Method for manufacturing a lamination stack for an electric machine, and lamination stack

Abstract

The invention relates to a method for manufacturing a laminated core (10) for an electric machine, in which: electrical steel sheet material is provided. At least one individual sheet (16) is produced from the electrical steel sheet material, wherein a contour of the at least one individual sheet (16) is manufactured. The at least one individual sheet (16) is subjected to at least one local mechanical post-treatment and / or at least one local heat treatment, thereby causing a local increase in the strength of the at least one individual sheet (16). The laminated core (10) is manufactured from the at least one individual sheet (16).

Description

[0001] The invention relates to a method for producing a laminated core for an electrical machine. The invention also relates to a laminated core for an electrical machine.

[0002] DE 10 2019 008 849 A1 discloses a rotor core for a rotor of an electrical machine.

[0003] The object of the present invention is to be able to realize a method for producing a laminated core for an electrical machine and a laminated core for an electrical machine, so that particularly advantageous mechanical properties of the laminated core can be realized in a particularly advantageous manner.

[0004] This object is achieved by a method having the features of patent claim 1 and by a laminated core having the features of patent claim 7. Advantageous embodiments with expedient further developments of the invention are set forth in the remaining claims.

[0005] A first aspect of the invention relates to a method for producing a laminated core for an electrical machine, in particular for a rotor and / or for a stator of an electrical machine. If the laminated core is used for the rotor, the laminated core is also referred to as a rotor laminated core. If the laminated core is used for the stator, the laminated core is also referred to as a stator laminated core. For example, in the fully manufactured state of the electrical machine, at least one permanent magnet and / or at least one winding is supported by the laminated core.

[0006] In the method, an electrical sheet material, also simply referred to as an electrical sheet, is provided. At least one individual sheet is produced from the electrical sheet material, wherein a contour, in particular an outer contour and / or an inner contour, of the at least one individual sheet is manufactured, i.e., formed. In the method, the at least one individual sheet is subjected to at least one local mechanical post-treatment and / or at least one local heat treatment, thereby locally increasing the strength of the at least one individual sheet. The laminated core is manufactured from the at least one individual sheet.

[0007] The invention enables optimization of local mechanical properties of individual laminations for producing at least one laminated core by subjecting the at least one individual lamination to local mechanical post-treatment and / or local heat treatment. For example, the local mechanical post-treatment comprises at least one local forming or deformation of the at least one individual lamination. In particular, the local forming or deformation is a micro-indentation, also referred to as micro-indentation. Such micro-indentations can achieve local hardening of the electrical sheet material, which is a material from which the at least one individual lamination is formed, locally, for example in the region of magnetic pockets of the laminated core.The basic idea of ​​the invention is to modify mechanical properties in areas of high mechanical load requirements and / or to optimize the magnetic flux flow of soft magnetic parts and components of an electrical machine. The invention is based in particular on the findings and considerations that the design of electrical machines is subject to a conflict of objectives between mechanical requirements in the rotor and magnetic requirements in the stator. The simultaneous maintenance of magnetic and mechanical properties of soft magnetic materials such as electrical steel sheet is subject to physical limits. High strength values ​​of soft mechanical materials can be achieved, for example, by alloying elements such as silicon. However, increasing the degree of alloying also leads to a reduction in saturation polarization and can therefore have a negative impact on the magnetic properties.Furthermore, mechanical strength can also be influenced by adjusting the grain size. Mechanical grades sometimes have significantly smaller grain sizes. Smaller grain sizes, however, can also have a detrimental effect on the magnetic reversal behavior. Therefore, in specific applications, different material grades are used in the rotor and stator of an electrical machine. This is associated with increased waste rates and higher costs. The basic idea of ​​the invention is local modification in the form of local mechanical post-treatment and / or local heat treatment, whereby the material properties can be locally optimized in areas exposed to high mechanical loads in order to counteract the aforementioned conflict of objectives in material design.The material selection for components of electrical machines, such as rotors and stators of radial flux machines and axial flux machines, is determined by the complex requirements profile of the soft magnetic materials used. In this case, mechanical properties, for example in the rotor, and magnetic properties must be evaluated equally. The invention can realize at least the following advantages: - local optimization of mechanical and / or magnetic material properties - Cost reduction, for example through the use of lower strength material grades and reduced processing costs for further processing, for example through punching - Optimization of machine efficiency by introducing flow barriers, for example through local forming.

[0008] Locations where local mechanical post-treatment and / or local heat treatment are performed are determined, for example, depending on a load profile that is determined or selected depending on the loads occurring during operation of the electrical machine. Compared to conventional solutions, the invention can improve the structural integrity and mechanical properties of the laminated core, allowing highly stressed areas to withstand requirements and loads. The aforementioned disadvantages, such as excessively high material grades and excessive waste, can be avoided.

