Patent ID: 8402941

Claim:
An intake system for an internal combustion engine, comprising: an intake port connected to a cylinder of the internal combustion engine; an intake valve for opening and closing the intake port provided at a downstream end of the intake port; an intake pipe connected to the intake port, a cross-section of the intake pipe including an upper portion and a lower portion, which each of the upper portion and the lower portion have a substantially rectangular cross-section; an intake flow control valve that includes a valve element provided upstream of the intake valve in the intake pipe and a rotary shaft that supports an end of the valve element, and that rotates the valve element about a side surface of the intake pipe that faces the end of the valve element supported by the rotary shaft; and a rotation device that rotates the rotary shaft, wherein the cross-section of the intake pipe is shaped such that when the valve element is in a first position, where the intake flow control valve is rotated by the rotation device until the intake pipe is closed, a clearance between a side surface of the valve element and an inner surface of the intake pipe is smaller than a clearance between the side surface of the valve element and the inner surface of the intake pipe when the valve element is in a second position, where the intake flow control valve is rotated by the rotation device to a neutral position and wherein the side surface of the valve element faces the inner surface of the intake pipe, and the side surface of the valve element is perpendicular to the rotary shaft.