Rotor shaft for a rotor, in particular of an electric machine

Abstract

The invention relates to a rotor shaft (1) for a rotor, in particular of an electric machine. The rotor shaft (1) comprises a hollow cylindrical shaft body (2) extending along an axial direction (A) and surrounding an inner space (4), which has a first axial body section (3a) and a second body section (3b) axially following the first body section (3a). Furthermore, the rotor shaft (1) comprises a hollow cylindrical support ring (5) arranged in the inner space (4). The support ring (5) abuts with an outer circumferential side (6) in the region of a transition (7) from the first (3a) to the second body section (3b) of the shaft body (2) against an inner circumferential side (8) of the shaft body (2), so that the support ring (5) is radially supported both on the first body section (3a) and on the second body section (3b).According to the invention, the two body sections are firmly connected to one another at the transition (7) from the first to the second body section (3b) by means of a welded joint (9).

Description

[0001] The present invention relates to a rotor shaft for a rotor, in particular of an electric machine. The invention also relates to a method for producing such a rotor shaft.

[0002] Hollow shaft rotor shafts for rotors are often made from two hollow cylinders that are welded together axially by laser welding.

[0003] Such a rotor shaft is described, for example, in DE 10 2018 221 569 A1.

[0004] It often proves to be problematic that during the welding process, welding fumes and welding spatter can undesirably enter the interior space delimited by the two hollow cylinders and thus into the interior of the later hollow cylindrical rotor shaft.

[0005] It is therefore an object of the present invention to provide an improved embodiment for a rotor shaft in which the aforementioned disadvantage is at least partially, ideally even completely, eliminated. A further object of the present invention is to provide an improved method for producing such a rotor shaft.

[0006] This object is achieved by the subject matter of the independent patent claims. Preferred embodiments are the subject matter of the dependent claims.

[0007] The basic idea of ​​the invention is therefore to provide a support ring in addition to the actual hollow cylindrical shaft body, which is created by welding the two hollow cylinders explained above. The two hollow cylinders can be arranged on the outer circumference of this support ring for welding together, so that the two mutually facing axial end surfaces of the two hollow cylinders can be welded together on the support ring. By means of the support ring essential to the invention, welding fumes and welding spatter are prevented from penetrating radially inwards into the interior space delimited by the hollow cylinders during the formation of the weld seam, since the support ring acts as a radial boundary for the welding area in which the weld connection between the two hollow cylinders is created. In addition, said support ring also serves to pre-fix the two hollow cylinders before the actual welding process.For this purpose, a press fit can be formed between the support ring and the two hollow cylinders. The support ring, which is essential to the invention, is therefore an additional component that enables improved welding of the two hollow cylinders forming the rotor shaft.

[0008] Following the inventive concept, a rotor shaft according to the invention designed as a hollow shaft comprises a hollow cylindrical shaft body extending along an axial direction and surrounding an interior space, said shaft body having a first axial body section and a second body section axially adjoining the first body section. The shaft body can have a central longitudinal axis extending along the axial direction and runs and, at a distance from this central longitudinal axis, rotates around the central longitudinal axis along a circumferential direction perpendicular to the axial direction. The two body sections preferably have the same radius, each measured along a radial direction - this extends orthogonally to both the axial direction and the circumferential direction away from the central longitudinal axis. Each of the two body sections of the shaft body can be formed by a tubular body.The hollow cylindrical design of the shaft body allows for a coolant to flow through it. This proves advantageous when electrically powered rotor coils of a rotor are arranged on the rotor shaft, which generate waste heat during operation that must be dissipated. By thermally coupling the coolant flowing through the shaft body to the rotor coils, the coolant can absorb waste heat from the rotor coils and dissipate it from the rotor shaft.

