| 摘要 |
PURPOSE:To secure the opening area which is sufficient for an oil groove and suppress the abrasion of a boss edge surface by making the recessed width on the boss edge surface of an oil groove at most equal to the pin hole diameter and making the groove surface nearly parallel to the piston center axis. CONSTITUTION:As for a piston 10, an oil groove 18 for opening a pin insertion hole 17 in a pin boss part 13 to a counter-piston head part side is formed in recessed form on the boss edge surface 16 which slidingly contacts the connecting rod large edge part 15 of the pin boss part 13. The recessed width W on the boss edge surface 16 of the oil groove 18 is set at most equal to the pin insertion hole diameter (d). Further, the oil groove 18 is constituted of the R-figure-shaped groove surface 19 which is nearly parallel to the center axis 10c of the piston 10. Therefore, the opening area which is necessary and sufficient for the oil groove 18 can be secured, and abrasion can be suppressed by the increase of the actual effective area on the boss edge surface. |
