Rotor shaft for an electrical machine

Abstract

The invention relates to a rotor shaft (2) for an electrical machine. The rotor shaft (2) comprises a load region (14) and a central region (16). The load region (14) extends in an axial direction (x) of the rotor shaft (2) on a first end face (S1) of the rotor shaft (2), wherein the central region (16) adjoins the load region (14) on a second end face (S2) of the rotor shaft (2). The rotor shaft (2) has a first stiffness (E1) within the central region (16) and a second stiffness (E2) within the load region (14), wherein the first stiffness (E1) assumes a higher value than the second stiffness (E2).

Description

[0001] Rotor shaft for an electric machine

[0002] The invention relates to a rotor shaft for an electrical machine.

[0003] Electric machines for driving a motor vehicle typically comprise a rotor shaft onto which a rotor lamination stack is mounted in a radial direction. This stack comprises several laminations stacked in an axial direction. When the electric machine is in operation, the front ends of the rotor shaft are subjected to thermal and mechanical stress. This can lead to laminations detaching from the rotor lamination stack at the front.

[0004] A rotor carrier for a rotor of an electrical machine is known from DE 10 2021 202 990 A1. An outer circumferential surface of the hollow rotor carrier forms a support area for a rotor core of a rotor, wherein the support area extends in an axial direction of the rotor carrier. The extension of the outer circumferential surface varies in a radial direction of the rotor carrier along the support area in the axial direction of the rotor carrier such that no maximum values ​​of contact pressure occur between the rotor carrier and the rotor core in the axial end sections of the support area when the rotor core is pressed onto the support area of ​​the rotor carrier. This solution requires increased manufacturing and measurement effort and is quality-sensitive.

[0005] One object of the present invention can be seen in providing an alternative technology that is characterized by reduced manufacturing and measurement effort and is less quality-sensitive. This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments are the subject matter of the dependent claims, the following description, and the figures.

[0006] According to the present invention, it is proposed to specifically optimize the stiffness curve of the rotor shaft. In particular, the stiffness at the end faces is reduced. This allows the end faces of the rotor shaft to be relieved. The center section of the rotor shaft can be constantly loaded. This enables particularly uniform loading across the rotor width, while stress peaks are avoided across the entire rotor width. This prevents stress peaks at the end faces of the rotor laminated core, reducing the risk of sheets of the rotor laminated core becoming accidentally loose at these points. This increases the reliability and service life of the rotor shaft. Furthermore, functional quality is increased and dependence on manufacturing is reduced, since manufacturing tolerances do not have a significant influence on the stiffness curve.In particular, a particularly durable rotor mount is made possible, as this is largely determined by rigidity and not by manufacturing tolerances.

[0007] In this sense, according to the present invention, a rotor shaft for an electrical machine is provided. The rotor shaft comprises a first load region and a central region. In an axial direction of the rotor shaft, the first load region extends on a first end face of the rotor shaft. On a second end face of the rotor shaft, the central region adjoins the first load region. The rotor shaft has a first stiffness within the central region and a second stiffness within the first load region, wherein the first stiffness assumes a higher value than the second stiffness. The central region can overlap a large part in the axial direction with a support region of the rotor shaft. Within the support region, a rotor laminated core can be fastened to an outer surface of the rotor shaft, in particular in a force-fitting and / or form-fitting manner.The rotor lamination stack is composed, in particular, of a plurality of disc- or ring-shaped laminations that are stacked in the axial direction of the rotor shaft and together form the rotor lamination stack. Such a rotor lamination stack has a first end on the first end of the rotor shaft. This first end of the rotor lamination stack lies, in particular, within the first load range. The stiffness distribution described above and the resulting load reduction within the first load range can reduce the risk of individual laminations arranged at the first end of the rotor lamination stack becoming detached from the rotor shaft. To achieve the different stiffnesses, the material thickness of the rotor shaft can be varied in a particularly simple and effective manner.In this sense, according to one embodiment, the rotor shaft has a first material thickness in the central region and a second material thickness in the first load region. The first material thickness assumes a higher value than the second material thickness. Within the central region, the material thickness can be constant throughout the axial direction. Alternatively, the material thickness can be varied within the central region, e.g. by making an inner surface concave, which is described in more detail below in connection with a further embodiment. Even within the first load range, the material thickness can be kept constant or varied along the axial direction.

