Method for producing a soft magnetic core, rotor of an electric machine, and electric machine

Abstract

The invention relates to a method for producing a soft magnetic core (2) for an electric machine (4), the method comprising the following steps: a) producing a layered laminate (18) on a substrate (8), comprising alternately at least one soft magnetic layer (12) and at least one electrically insulating layer (16), wherein b) the soft magnetic layer is produced by means of a doctor-blade method (10) and by means of a material paste (6), the material paste (6) comprising soft magnetic particles and organic binders, c) furthermore, the electrically insulating layer is produced by means of a second material paste (14) which comprises inorganic, electrically insulating particles and organic binders, d) a laminate structure (20) is produced by detaching the layered laminate (18) from the substrate (8), e) bending at least one laminate structure (20) to form a core package (22-1) in the green state, f) debinding the core package (22-1), and g) sintering the core package (22-2) to form the soft magnetic core (2).

Description

[0001] Description

[0002] Method for producing a soft magnetic core, rotor of an electrical machine and electrical machine

[0003] The invention relates to a method for producing a soft magnetic core according to claim 1, a rotor or a non-return stator of an electrical machine according to claim 12 and an electrical machine according to claim 14.

[0004] In electrical machines, especially electric motors and generators, soft magnetic cores, i.e. magnetic cores, are required depending on the operating concept, particularly in the stators and rotors. At medium and high frequencies and with a small core cross-section, the following are required to achieve the highest possible performance level: Firstly, high magnetization (for high induction) and high permeability of the magnetic core are necessary for high torque with a low weight of the electrical machine. Secondly, electromagnetic losses, particularly hysteresis losses and eddy current losses, should be low - especially in the stators. Due to the requirement for high magnetization and permeability, iron-based alloys are preferred. However, these have high electrical conductivity, which is why measures to suppress eddy currents must be taken.To date, there is no suitable construction method based on the available material classes for constructing such a magnetic core without a yoke, i.e. without a magnetic return, and possibly with a curved magnetic flux guide.

[0005] The current state of the art involves the use of powder compacts, so-called SMCs (soft magnetic composites), as well as rolled and punched sheet metal laminates, which require post-annealing if bent. Furthermore, amorphous iron materials are also produced and laid or wound into laminates, although this technology is still largely undeveloped. In punched and stacked sheet metal pieces, the impact of punching edges on the deterioration of magnetic properties is very significant, as is the case with axial flux motors. When constructed from wound or stacked amorphous thin strips, the magnetic performance is limited, and shaping technology, such as cost-effective punching or (waterjet) cutting, is not available on an industrial scale. In sintered compacts, i.e. SMC materials, with internal insulating layers in the structure, losses are very high, and magnetic permeability and polarization are greatly reduced.

[0006] The object of the invention is therefore to provide a magnetic core which, on the one hand, has better magnetization (induction) and permeability than the prior art and, at the same time, has lower hysteresis losses and eddy current losses.

[0007] The solution to the problem consists in a method for producing a soft magnetic core according to patent claim 1 and in a rotor of an electrical machine which comprises such a soft magnetic core which is produced according to such a method, as well as an electrical machine with a corresponding rotor or stator.

[0008] The method for producing a soft magnetic core for an electrical machine comprises the following steps: a) Producing a layered laminate from a substrate, comprising alternating layers of at least one soft magnetic layer and at least one electrically insulating layer. b) The soft magnetic layer is produced using a doctor blade method and a material paste, which material paste contains soft magnetic particles and organic binders. c) The electrically insulating layer is produced using a further material paste, which material paste comprises inorganic, electrically insulating particles and organic binders.d) A laminate structure is created by detaching the layered laminate from the substrate, e) the laminate structure is bent and stacked, wherein a stack comprises at least one laminate structure, so that a core package is created in the green state and f) this core package is debindered in the green state g) the core package is sintered, whereby the soft magnetic core is created.

