Rotor shaft for a machine, connecting pipe for a rotor shaft, machine with such a rotor shaft, and motor vehicle

Description

[0001] The present invention relates to a rotor shaft for a machine, which is, for example, designed as an electric traction machine for a motor vehicle. The invention further relates to a machine, in particular an electric traction machine, with such a rotor shaft. Moreover, the invention relates to a motor vehicle equipped with the machine and a connecting tube for the rotor shaft.

[0002] To ensure optimal operation of an electric drive or traction motor, efficient cooling during operation is essential. In particular, operating conditions should be avoided in which the traction motor's control system only provides reduced drive torque to prevent unwanted overheating of its components. If such an operating condition occurs, the user of the traction motor, especially the driver of a vehicle equipped with it, can no longer access the usual full power; the user is surprised by the reduction in drive torque (a phenomenon known as degradation) and must suddenly manage with the reduced performance. This can lead to problems during overtaking maneuvers, driving uphill or on inclines, towing trailers, etc.There is therefore a need to avoid such operating conditions as far as possible, which requires maximum-efficiency cooling of the traction motor. Machines whose rotor shaft is cooled internally by means of a cooling fluid are known from the prior art, for example from DE 949 611 B, DE 10 2012 217 361 A1 or DE 10 2014 204 133 A1.

[0003] Furthermore, DE 10 2020 107 533 A1 discloses a liquid-cooled rotor for an electromechanical energy converter. The rotor shaft is hollow, with a liquid guide tube extending into it, creating an annular space filled with liquid between the guide tube and the rotor shaft. The guide tube has a liquid outlet opening, which is fluidly connected to the annular space through an internal tube of the guide tube.

[0004] Furthermore, DE 10 2020 207 431 A1 discloses an electric machine in whose rotor shaft a cooling tube is mounted, such that an annular gap channel is formed between an inner wall of the rotor shaft and the cooling tube. A cooling path of the electric machine, through which a cooling medium flows, runs through the cooling tube and, after a deflection, through the annular gap channel.

[0005] The object of the present invention is to provide a solution for cooling a rotor shaft of a machine, in particular an electric machine, even more efficiently.

[0006] This task is solved by the subject matter of the independent claims.

[0007] Further possible embodiments of the invention are disclosed in the dependent claims, the description, and the figures. Features, advantages, and possible embodiments set forth in the description for one of the subject matter of the independent claims are to be regarded, at least analogously, across categories and embodiments as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as of any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the dependent claims.

[0008] According to the invention, a rotor shaft for a machine is proposed, which includes, among other things, a connecting pipe (which can also be referred to as a coolant lance). The invention further relates to said connecting pipe alone, as well as to a machine comprising the rotor shaft and, consequently, the connecting pipe. Furthermore, according to the invention, a motor vehicle is proposed, comprising the machine and, consequently, the rotor shaft with the connecting pipe. This means that the connecting pipe, in its intended installation position, forms a component of the rotor shaft, and the rotor shaft, in its intended installation position, forms a component of the machine. Once the machine is arranged in its intended installation position, it forms a component of the motor vehicle.The machine is specifically designed as an electric traction machine for the motor vehicle, which means that the motor vehicle is designed as a purely electric or hybrid-electric powered vehicle.

