| 摘要 |
PURPOSE:To ensure the stream velocity of a mixture even under low intake pressure upon low load running, by directly connecting intake passages of low and high loads to a carburetter of compound downdraft type provided with primary and secondary passages, and as well by communicating both intake passage together. CONSTITUTION:Upon low load running, an auxiliary throttle valve 16 closes an intake passage 29 of high load, and therefore, intake air pressure is selectively exerted to a carburetter 2 through intake passages 23 through 25 of low load, a distribution chamber 10 of low load and a sleelve 8. As a result, a mixture flows from the primary passage 3 through a throttle valve 5, and then flows down to the distribution chamber 10 of low load through the sleeve 8. Then, the mixture impinges to the bottom surface 11a of the distribution chamber 10 so that the mixture scatters, and then, flow from a suction port 26 into a combustion chamber 21 through the intake passages 25 through 23. At this time, the stream velocity of the mixture is accelerated through the intake passages 25 through 23 having small bores even under low intake pressure upon low load running, and therefore, strong vortex flow of mixture is generated in the combustion chamber 21, thereby the combustion efficiency of the mixture is enhanced. |
