Rotor for electric machine improving mountability of rotor laminated core and production method therefor

Abstract

To provide a production method for a step-wise rotor laminated core or a rotor which can be implemented in a technically simple and flexible manner.SOLUTION: A rotor (3b) for an electric machine is specified, which comprises a rotor shaft (2b), a rotor laminated core which is mounted on the rotor shaft (2b) with n sub-cores (SP1..SP6) which are stacked axially on one another, and a plurality of rotor magnets which is arranged in the sub-cores (SP1..SP6). Magnetic poles (P1, P2) of at least two sub-cores (SP1..SP6) are twisted in relation to one another by a gradation angle (αST). In addition, a disc mounted on the rotor shaft (2b) has multiple depressions which are spaced apart from each other by an angular distance. The present invention further relates to an electric machine having the rotor (3b) of the type mentioned above, a vehicle having such an electric machine, and a production method for such a rotor (3b).SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a rotor for an electric machine comprising a rotor shaft, a rotor lamination core mounted on the rotor shaft having n sub-cores axially stacked on one another, and a plurality of rotor magnets disposed within the sub-cores, each of the sub-cores having a plurality of rotor laminations axially stacked on one another, the rotor magnets forming the magnetic poles of the sub-core, each adjacent pole of the sub-core being spaced apart by a polar angle α P The magnetic poles of at least two sub-cores are spaced apart from each other by a step change angle α ST The rotors are twisted relative to one another only by . In addition, the invention relates to an electric machine having a rotor of the above-mentioned type, and to a vehicle having such an electric machine. Finally, the invention also relates to a method for manufacturing a rotor of the above-mentioned type. [Background technology]

[0002] The rotors, electric machines, vehicles and manufacturing methods of the above mentioned type are known in principle from the prior art. In such rotors, the magnetic poles are arranged in a stepped manner in the rotor lamination core in order to achieve a smoother torque profile of the associated electric machine. Such rotor lamination cores are therefore also called "stepped rotor lamination cores" or such rotors are also called "stepped rotors". During the manufacture of such rotors, a number of sub-cores are mounted on the rotor shaft, at least some of which are twisted with respect to each other. Particular care must be taken to ensure that a predefined angular offset of the magnetic poles is respected, since otherwise undesirable vibrations and excessive noise may occur. For this purpose, rotor laminations are often made with offset holes into which pins or screws are inserted to align the rotor laminations. A disadvantage is that due to the required offset of the holes the sub-cores are different, making their manufacture and storage difficult. In addition, different step changes can only be realized with great effort, since the design of the sub-cores must be changed each time, which means that the manufacture of stepped rotors according to the prior art is not only time-consuming but also inflexible. Summary of the Invention

[0003] It is therefore an object of the present invention 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, it is intended that the manufacture of a stepped rotor lamination core or rotor be made possible in a technically simple and flexible manner. In particular, it is intended that the use of identical rotor laminations be made possible.

[0004] The object of the invention is achieved by a rotor of the type mentioned in the introduction, in which the rotor shaft or the disks mounted thereon have a number of recesses, the recess with index i+1 being at an angular distance from the recess with index i ∝ i,i+1 =k ∝ p +∝ ST are spaced apart by where k is an even number.

[0005] Furthermore, the object of the invention is achieved by an electric machine having a rotor of the above-mentioned type, which may in particular comprise a housing, a stator arranged in the housing, and a rotor of the above-mentioned type arranged in the stator and mounted rotatably in the housing about a rotor axis.

[0006] Furthermore, the object of the invention is achieved by a vehicle having an electric machine of the above-mentioned type provided for driving the vehicle.

[0007] Additionally, an object of the present invention is to provide a method for manufacturing a rotor for an electric machine, the rotor being arranged such that the rotor is arranged at a pole angle α P and a rotor laminated core having n axially adjacent sub-cores, wherein the poles of at least two sub-cores are arranged at a step change angle α ST are twisted relative to each other, a) clamping the rotor shaft of the rotor in an assembly device at an angular position according to index i defined by a recess with index i in the rotor shaft or in a disk mounted on the rotor shaft; b) mounting a sub-core on a rotor shaft with an index i; c) using the assembly device to rotate the rotor shaft to an angular position according to index i+1 defined by a recess having index i+1 in the rotor shaft or in a disk mounted on the rotor shaft, the recess having index i+1 being at an angular distance from the recess having index i ∝ i,i+1 =k ∝ p +∝ ST are spaced apart by where k is an even number; d) recursively repeating steps b) and c) with ascending indexes i, starting with index i=1 in step a) and ending with index i=n in step b), until all of the sub-cores are populated; This is achieved by a method comprising:

[0008] It is advantageous if the locking pin of the assembly device engages in the recess with index i before step b). As a result, the positional fixation of the rotor shaft is particularly successful. For example, the locking pin can be spring-loaded or motorized. Furthermore, the locking pin can have a cylindrical or wedge-shaped or conical shape.

