| 摘要 |
<P>PROBLEM TO BE SOLVED: To achieve both of a function of not scraping up oil in the up stroke of a piston and a function of scraping down the oil in the downstroke of the piston. Ž<P>SOLUTION: A piston ring is constituted by an outer ring 16 received by a ring groove provided on a piston 3, and a plate expander 17, and a friction material 18 with a high coefficient of friction is applied to a part where a bottom surface 13a of the ring groove and the plate expander are abutted with each other. The hysteresis due to the influence of the friction material is generated in tension variation of the expander between the up stroke and the downstroke of the piston. Therefore, the outer ring is energized by increase of the tension of the expander and the oil scraping down performance is enhanced during the downstroke of the piston, and the oil is prevented from being scraped up by reduction of the tension of the expander compared to the time of the downstroke during the up stroke of the piston, and flow-in of the oil to a combustion chamber is reduced, and an oil consumption amount is reduced. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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