Motors: expansible chamber type – With motive fluid valve – Both inlet and exhaust controlled by motive fluid pressure...
Patent
1993-05-04
1995-04-11
Michalsky, Gerald A.
Motors: expansible chamber type
With motive fluid valve
Both inlet and exhaust controlled by motive fluid pressure...
91454, 13759617, 13762564, 3031192, F15B 13044
Patent
active
054047919
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a pressure regulation device for a hydraulic system.
It is particularly adapted to the braking systems of motor vehicles with antilocking of the wheels when braking. Present antilocking systems use, between a source of fluid under pressure and a receiver such as a hydraulic brake actuator, an electrovalve controlled by a computer in terms of signals representative of the rotation of the wheels of the vehicle in order, in a general manner, to release the pressure of the fluid in the hydraulic actuator when the computer detects the imminence of the locking of a wheel, and then to connect a second source of fluid under pressure in order to raise the pressure once again, up to a new detection of imminence of locking, the cycle then renewing itself. Electrovalves of the same type are used in anti-wheelspin systems in order to generate a pressure in a brake actuator of a driving wheel when the computer detects a tendency of this driving wheel to spin, and then to release this pressure when the tendency to spin has disappeared.
The electrovalves used are electrovalves with all-or-nothing operation. However, the antilocking or anti-wheelspin periods wherein cycles as described above follow one another, last for a very short time during which the electrovalve changes state a very large number of times. This causes an unpleasant noise of hammering of the movable part of the electrovalve.
Moreover, as the system operates in all-or-nothing manner, surges of pressure appear in the brakes producing poorly controlled transient conditions.
The object of the present invention is to obviate these disadvantages by using an electrovalve termed proportional ensuring in the user system a hydraulic pressure dependent on the current circulating in the coil of the electrovalve in a given range of displacement of the magnetic core of the electrovalve.
Such an electrovalve then has the advantage of being controllable simply by causing the current circulating in the coil to vary without necessitating hammering of the movable part; this therefore results in a major reduction in the pressure surges in the brakes. Furthermore, such an electrovalve may easily be controlled by a computer producing a chopping at variable frequency of a direct current such as is found on board a motor vehicle, or else a chopping at fixed frequency and with variable cyclic ratio, the intensity of the current integrated by the coil then being dependent on the cyclic ratio.
Such an electrovalve is for example described in U.S. Pat. No. 4,744,389. However, the electrovalve described in that Document cannot be arranged in a hydraulic braking system with antilocking of the wheels because of the pressures used, particularly during the energizing of the electrovalve. In fact, the electrovalve of that Document is designed in order to function continuously in a system for regulation of a relatively low pressure. This physical limitation therefore prohibits the use of such an electrovalve with high pressures in the hydraulic actuator. Furthermore, that electrovalve does not permit the pressure to be caused to increase linearly when the current decreases linearly in the coil and vice versa.
One object of the present invention is to produce an electrovalve serving to cause the pressure to vary linearly in terms of the current in the coil, capable of being energized with a high pressure in the hydraulic system, and which is of simple design and assembly.
The subject of the present invention is therefore a pressure regulation device for a hydraulic system comprising at least one generator of fluid under pressure, a hydraulic actuator and a reservoir of fluid under low pressure, and including an electrovalve controlled by a computer and comprising in a casing an electrical coil and a sliding magnetic core controlling a slide valve sliding in a bore provided in a body, the slide valve determining two chambers arranged on either side of the slide valve in the bore, the slide valve comprising a hydraulic chamber communicating with the hydraulic actuat
REFERENCES:
patent: 4744389 (1989-05-01), Ichihashi
patent: 5234030 (1993-08-01), Kervagoret et al.
patent: 5248191 (1993-09-01), Kondo et al.
Fabian et al, Machine Design, pp. 59-62, Jan. 24, 1991.
AlliedSignal Europe Services Techniques
Michalsky Gerald A.
Palguta Larry J.
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