Mass flow controller, operating method and electromagnetic valve

摘要

A mass flow controller comprising (a) a valve casing having a flow path for a fluid; (b) an electromagnetic actuator comprising a stationary yoke made of a soft magnetic material, an electromagnetic coil for magnetizing the stationary yoke, and a movable yoke made of a soft magnetic material and movable toward the stationary yoke, both of the stationary yoke and the movable yoke having a magnetic flux density of 1.5 T or more at 300 AT/m, whereby the temperature elevation of the valve casing is within 4 DEG C. from ambient temperature when the electromagnetic coil is energized; (c) a diaphragm valve means disposed in the flow path for adjusting the degree of opening the flow path; (d) a sensor pipe disposed on the upstream side of the diaphragm valve means and bypassing the flow path; and (e) a pair of sensor coils wound around the sensor pipe on the upstream and downstream sides.