| 摘要 |
PURPOSE:To improve scavenging efficiency by making the upper swirl angle larger than the lower one, providing and twisting the axis of an air path of a scavenging hole in the vertical direction. CONSTITUTION:A scavenging hole 2 consists of a plurality of round hole arranged parallel to the axis of a cylinder. A straight line Y1-Y1 interconnecting the centers O1, O3 of the lowermost and uppermost circles in the outer peripheral portion of said hole 2 is inclined in the opposite direction to that of scavenging swirl stream S, while the upper swirl angle theta3 is made larger than the lower one theta1. In the beginning of opening the scavenging hole 2 by an piston, storing swirl S is given to the scavenging hole since the scavenging hole is provided with the larger swirl angle theta3 so that exhaust in a portion A is blown off. When the scavenging hole is opened to the bottom, the swirl angle is reduced to theta1 to scavenge exhaust in the center of a cylinder. |
