To materialize normal action of a throttle valve at a low temperature, by preventing frost from accumulating on a throttle valve, and preventing the throttle valve from adhering due to deposited frost.
The throttle valve 118 includes a disc-shaped valve element 118A having a diameter same as an inner diameter of a bore in the throttle valve 118, a motor for actuating the valve element 118A from a fully-closed state to a fully-opened state, a throttle position sensor for detecting the opening of the valve element 118A, and a speed-reducing gear for transmitting rotating force to a gear provided on a rotating shaft of the valve element 118A by reducing the speed of rotating force from the gear provided on the rotating shaft of the motor. A square conical projecting portion or recessed portion with low height is provided on a surface of the valve element 118A, and a flow of air passing through the throttle valve 118 is irregularly disturbed by the projecting portion or recessed portion.
Toshio Morita
Takao Matsuyama
Tadashi Muto