Patent ID: 8435018

Claim:
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.