[0009] The rotor shaft has an outer tube, which is designed, for example, to support a rotor assembly of the electric machine in a rotationally fixed manner. Thus, for the machine, an outer circumferential surface of the outer tube and a rotor of the machine are rotationally fixed together. Inside the hollow interior of the outer tube, the rotor shaft has an inner tube, with the outer and inner tubes arranged coaxially. In other words, a longitudinal center axis of the outer tube and a longitudinal center axis of the inner tube coincide with a longitudinal center axis of the rotor shaft. The inner tube is mounted within the outer tube such that an annular space is formed between an inner wall of the outer tube and an outer wall of the inner tube.Furthermore, the inner tube has one or more openings in its wall, each opening completely penetrating an inner tube wall of the inner tube either parallel to or oblique to the radius. This allows communication between the hollow interior of the inner tube and the hollow interior of the outer tube, or between the hollow interior of the inner tube and the annular space of the outer tube. In particular, the inner tube has a conical base, which forms one of its ends and features axial grooves. The groove bottoms and the inner wall of the outer tube are radially spaced apart, creating axial channels between the base and the inner wall. The inner tube is also centered within the outer tube by means of the base, such that the outer diameter of the inner tube at the base—unlike the rest of the inner tube—corresponds to the inner diameter of the outer tube.Thus, the hollow interior of the inner tube and the outer tube annular space communicate both via the inner tube wall openings and via the grooves or channels of the inner tube base.

[0010] Furthermore, the rotor shaft has a hollow journal with a first and a second journal section that are rigidly connected to each other. In particular, the journal sections are formed integrally. The first journal section protrudes from the outer tube and thus forms an output element of the rotor shaft or the machine. For example, a spur gear ring is fixedly mounted to the first journal section of the hollow journal, designed to mesh with an external spur gear, such as a drive spur gear of a gearbox flanged to the machine. The second journal section of the hollow journal is arranged coaxially within the outer tube, i.e., in the hollow interior of the outer tube, and is spaced from the inner tube along the longitudinal center axis of the rotor shaft. The second journal section and the inner wall of the outer tube are tightly and rotationally fixedly connected to each other.The outer tube annular space is thus bounded or defined by the inner wall of the outer tube, the outer wall of the inner tube, an end annular surface of the second journal segment, and the inner tube base. The second journal segment has one or more journal wall openings, each of which completely penetrates a journal wall of the shaft journal, either parallel to or oblique to the radius. This allows communication between the hollow interior of the shaft journal and a drive-side opening of the outer tube, from which the first journal segment protrudes.

[0011] The connecting tube of the rotor shaft is made of plastic, for example as a plastic injection-molded part, and has a first connecting tube end that rests tightly against the inner wall of the shaft journal in the first journal section on its outer circumference. Furthermore, the connecting tube extends through the second journal section, protruding from it. As the connecting tube protrudes from the second journal section, it opens into the inner tube, with a tight seal between the inner tube and the connecting tube. An annular space is formed between the outer wall of the connecting tube and the inner wall of the shaft journal in the second journal section, and this annular space and the outer tube annular space are interconnected. A longitudinal center axis of the connecting tube and the longitudinal center axes of the outer tube, the inner tube, and the shaft journal coincide with the longitudinal center axis of the rotor shaft.

[0012] Due to this arrangement of the outer tube, the inner tube, the shaft journal, and the connecting tube, a coolant path through which a coolant, in particular an oil, can flow, is formed. During operation of the machine equipped with the rotor shaft, the coolant is fed into the hollow interior of the shaft journal. For this purpose, a supply line of a coolant or oil module is fluidically coupled to a shaft journal opening, i.e., to the hollow interior of the shaft journal. For example, a hollow nozzle can be inserted into the shaft journal opening, in particular pressed in, with a radial shaft seal provided between the supply line and the shaft journal opening, which prevents the coolant or oil from escaping at the coupling point between the supply line and the shaft journal. The oil is pumped, for example, by means of a pump of the coolant or oil module.The oil module is forced through the supply line and thus into the shaft journal and consequently into the rotor shaft. The oil flows through the shaft journal and then enters the connecting pipe, as its first end is in close contact with the inner wall of the shaft journal in the first section of the journal, preventing oil from escaping between the shaft journal and the connecting pipe. The oil then flows through the connecting pipe and subsequently out of it, entering the inner tube, as the connecting pipe terminates in the inner tube. The oil then exits the inner tube through the opening(s) in the inner tube wall and thus between the inner and outer tubes, i.e., into the annular space of the outer tube. Furthermore, the oil flows from the inner tube into the annular space of the outer tube via the grooves or channels located at the base of the inner tube. The size and number of the respective opening(s) in the inner tube wall are crucial.The respective groove is designed such that a large portion of the oil in the inner tube flows into the outer tube annular space through the inner tube wall opening(s), while a significantly smaller portion flows into the outer tube annular space through the groove(s). An end edge of the inner tube or inner tube base is spaced apart from a sealing element of the rotor shaft, so that the oil flows out of the inner tube at the end edge, into the channels / grooves, and thus into the outer tube annular space. In the outer tube annular space, the oil flows along the inner wall of the outer tube, where it absorbs and dissipates heat generated during machine operation.As the heated oil flows out of the outer tube annular space, it flows between the outer wall of the connecting tube and the inner wall of the shaft journal, i.e., into the shaft journal annular space. From there, the oil flows through the journal wall opening(s) and finally out of the rotor shaft through the output-side opening of the outer tube. Specifically, the rotor shaft connects via its output-side opening to a gearbox chamber of a gearbox flanged to the machine. It is specifically designed that the coolant used to cool the machine and the lubricant used to lubricate the gearbox are identical. In other words, the coolant circuit described here can be a component of a lubrication circuit in an arrangement comprising the machine and the gearbox.

