Method for producing a stator of an axial flow machine, and stator produced according to said method
Patent Information
- Application Number
- EP2023817969
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-12-19
- Filing Date
- 2023-11-30
- Publication Date
- 2025-10-29
AI Technical Summary
The production of stators for axial flux machines is complex and requires efficient methods to join stator poles while ensuring a media-tight and stable connection, particularly for cooling medium flow and insulation.
A method involving laser welding of stator poles with different materials, where one material is opaque and the other is transparent to a specific laser wavelength, allowing for precise energy absorption and welding, and optionally incorporating snap connections for initial pole interlocking before welding.
This method simplifies the assembly of stator poles by creating a media-tight and stable connection, enhancing the sealing of cooling spaces and insulation while reducing production complexity, and allows for efficient energy absorption during laser welding.
Smart Images
Figure 1.1
Abstract
Description
[0001] Method for producing a stator of an axial flux machine and stator produced by this method
[0002] The present invention relates to a method for producing at least part of a stator of an axial flux machine. Furthermore, the present invention relates to a stator for an axial flux machine and to an electric axial flux machine itself.
[0003] Axial flux machines can be implemented, for example, as disc-rotor motors, whose rotor and stator are disc-shaped. The magnetic field runs parallel to the axis of rotation.
[0004] The stator poles of an axial flux machine are arranged circumferentially. The individual teeth are usually insulated before the windings are applied. This insulation is achieved, for example, by overmolding the stator teeth with a plastic.
[0005] In the context of the production of electrical machines, certain techniques such as laser welding, overmolding, casting, and overmolding, as well as other methods, are well known. In this regard, reference is made to JP 2011193564 and WO 2011 / 037087. These documents also state, in particular, that the terminals can be laser-welded and / or overmolding for joining.
[0006] The documents US 2008 / 0315699 and DE 102016213 110 mention that plastic parts are joined together by laser welding and fastened in / on the engine.
[0007] JP 2006 325 345 describes a rotor whose plastic parts are joined together by laser welding. However, this is done with the aim of creating a media-tight, stable connection between the rotor components. The object of the present invention is to simplify the production of a stator for an axial flux machine.
[0008] According to the invention, this object is achieved by a method and a stator according to the independent claims. Advantageous developments of the invention emerge from the subclaims.
[0009] According to the invention, a method for producing at least part of a stator of an axial flux machine is provided. The claimed method primarily relates to the joining of two stator poles and thus only to part of a stator of an axial flux machine. Of course, more than two or all stator poles of a stator can also be joined in this way.
[0010] First, a first joining section made of a first material is attached to a first stator pole of the stator. A second joining section made of a second material is attached to a second stator pole of the stator in a similar manner. The joining sections serve to join the stator poles together. Typically, a stator pole will have not just one joining section, but usually four joining sections, two each for connecting to an adjacent stator pole.
[0011] It is provided that, when the first stator pole and the second stator pole are joined together, the first joining section overlaps with the second joining section in the circumferential direction of the stator in an overlap region. In an (axial) plan view of the overlap region, this means that the two joining sections lie one above the other.
[0012] The second joining section is located further outward relative to the center of the stator than the first joining section. In particular, the second joining section should be freely accessible from the outside, while the first joining section can be concealed by the second joining section. The distance from the center of the stator to the second joining section is therefore greater than the distance from the center to the first joining section.
[0013] The second material is at least largely transparent to a given laser wavelength, while the first material is opaque to the given laser wavelength. Thus, two different materials are used for the joining sections. Preferably, the second material of the outer second joining section is transparent and can also be referred to as a transmitter, while the material of the inner first joining section is opaque and can therefore also be referred to as an absorber.
[0014] Finally, the overlapping area is irradiated with laser radiation of the specified laser wavelength, welding the first joining section to the second joining section. Since the second, preferably transparent joining section is located on the outside, the laser radiation can reach the first joining section and be absorbed there. This means that most of the energy, or at least a large part, is absorbed in the inner first joining section, while little or no energy from the laser radiation is absorbed in the outer joining section. The energy of the laser radiation is sufficiently high to melt the first joining section and thus weld it to the second joining section. The second joining section may also be partially melted, at least in the surface area.
