Method for manufacturing a stator for an axial flux machine, stator manufactured by this method, axial flux electric machine

Abstract

To simplify the manufacture of stators for axial flux machines. A method for manufacturing at least a portion of a stator for an axial-flux machine includes providing a first joint (21) made of a first material on a first stator pole (11) of the stator and a second joint (22) made of a second material on a second stator pole (12), where the first joint (21) of the first stator pole (11) overlaps and joins with a second joint (22) of the second stator pole (12) in a circumferential direction of the stator at an overlap region (5). The second joint (22) is located outwardly relative to the center of the stator than the first joint (21). The second material is at least largely transparent to a predetermined laser wavelength, while the second material is opaque to the predetermined laser wavelength. The first joint (21) is welded to the second joint (22) by applying laser radiation (9) of a predetermined laser wavelength to the overlap region (5).Furthermore, a stator manufactured by this method is claimed.

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing at least part of a stator of an axial flux machine, and further to a stator of an axial flux machine and to an axial flux electric machine itself. [Background technology]

[0002] For example, an axial flux machine can be realized as a disk-type rotary motor, in which the rotor and the stator are formed in the shape of a disk, the magnetic field extending parallel to the axis of rotation.

[0003] The stator poles of an axial flux machine are arranged circumferentially adjacent to one another, and the individual teeth are typically insulated before the windings are attached, for example by overmolding the stator teeth with plastic.

[0004] In the context of the manufacture of electrical machines, certain techniques such as laser welding, casting, moulding, overmolding and other methods are well known, and in this respect reference can be made to documents such as US Pat. No. 5,629,997 and US Pat. No. 5,629,997, which inter alia state that the poles can be joined by laser welding and / or overmolding.

[0005] Documents such as US Pat. No. 5,629,999 and US Pat. No. 5,629,999 describe plastic parts that are connected to one another by laser welding and mounted in / on a motor.

[0006] Patent document 5 below describes a rotor in which plastic parts are connected to one another by laser welding, but this presents the challenge of creating a stable, medium-tight connection between the rotor components. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-193564 [Patent Document 2] International Publication No. 2011 / 037 087 [Patent Document 3] US Patent Application Publication No. 2008 / 0315699 [Patent Document 4] DE 10 2016 213 110 [Patent Document 5] Japanese Patent Application Laid-Open No. 2006-325345 Summary of the Invention [Problem to be solved by the invention]

[0008] SUMMARY OF THE INVENTION The object of the present invention is to simplify the manufacture of stators for axial flux machines. [Means for solving the problem]

[0009] According to the invention, this problem is solved by a method and a stator according to the independent claims. Advantageous developments of the invention emerge from the dependent claims.

[0010] Thus, according to the present invention, a method for manufacturing at least a portion of a stator of an axial flux machine is provided. The claimed method is primarily directed to joining two stator poles and therefore only relates to a portion of the stator of an axial flux machine. Of course, more than one or even all of the stator poles of the stator can also be joined in this manner.

[0011] First, a first joint made of a first material is attached to the first stator pole of the stator. Similarly, a second joint made of a second material is attached to the second stator pole of the stator. The joints are used to join the stator poles together. Typically, a stator pole has not just one joint, but often four, two of which are for connecting to adjacent stator poles.

[0012] In this case, in the joined state of the first stator pole and the second stator pole, the first joint portion is intended to overlap the second joint portion in the overlap region in the circumferential direction of the stator, which means that in the (axial) plan view of the overlap region, the two joint portions overlap.

[0013] The second joint is located further outward from the center of the stator than the first joint. In particular, the second joint must be freely accessible from the outside, while the first joint can be obscured by the second joint. In other words, the distance from the center of the stator to the second joint is greater than the distance from the center to the first joint.

[0014] The second material is at least largely transparent to the predetermined laser wavelength, while the first material is opaque to the predetermined laser wavelength. That is, two different types of materials are used for the joints. Preferably, the second material of the outer second joint is transparent and can be called a transmissive material, while the material of the inner first joint is opaque and can be called an absorber.

