Electrical sheet for an electrical machine with improved closure structure of an open recess and manufacturing method thereof

Abstract

An electrical steel sheet (11, 11a, 11b, 14) for an electrical machine (1) is specified, comprising a basic shape (15, 15a, 15b) made of a first metallic material, wherein the basic shape (15, 15a, 15b) has a ring structure with recesses (16) arranged therein, which are open towards an inner edge (B) or outer edge (C) of the ring structure. Furthermore, the electrical steel sheet (11, 11a, 11b, 14) comprises a closure structure (17a, 17b) made of a second metallic material that differs from the first metallic material, wherein the closure structure (17a, 17b) is arranged at an opening (D) of the recess (16) and closes it. The closure structure (17a, 17b) is produced using a metal printing process. Furthermore, a laminated core (10, 13) with such an electrical steel sheet (11, 11a, 11b, 14), an electrical machine (1) with such a laminated core (10, 13) and a vehicle (18) with such an electrical machine (1) are specified.Finally, a manufacturing process for such a . Electrical sheet (11, 11a, 11b, 14) is specified.

Description

TECHNICAL FIELDThe invention relates to an electric sheet for an electric machine, which comprises a basic shape made of a first metallic material, wherein the basic shape has a ring structure with recesses arranged therein, which are open towards an inner edge or outer edge of the ring structure. Furthermore, the electric machine comprises a closure structure made of a second metallic material, which differs from the first metallic material, wherein the closure structure is arranged at an opening of the recess and closes it. This means that the closure structure connects the basic shape of the electric sheet in the region of the opening. The invention also relates to a laminated core for a stator or rotor of an electric machine, which has a plurality of laminations of the above-mentioned type stacked on one another along an axis, to an electric machine having such a laminated core, and to a vehicle having such an electric machine. Finally, the invention also relates to a method for producing an electric sheet of the stated type.PRIOR ARTThe aforementioned electric sheet, a laminated core, an electric machine, a vehicle and a production method of the aforementioned type are fundamentally known from the prior art. In this case, the individual electrical laminations are first produced, which are stacked one above the other in a subsequent step to form a laminated core for a stator or rotor. The basic shape of the electrical sheets gives rise to the following problems:The mechanical rigidity of the electric sheet or of the laminated core is relatively low because of the recesses, as a result of which oscillations and noise problems can occur during operation of the electric machine.Harmonics in the magnetic conductivity are generated by the recesses. This causes magnetic losses, which reduce the efficiency of the electric machine. In addition, the harmonics in the magnetic conductivity also cause harmonics in the torque generated by the electric machine. As a result, the running behavior of the electric machine is also not optimum.The wave voltage in the rotor shaft caused by the capacitance of the stator winding is comparatively high.Strong air vortices are produced through the recesses, as a result of which aerodynamic friction losses are caused.DISCLOSURE OF THE INVENTIONIt is therefore an object of the invention to specify an improved electric sheet, an improved laminated core, an improved electric machine, an improved vehicle and an improved production method for an electric sheet. In particular, the above-mentioned disadvantages are to be overcome.The object of the invention is achieved with an electric sheet of the type mentioned at the beginning, in which the closure structure is produced by a metal printing method. The electric sheet can be designed as a stator sheet or as a rotor sheet.Furthermore, the object of the invention is achieved by a laminated core for a stator or rotor of an electric machine, wherein the laminated core has a plurality of electric laminations of the aforementioned type stacked on one another along an axis.In addition, the object of the invention is achieved by an electric machine having a stator and a rotor rotatably arranged therein, wherein the stator has a laminated core with stacked stator laminations of the above-mentioned type and / or the rotor has a laminated core with stacked rotor laminations of the above-mentioned type. In slots which are formed in a laminated core for a stator by the recesses lying one above the other, stator windings can be arranged. Furthermore, rotor windings can be arranged in slots which are formed in a laminated core for a rotor by the recesses lying one above the other.In addition, the object of the invention