Valve device, flow rate control method, fluid control device, semiconductor manufacturing method, and semiconductor manufacturing apparatus using the valve device

A valve device comprising:

• a valve body that defines a flow path through which a fluid flows and an opening that opens to the outside in a middle of the flow path;
• a valve seat provided around the opening of the valve body;
• a diaphragm as a valve element that covers the opening to separate the flow path from the outside, and contacts to and separates from the valve seat to open and close the flow path;
• an operating member for operating the diaphragm that is provided movably between a closed position at which the diaphragm closes the flow path and an open position at which the diaphragm opens the flow path;
• a main actuator that receives a pressure of a supplied drive fluid and moves the operating member to the open position or the closed position;
• an adjusting actuator for adjusting the position of the operating member positioned at the open position by utilizing a passive element that expands and contracts in response to a given input signal;
• a position detecting mechanism for detecting the position of the operating member with respect to the valve body;
• and
• an origin position determining unit that determines an origin position of the position detecting mechanism by utilizing the valve closed state in which the diaphragm contacts to the valve seat.