Patent attributes
Provided is a throttle valve device for an internal combustion engine which is favorably protected from icing, and enables a favorable control of the intake flow rate by avoiding an abrupt increase in the flow rate particularly in a small opening angle range. An upstream recess (21) and a downstream recess (22) are formed in a lower part of the throttle bore (11) of the throttle valve device. Moisture that may deposit on the inner wall of the throttle bore is allowed to be drained to the recesses. A cross sectional area of one of the recesses over which the lower edge of the throttle valve member sweeps as the throttle valve member (30) opens from the fully closed position is smaller than that of the other recess so that an abrupt change in the intake flow rate can be avoided in a small opening angle region.
