| 摘要 |
<p>PROBLEM TO BE SOLVED: To reduce the fluctuation of flow velocity, to eliminate turbulence, to reduce breathing resistance, to reduce the loss of pressure, and to accurately measure the flow rate of suction air by allowing gas flow being narrowed by a narrowing passage to pass through a flowmeter, and by increasing flow velocity. SOLUTION: When the inner-periphery wall of a narrowing plate is opened in the range of suction-air flow 102 with high flow velocity, the suction-air flow with the high flow velocity and large turbulence directly passes near both resistors, thus increasing the fluctuation of the detection signal of a flow meter 20. In the specific range of both the sides of an imaginary axis line 110 of the narrowing plate, when the inner-periphery wall of an end face 24a of the inlet side of the narrowing plate is opened, the suction-air flow 102 with the high flow velocity collides with any part of the end face 24a, and the suction-air flow 102 is narrowed toward a passage 31 for effectively making uniform the flow velocity, thus reducing the fluctuation of the detection signal of a flowmeter 20, and accurately measuring the flow rate of suction air. When the suction air passes through the passage 31, that part in contact with the passage 31 is limited to an outlet pipe and the inner-periphery wall of the narrowing plate, thus reducing the loss of pressure since the breathing resistance (friction) is small as compared with a rectifying lattice.</p> |