[0009] The proposed measure allows the precise positioning of adjacent sub-cores and thus the production of stepped rotor lamination cores or rotors to be achieved in a technically simple and flexible manner. This allows the angular offset of the magnetic poles of adjacent sub-cores to be precisely maintained, thus avoiding the generation of vibrations and excessive noise during operation of the electric machine. It is also particularly advantageous that the same rotor laminations can be used for the production of the sub-cores and the rotor lamination core. This means that changes in step changes can be implemented without much effort, which significantly improves the flexibility in the production of rotors.

[0010] Further advantageous configurations and developments of the invention are evident from the dependent claims and the description, when considered in conjunction with the figures.

[0011] The recesses can be advantageously arranged on the circumferential or end flanks in the rotor shaft or in a disk mounted thereon. If the recesses are arranged directly in the rotor shaft, the rotor shaft can be fixed in position particularly precisely, whereas disks offer more flexibility in designing the helix angle of the recesses. The disks can also be used for other purposes, for example for axial fastening of the rotor laminations. Circumferential recesses generally offer the advantage that the locking pins of the assembly device require less space in the axial direction. Conversely, end flank recesses offer the advantage that the locking pins of the assembly device require less space in the radial direction.

[0012] It is advantageous if the recess is arranged on a collar of the rotor shaft, as this makes it possible to prevent weakening of the rotor shaft.

[0013] It is further advantageous if the recess is designed as a cylindrical bore or has a conical or wedge-shaped profile, which has the advantage that the locking pin can fix the rotor shaft in position with particularly high precision, whereas a cylindrical bore can be manufactured more easily.

[0014] It is also particularly advantageous if the disk is mounted on the rotor shaft before step a) and removed from the rotor shaft again after assembly of the final subcore. In this way the disk can be used multiple times.

[0015] It is also advantageous if the disks are mounted in a form-fitting manner on the rotor shaft, which makes it possible to avoid undesirable relative rotation between the disks and the rotor shaft.

[0016] It is also particularly advantageous if the form fit is produced by splines on the rotor shaft, by grooves on the rotor shaft for hook spanners or by holes in the rotor shaft for face spanners, and the disks interact with the form fit elements described above in the mounted state. In this way, elements of the rotor shaft which may be present in either case and which are also used for other purposes can be used for the form fit connection between the disks and the rotor shaft. For example, splines can be used for the form fit connection of the pinion on the rotor shaft during subsequent operation. For example, grooves for hook spanners or holes for face spanners can also be used for retention purposes during mounting of the shaft nut.

[0017] It is also advantageous if the sub-cores are all pressed onto the rotor shaft in the same angular position relative to the assembly device, which simplifies the feeding of the sub-cores and can optionally be performed automatically.

[0018] In general, the step change angle is: - may be the same size for all of the subcores, or - if n is odd, the sign of the step change angle may change around the axial direction, or - may be zero around the axis direction, and if n is an even number, the sign of the step change angle may change.

[0019] The first embodiment variant allows the production of a straight stepped rotor, whereas the two other embodiment variants can be used to produce an arrow-shaped or V-shaped stepped rotor.

[0020] Exemplary embodiments of the present invention are illustrated by way of example in the accompanying schematic drawings. [Brief description of the drawings]