[0015] Finally, the overlapping area is irradiated with laser radiation of a predetermined laser wavelength, thereby welding the first joint to the second joint. Because the second, preferably transparent, joint is located on the outside, the laser radiation can reach the first joint and be absorbed there. This means that most, or at least a large portion, of the energy is absorbed by the first joint, which is located on the inside, while the energy of the laser radiation is not absorbed at all or only very little in the joint located on the outside. In this case, the energy of the laser radiation is sufficient to melt the first joint and weld it to the second joint. In this case, the second joint is also melted, possibly at least in its surface area.

[0016] In an advantageous embodiment of the method according to the invention, the joints are welded in such a way that the overlap region closes the hollow space or cooling space between the two stator poles in a medium-tight manner. Typically, the pole teeth of the stator poles are surrounded by their respective windings. There is usually a small gap between the windings of two adjacent stator poles, which can be used for the passage of a coolant. This creates a hollow space through which the coolant can flow. This hollow space can be sealed in the axial direction by the two joints. For this purpose, it is usually necessary to weld the two joints along their entire radial extent (which corresponds roughly to the radial extent of the stator poles). Naturally, this applies to both axial end faces.

[0017] In another advantageous exemplary embodiment, the stator has a central axis extending parallel to the stator poles or the main magnetic flux of the axial-flux machine. This central axis corresponds to the axis of the same name of the axial-flux machine. In that case, the second joint is arranged axially or radially outward of the first joint with respect to the central axis. This means that in the case of axial laser incidence, the laser beam first passes through the second (transparent) joint and then strikes the impermeable joint located axially inside and is absorbed therein.

[0018] In another embodiment, it is contemplated that the stator poles may each be provided with a winding before welding. Typically, the stator pole teeth or lamination core may be completely overmolded with the respective material or insulating material. The stator pole windings may then be pressed or wound onto this insulating material. Once the individual stator poles have been provided with windings, they may be fitted together and finally welded.

[0019] According to an advantageous embodiment of the method according to the invention, the two stator poles are fitted together before welding, so that the two joints engage with one another and / or form a positive connection. This engagement has the advantage that the stator poles are already held in contact with one another before being welded. The engagement can be achieved by a (releasable) snap connection. For example, the stator poles can be fitted together in a circumferential overlapping manner, so that they engage with one another. However, other types of positive connections between the stator poles can also be selected. For example, adjacent stator poles can be fitted together, for example, radially, according to the tongue-and-groove principle. In this case, for example, the groove is the joint on one side and the protrusion is the joint on the other side. If the groove is transparent and the protrusion is opaque, laser welding can also be performed here.

[0020] The above object can also be achieved by a stator for an axial flux machine, according to the present invention, comprising a first joint made of a first material on a first stator pole of the stator and a second joint made of a second material on a second stator pole of the stator, wherein in a joined state of the first stator pole and the second stator pole, the first joint overlaps with the second joint in the circumferential direction of the stator in an overlap region, and the second joint is located more outward with respect to the center of the stator than the first joint, the second material being at least largely transparent to a predetermined laser wavelength and the first material being opaque to the predetermined laser wavelength, and the first joint is welded to the second joint.

[0021] The possible variants and advantages mentioned above in connection with the method according to the invention also apply to the stator according to the invention, and corresponding method features can be considered as functional features in the stator.

[0022] In one exemplary embodiment, the first stator poles have a first joint type joint on the axially outer side of the side facing the second stator pole, and a first joint type joint on the opposite side of the first stator pole. Furthermore, the second stator poles have a second joint type joint on the axially outer side of the side facing the first stator pole, and a second joint type joint on the opposite side of the second stator pole. This means that the first stator pole has a first joint at each of its four corners in a radial plan view, which are opaque to the laser beam. In contrast, the second stator pole has joints at each of its four corners visible in a radial plan view, which are located on the outer side and made of a material that is transparent or transmissive to the laser. This can be easily achieved by two different overmolding forms for the stator poles, where the second stator pole is completely overmolded, for example, with a laser-transparent plastic, so that it always has an "outer overlap" (joint located on the outside) on both sides and in both circumferential overlap regions (all four overlap regions of the pole), and the first stator pole is completely overmolded, for example, with a laser-opaque plastic, so that it always has an "inner overlap" (joint located on the inside) on both sides and in both axial overlap regions. These different stator poles then need to be alternately arranged in the circumferential direction, so that the "outer overlap" (transparent) of the second stator pole can always overlap and be welded to the opaque "inner overlap" of the first stator pole. That is, in this example, there are two different types of stator poles.

