Stator housing and stator for axial flux motor

Abstract

The invention relates to a stator housing (1) for an axial flux machine having at least one rotor which can be rotated about an axis of rotation (2) and at least one stator (30) which is spaced apart from the rotor along the axis of rotation (2) and which has a fluid-tight interior (8), a coil receiving space (10) for receiving an electromagnetic coil assembly (31) is arranged in the inner space (8) in the circumferential direction about the axis of rotation (2), each coil assembly (31) having at least one coil (35) wound in the axial direction about stator teeth (33), and wherein the stator housing (1) has a liquid cooling system, the liquid cooling system comprises at least one first cooling channel (17) which extends in the stator housing (1) in the circumferential direction and at least one second cooling channel (19) which is separate from the at least one first cooling channel and which likewise extends in the stator housing (1) in the circumferential direction, the interior space (8) being filled with a cooling liquid. The cooling liquid is in thermal contact with the cooling liquid in the first and second cooling channels (17, 19).

Description

Technical Field

[0001] The invention relates to a stator housing for an axial flux electric machine having at least one rotor rotatable about a rotation axis and at least one stator spaced apart from the rotor along the rotation axis. The invention also relates to a stator for such an axial flux electric machine. Background Art

[0002] Axial flux machines (also called disc machines) are becoming increasingly important due to their high power density and other favorable properties and are also becoming increasingly interesting as drives for electric vehicles.

[0003] In such electrical machines, at least one rotor usually has a disk-like shape and is mounted rotatably about an axis of rotation, wherein the generated magnetic field extends essentially parallel to the axis of rotation.

[0004] Such axial flux machines are known, for example, from WO 2010 / 092400 and US 2015 / 0364956. The axial flux machines disclosed therein are so-called YASA machines (yokeless segmented armature), whose stators are without yokes and have segmented armatures. In relatively compact stators of this design, it is particularly challenging to dissipate the heat generated during operation. Summary of the invention

[0005] The object of the invention is to specify a stator for an axial flux machine in which the heat generated during operation can be dissipated effectively.

[0006] This object is achieved by the subject matter of the independent claims. Embodiments and developments are the subject matter of the dependent claims.

[0007] According to one aspect of the present invention, a stator housing for an axial flux motor is provided, wherein the axial flux motor has at least one rotor capable of rotating around a rotation axis and at least one stator spaced apart from the rotor along the rotation axis, the stator having a fluid-sealed internal space, wherein a coil receiving space for receiving an electromagnetic coil assembly is arranged in a circumferential direction around the rotation axis in the internal space, wherein each coil assembly has at least one coil wound around a stator tooth in an axial direction.

[0008] The stator housing has a liquid cooling system, which includes at least one first cooling channel extending in the stator housing in a circumferential direction and at least one second cooling channel separated from the at least one first cooling channel and also extending in the stator housing in a circumferential direction. The inner space is filled with a coolant, which is in thermal contact with the coolant in the first and second cooling channels.

[0009] The thermal contact may be a direct contact in the form of a flow connection between the cooling channel and the interior space, so that the coolant can move between the cooling channel and the interior space and thus transfer heat. Alternatively, the interior space can also be closed in a fluid-tight manner so that no exchange of coolant with the cooling channel is possible. However, in both cases, an exchange of heat energy can take place between the coolant in the cooling channel and the coolant in the interior space.

[0010] According to one embodiment, therefore, the inner space is closed in a fluid-tight manner and has no opening to the outside, so that the cooling liquid is enclosed in the inner space in a fluid-tight manner.

[0011] In this embodiment, different coolants can be used, one of which circulates in the cooling channels and the other is enclosed in the interior space. When, for example, a dielectric (electrically insulating) coolant is used in the interior space, it can be in direct contact with the coil, while a conventional coolant can be used in the cooling channels. The advantage of this immersion cooling is that the thermal energy can be well absorbed by the coolant in the interior space.

[0012] According to an alternative embodiment, the liquid cooling system further comprises at least one inlet opening fluidly connected to the first cooling channel to allow cooling liquid to enter the interior space, and at least one outlet opening fluidly connected to the second cooling channel to allow cooling liquid to leave the interior space, such that cooling liquid can flow from the first cooling channel into the interior space and from the interior space into the second cooling channel.

