| 摘要 |
PROBLEM TO BE SOLVED: To realize substantially same flow rate characteristic in the flow in the forward and reverse directions, at any valve orifice opening from full opening to full closing. SOLUTION: A valve element 31 is disposed between an upper valve seat 30a and a lower valve seat 24a formed on a valve body 24 side, an upper valve orifice 30b and a bottom valve orifice 24b are provided at the upper and lower facing positions of the valve seats 30a and 24a; and a through-hole 31b communicating with the upper valve orifice 30b and the bottom valve orifice 24b is opened in the valve element 31. In addition, an arc-shaped groove 31c, communicating with the upper and lower surfaces of the valve element with its sectional area successively changing, is formed at the corresponding positions of the upper and lower surfaces of the valve element 31 with their sectional areas matching each other.
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