Fluid-pressure and analogous brake systems – Speed-controlled – Having a valve system responsive to a wheel lock signal
Patent
1995-10-17
1997-07-15
Butler, Douglas C.
Fluid-pressure and analogous brake systems
Speed-controlled
Having a valve system responsive to a wheel lock signal
3031171, 13759617, 91433, B60T 832, F15B 13044
Patent
active
056476450
DESCRIPTION:
BRIEF SUMMARY
The invention relates mainly to a proportional solenoid valve for regulating the pressure of a hydraulic fluid, this valve being provided with a high-pressure inlet, with a low-pressure inlet, and with an outlet on which it can deliver a controlled pressure, this solenoid valve comprising:
a body pierced with a bore connecting first and second end chambers together, these further being connected to one another permanently by a duct;
a regulating slide valve sliding within the bore and having a cross-section for differential pressure capable of constituting the seat of application of a first force capable of urging this slide valve towards the first end chamber;
an elastic means exerting a second force, pointing in the opposite direction from the first, on the slide valve;
first and second orifices passing through the body and emerging in the bore respectively close to the first and second chambers, one of these orifices being connected to the high-pressure inlet;
a casing mounted in the extension of the body in order to close off the second end chamber in hermetic fashion, and in which there are housed an electric coil and a magnetic core plunger, this core plunger being capable of sliding in order to exert a third force in the same direction as the first on the slide valve; and
a valve placing the second end chamber selectively in communication with a third orifice made in the casing, this valve including a shut-off member which can be shifted from its shut-off position by the core plunger against a return force, and which is able, after a non-zero travel, in turn to transmit the said third force to the slide valve, the latter being capable of bringing about a first communication between the high-pressure inlet and the outlet, and a second communication between the low-pressure inlet and the outlet, and favouring the second communication over the first for increasing values of the third force.
A solenoid valve of this type is described, for example, in the patent U.S. Pat. No. 5,234,030 which corresponds to French Patent FR-2,679,299, and the teaching of which is incorporated into the present description by way of reference.
The essential application of this known solenoid valve is the production of braking systems for motor vehicles, provided with a wheel anti-lock function.
More precisely, the function of this solenoid valve is to regulate the braking pressure coming from the master cylinder actuated by the driver of the vehicle and/or from a pump which is substituted for it by way of a source of high pressure, so as to prevent untimely locking of the wheels.
However, insofar as the stability of a vehicle under braking is dangerously compromised when braking is not applied predominantly to the front wheels, and insofar as it is moreover indispensable, for any braking circuit, to envisage the possibility of breakdowns likely to affect it, the known solenoid valve cannot in practice be used without recourse to an additional regulator, which is installed in the braking circuit of the rear wheels, and whose function is to prevent this circuit from receiving the same pressure as the braking circuit for the front wheels, even in the event of electrical failure of the solenoid valve or of its supply circuit.
SUMMARY OF THE INVENTION
The invention lies within this context and its object is to provide on the one hand a method for regulating the hydraulic pressure in a braking circuit which makes it possible to prevent a loss in stability of the vehicle under braking, even in these extreme situations and without recourse to any additional regulator and, on the other hand, a solenoid valve which meets the requirements of this method.
The solenoid valve of the invention, which moreover complies with the preamble of the present description, is essentially characterized in that its outlet permanently communicates with the third orifice and in that the first and second orifices are, inside the bore, isolated from one another by the slide valve, which results in the fact that the outlet of the solenoid valve is isol
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Audrain Patrick
Bourlon Philippe
Michon Jean Pierre
Muller Philippe
AlliedSignal Europe Services Techniques
Butler Douglas C.
McCormick Jr. Leo H.
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