Rotor or stator assembly

Abstract

Rotor or stator assembly (1) for an electrical machine, comprising a rotor or stator (2) with a plurality of rotor or stator slots (4) for receiving an electrical conductor H within each rotor or stator slot (4), wherein an insulating coating (5) is applied to the inside of each of the rotor or stator slots (4), characterized in that the insulating coating (5) is formed in regions by at least one section of a fixing element (10).

Description

The invention relates to a rotor or stator assembly for an electric machine, having a rotor or stator with a plurality of rotor or stator grooves for receiving in each case an electrical conductor within a rotor or stator groove, wherein an insulation coating (5) is applied in each case on the inside of the rotor or stator grooves.Electric machines are known in the prior art in extensive applications and various configurations. In addition to categorization into static, i.e. static, electric machines and rotating, dynamic machines, a plurality of different configurations are again known within the dynamic category, for example grouped according to the type of current used, such as direct current, alternating current and three-phase alternating current, and various winding arrangements for generating a magnetic rotating field. Different modes of operation of the machines can be realized by commutator machines, asynchronous machines and synchronous machines.Electrical machines have electrical conductors arranged in various ways, such as wire coils or windings or so-called hair pins, I pins, through which the electrical current flows. Generally available descriptions of hairpin technology suggest that it is a winding technology for stators in electric motors and generators. It is used in particular in traction motors for electric vehicles. In contrast to the coil winding technique, the hairpin technology is based on plug-in coils which are inserted into the stator slots of the laminated core. These plug-in coils, so-called hair pins, consist of painted flat copper wires bent in a U-shape and resemble hairpins (engl. Hair pins). Generally, hair pins are understood to mean plug-in coils in U geometry. Besides hair pins in U geometry, the so-called I-pin technology and the concept of wave winding (continuous hair pin) also belong to the methods of plug-in coil technologies.The magnetic flux occurring as a result of the flow through the wire coils, hair pins, I pins is selectively guided in an iron core, which is also referred to as a magnetic circuit. This core consists of materials which can conduct the magnetic flux well, for example of a plurality of stacked electric sheets, which are also referred to as lamination stacks. These stacked or layered lamination stacks are designed within dynamic electric machines as stators or rotors, also referred to as armatures. The stacking together with the one-sided insulation of the lamination stacks serves to suppress eddy currents.In dynamic machines, lamination stacks, which can be designed as stators or rotors, are primary components and have a substantial influence on the properties of the machine and its economics. The magnetic fields generated in electric machines cause a movement of the machine parts relative to one another, usually a rotational movement, by the forces generated thereby. For the electrical insulation of the current-carrying parts with respect to one another and with respect to the external environment, electrical machines have insulation regions.Insulation regions for electrical insulation are required, inter alia, for example between the winding regions or hair pins or I pins and the lamination packs. For this purpose, depending on the design of the lamination stacks as stators or rotors, insulations are introduced by insulating paper, plastic sheathing or plastic injection-molding on inner surfaces of the lamination stacks and on the pole grooves. In insulation regions made of plastic, polymers are used, for example. If the insulation regions are formed by plastic injection molding, the polymers are preferably formed by injection-moldable thermosetting plastics or thermoplastics and form insulation layers in the form of winding supports around the individual lamination stack poles, which serve to accommodate the stator coils or rotor coils or the hair pins or I pins.A number of requirements and boundary conditions, which in some cases have a more stringent effect, are imposed on the insulation regions of such electrical machines since they have a very considerable influence on the costs and properties of the electrical machines, inter alia by the required material use, the installation space requirement, the processability, the respective processing method and the material properties. In order to promote the degree of winding fill of the winding regions in the pole slots on the one hand and to promote the greatest possible material wall thicknesses of the laminated packets in order to support the required magnetic flux in the laminated packets on the other hand, it is desirable to minimize the insulation region wall thicknesses. From the perspective of the insulation effect of the insulation regions and the realization within the scope of processing limits, the insulation wall thicknesses cannot be reduced arbitrarily.A further important requirement for insulation is that the electric machine must be cooled directly and internally. Effective cooling systems frequently operate with a liquid or flowable cooling medium, for example oil or cooling water. When such cooling media are used, the insulation must both seal the current-carrying components and be resistant to the cooling medium. For this