To let the heating of a motor connected to one end side efficiently escape to the other end side without taking much space, and also to prevent an excessive temperature rise in the motor or the like from occurring.

A wick 31 is installed in an inner wall surface forming a closed airspace of an external thread part 17a, and a coolant 34 is sealed up on the inside. This coolant 34 is evaporated in an evaporated part 32 to be situted at the left end side of the external thread part 17a, while this evaporated coolant 34 is condensed in a condensation part 22 being situated at the right end side of this external thread part 17a. With this condensation, the external thread part 17a functions as a heat pipe.