[0015] In an advantageous embodiment of the method according to the invention, the joining sections are welded in such a way that the overlapping area forms a media-tight seal between the two stator poles. The pole teeth of the stator poles are generally surrounded by respective windings. Between the windings of two adjacent stator poles there is generally a small gap which can be used for the flow of coolant. This creates a cavity through which a cooling medium can flow. This cavity can be sealed in the axial direction by the two joining sections. To do this, it is generally necessary to weld the two joining sections along their entire radial extent (roughly corresponding to the radial extent of the stator poles). This naturally applies to both axial end faces.
[0016] In a further advantageous embodiment, the stator has a central axis that runs parallel to a respective main magnetic flux of the stator poles or the axial flux machine. This central axis corresponds to the eponymous axis of the axial flux machine. The second joining section is then arranged axially or radially outside the first joining section with respect to the central axis. This means that with axial laser irradiation, the second (transparent) joining section is first penetrated by the laser beam before it hits the axially inner, opaque joining section and is absorbed there. In a further embodiment, the stator poles are each provided with a winding before welding. In general, the teeth or laminated cores of the stator poles can be completely overmolded with the respective material or insulating material.The respective stator pole winding can then be slid or wound onto this insulating material. Once the individual stator poles have their windings, they can be plugged together and finally welded.
[0017] According to an advantageous embodiment of the method according to the invention, the two stator poles are pushed together before welding, and the two joining sections engage with each other and / or form a positive connection. This locking has the advantage that the stator poles are already held together before they are welded. The locking can be achieved by a (removable) snap connection. For example, the stator poles can be pushed onto one another in the circumferential direction so that they engage with each other. However, other types of positive connection between the stator poles can also be selected. For example, adjacent stator poles can be pushed into each other using a tongue and groove principle, e.g. in the radial direction. In this case, for example, the groove represents one joining section and the tongue the other joining section. If the groove is transparent and the tongue opaque, laser welding can also be implemented here.
[0018] The above-mentioned object is also achieved according to the invention by a stator for an axial flux machine, comprising a first joining section made of a first material on a first stator pole of the stator, a second joining section 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 joining section overlaps with the second joining section in the circumferential direction of the stator in an overlap region, wherein the second joining section lies further outward with respect to a center of the stator than the first joining section, wherein the second material is at least largely transmissive to a predetermined laser wavelength, the first material is opaque to the predetermined laser wavelength, and the first joining section is welded to the second joining section.
[0019] The variation possibilities and advantages described above in connection with the method according to the invention also apply mutatis mutandis to the stator according to the invention. The corresponding method features can be viewed as functional features in the stator.
[0020] In one embodiment, it is provided that the first stator pole has, on a side facing the second stator pole, a joining section of the type of the first joining section on the axial outside in each case, and on an opposite side, a joining section of the type of the first joining section, likewise on the axial outside in each case. Furthermore, it is provided that the second stator pole has, on a side facing the first stator pole, a joining section of the type of the second joining section on the axial outside in each case, and on an opposite side, likewise on the axial outside in each case, a joining section of the type of the second joining section. This means that, in a radial plan view, the first stator pole has a first joining section at each of its four corners, and is opaque to the laser beam there.In contrast, the second stator pole has an outer joining section made of a laser-transparent or laser-permeable material at each of its four corners, visible in a radial plan view. This can be easily achieved by two different overmolding methods for the stator poles: the second stator pole, for example, is completely overmolded with a laser-transparent plastic, so that the "outer overlap" (outer joining section) is always molded on both sides and in the two overlapping areas in the circumferential direction (all four overlapping areas of a pole). The first stator pole, for example, is completely overmolded with a laser-opaque plastic, so that the "inner overlap" (inner joining section) is always molded on both axial sides and in the two overlapping areas in the circumferential direction (all four overlapping areas of a pole).These very different stator poles must then be arranged alternately in the circumferential direction so that an "outer overlap" (transparent) of the second stator pole always overlaps with the opaque "inner overlap" of the first stator pole and can be welded. In this example, there are therefore two different types of stator poles.
