Patent ID: 8181932

Claim:
A normally open type piezoelectric element driven metal diaphragm control valve comprising: (a) a body provided with a valve seat disposed on a bottom face of a valve chamber ( 7 a ′) formed in the body, wherein the valve chamber has an open upper end; (b) a metal diaphragm installed in an opposite direction to the valve seat so that an outer periphery of the metal diaphragm is hermitically sealed and so that the metal diaphragm makes contact with the valve seat ( 7 c ) by thrusting downward when thrust is present, and the metal diaphragm departs from contact with the valve seat due to an elastic force of the metal diaphragm when thrust is not present; (c) a diaphragm presser installed on an upper face side of the metal diaphragm ( 8 ); (d) an actuator box installed above the valve chamber so that a lower end portion of the actuator box is fixed to a side of the body; (e) a piezoelectric element installed inside the actuator box and disposed so as to provide thrust for thrusting the metal diaphragm by thrusting the diaphragm presser, wherein the piezoelectric element provides thrust by elongating downward when voltage is applied to the piezoelectric element; (f) a conical spring mechanism disposed between the diaphragm presser and the piezoelectric element so that the conical spring mechanism absorbs a first portion of the thrust provided by elongation of the piezoelectric element when voltage is applied to the piezoelectric element and the metal diaphragm makes contact with the valve seat so that a prescribed second portion of the thrust is applied to a seat part comprising the valve seat and a portion of the metal diaphragm that makes contact with the valve seat; and (g) a preload mechanism installed between the piezoelectric element and the conical spring mechanism and around the actuator box, wherein the preload mechanism constantly applies an upward compressive force to the piezoelectric element, wherein the compressive force applied to the piezoelectric element by the preload mechanism is externally adjustable.