US-12620874-B2 - Winding slot-embedded vapor chambers and heat pipes with endcap heat sinks for electric machines

US12620874B2US 12620874 B2US12620874 B2US 12620874B2US-12620874-B2

Abstract

Presented are electric machines with winding-slot embedded heat pipes/vapor chambers and endcap-integrated heat sinks, methods for making/using such machines, and vehicles equipped with such machines. An electric machine, such as a traction motor or electric generator, includes an outer housing, a stator assembly mounted to the housing, and a rotor assembly rotatably mounted adjacent the stator assembly. The stator assembly includes an annular stator core with one or more electromagnetic stator windings mounted on or in the stator core. The rotor assembly includes a cylindrical rotor core and one or more electromagnetic rotor windings mounted in rotor slots of the rotor core. One or more heat pipes are mounted in the rotor slot(s), adjacent the rotor winding(s), and projecting axially from one or both axial ends of the rotor core. Each heat pipe extracts thermal energy from the rotor winding(s) and transfers the thermal energy out from the rotor core.

Inventors

Muhammad A. Zahid
Alexander FORSYTH
Khorshed Mohammed Alam
Mazharul CHOWDHURY

Assignees

GM Global Technology Operations LLC

Dates

Publication Date: 20260505
Application Date: 20231006

Claims (20)