reason, paper-based insulation is frequently ruled out in cooled electrical machines, and plastic-based insulation materials are used. A more efficient approach for direct cooling of the electric machine within a stator or within the stator slots for the electric conductors such as hair pins or I pins (the term hair pins is used below for all forms such as hair pins, I pins, U pins etc.) is the guidance of the cooling medium directly along the stator slots. For this purpose, the media-tight separation between the current-carrying components and the cooling medium by means of a corresponding stator injection molding is necessary. A primary function of the stator injection molding is always the insulation effect.Various insulations are known in the prior art, for example by a combination of paper and resin or a plastic lining which fixes the current-carrying electrical conductors, such as hair pins, for example at a distance from the wall of the groove by means of stiffening ribs as shown in DE 10 2019,122 469 A1 or radially by means of a U-shaped lining as shown in DE 10 2004 016 655 A1, but also in the axial direction of the stator by means of supporting elements which secure the lining in the axial direction, as shown in EP 3 723 243 A1. That is, the prior art discloses solutions for fixing the hair pins within the stator or rotor grooves by means of the insulation liners.To produce the insulating and media-separating stator encapsulation, plastic injection molding methods or else pressing methods are used. To keep free the winding spaces of the stator or rotor slots for the hair pins, so-called slot cores are used inside the injection molding tool. These slot cores are in practice tool place holders which, during the injection molding process, keep free the space for the electrical conductors to be introduced later, such as hair pins or windings, of injection molding material and define the available space for the plastic insulation material to be injected. Due to the desired thin-wallness and shape precision of the insulation material, it is particularly important that the slot cores are guided and positioned in a particularly positionally stable and dimensionally stable manner within the stator or rotor slots. In this case, the considerable deformation and displacement forces which are exerted on the slot cores during the injection molding process by the insulation material introduced into the mold with high injection molding pressure must also be taken into account.DE 10 2022 100 944 A1 shows a tool system for the plastic casting of a stator injection molding with slot cores, which comprises axially movable slot cores in order to prevent the slot cores from being braced in the axial direction and undergoing a deformation that counteracts the required dimensional and positional accuracy.CN 113400570 B discloses an automatic alignment mechanism and an automatic alignment device for slot cores within an injection molding tool comprising a mounting seat, a positioning device and a fixing device, wherein the mounting seat is mounted on the underside of a press plate of a pressing mechanism, moves together with the press plate and is provided with a slot core mounting position, the positioning device is arranged at the slot core mounting position and is used for correcting the axial position of a slot core. The nut core is clamped and suspended in the radial direction by the automatic alignment mechanism, the automatic alignment is achieved by the positioning device. A radial adjustment mechanism is disposed in a stator mounting groove, the radial position of a stator can be adjusted during compression molding, therefore positioning errors are reduced.The solutions available in the prior art for groove core positioning are not only complicated and complicated, but also do not offer any solutions for the injection pressure gradients occurring in the injection molding tool, which bend the groove cores in the normal direction to their longitudinal extent, and can bend through. The bending in the normal direction means that the respective groove core is deformed radially and, or elastically or also plastically and frequently in an arcuate manner in the circumferential direction with respect to its longitudinal extension center axis.Injection pressure gradients are a consequence of the frequently tough flow behavior of the molten plastic insulation materials which are introduced with high pressure into the injection mold and the gap between stator or rotor grooves and the respective groove core. The same applies to pressing methods. Depending on the position of the injection into the injection mold and by forming flow fronts, locally different surface pressures, which also act on the slot cores, are formed within the flow gaps as a result of the pressure differences, the resulting force action directions of which can lead to the slot core bending. As a result, the wall thickness of the insulation coating to be sprayed is influenced at least in the regions of the deflection and can result in insulation thickness deviations as far as insulation defects. The result may be an electrical short circuit.The bending problem of grooved cores increases the greater the longitudinal extension of the grooved core relative to its cross section, the gap thickness for or the wall thickness of the insulation coating decreases and, or the injection chuck used and the plastic insulation material and its flow behavior in the plasticized state. Since minimum values are practically always sought for insulation wall thicknesses in electric motor construction, the permissible tolerances are extremely small, so that groove core bending must also be minimized.It is an object