Rotor with an overmolded balancing disc

Abstract

The present invention relates to a rotor (105) for an electric motor (102), comprising a rotor shaft (107) rotatable about an axis of rotation (109) of the electric motor (102); a rotor core (111) arranged in a rotationally fixed manner relative to the rotor shaft (107) and in which a plurality of magnets (116) are fixed; a cover (121) attached to an axial end face (113) of the rotor core (111), wherein the cover (121) comprises a radially inner first section (115) and a radially outer second section (120), wherein the first section (115) is formed annularly around the rotor shaft (107), wherein the second section (120) is applied by means of a forming process, in particular by overmolding the first axial end face (113) and / or the first section (115) with a potting material, such that the second section (120) at least partially surrounds the first section (115).The present invention further relates to an electric motor (102) for an at least partially electrified vehicle (100), an at least partially electrified vehicle (100), and a method (200) for manufacturing a rotor (105) for an electric motor (102).

Description

[0001] The present invention relates to a rotor for an electric motor. The present invention further relates to an electric motor for an at least partially electrified vehicle and to an at least partially electrified vehicle. The present invention further relates to a method for manufacturing a rotor for an electric motor.

[0002] Fully electric vehicles and hybrid vehicles are well known from the state of the art. These electric vehicles are powered exclusively or partially by one or more electric motors as drive units.

[0003] Electric axle drives for purely electric vehicles and hybrid electric vehicles are well known in the art. Such drive systems generally comprise an electric motor with a stator and a rotor rotatably mounted in the stator. The stator has several stator windings, known as phase strands, each of which is supplied with a corresponding phase current during operation. The phase currents are phase-shifted from one another, such that the current flowing through the stator windings generates a rotating magnetic field. The rotor has a rotor shaft and a rotor core fixed to the rotor shaft, in which several magnets are mounted. The magnetic interaction between the rotor magnets on the one hand and the rotating field on the stator side on the other generates a torque that sets the rotor in rotation.

[0004] For example, EP 3 540 919 A1 discloses a rotor for a rotating electric machine. The rotor includes end disks with balancing bores (balancing disks). The end disks comprise an inner component made of a metallic material and an outer component arranged around the inner component, made of a non-metallic material. The inner component may have a series of recesses in an outer edge region. The recesses are located near the rotor's permanent magnets to create a magnetic gap between the magnetic core and the inner component.

[0005] Common electric motor rotors typically use high-density magnetic materials to manufacture the balancing discs, which significantly contributes to the rotor's overall weight. Furthermore, joining two components to form the balancing discs often results in undesirable shapes and increased air resistance. Additionally, balancing discs with edges between the magnetic poles cause and exacerbate the pumping effect of the coolant within the motor, impairing a smooth coolant flow.

[0006] The object of the present invention is therefore to provide a rotor for an electric motor with which the aforementioned disadvantages are at least partially overcome.

[0007] The aforementioned technical problem is solved by the rotor for an electric motor, an electric motor for an at least partially electrified vehicle, an at least partially electrified vehicle, and a method for manufacturing a rotor for an electric motor according to the main claim and the dependent claims, respectively. Advantageous embodiments are the subject of the dependent claims. The advantages described in connection with the claims relating to the rotor also apply to the electric motor and the vehicle according to the invention, as well as the method according to the invention.

[0008] The present invention is based on the understanding that a cover for an efficient or improved rotor for an electric motor should fulfill several conditions simultaneously. Firstly, the cover should be relatively lightweight to avoid unnecessarily increasing the overall weight of the rotor and thus the electric motor. Simultaneously, the cover should be able to function as a balancing disc, avoiding a large number of balancing holes and / or large-dimensions balancing holes to ensure the cover's stability during operation of the electric motor. Furthermore, the magnets installed in the rotor should be magnetically shielded by an overlying material to prevent interference with the magnetic flux within the electric motor and to avoid a "magnetic short circuit."Ultimately, the cover should be designed with a regular pattern to minimize air resistance.

