Axial flux machine

Abstract

The invention relates to an axial flux machine comprising at least one stator (3, 4) with a stator support (13, 14) and a housing cover (11, 12), wherein the stator support (13, 14) is connected to the housing cover (11, 12) in the region of two opposing connecting surfaces (20, 21), and a plurality of welding protrusions (22) are provided on the connecting surfaces (20, 21) of the stator support (13, 14) or of the housing cover (11, 12), said welding protrusions being welded to the opposing connecting surfaces (20, 21) of the housing cover (11, 12) or of the stator support (13, 14) by means of resistance welding.

Description

[0001] axial flux machine

[0002] The invention relates to an axial flux machine comprising at least one stator with a stator carrier and a housing cover, wherein the stator carrier is connected to the housing cover in the region of two opposing connecting surfaces.

[0003] Axial flux machines have a disk-shaped design, which makes them particularly suitable for integration in tight installation spaces. They are characterized by high torque output and power density, which makes them particularly interesting for use as drive motors in motor vehicles. A characteristic of an axial flux machine is that the magnetic flux flows in the axial direction through the air gap between the stator and the rotor. In addition to a rotor-stator-rotor design, a stator-rotor-stator design is also known, i.e. a machine with an internal rotor and stators arranged axially on both sides. The stator is provided with corresponding coil windings, while the rotor has a permanent magnet arrangement. Each end stator is provided with a housing cover that closes it axially, essentially enclosing the machine axially like a housing.The housing cover is typically bonded to a stator support, where the coil windings are located, by means of an adhesive bond. Bonding is complex, as the assembly must be placed in an oven to cure the adhesive, which is time-consuming. Furthermore, there is the problem that the initially liquid adhesive can penetrate into any grooves provided on the cover or stator support through which a coolant flows, which is undesirable. The adhesive can also form an electrically insulating layer between the stator support and the housing cover, requiring separate grounding of the stator.

[0004] The invention is based on the problem of providing an improved axial flux machine. To solve this problem, an axial flux machine according to the invention is provided with a plurality of welding projections on the connecting surface of the stator carrier or the housing cover, which are welded to the opposite connecting surface of the housing cover or the stator carrier by resistance welding.

[0005] According to the invention, the housing cover is no longer glued to the stator carrier, but directly welded using resistance welding. This results in a material-to-material and extremely robust connection between the stator carrier and the housing cover. The welded joint also forms a conductive connection between the two components, allowing the stator as a whole to be grounded via the housing. Since no fluid adhesive is used, there is no risk of any grooves or similar structures becoming blocked by the adhesive, and the joining process can be significantly faster, as there is no need to place the parts in an oven, which would involve a curing and cooling time. Furthermore, it is also possible to easily weld the cover to the stator carrier from below, as this creates a direct weld that firmly joins both parts together.The two parts can therefore be positioned variably for connection.

[0006] To create the welded joint, corresponding welding projections are provided on the housing cover or the stator carrier. These projections are applied to a corresponding opposing joining surface of the other component during the welding process and are bonded to the joining surface by the high pressure and parallel current flow during resistance welding. Preferably, at least three welding projections are provided for secure welding and support, although more than three welding projections can also be provided, thus creating more than three local welded joints.

[0007] A welding projection preferably has a tapered cross-section. This means that each welding projection is designed as a contact point or welding tip. A welding projection can be elongated or linear, resulting in not just a point-like, materially bonded weld, but also an elongated, linear weld. The welding projection can be continuous or locally interrupted, i.e., formed by two or more individual sections adjoining one another along a line.

[0008] The welding projections are preferably arranged radially on the annular stator carrier or the annular housing cover. This means that the elongated or linear welding projections or contact points extend radially outward from a center of the respective annular component. The specific arrangement and geometry depends on the geometry of the facing surfaces to be joined and is naturally selected accordingly.

[0009] It is conceivable that the two connecting surfaces lie directly against each other. This means that the resistance welding is carried out in such a way that the local welds are created, which connect the two parts, but the finished welding arrangement is designed such that the welded connecting surfaces lie flat against each other, thus ensuring full-surface contact. Alternatively, it is also conceivable that a cooling gap remains between the two connecting surfaces. This means that there is no flat contact, but rather a narrow gap through which cooling air can be directed.

