Permanent magnet rotor and method and apparatus for making same

• US 5,345,129 A
• Filed: 02/16/1993
• Issued: 09/06/1994
• Est. Priority Date: 04/06/1992
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Molnar, David T.
• Primary Examiner(s): Stephan, Steven L.
• Assistant Examiner(s): NGUYEN, MATTHEW VAN
• Application Number:
  US08/017,533
• Time in Patent Office: 567 Days
• Field of Search: 310/40 R, 310/46, 310/89, 310/152, 310/156, 310/261, 29/598
• US Class Current: 310/156.28
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: F25D 17/06 by forced circulation
• CPC Class Codes: F25D 2400/04 Refrigerators with a horizontal mullion
• CPC Class Codes: F25D 29/00 Arrangement or mounting of control or safety devices
• CPC Class Codes: H02K 1/2726 the rotor consisting of a single magnet or two or more axially juxtaposed single magnets
• CPC Class Codes: H02K 1/2781 Magnets shaped to vary the mechanical air gap between the magnets and the stator
• CPC Class Codes: H02K 11/33 Drive circuits, e.g. power electronics H02K11/38 takes precedence
• CPC Class Codes: H02K 11/40 Structural association with grounding devices
• CPC Class Codes: H02K 15/03 having permanent magnets
• CPC Class Codes: H02K 21/18 having horse-shoe armature cores with homopolar co-operation H02K21/20
• CPC Class Codes: H02K 2211/03 Machines characterised by circuit boards, e.g. pcb
• CPC Class Codes: H02K 29/03 with a magnetic circuit specially adapted for avoiding torque ripples or self-starting problems
• CPC Class Codes: H02K 29/08 using magnetic effect devices, e.g. Hall-plates, magneto-resistors H02K29/12 takes precedence
• CPC Class Codes: H02K 3/524 for U-shaped, E-shaped or similarly shaped cores
• CPC Class Codes: H02K 5/02 Casings or enclosures characterised by the material thereof
• CPC Class Codes: H02K 5/08 Insulating casings
• CPC Class Codes: H02K 5/1672 radially supporting the rotary shaft at both ends of the rotor H02K5/1677 takes precedence
• CPC Class Codes: H02K 5/225 Terminal boxes or connection arrangements specially adapted for submersible motors H02K5/132
• CPC Class Codes: H02P 6/08 Arrangements for controlling the speed or torque of a single motor H02P6/10, H02P6/28 take precedence
• CPC Class Codes: H02P 6/12 Monitoring commutation; Providing indication of commutation failure
• CPC Class Codes: Y10S 310/06 : Printed-circuit motors and components
• CPC Class Codes: Y10T 29/49012 : Rotor
• CPC Class Codes: Y10T 29/53143 : Motor or generator

Abstract

A permanent magnet rotor includes a core and a plurality of magnetizable elements adhesively secured to the outer surface of the core. The core and adhered magnetizable elements are cold-pressed into a deep drawn cup-shaped outer metallic shell having a substantially closed end wall and an opposite open end defined by a peripheral edge which is rolled over the periphery of an end plate to encapsulate the core and magnetizable elements within the shell with an insulator disk disposed between each end of the core and the adjacent shell end wall and end plate. A method and apparatus for cold pressing the core and magnetizable elements into the cup-shaped shell and forming the peripheral edge of the shell over the end plate to effect encapsulation are also disclosed.

Claims

1. A permanent magnet rotor for use in an electric motor, said rotor comprising, in combination, a core, a plurality of magnetizable elements disposed about a generally fixed diameter cylindrical outer peripheral surface of said core, said magnetizable elements being arcuate in transverse cross-section and having arcuate outer surfaces lying in a common cylindrical envelope, and an outer cup-shaped relatively thin-walled metallic shell having an annular wall terminating at one end in a substantially closed end wall and having a peripheral edge defining an opposite open end, said core and magnetizable elements being disposed within said shell, said annular wall having an inner diameter to create an interference fit with said magnetizable elements when said core and elements are inserted into said shell, and an end plate within said open end of said shell opposite corresponding ends of said core and magnetizable elements, said peripheral edge of said shell being formed to overlie said end plate and retain said core and magnetizable elements in encapsulated relation within said shell.

2. A permanent, magnet rotor as defined in claim 1 wherein said shell and said end plate are made from stainless steel.

3. A permanent magnet rotor as defined in claim 1 wherein said interference fit is in the range of approximately 0.016-0.040 inch.

4. A permanent magnet rotor as defined in claim 1 including a first substantially electrically nonconducting insulating disk disposed within said shell between said closed end wall and adjacent ends of said core and magnetizable elements, and a second substantially electrically nonconducting insulating disk disposed between the opposite ends of said core and magnetizable elements and said end plate.

5. A permanent magnet rotor as defined in claim 4 wherein said first and second insulating disks are made of plastic.

6. A permanent magnet rotor as defined in claim 1 wherein said magnetizable elements are adhesively secured to the outer peripheral surface of said core.

7. A permanent magnet rotor as defined in claim 6 wherein said core has rib means formed on its outer peripheral surface, said magnetizable elements being interposed between said rib means, and an adhesive disposed between adjacent longitudinal side edges of said magnetizable elements.

8. A permanent magnet rotor as defined in claim 1 wherein said shell comprises a deep drawn shell having said end wall formed integral with said annular wall.

9. A permanent magnet rotor as defined in claim 1 wherein said shell is initially formed to flare outwardly at said peripheral edge to facilitate cold-pressing of said core and magnetizable elements into said shell.

