Patent ID: 6935787

Claim:
An oil-circulating structure for a fan comprising: an oily-bearing located in a fan housing of the fan and having: a) a central axis hole extending through a center thereof, a fan shaft of a fan hub of the fan being rotatably inserted into the central axis hole; and b) a hollow oil-collecting recess trench extending into an interior peripheral wall of the central axis hole and being spaced apart from two opposing ends of the central axis hole, the hollow oil-collecting recess trench having: i) a left-handed internal thread oil-guiding trench formed in an interior peripheral wall of and spirally extending a length of the hollow oil-collecting recess trench; and ii) a right-handed internal thread oil-guiding trench formed in the interior peripheral wall of and spirally extending the length of the hollow oil-collecting recess trench, the left-handed internal thread oil-guiding trench and the right-handed internal thread oil-guiding trench crisscrossing a predetermined number of times.