Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Reexamination Certificate
1998-11-25
2001-11-27
Graham, Matthew C. (Department: 3613)
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
C303S116100, C303S119100
Reexamination Certificate
active
06322163
ABSTRACT:
PRIOR ART
The invention relates to a hydraulic vehicle brake system with an antilock device.
The reference DE 4 422 518 A1 has disclosed a hydraulic vehicle brake system that constitutes the generic type, with a dual-circuit master cylinder, with two brake circuits in diagonal division for two front wheel brakes and two rear wheel brakes, and with an antilock device incorporated into the brake circuits, and for each brake circuit, this antilock device has a return feed pump with an inlet and an outlet, and has a first and a second electrically controllable valve, wherein the valves are embodied as normally open valves, wherein the first valve is disposed between the master cylinder and the respective front wheel brake and wherein the respective second valve is connected to the respective rear wheel brake. The respective second valve normally connects the rear wheel brake of a brake circuit to the front wheel brake of the same brake circuit. In antilock operation, this has the disadvantage that a brake pressure in the rear wheel brake cannot increase higher than a permissible brake pressure in the front wheel brake. If one desired to increase the brake pressure in the rear wheel brake above a permissible front wheel brake pressure, then the front wheel would have to be excessively braked for a short time, with the result of possibly impermissible brake slip, loss of steerability, and excessive tire wear. The desire for a higher brake pressure in the rear wheel brake in comparison to the brake pressure in a front wheel brake is brought about, for example, by virtue of the fact that with the release of the gas pedal, a drive motor of the vehicle, which motor is associated with the front wheels, acts in a braking manner on the front wheels, which on snow and ice can rapidly lead to a front wheel locking danger as soon as the brake pedal is actuated. Another reason for the desire for a higher brake pressure in a rear wheel brake relative to the brake pressure in a front wheel brake is that on a low-traction road surface with correspondingly low potential vehicle deceleration, the rear wheels can provide a relatively higher contribution to the vehicle deceleration than is possible on a high-traction road surface.
ADVANTAGES OF THE INVENTION
The hydraulic vehicle brake system according to the invention has the advantage that in antilock operation, at least on a low-traction road surface, a rear wheel brake pressure can at least temporarily be higher than a front wheel brake pressure and that depending on conditions, the brake pressure of the front wheel brake can even be temporarily increased and thereby can be set higher than the current rear wheel brake pressure, which where possible must be reduced at the same time as the increase in the brake pressure of the front wheel brake. The hydraulic vehicle brake system according to the invention thus provides the possibility of changing a front wheel brake pressure and a rear wheel brake pressure in opposite directions. Additionally, during a normal braking operation, it is possible to stop brake pressure increases in the rear wheel brakes by closing the second valves when a slip limit associated with the rear wheels is reached and to thus assure that when braking on a uniformly very high-traction road surface, the front wheels tend to lock before the rear wheels. Excessive locking danger would then trigger the antilock operation. The installation of rear wheel brake pressure control valves or rear wheel brake pressure limiting valves that function in a deceleration-dependent or rear axle load-dependent manner can therefore be avoided.
Advantageous improvements and updates of the hydraulic vehicle brake system disclosed are possible by means of the measures set forth herein.
The vehicle brake syatem has the advantage that inexpensive 2/2-way valves can be used, wherein 2/2-way valves from the prior art can be used.
The vehicle brake system has the advantage that inexpensive 2/2-way valves of a prior type and size can be used and that a flow resistance required to determine brake pressure increase speeds in at least one of the wheel brakes can be realized by means of the throttle according to the claim.
The vehicle brake system has the advantage that brake pressure change speeds can be adjusted by means of an electromagnet of the valve disposed between the master cylinder and the respective wheel brake and if need be, can be changed during an antilock operation. The excitation current of the electromagnet can be adjusted or regulated for this purpose.
The hydraulic vehicle brake system makes it possible to set the feed output of these return feed pumps lower, particularly when using constant valves, which also include differential pressure regulating valves, after a first large brake pressure reduction by means of greater feed output of the return feed pumps when, as the antilock operation continues, only slight or slow brake pressure changes are required. This has the advantage of lower energy consumption and lower noise generation.
The hydraulic vehicle brake system has the advantage that front wheel brake pressures and rear wheel brake pressures decrease rapidly when the brake pedal is released.
The improvement produces the advantage that with the further use of return feed pumps which are used to protect against wheel locking when braking by means of actuating the brake pedal, additional drive slip regulation by means of compensation of excess driving torque in drivable front wheels is possible by means of automatic braking.
The characterizing features disclose a structurally simple embodiment feature for this. The characterizing features counteract an undesirable brake pressure reduction in the rear wheel brake cylinders during a drive slip regulating operation, on the condition that the second valve connected in parallel to the check valve is closed by means of electrical control.
The characterizing features disclose a second exemplary embodiment furnished for drive slip regulating operation, which only needs four electrically controllable valves per brake circuit.
The characterizing features disclose a concrete embodiment example, which can be inferred from the reference WO 94/08831.
REFERENCES:
patent: 5531509 (1996-07-01), Kellner et al.
patent: 5586814 (1996-12-01), Steiner
patent: 5727852 (1998-03-01), Pueschel et al.
patent: 5927824 (1999-07-01), Pahl et al.
patent: 5988774 (1999-11-01), Jonner et al.
patent: WO 97/04998 (1997-02-01), None
patent: 06-211120 (1994-08-01), None
Graham Matthew C.
Greigg Ronald E.
Robert & Bosch GmbH
Sy Mariano
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