of the invention to improve insulation coatings in rotor or stator grooves produced by injection molding with respect to their wall thickness accuracy and to at least partially reduce the disadvantages of known solutions.For the solution, the invention proposes at least one fixing element with support regions that is an integral component within the insulation coating of a rotor or stator slot and that, during the production of the insulation coating by injection molding, supports a slot core normal to its longitudinal extent, i.e. radially and, or in the circumferential direction. The at least one fixing element of the insulation coating has at least similar insulation properties compared to the further insulation coating and is at least largely embedded in the insulation coating. Preferably, at least the at least one support region is produced from a similar or identical material to the insulation coating and is connected to the insulation coating of the rotor groove or stator groove in a medium-tight and at least largely materially integral manner.Depending on the manner in which the fixing elements are introduced into the rotor or stator, variant embodiments of the fixing elements can be distinguished into axial insertion elements, radial insertion elements or insert parts.Before the actual injection molding of the insulation coating by introducing pressurized, plasticized plastic insulation material into the injection mold and the flow gap, the at least one fixing element is inserted together with the slot core into a rotor slot or stator slot. The inner wall of the rotor or stator slot and the outer wall of the slot core form the cavity for the flow gap as a cavity for the later insulation coating. The at least one support region of the fixing element is positioned within the flow gap and supports the slot core against bending as a result of the plastic insulation material to be introduced, plasticized and pressurized, radially and, or in the circumferential direction of the slot core relative to its longitudinal extent, against the inner wall of the rotor or stator slot.When the plastic insulation material cools in the flow gap after it is injected into the injection mold, the at least one support region of the fixing element, after it has been completely surrounded by plastic insulation material at least on its end faces, is preferably connected to the plastic insulation material in a medium-tight manner in a largely materially integral manner. In this way, a surface-tight insulation coating is produced within a rotor or stator groove, which is both insulating with respect to an electrical conductor such as a hairpin or a winding and at the same time has largely media-tight properties, so that a sealing function with respect to an active liquid cooling of the electrical machine can be realized, for example, by oil.Usually, groove cores are often fixed at their ends within the injection molding tool, so that their ends are fixed. If such a clamping situation is present, then the bent geometry of the slot core resembles an arc, that is to say the radial deflection and deflection occurring or occurring in the circumferential direction without support is at a maximum in the central region thereof, as seen in the longitudinal extent of the slot core. Recognizing this relationship, the invention provides that the at least one fixing element is preferably arranged in or in the vicinity of the central region of the slot core. In this way, the flow gap thickness tolerances and thus the wall thickness tolerance of the insulation coating can be significantly reduced and the insulation thicknesses that can be produced can thus be reduced.With a particularly large axial extension of the lamination stacks of the rotor or of the stator and thus also of the axial longitudinal extension of the rotor or stator slots, slot cores with an axial longitudinal extension matched thereto are required. As a result, the ratio of the longitudinal extension of the slot core to its cross section becomes particularly large, so thatarranging the at least one supporting region of the at least one fixing element in or in the vicinity of the central region, andthe bending stiffness of grooved cores with a large longitudinal extension of the grooved core relative to its cross section decreases and thus benefits in particular from a support in the central region.Recognizing these facts, the invention provides that in a possible embodiment variant an axially transversely divided rotor or stator can be provided. The transverse division is preferably realized in the axial central region of the rotor or stator and thus also in the axial central region of the slot core and enables the positioning of at least one support region of the at least one fixing element in the central region without having to introduce it into the flow gap from the end of the slot core over a greater length of longitudinal extent. After the positioning of the at least one support region of the at least one fixing element in the region of the transverse graduation of the rotor or stator, both rotor or stator parts can be assembled detachably or non-detachably using suitable joining methods.In a further embodiment variant of the invention, the inventive concept is implemented in the case of undivided rotors or stators by fixing elements being inserted radially into the rotor or stator from the outside. For this purpose, the rotors or stators are provided with suitable radial bores which are accessible from the outside. Alternatively to radial bores within the rotor or stator, insertion pockets can be provided adjacent to the rotor or stator grooves, into which insertion pockets fixing elements