is achieved by a vehicle which has an electric machine of the abovementioned type which is provided for driving the vehicle.Finally, the object of the invention is achieved by a method for producing an electric sheet for an electric machine, which method comprises the following steps:providing a basic shape made of a first metallic material, wherein the basic shape has a ring structure with recesses arranged therein, which recesses are open toward an inner edge or outer edge of the ring structure, andproducing a closure structure from a second metallic material, which differs from the first metallic material, wherein the closure structure is produced at an opening of the recess with the aid of a metal printing method, and wherein the closure structure closes the opening after printing.The proposed measures overcome the disadvantages mentioned at the beginning. Among other things, the following advantages are achieved:The mechanical rigidity of the electric sheet or of the laminated core is significantly increased by the closure structure, as a result of which oscillations and noise during operation of the electric machine are significantly reduced.The closing structure reduces the magnetic losses. This improves the efficiency of the electric machine compared to the prior art. In addition, during operation of the electric machine, comparatively few harmonics in the magnetic conductivity and thus also a few harmonics are caused in the torque generated by the electric machine. As a result, the running behavior of the electric machine is also improved compared to the prior art.Compared to the conventional design, the wave voltage in the rotor shaft is reduced. This is because the capacitance of the stator winding to the rotor is shielded by a closed metallic surface.Due to the smooth inner surface of the laminated core, fewer air vortices are produced, as a result of which aerodynamic friction losses are reduced.Overall, the efficiency and the running behavior of the electric machine can be significantly improved by the proposed closure structure.With the aid of the metal printing process, particularly fine closure structures can be produced without the basic shape of the electrical sheet being deformed in the process, because practically no internal mechanical stresses are induced in the basic shape during the printing process. Furthermore, with the metal printing method, different metallic materials can be applied in a narrow space and mechanically connected to one another. Consequently, the closure structure can be designed to be very differentiated with regard to shape and material in order to achieve the mentioned advantages.It is noted at this point that the term "ring structure" does not mean that its outer contour or inner contour must be circular. It is sufficient if the outer contour or inner contour forms a ring with a general shape, or if the outer contour or inner contour forms a circular shape on average.It is also noted that the proposed measures are equally suitable for internal rotor machines and for external rotor machines. The following embodiments are therefore in particular conceivable:The closure structure is arranged radially on the inside of the stator in the case of an internal rotor machine.The closure structure is arranged radially on the outside of the rotor in the case of an internal rotor machine.The closure structure is arranged radially on the outside of the stator in the case of an external rotor machine.The closure structure is arranged radially on the inside of the rotor in the case of an external rotor machine.Further advantageous embodiments and developments of the invention are evident from the dependent claims and from the description taken together with the figures.It is advantageous ifthe first metallic material has a magnetic conductivity of μ R ≥20 (and is therefore magnetic), andthe second metallic material has a magnetic conductivity in a range of 1.1<μ R ≤10 (weakly magnetic) or a magnetic conductivity of 1.0≤μ R ≤1.1 (non-magnetic).As a result, the above-mentioned advantages, in particular with regard to the magnetic losses and, as a result, with regard to the efficiency and the running behavior of the electric machine, can be achieved particularly well. For this purpose, the magnetic conductivity of a weakly magnetic material may preferably be in a range of 1.1<μ R ≤5.By shaping the electric sheet in the region toward the opening of the recess, and by selecting a matching second metallic material for the closure structure, the profile of the magnetic conductivity or the air gap conductance can be advantageously influenced.In this context, it is particularly advantageous if a contour of the electric sheet is tapering towards the opening of the recess and the second metallic material has a magnetic conductivity of 1.0≤μ R≤1.1 (non-magnetic). The course of the magnetic conductivity then corresponds