[0013] Thanks to the rotor shaft, the oil or coolant flow can be directed particularly efficiently to those parts / components of the rotor shaft or machine that have a particularly high cooling requirement. This ensures highly efficient heat dissipation from these components and reliably protects the machine from overheating. Especially when the machine is used as an electric traction motor in a motor vehicle, degradation of the machine is effectively prevented.

[0014] In a possible further development, the connecting pipe is provided with a centering rib arrangement on its outer wall, through which fluid flows along the longitudinal center axis. This arrangement allows the connecting pipe to be coaxially supported in the second journal section. The centering rib arrangement comprises three or more ribs, each projecting radially outwards from the outer wall of the connecting pipe. In the rotor shaft, the outer wall of the connecting pipe and the inner wall of the shaft journal are spaced apart by the height of the respective centering rib. The centering rib arrangement is located within the annular space of the shaft journal or at least extends into it.Along an outer circumferential direction of the connecting tube, the centering ribs are evenly spaced apart from each other, so that on the one hand oil can flow between the centering ribs and on the other hand the connecting tube is particularly securely centered in the shaft journal.

[0015] According to another possible embodiment, the connecting pipe has a fluid-flowable contact collar on its outer wall, through which the fluid flows along the longitudinal center axis. This contact collar causes the connecting pipe to abut an end annular surface of the second journal section. This prevents the connecting pipe from unintentionally disengaging from its intended installation position during machine operation and, for example, from moving too far into the shaft journal. Furthermore, assembly of the rotor shaft is simplified. The contact collar comprises one or more contact elements, each of which is positioned axially, i.e., along the longitudinal center axis of the rotor shaft, directly against the end annular surface of the second journal section.If the coupling collar has two or more coupling elements, these are evenly spaced from one another along the outer circumference of the connecting pipe, so that, firstly, oil can flow between the coupling elements and, secondly, the connecting pipe is particularly securely axially secured to the shaft journal or its end ring surface. In particular, the centering rib arrangement and / or the coupling collar are formed integrally or monolithically with the connecting pipe. This means that during the primary forming process, especially injection molding, of the connecting pipe, the centering rib arrangement and / or the coupling collar are also formed.

[0016] According to another possible embodiment, the connecting pipe has a first sealing ring seat at its first end. In this context, the rotor shaft has a first sealing ring that is fixed in this first sealing ring seat and thus between the inner wall of the first journal section and the outer wall of the connecting pipe. This ensures a particularly reliable fluidically tight connection between the connecting pipe and the hollow interior of the journal. Furthermore, the output-side opening of the outer pipe and the journal annular space are sealed from each other with exceptional reliability.