[0009] First of all, it should be noted that with regard to features a), b) and c), the order of the soft magnetic layer and the electrical insulating layer with respect to the first layer applied to the substrate is fundamentally arbitrary. What is important is that there is an alternating order of soft magnetic layer and insulating layer. In this case, a sequence of an insulating layer and a soft magnetic layer is already referred to as a layered laminate, but from a process engineering perspective it is advantageous to repeat steps a) to c) several times so that the layered laminate has a number n of soft magnetic layers, where this number n is preferably between 5 and 100, particularly preferably between 5 and 15. The term layered laminate is used as long as the sequence of the soft magnetic layer and the insulating layer is on the substrate. When the layered laminate is detached from the substrate, it is referred to as a laminate structure.The laminate structure differs from the layered laminate in that, if the layered laminate does not have a near-net-shape representation of the layered laminate on the substrate, it may be separated from the layered laminate. Due to the nature of the layered laminate, this separation can be achieved by punching. However, it can also be performed using other separation processes, such as waterjet cutting or laser cutting.

[0010] The advantage of the present invention over the prior art is that, on the one hand, due to the soft magnetic particles used for the core, the functionally best materials can be used, which favors the electromagnetic properties, such as magnetization (induction) and permeability for the development of a high torque, particularly in an electrical machine in the form of an electric motor. In particular, an iron alloy with the highest possible iron content of more than 95%, in particular more than 99%, is used here. On the other hand, the advantage of the described method is that thin soft magnetic layers can be produced which are provided with an electrical insulating layer, thus making it possible to build a core with very low hysteresis losses and eddy current losses.Furthermore, this core can already be placed in the correct geometric shape so that the laminate structure produced in this way is, on the one hand, punchable and, on the other hand, flexible and handleable, so that the corresponding shape with the desired material properties can be adjusted even before a sintering process and sintering represents the only thermal step.

[0011] It should also be mentioned that a layered laminate, and thus subsequently the laminate structure, has at least one soft magnetic layer and one insulating layer, but that the number n is advantageously greater than 1 and less than 100, very particularly preferably between 5 and 15. Thus, a typical laminate structure has, for example, 10 soft magnetic layers, each separated from one another by an insulating layer. Such a laminate structure can in turn be debindered and sintered individually according to steps f) and g). However, steps f) and g) also allow the alternative of several laminate structures being stacked on top of one another before debinding and / or sintering. The term stacking is understood here to mean at least one laminate structure, but also a large number of laminate structures, for example 10 to 20 laminate structures.In principle, it is also possible that only one laminate structure according to feature e) is bent, debindered and sintered and, in the sintered state, several laminate structures produced in this way are stacked to form the soft magnetic core.

[0012] In one embodiment of the invention, it is expedient to use a stencil printing process or a slip casting or slip drawing process as the doctor blade process for producing the soft magnetic layer. Both processes make it possible to produce thin layers of less than 200 μm, preferably in a range between 80 and 150 μm, with a constant thickness, with process precision and suitable for large-scale production. A doctor blade process can also be used for applying or producing the insulating layer, although the insulating layer is significantly thinner than the soft magnetic layer, typically having a thickness between 5 μm and 10 μm. However, the insulating layer can also be produced using a spraying process.

[0013] The soft magnetic cores, which are typically used in a non-return stator of an axial flux machine, preferably have the shape of a hollow cylinder segment due to their arrangement in the rotor. For this purpose, it is expedient for the laminate structure to be bent along a cylindrical surface to produce this core package, from which the magnetic core emerges. Typically, several laminate structures bent along the cylindrical surface and stacked on top of one another thus result in a hollow cylinder segment. In principle, a laminate structure with a corresponding number n of layer sequences in a bent shape can also form a hollow cylinder segment.

[0014] To this end, it is again expedient, in order to maintain the stability of the core package, to place the individual laminate structures on a support device whose supporting surface has the radius of the hollow cylinder segment, and step f), i.e. the debinding according to claim 1, is carried out with the aid of this support structure. The same applies analogously to step g), the sintering process, whereby different support structures can be used for this. The term radius of the hollow cylinder segment can be the outer radius or the inner radius of the hollow cylinder segment, depending on whether the support structure is convex or concave. As an alternative to the described stacks of laminate structures, a laminate structure can also be wound into a hollow cylinder segment.This is possible because the laminated layer and the resulting laminate structure, especially in the unbound state, exhibit sufficient flexibility to allow deformation beyond bending. Even in the wound state, the core features magnetically and electrically separated soft magnetic layers, which significantly reduce hysteresis and eddy current losses.

[0015] A further component of the invention is a rotor of an electrical machine comprising a soft magnetic core manufactured according to the method according to the preceding claims. The soft magnetic core is installed along the rotor in such a way that the axis of the form-forming hollow cylinder segment is parallel to a rotor rotation axis. This arrangement of the hollow cylinder segment with respect to the rotor achieves particularly good magnetic properties, in particular good induction and / or permeability.

