DE102024116311A1 - Stator with hotspot-optimized cooling; and electric machine - Google Patents

Abstract

The invention relates to a stator (1) for an electric machine (2), comprising a substantially annular base body (3), a magnet coil assembly (4) mounted on the base body (3), and a cooling channel (5) formed at least partially through the base body (3), wherein the cooling channel (5) has at least one axially extending channel section (7) extending over an axial center (6) of the base body (3), and wherein a heat dissipation element (8) with an open-pore structure (9) is incorporated into the channel section (7) at the level of the axial center (6) of the base body (3). The invention also relates to an electric machine (2) with this stator (1).

Description

The invention relates to a stator for an electric machine, preferably a machine (e.g., as a drive machine) for use in a motor vehicle, such as a passenger car, truck, bus, or other commercial vehicle (e.g., agricultural vehicle), comprising a generally essentially ring-shaped base body, a magnet coil arrangement mounted on the base body, and a cooling channel formed at least partially through the base body, wherein the cooling channel has at least one axially extending channel section extending across an axial center of the base body. The invention further relates to an electric machine with such a stator.

Stators and electrical machines of this type are already well known from the prior art. For example, the WO 2019/ 002 289 A1 An electric machine with a stator featuring a multitude of cooling channels. During operation, these cooling channels are filled with fluid such as water or oil and are connected to external supply units/hydraulic circuits via an inlet and an outlet. In principle, to achieve higher power levels, the goal is to design the stator, and thus the electric machine, to be as axially large as possible. However, increasing the axial length of the stator also carries the risk that the heat generated during operation becomes difficult to predict, and that excessive temperature increases can occur, particularly in the axial center of the stator.

The object of the present invention is therefore to provide a stator that has the greatest possible axial length while simultaneously increasing the drive power of the electric machine.

This is achieved according to the invention by incorporating a heat dissipation body with an open-pore structure into the channel section at the (axial) level of the axial center of the base body. This open-pore structure is open at least axially on both sides (in the case of a heat dissipation body designed as a solid body) or at least on a radial inner side (in the case of a heat dissipation body designed as a tube body).

Such a heat sink significantly increases the cooling effect, particularly in the so-called thermal hotspot of the stator. The open-pore structure of the heat sink considerably enlarges the surface area exposed to the hydraulic fluid flow in the temperature-critical axial center, thus achieving a substantial improvement in heat dissipation. As a result, the electric machine becomes more efficient.

Further advantageous embodiments are claimed in the dependent claims and are explained in more detail below.

In this regard, it has proven advantageous for the heat sink to be made of (open-cell) metal foam. This allows for the most efficient production and insertion of the heat sink into the cooling channel. In principle, it is possible to first form the heat sink separately from the base body as a pin or tube and then insert it into the cooling channel. However, it is also theoretically possible to introduce the metal foam directly into the previously manufactured cooling channel while it is still uncured, for example, by injection. After subsequent curing, a solid heat sink is then formed.

Furthermore, it is advantageous if the heat sink is made of a material with a higher thermal conductivity than the base material. This further improves heat dissipation during operation.

It has also proven advantageous if the heat dissipation body is at least partially made of an aluminum-containing and/or copper-containing material, preferably exclusively of a material consisting purely of aluminum or an aluminum alloy, or of a material consisting purely of copper or a copper alloy.

If the heat dissipator is pin-shaped (solid body) or tubular (tube body), it can be manufactured and assembled particularly easily.

Furthermore, it is advantageous if the heat dissipation element has a length that is shorter than the length of the preferably straight channel section. This further optimizes material utilization while simultaneously keeping the flow resistance of the cooling channel as low as possible.

For optimal cooling of the stator, it is also beneficial if the heat dissipation body is arranged with its central plane on the axial center / at the level of the axial center of the base body.

It has also proven useful if the cooling channel has several inlets. The cooling channel has circumferential (preferably parallel) channel sections, each equipped with a heat dissipator. This further improves the cooling effect of the cooling channel through which hydraulic fluid flows during operation.

A further improvement in cooling is achieved by the cooling channel running in a meandering shape along the circumferential direction.

Furthermore, the invention relates to an electric machine for a motor vehicle, with a stator according to the invention in at least one of the embodiments described above and with a rotor rotatably mounted relative to the stator.

The invention will now be explained in more detail below with reference to figures, in which context various embodiments are also shown.