[0009] The rotor shaft further comprises a hollow cylindrical support ring arranged in the interior. The hollow cylindrical support ring can circumferentially delimit a support ring interior. The support ring rests with an outer circumferential side in the region of a transition from the first to the second body section of the shaft body against an inner circumferential side of the shaft body, so that the support ring is supported radially outwardly on both the first body section and the second body section, and the support ring delimits said transition radially inwardly. According to the invention, the two body sections are firmly connected to one another at the transition from the first to the second body section by means of a welded connection. The welded connection can comprise a weld seam. The welded connection or weld seam connects the two hollow cylinders in a materially bonded manner, is arranged axially between the two hollow cylinders and preferably extends along the radial direction.The welded joint or weld seam expediently extends across the two end faces of the two body sections. Since the transition, and thus the area in which the welded joint is formed between the two body sections, is delimited radially inward by the support ring, the support ring essential to the invention prevents the entry of weld spatter and the formation of weld fumes in the interior of the shaft body.

[0010] In a preferred embodiment, the support ring is frictionally connected to the shaft body by means of a press connection. This allows for stable mechanical pre-fixing of the two hollow cylinders to the support ring during the manufacture of the rotor shaft before the two hollow cylinders are welded together.

[0011] According to an advantageous development, the support ring can be designed as a closed ring, particularly in the circumferential direction. This closed ring or support ring has a central longitudinal axis extending along the axial direction and, at a distance from this central longitudinal axis, runs closed around the central longitudinal axis along a circumferential direction perpendicular to the axial direction. Such a closed ring or support proves to be particularly easy to manufacture and also particularly mechanically stable.

[0012] According to a further advantageous development which is an alternative to the development explained above, the support ring can also be designed as an open, so-called “slotted” ring which extends along the circumferential direction from a first end section to a second end section. By “open” we mean that the two end sections lie radially against one another but are not firmly connected to one another, so that the support ring can in principle be reduced in outer diameter. This can enable the support ring to be introduced into the interior space delimited by the shaft body by “compressing” the support ring. In this development, the two end sections overlap in the region of a ring joint along the circumferential direction and lie radially against one another in the region of this ring joint without being firmly connected to one another. By means of such an open orWith a slotted ring, the diameter of the ring can be varied over a certain amount, allowing manufacturing-related tolerances in the diameter of the two hollow cylinders to be welded together compared to the diameter of the support ring to be easily compensated. Particularly preferably, the open support ring can be preloaded radially outward against the shaft body for this purpose. In this way, even if manufacturing tolerances exist in the diameter of the two hollow cylinders compared to the diameter of the support ring, it is ensured that the two hollow cylinders are held securely on the support ring before welding.

[0013] In another preferred embodiment, the support ring or the open ring has, in the overlapping region of its end sections, two webs that project radially outwardly or radially inwardly from the first end section and extend in the circumferential direction, which webs are axially opposite one another. Said second end section is accommodated axially between these two webs. Thus, the two webs act as guides for the second end section with respect to the circumferential direction and as axial stops with respect to the axial direction.

[0014] According to a further advantageous development of the rotor shaft according to the invention, the first body section of the shaft body has, at an axial end facing the second body section, a first recess which is open towards the second body section and runs circumferentially on the inner circumferential side of the shaft body. A radially outer support ring section of the support ring is partially received in this first recess. A radially inner support ring section complementary to the radially outer support ring section can therefore protrude radially inward from the first recess. Accordingly, in this development, the second body section of the shaft body has, at an axial end facing the first body section, a second recess which is open towards the first body section and runs circumferentially on the inner circumferential side of the shaft body.A radially outer support ring section of the support ring can also be partially accommodated in this second recess. A radially inner support ring section complementary to the radially outer support ring section can therefore protrude radially inward from the second recess. The two recesses thus form a radial receptacle for the support ring, which in turn can act as an axial stop for the two body sections of the shaft body, allowing them to be positioned axially precisely relative to one another and also relative to the support ring for welding together. In this way, the welded connection formed between the two body sections can be improved.

