Intake air control device for an internal combustion engine

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

• an intake passage having a predetermined length and a substantially uniform section, except for an enlarged portion relatively close to an intake valve;
• a reed valve assembly arranged in said enlarged portion, and having side walls which divide an inside space of said enlarged portion into a first space surrounding said side walls and a second space surrounded by said side walls, to provide a section similar to said uniform section, and on which are mounted reed valves allowing an intake air to flow only from upstream to said first space;
• closing means for normally closing said second space downstream of said reed valves;
• communicating means for normally communicating said first space with said second space downstream of said closing means;
• first detection means for detecting a current engine speed condition;
• first control means for controlling said closing means in response to said current engine speed condition, to open said second space when the current engine speed condition is a high engine speed condition;
• and
• second control means for controlling said communicating means in response to said current engine speed condition, to interrupt said first space with said second space when the current engine speed condition is a high engine speed condition.