are inserted. When manufacturing the rotors or stators by stacking the laminations, this requires that the fixing elements, which are geometrically designed as insert parts, are inserted during the stacking of the laminations.It can be particularly advantageous to feed the plastic melt in the form of plasticized plastic insulation material radially laterally into the rotor groove or stator groove. At these injection points, particularly high pressure gradients and thus radially acting transverse forces are usually produced on the groove core. The invention provides that such injection points are preferably positioned adjacent to the at least one fixing element arranged in a central region of the respective slot core, since the supporting effect reduces or prevents a bending deformation of the slot core.A further advantage of the positioning of injection points in the central region and adjacent to the at least one fixing element arranged in a central region of the respective slot core is that practically the flow gap length in the axial extension is nearly halved compared to an end injection. The flow gap length is a critical geometric variable because with increasing flow gap length the risk of defects in the insulation coating increases considerably, in particular in the case of the desired thin-walled insulation layers.Locally adjacent to the injection points for the plastic insulation material and thus also to the fixing element, at least one coolant supply can also be arranged for realizing an active cooling of the electric machine.The invention is explained in more detail below with reference to exemplary embodiments in conjunction with the figures. The following are shown: FIG. 1 shows the perspective exploded illustration of a first exemplary embodiment of the rotor or stator assembly in a divided embodiment, and FIG. 2 shows the three-dimensional view of the fixing element formed as a fixing element ring with a plurality of support regions, and FIG. 3 shows a perspective partial section of the fixing element ring, and FIG. 4 is a perspective partial section of the transverse graduation area of the rotor or stator; and FIG. 5 shows a perspective view of a second exemplary embodiment of a fixing element designed as a fixing element slide-in device, and FIG. 6 shows a perspective, cut-away partial region of the rotor or stator with fixing element slides introduced radially from the outside, and FIG. 7 shows a perspective view of a third exemplary embodiment of a fixing element designed as a fixing element insert, and FIG. 8 shows a perspective, cut-away partial region of the rotor or stator with the fixing element insert inserted.FIG. 1 shows the perspective exploded illustration of a first exemplary embodiment of the rotor or stator assembly 1 in a divided embodiment.The rotor or stator assembly 1 is formed by a rotor or stator 2 and is constructed by a lamination stack 3 (not shown). The lamination stack is composed of a plurality of disk-shaped laminations stacked in the axial direction of the rotor or stator 2. The first exemplary embodiment of the rotor or stator assembly 1 shown in FIG. 1 is divided in a central region M of the rotor or stator 2 at a bearing surface of adjacent laminations and has, formed in the dividing plane as a transverse division Q, a fixing element 10 designed as a fixing element ring 11.For the purpose of illustration, some slot cores N and electrical conductors H are illustrated, which are both not part of the rotor or stator assembly 1. In each case, a slot core N is introduced before and during the injection molding process for producing the insulation coating 5 applied on the inside of the rotor or stator slot 4; a hairpin is provided in the fully assembled motor with rotor or stator assembly 1 in each rotor or stator slot 4.FIG. 2 shows the three-dimensional view of the fixing element 10 designed as a fixing element ring 11 with a plurality of support regions 14. The fixing element ring 11 can be used particularly advantageously in the case of rotor stators 2 having one or more transverse separations Q, that is to say in the case of two- or multi-part rotor stators 2 whose separations take place transversely with respect to the longitudinal extent thereof.FIG. 3 comprises a perspective partial section of the fixing element ring 10 with a recess 15 and support areas 14. The fixing element ring 11 has recesses 15 which are open inwards in number and position corresponding to the rotor or stator grooves 4 and are each provided with preferably at least two support areas 14.The support regions 14 are designed as planar regions; for example, a quadrangular geometry is shown for the purposes of illustration. All types of suitable other geometries with any other desired planar contour are likewise possible. The support regions 14 have a wall thickness, that is to say the wall thickness transversely with respect to the axial extent thereof, which is preferably below the wall thickness of the insulation coating 5. This makes it possible for the plastic insulation material of the insulation coating 5 to embed the surface side of the support regions 14 almost completely and thus to ensure a media-tight, integral embedding of the support regions in the insulation coating 5.The actual support of the slot cores N during the injection molding process for producing the insulation coating 5 by injection of molten plastic insulation material into the flow gap is effected by at least one support projection 16 in each case within the flat support region 14 directed toward the inner side of the rotor or stator slot 4 or recess 15.FIG. 4 shows a perspective partial section of the transverse graduation area of the rotor