Axial flow fan and series axial flow fan

Abstract

An axial floss fan includes: a casino, defining a wind tunnel; a frame haying a plurality of spokes extended from the casing to the center in the radial direction of the casing so as to be across the wind tunnel, and a frame hub connecting the plurality of spokes at the center in the radial direction of the casing; a stator supported by the frame hub, in which a winding is wounded around the stator; a rotor pivotally supported by the frame hub in a rotatable manner and having a permanent magnet; an impeller fixed to the rotor and having a plurality of rotor blades; and a step part formed in at least one surface of the frame hub.

What is claimed is: 
     
         1 . An axial flow fan comprising:
 a casing defining a wind tunnel;   a frame having a plurality of spokes extended from the casing to the center in a radial direction of the casing so as to be across the wind tunnel, and a frame hub connecting the plurality of spokes at the center in the radial direction of the casing;   a stator supported by the frame hub, wherein a winding is wounded around the stator;   a rotor pivotally supported by the frame hub in a rotatable manner and having a permanent magnet;   an impeller fixed to the rotor and having a plurality of rotor blades; and   a step part formed in at least one surface of the frame hub.   
     
     
         2 . The axial flow fan according to  claim 1 , wherein a plurality of the step parts are concentrically formed in an inner bottom surface of the frame hub. 
     
     
         3 . A series axial flow fan comprising a plurality of axial flow fans according to  claim 1 ,
 wherein the axial flow fans are connected in series in an axial direction of a rotating shaft of the rotor.   
     
     
         4 . A series axial flow fan comprising a plurality of axial flow fans according to  claim 2 ,
 wherein the axial flow fans are connected in series in an axial direction of a rotating shaft of the rotor.