[0021] In an alternative embodiment, the first stator pole has, on a side facing the second stator pole, a joining section of the first joining section type on the axial outside and, on an opposite side, a joining section of the second joining section type on the axial outside. The second stator pole has, on a side facing the first stator pole, a joining section of the second joining section type on the axial outside and, on an opposite side, a joining section of the first joining section type on the axial outside. This in turn means that the two stator poles can be designed identically. In the radial plan view, for example, they each have an outer overlap on one side and an inner overlap on the other side.This makes it possible to produce just one type of pole, which then has the outer overlap with the transparent material on one side (axial and / or circumferential direction) and the inner overlap with the opaque material on the other side. The pole would then be "asymmetrical" in the sense that two overlapping areas always have an outer overlap and two overlapping areas have an inner overlap. Geometrically correct, the pole would then be either axisymmetric to the axial center plane, axisymmetric to the center plane in the circumferential direction, or point-symmetric to the center of the pole. When joining the stator poles to form the stator ring, it is not necessary to alternate between the type of poles, but rather the spatial orientation, so that the outer and inner overlap always coincide.Such a stator pole would then have to be overmolded with two different materials, which can be done either in one step (using two or more injectors) or in several steps one after the other.
[0022] In a further exemplary embodiment, it is provided that the first stator pole has, on a side facing the second stator pole, the first joining section and, axially opposite, a joining section of the type of the second joining section, and on an opposite side in the circumferential direction, axially outside the first joining section, a joining section of the type of the second joining section, and axially opposite the latter, a joining section of the type of the first joining section, and the second stator pole has, on a side facing the first stator pole, the second joining section and, axially opposite, a joining section of the type of the first joining section, and on an opposite side in the circumferential direction, axially outside the second joining section, and axially opposite the latter, a joining section of the type of the second joining section.In the radial plan view, this means that the inner overlap (type of the first joining section) and the outer overlap (type of the second joining section) alternate around the stator pole. As in the previous exemplary embodiment, both outer overlaps and inner overlaps are provided on a stator pole, but a single type of stator pole is sufficient to produce the stator ring. In the radial plan view, a pole would then be point-symmetrical to the center of the pole. In an advantageous embodiment of the stator according to the invention, the joining sections are injection-molded onto pole shoes and / or pole teeth of the respective stator poles. If necessary, the respective stator pole can be completely overmolded with the respective (insulating) material. The material thus fulfills a multiple function, namely insulation and mechanically fixing the stator poles to one another.
[0023] In a further embodiment, one of the two joining sections has a bead in the overlap region and the other of the two joining sections has a cavity, wherein the bead protrudes into the cavity when the first stator pole and the second stator pole are joined together. In particular, this allows the two stator poles to be locked together. In particular, this can be achieved by having overlap regions on both axial sides of the stator poles each have such a bead and such a cavity, and the respective beads protrude into the respective cavities when the stator poles are locked together. The beads and cavities can, for example, be round, so that the stator poles can be releasably locked into one another. In principle, however, other geometric shapes of the beads and cavities can also be used.The ridges and cavities do not need to extend the entire radial length of the stator poles. If necessary, one or more short radial sections, where the respective ridges and cavities overlap, may suffice.
[0024] In a further advantageous embodiment of the stator according to the invention, it is provided that the joining sections welded together in the overlap region along the entire radial extent of the stator poles seal a cooling circuit (inside the stator poles). For example, the spaces created between the stator poles or between their windings when they are joined together can be used for a coolant flow. A corresponding cooling circuit can be routed through all of the stator poles of the stator or just through a portion of them. To seal this cooling circuit, the stator poles can be welded together along their entire radial extent (on both axial sides). Corresponding welds must then also be made on the radial end faces of the stator poles.
[0025] The joining sections can be positioned relative to one another such that they press against one another when the first stator pole and the second stator pole are joined. This preload can be used, in particular, to ensure that the joining sections lie firmly against one another during welding. For this purpose, it is advantageous, for example, if the outer joining section (outer overlap) has an undercut, so that it is designed to be resilient. The inner joining section (inner overlap) can then be pressed into this undercut, so that both joining sections press against one another when joined.
[0026] Furthermore, a tolerance gap can be formed in the circumferential direction between the first joining section and the second joining section. This can prevent, for example, manufacturing tolerances from preventing the joining sections from locking together precisely. This creates a stable, process-reliable (particularly with regard to tolerances), and media-tight connection between the poles or pole pieces.
