Rotor for an axial flux machine

Abstract

The invention relates to a rotor (R) for an axial flux machine, which in an installation position is arranged axially on one or both sides next to a stator, wherein the rotor (R) has a disk-shaped squirrel cage (1). According to the invention, the squirrel cage (1) is an extruded part produced in an extrusion process.

Description

[0001] The invention relates to a rotor for an axial flux machine according to the preamble of claim 1 and to a method for manufacturing such a rotor according to claim 14.

[0002] In an axial flux machine, unlike a radial flux machine, the magnetic field runs parallel to the rotor's axis of rotation. The rotor is arranged axially next to at least one disk-shaped stator in one installation position.

[0003] A typical rotor for such an axial flux machine features a disk-shaped squirrel cage with an outer ring and an inner ring with a hub. The outer and inner rings are connected by spoke-like radial webs. These webs define circumferentially distributed pockets in the rotor's circumference, into which rotor guide elements, made primarily of soft magnetic material, are inserted. During operation, the squirrel cage conducts the necessary currents, while the guide elements conduct the magnetic field. Accordingly, energizing the stator generates an axial magnetic flux in the guide elements, causing the rotor to rotate.

[0004] In current technology, the short-circuit cage is typically manufactured as a casting from an aluminum or copper alloy using a casting process, which involves high manufacturing effort and high costs.

[0005] The object of the invention is to provide a rotor for an axial flux machine which, with reduced manufacturing effort, has improved rotor properties compared to the prior art, in particular higher conductivity and / or higher material strength or rotor component stiffness.

[0006] The problem is solved by the features of claim 1 or 14. Preferred embodiments of the invention are disclosed in the dependent claims.

[0007] The invention relates to a rotor for an axial flux machine, which, in its installed position, is arranged axially on one or both sides of a stator. The rotor has a disk-shaped squirrel cage with an outer ring and an inner ring with a hub. The outer ring and the inner ring are connected to each other via spoke-like radial webs, which define circumferentially distributed receiving pockets in the rotor's circumferential direction. Rotor guide elements, made of a particularly soft magnetic material, are inserted into these pockets. By energizing the stator, a magnetic flux in the axial direction is generated in the guide elements, causing the rotor to rotate.

[0008] The invention is based on the finding that wrought alloys of aluminum or copper are superior to cast alloys of aluminum and copper (used in casting a short-circuit cage) with regard to material strength and conductivity. Against this background, according to the characterizing part of claim 1, the disc-shaped short-circuit cage is no longer manufactured by a casting process, but by an extrusion process. Furthermore, such an extrusion process involves significantly reduced manufacturing effort and costs compared to the casting process. In the extrusion process, a continuous extrusion profile is first produced, from which a raw short-circuit cage is cut to length. The short-circuit cage is then manufactured from the raw short-circuit cage in a post-processing operation, for example, by machining such as milling and / or drilling.The material of the disc-shaped short-circuit cage can preferably consist of the wrought alloy AW6101.

[0009] In one technical implementation, the rotor guide elements can project axially from an annular guide element body as teeth with tooth gaps arranged in the rotor's circumferential direction. Within the annular squirrel cage, the radial webs can be offset axially from one end face of the cage, particularly by means of milling the raw cage. This creates an annular receiving space at the end face, extending radially between the outer and inner rings of the squirrel cage. The annular guide element body can be inserted into this receiving space, while its rotor guide elements project through the receiving pockets of the squirrel cage towards the stator side.The axial offset is dimensioned to be exactly the same size as the thickness of the ring-shaped base body in the axial direction, resulting in a flush transition between the outer ring, the ring-shaped guide element base body and the inner ring on the short-circuit cage end face facing away from the stator.

[0010] The squirrel cage is fixed to a rotor shaft via the hub. In one embodiment, the hub can be a single, integral part of the inner ring of the squirrel cage, made of a single material. Alternatively, the hub can be a single, integral part of the rotor shaft, made of a single material.

[0011] Alternatively, the hub can be assembled with the squirrel cage as a separate component. In this case, a rotationally fixed connection between the squirrel cage and the hub can be provided as follows: The hub can have a radially outwardly widening hub flange on a rotor end face facing the stator. The hub flange, the annular squirrel cage, and an annular backplate can form an axial composite in which the squirrel cage is axially supported between the annular backplate and the hub section. The hub flange, the annular squirrel cage, and the annular backplate can be force-transmittingly connected to each other by means of at least one transverse bolt. In this way, not only is a rotationally fixed connection between the squirrel cage and the hub provided, but the rotor component stiffness is also significantly increased.This prevents squirrel cage deformation and lifting of the squirrel cage from the hub, especially at high speeds.

