PURPOSE: To prevent the air-fuel ratio from becoming irregular among a plurality of cylinders by a method wherein throttle valves provided in a plurality of branched air intake passages and linked to one another are provided with vent holes, resectively, so that the flow rates of air in the passages are equalized.
CONSTITUTION: Air sucked into a main air intake passage 3 through an air cleaner 1 during the operation of the engine is distributed into the branched air intake passages 6 through a distribution chamber 5 and then introduced into the cylinder 8. At the same time, a fuel is injected from each of injectors 13 toward the downstream side of the throttle valves 10 in the passages 6. In this case, each of the throttle valves 10 is provided with the vent hole 15 having the same surface area of opening, and therefore the quantity of air flowing through the vent hole 15 is made equal throughout the passages 6. That is, it is possible to prevent the distribution of the sucked air into the branched air intake passage 6 by the distribution chamber 5 from becoming irregular and to prevent the quantities of the air in the passages 6 from becoming irregular due to the differences among the opeing degrees of the throttle valves 10. Accordingly, it is possible to prevent the air-fuel ratio from becoming irregular throughout the cylinders 8.
UKEI HIRONOBU
OKADO TOSHIHIRO