[0013] According to this embodiment, the fluid-tight inner space of the stator is understood to be a cavity inside the stator, which is designed in a fluid-tight manner except for its inlet opening and outlet opening (the inlet opening and outlet opening are part of the liquid cooling system, so that the coolant can flow into the inner space and flow out again without leaving the liquid cooling system). Therefore, the coolant of the liquid cooling system can circulate in the inner space and thus ensure efficient heat dissipation. Here, the inner space of the stator is particularly partially limited by the electrical coil assembly, in particular by the stator teeth that carry the winding. It is achieved that the coolant can be in close contact with the heat source. An electrically insulating coolant such as oil can be used as the coolant.

[0014] The stator housing can be made of metal, such as aluminum, in particular, and therefore has very good thermal conductivity. Alternatively, however, non-metallic materials (such as plastic) can also be used for the stator housing, which can reduce the losses caused by eddy currents.

[0015] The advantage of this stator housing is that the liquid cooling system enables particularly good dissipation of heat generated during operation with a coolant circulating in the fluid-tight interior, which is supplied to the interior via the first cooling channel and discharged from the interior via the second cooling channel.

[0016] It is particularly advantageous that the cooling liquid can come into direct contact with the component to be cooled, that is to say the coil component, in the fluid-tight interior space. This reduces the number of heat exchanges between the materials and thus improves heat transfer.

[0017] According to an embodiment, the stator housing comprises an outer housing component and an inner housing component, wherein the inner housing component is concentrically arranged within the outer housing component, and at least one first cooling channel and at least one second cooling channel are formed between the inner housing component and the outer housing component.

[0018] In this case, it can be provided in particular that the at least one first cooling channel and / or the at least one second cooling channel are formed as recesses in an outer side of the inner housing component.

[0019] In this embodiment, the coolant circulates at least partially along the circumference of the stator housing. Since the housing is a two-part design with an outer housing component and an inner housing component, wherein the cooling channel is arranged between the housing components and is designed as a recess in the outer side of the inner housing component or alternatively as a recess in the inner side of the outer housing component, the housing is very easy to manufacture and assemble.

[0020] According to one embodiment, at least one first cooling channel extends approximately semicircularly in a first half of the stator. At least one second cooling channel extends approximately semicircularly in a second half of the stator, wherein the first half and the second half are opposite each other along a symmetry plane containing the axis of rotation, and wherein a plurality of inlet openings are arranged along the first cooling channel and a plurality of outlet openings are arranged along the second cooling channel.

[0021] In this embodiment, the two cooling channels extend along almost the entire circumference of the stator housing. In the first half of the stator, the coolant is supplied via the first cooling channel and enters the interior through the discharge openings arranged along the first cooling channel. The coolant absorbs heat in the interior and leaves the interior through the discharge openings in the second half of the stator and enters the second cooling channel, from which it can be discharged. In particular, a corresponding coolant pump is provided for the circulation of the coolant.

[0022] According to one embodiment, the separating ribs extend between the coil receiving spaces from the outside to the inside into the interior space, wherein the separating ribs have at least one inlet opening and at least one outlet opening.

[0023] In this embodiment, at least in the outer region of the stator, the individual coil receiving spaces are separated from one another by dividing ribs, which can be made of metal in particular. The dividing ribs extend in particular into the interior space but not into the center, that is to say not to the axis of rotation, but only inwardly over, for example, one third or half of the radius. The dividing ribs can in particular be designed to be essentially hollow and have an inlet or outlet opening at their tip that projects into the interior space.

[0024] The separating ribs can be made of metal in particular and therefore have good thermal conductivity, which serves both to supply coolant to the interior and to absorb heat directly from the coil assembly in thermal contact therewith.

[0025] According to one embodiment, the stator housing also has a positioning aid for positioning or centering the stator teeth for each coil receiving space. This has the advantage that an exact positioning of the stator teeth is facilitated. This positioning is particularly important in view of the air gap between the stator and the rotor of the axial flux machine, which must be dimensioned as accurately as possible. The positioning aid can be designed, for example, as a structure on the stator housing, which interacts with a corresponding opening or structure of the stator teeth.

[0026] According to another aspect of the present invention, a stator of an axial flux motor is provided, which has the described stator housing and a plurality of electromagnetic coil assemblies arranged on a coil receiving space, wherein the stator housing is partially cast with a plastic injection molding material.

[0027] The plastic injection molding material is particularly arranged in the stator housing so that the plastic injection molding material partially connects the coil assembly to each other. The plastic injection molding material is particularly embedded in the outer region of the coil assembly. The inner region of the coil assembly, that is to say, the stator teeth provided with the winding, extends into the inner space of the stator housing, wherein the inner space is closed in a fluid-tight manner by the plastic injection molding material in the outer region of the stator housing. Here, it is also possible to partially cast the dividing ribs between the coil receiving spaces in order to seal the gap between the dividing ribs and the coil assembly. Here, in the case where there are inlet openings and outlet openings in the dividing ribs, the inlet openings and outlet openings do not contain plastic injection molding material. On the other hand, the electrical leads connected to the coil assembly can be cast together and sealed.

