EP-4738664-A1 - AXIAL OIL COOLING OF CONDUCTIVE ELEMENTS IN AN ELECTRIC MACHINE

EP4738664A1EP 4738664 A1EP4738664 A1EP 4738664A1EP-4738664-A1

Abstract

A cooling ring for an electric machine, the cooling ring including a first portion with an exterior surface having a first end and a second end, and a hollow interior extending along a longitudinal axis of the cooling ring, wherein the hollow interior is configured to encompass a first end of a stator; and a shoulder at the first end of the first portion extending radially outward, wherein the shoulder comprises an axial opening extending in a first direction, wherein the first direction is substantially parallel to the longitudinal axis of the cooling ring.

Inventors

OLDENBURG, Martina
Fredriksson, Ylva

Assignees

Volvo Car Corporation

Dates

Publication Date: 20260506
Application Date: 20241030

Claims (15)

A cooling ring for an electric machine, the cooling ring comprising: a first portion with an exterior surface having a first end and a second end, and a hollow interior extending along a longitudinal axis of the cooling ring, wherein the hollow interior is configured to encompass a first end of a stator; and a shoulder at the first end of the first portion extending radially outward, wherein the shoulder comprises an axial opening extending in a first direction, wherein the first direction is substantially parallel to the longitudinal axis of the cooling ring.
The cooling ring of claim 1, wherein the first portion forms one or more radially inward depressions spaced around at least part of the circumference of the first portion at the first end.
The cooling ring of claim 2, wherein each of the one or more depressions comprises a shoulder at the first end of the first portion extending radially outward and the axial opening.
The cooling ring of any of the previous claims, wherein the cooling ring is disposed between a housing and the first end of the stator, wherein a position of the cooling ring creates a gap between the housing and the exterior surface of the cooling ring.
The cooling ring of any of the previous claims, wherein a position of the axial opening is axially facing a first conductive element, wherein that the first conduct element is substantially in the first direction relative to the axial opening.
The cooling ring of claim 5, wherein the first conductive elements is a busbar.
The cooling ring of claim 5, wherein the first conductive elements is a winding.
The cooling ring of claim 5, wherein the first conductive elements is an I-pin.
The cooling ring of any of claims 4-8, wherein the gap, including the depression, is configured to fill with cooling fluid.
The cooling ring of any of the preceding claims, further including a radial opening extending in a second direction, wherein the second direction is substantially perpendicular to the first direction, and wherein the cooling fluid passes through the radial opening in substantially the second direction.
The cooling ring of claim 10, wherein a position of the one radial opening is radially facing a second conductive element.
The cooling ring of claim 11, wherein the second conductive element is at the first end of the stator.
The cooling ring of claims 11 or 12, wherein the second conductive element is a winding of the stator and/or an I-pin of the stator.
The cooling ring of any of the preceding claims, wherein the cooling ring is formed of plastic.
A stator cooling assembly for an electric machine, the stator assembly comprising: a housing comprising a cooling fluid reservoir and a hollow opening, wherein the cooling fluid reservoir comprises a fluid opening extending radially inward from the cooling reservoir to the hollow opening; a stator comprising a core and a first conductive element extending from the core in an axial direction, wherein the core comprises a cooling fluid channel, and wherein the fluid channel is positioned to align with the fluid opening of the housing; and a cooling ring comprising: a first portion with an exterior surface having a first end and a second end, and a hollow interior extending along a longitudinal axis of the cooling ring, wherein the hollow interior is configured to encompass the first conductive element of the stator, a shoulder at the first end of the first portion extending radially outward, wherein the shoulder comprises an axial opening extending in a first direction, wherein the first direction is substantially parallel to the longitudinal axis of the cooling ring, wherein the cooling ring is positioned in the hollow opening of the housing such that the second end is adjacent to the core, and an interior surface of the housing and the exterior surface of the cooling ring create a gap, and the axial opening faces a second conductive element, and wherein the stator cooling assembly is configured to distribute cooling fluid from the cooling fluid reservoir through the cooling fluid channel to fill the gap, and further distribute the cooling fluid through the axial opening to the second conductive element.

Description

Technical Field The present disclosure relates generally to electric machines, in particular electric machines in the automotive fields. More particularly, the present disclosure relates to a ring for a stator cooling assembly of an electric machine, such as that used in an electric vehicles. Background of the Present Disclosure An electric machine generates heat during operation. Means of cooling the electric machine may include a stator back water jacket or using cooling fluids such as oil to cool conductive elements of the electric machine. Oil cooled electric machines are very efficient with respect to rotor cooling, but stator assembly cooling is complicated. In particular, it is difficult to effectively cool the conductive elements of the stator assembly beyond the stator windings. As the temperature of the electric machine rises, the performance of the electric machine may degrade. To maintain performance of the electric machine within a desired temperature range, an electric machine assembly may distribute cooling fluid in a radial direction to the windings of the electric machine assembly. Overheated conductive elements, such as busbars, may suffer from high temperatures. This may be a result of their proximity to cooling fluid, for example when conductive elements are relatively far from existing cooling fluid distribution mechanisms. However, there is a trend to make things more compact which may make it harder to incorporate space to implement a distribution for the cooling fluid to other conductive elements in an axial direction. Thus, it would be desired to have an improved stator cooling assembly for distributing a cooling fluid such as oil, liquid, gas or other fluid, to cool an electric machine. The background section relating to using a stator cooling assembly is merely intended to provide a contextual overview of some current issues and is not intended to be exhaustive. Other contextual information may become apparent to a person of skill in the art upon review of the following detailed description. Summary of the Present Disclosure Providing a ring with axial openings results in the ability to distribute cooling fluid to conductive elements positioned in an axial direction relative to the cooling ring. The cooling ring may distribute cooling fluid in multiple directions which reduces or eliminates the risk of an electric machine overheating. For example, the cooling ring may distribute cooling fluid in both a radial and axial direction. The cooling ring may surround windings of a stator such that the windings are positioned in a radial direction relative to the cooling ring. In addition to distributing cooling fluid to the windings, the axial openings may be configured to distribute cooling fluid to other conductive elements, such as busbars. During operation of an electric machine, the windings of the stator and the busbars, or any other conductive element, conductively connected to the windings, may generate heat. As the temperature of the electric machine increases, performance of the electric machine may degrade. Distributing cooling fluid to the conductive elements which are conductively connected to the windings may maintain the electric machine within a desired temperature range. For example, an electric machine assembly may distribute cooling fluid in multiple directions of the electric machine assembly. Including axial openings in a cooling ring can distribute cooling fluid to conductive elements beyond the windings of stator without having to increase the size the of an electric machine housing or redesign any other component of an electric machine assembly. As a result, there is a potential to maintain the temperature of an electric machine without introducing additional parts to an electric machine housing system. According to an embodiment, the cooling ring includes one or more radially inward depressions spaced around at least part of the circumference of the first portion at the first end. Such inward depressions may be incorporated in spaces available in existing machine housings. Additionally, the inward depressions may reduce the amount of cooling fluid required in the electric machine housing by taking advantage of existing cooling fluid distributions mechanisms. For example, using the existing cooling fluid reservoir to cool further conductive elements. According to an embodiment, the radially inward depressions include a shoulder at the first end of the first portion extending radially outward and the axial opening. Such shoulder provides for a surface for the axial openings, without increasing a circumference of the cooling ring. According to an embodiment, the cooling ring is disposed between a housing and the first end of the stator, wherein a position of the cooling ring creates a gap between the housing and the exterior surface of the cooling ring. Such a gap creates a sealed chamber or reservoir for receiving a cooling fluid such that it can be distributed thro