Rotor for an electric machine with improved fixing of a shaft nut for axially securing a laminated rotor core
Patent Information
- Application Number
- EP2024712209
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-03-28
- Filing Date
- 2024-03-14
- Publication Date
- 2026-02-11
AI Technical Summary
Existing methods for axially securing a rotor laminated core in electrical machines require additional securing elements like locking rings, increasing the number of parts and complicating assembly, especially in automated production.
The external and internal threads of the rotor shaft and shaft nut are shaped differently to create local pressure peaks, allowing for cold welding and thus simplifying the fixation of the shaft nut without additional parts, enabling adjustable axial pressure for reliable fixation.
This approach reduces the number of parts needed, simplifies and secures the assembly process, and allows for reliable axial securing of the rotor laminated core with adjustable axial pressure, enhancing the robustness of the electrical machine.
Smart Images
Figure EP2024056851_03102024_PF_FP_ABST
Abstract
Description
[0001] Rotor for an electrical machine with improved fixation of a shaft nut for axially securing a rotor laminated core
[0002] TECHNICAL FIELD
[0003] The invention relates to a rotor for an electrical machine, comprising a rotor shaft, a rotor core with a plurality of axially stacked rotor cores, which is mounted on the rotor shaft, and a shaft nut, which is screwed onto the rotor shaft and axially secures the rotor core. Furthermore, the invention relates to an electrical machine with a rotor of the aforementioned type and to a vehicle with such an electrical machine. Finally, the invention also relates to a method for producing a rotor of the aforementioned type.
[0004] STATE OF THE ART
[0005] A rotor, an electric machine, a vehicle, and a manufacturing method of the aforementioned type are generally known from the prior art. The rotor laminations are stacked on top of each other to form a rotor lamination stack, which is then axially secured with a shaft nut. To prevent the shaft nut from coming loose during subsequent operation of the electric machine, it is often secured, for example, with special retaining rings, cotter pins, and the like.
[0006] The disadvantage of this method is that it requires a separate part in addition to the shaft nut. This increases the number of parts required for the electrical machine, while at the same time, securing elements are often relatively delicate and therefore difficult to handle or install, especially mechanically. DISCLOSURE OF THE INVENTION
[0007] An object of the invention is therefore to provide an improved rotor, an improved electric machine, an improved vehicle, and an improved manufacturing method for a rotor of an electric machine. In particular, the fixation of a shaft nut and thus the axial securing of the rotor core should be simplified. In particular, automated production of the rotor should be simplified and made more reliable.
[0008] The object of the invention is achieved with a rotor of the type mentioned above, in which an external thread of the rotor shaft and an internal thread of the shaft nut are shaped differently, such that local pressure peaks occur between the shaft nut and the rotor shaft, and the shaft nut and the rotor shaft are cold-welded at these points. In other words, an external thread of the rotor shaft and an internal thread of the shaft nut are shaped differently, and the shaft nut and the rotor shaft are cold-welded at points where local pressure peaks occur between the shaft nut and the rotor shaft.
[0009] Furthermore, the object of the invention is achieved by an electric machine with a rotor of the above-mentioned type. The rotor can, in particular, have a plurality of rotor magnets or rotor windings arranged in the rotor core. The electric machine can, in particular, comprise a housing and a stator arranged in the housing, as well as the rotor of the above-mentioned type arranged in the stator and mounted in the housing for rotation about a rotor axis.
[0010] Furthermore, the object of the invention is achieved by a vehicle which has an electric machine of the type mentioned above, which is intended to drive the vehicle. Finally, the object of the invention is achieved by a method for producing a rotor, which method has the following steps: a) mounting a rotor laminated core with a plurality of axially stacked rotor laminates on a rotor shaft and b) screwing a shaft nut onto the rotor shaft so that the shaft nut axially secures the rotor laminated core, wherein an external thread of the rotor shaft and an internal thread of the shaft nut are shaped differently so that local pressure peaks occur between the shaft nut and the rotor shaft and the shaft nut and the rotor shaft are cold-welded at these points.