[0016] A further component of the invention is an electric machine with a rotor according to claim 12 or 13, wherein the electric machine, in an advantageous embodiment, is a reluctance motor. Reluctance motors, in particular, require soft magnetic cores with the described properties, preferably with the corresponding arrangement according to claim 13.

[0017] Further embodiments and further features of the invention are explained in more detail with reference to the following figures. These are purely schematic representations that do not limit the scope of protection and serve only for illustration purposes. Features with the same meaning but in different embodiments are provided with the same reference numerals. In the following:

[0018] Figure 1 is a three-dimensional exploded view of an electrical machine in the form of an electric motor,

[0019] Figure 2 a - e is a schematic representation of the manufacturing process for producing a magnetic core,

[0020] Figure 3 a - c shows a typical structure of a rotor with a magnetic core that can be produced by a method according to Figure 2, Figure 4 shows a magnetic core that is wound into a hollow cylinder segment with a laminate structure.

[0021] Figure 1 shows an exploded view of an electrical machine 4 in the form of an electric motor. This electrical machine 4 has a housing 38 as well as a rotor 32 and a stator 36. A rotor 32, similar to that in Figure 1, is schematically illustrated in Figures 3b and c. Figure 1 serves to illustrate the basic structure of an electrical machine and is not necessarily equivalent to the rotors and stators described below.

[0022] Figure 2 initially schematically illustrates a method, wherein in Figure 2a, a second material paste 14 is first applied by means of a spray device 40 to a conveyor belt 52, the surface of which serves as the substrate 8, thereby producing an electrical insulating layer 16. The second material paste 14 comprises, as functional components, inorganic particles, for example aluminum oxide or silicon oxide, which have a high electrical resistance. Furthermore, the second material paste 14 comprises organic binders which ensure a specific application in very thin thicknesses of the insulating layer and subsequent flexibility. The insulating layer 16 has a very thin thickness of less than 10 pm; in this example, it is applied by means of a spraying process, but it can also be produced by means of a doctor blade process.This is followed by initial drying of the surface of the insulating layer 16 using a drying device 42, after which a first material paste 6 is applied to the insulating layer 16 using a slip casting device 44. The first material paste 6 is evenly distributed using a doctor blade 46, thereby forming the soft magnetic layer 12. The soft magnetic layer 12 is characterized in that the first material paste 6 comprises, in addition to preferably organic binders, soft magnetic particles, in this example 99% iron particles. This almost pure iron has very good magnetization and exhibits very good soft magnetic properties, which means that in a sintered state, the material of the soft magnetic layer 12 can be very easily remagnetized, resulting in low hysteresis losses.

[0023] In Figure 2a, purely by way of example, the insulating layer 16 is first applied to the substrate and then the soft magnetic layer 12 is produced on the insulating layer 16. This can also be done in the reverse order, so that first the soft magnetic layer 12 is applied to the substrate 8 and then the insulating layer 16 follows. The order chosen here is for purely process-related reasons and depends on the stability of the individual material pastes 6, 14 used and their adhesion to one another or to the substrate 8. Furthermore, a continuous process is shown in Figure 2a, this is a doctor blade process 10, in which a slip casting process or a slip drawing process is used to produce the soft magnetic layer 12. It is also fundamentally possible to use a stencil printing process orA screen printing process, which can be subsumed under the stencil printing process, is used. A stencil printing process has the advantage of allowing a near-net-shape production of the desired structure, in this case the laminate structure 20.

[0024] Figure 2a also shows only one iteration for producing a layered laminate 18 comprising at least one insulating layer 16 and a soft magnetic layer 12. The section from Figure 2a can be repeated as often as desired, even on the same conveyor belt 52, so that the layered laminate 18 can consist of a number n of layer sequences of the soft magnetic layer 12 and the insulating layer 16. Typically, a layered laminate 18 has between 5 and 15 sequences of these two layers. The layered laminate 18 is then detached from the substrate 8, and in a continuous laminate structure, as produced by the slip casting process described, a laminate structure 20 is separated out. This separation can be carried out, for example, by a punching process, which is not explicitly shown in Figure 2.If the layered laminate 18 is produced by a stencil printing process, which is also a doctor blade process 10, the layered laminate already has a structure very close to the final contour. In this case, immediately after the layered laminate 18 is detached from the substrate 8, the laminate structure 20 is formed. However, depending on how close to the final contour the layered laminate 18 was produced by the stencil printing process, this structure also requires slight post-processing, possibly also by a punching process. Furthermore, a laser cutting process or a waterjet process may also be suitable for separating the laminate structure 20.