[0015] According to another advantageous development, the hollow cylindrical support ring comprises a circumferential wall extending along the axial direction, which radially defines a support ring interior. In this development, an annular collar extending along the circumferential direction protrudes radially inward from an inner circumferential side of the circumferential wall into the support ring interior. In this way, a separation of the interior circumferentially defined by the shaft body into two axially adjacent chambers can be achieved in order to implement a defined guidance of the cooling medium flowing through the shaft body from or to the respective shaft end.

[0016] Particularly preferably, the annular collar can be arranged axially at a first axial end of the circumferential wall in the support ring interior. In an alternative variant, however, it can also be provided that the annular collar is arranged between the first axial end and a second axial end of the circumferential wall, in particular axially centrally, in the support ring interior. This allows said two chambers to be dimensioned differently.

[0017] In a preferred embodiment, a recess extending along the circumferential direction around the central longitudinal axis of the support ring, preferably formed as a circumferential groove, can be provided on an outer circumferential side of the support ring or the circumferential wall, axially at the level of the annular collar. A weld bead resulting from the welding of the two hollow cylinders or body sections can be received or is received in this recess.

[0018] A material of the first body portion and, alternatively or additionally, of the second body portion can be a suitable metal or a suitable metal alloy, in particular a material known under the designation "42CrMo4." A material of the support ring can, in particular, be steel. Particularly preferably, the material of the shaft body is different from the material of the support ring. This allows the material of the shaft body to be optimized with regard to strength and other requirements of the rotor shaft to be formed, whereas the material of the support ring can be designed to optimize or at least improve the welded connection between the two body portions.

[0019] The invention further relates to a method for producing a rotor shaft according to the invention as presented above. The advantages of the rotor shaft according to the invention explained above are therefore transferred to the method according to the invention, which comprises four mandatory steps a), b), c), and d).

[0020] In one measure a), the hollow cylindrical support ring of the future rotor shaft is provided. The hollow cylindrical support ring can circumferentially define a support ring interior. The support ring can be a tubular body with a hollow cylindrical geometric shape.

[0021] In a further measure b), a first hollow cylinder, which later forms the first body portion of the rotor shaft, is pushed along the axial direction onto a first axial portion of the outer peripheral side of the support ring. The first hollow cylinder can be formed, in particular, by a (first) tubular body through which a coolant, in particular, can flow, preferably with the geometric shape of a hollow cylinder.

[0022] In a further measure c), a second hollow cylinder forming the later second body section of the rotor shaft is pushed axially onto a second axial section of the outer circumferential side adjoining the first axial section, specifically in the opposite direction to the axial direction, i.e. towards the first hollow cylinder already arranged on the support ring. The second hollow cylinder can also be formed in particular by a (second) tubular body through which, in particular, a coolant can flow, preferably with the geometric shape of a hollow cylinder. A second radius of the second hollow cylinder measured along the radial direction is preferably identical to a first radius of the first hollow cylinder likewise measured along the radial direction.

[0023] The axial sliding of the second hollow cylinder in the opposite direction to the axial direction takes place at least until the two hollow cylinders are axially in contact with each other.

[0024] Advantageously, the first hollow cylinder can be provided, at an axial end facing the second body section, with a first recess that is open toward the second hollow cylinder and runs circumferentially along its inner peripheral side. Likewise, the second hollow cylinder can be provided, at an axial end facing the first body section, with a second recess that is open toward the first hollow cylinder and runs circumferentially along its inner peripheral side. These two recesses can act as an axial stop when the two hollow cylinders are pushed onto the support ring, ensuring their axially precise positioning. This proves advantageous for the quality of the welded joint yet to be formed between the two hollow cylinders.

[0025] In a further measure d), the rotor shaft is produced by welding, in particular by laser welding, the two hollow cylinders together in the region of the transition or in the region of the two end or contact surfaces between the two hollow cylinders. In this case, a weld seam can be created at the transition from the first to the second hollow cylinder. After welding, the first hollow cylinder forms the first body section of a rotor shaft according to the invention and the second hollow cylinder forms the second body section of this rotor shaft. Due to the support ring present in the interior, no welding spatter or welding fumes generated during welding can enter the interior of the shaft body formed by welding.

