# US 2014/0197702 A1 · Electric motor rotor thermal interface with axial heat sinks > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197702 A1 - Document ID: US20140197702A1 - Status: Published application - Kind: A1 - Application number: 13/744,167 - Filed: 2013-01-17 - Published: 2014-07-17 - Earliest claimed: 2013-01-17 - Assignees: Remy Technologies, L.L.C. - Applicants: Remy Technologies, LLC - Inventors: Bradley D. Chamberlin - Web page: https://patentgrep.com/patent/US20140197702A1 ## CPC - H02K 9/223: {Heat bridges} - H02K 9/227: {Heat sinks} - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract A cooling system of an electric machine first and second heat sinks respectively mounted to axial ends of a rotor core, and a thermal interfacial material interposed between respective complementary surfaces of the heat sinks and the rotor core for substantially eliminating air gaps therebetween. A method of cooling includes placing thermal interfacial material onto a heat transfer interface between the rotor core and the heat sink, whereby the thermal interfacial material reduces contact resistance at the heat transfer interface. A method of cooling includes coating an axially outer surface of the rotor core and/or an axially inner surface of an annular heat sink with thermal interfacial material, and attaching the heat sink to the rotor, whereby thermal interfacial material is interposed between the inner surface of the heat sink and the outer surface of the rotor core. ## Claims ### Claim 1 A cooling system of an electric machine, comprising: a rotor core; first and second heat sinks respectively mounted to axial ends of the rotor core; and a thermal interfacial material interposed between respective complementary surfaces of the heat sinks and the rotor core for substantially eliminating air gaps therebetween. ### Claim 2 (depends on 1) The cooling system of claim 1, wherein the heat sinks each include an annular mounting portion and fins extending axially outward from the mounting portion. ### Claim 3 (depends on 1) The cooling system of claim 1, further comprising an annular perimeter seal around the thermal interfacial material at each axial end for enclosing the material between the complementary surfaces. ### Claim 4 (depends on 3) The cooling system of claim 3, wherein the seals include epoxy. ### Claim 5 (depends on 3) The cooling system of claim 3, wherein the enclosed thermal interfacial material remains in a liquid state. ### Claim 6 (depends on 1) The cooling system of claim 1, further comprising a hub, wherein the heat sinks have an interference fit with the hub. ### Claim 7 (depends on 6) The cooling system of claim 6, wherein the interference fit includes respective outside diameter surfaces of the heat sinks and an inside diameter surface of the hub. ### Claim 8 (depends on 1) The cooling system of claim 1, wherein the thermal interfacial material is substantially uncurable thermal grease. ### Claim 9 (depends on 1) The cooling system of claim 1, wherein the thermal interfacial material has a nominal thickness between 0.002 mm and 0.5 mm. ### Claim 10 A method of cooling an electric machine having a heat sink and a rotor core, comprising placing a thermal interfacial material onto a heat transfer interface between the rotor core and the heat sink, whereby the thermal interfacial material reduces contact resistance at the heat transfer interface. ### Claim 11 (depends on 10) The method of claim 10, wherein the electric machine further comprises a hub, the method further comprising: heating and thereby expanding the hub; installing an annular heat sink within the hub; and cooling the hub so that the heat sink is interference fit therein. ### Claim 12 (depends on 10) The method of claim 10, wherein the heat sink comprises a plurality of fins extending axially away from the heat transfer interface, and wherein the method further comprises balancing the electric machine by bending at least one fin. ### Claim 13 (depends on 10) The method of claim 10, further comprising balancing the electric machine by at least one of depositing and removing material from the heat sink. ### Claim 14 A method of cooling a rotor of an electric machine, comprising: coating at least one of an axially outer surface of a rotor core and an axially inner surface of an annular heat sink with a thermal interfacial material; and attaching the heat sink to the rotor; whereby the thermal interfacial material is interposed between the inner surface of the heat sink and the outer surface of the rotor core. ### Claim 15 (depends on 14) The method of claim 14, further comprising sealing the heat sink to the rotor, thereby enclosing at least one radial end of the thermal interfacial material. ### Claim 16 (depends on 15) The method of claim 15, wherein the sealing comprises curing the thermal interfacial material. ### Claim 17 (depends on 15) The method of claim 15, wherein the sealing comprises applying a bead of epoxy. ### Claim 18 (depends on 14) The method of claim 14, wherein the coating includes biasing the thermal interfacial material against the surface being coated. ### Claim 19 (depends on 14) The method of claim 14, further comprising balancing the rotor by at least one of depositing and removing material from the heat sink. ### Claim 20 (depends on 15) The method of claim 15, wherein the heat sink comprises a plurality of fins extending axially away from the thermal interfacial material, and wherein the method further comprises balancing the electric machine by bending at least one fin.