Fuji Electric Co., Ltd.

Masahiro Ohsawa

Eiichi Yonezawa

The invention provides a spindle motor for magnetic disk devices capable of coping with small magnetic disks, in which the leaking magnetic flux in the motor section does not adversely affect the magnetic head. The spindle motor consists of a stator, a magnetic disk mounting hub axially supported on a frame of the stator, a bowl-like rotor yoke protruding from the base of the hub in the radial direction and covering the top and circumference of the stator, and a rotor magnet fitted over the inner circumference of the rotor yoke in a position opposite to the magnetic pole of the stator. A clearance space comprising is provided between a mounting seat of the magnetic disk and the top of the rotor yoke. The outer diameter of the hub base is also smaller than the information-recording region of the magnetic disk, and the rotor yoke is fitted as a magnetic body on the hub, which is made from the same material as the substrate of the magnetic disk.

Spindle motor for magnetic disk devices

A spindle motor for rotating magneto-optical discs that are attracted and held on a fixed position at an end of a motor driven shaft by means of a clamping rotor with internal field magnets. The spindle motor has a set of stator coils and a set of field magnets held internally mounted on the shaft side of the clamping rotor. The field magnet and stator coil sets are arranged at a regular interval in a ring around the circumference of the clamping rotor and of a shield member of the spindle motor respectively, leaving a thin gap between the stator coils and the field magnets. The saucer-like clamping rotor is made of a non-magnetic material and applied at the disc side, on which side a magneto-optical disc is charged, of the rotary shaft. The field magnets, being fitted on the face of the clamping rotor opposed to the magneto-optical disc mounted face, function both as a means for driving the clamping rotor for motor operation, and as a disc-attracting device.

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Machida, Japan

Masahiro Ohsawa