| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston made of aluminum alloy for an internal combustion engine capable of relieving stress concentration exerted on a pin hole, and of highly setting a bearing resistance. SOLUTION: This piston made of aluminum alloy for an internal combustion engine 10 is provided with a pair of pin holes 21, 31 into which a piston pin 40 is inserted. The pin holes 21, 31 comprise a cylindrical hole 22 coming into contact with the piston pin 40, and conical holes 23, 33 diameters of which expand from ends of cylindrical holes 22, 23 towards the center of the piston 10 so that the conical holes 23, 33 do not come into contact with the piston pin 40. An anode oxide film 50 of electrolyte of mixture of phosphate and fluoride is formed on the conical holes 22, 33 and the cylindrical holes 22, 32, and fine holes of the anode oxide film 50 are impregnated with lubricant.
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