| 摘要 |
PURPOSE:To improve a cooling effect in a piston's top wall part, by installing a passage, serving as a doorway of oil to an oil sump part, in at least either of a cuplike piston body or a flexible film partitioning the oil sump part at a top wall part of space inside the piston body. CONSTITUTION:A piston body 1 is of a cuplike form having a cylindrical side peripheral wall 2 and a top wall part 3, and at an inner circumferential surface of the piston body 1, an annular projection strip 6 directed from a piston inner circumferential edge to a piston central part is installed in interspaced positions in a piston axial direction from a peripheral edge of the backside of the top wall part 3. A flexible film 10 is made up of rubber or the like and attached to the annular projection strip 6 by means of a setting metal device 7. In addition, at the annular projection strip 6, a lubricating oil feed hole 8 leading the lubricating oil spouted out of a lubricating oil injection nozzle N into an oil sump part A, and a lubricating oil discharge hole 9 discharging the oil from the oil sump part A are installed so as to be isolated from each other. |