or stator 2 of the rotor or stator assembly 1 in the exemplary embodiment variant with a rotor or stator 2 divided two or more times. At least one fixing element 10 is inserted or interposed in the transverse graduation Q lying orthogonally to the axial extension of the rotor or stator 2.A slot core N (introduced for producing the insulation coating 5 and supported by the support regions 14) or hairpin H (introduced into the fully assembled electric motor and insulated by the insulation coating with integrated support regions 14 of the fixing element 10) is outlined by way of example. The recesses 15 of the fixing element ring 11 are positioned axially flush with each other with the rotor or stator grooves 4; the support regions 14 engage at least in regions in the rotor or stator grooves 4. Preferably, insertion pockets 7 are worked into the engagement sections of the support regions into the rotor or stator grooves 4.FIG. 5 shows a perspective view of a second exemplary embodiment of the fixing element 10 designed as a fixing element slide-in 13, This second exemplary embodiment of the invention is particularly advantageous if, in the case of undivided rotor or stators 2, that is to say in the case of rotor or stators 2 without a transverse division Q, the fixing element 10 is intended to support a slot core in the central region M of the rotor or stator 2 normal to the longitudinal extent thereof, that is to say radially and, or in the circumferential direction, during the injection-molding production of the insulation coating 5, and the support region 14 is an integral constituent part of the insulation coating 5 after the insulation coating production.The fixing element slide-in 13 is designed in its axial cross section to correspond to a radial bore 6 in the central region M of the rotor or stator 2, so that the fixing element slide-in 13 can be pushed into the radial bore 6 with the support regions 14 leading in the insertion direction ER.The fixing element slide-in 13 can have a box-shaped base body from which the support regions 14 extend. In this exemplary embodiment of the fixing element slide-in 13 shown here, the support regions 14 are designed similar to slide-in blades and each have at least one support projection 16 on the inside of one another.FIG. 6 shows a perspective partial region of the one-piece rotor or stator 2 in a sectional illustration with fixing elements 10 in the form of fixing element inserts 13 introduced radially from the outside. Since the supporting effect of the fixing elements 10, 13 on the respective slot core N (not illustrated) is particularly advantageous in the central region M of the rotor or stator 2, the radial bores 6 are provided in the central region M. Arrangements which differ from these arrangements as desired are likewise possible.In the radially inserted position of the fixing element slides 10, 13, the support regions 14 engage in the respective rotor or stator slot 4 and can support the slot core N via the support projections 16.FIG. 7 depicts a perspective view of a third exemplary embodiment of a fixing element 10 designed as a fixing element insert 12. The U-shaped basic geometry is substantially formed by the support regions 4 with a transverse connection lying therebetween.This third exemplary embodiment of the invention is particularly advantageous if, in the case of non-divided rotor or stators 2, that is to say in the case of rotor or stators 2 without transverse division Q, the fixing element 10, designed as a fixing element insert 12, is introduced during the production of the rotor or stator 2.The rotor or stator 2 is designed as a lamination stack 3 and is constructed by axially stacking the individual laminations one on top of the other. In the fixing element 10 shown in FIG. 7, implemented as a fixing element insert 12, the latter is inserted into suitable insert pockets 7 during the stacking process of the laminations, preferably in the central region M of the rotor or stator 2.FIG. 8 shows a perspective partial region of the one-piece rotor or stator 2 in a sectional illustration with a fixing element 10 in the form of a fixing element insert 12 which is exemplarily inserted into the rotor or stator groove 4 illustrated on the left side. The rotor or stator groove 4 illustrated on the right side is outlined without a fixing element insert 12 and thus allows the insertion pocket 7 to be illustrated which is realized in the form of a groove and adjacent to the rotor or stator groove 4 in that the laminations 3 of the rotor or stator 2 have corresponding notches in this region.Depending on the design of the fixing element 10 as a fixing element ring 11, as a fixing element insert 12 or as a fixing element insert 13, the geometry of the insert pocket 7 is different, but is constructed in a manner corresponding to the respective fixing element type 10, 11, 12, 13.Regardless of the configuration of the fixing element 10 as an axial insertion element, a radial insertion element or as an insert, its material base is selected in a compatible manner with the material of the insulation coating; for example, thermoplastic materials such as liquid-crystalline polymers or thermosets can be used.Reference numerals denote reference numerals1 Rotor or stator assembly 2 Rotor or stator 3 Lamination stack 4 Rotor or stator groove 5 Insulation coating 6 Radial bore 7 Insertion pocket 10 Fixing element 11 Fixing element ring 12 Fixing element insert 13 Fixing element insert 14 Support region 15 Recess 16 Support projection Q Transverse pitch N Slot core M Central region ER Insertion direction H Electrical conductorReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2019 122 469 A1

