| 摘要 |
<p>PURPOSE:To measure an average air flow rate accurately by disposing two heating resistors in an air suction channel and subtracting the reverse flow rate automatically from a forward flow rate in case of a pulsating flow accompanied with reverse flow using the heat generated from the heating resistors. CONSTITUTION:Two heating resistors 2, 3 are disposed in a suction channel while being separated by 0.1-1.5mm and heated by means of hot wire circuits 1a, 1b. A signal from the upstream side resistor 2 is detected as a flow rate signal for forward flow. In case of reverse flow, the air heated by the downstream side resistor 3 covers the upstream side resistor 2 and the flow rate signal is decreased. At the initial stage of a subsequent forward flow, air heated by the resistors 2, 3 comes back to cover the upstream side resistor 2 thus decreasing the flow rate signal. In other words, the flow rate signal decrease two times and the reverse flow rate is subtracted automatically thus realizing accurate detection of the average flow rate of pulsating air flow containing a reverse flow.</p> |
