| 摘要 |
An air-fuel mixture intake construction for an internal combustion engine comprises a primary intake system for supplying an air-fuel mixture under a full range of engine loads, a secondary intake system for supplying an air-fuel mixture under medium and high engine loads, and an induction passage having one end opening into a secondary intake passage immediately upstream of a secondary throttle valve disposed therein, and the other end opening immediately upstream of an intake valve for a combustion chamber. The open end of the induction passage in the secondary intake passage is spaced inwardly from an inner wall surface of the secondary intake passage to prevent fuel in liquid form from flowing into the induction passage from the secondary intake passage. According to another embodiment, a plurality of induction passages are provided respectively for combustion chambers and connected to a common passage which communicates with primary intake passages immediately downstream of a primary throttle valve and also with a slow fuel supply passageway in the secondary intake system. The induction passages comprise pipes opening into secondary intake passages, respectively, immediately upstream of secondary throttle valves. When the engine operates, the induction passage ejects air or an air-fuel mixture into the combustion chambers at high speeds to thereby form swirls therein for promotion of fuel combustion. With fuel supplied continuously from the slow fuel supply passageway into the induction passage, there is no danger for vapor lock to take place within the slow fuel passageway.
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