Air intake device for internal combustion engine

An air intake device for an internal combustion engine, comprising:

• a duct having therein a first air flow passage configured to conduct air into a combustion chamber of the internal combustion engine;
• a housing arranged to surround a periphery of the duct and having therein a second air flow passage that allows the first air flow passage to communicate with an intake port of the internal combustion engine;
• a rotary shaft rotatably supported by the housing;
• and
• a rectangular U-shaped rotary valve configured to reciprocate around the shaft in a rotational direction, the rotary valve having a valve plate, wherein
• an opening is defined between a downstream end of the duct and the valve plate and configured to generate a localized flow in the intake port of the internal combustion engine when the rotary valve is in a fully-closed state,
• the valve plate is configured to reciprocate around the shaft in the rotational direction so as to move outside the duct and along the downstream end of the duct, so that opening areas of the first and second air flow passages are changed,
• the valve plate has a circular curved surface portion having a radius of curvature centered on the shaft,
• the housing has a pair of opposed walls arranged at a downstream side of a moving path of the rotary valve in an air flow direction,
• the opposed walls are opposed to each other with the second air flow passage interposed between the opposed walls, and
• each of the opposed walls has a circular opposed surface that is opposed to the curved surface portion.