[0012] The annular backplate can be axially supported with its inner circumference against an annular shoulder on the outer circumference of the hub. Furthermore, the shear bolt can be guided through corresponding locating holes in the axial assembly, i.e., through locating holes in the backplate, in the short-circuit cage, and in the hub flange.

[0013] Depending on the desired speed requirement, the rotor strength can be further increased as follows: The outer ring of the squirrel cage can be encased by a reinforcing ring, which is made of high-strength steel or carbon fiber reinforced plastic. The reinforcing ring can, for example, be heat-shrink-fitted. This applies a preload to the squirrel cage, preventing it from lifting off the hub due to centrifugal force.

[0014] The reinforcing ring and the backplate can be installed as separate components within the rotor. In this case, the following measure can be taken to ensure the reinforcing ring is securely mounted: The annular backplate can extend radially outwards beyond the squirrel cage. This extension, along with an axially spaced rim running around the outer circumference of the squirrel cage, can form axial movement stops for the reinforcing ring.

[0015] In contrast, a structurally simpler and more rigid composite can be achieved as follows: The reinforcing ring and the back plate can be integrated into a single, cup-shaped component, made of the same material and / or as a single piece. In this case, the cup-shaped component can be easily manufactured as a deep-drawn sheet metal part.

[0016] With a view to the efficient manufacturing of the guide element base body and the axially projecting guide elements, it is preferred that these are components of a laminated core wound from a strip of sheet metal. The layers of this core are stacked radially on top of each other in the wound state. To further increase the rotor component stiffness, the laminated core can be force-transmittingly connected to the back plate by means of welded joints.

[0017] Especially in high-performance axial flux machines, additional rotor cooling is advantageous. One example is internal rotor cooling, where coolant is directed via the hollow rotor shaft and at least one coolant inlet in the hub into coolant channels in the squirrel cage and / or the annular guide element body or guide elements. From there, the coolant is discharged via a coolant outlet into a coolant sump.

[0018] An embodiment of the invention is described below with reference to the accompanying figures.

[0019] They show: Fig. 1, Fig. 2, Fig. 3, Fig. 4, Fig. 5, Fig. 6 to Fig. 7 different views, each illustrating the construction of a rotor according to the invention for an axial flux machine.

[0020] In the Fig. 1, Fig. 2 to Fig. Figure 3 shows an assembled rotor R for an axial flux machine in different views. The rotor R has a disk-shaped squirrel cage 1 with an outer ring 3 and an inner ring 5. A hub 7, designed as a separate component, is inserted in the inner circumference of the inner ring 5 and can be mounted non-rotatably on a rotor shaft (not shown). The outer ring 3 and the inner ring 5 are connected to each other via radial webs 9, which have circumferentially distributed receiving pockets 13 in the rotor's circumferential direction ( Fig. 5, Fig. 6 to Fig. 7) limit, into which rotor guide elements 15 are inserted. The rotor guide elements 15 project axially from an annular guide element base body 17 as teeth with tooth gaps arranged in the circumferential direction of the rotor, as shown in the Fig. 4 is indicated. The Fig. Figure 4 shows the rotor R with the short-circuit cage 1 omitted.

[0021] In the assembled state according to the Fig. 1. The upper surfaces of the teeth of the guide element body 17 are flush with the stator-facing end face of the squirrel cage. In contrast, in an alternative embodiment, the upper surfaces of the teeth of the guide element body 17 can be axially recessed from the stator-facing end face of the squirrel cage (for example, by 1 to 2 mm), i.e., they can be recessed relative to the stator-facing end face of the squirrel cage, which offers electromagnetic advantages.

[0022] According to the Fig. 3 and Fig. In the annular short-circuit cage 1, the radial webs 9 are set back by an axial offset a from a short-circuit cage end face facing away from the stator. This forms an annular receiving space 19 ( Fig. 3 or Fig. 6) between the outer ring 3 and the inner ring 5, in which the annular guide element base body 17 can be inserted, while its rotor guide elements 15 project through the receiving pockets 13 of the squirrel cage 1. The axial offset a and the thickness d of the annular guide element base body 17 are of equal magnitude, so that the annular guide element base body 17 is flush with the stator-facing end face of the squirrel cage, as can be seen from the Fig. 3. On the stator-facing end face of the squirrel cage, the radial webs 9, on the other hand, merge flush into the inner and outer rings 3, 5, as can be seen from the Fig. 5 and Fig. 7 emerges.

