The main parameters "DC Fan" cooling fan including flow, pressure, speed, power, etc fan bearing system generally recommended best selection of ball bearing fan heat fan because life often depends on the reliability of its bearings, ball bearing system has been It has been shown to have high efficiency and low heat characteristics. Genus rolling friction ball bearing, rolling a metal beads, small contact surface friction coefficient; and oil bearing sliding friction, a large contact surface, after long-term use, the oil will be volatile, bearing easy to wear, friction coefficient, the larger the noise late , short life.