Electrician lamination stack for electric machine

Abstract

The utility model relates to an electrical lamination stack (2) for an electrical machine, comprising a plurality of individual laminations (3) which are stacked in an electrically insulated manner from one another and which have openings (4, 8) aligned with one another, and a thermosetting casting element (5) which passes through the openings (4, 8) and which engages the individual laminations (3) in a form-fitting manner.

Description

Field of the Invention

[0001] The present disclosure relates to an electrical lamination stack for a stator or rotor of an electric machine. Furthermore, the present disclosure relates to a method for manufacturing an electrical lamination stack suitable for use in an electric machine. Background Art

[0002] EP 0 729 665 B1 discloses a method for manufacturing an armature for an electric motor. The method can include generating a plastic filling by injection molding, transfer molding, or compression molding. The plastic filling in the case of EP 0 729 665 B1 belongs to a commutator, which is arranged on a shaft like a lamination stack.

[0003] Differently from injection molding for processing thermoplastic materials, in transfer molding, thermosetting materials are processed. This can occur in such a way that the molding material is introduced from a heated front cavity into a cavity by means of a piston and cured there. In principle, it is known to manufacture fiber-reinforced workpieces by transfer molding.

[0004] The injection molding of a stator of an electric machine with a thermosetting material is described, for example, in DE 10 2013 227 054 A1. In this case, a floating bearing is molded during injection molding. Instead of thermosetting materials, fiber-matrix semi-finished products with a thermosetting matrix should also be usable. The stator can in particular be configured as a segmented stator.

[0005] DE 10 2015 212 007 A1 discloses an apparatus for forming at least a section of injection molding. In this case, a rotor shaft is injection molded with a thermosetting or thermoplastic material. The apparatus according to DE 10 2015 212 007 A1 includes clamping elements, which are configured to fix an insert in an insertion recess.

[0006] A slot wall insulator for a stator of an electric motor is known from DE 10 2017 220 123 A1. The slot wall insulator should be able to be formed directly on the surface of a stator lamination in an injection molding process. Thereby, the slot wall insulator is formed in a toothed shape. By the toothed configuration, voids are formed, which are suitable for accommodating electrical conductors.

[0007] DE 10 2008 032 214 B4 discloses a reluctance motor, the rotor of which has regularly arranged void regions in the circumferential direction. The rotor is configured as a lamination stack, in which voids are punched out from the lamination pieces. The individual lamination pieces can be held together by stamping and stacking. Optionally, the voids are filled with plastic injection.

[0008] DE 10 2016 24 249 A1 describes a method for manufacturing a rotor for a synchronous reluctance machine, the method comprising the method steps of stacking rotor groups and injecting a flow barrier within the rotor core with a plastic material containing magnet particles. Furthermore, the orientation of the magnet particles is set by applying an external magnetic field.

[0009] A short-circuit rotor for an electric machine is known from DE 25 36 390 B1, the short-circuit rotor having a short-circuit cage injected into the rotor lamination stack. The short-circuit cage presses the rotor lamination stack together and includes end-side short-circuit rings, wherein at least one of the short-circuit rings engages torsion-proof or movement-proof with the rotor hub or the rotor shaft. Summary of the Utility Model

[0010] The present disclosure is based on the object of further developing components of an electric machine, namely an electric motor, a generator or a transformer, especially in terms of production technology, relative to the prior art, and using potting in its manufacture.

[0011] Hereinafter, the design solutions and advantages of the present disclosure explained in connection with the manufacturing method meaningfully also apply to devices, namely electrical lamination stacks designed for use in electric machines, and vice versa.

[0012] The electrical lamination stack includes a plurality of single laminations, the laminations being stacked electrically insulated from each other and having through-holes aligned with each other. Furthermore, a thermosetting potting element produced by potting is proposed, the potting element passing through all the through-holes and engaging the single laminations form-fittingly at the back.

[0013] The thermosetting material processed by transfer molding has electrical insulation properties. Thereby, in particular, electrical arcing between the electrical circuit and the laminations of the electrical lamination stack is excluded. At the same time, the material composition can be selected such that a sufficiently high thermal conductivity is obtained for the application case. In particular, an epoxy resin can be used as the thermosetting material, which is commercially available, for example, under the name EP 3161.