[0009] The present invention proposes a rotor for an electric motor comprising a rotor shaft and a rotor core. The rotor shaft is rotatably mounted about an axis of rotation of the electric motor. The rotor core is arranged around the rotor shaft in a rotationally fixed manner, preferably also rotationally symmetrical. A plurality of magnets (rotor magnets) are mounted in the rotor core. The rotor core can have an arrangement of axially laminated, electrically insulated sheet metal parts (laminates), for example, steel sheet metal parts. This creates a laminated core for the rotor core. This design of the rotor core reduces eddy current losses that arise in solid metal parts due to alternating magnetic fields. By using electrically insulated laminates, the path for such eddy currents is interrupted, which significantly reduces the losses.This can also result in improved heat dissipation from the rotor core, which increases the service life of the electric motor.

[0010] The rotor further comprises a cover attached to an axial end face, particularly an end face, of the rotor core. The cover, which preferably functions as a balancing disc with balancing bores, is multi-part, for example, two-part, and has a radially inner first section and a radially outer second section. The first section is annular, preferably rotationally symmetrical, around the rotor shaft, such that the axis of rotation or the rotor shaft extends through a central opening in the first section. The second section is applied by injection molding, in particular by overmolding the first axial end face and / or the first section with a potting compound. If the cover functions as a balancing disc, then a balancing disc overmolded with the potting compound is present.The second section, provided in this manner, at least partially surrounds the first section. The second section can be in contact with the first section and thus adhere to it or hold it at its axial end face, particularly if the second section is formed by overmolding the first section with the potting compound. Alternatively, if the second section is formed by overmolding the axial end face or the end face of the rotor core with the potting compound, it can be at least slightly spaced away from the first section.

[0011] The first section preferably has a non-circular, in particular a star-shaped, outer contour. Accordingly, the first section has several recesses arranged symmetrically with respect to the axis of rotation and / or uniformly distributed in the circumferential direction, extending inwards from an outer edge of the first section. Toothed elements are formed between adjacent recesses. The first section, and in particular the toothed elements, is arranged to overlap the rotor magnets in the axial direction. The non-circular (preferably also symmetrical) shape, in particular the star shape, allows the use of a high-density material, in particular an iron alloy, without bridging the rotor magnets, which would cause an undesirable "magnetic short circuit". The balancing bores are arranged in the outer areas of the first section, in particular in the toothed elements.The resulting relatively large distance between the balancing holes and the center point of the balancing disc allows for a reduction in the number and / or dimensions of the balancing holes. This enables the balancing disc to have almost the maximum radius of the rotor in the area of ​​the "rays" or "points" of the star shape, making the balancing holes more effective.

[0012] The first section preferably acquires a round, preferably circular, outer contour by overmolding with the potting compound. By overmolding the first axial end face of the rotor core and / or the first section, the surface and / or volume areas of the radial recesses on the outer edge of the first section, with or without direct contact between the first section and the second section, are preferably substantially covered by the potting compound or at least partially, and more preferably completely, filled with the potting compound. The second section can have a round, in particular circular, shape, the radius of which corresponds to the maximum radius of the non-round or star-shaped first section. The thickness / height of the round or circular shape of the second section can correspond to the thickness / height of the first section.In this way, the non-circular, especially star-shaped, outer contour of the first section is "rounded off" or "completed" to a circular outer contour by the second section.

[0013] The first section can be completely enclosed by the second section by overmolding the axial end face or the first section entirely with the potting compound. Alternatively, the second section can comprise several circumferentially distributed, preferably spaced-apart, subsections. These subsections may, for example, have arcuate ribs whose radius can correspond to the maximum radius of the non-circular / star-shaped first section. The arcuate ribs are separated from each other by the serrated elements of the first section in order to form a circular shape together with the latter. In this way, the non-circular or star-shaped outer contour of the first section is "rounded off" or "completed" into a circular outer contour by the second section, so that the first section acquires a round, and in particular circular, outer contour.The subsections or arc-shaped ribs can be in direct contact with the first section or spaced apart from it. Alternatively or additionally, the arc-shaped ribs can have a radial width that corresponds to or is less than the radial dimension of the recesses in the first section. This allows for a further reduction in the amount of potting material required to create the second section, enabling a particularly lightweight rotor design.

[0014] The potting compound is preferably applied by overmolding to the axial end face of the rotor core or the first section in such a way that it bridges several magnet pockets formed in the rotor core that accommodate the magnets. For this purpose, the potting compound is preferably neither magnetically nor electrically conductive. This ensures reliable fixation of the magnets in the rotor core while simultaneously reducing or even eliminating magnetic short circuits.

