Patent ID: 9574565
Date: 2017-02-21
CPC Classifications: F04D

Claim:
1. A centrifugal fan comprising: an impeller arranged to rotate about a rotation axis; an impeller case arranged to accommodate the impeller; a motor arranged to rotate the impeller; and a motor case joined to the impeller case and arranged to accommodate the motor; wherein the impeller comprises: each blade is arranged to extend radially outward away from the rotation axis; an inner wall of the impeller case is arranged to cover the blades, and comprises an inside surface extending radially outward along an upper end portion of each blade; and the impeller case comprises an air inlet defined in a central portion thereof, with a side end portion of the air inlet comprising a curved surface projecting radially inward; wherein the curved surface of the air inlet is arranged to have an axial dimension smaller than a radial dimension thereof, the radial dimension being a dimension in a radial direction from a most radially inner point of the curved surface to a point where the curved surface extends furthest away from the impeller in an axial direction; wherein the blades comprise: the main blade has an axially upper end projecting upward and positioned radially outward of the radially innermost end of the curved surface of the air inlet; a distance between the main blade and the inside surface of the impeller case is arranged to be shortest at the axially upper end of the main blade; and wherein a plurality of auxiliary blades is equidistantly located between the two adjacent main blades.