylinder has the same diameter as the dual-circuit emergency brake cylinder and is formed onto it integrally, coaxially to it in the manner of an extension. In order to introduce a pressure medium from the hydraulic power-assistance source into the two brake circuits leading to the wheel brakes, to produce brake pressure, two hydraulically controllable brake pressure control valves are provided. The hydraulic control is achieved by means of pressure from two cylinder chambers of the dual-circuit emergency brake cylinder. Using electromagnetically controllable directional control valves in the brake circuits between the brake pressure control valves and the wheel brakes, this power-assisted brake system is developed in order to avoid the risk of wheels locking. U.S. Pat. No. 43 27 414 discloses a power-assisted brake system with an electrical control logic, with at least one electrically controllable pressure modulator and with a brake signal transmitter which can be adjusted by the pedal and whose electrical output signal is processed as a desired value of the desired vehicle deceleration in the control logic. In order to increase the operational capability, the brake signal transmitter is constructed in such a way that it simultaneously transmits two mutually independent redundant signals to the control logic. Transmission faults
REFERENCES:
patent: 4327414 (1982-04-01), Klein
patent: 4462642 (1984-02-01), Leiber
patent: 4489989 (1984-12-01), Belart et al.
patent: 4715661 (1987-12-01), Leiber
patent: 4919493 (1990-04-01), Leiber
patent: 5031968 (1991-07-01), Takata
patent: 5178441 (1993-01-01), Heibel et al.
Butler Douglas C.
Greigg Edwin E.
Griegg Ronald E.
Robert & Bosch GmbH
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