# US 12,603,533 B2 · Rotor assembly for an electric machine > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,603,533 B2 - Document ID: US12603533B2 - Status: Granted - Kind: B2 - Application number: 18/379,320 - Filed: 2023-10-12 - Published: 2024-08-29 - Granted: 2026-04-14 - Earliest claimed: 2023-02-24 - Assignees: BorgWarner Inc. - Applicants: BorgWarner Inc. - Inventors: Kevin Patrik Geimer; Henning Scheel; Tim Weiland - Web page: https://patentgrep.com/patent/US12603533B2 ## CPC - H02K 1/32: with channels or ducts for flow of cooling medium - H02K 7/003: {Couplings; Details of shafts (means for mounting rotors on shafts H02K1/28)} - H02K 9/19: for machines with closed casing and closed-circuit cooling using a liquid cooling medium, e.g. oil - H02K 2213/03: Machines characterised by numerical values, ranges, mathematical expressions or similar information - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) ## Abstract The present disclosure relates to a rotor assembly for an electric machine. The rotor assembly comprises a rotating shaft, a rotor and a fluid cooling system. The rotor is fixed to the rotating shaft. The rotor comprises a rotor core, a first end plate and a second end plate. The first end plate is provided at a first axial end of the rotor core. The second end plate is provided at a second axial end of the rotor core. The fluid cooling system comprises at least one fluid cooling pathway provided internally in the rotor. The at least one fluid cooling pathway is configured to guide cooling fluid through the rotor, and comprises at least one cooling channel and a downstream end plate channel. The at least one cooling channel extends through the rotor core from the first axial end to the second axial end. The downstream end plate channel is fluidically connected to a downstream end of the at least one cooling channel. The downstream end plate channel is restricted radially outwards by a radially outer wall portion. The at least one cooling channel is restricted radially inwards by a radially inner wall portion. A radially innermost position of the radially outer wall portion is arranged in a range about or at or radially inwards of a radially innermost position of a radially inner wall portion. ## Claims ### Claim 1 A rotor assembly for an electric machine comprising: a rotating shaft, a rotor fixed to the rotating shaft, the rotor comprising a rotor core, a first end plate provided at a first axial end of the rotor core and a second end plate provided at a second axial end of the rotor core, and a fluid cooling system comprising at least one fluid cooling pathway provided internally in the rotor, the at least one fluid cooling pathway being configured to guide cooling fluid through the rotor, wherein the at least one fluid cooling pathway comprises: at least one cooling channel extending through the rotor core from the first axial end to the second axial end, a downstream end plate channel being fluidically connected to a downstream end of the at least one cooling channel, wherein a radially innermost position of a radially outer wall portion restricting the downstream end plate channel radially outwards is arranged in a range about or at or radially inwards of a radially innermost position of a radially inner wall portion restricting the at least one cooling channel radially inwards; wherein the downstream end plate channel is a first downstream end plate channel which is further configured as an outlet channel of the at least one fluid cooling pathway to guide cooling fluid out of the rotor, and wherein the outlet channel comprises a first channel portion which is radially inwardly inclined relative to the axial direction and a second channel portion which is radially outwardly inclined, and wherein the second channel portion is arranged downstream of the first channel portion. ### Claim 2 (depends on 1) The rotor assembly of claim 1, wherein the range extends 50% of a radial height of the at least one cooling channel radially outwards and radially inwards from the radially innermost position. ### Claim 3 (depends on 1) The rotor assembly of claim 1, wherein the range extends 10% of a radial height of the at least one cooling channel radially outwards and radially inwards from the radially innermost position. ### Claim 4 (depends on 3) The rotor assembly of claim 3, wherein a pathway outlet is arranged at a radially outer circumference of the rotor or at a side face of the rotor. ### Claim 5 (depends on 1) The rotor assembly of claim 1, wherein the range extends 5% of a radial height of the at least one cooling channel radially outwards and radially inwards from the radially innermost position. ### Claim 6 (depends on 1) The rotor assembly of claim 1, wherein the at least one fluid cooling pathway extends from a pathway inlet in one of the first end plate or the second end plate to a pathway outlet in one of the first end plate or the second end plate. ### Claim 7 (depends on 6) The rotor assembly of claim 6, wherein the pathway outlet is arranged to discharge cooling fluid to an exterior of the rotor and