[0021] [Figure 1] 1 illustrates an exemplary electric machine shown diagrammatically in half cross-section; [Diagram 2] 1 illustrates a perspective view of an exemplary rotor for an electric machine. [Diagram 3] FIG. 2 shows a front view of a rotor shaft having circumferentially disposed recesses for fixing the rotor shaft in place. [Figure 4] FIG. 2 shows a front view of a rotor shaft having recesses disposed on the end sides for fixing the rotor shaft in place. [Diagram 5] FIG. 2 shows a front view of an arrangement having a rotor shaft and a disk mounted on the rotor shaft and having circumferentially arranged recesses for fixing the rotor shaft in place. [Figure 6] A top view of a configuration having a rotor shaft and a disk mounted on the rotor shaft and having a recess located on its end side for fixing the rotor shaft in place is shown. [Figure 7] 1 shows a schematic diagram of a sequence during installation of a rotor lamination core; [Figure 8] 1 shows an exemplary vehicle having an electric machine of the proposed type; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] By way of introduction, it is stated that identical parts in different embodiments are given the same reference number or the same component name, and are given different indexes as necessary. Thus, the disclosure of a component contained in the description may be transferred to another component having the same reference number or the same component name. Also, the positional terms selected in the description, such as "top", "bottom", "rear", "front", "side", etc., should be directly related to the description and the illustrated figures, and should be transferred to the new position accordingly if the position is changed.

[0023] FIG. 1 shows an exemplary electric machine 1, shown diagrammatically in half section. The electric machine 1 comprises a rotor shaft 2a as part of a rotor 3a, which is rotatably mounted by (rolling) bearings 4a, 4b about a rotor axis or axis of rotation A relative to a stator 5. In particular, a first bearing 4a seats on a first front end plate 6 and a second bearing 4b seats on a second rear end plate 7. Furthermore, the electric machine 1 comprises a central housing part 8, which connects the front end plate 6 and the rear end plate 7 and houses the stator 5. In this example, the front end plate 6, the rear end plate 7 and the housing part 8 form a housing 9 of the electric machine 1. The stator 5 comprises a stator lamination core 10, not shown in detail, which has a number of stator laminations and a stator winding 11 arranged therein.

[0024] The rotor 3a comprises a rotor lamination core 12 with n sub-cores SP1..SP5 stacked axially on one another, n being a natural number, in the example n=5. The sub-cores SP1..SP5 each comprise a number of rotor laminations 13 stacked axially on one another and axially fixed by optional end disks 14a, 14b mounted on the rotor shaft 2a in this example. The rotor lamination core 12 may also be axially fixed by a shaft shoulder of the rotor shaft 2a and / or a shaft nut screwed onto the rotor shaft 2a. In addition, the rotor lamination core 12 has rotor magnets 15 arranged in the sub-cores SP1..SP5. Finally, in FIG. 1 a recess V is provided in the end disk 14b, the significance of which will be explained in more detail below.

[0025] 2 shows another exemplary rotor 3b in a perspective view. In this example, the rotors 3b are axially stacked on top of each other and each have a step change angle α ST The sub-cores SP1..SP6 have n=6 sub-cores SP1..SP6 which are twisted relative to each other by a polar angle α P For example, pole P1 is a north pole N, while pole P2 is a south pole S. Magnets 15 are not explicitly shown in Figure 2. Instead, Figure 2 shows recesses 16a..16c into which magnets 15 will be placed in the completed rotor 3b. Although rotor 3b is linearly stepped, arrow-shaped step changes are also conceivable, as shown by the dotted lines in Figure 2.

[0026] On the rotor shaft 2b, specifically in the shaft shoulder or shaft collar 17, there are provided two rotors with angular distances α 1,2 The recesses V1 and V2 are located in the ∝ 1,2 =k ∝ p +∝ ST where k is an even number.

[0027] The recesses V1, V2 are used to fix the rotor shaft 2b in place during installation of the rotor laminated core 12 (see also FIG. 7 in this regard). The design of the recesses V1, V2 in FIG. 2 is merely an example, other designs are possible.

[0028] To this end, Fig. 3 shows a front view of a rotor shaft 2c having circumferentially arranged recesses V1, V2, in this example formed by axially extending grooves with a wedge-shaped cross section. For example, a spring-loaded locking pin 18a may engage or latch into the recesses V1, V2 to secure the rotor shaft 2c in place. In addition to the recesses V1, V2, the rotor shaft 2c also has an optional recess 19 for a hook spanner, for example to be able to hold the rotor shaft 2c when fitting a shaft nut (not shown) onto the rotor shaft 2c.

[0029] Figure 4 shows another rotor shaft 2d, which is similar to the rotor shaft 2c shown in Figure 3. In contrast, in the shaft collar 17b, the recesses V1, V2 for fixing the rotor shaft 2d are arranged on the end sides, rather than circumferentially. In addition, the rotor shaft 2d has an optional recess 20 for a face spanner, which also serves to facilitate the installation of the shaft nut.