[0009] DE 10 2004 016 655 A1

[0009] EP 3 723 243 A1

[0009] DE 10 2022 100 944 A1

[0011] CN13405570 B

[0012]

Claims

Rotor or stator assembly (1) for an electric machine, having a rotor or stator (2) with a plurality of rotor or stator grooves (4) for receiving in each case an electric conductor H within a rotor or stator groove (4), wherein an insulation coating (5) is applied in each case on the inside of the rotor or stator grooves (4), characterized in that the insulation coating (5) is formed in regions by at least one section of a fixing element (10).Rotor or stator assembly (1) for an electric machine according to Claim 1, characterized in that the at least one section of the fixing element (10) is an integral constituent part of the insulation coating (5) such that the insulation coating (5) is largely media-tight.Rotor or stator assembly (1) for an electric machine according to Claim 1, characterized in that the at least one section of the fixing element (10) is a supporting region (14).Rotor or stator assembly (1) for an electric machine according to Claim 3, characterized in that at least one support projection (16) is arranged within a support region (14).Rotor or stator assembly (1) for an electric machine according to Claim 4, characterized in that the fixing element (10) and, or the at least one support region (16) of the fixing element (10), are arranged within an insertion pocket (7) of the rotor or stator (2) adjacent to the respective rotor or stator groove (4).Rotor or stator assembly (1) for an electric machine according to Claim 1, characterized in that the fixing element (10) is designed as a fixing element insert (12).Rotor or stator assembly (1) for an electric machine according to Claim 6, characterized in that the fixing element insert (12) has a U-shaped base body.Rotor or stator assembly (1) for an electric machine according to Claim 1, characterized in that the fixing element (10) is designed as a fixing element slide-in device (13).Rotor or stator assembly (1) for an electric machine according to Claim 8, characterized in that the rotor or stator (2) has at least one radial bore (6) corresponding in each case to a rotor or stator groove (4) and the fixing element slide-in (13) has a cross section corresponding to the radial bore (6), with the result that the fixing element slide-in (13) can be pushed into the radial bore (6) in the direction of slide-in ER and the at least one support region (14) is arranged within the insulation coating (5).Rotor or stator assembly (1) for an electric machine according to Claim 1, characterized in that the rotor or stator (2) has at least one transverse graduation Q lying in its axial extent.Rotor or stator assembly (1) for an electric machine according to Claim 10, characterized in that at least one transverse graduation Q is preferably located in a central region M of the rotor or stator 2.Rotor or stator assembly (1) for an electric machine according to Claim 10, characterized in that a fixing element (10), designed as a fixing element ring (11), is arranged in at least one transverse pitch Q of the rotor or stator 2.Rotor or stator assembly (1) for an electric machine according to Claim 12, characterized in that the fixing element ring (11) has a cutout (15) which corresponds in number and position to the rotor or stator grooves (4).Rotor or stator assembly (1) for an electric machine according to Claim 1, characterized in that the fixing element (10) consists of a thermoplastic material, for example a polymer or thermoset.Electric machine having a rotor or stator assembly (1) according to one of the preceding claims.

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