Method for providing a rotor for an electric motor with compensation of a front-side deformation

Abstract

The present invention relates to a method for providing a rotor (116) for an electric motor (102), wherein the rotor (116) comprises a rotor shaft (122) and a magnetically actuated rotor core assembly (118), the method comprising providing the rotor shaft (122) and the rotor core assembly (118) such that the rotor core assembly (118) is rotationally fixed to the rotor shaft (122) to form a rotor unit such that the rotor shaft (122) extends through a central cavity formed in the rotor shaft (122); performing a pressing operation in which at least one end face (128, 130) of the rotor core assembly (118) is subjected to a pressing force in order to compensate for a deformation formed on the at least one end face (128, 130) of the rotor core assembly (118), in particular a bending, bulging and / or curvature.The present invention further relates to a rotor (116), an electric motor (102) and an at least partially electrified vehicle (100).

Description

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

[0002] Fully electric vehicles and hybrid vehicles are well known from the prior art. These electric vehicles are driven exclusively or partially by one or more electric motors as drive units. The electric motor is generally equipped with a stator and a rotor rotatably mounted within the stator. The stator has several stator windings, which serve as phase strands and are each 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 creates a rotating magnetic field. The rotor has a rotor shaft and a rotor core assembly, fixed to the rotor shaft, in which magnetically active components are installed.The magnetic interaction between the rotor on the one hand and the stator-side rotating field on the other hand therefore generates a torque which sets the rotor in rotation.

[0003] In rotor systems known from the prior art, a problem arises: deformation, in particular bending or warping, occurs on the rotor's end faces. This deformation is due to the fact that, during the assembly of the rotor core assembly with the rotor shaft, the rotor core assembly is first heated to facilitate the central insertion of the rotor shaft into the rotor core assembly. After heating the rotor core assembly and installing the rotor shaft, the rotor unit is cooled. During this process, the end face of the rotor core assembly deforms due to differences in the thermal properties of the various materials used in the rotor unit.

[0004] The deformation of the rotor core assembly means that components, especially balancing parts such as balancing rings or discs, which are attached to the end face of the rotor core assembly, cannot be fitted precisely and sit flush against the end faces of the rotor core assembly. Instead, a gap forms between the component and the end face of the rotor core assembly. This reduces the rotor's mechanical stability, particularly at higher speeds. Furthermore, it leads to undesirable and increased noise generation. The functionality of the entire electric motor is therefore impaired.

[0005] The object of the present invention is therefore to provide a method for providing a rotor which at least partially overcomes the aforementioned disadvantages.

[0006] The aforementioned technical problem is solved by a method for providing a rotor, a rotor, an electric motor, and an at least partially electrified vehicle according to the main claim and the dependent claims. Advantageous embodiments are the subject of the dependent claims. The advantages described in connection with the claims directed to the method also apply to the rotor, the electric motor, and the vehicle according to the invention.

[0007] In a first aspect of the present invention, a method for providing a rotor in an electric motor of an at least partially electrified vehicle is proposed.

[0008] The electric motor comprises a stator and a rotor rotatably mounted within the stator about an axis of rotation. The stator typically has several phase strands configured as stator windings, each of which receives its corresponding phase current. These phase currents are generated based on a DC input voltage by means of a DC / AC inverter, which converts the DC input voltage into an AC output voltage by switching several circuit breakers connected as half-bridges. This process generates a rotating magnetic field in the stator (stator magnetic field). The rotor is rotatably mounted about an axis of rotation of the electric motor and is magnetically active. For this purpose, the rotor has a rotor shaft and a magnetically active rotor core assembly, which is preferably designed as an arrangement of several laminated sheet metal parts, preferably made of steel (laminated lamination stack).In the case of a permanent magnet synchronous motor (PMSM), several permanent magnets can be housed inside the rotor core assembly, for example, in designated magnet pockets. Alternatively, in the case of an externally / electrically excited synchronous motor (EESM), several electromagnets, each formed by wrapping a conductor around a rotor core, can be arranged inside the rotor core assembly, with the rotor cores distributed circumferentially around the axis of rotation or the rotor shaft. The magnetic interaction between the stator and the rotor generates a torque, which is transmitted to an axle of the vehicle via a gearbox, such as a reduced / single-stage gearbox.