[0030] 5 shows the configuration of the rotor shaft 2e on which the disk 21a is mounted. In this example, the recesses V1, V2 for fixing the rotor shaft 2e in place are arranged on the disk 21a. In this case, it is advantageous if the disk 21a has an extension 22a which engages in or interacts with the recess 19 for the hook spanner and thus ensures a form-fit fixing of the disk 21a in place relative to the rotor shaft 2e. The disk 21a may be permanently mounted on the rotor shaft 2e or may be mounted on the rotor shaft 2e only temporarily during the mounting of the rotor lamination core 12.

[0031] FIG. 6 shows in a top view a further configuration of the rotor shaft 2f on which the disk 21b is mounted. In this example, the recesses V1, V2 for fixing the rotor shaft 2f in place are also arranged in the disk 21b, but unlike FIG. 5, they are arranged on the end side. In addition, the recesses V1, V2 are not wedge-shaped, but rather in the form of a cylindrical bore. It is advantageous if the disk 21b in turn has an extension 22b which engages in or interacts with the recess 20 for the face spanner, thus ensuring a form-fit fixing of the disk 21b in place relative to the rotor shaft 2f. The disk 21b in turn may be permanently mounted on the rotor shaft 2f or may only be temporarily mounted on the rotor shaft 2f during the mounting of the rotor lamination core 12.

[0032] In the example shown in figures 5 and 6, the form fit is created by recesses 19 and 20. Alternatively, it is conceivable to create the form fit by, for example, splines on the rotor shafts 2a..2f.

[0033] Figure 7 shows diagrammatically the sequence during the mounting of the rotor laminated core 12. In particular, it shows an assembly device 23 having two clamping jaws 24a, 24b by means of which the rotor shaft 2 is clamped. Also shown in Figure 7 are four sub-cores SP1..SP4.

[0034] The method for manufacturing the rotors 3a, 3b is as follows: a) clamping the rotor shaft 2, 2a..2f of the rotor 3a, 3b in an assembly device 23 in an angular position according to index i defined by recesses V, V1, V2 with index i in the rotor shaft 2, 2a..2f or in discs 14b, 21a, 21b mounted on the rotor shaft 2, 2a..2f; b) mounting the sub-cores SP1..SP6 on the rotor shafts 2, 2a..2f with index i; c) Using the assembly device 23, rotating the rotor shafts 2, 2a..2f to an angular position according to index i+1 defined by depressions V, V1, V2 having index i+1 within or on the rotor shafts 2, 2a..2f, wherein the depressions V, V1, V2 having index i+1 are angularly displaced from the depressions V, V1, V2 having index i by an angular distance ∝ i,i+1 =k·∝ p +∝ ST only, where k is an even number, the step of rotating, and d) Recursively repeating steps b) and c) with an ascending index i starting from index i = 1 in step a) and ending at index i = n in step b) until all of the sub-cores SP1..SP6 are mounted, and may be included.

[0035] To ensure reliable fixation of the rotor shafts 2, 2a..2f in place, the locking pins 18a..18c of the assembly device 23 may be engaged within the depressions V1, V2 having index i before step b), as shown by the locking pin 18c in FIG. 7. For example, the locking pin 18c may be spring-loaded or electrically operated. Further, the locking pin 18c may have a cylindrical shape or a wedge shape or a conical shape.

[0036] By the proposed measure, it is possible to accurately maintain the offset of the magnetic poles P1, P2 of the adjacent sub-cores SP1..SP6 by the step change angle α ST only, and as a result, vibrations and excessive noise generation during the operation of the electromechanical device 1 can be avoided. It is also particularly advantageous that the same rotor stack 13 can be used for manufacturing the sub-cores SP1..SP6 and the rotor laminated core 12.

[0037] Advantageously, the sub-cores SP1..SP4 are all pressed onto the rotor shaft 2 in the same angular position relative to the assembly device 23. This simplifies the supply of the sub-cores SP1..SP4 and can optionally be performed automatically.