[0014] To establish the required form-fitting with the metal components of the lamination stack, the overall elongate potting element has a width that is not uniform over its length. For example, the potting element has a maximum width that results respectively between two single laminations, the maximum width being at least 1.5 times the minimum width of the potting element to be measured in the through-holes. The maximum width is in particular not greater than three times the minimum width of the potting element.

[0015] According to different possible embodiments, single laminations are stacked on top of each other without a form fit being directly formed between the single laminations. This has the advantage that method steps for shaping the single laminations by means of a snap connection, for example, can be dispensed with. Similarly, steps such as laser welding can be dispensed with. At least one casting element produced by transfer molding can be the only mechanism for holding the entire electrical lamination stack together.

[0016] In terms of the shape of the through openings involved in the lamination stack, different modifications are possible. If the through opening has a closed peripheral edge, it can in particular be a circular, oval or polygonal hole. Similarly, the through opening can, for example, have a cloverleaf shape, a standing clock shape or a dovetail shape. In all cases, stresses can be generated within the electrical lamination stack by curing the thermosetting material, wherein the casting element is particularly suitable for transmitting tensile forces and can thus be a tie rod. The form fit established several times between the casting element and the individual laminations of the electrical lamination stack can ensure here that the forces are transmitted not over the entire length of the casting member, but only over a small part of its length. Overall, high forces can thus be transmitted within the electrical lamination stack compared to the dimensions of the casting element.

[0017] In the case of a through opening without a closed peripheral edge, the through opening in particular forms a groove, such as a U-shaped groove of a stator. Electrical conductors can be introduced into the stator groove. It is also feasible for the conductor to be directly injection-molded with a thermosetting material within the stator groove. In the case of introducing a copper winding by the hairpin method, the groove can be directly closed by transfer molding, so that no closing wedges need to be introduced.

[0018] Generally, an electrical lamination stack can be manufactured by stacking electrically insulated single laminations with aligned through openings and providing them by transfer molding with an overall bolt-shaped thermosetting casting element introduced into the through openings, the casting element being configured to absorb tensile forces between any of the single laminations in the single laminations. In transfer molding, i.e., injection molding, the thermosetting material is in particular introduced between the single laminations such that a form fit is produced between each single lamination and the casting element.

[0019] If the electrical lamination stack is part of a rotor of an electric motor to be equipped with permanent magnets, the fixing of the individual magnets can be carried out in a single process together with the establishment of a connection between the single laminations by transfer molding. Epoxy resin is in particular a suitable material for this. Compared to traditional manufacturing methods, this reduces the number of process steps and the coordination effort, while at the same time enabling a high geometric accuracy of the final product, namely the electrical lamination stack including the permanent magnets.

[0020] The transfer molding process can be combined with the magnetic fixation of the stack. This applies in particular to the method variant in which the stator slots are insulated by transfer molding. Irrespective of the type of stack, the individual laminations can be centered by means of an expanding mandrel which is also used for the required perpendicularity within the device to be installed. At the same time, by pressing together the molds provided for transfer molding, the stack can be calibrated in terms of its dimensions in the axial direction, i.e., the direction perpendicular to the plane in which the individual laminations are arranged.

[0021] The advantages of the present disclosure lie in particular in that manufacturing steps which are time-consuming in the manufacture of stators or rotors of electric motors or generators, such as bonding or shaping, can be completely dispensed with or at least significantly simpler to implement compared to conventional solutions. Here, the functional limitations of the manufactured components, i.e., the stator or rotor, are not considered. Rather, the manufacturing method is characterized by its usability in a plurality of different electrical engineering products, the components of which are loaded by forces determined by operation. An electrical stack held together by one or more thermosetting casting elements cannot usually be disassembled without damage. Electrical stacks can be manufactured using standardized electrical laminations without cladding. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Multiple embodiments of the present invention will be described in detail below with reference to the drawings. Shown therein are:

[0023] Figure 1 A schematic sectional view showing the structure of an electrical stack for an electric machine,

[0024] Figure 2 A perspective view showing the electrical stack of the stator of an electric motor,

[0025] Figure 3 A device for connecting individual laminations of an electrical stack according to Figure 2 by means of transfer molding,

[0026] Figure 4 A device according to Figure 3 without an electrical stack,

[0027] Figure 5 Details of the electrical stack of the rotor of an electric motor,

[0028] Figure 6 A cross-section of a casting element of a device according to Figure 1 shown,

[0029] Figure 7 A view similar to Figure 6 showing another casting element for an electrical stack,

[0030] Figure 8Top view of a rotor of an electric motor, including an electrical lamination stack, shown locally

[0031] Figure 9 Shows a perspective view of a device according to Figure 8 .