[0015] According to one embodiment, an end face of the first section is at least partially free of the potting compound when the first axial end face or the first section is overmolded. The end face of the first section can be completely free of the potting compound, or alternatively, only partially covered. This measure ensures reliable fixation of the second section to the first section. In particular, the amount of potting compound used to apply the second section can be comparatively reduced, allowing the rotor to be designed with a lightweight construction.

[0016] According to a further embodiment, a radial outer surface of the first section and / or an end face of the rotor core are coated with the potting compound during overmolding. The radial outer surface forms a radial outer wall surface of the first section, which extends axially corresponding to the thickness / height of the plate-shaped first section. This measure ensures particularly reliable adhesion of the second section to the first section, which increases the stability of the cover and thus also of the rotor as a whole. Furthermore, this allows the rotor magnets to be fixed more securely within the rotor core. Preferably, the overmolding of the end face can be limited to a portion of the rotor core's end face that is not covered by the first section and is therefore exposed, in order to avoid unnecessary weight increase.

[0017] According to one embodiment, the first section is formed from a magnetic material, preferably an iron material, and / or the non-magnetic potting material is furthermore electrically insulating, preferably a polymer material. Suitable iron materials include iron and iron alloys, such as cast iron and, in particular, steels. Non-magnetic materials, within the scope of the present invention, include non-ferromagnetic materials, for example, non-ferromagnetic metals and metal alloys, such as aluminum or copper. Preferred non-magnetic materials include polymers, in particular molding compounds, for example, epoxy molding compounds or epoxy resins with or without fillers. It is understood that any fillers are preferably also non-magnetic and optionally also electrically non-conductive.Particularly suitable polymer materials are those that match the molding compound used to fix the magnets in the rotor core, or that can form a material-bonded connection with the molding compound without the use of other materials, such as adhesives. Polymer materials are easy to handle, are characterized by their low weight compared to metals, and allow for simplified manufacturing and attachment of the cover to the rotor.

[0018] According to one embodiment, the first section has one or more bores, preferably wherein the one or more bores are arranged in radially outer regions of the first section, even more preferably between the plurality of recesses. Due to the arrangement of the one or more bores in the magnetic, in particular ferromagnetic, material of the first section, few bores and / or bores with small dimensions are required for balancing the rotor. The effectiveness of the bores can be further increased by arranging them between the plurality of recesses, preferably in those of the "rays" or "prongs" of the star shape.

[0019] Within the scope of the present invention, an electric motor for an at least partially electrified vehicle is further proposed, comprising a rotor according to any of the embodiments disclosed herein and a stator. The electric motor can be a permanent magnet synchronous motor (PSM), an externally excited synchronous motor (EESM or SSM), an asynchronous motor (ASM), an induction motor, or any other type of electric motor. The electric motor can function as the sole drive unit or alternatively as one of several drive units, for example, in the case of a hybrid electric vehicle (HEV) with a combination of an electric drive unit and an internal combustion engine. The electric motor can have a substantially cylindrical outer contour or a conical outer contour, for example, for a brake motor.

[0020] Within the scope of the present invention, an at least partially electrified vehicle comprising the electric motor according to the invention is proposed. The at least partially electrified vehicle can, for example, be a purely electric vehicle (EV), such as a battery electric vehicle (BEV), or a hybrid electric vehicle (HEV).

[0021] Within the scope of the present invention, a method for manufacturing a rotor for an electric motor is additionally proposed. The method comprises the following steps: providing a rotor shaft rotatable about an axis of rotation of the electric motor; providing a rotor core fixed to the rotor shaft and attaching a plurality of magnets in the rotor core; attaching a cover to an axial end face of the rotor core, wherein the cover comprises a radially inner first section and a radially outer second section, the first section being annular around the rotor shaft, and the second section being applied by means of a forming process, such as an injection molding process, in particular by overmolding the first axial end face and / or the first section with a potting material, such that the second section at least partially surrounds the first section.

[0022] The overmolding process is preferably carried out using a first tool segment, preferably plate-shaped, positioned at the end face of the rotor core, and / or a second tool segment positioned around the circumference of the first section. The first and second tool segments serve to overmold the axial end face and the first section, respectively, with the potting material and can be designed as clamping tools. After the non-magnetic potting material has been applied to the rotor core and optionally cured, the first and second tool segments are removed.

