Valve device

A valve device comprising:

• a valve body made of metallic-alloy defining a first flow path and a second flow path and having an annular protrusion formed around an opening of the first flow path;
• a valve seat having an inner periphery fitted to the outer periphery of the annular protrusion and disposed on the valve body;
• an inner disk made of metallic-alloy comprising:
• an inner annular portion that engages the valve seat to restrain the valve seat on the valve body;
• an outer annular portion disposed on the outer peripheral side of the inner annular portion and in contact with the valve body;
• and a connecting portion that connects the inner annular portion and the outer annular portion and has a plurality of openings communicating with the second flow path;
• a diaphragm made of metallic-alloy, having a peripheral edge portion in contact with the outer annular portion, covering the inner disk and the valve seat and moving between an open position at which the diaphragm does not contact with the valve seat and a closed position at which the diaphragm contacts with the valve seat to enable and shut off communication between the first flow path and the second flow path;
• and a presser adapter that presses a surface of the peripheral portion of the diaphragm opposite to the side of the outer annular portion toward the outer annular portion to provide seals between the outer annular portion and the diaphragm and between the outer annular portion and the valve body,
• wherein the inner disk has a hardness higher than the valve seat and lower than both the valve body and the diaphragm.