• 1 eine Längsschnittdarstellung einer elektrischen Maschine aufweisend einen erfindungsgemäß ausgebildeten Stator nach einem ersten Ausführungsbeispiel, wobei der Stator im Bereich eines axial verlaufenden, mit einem Wärmeableitkörper versehenen Kanalabschnitts geschnitten ist,
• 2 eine Detailansicht des Stators nach 1 im Bereich des Wärmeableitkörpers,
• 3 eine perspektivische Darstellung des in 1 eingesetzten Stators, unter Veranschaulichung eines in ihn eingebrachten mäanderförmigen Kühlkanals,
• 4 eine Längsschnittdarstellung eines erfindungsgemäßen Stators nach einem zweiten Ausführungsbeispiel im Bereich eines Wärmeableitkörpers, der im Vergleich zu dem ersten Ausführungsbeispiel nicht als ein vor Einbringung in den Stator fertig ausgeformtes Teil, sondern als ein unmittelbar in den Kühlkanal eingebrachtes und expandiertes Teil ausgebildet ist,
• 5 eine Schnittdarstellung des in den 1 bis 4 eingebrachten Wärmeableitkörpers, unter Darstellung seiner offenporigen Struktur,
• 6 eine Längsschnittdarstellung eines erfindungsgemäßen Stators nach einem dritten Ausführungsbeispiel im Bereich eines Wärmeableitkörpers, wobei der Wärmeableitkörper im Vergleich zu dem ersten Ausführungsbeispiel nicht als Vollkörper, sondern als Rohrkörper ausgebildet ist,
• 7 eine Längsschnittdarstellung eines erfindungsgemäßen Stators nach einem vierten Ausführungsbeispiel im Bereich eines Wärmeableitkörpers, der im Vergleich zu dem dritten Ausführungsbeispiel nicht als ein vor Einbringung in den Stator fertig ausgeformtes Teil, sondern als ein unmittelbar in den Kühlkanal eingebrachtes und expandiertes Teil ausgebildet ist, sowie
• 8 eine Querschnittdarstellung des in den 6 und 7 eingebrachten Wärmeableitkörpers, unter Darstellung seiner offenporigen Struktur.

They show:

• 1 a longitudinal section view of an electrical machine comprising a stator designed according to the invention in a first embodiment, wherein the stator is cut in the area of an axially extending channel section provided with a heat dissipation element,
• 2 a detailed view of the stator after 1 in the area of the heat sink,
• 3 a perspective representation of the in 1 stator used, illustrating a meandering cooling channel incorporated into it,
• 4 a longitudinal section view of a stator according to the invention in a second embodiment in the area of a heat dissipation body, which, in comparison to the first embodiment, is not formed as a part that is fully formed before being inserted into the stator, but as a part that is directly inserted into the cooling channel and expanded,
• 5 a cross-sectional view of the in the 1 to 4 inserted heat dissipation body, showing its open-pore structure,
• 6 a longitudinal sectional view of a stator according to a third embodiment in the area of a heat dissipation body, wherein the heat dissipation body is designed as a tube body instead of a solid body compared to the first embodiment,
• 7 a longitudinal sectional view of a stator according to the invention in a fourth embodiment in the area of a heat dissipation body, which, in comparison to the third embodiment, is not formed as a part that is fully formed before being inserted into the stator, but as a part that is directly inserted into the cooling channel and expanded, as well as
• 8 a cross-sectional view of the in the 6 and 7 inserted heat dissipation body, showing its open-pore structure.

The figures are purely schematic and serve solely to illustrate the invention. The same elements are identified by the same reference symbols.

With 1 The basic structure of an electric machine 2 comprising a stator 1 according to the invention, as shown in a first embodiment, is clearly visible. The electric machine 2 is preferably designed as a drive machine for a motor vehicle, in particular a commercial vehicle, such as an agricultural vehicle (agricultural tractor).

The electric machine 2 typically has a stator 1 that is entirely ring-shaped/sleeve-shaped. Radially inside the stator 1, a rotor 11 of the electric machine 2 is mounted so that it can rotate relative to the stator 1. One axis of rotation of the rotor 11 is located in 1 Designated with the reference numeral 12, this axis of rotation 12 also forms a longitudinal axis of the stator 1. Based on this, the directional terms used here – axial, radial, and circumferential – refer to this axis of rotation 12. Axial direction therefore refers to a direction along/parallel to the axis of rotation 12, radial direction to a direction perpendicular to the axis of rotation 12, and circumferential direction to a direction along a circle that rotates coaxially around the axis of rotation 12.

