| 摘要 |
PURPOSE:To ensure optimum area for a scavenge passage in a full range of load, by providing a rotary valve which changes area of the scavenge passage in such a manner as to increase the area of the scavenge passage synchronously with increase of a throttle opening. CONSTITUTION:A pressure relief passage 10 is provided between one of the plural scavenge passages 6, 6 and the internal surface 12 of a cylinder wall in the upper from an exhaust port 7, and a rotary valve 11, interlocking to a throttle pedal 26, is provided in a connection part of said passage to the scavenge passage 6. Then the rotary valve 11 is constituted in such a manner that the pressure relief passage 10 is communicated to the scavenge passage 6 only when a throttle is fully closed or almost fully closed, and area of the scavenge passages 6, 6 are increased synchronously with increase of a throttle opening. In this way, optimum area of the scavenge passage can be obtained in a full range of load, and scavenge flow speed of a mixture, flowing into a combustion chamber 31 from the scavenge passages 6, 6, can be increased to fully perform scavenge action, then a turbulence flow for effective combustion can be obtained. |