[0026] In a preferred embodiment of the method according to the invention, the welding in step d) is carried out by means of laser welding. In this embodiment, during the laser welding, a laser beam is directed onto the transition or the contact surfaces of the two hollow cylinders, so that the welded connection having a weld seam is formed there between the two hollow cylinders or between the two body sections of the shaft body of the rotor shaft. The laser beam can be generated by a laser light source which is arranged radially outwards in the region of the transition at a distance from the latter, so that it emits laser light radially inwards along the radial direction, so that this laser light strikes the transition and creates the desired welded connection there. The welded connection orWeld seam connects the two hollow cylinders in a material-to-material manner, is arranged axially between the two hollow cylinders and extends along the radial direction or in a plane perpendicular to the axial direction.

[0027] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures with reference to the drawings.

[0028] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0029] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0030] They show, schematically: Fig. 1 an example of a rotor shaft according to the invention in a longitudinal section, Fig. 2 a detailed representation of the Fig. 1 in the area of ​​the welded joint between two body sections of the shaft body of the rotor shaft, Fig. 3 the support ring of the Fig. 1 in separate representation, Fig. 4 a variant of the example of Fig. 1 to 3, in which the annular collar is arranged axially at a first axial end, Fig. 5 a further development of the example of Fig. 1 to 3, in which a recess is provided on the outer peripheral side of the support ring, Fig. 6 a top view of the support ring of the Fig. 1 to 5 along the axial direction, Fig. 7 a simplified version of the support ring of the Fig. 1 to 6 without a collar projecting radially inwards from the peripheral wall of the support ring in a longitudinal section along the axial direction, Fig. 8 a top view of the support ring of the Fig. 7 along the axial direction, Fig. 9a, Fig. 9b another variant with an open support ring, Fig. 10a, Fig. 10b a top view of the support ring of the Fig. 9 with a representation of the overlap of the ring ends with and without lateral limitation of the overlap area, Fig. 11 is a flowchart illustrating the method according to the invention, Fig. 12a-d four different representations illustrating the execution of the method according to the invention in the form of snapshots taken at different execution times.

[0031] The Fig. 1 shows a longitudinal section of an example of a rotor shaft 1 according to the invention. The rotor shaft 1 comprises a hollow cylindrical shaft body 2 which extends along an axial direction A and surrounds an interior space 4 and which has a first axial body section 3a and a second body section 3b which adjoins the first body section 3a axially. A first radius r1 of the first body section 3a, measured along the radial direction R, is equal to a first second radius of the second body section 3b, also measured along the radial direction R. The shaft body 2 has a central longitudinal axis M which extends along the axial direction A. A radial direction R extends perpendicular to the axial direction A away from the central longitudinal axis M. A circumferential direction U runs perpendicular to both the axial direction A and the radial direction R around the central longitudinal axis M.

[0032] Furthermore, the rotor shaft 1 comprises a hollow cylindrical support ring 5 arranged in the interior 4. The hollow cylindrical support ring 5 can circumferentially delimit a support ring interior 14. The support ring rests with an outer circumferential side 6 in the region of an axial transition 7 from the first body section 3a to the second body section 3b of the shaft body 3 against an inner circumferential side 8 of the shaft body 2, so that the support ring 5 is supported radially on the outside both on the first body section 3a and on the second body section 3b. The two body sections 3a, 3b are firmly connected to one another at the transition 7 from the first body section 3a to the second body section 3b by means of a welded connection 9. The welded connection 9 can comprise a weld seam 9a. The welded connection 9 or weld seam 9a connects the two body sections 3a, 3b in a materially bonded manner and is in this caseThe welded joint 9 or weld seam 9a is arranged in the axial direction A between the two body sections 3a, 3b and extends along the radial direction. The welded joint 9 or weld seam 9a expediently extends over two mutually facing end faces 18a, 18b of the two body sections 3a, 3b.

