| 摘要 |
A valve is connected to a valve stem, and is closed by the elastic force of a spring acting on it via the valve stem. The valve is opened, on the other hand, when a stepping motor displaces the valve stem coaxially against the force of the spring via a rotor shaft. A predetermined clearance D is set between the rotor shaft in a predetermined position and the valve stem in a seating position. When a fault is detected in the closing of the valve, the rotor shaft is displaced beyond this clearance D so as to directly drive the valve stem in the valve closing direction and thereby close the valve forcibly without the agency of the spring. |
