| 摘要 |
PURPOSE:To reduce the frictional force acted between a top ring and a cylinder, by enhancing the lubricating oil feeding effect between the top ring and the cylinder through employment of such an arrangement that the cylinder has a lower surface roughness at the region near the top dead point where the top ring of a piston is stopped than other regions of the cylinder. CONSTITUTION:The surface roughness Ra of a cylinder 1 is finished to a value lower than 0.16a in the region extending from the position near the top dead point where a top ring 3 is stopped to the top deck and to 0.25a-0.63a in the region extending downward from the former region. With such an arrangement, the maximum height of the surface ruggedness of the cylinder 1 is made smaller than 0.6S in the region where the surface roughness is lower than 0.16a. Therefore, even if the gas pressure at the back of the top ring 3 is fairly high, the lubricating oil feeding effect between the top ring 3 and the cylinder 1 is enhanced, so that oil film having a sufficient thickness is formed between them. Thus, the frictional force acted therebetween can be reduced. |
