Patent ID: 9039360
Filing Date: 2015-05-26
Classification: F04D

Abstract:
1. A centrifugal fan configured such that an impeller, having a plurality of blades along a circumferential direction and disposed between a disk-shaped main plate and an annular shroud, is housed in a casing configured by an upper casing and a lower casing, and that an air suctioned from a suction opening is discharged outward in a radial direction of the impeller by a centrifugal force due to a rotation of the impeller, wherein the shroud has a curved surface formed from an outer edge portion toward a center thereof, wherein the shroud has a plurality of protrusion portions thereon which are formed annularly and spirally on the curved surface of the shroud and arranged such that a gap is formed between each of the protrusion portions and the upper casing, and wherein a lower surface of the upper casing is faced to the top end of the protrusion portions such that each of the gaps therebetween are the same.