Diaphragm type actuator

A diaphragm-type actuator that drives an operation rod in an axial direction of the operation rod, comprising:

• a diaphragm which is connected to the operation rod at a first end thereof;
• a low pressure chamber which is adjacent to a first end side of the diaphragm in the axial direction;
• a high pressure chamber which is adjacent to a second end side of the diaphragm in the axial direction;
• a return spring which is provided in the low pressure chamber and urges the diaphragm toward the high pressure chamber;
• a retainer which is provided on a surface near the high pressure chamber in the diaphragm;
• and
• an elastic member that is disposed between the retainer and a wall surface facing the retainer so as to contact the retainer in the axial direction inside the high pressure chamber when a pressure in the low pressure chamber is greater than a predetermined value,
• wherein the operation rod extends from the diaphragm toward the high pressure chamber and penetrates the wall surface facing the retainer of the high pressure chamber in the axial direction,
• wherein a bearing portion holding the operation rod is supported by the wall surface, the bearing portion including a cylindrical bush and a bush housing which receives the cylindrical bush, the bush housing including a cylindrical portion which protrudes from the wall surface toward a second end of the operation rod, a first end of the cylindrical portion in the axial direction being continuous with the wall surface, and a front wall formed at a second end of the cylindrical portion in the axial direction, and
• wherein the elastic member is attached to the wall surface.