Laminated core of an electrical machine and method for producing a laminated core

Abstract

The present invention relates to a laminated core (1) of an electrical machine, which is formed from a plurality of laminated laminations (3), wherein the laminated laminations (3) are made of a steel and have an insulating coating, characterized in that annular or radial thickenings (4) and annular or radial depressions (5) located therebetween are formed in the laminated laminations (3).

Description

State of the art

[0001] The present invention relates to a laminated core for an electrical machine. Furthermore, the invention relates to a method for producing such a laminated core.

[0002] It is known from the prior art to use laminated cores instead of solid metal bodies in electrical machines. The use of individual laminations that are electrically insulated from each other and stacked into a core helps suppress the propagation of eddy currents in these laminated cores. Disclosure of the invention

[0003] The laminated core according to the invention reduces eddy currents in the electrical steel sheet. This is achieved through innovative sheet geometries that limit the expansion of eddy currents.

[0004] The laminated core of an electrical machine is made up of a multitude of laminations. The laminations are made of steel and have an insulating coating. Thickened portions and recesses between them are formed within the laminations. The thickened portions and recesses can be arranged annularly or radially. The recesses have a particularly low electrical conductivity. This is due to the fact that the lamination material is reduced at the recesses, leaving a small amount of electrically conductive material.

[0005] However, the insulating coating remains in place, so that overall electrical conductivity in the recessed area is minimized. This further suppresses the propagation of eddy currents.

[0006] The subclaims show preferred developments of the invention.

[0007] Preferably, the annular thickenings and the annular depressions of the same lamination are arranged concentrically with respect to a stack axis of the lamination stack. Thus, the formation of eddy currents is further suppressed due to the higher electrical resistance. Furthermore, a regular pattern of thickenings and depressions is achieved, making the laminations easy to stack.

[0008] The annular thickenings and the annular depressions of the same lamination advantageously form a concentric wave contour on a top and / or bottom side of the lamination. This allows for the uniform introduction of areas of low electrical conductivity, namely at the depressions. Thus, advantageous areas for suppressing the propagation of eddy currents are formed across the entire lamination.

[0009] Alternatively or additionally, the radial thickenings and the radial depressions of the same lamination are preferably arranged radially relative to a stack axis of the lamination stack. The higher electrical resistance further suppresses the formation of eddy currents. Furthermore, a regular pattern of thickenings and depressions is achieved, making the laminations easy to stack.

[0010] The radial thickenings and the radial depressions of the same lamination advantageously form a radial wave contour on the top and / or bottom of the lamination. This allows for the uniform introduction of areas with low electrical conductivity, namely the depressions. Thus, advantageous areas for suppressing the propagation of eddy currents are formed across the entire lamination.

[0011] The thickened portions form, in particular, a positive contour, and the depressions form, in particular, a negative contour. The positive and negative contours are preferably designed to correspond, in particular, to be identical in shape. This leads to ideal stackability.

[0012] Preferably, the thickened portions of the sheet metal laminations extend correspondingly into the recesses of adjacent sheet metal laminations. It is particularly preferred that there be no hollow spaces between adjacent sheet metal laminations. This ensures optimal stackability. Avoiding hollow spaces, in particular, ensures advantageous magnetic conductivity.

[0013] The annular thickenings of adjacent laminations are preferably offset from each other with respect to the stack axis. This allows projections of laminations, in particular, to engage with recesses of adjacent laminations.

[0014] The laminations are advantageously made of a cold-forming steel. The cold-forming steel is, in particular, a deep-drawing steel. The steel is particularly preferably of grades DC01 to DC07. Thus, a cost-effective material is used for the laminations, minimizing the manufacturing costs of the lamination stack.

[0015] At least several of the sheet metal laminations are alloyed on a top and / or bottom side by diffusing in at least one alloying element. The alloying element is, in particular, aluminum or silicon.

[0016] The invention also relates to a method for producing a laminated core of an electrical machine. The method comprises the following steps: First, step a) involves providing uncoated sheet metal lamination blanks. The sheet metal lamination blanks are made, in particular, of deep-drawing steel and are therefore a cost-effective material.

[0017] A step b) of cold forming the sheet metal lamination blanks takes place in a forming tool. This involves, in particular, extrusion of the sheet metal lamination blanks in an extrusion tool. This results in the production of sheet metal laminations from the sheet metal lamination blanks. The cold forming leads to the imprinting of a concentric wave contour with annular thickenings and intervening annular depressions on an upper and lower side of the sheet metal lamination blanks. Furthermore, a step c) of applying a functional layer to the upper and / or lower side of the sheet metal laminations takes place. The functional layer is, in particular, a separate layer or an applied coating. It is provided that the functional layer comprises an electrically insulating material, in particular aluminum oxide and / or silicon oxide, and at least one alloying element for alloying the sheet metal laminations, in particular aluminum or silicon.

