Rotor for an electric machine, method for producing a rotor, and electric machine

Abstract

The invention relates to a rotor (1) comprising a rotor body (4) which has a first group of electric sheets (7) with a first sheet thickness (11) and a second group of electric sheets (8) with a second sheet thickness (12), wherein the first group of electric sheets (7) has, at at least one opening (10) defining a first magnet pocket (5), a first tab (9) designed monolithically with the respective electric sheet (7), said tab extending into the rotor body (4) in the axial direction (13) and resting against a permanent magnet (6) positioned in the magnet pocket (5), wherein the axial extent (26) of the first tab (9) is smaller than the sum of the second sheet thicknesses (12) of electric sheets (8) of the second group arranged between axially adjacent electric sheets (7) of the first group, wherein the second group of electric sheets (8) has at least one opening (16) defining a magnet pocket (5) and having an opening width (17), which is oriented flush to the opening (10) of the electric sheets (7) of the first group, wherein the opening width (17) of the opening (16) of the second group of electric sheets (8) corresponds to the magnet width (15) plus the sheet thickness (11) of the first group of electric sheets (7).

Description

[0001] Rotor for an electrical machine, method for producing a rotor and electrical machine

[0002] The present invention relates to a rotor for an electrical machine, comprising a rotor body formed from stacked electrical steel sheets, in which magnetic pockets extending axially through the rotor body are formed, distributed circumferentially and having a magnetic pocket width, in which permanent magnets of a magnetic width are accommodated. The invention further relates to a method for producing a rotor and an electrical machine.

[0003] Electric motors are increasingly being used to power motor vehicles, creating alternatives to combustion engines that require fossil fuels. Considerable efforts have already been made to improve the everyday suitability of electric drives and also to provide users with the same level of driving comfort they are accustomed to.

[0004] In the manufacturing process of rotors for electrical machines, such as those used in the drivetrains of electric vehicles, electrical laminations coated with an insulating layer are first punched. These laminations form the basis for the rotor stacks (also known as rotor cores or rotor bodies). These punched laminations are then carefully stacked. The insulating layer can be applied, for example, as a special baked varnish, which serves both to insulate the individual laminations and to optimize the magnetic and mechanical properties of the stack.

[0005] In the next step, the stacked laminated cores, coated with the bonding varnish, are placed in a special tool and heated. This baking process serves to harden the bonding varnish and firmly bond the individual laminations together, which contributes to the structural integrity of the rotor. After this process is complete and the stacks have cooled, the laminated cores with the hardened bonding varnish are transferred to a new tool. At this stage of the process, for example, the magnets, which are essential for generating the magnetic poles in the rotor, can be inserted into the formed rotor body. This rotor body, now equipped with the magnets, is then subjected to another heating process. Subsequently, a special molding material, typically a thermoplastic or thermoset, is introduced into the structure of the rotor body in the transfer molding process.This material helps to fix the magnets in the magnet pockets of the rotor body, seal the rotor and ensure its geometric shape and mechanical strength.

[0006] To secure the permanent magnets in the magnet pockets of the rotor body using transfer molding, a so-called secondary air gap is typically provided, so that the magnet pockets in the laminated cores are wider in the magnetization direction than the magnets themselves. This secondary air gap results, among other things, in more magnetic mass being required to achieve the same torque. However, particularly in view of the rapidly rising material costs for the raw materials contained in permanent magnets (especially neodymium, dysprosium, and terbium), there is a continuing need to reduce the quantity of permanent magnets in such rotors.

[0007] The object of the invention is therefore to eliminate or at least reduce the problems known from the prior art and to provide an improved rotor that can be manufactured cost-effectively and requires the smallest possible amounts of permanent magnet material. Furthermore, the object of the invention is to realize an improved method for manufacturing a rotor and an optimized electrical machine.

[0008] This object is achieved by a rotor for an electrical machine, comprising a rotor body formed from packaged electrical sheets, in which magnetic pockets are formed circumferentially distributed axially through the rotor body, extending with a magnetic pocket width, in which permanent magnets are accommodated with a magnetic width, wherein the rotor body has a first group of electrical sheets with a first sheet thickness and a second group of electrical sheets with a second sheet thickness, wherein the first group of electrical sheets has, at at least one opening defining a magnetic pocket, a first tab formed monolithically with the respective electrical sheet, which extends in the axial direction into the rotor body and bears against a permanent magnet positioned in the magnetic pocket, wherein the axial extent of the first tab is smaller,as the sum of the second sheet thicknesses of electrical sheets of the second group arranged between axially adjacent electrical sheets of the first group, wherein the second group of electrical sheets has at least one opening defining a magnet pocket with an opening width that is aligned with the opening of the electrical sheets of the first group, wherein the opening width of the opening of the second group of electrical sheets corresponds to the magnet width plus the sheet thickness of the first group of electrical sheets, so that the first tab rests against the opening of the second group of electrical sheets and defines the magnet pocket width of the magnet pockets with its side facing into the magnet pocket.