[0010] In principle, it is conceivable that one or more groove-shaped recesses are provided on the stator carrier or the housing cover, which are covered by the opposing connecting surface, forming one or more cooling channels. Thus, one or both connecting surfaces have corresponding geometric structures with groove-shaped recesses, over which a cooling structure is formed.

[0011] The respective recess is covered by the connecting surface of the other component, creating a cross-section of a tightly closed cooling channel through which a coolant can be guided. Furthermore, the connecting surface areas adjacent to the groove-shaped recesses define corresponding support areas through which the two components are supported against each other. In this design, the connecting surfaces lie flat against each other.

[0012] It is also advantageous if the inner diameter of the housing cover is smaller than the inner diameter of the stator support and the outer diameter of the housing cover is larger than the outer diameter of the stator support, with the elongated welding projections radially overlapping the stator support on the inside and / or outside. Thus, there is a corresponding radial overlap on the inside and outside of the housing cover and the contact tips.

[0013] The invention is explained below using exemplary embodiments with reference to the drawings. The drawings are schematic representations and show:

[0014] Figure 1 is a schematic diagram, sectioned, of an axial flow machine according to the invention,

[0015] Figure 2 shows a schematic diagram in the form of a partial view of the stator carrier and the housing cover before welding,

[0016] Figure 3 shows the arrangement from Figure 2 after welding,

[0017] Figure 4 is an enlarged partial view of the welding area from Figure 3,

[0018] Figure 5 shows a schematic diagram of a welding device with inserted components,

[0019] Figure 6 is a perspective view of a stator carrier and housing cover,

[0020] Figure 7 is an enlarged partial view of the radially outer connection area, Figure 8 is an enlarged partial view of the radially inner connection area, and

[0021] Figures 9-26 show various schematic diagrams of different designs of the stator carrier and the housing cover with regard to the welding projections and any groove-shaped recesses, each in a partial view before welding and after welding.

[0022] Figure 1 shows an axial flux machine 1 according to the invention, comprising a rotor 2 which, viewed axially, is arranged centrally between two stators 3, 4 and can be rotated about a rotation axis 6 between the two annular stators 3, 4 via a central rotor shaft 5. The two stators have corresponding windings 7, 8 which serve to generate electromagnetic fields which interact with permanent magnets arranged on the rotor 2 in a manner known per se. Furthermore, a housing 9 is provided, on which the rotor 2 or the rotor shaft 5 is rotatably mounted via corresponding rolling bearings 10. The housing 9 has two housing covers 11, 12, each of which is connected to a stator carrier 13, 14 of the respective stator 3, 4, on which stator carrier 13, 14 the windings 7, 8 are arranged, via materially bonded welds produced by resistance welding.The housing covers are further axially spaced from each other on this side by a radially outer circumferential spacer 15. Finally, the two stators 3, 4 themselves are overlapped by corresponding covers 16, 17. The basic design of such an axial flux machine 1 with a stator-rotor-stator arrangement is known.

[0023] Figures 2 - 4 show three schematic diagrams illustrating the formation of the respective resistance welded connection between the respective stator carrier 13, 14 and the respective cover 11, 12, wherein only the stator carrier 13 and the cover 11 are shown as examples in the figures. The stator carrier 13, which has corresponding stator teeth 18 and corresponding yokes 19, has a connecting surface 20. The housing cover 11, which also has a connecting surface 21, is welded to this surface. On the connecting surface 21 of the housing cover 11, projecting towards the connecting surface 20, a plurality of welding projections 22 are provided, which, as will be discussed below, are designed as elongated structures. Each welding projection 22 tapers to a point, i.e., has a quasi-triangular cross-section, so that it is designed as a contact tip.Adjacent to each elongated welding projection 23, two axially projecting stops 23 are formed, which represent a stop for limiting the axial movement during the welding process.