[0018] This is followed by step d) of stacking the laminations (3) with the applied functional layer. Furthermore, step e) of producing the laminated core by heat-treating the stacked laminations is performed. During this process, the alloying element of the functional layers diffuses into the laminations, and the insulating material forms an electrical insulation layer between the laminations.

[0019] As a result of the forming process, the sheet metal lamination blanks have a geometry with a stacking factor of at least 95%, in particular at least 98%. Furthermore, the sheet metal lamination blanks are formed from a material with a silicon content of less than 2%.

[0020] The functional layer is preferably a powder coating. The functional layer comprises, in particular, an electrically insulating powder. Suitable materials for the electrically insulating powder are electrically insulating solids that are preferably stable up to at least 1250°C in a water atmosphere and do not melt. In a hydrogen atmosphere, a significant reduction of aluminum oxide by a mass fraction of a maximum of 20% only occurs above 1300°C. At a heat treatment temperature of 1250°C, a maximum of 7% of the aluminum oxide is reduced. Silicon oxide (SiO2) and mullite (Al (4+2x) Si (2-2x) O (10-x) with x = 0.17 to x = 0.59) are stable in a strongly reducing water atmosphere up to 1250°C and do not melt, so they are also suitable as electrically insulating solids.

[0021] The functional layer preferably comprises a carrier foil. The carrier foil is preferably made of aluminum. A powder containing the alloying element and / or insulating material is preferably applied to the carrier foil. The functional layer is advantageously applied by inserting the carrier foil between two adjacent sheet metal laminations during stacking of the sheet metal laminations.

[0022] Preferably, the sheet metal lamination blanks have punched areas. These punched areas are intended for subsequent blanking, whereby the punched areas are not formed during the forming step. Thus, blanking can be performed without creating thickened portions and depressions, making the blanking process easier.

[0023] This allows for the cost-effective production of laminated cores with advantageous properties. This makes it particularly possible to economically realize very powerful electric motors, for example, for electric vehicles, electric bicycles, or hybrid drives. Short description of the drawings

[0024] Embodiments of the invention are described in detail below with reference to the accompanying drawings. In the drawing: Fig. 1a to 1e show a schematic representation of the production of a laminated core according to an embodiment of the invention. Embodiments of the invention

[0025] Fig. 1a to 1e show the sequence of a manufacturing method for a laminated core 1 according to an embodiment of the invention. This is carried out with the following steps: First, uncoated sheet metal lamella blanks 2 are provided ( Fig. 1a). The sheet metal lamella blanks are made of a deep-drawing steel, for example, with one of the grades DC01 to DC07. This is followed by cold forming 100 of the sheet metal lamella blanks 2 in a forming tool. The cold forming 100 is, in particular, an extrusion in an extrusion tool. In this way, sheet metal lamellas 3 are produced by stamping a concentric wave contour with annular thickenings 4 and annular depressions 5 located therebetween on a top side 3a and bottom side 3b of the sheet metal lamella blanks 2, which in Fig. 1b. Alternatively or additionally, sheet metal lamellae 3 are produced by embossing a radial wave contour with radial thickenings 4 and intermediate radial depressions 5 on a top side 3a and bottom side 3b of the sheet metal lamella blanks 2.

[0026] For example, the sheet metal lamella blanks 2 have an initial thickness d0 of at least 0.3 mm, preferably at least 0.4 mm. After cold forming 100, a first thickness d1 of the thickened portions 4 is greater than a second thickness d2 of the recesses 5.

[0027] In addition, a functional layer 6 is applied 200 to the top side 3a and / or bottom side 3b of the sheet metal laminations 3, which Fig. 1c. The functional layer 6 comprises an electrically insulating material, in particular aluminum oxide and / or silicon oxide, and at least one alloying element 8 for alloying the sheet metal laminations 3, in particular aluminum or silicon. The functional layer 6 is applied either as a separate layer or as an applied coating.

[0028] The functional layer 6 is, for example, a powder coating or a carrier foil made of aluminum. Particularly advantageously, a powder containing the alloying element 8 and / or insulating material is applied to the carrier foil.

[0029] The sheet metal lamination blanks 2 preferably have punching areas 7 in which a punching operation takes place. These punching areas 7 are not formed in the cold forming step 100.

[0030] Furthermore, a stacking 300 of the sheet metal laminations 3 with the applied functional layer 6 takes place. The stacking 300 is advantageously made possible because the thickenings 4 and the depressions 5 interlock. The thickenings 4 and the depressions 5 of the same sheet metal lamination 3 form a, for example, concentric, wave contour on an upper side 3a and / or underside 3b of the sheet metal lamination 3. The thickenings 4 represent a positive contour and the depressions 5 a negative contour, wherein the positive contour and the negative contour are designed to correspond. If the sheet metal laminations 3 are stacked, the, for example, annular, thickenings 4 of the sheet metal laminations 3 extend correspondingly into, for example, annular, depressions 5 of adjacent sheet metal laminations 3. In particular, there is no hollow space between adjacent sheet metal laminations 3. The stacked sheet metal laminations 3 are in Fig. 1d shown.

