Patent ID: 7585155

Claim:
An axial flow fan, comprising: a hub; and a plurality of blades arranged along a circumferential outer surface of the hub in a radial direction such that the direction of a sweeping angle of each of the plurality of blades alternately changes in a region between a blade root and a blade tip, the blade root being at a junction of the blade and a hub having a center, wherein a chord length extending between a leading edge and a trailing edge of the blade gradually decreases from the blade root to at the junction of the blade and the hub to an intermediate portion of the blade and has a minimum value at a predetermined position on the intermediate portion of the blade, and the chord length gradually increases from the predetermined position of the intermediate portion of the blade having the minimum value to the blade tip, first and second inflection points respectively at first and second points where the sweeping angle of the blade changes between a backward sweeping angle and a forward sweeping angle, the first and second inflection points being spaced apart from each other and the blade root by a predetermined distance on a mid-chord line connecting middle points between the leading edge and the trailing edge, the second inflection point being ahead of the first inflection point, based on a first line passing through both the hub center and an intersection point between the mid-chord line and the blade root, in the direction of blade rotation.