[0009] It can be seen that the local mechanical post-treatment and the local heat treatment are local modifications of the soft magnetic individual lamination and thus of the laminated core. In comparison to conventional solutions, the invention therefore details the individual laminations, also referred to as lamination cuts, of the laminated core in order to achieve the highest possible performance and particularly high efficiency of the electrical machine. For example, the focus here can be on reducing the air gap between the rotor and the stator and maximizing the magnetic mass and slot fill factor of a winding of the electrical machine, whereby the winding is supported, for example, by the laminated core. Furthermore, the reduction of rotating masses in the rotor is also a priority, particularly in high-speed motor concepts.These optimizations are accompanied by reduced web widths, for example, between the magnet pairs or in the cross-section of the air gap. Mechanical forces occurring during operation, in particular centrifugal forces or centrifugal forces, magnetic and electromagnetic forces, significantly determine the material requirements. These forces and the associated material requirements are limited very locally to the lamination intersection point. This means that the material selection is driven by local stress increases in the highly stressed cross-sectional areas, such as the areas around the magnet pockets, while the mechanical requirements for the remaining cross-sectional area are significantly lower. The possibility of only locally modifying these locally highly stressed areas to increase strength allows considerable freedom in the material selection of the lamination sections for the rotor and stator.For example, a higher magnetically valuable electrical steel grade could be used in the rotor and stator, and the mechanical requirements could be optimized by means of local micro-indentation, thereby increasing machine efficiency.

[0010] Compared to conventional solutions, the invention can reduce waste rates since, for example, it is possible for laminated cores for the rotor and laminated cores for the stator to be produced from the same starting material in the form of the said electrical sheet material, wherein the local mechanical post-treatment and the local heat treatment are treatments by means of which, in particular, mechanical properties of the respective individual sheet can be adjusted at least locally in a targeted manner.

[0011] The electrical sheet material is a starting material from which the contour of the individual sheet is machined, for example by punching and / or waterjet cutting and / or laser cutting and / or eroding. The advantage here is very minimal material loss. Alternatively, the contours for the rotor and stator can be taken from different sheet materials. High mechanical properties are particularly required for the rotor, i.e., high static and / or high dynamic strength. However, this does not apply to the entire component, but usually only locally. Local mechanical post-treatment and local heat treatment are suitable for achieving a local increase in strength, particularly on the rotor.Local mechanical post-treatment includes, for example, local rolling and / or local plasticizing by pressing and / or local plasticizing by micro-indentation and / or local exposure to a blasting medium, in particular a shot peening process. Through these mechanical processes or a combination of these processes, the dislocation density is increased and / or compressive residual stresses are locally induced in the material. By increasing the dislocation density, the resistance to plastic deformation increases, thus increasing the static strength. By inducing the compressive residual stresses, the dynamic strength of the sheet material is increased, in particular. The invention enables cost reduction through the use of the same sheet grades for the stator and rotor, as well as cost advantages through efficient resource utilization.It is also possible to achieve cost reductions in raw material selection and processing costs by avoiding the use of particularly high-strength electrical steel grades. It is also possible to achieve efficiency improvements through the use of soft magnetic steel with higher magnetic properties. It is also possible to increase the speed stability of the electrical machine.

[0012] A second aspect of the invention relates to a laminated core for an electrical machine, in particular for a rotor or a stator of an electrical machine, wherein the laminated core is produced by a method according to the first aspect of the invention. Advantages and advantageous embodiments of the first aspect of the invention are to be regarded as advantages and advantageous embodiments of the second aspect of the invention, and vice versa.

[0013] Further advantages, features and details of the invention will become apparent from the following description of a preferred embodiment and from the drawing. The features and combinations of features mentioned above in the description as well as the following ones mentioned in the description of the figures and / or in the Fig. The features and combinations of features shown in Figures 1 to 3 alone can be used not only in the combination entered in each case, but also in other combinations or on their own, without departing from the scope of the invention.

[0014] The drawings show: - in the Fig. 1 shows a partial schematic front view of a laminated core for an electrical machine in a first embodiment, - in the Fig. 2 shows a partial schematic front view of a laminated core for an electrical machine in a second embodiment variant and - in the Fig. 3 shows a partial schematic front view of a laminated core for an electrical machine in a third embodiment.

