JP2019193485A - Rotary motor - Google Patents

Abstract

To provide a rotary motor that can improve power density.SOLUTION: A rotary motor (1) includes: a stator core (21); a rotor (10) having a first rotor element (11) arranged in a radial direction of the stator core and receiving magnetic force, and a second rotor element (15) arranged in an axial direction of the stator core and receiving magnetic force; and a coil (25) wound around the stator core such that a magnetic flux penetrates in the radial direction from an end surface facing the first rotor element of the stator core, and having a coil end portion (25B) outside the end surface in the axial direction of the stator core. The coil end portion (25B) bends in the radial direction and overlaps with the second rotor element (15) when viewed from the axial direction.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a rotary electric motor.

  2. Description of the Related Art As a rotary electric motor, there is a radial gap motor having a stator in which a coil is wound around a stator core and a rotor arranged with a gap in the radial direction from the stator. A coil of a radial gap motor generally has a coil end that protrudes outward from an end portion of the stator core in the axial direction.

While the coil end does not contribute to the torque of the rotor, it occupies a relatively large space in the stator accommodating space, and therefore causes a reduction in the output density of the rotary motor (volume ratio of motor output: W / m ³ ). . For this reason, techniques for reducing the size of the coil end have been proposed. For example, Patent Document 1 discloses a technique in which a part of a coil wiring is flattened to reduce the coil end in the radial direction.

JP 2013-251990 A

  However, since the same current flows through the coil end as that of the main wiring part of the coil that generates a magnetic field, the wiring cross-sectional area of the coil end cannot be reduced unnecessarily, and there is a limit to downsizing the coil end. For this reason, there was a limit in reducing the coil end size and improving the output density of the rotary motor.

  An object of this invention is to provide the rotary electric motor which can improve a power density.

The rotary electric motor according to the present invention is
A stator core;
A rotor having a first rotor element arranged in a radial direction of the stator core and receiving a magnetic force, and a second rotor element arranged in an axial direction of the stator core and receiving a magnetic force;
A coil wound around the stator core so that a magnetic flux penetrates in a radial direction from an end surface of the stator core facing the first rotor element, and having a coil end portion outward from an end surface in the axial direction of the stator core;
With
The coil end portion is configured to bend in the radial direction and overlap the second rotor element when viewed from the axial direction.

  According to the present invention, the output density of the rotary motor can be improved.

It is a perspective view which shows the rotary electric motor of Embodiment 1 of this invention. It is a perspective view which shows the structure except the disk part of the 2nd rotor element from the structure of FIG. FIG. 3 is a perspective view showing a configuration in which a permanent magnet of a second rotor element is removed from the configuration of FIG. 2. It is the sectional view on the AA line of FIG. It is a longitudinal cross-sectional view of the rotary electric motor of FIG. It is a figure explaining the electromagnetic effect | action from a stator to a rotor. It is a figure explaining the modification 1 of a stator. It is a figure which shows the 1st example (A) and 2nd example (B) of a 1st rotor element. It is a figure which shows the 1st example (A) and 2nd example (B) of a 2nd rotor element. It is a longitudinal cross-sectional view explaining the structure of the rotary electric motor of Embodiment 2 of this invention. It is the figure which looked at the stator of Embodiment 2 from the inner peripheral side. It is a figure which shows the 1st example (A) and 2nd example (B) of the 1st rotor element of Embodiment 2. FIG.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1)
FIG. 1 is a perspective view showing a rotary electric motor according to Embodiment 1 of the present invention. FIG. 2 is a perspective view showing a configuration in which the disk portion of the second rotor element is removed from the configuration of FIG. FIG. 3 is a perspective view showing a configuration in which the permanent magnet of the second rotor element is removed from the configuration of FIG. FIG. 4 is a cross-sectional view taken along line AA in FIG. FIG. 5 is a longitudinal sectional view of the rotary electric motor of FIG. In this specification, a direction along the rotation axis O1 is defined as an axial direction, a direction orthogonal to the rotation axis O1 is defined as a radial direction, and a rotation direction around the rotation axis O1 is defined as a circumferential direction.

