| 摘要 |
PURPOSE:To reduce the frictional loss, by shaping an oil ring such that its outer surface is tapered in the direction of a combustion chamber and its lower surface is tapered toward the inside in the state that the oil ring is fitted freely in an oil-ring groove, and forming a lubricating-oil return passage along the lower surface of the oil-ring groove which is shaped substantially in a similar form as the oil ring. CONSTITUTION:An oil ring 10 fitted in an oil-ring groove 20 formed in a piston 9 is shaped to have a quadrilateral cross section. In the state that the oil ring 10 is fitted freely in the oil-ring groove 20, the upper surface 11 of the oil ring 10 is horizontal while the inner surface 12 is vertical. On the other hand, the outer surface 13 of the oil ring 10 is tapered in the direction of a combustion chamber and the lower surface 14 is tapered toward the inside. The oil-ring groove 20 is shaped substantially in a similar form as the oil ring 10, and a lubricating-oil return passage 25 is formed along the lower surface 24 of the oil- ring groove 20. Further, the oil ring 10 is formed in a unit. With such an arrangement, the contact area between the oil ring 10 and the oil-ring groove 20 can be reduced by the tapered outer surface 13 of the oil ring 10. |
