Patent ID: 8675304

Claim:
A motor comprising: a stationary portion including a stator; and a rotating portion including a rotor magnet, and rotatably supported by the stationary portion through a lubricating oil; wherein the stationary portion includes: a shaft portion arranged to have a central axis extending in a vertical direction as a center thereof; the rotating portion includes: a sleeve portion arranged to have the shaft portion inserted therein; and a cover portion arranged to extend radially outward from the sleeve portion; the sleeve portion includes: a communicating hole arranged to extend through the sleeve portion; the rotating portion includes a hole portion defined therein; the hole portion is arranged radially outside the communicating hole; and V 2 <(σ 1 /σ 2 )·V 1 where σ1 is a density of the sleeve portion, V 1 is a volume of the communicating hole, σ 2 is a density of the cover portion, and V 2 is a volume of the hole portion.