Hybrid rotor assembly

1. An electric motor comprising:

a stator;

a rotor assembly comprising:

a hollow rotor shaft;

a differential gear assembly contained in the hollow rotor shaft;

a lamination stack mounted on said hollow rotor shaft;

a plurality of lamination cavities within said lamination stack, wherein each of said plurality of lamination cavities is defined by a first portion and a second portion, the lamination stack defining, for each of the plurality of lamination cavities, first and second tabs that extend into the lamination cavity;

a plurality of sintered permanent magnets corresponding to said plurality of lamination cavities, wherein said plurality of sintered permanent magnets is contained within said first portion of said plurality of lamination cavities, and wherein the first and second tabs abut the sintered permanent magnet at opposite ends thereof; and

a plurality of bonded magnets corresponding to said plurality of lamination cavities, wherein said plurality of bonded magnets is contained within said second portion of said plurality of lamination cavities, wherein each of the first and second tabs abuts one of the bonded magnets; and

a first planetary assembly positioned at a first end of the rotor assembly, and a second planetary assembly positioned at a second end of the rotor assembly, wherein the first and second planetary assemblies and the differential gear assembly are coaxially aligned.

2. The electric motor of claim 1 , wherein said plurality of sintered permanent magnets are comprised of a material selected from the group of materials consisting of ferrite, ceramic, alnico, samarium cobalt, neodymium and neodymium-iron-boron.

3. The electric motor of claim 1 , wherein said plurality of bonded magnets are comprised of a magnetic material and a binder.

4. The electric motor of claim 3 , wherein said magnetic material is selected from the group of materials consisting of samarium, samarium cobalt, neodymium, neodymium-iron-boron and strontium ferrite.

5. The electric motor of claim 3 , wherein said binder is selected from the group of materials consisting of nylon, polyphenylene sulfide, epoxy and polyamide.

6. The electric motor of claim 1 , wherein said plurality of bonded magnets consist of a plurality of anisotropic bonded magnets.

7. The electric motor of claim 1 , wherein said plurality of bonded magnets consist of a plurality of isotropic bonded magnets.

8. The electric motor of claim 1 , wherein said plurality of bonded magnets consist of injection molded bonded magnets.

9. The electric motor of claim 1 , wherein said plurality of bonded magnets consist of compression molded bonded magnets.

10. The electric motor of claim 1 , wherein said plurality of lamination cavities are configured as a plurality of pairs, wherein each pair corresponds to a pole of said electric motor.

11. The electric motor of claim 1 , wherein said plurality of lamination cavities are configured as a plurality of pairs, wherein each pair of said plurality of pairs is arranged in a V-shaped configuration.

12. The electric motor of claim 1 , wherein said electric motor is selected from the group consisting of interior permanent magnet motors, permanent magnet synchronous motors, interior permanent magnet brushless DC motors, and interior permanent magnet synchronous reluctance motors.

13. The electric motor of claim 1 , wherein both of the first and second tabs are positioned on a same side of the lamination cavity.