| 摘要 |
PROBLEM TO BE SOLVED: To provide a fluid shutoff device reducing mechanical stress applied to a valve seat under normal conditions, and certainly shutting off fluid when channel shutoff operation is defective. SOLUTION: When a channel is shut off under the normal conditions, after performing control drive of rotation in a shutting off direction exceeding the bottom dead center of a closed valve at which the vale seat 87 made of a flexible body abuts on a valve seat 83 and the valve seat 87 is compressively deformed, the mechanical stress is relaxed by performing reverse rotation control within a range where the valve seat 87 keeps abutting on the valve seat 83. Therefore, malfunction such as deterioration and inoperative condition due to thermal stress is prevented. Since a flow rate is a prescribed rate or more after a channel shutting off operation, if it is detected that the channel shutoff state of a shutoff valve 43 is defective, a shutoff signal 50 showing the presence of a flow rate during shutting off is output from a section 51 determining the presence of the flow rate during shutting off and the shutoff valve 43 is shut off and driven again without performing the reverse rotation control for a stress relaxing process. Accordingly, the shutoff valve 43 shuts off a gas channel at a higher rate, and fluid can be certainly shut off. COPYRIGHT: (C)2009,JPO&INPIT
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