Electric machine thermal management assembly and method

An electrical machine assembly includes a shaft rotatable about an axis of an electric machine and first and second endcaps mounted to the shaft. The first endcap includes a first endcap coolant channel. The second endcap includes a second endcap coolant channel. A rotor is mounted to the shaft axially between the first and second endcaps. The rotor includes first rotor coolant channels and second rotor coolant channels. The first rotor coolant channels are configured to communicate liquid coolant that is received from the first endcap coolant channel axially through the rotor in a first direction. The second rotor coolant channels are configured to communicate liquid coolant that is received from the second endcap coolant channel axially through the rotor in a second direction that is opposite the first direction.

TECHNICAL FIELD

This disclosure relates generally to managing thermal energy within an electric machine.

BACKGROUND

Electrified vehicles differ from conventional motor vehicles because electrified vehicles include a drivetrain having one or more electric machines. In some electrified vehicles, the electric machines can drive the electrified vehicles instead of, or in addition to, an internal combustion engine. Electric machines are also used in pumps, machine tools, household appliances, power tools, and in many other devices.

SUMMARY

In some aspects, the techniques described herein relate to an electrical machine assembly, including: a shaft rotatable about an axis of an electric machine; first and second endcaps mounted to the shaft, the first endcap including a first endcap coolant channel, the second endcap including a second endcap coolant channel; and a rotor mounted to the shaft axially between the first and second endcaps, the rotor including a plurality of first rotor coolant channels and a plurality of second rotor coolant channels, the plurality of first rotor coolant channels configured to communicate liquid coolant that is received from the first endcap coolant channel axially through the rotor in a first direction, the plurality of second rotor coolant channels configured to communicate liquid coolant that is received from the second endcap coolant channel axially through the rotor in a second direction that is opposite the first direction.

In some aspects, the techniques described herein relate to an electric machine assembly, wherein the first and second rotor coolant channels each extend axially from the one of the first or the second endcap to the other of the first or the second endcap.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the first and second rotor coolant channels each have a triangular cross-sectional profile.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the first rotor coolant channels are circumferentially offset from the second rotor coolant channels.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the first endcap coolant channel includes an annular portion and a plurality of spoke portions that extend radially outward from the annular portion to one of the first rotor coolant channels.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the first and second endcap coolant channels each open to the rotor.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the plurality of first rotor coolant channels are configured to communicate coolant axially in the first direction from the first endcap on a first axial side of the rotor, to a plurality of exit openings within the second endcap on an opposite second axial side of the rotor, wherein the plurality of second rotor coolant channels are configured to communicate coolant axially in the second direction from the second endcap on the second axial side of the rotor to a plurality of exit openings within the first endcap on the first side of the rotor.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the first and second rotor coolant channels are radially outer coolant channels, and further including a plurality of radially inner coolant channels.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the plurality of radially inner coolant channels are formed within the shaft.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the plurality of radially inner coolant channels are configured to communicate liquid coolant axially to the first and second endcap coolant channels.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the shaft includes a plurality of radially extending bores that are each configured to communicate liquid coolant from the shaft to one of the radially inner coolant channels.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the plurality of radially extending bores are disposed equidistant from the first endcap and the second endcap.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the plurality of radially extending bores are disposed at an axial center of the rotor.

In some aspects, the techniques described herein relate to an electrical machine assembly, wherein the radially inner coolant channels communicate some of the liquid coolant received from one of the radially extending bores in the first direction, and communicate some of the liquid coolant received from the one of the radially extending bores in the second direction.

In some aspects, the techniques described herein relate to an electric machine thermal management method, including: communicating liquid coolant that is received from a first endcap of an electric machine in a first direction through a plurality of first rotor coolant channels within a rotor of the electric machine; and communicating liquid coolant that is received from a second endcap of the electric machine in an opposite second direction through a plurality of second rotor coolant channels within the rotor of the electric machine.

In some aspects, the techniques described herein relate to an electric machine thermal management method, wherein the first and second rotor coolant channels are radially outer coolant channels, and further including communicating liquid coolant to the first and second endcaps through a plurality of radially inner coolant channels.

In some aspects, the techniques described herein relate to an electric machine thermal management method, further including communicating liquid coolant to the plurality of radially inner coolant channels from a shaft of the electrical machine through a plurality of radially extending bores within the shaft.

In some aspects, the techniques described herein relate to an electric machine thermal management method, wherein the plurality of radially extending bores are disposed equidistant from the first endcap and the second endcap.

In some aspects, the techniques described herein relate to an electric machine thermal management method, wherein the radially inner coolant channels communicate some of the liquid coolant received from one of the radially extending bores in the first direction, and communicate some of the liquid coolant received from the one of the radially extending bores in the second direction.

In some aspects, the techniques described herein relate to an electric machine thermal management method, wherein the plurality of first rotor coolant channels are configured to communicate coolant axially in the first direction from the first endcap on a first axial side of the rotor, to a plurality of end-windings on an opposite second axial side of the rotor, wherein the plurality of second rotor coolant channels are configured to communicate coolant axially in the second direction from the second endcap on the second axial side of the rotor, to a plurality of end-windings on the first side of the rotor.

DETAILED DESCRIPTION

This disclosure details exemplary assemblies and methods for managing thermal energy levels within an electric machine, and particularly a rotor of the electric machine. A coolant circuit within the electric machine can communicate coolant through the electric machine in a way that facilitate, among other things, evenly cooling the electric machine.