substantially to that of the prior art, but the closed openings are mechanically more rigid. This results in better vibration behavior and a reduction in disturbing noises.Alternatively, it is also particularly advantageous if a contour of the electric sheet is formed to be wide (or blunt) towards the opening of the recess and the second metallic material has a magnetic conductivity in a range of 1.1<μ R ≤10 (weakly magnetic). For this purpose, the magnetic conductivity of a weakly magnetic material can preferably again be in a range of 1.1<μ R ≤5. The course of the magnetic conductivity is superimposed with wide but flat gaps. The mechanical stability is again improved compared to the prior art. The average value of the air gap conductance is substantially equal to that of the aforementioned solution, and particularly few harmonics are caused. As a result, the above-mentioned advantages, in particular with regard to the magnetic losses and, as a result, with regard to the efficiency and the running behavior of the electric machine, again become very significant.The basic shape of the electric sheet can be stamped or cut with a laser, for example. However, it is also advantageous if the basic shape is produced using a metal printing method, in particular using the same metal printing method as the closure structure. With the aid of the metal printing process, particularly fine structures can be produced in the basic shape of the electrical sheet without deformations or internal mechanical stresses building up in the process. Consequently, the basic structure can also be designed to be very differentiated with regard to shape and material in order to achieve the mentioned advantages.In a preferred embodiment, a metal screen printing method can be provided as the metal printing method. This method has been found to be particularly suitable for the production of an electric sheet.The metal printing process can be carried out with a homogeneous base material comprising only grains of the same metal alloy. However, it is also conceivable for the metal printing process to be carried out with an inhomogeneous base material which has grains of different metals and / or metal alloys. Accordingly, the closure structure of the electric sheet and optionally the basic shape of the electric sheet can consist of a homogeneous base material which only comprises grains of the same metal alloy, or of an inhomogeneous base material which comprises grains of different metals and / or metal alloys.The non-magnetic material can be, in particular, a stainless steel. The light magnetic material may be, for example, a mixture of a stainless steel and a powder mainly containing iron and some phosphorus. As a result, the rigidity of the electric sheet can be increased.Generally, the electrical sheet may be heated after printing for a sintering operation to permanently bond the printed components and to ensure stability of the electrical sheet.At these points it is noted that the embodiments mentioned with respect to the electric sheet and the advantages resulting therefrom can also be applied analogously to the presented method and vice versa.BRIEF DESCRIPTION OF THE FIGURESExemplary embodiments of the invention are illustrated by way of example in the appended schematic figures. The following are shown: FIG. 1 shows an exemplary electric machine schematically illustrated in half section; FIG. 2 shows an exemplary basic shape of a stator lamination in a front view; FIG. 3 shows a first exemplary embodiment of a closure structure in detailed view; FIG. 4 shows a second exemplary embodiment of a closure structure in a detailed view, and FIG. 5 shows an exemplary vehicle having an electric machine of the proposed type.DETAILED DESCRIPTION OF THE INVENTIONIt is stated by way of introduction that identical parts are provided with identical reference symbols or identical component names in the different embodiments, optionally with different indices. The disclosure of a component contained in the description can be transferred analogously to another component with the same reference sign or the same component designation. The position information selected in the description, such as for example "top", "bottom", "rear", "front", "lateral" and so forth, also relate to the directly described and illustrated figure and, in the event of a position change, are to be transferred analogously to the new position.FIG. 1 shows a half section through a schematically illustrated electric machine 1. the electric machine 1 comprises a rotor shaft 2 and a rotor 3 mounted thereon, wherein the rotor shaft 2 is rotatably mounted about a rotor axis or stator axis A with the aid of (rolling) bearings 4 a, 4 b. The electric machine 1 also comprises a stator 5, in which the rotor 3 is arranged. In addition, the electric machine 1 comprises a (first or front) bearing shield 6, a (second