[0011] The proposed measures simplify the permanent fixation of a shaft nut and thus the axial securing of the rotor core. This reduces the number of parts required for the electric machine and simplifies and ensures process reliability for automated rotor production.
[0012] Although the phenomenon of cold welding in screw connections is generally known, with conventional threads it only occurs - if at all - under very high axial pressures. As a rule, this axial pressure exceeds the permissible or desired axial pressure in the rotor laminated core for typical shaft nut dimensions by several times. In addition, the fixation of the shaft nut is directly dependent on the axial pressure in the rotor laminated core, so that reliable fixation of the shaft nut cannot be guaranteed at a predetermined axial pressure in the rotor laminated core. However, the proposed measures allow the axial pressure at which cold welding occurs to be freely selected or adjusted. This is particularly advantageous if the rotor laminated core is axially preloaded with a press between steps a) and b) and the shaft nut is screwed on without any significant axial pressure and only serves to secure the rotor laminated core.To achieve the objective, the external thread of the rotor shaft and the internal thread of the shaft nut may have different thread pitches, different thread heights, different flank angles and / or different flank widths.
[0013] This automatically creates the local pressure peaks required for cold welding when the shaft nut is screwed onto the rotor shaft. In the above context, the different shaping can be applied in sections or along the entire length of the thread. The measures can be used in any combination. A combination can be applied in sections or along the entire length of the thread. Different measures or combinations of measures can also be selected for different sections of the thread.
[0014] Further advantageous embodiments and developments of the invention emerge from the subclaims and from the description in conjunction with the figures.
[0015] As a rule, it is advantageous if the external thread and / or the internal thread are shaped differently from a standard intended for a screw connection, since standard threads are generally designed in such a way that cold welding does not occur if possible or only occurs at very high axial pressures.
[0016] It is particularly advantageous if the external thread or the internal thread is formed according to a standard for a screw connection and the total axial force acting between the shaft nut and the rotor shaft is less than 30% of the axial force permissible according to the standard, especially when cold welding occurs. With this design variant, at least one of the threads can be manufactured according to the standard and therefore with readily available means. The non-standard thread is designed in such a way that cold welding occurs well below the axial force permissible according to the standard for the standard-compliant thread. Therefore, with conventional diameters of shaft nut and rotor shaft, cold welding occurs before or when the desired axial pressure in the rotor laminated core is reached.If the rotor core is preloaded by a press during assembly, cold welding can occur even at significantly lower axial pressures than those present after the press is released or during operation of the electric machine. In particular, cold welding can also occur without a combined axial force acting between the shaft nut and the rotor shaft. Here, too, the shaft nut is only fully loaded when the press is released.
[0017] It is particularly advantageous if the external thread of the rotor shaft and the internal thread of the shaft nut are shaped differently only in certain sections. This simplifies screwing the shaft nut onto the rotor shaft. Furthermore, the load-bearing thread length can be freely selected and adapted to the desired axial pressure in the rotor core.
[0018] It is also advantageous if the external thread of the rotor shaft and the internal thread of the shaft nut have different shapes along their entire length, for example, along their entire axial length or along their entire thread length. This allows the external and internal threads to be easily manufactured.
[0019] It is also advantageous if the shaft nut is screwed onto the rotor shaft dry (i.e., without lubricant). This allows for particularly good and reliable cold welding.
[0020] Finally, it is advantageous if the shaft nut is heated in the area of the external thread relative to the rotor shaft before step b) and / or the rotor shaft is cooled in the area of the external thread relative to the shaft nut before step b), and the temperature of the shaft nut and the rotor shaft are equalized during and after step b), wherein the shaft nut is additionally pressed onto the rotor shaft.
[0021] The fixation of the shaft nut can be further improved in this way.