The stator 1 designed according to the invention has a 3 The (also ring-shaped) base body 3 is also particularly easy to see. The base body 3 is preferably formed from a plurality of axially stacked individual sheets, forming a complete sheet metal package. In principle, however, it is also possible to form the base body 3 in other ways.

The base body 3, in turn, has several circumferentially distributed stator teeth 13 on its radial inner side. Considering the 1 and the 3 It can also be seen in this regard that in the gaps formed in the circumferential direction between the stator teeth 13 / stator A magnetic coil assembly 4 of the stator 1 is inserted/received in each of the stator slots 14. The magnetic coil assembly 4 can, for example, be a coil winding that is received with a section in each stator slot 14.

Furthermore, a cooling channel 5 is incorporated radially outside the stator teeth 13 and thus also radially outside the magnet coil arrangement 4 in the base body 3. Considering the 3 It is evident that the cooling channel 5 preferably runs in a meandering shape in the circumferential direction / along a circumference of the base body 3. The cooling channel 5 has, in particular, several channel sections 7 extending in the axial direction. These axially extending channel sections 7 of the cooling channel 5 preferably run parallel to each other and are arranged circumferentially relative to each other.

In this regard, in 1 It can be seen in principle that each channel section 7 completely penetrates the base body 3 axially. In the area of housing parts 15a, 15b attached to the end face of the base body 3, the axially extending channel sections 7 are connected to each other circumferentially via corresponding connecting sections 16, forming the meandering cooling channel 5.

It can also be seen that each channel section 7 is introduced into the base body 3 in the sense of an axial through-hole and is thus limited by the material of the base body 3 both on its radial outside and on its radial inside.

It should be noted, however, that the cooling channel 5 can also be formed in any other way. The cooling channel 5 always has at least one axially extending channel section 7 that extends over an axial center 6 of the base body 3. An axial center 6 is defined in the 1 and 2 accordingly marked as a division level.

According to the invention, a heat dissipation body 8 with an open-pore structure 9 is incorporated into the respective channel section 7. As explained in more detail below, the heat dissipation body 8 can be designed and incorporated in different ways. These different designs are distinguished with regard to the 1 to 8 Each is illustrated. However, since the remaining structure of stator 1 corresponds to that of the first embodiment, for the sake of brevity, only the differences to the first embodiment will be described with regard to the further embodiments.

In the first embodiment, a heat dissipation body 8, manufactured separately from the base body 3 and pre-assembled in the base body 3, is inserted. This heat dissipation body 8 is formed from an open-pore metal foam, as shown in 5 This is particularly easy to see. Aluminum foam is preferably used for this purpose.

The heat dissipation body 8 of the first embodiment is essentially pin-shaped. The heat dissipation body 8 has a length (axial extent) that is many times shorter than the length of the channel section 7. Preferably, the heat dissipation body 8 is aligned centrally with the axial center 6, which means that its (axial) center plane 10 is located on the axial center 6.

In the first embodiment, the heat dissipation body 8 is preferably manufactured beforehand with a solid skin and subsequently mechanically inserted into the channel section 7.

Considering the second embodiment according to 4 It should be noted that, alternatively, the heat dissipator 8 can also, in principle, be initially inserted into the channel section 7 in its uncured state and only subsequently expanded, for example, by applying or activating it with heat. In a preferred embodiment of the heat dissipator 8 as an aluminum foam (or alternatively, copper foam), the aluminum foam is produced, for example, by mixing aluminum with another substance that becomes gaseous under temperature (e.g., while still liquid) and then foaming at a specific temperature, particularly when the other substance becomes gaseous. The aluminum (entirely) and the other substance are not liquid in this process. Even in this embodiment, the fully cured heat dissipator 8 ultimately exhibits the open-pore structure 9. 5 on.

In connection with the 6 to 8 In this regard, it should also be mentioned that the heat dissipation body 8 does not necessarily have to be designed as a solid body (open-pore structure 9 across the entire cross-section of the channel section 7), but can in principle also be hollow / tubular.

In this regard, it should be noted that such a tubular heat dissipation body 8 is preferably made of a copper material, while the heat dissipation body 8 of the 2 and 4 preferably made of an aluminum material.

