The present invention is provided with a stator 32 wherein an internal peripheral surface is formed as a female thread, a rotor 33 comprising a male screw shaft body that can be inserted into the stator 32, an external housing 31 capable of movement between a first position capable of compressing the stator 32 and second position in which at least the compression state of the stator 32 is eased, and guide members 55, 56 that guide an end part of the external housing 31 and that are capable of limiting movement of the external housing 31 in a stator peripheral direction while permitting movement of the external housing 31 in a stator radial direction.