Magnetic lamination semi-finished product, magnetic lamination, rotor for an electric machine, and electric machine

Abstract

The invention relates to a semi-finished product of a rotationally symmetrical magnetic lamination for a rotor of an electric machine, - which is composed of at least two material components, - a first material component, which comprises a magnetic material and - a second material component, which comprises a non-magnetic material, - wherein the second material component runs diametrically along an axis, a so-called d-axis, wherein at least two such d-axes are provided, - which in turn include at least four magnetic regions, which are each formed by the magnetic first material component, - which run in a concave arc relative to a magnetic lamination centre point, characterised in that - surfaces (3) radially outside of the magnetic regions are also formed by the non-magnetic material, and in that - the magnetic lamination semi-finished product is surrounded by an annularly closed region (5) made of non-magnetic material.

Description

[0001] Description

[0002] Magnetic sheet semi-finished product, magnetic sheet, rotor for an electrical machine and electrical machine

[0003] The invention relates to a magnetic sheet semi-finished product according to patent claim 1, a magnetic sheet according to patent claim 14, a rotor according to patent claim 15 and an electrical machine according to patent claim 16.

[0004] A new process for producing magnetic sheets for electrical machines is screen printing or stencil printing. This can be regarded as an additive manufacturing process. A printing paste is printed onto a substrate using a stencil, the open areas of which can also be provided with a screen. This is referred to as stencil printing or screen printing, with stencil printing being a generic term for screen printing. In addition to solvents and / or binders, the printing paste contains metal powder which has a functional role in the final component. The screen printing technique produces a green body which, after further thermal treatment, is usually first debindered and then subjected to a sintering process at a higher temperature. The metallic powder grains sinter together to create a structured sheet, the magnetic sheet.

[0005] In order to achieve greater mechanical strength in such sheets, particularly at high speeds of rotors in electrical machines, the manufacturability of two-component magnetic sheets is becoming increasingly important. An example of this is described in EP 3 932 591 A1. A fundamental problem with such two-component magnetic sheets, which are produced using the stencil printing process, is that the different materials, even if they have good magnetic properties and high strength, usually have different thermal expansion coefficients. For example, high-strength steel, which is a component of the mechanical strength of the magnetic sheet, has an expansion coefficient of 16 x 10 -6 K -1. Another soft magnetic low-alloy steel has a thermal expansion coefficient between 10 - 12 x IO in a temperature range between 0 and 100 ° C. -6 K -1 When such different material components or material pairs are sintered together in a green body to form a magnetic sheet, these different thermal expansion coefficients lead to the formation of high mechanical stresses in the connection or seam areas between these material components, particularly during cooling from the sintering temperatures to room temperature. This can lead to warping or cracks, or overall mechanical stresses in the magnetic sheet, which can significantly impair the mechanical or magnetic properties.

[0006] A typical electrical machine in the form of a reluctance motor, in which the rotor is constructed from single-component magnetic sheets, is described in EP 2 790 296 A1. Such constructions always represent a material compromise between high strength and good magnetic properties of the magnetic sheet material. In particular, however, magnetic stray fluxes always occur between the individual magnetic poles, which reduce the motor's performance.

[0007] The object of the invention is to provide a semi-finished product for a magnetic sheet and a magnetic sheet, as well as a rotor for an electrical machine and an electrical machine, in which the magnetic sheet semi-finished product (so-called laminated core) and the magnetic sheet have a higher strength and fewer intrinsic stresses, in particular at the boundary lines of the materials and in the stack, compared to the prior art when at least two material components are used within the magnetic sheet.

[0008] The solution to the problem consists in a magnetic sheet semi-finished product according to patent claim 1, a magnetic sheet according to patent claim 14, a rotor according to patent claim 15 and an electrical machine according to patent claim 16.

[0009] The semi-finished product of a rotationally symmetrical magnetic sheet according to patent claim 1 for a rotor of an electrical machine comprises at least two material components, wherein a first material component comprises a magnetic material and a second material component comprises a non-magnetic material. In a plan view of a topography of the magnetic sheet, the second material component runs diametrically opposite an axis which runs radially through the center point of the rotationally symmetrical semi-finished product and which is also referred to as the d-axis in the electrical engineering description of electrical machines, and wherein at least two of these d-axes are provided. These two d-axes are arranged such that at least four magnetic regions run between them. These magnetic regions are in turn formed by the magnetic first material component.The magnetic regions are designed to extend in a concave arc with respect to the center of the magnetic sheet. The magnetic sheet semi-finished product is characterized by the fact that surfaces radially outside the magnetic regions are also formed of the non-magnetic material, and that the magnetic sheet semi-finished product is surrounded by a closed, ring-shaped region of non-magnetic material.