[0008] Similar to the first load range, the rotor shaft can comprise a second load range, wherein the second load range extends in the axial direction of the rotor shaft on the second end face of the rotor shaft. The central region extends between the first load range on the one hand and the second load range on the other. The two load ranges thus frame the central region in the axial direction. The rotor shaft has a third stiffness within the second load range, wherein the first stiffness assumes a higher value than the third stiffness. A second end face of the rotor laminated core described above can be arranged on the second end face of the rotor shaft. This second end face of the rotor laminated core lies in particular within the second load range.The stiffness distribution described above and the resulting load reduction within the second load range can reduce the risk of individual laminations arranged at the second front end of the rotor lamination stack becoming detached from the rotor shaft.

[0009] In the second load range, the third stiffness can also be achieved through the material thickness of the rotor shaft. In this sense, according to a further embodiment, the rotor shaft has the first material thickness described above in the central region, whereas the rotor shaft has a third material thickness in the second load range. The first material thickness assumes a higher value than the third material thickness. Even within the second load range, the material thickness can be kept constant or varied along the axial direction.

[0010] It has been found that the loads within the load regions arranged in the area of ​​the end faces of the rotor shaft can be reduced particularly effectively if the material thickness within the central region is at least twice as high as in the first load region and / or in the second load region. In this sense, according to a further embodiment, the value of the first material thickness is at least twice or three times higher than the value of the second material thickness. Alternatively, the value of the first material thickness can be at least twice or three times higher than the value of the third material thickness. Furthermore, the value of the first material thickness can be at least twice or three times higher than the value of the second material thickness and the third material thickness.

[0011] The rotor shaft comprises in particular the aforementioned outer surface which forms the support region. The outer surface is oriented outwards in a radial direction of the rotor shaft. Furthermore, the rotor shaft can comprise an inner surface which, in contrast to the outer surface, is oriented inwards in the radial direction. The inner surface defines or delimits an inner cavity of the rotor shaft, which is in particular sleeve-shaped. The outer surface can advantageously be rectilinear and constant in the radial direction, in particular within the central region and in the first load region and / or in the second load region. To vary the material thickness, only the course of the inner surface can be varied in a particularly simple yet effective manner.In this sense, according to a further embodiment, the outer surface in the central region runs consistently along the axial direction in a radial direction of the rotor shaft. In contrast, the inner surface in the central region extends further inward in the radial direction than in the first load region and / or in the second load region. As a result, the value of the first material thickness is higher than the value of the second material thickness and / or the third material thickness.

[0012] As already mentioned, the outer surface of the rotor shaft can form a support area for receiving the rotor laminated core. The central area extends within the support area between the two load areas. The support area overlaps with one of the load areas on each of the end faces. In order to keep the load within the load areas particularly low, the material thickness can be reduced in a curve on both end faces. In this sense, according to a further embodiment, the inner surface runs along a first curve in a first overlap area between the support area and the first load area, so that the first material thickness decreases continuously within the first overlap area down to the second material thickness, the value of which is reached in the first load area.Analogously, the inner surface can extend along a second curve in a second overlap region between the load-bearing region and the second load region, so that the first material thickness within the second overlap region continuously decreases to the third material thickness, the value of which is reached in the second load region.

