To improve an oil circulation from a thrust side and an anti-thrust side to intermediate phase positions thereof, between an inner circumferential surface of a cylinder and an outer peripheral surface of a piston in an internal combustion engine.
In an oil ring groove 22 of the piston 2, oil return holes 28, 30, 32, 34, 36, 38 are opened to a front side and a rear-side, and are not opened to the thrust side and the anti-thrust side. Accordingly, the highly pressurized oil at the thrust side and the anti-thrust side enters the oil ring groove 22 and promptly flows to the front side and the rear-side where the oil return holes 28-38 are present. Consequently, the oil can be supplied enough to the phase where the oil is insufficient, and thereby the oil circulation being a problem can be improved. The oil spreads enough in a circumference and has a superior lubrication effect, thereby effectively reducing friction in the internal combustion engine.
IWADE JUN
TAKI HISATO
HATA YOSHIHARU
OKADA NAOYA
TOYOTA MOTOR CORP
Makoto Onda