[0017] Another possible embodiment provides a connecting sleeve by means of which the connecting pipe and the inner pipe are tightly connected. The connecting sleeve circumferentially encircles a second connecting pipe end facing the inner pipe and an inner pipe end also facing the connecting pipe. The outer diameter of the connecting sleeve is smaller than the inner diameter of the outer pipe, so that the inner wall of the outer pipe and the connecting sleeve are radially spaced apart. In this way, the connecting sleeve is positioned within the annular space of the outer pipe and is surrounded by oil during operation. The connecting sleeve ensures a particularly stable and reliably tight connection between the connecting pipe and the inner pipe.

[0018] According to a possible further development, the connecting pipe has a second sealing ring seat at its second end. In this context, the rotor shaft has a second sealing ring that is fixed in this second sealing ring seat. If the rotor shaft has the previously described connecting sleeve, it is specifically designed that the second sealing ring, located in the second sealing ring seat, is inserted between the outer wall of the connecting pipe and an inner wall of the connecting sleeve. This ensures a particularly reliable and tight fluid seal between the connecting pipe and the inner pipe. Due to the first and / or the second sealing ring, the annular space of the outer pipe and the annular space of the shaft journal are particularly securely sealed against the respective hollow interiors of the shaft journal, the connecting pipe, and the inner pipe, thus facilitating particularly efficient cooling of the rotor shaft.

[0019] The cooling of the rotor shaft during machine operation is even more efficient if—as another possible embodiment provides—the inner wall of the outer tube has a surface-enhancing structure within the annular space. This surface-enhancing structure comprises, for example, a multitude of annular grooves and / or notches that are equidistant from one another or directly adjacent to each other. This creates a multitude of depressions, each extending radially from the inner wall of the outer tube towards the outer wall. In this embodiment, thanks to the surface-enhancing structure, the annular space of the outer tube has a particularly large surface area, allowing a larger volume of oil to flow directly along the outer tube material simultaneously during machine operation.This allows a particularly large amount of heat to be carried away from the outer pipe at a given oil flow rate.

[0020] As explained above, the invention also relates to the connecting tube for the rotor shaft. The connecting tube has a fluidically flowable contact collar on its outer wall along its longitudinal central axis, by means of which it can contact the end ring surface of the second journal portion.

[0021] Further features of the invention may become apparent from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and / or in the figures themselves, can be used not only in the combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

[0022] The drawing shows in: Fig. 1 a sectional view of a machine having a rotor shaft with a connecting tube, Fig. 2 a sectional view of the connecting tube and Fig. 3 a perspective view of the connecting tube.

[0023] The following section describes a rotor shaft 1 for a machine 2, a connecting pipe 3 of the rotor shaft 1, the machine 2, and a motor vehicle comprising the machine 2 (not shown) in a joint description. In the figures, identical and functionally equivalent elements are designated with the same reference numeral.

[0024] The connecting tube 3 forms part of the rotor shaft 1, which, in its intended installation position (as shown in the figures), forms part of the machine 2. The machine 2 is designed as an electric traction machine, and the vehicle, as a purely electric or hybrid-electric vehicle, incorporates the traction machine 2.

[0025] Fig. 1Figure 1 shows a sectional view of machine 2, whose rotor shaft 1 comprises the connecting tube 3, an outer tube 4, an inner tube 5, and a hollow shaft journal 6. With respect to a longitudinal center axis 7 of the rotor shaft 1, the outer tube 4 and the inner tube 5 are arranged coaxially, with an outer tube annular space 10 formed between an inner wall 8 of the outer tube and an outer wall 9 of the inner tube. The outer tube annular space 10 and a hollow interior 11 of the inner tube 5 communicate with each other by virtue of the inner tube 5 having an inner tube wall opening 12, in this case two or more inner tube wall openings 12. The inner tube wall openings 12 are arranged in the immediate vicinity of a conical inner tube base 13 of the inner tube 5, by means of which the inner tube 5 is centrally mounted within the outer tube 4.At the conical inner tube base 13, which forms a first end of the inner tube 5, an outer diameter of the inner tube 5 is widened relative to the rest of the inner tube 5, to the extent of an inner diameter of the outer tube 4, so that the inner tube 5 rests against the inner wall 8 of the outer tube 4 via its inner tube base 13. Along an outer circumferential direction, the inner tube base 13 has axially arranged grooves 13a, the respective groove bottoms of which and the inner wall 8 of the outer tube 4 are radially spaced apart. Thus, the grooves 13a and the inner wall 8 of the outer tube 4 form axial channels. An end edge of the inner tube 5, or inner tube base 13, is spaced apart from a closure element 1a of the rotor shaft 1.