[0023] Preferably, a radial outer surface, in particular an axially extending outer wall surface, of the first section is overmolded with the potting material. More preferably, the outer surface (or end face) of the first section facing away from the axial end face of the rotor core is not overmolded, while a portion of the axial end face (or end face) of the rotor core not covered by the first section is at least partially coated with a layer of the potting material (e.g., epoxy molding compound), preferably with the exception of a margin a few millimeters wide, for example, 1 mm to 5 mm, for contact with at least one of the tool segments. This allows shear forces to be transferred directly to the overmolded end face of the rotor core, thus effectively preventing the potting material from detaching from the first section or the balancing disc under centrifugal force, while requiring a reduced amount of potting material.Additionally, the potting material can absorb tensile forces in the circumferential direction.

[0024] To further reduce mass, parts of the end-face overmolding of the rotor core can be omitted. Furthermore, instead of completely overmolding the first section or the portion of the axial end face of the rotor core that encloses the first section, the round, especially circular, outer contour of the first section (or the balancing disc) can also be achieved by attaching only narrow, arcuate ribs, thus achieving an additional mass reduction with essentially the same aerodynamic effect.

[0025] The overmolding of the axial end face or the first section is preferably carried out in a single operation together with the overmolding of the majority of magnets. This means that the potting material is injected simultaneously or within the same time interval both into the exposed spaces between the magnet pockets and overmolded onto the axial end face and / or the first section of the cover. In this way, the manufacturing efficiency of the rotor according to the invention can be increased.

[0026] The aspects mentioned above serve illustrative purposes and are not intended to limit the scope of the invention. Numerous variations of the aspects described above are possible. The various aspects discussed in this disclosure can be combined in any way to produce additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

[0027] The invention is explained below with reference to examples using the embodiments shown in the figures. The figures show: Fig. 1 a schematic representation of a vehicle comprising an electric axle drive; Fig. 2 a schematic representation of an electric motor in the electric axle drive with a stator and a rotor; Fig. 3A a schematic representation of the rotor according to one embodiment in a perspective view; Fig. 3B a schematic representation of the rotor according to one embodiment in a side view; Fig. 4A a schematic representation of the rotor according to the one in Fig. 3A embodiment shown in a top view, wherein a multi-part cover with a radially inner first section and a radially outer second section fully surrounding the first section is attached to an axial end side of the rotor; Fig. 4B a schematic representation of the rotor according to the one in Fig. 4A embodiment shown in a perspective view; Fig. 5A a schematic representation of the rotor according to a further embodiment in a top view, wherein a further multi-part cover with a radially inner first section and a radially outer second section partially surrounding the first section is attached to an axial end side of the rotor; Fig. 5B a schematic representation of the rotor according to the one in Fig. 5A embodiment shown in a perspective view; Fig. 6A a schematic representation of the rotor according to a further embodiment in a top view, wherein a further multi-part cover with a radially inner first section and a radially outer second section partially surrounding the first section is attached to an axial end side of the rotor; Fig. 6B a schematic representation of the rotor according to the one in Fig. 5A embodiment shown in a perspective view; Fig. 7 a schematic block diagram of a method for manufacturing the rotor according to one embodiment; Fig. 8A A schematic representation of the method for manufacturing the rotor according to a further embodiment using a first tool segment placed at the end face of the rotor and a second molded part placed around the circumference of the first section, in a top view; and Fig. 8B a schematic representation of the process for manufacturing the rotor according to the in Fig. 8A embodiment shown in a side view. The same objects, functional units, and comparable components are labelled with the same reference numbers in the figures. These objects, functional units, and Comparable components are identical in terms of their technical characteristics, unless the description explicitly or implicitly reveals otherwise.

