| 摘要 |
A hard disk drive (HDD) including a disk, a spindle motor to rotate the disk, the spindle motor including a spindle shaft, a plurality of magnetic circuits having cores and coils wound around the cores, the magnetic circuits being installed along a peripheral portion of the spindle shaft, a base plate to support the spindle motor, and an actuator to move a head. The magnetic circuits include a first magnetic circuit installed in an operating region of the actuator, and a second magnetic circuit installed outside the operating region of the actuator. The first and second magnetic circuits have different shapes. The first magnetic circuit has a larger length in a respective core direction thereof parallel to the base plate and the second magnetic circuit has a larger thickness in a direction perpendicular to the respective core direction and perpendicular to the base plate. Thus, a sufficient torque of the spindle motor can be ensured by increasing a number of windings of the wire of the magnetic circuits without increasing an electric current.
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