Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1996-08-05
1998-11-03
Graham, Matthew C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031161, B60T 826
Patent
active
058298460
DESCRIPTION:
BRIEF SUMMARY
PRIOR ART
The invention is based on a hydraulic brake system as generically defined by the preamble to the claim. In such a brake system, the second 2/2-way valve is disposed in the third line. It has a spring-actuated blocking position and an electromagnetic, switchable open position. By suitable switching of the two multiposition valves, and the aid of the pump in the anti-lock control mode, brake pressure modulation in the respective brake circuit is possible; this modulation includes phases for pressure reduction, pressure holding and pressure buildup in the wheel brake cylinders. Individual-wheel pressure control, however, is impossible because of how the valves are equipped. Moreover, to attain the most optimal possible braking action in different vehicle loading states, as a rule a load-dependent pressure reducer is necessary in the second line leading to the respective wheel brake cylinder of the rear axle.
Such hydraulic brake systems are used in passenger cars in the lower price category. These motor vehicles have front-wheel drive and their wheel brakes associated with the rear wheels are relatively greatly relieved in a braking operation. The known, relatively inexpensive brake system in this vehicle price category does not meet all the demands made of it.
ADVANTAGES OF THE INVENTION
The hydraulic brake system of the invention, having the characteristics of the body of the claim, has the advantage over the prior art that with the same number of valves per brake circuit, individual-wheel control is possible within limits both during normal braking and in the anti-lock control mode. Pressure reducers on the rear axle can be omitted. It is moreover possible, with simultaneous pressure reduction at the rear axle, to attain pressure buildup and pressure holding at the front axle, which in certain road surface conditions, such as an abrupt change in the coefficient of friction, brings about improvements in the braking action.
DRAWING
One exemplary embodiment of the invention is shown in the drawing in the form of a circuit diagram of a brake system with an anti-lock system.
DESCRIPTION OF THE EXEMPLARY EMBODIMENT
A hydraulic brake system 1 schematically shown in the drawing is intended for use in a front-wheel-drive passenger car with diagonal brake circuit distribution. The brake system 1 is equipped with an anti-lock system 2. The brake system 1 has a dual-circuit pedal-actuated master cylinder 3 with a pressure fluid reservoir 4. A first brake circuit I is intended for actuating wheel brakes 5 and 6, which are associated with the left front wheel and the right rear wheel of the vehicle. The wheel brakes 7 and 8 of the right front wheel and the left rear wheel are connected to a second brake circuit II. Both brake circuits I and II are equipped identically. Brake circuit I will therefore be described in further detail below.
In brake circuit I, a first line 11 leads from the master cylinder 3 to a wheel brake cylinder 12 of the wheel brake 5 associated with the left front wheel. A first 2/2-way valve 13 is located in the first line 11. It assumes its open position when spring-actuated and its blocking position when electromagnet-actuated. A second line 14, to which a wheel brake cylinder 15 of the wheel brake 6 associated with the right rear wheel is connected, begins at the first line 11 between the first multiposition valve 14 and the wheel brake cylinder 12. A second 2/2-way valve 16 with a spring-actuated open position and an electromagnetically switchable blocking position is located in the second line 14.
Moreover, a third line 17 is provided, having a pump for pumping pressure fluid from the wheel brake cylinders 12 and 15 to the master cylinder 3. The portion 17.1 of the third line 17 leading to the intake side of the pump 18 is connected to the second line 14 between the second multiposition valve 16 and the wheel brake cylinder 15. The portion 17.2 of the third line 17 on the pressure side communicates with the first line 11 between the first multiposition valve 13 and the maste
REFERENCES:
patent: 5021957 (1991-06-01), Yoshino
patent: 5417483 (1995-05-01), Sigl
patent: 5445445 (1995-08-01), Yukio
Borsik Martin
Breitenbacher Juergen
Heinsohn Rainer
Kaess Hermann
Klug Andreas
Graham Matthew C.
Greigg Edwin E.
Greigg Ronald E.
Robert & Bosch GmbH
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