[0033] At the two axially opposite ends 24a, 24b of the shaft body 2, in the example scenario, the Fig. 1 axially a first and second axial shaft end piece 25a, 25b, in which a first and second coolant inlet 26a, 26b is formed, respectively, for introducing cooling medium into the interior 4. In the hollow cylindrical shaft body 2, radially extending openings 27 can be formed, through which the cooling medium can exit the interior 4 and in this way reach the rotor coils to be cooled (not shown in the figures). In the example, a Fig. 1, a tooth structure 28 is provided for drivingly connecting the rotor shaft 1 to an external drive component (not shown). The support ring 5 is secured by means of a Fig. 1 is frictionally connected to the shaft body 2 by a press connection 10 (not shown in detail). The press connection 10 forms a press fit for the two body sections 3a, 3b of the shaft body 2. In the example, a material of the shaft body 2 is different from a material of the support ring 5. For example, the material 42CrMo4 can be considered as the material for the shaft body 2, and a steel material can be considered as the material for the support ring 5.

[0034] The Fig. 2 is a detailed view of the Fig. 1 in the area of ​​the transition 7 between the two body sections 3a, 3b. As Fig. 2, the first body section 3a of the shaft body 2 has, at an axial end 23a facing the second body section 3b, a groove which is open towards the second body section 3b and which is arranged on the inner circumferential side 8 of the shaft body 2 in the circumferential direction U (cf. Fig. 1) circumferential first recess 12a. Likewise, the second body portion 3b of the shaft body 2 has, at an axial end 23b facing the first body portion 3a, a second recess 12b which is open towards the first body portion 3a and which extends circumferentially on the inner circumferential side 8 of the shaft body 2 in the circumferential direction U, in which the support ring 5 is partially received. According to Fig. 2, a radially outer support ring section 31 of the support ring 5 is partially received in the two recesses 12a, 12b, whereas a radially inner support ring section 32 complementary to the radially outer support ring section 31 protrudes radially inwards from the two recesses 12a, 12b.

[0035] The Fig. 3 shows the support ring of the Fig. 1 in a separate illustration. Accordingly, the hollow cylindrical support ring 5 comprises a circumferential wall 13 extending along the axial direction A, which radially delimits a support ring interior 14. From an inner circumferential side 15 of the circumferential wall 13, an annular collar 16 extends radially inward into the support ring interior 14 along the circumferential direction U. The collar 16 also runs completely around the central longitudinal axis M along the circumferential direction U.

[0036] The collar 16 can be formed integrally on the peripheral wall 13, which means that the peripheral wall 13 and collar 16 are formed in one piece and from the same material.

[0037] In the example of Fig. 1 to 3, the annular collar 16 is arranged axially centrally between the first axial end 17a and a second axial end 17b of the peripheral wall 13 in the support ring interior 14.

[0038] In a Fig. 4 shown variant of the example of Fig. 1 to 3, the annular collar 16 is arranged axially at an axial end 17 of the peripheral wall 13 in the support ring interior 14.

[0039] In a Fig. 5 shown further development of the example of Fig. 1 to 3, on the outer circumferential side 6 of the support ring 5 or the circumferential wall 13, axially at the level of the annular collar 16, there may be a recess 19 which runs completely around the central longitudinal axis M along the circumferential direction U and which may be designed as a circumferential groove 20.

[0040] The Fig. 6 shows a top view of the support ring 5 of the Fig. 1 to 5 along the axial direction A. Accordingly, the support ring 5 can be designed as a closed ring 5a with respect to the circumferential direction U. The closed ring 5a or support ring 5 runs according to Fig. 6 at a distance from the central longitudinal axis M along the circumferential direction U completely around the central longitudinal axis M.

