| 摘要 |
PROBLEM TO BE SOLVED: To prevent deterioration in mechanical strength and influence on the service life of a piston by forming a rib projection part on the rear surface side of an oil groove, which corresponds thereto. SOLUTION: A piston 10 comprises a crown part 10a, a skirt part 10b extending downward therefrom in a thin-plate shape, a rib projection part formed on the surface thereof protruding to the rear surface side, and a groove part formed by denting a front surface side corresponding to the rib projection part. Since the groove part formed on the skirt part 10b surface has a simple windowpane shape, spread over the entire skirt part 10b surface, when an internal combustion engine starts, oil is actively supplied to the surface thereof without generating local stress on the piston 10 surface. The groove part spreads over the entire surface of the skirt part 10b, with vertical and lateral grooves T1-3, Y1-3 communicating with each other, so that the oil scavenged and stored in the groove part circulates in the groove part and is supplied smoothly and widely in flat parts 12, 12a, 12b surrounded by the groove part.
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