1 . An electric machine, comprising: a housing; a stator assembly including a stator core attached to the housing and an electromagnetic stator winding mounted in a stator slot of the stator core; a rotor assembly including a rotor core rotatably attached to the housing adjacent the stator assembly and an electromagnetic rotor winding mounted in a rotor slot of the rotor core, the rotor winding configured to magnetically mate with the stator winding; a heat pipe mounted in the rotor slot adjacent the rotor winding and projecting axially from an axial end of the rotor core, the heat pipe being configured to passively extract thermal energy from the rotor winding and transfer the thermal energy out from the rotor core; a rotor endcap attached adjacent the axial end of the rotor core and abutting a longitudinal end of the heat pipe to receive therefrom the extracted thermal energy transferred out from the rotor core, the rotor endcap including a heat pipe cavity recessed into an axial surface of the rotor endcap and nesting therein the longitudinal end of the heat pipe.
2 . The electric machine of claim 1 , wherein the rotor winding includes a bundle of rotor windings mounted in the rotor slot, and the heat pipe includes a plurality of heat pipes mounted in the rotor slot and embedded in the bundle of rotor windings.
3 . The electric machine of claim 2 , wherein the heat pipes are stacked in a rectilinear line extending radially with respect to the rotor core.
4 . The electric machine of claim 3 , wherein the heat pipes are mutually parallel and radially spaced from one another.
5 . The electric machine of claim 1 , wherein the heat pipe includes a sealed canister containing a working fluid configured to change phases between a liquid phase and a gas phase to thereby extract the thermal energy from the rotor winding and transmit the extracted thermal energy out through the axial end of the rotor core.
6 . The electric machine of claim 5 , wherein the heat pipe further includes a wick structure located inside the sealed canister and configured to transfer the working fluid, when in the liquid phase, from axial ends of the sealed canister to a central region of the sealed canister.
7 . The electric machine of claim 1 , wherein the rotor slot includes a plurality of rotor slots extending axially through and spaced circumferentially around the rotor core, the rotor winding includes a plurality of rotor windings wound through the rotor slots, and the heat pipe includes a plurality of heat pipes extending axially through the rotor slots substantially parallel to an axis of rotation of the rotor core.
8 . The electric machine of claim 7 , wherein the heat pipes are arranged in a plurality of pipe stacks spaced circumferentially around the rotor core, embedded in the rotor windings, and each located in a respective one of the rotor slots.
9 . The electric machine of claim 1 , wherein the rotor endcap further includes a plurality of endcap fins protecting away from the rotor core and configured to dissipate the extracted thermal energy transferred out from the rotor core and received by the rotor endcap.
10 . The electric machine of claim 9 , further comprising an active thermal management (ATM) system configured to splash or spray a coolant fluid onto the endcap fins.
11 . An electric machine, comprising: a housing; a stator assembly including a stator core attached to the housing and an electromagnetic stator winding mounted in a stator slot of the stator core; a rotor assembly including a rotor core rotatably attached to the housing adjacent the stator assembly and an electromagnetic rotor winding mounted in a rotor slot of the rotor core, the rotor winding configured to magnetically mate with the stator winding; a heat pipe mounted in the rotor slot adjacent the rotor winding and projecting axially from an axial end of the rotor core, the heat pipe including: a sealed canister containing a working fluid configured to change phases between a liquid phase and a gas phase to thereby passively extract thermal energy from the rotor winding and transmit the extracted thermal energy out from the rotor core through the axial end of the rotor core; a wick structure located inside the sealed canister and configured to transfer the working fluid, when in the liquid phase, from axial ends of the sealed canister to a central region of the sealed canister, wherein the wick structure abuts an interior surface of the sealed canister and defines an elongated central vapor channel configured to pass the working fluid, when vaporized to the gas phase, to the axial ends of the sealed canister and pass the working fluid, when condensed to the liquid phase, into the wick structure.
12 . The electric machine of claim 11 , further comprising a rotor endcap attached to the axial end of the rotor core and abutting a longitudinal end of the heat pipe to receive therefrom the extracted thermal energy transferred out from the rotor core.
13 . The electric machine of claim 12 , wherein the rotor endcap includes a heat pipe cavity recessed into an axial surface of the rotor endcap and nesting therein the longitudinal end of the heat pipe.
14 . The electric machine of claim 12 , wherein the rotor endcap further includes a plurality of endcap fins protecting away from the rotor core and configured to dissipate the extracted thermal energy transferred out from the rotor core and received by the rotor endcap.
15 . The electric machine of claim 14 , further comprising an active thermal management (ATM) system configured to splash or spray a coolant fluid onto the endcap fins.
16 . A method of assembling an electric machine, the method comprising: receiving a housing of the electric machine; attaching a stator assembly to the housing, the stator assembly including a stator core and an electromagnetic stator winding mounted in a stator slot of the stator core; attaching a rotor assembly to the housing such that the rotor assembly is adjacent and rotatable with respect to the stator assembly, the rotor assembly including a rotor core and an electromagnetic rotor winding mounted in a rotor slot of the rotor core; mounting a heat pipe in the rotor slot such that the heat pipe is adjacent the rotor winding and projects axially from an axial end of the rotor core, wherein the heat pipe is configured to passively extract thermal energy from the rotor winding and transfer the thermal energy out from the rotor core; attaching a rotor endcap adjacent the axial end of the rotor core such that the rotor endcap abuts a longitudinal end of the heat pipe to receive therefrom the extracted thermal energy transferred out from the rotor core, the rotor endcap including a heat pipe cavity recessed into an axial surface of the rotor endcap and nesting therein the longitudinal end of the heat pipe.
17 . The method of claim 16 , wherein the rotor winding includes a bundle of rotor windings mounted in the rotor slot, and the heat pipe includes a plurality of heat pipes mounted in the rotor slot and embedded in the bundle of rotor windings.
18 . The method of claim 17 , wherein the heat pipes are stacked in a rectilinear line extending radially with respect to the rotor core, the heat pipes being mutually parallel and radially spaced from one another.
19 . The method of claim 16 , wherein the heat pipe includes a sealed canister containing a working fluid configured to change phases between a liquid phase and a gas phase to thereby extract the thermal energy from the rotor winding and transmit the extracted thermal energy out through the axial end of the rotor core.
20 . The method of claim 19 , wherein the heat pipe further includes a wick structure located inside the sealed canister and configured to transfer the working fluid, when in the liquid phase, from axial ends of the sealed canister to a central region of the sealed canister.

