Axial flow fan

Abstract

An axial flow fan has structural stability, decreased deformation, decreased blade unbalance and low noise level because the blade distribution angle has an optimum clearance angle and uneven rate.

1 . An axial flow fan comprising a hub, a plurality of blades arranged radially in a circumference of the hub and having a sweeping angle of which direction changes alternately in an area between a root and a tip of the blade, and a fan band for connecting integrally the tips of the each blade,
 wherein, a distribution angle A 1  of the blade is an angle between two lines which pass through the center of the hub and the middle of each root of the blade, respectively, where the adjacent two blades and the hub contact each other, and an angle of an equiangular distribution angle is 360/n, where n is the number of blades is n, the blades are arranged so that the clearance angle is in a range of 4° to 9°, while satisfying the equation: distribution angle of the blade=equiangular distribution angle±the clearance angle.   
     
     
         2 . The axial flow fan according to  claim 1 , wherein the clearance angle is in the range of 6° to 7°. 
     
     
         3 . The axial flow fan according to  claim 2 , wherein, an angle between two lines which pass through the center of the hub and the middle of each root of the blade, respectively, where the adjacent two blades and the hub come into contact, is a hub-side distribution angle of the blade, and an angle between two lines which pass through the center of the hub and the middle of each tip of the two blades, respectively is a tip-side distribution angle of the blade, the hub-side distribution angle of the blade and the tip-side distribution angle of the blade are same. 
     
     
         4 . The axial flow fan according to  claim 3 , wherein the blade has a sweeping angle which changes gradually as it goes from the tip of the blade having a forward angle to the root of the blade having a backward angle and connected to the hub and a plurality of flow dispersing areas between the forward angle area of a side of the tip of the blade and the backward angle area of a side of the root of the blade, in which the direction of the sweeping angle is alternately reversed. 
     
     
         5 . The axial flow fan according to  claim 4 , wherein the blade has a leading edge extending from the tip of the blade to the root of the blade, and the direction of the sweeping angle of the leading edge changes gradually from a maximum backward angle at the root of the blade to a maximum forward angle at the tip of the blade,
 wherein the direction of the sweeping angle is reversed from the backward angle at a side of the root of the blade to a forward angle, then reversed to a backward angle and reversed again to a forward angle so as to be connected to a forward angle at a side of the tip of the blade.   
     
     
         6 . The axial flow fan according to  claim 4 , wherein the blade has a trailing edge extending from the tip of the blade to the root of the blade, and a changing pattern of a sweeping angle of the trailing edge is the same as that of the leading edge. 
     
     
         7 . The axial flow fan according to  claim 1 , wherein, an angle between two lines which pass through the center of the hub and the middle of each root of the blade, respectively, where the adjacent two blades and the hub come into contact, is a hub-side distribution angle of the blade, and an angle between two lines which pass through the center of the hub and the middle of each tip of the two blades, respectively is a tip-side distribution angle of the blade, the hub-side distribution angle of the blade and the tip-side distribution angle of the blade are same.