| 摘要 |
PROBLEM TO BE SOLVED: To provide a technology which improves the durability of a heat insulation layer at a crown face of a piston, and can form the heat insulation layer by a relatively simple construction method.SOLUTION: A heat insulation layer 4 composed of a porous sintered metal body 4a is formed at a crown face 2 of a piston 1. The heat insulation layer 4 is embedded in the crown face 2 of an aluminum-alloy made piston base material by an insert casting method. A hole sealing part 5c is formed at an air hole part 5a of a surface layer part of the heat insulation layer 4 by a plastic flow by machining with a vacant hole part 5a in the heat insulation layer 4 left, and hole-sealing processing is applied by the hole sealing part 5c. The machining for the hole sealing processing is one of at least either of, for example, cutting processing such as ball end milling or the like, grinding processing, and plastic processing such as shot peening. |