[0009] The method for providing the rotor comprises a first step in which the rotor shaft and the rotor core assembly are provided, such that the rotor core assembly is fixed to the rotor shaft in a rotationally fixed manner. This results in a rotor unit such that the rotor shaft extends through a central cavity formed in the rotor shaft. To form the rotor unit, the rotor core assembly is preferably first heated to cause the axially extending central cavity within the rotor core assembly to expand using the heat supplied to the rotor core assembly. This facilitates the subsequent insertion of the rotor shaft into the central cavity, preferably axially through the central cavity. The resulting unit, consisting of the rotor core assembly and the rotor shaft contained therein, is then cooled so that the central cavity narrows again.This strengthens the connection between the rotor shaft and the rotor core assembly on the inner wall of the central cavity, thus securing the rotor shaft more firmly within the rotor core assembly. This process, known as shrinkage, is advantageous because it allows for the simple creation of a secure rotor unit.

[0010] The method for providing the rotor comprises a further process step in which a pressing operation is performed. In the pressing operation, at least one end face of the rotor core assembly is subjected to a pressing force in order to compensate for a deformation formed on the at least one end face of the rotor core assembly, in particular a bending, bulging, and / or curvature. The deformation, or bending, bulging, and / or curvature, occurs because, during the cooling of the rotor unit, the end face surface of the rotor core assembly deforms due to differences in the thermal properties between the various materials used in the rotor unit. By applying a pressing force to the at least one end face, preferably both end faces (further preferably simultaneously and / or in step), the deformation is corrected so that a flat surface is formed on the end face.the end faces of the rotor core assembly. The pressing force preferably acts in the axial direction, and more preferably entirely in the axial direction, thus further simplifying the correction of the end-face deformation. This measure is advantageous in that components, especially balancing parts such as balancing rings or balancing discs, which are attached to the end faces of the rotor core assembly, can be arranged precisely and planarly on the end faces of the rotor core assembly. There is no, or at least only a reduced, gap formation between the respective component and the end face surface of the rotor core assembly. This increases the mechanical stability of the rotor, which is essential, especially at higher speeds. Furthermore, this effectively prevents unwanted and increased noise generation. The functionality of the entire electric motor is therefore restored.

[0011] According to an exemplary embodiment, a component, in particular a balancing component, is attached to at least one end face of the rotor core assembly before the pressing process. The balancing component is preferably designed as a balancing ring and / or balancing disc. To attach the component or balancing component, it is preferably first heated, for example to a final temperature of 130 °C. The heated component or balancing component is then attached to the end face of the rotor core assembly. This is preferably done after the rotor unit has cooled. The rotor core assembly is then subjected to a pressing force at the end face, preferably a maximum of 1 kN. Alternatively or additionally, the pressing force can act on the outer surface of the component or balancing component facing away from the rotor core assembly.This measure makes it possible to initially apply the pressing force to an outside of the component, in particular the balancing component, during the pressing process, in order to transfer the pressing force to the end face of the rotor core assembly via a contact between the component or the balancing component and the end face of the rotor core assembly.

[0012] According to another exemplary embodiment, during the pressing process, the rotor unit is mounted between two tool halves of a press device positioned at the ends of the rotor core assembly. This allows the pressing force to be applied to both ends of the rotor core assembly, thus correcting the deformation on both sides. Preferably, the press device is designed to enable a positive-locking and / or force-locking connection between the rotor core assembly and the respective tool half. At least one of the tool halves is preferably plate-shaped and / or ring-shaped. Alternatively or additionally, at least one of the tool halves can have a central recess for guiding the rotor shaft.

