Actuator device

A flow rate control apparatus comprising:

• a flow rate control valve that controls a flow rate in a flow path, and
• an actuator device coupled to said flow rate control valve,
• wherein said actuator device comprises:
• an actuator element which has a shortest length when no electric voltage is applied thereto and which is increased in length as an electric voltage applied thereto becomes higher,
• a displacement extracting part, and
• a converter mechanism which carries out conversion of a change in length of said actuator element into a displacement of said displacement extracting part;
• wherein said converter mechanism comprises:
• a first holder having a center portion fixed to a first end of said actuator element, a peripheral portion surrounding said center portion, and a notch formed between said center portion and said peripheral portion,
• a second holder fixed to a second end of said actuator element, and
• a transmission member of a cylindrical shape having first and second ends and an intermediate portion between said first and said second ends, said first end of said transmission member being fixed to said second holder so that said intermediate portion of said transmission member covers said actuator element with a gap between said intermediate portion and said actuator element and so that said second end of said transmission member passes through said notch of said first holder to protrude outward from said first holder;
• wherein said displacement extracting part is fixed to said second end of said transmission member
• wherein:
• said converter mechanism further comprises a cylindrical spring member,
• said cylindrical spring member is arranged in said gap between said actuator element and said intermediate portion of said transmission member covering said actuator element, and
• said spring member has a first end fixed to said center portion of said first holder and a second end fixed to said second holder;
• wherein said converter mechanism carries out said conversion so that the displacement of said displacement extracting part is decreased as the length of said actuator element is increased;
• and
• wherein said flow rate control valve closes said flow path in response to the displacement of said displacement extracting part of said actuator device, when no electric voltage is applied to said actuator element of said actuator device.