or rear) bearing shield 7 and a stator housing 8, which together form the machine housing 9 or are at least surrounded by it. The end shield 6 accommodates the bearing 4 a, the end shield 7 accommodates the bearing 5 b, and the stator case 8 accommodates the stator 5.The stator 5 comprises in detail a stator laminated core 10 with a plurality of stator laminations 11 axially stacked one on top of the other and optional stator windings 12 arranged in the stator laminated core 10. The rotor 5 comprises in detail a laminated rotor core 13 having a plurality of axially stacked laminated rotor sheets 14 and optional rotor windings or rotor magnets (not shown in FIG. 1 ) arranged in the laminated rotor core 13. In general, the stator laminations 11 and the rotor laminations 14 are electrical laminations 11, 14, and the stator lamination stack 10 and the rotor lamination stack 13 are generally lamination stacks 10, 13.FIG. 2 shows an electric sheet or stator sheet 11 in a front view. The stator lamination 11 comprises a basic shape made of a first metallic material, wherein the basic shape 15 has a ring structure with recesses 16 arranged therein, which in this example are open towards an inner edge B of the ring structure. The recesses 16 are closed with a closure structure 17 a, 17 bmade of a second metallic material, which is different from the first metallic material. Specifically, the closure structure 17 a, 17 bis arranged at the opening D of the recess 16 and closes it (see FIGS. 3 and 4 ).In general, the closure structure 17 a, 17 bis produced by a metal printing method, wherein the first metallic material has in particular a magnetic conductivity of μ R ≥20 and is therefore magnetic, and wherein the second metallic material has in particular a magnetic conductivity in a range of 1.1<μ R ≤10 and is therefore weakly magnetic or in particular has a magnetic conductivity of 1.0≤μ R ≤1.1 and is therefore non-magnetic. In the case of weakly magnetic materials, a value for the magnetic conductivity in a range of 1.1<μ R ≤5 can further preferably be provided.FIG. 3 now shows a detail view of a first example of an electric sheet or stator sheet 11 ain a front view. A contour of the electric sheet 11 ais in this case formed to be wide or blunt towards the opening D of the recess 16, and the second metallic material of the closure structure 17 ahas a magnetic conductivity in a range of 1.1<μ R ≤10 (weakly magnetic). Preferably, a value for the magnetic conductivity in a range of 1.1<μ R ≤5 can also be provided.FIG. 3 also shows the course of the magnetic conductivity P over the rotation angle φ. As can be seen from FIG. 3, in this embodiment a substantially trapezoidal course of the magnetic conductivity P results. The provision of the closure structure 17 aprovide some advantages, namely, among other things:The mechanical rigidity of the stator lamination 11a or of the stator lamination stack 10 is significantly increased.Oscillations and noise during the operation of the electric machine 1 are significantly reduced.The weak magnetic material causes lower losses than without a closure structure 17 a. The average value of the air gap conductance is high and comparatively few harmonics are caused in the magnetic conductivity P and thus in the currents absorbed by the electric machine 1.The wave voltage is reduced compared to stator laminations 11 aand stator lamination stacks 10 without a closure structure 17 a. This is because the capacitance of the stator winding 12 to the rotor 3 is shielded by a closed metallic surface.Due to the smooth inner surface of the stator laminated core 10, fewer air vortices are produced, as a result of which aerodynamic friction losses are reduced.Overall, the efficiency and the running behavior of the electric machine 1 can be significantly improved by the closure structure 17 a.FIG. 4 shows an alternative embodiment of an electric sheet or stator sheet 11 b, in which a contour of the electric sheet 11 tapers towards the opening D of the recess 16 and in which the second metallic material of the closure structure 17 bhas a magnetic conductivity of 1.0≤μ R≤1.1 (non-magnetic). The course of the magnetic conductivity P substantially corresponds to that of the prior art. In comparison with FIG. 3, the gaps are narrower but deeper in the course of the magnetic conductivity P. The average value of the air gap conductance, which is drawn in dashed lines in FIGS. 3 and 4 in each case, is substantially the same, but more harmonics are generated in the magnetic conductivity P, and there are more harmonics in the torque generated by the electric machine. The advantages mentioned above with respect to rigidity, bearing currents and air turbulences apply analogously, the magnetic losses are not improved or are only improved to a slight extent compared to the prior art.In the examples shown so far, the electric machine 1 