| 摘要 |
PURPOSE:To reduce the consumption of oil, by forming the abutment section of a top ring in such a shape that the opening area on the combustion side is greater when the top ring is seated on the lower surface of the ring groove, than the opening area on the second land side when the ring is seated on the upper surface of the ring groove. CONSTITUTION:A top ring 22 and a second ring 24 are disposed in ring grooves 18, 20 in a piston 10. The abutment section 22a of the top ring 2 is formed such that the opening area on the combustion chamber 16 side is greater than the opening area on the second land 26 side. Therefore, the top ring 22 is seated on the lower surface of the ring groove 18 during initial stage of every combustion stroke, so that the opening area S2 of the abutment section 22a allows the combustion pressure to be introduced into the second land 26 to raise the pressure thereof, and when the ring 22 is sealed on the upper surface of the ring groove 18, the displacement of oil from the second land into the combustion chamber 16 is resisted by small opening area S1, thereby it is possible to reduce the consumption of oil.
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