[0025] The following will look in more detail at the nature and different names for material pastes depending on the application. Depending on the viscosity of a material paste, it is referred to as a slip or a screen printing paste in relation to the usual application of this material paste. As an example of a material composition for a low-viscosity material paste in the form of a slip, as used in the example shown in Figure 2, this is described as follows. This material paste has as its central, functional component a powder which comprises inorganic, usually metallic particles, here in the form of 99% iron with soft magnetic properties. This inorganic powder is dispersed in a liquid carrier material. The liquid carrier material is preferably water-based for large-scale, cost-effective production.However, other functional liquid components can also be added to the liquid carrier material. These can be wholly or partly alcohols, ethers, esters, ketones, amines, amides, acids, alkalis, or more generally hydrocarbons such as pentane, hexane, heptane, or benzene derivatives. These substances can be present individually or as additives or mixtures, thus forming the liquid carrier. A high water content of 90% or more is also advantageous, as this can be produced economically on an industrial scale. In this embodiment, the iron powder has a d50 value of 50 pm. This means that 50% of the individual particles have a diameter of less than 50 pm. The maximum diameter should not exceed 100 pm.

[0026] Furthermore, it is necessary to add a binder, particularly an organic binder, to the material paste. A wide variety of organic binders are available, such as celluloses, polyvinyl alcohols, polyvinyl acetates (PVA), or polyvinyl butyrals (PVB), as well as acrylate dispersions. This organic binder serves to solidify the inorganic particles in a green state after drying and thus after at least partial removal of the liquid carrier.

[0027] An example of the composition of a material paste in the form of a slip with a relatively low viscosity is given as follows: aqueous screen printing paste

[0028] An alternative composition of a material paste is given as follows: organic paste example weight weight % volume %

[0029] By varying the proportion of the carrier agent, in this preferred case water, and by varying the additives, such as the setting agent or the thixotropic agent, the viscosity of the material paste can be adjusted according to the requirements of the application method.

[0030] The iron powder contains impurities of oxygen, carbon, nitrogen, and sulfur, with the most significant impurity being oxygen, which, however, amounts to a maximum of 0.22 wt.%. The remaining impurities are less than 0.02 wt.%. Iron alloys containing up to 4 wt.% silicon can also be included in the material paste as soft magnetic particles. The grain distribution of the ice particles in the second example is given as follows: D 3.71 pm

[0031] D5O 5.74 pm

[0032] D90 10.05 pm

[0033] After separation, the laminate structure can, as already described, comprise between one layer sequence and 100 or more layer sequences, so that it can already have a thickness of between 100 μm and 1 cm. Thus, in principle, it would be possible, starting from the thickest assumed laminate structure 20, to already speak of a core package 22-1 in the green state. In the present example, however, it is expedient to stack several laminate structures, which have, for example, 10 sequences of layers 12, 16, on top of one another and to bring them into a bent state as shown in Figure 2b. This proves to be a technological advantage of the described method, since the laminate structure 20 is so strong on one side after the described manufacturing method that, unlike a very thin film, it can be easily punched out and can therefore have a precisely defined contour.Furthermore, the separated edges of the laminate structure 20 continue to be defined by the layer sequence of the soft magnetic layer 12 and the insulating layer 16 as a result of the separation, without any significant smearing occurring in the edge region, which could lead to magnetic and electrical short circuits and thus eddy current losses. On the other hand, the laminate structure is flexible enough to form the corresponding contour of a soft magnetic core, which preferably corresponds to that of a hollow cylinder segment. For this purpose, a support structure 24 is preferably used, as shown in Figure 2b, which in this case is convex and has a radius 28 on its supporting surface 26, which in this case represents the inner radius of the hollow cylinder segment 30.