[0013] According to another exemplary embodiment, the pressing force exerts pressure on the end face of the rotor core assembly or on the outer surface of a component attached to the end face of the rotor core assembly, in particular a balancing component, wherein the pressure scales with the dimensions, mass, and / or degree of deformation of the rotor core assembly and / or lies within a range of 5 kN to 3,000 kN. In this way, the pressing force applied to the rotor core assembly can be selected depending on the characteristics of the rotor core assembly, thus making deformation correction more effective. Alternatively or additionally, the pressure can vary over time according to a predefined pressure scheme in which the pressure value is described as a function of time. The predefined pressure scheme can be generated using artificial intelligence (AI), in particular a neural network model (NN model) or a machine learning model (ML model).The AI ​​or NN / ML model is preferably pre-trained with training data relating to several parameters concerning physical and / or geometric properties of the rotor core arrangement and deformation.

[0014] According to another exemplary embodiment, the pressing force acts on an effective surface, in particular an annular surface, which is the total area or a partial area of ​​the end face of the rotor core assembly or of an outer surface of a component (or a balancing component) attached to the end face of the rotor core assembly. The effective surface or annular surface scales with the dimensions, mass, and / or degree of deformation of the rotor core assembly and / or lies within a range of 10% to 100%. In this way, the pressing force applied to the rotor core assembly can be selected depending on the characteristics of the rotor core assembly, thus making deformation correction more effective. Alternatively or additionally, the effective surface or annular surface can vary over time according to a predefined area scheme in which the area value is described as a function of time.The predefined surface pattern can be generated using artificial intelligence (AI), in particular a neural network model (NN model) or a machine learning model (ML model). The AI ​​or NN / ML model is preferably pre-trained with training data relating to several parameters concerning the physical and / or geometric properties of the rotor core arrangement and the deformation. The annular surface is referenced to the rotor shaft, concentrically surrounding it.

[0015] According to another exemplary embodiment, the pressing process is carried out for a duration that scales with the dimensions, mass, and / or degree of deformation of the rotor core assembly and / or lies within a range of 12 to 24 hours. The process duration describes the time the pressing force is applied. In the case of continuous pressing force application, the process duration is the time difference between the start and end times of the pressing process. In the case of non-continuous pressing force application (i.e., the pressing process has several separate phases), the process duration is calculated as the sum of the individual durations of the phases. In this way, the pressing force applied to the rotor core assembly can be selected depending on the characteristics of the rotor core assembly, thus making deformation correction more effective.

[0016] According to another exemplary embodiment, the pressing process is carried out during or after a heating process in which the rotor unit is at least partially heated. The rotor unit is therefore subjected to heat treatment to increase its temperature. The heating process can take place before the pressing process, in which case it can be completed before the start of the pressing process, or optionally, it can continue during the pressing process, or at least during part of it. Alternatively, the heating process can begin simultaneously with the pressing process or only after the start of the pressing process. The heat treatment of the rotor unit results in a softer end-face surface of the rotor core assembly, thus facilitating the execution of the pressing process.

[0017] According to another exemplary embodiment, the heating process is carried out using heat from a casting process for encasing the rotor unit with a casting material, in particular a plastic material such as a polymer. During the casting process, the rotor unit is encased with the casting material, for example, by means of an injection molding process. Preferably, during the casting process, the casting material is introduced into the spaces between several magnets arranged inside the rotor core assembly to fix the magnets in the rotor core assembly and / or to insulate the magnets from one another. In this way, the heating process does not require an additional or external heat source, but utilizes the existing internal heat source, namely the heat generated and remaining during the casting process. This measure enables increased energy efficiency in the manufacturing process of the rotor.