is designed as an internal rotor machine, and the closure structure 17 a, 17 bis arranged on the inside of the stator lamination 11, 11 a, 11 b. However, this is by no means the only possible application of the closure structure 17 a, 17 b. Rather, the basic shape 15, 15 a, 15 bmay have a ring structure with recesses 16 arranged therein, which are open towards the outer edge C of the ring structure. In summary, the following embodiments are in particular conceivable:The closure structure 17 a, 17 bis arranged radially on the inside of the stator 5 in the case of an internal rotor machine (as illustrated in the figures).The closure structure 17 a, 17 bis arranged radially on the outside of the rotor 3 in the case of an internal rotor machine.The closure structure 17 a, 17 bis arranged radially on the outside of the stator 5 in the case of an external rotor machine.The closure structure 17a, 17b is arranged radially on the inside of the rotor 3 in the case of an external rotor machine (similar to that shown in FIGS. 2 to 4).The proposed measures can furthermore be provided within an electric machine 1 both on the rotor 3 and on the stator 5.In the slots which are formed in a laminated core 10 for a stator 5 by the recesses 16 lying one above the other, stator windings 12 can be arranged. Alternatively or additionally, rotor windings can be arranged in the grooves which are formed in a laminated core 13 for a rotor 3 by the recesses 16 lying one above the other.A method for producing an electric sheet 11, 11 a, 11 b, 14 for an electric machine 1 can now have the following steps:providing the basic shape 15, 15 a, 15 bfrom a first metallic material, wherein the basic shape 15, 15 a, 15 bhas a ring structure with recesses 16 arranged therein, which are open toward an inner edge B or outer edge C of the ring structure,producing the closure structure 17 a, 17 bfrom a second metallic material, which differs from the first metallic material, wherein the closure structure 17 a, 17 bis produced at an opening D of the recess 16 with the aid of a metal printing method, and wherein the closure structure 17 a, 17 blos the opening D after printing.The basic shape 15, 15 a, 15 bmay be stamped or cut out with a laser, for example. However, it is also conceivable in particular for the basic shape 15, 15 a, 15 bto be produced using a metal printing method, in particular using the same metal printing method as the closure structure 17 a, 17 b.In a preferred embodiment, a metal screen printing method can be provided as the metal printing method. This method has proven to be particularly suitable for the production of an electric sheet 11, 11 a, 11 b, 14.The metal printing process can be carried out with a homogeneous base material comprising only grains of the same metal alloy. However, it is also conceivable for the metal printing process to be carried out with an inhomogeneous base material which has grains of different metals and / or metal alloy.The non-magnetic material can be, in particular, a stainless steel. The light magnetic material may be, for example, a mixture of a stainless steel and a powder mainly containing iron and some phosphorus. As a result, the rigidity of the electric sheet 11, 11 a, 11 b, 14 can be increased.Generally, the electric sheet 11, 11 a, 11 b, 14 may be heated after printing for sintering to permanently bond the printed components to each other and to ensure the stability of the electric sheet 11, 11 a, 11 b, 14.FIG. 5 finally shows the electric machine 1 installed in a vehicle 18. Specifically, the electric machine 1 is connected via an optional transmission 19 to the half axles 20 of the rear axle or front axle. Finally, the driven wheels 21 are mounted on the half axles 20. The electric machine 1, the transmission 19 and the half axles 20 are part of the drive train of the vehicle 18 in this case. the drive of the vehicle 18 is effected at least partially or temporarily by the electric machine 1. that is, the electric machine 1 can serve for the sole drive of the vehicle 18 or be provided, for example, in combination with an internal combustion engine (hybrid drive).Finally, it is to be noted that the scope of protection is defined by the claims. However, the specification and drawings are to be used to interpret the claims. The features contained in the figures can be interchanged and combined with one another as desired. In particular, it is also noted that the devices shown can also comprise more or fewer components than those shown in reality. In some cases, the devices shown or their components can also be shown in an unscaled and / or enlarged and / or reduced form.List of reference characters1 Electric machine 2 Rotor shaft 3 Rotor 4 a, 4 bMount 5 Stator 6 First bearing plate 7 Second bearing plate 8 Stator housing 9 Machine housing 10 Laminated core (Stator laminated core) 11, 11 a, 11 bElectric sheet (Stator laminated core) 12 Stator winding 13 Laminated core (Rotor laminated core) 14 Electric sheet (Rotor laminated core) 15, 15 a, 15 b Grundform shape 16 Recess 17 a, 17 b Verschluss structure 18 Vehicle 19 Transmission 20 Half axis 21 Wheel A Axis (Rotor axis / Stator axis) B Inner edge of the ring structure C Outer edge of the ring structure D Opening P Magnetic conductivity φ Angle of rotation

