Fluid-pressure and analogous brake systems – Speed-controlled – Independent control for each wheel
Patent
1997-05-21
1999-11-23
Oberleitner, Robert J.
Fluid-pressure and analogous brake systems
Speed-controlled
Independent control for each wheel
3031135, 303900, B60T 862, B60T 834
Patent
active
059887745
DESCRIPTION:
BRIEF SUMMARY
HYDRAULIC BRAKE SYSTEM WITH ANTI-LOCK ARRANGEMENT
The invention relates to a hydraulic brake system with an anti-lock arrangement for a vechicle.
Published German Patent Application DE 4 422 518 A1 discloses a hydraulic brake system defining this generic type, having a dual-circuit master cylinder, with two brake circuits in a diagonal configuration for two front wheel brakes and two rear wheel brakes, and with an anti-lock arrangement incorporated into the brake circuits; per brake circuit, the anti-lock arrangement has one return pump with an inlet and an outlet and one first and one second electrically controllable valve; these valves are embodied as normally open valves, the first valve being disposed between the master cylinder and the respective front-wheel brake and each second valve being connected to the associated rear wheel brake. The respective second valve normally connects the rear wheel brake of one brake circuit to the front wheel brake of the same brake circuit. In the anti-lock mode, this had the disadvantage that a brake pressure in the rear wheel brake cannot rise any higher than a brake pressure in the front wheel brake. If one wanted to raise the brake pressure in the rear wheel brake above an allowable front wheel brake pressure, then one would have to briefly overbrake the front wheel with the consequence of possibly excessive brake slip, loss of steerability, and excessive tire wear. The demand for a higher brake pressure in the rear wheel brake compared with the brake pressure of a front wheel brake is dictated for instance by the fact that when the gas pedal is released, a drive motor of the vehicle associated with the front wheels acts to brake the front wheels, which especially on snow and ice once the brake pedal is actuated can rapidly lead to the danger of front wheel locking. Another reason for the demand for a relatively higher brake pressure in a rear wheel brake than in a front wheel brake is that on a road surface with poor traction and accordingly less capability of slowing down the vehicle, the rear wheels can make a relatively greater contribution to vehicle deceleration than is possible on a road surface with good traction.
The hydraulic vehicle brake system according to the invention has the advantage that in the anti-lock mode, at least on a road surface with poor traction, a rear wheel brake pressure can at least intermittently be higher than a front wheel brake pressure.
Advantageous further features of and improvements to the hydraulic brake system disclosed herein are possible with the provisions recited hereinafter.
The system has the advantage that conditionally in the anti-lock mode, the brake pressure of the front wheel brake can be intermittently set higher than the instantaneous rear wheel brake pressure. Additionally there is the possibility during normal braking, on reaching a slip limit associated with the rear wheels, to discontinue brake pressure increases in the rear wheel brakes by closing the second valves and thereby to assure that in braking on a road surface with very good traction, the front wheels will tend to lock before the rear wheels. As a result, it is possible to avoid installing rear wheel brake pressure regulating valves or rear wheel brake pressure limiting valves that operate as a function of deceleration or rear axle load.
The vehicle brake system has an advantage that economical values can be used, and it is possible to use 2/2-way valves from the prior art.
The vehicle brake system has the advantage that economical 2/2-way valves of conventional design and size can be used, and that a flow resistance necessary in at least one of the wheel brakes in order to determine brake pressure buildup speeds is realized by means of a throttle.
The vehicle brake system has the advantage that brake pressure change rates are adjustable by means of an electromagnet in the valve located between the master cylinder and the respective wheel brake and can optionally be varied during the anti-lock mode. To that end, the exciting current of the elec
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patent: 5040854 (1991-08-01), Arikawa
patent: 5046788 (1991-09-01), Lindenman
patent: 5178442 (1993-01-01), Toda et al.
patent: 5219210 (1993-06-01), Maehara
patent: 5375919 (1994-12-01), Furuhashi
patent: 5441336 (1995-08-01), Takeuchi
Breitenbacher Juergen
Heinsohn Rainer
Jonner Wolf-Dieter
Kaess Hermann
Klug Andreas
Greigg Edwin E.
Greigg Ronald E.
Oberleitner Robert J.
Robert & Bosch GmbH
Woller Jeffrey
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