Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Patent
1994-02-23
1995-10-24
Nilson, Robert G.
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
G05D 701
Patent
active
054601991
DESCRIPTION:
BRIEF SUMMARY
FIELD OF APPLICATION IN INDUSTRY
The present invention relates to a flow control valve and control method therefor, and makes possible both the prevention of leakage of hydraulic fluid when the valve is closed and continuous flow control in a flow control valve for a car-borne hydraulic apparatus for steering, suspension or the like, and especially in a flow control valve suitable for use in the brake hydraulic control system of an anti-lock hydraulic control system or such like.
DESCRIPTION OF THE RELATED ARTS
Various conventional flow control valves suitable for the hydraulic apparatus of a brake hydraulic control system have been provided, and the present applicant, for example, proposes a flow control valve of this kind in Japanese Laid-Open Patent Application Nos. 3-90462, 3-223578 and 3-234987.
FIG. 8 shows an example of the flow control valve described in Japanese Laid-Open Patent Application No. 3-90462.
In this flow control valve, a piston 2 is freely slidably disposed in a housing 1, and a first fluid chamber A and a second fluid chamber B are respectively provided between each end portion of the piston 2 and housing 1. A conduit 2B with an orifice 2A is provided axially in the piston 2, and a surface passage 2C connected to the conduit 2B is provided in the circumferential surface of the piston 2. In addition, the piston 2 is urged in an axial direction by a spring 3 and electromagnet 4. Furthermore, an inlet port 1A connected to the conduit 2B by the surface passage 2C and an outlet port 1B connected to the second liquid chamber B are provided in the housing 1.
The flow rate through the orifice 2A is determined by the differential pressure on either side of the orifice connecting the first fluid chamber A and second fluid chamber B, and the differential pressure is determined by the urging force of the spring 3 and electromagnet 4 against the piston 2. A closing valve which connects and isolates the inlet port 1A and surface passage 2C is formed by the sliding of the piston 2 in the housing 1, and the differential pressure on either side of the orifice 2A is maintained by this closing valve. Consequently, the flow rate of hydraulic fluid flowing from the inlet port 1A to the outlet port 1B can be continually adjusted in the flow control valve by adjusting the electric current applied to the electromagnet 4 so as to change the urging force that acts against the piston 2.
In addition, although in this flow control valve the fluid pressure of the outlet port 1B acts in the direction of the axis of the piston 2, the fluid pressure of the inlet port 1A acts via the closing valve formed by the inlet port 1A and the surface passage 2C formed on the circumferential surface of the piston 12, and so does not exert an axial force against the piston 2. The following Formula (1) for differential pressure Pa-Pb on either side of the orifice 2A maintained by the action of the closing valve is thus formed, where Pa is the pressure of the first liquid chamber A, Pb is the pressure of the second liquid chamber B, f is the urging force of the spring, F is the urging force of the electromagnet, and A is the sectional area of the piston:
As Formula (1) indicates, differential pressure Pa-Pb on either side of the orifice 2A bears no relation to the fluid pressure of the inlet port 1A and outlet port 1B in the flow control valve, and is determined solely by the urging forces f and F, and the sectional area A. A flow rate proportional to the square root of the differential pressure passes through the orifice 2A. Namely, the flow control valve has an effect (pressure compensation effect) which makes it possible to control the flow rate regardless of input fluid pressure and output fluid pressure.
When the urging force F of the electromagnet 4 is set higher, the discharge port 1C in FIG. 8 forms a closing valve with the surface passage 2C, and hydraulic fluid with a flow rate corresponding to the urging force F flows from the inlet port 1A to the discharge port 1C.
However, as in the above conventional flow control
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Hashida Koichi
Takata Koji
Nilson Robert G.
Sumitomo Electric Industries Ltd.
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