Claims

Electric sheet (11, 11a, 11b, 14) for an electric machine (1), comprising - a basic shape (15, 15a, 15b) made of a first metallic material, wherein the basic shape (15, 15a, 15b) has a ring structure with recesses (16) arranged therein, which recesses are open towards an inner edge (B) or outer edge (C) of the ring structure, and - a closure structure (17a, 17b) made of a second metallic material, which differs from the first metallic material, wherein the closure structure (17a, 17b) is arranged at an opening (D) of the recess (16) and closes it, characterized in that - the closure structure (17a, 17b) is produced using a metal printing method.Electric sheet (11, 11a, 11b, 14) according to Claim 1, characterized in that - the first metallic material has a magnetic conductivity of μ R ≥ 20, and - the second metallic material has a magnetic conductivity in a range of 1.1 < μ R ≤ 10 or a magnetic conductivity of 1.0 ≤ μ R ≤ 1.1.Electric sheet (11, 11a, 11b, 14) according to Claim 1 or 2, characterized in that a contour of the electric sheet (11, 11a, 11b, 14) tapers to a point towards the opening (D) of the recess (16), and the second metallic material has a magnetic conductivity of 1.0 ≤ μ R ≤ 1.1.Electric sheet (11, 11a, 11b, 14) according to Claim 1 or 2, characterized in that a contour of the electric sheet (11, 11a, 11b, 14) is formed so as to be broad towards the opening (D) of the recess (16), and the second metallic material has a magnetic conductivity in a range of 1.1 < μ R ≤ 10.Electric sheet (11, 11a, 11b, 14) according to one of Claims 1 to 4, characterized in that it is designed as a stator sheet (11) or as a rotor sheet (14).Laminated core (10, 13) for a stator (5) or rotor (3) of an electric machine (1), characterized bya plurality of electric laminations (11, 11a, 11b, 14) according to one of Claims 1 to 5 stacked one on top of the other along an axis (A).Laminated core (10, 13) according to Claim 6, characterized in that - stator windings (12) are arranged in slots which are formed in a laminated core (10) for a stator (5) by the recesses (16) lying one above the other, or - rotor windings are arranged in slots which are formed in a laminated core (13) for a rotor (3) by the recesses (16) lying one above the other.Electric machine (1) having a stator (5) and a rotor (3) rotatably arranged therein, characterized in that - the stator (5) has a laminated core (10) according to Claim 6 or 7 with stator laminations (11) according to Claim 5 stacked one on top of the other, and / or - the rotor (3) has a laminated core (13) according to Claim 6 or 7 with rotor laminations (14) according to Claim 5 stacked one on top of the other.Vehicle (18), characterized byan electric machine (1) according to Claim 8, which is provided for driving the vehicle (18).Method for producing an electrical sheet (11, 11a, 11b, 14) for an electrical machine (1), comprising the steps of - providing a basic shape (15, 15a, 15b) made of a first metallic material, wherein the basic shape (15, 15a, 15b) has a ring structure with recesses (16) arranged therein, which recesses are open towards an inner edge (B) or outer edge (C) of the ring structure, - producing a closure structure (17a, 17b) made of a second metallic material, which differs from the first metallic material, wherein the closure structure (17a, 17b) is produced at an opening (D) of the recess (16) with the aid of a metal printing method, and wherein the closure structure (17a, 17b) closes the opening (D) after the printing.Method according to claim 10, characterised in that the provision of the basic shape (15, 15a, 15b) comprises the production thereof by a metal printing method.Method according to Claim 10 or 11, characterized in that a metal screen printing method is provided as the metal printing method.Method according to one of Claims 10 to 12, characterized in that the basic shape (15, 15a, 15b) is produced using the same metal printing method as the closure structure (17a, 17b).Method according to any one of claims 10 to 13, characterised in that the metal printing process is carried out with a homogeneous base material which only comprises grains of the same metal alloy, or with an inhomogeneous base material which comprises grains of different metals and / or metal alloys.Method according to one of Claims 10 to 14, characterized in that the electric sheet (11, 11a, 11b, 14) is heated for a sintering operation after the printing.

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