[0024] Figure 2 shows the situation before the start of the welding process. The stator support 13 and the cover 11 are spaced apart from one another. Figure 3 shows the arrangement at the time when the welding process is completed, with Figure 4 showing an enlarged partial view of area IV from Figure 3. It is clear that a positive-locking weld connection to the connecting surface 20 has been achieved via the respective welding projection 22. In the final position, the two connecting surfaces 20, 21 are slightly spaced apart from one another because the stops 23 bear against the connecting surface 20, resulting in a cooling gap 24 between the connecting surfaces 20, 21. With the formation of the respective resistance weld, an extremely robust, strong, material-to-material weld is created between the stator support 13 and the housing cover 11; this naturally applies to both stators 3, 4.This welded connection also creates an electrically conductive connection between the respective stator carrier and the respective housing cover, so that the respective stator 3, 4 can be earthed directly via the housing cover.

[0025] Figure 5 shows a schematic diagram of how the welding process is carried out. It shows a welding device 25 with a holder 26 onto which the respective stator support 13, 14 is placed. The respective housing cover 11, 12 is then placed onto the stator support 13, wherein in the example shown, the welding projections 22 and the stops 23 are formed on the stator support 13. A press die 27 is then placed onto the respective housing cover 11, 12 and pressed on under current indication, as indicated by the force arrows 28, whereby the pressing and simultaneous welding takes place until the stops 23 are in contact. If the stator has a stator support 13 that is already wound, i.e., already has windings 7, 8, the pressing force can be adjusted so that the sheet metal turns of the windings are smoothed during welding.This allows for better flatness and thus more precise dimensional accuracy towards the air gap between the stator and the adjacent rotor.

[0026] Figure 6 shows an example of a stator carrier 13, 14, wherein again only the stator carrier 13 is shown as an example, as well as the associated housing covers 11, 12, wherein again only the housing cover 11 is shown as an example. The respective stator teeth 18, around which the windings are subsequently wound, are clearly visible. The housing cover 11 clearly shows the welding projections 22, which here are designed as elongated, linear welding projections 22 or pointed contact tips. The design is such that the housing cover 11 engages over the stator carrier 13 radially inward and radially outward, while the length of the elongated welding projections 22 is also dimensioned such that they engage over the stator carrier 13 radially inward and radially outward. This is shown in Figure 7, where the respective welding projection 22 clearly protrudes radially slightly beyond the outer circumference or the inner circumference of the stator carrier 13.

[0027] Figures 9-26 show various schematic diagrams regarding the design of the respective stator carrier 13, 14 and the respective cover 11, 12, whereby only the stator carrier 13 and the housing cover 11 are shown as examples. The odd-numbered figures each show an exploded view before welding, while the following even-numbered figure shows the arrangement after welding.

[0028] Figure 9 shows an enlarged partial view, similar to that already shown in Figures 2 and 4. Shown are a welding projection 22 and the two adjacent stops 23. As described, the configuration forms a cooling gap 24 between the connecting surfaces 20, 21.

[0029] Figures 11 and 12 show an arrangement with a welding projection 22 and several groove-shaped recesses 29 arranged adjacent thereto, which, in the welded state, are covered by the connecting surface 20 of the stator carrier 13, forming corresponding cooling channels 30 through which a fluid can circulate. The respective cover is geometrically structured accordingly, whereby the structure can be produced, for example, by pressing.

[0030] Figures 13 and 14 show a similar design. Adjacent to the welding projection 22, two groove-shaped recesses 29 are also provided here, so that corresponding cooling channels 30 are formed after welding.

[0031] In the embodiment according to Figures 15 and 16, the stator carrier has a groove-shaped recess 31 in which the welding projection is arranged. The housing cover 11 is also structured and has a projection 32 that engages in the recess 31 and to which the welding projection 22 is welded. This structure also forms suitable cooling channels 30. Outside of this area, the connecting surfaces lie flat against one another. There is no cooling gap here.

[0032] The arrangement of Figures 17 and 18 is similar to Figures 15 and 16. Again, the stator carrier 13 has a recess 31 with a welding projection 22 arranged therein, and the housing cover 11 has a projection 32. However, here the geometry is such that after welding, a flat contact is achieved in the welding area, and a corresponding cooling gap 24 is formed on both sides of it.