[0010] The advantage over a conventional, at least two-component magnetic sheet from the prior art is that, in particular, the ring-shaped, closed region of the semi-finished product creates a clamping effect for the entire rotationally symmetrical semi-finished product during the sintering process and, above all, during the cooling process from the sintering temperature, thus exerting a bonding effect between the interfaces between the individual material components. The described adverse effect of the different expansion coefficients of the two material components is minimized by the clamping, ring-shaped, closed region.The special clamping effect of the ring-shaped, closed area is further supported by the fact that the surfaces lying radially outside the magnetic areas are also made of the non-magnetic material, meaning that the rotationally symmetrical semi-finished product of a magnetic sheet is completely filled in a circle. If, as is usual in the prior art, there were lens-shaped recesses that formed the concave image of the magnetic areas, the ring-shaped area would only be able to inadequately fill its clamping effect. Furthermore, these lens-shaped, radially outer areas result in lower air resistance during the rotation of a rotor (which is constructed from the magnetic sheets or magnetic sheet semi-finished products and is part of patent claim 15), which in turn reduces the rotational resistance of the rotor and also contributes to a certain reduction in noise.

[0011] With regard to patent claim 1, reference is made to a semi-finished product because the ring-shaped, closed region has the described clamping effect during production of the magnetic sheet. However, this is not a functional component of the magnetic sheet. This ring-shaped, closed region must be removed when the large number of magnetic sheets are assembled to form a laminated core, which in turn is a component of the rotor. This closed region can be removed from the semi-finished product, for example, by punching it out after the sintering process, so that the magnetic regions, which will later become the magnetic poles in the rotor, are exposed on the circumference of the magnetic sheet. The ring-shaped, closed region can also be separated off after the individual semi-finished products have been stacked to form a laminated core and after they have been connected to the shaft to form a rotor, by turning it off together for the entire number of semi-finished products.This transition from a magnetic sheet semi-finished product to a magnetic sheet is part of the invention according to patent claim 14.

[0012] The terms used in the claims are defined as follows: The magnetic sheet is, as already mentioned, a flat structure which is produced very thinly by an additive process, in particular a screen or stencil printing process or also by a tape casting process. It usually has a thickness of between 80 pm and 200 pm. The d-axis referred to for this purpose therefore runs through the center of the flat surface of the magnetic sheet. The magnetic sheet described is made up of at least two material components, the first material component comprising a magnetic material, in particular a soft magnetic material. A soft magnetic material is characterized in that elementary magnetization processes as well as wall displacements and rotation processes of the individual domains and grains take place easily and uninhibited. This means that the magnetic material can be easily magnetized and demagnetized.This contrasts with hard magnetic materials, which are characterized by a high coercive field strength and a pronounced hysteresis loop. Soft magnetic materials, which can maintain or change their polarization even with low magnetic fields, are particularly advantageous in the rotors of reluctance motors that do not have additional windings or permanent magnets.

[0013] Non-magnetic or amagnetic materials are, in particular, materials that are not ferromagnetic. They can be paramagnetic or diamagnetic. To define this parameter, particularly in steels, it has proven advantageous for the saturation magnetization of the non-magnetic or amagnetic material of the second material component to be less than 10% of the saturation magnetization of the magnetic material of the first material component. In particular, it should not be more than 5% of the saturation magnetization of the first material component.

[0014] The boundary between the two material components appears as a line when looking at the magnetic sheet from above and is therefore referred to as the boundary line. The height of the boundary line corresponds to the height of the magnetic sheet, preferably between 80 pm and 200 pm. Due to manufacturing reasons (which will be discussed later), the boundary line is not a discrete line; rather, it is a zone in which the different material components meet and are bonded to one another as a result of diffusion-induced processes during the sintering process. The boundary line therefore has the width of a diffusion zone, which can be up to one mm depending on the materials.