[0026] The hollow shaft journal 6 has a first journal section 14 and a second journal section 15, which are formed integrally in this example. The first journal section 14 carries a rotationally fixed spur gear rim 16, which meshes with an external drive spur gear 17 of a gearbox 18 flanged to the machine 2 in its gearbox chamber 19. The first journal section 14 projects from an output-side opening 20 of the outer tube 4 and thus into the gearbox chamber 19. The journal sections 14 and 15 merge into one another at a press fit element 21 of the shaft journal 6, whereby the shaft journal 6 is pressed into the outer tube 4 by means of the press fit element 21. To prevent relative rotation between the shaft journal 4 and the outer tube 4, a splined connection 22 is arranged between the shaft journal 6 and the outer tube 4.The splined connection 22 is arranged in particular on the second journal section 15, which is arranged coaxially in the outer tube 4. In this way, the second journal section 15 and the inner wall 8 of the outer tube are tightly and rotationally fixedly connected to each other. Along the longitudinal center axis 7 of the rotor shaft 1, an end ring surface 23 of the second journal section 15 and the inner tube 5 are spaced apart from each other by a straight distance.

[0027] The connecting pipe 3 - which is in Fig. 2 and Fig. 3The connecting pipe 3, shown in isolation in its respective view, has a first connecting pipe end 24 and a second connecting pipe end 25. At the first connecting pipe end 24, a first sealing ring seat 26 is arranged, in which a first sealing ring 27 sits on the rotor shaft 1. At the second connecting pipe end 25, a second sealing ring seat 28 is arranged, in which a second sealing ring 29 sits on the rotor shaft 1. Between the ends 24 and 25, the connecting pipe 3 in this example has a centering rib arrangement 30 and a stop collar 31, both of which are designed to allow fluid flow. The centering rib arrangement 30 has three or more, in this example four, centering ribs 32, and the stop collar has at least one stop element 33, in this example four stop elements 33.

[0028] In Fig. 1It can be seen that the connecting pipe 3 is arranged between the shaft journal 6 and the inner tube 5, the first end 24 of which rests tightly against the outer circumference of the shaft journal 34 of the shaft journal 6. The first sealing ring 27, seated in the first sealing ring seat 26, is clamped between the inner wall 34 of the shaft journal and the outer wall 35 of the connecting pipe. In other words, the first sealing ring 27 is fixed between the inner wall 34 of the shaft journal in the first journal section 14 and the outer wall 35 of the connecting pipe by means of the first sealing ring seat 26. The connecting pipe 3 extends through the second journal section 15 and is coaxially supported in the second journal section 15 by means of the centering rib arrangement 30 or centering ribs 32. The connecting tube 3 abuts the end ring surface 23 of the second pin part 15 via its abutment collar 31 or abutment element 33.The connecting pipe 3 extends further out of the second journal section 15, thus bridging the gap between the second journal section 15 and the inner pipe 5. The connecting pipe 3 then connects tightly to the inner pipe 5, or rather to its hollow interior 11, at its second connecting pipe end 25. In this example, the connecting pipe 3 and the inner pipe 5 are tightly connected by means of a connecting sleeve 36, which circumferentially encloses the second connecting pipe end 25 and an inner pipe end 37 facing the connecting pipe 3. The second sealing ring seat 28 secures the second sealing ring 29 between the outer wall 35 of the connecting pipe and an inner wall 38 of the connecting sleeve 36. Between the outer wall 35 of the connecting pipe and the inner wall 34 of the shaft journal, a shaft journal annular space 39 is formed in the second journal section 15, communicating with the outer pipe annular space 10.At the first journal section 14, the shaft journal 6 has a journal wall opening 40, or in this case two or more journal wall openings 40, through which the shaft journal annular space 39 and the output-side opening 20 of the outer tube 4 communicate with each other. The output-side opening 20, which in this example opens into the gearbox chamber 19, and the shaft journal annular space 39 are fluidically sealed from each other on the outer circumference of the shaft journal 6, here by means of the press-fit element 21.

