| 摘要 |
PURPOSE:To improve efficiency, by providing an opening part in the internal final end of a spaced part, formed between both inner and outer guide walls, so as to enhance a silencing effect while constituting the inner guide wall higher than the outer guide wall so as to smooth a flow in a return passage part. CONSTITUTION:A guide wall, constituting a return passage 20 of an air guide 14, is formed by inner and outer guide walls 22, 23, while a spaced part 25, having an opening part in the internal final end, is set between these guide walls 22, 23. As a result, the above spaced part 25, constituting a silencer and serving as a side branch in an acoustic circuit, enables a noise to be reduced. Further the inner guide wall 22 is constituted higher than the outer guide wall 23. In this way, even if the outer guide wall 23 comes to easily generate exfoliation of an air stream, the blower, supplying air as shown in the drawing from a step difference H generated by a difference of height between said guide walls, holds the air stream to be balanced. Air is supplemented to the spaced part 25 from the opening part 24 provided in the internal peripheral end. Thus fan efficiency can be enhanced by smoothing a flow in the return passage part 20.
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