Stator of heat dissipation fan

Abstract

A stator includes a stator core, two insulation frames, and a plurality of coils. The stator core includes a plurality of yokes stacked one on the other along an axial direction of the stator core. The stator core has a larger outer size at one end thereof than the other end thereof. The insulation frames respectively cover the one end and the other end of the stator core. Each coils wounds around the insulation frames and corresponding portions of the stack of yoke. Each of the yokes includes an annular plate and a plurality of arms extending outwardly from an outer periphery of the annular plate, outer edges of the arms of each yoke are located on a same imaginary circle which has a common center with the annular plate, and diameters of the imaginary circles of the yokes are different from each other.

What is claimed is: 
     
         1 . A stator comprising:
 a stator core having an axis and comprising a plurality of yokes stacked one on the other along the axis, wherein the stator core has a first perimeter at one end thereof that is greater than a second perimeter at another end;   two insulation frames respectively covering the one end and the other end of the stator core; and   a plurality of coils each wound around one of the two insulation frames and corresponding portions of the plurality of yokes;   wherein each of the plurality of yokes comprises an annular plate and a plurality of arms extending outwardly from an outer periphery of the annular plate, outer edges of the plurality of arms of each yoke are located on a same imaginary circle which has a common center with the annular plate, so that there are a plurality of imaginary circles, and one of the imaginary circles being different from another thereof.   
     
     
         2 . The stator of  claim 1 , wherein the imaginary circles are increasing along the axis from the direction from a top end of the stator core to a bottom end of the stator core. 
     
     
         3 . The stator of  claim 1 , wherein a cylindrical receiving space is cooperatively defined in a central portion of the stator core by inner peripheries of the annular plates of the yokes, and outer peripheries of the arms of the yokes are located a same imaginary tapered surface. 
     
     
         4 . The stator of  claim 3 , wherein the diameter of the imaginary tapered surface decreases from the one end of the stator core to the other end of the stator core. 
     
     
         5 . The stator of  claim 1 , wherein the outer size of the stator core decreases along the axial direction thereof.