[0034] According to Figure 2b, in this example, only three laminate structures 20 are stacked to form a core package 22-1 in the green state. As already mentioned, only one laminate structure 20 could be bent in this state and then, as shown in Figure 2c, first subjected to a debinding process in a debinding furnace 48 and then to a sintering process in a sintering furnace 50. In the debinding furnace 48, the core package 22-1 in the green state is heated to a temperature of approximately 300°C to 400°C, during which the mostly organic components of the binders are thermally decomposed. These escape from the pores of the laminate structure 20, so that after the debinding process, the core package 22-2 is in the debindered state.In the debindered state, the respective functional particles—the iron particles in layer 12 and the inorganic, electrically insulating particles in insulating layer 16—are clamped next to one another, being more brittle in this state than in the non-debindered green state. The sintering process then follows, with Figure 2c depicting the debinding furnace 48 and the sintering furnace 50 in the form of a continuous tunnel furnace, where one heat treatment phase, debinding, transitions into the second heat treatment phase, sintering. In principle, it is also possible to use two different furnaces for both processes, debinding and sintering, in which the respective core packages 22-1 and 22-2 are subjected to a corresponding temperature treatment. Separate furnaces have the advantage that the atmosphere required for the respective process can be better adjusted.However, a continuous furnace described here, which integrates the debinding furnace 48 and the sintering furnace 50, is more economical to operate on an industrial scale.

[0035] Figure 2c further shows that both the debinding in the debinding furnace 48 and the sintering in the sintering furnace 50 are carried out using the support structure 24. In this way, the radius 28 of the subsequent hollow cylinder segment 30 remains stable. It should be noted at this point that the hollow cylinder segment 30 can also be designed in the form of a wound laminate structure 20, which forms the core package 22, and that this can be fed to both the debinding process and the sintering process, as shown in Figure 2c. From this, the core 2 is then created in an analogous form, but in a wound structure.

[0036] The term sintering process refers to a temperature treatment in which the particles, in particular inorganic particles, which are present in the core package 22-2, i.e. in the debindered state in a clamped form, are heat-treated without reaching the respective melting temperature. During this heat treatment below the melting temperature, diffusion processes lead to the formation of so-called sintering necks, which gradually shrink the pores between the particles and thus lead to a monolithic structure. In principle, a sintering process is associated with a certain amount of sintering shrinkage, so that the shrinkage caused by sintering and debinding is taken into account during the production of the core package 22, so that the structure of the subsequent soft magnetic core is as close to its final shape as possible.

[0037] The advantage of winding according to Figure 4 is, in particular, that after the sintering process, the soft magnetic core 2 is thus finished. It may require further fine finishing. However, Figure 2d shows a robot arm 54, in which the sintered core packages 22 are further stacked to form the final soft magnetic core 2. This is an optional process step if the core package 22-1, as shown in Figure 2b, comprises only three laminate structures 20. In principle, it would also be possible to stack several laminate structures 20 on top of one another, which already have the full structure of the subsequent core 2.How this is implemented depends on the respective shape and size as well as on the type of material pastes 6, 14 used, which either allow several laminate structures to be stacked on top of one another and subsequently sintered, or to stack only a few on top of one another and, in this form, sinter, for example, only three laminate structures 20 together. Finally, Figure 2e shows a finished core 2, which has the shape of the hollow cylinder segment 30, which in turn includes the inner radius 28.

[0038] Figure 3a schematically illustrates the structure of a rotor 32, which in turn has a plurality of magnetic sheets 58 stacked one above the other on a shaft 56. In a particularly advantageous embodiment, the magnetic sheets 58 can also be produced using a doctor blade method 10 as already described and can be punched out accordingly or manufactured to a near-net shape. In this case, it would be expedient to use a different alloy for the metallic particles, for example, a stainless steel alloy, in particular an iron-chromium-nickel alloy, which in this case produces supporting (magnetic) sheets (in this case, they would be non-magnetic) with particularly high strength.

[0039] Figure 3b shows a schematic exploded view of how the magnetic core 2, the production of which is described in Figure 2, is inserted into recesses in the magnetic lamination stack made up of the magnetic laminations 58. The axis of the hollow cylinder segment 30, which the core 2 forms, runs parallel to the axis of the shaft 56 of the rotor 32. This in turn means that a stacking normal at the reversal point (reversal line) for stacking the individual laminate structures and for forming the core 2 runs perpendicular to a stacking normal of the individual magnetic laminations 58, which in turn coincides with the axis of the rotor shaft 56. This course of the individual stacked laminate structures is schematically illustrated again in Figure 3c in an assembled state of the rotor 32.This design provides a rotor, particularly for a reluctance motor, which, on one side, has high-strength magnetic laminations on the shaft 56, which are ideally non-magnetic in themselves, and which are supplemented by the soft magnetic core 2. The soft magnetic core is characterized by a layered structure in which soft magnetic layers 12 and insulating layers 16 are interrupted, thereby causing, on the one hand, very low hysteresis losses and eddy current losses, and, on the other hand, allowing the use of a soft magnetic material in the form of almost pure iron, which has particularly good soft magnetic properties. List of reference symbols.

