PURPOSE: To make it possible to infer exactly the amount of the suction air in an internal combustion engine by providing a channel area changeable member in the air flow channel at the downstream of a body that develops vortex in order to adjust the air channel area.
CONSTITUTION: Firstly a vortex type air flow meter 17 is fixed at a specified position in the air channel 5 that is formed in a throttle body. Next, the amount of projection into the channel 18 of a variable resisting member 22 is adjusted by an adjusting screw 23. Then the frequency of Karman vortex generation caused by the amount that passes through the air channel 5 and the vortex generating body 11 is adjusted by the adjusting screw 23, that is, the frequency is made to have a constant relation with the air speed through the channel 18 by changing the cross-sectional area of the outlet side of the channel 18. An internal combustion engine provided with the vortex air flow meter 17 thus adjusted is started, and if the speed of the air that flows in the air cleaner is sought from the frequency of Karman vortex generation, the amount of the air passing the air cleaner can be inferred exactly, because the relation between the air speed and the amount of the air that passes through the air channel 5 has been adjusted to have a constant relation.
YAMAMOTO TADAHIRO
MIWAKEICHI HIROSHI
OOTA TADAKI