[0028] The advantage of this stator is that it has a particularly effective cooling system and can therefore dissipate the heat generated during operation particularly well. By enclosing the interior space by casting certain areas with plastic material, it is possible to achieve that the coolant can circulate freely in the remaining areas of the interior space without the need for further encapsulation of the liquid cooling system in the interior space. This achieves a very good heat transfer between the coil assembly and the coolant.

[0029] According to one embodiment, a cover plate is arranged on at least one side of the stator, and a gap between the cover plate and an element of the stator is cast with a plastic injection molding material.

[0030] The stator designed as a flat cylinder has, in addition to its side, two disk-shaped side surfaces, which also define the inner space and thus must be sealed. For this reason, a cover plate can be provided respectively, which can also be made of metal, thereby having good thermal conductivity.

[0031] According to one embodiment, an O-ring as a seal is arranged between the cover plate and the inner ring element of the stator housing and the outer ring element of the stator housing, wherein the O-ring can be designed as a rubber seal in particular. The inner ring element of the stator housing can be a ring around the rotation axis of the rotor in particular. The outer ring element can be the outer surface of the stator housing in particular.

[0032] The advantage of this embodiment is that the interior space in which the coolant can circulate is bounded and closed in a fluid-tight manner by the inner ring element, a cover plate or multiple cover plates cast with plastic injection molding material, and an outer ring element likewise cast with plastic injection molding material and stator teeth protruding into the interior space.

[0033] According to one aspect of the present invention, an axial flux motor having the stator is provided. In addition, the axial flux motor also has at least one rotor, which can be designed to be brushless and can include permanent magnets that interact with the magnetic field of the stator. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The following describes the implementation of the present invention with reference to schematic diagrams.

[0035] Figure 1 A view showing a stator housing according to an embodiment of the present invention viewed from a first side is shown;

[0036] Figure 2 Shown from the same side Figure 1 A perspective view of a stator housing;

[0037] Figure 3 Shown is a diagram of a structure viewed from the opposite side. Figure 1 A view of the stator housing;

[0038] Figure 4 Shows the Figure 3 A slightly perspective view of the stator housing from the same side view;

[0039] Figure 5 Shown with Figure 3 a view of the same stator housing, wherein however only the inner housing components are shown;

[0040] Figure 6 Shown with Figure 4 A view of the same stator housing, wherein however only the inner housing component of the stator housing is shown;

[0041] Figure 7 Shown with Figure 3 A view of the same stator housing, but with the coil assembly inserted into the stator housing and partially cast with plastic material;

[0042] Figure 8 Shown according to Figure 7 A perspective view of a stator housing with a coil assembly;

[0043] Fig. 9 shows a cross section of a stator according to an embodiment of the invention, and

[0044] Fig.10 Shown according to Fig. 9 Cross-sectional view of the stator. DETAILED DESCRIPTION

[0045] Figure 1 and Figure 2 The figure shows a view of a stator housing 1 of an axial flux motor according to a first embodiment of the present invention, viewed from a first side. The stator housing 1 is arranged rotationally symmetrically around a rotation axis 2 of an associated rotor (not shown) of the axial flux motor. The stator housing 1 has an outer housing component 3 and an inner housing component 4, wherein the outer housing component 3 concentrically surrounds the inner and outer housing components 4, and the inner side of the outer housing component 3 is in contact with the outer side of the inner housing component 4. The stator housing 1 has a substantially flat cylindrical shape, wherein the cylinder has no cover but is open to one side, and the bottom has a series of openings 5, which are separated from each other by webs 6.

[0046] The stator housing 1 has a stator housing 1 (in Figure 1 and 2 2 , and a liquid cooling system for the interior space of the device (not shown), the liquid cooling system having an inlet line 21 and a return line 22, through which a liquid coolant is pumped during operation.

[0047] Figure 3 and Figure 4 Shown according to Figure 1 and Figure 21 , wherein the view through the open cover surface into the interior space 8 of the stator housing 1 is shown. A total of twelve coil receiving spaces 10 are formed in the interior space 8 of the stator housing 1. Alternatively, more or fewer coil receiving spaces can also be provided, depending on the design of the electric machine. The coil receiving spaces 10 are arranged rotationally symmetrically around the axis of rotation or around the inner ring element 15 of the stator housing 1 and are separated from each other by dividing ribs 9.