[0032] Unless otherwise stated, the following explanations relate to all embodiments. Components that correspond to each other or have the same principle function are denoted by the same reference numerals in all the figures. Detailed Description

[0033] The functional components of the electric motor, denoted generally by reference numeral 1, i.e., the stator or the rotor, include an electrical lamination stack 2, which is constructed from a plurality of individual laminations 3. An electrical insulation layer is present between the individual laminations 3, which can be provided by separate components or by a coating of the individual laminations 3. It is also possible that the electrical insulation within the electrical lamination stack 2 is produced only by transfer molding, which will be discussed in more detail below.

[0034] In all cases, the individual laminations 3, which are stacked on top of each other, i.e., the individual electrical laminations, have a plurality of through openings 4, in particular circular holes, with a closed periphery, and / or slots 8, which are generally referred to as through openings without a closed periphery. The through openings 4, 8 can be produced, for example, by punching. At least each of the through openings 4, 8 is completely or partially filled with a casting element 5 made of a thermosetting material. The casting element 5 is electrically insulating and establishes a form-fitting, mechanically loadable connection between the individual laminations 3.

[0035] Each casting element 5 extends parallel to the central axis of the functional component 1 and includes so-called shrinkage sections 6 and form-fitting sections 7, which are arranged alternately. The width of the shrinkage section 6 is denoted by B min and the width of the form-fitting section 7 is denoted by B max . In the axial direction of the functional component 1 and thus also of the casting element 5, each shrinkage section 6 has a thickness D E corresponding to the thickness of the individual lamination 3. The thickness of the form-fitting section 7, which results between the individual laminations 3, is denoted by D 7 .

[0036] In an embodiment according to Figure 1 , the casting element 5 has the shape of a bolt, the shrinkage section 6 of which is configured as an annularly surrounding groove. The diameter of the cylinder describing the bolt has a diameter corresponding to the maximum width B max . The form-fitting section 7 and the shrinkage section 6 arranged therebetween have the shape of a disk or a rod section. The forces acting on the individual lamination 3, i.e., the axial forces with respect to the central axis of the functional component 1, are absorbed by the form-fitting section 7 via the casting element 5. This also applies to the case where - as opposed to in Figure 1The different - form - fitting section 7 shown extends significantly less in the axial direction than the shrinkage section 6.

[0037] The steps for manufacturing the electrical lamination stack 2 according to Figure 2 are described in detail below according to Figure 3 and 4 To introduce the mechanically loadable casting element 5, a mold designated as a whole by 11 is used, which mold includes a sprue plate 12, a vent plate 13, and a carrier plate 14 and is configured as a transfer - molding mold, i.e., a mold for pressure casting. In the Figure 3 visible state, the thermosetting, pre - heated material is extruded from the sprue plate 12 through the through - holes 4, where the through - holes 4 are present in the current case in the form of nine through - holes evenly distributed over the circumference of the stator 1.

[0038] During pressure casting, i.e., transfer molding, the form - fitting section 7 of the casting element 6 is automatically also produced, where the actual shape of the form - fitting element 7 can differ from the ideal shape shown in Figure 1 and 6 After the casting element 5 has cured, the functional part 1 can be removed from the mold 11. As can be seen from Figure 4 the mold 11 has, in its central section, a plurality of, in this case three, plate - shaped centering braces 15, the height of the central section corresponding to the axial extension of the stator 1, by means of which the correct positioning of the electrical lamination stack 2 relative to the mold 11 during pressure casting is ensured.

