A cooling fan includes a fan housing ( 10 ) having a shaft seat ( 16 ) extending downwardly therefrom, a stator ( 20 ) being fixedly mounted around the shaft seat, a shaft ( 80 ) with a top end being fixedly connected to the shaft seat and a free end ( 82 ) extending downwardly therefrom, a rotor ( 30 ) comprising a hub ( 32 ) having a plurality of blades ( 34 ) extending radially and outwardly, and a sleeve bearing ( 40 ). A fixing tube ( 36 ) extends upwardly from a center of the hub. The fixing tube has a closed bottom end and defines a fixing hole ( 360 ) therein. The sleeve bearing is fixedly received in the fixing hole of the fixing tube to rotate with the rotor. A bearing hole is defined in the sleeve bearing for extension of the free end of the shaft therethrough.
1. A cooling fan comprising:
a fan housing having a shaft seat extending downwardly therefrom;
a shaft having a top end being fixedly connected to the shaft seat of the housing and a free end extending downwardly from the shaft seat;
a stator being fixedly mounted around the shaft seat of the fan housing;
a rotor comprising:
a hub having a plurality of blades extending radially and outwardly therefrom; and
a fixing tube extending upwardly from the hub, the fixing tube having an open top end and a closed bottom end, a fixing hole being defined in the fixing tube communicating with the open top end; and
a sleeve bearing being fixedly received in the fixing hole of the fixing tube to rotate with the rotor during operation of the cooling fan, a bearing hole being defined in the sleeve bearing for extension of the free end of the shaft therethrough;
wherein the open top end of the fixing tube is higher than a top end of the sleeve bearing;
wherein the shaft defines an annular slot in a circular circumference thereof, near the top end of the shaft adjacent to the shaft seat of the fan housing, the slot being located higher than the top end of the sleeve bearing and between the top end of the sleeve bearing and the open top end of the fixing tube; and
wherein an oil retaining ring is fixedly mounted in the open top end of the fixing tube to enclose the open top end of the fixing tube, and an oil buffer is defined among the fixing tube, the sleeve bearing, the oil retaining ring and the shaft.
2. The cooling fan as claimed in claim 1 , wherein a middle portion of the sleeve bearing has an inner diameter larger than that of two opposite ends of the sleeve bearing, and a space is defined between the middle portion of the sleeve bearing and the shaft for improving a supply of lubrication oil to the sleeve bearing.
3. The cooling fan as claimed in claim 1 , wherein a plurality of channels communicating with the bearing hole are defined in an outer surface of the sleeve bearing.
4. The cooling fan as claimed in claim 1 , wherein an annular protrusion extends inwardly from an inner surface of the bottom end of the fixing tube, and the sleeve bearing is arranged on the protrusion.
5. The cooling fan as claimed in claim 4 , wherein a locking washer is arranged between the sleeve bearing and the protrusion of the fixing tube, the shaft defining an annular notch near the free end thereof, the locking washer engaging into the notch of the shaft to limit relative motion of the shaft and the sleeve bearing along an axial direction thereof.
6. A cooling fan comprising:
a fan housing having a shaft seat extending downwardly therefrom;
a shaft having a top end being fixedly connected to the shaft seat of the housing and a free end extending downwardly from the shaft seat;
a stator being fixedly mounted around the shaft seat of the fan housing;
a rotor comprising:
a hub having a plurality of blades extending radially and outwardly therefrom; and
a fixing tube extending upwardly from the hub, the fixing tube having an open top end and a closed bottom end, a fixing hole being defined in the fixing tube communicating with the open top end; and
a sleeve bearing being fixedly received in the fixing hole of the fixing tube to rotate with the rotor during operation of the cooling fan, a bearing hole being defined in the sleeve bearing for extension of the free end of the shaft therethrough;
wherein a middle portion of the sleeve bearing has an inner diameter larger than that of two opposite ends of the sleeve bearing, and a space is defined between the middle portion of the sleeve bearing and the shaft for improving a supply of lubrication oil to the sleeve bearing.
7. A cooling fan comprising:
a fan housing having a shaft seat extending downwardly therefrom;
a shaft having a top end being fixedly connected to the shaft seat of the housing and a free end extending downwardly from the shaft seat;
a stator being fixedly mounted around the shaft seat of the fan housing;
a rotor comprising:
a hub having a plurality of blades extending radially and outwardly therefrom; and
a fixing tube extending upwardly from the hub, the fixing tube having an open top end and a closed bottom end, a fixing hole being defined in the fixing tube communicating with the open top end; and
a sleeve bearing being fixedly received in the fixing hole of the fixing tube to rotate with the rotor during operation of the cooling fan, a bearing hole being defined in the sleeve bearing for extension of the free end of the shaft therethrough;
wherein an annular protrusion extends inwardly from an inner surface of the bottom end of the fixing tube, and the sleeve bearing is arranged on the protrusion.
8. The cooling fan as claimed in claim 7 , wherein a locking washer is arranged between the sleeve bearing and the protrusion of the fixing tube, the shaft defining an annular notch near the free end thereof, the locking washer engaging into the notch of the shaft to limit relative motion of the shaft and the sleeve bearing along an axial direction thereof.