[0013] Through even more targeted optimization of the stiffness curve of the rotor shaft, the end faces can be relieved of load and the central area can also be constantly utilized. To achieve this, the stiffness of the end faces is reduced and the central area is designed to be concave. Load peaks can thus be reduced particularly effectively, increasing reliability and service life. Furthermore, the functional quality becomes even more robust and is no longer as dependent on manufacturing, since manufacturing tolerances do not have a significant influence on the stiffness curve. In this sense, according to a further embodiment, the inner surface in the central area has a curved curve oriented outwards in the radial direction (concave curve of the inner surface). To further optimize the load, the inner surface within the central area can run along a third curve.Regarding the shape of the third curve, the third curve may have a first maximum at an end of the central region facing the first end face and a second maximum at an end of the central region facing the second end face. Between the first maximum and the second maximum, the third curve has a minimum.

[0014] In the following, embodiments of the invention are explained in more detail with reference to the schematic drawing, wherein identical or similar elements are provided with the same reference numerals.

[0015] Fig. 1 is a longitudinal sectional view of a rotor with a rotor shaft and a rotor core mounted thereon,

[0016] Fig. 2 is a longitudinal sectional view of a first embodiment of a rotor shaft according to the invention for the rotor according to Fig. 1, wherein a stress profile is shown due to a pressure between the rotor shaft and a rotor laminated core, wherein the rotor shaft is not rotating and is not deformed,

[0017] Fig. 3 is a longitudinal sectional view of the rotor shaft according to Fig. 2, showing a stress profile due to the pressure between the rotor shaft and the rotor core, with the rotor shaft rotating and any deformations of the rotor shaft occurring in this process being exaggerated,

[0018] Fig. 4 is a longitudinal sectional view of a second embodiment of a rotor shaft according to the invention for the rotor according to Fig. 1, wherein a stress profile is shown due to a pressure between the rotor shaft and a rotor laminated core, wherein the rotor shaft is not rotating and is not deformed, and

[0019] Fig. 5 is a longitudinal sectional view of the rotor shaft according to Fig. 4, showing a stress profile due to the pressure between the rotor shaft and the rotor laminated core, the rotor shaft rotating and any deformations of the rotor shaft occurring in the process being exaggerated.

[0020] Fig. 1 shows a rotor 1, which in particular comprises a rotor carrier in the form of a rotor shaft 2 and a rotor laminated core 3. The rotor laminated core 3 is fastened to the rotor shaft 2 in a force-fitting manner by a press fit. The rotor laminated core 3 can in particular comprise a plurality of disc-shaped or ring-shaped sheets (not shown individually in Fig. 1, but only as a block or pack) which are stacked in an axial direction x of the rotor 1 or the rotor shaft 2. A stator, not shown, can surround the rotor 1 in its radial direction r. In this case, there is a gap in the radial direction r between an outer surface of the rotor laminated core 3 and an inner surface of the stator. The rotor 1 is designed to rotate about a longitudinal axis L, such that currents can be transmitted between the rotor 1 and the non-rotating stator by induction in order to operate the motor orto enable generator operation of an electrical machine (not shown in detail), within which the rotor 1 and the stator can be used.

[0021] The rotor shaft 2 is rotatably mounted in the region of a first end face S1, which is shown on the left in Fig. 1, in a loose bearing 4, which is held by a first bearing housing 5 of the electric machine. On a second end face S2 opposite the first end face S1, which is shown on the right in Fig. 1, the rotor shaft 2 is rotatably mounted in a fixed bearing 6. The fixed bearing 6 is held by a second bearing housing 7, which can, for example, be formed integrally with the first bearing housing 5. In the exemplary embodiment shown, the fixed bearing 6 comprises angular contact ball bearings in an X arrangement without a support base. A retaining ring 8 is fastened to the rotor shaft 2 on the first end face S1. The retaining ring 8 is designed to prevent the rotor laminated core 3 from moving in the axial direction x beyond the retaining ring 8 towards the first end face S1.On the second end face S2, a securing element 9 is fastened to the second bearing housing 7. The securing element 9 is designed to prevent the fixed bearing 6 from moving beyond the securing element 9 in the axial direction x towards the second end face S2. The rotor shaft 2 is not a solid body, but is hollow on the inside. In particular, the rotor shaft 2 is sleeve-shaped with an annular cross-section. For example, a semi-finished product for producing the rotor shaft 2 can be machined with a through-going longitudinal bore. The rotor shaft 2 comprises an outer surface 10 and an inner surface 11. The outer surface 10 forms a support region 12 which extends in the axial direction x between the securing ring 8 and a radial shoulder 13. In the exemplary embodiment shown, the radial shoulder 13 is formed by the outer surface 10 of the rotor shaft 2.For this purpose, the outer surface 10 of the rotor shaft 8 is stepped in the radial direction r in the region of the radial shoulder 13. The radial shoulder 13 is designed to prevent the rotor core 3 from moving in the axial direction x beyond the radial shoulder 13 toward the second end face S2. Thus, the rotor core 3 is secured against displacement in the axial direction x on the first end face S1 by the retaining ring 8 and on the second end face S2 by the radial shoulder 13.