[0015] Fig. 1 shows a partial schematic front view of a laminated core 10 of an electrical machine, in particular of a motor vehicle, in a first embodiment. In its fully manufactured state, the electrical machine has a rotor and a stator, by means of which the rotor can be driven and is thus rotatable about a machine axis of rotation relative to the stator. In particular, the electrical machine can provide drive torques for driving the motor vehicle via its rotor. The laminated core 10 can be used as a laminated core for the rotor and / or as a laminated core for the stator. The laminated core 10 is formed from individual laminated core segments, wherein the respective laminated core segment is also referred to as an individual sheet. The laminated core segments are formed from an electrical sheet material, which is also referred to as electrical sheet. In particular, the laminated core segments of the laminated core 10 are formed from the same electrical sheet material.The electrical steel sheet material is a soft magnetic material. This soft magnetic material can be a non-grain-oriented and / or grain-oriented electrical steel strip. This electrical steel strip is an iron alloy with up to 9 wt.% silicon and up to 3 wt.% aluminum. Furthermore, the laminated core can also consist of a soft magnetic cobalt-iron alloy or nickel-iron alloy. The laminated core, in particular the individual layers of the laminated sections of the core, can consist of a single material or be constructed from several different materials. For example, the laminated core segments are formed separately from one another and bonded to one another, in particular using a resin.

[0016] Out of Fig. 1 shows that the laminated core 10 has receptacles 12. In the Fig. 1, the respective receptacle 12 is a respective magnetic pocket in which at least or exactly one respective permanent magnet 14 is at least partially received. The permanent magnets 14 are formed separately from the laminated core 10 and are fastened to the laminated core 10 and are thereby supported by the laminated core 10. Furthermore, it would be conceivable for the respective receptacle 12 to be a respective groove of the laminated core 10. It would also be conceivable for a winding formed separately from the laminated core 10 to be provided, which winding is held on the laminated core 10 and is thereby supported by the laminated core 10. In this case, for example, respective length regions of the winding are arranged in the respective groove. By means of the winding, for example, a magnetic field for driving the rotor can be generated.The previous and following statements regarding the receptacles 12, which are designed as magnetic pockets in this case, can thus be readily applied to the aforementioned grooves. Furthermore, the previous and following statements regarding the permanent magnets 14 can be readily applied to the length ranges arranged in the grooves, and vice versa.

[0017] For example, the electric machine is designed as a radial flux machine (RFM). It would also be conceivable for the electric machine to be designed as an axial flux machine, which is also referred to as an axial flux motor (AFM).

[0018] Furthermore, it would be conceivable that the electrical machine is designed as a combination of radial and axial flux machine, which is often also referred to as radial flux machine.

[0019] The respective receptacle 12 and / or at least one region of the laminated core 10 directly adjacent to the respective receptacle 12 is a region in which high mechanical and / or magnetic loads on the laminated core 10 can occur during operation of the electrical machine.

[0020] In order to achieve particularly advantageous mechanical properties of the laminated core 10 and, consequently, high performance and high efficiency of the electrical machine, the laminated core 10 is manufactured using a method explained below. In this method, the electrical sheet material is provided. In this method, the respective sheet segment is produced from the electrical sheet material, wherein a respective contour, in particular a respective outer contour and / or inner contour, of the respective sheet segment is manufactured.

[0021] In the method, at least one of the sheet metal segments is subjected to at least one local mechanical post-treatment and / or at least one local heat treatment, thereby locally increasing the strength of the at least one sheet metal segment, particularly in the respective, previously mentioned, highly stressed area. In the method, the laminated core 10 is produced from the sheet metal segments and thus also from the at least one sheet metal segment, for example, by stacking the sheet metal segments on top of one another and connecting them to one another.

[0022] In the Fig. 1, the at least one sheet metal segment which is subjected to the at least one local mechanical post-treatment and / or at least one local heat treatment is partially visible and designated by 16.

[0023] In the Fig. In the embodiment shown in Figure 1, the local mechanical post-treatment comprises local forming or deformation of the sheet metal segment 16, wherein the local forming or deformations are micro-indentations 18. The micro-indentations 18 are or form a local modification of the sheet metal segment 16 in order to effect a local increase in the strength of the sheet metal segment 16 in a region in which the micro-indentations 18 are formed.

[0024] In the Fig. In the embodiment shown in Figure 1, the micro-indentations 18 are used as a flux barrier. In other words, the micro-indentations 18 are, or in this case, form a flux barrier. This allows for targeted magnetic flux guidance in an iron core of the electrical machine formed by the laminated core 10.

[0025] In the cross-sectional areas between two pairs of magnets, such as the rotor, a magnetic short circuit is undesirable. Attempts are made to introduce flux barriers into the electrical sheet material, also known simply as the material, by geometrically adjusting the sheet segments (also known as lamination cuts). A common measure to prevent short-circuit gaps is to widen the magnetic pockets. However, this widening leads to a reduction in the load-bearing cross-sectional areas between the respective magnetic pockets and an air gap in the electrical machine. Due to the mechanical demands placed on the rotor of the electrical machine, there are physical limits to this measure.The microindentations 18 can be used here to hinder domain movement in the lamination cut and thus reduce the effect of short-circuit paths in the rotor lamination cut, without possibly having adverse effects on the mechanical properties of the lamination cut.

