A pressure-receiving member that can be moved along an urging axial center, and a compression coil spring for urging the pressure-receiving member in the direction of an engaging body, are provided between the engaging body in an inside end position of an operating rod and a bottom wall part of a casing. A plurality of protruding pieces for restricting tilting by making contact with the pressure-receiving member is provided to the internal surface of a cylindrical part of a rotor that engages and integrally rotates with engaging pieces of the external periphery of the engaging body.