[0018] According to a further exemplary embodiment, during the heating process the rotor unit is brought to a temperature that scales with the dimensions, mass, and / or degree of deformation of the rotor core assembly and / or lies in a range of 50 to 250 °C, preferably 100 to 200 °C, more preferably 120 to 180 °C, even more preferably 150 to 170 °C, and still more preferably 160 to 165 °C. In this way, the heating process can be selected depending on the characteristics of the rotor core assembly, thus making deformation correction more effective.

[0019] According to another exemplary embodiment, the heating process is carried out for a heating duration that scales with the dimensions, mass, and / or degree of deformation of the rotor core assembly and / or lies in a range of 30 seconds to 48 hours. The heating duration describes the length of time the rotor unit is subjected to heat treatment. In the case of a continuous heating process, the heating duration is the time difference between the start and end times of the heating process. In the case of a non-continuous heating process (i.e., the heating process has several separate process segments), the heating duration is calculated as the sum of the individual durations of the process segments. In this way, the heat treatment of the rotor core assembly can be selected depending on the characteristics of the rotor core assembly, thus making deformation correction more effective.

[0020] According to another exemplary embodiment, the duration of the pressing process and / or the pressure generated on the end face(s) can depend on the heating duration and / or the amount of heat supplied to the rotor unit during the heating process and / or the final temperature to which the rotor unit is brought during the heating process. For example, the duration of the pressing process and / or the pressure can be correspondingly lower with a longer heating duration, a greater amount of heat supplied, and / or a higher final temperature of the heating process, and vice versa. This measure takes into account a multitude of the process parameters relevant to the overall manufacturing process of the rotor and the interrelationships between these process parameters. Process and energy efficiency are therefore further increased as a result.

[0021] Furthermore, a rotor for an electric motor is proposed within the scope of the present invention, which is manufactured using a method according to one of the embodiments of the invention. The rotor thus has at least one structural feature described in connection with the above and following methods. The rotor can comprise an arrangement of laminated sheet metal parts (laminated stacks) made of steel.

[0022] Within the scope of the present application, 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, in particular, be designed as a permanent magnet synchronous motor (PMSM) or an externally or electrically excited synchronous motor (EESM), especially an inductively excited synchronous motor (IEESM). 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, e.g., for a brake motor.

[0023] 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 be, for example, a purely electric vehicle (EV), such as a battery electric vehicle (BEV), or a hybrid electric vehicle (HEV).

[0024] 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.

[0025] 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 with an electric motor; Fig. 2 a schematic representation of a rotor of the electric motor in a side view; Fig. 3-6 each represent a schematic representation of a process state of a process for providing the rotor.

[0026] The same objects, functional units, and comparable components are identified in the figures by the same reference numbers. These objects, functional units, and comparable components are identical with respect to their technical characteristics unless the description explicitly or implicitly reveals otherwise.

[0027] 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 is, for example, designed as a permanent magnet synchronous motor (PMSM). The electric motor 102 comprises a stator (not shown in detail here) with several phase strands arranged as stator windings and a rotor 116 (see Figure 1). Fig. 2), in which several magnets, not shown in detail here, are incorporated, such that the rotor 116 is magnetically active. The inverter 106 is 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. In particular, several preferably sinusoidal, phase-shifted phase currents for the phase strands of the stator are generated by opening and closing several power switches installed in the inverter 106. The phase currents, each fed into one of the several phase strands of the stator, cause a rotating magnetic field inside the stator. A torque is generated based on the interaction between the rotating stator magnetic field and the stationary rotor magnetic field., which is transmitted by means of the transmission 112, which preferably has a reduced transmission, to an axle 110, here by way of example the rear axle of the vehicle 100, and finally to wheels 114, here by way of example rear wheels.

