| 摘要 |
PURPOSE:To enable the ignition to be surely performed, by providing in a predetermined period a non-combustible cycle in which air, being inducted into a crankcase in accordance with the rising of a piston compressing mixed gas in a combustion chamber, is supplied to the combustion chamber in a scavenge stroke, scavenging exhaust gas. CONSTITUTION:An engine, when it is in partial load operation at a low speed, opens an atmospheric air communication path 22 by a control valve 28, enabling a crankcase 4 to perform suction of air. Under this condition, when a piston 6 rises in a non-combustible cycle, the engine, generating negative pressure in the crankcase 4 by shutting of the atmospheric air communication path 22 through an opening and closing valve 23, sucks mixture gas into the crankcase 4. In the next combustible cycle, the engine, increasing a pressure in the crankcase 4 by a descent of the piston 6, supplies the mixture gas from a scavenge passage 16 to a combustion chamber 14. And the following rise of the piston 6 generates a negative pressure in the crankcase 4, but the engine, opening the opening and closing valve 23, inducts air into the crankcase 4 to be utilized for scavenging exhaust gas in a scavenge stroke. |