[0038] In one embodiment variant, it may be provided that after the mounting of the rotor lamination core, the disks 14b, 21a, 21b remain on the rotor shaft 2, 2a..2f. This applies, for example, to the disk 14b intended for axially fixing the rotor lamination core 12 even when the electric machine is running. However, it is also conceivable that the disks 21a, 21b are mounted (only) on the rotor shaft 2, 2a..2f before step a) and are removed again from the rotor shaft 2, 2a..2f after the mounting of the last sub-cores SP1..SP6. In this way, the disks 21a, 21b may be used multiple times.

[0039] In general, the step change angle α ST can be the same magnitude for all of the sub-cores SP1..SP6, as is the case for example in FIG. 2. This embodiment variant allows the manufacture of a linear stepped rotor 3b. Also, the step change angle α ST It is also conceivable that is zero around the axial direction and changes its sign when n is even, so that an arrow-shaped stepped rotor 3b can be produced. In FIG. 2, such an embodiment is shown by dotted lines. Finally, when n is odd, the step change angle α ST It is also conceivable that the sign of θ = θ θ θ c can change around the axial direction, which likewise produces an arrow-shaped stepped rotor 3b, but in this case n is an odd number, so that there are no sub-cores SP3, SP4 with the same angular position at their centers.

[0040] Finally, FIG. 8 shows the electric machine 1 installed in a vehicle 25. The vehicle 25 has two axles, one of which is driven. In particular, the electric machine 1 is connected to a half-axle 27, either the rear or the front axle, via an optional gearbox 26. Finally, driven wheels 28 are mounted on the half-axle 27. The electric machine 1, the gearbox 26 and the half-axle 27 are part of the drive train of the vehicle 25. The drive of the vehicle 25 is at least partially or temporarily performed by the electric machine 1. This means that the electric machine 1 may function as the only drive of the vehicle 25 or may be provided together with, for example, an internal combustion engine (hybrid drive).

[0041] In conclusion, it is emphasized that the scope of protection is determined by the claims. However, the specification and the drawings should be used to interpret the claims. The features contained in the figures can be exchanged and combined with each other as necessary. In particular, it is also emphasized that the illustrated devices can actually comprise more or fewer components than are illustrated. In some cases, the illustrated devices or their components can also be illustrated not to scale and / or at an enlarged scale and / or at a reduced scale. [Explanation of symbols]

[0042] 1 Electrical machinery 2, 2a..2f rotor shaft 3a, 3b rotor 4a, 4b Bearings 5 Stator 6 First End Plate 7 Second End Plate 8 Stator housing 9 Machine Housing 10 Stator laminated core 11 Stator Winding 12 Rotor laminated core 13 Rotor Laminations 14a, 14b End discs 15 Rotor magnet 16a..16c Recesses for rotor magnets 17, 17a, 17d Shaft shoulder / shaft color 18a..18c Lock pin 19 Hook spanner recess 20 Recess for face spanner 21a, 21b (latch) disk 22a, 22b extension part 23 Assembly Equipment 24a, 24b Clamp jaw 25 vehicles 26 Gearbox 27 half axle 28 wheels A Rotor shaft NN pole P1, P2 magnetic pole SS pole SP1..SP6 subcore V, V1, V2 recesses α ST Step change angle α P Polar Angle α 1,2 Angular distance between recesses

Claims

1. - rotor shaft (2, 2a...2f), - n sub-cores (SP) each having a plurality of rotor laminations (13) axially stacked on one another; １ . . SP ６ a rotor laminated core (12) mounted on said rotor shaft (2, 2a...2f), - the sub-core (SP １ . . SP ６ ) and is disposed within the sub-core (SP １ . . SP ６ ) magnetic pole (P １ , P ２ A plurality of rotor magnets (15) forming a sub-core (SP １ . . SP ６ ) adjacent magnetic pole (P １ , P ２ ) are the polar angles (α Ｐ ) and at least two sub-cores (SP １ . . SP ６ ) of the magnetic pole (P １ , P ２ ) is the step change angle (α ＳＴ A plurality of rotor magnets (15) twisted relative to each other by A rotor (3a, 3b) for an electric machine (1) comprising: - said rotor shaft (2, 2a...2f) or a disk (14b, 21a, 21b) mounted on said rotor shaft (2, 2a...2f) has a number of recesses (V, V １ , V ２ ), and a depression (V, V １ , V ２ ) is a dent (V, V) with index i １ , V ２ ) from the angular distance ∝ ｉ，ｉ＋１ =k・∝ ｐ +∝ ＳＴ are spaced apart by wherein k is an even number. Rotor (3a, 3b).