  A rotary electric motor 1 according to Embodiment 1 of the present invention is a motor that is driven to rotate by, for example, a three-phase alternating current, and includes a rotor 10, a stator 20, and a housing (not shown). The stator 20 has a stator core 21 and a coil 25. The rotor 10 includes a first rotor element 11 and a second rotor element 15. The housing covers the rotor 10 and the stator 20 except for the motor shaft 19.

  The stator core 21 is a magnetic body such as iron and has an annular shape surrounding the first rotor element 11 from the radial direction. The stator core 21 has a plurality of teeth 22 projecting inwardly on the inner periphery (see FIGS. 2 to 4). A slit 23 is provided between two adjacent tooth portions 22 (see FIG. 4). Each tooth part 22 and each slit 23 have a form that is continuous from one end to the other end of the stator core 21 in the axial direction, and the plurality of tooth parts 22 and the plurality of slits 23 are alternately arranged in the circumferential direction.

  The coil 25 is configured by winding three lines of wiring through which currents of u-phase, v-phase, and w-phase respectively flow around a plurality of teeth 22 of the stator core 21. If attention is paid to the one-segment coil 25 wound around one tooth portion 22, the wiring of the coil 25 includes the main wiring portion 25 </ b> A passed through the two slits 23 adjacent to the tooth portion 22 and the axial of the stator core 21. Coil end portion 25B protruding outward from the end face in the direction (see FIG. 5). The main wiring portion 25 </ b> A generates a radial magnetic flux from the inner peripheral surface of the tooth portion 22 when a current flows.

  The coil end portion 25B is bent in the radial direction. That is, the wiring extending in the direction along the slit 23 in the main wiring portion 25A is bent so as to extend outward in the radial direction at the coil end portion 25B. The coil end portion 25B includes a wiring portion b extending in the radial direction and a wiring portion c extending in the circumferential direction on the terminal end side (see FIG. 3). These wiring parts b and c generate magnetic flux in the axial direction when current flows.

  The rotor 10 is configured by connecting a motor shaft 19, a first rotor element 11, and a second rotor element 15, and is held rotatably about a rotation axis O <b> 1 (see FIG. 5).

  The first rotor element 11 is arranged at a radial interval from the inner circumferential surface of the stator core 21, receives a radial magnetic flux from the stator core 21, and generates torque by electromagnetic force. The first rotor element 11 includes a plurality of permanent magnets 11a and a holding body 11b that holds them. The plurality of permanent magnets 11a are arranged side by side in the circumferential direction so that the north and south poles are alternately directed in the radial direction.

  The second rotor element 15 is disposed with an interval in the axial direction from the axial end of the stator 20, receives the magnetic flux in the axial direction from the stator core 21, and generates torque by electromagnetic force. The second rotor element 15 has a plurality of permanent magnets 15a and a disk portion 15b for holding them. The plurality of permanent magnets 15a are arranged so as to overlap with the coil end portion 25B when viewed in the axial direction. The plurality of permanent magnets 15a are arranged side by side in the circumferential direction so that the N pole and the S pole are alternately oriented in the axial direction.

  FIG. 6 is a diagram for explaining the electromagnetic action from the stator to the rotor.

  According to the rotary electric motor 1 configured as described above, a three-phase current is passed through the coil 25 and torque is generated in the rotor 10. Specifically, the radial magnetic flux Φ1 generated by the current of the main wiring portion 25A of the coil 25 acts, and torque is generated in the first rotor element 11. Further, the axial direction magnetic flux Φ2 generated by the current of the coil end portion 25B acts to generate torque in the second rotor element 15. These are added together and torque is output to the motor shaft 19.

  Whereas the coil end portion of the conventional radial gap motor does not contribute to the torque and the stator accommodating space is increased, the coil end portion 25B of the first embodiment generates the magnetic flux Φ2 to generate the motor shaft 19. Torque to. Therefore, in the rotary electric motor 1 of the first embodiment, a large torque can be obtained as compared with the volume of the rotary electric motor 1 by effectively utilizing the magnetic field of the coil end portion 25B. Thereby, the output density of the rotary motor 1 is improved.