[0015] The advantage of the present invention over conventional single-component magnetic sheets and the rotors or electrical machines made from them is that the non-magnetic material component minimizes the formation of stray fluxes between the individual magnetic regions along the described d-axes. Such stray fluxes always occur in conventional monomaterials, which are mainly used to form rotors according to the prior art. Although they can be reduced by design features, minimization as achieved by the described two-component structure with the non-magnetic material cannot be achieved with a monomaterial. In this case, magnetic stray fluxes are always conducted through the soft magnetic material and are unavoidable.The measure described makes it possible to significantly increase the maximum torque on the motor in electrical machines of the type described, particularly in reluctance motors.

[0016] It may be advantageous for the rotor structure, and thus the magnetic sheet and the magnetic sheet semi-finished product, to have a large number of magnetic areas. The number of magnetic areas is 2 x n of the number of axes, where n is a natural number. Thus, there is always an even number of magnetic areas, which in certain motor designs can be well over 100.

[0017] In a further embodiment of the invention, the semi-finished product has a central shaft bore, wherein the shaft bore is continuously surrounded by a non-magnetic material. This serves in particular to ensure the central strength of the magnetic material since, as will be described in more detail, the non-magnetic material has a higher mechanical strength. This measure therefore ensures high mechanical strength, particularly along the shaft bore and the rotating shaft of the rotor contained therein. This distinguishes the magnetic sheet according to the invention and the rotor resulting therefrom from a mono-material rotor as is common in the prior art.

[0018] It is common for the angle bisectors of two adjacent d-axes to be referred to as q-axes. In an advantageous embodiment, the soft magnetic regions are symmetrical to the q-axes, specifically concave to the center of the magnetic sheet or magnetic sheet semi-finished product. This geometric configuration optimally directs the magnetic flux through the magnetic region for rotational movement. The q-axes also run radially through the center of the semi-finished product.

[0019] The ring-shaped, closed regions surrounding the semi-finished product can have different thicknesses. For example, it may be appropriate for the closed regions to have a greater thickness at the intersection with the q-axes than at the intersection with the d-axes. This can be advantageous because, at certain points around the circumference of the semi-finished product, higher stresses occur due to the sintering process during cooling from the sintering temperature, and thus, higher thicknesses are required locally along the circumference of the semi-finished product.

[0020] The described annular closed region of the semi-finished product serves as a clamp, particularly during cooling from the sintering temperature, which compensates for the thermal stresses that occur through its annular force. Other thermal stresses or mechanical stresses that can occur in the magnetic sheet are stresses during operation of the magnetic sheet in its function as a component of the rotor. Temperatures of over 100 °C can also occur here, which can also cause considerable thermal stresses at boundary lines between the magnetic region of the first components and the a-magnetic region of the second component. To compensate for these thermally induced mechanical stresses, it is also expedient to provide relief recesses that are intersected by the d-axis and are symmetrical to it.This finding is based on simulation calculations that describe mechanical and thermal stresses in the area of ​​these material boundaries and that are minimized due to the described relief recesses at the material boundaries.

[0021] In a further embodiment of the invention, the first material component is an iron alloy containing at least 95 wt.%, in particular at least 97 wt.%, and most preferably at least 99 wt.% iron. Ideally, this is pure iron, since pure iron has the best ferritic or martensitic microstructure and comprises very good soft magnetic properties, which are advantageous for the respective magnetization and remagnetization in an electrical machine.

[0022] The second, non-magnetic material component comprises an iron-chromium alloy, which also represents a mechanically supporting material component. This preferably has a chromium content of between 10 wt.% and 20 wt.%, in particular between 12 wt.% and 18 wt.%. The chromium is a ferrite former, which promotes the formation of ferrite crystals upon appropriate cooling from the sintering process.

[0023] Furthermore, the alloy has a nickel content of between 4 wt.% and 10 wt.%, in particular between 6 wt.% and 8 wt.%. Nickel is a so-called austenite former, which promotes the formation of austenitic phase components on cooling. Both phase components, austenite and ferrite, are preferred components in the equilibrium of the second material component, since the described ratios prevent both mechanical strength and soft magnetic behavior. Such chromium-nickel steels, which are also known as duplex steels, have not only high tensile strength but also relatively high ductility, which is why they are particularly well suited as a load-bearing component for the magnetic sheet described.

