| 摘要 |
PROBLEM TO BE SOLVED: To enable a sufficient amount of oil to be always retained between an inner wall surface of a cylinder and a peripheral wall of a piston, thereby continually reducing sliding friction of the piston and improving sliding performance thereof. SOLUTION: A recessed oil reservoir portion 5 for storing engine oil therein is provided in a skirt portion 3 of the piston 1 which reciprocatingly slides in a hollow portion of the cylinder S. The oil reservoir portion 5 is formed by cutting a part of a spiral striation R and has a roughened recessed bottom surface. The size of opening of the oil reservoir portion 5 is approximately 1 mm to 10 mm, the depth thereof is approximately 2μm to 30μm. The opening of the oil reservoir portion 5 is formed in any of circular, elliptical, triangular, square, polygonal, trapezoidal, lozenge, star, digit, letter and symbol shapes. Further, the weight of the piston 1 can be equalized in subgram level thereof by adjusting the size of opening, the depth and the numerical quantity of the oil reservoir portion 5. The shape of opening and the pattern of arrangement of the oil reservoir portion are so adjusted as to record information on manufacturing history or the like as engraved mark. It is thus possible to identify the piston 1 by individualization thereof. COPYRIGHT: (C)2008,JPO&INPIT
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