| 摘要 |
PURPOSE:To improve an efficiency of each of the intake, exhaust and scavenging operations by a method wherein a cross sectional shape of a cylinder bore is made to be oval and each of the ports for intake, exhaust and scavenging operations is opened at the inner wall of the cylinder bore. CONSTITUTION:Cylinder bore 4 having a cross section of oval shape is formed in the cylinder block 1 of two-cycle internal combustion engine, and a piston 5 having the same shape as that of the cylinder bore 4 is slidably fitted in the cylinder bore 4. One of both inner walls having a line surface or a large radius of curvature surface in a longitudinal direction of a cross section of the cylinder bore 4 is formed with an intake port 14, and the other is formed with exhaust port 15. Exhaust port 20 is opened at each of both inner wall having a small radius of curvature in a short axis direction of a cross section in the cylinder bore 4. With this arrangement, it is possible to provide a longer circumferential length of inner wall of the cylinder bore 4 as compared with that of a conventional circular cross section and to increase an area of opening of each of the ports 14, 15 and 20. |
