TWO-CYCLE INTERNAL COMBUSTION ENGINE

摘要

[PROBLEMS] To reduce the consumed amount of a lubricating oil and wear in a two-cycle internal combustion engine in which openings into a cylinder formed in scavenging ports (7) to the cylinder (2) or exhaust ports from the cylinder are formed to be opened and closed by a piston (6) reciprocatingly moving in the cylinder. [MEANS FOR SOLVING PROBLEMS] The opening parts into the inside wall surface of the cylinder (2) formed in the scavenging ports (7) or the exhaust ports are disposed at the portions of the outer peripheral surface of the piston (6) corresponding to area portions (6a) and (6b) on both axial right and left sides of a piston pin (12) as viewed from the axial direction (2a) of the cylinder. Oil sump spaces (13) into which the lubricating oil between the portions of the outer peripheral surface of the piston corresponding to area portions (6c) and (6d) on both right and left sides of the axis of the piston pin (12) and the inner wall surface of the cylinder is forced out are formed between the portions of the outer peripheral surface of the piston corresponding to the opening parts in the scavenging ports or the exhaust ports and the inner wall surface of the cylinder.