[0029] Out of Fig. 1It is further evident that, according to the present example, the inner wall of the outer tube 8 has a surface enhancement structure 41 in the outer tube annular space 10, which has a plurality of annular grooves 42. The annular grooves 42 each form a depression that extends radially from the inner wall of the outer tube 8 towards an outer tube wall 43. Since the machine 2 is an electric machine, a rotor assembly 44 is rotationally fixed to the outer tube wall 43.

[0030] During operation of machine 2, the coolant, which is primarily oil, is fed into the shaft journal 6. For this purpose, a supply line 45 of a coolant or oil module 46 is fluidically coupled to a shaft journal opening 47 of the shaft journal 6.

[0031] In this example, a hollow nozzle 48 is pressed into the journal opening 47, with a radial shaft seal 49 provided between the supply line 47 and the journal opening 47. The oil is pumped through the supply line 45 by means of the coolant / oil module 16 and thus driven into the journal 6, whereupon the oil flows through the journal 6 and enters the connecting pipe 3. The oil then flows through the connecting pipe 3 and out of it, i.e., into the inner pipe 5. The oil then flows out of the inner pipe 5 through the openings 12 in the inner pipe wall and through the channels 13a, and thus into the outer pipe annular space 10. There, the oil flows along the inner wall 8 of the outer pipe, in particular along the surface area 41, where it absorbs and dissipates heat generated during the operation of the machine 2.The heated oil flows from the outer tube annular space 10 into the shaft journal annular space 39, from where it flows out of the rotor shaft 1 through the journal wall openings 40 and finally through the output-side opening 20 of the outer tube 4. Since, in this example, the rotor shaft 1 opens into the gearbox chamber 19 of the gearbox 18 via the output-side opening 20, the oil flowing out of the rotor shaft 1 enters the gearbox chamber 19.

[0032] The rotor shaft 1, in particular its connecting tube 3, the machine 2, and the motor vehicle demonstrate a possible way in which a rotor shaft of a machine, especially an electric machine, can be cooled even more efficiently. The core idea of ​​the invention is to ensure, through the component topology described herein, a targeted flow of the cooling medium oil into thermally highly stressed zones of the rotor shaft 1. In this way, heat is optimally and selectively dissipated from the system, thereby preventing overheating of the rotor and, consequently, degradation of the machine 2. Reference symbol list

[0033] 1 Rotor shaft 1a Locking element 2 Machine 3 Connecting tube 4 Outer tube 5 Inner tube 6 Shaft journal 7 Longitudinal center axis 8 Outer tube inner wall 9 Inner tube outer wall 10 Outer tube annular space 11 Inner space of the inner tube 12 Inner tube wall opening 13 Inner tube base 13a Groove 14 First journal portion 15 Second journal portion 16 Spur gear rim 17 Drive spur gear 18 Gearbox 19 Gearbox chamber 20 Output-side opening 21 Press-fit element 22 Splined connection 23 Annular surface 24 First connecting tube end 25 Second connecting tube end 26 First sealing ring seat 27 First sealing ring 28 Second sealing ring seat 29 Second sealing ring 30 Centering rib arrangement 31 Impact collar 32 Centering rib 33 Impact element 34 Shaft journal inner wall 35 Connecting pipe outer wall 36 Connecting sleeve 37 Inner pipe end 38 Connecting sleeve inner wall 39 Shaft journal annular space 40 Journal wall opening 41 Surface enlargement structure 42 Ring notches 43 Outer pipe outer wall 44 Rotor assembly 45 Inlet line 46 Coolant orOil module 47 Shaft journal opening 48 Nozzle 49 Radial shaft seal.