[0023] In an alternative embodiment, the first stator poles each have a first joint type axially outward on the side facing the second stator pole and a second joint type axially outward on the opposite side, and the second stator poles each have a second joint type axially outward on the side facing the first stator pole and a first joint type axially outward on the opposite side. This also means that the two stator poles can be made identical. In a radial plan view, the stator poles each have, for example, an outer overlap on one side and an inner overlap on the opposite side. This means that only one type of pole can be made: one with an outer overlap on one side (axially and / or circumferentially) and a corresponding inner overlap on the other side with an opaque material. In this case, the poles themselves are "asymmetric" in the sense that two overlap regions always have one outer overlap and two overlap regions always have one inner overlap. Geometrically speaking, the poles can be axisymmetric about the axial center plane, axisymmetric about the circumferential center plane, or point symmetric about the pole center. When joining stator poles to form a stator ring, the only consideration is a spatial orientation that always results in simultaneous outer and inner overlaps, rather than alternating pole types. However, in this case, such stator poles must be overmolded with two different materials, which can be done in one step (with two or more injectors) or sequentially in multiple steps.

[0024] In another exemplary embodiment, a first stator pole has a first joint on its side facing the second stator pole, a joint of a second joint type on its axially opposite side, a joint of a second joint type axially outwardly and circumferentially opposite the first joint, and a joint of the first joint type axially opposite the first joint, and a second stator pole has a second joint on its side facing the first stator pole, a joint of the first joint type on its axially opposite side, a joint of the first joint type axially outwardly and circumferentially opposite the second joint, and a joint of the second joint type axially opposite the latter, which means that in a radial plan view, inner overlaps (first joint type) and outer overlaps (second joint type) alternate around the stator pole. In that case, as in the previous exemplary embodiment, the stator poles are provided with both outer and inner overlaps, but only one type of stator pole is sufficient to make the stator ring. In a radial plan view, the poles are point symmetrical about the pole center.

[0025] In an advantageous embodiment of the stator according to the invention, the joints are integrally injection molded onto the pole pieces and / or pole teeth of the respective stator poles. In some cases, the respective stator poles can be completely overmolded with the respective (insulating) material, which thereby performs the dual function of insulating and mechanically fixing the stator poles.

[0026] In another exemplary embodiment, one of the two joints in the overlap region has a bead (protrusion) and the other of the two joints has a cavity (recess), and the bead protrudes into the cavity when the first stator pole and the second stator pole are joined. This allows the two stator poles to be engaged with each other. This can be achieved by having the overlap region on both axial sides of the stator poles each have such a bead and such a cavity, and when the stator poles are engaged, each bead protrudes into its respective cavity. The bead and the cavity can be designed, for example, to be round, so that the stator poles can be releasably engaged with each other. However, other geometric shapes of the bead and the cavity can also be used. The bead and the cavity do not necessarily need to extend over the entire radial length of the stator pole. In some cases, one or more short radial sections where the respective bead and the cavity protrude into each other are sufficient.

[0027] In another advantageous embodiment of the stator according to the invention, it is provided that the joints welded together along the entire radial extension of the stator poles in the overlap region seal off the cooling circuits (inside the stator poles). For example, when the stator poles are joined together, the space that is created between them or between the windings can be used for the flow of coolant. A corresponding cooling circuit can be guided through all the stator poles of the stator, or only through some of them. To seal off this cooling circuit, the stator poles can be welded together along their entire radial extension (on both axial sides). Corresponding welding can then be performed on the radial end faces of the stator poles.

[0028] The joints can be aligned with one another so that the first and second stator poles bias against one another in the joined state. This preload can be used to bring the joints into close contact with one another, especially during welding. For this purpose, it is advantageous, for example, if the outer joint (outer overlap) has an undercut so that this outer joint is formed elastically. The inner joint (inner overlap) can then be pressed into this undercut, so that the two joints bias against one another in the joined state.

