| 摘要 |
A piston (1), wherein the surface roughnesses of the rear surface (10a) of a combustion chamber (10) and the inner wall surface (11a) of a cooling cavity (11) are set to 6.3 S or less (portions a' and b' indicated by chain-double dashed lines), and these portions with the surface roughness of 6.3 S or less are surface-coated with the film of a self-purifying catalyst. Since oil is less accumulated in the surface-coated portions, the caulking of the oil can be suppressed to prevent the coefficient of heat transfer from being deteriorated so as to suppress the rise of temperature, and accordingly, the strength of the piston can be prevented from being lowered by the caulking. As a result, since an increase in the amount of a cooling oil and an increase in the capacity of an oil cooler due to an increase in the output of an engine can be eliminated, the piston (1, 30) for the internal combustion engine simple in structure and capable of easily coping with an increase in the output of the engine can be provided without causing an increase in installation space and cost.
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