Laminated back iron structure for increased motor efficiency

• US 5,812,341 A
• Filed: 05/21/1997
• Issued: 09/22/1998
• Est. Priority Date: 06/06/1995
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Boutaghou, Zine-Eddine, Luoma, Richard W.
• Primary Examiner(s): Cao, Allen T.
• Application Number:
  US08/861,237
• Time in Patent Office: 489 Days
• Field of Search: 360/99.08, 360/98.07, 360/98.06, 360/98.01, 310/67 R, 310/156, 310/46
• US Class Current: 360/99.08
• CPC Class Codes: H02K 1/2788 the rotor consisting of a single magnet or two or more axially juxtaposed single magnets

Abstract

A rigid disk drive spindle motor includes a bobbin carried by the motor hub which has a permanent magnet attached to the inner cylindrical surface and a laminated back iron mounted at the outer cylindrical surface. The laminated back iron may be in the form of concentric cylinders or a spiral wound strip with adjoining cylinders or convolutions secured to and electrically separated from one another by an adhesive material. In another form, the back iron may be formed as a series of washer like rings mounted on the bobbin which is a configuration similar to the laminations used in the motor stator and would permit fabrication using the same manufacturing techniques. The back iron is formed of high resistance silicon steel so that both the back iron material and the laminated structure discourage Eddy current formation. The spiral wound embodiment may also be modified by having the spiral strip periodically, axially interrupted to further reduce undesired induced currents. Use of the bobbin serves to assure the concentricity of the closely adjoining stationary and rotary parts of the spindle motor and to facilitate easier manufacture and assembly. To further confine the magnetic fields, laminated fringe ring assemblies are provided at each axial end of the back iron structure. These assemblies are formed of washer like rings of permeable material that are secured to one another and electrically separated by adhesive material.

Claims

1. A rigid disk data storage device comprising

a base member;

an actuator mounted on said base member which carries and positions a plurality of transducer assemblies;

a spindle assembly including a spindle motor with at least one data storage disk secured to rotate in unison with a rotor assembly of said spindle motor, wherein the rotor assembly further comprises a bobbin having a central cylindrical portion comprising an inside and an outside;

a permanent magnet mounted on the inside of the bobbin central cylindrical portion with a cylindrical laminated back iron radially adjoining and substantially concentrically mounted with respect to said permanent magnet on the outside of the bobbin central cylindrical portion, wherein said laminated back iron comprises a spiral wound strip of magnetically permeable material, wherein said spiral wound strip comprises adjoining convolutions, wherein each of the adjoining convolutions has a surface and wherein the surfaces are separated and electrically isolated from one another; and

a first laminated fringing ring assembly disposed at one axial end of said cylindrical laminated back iron and axially aligned with said back iron to suppress fringe fields, wherein said first laminated fringing ring assembly is formed of a series of flat, washer shaped rings that are separated and electrically isolated from adjoining rings, and wherein laminations of the first laminated fringing ring assembly are substantially perpendicular to laminations of the cylindrical laminated back iron.

2. The rigid disk data stooge device of claim 1 wherein said laminated back iron is formed of a strip of silicon steel and said surfaces are separated by an adhesive material.

3. The rigid disk data storage device of claim 1 wherein the adjacent washer shaped rings of said first fringing ring assembly are separated by an adhesive material.

4. The rigid disk data storage device of claim 2 wherein said spiral wound back iron is periodically interrupted by axially extending separations to further reduce undesired induced currents.

5. The rigid disk data storage device of claim 1, further comprising:

A second laminated fringing ring assembly disposed at another axial end of said cylindrical laminated back iron and axially aligned with said back iron to suppress fringe fields.

6. A rigid disk data storage device comprising

a base member;

an actuator mounted on said base member which carries and positions a plurality of transducer assemblies;

a spindle assembly including a spindle motor with at least one data storage disk secured to rotate in unison with a rotor assembly of said spindle motor, wherein the rotor assembly further comprises a bobbin having a central cylindrical portion comprising an inside and an outside;

a permanent magnet mounted on the inside of the bobbin central cylindrical portion with a cylindrical laminated back iron radially adjoining and substantially concentrically mounted with respect to said permanent magnet on the outside of the bobbin central cylindrical portion, wherein said laminated back iron comprises a sequence of concentric cylinders of high resistance silicon steel with adjoining concentric cylinders separated by a continuous layer of adhesive, electrically insulating material; and

a first laminated ring assembly disposed at one axial end of said cylindrical laminated back iron and axially aligned with said back iron to suppress fringe fields, wherein said first laminated fringing ring assembly is formed of a series of flat, washer shaped rings that are separated and electrically isolated from adjoining rings, and wherein laminations of the first laminated fringing ring assembly are substantially perpendicular to laminations of the cylindrical laminated back iron.