  In Embodiment 1 described above, the stator core 21 has been described as an integral configuration in a ring shape. However, the stator core 21 may be divided into a plurality of parts in the circumferential direction. And after winding a coil around each element of the divided stator core 21, you may manufacture the one stator 20 by arrange | positioning so that the divided stator core 21 may be located in a line with the circumferential direction. By such a manufacturing method, the workability of the winding process of the coil 25 including the coil end portion 25B that bends in the radial direction is improved, and the winding process can be simplified.

(Modification 1)
7A and 7B are diagrams for explaining a first modification of the stator. FIG. 7A is a view of a part of the stator as viewed from the axial direction, and FIG. 7B is a line BB in FIG. 7A. It is sectional drawing.

  In the stator 20A of the first modification, a plurality of terminal cores 27 for increasing the magnetic flux Φ2 in the axial direction are added to the stator 20 of the first embodiment described above. The termination core 27 is a magnetic body such as iron and has an end surface facing in the axial direction. The termination core 27 faces the second rotor element 15 and is surrounded by the wiring parts b and c (see FIG. 7A) constituting the coil end part 25B, so that the inner peripheral part of each coil end part 25B Is arranged.

  The terminal core 27 is fixed to the stator core 21 via a non-magnetic intermediate member 28. That is, the terminal core 27 and the stator core 21 are separated via the interposition member 28 so that the degree of magnetic coupling is lower than in the case where they are integrated.

  As described above, according to the rotary motor of the first modification, the terminal core 27 facing the second rotor element 15 is provided on the inner peripheral portion of each terminal core 27, and the magnetic flux in the axial direction generated by the current of the terminal core 27. Φ2 is enhanced. Thereby, the torque of the 2nd rotor element 15 obtained by the effect | action of magnetic flux (PHI) 2 becomes large, and the output density of the rotary electric motor 1 can be improved more.

  Moreover, since the termination | terminus core 27 and the stator core 21 are isolate | separated via the non-magnetic material, the interference from the magnetic flux which passes along the stator core 21 is suppressed, and the termination | terminus core 27 is an axial direction according to the electric current of the coil end part 25B. A large amount of magnetic flux can be generated.

(Modification 2)
FIG. 8 is a diagram illustrating a first example (A) and a second example (B) of the first rotor element. FIG. 9 is a diagram illustrating a first example (A) and a second example (B) of the second rotor element.

  The rotary electric motor according to the second modification of the first embodiment includes the first rotor element 13 of FIG. 8B instead of the first rotor element 11 of the first embodiment described above (FIG. 8A). Is done. The first rotor element 13 has two end rings 13a and a plurality of conductive bars 13b. The end ring 13a and the conductive bar 13b are conductors and are joined so that a current flows between them. The two end rings 13 a have an annular shape centering on the rotation axis O <b> 1 and are disposed at one end and the other end of the first rotor element 13 in the axial direction. The plurality of conductive bars 13b are passed between the two end rings 13a so as to cross the radial magnetic flux Φ1 generated from the inner peripheral surface of the stator core 21 as the first rotor element 13 rotates.

  In the rotary electric motor according to the second modification, the first rotor element 13 having the end ring 13a and the conductive bar 13b receives the magnetic flux Φ1 generated from the stator core 21, and an induced current flows through them to the first rotor element 13. Torque corresponding to the slip is generated. At the same time, the second rotor element 15 having the permanent magnet 15a receives the axial direction magnetic flux Φ2 generated by the current of the coil end portion 25B, and a torque synchronized with the magnetic flux Φ2 is generated in the second rotor element 15. These torques are added together and output to the motor shaft 19.

(Modification 3)
The rotary electric motor of Modification 3 of Embodiment 1 includes the second rotor element 17 of FIG. 9B instead of the second rotor element 15 of Embodiment 1 (FIG. 9A) described above. Is done. The second rotor element 17 includes two end rings 17a1 and 17a2 having different radii and a plurality of conductive bars 17b extending radially. The end rings 17a1 and 17a2 and the conductive bar 17b are conductors and are joined so that a current flows between them. The two end rings 17a1 and 17a2 have an annular shape centering on the rotation axis O1, and are concentrically arranged on the same plane. The plurality of conductive bars 17b are passed between the two end rings 17a1 and 17a2 so as to cross the axial magnetic flux Φ2 generated from the coil end portion 25B as the second rotor element 15 rotates.

