ELECTRIC MOTOR ROTOR THERMAL INTERFACE FOR HUB/SHAFT

1 . A cooling system of an electric machine, comprising:

a hub member;

a rotor core; and

a thermal interfacial material interposed between respective complementary mating surfaces of the hub member and the rotor core for substantially eliminating air gaps therebetween.

2 . The cooling system of claim 1 , wherein the hub member includes a substantially cylindrical surface with an annular rim at an axial end thereof.

3 . The cooling system of claim 1 , wherein the hub member includes a hub and a shaft with thermal interfacial material placed therebetween.

4 . The cooling system of claim 1 , further comprising an annular heat sink secured to an axial end of the hub member, wherein the thermal interfacial material is interposed between the heat sink and the hub member.

5 . The cooling system of claim 1 , further comprising an annular perimeter seal around at least one axial end of the thermal interfacial material for enclosing the material between the complementary mating surfaces.

6 . The cooling system of claim 5 , wherein the seal(s) include epoxy.

7 . The cooling system of claim 5 , wherein the enclosed thermal interfacial material remains in a liquid state.

8 . The cooling system of claim 1 , wherein the complementary mating surfaces have an interference fit.

9 . The cooling system of claim 1 , wherein the thermal interfacial material is substantially uncurable thermal grease.

10 . The cooling system of claim 1 , wherein the thermal interfacial material has a nominal thickness between 0.002 mm and 0.5 mm.

11 . The cooling system of claim 1 , wherein the hub member comprises a unitary shaft.

12 . A method of cooling an electric machine having a rotor core and a hub member, comprising placing a thermal interfacial material onto a heat transfer interface between the rotor core and the hub member, whereby the thermal interfacial material reduces contact resistance at the heat transfer interface.

13 . The method of claim 12 , further comprising:

heating and thereby expanding the rotor core;

cooling and thereby shrinking the hub member;

installing the cooled hub member within the heated rotor core; and

cooling the rotor core so that the hub member is interference fit therein.

14 . A method of cooling a stator of an electric machine, comprising:

providing a rotor core having a radially inner surface;

coating at least one of a radially outer surface of a hub member and the radially inner surface of the rotor core with a thermal interfacial material; and

inserting the hub member into the rotor core;

whereby the thermal interfacial material is interposed between the inner surface of the rotor core and the outer surface of the hub member.

15 . The method of claim 14 , further comprising sealing the rotor core to the hub member, thereby enclosing axial ends of the thermal interfacial material.

16 . The method of claim 15 , wherein the sealing comprises curing the thermal interfacial material.

17 . The method of claim 15 , wherein the sealing comprises applying a bead of epoxy.

18 . The method of claim 15 , wherein the sealing comprises extending the thermal interfacial material to an axial end surface of the rotor core and covering the extended thermal interfacial material with a radially-extending portion of a structure coupled to the same axial end of the rotor core.

19 . The method of claim 14 , further comprising machining the outer surface of the hub member to thereby substantially remove surface irregularities.

20 . The method of claim 14 , wherein the coating includes radially biasing the thermal interfacial material against the surface being coated.