[0029] Furthermore, it is possible to provide for a tolerance gap to be formed in the circumferential direction between the first and second joints, which makes it impossible for manufacturing tolerances to prevent the joints from precisely engaging with each other, thereby creating a stable, process-reliable (especially with regard to tolerances) and medium-tight connection between the poles or pole pieces.

[0030] In another exemplary embodiment, each of the two stator poles has a winding, and the joint is located axially outside the winding. Optionally, the joint can be located exactly between the stator poles. Optionally, the joint can also extend axially beyond the stator poles. For example, the overlap region can be advantageously located outside the coil region or winding region. In that case, they can also extend slightly beyond the pole pieces and poles (possibly symmetrically between the outer overlap and the inner overlap), so that the connection point is located exactly between the two poles. However, this can also be designed asymmetrically, so that only the outer overlap extends beyond the poles, while the inner overlap is still located in the pole region. In that case, the connection point is still in the pole region, not between the two poles (in the center).

[0031] According to the invention, the above object is also achieved by an axial flux electric machine comprising a stator of the above-mentioned kind.

[0032] Further advantages, features and details of the invention will become apparent from the following description based on preferred embodiments and on one or more of the drawings. The features and combinations of features mentioned in the above description and in the following description of the figures and / or shown only in the figures can be used not only in the respective combinations presented, but also in other combinations or alone without departing from the scope of the invention. [Brief explanation of the drawings]

[0033] [Figure 1] FIG. 1 shows a portion of the stator of an axial flux machine. [Figure 2] FIG. 2 is a cross-sectional view of the stator of FIG. [Figure 3] FIG. 3 is a partially enlarged view of FIG. 2. [Figure 4] FIG. 4 is a partially enlarged view of FIG. DETAILED DESCRIPTION OF THE INVENTION

[0034] The exemplary embodiments described in more detail below represent preferred embodiments of the present invention.

[0035] Figure 1 shows in perspective a portion of the stator of an axial flux machine. The stator is formed by an annular arrangement of stator poles 1 joined together. The annular stator has a central axis 2 which not only forms the axis of rotation of one or more rotors (not shown), but also indicates the main magnetic flux direction. The following (and above) discussion of the radial, axial and circumferential directions always relates to this central axis 2.

[0036] Each stator pole 1 has a pole piece 3 on each of its axial sides. In this example, the pole pieces 3 are overmolded with plastic 4, which may have retention and / or insulation tasks. The individual stator poles 1 are first manufactured separately and then overmolded with plastic 4. The individual stator poles 1 are then joined together to form the annular stator shown in Figure 1. The plastic overmoldings 4 of two stator poles 1 butt up against each other when the stator poles 1 are joined together, forming an overlap region 5 that extends substantially radially.

[0037] Each stator pole 1 has a respective winding 6 disposed between respective axially spaced pole pieces 3 on a respective pole tooth not visible here.

[0038] FIG. 2 shows a cross-sectional view of several stator poles 1 parallel to the central axis 2. This cross-sectional view shows the arrangement of the respective pole teeth 7 between the pole pieces 3 for each stator pole 1. Each pole tooth 7 is surrounded by a respective winding 6. The partial area of ​​the cross-section where the two windings 6 of two adjacent stator poles 1 meet, and where part of the overlap area 5 is also located, is indicated by III. This partial area III is shown enlarged in FIG. 3. From this enlargement, it can be seen that the pole teeth 7 can have a first overmold, also referred to here as a (plastic) overmold 4. Each winding 6 is respectively provided on this first overmold in the area of ​​the pole tooth 7. Between the windings 6 of two adjacent stator poles 1, there is a cooling space 8 which can be filled with a cooling medium.

[0039] In the example of Figure 3, the stator pole shown at the bottom in the drawing can be referred to as the first stator pole 11, and the pole shown at the top in the drawing can be referred to as the second stator pole 12. Each of the first stator poles 11 has a first joint 21 on both axial sides. The first joint 21 protrudes beyond the pole piece 3 in the circumferential direction. The first joint 21 is preferably formed integrally with an overmold 41 of the pole tooth 7 of the first stator pole 11. In particular, the overmold 41 and the first joint 21 are made of the same (plastic) material.

[0040] Similarly, the second stator pole 12 has second joints 22 on both axial sides thereof, which also protrude beyond the pole piece 3 of the second stator pole 12 in the circumferential direction.

