| 摘要 |
[SUBJECT] Obtaining a normally-closed valve having a microflow rate adjusting device. [PROBLEM-SOLVING MEANS] Includes a valve stem for opening and closing a fluid passage; a biasing device for biasing the valve stem in a direction to close the fluid passage; a piston body which is engaged in a cylinder in an air-tight manner to form a pressure chamber for moving the valve stem in a valve opening direction against the biasing device; and a stopper mechanism, provided on the cylinder, for controlling a limit of movement of the piston body in the valve opening direction. The stopper mechanism comprises a stroke adjustment member which is screw-engaged with the cylinder coaxially with the valve stem so that a position of the stroke adjustment member relative to the cylinder can be adjusted, and includes an annular tapered surface at an end of the stroke adjustment member which faces the piston body;
a movable valve opening control surface provided on the piston body to be positioned radially outside of the annular tapered surface; a stationary valve opening control surface provided integrally with the cylinder to face the movable valve opening control surface, at least one of the movable valve opening control surface and the stationary valve opening control surface comprising a tapered surface which is tapered to reduce a distance between the movable valve opening control surface and the stationary valve opening control surface in a direction toward an outer edge of the tapered surface; and a plurality of balls capable of coming in simultaneous contact with each of the annular tapered surface, the movable valve opening control surface and the stationary valve opening control surface.
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