[0024] Furthermore, in advantageous embodiments, the iron-chromium alloy comprises molybdenum in proportions between 2 wt.% and 5 wt.%, in particular between 3 wt.% and 4 wt.%. The proportion of tungsten is preferably between 0.3 wt.% and 1.2 wt.%, in particular between 0.5 wt.% and 1 wt.%. The last two alloy components, molybdenum and tungsten, contribute to the alloy's increased strength, and are also suitable for setting the desired coefficient of expansion, which is close to that of the magnetic component.

[0025] In addition to the described semi-finished product, as already described, a magnetic sheet with a separated, annularly closed region is also part of the invention. This magnetic sheet is in turn a component of a rotor of an electrical machine, wherein this magnetic sheet is stacked to form a stack of magnetic sheets. A further component of the invention is an electrical machine comprising a rotor according to claim 15, wherein, in a particular embodiment of the invention, this electrical machine is a reluctance motor.

[0026] Further embodiments and further features of the invention are explained in more detail with reference to the following figures. These are merely schematic embodiments and do not represent a limitation of the scope of protection. Features that describe the prior art and have the same designation as those used in relation to the invention are indicated with a prime.

[0027] Showing:

[0028] Figure 1 shows a schematic plan view of a two-component magnetic sheet according to the prior art, Figure 2 shows a simulation representation of occurring mechanical stresses in a two-component magnetic sheet according to the prior art,

[0029] Figure 3 shows a semi-finished product of a two-component magnetic sheet with a ring-shaped, closed area with clamping effect,

[0030] Figure 4 shows a magnetic sheet derived from the figure with relief recesses,

[0031] Figure 5 shows a magnetic sheet analogous to Figure 4 with a different design of relief recesses,

[0032] Figure 6 shows the mechanical stresses analogous to Figure 2 after the relief cutouts have been applied,

[0033] Figure 7 shows a laminated core or a magnetic sheet stack of a plurality of magnetic sheets from one of the preceding drawings,

[0034] Figure 8 shows a cross section through a rotor with a laminated core,

[0035] Figure 9 is a schematic representation of the production of a two-component magnetic sheet.

[0036] Figure 1 shows a conventional magnetic sheet 2' from the prior art. This magnetic sheet 2' is particularly suitable for a reluctance motor and has two material components: a first material component 6' and a second material component 8'. Furthermore, a shaft bore 16' is provided, which extends around a center point 14' of the rotationally symmetrical magnetic sheet 2'.

[0037] Figure 2 shows a simulation representation of mechanical

[0038] Stresses of the magnetic sheet 2 ' according to the prior art from Figure 1. The material areas 6 ' made of magnetic material and 8 ' made of non-magnetic material are shown and it can be seen that in the area of ​​the shaft bore 16 ' considerable mechanical stresses 28 ' occur which can lead to a breakage or bulging of the magnetic sheet 2 ' if the magnetic sheet 2 ' is subjected to mechanical stress during operation.

[0039] Figure 3 shows a magnetic sheet semi-finished product 1 which also has two material components: a first material component 6 and a second material component 8. The first material component 6 is a magnetic material consisting of 99% by weight iron. An iron material of this type has very good saturation magnetization with a ferritic structure and also has very good soft magnetic properties, i.e. depending on the magnetic induction from the stator of the electrical machine, the material of the first material component 6 can be easily remagnetized.

[0040] Furthermore, the magnetic sheet semi-finished product 1 comprises an amagnetic region which is present in a second material component 8. This is an iron-chromium alloy with a chromium content of 10 wt. % to 18 wt. % optionally up to 28 wt. %, which further has a nickel content of between 6 and 8 wt. %. Nickel contents below 18 wt. % have proven to be more advantageous for the sintering process. It is an austenitic stainless steel which has a particularly high level of strength. This amagnetic material component 8 is therefore present in particular along so-called d-axes 10, which in turn enclose magnetic regions 12 which comprise the first material component 6. The amagnetic regions with the second material component 8 thus form a mechanically supporting basic structure of the magnetic sheet semi-finished product 1 orof the further magnetic sheet 2, which ensures the mechanical strength of the magnetic sheet 2, particularly at high rotational speeds. A further advantage of this structural arrangement of the non-magnetic regions 8, which enclose the magnetic regions 12, is that, as already mentioned, stray fluxes through the magnetic component 6, as is inevitably the case with monomaterials, are avoided. This results in lower rotational resistance of the rotor and higher torque, which is of considerable importance in the practical application of an electrical machine. The efficiency of the electrical machine is thereby increased.

