Patent ID: 9709073
Date: 2017-07-18
CPC Classifications: F04D

Claim:
1. A centrifugal fan comprising: an impeller rotatable about a rotation axis; and a lower casing which is provided below the impeller, wherein the impeller includes an upper shroud having an upper portion formed with an inlet, a lower shroud, and a plurality of blades arranged along a circumference direction between the upper shroud and the lower shroud, and a fluid introduced from the inlet is discharged to a side of the impeller according to rotation of the impeller, wherein the blades extend from an inner side area to an outer side area in a radial direction, and the blades are only connected to the lower shroud with the inner side area of the blades such that at least an outer circumferential side portion of each blade faces an upper surface of the lower casing, wherein a surface of the lower casing, which faces the impeller, configures a portion of a wall surface which guides the fluid introduced from the inlet, wherein a surface of each blade is formed with a discontinuous portion having a step shape, the discontinuous portion being disposed closer to a leading edge portion of the blade than to a trailing edge portion of the blade, wherein each blade has a pressure surface and a negative pressure surface, the pressure surface being directed to a leading side of the impeller, the negative pressure surface being directed to a side opposite from the leading side to which the pressure surface is directed, wherein the pressure surface is inclined to be tapered toward the negative pressure surface at a constant taper angle, and wherein a distance between the pressure surface and the negative pressure surface is gradually decreased in a direction from the upper shroud to the lower casing.