| 摘要 |
PROBLEM TO BE SOLVED: To provide a cylinder reducing reciprocating friction with a piston, and avoiding longitudinal scratch and excessive friction that possibly occur between a piston skirt portion and a cylinder. SOLUTION: In a stroke central part region which is a region ranging from a lower surface position of a ring groove of a lowermost piston ring in a top dead center of the piston, to an upper surface position of a ring groove of an uppermost piston ring in a bottom dead center of the piston, a plurality of recessed portions are formed so that at least one recessed portion in all cross-sections in a circumferential direction of cylinder exists, and the recessed portion is not formed in a region except for the stroke central region, out of inner wall surfaces of the cylinder. A total of areas of all recessed portions is to be within a range of 1 to 80%, when an area of the stroke central region is assumed to be 100%. Out of a region that slides with a piston skirt at a thrust side of the piston used in combination with the cylinder, in the stroke central region, at least 1/4 or more thereof is to be a region where the recessed portion is not formed. COPYRIGHT: (C)2011,JPO&INPIT |
