| 摘要 |
PROBLEM TO BE SOLVED: To reduce the manufacturing cost of a closed cavity piston. SOLUTION: This closed cavity piston 34 is provided with a slender piston body 32 and a separately formed piston cap having a slender stem 52 and a head 54. The piston body is provided with a cavity 38 having a closed end and an opened end, a bottom wall 40 adjacent to the closed end, and an outer wall 42 serving as a mouth edge at the opening end. The stem of the piston cap is inertial friction-welded to the bottom wall of the piston body, the head of the piston cap is welded to the mouth edge of the piston body, thereby the opening end is shielded, and the cavity is sealed. The stem of the piston cap is inserted into the cavity of the piston body until abutting the bottom wall. The piston cap is inertial friction-welded at a junction between the stem and the bottom wall and a junction between the cap head and the mouth edge.
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