[0028] Fig. Figure 2 shows a schematic representation of the rotor 116. The rotor 116 has a rotor shaft 122, which defines a rotational axis 120 of the electric motor 102. The rotor 116 has a rotor core assembly 118 in which several magnet pockets (not shown in detail here) are formed to receive several permanent magnets. The rotor core assembly 118 is preferably designed as an arrangement of several laminated sheet metal parts (laminated rotor stack), for example made of steel. For the purpose of insulating the permanent magnets from each other and / or for fixing the permanent magnets in the magnet pockets or in the rotor core assembly 118, the rotor core assembly 118 is preferably lined with an electrically insulating, plastic-based casting material. The casting material is poured into the spaces between the permanent magnets in a casting process, such as an injection molding process, in which the rotor core assembly 118 is subjected to heat.inserted between these and the inner walls of the magnetic pockets (i.e., into the residual volumes of the magnetic pockets remaining after the permanent magnets have been inserted).

[0029] The rotor shaft 122 and the rotor core assembly 118 form a rotor unit, as shown in Fig. Figure 3 is shown purely schematically and by way of example. For the purpose of forming the rotor unit, the rotor core assembly 118 is preferably first heated to cause the central cavity 119, which extends axially within the rotor core assembly 118, to expand by means of the heat supplied to the rotor core assembly 118. Subsequently, the rotor shaft 122 is guided axially through the central cavity 119 so that the rotor shaft 122 projects beyond a first end face 128 and a second end face 130 axially opposite the first end face 128. The rotor unit thus formed is then cooled so that the central cavity 119 narrows again. This strengthens the connection between the rotor shaft 122 and the rotor core assembly 118 at the inner wall of the central cavity 119, so that the rotor shaft 122 is more securely held inside the rotor core assembly 118. This is called shrinkage (English: shrinkage).The process referred to as shrinkage is advantageous in that a safe rotor unit can be achieved in a simple way.

[0030] The rotor 116 additionally comprises a first component 124 and a second component 126 on the first end face 128 and the second end face 130 of the rotor core assembly 118, respectively, which are preferably each designed as a balancing component or balancing ring and / or balancing disc. To attach the components, in particular the balancing components or balancing discs 124, 126, they are preferably first heated, for example to a final temperature of 130 °C. The respective heated component or balancing component / balancing disc 124, 126 is then attached to the corresponding end face 128, 130 of the rotor core assembly 118, as shown in Fig. Figure 4 shows this purely schematically and by way of example. This preferably takes place after the rotor unit has cooled down. Then, an outer surface 129, 131 of the component or balancing part / balancing disc 124, 126 facing away from the rotor core assembly 118 is subjected to a compressive force, the compressive force preferably being a maximum of 1 kN.

[0031] Fig. Figure 5 shows a further schematic and purely exemplary representation of the rotor 116 in a heating process, in which the rotor 116 or the rotor unit is at least partially heated. The rotor 116 is therefore subjected to heat treatment, the heat required for which is supplied by a heat source 132 (in Fig. 5 (indicated schematically as dashed brackets) is provided. The heating process is preferably carried out using heat from the aforementioned casting process for casting the rotor unit with the plastic-based casting material. In this way, the heating process does not require an additional or external heat source, but makes use of the already existing internal heat source 132, namely the heat generated and remaining in the casting process. This measure enables increased energy efficiency in the manufacturing process of the rotor 116.

[0032] During the heating process, the rotor 116 or the rotor unit is brought to a final temperature that is scaled according to the dimensions, mass, and / or degree of deformation of the rotor 116 or the rotor core assembly 118 and / or lies in a range of 50 to 250 °C, preferably 100 to 200 °C, more preferably 120 to 180 °C, even more preferably 150 to 170 °C, and still more preferably 160 to 165 °C. In this way, the heating process can be selected depending on the properties of the rotor 116 or the rotor core assembly 118, so that the subsequent correction of the deformation, as described below, is more effective.

[0033] The heating process is carried out for a heating duration that scales with the dimensions, mass, and / or degree of deformation of the rotor 116 or the rotor core assembly 118 and / or lies in a range of 30 s to 48 h. In this way, the heat treatment of the rotor 116 or the rotor core assembly 118 can be selected depending on the properties of the rotor 116 or the rotor core assembly 118, so that the correction of the deformation is more effective.