[0041] Compared to the two-component sheet according to the prior art, the magnetic sheet semi-finished product 1 according to Figure 3 has two further additional features. Firstly, regions 3 are provided which are located radially outwards with respect to the magnetic regions 12. These regions 3 are shaped such that they fill the magnetic sheet semi-finished product 1 and the later magnetic sheet 2 to form a complete circle. These regions 3 have the advantage over a magnetic sheet 2' according to the prior art that the air resistance is reduced when the later rotor 4 rotates. Secondly, they also serve as filler material for an additional, closed ring-shaped region 5 which is arranged around the entire magnetic sheet semi-finished product 1. The type of production of the magnetic sheet semi-finished product will be discussed in more detail with reference to Figure 9.The regions 3 fill any empty spaces between the magnetic regions 12 and the annular region 5 , which is why the effect of the annular region 5 is further enhanced .

[0042] The annular region 5 acts in the arrangement as illustrated in Figure 3 like a clamp, which contracts upon cooling from the sintering temperature and thus presses the individual components 6 and 8 of the magnetic sheet semi-finished product together in their surface. In this way, boundary lines 9 are also strengthened and prevent cracking, which arise in particular from the different thermal expansion coefficients of the individual material components. The annular region 5 acts similarly to a clamping ring around a wooden barrel, which is applied there heated during production and contracts upon cooling.Since the enormous thermal stresses on the boundary lines 9 are particularly high during cooling to room temperature from the sintering temperature, which is for example 900 °C, and then reach a state of equilibrium after cooling, the clamping effect of the annular region 5 is no longer necessary after cooling. The annular region 5 of the semi-finished product 1 can therefore be removed after the sintering process. It should also be removed because the magnetic regions 12 should reach the radial outer surface of the then finished magnetic sheet 2 in their end regions. This is for magnetic reasons because the non-magnetic annular region 5 would shield the magnetic flux and the induction of the magnetic regions 12. For this reason, the structure according to Figure 3 is referred to as a magnetic sheet semi-finished product 1. The structure according to Figure 4, in which the annular region 5 has now been separated, is referred to as the magnetic sheet 2.

[0043] The annular region 5 therefore only has an effect during the very high temperature change from the sintering temperature to room temperature, which is approximately 900 °C. Such temperature differences naturally do not occur during the intended use of the magnetic sheet in an electrical machine. However, temperature gradients of approximately 100 °C do occur here when the rotor is subjected to very high loads. It is therefore expedient to take further measures to relieve stresses 28 at the boundary lines 9 if necessary. Simulation calculations of the mechanical and thermal stresses 28 in the magnetic sheet 2 have shown that relief recesses 18 which lie on the d-axis and are symmetrical to it can reduce them considerably. This is shown schematically in Figure 6, which shows that the stresses 28 are significantly lower there and are more homogeneously distributed than is shown in Figure 2 according to the prior art.

[0044] Figure 6 shows the stress pattern of a magnetic sheet 2 according to Figure 5, which also has relief recesses 18 that are arranged symmetrically to the d-axis, but are designed in the form of ring segments, wherein these ring-segment-shaped relief recesses 18 lie on a circle 22 that is concentric with respect to the shaft bore 16. This concentric circle 22 ideally touches the boundary line 9 between the non-magnetic region 8 and the magnetic region 12. However, it can also be expedient to slightly enlarge or reduce this concentric circle 22 radially, so that the radial distance from the tangent situation makes up to 5% of the total radius of the magnetic sheet 2. In this range, the best results for reducing the stresses 28 at the boundary line 9 have been calculated by simulation.

[0045] Figure 7 shows the further path of the magnetic sheet 2 for assembly into a rotor 4. The magnetic sheets 2 are stacked together to form a laminated core 30, i.e. a magnetic sheet stack, wherein the interfaces between the magnetic sheets 2 (not shown here) are electrically insulated from one another by an electrical insulation layer which is, for example, sprayed onto the magnetic sheets 2. Figure 7 is a simplified three-dimensional representation which, like in Figures 4 and 5, also contains relief recesses 18 which are advantageous in this context but not absolutely necessary.

