| 摘要 |
PROBLEM TO BE SOLVED: To solve four problems in a conventional carburetor for a spark- ignition internal combustion engine: (1) bleed air lead-in instability, (2) clogging of dust in fuel, (3) the necessity of repeated work in an air-fuel ratio characteristic improvement method of a low speed system due to two-point air-fuel ratio adjustment, which are all related to a pilot screw, and (4) the aging effect of an air-fuel ratio characteristic caused by sludge sticking to an intake passage, which is related to the pilot screw or an air screw. SOLUTION: To solve the problems (1), (2), an air by-pass is provided for communicating the upper reaches and lower reaches of a throttle valve at least during idling, and a by-pass control throttle is provided for controlling the ventilation resistance of the air by-pass. To solve the problems (3), (4), the air by-pass is constituted not to communicate the upper reaches with lower reaches of the throttle valve at a certain fixed opening or more of the throttle valve. |