[0022] When the rotor shaft 1 rotates during operation of the electric machine, mechanical and / or thermal loads occur. The mechanical loads can occur, for example, in the form of mechanical stresses. The thermal loads can occur, for example, in the form of elevated temperatures. These loads are particularly pronounced in a first load region 14 on the first end face S1 and in a second load region 15 on the second end face S2. A first end region 21 of the rotor lamination stack 3, which lies on the first end face S1 of the rotor shaft 2, is located within the first load region 14. A second end region 22 of the rotor lamination stack 3, which lies on the second end face S2 of the rotor shaft 2, is located within the second load region 15.

[0023] 2 and 4, the two load areas 14, 15 are roughly marked purely as an example. The first load area 14 begins, for example, at the end of the rotor shaft 2 on the first end face S1 and extends in the axial direction x a little beyond the position of the retaining ring 8 (cf. Fig. 1) in the direction of the second end face S2. The first load area 14 thus overlaps in a first overlap area 17 in the axial direction x on the first end face S1 with the support area 12 and thus also with the first end 21 of the rotor laminated core 3. The second load area 15 begins, for example, in the area of ​​the position of the fixed bearing 6 (cf. Fig. 1) on the second end face S2 and extends in the axial direction x a little beyond the position of the radial shoulder 13 in the direction of the first end face S1.The second load area 15 thus overlaps in a second overlap area 18 in the axial direction x on the second end face S2 with the support area 12 and thus also with the second end area 22 of the rotor laminated core 22. A central area 16 extends between the first load area 14 and the second load area 15. Within the load areas 14, 15, the loads are in particular not constant and do not end at the boundaries of the load areas 14 and 15, but decrease there.

[0024] 2 and 3 show how the loads in the rotor shaft 2 can be reduced by optimizing the stiffness, particularly in the load areas 14 and 15. In the central area 16, the load on the rotor shaft 2 can still be slightly increased. An axial stiffness profile of the rotor shaft 2 is improved by varying a radial material thickness Δd. In particular, the radial material thickness Δd is reduced in the area of ​​the two end faces S1, S2 compared to the central area 16. The radial material thickness Δd results from a difference between an outer diameter da of the rotor shaft 2 and an inner diameter di of the rotor shaft 2. The outer diameter da is defined by the outer surface 10 of the rotor shaft 2. The inner diameter di is defined by the inner surface 11 of the rotor shaft 2.

[0025] 2 and 3, a first material thickness Δd1 is higher in the central region 16 than outside the central region 16. The outer surface 10 runs in a straight line, ie along the axial direction x it is essentially constant in the radial direction r. In contrast, the inner surface 11 in the central region 16 and in the predominant part of the support region 12 according to Fig. 2 and 3 extends further inwards in the radial direction r than in the load regions 14 and 15 on the first end face S1 and on the second end face S2, respectively.

