PURPOSE: To provide a fuel-air mixture form in a cylinder wherein rich fuel-air mixture flows to the vicinity of an ignition plug by a method wherein a flow of air that air flows in a cylinder from the inner side of an intake air valve occurs despite of the shape of an intake air port.
CONSTITUTION: An intake air control valve device formed in such a way that a valve body 29 arranged in an intake air passage 24 is closed in a given engine running state and a flow of intake air is controlled is provided. A valve body 29 is formed in a shape in which upper parts on both sides are respectively notched and a part of a plate member wherein the valve body 29 is formed between notch parts 29A is caused to remain as a plate part 29B. This constitution causes gathering of inflow air flowing to an engine during closing of the valve body 29 in a space between two intake air ports 25, the generation of a flow of air from the inner side of an intake air valve 22 to the inner central part of the cylinder 21 by means of the inflow air, and provision of a fuel-air mixture form in the cylinder 21 wherein rich fuel-air mixture flows to the vicinity of an ignition plug 26.
ARAMAKI KAZUYOSHI
IIYAMA AKIHIRO
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