[0022] SHORT DESCRIPTION OF THE CHARACTERS
[0023] Embodiments of the invention are illustrated by way of example in the accompanying schematic figures. They show:
[0024] Fig. 1 shows a schematic half-section of an exemplary rotor of an electrical machine;
[0025] Fig. 2 a thread in detailed view;
[0026] Fig. 3 shows an enlarged view of a point in the thread where cold welding occurs;
[0027] Fig. 4 a rotor in half section during assembly of the rotor core and
[0028] Fig. 5 shows an exemplary vehicle with an electric machine of the proposed type.
[0029] DETAILED DESCRIPTION OF THE INVENTION By way of introduction, it should be noted that identical parts in the different embodiments are provided with the same reference symbols or component designations, possibly with different indices. The disclosure of a component contained in the description can be applied analogously to another component with the same reference symbol or component designation. Furthermore, the positional information chosen in the description, such as "top," "bottom," "rear," "front," "side," and so on, refers to the directly described and illustrated figure and, in the event of a change in position, is to be applied analogously to the new position.
[0030] Fig. 1 shows a half-section through a schematically illustrated rotor 1 of an electrical machine. The rotor 1 comprises a rotor shaft 2 with a rotor axis A and a rotor laminated core 3 with a plurality of axially stacked rotor laminates 4, which is mounted on the rotor shaft 2. Optional end plates 5, 6 are arranged on the front side of the axial ends of the rotor laminated core 3, wherein the end plate 5 rests against a shaft shoulder 7 and the end plate 6 is pressed against the rotor laminated core 3 with the force FM by a shaft nut 8 screwed onto the rotor shaft 2. Fig. 1 also shows the two (rolling) bearings 9, 10, with the aid of which the rotor 3 can be rotatably mounted relative to a stator (not shown).
[0031] Fig. 2 shows a detailed view of the external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8. For clarity, the threads are shown slightly spaced apart and not engaged. Specifically, Fig. 2 shows the following thread parameters: the flank angle cc, the (average) flank width b, the thread height h, and the thread pitch s.
[0032] In order to prevent the shaft nut 8 from becoming accidentally loose during operation of the electrical machine, the external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8 are shaped differently, such that local pressure peaks occur between the shaft nut 8 and the rotor shaft 2, and the shaft nut 8 and the rotor shaft 2 are cold-welded at these points C. Fig. 3 shows an enlarged view of such a point C in the thread, where cold welding occurs. It can clearly be seen that the thread flanks of the external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8 are pressed together and into one another at point C with high pressure, ultimately creating a permanent connection in the form of a cold weld. Point C is chosen purely as an example, and cold welding could equally occur at another point C.
[0033] To achieve the objective, the external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8 can have different thread pitches s, different thread heights h, different flank angles a and / or different flank widths b.
[0034] In the above context, the different shaping can be carried out in sections or along the entire length of the threads G1 and G2. The measures can be implemented in any combination. A combination can be carried out in sections or along the entire length of the threads G1 and G2. Different measures or combinations of measures can also be selected for different sections of the threads G1 and G2.
[0035] It is advantageous if the external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8 are shaped differently only in certain sections. This simplifies screwing the shaft nut 8 onto the rotor shaft 2. Furthermore, the load-bearing thread length can be freely selected and adapted to the desired axial pressure in the rotor core 3. This means that the shaft nut 8 can be screwed on normally over a first section of the threads G1, G2 before reaching a second section where cold welding occurs.
[0036] It is also conceivable that the external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8 are shaped differently along their entire length. This makes it particularly easy to manufacture the external thread G1 and the internal thread G2.
[0037] It is also advantageous if the shaft nut 8 is screwed onto the rotor shaft 2 in a dry state (i.e., without lubricant). This allows for the onset of cold welding to be particularly effective and process-reliable.
[0038] As a rule, it is advantageous if the external thread G1 and / or the internal thread G2 are shaped differently from a standard intended for a screw connection, since standard threads are generally designed in such a way that cold welding does not occur if possible or only at very high axial pressures.
