| 摘要 |
PURPOSE:To eliminate the affection of upstream side, detect an average flow speed and permit to control the amount of inflow air correctly by a method wherein an airflow direction changing device, in which a ring is pivotted due to the biased distribution of air speed to flow the air-having average flow speed toward an air speed sensor, is provided in the device. CONSTITUTION:The airflow direction changing device 15 is consisting of a trunkated conical table-like ring 16, whose diameter is reduced from upstream side toward downstream side, and plate-like stoppers 17, 17 which are opposing thereto. According to this method, even if the air speed distribution in a small diametral tube section 11b is biased, the ring 16 of the airflow direction changing device 15 is pivotted by the unbalanced force of air pressure until it is abutted against the stopper 17 and is stopped, as a result, the airflow, having the average flow speed V1, is flowed toward the air speed sensor 12 by the inner peripheral surface of the ring 16. The air speed sensor 12 detects the average air speed V1 and outputs a signal to a regulating unit 21 while the regulating unit 21 compares the input signal from the air speed sensor 12 with an objective signal and outputs a control signal to a control motor 22. The control motor 22 controls the opening degree of a multi-blade damper 13 so that the average speed V1, detected by the air speed sensor 12, becomes a desired average air speed.
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