[0040] 2 soft magnetic core

[0041] 4 electric machine

[0042] 6 Material paste

[0043] 8 Substrat

[0044] 10 doctor blade processes

[0045] 12 soft magnetic layer

[0046] 14 second magnetic paste

[0047] 16 Insulating layer

[0048] 18 layer laminate

[0049] 20 Laminate structure

[0050] 22 Core package 1 in ground state

[0051] 24 Core package 2 in debound state

[0052] 26 load-bearing surface

[0053] 28 Radius outside / inside

[0054] 30 hollow cylinder segment

[0055] 32 rotors

[0056] 34 Pipe axis

[0057] 36 Stator

[0058] 38 housings

[0059] 40 spray device

[0060] 42 Drying device

[0061] 44 Slip casting device

[0062] 46 squeegees

[0063] 48 Debinding furnace

[0064] 50 sintering furnace

[0065] 52 Conveyor belt

[0066] 54 Robot arm

[0067] 56 Wave

[0068] 58 magnetic sheet

Claims

Patent claims 1. A method for producing a soft magnetic core (2) for an electrical machine (4), comprising the following steps: a) producing a layered laminate (18) on a substrate (8) comprising alternately at least one soft magnetic layer (12) and at least one electrical insulating layer (16), wherein b) the soft magnetic layer is produced by means of a doctor blade method (10) and by means of a material paste (6), wherein the material paste (6) comprises soft magnetic particles and organic binders, c) furthermore, the electrical insulating layer is produced by means of a second material paste (14) comprising inorganic, electrically insulating particles and organic binders, d) a laminate structure (20) is produced by detaching the layered laminate (18) from the substrate (8), e) bending at least one laminate structure (20) into a core package (22-1) in the green state,f) debinding the core package (22-1) and g) sintering the core package (22-2) to form the soft magnetic core (2)., 2. Method according to claim 1, characterized in that step a) and step b) are repeated several times, so that the layer laminate (18) has a number n of soft magnetic layers (12) and insulating layers (16).

3. Method according to claim 2, characterized in that the number n is between 5 and 100, in particular between 5 and 15.

4. Method according to one of the preceding claims, characterized in that the doctor blade method (10) is a stencil printing method or a slip casting method (10-1).

5. Method according to one of the preceding claims, characterized in that the soft magnetic particles consist of an iron alloy, wherein the iron content is more than 96 wt. %, in particular more than 99 wt. %.

6. Method according to one of the preceding claims, characterized in that after one of the steps e), f) and / or g) a stacking of several laminate structures (20) takes place, which in stacked form form the core (2).

7. Method according to one of the preceding claims, characterized in that the laminate structure (20) is bent along a cylinder surface to form the core package (22).

8. Method according to claim 6, characterized in that the core package (22) and thus the soft magnetic core (2) have substantially the shape of a hollow cylinder segment (30).

9. Method according to claim 6 or 7, characterized in that the laminate structure (20) is placed on a support device (24) whose supporting surface (26) has the radius (28) of the hollow cylinder segment (30) and step f) and / or step g) according to claim 1 is carried out with the aid of the support structure (24).

10. Method according to one of claims 1 to 5, characterized in that the layer laminate (18) is wound into the hollow cylinder segment (30).

11. Method according to one of the preceding claims, characterized in that the laminate structure (20) is produced by separating it from the layer laminate (18).

12. Rotor or short-circuit-free stator of an electrical machine (4) comprising a soft magnetic core (2), manufactured by a method according to one of the preceding claims.

13. Rotor or non-return stator according to claim 12, characterized in that the soft magnetic core (2) is installed along the rotor (32) in such a way that the axis of the shape-forming hollow cylinder segment (30) is parallel to a rotor rotation axis (34).

14. An electrical machine having a rotor (32) according to one of claims 12 or 13.

15. Electrical machine according to claim 14, characterized in that the electrical machine (4) is a reluctance motor.

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