[0009] This provides the advantage that the magnet pocket geometry and the tab can achieve both magnet fixation and secondary air gap minimization as well as interface eddy current loss reduction.

[0010] By fixing the permanent magnets and thermally connecting the magnet surface directly to the laminated core via the tab, an additional process for magnet fixing (such as transfer molding, roll dipping) can be eliminated, which can significantly reduce the manufacturing costs of the rotor.

[0011] The rotor according to the invention also achieves an improvement in motor performance at the same cost or a reduction in costs at the same performance by minimizing the secondary air gap and reducing the boundary eddy current losses.

[0012] When forming a tab, it is particularly preferred that the tab extends in the magnetization direction, i.e., in the subsequent flux direction of the permanent magnets used. The first sheet thickness and the second sheet thickness can be identical or different from each other.

[0013] First, the individual elements of the claimed subject matter of the invention are explained in the order of their relevance or their mention in the set of claims, and particularly preferred embodiments of the subject matter of the invention are described below.

[0014] A rotor is the rotating part of an electrical machine. The rotor comprises, in particular, a rotor shaft and one or more rotor bodies formed from rotor cores, arranged in a rotationally fixed manner on the rotor shaft. The rotor shaft can be hollow, which not only reduces weight but also allows the supply of lubricant or coolant to the rotor body.

[0015] A rotor lamination stack is understood to be a plurality of individual laminations or rotor laminations, usually made of electrical steel sheet, which are stacked and packaged together to form a so-called rotor lamination stack. The individual laminations can then be held together in the lamination stack, for example, by gluing, welding, or screwing. A rotor lamination stack can also, in particular, include magnetic elements incorporated into the pockets of the rotor lamination stack or fixed circumferentially to the rotor lamination stack, as well as optionally axial cover parts for closing the pockets.

[0016] Electrical laminations can be stacked using various methods. For example, the electrical laminations can be designed as stacked laminations, where the individual laminations are simply stacked on top of one another. This is the simplest and most cost-effective type of lamination. To reduce these costs, a lamination stack arrangement can also be configured as a layered lamination, where the laminations are arranged in layers, with each layer rotated by a specific angle. This reduces eddy current losses and improves magnetic behavior. It is also conceivable to package the electrical laminations using a segmented lamination, where the laminations are divided into segmented parts that are then assembled into a complete stack. This can contribute to precise control of the magnetic properties and a reduction in eddy current losses.

[0017] It is fundamentally possible to arrange the permanent magnets in various configurations within a rotor, and thus also within a rotor segment. It is preferred to design the permanent magnets as embedded permanent magnets (also known as interior permanent magnets, IPM). The magnets are embedded in magnetic pockets within the rotor, which provides better protection for the magnets, improves thermal properties, and allows for more complex magnetic flux paths. The permanent magnets can also be placed in a V-shaped pattern or at an angle within the rotor. This arrangement can help improve the magnetic flux concentration and reduce the so-called

[0018] Cogging Torque I To reduce cogging torque.

[0019] In a preferred embodiment of the invention, the magnetic pockets are arranged in pairs in a V-shape, with the tips of the V-shaped magnetic pockets pointing radially inward. The V-shaped arrangement of the magnets can improve the magnetic flux density in the air gap between the rotor and stator. This can increase the efficiency of the machine because it enables a stronger magnetic coupling between the rotor and stator. A V-shaped arrangement of the magnets can also help reduce cogging torque, resulting in smoother running of the machine. Cogging torque refers to the jerky torque that can arise from the interaction between the rotor magnets and the stator teeth.

[0020] The rotor magnets are the permanent magnets that are inserted into the magnetic pockets of the rotor core. Each pocket can contain a single, larger rotor magnet designed as a bar magnet or several smaller permanent magnet elements.

