| 摘要 |
PURPOSE:To efficiently form a piston which is favorable in its heat insulating ability in such a way that spot facing machining is done with the radius larger than that of the rim of a combustion chamber, and heat resistive material is thermally sprayed to stick on the face in a layer form. CONSTITUTION:The rim of a combustion chamber 2 is machined by spot facing 6 with a radius r1 larger than that of the rim of the combustion chamber 2, taking the center point of the combustion chamber as the center of radius, and releasing recessed portions 3, 4 are machined by spot facing 7 with the same radius r2 taking said center point as the center of radius. Depth of these spot facings 6, 7 is decided to be the thickness of the layer formed by thermal spray of heat resistive material. And, heat resistive material, such as metal or ceramics etc. is thermally sprayed on the spot facing 6, 7 so that layers 8, 9 of the heat resistive materials may be formed. Thus, the heat resistive materials 8, 9 are formed around the rim of the combustion chamber 2 and on the surfaces of releasing recessed portions 3, 4, and particularly countermeasures against heat load can be effectively provided at the crossing portion of the combustion chamber 2 and the releasing recessed portions 3, 4 where cracks are liable to occur. |