This also applies to the two exemplary embodiments of the 6 and 7 The same applies as for the 2 and 4 , after which the heat sink 8 ent neither can be fully prepared before being introduced into canal section 7 ( 6 ) or can be fully formed directly in channel section 7 ( 7 ).

It is furthermore through the 4 and 8 It can also be seen that the heat dissipation body 8 can be inserted into radial (local) extensions 17 of the channel section 7, which extension 17 also partially covers the heat dissipation body on its front side.

In other words, the meandering design is preferably combined with the incorporation of a more thermally conductive material, which, due to its significantly larger surface area, considerably increases the heat flow from the sheet metal (base body 3) into the cooling oil/hydraulic fluid at these locations. This allows the cooling capacity at the thermal hotspots to be increased and the peak-to-continuous power difference to be reduced.

Preferably, metal foam or metal tubes (heat dissipators 8) with foam-like inner surfaces are implemented in sheet metal stack cooling channels (channel sections 7) to locally increase cooling.

A heat hotspot is located in the center 6 of the base body 3 / stator 1. In an exemplary cooling system, the laminated core (base body 3) contains meandering channels (cooling channel 5) that guide the oil axially through the core. These can also be parallel axial channels (channel sections 7). According to the invention, a thermally conductive insert (heat sink 8) is used to increase the cooling capacity and flow rate in the heat hotspot.

In the 2 and 4 to 8 Various solutions for locally increasing the cooling capacity of channel sections 7 are shown.

In 2 , 4 and 5 Metal foam, using aluminum foam as an example, was introduced into the sheet metal package. This can form a solid skin ( 2 ) manufactured / fully expanded and mechanically inserted or expanded in cooling channel 5 by applying / activating heat ( 4 ). In this process, good mechanical and thermal contact with the sheet metal can be ensured by pressing or thermal expansion, and good heat transfer to the cooling oil can be ensured by the large surface area of the foam.

In the 6 to 8 Another variant shown is a copper cooling tube as a heat dissipator 8 with a foam-like inner surface. This could be mechanically integrated during the assembly of the stack / sheet metal package ( 7 Here too, pressing the foam in would create a good thermal connection to the sheet metal. For both variants, the cooling oil channels could be made larger locally within the sheet metal to further minimize pressure losses due to the foam.

Reference symbol list

1

stator

2

electric machine

3

basic body

4

Magnetic coil arrangement

5

Cooling channel

6

axial center

7

Canal section

8

heat dissipators

9

open-pore structure

10

middle level

11

rotor

12

axis of rotation

13

Stator tooth

14

Stator slot

15a

first housing part

15b

second housing part

16

Connection section

17

Extension

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• WO 2019/ 002 289 A1 [0002]

Claims (10)

Stator (1) for an electric machine (2), comprising a generally essentially ring-shaped base body (3), a magnet coil arrangement (4) mounted on the base body (3), and a cooling channel (5) formed at least partially through the base body (3), wherein the cooling channel (5) has at least one axially extending channel section (7) extending over an axial center (6) of the base body (3), characterized in that a heat dissipation body (8) with an open-pore structure (9) is introduced into the channel section (7) at the level of the axial center (6) of the base body (3). Stator (1) after Claim 1 , characterized in that the heat dissipation body (8) is made of a metal foam. Stator (1) after Claim 1 or 2 , characterized in that the heat dissipation body (8) consists of a material which has a higher thermal conductivity than a material of the base body (3). Stator (1) after one of the Claims 1 until 3 , characterized in that the heat dissipation body (8) is at least partially made of an aluminium-containing and/or copper-containing material. Stator (1) after one of the Claims 1 until 4 , characterized in that the heat dissipation body (8) is pin-shaped or tubular. Stator (1) according to one of the Claims 1 until 5 , characterized in that the heat dissipation body (8) has a length that is less than the length of the preferably straight channel section (7). Stator (1) according to one of the Claims 1 until 6 , characterized in that the heat dissipation body (8) is arranged with its central plane (10) on the axial center (6) of the base body (3). Stator (1) according to one of the Claims 1 until 7 , characterized in that the cooling channel (5) has several channel sections (7) extending in a circumferential direction (preferably parallel to each other), each of which is equipped with a heat dissipation body (8). Stator (1) according to one of the Claims 1 until 8 , characterized in that the cooling channel (5) runs in a meandering shape along the circumferential direction. Electric machine (2) for a motor vehicle, with a stator (1) according to one of the Claims 1 until 9 and a rotor (11) rotatably mounted relative to the stator (1).