# US 5,334,896 A · Spindle motor for magnetic disk devices

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- Number: US 5,334,896 A
- Document ID: US5334896A
- Status: Granted
- Kind: A
- Application number: 07/936,501
- Filed: 1992-08-28
- Granted: 1994-08-02
- Earliest claimed: 1991-08-30
- Assignees: Fuji Electric Co., Ltd.
- Inventors: Masahiro Ohsawa
- Web page: https://patentgrep.com/patent/US5334896A

## CPC

- G11B 17/038: Centering or locking of a plurality of discs in a single cartridge
- G11B 19/2009: {Turntables, hubs and motors for disk drives; Mounting of motors in the drive (means for clamping of disk to turntable G11B17/022 and subgroups)}
- G11B 25/043: {using rotating discs}
- G11B 33/14: Reducing influence of physical parameters, e.g. temperature change, moisture, dust
- H02K 7/14: Structural association with mechanical loads, e.g. with hand-held machine tools or fans (with fan or impeller for cooling the machine H02K9/06)
- H02K 21/22: with magnets rotating around the armatures, e.g. flywheel magnetos
- G11B: INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER (recording measured values in a way that does not require playback through a transducer G01D9/00; recording or playback apparatus using mechanically marked tape, e.g. punched paper tape, or using unit records, e.g. punched or magnetically marked cards G06K; transferring data from one type of record carrier to another G06K1/18; circuits for coupling output of reproducer to radio receiver H04B1/20; gramophone pick-ups or like acoustic electromechanical transducers or circuits therefor H04R)
- H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53})

## Abstract

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.

## Claims

### Claim 1

A spindle motor for magnetic disk devices comprising: a stator; a hub axially supported on a frame of a stator; a bowl-like rotor yoke protruding from a base of the hub in a radial direction and covering a top and circumference of the stator; and a rotor magnet fitted to an inner circumference of the rotor yoke in a position opposite to a magnetic pole of the stator; a magnetic disk seated on the hub; wherein a clearance is provided between the magnetic disk seated on the hub and a top of the rotor yoke; wherein the rotor yoke is a magnetic body and the hub is made of an identical material as a substrate of the magnetic disk.

### Claim 2 (depends on 1)

A spindle motor for magnetic disk drives, as claimed in claim 1, wherein the clearance is sufficient to permit a magnetic head to be positioned between the magnetic disk and the top of the rotor yoke.

### Claim 3 (depends on 1)

A spindle motor for magnetic disk drives, as claimed in claim 1, wherein the information recording region of the magnetic disk extends over the top of the rotor yoke.