| 摘要 |
PURPOSE:To secure a scavenging port area ample enough as well as to aim at improvements in scavenging efficiency and engine output, by forming a concave part to be opened to a piston sliding surface, at the suction port side of an upper end part of a scavenging passage. CONSTITUTION:A scavenging passage 5 consisting of a concave groove opened to a piston sliding surface 2 is formed in a peripheral wall part of a cylinder 1. This scavenging passage 5 is set up to spots at both sides of a suction port 3A, and extends as far as the specified height each from a lower end of the cylinder 1. And, when a piston 6 passes through a bottom dead point zone, a scavenging port 7 is formed there with a top surface 6A of the piston 6 and an upper end part of the scavenging passage 5. At the above-mentioned, a concave part 11 to be opened to the piston sliding surface 2 is formed at the side of the suction port 3A at the upper end part of the scavenging passage 5. And, an area of the scavenging port 7 is enlarged as far as a portion for opening area to a combustion chamber of the concave part 11. With this constitution, improvements in scavenging efficiency and engine output come to fruition. |