A rotor of an electric motor is typically a rotating part of the electric motor that rotates due magnetic fields. The rotation of the rotor develops a torque about an axis of the rotor. During the rotation of the rotor, thermal energy levels in the electric machine can increase due to, among other things, changing magnetic fields. Conventionally, a coolant (lubricating oil or lube oil) is circulated through the electric motor. The coolant can move along a coolant circuit within the electric motor. The coolant cools and lubricating the rotor and other components, such as stator end windings and permanent magnets of the electric motor.

With reference toFIG.1, an electrified vehicle10includes a traction battery14, an electric machine18, and wheels22. The traction battery14powers the electric machine18, which converts electrical power to torque to drive the wheels22.

The electrified vehicle10includes a charge port26. The electrified vehicle10can be electrically coupled an external power source through the charge port26. The traction battery14can be recharged from the external power source.

The traction battery14is, in the exemplary embodiment, secured to an underbody of the electrified vehicle10. The traction battery14could be located elsewhere on the electrified vehicle10in other examples.

The electrified vehicle10is an all-electric vehicle. In other examples, the electrified vehicle10is a hybrid electric vehicle, which can selectively drive wheels using torque provided by an internal combustion engine instead, or in addition to, an electric machine. Generally, the electrified vehicle10can be any type of vehicle having a traction battery and an electric machine.

With reference now toFIGS.2and3, the electric machine18includes a shaft30, a rotor34, a stator38, a first endcap42, and a second endcap46. The rotor34is mounted to the shaft30between the first endcap42and the second endcap46. The shaft30, the rotor34, the first endcap42, and the second endcap46are configured to rotate together about an axis X of the electric machine18. The first endcap42is located near a bearing (not shown). The second endcap46is located near the point from where the lube oil enters the shaft30.

Referring now toFIGS.4and5with continuing reference toFIGS.2and3, the electric machine18includes a coolant circuit50. A liquid coolant can be moved along the coolant circuit50to manage thermal energy levels within the electric machine18.

The shaft30is a hollow shaft that has a shaft channel54. Coolant, such as a liquid coolant, can be communicated from the shaft channel54through a plurality of radially extending bores58, through at least one radially inner coolant channel62, through at least one endcap coolant channel66, through at least one radially outer coolant channel70, and then through an endcap exit opening74. The coolant can be communicated to the shaft channel54of the shaft30from a coolant supply78.

In this example, the radially extending bores58are disposed equidistant from the first endcap42and the second endcap46, and are at an axial center of the rotor34. The radially extending bores58receive coolant from the shaft channel54, and communicate the coolant radially to one of the radially inner coolant channels62.

The radially inner coolant channels62are, in this example, grooves within the shaft30. In another example, the radially inner coolant channels62could be provided, or partially provided, by grooves in the rotor34.

The grooves with the shaft30open radially outward. The radially inner coolant channels62have a rectangular cross-sectional profile in this example. Within the radially inner coolant channels62some of the coolant moves in an axial direction D1between the shaft30and the rotor34toward the first endcap42, and some of the coolant moves in an axial direction D2between the shaft30and the rotor34toward the second endcap46. The axial direction D1is opposite the axial direction D2.

The endcap coolant channel66within the first endcap42receives the coolant that has moved in the axial direction D1from the radially inner coolant channels62. The endcap coolant channel66within first endcap42receives the coolant that has moved in the axial direction D1from the radially inner coolant channels62. The endcap coolant channel66within second endcap46receives the coolant that has moved in the axial direction D2from the radially inner coolant channels62. From the endcap coolant channels66, the coolant is delivered to the radially outer coolant channels70.

The endcap coolant channels66are open to the rotor34. The endcap coolant channels66each include an annular portion80and a plurality of spoke portions84. The annular portion80is radially aligned with the radially inner coolant channels62and is disposed about the axis X. The spoke portions84extend radially from the annular portion80to the radially outer coolant channels70. In this example, the spoke portions84taper downward moving radially outward away from the annular portion80.

The radially outer coolant channels70each have a triangular cross-sectional profile. The radially outer coolant channels70are circumferentially distributed about the axis X. The radially outer coolant channels70are radially outside the radially inner coolant channels62. The radially outer coolant channels70can be repurposed air channels of the rotor34.

The radially outer coolant channels70include a plurality of first radially outer coolant channels70A, and a plurality of second radially outer coolant channels70B. The plurality of first radially outer coolant channels70A are circumferentially offset from the plurality of second radially outer coolant channels70B.

The plurality of first radially outer coolant channels70A each receive coolant from one of the spoke portions84of the endcap coolant channel66in the first endcap42. The plurality of first radially outer coolant channels70A communicate the coolant axially in the axial direction D1from the first endcap42on a first axial side of the rotor34to the second endcap46on an opposite second axial side of the rotor34. The coolant then moves through one of the endcap exit openings74in the second endcap46and sprays onto windings92of the electric machine18.

The plurality of second radially outer coolant channels70B each receive coolant from one of the spoke portions84of the endcap coolant channel66in the second endcap46. The plurality of second radially outer coolant channels70B communicate the coolant axially in the axial direction D2from the second endcap46on a second axial side of the rotor34to the first endcap42on the first axial side of the rotor34. The coolant then moves through one of the endcap exit openings74in the second endcap46and sprays onto the windings92of the electric machine18.

The coolant circuit50facilitates evenly distributing coolant within the electric machine18and particularly the rotor34. Also, the flow bias at relatively elevated rotor speeds can be reduced or eliminated when using the exemplary coolant circuit of this disclosure.

Features of the disclosed examples include a coolant supply system that can facilitate temperature reductions in the rotor material and nearby components, such as magnets.