[0021] Leakage flux barriers can be formed on the magnetic pockets. For the purposes of this application, leakage flux barriers are design features that help reduce magnetic leakage flux and improve the performance of the electrical machine. They help concentrate the magnetic flux of the permanent magnets directly onto the stator winding, thereby increasing magnetic coupling and thus the efficiency of the electrical machine. By preferentially interrupting the magnetic flux between the poles, the leakage flux barriers also reduce the leakage flux and thus minimize the magnetic losses in the rotor. Since the leakage flux barriers can thus help reduce magnetic losses, they also contribute to reducing the temperature in the rotor during operation, which can increase the service life and reliability of the electrical machine.Leakage flux barriers are preferably made of non-magnetic materials such as plastic, ceramic, or aluminum, which interrupt the magnetic field and direct the magnetic flux within a rotor segment in a desired direction. A leakage flux barrier can also be formed, for example, from a ceramic such as ferrite or aluminum oxide. Furthermore, it is possible for a leakage flux barrier to be made of a plastic such as polytetrafluoroethylene (PTFE) or polyetheretherketone (PEEK). In principle, it is also conceivable for a leakage flux barrier to be made of air or to be designed as an air-filled cavity. The leakage flux barriers are advantageously positioned in the rotor segment near the permanent magnets. The shape and size of the leakage flux barriers depend on the specific application and the desired magnetic flux path within a rotor segment.

[0022] Advantageous embodiments of the invention are specified in the dependent claims. The features listed individually in the dependent claims can be combined with one another in a technologically expedient manner and can define further embodiments of the invention. Furthermore, the features specified in the claims are further specified and explained in the description, where further preferred embodiments of the invention are presented.

[0023] According to an advantageous embodiment of the invention, it can be provided that the first group of electrical sheets has a second tab formed monolithically with the respective electrical sheet at the opening defining the magnet pocket, which second tab is opposite the first tab and extends axially into the rotor body and bears against a permanent magnet positioned in the magnet pocket, wherein the axial extent of the second tab is smaller than the sum of the second sheet thicknesses of electrical sheets of the second group arranged between axially adjacent electrical sheets of the first group, wherein the opening width of the opening of the second group of electrical sheets corresponds to the magnet width plus twice the sheet thickness of the first group of electrical sheets,so that the first tab and the second tab rest against the opening of the second group of electrical sheets and, with their respective sides facing into the magnetic pocket, define the magnetic pocket width of the magnetic pockets. The advantage of this design is that the second tab further improves the clamping of the permanent magnet in the magnetic pocket. The clamping force can also act more evenly on the usually quite brittle permanent magnet, thus preventing unwanted material damage in or on the permanent magnet.

[0024] According to a further preferred development of the invention, it can also be provided that the first group of electrical sheets and / or the second group of electrical sheets are covered at least in sections by an electrical insulator, in particular a baking varnish. This can prevent an electrical connection between the punched edges of the electrical sheets and the magnet surface in order to avoid an increase in eddy current losses at this interface resulting from this contact. For this purpose, the baking process is then preferably only carried out after the permanent magnets have been introduced into the magnet pockets in order to use the insulator, which is preferably designed as a baking varnish, not only for baking the sheet but also for fixing the magnet. The insulator and in particular also the baking varnish can be applied to the electrical sheets in various ways. The insulator orthe baking varnish is applied to the electrical sheets by means of a process selected from the group of baptism processes, spray processes, roller processes, impregnation processes and / or powder coating processes.

[0025] In the baptism process, the stacked electrical sheets are dipped into the bonding varnish. After dipping, the excess varnish is drained off, and the sheets are subjected to the thermal curing process, during which the varnish hardens, bonds the sheets together, and insulates them. In a spray process, the bonding varnish is sprayed onto the electrical sheets. This allows the varnish to be precisely applied to the desired areas. After the varnish has been applied, the stack of electrical sheets is thermally cured to ensure a strong bond and insulation. In the roller process, the varnish is applied to the electrical sheets using rollers. This allows the varnish to be evenly distributed over the entire surface of the electrical sheets. After the varnish has been applied, the thermal curing process follows to fix and insulate the sheets.In the impregnation process, the stacked electrical sheets are impregnated with the liquid bonding varnish, allowing the varnish to penetrate the spaces between the sheets. After impregnation, the sheets are thermally cured, which hardens the varnish and forms a solid, insulating layer between the sheets. In a powder coating process, a powder coating is electrostatically applied to the electrical sheets and then thermally baked. This forms a continuous, insulating layer that effectively bonds the sheets.

[0026] A baking varnish can, for example, be selected from the group of epoxy resins, polyester resins, polyurethane resins, alkyd resins, silicone resins, acrylic resins, phenolic resins, melamine resins.

[0027] Furthermore, according to a likewise advantageous embodiment of the invention, it can be provided that a plurality of the magnetic pockets, preferably all of the magnetic pockets, have / have a first tab and / or a second tab. Preferably, a plurality, preferably all of the electrical sheets of the first group have a first tab and / or a second tab. Furthermore, in this context, the invention can also be further developed such that the first group of electrical sheets and the second group of electrical sheets are stacked in such a way that a plurality of electrical sheets of the second group are stacked on top of one another, and an electrical sheet of the first group of electrical sheets is arranged on at least one end face of the stacked electrical sheets of the first group.This allows the axial extension of a tab to be adjusted accordingly, which particularly affects the spring action of the tab and thus the spring force acting on the permanent magnet. It has proven particularly advantageous to select the number of electrical sheets in the second group between 4 and 10, preferably between 5 and 8, with the sheet thickness of the first group of electrical sheets in this case being equal to the sheet thickness of the second group of electrical sheets.

