| 摘要 |
In a back-pressure responsive valve that receives large back pressure, the influence of the back pressure is minimized to limit or prevent an increase in size of an actuator and to maintain the valve function. A back-pressure responsive valve (1A) includes a plug-type valve element (10A) that moves up and down in a valve chamber (2) to open and close a fluid channel (3), an urging part that holds the valve element (10A) in one of a fully closed position or a fully open position, an opening/closing mechanism that opens and closes the valve element (10A) with an operating force larger than that of the urging part, and a diaphragm (8) connected to a shaft (12) of the valve element (10A) and receiving back pressure from the fluid in the fully closed position of the valve element (10A), wherein the diameter of the valve element (10A) is set smaller at a diaphragm (8)-side base portion connected to the shaft (12) than at a valve-seat (7)-side end portion (11).
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