| 摘要 |
A piston ring comprises a plurality of recesses that are formed in its outer peripheral edge. The recesses have any of a number of profiles such as semicircular, chordal, arcuate, and triangular. The piston ring controls the passage of lubricant between a region defined between the piston ring and an upper compression sealing ring. The recesses can be positioned to pass over an exhaust port formed in a cylinder wall or to pass over other regions of the cylinder wall. By passing over the exhaust port, the piston ring better accommodates fluctuations in dimensions that are induced by temperature changes by passing over other regions of the cylinder wall, the piston ring enhances the distribution of lubricant, especially in cylinders having a generally horizontal or inclined center axis.
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