[0028] According to another particularly preferred embodiment of the invention, the first group of electrical sheets and the second group of electrical sheets can be arranged substantially identically and offset from one another in the circumferential direction. This allows, in particular, the effect of securing the permanent magnets in the magnet pockets with only one sheet cut, in which a tab or a pair of tabs is then preferably provided on a magnet pocket for each pole. By stacking in a helical configuration (twisting around one pole each between two sheets), all poles can be covered with tabs over most of the active length of the rotor body.

[0029] The object of the invention can further be achieved by a method for producing a rotor of an electrical machine comprising the following steps:

[0030] Providing a plurality of permanent magnets with a magnet width for insertion into magnet pockets of a rotor body formed from stacked electrical sheets, providing a first group of electrical sheets with a first sheet thickness, wherein the first group of electrical sheets has, at at least one opening defining a magnet pocket, a first tab formed monolithically with the respective electrical sheet, which tab extends into the magnet pocket;

[0031] Providing a second group of electrical sheets having a second sheet thickness, wherein the second group of electrical sheets has at least one opening defining a magnet pocket with an opening width that can be aligned with the opening of the electrical sheets of the first group, wherein the opening width of the opening of the second group of electrical sheets corresponds to the magnet width plus the sheet thickness of the first group of electrical sheets;

[0032] Stacking the first group of electrical sheets and the second group of electrical sheets in such a way that a plurality of electrical sheets of the second group are arranged stacked on top of one another and an electrical sheet of the first group of electrical sheets is arranged on at least one end face of the stacked electrical sheets of the second group, wherein the opening of the first group of electrical sheets and the opening of the second group of electrical sheets are aligned with one another;

[0033] Axial insertion of a permanent magnet into a magnetic pocket in such a way that, when the permanent magnet is inserted, the first tab extends in the axial direction into the rotor body and rests against a permanent magnet positioned in the magnetic pocket as well as against the opening of the second group of electrical sheets, and the first tab, with its side facing into the magnetic pocket, defines the magnetic pocket width of the magnetic pockets.

[0034] This makes it possible to mechanically fix the permanent magnets in the magnetic pockets. It may also be advantageous to further develop the invention such that, before the permanent magnet is axially inserted into a magnetic pocket, the first tab is bent from its extension projecting into the magnetic pocket into an axial extension. This makes it possible to dispense with the bending of the tabs by the permanent magnet while it is being inserted into one of the magnetic pockets. This can reduce the risk of mechanically damaging the generally comparatively brittle permanent magnet during this process. A tool can be used for bending which has approximately the geometry of a permanent magnet but can be inserted and removed from the magnetic pockets with some play.

[0035] Preferably, a tab is bent at an angle of 80°, preferably at an angle between 80-90° to the direction of extension of the magnetic pocket.

[0036] According to a further preferred embodiment of the subject matter of the invention, it can be provided that the first group of electrical sheets and / or the second group of electrical sheets are at least partially covered by an electrical insulator, in particular a baked enamel, and the rotor body with the permanent magnet positioned in a magnetic pocket is subjected to a thermal treatment. This can achieve a bonding or material connection between the electrical sheets or the tabs and the permanent magnet, thereby further improving the fixation of the permanent magnet in the magnetic pocket.

[0037] Finally, the object of the invention can also be achieved by an electrical machine comprising a rotor according to one of claims 1-6.

[0038] The invention will be explained in more detail below with reference to figures without limiting the general inventive concept. It shows:

[0039] Figure 1 shows an electrical sheet of the first group of electrical sheets and an electrical sheet of the second group of electrical sheets, each in a top view.

[0040] Figure 2 is a schematic axial sectional view of a rotor body in a first manufacturing status,

[0041] Figure 3 is a schematic axial sectional view of a rotor body in a second manufacturing status,

[0042] Figure 4 is a schematic axial section view of a rotor body in a third manufacturing status,

[0043] Figure 5 is a schematic axial section view of a rotor body in a third manufacturing state with an insulator,

[0044] Figure 6 shows a detailed view of three different production stages of an electrical sheet of the first group of electrical sheets,

[0045] Figure 7 shows a detailed view of three different production states of an electrical sheet of the second group of electrical sheets,

[0046] Figure 8 shows an embodiment of an electrical sheet in which the first group and the second group of electrical sheets are identical,

[0047] Figure 9 shows an electric machine with a rotor in a schematic axial section. Figures 1-4 show a first embodiment of a rotor 1 for an electric machine 2, as also sketched by way of example in Figure 9. The electric machine 2 is configured as a radial flux machine with an internally rotating, permanently excited rotor 1, which is rotatably mounted in the hollow cylindrical stator 24.

