| 摘要 |
PURPOSE:To prevent a skirt part from being projectingly deformed, by a method wherein the ovalness quantity of an outside peripheral surface of piston skirt parts where an oil-introducing part and an oil-discharging part are located is set to be larger than that at positions symmetrical with the parts with respect to an axis orthogonal to the direction of a pin boss. CONSTITUTION:A cooling oil passage 12 is provided at a piston head part 1, and an oil-introducing part 13 and an oil-discharging part 14 are provided at the skirt part 2 of the piston in a projecting form. The ovalness quantity (a) of the skirt part 2, where the oil-introducing part 13 and the oil-discharging part 14 are located, is set to be larger than that (b) of the outside peripheral surface of the skirt part 2 at positions symmetrical with the parts 13 and 14 with respect to the axis orthogonal to the direction of a pin boss. Accordingly, when a side pressure is exerted on a piston due to the movement of the piston, a projecting deformation of the skirt part 2 where the oil-introducing part 13 and the oil-discharging part 14 are located is canceledly absorbed by the ovalness quantity (a) which is previously set to be large enough to allow for the deformation. |