[0034] Fig. Figure 6 shows a further schematic and purely exemplary representation of the rotor 116 in a pressing process, in which both end faces 128, 130 of the rotor core assembly 118 are subjected to a pressing force using a pressing device with two end-face tool halves 134, 136. The pressing process serves to compensate for a deformation formed on the end faces 128, 130 of the rotor core assembly 118, in particular a bending, bulging and / or curvature. The deformation or bending, bulging and / or curvature occurs because, during the cooling of the rotor unit, the end-face surface of the rotor core assembly 118 deforms due to differences in the thermal properties between the different materials used in the rotor unit.

[0035] During the pressing process, the tool halves 134, 136 of the pressing device are brought into contact with their respective outer surfaces 129, 131. The pressing device is preferably selected such that a predefined minimum effective area (annular area), corresponding to the contact area between the respective tool half 134, 136 and the associated outer surface 129, 131, is reached or exceeded. The tool halves 134, 136 can be, as in Fig. Figure 6, shown purely as an example, is designed in a ring shape to allow the rotor shaft 122 to be guided through an annular opening in the respective tool halves 134, 136. The pressing device generates the pressing force (in Fig.(6 indicated by arrows) in an axial direction inwards, which initially acts on the outer surfaces 129, 131 of the balancing discs 124, 126 and is subsequently transferred to the end faces 128, 130 of the rotor core assembly 118. In this way, the rotor core assembly 118 is (indirectly) subjected to the pressing force. However, this is not essential for the present invention. A pressing device can be used with which both the balancing discs 124, 126 and the rotor core assembly 118, or alternatively only the rotor core assembly 118, are directly subjected to the pressing force.

[0036] The deformation is corrected by applying pressing force to the end faces 128, 130, preferably both end faces 128, 130 simultaneously and / or in sync (i.e., both end faces 128, 130 are subjected to pressing force at the same initial times or intervals during the pressing process and are not subjected to pressing force at the same subsequent times or intervals). This results in a flat surface on the end faces 128, 130 of the rotor core assembly 118. Therefore, when the balancing discs 124, 126 are attached, no gap forms, or at least the gap is significantly reduced, between the respective balancing disc 124, 126 and the end face of the rotor core assembly 118. This increases the mechanical stability of the rotor 116, which is essential, especially at higher rotational speeds. Furthermore, this effectively prevents unwanted and increased noise generation.The functionality of the entire electric motor 102 has therefore been restored.

[0037] The magnitude of the pressing force, or the pressure generated by the pressing force on the balancing discs 124, 126 and / or the rotor core assembly 118, and / or the duration of the pressing process can be selected depending on the dimensions, mass, and / or degree of deformation of the rotor 116 or the rotor core assembly 118. Alternatively or additionally, the duration of the process and / or the pressing force or the generated pressure can be selected depending on the heating duration and / or the amount of heat supplied to the rotor unit during the heating process and / or the final temperature to which the rotor unit is heated. This measure takes into account a multitude of the process parameters relevant to the overall manufacturing process of the rotor 116 and the interrelationships between these process parameters. This further increases process and energy efficiency. Reference symbol list 100 at least partially electrified vehicles 102 Electric motor 104 drive battery 106 DC / AC inverters 108 Control unit 110 rear axle 112 gearboxes 114 rear wheels 116 Rotor 118 Rotor core arrangement 119 central cavity 120 rotary axis 122 Rotor shaft 124 Component / Balancing component / Balancing disc / Balancing ring 126 Component / Balancing component / Balancing disc / Balancing ring 128 Front 129 Outside 130 Front 131 Outside 132 Heat source 134 Tool half 136 Tool half