[0041] The Fig. 7 and Fig. 8 show a simplified version of the examples of Fig. 1 to 6, in which the support ring 5 is the same as in the example of Fig. 1 to 6 is designed as a closed ring 5a, but without the Fig. 1 to 6 each recognizable fret 16. The Fig. 7 shows a Fig. 3 to 5 corresponding longitudinal section of the support ring 5 along the axial direction A, whereas the Fig. 8 one with the Fig. 6 shows a corresponding top view along the axial direction A. As the Fig. 7 and Fig. 8 can be removed directly, the support ring 5 does not have the Fig. 7 and Fig. 8 the collar 16 projecting radially inwards from the peripheral wall 13 without replacement.

[0042] The Fig. 9a and Fig. 9b show an example of a further variant of the support ring 5, in which it is not, as in the example of Fig. 7 and Fig. 8 is not designed as a closed ring, but as an open ring 5b. A support ring designed in this way is also known to those skilled in the art as a “slotted ring”. Fig. 9b is an enlarged view of the Fig. 9a by a dashed line with the reference symbol X.

[0043] The support ring 5, designed as an open or slotted ring 5b, extends according to the Fig. 9a and Fig. 9b along the circumferential direction U from a first end section 11a to a second end section 11b. In this variant, the two end sections 11a, 11b overlap along the circumferential direction U in the region of a ring joint 33 and lie radially against one another without being firmly connected to one another. According to the Fig. 9a, Fig. 9b therefore expressly does not mean that the ring has an interruption along the circumferential direction U; rather, the term "open ring" in the context of the present invention is to be interpreted as meaning that the two end sections 11a, 11b are radially adjacent to one another, but are not firmly connected to one another, so that the support ring 5 can in principle be "opened" by radial expansion, or its circumference as well as its inner diameter can be reduced by compression. This simplifies the insertion of the support ring 5 into the interior space 4. The support ring 5 described above, designed as an open ring 5b, can therefore be preloaded radially outwards against the shaft body 2 (not shown).

[0044] As can be seen from the Fig. 9a and Fig. As can be seen in Figure 9b, the outer peripheral side 6 of the support ring 5 has a ring radius r that is constant along the circumferential direction U and measured along the radial direction R. For this purpose, the second end section 11b is arranged radially offset inwardly relative to a ring section 11c that is complementary to the second end section 11b and also includes the first end section 11a.

[0045] The Fig. 10a and Fig. 10b show a plan view along the radial direction R of a support ring 5 according to Fig. 9a and 9b respectively, showing an overlapping area of ​​the open ends with the first end section 11a and with the second end section 11b. In the Fig. In the variant shown in Figure 10b, the support ring 5 or the open ring 5b has, in the overlapping area of ​​its two end sections 11a, 11b, two webs 36a, 36b, each extending parallel to one another in the circumferential direction U and projecting radially outward, or, in a possible alternative (not shown), inwardly projecting webs, which are axially opposite one another. The second end section 11b, designed as a tongue, is received axially between these two webs. Thus, the two webs 36a, 36b act as a guide for the second end section 11b with respect to the circumferential direction U and as stops with respect to the axial direction. The two webs 36a, 36b close the area of ​​the support ring 5 which is otherwise laterally open due to the sliding of a first end section 11a under a second end section 11b of the support ring 5 and is not covered by the second end section 11b.

[0046] The following flow chart shows the Fig. 11 and based on the Fig. 12a to 12d, which show snapshots associated with various steps of the procedure during the implementation of the procedure.

[0047] According to the flow chart of the Fig. 11, the method according to the invention comprises four mandatory measures a), b), c) and d), which are carried out consecutively in this order.

[0048] In a first measure a) as in Fig. 12a shows an example of the already shown Fig. 3 explained support ring 5 of the later rotor shaft 1 with a collar 16 projecting radially inwards from the circumferential wall 13. In variants of the example, alternatively, the one shown in the example of the Fig. 4, Fig. 5 or Fig. 7 each shown support ring 5 is provided.

