A cooling fan ( 1 ) includes a fan housing ( 10 ), a stator ( 20 ), a rotor ( 30 ) and a bearing assembly ( 40 ). A tube ( 111 ) extends upwardly from a central portion of the fan housing. The stator is mounted around the tube. The bearing assembly includes a ball bearing ( 333 ) and a sleeve bearing ( 335 ) received in two ends of the tube, respectively. The rotor has a shaft ( 336 ) extending into and rotatably supported by the bearing assembly. An elastic element ( 332 ) is arranged on the ball bearing to provide a pressing force on the ball bearing toward the sleeve bearing. An oil retaining element ( 339 ) is arranged around a bottom end of the shaft and spaced from the shaft. The oil retaining element is attached to the sleeve bearing to provide oil for the sleeve bearing.
1. A cooling fan, comprising:
a tube with a through hole defined therein and extending along an axial direction thereof, the through hole comprising an upper portion and a lower portion with a diameter larger than that of the upper portion, a step being formed between the upper portion and the lower portion;
a stator mounted around the tube;
a bearing assembly comprising a ball bearing received in the upper portion of the tube and a sleeve bearing received in the lower portion of the tube, an elastic element arranged adjacent to the ball bearing to provide a pressing force on the ball bearing, and an oil retaining element arranged adjacent to the sleeve bearing to provide oil for the sleeve bearing;
a rotor having a shaft extending into and rotatably supported by the bearing assembly; and
a cover coupled to a bottom end of the tube to seal the bottom end of the tube, the sleeve bearing being sandwiched between the step and the cover;
wherein the oil retaining element is arranged in the cover, a top end of the oil retaining element abutting a bottom end of the sleeve bearing, an inner diameter of the oil retaining element being larger than a diameter of the shaft, and a bottom end of the shaft extending into the oil retaining element.
2. The cooling fan of claim 1 , wherein the oil retaining element is made of one of sponge and felt.
3. The cooling fan of claim 1 , wherein an annular flange extends radially and inwardly from a top end of the tube, and a locking plate is engaged with a middle of the shaft, the ball bearing being arranged on the locking plate, a top end of the ball bearing abutting a bottom end of the elastic element, and a top end of the elastic element abutting the flange of the tube.
4. A cooling fan, comprising:
a tube with a through hole defined therein and extending along an axial direction thereof, the through hole comprising an upper portion and a lower portion with a diameter larger than that of the upper portion, a step being formed between the upper portion and the lower portion;
a stator mounted around the tube;
a bearing assembly comprising a ball bearing received in the upper portion of the tube and a sleeve bearing received in the lower portion of the tube, an elastic element arranged adjacent to the ball bearing to provide a pressing force on the ball bearing, and an oil retaining element arranged adjacent to the sleeve bearing to provide oil for the sleeve bearing;
a rotor having a shaft extending into and rotatably supported by the bearing assembly; and
a cover coupled to a bottom end of the tube to seal the bottom end of the tube, the sleeve bearing being sandwiched between the step and the cover;
wherein a groove is defined in an outer circumference of a bottom end of the sleeve bearing, and the oil retaining element is received in the groove.
5. A cooling fan, comprising:
a tube with a through hole defined therein and extending along an axial direction thereof, the through hole comprising an upper portion and a lower portion with a diameter larger than that of the upper portion, a step being formed between the upper portion and the lower portion;
a stator mounted around the tube;
a bearing assembly comprising a ball bearing received in the upper portion of the tube and a sleeve bearing received in the lower portion of the tube, an elastic element arranged adjacent to the ball bearing to provide a pressing force on the ball bearing, an oil retaining element arranged adjacent to the sleeve bearing to provide oil for the sleeve bearing, and a second oil retaining element arranged between a top end of the sleeve bearing and the step of the tube; and
a rotor having a shaft extending into and rotatably supported by the bearing assembly.