| 摘要 |
<p>Friction between a rotary disk (13) and a fixed disk (14) is prevented from being produced by providing a transmission interruption unit (a stopper (25) and an engaging portion (26)) for interrupting power transmission from a motor (28) to the rotary disk (13) in a safety valve operation range to stop rotation of the rotary disk in the safety valve operation range. Moreover, an adhesion varying unit (a spring member (27) and a carriage lifting-lowering cam unit) for varying adhesion of the rotary disk (13) to the fixed disk (14) is further provided, and the adhesion of the rotary disk (13) to the fixed disk (14) in a flow rate control range is lessened from that in the safety valve operation range, so that friction to be produced between the rotary disk (13) and the fixed disk (14) can be suppressed in the flow rate control range.</p> |