[0026] Starting from the first material thickness Δd1, which the rotor shaft 2 has in its central region 16, the material thickness Δd decreases within the first overlap region 17 until it reaches the value of a second material thickness Δd2 within the first load region 14. The material thickness Δd does not change abruptly, but continuously. In the exemplary embodiment shown in FIGS. 2 and 3, the inner surface 11 runs along a first curve 19. The first material thickness Δd1 decreases along the first curve 19 down to the second material thickness Δd2. The second material thickness Δd2 is thus less than the first material thickness Δd1.

[0027] The stiffness of the rotor shaft 2 is higher where the material thickness Δd assumes a higher value. In particular, the rotor shaft 2 has first stiffness values ​​in the central region 16 and second stiffness values ​​in the first load region 14. Consequently, the stiffness is higher in the central region 16 than in the first load region 14 and in the first overlap region 17. In the illustrated embodiment, the first material thickness Δd1 can, for example, assume values ​​that are at least twice or three times as high as the second material thickness Δd2.

[0028] In a similar way, the material thickness Δd decreases, starting from the first material thickness Δd1, which the rotor shaft 2 has in its central region 16, within the second overlap region 18, until it reaches the value of a third material thickness Δd3 within the second load region 15. The material thickness Δd does not change abruptly, but continuously. In the exemplary embodiment shown in Figs. 2 and 3, the inner surface 11 runs along a second curve 20 within the second overlap region 18. The first material thickness Δd1 decreases along the second curve 20 down to the third material thickness Δd3. The third material thickness Δd3 is thus less than the first material thickness Δd1. The third material thickness Δd3 can have the same value as, or at least a very similar value to, the second material thickness Δd2.

[0029] The stiffness of the rotor shaft 2 is higher where the material thickness Δd assumes a higher value. In particular, the rotor shaft 2 has third stiffness values ​​in the second load region 15. Thus, the stiffness is higher in the central region 16 than in the second load region 15 and in the second overlap region 18. In the illustrated embodiment, the first material thickness Δd1 can, for example, assume values ​​that are at least twice or three times as high as the third material thickness Δd3.

[0030] Fig. 4 and 5 show how the loads in the rotor shaft 2 can be reduced by an alternative stiffness optimization. The loads are reduced not only in the load areas 14 and 15 but also in the central area 16. The axial stiffness curve of the rotor shaft 2 is improved by varying the radial material thickness Δd. In particular, the radial material thickness Δd is reduced in the area of ​​the two end faces S1, S2 compared to the central area 16. This reduces the load in the load areas 14, 15. If the material thickness Δd of the rotor shaft 2 is viewed along the axial direction x or in longitudinal section, the material thickness Δd is concave in the central area 16. As a result, the stiffness of the rotor shaft 2 within the central region 16 is changed or optimized in such a way that a more constant stress or load is present in the central region 16.The radial material thickness Δd results, as in Figs. 2 and 3, from a difference between an outer diameter da of the rotor shaft 2 and an inner diameter di of the rotor shaft 2. The outer diameter da is defined by the outer surface 10 of the rotor shaft 2. The inner diameter di is defined by the inner surface 11 of the rotor shaft 2.

[0031] In the embodiment according to Figs. 4 and 5, a first material thickness Δd1 is higher in the central region 16 than outside the central region 16. The profile of the outer surface 10 was not changed. Instead, the profile of the inner surface 11 was varied, which extends further inward in the radial direction r in the central part 16 according to the present invention than in regions on the first end face S1 and on the second end face S2.

[0032] Starting from the first material thickness Δd1, which the rotor shaft 2 has at an end of the central region 16 facing the first end face S1, the material thickness Δd decreases within the first overlap region 17 until it reaches the value of a second material thickness Δd2 within the first load region 14. The material thickness Δd does not change abruptly, but continuously. In the embodiment shown in Figs. 4 and 5, the inner surface 11 runs along a first curve 19. The first material thickness Δd1 decreases along the first curve 19 down to the second material thickness Δd2. The second material thickness Δd2 is thus less than the first material thickness Δd1.