[0027] In a further embodiment, the two stator poles each have a winding, and the joining sections are each arranged axially outside the windings. Optionally, the joining sections can be arranged exactly between the stator poles. Likewise optionally, the joining sections can protrude axially beyond the stator poles. For example, the overlapping areas can advantageously be arranged outside the coil areas or winding areas. They can also protrude slightly beyond the pole shoe and the pole (if necessary symmetrically between the outer overlap and inner overlap), so that the connection point is also located exactly between two poles. Optionally, however, this can also be designed asymmetrically, so that only the outer overlap protrudes beyond the pole and the inner overlap is still arranged in the pole area. In this case, the connection point is still in the pole area and not (centered) between the two poles.
[0028] The above-mentioned object is also achieved according to the invention by an electric axial flux machine with a stator of the type described above.
[0029] Further advantages, features, and details of the invention will become apparent from the following description of preferred embodiments and from the drawing(s). The features and feature combinations mentioned above in the description, as well as the features and feature combinations mentioned below in the description of the figures and / or shown alone in the figures, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention. In the drawings:
[0030] Fig. 1 shows part of a stator of an axial flux machine;
[0031] Fig. 2 is a sectional view of the stator of Fig. 1;
[0032] Fig. 3 is an enlarged section of Fig. 2; and
[0033] Fig. 4 is an enlarged section of Fig. 3.
[0034] The exemplary embodiments described in more detail below represent preferred embodiments of the present invention.
[0035] Fig. 1 shows a perspective view of a section of a stator of an axial flux machine. The stator is formed by an annular arrangement of a plurality of stator poles 1 joined to one another. The annular stator has a central axis 2, which not only forms the axis of rotation for one or more rotors (not shown), but also indicates the main magnetic flux direction. The following descriptions (as well as the above explanations) regarding radial directions, axial directions, and circumferential directions always refer to this central axis 2.
[0036] Each stator pole 1 has pole shoes 3 on its axial sides. In the present example, the pole shoes 3 are overmolded with a plastic 4, which can have holding and / or insulating functions. Each individual stator pole 1 was originally manufactured separately and overmolded with the plastic 4. The individual stator poles 1 were then joined together to form the annular stator shown in Fig. 1. The plastic overmolds 4 of two stator poles 1 meet when the stator poles 1 are joined together and form an overlap region 5 that runs essentially in the radial direction.
[0037] Each stator pole 1 has a winding 6 which is arranged between the axially spaced respective pole shoes 3 on a respective pole tooth not visible here.
[0038] Fig. 2 shows a section through several stator poles 1 parallel to the central axis 2. The section shows the arrangement of a respective pole tooth 7 between the pole shoes 3 for each stator pole 1. Each pole tooth 7 is surrounded by a respective winding 6. A partial area of the section, in which two windings 6 of two adjacent stator poles 1 meet and in which part of the overlapping area 5 also lies, is marked III. This partial area III is shown enlarged in Fig. 3. From this enlargement it can be seen that the pole tooth 7 can have an initial overmolding, which is also referred to here as (plastic) overmolding 4. A respective winding 6 is applied to this initial overmolding in the area of the pole tooth 7. Between the windings 6 of the two adjacent stator poles 1 there is a cooling chamber 8 which can be filled with a cooling medium.
[0039] In the example of Fig. 3, the stator pole shown at the bottom of the drawing can be referred to as the first stator pole 11, and the pole shown at the top of the drawing can be referred to as the second stator pole 12. The first stator pole 11 has a first joining section 21 on both axial sides. The first joining section 21 protrudes circumferentially beyond the pole shoes 3. The first joining section 21 is preferably formed integrally with the overmolding 41 of the pole tooth 7 of the first stator pole 11.
[0040] In particular, the overmolding 41 and the first joining section 21 are made of the same (plastic) material.
[0041] Similarly, the second stator pole 12 has a second joining section 22 on both axial sides. This second joining section 22 also projects in the circumferential direction beyond the pole shoes 3 of the second stator pole 12.
