Interior permanent magnet rotors with multiple properties and methods of making same
View Patent ↗An armature for use in an electric traction motor comprises a rotor having a central portion and a peripheral portion with the peripheral portion having a plurality of cavities. Permanent magnets solidified from liquid magnetic material are disposed in the cavities to form poles of the rotor with at least a portion of the cavities having directly abutting permanent magnets comprised of at least first and second magnetic materials of different properties injected in liquid or mobile form into single cavities. In interface regions between the at least first and second magnetic materials the first and second magnetic materials are intermingled to form a transition zone. A method of making the armature includes injecting the magnetic materials simultaneously as well as injecting a subsequent magnetic material when the initial magnetic material is still fluidly mobile.
1. A method of fabricating a rotor to form an armature for an electric traction motor wherein the rotor has a periphery and cavities adjacent the periphery, the method comprising:
injecting into a first portion of the cavities a first magnetic material in liquid or mobile form, the first magnetic material having a first magnetic property;
while the first magnetic material is still in liquid or mobile form injecting into a second portion of the cavities at least a second magnetic material having a second property, different from the first property, wherein selected cavities have both the first and second magnetic materials therein with an interface region between the first and second magnetic materials, and allowing the magnetic materials to solidify with the interface region having both materials intermingled in the interface region.
2. The method of claim 1 wherein the magnetic materials differ in magnetic strength or temperature stability.
3. The method of claim 1 wherein the first magnetic material is Nd Fe B and the second magnetic material is ferrite.
4. The method of claim 3 wherein the cavities are formed in the armature with a first portion adjacent the periphery of the rotor and a second portion formed inboard of the first portion and wherein the Nd Fe B is injected in the first portion and ferrite is injected into the second portion.
5. The method of claim 1 wherein the magnetic material is injected in cavity portions disposed at separate radial distances from the periphery of the rotor.
6. The method of claim 5 wherein there are high energy and low energy magnetic materials, the high energy magnetic materials being injected into a cavity portion proximate the periphery of the rotor and the low energy magnetic material being injected into a cavity portion inboard of the high energy magnetic materials.
7. The method of claim 6 wherein the cavities are formed in the armature with a first portion adjacent the periphery of the rotor and a second portion formed inboard of the first portion, and wherein the Nd Fe B is injected into the first portion and ferrite is injected into the second portion.
8. The method of claim 1 further including injecting with the first and the second magnetic material a third magnetic material in liquid or mobile form at a location between the first and second magnetic materials to create a third region, the third region being separated from the first and second magnetic materials by interface regions in which magnetic materials are mixed and remain mixed as the materials solidify.
9. The method of claim 8 wherein the first, second and third magnetic materials are injected simultaneously.
10. The method of claim 1 wherein the first and second magnetic materials are injected simultaneously.