| 摘要 |
PURPOSE:To reduce a blow-through of a fresh air, and realize an improvement of the relative output and the fuel expense rate, and the like, by forming the section form on the way of a scavenging passage, to make the flow speed of the scavenging flow at the scavenging port wall side close to the exhaust port higher than that at the scavenging port wall side far from the exhaust port. CONSTITUTION:As a means to feed the scavenging flow from the front area scavenging route 3' into a cylinder 8 slower than that of the rear area scavenging route 3, the inlet section area at the crank case side of the front area scavenging route 3' is formed smaller than the section area of the bend 5' of the cylinder. The form of the rear area scavenging route 3 is made inversely to the front area scavenging route 3', making the section area of the crank case side inlet 4 larger and in a restricting form gradually up to the cylinder wall opening. Therefore, since the flowing energy from the rear area scavenging route 3 to the cylinder 8 is larger, and flows in the cylinder 8 earlier than the flow from the front area scavenging route 3', the air flow striking in the front area cylinder wall surface shown as the shaded portion B can be secured with receiving little influence from the two streams striking-and-expansion A.
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