[0023] In the Fig. 1 or Fig. 3 The hub 7 has a radially outwardly widening hub flange 21 on the rotor end face facing the stator. The hub flange 21, the annular squirrel cage 1, and an annular backplate 23 positioned on the rotor end face facing away from the stator form an axial assembly in which the squirrel cage 1 is axially supported between the backplate 23 and the hub flange 21. The hub flange 21, the annular squirrel cage 1, and the backplate 23 are force-transmittingly connected to each other by means of circumferentially distributed transverse bolts 25. Each of the transverse bolts 25 is connected by corresponding locating holes 24 ( Fig. 5, Fig. 6 to Fig. 7) in the back plate 23, the short-circuit cage inner ring 5 and the hub flange 21. In addition, the annular back plate 23 is axially guided with its inner circumference against an annular shoulder 27 ( Fig. 3) supported on the outer circumference of the hub. In the assembled state, the ring-shaped guide element base body 17 is materially connected to the back plate 23 via welds 29.

[0024] The outer ring 3 of the short-circuit cage 1 is enclosed by a reinforcing ring 31. This can be shrunk onto the short-circuit cage 1, for example, using a heat-shrinking process. To ensure the reinforcing ring 31 is positioned securely, the back plate 23 projects beyond it with an overhang 33 ( Fig. 3) the short-circuit cage 1 radially outwards. The backplate projection 33, together with an axially spaced edge rib 34 formed on the outer circumference of the short-circuit cage, forms axial movement stops for the reinforcing ring 31.

[0025] The annular guide element base body 17 and the guide elements 15 projecting axially from it are components of a sheet metal stack (not shown) wound from a strip of sheet metal, the layers of which are stacked radially on top of each other. The sheet metal stack is connected by welded joints 29 ( Fig. 2) attached to the back plate 23 to increase the rotor component stiffness.

[0026] The rotor R is equipped as an example with internal rotor cooling, in which coolant is supplied via the rotor shaft, which is designed as a hollow shaft, and via at least one coolant inlet 35 formed in the hub 7 ( Fig. 3) is directed into coolant channels (not shown) of the squirrel cage 1 and / or the annular guide element base body 17 or the rotor guide elements 15. From there, the coolant is discharged via coolant outlets 37, which are arranged according to the Fig. 2 are formed in the back plate 23, and are discharged into a coolant sump.

[0027] A key aspect of the invention is that the squirrel cage 1 is no longer manufactured as a casting in a casting process, but rather by extrusion. The invention is based on the understanding that wrought aluminum / copper alloys suitable for extrusion offer significantly better conductivity and higher material strength compared to similar aluminum / copper casting alloys (used to manufacture a squirrel cage as a casting). Furthermore, the manufacturing effort for extrusion is considerably reduced compared to casting.

[0028] In the extrusion process, a continuous extrusion profile is first produced, from which a raw short-circuit cage is cut to length. In a post-processing step, the raw short-circuit cage undergoes milling, in which the radial webs 9 are recessed by the axial offset a from one end face of the raw short-circuit cage. This creates the annular receiving space 19 into which the annular guide element base body 17 can be inserted. Furthermore, drilling is performed to create the locating holes 24 for the transverse force bolts 25 in the inner ring 5 of the short-circuit cage 1. Similarly, any necessary coolant channels are drilled into the raw short-circuit cage. Reference symbol list 1 short-circuit cage 3 Outer ring 5 inner ring 7 hub 9 radial web 13 Recording bag 15 Rotor guide element 17 guide element base body 19 ring-shaped recording chamber 21 Hub flange 23 Backplate 24 Passhole 25 shear bolts 27 Ring shoulder 29 weld seam 31 Reinforcing ring 33 Overhang 34 Edge 35 Coolant inlet 37 Coolant outlet R Rotor A rotor axis a axial offset d thickness of the ring-shaped guide element base body

