Piston assembly of cooler

摘要

There is provided a piston assembly configured to include: a hollow cylinder-shaped magnet sleeve having a magnet(s) bonded on external circumferential surface thereof; a hollow cylinder-shaped piston inserted into a hollow space of the magnet sleeve; and a hollow disc-shaped ring fixed to the piston by a shrink fitting process, and welded to the magnet sleeve which is made of the same material as the ring so as to obtain a configuration of the piston assembly in which the magnet sleeve and the piston are coupled to each other.