OIL RING MECHANISM OF A PISTON

摘要

An oil ring mechanism of a piston (10) includes a circumferential ring groove (13) formed in an outer peripheral surface of the piston (10), and a two-piece oil ring (16) having a ring-shaped ring main body (17) that is arranged in the ring groove (13) and urged in the outer peripheral direction inside the ring groove (13) by a coil expander (21) arranged on the inner peripheral side of the oil ring main body (17). On lower side surface (13b) on a crankcase side of a side wall surface of the ring groove (13) that is on the opposite side of the ring groove (13) from an engine combustion chamber, first and second recessed portions (22, 23, 26, 27, 30 to 35) that reduce the abutment area where a lower surface (17b) of the ring main body (17) abuts against the lower side surface (13b) are formed in a lower side abutment surface (13g, 17g) that serves as a surface for abutting against the lower surface (17b) of the ring main body (17).