Patent ID: 8640669

Claim:
A piston of an internal combustion engine, comprising: a head; a pair of piston pin bore forming walls depending from diametrically opposing sides of the head in an axial direction; a pair of skirts depending from diametrically opposing sides of the head in the axial direction and extending circumferentially between the piston pin bore forming walls; and a resin coating deposited substantially entirely on an outer surface of each skirt; a plurality of dimples, which are circular in shape, the plurality of dimples being formed in a part of the resin coating that receives a relatively large load from an inner cylinder wall, wherein each skirt comprises a thin walled portion formed in a circumferentially central part thereof and a pair of thick walled portions formed on either side of the thin walled portion, and the dimples are formed at least in the resin coating deposited on the thick walled portions; and wherein each skirt comprises: a skirt main body provided in an axially middle part thereof, the skirt main body extending in the axial direction at an equidistance from a central axial line of the piston, and a first reduced diameter portion depending from a lower end of the skirt main body and defining a progressively diminishing distance to the central axial line of the piston toward a lower end thereof, and the dimples are additionally formed on a circumferentially extending ridge line defined in a first boundary between the skirt main body and the first reduced diameter portion.