[0033] The stiffness of the rotor shaft 2 is higher where the material thickness Δd assumes a higher value. In particular, the rotor shaft 2 has first stiffness values ​​in the central region 16 and second stiffness values ​​in the first load region 14. Consequently, the stiffness is higher in the central region 16 than in the first load region 14 and in the first overlap region 17. In the illustrated embodiment, the first material thickness Δd1 can, for example, assume values ​​that are at least twice or three times as high as the second material thickness Δd2.

[0034] In a similar way, the material thickness Δd decreases within the second overlap region 18, starting from the first material thickness Δd1, which the rotor shaft 2 has at an end of the central region 16 facing the second end face S2, until it reaches the value of a third material thickness Δd3 within the second load region 15. The material thickness Δd does not change abruptly, but continuously. In the exemplary embodiment shown in FIGS. 4 and 5, the inner surface 11 runs along a second curve 20. The first material thickness Δd1 decreases along the second curve 20 down to the third material thickness Δd3. The third material thickness Δd3 is thus less than the first material thickness Δd1. The third material thickness Δd3 can have the same value or at least a very similar value as the second material thickness Δd2.

[0035] The stiffness of the rotor shaft 2 is higher where the material thickness Δd assumes a higher value. In particular, the rotor shaft 2 has third stiffness values ​​in the second load region 15. Thus, the stiffness is higher in the central region 16 than in the second load region 15 and in the second overlap region 18. In the illustrated embodiment, the first material thickness Δd1 can, for example, assume values ​​that are at least twice or three times as high as the third material thickness Δd3.

[0036] 4 and 5 is not constant in the central region 16, but concave. The outer surface 10 runs constant or straight in the axial direction x within the central region 16. In contrast, the axial course of the inner surface 11 within the central region 16 has an outwardly curved and thus concave course. At the ends of the central region 16 facing the first end face S1 and the second end face S2 of the rotor shaft 2, the first material thickness Δd1 of the rotor shaft 2 has its maximum values. Between the maximum values, the first material thickness Δd1 of the rotor shaft 2 decreases in accordance with the concave deformation of the rotor shaft 2.

[0037] 4 and 5, the inner surface 11 runs within the central region 16 and thus also the first material thickness Δd1 along a third curve 23. The third curve 23 has a first maximum 24 at the end of the central region 16 facing the first end face S1. The curve 23 has a second maximum 25 at the end of the central region 16 facing the second end face S2. The maxima 24, 25 relate to the extent of the inner surface 11 in the inner radial direction r and to the first material thickness Δd1, respectively. In the region of the first maximum 24 and the second maximum 25, the first material thickness Δd1 has its highest values. Between the first maximum 24 and the second maximum 25, the first material thickness Δd1 decreases according to the course of the inner surface 11 defined by the third curve 23 and reaches a minimum 26 in the middle between the two maxima 24, 25.

[0038] Reference symbol Δd1 first material thickness dal first outer diameter di2 first inner diameter Δd2 second material thickness da2 second outer diameter di2 second inner diameter Δd3 third material thickness da3 third outer diameter di3 third inner diameter

