Multi-metallic mechanical retention hoop
A retention structure can be created using two or more different materials (e.g., one magnetic material, and one non-magnetic material) as a composite structure. The retention structure can include a cylindrical hoop comprising one or more one or magnetic regions tangentially alternating with one or more non-magnetic regions configured to surround and retain a plurality of magnets to a rotor, wherein the one or more magnetic regions are aligned with each one of the plurality of magnets and the one or more non-magnetic regions are aligned with one or more spaces between the plurality of magnets on the rotor. The magnetic material allows flux from the permanent magnets to flow through to the stators and the non-magnetic sections reduce leakage of magnetic flux to adjoining permanent magnets through use of non-magnetic materials. The retention structure can be fabricated using a hot isostatic press process.
1. A structure comprising:
a rotor;
a plurality of permanent magnets positioned around the rotor;
a plurality of spaces separating each permanent magnet of the plurality of permanent magnets; and
a cylindrical hoop configured to retain the plurality of permanent magnets to the rotor, the cylindrical hoop comprising:
a plurality of non-magnetic regions, wherein each of the plurality of non-magnetic regions is aligned with a corresponding space of the plurality of spaces; and
a plurality of magnetic regions, wherein each of the plurality of magnetic regions is aligned with a corresponding permanent magnet of the plurality of permanent magnets, tangentially alternates with each of the plurality of non-magnetic regions, and is joined to adjacent non-magnetic regions at a bond interface including a portion of each magnetic region extending into the adjacent non-magnetic region.
2. The structure of claim 1 , further comprising:
a stator surrounding the structure and having a second plurality of magnetic regions, wherein the cylindrical hoop provides for a continuous radial magnetic air gap between the plurality of permanent magnets positioned around the rotor and the second plurality of magnetic regions of the stator while reducing magnetic flux leakage across the plurality of non-magnetic regions.
3. The structure of claim 1 , wherein the plurality of magnetic regions and the plurality of non-magnetic regions form staves of the cylindrical hoop.
4. The structure of claim 1 , wherein the cylindrical hoop is sized to provide a pre-load force to the plurality of permanent magnets positioned around the rotor.
5. The structure of claim 1 , wherein the plurality of magnetic regions are a combination of a plurality of materials forming different layers.
6. The structure of claim 1 , wherein the plurality of non-magnetic regions are a combination of a plurality of materials forming different layers.
7. The structure of claim 1 , wherein each of the plurality of magnetic regions comprises a crowned exterior surface to shape flux lines of the plurality of permanent magnets positioned around the rotor.
8. The structure of claim 7 , wherein the bond interface extends along each crowned exterior surface.
9. The structure of claim 1 , wherein an interior surface of the cylindrical hoop is not circular, and wherein the plurality of permanent magnets positioned around the rotor are rectangular.
10. The structure of claim 1 , wherein an exterior surface of the cylindrical hoop is continuous.
11. The structure of claim 1 , wherein at the bond interface, the adjacent non-magnetic region partially surrounds the portion of each magnetic region.
12. An electric machine, comprising:
a housing;
a rotor assembly positioned inside the housing and including a plurality of permanent magnets separated by a plurality of spaces;
a retaining sleeve positioned around the rotor assembly and configured to retain the plurality of permanent magnets to the rotor assembly, the retaining sleeve comprising:
a plurality of non-magnetic regions, wherein each of the plurality of non-magnetic regions is aligned with a corresponding space of the plurality of spaces; and
a plurality of magnetic regions, wherein each of the plurality of magnetic regions is aligned with a corresponding permanent magnet of the plurality of permanent magnets, tangentially alternates with each of the plurality of non-magnetic regions, and is joined to adjacent non-magnetic regions at a bond interface including a portion of each magnetic region extending into the adjacent non-magnetic region; and
a stator surrounding the rotor assembly and the retaining sleeve and having a second plurality of magnetic regions.
13. The electric machine of claim 12 , further comprising:
an air gap between the rotor assembly and the stator, wherein the retaining sleeve provides for a continuous radial magnetic air gap between the plurality of permanent magnets and the second plurality of magnetic regions of the stator while reducing magnetic flux leakage across the plurality of non-magnetic regions.
14. The electric machine of claim 12 , wherein the plurality of magnetic regions and the plurality of non-magnetic regions form staves of the retaining sleeve.
15. The electric machine of claim 12 , wherein the retaining sleeve is cylindrical and is sized to provide a pre-load force to the plurality of permanent magnets of the rotor assembly.
16. The electric machine of claim 12 , wherein the plurality of non-magnetic regions are a combination of a plurality of materials forming different layers.
17. The electric machine of claim 12 , wherein each of the plurality of magnetic regions comprises a crowned exterior surface to shape of flux lines of the plurality of permanent magnets.
18. The electric machine of claim 12 , wherein an interior surface of the retaining sleeve is not circular, and wherein the plurality of permanent magnets are rectangular.
19. The electric machine of claim 12 , wherein an exterior surface of the retaining sleeve is continuous.
20. The electric machine of claim 12 , wherein the rotor assembly further comprises:
a shaft;
a pole retention structure connecting the plurality of permanent magnets to the shaft; and
a plurality of spokes, each spoke of the plurality of spokes having a proximal end and a distal end, wherein the proximal end of each spoke is attached to the shaft, and wherein the distal end of each spoke is attached to a non-magnetic region of the plurality of non-magnetic regions.