[0041] In the joined state of the first stator pole 11 and the second stator pole 12 shown in Figure 3, the first joint portion 21 and the second joint portion 22 overlap in the overlap region 5. The second joint portions 22 are located axially outward of the first joint portion 21 on both sides. Therefore, the first joint portion 21 can be referred to as an inner overlap, and the second joint portion 22 can be referred to as an outer overlap.

[0042] The first joint 21 and the second joint 22, i.e. the inner and outer overlaps, are joined together by laser welding. For this purpose, the outer second joint 22 is made of a (mostly) transparent material, so that the laser beam 9 passes through the second joint 22 and the main energy of the laser beam 9 reaches the inner first joint 21. This first joint 21 then melts a little and joins with the outer second joint 22. This laser welding is carried out in the same way on the opposite axial side.

[0043] FIG. 4 shows an enlarged view of the overlapping region 5 indicated by IV in FIG. 3. The main portion of the overlapping region 5 is located between the pole pieces 3 of the two stator poles that are located opposite each other in the circumferential direction. In particular, the transparent or partially transparent portion 221 of the second joint portion 22 is located between the pole piece side surfaces 31 of the pole pieces 3 that are located opposite each other in the circumferential direction. Behind it in the axial direction (with respect to the incidence of the laser beam) is the opaque portion 211 of the first joint portion 21, which is located on the inside. The laser beam, which is incident from the left and passes through the transparent portion 221 (not shown in FIG. 4), melts the opaque portion 211 at the contact region 10. In this case, a melted region is formed, which is located at the contact region 10. As a result, the first joint portion 21 and the second joint portion 22 are materially connected by laser welding.

[0044] The joints 21 and 22 are formed on both sides opposite each other in the axial direction so that they are biased against each other before welding after the stator poles 11 and 12 are fitted together, thereby generating the necessary contact pressure between the joints during laser welding.

[0045] In the example of FIG. 4, the transparent part 221 has a cavity 222 that opens towards the center of the stator pole, i.e., in the direction of the winding 6. In contrast, the opaque part 211 has a bead 212. In the example shown, both the cavity 222 and the bead 212 are round in cross section. Different contours, such as pointed ends, can be selected for these two components. It is advantageous to geometrically design the cavity 222 and the bead 212 so that they engage with each other when the two stator poles 11, 12 are mated. This has the advantage that the stator ring is already held together before welding. To ensure the aforementioned contact pressure, when the two stator poles 11, 12 are not joined, the axial distance between the tips of the bead 212 must be somewhat greater than the distance between the lowest points of the cavities 222 in the transparent parts 221 that are axially opposite each other.

[0046] During welding, the laser beam is guided, for example, radially over the entire radial extent of the overlap region 5. This welding results in a medium-tight joint composite at least on both axial sides. To obtain a medium-tight cooling circuit, the outer periphery of the stator can be sealed in a suitable manner, possibly also by overlapping and laser welding. [Explanation of symbols]

[0047] 1 stator pole 2 center axis 3 pole piece 4 (Plastic) Overmolding 5. Overlap Area 6 windings 7 Polar teeth 8 Hollow or cooling space 9 Laser Beam 10 Contact area 11 First stator pole 12 Second stator pole 21 First Junction 22 Second Junction 31 Pole side 41 Overmolding with opaque materials 42 Overmolding with transparent material 211 Opaque Area 212 Bead 221 Transparent Parts 222 Cavity III Partial area IV subregion

Claims

1. 1. A method of manufacturing at least a portion of a stator of an axial flux machine, comprising the steps of: - attachment of a first joining part (21) made of a first material to a first stator pole (11) of said stator; - attachment of a second joining part (22) made of a second material to a second stator pole (12) of said stator, - In a joined state between the first stator pole (11) and the second stator pole (12), the first joint portion (21) overlaps with the second joint portion (22) in the circumferential direction of the stator in an overlapping region (5), - the second joint (22) is located further outward with respect to the center of the stator than the first joint (21); - said second material is at least largely transparent to the predetermined laser wavelength, - said first material is opaque to said predetermined laser wavelength; Installation and - welding of said first joint (21) to said second joint (22) by applying laser radiation (9) of said predetermined laser wavelength to said overlapping area; A method characterized by carrying out the steps of:

2. The joint is welded in such a way that the overlapping area (5) seals the hollow space (8) between the two stator poles (11, 12) in a medium-tight manner.