[0028] Fig. Figure 1 shows a schematic representation of a vehicle 100 that is at least partially electrified. The vehicle 100 can be a purely electric vehicle or a hybrid vehicle. The vehicle 100 is equipped with an electric axle drive comprising an electric motor 102, a DC / AC inverter 106, and a gearbox 112. The electric motor 102, which is located in Fig. Figure 2, shown purely schematically and by way of example, comprises a stator 103 and a magnetically actuated rotor 105 mounted in the stator 103, with a rotor shaft 107 rotatably mounted about a rotational axis 109. The inverter 106 is arranged or connected between the drive battery 106 and the electric motor 102 for the purpose of converting a DC input voltage provided by a drive battery 104 into an AC output voltage. For this purpose, the inverter 106 has a plurality of power switches (not shown in detail here) that form a bridge circuit with several half-bridges and are controlled by control signals generated by a control unit 108. The control signals are preferably configured to switch the power switches of the inverter 106 according to pulse width modulation (PWM).In particular, opening and closing the circuit breakers generates several preferably sinusoidal, phase-shifted phase currents for the phase strands of the stator 103 of the electric motor 102. These phase currents, each fed into one of several stator windings of the stator 103 (not shown in detail here), create a rotating magnetic field inside the stator 103. This rotating magnetic field interacts with the magnetic field of the rotor 105, thereby generating a torque. The gearbox 112, which preferably has a reduced gear ratio, is designed to transmit the torque of the electric motor 102 to an axle 110 (example: a rear axle of the vehicle 100) and finally to wheels 114 (example: rear wheels).

[0029] Fig. 3A and Fig. Figures 3B each show a schematic representation of rotor 105 in a perspective view ( Fig. 3A) or a side view ( Fig. 3B). The rotor shaft 107 is surrounded by a rotor core 111 of the rotor 105, which, as in Fig. As shown in 3B, which is purely an example, it comprises an axially laminated arrangement of sheet metal parts. Fig. Figure 3A shows an axial end face 113 (or end face) of the rotor core 111. Several rotor magnets 116, preferably designed as permanent magnets and arranged in magnet pockets, extend from the axial end face 113 inside the rotor core 105. The rotor magnets 116 comprise, as shown in Fig. Figure 3B shows, purely by way of example, several (here, for example, six) edge regions, each with two rows of arc-shaped magnetic elements. However, this is not limiting for the present invention. Preferably, the rotor magnets 116 are arranged rotationally symmetrically around the rotor shaft 107.

[0030] At the axial end face 113, the rotor core 105 is fitted with a cover 121 (see Fig. 4A and Fig. 4B) provided, from which in Fig. Figure 3A shows a first section 115. The first section 115 is annular with a central opening through which the rotor shaft 107 projects beyond the axial end face 113. The first section 115 also has a radial outer surface 117 that runs along a non-circular, for example, star-shaped outer contour. For this purpose, several toothed elements 118 are formed in a radial outer area of ​​the first section 115. A recess 119 is formed between adjacent toothed elements 118. The arrangement of the recesses 119 corresponds to the arrangement of the edge regions of the rotor magnets 116.

[0031] The plate-shaped first section 115 is preferably configured as a balancing disc, or alternatively functions as such. For this purpose, several balancing bores, not shown in detail here, are formed in the first section 115 or in the balancing disc. The non-circular shape, in particular the star shape, of the first section 115 advantageously allows the use of a magnetic, in particular ferromagnetic, material, for example, an iron material, from which the first section 115 is formed, without bridging the magnets 116 or permanent magnets, which would cause an undesirable "magnetic short circuit". The non-circular shape, in particular the star shape, of the first section has a varying radius, wherein the maximum radius (approximately in the areas of the toothed elements 118 in the case of the star shape shown here) preferably corresponds substantially to the radius of the cylindrical rotor core 111.This results in more effective balancing using the non-circular, especially star-shaped, balancing disc than, for example, with a balancing disc with a uniform and smaller radius.

