Fan structure

A fan structure, comprising:

• a hub;
• and
• a plurality of blades surrounding the hub, wherein each of the blades comprises:
• a first segment connected to the hub, wherein the first segment and the hub form a first surface therebetween, and the first surface has a first setting angle relative to a base plane of the fan structure, and the base plane is perpendicular to a central axis of the fan structure;
• a second segment extended outwardly from the first segment, wherein the second segment and the first segment form a second surface therebetween, and the second surface has a second setting angle relative to the base plane of the fan structure, and the first setting angle exceeds the second setting angle;
• and
• a third segment extended outwardly from the second segment, wherein the second and third segments form a third surface therebetween, and the third segment forms a fourth surface opposite to the third surface, wherein the height of the second segment along the central axis is less than that of the first segment, and the height of the third segment along the central axis is less than that of the second segment;
• wherein the first and second surfaces are equidistant from a first middle line of the first segment, the second and third surfaces are equidistant from a second middle line of the second segment, and the third and fourth surfaces are equidistant from a third middle line of the third segment, wherein the second middle line is longer than the third middle line.