2. The method according to claim 1, characterized in that

3. The stator has a central axis (2) extending parallel to the main magnetic flux of each of the stator poles (11, 12), The second joint portion (22) is disposed axially outward of the first joint portion (21) with respect to the central axis.

3. The method according to claim 1 or claim 2, characterized in that

4. The stator poles (11, 12) are each provided with a winding (6) before welding. The method according to any one of claims 1 to 3, characterized in that

5. The two stator poles (11, 12) are fitted together before welding, and the two joints (21, 22) engage with each other and / or form a positive connection. The method according to any one of claims 1 to 4, characterized in that

6. In the stator of an axial flux machine, a first joint (21) made of a first material on a first stator pole (11) of said stator; a second joint (22) made of a second material on a second stator pole (12) of said stator; Equipped with - In a joined state between the first stator pole (11) and the second stator pole (12), the first joint portion (21) overlaps with the second joint portion (22) in the circumferential direction of the stator in an overlapping region (5), - the second joint (22) is located further outward with respect to the center of the stator than the first joint (21); - said second material is at least largely transparent to the predetermined laser wavelength, - said first material is opaque to said predetermined laser wavelength; - said first joint (21) is welded to said second joint (22) A stator characterized by:

7. - the first stator poles (11) have, on the side facing the second stator poles (12), respectively axially outwardly, a joint of the type of the first joint (21), and also on the opposite side, respectively axially outwardly, a joint of the type of the first joint (21), the second stator poles (12) have, on the side facing the first stator poles (11), respectively, axially outwardly, a joint of the type of the second joint (22), and also, on the opposite side, respectively, axially outwardly, a joint of the type of the second joint (22); 7. The stator according to claim 6, wherein the stator comprises:

8. - the first stator poles (11) have, on the side facing the second stator poles (12), respectively axially externally, a joint of the type of the first joint (21) and, on the opposite side, respectively axially externally, a joint of the type of the second joint (22); the second stator poles (12) have, on the side facing the first stator poles (11), respectively, axially externally, a joint of the type of the second joint (22), and, on the opposite side, respectively, axially externally, a joint of the type of the first joint (21); 7. The stator according to claim 6, wherein the stator comprises:

9. - the first stator pole (11) has, on the side facing the second stator pole (12), the first joint (21) and, on the axially opposite side, a joint of the second joint (22) type, and, circumferentially opposite to the first joint (21), axially outwardly, a joint of the second joint (22) type, and, axially opposite to the latter, a joint of the first joint (21) type, the second stator pole (12) has the second joint (22) on the side facing the first stator pole (11), a joint of the type of the first joint (21) on the opposite axial side, a joint of the type of the first joint (21) axially outwardly and circumferentially opposite the second joint (22), and a joint of the type of the second joint (22) on the opposite axial side of the latter; 7. The stator according to claim 6, wherein the stator comprises:

10. The joints (21, 22) are integrally injection molded onto the pole pieces (3) and / or pole teeth (7) of the respective stator poles (11, 12). The stator according to any one of claims 6 to 9, characterized in that:

11. One of the two joints (21, 22) in the overlapping region (5) has a bead (212), and the other of the two joints has a cavity (222), and when the first stator pole (11) and the second stator pole (12) are joined together, the bead (212) protrudes into the cavity (222). The stator according to any one of claims 6 to 10, characterized in that:

12. In the overlapping region (5), the stator poles (11, 12) are welded together along their entire radial extension to seal the cooling circuit. The stator according to any one of claims 6 to 11, characterized in that:

13. An allowable gap is formed in the circumferential direction between the first joint portion (21) and the second joint portion (22). The stator according to any one of claims 6 to 12, characterized in that:

14. The two stator poles (11, 12) each have a winding (6), and the joints (21, 22) are disposed axially outward of the winding (6). The stator according to any one of claims 6 to 13, characterized in that:

15. An axial flux electric machine comprising the stator according to any one of claims 6 to 14.

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