[0032] Fig. 4A and Fig. 4B each show the rotor 105 from Fig. 3A and Fig. 3B schematically in an axial top view ( Fig. 4A) or a perspective view ( Fig. 4B). Here, in addition to the annular first section 115 with the non-circular, in particular star-shaped, outer contour, a second section 120 is also shown. The second section 120 is formed such that it completely surrounds the first section 115. The second section 120 is formed by overmolding the axial end face 113 (see Fig. 3A and Fig. 3B) formed with a potting material. The potting material is a non-magnetic and also electrically non-conductive material whose density is lower than that of the first material of the first section 115. Polymer materials, preferably epoxy molding compounds, are suitable for this purpose. The use of the non-magnetic, preferably non-ferromagnetic, and in particular also electrically non-conductive, potting material such as a polymer material makes it possible to effectively prevent the magnetic pockets from bridging with each other. The potting material is also applied both in an outer edge region and in the areas of the recesses 118 of the axial end face 113 of the rotor core 111. This results in a circular outer ring 123 and several projections 122 oriented radially inwards from the circular outer ring 123, which define the volume of the recesses 118, as in Fig. 4A and Fig. Figure 4B is shown purely as an example; fill in completely. The projections 122 have a greater thickness than the circular outer ring 123, so that a radial outer surface 124 is formed, preferably at the same height as the first section 115, which runs along a round, in particular circular, outer contour.

[0033] In this way, the initially non-circular, particularly star-shaped, outer contour of the first section 115 is "rounded off" after the application of the potting material, so that the first section 115 acquires a round, particularly circular, outer contour through the second section 120. This advantageously reduces the air resistance of the rotor 105 during operation of the electric motor 100, especially at high speeds. Furthermore, the two-stage design of the second section 120, with its thinner outer ring 123 and thicker projections 122, reduces the amount of potting material required, thus enabling a lightweight construction.

[0034] Fig. 5A and Fig. Figures 5B each show the rotor 105 schematically in a top view ( Fig. 5A) or a perspective view ( Fig. 5B). Here too, the first section 115 of the cover 121 attached to the axial end face 113 of the rotor core 111 is shown. In contrast to the one in Fig. 4A and Fig. In the embodiment shown in Figure 4B, the second section 120 comprises several circumferentially distributed subsections 125. As in Fig. 5A and Fig. As shown in Figure 5B, adjacent sections 125 are separated from each other by a gap 126 in the axial end face 113 that is not overmolded. In the injection molding process, the axial end face 113 is not fully, but only partially, overmolded with the potting compound with respect to the first section 115. Thus, the first section 115 is partially, and therefore partially, surrounded by the second section 120 instead of being completely or fully overmolded. As shown in Fig. As can be seen in more detail in Figure 5B, the subsections 125 each have an outer ring part 129 and an arcuate rib 128 extending radially inwards from the outer ring part 129. The arcuate ribs 128 are arranged in the areas of the recesses 119 of the first section 115 and fill them, as shown in Fig. Figure 5B is shown purely as an example. However, this is not limiting for the present invention. As in Fig. 6A and Fig. As shown schematically and by way of example in Figure 6B, the arc-shaped ribs 128 can alternatively be designed with a comparatively smaller radial extent and thus spaced further apart from the radial outer surface 117 of the first section 115. The arc-shaped ribs 128 have a greater thickness than the outer ring sections 129. This two-stage design creates a radial outer surface 127 that runs section by section along a round, in this case circular, outer contour. For example, the radial outer surface 127 is not at the same height as the first section 115, but rather has a comparatively reduced height. The above measures also reduce the amount of potting material required to produce the second section 120, allowing the rotor 105 to be made even lighter.

[0035] In the Fig. 5A and Fig. 5B as well Fig. 6A and Fig. In the embodiments shown in Figure 6B, the initially non-circular, in particular star-shaped, outer contour of the first section 115 is "completed" by overmolding the first axial end face 113 with the potting compound. Specifically, the serrated elements 118 of the first section 115 are located on the outside between two adjacent arcuate ribs 128, so that the radial outer surface 117 in the areas of the serrated elements 118 and the radial outer surfaces 127 of the arcuate ribs 128 combine to form a substantially round, in particular a completely circular, outer contour. In this way, the first section 115 is given a round, in particular a circular, outer contour by the second section 120.

[0036] Fig. Figure 7 shows a schematic block diagram of a method 200 for manufacturing the rotor 105 for the electric motor 100. The method 100 comprises a process step 202 in which a rotor shaft 107 rotatable about a rotational axis 109 of the electric motor 100 is provided. The method 200 comprises a further process step 204 in which a rotor core 105, in which a plurality of magnets 116 are attached, is arranged non-rotatably relative to the rotor shaft 107. The method 200 further comprises a further process step 206 in which a cover 121 is attached to an axial end face 113 of the rotor core 105.The cover 121 has a radially inner first section 115 and a radially outer second section 120, wherein the first section 115 is formed annularly around the rotor shaft 107, wherein the second section 120 is applied by means of a forming process, in particular by overmolding the first axial end side 113, potting the magnet pockets and / or the first section 115 with a potting material, such that the second section 120 at least partially surrounds the first section 115.