[0048] The rotor 1 comprises a rotor body 4 formed from packaged electrical sheets 3, in which rectangular magnetic pockets 5 are formed, which extend circumferentially and axially through the rotor body 4 and have a magnetic pocket width 14, in which rectangular permanent magnets 6 with a magnet width 15 are accommodated.

[0049] As can be clearly seen from Figures 1-4, the rotor body 4 has a first group of electrical sheets 7 with a first sheet thickness 11 and a second group of electrical sheets 8 with a second sheet thickness 12. The first group of electrical sheets 7 is connected to each of its openings 10 defining a magnetic pocket 5 by a first tab 9 formed monolithically with the respective electrical sheet 7, which, when the rotor 1 is assembled, extends in the axial direction 13 into the rotor body 4 and bears against a permanent magnet 6 positioned in the magnetic pocket 5. This assembly state is illustrated in Figure 4.From Figure 4 it can also be seen that the first group of electrical sheets 7 has, at the opening 10 defining the magnetic pocket 5, a second tab 19 which is formed monolithically with the respective electrical sheet 7, which is opposite the first tab 9 and which extends in the axial direction 13 into the rotor body 4 and bears against a permanent magnet 6 positioned in the magnetic pocket 5.

[0050] Furthermore, Figure 4 clearly shows that the axial extension 26 of the first tab 9 is smaller than the sum of the second sheet thicknesses 12 of the electrical sheets 8 of the second group arranged between axially adjacent electrical sheets 7 of the first group. Similarly, the axial extension 20 of the second tab 19 is also smaller than the sum of the second sheet thicknesses 12 of the electrical sheets 8 of the second group arranged between axially adjacent electrical sheets 7 of the first group. The first tab 9 and the second tab 19 are essentially identical in the illustrated embodiment.

[0051] As can also be clearly seen from the combination of Figures 1-4, the second group of electrical sheets 8 has a plurality of openings 16 defining magnetic pockets 5, each having an opening width 17, which are aligned with the openings 10 of the electrical sheets 7 of the first group, wherein the opening width 17 of the opening 16 of the second group of electrical sheets 8 corresponds to the magnet width 15 plus twice the sheet thickness 11 of the first group of electrical sheets 7, so that the first tab 9 and the second tab 19 rest against the opening 16 of the second group of electrical sheets 8 and, with their respective side 18 pointing into the magnetic pocket 5, define the magnetic pocket width 14 of the magnetic pockets 5.

[0052] The first group of electrical sheets 7 and the second group of electrical sheets 8 are stacked in such a way that seven electrical sheets 8 of the second group are stacked one on top of the other, and an electrical sheet 7 of the first group of electrical sheets 7 is arranged on at least one end face 22 of the stacked electrical sheets 8 of the first group. This arrangement is then repeated several times in the axial direction and thus essentially defines the axial extent of the rotor body 4.

[0053] Figure 5 shows an embodiment of a rotor 1 in which the first group of electrical sheets 7 is partially covered by an electrical insulator 21, in this case a baking varnish additionally applied to an existing insulating coating of the electrical sheets 7. Thus, the baking varnish lies directly against the surface of the permanent magnet 6 and, through baking, can form a material-to-material connection between the permanent magnet 6 and the tabs 9, 19. In principle, it would also be conceivable to insert a separate insulator 21, for example in the form of insulating paper, into the magnet pockets 5.

[0054] In the embodiment of Figure 4, the electrical sheets 7, 8 have an insulating coating, which, however, has not been shown separately in the figures for the sake of clarity. Therefore, the embodiment shown in Figure 4 can also have an insulator 21 in the form of an insulating baked enamel coating, which, however, is formed integrally with the electrical sheets 7, 8 and was not subsequently applied to the electrical sheets 7, 8 after packaging. This baked enamel coating can also be used to firmly fix the permanent magnets 6 in the magnetic pockets 5. In this case, a heat-adhesive molded part can be positioned between the magnetic pocket 5 and the permanent magnet 6, which can then be bonded by heating, so that the permanent magnet 6 is positively fixed in the magnetic pocket 5.In this case, the heat-bonded molded part does not necessarily have to have electrically insulating properties, since the electrical sheets 7, 8 already have an electrically insulating coating. However, it is definitely preferable for the heat-bonded molded part to also have electrically insulating properties.

