| 摘要 |
PURPOSE:To improve the efficiency of engine through enlargement of the opening areas of exhaust and scavenging ports, by providing an exhaust port which is opened to one side of the wide side walls of a cylinder having an oblong cross sectional form and forming scavenging ports which are opened to the other side and narrow side walls. CONSTITUTION:An exhaust port 16 is opened to one wide side wall of a cylinder hole 5 having an oblong cross sectional form and a suction port 19 is opened to the other wide side wall. Further, 3 pairs of scavenging ports 21, 24, and 27 are opened to both narrow side wall 5c of the cylinder hole 5, at their respective one ends and are open to the crank chamber a crank case 4 at the other ends. In case the cylinder hole 5 has the same area as that of a conventional circular hole, the peripheral length can be increased, the opening areas of an exhaust port opening part 17, a suction port opening part 20, and scavenging port outlet opening parts 22, 25 and 28 can be set to increased values, thus flow resistance is reduced, resulting in improvement of efficiency. |
