| 摘要 |
An internal combustion engine having a gas sealing device including an L-shaped keystone piston ring groove formed on the outer circumferential surface of a piston, and an L-shaped keystone piston ring in pressing contact with the inner surface of a cylinder and fitted in the L-shaped keystone piston ring groove forming a gap for introducing a gas pressure from a combustion chamber into the piston ring groove. The L-shaped keystone piston ring groove includes an outer groove portion underlying a top land formed in the piston, and a wedge-shaped groove portion contiguous with the outer groove portion and tapering in going toward the center axis of the piston. The L-shaped keystone piston ring includes an outer ring portion disposed in the outer groove portion of the piston ring, and a wedge-shaped ring portion disposed in the wedge-shaped groove portion of the piston ring groove. The top land has a smaller diameter than a second land formed in the piston adjacent the piston ring groove on a side thereof opposite the top land, so that a gap is formed between the top land and the inner surface of the cylinder to communicate with the gap for introducing the gas pressure from the combustion chamber into the piston ring groove.
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