[0049] In a second measure b) as in Fig. 12b, a first hollow cylinder 21a forming the later first body section 3a of the shaft body 2 of the later rotor shaft 1 extends along the axial direction A (cf. arrow P in Fig. 12b. The first hollow cylinder 21a can be formed by a tubular body 29a.

[0050] In a third measure c) as in Fig. 12c shows a second hollow cylinder 21b forming the later second body section 3b of the shaft body 2 of the rotor shaft 1, pushed axially onto a second axial section 22b of the outer peripheral side 6 adjoining the first axial section 22a, in the opposite direction to the axial direction A (cf. arrow Q in Fig. 12c). The second hollow cylinder 20b can also be formed by a tubular body 29b. A second radius R2 of the second hollow cylinder 21b, measured along the radial direction R, corresponds in the example to a first radius R1 of the first hollow cylinder 21a, also measured along the radial direction R.

[0051] The sliding in the opposite direction to the axial direction A is carried out in measure c) until the mutually facing end faces 18a, 18b of the two hollow cylinders 21a, 21b abut against each other without forming a joint gap.

[0052] In a fourth measure d), as in Fig. 12d shows the rotor shaft 1, the two hollow cylinders 21a, 21b at the transition 30 between the two hollow cylinders 21a, 21b, in which the two end faces 18a, 18b abut against each other, welded together between the two hollow cylinders 21a, 21b by means of laser welding, i.e. by means of a welding process.

[0053] In the example, the welding in step d) is carried out by means of laser welding. In this embodiment, during the laser welding, a laser beam 34 is directed onto the transition 30 between the two hollow cylinders 21a, 21b, so that the welded joint between the two hollow cylinders 21a, 21b or body sections 3a, 3b of the shaft body 2 of the rotor shaft 1 is formed there. The laser beam 34 can be generated by a laser light source 35, which is arranged radially outward in the region of the transition 30 at a distance from the transition, so that it emits the laser light 34 radially inward along the radial direction R, which strikes the transition 30 and creates the desired welded joint 9 therein.

[0054] During the welding process, a weld seam 9a can be formed as part of the welded joint 9. The welded joint 9 or weld seam 9a connects the two hollow cylinders 21a, 21b in a materially bonded manner. The welded joint 9 or weld seam 9a is arranged axially between the two hollow cylinders and extends along the radial direction R across the two end faces 18a, 18b of the two hollow cylinders 21a, 21b or body sections 3a, 3b.

[0055] After carrying out measure d), the production of the rotor shaft 1 according to the invention is completed. QUOTES CONTAINED IN THE DESCRIPTION

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

[0000] DE 10 2018 221 569 A1

[0003]