[0055] Figure 8 shows a further possible embodiment of the electrical sheets 3, in which the first group of electrical sheets 7 and the second group of electrical sheets 8 are essentially identical and arranged offset from one another in the circumferential direction. This variant thus allows the realization of a rotor 1 according to the invention with only one lamination section. At some poles, the lamination section has the shape of a lamination section without tabs 9, 19, while at the other poles at 12 and 6 o'clock, it has the shape of a lamination section with tabs 9, 19. By stacking the electrical sheets 7, 8 in a helical shape (twisting by one pole each between two sheets), all poles are covered with tabs 9, 19 over the majority of the active length of the rotor body 4. The axial extension 20, 26 of the tabs 9, 19 in the assembled state of the rotor 1 results from the ratio of the poles with and without tabs 9, 19.In the example shown in Figure 8, two poles have tabs 9,19 at 12 o'clock and 6 o'clock, while ten poles are designed without the tabs 9,19. The poles are defined by the V-shaped alignment of two adjacent magnetic pockets 5. The tabs 9,19 must therefore each axially cover five electrical sheets 7,8 when the rotor 1 is in the assembled state. With a sheet thickness 11,12 of the electrical sheets 7,8 of, for example, 0.25 mm, the tabs 9,19 must therefore have an axial extension 20,26 of 1.25 mm when the rotor 1 is in the assembled state. The production of a rotor 1 can comprise the following steps. First, a plurality of permanent magnets 6 with a magnet width 15 are provided for insertion into magnetic pockets 5 of a rotor body 4 formed from stacked electrical sheets 3.Furthermore, a first group of electrical sheets 7 with a first sheet thickness 11 is provided, wherein the first group of electrical sheets 7 has a first tab 9 formed monolithically with the respective electrical sheet 7 on at least one opening 10 defining a magnet pocket 5, which tab extends into the magnet pocket 5, and a second group of electrical sheets 8 with a second sheet thickness 12 is provided, wherein the second group of electrical sheets 8 has at least one opening 16 defining a magnet pocket 5 with an opening width 17 which can be aligned flush with the opening 10 of the electrical sheets 7 of the first group, wherein the opening width 17 of the opening 16 of the second group of electrical sheets 8 corresponds to the magnet width 15 plus the sheet thickness 11 of the first group of electrical sheets 7.

[0056] Then, the first group of electrical sheets 7 and the second group of electrical sheets 8 are first stacked together in such a way that a plurality of electrical sheets 8 of the second group are arranged stacked on top of one another, and an electrical sheet 7 of the first group of electrical sheets 7 is arranged on at least one end face 22 of the stacked electrical sheets 8 of the first group, wherein the opening 10 of the first group of electrical sheets 7 and the opening 16 of the second group of electrical sheets 8 are aligned with one another. This assembly state is shown in Figure 2.

[0057] Before the permanent magnet 6 is axially inserted into a magnetic pocket 5, the tabs 9, 19 are bent from their extension pointing into the magnetic pocket 5 into an axial extension 20, 26 around the bending edge 23. This manufacturing stage is depicted in Figure 3. For this purpose, a tool part can be pressed axially through the magnetic pockets 5 in order to pre-deform the tabs 9, 19 before a permanent magnet 6 is later inserted into the corresponding magnetic pocket 5. The tool part can be made of steel, for example, and is thus far less brittle than the permanent magnet itself. It is also advantageous for the tool part to be polished, which can help minimize the risk of damaging the insulation layer on the electrical steel sheet 7, 8.The permanent magnet 6 itself then only requires a slight pressing force when inserted into the thus prepared magnetic pocket 5, which correspondingly reduces the risk of mechanical damage to the permanent magnet 6. Figure 3 shows a bend of the tabs 9, 19 of approximately 85°, so that the tabs 9, 19 have a springback of approximately 5° even before the permanent magnet 6 is inserted. The tabs 9, 19 are therefore elastically deformed, which then allows the permanent magnets 6 to be clamped by the tabs 9, 19. The tabs 9, 19 are configured such that the permanent magnets 6 are fixed in the magnetic pockets 5 or at least pre-fixed to such an extent that their position can no longer be changed under slight forces (in particular their own gravity).

