Inner-rotor fan

Abstract

An inner-rotor fan includes a hub, a retaining tube, and a magnetic ring. The retaining tube is disposed in the hub, and the magnetic ring is disposed on the retaining tube. The retaining tube and the hub are formed as a single piece, and thus the stability of the fan is increased. Moreover, the magnetic flux in an inner hole of the magnetic ring is about 0 Wb, and thus an iron ring within the magnetic ring may be excluded.

What is claimed is: 
     
         1 . An inner-rotor fan, comprising:
 a fan frame;   a bearing disposed on the fan frame; and   a rotor comprising:
 a hub; 
 a retaining tube disposed in the hub; 
 a magnetic ring, having an inner hole, wherein the retaining tube is disposed in the inner hole; 
 a shaft, disposed on the hub, located within the retaining tube, and passing through the bearing; and 
 a plurality of blades disposed around the hub, 
   wherein the retaining tube and the hub are formed as a single piece, and a magnetic flux in the inner hole is about 0 Wb.   
     
     
         2 . The inner-rotor fan as claimed in  claim 1 , wherein the magnetic ring is a plastic magnetic ring, and made of magnetic powder and plastic. 
     
     
         3 . The inner-rotor fan as claimed in  claim 2 , wherein the hub and the retaining tube have the same material, and the hub and the retaining tube is made of plastic. 
     
     
         4 . The inner-rotor fan as claimed in  claim 1 , wherein the magnetic ring has a groove adjacent to the retaining tube. 
     
     
         5 . The inner-rotor fan as claimed in  claim 1 , excluding a magnetic field shielding element located between the magnetic ring and the shaft. 
     
     
         6 . The inner-rotor fan as claimed in  claim 1 , wherein the retaining tube has a plurality of first positioning structures, and the magnetic ring has a plurality of second positioning structures disposed on the inner hole, wherein the first positioning structure is retained on the second positioning structure to make the magnetic ring rotate following the retaining tube. 
     
     
         7 . The inner-rotor fan as claimed in  claim 6 , wherein the first positioning structure is a rib, the second positioning structure is a groove, and the rib is located in the groove. 
     
     
         8 . The inner-rotor fan as claimed in  claim 6 , wherein the first positioning structure is a groove, the second positioning structure is a rib, and the rib is located in the groove. 
     
     
         9 . The inner-rotor fan as claimed in  claim 1 , wherein the fan frame comprises a base and a sleeve disposed on the base, and the bearing is disposed in the sleeve. 
     
     
         10 . The inner-rotor fan as claimed in  claim 9 , wherein the fan frame further comprises a holding portion disposed on the base and around the sleeve. 
     
     
         11 . The inner-rotor fan as claimed in  claim 10 , further comprising a stator disposed on the holding portion, and corresponding to the magnetic ring. 
     
     
         12 . The inner-rotor fan as claimed in  claim 11 , wherein the sleeve further comprises a support portion, the stator further comprises an electric power board fixed on the support portion and a coil electrically connected with the electric power board and corresponding to the magnetic ring.