Diskette incorporating permanent magnet generator with reduced cogging torque and permanent magnet generator for use in diskette

• US 6,265,800 B1
• Filed: 11/24/1999
• Issued: 07/24/2001
• Est. Priority Date: 11/27/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi Metals (Thailand) Ltd.
• Original Assignee: Hitachi Metals (Thailand) Ltd.
• Inventors: Masuzawa, Masahiro, Mita, Masahiro, Kimura, Fumio, Takahashi, Toshiko
• Primary Examiner(s): Ramirez, Nestor
• Assistant Examiner(s): LE, DANG D
• Application Number:
  US09/448,828
• Time in Patent Office: 608 Days
• Field of Search: 360/137, 310/152, 310/156, 310/254, 310/259, 310/185, 310/186, 310/187, 310/193, 310/216
• US Class Current: 310/152
• CPC Class Codes: 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
• CPC Class Codes: G11B 23/0327 for special applications not otherwise provided for
• CPC Class Codes: H02K 21/16 having annular armature cores with salient poles with homopolar co-operation H02K21/20
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02K 7/1807 Rotary generators H02K7/006 takes precedence

Abstract

A permanent magnet generator is so thin as to be incorporated in a 3.5″ diskette. The generator having so low cogging torque that can be rotated smoothly even by a low torque driving source as a 3.5″ FDD to generate stable output is disclosed. It has stator magnetic poles facing via a magnetic gap an outer circumferential surface of the stator permanent magnet having a plurality of magnetic poles on it. One to six of the stator magnetic poles are removed and instead of the removed magnetic poles provided is a soft magnetic piece to face the rotor magnetic poles. Grooves are preferably provided on the soft magnetic piece, facing the rotor magnetic poles. A notch is provided on the permanent magnet generator to avoid interference with an input/output terminal and/or a card contact terminal of the diskette for inserting a memory card.

Claims

1. A diskette comprising:

a diskette case;

a hub rotatable mounted in the diskette case; and

a permanent magnet generator provided in the diskette case, for converting mechanical energy into electrical energy while the hub is being positively driven to rotate, the permanent magnet generator having

(1) a a ring-shaped permanent magnet provided on the hub and rotatable with the hub, the permanent magnet having a circumferential surface on which a plurality of rotor magnetic poles are arranged, the rotor magnetic poles having alternately different polarities in a circumferential direction, and

(2) a stator mounted in the diskette case and extending around the permanent magnet, the stator having a plurality of magnetic pole teeth made of soft magnetic material, the magnetic pole teeth

(I) having radially inner ends on which stator magnetic poles are respectively provided, the stator magnetic poles facing the rotor magnetic poles via a magnetic gap,

(II) extending radially outward from the stator magnetic poles and having respective stator coils wound thereon, and

(III) having radially outer ends that are connected together by a back yoke made of soft magnetic material,

the stator having at least one soft magnetic piece positioned between adjacent magnetic pole teeth, the soft magnetic piece having a circumferential width that is equal to or greater than a circumferential width of one of the rotor magnetic poles,

wherein an axial thickness of the stator magnetic poles is smaller than an axial thickness of the permanent magnet.

2. The diskette as set forth in claim 1, wherein only 12 to 24 rotor magnetic poles are disposed at substantially equal angular intervals on the circumferential surface of the permanent magnet.

3. A permanent magnet generator incorporated in a diskette case in which a hub is rotatable mounted, the permanent magnet generator comprising:

(1) a ring-shaped permanent magnet provided on the hub and rotatable with the hub, the permanent magnet having a circumferential surface on which a plurality of rotor magnetic poles are arranged, the rotor magnetic poles having alternately different polarities in a circumferential direction; and

(2) a stator extending around the permanent magnet, the stator having a plurality of magnetic pole teeth made of soft magnetic material, the magnetic pole teeth

(I) having radially inner ends on which stator magnetic poles are respectively provided, the stator magnetic poles facing the rotor magnetic poles via a magnetic gap,

(II) extending radially outward from the stator magnetic poles and having respective stator coils wound thereon, and

(III) having radially outer ends that are connected together by a back yoke made of soft magnetic material,

the stator having at least one soft magnetic piece positioned between adjacent magnetic pole teeth, the soft magnetic piece having a circumferential width that is equal to or greater than a circumferential width of one of the rotor magnetic poles,

wherein an axial thickness of the stator magnetic poles is smaller than an axial thickness of the permanent magnet, and

wherein the permanent magnet generator converts mechanical energy into electrical energy while the hub is being positively driven to rotate.

4. The permanent magnet generator as set forth in claim 3, wherein only 12 to 24 rotor magnetic poles are disposed at substantially equal angular intervals on the circumferential surface of the permanent magnet.