[0033] Figures 19 and 20 again show a stator support with several welding projections 22 arranged thereon, which protrude directly from the connecting surface 20. The housing cover 11 is again structured and has projections 32 that define corresponding groove-shaped recesses 31 into which the welding projections 22 engage. The cooling channels 30 are again formed in this area of ​​influence, as shown in Figure 20.

[0034] The design of Figures 21, 22 shows a stator support 13 corresponding to that of Figure 19 with several welding projections 22 protruding from the connecting surface 20. However, the housing cover 11 is designed here as a flat, non-structured component. This results in a full-surface welded joint, as shown in Figure 22.

[0035] In the arrangement of Figures 23, 24, the stator carrier 13 again has a groove-shaped recess 31, with the two welding projections 22 arranged on both sides outside the recess 31. After welding, see Figure 24, a cooling channel 30 is created on the one hand, and on the other hand, the connecting surfaces 20, 21 are in full contact with one another.

[0036] Finally, Figures 25 and 26 show an arrangement that is virtually the reverse of that of Figures 23 and 24. The stator carrier 13 again has a groove-shaped recess 31, while the two welding projections 22 are provided on the housing cover 11.

[0037] In the welding position, a cooling channel 30 is again formed, since the recess 31 is again covered by the cover 11. Otherwise, the connecting surfaces 20, 21 lie flat against each other.

[0038] The examples shown in Figures 9-26 are not limiting. To illustrate the respective welded joint, the welding projections 22 are also shown in the figures showing the welded position; however, they are engaged with the respective counterpart, over which the welded joint is illustrated. Although, as described, only the stator carrier 13 and the housing cover 11 are shown, the same assembly method also applies to the stator carrier 14 and the housing cover 12.

[0039] List of reference symbols

[0040] Axial flux machine rotor stator stator

[0041] Rotor shaft Rotation axis Winding Winding Housing Rolling bearing Housing cover Housing cover Stator carrier Stator carrier Spacer Cover Cover Stator teeth Yoke

[0042] Connecting surface Connecting surface Welding projection Stop Cooling gap

[0043] Welding device holder press stamp force arrow recess cooling channel recess projection

Claims

Patent claims 1. Axial flux machine, comprising at least one stator (3, 4) with a stator carrier (13, 14) and a housing cover (11, 12), wherein the stator carrier (13, 14) is connected to the housing cover (11, 12) in the region of two mutually opposite connecting surfaces (20, 21), characterized in that a plurality of welding projections (22) are provided on the connecting surface (20, 21) of the stator carrier (13, 14) or of the housing cover (11, 12), which welding projections are welded to the opposite connecting surface (20, 21) of the housing cover (11, 12) or of the stator carrier (13, 14) by resistance welding.

2. Axial flow machine according to claim 1, characterized in that the welding projections (22) have a tapered cross-section.

3. Axial flow machine according to claim 1 or 2, characterized in that a welding projection (22) is elongated or linear.

4. Axial flow machine according to one of the preceding claims, characterized in that the welding projections (22) are arranged radially on the annular stator carrier (13, 14) or the annular housing cover (11, 12).

5. Axial flow machine according to one of the preceding claims, characterized in that the two connecting surfaces (20, 21) lie directly against one another, or that a cooling gap (24) is provided between the two connecting surfaces (20, 21).

6. Axial flow machine according to one of the preceding claims, characterized in that one or more groove-shaped depressions (31) are provided on the stator carrier (13, 14) or on the housing cover (11, 12), which are covered by the opposite connecting surface (21, 21) to form a cooling channel (30).

7. Axial flow machine according to one of the preceding claims, characterized in that the inner diameter of the housing cover (11, 12) is smaller than the inner diameter of the stator carrier (13, 14) and the outer diameter of the housing cover (11, 12) is larger than the outer diameter of the stator carrier (13, 14), wherein the elongated welding projections (22) cover the stator carrier (13, 14) radially inwardly and / or outwardly.

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