| 摘要 |
PROBLEM TO BE SOLVED: To enable avoiding of reduction of the mechanical strength effectively without reducing cooling effect. SOLUTION: This piston is includes an upper forming portion 2 and a lower forming portion 3. A cooling cavity 10 is formed between the upper forming portion 2 and the lower forming portion 3. A joint 14 between the upper forming portion 2 and the lower forming portion 3 is welded. This piston is configured so that the end portion of the joint 14 located inside the cooling cavity 10 becomes wider toward the inside of the cooling cavity 10 in a club-shaped manner. |