10. A permanent magnet rotor for use in an electric motor, said rotor comprising, in combination, a core, a plurality of magnetizable elements disposed about a generally cylindrical outer peripheral surface of said core, said magnetizable elements being arcuate in transverse cross-section and having arcuate outer surfaces lying in a common cylindrical envelope, and an outer cup-shaped metallic shell having an annular wall terminating at one end in a substantially closed end wall and having a peripheral edge defining an opposite open end, said core and magnetizable elements being disposed within said shell, an end plate within said open end of said shell opposite corresponding ends of said core and magnetizable elements, a first substantially electrically nonconducting insulating disk disposed within said shell between said closed end wall and adjacent ends of said core and magnetizable elements, a second substantially electrically nonconducting insulating disk disposed between the opposite ends of said core and magnetizable elements and said end plate, said peripheral edge of said shell being formed to overlie said end plate and retain said core and magnetizable elements in encapsulated relation within said shell, said core having an axial bore formed therethrough, said closed end of said shell having a central aperture therethrough, and said end plate and first and second insulating disks having annular configurations so as to expose opposite ends of said axial bore.

11. A permanent magnet rotor for use in an electric motor and comprising a plurality of arcuate magnetizable segments secured to an outer substantially cylindrical surface of a core, said core and magnetizable segments having generally equal longitudinal lengths and being disposed within a metallic cup-shaped shell having an annular wall surrounding said magnetizable segments in a press fit therewith, said shell having a substantially closed end wall defining one end thereof and having a peripheral edge defining an opposite open end thereof, a metallic end plate disposed within said open end of said cup, said peripheral edge being formed to create a lip over said end plate to encapsulate said core and magnetizable segments within said shell between said closed end and said end plate.

12. A permanent magnet rotor as defined in claim 11 including a first insulator disk disposed between said closed end of said shell and first ends of said core and magnetizable segments, and a second insulator disk disposed between said end plate and opposite ends of said core and magnetizable segments, said insulator disks being operative to inhibit galvanic action between said core and said shell and end plate.

13. A permanent magnet rotor as defined in claim 12 wherein said peripheral edge of said shell is flared outwardly from said annular wall prior to forming said peripheral edge so as to facilitate insertion of said core and magnetizable segments into said shell and placement of said end plate within said open end of said shell.

14. A permanent magnet rotor as defined in claim 11 wherein said Shell comprises a deep drawn one-piece stainless steel shell pressed over the outer peripheral surfaces of said magnetizable segments, said annular wall having an interference fit with the outer surfaces of said magnetizable segments in the range of approximately 0.016-0.040 inch.

15. A permanent magnet rotor as defined in claim 14 wherein said end plate comprises an annular stainless steel disk, and including a substantially electrically nonconductive insulator disk interposed between said annular disk and adjacent ends of said core and magnetizable segments.

16. A permanent magnet rotor as defined in claim 11 wherein said magnetizable segments are made from ferrite material having a density of at least 4.8 grams per cubic centimeter.

17. Apparatus for making a permanent magnet rotor which includes a core having a plurality of magnetizable elements adhered to an outer peripheral surface of the core with the magnetizable elements having outer surfaces lying in a cylindrical envelope, and a cup-shaped metallic shell having an annular wall terminating at one end in a generally closed end wall and having an open opposite end defined by a peripheral edge, said apparatus comprising, in combination,

stripper plate means defining a generally cylindrical recess adapted to have a cup-shaped shell inserted therein with its open end exposed,

press shaft means disposed within said recess in a manner enabling relative movement between said stripper plate means and said press shaft means, said press shaft means defining a support end enabling placement of the closed end of a cup-shaped shell thereon when inserted into said recess with the open end of the shell oriented to have a core and adhered magnetizable elements placed on the shell in axial alignment with said open end, and

press plate means operative to cold-press the core and adhered magnetizable elements into the shell while simultaneously effecting progressive release of the shell from said recess as the core and magnetizable elements enter the shell.

18. Apparatus as defined in claim 17 wherein the annular wall of the shell has a predetermined outer diameter, said cylindrical recess in said stripper plate means receiving said annular wall in relatively close-fitting relation.

19. Apparatus as defined in claim 17 wherein the peripheral edge defining the open end of the shell is flared outwardly, said support end of said press shaft means being positioned to cause the flared end of the shell to extend outwardly of said recess when the shell is initially placed in said recess.

20. Apparatus as defined in claim 17 wherein said closed end wall of said shell has a central aperture therethrough, said support end of said shaft means having an axial pilot pin adapted to extend through said central aperture when the shell is placed within said recess.

21. Apparatus as defined in claim 17 including resilient means biasing said stripper plate means to a first position relative to said press shaft means to maximize the depth of said recess, said press plate means carrying means to engage and move said stripper plate means in a direction to cause the shell to be progressively ejected from the stripper plate recess as the core and magnetizable elements are pressed into the shell.

22. Apparatus for use in making a permanent magnet rotor which includes a cup-shaped shell having an annular wall terminating at one end in a generally closed end wall and having an open opposite end defined by a peripheral edge, a core having a plurality of magnetizable elements adhered to an outer peripheral surface of the core with the magnetizable elements having outer surfaces lying in a generally cylindrical envelope, said core and magnetizable elements being disposed within said shell so that the peripheral edge of the shell extends outwardly from the core and elements, and an end plate within the open end of the shell and overlying the core and magnetizable elements, said apparatus comprising, in combination,

rotatable support means defining a generally horizontal rotor support surface adapted to support a rotor thereon with the peripheral edge of the shell exposed,

clamp means operative to clamp the rotor to said support surface while maintaining said peripheral edge exposed,

means for effecting rotation of said support means so that the rotor rotates about a longitudinal axis of the shell,

and forming means movable from a non-operating position spaced from the rotor to an operating position to roll the exposed peripheral edge of the shell over the periphery of the end plate to encapsulate the core and magnetizable elements within the shell.