[0042] In the joined state of the first stator pole 11 and the second stator pole 12 shown in Fig. 3, the first joining section 21 and the second joining section 22 overlap in the overlap region 5. The second joining section 22 lies axially outside the respective first joining section 21 on both sides. Therefore, the first joining section 21 can be referred to as an inner overlap and the second joining section 22 as an outer overlap.
[0043] The first joining section 21 and the second joining section 22, i.e., the inner overlap and the outer overlap, are joined together by laser welding. For this purpose, the second joining section 22, which is located on the outside, is made of a (largely) transparent material, so that a laser beam 9 can penetrate the second joining section 22, and the substantial energy of the laser beam 9 can reach the inner first joining section 21. This first joining section 21 melts and joins with the outer second joining section 22. This laser welding is performed in the same way on the opposite axial side.
[0044] In Fig. 4, the overlap region 5, which is also designated IV in Fig. 3, is shown enlarged. The essential part of the overlap region 5 is located between the pole pieces 3 of the two stator poles, which are opposite in the circumferential direction. In particular, a transparent or partially transparent section 221 of the second joining section 22 is located between circumferentially opposite pole piece side surfaces 31 of the respective pole pieces 3. In the axial direction behind this (relative to the incidence of the laser beam) there is an opaque section 211 of the inner first joining section 21. The laser beam (not shown in Fig. 4) arriving from the left and penetrating the transparent section 221 melts the opaque section 211 in a contact region 10. This results in a melting region which lies in the contact region 10.Thus, the first joining section 21 and the second joining section 22 are integrally connected by laser welding.
[0045] The joining sections 21 and 22 are designed on both opposite axial sides so that they press against each other even before welding, after the stator poles 11 and 12 have been joined. This creates the contact pressure between the joining partners required for laser welding.
[0046] In the example of Fig. 4, the transparent section 221 is formed with a cavity 222 that is open towards the center of the stator pole, i.e., in the direction of the windings 6. In contrast, the opaque section 211 has a bead 212. In the example shown, both the cavity 222 and the bead 212 are round in cross-section. However, the contours of these two components can also be selected differently, e.g., pointed. It is advantageous if the cavity 222 and the bead 212 are geometrically designed such that they engage with one another when the two stator poles 11 and 12 are plugged together. This has the advantage that the stator ring is held together even before welding.To ensure the aforementioned contact pressure, the axial distance between the tips of the beads 212 in the unjoined state of the two stator poles 11 and 12 should be slightly greater than the distance between the deepest points of the cavities 222 of the axially opposite transparent sections 221. During welding, the laser beam is guided, for example, in a radial direction over the entire radial extent of the overlap region 5. This welding creates a media-tight joint, at least on the axial sides. The stator can be sealed appropriately on the outer circumference (if necessary, also by overlapping and laser welding) to create a media-tight cooling circuit.
[0047] List of reference symbols
[0048] 1 stator pole
[0049] 2 central axis
[0050] 3 pole shoes
[0051] 4 (Plastic) overmolding
[0052] 5 Overlap area
[0053] 6 winding
[0054] 7 pole tooth
[0055] 8 Cavity or cold storage space
[0056] 9 Laser beam
[0057] 10 Contact area
[0058] 11 first stator pole
[0059] 12 second stator pole
[0060] 21 first joining section
[0061] 22 second joining section
[0062] 31 Pole shoe side surfaces
[0063] 41 Overmolding with opaque material
[0064] 42 Overmolding with transparent material
[0065] 211 opaque section
[0066] 212 bulge
[0067] 221 transparent section
[0068] 222 Cavity
[0069] III Sub-area
[0070] IV Sub-area
Claims
Patent claims 1. Method for producing at least part of a stator of a Axial flux machine characterized by - Attaching a first joining section (21) made of a first material to a first stator pole (11) of the stator, - Attaching a second joining section (22) made of a second material to a second stator pole (12) of the stator, wherein in a joined state of the first stator pole (11) and the second stator pole (12), the first joining section (21) is connected to the second joining section (22) in the circumferential direction of the stator in a Overlap region (5), wherein the second joining section (22) is located further outward with respect to a center of the stator than the first joining section (21), wherein the second material is at least largely transmissive to a predetermined laser wavelength, the first material is opaque to the predetermined laser wavelength, and irradiating the overlap region with laser radiation (9) of the predetermined laser wavelength, whereby the first joining section (21) is welded to the second joining section (22).