[0031] Preferably, a stack axis 500 is provided. The thickened portions 4 and the recesses 5 are either annular and arranged concentrically around the stack axis 500 or radial and arranged radially around the stack axis 500. In this case, adjacent laminations 3 are offset from one another with respect to the stack axis 500.

[0032] Finally, a heat treatment 400 of the stacked laminations 3 is carried out, whereby the alloying element 8 of the functional layers 6 diffuses into the laminations 3 and the insulation material between the laminations 3 forms an electrical insulation layer 9. The laminated core 1 produced in this way is in Fig. 1e shown.

[0033] The inward diffusion reduces the electrical conductivity of the outer regions of the sheet metal laminations 3. Cold forming 100 results in the formation of an electrically insulating area, particularly at the recesses 5, since inward diffusion occurs from both sides of the sheet metal lamination, with little or no electrically conductive material remaining due to the reduced thickness d2.

Claims

[1] Laminated core (1) of an electrical machine, which is formed from a plurality of laminations (3), wherein the laminations (3) are made of a steel and have an insulating coating, characterized by that annular thickenings (4) and intermediate annular depressions (5) or radial thickenings (4) and intermediate radial depressions (5) are formed in the sheet metal lamellae (3). [2] Laminated core (1) according to claim 1, characterized by that the annular thickenings (4) and the annular depressions (5) of the same lamination (3) are arranged concentrically with respect to a package axis (500) of the lamination (1) and / or the radial thickenings (4) and the radial depressions (5) of the same lamination (3) are arranged radially with respect to a package axis (500) of the lamination (1). [3] Laminated core (1) according to one of the preceding claims characterized bythat the thickenings (4) and the depressions (5) of the same sheet metal lamella (3) form a wave contour, in particular a concentric wave contour, on an upper side (3a) and / or underside (3b) of the sheet metal lamella (3). [4] Laminated core (1) according to one of the preceding claims, characterized by that the thickenings (4) form a positive contour and the depressions (5) form a negative contour, wherein the positive contour and the negative contour are formed correspondingly. [5] Laminated core (1) according to one of the preceding claims, characterized by that the thickenings (4) of the sheet metal lamellae (3) extend correspondingly into depressions (5) of adjacent sheet metal lamellae (3), wherein in particular there is no hollow space between adjacent sheet metal lamellae (3). [6] Laminated core (1) according to one of the preceding claims, characterized by that the thickenings (4) of adjacent sheet metal laminations (3) are offset from one another with respect to the package axis (500). [7] Laminated core (1) according to one of the preceding claims, characterized by that the sheet metal lamellae (3) are made of a cold-formable steel, in particular deep-drawing steel, which in particular has one of the grades DC01 to DC07. [8] Laminated core (1) according to one of the preceding claims, characterized by that at least several of the sheet metal laminations (3) are each alloyed on an upper side (3a) and / or lower side (3b) by diffusing in at least one alloying element (8), in particular aluminum or silicon. [9] Method for producing a laminated core (1) of an electrical machine, comprising the steps: a) Providing uncoated sheet metal lamella blanks (2), in particular made of deep-drawing steel, b) cold forming (100), in particular extrusion, of the sheet metal lamella blanks (2) in a forming tool, in particular extrusion tool, for producing sheet metal lamellas (3) by impressing a concentric wave contour with annular thickenings (4) and annular depressions (5) therebetween on an upper side (3a) and underside (3b) of the sheet metal lamella blanks (2) or a radial wave contour with radial thickenings (4) and radial depressions (5) therebetween on an upper side (3a) and underside (3b) of the sheet metal lamella blanks (2), c) applying (200) a functional layer (6), in particular as a separate layer or applied coating, to the upper side (3a) and / or underside (3b) of the sheet metal laminations (3), wherein the functional layer (6) comprises an electrically insulating insulation material, in particular aluminum oxide and / or silicon oxide, and at least one alloying element (8) for alloying the sheet metal laminations (3), in particular aluminum or silicon, d) stacking (300) the sheet metal laminations (3) with the applied functional layer (6), and e) producing the laminated core (1) by carrying out a heat treatment (400) of the stacked laminations (3), wherein the alloying element (8) of the functional layers (6) diffuses into the laminations (3) and the insulation material forms an electrical insulation layer (9) between the laminations (3). [10] Method according to one of the preceding claims, characterized bythat the functional layer (6) is a powder coating. [11] Method according to one of the preceding claims, characterized by in that the functional layer (6) comprises a carrier foil, in particular made of aluminum, wherein a powder with the alloying element (8) and / or insulating material and a binder is applied to the carrier foil, and wherein the application (200) of the coating (6) takes place by inserting the carrier foil between two adjacent sheet metal laminations (3) during the stacking (300) of the sheet metal laminations (3). [12] Method according to one of the preceding claims, characterized by that the sheet metal lamella blank (2) has punching areas (7) in which punching takes place, wherein in the cold forming step (100) the punching areas are not formed.

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