| 摘要 |
PURPOSE:To find a vortex frequency from variation in differential pressure and also find in-pipe pressure from the mean output of one sensor, and to calculate a mass flow rate directly by a Karman type air flowmeter by detecting the pressure values of vortexes in opposite phases which are generated alternately behind a vortex generation body by a couple of pressure sensors. CONSTITUTION:The couple of absolute pressure sensors 4 and 7 which detect variations in pressure of opposite-phase vortexes 6 and 7 generated alternately are provided behind the vortex generation part 2 arranged in the intake pipe 1 of a Karman type air flowmeter. The detection outputs of both sensors 4 and 5 are inputted to a differential amplifier 13 through LPFs 11 and 12 of a processing circuit to detect the difference between the detection outputs, and an output which varies with the vortex frequency is processed by a comparing circuit 14 and inputted to an arithmetic circuit 16. Further, the output of one sensor 5 is averaged by an averaging circuit 15 and inputted to the arithmetic circuit 16. Then, the arithmetic circuit 16 calculates air mass G by using the output frequency of the comparing circuit 14 and the output level Pav of the circuit 15 as variables to accurately determine the quantity of injected fuel.
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