| 摘要 |
PROBLEM TO BE SOLVED: To improve impeller characteristics by controlling reduction in fan efficiency caused by an air counter flow between a front panel and an impeller occurred when the fan is pressurized. SOLUTION: This fan comprises an impeller 104 having a plurality of blades 104A mounted so as to be sandwiched between a main plate 110 and a side plate 109. In this fan, a spirallike ventilation flue 102A starting at a tongue portion around the impeller 104 and a scroll casing 102 for sandwiching the spirallike ventilation flue 102A with a front panel 102B with a suction opening 105 of a bell mouth shape 113 are formed. This fan also comprises a shaft 103A which provides rotational torque for the main plate 110. With regard to the shape of the tongue, a tongue curvature R1 between the front panel 102B and the impeller 104 is made smaller than a tongue curvature R2 on the impeller 104. In addition, the height of a sub-tongue 1 between the front panel 102B and the impeller 104 is made larger than that of a main tongue 2 on the impeller 104.
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