| 摘要 |
PURPOSE: A scroll case for a blower unit is provided to effectively control counterflow and vortex phenomena in a cut off without generating whistle noise and increasing a relative size of the cut off part with relation to the scroll case, thereby reducing noise of a low frequency band for preventing unpleasant or fatigue feelings. CONSTITUTION: A scroll case for a blower unit includes a scroll part(1) having a first winding part(B-P) of which curvature is gradually decreased with a uniform ratio from a scroll ending point(P) upward along a periphery of a centrifugal fan(2), the scroll ending point being meeting a guide wall surface(31) of a plane surface connected to a discharge hole(3), and a second winding part(A-B) for connecting the first winding part to an ending point formed with a cut off(12) in a winding angle below 90deg. with relation to a center of the centrifugal fan in a different geometrical shape, wherein the cut off is formed in a position satisfying a relationship formula: (WF-WC)/pi is larger than or equal to -0.25 and smaller than or equal to 0.16, wherein WC represents a distance of a line extended from the cut off to the guide wall surface in parallel with the guide wall surface, WF represents a distance between tangent lines from an outer periphery of the centrifugal fan to the guide wall surface in parallel to the guide wall surface, and pi represents an outer diameter of the centrifugal fan.
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