[0046] In a further step according to Figure 8, a shaft 32 is fed to the laminated core 30, wherein this illustration is a sectional view through a rotor 4 for an electrical machine. In particular, the three-dimensional illustration according to Figure 7 shows a laminated core 30 or a rotor 4 for a reluctance motor.

[0047] Conventional monomaterial magnetic sheets according to the prior art are known to be produced by punching these sheets out of a continuous sheet material, a rolled sheet. It is obvious that a magnetic sheet 2 with at least two components 6 and 8, as described in the preceding figures, cannot be produced in this form using a punching process. Therefore, a typical manufacturing process for a described magnetic sheet 2 or magnetic sheet semi-finished product 1 is discussed with reference to Figure 9.

[0048] The described magnetic sheet 2 is produced by an additive process, in particular by a stencil printing process, in particular a screen printing process. In this process, a stencil 36 with a screen is placed on a substrate 40 at stencil cutouts and a paste 42, 44 with functional metallic components and with binding agents is pressed through the stencil cutouts or through the screen (screen printing) by means of a squeegee 38. Figure 9a shows two paste components: a paste 42 with the first component and a paste 44 with the second component. The second component corresponds to the non-magnetic second material component 8 of the finished magnetic sheet 2, and the first component corresponds to the first, magnetic component 6. Figure 9a is simplified in that at least two processes are necessary to apply the pastes 42 and 44.For example, paste 42 is applied first, followed by paste 44 in a second step. For example, the substrate can be transferred from one stencil 36 to the next stencil 36, or the stencils 36 can be exchanged sequentially during a continuous production process.

[0049] After such a green body 52, which therefore comprises the raw pastes 42 and 44, has been printed, it is subjected to extensive heat treatment. First, a drying process 48 is carried out in a continuous furnace 46, in which organic components from the pastes 42 and 44 as well as solvents such as water are evaporated or thermally decomposed. In a preferred form of the continuous furnace 46, a sintering process 50 is carried out in a second part of the furnace 46. The green body 52 is conveyed on a conveyor belt 54 into a higher temperature zone, with the sintering process 50 taking place in the green body 52. ​​A sintering process is understood to be an essentially diffusion-controlled process for forming a monolithic material. At interfaces between individual grains or metallic particles contained in the pastes 42 and 44, material is exchanged by diffusion processes.The sintering process differs from a melting process in particular in that, if a liquid phase occurs, it is only to a very limited extent, depending on the phase diagram of the alloy used. However, the dimensional stability of the green body 52, which is then transformed into the magnetic sheet semi-finished product 1, is always ensured.

[0050] The magnetic sheet semi-finished product 1 produced in this way is, as already mentioned, freed from the annular region 5, if necessary by a punching process, and stacked into a magnetic sheet stack 30 or a sheet package 30 by means of a robot 56 as shown in Figure 9c. Figures 9a - 9c are shown very schematically and by no means include all of the detailed process steps. Alternative manufacturing methods, such as additive manufacturing as shown in Figure 9a and the sintering process as shown in Figure 9b, are also possible. Furthermore, the separation of the annular region 5 from the magnetic sheet semi-finished product 1 to create the magnetic sheet 2 is not shown in Figure 9. There are two possibilities here: Either the annular region 5 is separated by a punching process after the sintering process 50 as shown in Figure 9b, or the region 5 is turned off after the magnetic sheet semi-finished products 1 have been stacked to form the sheet package 30.Which of the two methods is appropriate here depends in particular on the size and nature of the rotor 4 to be manufactured. If necessary, the punching and subsequent fine turning of the laminated core 30 can be combined.

[0051] The introduction of the relief recesses 18 can also be achieved using various processes. On the one hand, it is possible to cut out the relief recesses 18 in the resulting green body during the stencil printing 34. This is possible through an appropriate stencil design. On the other hand, it is also possible to finally punch out the relief recesses 18 together with the annularly closed area 5. However, the necessity of introducing relief recesses 18 depends on the overall design of the magnetic sheet 2 or the laminated core 30 or the rotor 4 and is not absolutely necessary in every case.