[0039] E1 Elastic modulus central area

[0040] E2 Elastic modulus first load range

[0041] E3 Elastic modulus second load range

[0042] L longitudinal axis r radial direction

[0043] 51 first front side

[0044] 52 second end face x axial direction

[0045] 1 rotor

[0046] 2 rotor shaft

[0047] 3 rotor lamination pack

[0048] 4 loose bearings

[0049] 5 first bearing housing

[0050] 6 fixed bearings

[0051] 7 second bearing housing

[0052] 8 Retaining ring

[0053] 9 Securing element

[0054] 10 outer surface

[0055] 11 inner surface

[0056] 12 Load-bearing area

[0057] 13 radial shoulder 14 first load area

[0058] 15 second load area

[0059] 16 central area

[0060] 17 first overlap area

[0061] 18 second overlap area

[0062] 19 first curve

[0063] 20 second curve

[0064] 21 first end area of ​​rotor core

[0065] 22 second end area of ​​the rotor core

[0066] 23 third curve

[0067] 24 first maximum third curve

[0068] 25 second maximum third curve

[0069] 26 Minimum third curve

Claims

Patent claims 1 . Rotor shaft (2) for an electrical machine, the rotor shaft (2) comprising - a first load area (14) and - a central area (16), wherein - the first load area (14) is in an axial direction (x) of the rotor shaft (2) extends on a first end face (S1) of the rotor shaft (2), - the central region (16) on a second end face (S2) of the rotor shaft (2) adjoins the first load region (14), - the rotor shaft (2) has a first stiffness (E1) within the central region (16), - the rotor shaft (2) has a second stiffness (E2) within the first load range (14), and - the first stiffness (E1) takes a higher value than the second stiffness (E2).

2. Rotor shaft (2) according to claim 1, wherein - the rotor shaft (2) has a first material thickness (Δd1) in the central region (16), - the rotor shaft (2) has a second material thickness (Δd2) in the first load area (14), - the first material thickness (Δd1) has a higher value than the second material thickness (Δd2).

3. Rotor shaft (2) according to claim 1 or 2, the rotor shaft (2) further comprising a second load area (15), wherein - the second load area (15) is in the axial direction (x) of the rotor shaft (2) extends on the second end face (S2) of the rotor shaft (2), - the central region (16) extends between the first load region (14) on the one hand and the second load region (15) on the other hand, - the rotor shaft (2) has a third stiffness (E3) within the second load range (15) and - the first stiffness (E1) takes a higher value than the third stiffness (E2).

4. Rotor shaft (2) according to claim 3, wherein - the rotor shaft (2) has a first material thickness (Δd1) in the central region (16), - the rotor shaft (2) has a third material thickness (Δd3) in the second load area (15), - the first material thickness (Δd1) has a higher value than the third material thickness (Δd3).

5. Rotor shaft (2) according to one of the preceding claims, wherein the value of the first material thickness (Δd1) is at least twice or three times higher than the value of the second material thickness (Δd2) and / or the third material thickness (Δd3).

6. Rotor shaft (2) according to one of the preceding claims, the rotor shaft (2) further comprising - an outer surface (10) and - an inner surface (11 ), wherein - the outer surface (10) in the central region (16) runs constantly along the axial direction (x) in a radial direction (r) of the rotor shaft (2), and - the inner surface (11) in the central region (16) extends further inwards in the radial direction (r) than in the first load region (14) and / or in the second load region (15), so that the value of the first material thickness (Δd1) is higher than the value of the second material thickness (Δd2) and / or the third material thickness (Δd3).

7. Rotor shaft (2) according to claim 6, wherein - the outer surface (10) forms a support area (12) for receiving a rotor lamination stack (3) and - the inner surface (11) runs along a first curve (19) in a first overlap region (17) between the support region (12) and the first load region (14), so that the first material thickness (Δd1) decreases continuously within the first overlap region (17) to the second material thickness (Δd2), the value of which is reached in the first load region (14).

8. Rotor shaft (2) according to claim 7, wherein the inner surface (11) runs along a second curve (20) in a second overlap region (18) between the support region (12) and the second load region (15), so that the first material thickness (Δd1) decreases continuously within the second overlap region (18) down to the third material thickness (Δd3), the value of which is reached in the second load region (15).

9. Rotor shaft (2) according to one of claims 6 to 8, wherein the inner surface (11) in the central region (16) has a curved course oriented outwards in the radial direction (r).

10. Rotor shaft (2) according to claim 9, wherein - the inner surface (11) within the central region (16) runs along a third curve (23), - the third curve (23) has a first maximum (24) at an end of the central region (16) facing the first end face (S1), - the third curve (23) has a second maximum (25) at an end of the central region (16) facing the second end face (S2), and - the third curve (23) reaches a minimum (26) between the first maximum (24) and the second maximum (25).

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