Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1998-12-04
2001-02-13
Oberleitner, Robert J. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C188S116000
Reexamination Certificate
active
06186602
ABSTRACT:
PRIOR ART
The invention is based on a hydraulic vehicle brake system for a vehicle.
FIGS. 1 and 2
of SAE Paper 96 0991 have disclosed two hydraulic vehicle brake systems with four wheel brakes for braking four wheels distributed on two vehicle axles by means of external hydraulic energy during normal brake operation, the service brake operation, and if need be, for example when there is a lack of or want of external hydraulic energy or electrical energy for controlling valves, for braking at least two wheels by means of muscle-powered energy in the so-called auxiliary brake operation. For the service brake operation, both vehicle brake systems have an external hydraulic energy source with a reservoir, pump, and pressure storage chamber, and between this external energy source and each of the four wheel brakes, have an electrically controllable brake valve device, which can be controlled at least indirectly as a function of a braking power signal from a braking power transmitter that can be adjusted by means of a brake pedal. For the auxiliary brake operation, the first vehicle brake system has a master cylinder that is embodied with a single circuit and can be actuated by means of the brake pedal, and connected to this, has an operation mode reversing valve, which is normally open and through which, by actuation of the brake pedal, the wheel brakes of the front vehicle axle can be actuated by means of hydraulic fluid from the master cylinder. For the auxiliary brake operation, the second vehicle brake system has a master cylinder that is embodied with two circuits and can be actuated by means of the brake pedal, and connected to this, has a first and a second operation mode reversing valve, wherein the front wheel brakes can be supplied by means of the first operation mode reversing valve and the rear wheel brakes can be supplied by means of the second one. The service brake valve devices of the second hydraulic vehicle brake system are each comprised of a first and a second normally closed 2-connection valve of the “throttling proportional directional control valve” type. The first throttling proportional directional control valve respectively constitutes a valve for increasing brake pressure and the second throttling proportional directional control valve constitutes a valve for decreasing brake pressure in the respectively associated wheel brake. Each wheel brake is associated with a pressure sensor for reporting the respective brake pressure present in the wheel brake to a regulator which is supplied with the braking power signal of the brake pedal-adjustable braking power transmitter in an altered or unaltered state and which, as a result of determined regulation variances, controls the throttling proportional directional control valves of the service brake valve devices associated with the wheel brakes with the intent of reducing regulation variances. For example, at least one of the throttling proportional directional control valves used for increasing the brake pressure is modified for a pressure regulating function to protect the external hydraulic energy source from pressure overload. For example, according to the prior application DE 196 36 432.9, the throttling proportional directional control valves mentioned can be exchanged for electrically or electromagnetically controllable proportional pressure valves of the “differential pressure regulating valve” type. By keeping the wheel brake pressure sensors used for the previously known hydraulic vehicle brake system, brake pressures can likewise be adjusted so that manufacture conditional tolerances of the proportional pressure valves can be compensated for.
A hydraulic vehicle brake system that has been disclosed by DE 40 37 662 A1, with four wheel brakes distributed on two vehicle axles, has a dual-circuit master cylinder that can be actuated by means of a brake pedal and disposed after it, two operation mode reversing valves in the form of 2/2-way valves, which are normally open, to supply the front and rear wheel brakes in the auxiliary brake operation by means of muscle-powered energy that is supplied to the brake pedal. For service brake operations, this hydraulic vehicle brake system has an external hydraulic energy source and for both of the rear wheel brakes jointly, has a cylinder/piston device and between this and the external energy source, has a common service brake valve device, which in this instance is simply comprised of two 2/2-way valves. A combination of a cylinder/piston device and a service brake valve device disposed between this cylinder/piston device and the external hydraulic energy source are also provided for the two front wheel brakes jointly, wherein this cylinder/piston device is embodied in a complex fashion for the purpose of distributing brake force between the front wheels and the rear wheels. The cylinder/piston devices prevent a mixing of the hydraulic fluid of the external hydraulic energy source with the hydraulic fluid that is common to the master cylinder and the wheel brakes, with the advantage that air and/or energy storage gas aspirated by a pump of the external hydraulic energy source, which air or gas is contained inside an external energy accumulator embodied as a membrane accumulator or a piston-type accumulator and could get into the hydraulic fluid, does not get into a wheel brake. Because the air or gas could form compressible bubbles there and as a result, could jeopardize an auxiliary brake operation with the intrinsically very limited pump capacity of the master cylinder. By respectively disposing an additional, normally open 2/2-way valve between each cylinder/piston device and the respectively associated wheel brakes, by temporarily closing the one or the other 2/2-way valve and by moving the associated piston of the cylinder/piston device in time-multiplex operation, it is possible to change brake pressures differently in the left and right wheel brakes for regulating wheel slip at least in the event of excessive brake pedal actuation. The time-multiplex operation prevents brake pressures in the left and right wheel brake of a vehicle axle from having the ability to be changed in opposition, i.e. the one brake pressure cannot increase while the other is being decreased.
DE 34 23 944 A1 has disclosed a power brake circuit for a left and a right wheel brake of an axle. Each wheel brake is associated with a separate multiposition valve for regulating brake pressure by monitoring by means of a pressure sensor or for preventing disadvantageously great wheel slip when braking. Both multiposition valves are connected to a normally closed two-position valve, which is in turn connected to a pressure reservoir. The valves are embodied so that their electromagnets are only to be acted upon with electrical excitation current in the event of the generation or alteration of brake pressures. As a result of an unavoidable leakage of valve element pairings that are disposed between the reservoir and the wheel brakes, since it cannot be prevented that undesirable wheel brake pressure could be produced despite existing wheel brake pressure sensors, the power brake circuit is associated with a pressure relief valve, which is embodied in the form of an electrically controllable 2/2-way valve that is normally open. Hydraulic fluid seeping through the above-mentioned two-position valve thus finds a path away from the wheel brakes. In the event of braking operations, the pressure relief valve is closed so that a wheel brake pressure can if necessary be increased to the pressure that prevails in the pressure reservoir.
ADVANTAGES OF THE INVENTION
The hydraulic vehicle brake system, combines the keeping of air or gas, which is disposed in the hydraulic fluid of the external hydraulic energy source, out of the wheel brakes of the vehicle axle most strongly involved in the vehicle deceleration to the advantage of auxiliary brake operations with the simultaneous advantage that for example brake pressure changes in opposition can be carried out simultaneously in the left and right wheel br
Binder Jurgen
Engfer Ortwin
Gottwick Ulrich
Hachtel Juergen
Jonner Wolf-Dieter
Greigg Edwin E.
Greigg Ronald E.
King Bradley
Oberleitner Robert J.
Robert & Bosch GmbH
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