[0058] After the tabs 9, 19 have been pre-formed, the permanent magnet 6 is inserted axially into one of the magnetic pockets 5 in such a way that, when the permanent magnet 6 is inserted, the tab 9, 19 extends in the axial direction 13 into the rotor body 4 and rests against a permanent magnet 6 positioned in the magnetic pocket 5 as well as against the opening 16 of the second group of electrical sheets 8. As a result, the tabs 9, 19, with their side 18 facing into the magnetic pocket 5, define the magnetic pocket width 14 of the magnetic pockets 5. After the permanent magnets 6 have been pressed in, there is no or only a very small secondary air gap between the permanent magnet 6 and the magnetic pocket 5, since the tabs 9, 19 are now spring-loaded in the circumferential direction and rest against the permanent magnet 6 on both sides. In this case, no punched edges are in contact with the magnetic surface of the permanent magnet 6, but only the tabs 9,19 of the electrical sheet 7.As a rule, the electrical sheets 7, 8 are designed to be electrically insulated, so that the tabs 9, 19 and the permanent magnet 6 are also electrically insulated from one another, thereby minimizing or eliminating interfacial eddy current losses. The manufacturing states of the rotor 1 shown in an axial section in Figures 2-4 are shown in a plan view in Figures 6-7 for each group of electrical sheets 7, 8. Figures 6-7 show the individual process steps for each group of electrical sheets 7, 8, with figures c showing the initial state and figure a showing the final state of the respective manufacturing state. Figure c of Figure 6 shows the tabs 9, 19 of the first group of electrical sheets 7 in their undeformed state.Figure b of Figure 6 shows the tabs 9, 19 of the first group of electrical sheets 7 in their formed state, with the magnetic pocket 5 released, into which the permanent magnet 6 is then inserted, as shown in Figure a of Figure 6. Similarly, Figure 7 shows an electrical sheet 8 from the second group before the tabs 9, 19 are folded over. The state with the folded tabs 9, 19 can then be seen in Figure b. Figure c of Figure 7 then shows the second group of electrical sheets 8 with the permanent magnet 6 inserted.

[0059] In the event that the first group of electrical sheets 7 and / or the second group of electrical sheets 8 are covered by an electrical insulator 21, in particular a baking varnish, as can also be seen in Figure 5, the rotor body 4 with the permanent magnet 6 positioned in a magnetic pocket 5 can then also be subjected to a thermal treatment. It is understood that the permanent magnets 6 are introduced into the magnetic pockets 5 before the rotor body 4 is baked. The baking varnish covering the tabs 9, 19 is then in contact with the surface of the permanent magnets 6, so that not only the electrical sheets 3 of the rotor body 4 are baked in the baking process, but an additional material-to-material magnetic fixation of the permanent magnets 6 in the magnetic pockets 5 is achieved via the baking varnish.

[0060] The invention is not limited to the embodiments illustrated in the figures. The above description is therefore not to be considered restrictive, but rather explanatory. The following claims are to be understood in such a way that a stated feature is present in at least one embodiment of the invention. This does not exclude the presence of further features. Where the claims and the above description define 'first' and 'second' features, this designation serves to distinguish between two similar features without establishing a priority.

[0061] List of reference symbols

[0062] 1 rotor

[0063] 2 electric machine

[0064] 3 electrical sheets

[0065] 4 rotor bodies

[0066] 5 magnetic pockets

[0067] 6 permanent magnet

[0068] 7 electrical sheets

[0069] 8 electrical sheets

[0070] 9 tab

[0071] 10 Opening

[0072] 11 Sheet thickness

[0073] 12 sheet thickness

[0074] 13 direction

[0075] 14 magnetic pocket width

[0076] 15 magnet width

[0077] 16 Opening

[0078] 17 opening width

[0079] 18 page

[0080] 19 Tab

[0081] 20 Extension

[0082] 21 Insulator

[0083] 22 front side

[0084] 23 Bending edge

[0085] 24 Stator

[0086] 26 Extension

Claims

Claims 1. Rotor (1) for an electrical machine (2) comprising a rotor body (4) formed from stacked electrical sheets (3), in which magnetic pockets (5) are formed, circumferentially distributed axially through the rotor body (4), with a magnetic pocket width (14), in which permanent magnets (6) with a magnet width (15) are accommodated, characterized in that the rotor body (4) has a first group of electrical sheets (7) with a first sheet thickness (11) and a second group of electrical sheets (8) with a second sheet thickness (12), wherein the first group of electrical sheets (7) has, at at least one opening (10) defining a magnetic pocket (5), a first tab (9) formed monolithically with the respective electrical sheet (7), which extends in the axial direction (13) into the rotor body (4) and bears against a permanent magnet (6) positioned in the magnetic pocket (5),wherein the axial extent (26) of the first tab (9) is smaller than the sum of the second sheet thicknesses (12) of electrical sheets (8) of the second group arranged between axially adjacent electrical sheets (7) of the first group, wherein the second group of electrical sheets (8) has at least one opening (16) defining a magnetic pocket (5) with an opening width (17) aligned with the opening (10) of the electrical sheets (7) of the first group, wherein the opening width (17) of the opening (16) of the second group of electrical sheets (8) corresponds to the magnet width (15) plus the sheet thickness (11) of the first group of electrical sheets (7), so that the first tab (9) rests against the opening (16) of the second group of electrical sheets (8) and, with its side (18) facing into the magnetic pocket (5), defines the magnetic pocket width (14) of the magnetic pockets (5).