Claims

[1] Rotor shaft (1) for a rotor, in particular of an electrical machine, - with a hollow cylindrical shaft body (2) extending along an axial direction (A) and surrounding an interior space (4), which has a first axial body section (3a) and a second body section (3b) axially adjoining the first body section (3a), - with a hollow cylindrical support ring (5) arranged in the interior (4), which bears with an outer peripheral side (6) in the region of a transition (7) from the first (3a) to the second body section (3b) against an inner peripheral side (8) of the shaft body (2), so that the support ring (5) is supported on both the first (3a) and the second body section (3b), - wherein the two body sections (3a, 3b) are firmly connected to one another at the transition (7) from the first to the second body section (3b) by means of a welded joint (9). [2] Rotor shaft according to claim 1, characterized bythat the support ring (5) is frictionally connected to the shaft body (2) by means of a press connection (10). [3] Rotor shaft according to claim 1 or 2, characterized by that the support ring (5) is designed as a closed ring (5a) which has a central longitudinal axis (M) extending along the axial direction (A) and, at a distance from this central longitudinal axis (M), rotates in a closed manner around the central longitudinal axis (M) along a circumferential direction (U) perpendicular to the axial direction (A). [4] Rotor shaft according to claim 1 or 2, characterized by that the support ring (5) is designed as an open ring (5b) which extends along the circumferential direction (U) from a first end section (11a) to a second end section (11b), wherein the two end sections (11a, 11b) overlap along the circumferential direction (U) and bear radially against one another. [5] Rotor shaft according to claim 4, characterized in that the support ring (5) or the open ring (5b) in the overlap region (38) of its end sections (11a, 11b) has two webs (36a, 36b) extending in the circumferential direction (U), projecting radially outwards and / or radially inwards and axially opposite one another, between which the second end section (11b) is axially received, so that the two webs (36a, 36b) act as a guide for the second end section (11b) with respect to the circumferential direction (U) and as axial stops with respect to the axial direction. [6] Rotor shaft according to claim 4 or 5, characterized by that the support ring (5) or the open ring (5b) is preloaded radially outwards against the shaft body (2). [7] Rotor shaft according to one of the preceding claims, characterized by , that - the first body section (3a) has, at an axial end (11a) facing the second body section (3b), a first recess (12a) which is open towards the second body section (3b) and runs around the inner circumferential side (8) of the shaft body (2) in the circumferential direction (U), in which the support ring (5) is partially received; and that - the second body section (3b) has, at an axial end (11b) facing the first body section (3a), a second recess (12b) which is open towards the first body section (3a) and runs around the inner circumferential side (8) of the shaft body (2) in the circumferential direction (U), in which the support ring (5) is partially received. [8] Rotor shaft according to one of the preceding claims, characterized by that the hollow cylindrical support ring (5) comprises a circumferential wall (13) extending along the axial direction (A) and radially outwardly delimiting a support ring interior (14), - an annular collar (16) extending along the circumferential direction (U) projects radially inwards from an inner circumferential side (15) of the circumferential wall (13) into the support ring interior (14). [9] Rotor shaft according to claim 8, characterized by that the annular collar (16) is arranged at a first axial end (17) of the peripheral wall in the support ring interior (14). [10] Rotor shaft according to claim 8, characterized by that the annular collar (16) is arranged between a first axial end (17a) and a second axial end (17b) of the peripheral wall (13), in particular axially centrally, in the support ring interior (14). [11] Rotor shaft according to one of the preceding claims, characterized bythat on the outer circumferential side (6) of the support ring (5) or the circumferential wall (13) axially at the level of the annular collar (16) there is a recess (19) which runs along the circumferential direction (U) around the central longitudinal axis (M) of the support ring (5), and which is preferably designed as a circumferential groove (20). [12] Rotor shaft according to one of the preceding claims, characterized by that a material of the shaft body (2) is different from a material of the support ring (5). [13] Method for producing a rotor shaft (1) according to one of the preceding claims, comprising the following measures: a) providing a hollow cylindrical support ring (5), b) axially pushing a first hollow cylinder (21a) forming the later first body section (3a) of the shaft body (3) of the rotor shaft (1) onto a first axial section (22a) of the outer peripheral side (6) of the support ring (5) along the axial direction (A), c) axially pushing a second hollow cylinder (21b) forming the later second body section (3b) of the shaft body (3) of the rotor shaft (1) onto a second axial section (22b) of the outer peripheral side (6) of the support ring (5) adjoining the first axial section (22a) opposite to the axial direction (A) opposite to the axial direction (A) towards the first hollow cylinder (21a), d) forming the rotor shaft (1) by welding, in particular by means of laser welding, the two mutually facing axial end faces (18a, 18b) of the two hollow cylinders (21a, 21b) together. [14] Method according to claim 13, characterized by , that - the welding in measure d) is carried out by laser welding, - During laser welding, a laser beam (34) is directed onto an axial transition (7) between the two hollow cylinders (21a, 21b) so that the welded joint is formed there.

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