Description

INTRODUCTION The present disclosure relates generally to electric machines. More specifically, aspects of this disclosure relate to thermal management systems for regulating the operating temperatures of separately excited motor (SEM) assemblies. Current production motor vehicles, such as the modern-day automobile, are originally equipped with a powertrain that operates to propel the vehicle and power the vehicle's onboard electronics. In automotive applications, for example, the vehicle powertrain is generally typified by a prime mover that delivers driving torque through an automatic or manually shifted power transmission to the vehicle's final drive system (e.g., differential, axle shafts, corner modules, road wheels, etc.). Automobiles have historically been powered by a reciprocating-piston type internal combustion engine (ICE) assembly due to its ready availability, relative light weight, and overall efficiency. Such engines include compression-ignited (CI) diesel engines, spark-ignited (SI) gasoline engines, two, four, and six-stroke architectures, and rotary engines, as some non-limiting examples. Hybrid-electric and full-electric vehicles (collectively “electric-drive vehicles”), on the other hand, utilize alternative power sources to propel the vehicle and, thus, minimize or eliminate reliance on a fossil-fuel based engine for tractive power. A full-electric vehicle (FEV)—colloquially labeled an “electric car”—is a type of electric-drive vehicle configuration that altogether omits an internal combustion engine and attendant peripheral components from the powertrain system, relying instead on a rechargeable energy storage system (RESS) and a traction motor for vehicle propulsion. The engine assembly, fuel supply system, and exhaust system of an ICE-based vehicle are replaced with a single or multiple traction motors, rechargeable battery cells, and battery cooling and charging hardware in a battery-based FEV. Hybrid-electric vehicle (HEV) powertrains, in contrast, employ multiple sources of tractive power to propel the vehicle, most commonly operating an internal combustion engine assembly in conjunction with a battery-powered or fuel-cell-powered traction motor. Since hybrid-type, electric-drive vehicles are able to derive their power from sources other than the engine, HEV engines may be turned off, in whole or in part, while the vehicle is propelled by the electric motor(s). SUMMARY A traction motor is an electric machine that converts electrical energy into rotational mechanical energy to propel a vehicle, such as FEV and HEV-type automobiles. Many traction motors contain a fixedly mounted stator that carries multiphase electromagnetic windings, such as copper hairpin or I-pin bars, and a rotatable rotor that bears an engineered pattern of magnets, such as core-mounted permanent magnets (PM), or electromagnetic armature windings, such as core-mounted copper coils. Traction motors may be categorized as alternating current (AC) or direct current (DC), brushed or brushless, rotary or linear, and radial flux or axial flux. In radial-flux, internal-rotor designs, the rotor may be coaxially nested inside the stator, whereas axial-flux rotary designs may juxtapose the rotor and stator as facing, coaxial plates. Rotational excitation of the rotor assembly may be effected by a magnetic field that is produced by passing current through multiphase AC stator windings; this stator-emitted magnetic field interacts with a mating magnetic field that is produced by rotor-borne permanent magnets or DC armature coils. The rotor assemblies for many modern-day traction motors include a rotor core that is fabricated from thin ferromagnetic discs that are stacked and laminated together into a cylindrical body. Each rotor disc has several openings that, when aligned with the openings of neighboring discs, form rotor slots that extend axially through the length of the rotor core. Persistent-state or electrically excited magnetic elements, such as PM bars or copper coils, are inserted into these rotor slots and secured to the rotor core. Unlike permanent magnet motor constructions, in which the rotor assembly bears internal or surface-mounted magnets, a separately excited motor (SEM) is generally typified by rotor-borne armature windings that electromagnetically mate with stator-borne field windings to convert electrical energy into mechanical energy. The rotor core may be mounted onto a motor shaft for outputting propulsion-generating motor torque produced by the motor or for inputting electricity-generating regenerative torque received by the motor. During operation of a traction motor, the internal electrical and electromagnetic hardware may generate a significant amount of heat, e.g., due to windage, friction, and hysteresis losses. An integrated motor cooling system may be employed to prevent undesirable overheating conditions within the motor. Active thermal management (ATM) systems, for example, employ a central