[0037] When applying the second section 120, preferably one end face of the first section 115 is not overmolded, as in the embodiments from Fig. 4A-6B, for example, is the case. Alternatively or additionally, the radial outer surface 117 of the first section 115 can be overmolded, as shown in the exemplary embodiment from Fig. 4A and Fig. 4B applies. The radial outer surface 117 can be completely overmolded with the potting material. Alternatively, however, a gap can be created between the second section 120 and the radial outer surface 117 of the first section 115, as in the embodiments shown in Fig. Figures 5A to 6B are shown as examples. As in all embodiments from Fig. As shown by way of example in Figures 4A to 6B, the overmolding of the axial end face 113 of the rotor core 105 is limited to a partial area that is not covered by the first section 115. This partial area is preferably one that completely covers the first section 115 (see Figure 4A to 6B). Fig. 4A and Fig. 4B) or partially (see Fig. 5A to 6B) surrounding outer surface of the axial end face 113, apart from a preferably few (for example, 1 to 5) millimeter wide edge region which serves for the attachment of tool segments (for example, forming tools) to limit the casting compound in the forming process. In this way, casting compound is avoided on undesirable surfaces of the rotor while simultaneously forming the first section 115 in a circular shape.

[0038] The overmolding is preferably carried out using a first tool segment 211, 213 placed on / resting on the end face 113 of the rotor core 105 and a second tool segment 212, 214 placed along the circumferential direction of the first section 115, wherein these two tool segments can also be designed as a single tool segment. If the tool segments 211, 213 and 212, 214 are designed as two segments, they are to be movable relative to each other, with a displacement of the segment 211, 213 towards 212, 214 serving to improve the seal on the balancing disc 118 or the axial end face 126 of the rotor core 111. This is in Fig. Figures 8A (axial top view) and 8B (side view) are shown purely schematically and by way of example, where the application of the tool segments 213, 214 to a further axial end face or end face of the rotor core 111 opposite the axial end face 113 is also indicated. The first and second tool segments 211, 212, 213, 214 define the shape of the potting compound and can therefore be designed as a sealing tool. The first tool segment 211, 213, whose outer circumference is shown in the top view as... Fig. 8A, indicated by the inner dashed circle, is preferably plate-shaped. Accordingly, the radially inner part of the first section 115 with the smaller thickness, i.e., the projections 122 (see figure), is formed by means of the first tool segment 211, 213. Fig. 4A and Fig. 4B) or the arc-shaped ribs 128 (see Fig. 5A to 6B), formed. The second tool segment 212, 214, whose outer circumference in the top view is made of Fig. 8A, indicated by the outer dashed circle, extends along the circumferential direction of the rotor core 111 around the first tool segment 211, 213. The second tool segment 212, 214 accordingly forms the radially outer part of the first section 115 with the greater thickness, i.e., the outer ring 123 (see Fig. 4A and Fig. 4B) or the outer ring parts 129 (see Fig. 5A to 6B), formed. The in Fig. 8A and Fig.The purely schematic representation shown in Figure 8B serves only for illustration and does not depict the exact geometry of the forming tool segments 211, 212, 213, 214, in particular the mold details required for forming the projections 122, the arcuate ribs 128, and the outer ring parts 129. After the application and optional curing of the non-magnetic potting compound, which forms the second section 120, 120' of the cover 121, the first tool segment and the second tool segment 211, 212, 213, 214 are removed.

