Cooling fan having bent bearing housing for retaining lubricant

Abstract

A cooling fan includes a stator, a base supporting the stator, and a rotor positioned to rotate with respect to the stator. The base includes a bearing housing and a central hole defined in the bearing housing. The rotor includes a hub and a shaft extending from the hub. An end of the shaft is fixed in the hub, and another end of the shaft is extending in the central hole defined in the bearing housing. The bearing housing includes a main cylindrical portion and a protruding portion bent radially inward from a top end of the main portion, and the protruding portion thus serves as a lubricant retaining portion of the bearing housing.

What is claimed is: 
     
         1 . A cooling fan comprising:
 a stator;   a rotor positioned to rotate with respect to the stator, the rotor comprising a hub and a shaft extending from the hub, an end of the shaft being fixed in the hub; and   a base supporting the stator, the base comprising a bearing housing and a central hole defined in the bearing housing, another end of the shaft extending in the central hole of the bearing housing, wherein the bearing housing comprises a main cylindrical portion and a protruding portion bent radially inward from a top end of the main portion, and the protruding portion thus serves as a lubricant retaining portion of the bearing housing.   
     
     
         2 . The cooling fan of  claim 1 , wherein the lubricant retaining portion is annular, and defines a through hole in the center thereof. 
     
     
         3 . The cooling fan of  claim 1 , wherein the shaft defines an annular slot in a circumferential wall thereof, at a position near a top end of the shaft close to the hub. 
     
     
         4 . The cooling fan of  claim 3 , wherein the slot is located in the central hole, and is completely below the lubricant retaining portion. 
     
     
         5 . The cooling fan of  claim 3 , wherein the lubricant retaining portion extends into the slot. 
     
     
         6 . The cooling fan of  claim 3 , wherein an upper surface of the lubricant retaining portion is near and spaced from the hub, to define a gap therebetween. 
     
     
         7 . The cooling fan of  claim 1 , wherein inner cylindrical surfaces of the main portion and the protruding portion are coplanar before the protruding portion is bent radially inward from the top end of the main portion. 
     
     
         8 . The cooling fan of  claim 7 , wherein an outer diameter of the protruding portion is smaller than an outer diameter of the main portion before the protruding portion is bent radially inward from the top end of the main portion. 
     
     
         9 . The cooling fan of  claim 1 , wherein the lubricant retaining portion is a hot-melted portion of the bearing housing. 
     
     
         10 . The cooling fan of  claim 1 , further comprising a bearing received in the bearing housing, wherein the shaft extends through the bearing, a plurality of channels is defined in the bearing, and each channel extends from a center of a top end of the bearing radially outward to a peripheral side surface of the bearing, and then down along a peripheral wall of the bearing along a direction parallel to an axis of the bearing to a bottom of the bearing. 
     
     
         11 . The cooling fan of  claim 10 , wherein the bearing defines an axial hole therein, the shaft extends through the axial hole, each channel is L-shaped, innermost extremities of the channels at the top end of the bearing communicate with the axial hole, and the channels are radially symmetrically arranged around the axis of the bearing. 
     
     
         12 . The cooling fan of  claim 1 , further comprising a bearing received in the bearing housing, wherein the shaft extends through the bearing, and the lubricant retaining portion, the bearing and the shaft cooperatively form a lubricant reservoir above a top portion of the bearing. 
     
     
         13 . A cooling fan comprising:
 a base;   a bearing housing extending upwardly from the base, the bearing housing defining a central hole therein; and   a rotor positioned to rotate with respect to the base and bearing housing, the rotor comprising a shaft, the shaft extending in the central hole of the bearing housing, wherein the shaft defines an annular slot in a circumferential wall thereof, a top end of the bearing housing is bent radially inward and extends into the annular slot, and the top end of the bearing housing serves as a lubricant retaining portion substantially sealing a top end of the central hole of the bearing housing.   
     
     
         14 . The cooling fan of  claim 13 , wherein the bearing housing includes a main cylindrical portion and the top end extending from the main portion and the top end is bent radially inward from the main portion to serve as the lubricant retaining portion. 
     
     
         15 . The cooling fan of  claim 13 , wherein the lubricant retaining portion is a hot-melted portion of the bearing housing. 
     
     
         16 . The cooling fan of  claim 13 , wherein a disk is located at a bottom end of the central hole, and the disk is made of wear-resistant material.