| 摘要 |
PURPOSE:To increase the output of an engine, by promoting atomization of fuel by forming a plurality of parallel intake passages by vertically dividing the intake passage on the downstream side of a throttle valve constituting a variable venturi carburetor, and opening the plurality of parallel intake passages successively along with downward movement of the throttle valve. CONSTITUTION:At the time of high-load operation of an engine, a piston-like throttle valve 6 is in its upper position, so that a primary in-take passage 18 and a secondary intake passage 20 of an intake passage 12 divided by a partition wall 16 are both fully opened. Resultantly, a large amount of intake air is passed through the passages 18, 20. Here, since the effective jet area of a main jet 10 is large, a large amount of fuel is also ejected from the main jet 10 and air-fuel mixture is supplied to a combustion chamber 26 via a crankcase 14 and a scavenging passage 22. At the time of low-load operation of the engine, on the other hand, the throttle valve 6 is in its lower position, so that only the primary intake passage 18 is opened. Resultantly, all of intake air is introduced into the primary passage 18 and the velocity of intake-air flow is increased, so that sufficiently atomized fuel is supplied to the combustion chamber 26. |