2. Rotor (1) according to claim 1, characterized in that the first group of electrical sheets (7) has, at the opening (10) defining the magnetic pocket (5), a second tab (19) formed monolithically with the respective electrical sheet (7), which second tab is opposite the first tab (9) and extends in the axial direction (13) into the rotor body (4) and bears against a permanent magnet (6) positioned in the magnetic pocket (5), wherein the axial extent (20) of the second tab (19) is smaller than the sum of the second sheet thicknesses (12) of electrical sheets (8) of the second group arranged between axially adjacent electrical sheets (7) of the first group, wherein the opening width (17) of the opening (16) of the second group of electrical sheets (8) corresponds to the magnet width (15) plus twice the sheet thickness (11) of the first group of electrical sheets (7),so that the first tab (9) and the second tab (19) rest against the opening (16) of the second group of electrical sheets (8) and define the magnetic pocket width (14) of the magnetic pockets (5) with their respective side (18) pointing into the magnetic pocket (5).

3. Rotor (1) according to claim 1 or 2, characterized in that the first group of electrical sheets (7) and / or the second group of electrical sheets (8) are covered at least in sections by an electrical insulator (21), in particular a baked enamel.

4. Rotor (1) according to one of the preceding claims, characterized in that a plurality of the magnetic pockets (5), preferably all magnetic pockets (5), have / have a first tab (9) and / or a second tab (19).

5. Rotor (1) according to one of the preceding claims, characterized in that the first group of electrical sheets (7) and the second group of electrical sheets (8) are arranged substantially identically and offset from one another in the circumferential direction.

6. Rotor (1) according to one of the preceding claims, characterized in that the first group of electrical sheets (7) and the second group of electrical sheets (8) are packaged in such a way that a plurality of electrical sheets (8) of the second group are stacked on top of one another and an electrical sheet (7) of the first group of electrical sheets (7) is arranged on at least one end face (22) of the stacked electrical sheets (8) of the second group.

7. A method for producing a rotor (1) of an electrical machine (2) comprising the following steps: Providing a plurality of permanent magnets (6) with a magnet width (15) for insertion into magnet pockets (5) of a rotor body (4) formed from packaged electrical sheets (3), Providing a first group of electrical sheets (7) with a first sheet thickness (11), wherein the first group of electrical sheets (7) has, on at least one opening (10) defining a magnetic pocket (5), a first tab (9) which is formed monolithically with the respective electrical sheet (7) and extends into the magnetic pocket (5); Providing a second group of electrical sheets (8) with a second sheet thickness (12), wherein the second group of electrical sheets (8) has at least one opening (16) defining a magnet pocket (5) with an opening width (17) which can be aligned in alignment with the opening (10) of the electrical sheets (7) of the first group, wherein the opening width (17) the opening (16) of the second group of electrical sheets (8) corresponds to the magnet width (15) plus the sheet thickness (11) of the first group of electrical sheets (7); Stacking the first group of electrical sheets (7) and the second group of electrical sheets (8) in such a way that a plurality of electrical sheets (8) of the second group are arranged stacked on top of one another and an electrical sheet (7) of the first group of electrical sheets (7) is arranged on at least one end face (22) of the stacked electrical sheets (8) of the second group, wherein the opening (10) of the first group of electrical sheets (7) and the opening (16) of the second group of electrical sheets (8) are aligned with one another; Axial insertion of a permanent magnet (6) into a magnetic pocket (5) in such a way that, when the permanent magnet (6) is inserted, the first tab (9) extends in the axial direction (13) into the rotor body (4) and rests against a permanent magnet (6) positioned in the magnetic pocket (5) and against the opening (16) of the second group of electrical sheets (8), and the first tab (9) defines the magnetic pocket width (14) of the magnetic pockets (5) with its side (18) pointing into the magnetic pocket (5).

8. Method according to claim 7, characterized in that before the axial insertion of the permanent magnet (6) into a magnetic pocket (5), the first tab (9) is bent from its extension pointing into the magnetic pocket (5) into an axial extension.

9. Method according to claim 7 or 8, characterized in that the first group of electrical sheets (7) and / or the second group of electrical sheets (8) are covered at least in sections by an electrical insulator (21), in particular a baked enamel, and the rotor body (4) is provided with the permanent magnet (6) positioned in a magnet pocket (5) of a undergoes thermal treatment.

10. Electrical machine (2) comprising a rotor (1) according to one of the claims

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