To solve operational instability such as the fluctuation, vibration and noise of secondary side pressure by providing a flame-shaped part having an opposite surface to a valve seat surface provided in an orifice, projectingly outward perpendicularly to an axial direction in a valve disc and also providing a specific gap between the valve seat surface and the opposite surface of the flame-shaped part in a valve closed state.
A sheet part 1 consists of a orifice guide 3 and a valve disc 5 opening/closing an orifice 4 provided in the guide 3. Also, a flame-shaped part 11 is made to project outward perpendicularly to an axial direction, an opposite surface 10 is provided parallelly to a valve seat surface 7, and a small gap (t) is provided between the surfaces 7 and 10 in a closed (closed valve in which a seating part 8 comes into contact with a contact part 12) state. The outer diameter D of the disc 5 is set within the range of about 1.2 to 1.6 times as long as the inner diameter (d) of the orifice, and the gap (t) between the surfaces 7 and 10 is set within the range about 0.5 to 0.8 mm in a closed valve state. Then, pressure can be controlled in two stages, i.e., in the gap (t) between the surface 7 and the surface 10 of the part 11 and the gap between the part 8 and the part 12 of the disc 5.
NISHIYAMA TOSHIHIRO
NAGASAKA TAKASHI
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