inside a housing interior of a machine housing of the electric machine. ### Claim 8 (depends on 1) The rotor assembly of claim 1, wherein the at least one fluid cooling pathway comprises a first cooling channel and a second cooling channel, wherein a downstream end of the second cooling channel is fluidically connected to the outlet channel. ### Claim 9 (depends on 8) The rotor assembly of claim 8, wherein the first cooling channel and the second cooling channel are at least one of radially distanced and circumferentially distanced. ### Claim 10 (depends on 8) The rotor assembly of claim 8, wherein the at least one fluid cooling pathway further comprises a second downstream end plate channel which is configured as a connector channel to fluidically connect a downstream end of the first cooling channel and an upstream end of the second cooling channel. ### Claim 11 A rotor assembly for an electric machine comprising: a rotating shaft, a rotor fixed to the rotating shaft, the rotor comprising a rotor core, a first end plate provided at a first axial end of the rotor core and a second end plate provided at a second axial end of the rotor core, and a fluid cooling system comprising at least one fluid cooling pathway provided internally in the rotor, the at least one fluid cooling pathway being configured to guide cooling fluid through the rotor, wherein the at least one fluid cooling pathway comprises: at least one cooling channel extending through the rotor core from the first axial end to the second axial end, a downstream end plate channel being fluidically connected to a downstream end of the at least one cooling channel, wherein a radially innermost position of a radially outer wall portion restricting the downstream end plate channel radially outwards is arranged in a range about or at or radially inwards of a radially innermost position of a radially inner wall portion restricting the at least one cooling channel (124, 126) radially inwards; wherein the at least one fluid cooling pathway comprises a first cooling channel and a second cooling channel, wherein the downstream end plate channel is a first downstream end plate channel which is further configured as a connector channel to fluidically connect a downstream end of the first cooling channel and an upstream end of the second cooling channel, wherein the at least one fluid cooling pathway further comprises a second downstream end plate channel which is configured as an outlet channel to guide cooling fluid out of the rotor, and wherein the outlet channel comprises a first channel portion which is radially inwardly inclined relative to the axial direction and a second channel portion which is radially outwardly inclined, and wherein the second channel portion is arranged downstream of the first channel portion. ### Claim 12 (depends on 11) The rotor assembly of any one of claim 11, wherein the outlet channel is configured and arranged to guide cooling fluid out of the fluid cooling pathway radially outwardly inclined relative to the axial direction. ### Claim 13 (depends on 1, 11) The rotor assembly of any one of claim 1 or 11, wherein the rotor core comprises a plurality of circumferentially distributed permanent magnets. ### Claim 14 (depends on 1, 11) The rotor assembly of any one of claim 1 or 11, wherein the at least one fluid cooling pathway extends from a pathway inlet in one of the first end plate or the second end plate to a pathway outlet in one of the first end plate or the second end plate, and wherein the outlet channel defines the pathway outlet. ### Claim 15 (depends on 1) The rotor assembly of claim 1, wherein the at least one fluid cooling pathway further comprises an inlet end plate channel to guide cooling fluid into the rotor, and wherein the inlet end plate channel is arranged in one of the first end plate and the second end plate. ### Claim 16 (depends on 1) The rotor assembly of claim 1, wherein the fluid cooling system further comprises a cooling fluid supply arranged in the rotating shaft and fluidically connected to the at least one fluid cooling pathway. ### Claim 17 (depends on 1) The rotor assembly of claim 1, wherein the fluid cooling system comprises a plurality of fluid cooling pathways which are distributed circumferentially in the rotor. ### Claim 18 (depends on 1, 11) An electric machine comprising: a machine housing defining a housing interior, a stator assembly arranged in the housing interior, and a rotor assembly according to claim 1 or claim 11, wherein the rotor assembly is arranged in the housing interior. ### Claim 19 (depends on 18) The electric machine of claim 18, wherein the stator assembly comprises a stator core and stator windings. ### Claim 20 (depends on 19) The electric machine of claim 19, wherein the at least one fluid cooling pathway extends from a pathway inlet in one of the first end plate or the second end plate to a pathway outlet in one of the first end plate or the second end plate, and wherein the pathway outlet is arranged to discharge cooling fluid to end turns of the stator windings inside the housing interior.