Patent ID: 8919319
Filing Date: 2014-12-30
Classification: F16J

Abstract:
1. A piston for an internal combustion engine, which is made of an aluminum alloy and is reciprocally movable in a sleeve made of gray cast iron or an aluminum alloy, comprising: a coating selected from the group consisting of silver, a silver alloy, copper, or a copper alloy, the coating covering line marks on a piston skirt, wherein: the coating includes a surface having an undulation therein including recesses and ridges; a height difference between lowest valleys of the recesses and highest crests of the ridges ranges from 8 to 15 μm; and a pitch between adjacent ones of the ridges corresponds to a pitch between ridges of the line marks, and the crests of the ridges have an arithmetically averaged roughness Ra of 60 nm or smaller, wherein the line marks are formed on an outer surface of the piston skirt on a side in sliding contact with the sleeve, wherein the sum of thermal conductivities of the coating and the sleeve is 350 W/m·K or higher, and the absolute value of the difference between the Young's modulus of the coating and the Young's modulus of the sleeve is 10 GPa or greater.