A scope part includes a heat exchanger provided in an end part and having a flow passage for cooling liquid for cooling an functional element, a first tube having a first end connected to a first end of the flow passage of the heat exchanger and extending toward a shaft part, a second tube having a first end connected to a second end of the flow passage of the heat exchanger and extending toward the shaft part, and a displacement-to-flow converting part connected to a second end of the first tube and a second end of the second tube to convert a displacement of a predetermined part to a flow of the cooling liquid. An external device includes a displacement generating part that generates a displacement. The predetermined part of the displacement-to-flow converting part and the displacement generating part are connected by a displacement transmission part.