[0052] Reference symbol list

[0053] 1 semi-finished products

[0054] 2 magnetic sheets

[0055] 3 radially outward surfaces

[0056] 4 Rotor

[0057] 5 ring-shaped closed area

[0058] 6 first material component

[0059] 8 second material component

[0060] 9 Boundary line

[0061] 10 d-axis

[0062] 12 magnetic range

[0063] 14 Magnetic sheet center

[0064] 16 Shaft bore

[0065] 18 relief recesses

[0066] 20 non-magnetic material range

[0067] 22 concentric circle

[0068] 24 non-magnetic area

[0069] 26 q-axes

[0070] 28 mechanical stresses

[0071] 30 sheet packages

[0072] 32 Wave

[0073] 34 Stencil printing

[0074] 36 template

[0075] 38 squeegees

[0076] 40 Substrat

[0077] 42 Paste Component 1

[0078] 44 Paste Component 2

[0079] 46 runs of en

[0080] 48 Drying process

[0081] 50 Sintering process

[0082] 52 green bodies

[0083] 54 Conveyor belt

[0084] 56 robots

Claims

Patent claims 1 . Semi-finished product of a rotationally symmetrical magnetic sheet for a rotor of an electrical machine, - which is composed of at least two material components, - a first material component comprising a magnetic material and - a second material component comprising a non-magnetic material, - wherein the second material component runs diametrically along an axis, a so-called d-axis, wherein at least two of these d-axes are provided, - which in turn include at least four magnetic regions, each formed by the magnetic first material component, - which extend in a concave arc shape with respect to a magnetic sheet center, characterized in that - surfaces lying radially outside the magnetic areas ( 3 ) are also formed by the non-magnetic material and - that the magnetic sheet semi-finished product is surrounded by a ring-shaped closed area ( 5 ) made of non-magnetic material and - the ring-shaped closed area made of non-magnetic material has radially different thicknesses.

2. Semi-finished product according to claim 1, characterized in that the number of magnetic regions is 2 * n of the number of axes, where n is a natural number.

3. Semi-finished product according to claim 1 or 2, characterized in that the semi-finished product has a central shaft bore, wherein the shaft bore (16) is continuously surrounded by an amagnetic material region (24).

4. Semi-finished product according to one of claims 1 to 3, characterized in that the angle bisectors of two adjacent d-axes are referred to as q-axes and the soft magnetic regions are designed symmetrically to the q-axes.

5. Semi-finished product according to claim 4, characterized in that the annularly closed region has a greater thickness at the intersection point with the q-axis than at the intersection point with the d-axis.

6. Semi-finished product according to one of the preceding claims, characterized in that a relief recess is provided which is intersected by the d-axis and is symmetrical thereto.

7. Semi-finished product according to one of the preceding claims, characterized in that the saturation magnetization of the non-magnetic material of the second material component is less than 10% of the saturation magnetization of the magnetic material of the first material component.

8. Semi-finished product according to one of the preceding claims, characterized in that the first, soft magnetic material component (4) has an iron content which is higher than 95 wt. %, in particular higher than 98 wt. %.

9. Semi-finished product according to one of the preceding claims, characterized in that the second, non-magnetic material component is an iron-chromium alloy of the supporting material component (10) has a chromium content of between 10 wt.% and 20 wt.%, in particular between 12 wt.% and 18 wt.%.

10. Semi-finished product according to claim 9, characterized in that the iron-chromium alloy of the supporting material component (8) has a nickel content of between 4 wt.% and 10 wt.%, in particular between 6 wt.% and 8 wt.%.

11. Semi-finished product according to claim 9 or 10, characterized in that the iron-chromium alloy of the supporting material component a molybdenum content of between 2 wt.% and 5 wt.%, in particular between 3 wt.% and 4 wt.%.

12. Semi-finished product according to one of claims 9 to 11, characterized in that the iron-chromium alloy of the mechanically supporting material component has a tungsten content of between 0.3 wt.% and 1.2 wt.%, in particular between 0.5 wt.% and 1 wt.%.

13. Magnetic sheet for a rotor of an electrical machine comprising a semi-finished product according to one of claims 1 to 12, wherein the annularly closed region made of non-magnetic material is removed.

14. Rotor of an electrical machine comprising a stack of magnetic sheets according to claim 13.

15. An electric machine comprising a rotor according to claim 14.

16. Electrical machine according to claim 15, characterized in that the machine is a reluctance machine.

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