Patent ID: 6908287

Claim:
An axial flow fan including a hub, and a plurality of blades extending radially around the hub, wherein: each of the blades has a sweep angle varying gradually from a backward angle at a root of the blade connected to the hub to a forward angle at a tip of the blade; each of the blades has a flow dispersion region having a plurality of regions where the sweep angle is alternately changed, at a region defined between a backward sweep angle region at the root of the blade and a forward sweep angle region at the tip of the blade; and each of the blades has a leading edge extending from the root of the blade to the tip of the blade, and has a sweep angle varying gradually from a maximum backward angle at the root of the blade to a maximum forward angle at the tip of the blade while being alternately changed in direction at an intermediate portion of the leading edge from a backward direction, corresponding to a sweep direction at the root of the blade, to a forward direction, and then from the forward direction to the backward direction, so that the sweep angle is finally changed from the backward direction to the forward direction corresponding to a sweep direction at the tip of the blade.