US Patent 7229214 Fluid dynamic bearing unit

A fluid dynamic bearing unit includes a bearing housing (20) axially defining therein a bearing hole (21), a rotary shaft rotatably received in the bearing hole with a radial space formed between the rotary shaft and the bearing housing, and lubricant filled in the radial space. A ventilating path (25) is formed in a wall of the bearing housing to communicate a bottom of the bearing hole with an exterior of the bearing housing.