Claims

1. Rotor shaft (1) for a machine (2), comprising, - an outer tube (4), - an inner tube (5) which is arranged coaxially in the outer tube (4), wherein an outer tube annular space (10) is formed between an outer tube inner wall (8) and an inner tube outer wall (9), and the inner tube (5) has an inner tube wall opening (12), - a hollow shaft journal (6), the first journal portion (14) of which protrudes from the outer tube (4), wherein a second journal portion (15) of the shaft journal (6) is arranged coaxially in the outer tube (4), is spaced apart from the inner tube (5) along a longitudinal central axis (7) of the rotor shaft (1) and is connected to the outer tube inner wall (8) in a sealed and rotationally fixed manner and has a journal wall opening (40), - a connecting tube (3), the first connecting tube end (24) of which bears sealingly on an outer circumferential side against a shaft journal inner wall (34) in the first journal portion (14), wherein the connecting tube (3) extends through the second journal portion (15), protrudes from the second journal portion (15) and thereby opens sealingly into the inner tube (5), wherein between a connecting tube outer wall (35) and the shaft journal inner wall (34) in the second journal portion (15) a shaft journal annular space (39) communicating with the outer tube annular space (10) is formed.

2. Rotor shaft (1) according to claim 1, characterized in that the connecting tube (3) has on its connecting tube outer wall (35) a centering rib arrangement (30) which can be fluidically flowed through along the longitudinal central axis (7), by means of which the connecting tube (3) is mounted coaxially in the second journal portion (15).

3. Rotor shaft (1) according to claim 1 or 2, characterized in that the connecting tube (3) has on its connecting tube outer wall (35) an abutment collar (31) which can be fluidically flowed through along the longitudinal central axis (7), by means of which the connecting tube (3) abuts against an end annular surface (23) of the second journal portion (15).

4. Rotor shaft (1) according to one of the preceding claims, characterized in that the connecting tube (3) has at the first connecting tube end (24) a first sealing ring seat (26), wherein in the first sealing ring seat (26) and thereby between the shaft journal inner wall (34) in the first journal portion (14) and the connecting tube outer wall (35) a first sealing ring (27) is fixed.

5. Rotor shaft (1) according to one of the preceding claims, characterized in that the connecting tube (3) and the inner tube (5) are sealingly connected to one another by means of a connecting sleeve (36) which engages around an outer circumferential side of a second connecting tube end (25) facing the inner tube (5) and an inner tube end (37) facing the connecting tube (3).

6. Rotor shaft (1) according to one of the preceding claims, characterized in that the connecting tube (3) has at the second connecting tube end (25) a second sealing ring seat (28) in which a second sealing ring (29) is fixed, in particular between the connecting tube outer wall (35) and a connecting sleeve inner wall (38) of the connecting sleeve (36) configured according to claim 5.

7. Rotor shaft (1) according to one of the preceding claims, characterized in that the outer tube inner wall (8) has in the outer tube annular space (10) a surface enlargement structure (41).

8. Machine (2), in particular electric traction machine (2) for a motor vehicle, with a rotor shaft (1) configured according to one of claims 1 to 7.

9. Motor vehicle with a machine (2) configured according to claim 8.

10. Connecting tube (3) for a rotor shaft (1) configured according to one of claims 1 to 7, which has on its connecting tube outer wall (35) an abutment collar (31) which can be fluidically flowed through along its longitudinal central axis (7), by means of which the connecting tube (3) can abut against an end annular surface (23) of the second journal portion (15).