| 摘要 |
PURPOSE:To improve the efficiency of fuel consumption by constricting a pair of scavenging air passages on both sides of a piston toward a scavenging port, thereby increasing the velocity at which the stream of scavenging air flows into the cylinder through the scavenging port. CONSTITUTION:A pair of scavenging air passages 13 provided on both sides of a piston 14 are constricted toward a scavenging port 15 so that the horizontal cross sectional area S1 of the scavenging air passage 13 facing the lower end 15a of the scavenging port 15 is less than 60% of the horizontal cross sectional area S2 of the scavenging air passage 13 facing the upper end 16a of the scavenging port 16 when the piston 14 is at BDC. This increases the velocity at which the scavenging air A flow into the cylinder 12 through the scavenging port 15. As a result the incoming scavenging air A flows, smoothly guided, along the inside 12a of the cylinder facing the exhaust port 17. Thus the scavenging air is prevented from flowing into the exhaust port 17 as indicated by arrow B, thus so much improving the fuel consumption efficiency. |