Claims

Rotor (R) for an axial flux machine, which is arranged axially on one or both sides next to a stator in an installation position, wherein the rotor (R) has a disk-shaped squirrel cage (1) with an outer ring (3) and an inner ring (5) with hub (7), wherein the outer ring (3) and the inner ring (5) are connected to each other via spoke-like radial webs (9) which define circumferentially distributed receiving pockets (13) in the rotor circumferential direction, in which rotor guide elements (15) made of, in particular, soft magnetic material are inserted, characterized in that the disk-shaped squirrel cage (1) is an extruded part, and that, in particular, a raw squirrel cage can be cut to length from an endless extrusion profile in an extrusion process, from which the squirrel cage (1) can be produced in a post-processing process. Rotor according to claim 1, characterized in that the material of the disc-shaped short-circuit cage (1) is a wrought alloy, in particular AW6101, and that in particular by means of the wrought alloy - in comparison to a cast alloy of a short-circuit cage produced as a casting - better conductivity with higher material strength can be achieved. Rotor according to claim 1 or 2, characterized in that the rotor guide elements (15) project axially from an annular guide element base body (17) as teeth with tooth gaps arranged in the circumferential direction of the rotor. Rotor according to claim 3, characterized in that in the squirrel cage (1) the radial webs (9), in particular as a result of milling the raw squirrel cage, are set back by an axial offset (a) from a squirrel cage end face, in particular facing away from the stator, so that an annular receiving space (19) is formed between the outer ring (3) and the inner ring (5) of the squirrel cage (1), in which the annular guide element base body (17) can be inserted, while its rotor guide elements (15) project through the receiving pockets (13) of the squirrel cage (1), and in particular that the axial offset (a) corresponds to the thickness (d) of the annular guide element base body (17) in the axial direction. Rotor according to one of the preceding claims, characterized in that the hub (7) is a single-piece component of the inner ring (5) of the squirrel cage (1), or that the hub (7) is a single-piece component of a rotor shaft, or that the hub (7) is arranged radially between the squirrel cage (1) and the rotor shaft as a separate component. Rotor according to one of claims 1 to 5, characterized in that the hub (7), which is designed in particular as a separate component, has a radially outwardly widening hub flange (21) on a rotor end face facing the stator, and that the hub flange (21), the squirrel cage (1) and a back plate (23) form an axial composite in which the squirrel cage (1) is axially supported between the back plate (23) and the hub flange (21), and that in particular the hub flange (21), the squirrel cage (1) and the back plate (23) can be force-transmittingly connected by means of at least one transverse force bolt (25), thereby providing a rotationally fixed connection of the squirrel cage (1) with the hub (7) and increasing the component stiffness of the rotor (R). Rotor according to claim 6, characterized in that the back plate (23) is axially supported with its inner circumference against an annular shoulder (27) formed on the outer circumference of the hub, and / or that the transverse force bolt (25) is guided through fitting holes (24) in the axial connection. Rotor according to one of the preceding claims, characterized in that the outer ring (3) of the short-circuit cage (1) is enclosed by a reinforcing ring (31), in particular made of steel or carbon fiber reinforced plastic. Rotor according to claim 8, characterized in that the reinforcing ring (31) and the back plate (23) are installed as separate components in the rotor (R). Rotor according to claim 9, characterized in that the back plate (23) projects radially outwards beyond the short-circuit cage (1) with a projection (33), and that the projection (33) and an axially spaced edge web (34) circumferentially around the outer circumference of the short-circuit cage form axial movement stops for the reinforcing ring (31). Rotor according to claim 8, characterized in that the reinforcing ring (31) and the back plate (23) are integrated in a common pot-shaped component in a single material and / or in one piece, and in particular that the component is realized as a sheet metal deep-drawn part. Rotor according to one of claims 3 to 11, characterized in that the annular guide element base body (17) and the guide elements (15) projecting axially from it are components of a laminated core wound from a strip of sheet metal, the layers of which are stacked radially on top of each other, and / or that the annular guide element base body (17) is connected to the back plate (23) via a welded connection (29) in a force-transmitting manner in order to increase the component stiffness of the rotor (R). Rotor according to one of the preceding claims, characterized in that the rotor (R) is designed with internal rotor cooling, in which a coolant is guided via a rotor shaft designed as a hollow shaft and via at least one coolant inlet (35) in the hub (7) into coolant channels of the squirrel cage (1) and / or the annular guide element base body (17) or the guide elements (15), and is discharged from there via a coolant outlet (37) into a coolant sump. Method for manufacturing a rotor (R) according to one of the preceding claims.

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