Bearing structure for cooling fan

Abstract

A cooling fan includes a fan housing ( 50 ) having a central tube ( 52 ), a bearing structure received in the central tube, a stator ( 60 ) mounted around the central tube, and a fan blade set ( 70 ). The bearing structure includes a shaft ( 30 ) being rotatably received in the central tube and connecting to the fan blade set. An inner bearing ( 20 ) is fixedly mounted around the shaft to rotate with the shaft. Upper and lower outer bearings ( 10 ) are fixedly mounted into the central tube and are mounted around two opposite ends of the inner bearing, respectively. The inner and outer bearings are made of magnetic materials. The inner bearing floats between the outer bearings whereby rotation of the shaft does not cause the inner and outer bearings to wear.

1 . A cooling fan comprising:
 a fan housing having a central tube extending upwardly, the central tube defining a central hole therein;   a bearing structure comprising a shaft being rotatably received in the central hole of the central tube, an inner bearing being fixedly mounted around the shaft to rotate with the shaft, and a pair of outer bearings being fixedly mounted into the central tube and being mounted around two opposite upper and lower ends of the inner bearing, respectively, the inner and outer bearings being made of magnetic materials;   a stator mounted around the central tube; and   a fan blade set being connected with the shaft to rotate with the shaft to generate forced airflow.   
   
   
       2 . The cooling fan of  claim 1 , wherein an annular flange extends inwardly from a top of the central tube and is located over an upper one of the outer bearings for limiting movement of the upper outer bearing along an axial direction thereof. 
   
   
       3 . The cooling fan of  claim 2 , wherein the central hole extends through the central tube, a plug being coupled to a bottom of the central hole to seal the bottom of the central tube. 
   
   
       4 . The cooling fan of  claim 1 , wherein each outer bearing defines an inner space therein, the two opposite upper and lower ends of the inner bearing being respectively received in the inner spaces of the outer bearings, each outer bearing and a corresponding end of the inner bearing defining a gap therebetween. 
   
   
       5 . The cooling fan of  claim 4 , wherein the inner space is bowl-shaped, and an outer surface of each end of the inner bearing is arc-shaped. 
   
   
       6 . The cooling fan of  claim 4 , wherein the inner space is hemispheroidal-shaped, and an outer surface of each end of the inner bearing is hemispheroidal-shaped. 
   
   
       7 . The cooling fan of  claim 1 , wherein an outer surface of each outer bearing has one of the following shapes: bowl, hemispheroid and column. 
   
   
       8 . The cooling fan of  claim 1 , wherein two opposite ends of the shaft extend through the two opposite upper and lower ends of the inner bearing and the two outer bearings, and each outer bearing defines a through hole with a diameter larger than that of the shaft for extension of the shaft therethrough. 
   
   
       9 . The cooling fan of  claim 1 , wherein a top end of the shaft extends through the inner bearing and an upper one of the outer bearings arranged on the upper end of the inner bearing and connects to the fan blade set, a bottom end of the shaft being received within the inner bearing. 
   
   
       10 . The cooling fan of  claim 1 , wherein each end of the inner bearing and a side of a corresponding outer bearing facing to each other have same polarity, thereby generating repelling magnetic forces therebetween. 
   
   
       11 . A bearing structure, comprising:
 a shaft;   an inner bearing being fixedly mounted around the shaft to rotate with the shaft; and   a pair of outer bearings being mounted around two opposite ends of the inner bearing, respectively;   
     wherein the inner and outer bearings are made of magnetic materials, each end of the inner bearing and a side of a corresponding outer bearing facing to each other having same polarity, thus generating a repelling magnetic force therebetween. 
   
   
       12 . The bearing structure of  claim 11 , wherein each of the outer bearings defines an inner space therein, the two opposite ends of the inner bearing being respectively received in the inner spaces of the outer bearings, each end of the inner bearing and the corresponding outer bearing defining a gap therebetween. 
   
   
       13 . The bearing structure of  claim 12 , wherein the inner space and an outer surface of each end of the inner bearing each are one of bowl-shaped and hemispheroidal-shaped, and an outer surface of each outer bearing has one of the following shapes: bowl, hemispheroid and column. 
   
   
       14 . The bearing structure of  claim 11 , wherein two opposite ends of the shaft extend through the two ends of the inner bearing and the two outer bearings, and each outer bearing defines a through hole with a diameter larger than that of the shaft for extension of the shaft therethrough. 
   
   
       15 . The bearing structure of  claim 11 , wherein a top end of the shaft extends through the inner bearing and one of the outer bearings arranged on a top end of the inner bearing, a bottom end of the shaft being received within the inner bearing.