2. The depression (V, V １ , V ２ 2. The rotor (3a, 3b) according to claim 1, characterized in that the rotor shaft (2, 2a..2f) is provided with a pair of rotor shafts (14b, 21a, 21b) on their circumferential or end sides, or in the disks (14b, 21a, 21b) mounted on the rotor shaft (2, 2a..2f).

3. The depression (V, V １ , V ２ 3. The rotor (3a, 3b) according to claim 1 or 2, characterized in that a collar (17, 17a..17d) of the rotor shaft (2, 2a..2f) is arranged on the collar (17, 17a..17d) of the rotor shaft (2, 2a..2f).

4. The depression (V, V １ , V ２ 4. A rotor (3a, 3b) according to claim 1, characterized in that the rotor (3a, 3b) is designed as a cylindrical bore or has a conical or wedge-shaped profile.

5. An electric machine (1) comprising a rotor (3a, 3b) according to any one of claims 1 to 4.

6. A vehicle (25) comprising an electric machine (1) according to claim 5, said electric machine (1) being arranged to drive said vehicle (25).

7. A method for manufacturing rotors (3a, 3b) for an electric machine (1), the rotors (3a, 3b) being arranged with a polar angle (α Ｐ ) having a plurality of magnetic poles (P １ , P ２ ) and n axially adjacent sub-cores (SP １ . . SP ６ A rotor laminated core (12) having at least two sub-cores (SP １ . . SP ６ ) of the magnetic pole (P １ , P ２ ) is the step change angle (α ＳＴ ) are twisted relative to each other, a) inserting the rotor shaft (2, 2a..2f) of the rotor (3a, 3b) into a recess (V, V) with index i in the rotor shaft (2, 2a..2f) or in a disk (14b, 21a, 21b) mounted on the rotor shaft (2, 2a..2f) １ , V ２ clamping in an assembly device (23) at an angular position according to an index i defined by b) Subcore (SP) １ . . SP ６ ) on said rotor shaft (2, 2a..2f) with said index i; c) using said assembly device (23), assembling said rotor shaft (2, 2a..2f) to a recess (V, V) having said index i+1 in said rotor shaft (2, 2a..2f) or in said disk (14b, 21a, 21b) mounted on said rotor shaft (2, 2a..2f). １ , V ２ ) to an angular position according to the index i+1 defined by the recess (V, V １ , V ２ ) is the depression (V, V) having the index i １ , V ２ ) from the angular distance ∝ ｉ，ｉ＋１ =k・∝ ｐ +∝ ＳＴ are spaced apart by where k is an even number; d) the subcore (SP １ . . SP ６ recursively repeating steps b) and c) with ascending indexes i, starting with said index i=1 in step a) and ending with said index i=n in step b), until all of the A method comprising:

8. The discs (21a, 21b) are mounted on the rotor shaft (2, 2a...2f) before step a) and the final sub-core (SP １ . . SP ６ 8. The method according to claim 7, characterized in that after assembly of the rotor shaft (2, 2a..2f), the rotor shaft (2, 2a..2f) is again detached from the rotor shaft (2, 2a..2f).

9. 9. Method according to claim 7 or 8, characterized in that the disks (14b, 21a, 21b) are mounted in a form-fitting manner on the rotor shaft (2, 2a..2f).

10. 10. The method according to claim 9, characterized in that a form fit is generated by splines on the rotor shaft (2, 2a..2f), by grooves on the rotor shaft (2, 2a..2f) for hook spanners or by holes in the rotor shaft (2, 2a..2f) for face spanners, and the disks (14b, 21a, 21b) interact with form-fitting elements in the mounted state.

11. The locking pins (18a..18c) of the assembly device (23) are aligned with the recesses (V 、 V １、 V ２ 11. The method according to claim 7, further comprising engaging in a groove in the groove.

12. The sub-core (SP １ . . SP ６ 12. The method according to claim 7, wherein all of the rotor shafts (2, 2a..2f) are pressed onto the rotor shaft (2, 2a..2f) in the same angular position relative to the assembly device (23).

13. The step change angle (α ＳＴ )but, - the sub-core (SP １ . . SP ６ ) are the same size for all When −n is an odd number, the step change angle (α ＳＴ ) changes sign around the axis, or When n is an even number, the step change angle (α ＳＴ ) changes sign 13. The method according to any one of claims 7 to 12, characterized in that

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