| 摘要 |
In this piston, portions to which load is applied are avoided, portions where the discontinuation of an oil film easily occurs are selected, and an oil groove (5) is formed in the surface of a skirt portion (3) on thrust and opposite-to-thrust sides. The oil groove (5) is formed in a position above a piston pin (22) and below a piston ring groove (12). In addition, a cooling cavity (45) and the oil groove (5) are caused to communicate with each other via an oil path (47), and the cooling cavity (45) and an opening portion (48) in a lower portion of a piston main body (1) are caused to communicate with each other via an oil path (46). Thus, even when the piston is inclined towards the opposite-to-thrust side, oil is supplied in a gap between an outer ring member (7) and the skirt portion (3) to thereby prevent the discontinuation of the oil film. Even when the piston main body (1) is inclined towards the thrust side to collide with the outer ring member (7), sufficient oil film is secured in the gap around a colliding portion and oil in the gap is pushed out to thereby cushion the collision of the piston against a cylinder liner by oil, thereby making it possible to remarkably reduce piston slap.
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