Claims

Method for providing a rotor (116) for an electric motor (102), wherein the rotor (116) comprises a rotor shaft (122) and a magnetically actuated rotor core assembly (118), the method comprising: - providing the rotor shaft (122) and the rotor core assembly (118) such that the rotor core assembly (118) is rotationally fixed to the rotor shaft (122) to form a rotor unit such that the rotor shaft (122) extends through a central cavity (119) formed in the rotor shaft (122); and - performing a pressing operation in which at least one end face (128, 130) of the rotor core assembly (118) is subjected to a pressing force in order to compensate for a deformation formed on the at least one end face (128, 130) of the rotor core assembly (118), in particular a bending, bulging and / or curvature. Method according to claim 1, wherein a component, in particular a balancing component (124, 126), is attached to at least one end face (128, 130) of the rotor core assembly (118) prior to the pressing process, wherein the balancing component (124, 126) is preferably designed as a balancing ring and / or balancing disc (124, 126). Method according to claim 2, wherein in the pressing process the pressing force is first applied to an outer surface (129, 131) of the component, in particular the balancing component (124, 126), and is transferred to the end face (128, 130) of the rotor core arrangement (118) via a contact between the component or the balancing component (124, 126) and the end face (128, 130). Method according to one of claims 1 to 3, wherein in the pressing process the rotor unit is mounted between two tool halves (134, 136) of a pressing device positioned at the end face of the rotor core arrangement (118). Method according to one of the preceding claims, wherein the pressing force is configured to generate a pressure on the end face (128, 130) of the rotor core assembly (118) or an outer surface (129, 131) of a component attached to the end face (128, 130) of the rotor core assembly (118), in particular a balancing component (124, 126), wherein the pressure is scaled with the dimension, mass and / or degree of deformation of the rotor core assembly (118) and / or is in a range of 0.1 N / mm2 to 500 N / mm2. Method according to one of the preceding claims, wherein the pressing force acts on an effective surface, in particular an annular surface, on the end face (128, 130) of the rotor core assembly (118) or on an outer surface (129, 131) of a component attached to the end face (128, 130) of the rotor core assembly (118), in particular a balancing component (124, 126), wherein the effective surface or the annular surface is scaled with the dimension, mass and / or degree of deformation of the rotor core assembly and / or lies in a range of 0.1 N / mm2 to 500 N / mm2. Method according to one of the preceding claims, wherein the pressing process is carried out for a duration that scales with the dimension, mass and / or degree of deformation of the rotor core arrangement and / or is in a range of 12 h to 24 h. Method according to one of the preceding claims, wherein in the pressing process both end faces (128, 130) of the rotor core arrangement (118) are subjected to the pressing force, preferably simultaneously and / or in step. Method according to one of the preceding claims, wherein the pressing process is carried out during or after a heating process in which the rotor unit is at least partially heated. Method according to claim 9, wherein the heating process is carried out using heat from a casting process for casting the rotor unit with a casting material, in particular a plastic material such as polymer. Method according to claim 10, wherein in the casting process the casting material is introduced into spaces between several magnets arranged inside the rotor core assembly (118) for the purpose of fixing the magnets in the rotor core assembly (118) and / or for the purpose of isolating the magnets from each other. Method according to one of claims 9 to 11, wherein in the heating process the rotor unit is brought to a temperature that scales with the dimension, mass and / or degree of deformation of the rotor core arrangement and / or is in a range of 50 to 250 °C, preferably 100 to 200 °C, more preferably 120 to 180 °C, even more preferably 150 to 170 °C, even more preferably 160 to 165 °C. Method according to any one of claims 9 to 12, wherein the heating process is carried out for a heating duration that scales with the dimension, mass and / or degree of deformation of the rotor core arrangement and / or is in a range of 30 s to 48 h. Rotor (116) for an electric motor (102), wherein the rotor (116) is manufactured by the method according to any one of claims 1 to 13. Electric motor (102) for an at least partially electrified vehicle (100), comprising the rotor (116) according to claim 14. At least partially electrified vehicle (100) comprising an electric motor (102) according to claim 15.

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