| 摘要 |
PROBLEM TO BE SOLVED: To excellently suppress both a problem in which a piston skirt part is scuffed in a high-surface pressure area and a problem in which sliding resistance is continued for a long period of time in a low-surface pressure area, in an engine piston having a plurality of streak grooves which is circumferentially formed in the outer surface of the skirt part being in sliding contact with the cylinder inner wall surface of an engine. SOLUTION: On the outer surface of the skirt part 4 of the piston 1, the streak grooves 7 are formed deeper in the high-surface pressure area a where surface pressure between the outer surface and the cylinder inner wall surface is relatively high, than in the low-surface pressure area b where surface pressure therebetween is relatively is low, and the ratio of the width of a top part between the adjacent streak grooves 7, 7 with respect to the sum of the width of the top part between the adjacent streak grooves 7, 7 and the width of the streak groove 7 (pitch of the streak groove 7) is made small. COPYRIGHT: (C)2008,JPO&INPIT
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