2. Method according to claim 1, characterized in that the joining sections are welded in such a way that the overlapping region (5) closes off a cavity (8) between the two stator poles (11, 12) in a media-tight manner.
3. Method according to claim 1 or 2, characterized in that the stator has a central axis (2) which runs parallel to a respective main magnetic flux of the stator poles (11, 12), the second joining section (22) is arranged axially outside the first joining section (21) with respect to the central axis.
4. Method according to one of the preceding claims, characterized in that the stator poles (11, 12) are each provided with a winding (6) before welding.
5. Method according to one of the preceding claims, characterized in that the two stator poles (11, 12) are plugged together before welding, and the two joining sections (21, 22) snap into one another and / or form a positive connection.
6. Stator for an axial flux machine, characterized by a first joining section (21) made of a first material on a first stator pole (11) of the stator, a second joining section made of a second material on a second stator pole (12) of the stator, wherein in a joined state of the first stator pole (11) and the second stator pole (12), the first joining section (21) overlaps with the second joining section (22) in the circumferential direction of the stator in an overlap region (5), wherein the second joining section (22) is located further outward with respect to a center of the stator than the first joining section (21), wherein the second material is at least largely transmissive for a predetermined laser wavelength, the first material is opaque for the predetermined laser wavelength, and the first joining section (21) is welded to the second joining section (22).
7. Stator according to claim 6, characterized in that - the first stator pole (11) has, on a side facing the second stator pole (12), a joining section of the type of the first joining section (21) on the axial outside and, on an opposite side, a joining section of the type of the first joining section (11) on the axial outside, and - the second stator pole (12) has, on a side facing the first stator pole (11), a joining section of the type of the second joining section (22) on the axial outside and, on an opposite side, a joining section of the type of the second joining section (22) on the axial outside.
8. Stator according to claim 6, characterized in that - the first stator pole (11) has, on a side facing the second stator pole (12), a joining section of the type of the first joining section (21) on the outside axially and, on an opposite side, a joining section of the type of the second joining section (22) on the outside axially and - the second stator pole (12) has, on a side facing the first stator pole (11), a joining section of the type of the second joining section (22) on the axial outside and, on an opposite side, a joining section of the type of the first joining section (21) on the axial outside.
9. Stator according to claim 6, characterized in that - the first stator pole (11) has, on a side facing the second stator pole (12), the first joining section and, axially opposite, a joining section of the type of the second joining section (22) and, on an opposite side in the circumferential direction, axially outside the first joining section (21), a joining section of the type of the second joining section (22) and, axially opposite the latter, a joining section of the type of the first joining section (21) and - the second stator pole (12) has, on a side facing the first stator pole (11), the second joining section (22) and, axially opposite, a joining section of the type of the first joining section (21), and, on an opposite side in the circumferential direction, axially outside the second joining section (22), a joining section of the type of the first joining section (21), and, axially opposite the latter, a joining section of the type of the second joining section (22).
10. Stator according to one of claims 6 to 9, characterized in that the joining sections (21, 22) are injection-molded onto pole shoes (3) and / or pole teeth (7) of the respective stator poles (11, 12).
11. Stator according to one of claims 6 to 10, characterized in that one of the two joining sections (21, 22) in the overlap region (5) has a bead (212) and the other of the two joining sections has a cavity (222), wherein in the joined state of the first stator pole (11) and the second stator pole (12) the bead (212) projects into the cavity (222).
12. Stator according to one of claims 6 to 11, characterized in that the joining sections (21, 22) welded together in the overlapping region (5) along the entire radial extent of the stator poles (11, 12) seal a cooling circuit.
13. Stator according to one of claims 6 to 12, characterized in that a tolerance gap is formed in the circumferential direction between the first joining section (21) and the second joining section (22).
14. Stator according to one of claims 6 to 13, characterized in that the two stator poles (11, 12) each have a winding (6), and the joining sections (21, 22) are each arranged axially outside the windings (6).
15. Electric axial flux machine with a stator according to one of claims 6 to