[0039] It is also particularly advantageous if the external thread G1 or the internal thread G2 is formed according to a standard provided for a screw connection and the total axial force FM acting between the shaft nut 8 and the rotor shaft 2 is less than 30% of the axial force FM permissible according to the standard, in particular when cold welding occurs. In this design variant, at least one of the threads G1, G2 can be produced in accordance with the standard and therefore using technically readily available means. The non-standard thread G1, G2 is designed in such a way that cold welding occurs well below the axial force of the standard thread permissible according to the standard. Therefore, with conventional diameters of shaft nut 8 and rotor shaft 2, cold welding occurs before or when the desired axial pressure in the rotor laminated core 3 is reached. This is particularly advantageous if the rotor laminated core 3 is pre-tensioned by a press during assembly.
[0040] Fig. 4 shows a schematic representation of the rotor 1 in half section during an exemplary assembly of the rotor laminated core 3 or during an exemplary assembly of the shaft nut 8 on the rotor shaft 2. For this purpose, the shaft shoulder 7 is placed on a press table 11 and a press force Fp is applied to the end plate 6 and thus to the rotor laminated core 3 using a press ram 12. This means that the rotor laminated core 3 is axially pre-tensioned using a press. In a further step, the shaft nut 8 is screwed on. This causes cold welding between the shaft nut 8 and the rotor shaft 2 in the manner already described. The external thread G1 of the rotor shaft 2 and the internal thread G2 of the shaft nut 8 can be shaped such that when cold welding occurs, an axial force FM acting in addition to the press force Fp is applied to the rotor laminated core 3 by the shaft nut 8 and the latter is additionally tensioned.For example, the total force acting on the rotor core 3 can be measured, and the screwing on of the shaft nut 8 can be controlled accordingly. It is also conceivable that the shaft nut 8 is screwed onto the rotor shaft 2 in a torque-controlled and / or rotational angle-controlled manner. However, it is also conceivable in principle that the cold welding occurs without such an axial force FM, and consequently, no axial force FM acting on the rotor core 3 via the shaft nut 8 is applied via the pressing force Fp.
[0041] In an alternative embodiment, it can also be provided that the shaft nut 8 is heated in the area of the external thread G1 before screwing onto the rotor shaft 2 and / or the rotor shaft 2 is cooled in the area of the external thread G1 before screwing onto the shaft nut 8, and the temperature of the shaft nut 8 and the rotor shaft 2 equalize during and after screwing, wherein the shaft nut 8 is additionally pressed onto the rotor shaft 2. The fixation of the shaft nut 8 can be further improved in this way.
[0042] Finally, Fig. 5 shows an electric machine 14 installed in a vehicle 13, which has the presented rotor 1. The vehicle 13 has two axles, one of which is driven. Specifically, the electric machine 14 is connected to the semi-axles 16 of the rear axle or front axle via an optional transmission 15. Finally, the driven wheels 17 are mounted on the semi-axles 16. The electric machine 14, the transmission 15, and the semi-axles 16 are part of the drive train of the vehicle 13. The vehicle 13 is driven at least partially or temporarily by the electric machine 14. This means that the electric machine 14 can serve to drive the vehicle 13 alone or, for example, be provided in conjunction with an internal combustion engine (hybrid drive).