[0048] The dividing ribs 9 thus divide the interior space 8 of the stator housing 1 into twelve coil receiving spaces 10. Therefore, twelve dividing ribs 9 are also provided, which extend inwardly from the outer ring element 16 of the stator housing 1, wherein they extend inwardly approximately one third of the radius of the stator housing 1. The dividing ribs 9 are connected to the outer ring element 16, in particular are formed integrally therewith.

[0049] The stator housing 1 has an outer housing component 3 and an inner housing component 4 , wherein the inner housing component 4 includes an outer ring element 16 , partition ribs 9 , webs 6 and an inner ring element 15 . The stator housing 1 is made of metal (eg aluminum) and therefore has very good thermal conductivity.

[0050] As in Figure 4 As can be seen in the perspective view of FIG. 1 , the partition rib 9 is at least partially designed to be hollow and has an inlet opening and an outlet opening for the liquid coolant at its inwardly protruding tip. The partition rib 9 is designed to be wider in its outer region 11 than in its inner region 12, so that the partition rib tapers toward the center of the stator housing 1.

[0051] Furthermore, each coil receiving space 10 has a positioning aid 13 in the form of a tip protruding into the interior space 8 , which serves for the correct positioning of the stator tooth to be positioned in the coil receiving space 10 .

[0052] Figure 5 and 6 4. In these views, the internal components 4 are shown. Figure 3 and 4 In contrast to the view shown in , it can be seen that the first cooling channel 17 and the second cooling channel 19 are arranged in the outer side 23 of the inner housing component 4, the first and second cooling channels each extending approximately half of the circumference of the inner housing component 4 and formed as a recess in the inner housing component or its outer side 23. The separating web 20 separates the first cooling channel 17 from the second cooling channel 19. In the cooling channels 17, 19, openings 18 are provided in the hollow separating ribs 9. Therefore, the first cooling channel 17 and the second cooling channel 19 are in fluid communication with the interior space 8 of the stator housing 1 via the cavities in the separating ribs 9.

[0053] Figure 7 and Figure 8 A view of a stator 30 of an axial flux motor according to an embodiment of the present invention is shown, wherein twelve assemblies 31 have been positioned in the coil receiving space 10 in the stator housing 1 of the stator 30. The coil assemblies 31 in particular each include a stator tooth 33 made of a magnetic material and a coil 35 wound around the stator tooth 33 and in the axial direction.

[0054] In operation, the coolant flows into the first cooling channel 17 via the feed line 21, flows from the first cooling channel through the opening 18 into the interior of the dividing rib 9, and flows into the interior 8 of the stator housing 1 via the inlet opening 14. Here, the coolant (for example, oil) flows around the large area of ​​the coil assembly 31. The coolant flows out of the interior 8 again through the outlet opening 14 in the dividing rib 9, which is fluidically connected to the second cooling channel 19, and is discharged via the return line 22.

[0055] Fig. 9 FIG. 4 shows a portion of the stator 30 as seen from above. Figure 7 and Figure 8 As shown, Fig. 9 The outer housing member 3 is not shown in the figure. The stator teeth 33 are formed by a plurality of stacked lamination layers 34 to reduce eddy currents. Alternatively, they can also be made of epoxy resin bonded powder (also known as SMC material, soft magnetic compound).

[0056] The stator teeth 33 have windings of coils 35 along their circumference. Fig. 9 The electrical leads are not shown in the figure, which can be arranged in particular in the outer region 11 of the stator tooth 33. An insulation 39 is provided between the laminated core of the stator tooth 33 and the coil 35. Fig.10 Shown in.

[0057] In order to seal the interior 8 in a fluid-tight manner, after the coil assemblies 31 have been inserted, the outer region of the stator housing 1 is cast with an injection molding compound 32. The injection molding compound fills in particular the volume between the outer ring element 16, the coil assemblies 31 and the dividing ribs 9. The injection molding compound partially fills the gaps 38 between the coil assemblies 31, but does not extend as far inward as the dividing ribs 9, so that the inlet or outlet opening 14 remains free of injection molding compound.

[0058] In order to make the inner space 8 relative to Fig. 9 To seal the cover plate (not shown), an O-ring 36 made of a rubber elastic material is inserted into the recess of the inner ring element 15 , and another O-ring 37 is inserted into the recess of the outer ring element 16 .

