Piezoelectric-element-driven valve and flow rate control device
A piezoelectric-element-driven valve includes a valve seat provided on a flow path, a valving element detachably seated on the valve seat, and a piezoelectric element, and is configured to move the valve body by extension of the piezoelectric element. The piezoelectric-element-driven valve also is provided with a detection mechanism for detecting an extension amount of the piezoelectric element, the detection mechanism including a strain sensor, and being capable of detecting an movement amount of the valving element from an output of the strain sensor.
1. A piezoelectric-element-driven valve comprising:
a valve seat provided in a flow path and a valving element detachably seated on the valve seat;
a piezoelectric element; and
a detection mechanism including a strain sensor for detecting an extension amount of the piezoelectric element,
wherein the piezoelectric-element-driven valve is configured to move the valving element by extension of the piezoelectric element; and a movement amount of the valving element is determined according to an output of the strain sensor,
wherein the strain sensor is directly fixed to a side surface of the piezoelectric element and the strain sensor includes a longitudinal strain gauge for detecting a strain in an extension direction of the piezoelectric element, and a lateral strain gauge for detecting a strain in a direction orthogonal to the extension direction of the piezoelectric element.
2. The piezoelectric-element-driven valve according to claim 1 , further comprising a support cylinder for housing the piezoelectric element, the support cylinder being configured to move by extension of the piezoelectric element,
wherein the valving element is configured to move by movement of the support cylinder.
3. The piezoelectric-element-driven valve according to claim 2 , further comprising a storage device for storing a table indicating a relationship between an output of the strain sensor and a movement amount of the support cylinder, wherein the piezoelectric-element-driven valve is configured to determine movement amounts of the support cylinder and the valving element by the table.
4. A flow control device comprising: a restriction part; a piezoelectric-element-driven valve according to claim 1 provided upstream of the restriction part; a pressure sensor for measuring a gas pressure between the restriction part and the piezoelectric-element-driven valve; and an arithmetic processing circuit for determining a driving voltage of the piezoelectric-element-driven valve according to an output of the pressure sensor.
5. The piezoelectric-element-driven valve according to claim 1 , wherein the movement amount of the valving element is monitored by the detection mechanism and the movement amount is compared with that in a normal state to determine a presence or absence of an abnormality in a piezoelectric actuator including the piezoelectric element.
6. The piezoelectric-element-driven valve according to claim 1 , wherein the piezoelectric-element-driven valve is a normally-closed-type control valve.
7. The piezoelectric-element-driven valve according to claim 1 , wherein the piezoelectric-element-driven valve is used as a variable orifice device, and is configured to detect an orifice opening degree and control an opening position using the detection mechanism.
8. A flow rate control device comprising: the piezoelectric-element-driven valve according to claim 7 ; and an arithmetic processing circuit provided for the piezoelectric-element-driven valve, wherein the arithmetic processing circuit is configured to feedback control the piezoelectric-element-driven valve according to an output of the strain sensor.