[0043] Finally, it is noted that the scope of protection is determined by the patent claims. However, the description and drawings must be used to interpret the claims. The features contained in the figures can be interchanged and combined with one another as desired. In particular, it is also noted that the devices shown may in reality comprise more or fewer components than shown. In some cases, the devices shown or their components may also be shown not to scale and / or enlarged and / or reduced in size. List of reference symbols
[0044] 1 rotor
[0045] 2 rotor shaft
[0046] 3 rotor lamination pack
[0047] 4 rotor lamination
[0048] 5 End plate
[0049] 6 End plate
[0050] 7 wave shoulder
[0051] 8 shaft nut
[0052] 9 (rolling) bearings
[0053] 10 (rolling) bearings
[0054] 11 Press table
[0055] 12 press stamps
[0056] 13 vehicles
[0057] 14 electric machine
[0058] 15 gearboxes
[0059] 16 semi-axle
[0060] 17 Wheel cc Flank angle b Flank width h Thread height s Thread pitch
[0061] A rotor axis
[0062] C Location of a cold weld
[0063] FM axial force on shaft nut
[0064] Fp pressing force
[0065] G1 external thread of the rotor shaft
[0066] G2 internal thread of the shaft nut
Claims
Patent claims 1. Rotor (1) for an electrical machine (14), comprising a rotor shaft (2), a rotor laminated core (3) with a plurality of axially stacked rotor laminates (4), which is mounted on the rotor shaft (2), and a shaft nut (8) which is screwed onto the rotor shaft (2) and axially secures the rotor laminated core (3), characterized in that an external thread (G1) of the rotor shaft (2) and an internal thread (G2) of the shaft nut (8) are shaped differently, so that local pressure peaks occur between the shaft nut (8) and the rotor shaft (2) and the shaft nut (8) and the rotor shaft (2) are cold-welded at these points (C).
2. Rotor (1) according to claim 1, characterized in that the external thread (G1) and / or the internal thread (G2) are shaped differently from a standard provided for a screw connection.
3. Rotor (1) according to claim 1 or 2, characterized in that the external thread (G1) or the internal thread (G2) is formed according to a standard provided for a screw connection and an axial force (FM) acting in total between the shaft nut (8) and the rotor shaft (2) is less than 30% of an axial force (FM) permissible according to the standard, in particular when cold welding occurs.
4. Rotor (1) according to one of claims 1 to 3, characterized in that the external thread (G1) of the rotor shaft (2) and the internal thread (G2) of the shaft nut (8) are shaped differently only in sections.
5. Rotor (1) according to one of claims 1 to 3, characterized in that the external thread (G1) of the rotor shaft (2) and the internal thread (G2) of the shaft nut (8) are shaped differently over their entire length.
6. Rotor (1) according to one of the preceding claims, characterized in that the external thread (G1) of the rotor shaft (2) and the internal thread (G2) of the shaft nut (8) have different thread pitches (s), different thread heights (h), different flank angles (a) and / or different flank widths (b).
7. Rotor (1) according to one of the preceding claims, characterized in that the shaft nut (8) is screwed dry onto the rotor shaft (2).
8. Electrical machine (14) with a rotor (1) according to one of the preceding claims.
9. Vehicle (13) with an electric machine (14) according to claim 8, which is provided for driving the vehicle (13).
10. Method for producing a rotor (1) for an electrical machine (14), comprising the steps of a) mounting a rotor lamination stack (3) with a plurality of axially stacked rotor laminations (4) on a rotor shaft (2) and b) screwing a shaft nut (8) onto the rotor shaft (2) so that the shaft nut (8) axially secures the rotor lamination stack (3), wherein an external thread (G1) of the rotor shaft (2) and an internal thread (G2) of the shaft nut (8) are shaped differently so that local pressure peaks occur between the shaft nut (8) and the rotor shaft (2) and the Shaft nut (8) and the rotor shaft (2) are cold welded at these points (C).
11. Method according to claim 10, characterized in that the rotor core (3) is axially prestressed with a press between steps a) and b).
12. Method according to claim 10 or 11, characterized in that the external thread (G1) or the internal thread (G2) is formed according to a standard provided for a screw connection and a total axial force (FM) acting between the shaft nut (8) and the rotor shaft (2) when screwing the shaft nut (8) onto the rotor shaft (2) is less than 30% of an axial force (FM) permissible according to the standard, in particular when cold welding occurs.
13. Method according to one of claims 10 to 12, characterized in that the shaft nut (8) is heated in the region of the external thread (G1) relative to the rotor shaft (2) before step b) and / or the rotor shaft (2) is cooled in the region of the external thread (G1) relative to the shaft nut (8) before step b), and the temperature of the shaft nut (8) and the rotor shaft (2) are equalized during and after step b), so that the shaft nut (8) is additionally pressed onto the rotor shaft (2).