| 摘要 |
PROBLEM TO BE SOLVED: To reduce friction by effectively enhancing lubricity of especially the axial intermediate portion of the thrust surface of a skirt portion, and to prevent abrasion of the low-friction resin coating film of the axial intermediate portion. SOLUTION: An upper area 7, an intermediate area 8 and a lower area 9 which are arranged along a piston axis Y from the side of a head 1 are set on the thrust surface 3a of the skirt portion 3, and the low-friction resin coating film 6 in the intermediate area 8 is formed with oil pits 10; meanwhile, the low-friction resin coating film 6 in the upper area 7 is formed with a plurality of first oil catching/guiding grooves 11 for catching lubricating oil interposed between the inner wall Ca of the cylinder C of an engine and the thrust surface and guiding the caught lubricating oil to the intermediate area 8, when the piston P is in an upstroke, and the low-friction resin coating film 6 in the low area 9 is formed with a plurality of second oil catching/guiding grooves 12 for catching the lubricating oil interposed between the inner wall Ca of the cylinder C and the thrust surface and guiding the caught lubricating oil to the intermediate area 8, when the piston P is in a downstroke. COPYRIGHT: (C)2011,JPO&INPIT
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