Abstract: A flow force compensating method for a flow control valve and a flow control valve using the same method, in which a spool is supported by hydrostatic bearings within a sleeve and fluid flow from the hydrostatic bearing flows into a valve space defined between a spool land and a circumferential groove of the sleeve, wherein a circumferential groove is formed in the spool land, bearing fluid flow flowing out of the bearing into the valve space defined between the circumferential groove and the sleeve groove is directed toward a central axis of the spool, and control flow is swirled by the bearing fluid flow, thereby compensating a flow force, acting on the spool.

Abstract: A water hydraulic proportional control valve comprising: a valve body having a supply port, a control port and a return port; a spool axially movably disposed in the valve body for changing a direction of the working fluid and a flow rate of the working fluid; a direct driving mechanism which directly converts electric signals into a driving force for moving the spool, the valve opening of the control valve is controlled by means of a proportional control of the amount of a displacement of the spool from a neutral position thereof toward one direction or another according to an input signal supplied to the direct driving mechanism; spool side chambers provided on both sides of the spool; and drain channels formed in communication to each of the spool side chambers; wherein a water is used as the working fluid, and a flow passages is provided for introducing a pressurized fluid into said spool side chambers, whereby water filling the chamber is constantly replaced by a fresh water thereby preventing generation

Abstract: A hydraulic servovalve controls the direction of flow of a working fluid and a flow rate of a working fluid between a plurality of ports. The hydraulic servovalve includes a spool axially movably disposed in a valve body for changing a direction of a working fluid and varying a flow rate of the working fluid, a sleeve disposed in the valve body and having a spool hole for housing the spool, a pair of hydrostatic bearings disposed in the sleeve around respective opposite end portions of the spool, and a plurality of windows defined in the sleeve as control orifices for controlling a flow rate of a working fluid. The hydraulic servovalve further includes a fluid passageway communicating between the supply port and the control port through one of the windows, and a fluid passageway communicating between the control port and the return port through the other of the windows.