| 摘要 |
PURPOSE:To prevent exhaust gas in a cylinder from reversely flowing through a scavenging port to the air feed pipe side, by a method wherein, during the terminal stage of the expansion stroke of a piston, the internal pressure of the cylinder is reduced through exhaust of exhaust gas in the cylinder through first and second exhaust ports before the scavenging port is opened. CONSTITUTION:During an expansion stroke in which a piston 2 is in descending condition, exhaust gas in a cylinder 1 is exhausted through a first exhaust port 4a to the exhaust receiver 5 side by the opening action of an exhaust valve 4. When the piston 2 reaches position shown by a one-dotted chain line, a valve 11 is opened, and exhaust gas is exhausted through the valve 11 and a pipe path 12 from an exhaust port 10 to the exhaust receiver 5 side. When the piston 2 is further lowered and a scavenging port 3 is opened, the valve 11 is closed, and scavenging is effected by means of a fresh air through the scavenging port 3. |