[0026] As is widely known in the prior art, cavities 20 are introduced on or around the magnets in the rotor to guide flux. These cavities 20 serve to prevent interference fluxes, for example between two adjacent magnet pairs, by acting as a flux barrier. These cavities 20 largely determine the web width between the magnet pairs and between the permanent magnets 14 and the outer contour of the rotor lamination. By introducing adjacent microindentations 18, which also serve as flux barriers, the cavities 20 for forming flux barriers can be made significantly smaller or even eliminated entirely. This can, in turn, be used to increase magnet mass and / or to position the magnets radially further outwards on the rotor. Both measures have a beneficial effect on the performance of the electric machine.

[0027] The laminated core 10 is a component, in particular for an electric motor drive unit, wherein the previous and following statements regarding the laminated core 10 can be readily applied to other components, in particular for electric motor drive units, and vice versa. The component has at least one soft magnetic sheet, in the present case in the form of the sheet segment 16. In the Fig. In the embodiment shown in Figure 1, the component, namely the laminated core 10, comprises a stack of soft magnetic sheets in the form of the aforementioned sheet segments. The at least one soft magnetic sheet, namely the sheet segment 16 in this case, is at least largely grain-oriented or non-grain-oriented in some sections.

[0028] Preferably, the soft magnetic sheet, hence the sheet segment 16, is formed from an iron-based material, which can in particular be the aforementioned electrical sheet material. The iron-based material, in particular in the form of an electrical sheet, contains at least 0.5 weight percent silicon, in particular at least 1 weight percent silicon, as an alloying component and preferably also contains other alloying elements such as aluminum and manganese. Furthermore, it is conceivable that the material is a cobalt-iron sheet (CoFe) with a cobalt content of at least 10 weight percent or a nickel-iron sheet (NiFe) with a nickel content of at least 10 weight percent.

[0029] Fig. 2 shows a partial schematic front view of a laminated core 10 of an electrical machine, in particular of a motor vehicle, in a second embodiment.

[0030] The micro-indentations 18 are arranged radially outside the receptacles 12 in order to better accommodate the soft magnetic material for the high mechanical loads that the permanent magnets 14 exert on the receptacle 12 during operation due to centrifugal forces when rotating. For example, the micro-indentations 18 are arranged in a line parallel to the edge of the receptacle 12 in its overlap.

[0031] Fig.3 shows a partial schematic front view of a laminated core 10 of an electrical machine, in particular of a motor vehicle, in a third embodiment. Here, the micro-indentations 18 are arranged in the circumferential direction between the receptacles 12 in order to act as a flux barrier in the soft magnetic material. Between the receptacles 12 for the permanent magnets 14, cavities 20 are usually provided, which serve as a flux barrier between the permanent magnets 14 in order to dampen, reduce, or completely prevent unwanted interference fluxes between the magnets. Due to the micro-indentations 18, which also serve as a flux barrier, a cavity 20 can be made smaller or can be omitted entirely, so that more material can remain between the permanent magnets 14 and thus the strength and structure at this point is also increased.

[0032] Micro-indentations 18 can also be arranged between the permanent magnets 14 and the radial edge of the laminated core 10. These can also serve as a flux barrier and counteract the high mechanical loads. This allows cavities 20 to be omitted in this area B, or they can be made smaller, so that the receptacle 12 and thus the permanent magnet 14 can be arranged closer to the radial edge of the laminated core 10. List of reference symbols 10 sheet packages 12 recordings 14 Permanent magnet 16 sheet segments 18 microindentations 20 cavities B area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 008 849 A1

[0002]

Claims

[1] Method for producing a laminated core (10) for an electrical machine, in which: - an electrical sheet material is provided; - at least one individual sheet (16) is produced from the electrical sheet material, wherein a contour of the at least one individual sheet (16) is manufactured; - the at least one individual sheet (16) is subjected to at least one local mechanical post-treatment and / or at least one local heat treatment, thereby causing a local increase in the strength of the at least one individual sheet (16); and - the laminated core (10) is produced from at least one individual sheet (16). [2] Method according to claim 1, characterized by that the contour is produced by punching, fine blanking, water jet cutting, laser cutting and / or erosion. [3] Method according to claim 1 or 2, characterized bythat the local mechanical post-treatment comprises at least one local forming and / or deformation of the at least one individual sheet (16). [4] Method according to claim 3, characterized by that the local transformation or deformation is a microindentation (18). [5] Method according to one of the preceding claims, characterized by that the local mechanical post-treatment comprises local rolling and / or local plasticising by pressing and / or local plasticising by micro-indentation and / or local exposure to a blasting medium. [6] Method according to claim 5, characterized by that the local application of a blasting medium is a shot blasting process. [7] Laminated core (10) for an electrical machine, wherein the laminated core is produced by means of a method according to one of the preceding claims.

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