[0039] The overmolding of the axial end face 113 of the rotor core 111, or of the first section 115, is preferably carried out in a single operation together with the overmolding of the rotor magnets 116. This means that the potting material is injected simultaneously, or within the same time interval, both into the exposed spaces between the magnet pockets and overmolded onto the axial end face 113 and / or the first section 115 of the cover 121. In this way, the manufacturing efficiency of the rotor 105 according to the invention can be increased. The overmolded cover 121 serves as a flow aid during the molding process and enables a fluidic connection between the potting compound and the magnet pockets. Reference symbol list 100 at least partially electrified vehicles 102 Electric motor 103 Stator 104 drive battery 105 Rotor 106 DC / AC inverters 107 Rotor shaft 108 Control unit 109 Axis of rotation 110 rear axle 111 Rotor core 112 gearboxes 113 axial end face (front face) 114 rear wheels 115 first section 116 rotor magnets 117 axial outer side 118 toothed elements 119 cutouts 120, 120' second section 121 Coverage 122 protrusions 123 Outer ring 124, 127 axial outer side 125 subsections 126 gap 128 arched ribs 129 outer ring parts 200 procedures 202-206 Procedural steps 211, 213 first tool segment 212, 214 second tool segment QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 3 540 919 A1

[0004]

Claims

Rotor (105) for an electric motor (102), comprising: - a rotor shaft (107) rotatable about an axis of rotation (109) of the electric motor (102); - a rotor core (111) fixedly arranged relative to the rotor shaft (107) and in which a plurality of magnets (116) are mounted; - a cover (121) attached to an axial end face (113) of the rotor core (111), the cover (121) comprising a radially inner first section (115) and a radially outer second section (120), the first section (115) being formed annularly around the rotor shaft (107), the second section (120) being applied by a forming process, in particular by overmolding the first axial end face (113) and / or the first section (115) with a potting material, such that the second section (120) covers the first section (115) surrounds at least partially. Rotor (105) according to claim 1, wherein the first section (115) has a non-circular, preferably star-shaped, outer contour. Rotor (105) according to claim 2, wherein the first section (115) is given a round, preferably circular, outer contour by overmolding with the potting material. Rotor (105) according to one of the preceding claims, wherein the second section (120) comprises several circumferentially distributed, preferably spaced apart, subsections (125), in particular arc-shaped ribs (128). Rotor (105) according to claim 4, wherein the subsections (125) of the second section (120) are arranged correspondingly to several toothed elements (118) formed on an outer edge of the first section (40), preferably wherein the subsections (128) are each arranged in a recess (119) between adjacent toothed elements (118). Rotor (105) according to one of the preceding claims, wherein the cover (121), preferably the first section (115), is designed as a balancing disc, in particular as a balancing disc overmolded with the potting material. Rotor (105) according to one of the preceding claims, wherein the potting material is applied in such a way that it fills several magnet pockets formed in the rotor core (111) which receive the magnets (116). Rotor (105) according to one of the preceding claims, wherein the first section (115) is formed from a first material which has a higher density than the potting material and / or which is magnetic, preferably ferromagnetic, wherein the potting material is non-magnetic, preferably also electrically non-conductive. Rotor (105) according to one of the preceding claims, wherein an end face of the first section (115) is kept free of the potting material during overmolding of the first axial end face (113) or of the first section (115). Rotor (10) according to one of the preceding claims, wherein a radial outer surface (117) of the first section (115) and / or an end face of the rotor core (111) are covered by the potting material. Electric motor (102) for an at least partially electrified vehicle (100), comprising the rotor (105) according to one of the preceding claims and a stator (103). At least partially electrified vehicle (100) comprising the electric motor (102) according to claim 11. Method (200) for manufacturing a rotor (105) for an electric motor (102), comprising: - providing (202) a rotor shaft (107) rotatable about an axis of rotation (109) of the electric motor (102); - providing (204) a rotor core (111) fixedly to the rotor shaft (107) and in which a plurality of magnets (116) are mounted; - attaching (206) a cover (121) to an axial end face (113) of the rotor core (111), wherein the cover (121) comprises a radially inner first section (115) and a radially outer second section (120), wherein the first section (115) is formed annularly around the rotor shaft (107), and wherein the second section (120) is formed by a shaping process, in particular by overmolding the first axial end face (113) and / or the first section (115) is applied with a casting material such that the second section (120) at least partially surrounds the first section (115). Method (200) according to claim 13, wherein the overmolding is carried out using a first tool segment (211, 213) to be placed on the end face of the rotor core (111), preferably plate-shaped, and / or a second tool segment (212, 214) to be placed on the circumferential side of the first section (115). Method (200) according to claim 13 or 14, wherein the overmolding of the axial end side (113) or of the first section (115) is carried out in a common operation with an overmolding of the plurality of magnets (116).

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