[0039] Figure 5 The rotor 1, which is shown locally as the functional part of the electric motor, i.e., the inner rotating part, can also be manufactured with the aid of the mold 11, the basic construction of the mold corresponding to the structural form according to Figure 3 and 4 In the Figure 5 case, the through - holes 8 are present in the form of slots, the slot sides of which are designated by 9 and the slot bottom by 10. In the case of a casting element 5 that matches the shape of the slot 8, the casting element 5 also has a U - shaped cross - section. The open area of the slot 8 can be filled with windings or magnets. In a manner not shown, the windings or magnets can be directly embedded in the casting element 5.

[0040] According to Figure 5 the form - fitting section 7 of the U - shaped casting element 5 extends beyond the slot sides 9 and the slot bottom 10 into the area between the single laminations 3, such that in this case, as in the embodiment according to Figure 1 and 6 a desired form - fitting between the single laminations 3 is also obtained.

[0041] Figure 7The dovetail cross-sectional configuration of the thermosetting casting element 5 is shown, which is considered for use as a stator and rotor of a functional component 1 of an electric motor or generator. In a manner not shown, the casting element 5 can also have a cross-section of the type of a standing clock or a four-leaf clover. In all cases, in the lateral direction of the overall elongated casting element 5, the form-fitting section 7 projects beyond the shrinkage section 6, such that the desired form-fitting function is obtained. In order to establish the required mechanical stability of the functional component 1, no additional connection between the single laminations 3, such as by stamping and stacking, bonding or welding, is required.

[0042] In Figure 8 and 9 the rotor 1 of an electric motor is shown locally, where magnets 17, i.e. permanent magnets, are present in a large number of recesses 16 provided by the electrical lamination stack 2 of the rotor 1. Furthermore, in Figure 8 and 9 a through-opening 4 with a closed periphery is visible, which is provided for receiving a casting element 5 made of a thermosetting material, namely epoxy resin, not shown in this case.

[0043] The through-opening 4 is configured in the type of a four-leaf clover in the current case and is thus particularly suitable for absorbing forces in different directions. When the material for forming the casting element 5 cures, mechanical stresses occur, which hold the electrical lamination stack together particularly effectively. A plurality of four-leaf clover-shaped through-openings 4 of the shown type are distributed over the cross-section of the electrical lamination stack 2 and replace particularly separate, metallic connecting elements as well as the connections formed by the deformation of the single laminations 3 in a common electric motor.

[0044] List of reference numerals

[0045] 1 Functional component, stator, rotor

[0046] 2 Electrical lamination stack

[0047] 3 Single lamination

[0048] 4 Through-opening with a closed periphery

[0049] 5 Casting element

[0050] 6 Shrinkage section of the casting element

[0051] 7 Form-fitting section of the casting element

[0052] 8 Slot

[0053] 9 Slot side

[0054] 10 Slot bottom

[0055] 11 Mold

[0056] 12 Sprue plate

[0057] 13 Ventilation plate

[0058] 14 Bearing plate

[0059] 15 Centering brace

[0060] 16 Recess

[0061] 17 Magnet

[0062] B max Maximum width

[0063] B min Minimum width

[0064] D 7 Thickness of the form-fitting section

[0065] D E Thickness of a single lamination.

Claims

1. An electrical lamination stack (2) for an electric machine, having a plurality of individual laminations (3), characterized in that The individual laminations are stacked in electrical insulation from one another and have through-openings (4, 8) that are aligned with one another, and a thermosetting casting element (5) that passes through the through-openings (4, 8) and engages behind the individual laminations (3) in a form-fitting manner, the casting element (5) having a maximum width (B max ), which maximum width is determined between two individual laminations (3) and is at least 1.5 times the minimum width (B min ) of the casting element (5) determined in the through-openings, the maximum width (B max ) being no greater than three times the minimum width (B min ) of the casting element (5).

2. The electrical lamination stack (2) according to claim 1, characterized in that the individual laminations (3) are stacked on top of one another without a form-fit being formed between the individual laminations (3).

3. The electrical lamination stack (2) according to claim 1, characterized in that the through-openings (4) each have a closed peripheral edge.

4. The electrical lamination stack (2) according to claim 1, characterized in that the through-openings (8) are configured as grooves.

5. The electrical lamination stack (2) according to claim 1, characterized in that the electrical lamination stack belongs to the rotor of the electric machine.

6. The electrical lamination stack (2) according to any one of claims 1 to 4, characterized in that the electrical lamination stack belongs to the stator of the electric machine.

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