Disk drive spindle motor with radial gap and field generating coils interconnected by ring flux guide

• US 5,742,450 A
• Filed: 03/08/1995
• Issued: 04/21/1998
• Est. Priority Date: 03/08/1995
• Status: Expired due to Fees

• Current Assignee: Hitachi Global Storage Technologies Netherlands BV (Western Digital Corporation)
• Original Assignee: International Business Machines Corporation
• Inventors: Moser, Michael Anthony
• Primary Examiner(s): Renner, Craig A.
• Application Number:
  US08/400,645
• Time in Patent Office: 1,140 Days
• Field of Search: 360/99.08, 360/98.07, 360/99.04, 310/67 R, 310/254, 369/258, 369/266
• US Class Current: 360/99.08
• 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: H02K 21/14 with magnets rotating within the armatures
• CPC Class Codes: H02K 21/22 with magnets rotating around the armatures, e.g. flywheel magnetos
• CPC Class Codes: H02K 2201/12 Transversal flux machines
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems

Abstract

A brushless permanent magnet DC motor for use as a disk drive spindle motor has a radial working gap but uses flat coils that generate magnetic fields that interact with the permanent magnet fields across the radial gap. The stator includes a plurality of angularly spaced stator teeth that have faces radially spaced across the gap from the permanent magnet. The magnetic flux from the permanent magnet is directed radially across the gap and into the stator teeth. Each stator tooth has an axially oriented post around which is wound a flat coil that generates an axial field. The central axis of the coil forms part of the magnetic circuit. The magnetic flux directed radially into each stator tooth is turned axially into the post. The axially directed magnetic flux through the coil and post on each tooth is redirected from the axial direction to the circumferential direction by a ring magnetic flux guide. The ring flux guide interconnects the stator teeth and forms part of the magnetic circuit.

Claims

1. A brushless direct current motor comprising:

a base;

a rotor attached to the base and rotatable about a rotational axis;

a magnet attached to the rotor for generating magnetic fields in a radial direction generally perpendicular to the rotational axis;

a plurality of stator teeth attached to and located on top of the base and circumferentially spaced around the rotational axis radially outwardly from the magnet, each stator tooth having a radially inner portion with a face radially spaced from the magnet to define a radial gap and a radially outer portion with an axial thickness less than the axial thickness of the face on the inner portion;

a like plurality of conductive coils, each coil being attached to and located on top of a corresponding stator tooth'"'"'s radially outer portion and generating a magnetic field in an axial direction generally parallel to said rotational axis when conducting electrical current; and

a ring flux guide of magnetically permeable material located above the coils and interconnecting the radially outer portions of the stator teeth in a generally circumferential direction;

whereby magnetic flux from the magnet across the radial gap to the face on the inner portion of a first one of said stator teeth is directed radially from the inner to the outer portion of said first stator tooth, axially through the coil on the outer portion of said first stator tooth, circumferentially by the ring flux guide to the coil on the outer portion of a second one of said stator teeth circumferentially adjacent said first stator tooth, axially through the coil on the outer portion of said second stator tooth, radially from the outer to the inner portion of said second stator tooth, and radially from the face on the inner portion of said second stator tooth across the radial gap to the magnet.

2. The motor according to claim 1 wherein the ring flux guide has a like plurality of axially directed holes and further comprising a like plurality of magnetically permeable posts, each post being attached to and extending axially from a corresponding stator tooth, wherein each of the coils is wound around a corresponding post and wherein each post is inserted through a corresponding hole of the ring flux guide for mechanical connection of the ring flux guide to the posts.

3. The motor according to claim 1 wherein each of the coils is a flat wound coil.

4. The motor according to claim 1 wherein the axial thickness of the radially outer portion of each of the stator teeth and its attached coil is less than the axial thickness of the magnet near the radial gap.

5. The motor according to claim 1 further comprising a bearing assembly having inner and outer races and fixed to and axially extending from the base, wherein the rotor comprises a sleeve mounted on the outer race of the bearing assembly and a magnetically permeable backing rim attached to the sleeve, and wherein the magnet is a magnetically segmented ring magnet attached to the backing rim;

whereby the backing rim provides a magnetic flux path between adjacent magnet segments.

6. A data disk drive motor assembly comprising:

the motor according to claim 1; and

a data disk mounted to the rotor of the motor.

7. A data recording disk drive comprising:

a base;

a spindle motor attached to the base comprising;

a bearing assembly having inner and outer races and fixed to and extending axially from the base;

a generally cylindrical sleeve mounted on the outer race of the bearing assembly and rotatable about a central rotational axis;

an annular magnetically permeable backing rim attached to and located radially outwardly of the sleeve;

a magnetically segmented ring magnet attached to and located radially outwardly of the backing rim for generating magnetic fields in a generally radial direction;

a plurality of stator teeth attached to and circumferentially spaced on top of the base around said rotational axis, each stator tooth having a radially inner portion with a face radially spaced from the radially outer surface of the ring magnet to define a radial gap and a radially outer portion with an axial thickness less than the axial thickness of the face on the radially inner portion;

a like plurality of conductive coils, each coil being attached to and located on top of a corresponding stator tooth'"'"'s radially outer portion and generating a magnetic field in an axial direction generally parallel to said rotational axis when conducting electrical current, the axial thickness of the radially outer portion of each of the stator teeth and its attached coil being less than the axial thickness of the ring magnet near the radial gap; and

a ring flux guide of magnetically permeable material located above the coils and mechanically interconnecting the radially outer portions of the stator teeth in a generally circumferential direction;

whereby magnetic flux from the ring magnet across the radial gap to the face on the inner portion of a first one of said stator teeth is directed radially from the inner to the outer portion of said first stator tooth, axially through the coil on the outer portion of said first stator tooth, circumferentially by the ring flux guide to the coil on the outer portion of a second one of said stator teeth circumferentially adjacent said first stator tooth, axially through the coil on the outer portion of said second stator tooth, radially from the outer to the inner portion of said second stator tooth, across the radial gap to the ring magnet, and through the ring magnet to the backing rim;

a data disk having data tracks and attached to the sleeve of the spindle motor;

a data read or write head for reading data from or writing data to the data tracks on the disk; and

an actuator attached to the base and supporting the head for positioning the head to the data tracks on the disk.

8. The disk drive according to claim 7 wherein the ring flux guide has a like plurality of axially directed holes and further comprising a like plurality of magnetically permeable posts, each post being attached to and extending axially from a corresponding stator tooth, wherein each of the coils is wound around a corresponding post and wherein each post is inserted through a corresponding hole of the ring flux guide for mechanical connection of the ring flux guide to the posts.

9. The disk drive according to claim 7 wherein each of the coils is a flat wound coil.