[0059] Fig.10 Shown according to Fig. 9, wherein the outer housing component 3 and the cover plate 40 are also shown. The cover plate 40 has openings at the location of the stator teeth 33 in the embodiment shown and is placed on the stator housing 1 after the injection molding material 32 has been introduced. Subsequently, a thin layer 41 of injection molding material can be applied to the entire front side of the stator 30 (optionally omitting the region of the stator teeth 33) in order to close the gap between the cover plate 40 and the other elements of the stator housing 1 in a fluid-tight manner.

[0060] The interior 8 of the stator 30 is thus closed in a fluid-tight manner and has no openings to the outside except for the inlet or outlet opening 14, so that it can be flowed through by liquid coolant during operation. Since the coolant is in direct contact with the large surface of the coil assembly 31, heat dissipation is particularly effective.

Claims

1. A stator housing (1) for an axial flux electric machine, the axial flux electric machine having at least one rotor rotatable about a rotation axis (2) and at least one stator (30) spaced apart from the rotor along the rotation axis (2), the stator having a fluid-tight interior space (8), wherein: A coil receiving space (10) for receiving an electromagnetic coil assembly (31) is arranged in the inner space (8) in a circumferential direction around the rotation axis (2), wherein each coil assembly (31) has at least one coil (35) wound around a stator tooth (33) in an axial direction. The stator housing (1) has a liquid cooling system, which includes at least one first cooling channel (17) extending in the stator housing (1) in a circumferential direction and at least one second cooling channel (19) separated from the at least one first cooling channel and also extending in the stator housing (1) in a circumferential direction, wherein the inner space (8) is filled with a coolant, which is in thermal contact with the coolant in the first and second cooling channels (17, 19).

2. The stator housing (1) according to claim 1, wherein: The inner space (8) is closed in a fluid-tight manner and has no opening to the outside, so that the cooling liquid is enclosed in the inner space (8) in a fluid-tight manner.

3. The stator housing (1) according to claim 1, wherein: The liquid cooling system also includes: - at least one inlet opening (14) in fluid connection with the first cooling channel (17) to allow cooling liquid to enter the inner space (8), and - at least one outlet opening (14) in fluid connection with the second cooling channel (19) to allow cooling liquid to leave the interior space (8), thereby enabling cooling liquid to flow from the first cooling channel (17) into the interior space (8) and from the interior space into the second cooling channel (19).

4. The stator housing (1) according to any one of claims 1 to 3, wherein the stator housing has an outer housing component (3) and an inner housing component (4), wherein the inner housing component (4) is concentrically arranged in the outer housing component (3), and the at least one first cooling channel (17) and the at least one second cooling channel (19) are formed between the inner housing component (4) and the outer housing component (3).

5. The stator housing (1) according to claim 4, wherein: The at least one first cooling channel (17) and / or the at least one second cooling channel (19) are formed as recesses in an outer side surface (23) of the inner housing component (4).

6. The stator housing (1) according to any one of claims 3 to 5, wherein: The at least one first cooling channel (17) extends approximately semicircularly in a first half of the stator housing (1), and the at least one second cooling channel (19) extends approximately semicircularly in a second half of the stator housing (1), wherein the first half and the second half are opposite to each other along a symmetry plane containing the rotation axis (2), wherein a plurality of inlet openings (14) are arranged along the first cooling channel (17) and a plurality of outlet openings (14) are arranged along the second cooling channel (19).

7. The stator housing (1) according to any one of claims 3 to 6, wherein: The partition rib (9) extends between the coil receiving spaces (10) from outside to inside into the inner space (8), wherein the partition rib (9) has the at least one inlet opening (14) and the at least one outlet opening (14).

8. The stator housing (1) according to any one of claims 1 to 7, further comprising, for each coil receiving space (10), a positioning aid (13) for positioning or centering a stator tooth (33).

9. A stator (30) for an axial flux motor, comprising a stator housing (1) according to any one of claims 1 to 8 and a plurality of electromagnetic coil assemblies (31) arranged on a coil receiving space (10), wherein the stator housing (1) is partially cast with a plastic injection molding material.

10. The stator (30) according to claim 9, wherein: A cover plate (40) is arranged on at least one side of the stator (30), and a gap (38) between the cover plate (40) and an element of the stator (30) is cast with a plastic injection molding material.

11. The stator (30) according to claim 9 or 10, wherein: O-rings (36, 37) are arranged as seals between the cover plate (40) and an inner ring element (15) of the stator housing (1) and an outer ring element (16) of the stator housing (1).

12. An axial flux electric machine having at least one stator (30) according to any one of claims 9 to 11.

Images