  In the rotary electric motor of Modification 3, the first rotor element 11 having the permanent magnet 11a receives the magnetic flux Φ1 generated from the stator core 21, and the torque synchronized with the magnetic flux Φ1 is generated in the first rotor element 11. At the same time, the second rotor element 17 having the end rings 17a1 and 17a2 and the conductive bar 17b receives the axial direction magnetic flux Φ2 generated by the current of the coil end portion 25B, and the induced current flows through them to cause the second rotor to flow. A torque corresponding to the slip is generated in the element 17. These torques are added together and output to the motor shaft 19.

(Modification 4)
The rotary electric motor according to the fourth modification of the first embodiment is different from the rotary electric motor 1 according to the first embodiment described above in place of the first rotor element 11 (FIG. 8A). The first rotor element 13 is provided, and the second rotor element 17 of FIG. 9B is provided instead of the second rotor element 15 (FIG. 9A).

  In the rotary electric motor of the modification 4, the first rotor element 13 having the end ring 13a and the conductive bar 13b receives the magnetic flux Φ1 generated from the stator core 21, and an induced current flows through them to the first rotor element 13. Torque corresponding to the slip is generated. At the same time, the second rotor element 17 having the end rings 17a1 and 17a2 and the conductive bar 17b receives the axial direction magnetic flux Φ2 generated by the current of the coil end portion 25B, and the induced current flows through them to cause the second rotor to flow. A torque corresponding to the slip is generated in the element 17. These torques are added together and output to the motor shaft 19.

  As described above, also in the rotary motors of Modifications 2 to 4, the axial magnetic flux Φ2 generated by the current of the coil end portion 25B contributes to the torque of the motor shaft 19, so the output density of the rotary motor Can be improved.

(Embodiment 2)
FIG. 10 is a longitudinal sectional view for explaining the structure of the rotary electric motor according to the second embodiment of the present invention. FIG. 11 is a view of the stator according to the second embodiment as viewed from the inner peripheral side.

  The rotary electric motor 1A according to the second embodiment is configured such that the stator 40 is divided into two in the axial direction, and the polarities of the permanent magnets 31a and 35a provided in the rotor 30 are reversed between one and the other in the axial direction. The rotary motor 1A is a motor that is driven to rotate by a three-phase alternating current, for example, and includes a rotor 30, a stator 40, and a housing (not shown). The stator 40 has a stator core 41 and a coil 45. The rotor 30 includes a first rotor element 31 and a second rotor element 35. The housing covers the rotor 30 and the stator 40 except for the motor shaft 39.

  The stator core 41 is a magnetic body such as iron except for the gap portion 41h in the central portion in the axial direction, and has an annular shape surrounding the first rotor element 31 from the radial direction. The gap portion 41h functions as a flux flux barrier, divides one side and the other side of the stator core 41 in the axial direction, and suppresses magnetic coupling of the stator core 41 passing through the gap portion 41h. One of the divided portions is referred to as a core portion 41u, and the other is referred to as a core portion 41d. The gap portion 41h is made of a nonmagnetic material. Or the gap part 41h may be comprised from the frame body of nonmagnetic material, and the air in a frame body.

  The stator core 41 has a plurality of teeth 42 projecting inwardly on the inner periphery (see FIG. 11). The tooth part 42 is divided into a plurality of parts in the circumferential direction as in the tooth part 22 of the first embodiment, and is also divided into two parts corresponding to the two core parts 41u and 41d in the axial direction. A slit 43 is provided between two tooth portions 42 adjacent in the axial direction or the circumferential direction.

  The coil 45 is configured by winding three lines of wiring through which currents of u-phase, v-phase, and w-phase respectively flow around a plurality of teeth 42 of the stator core 41. If attention is paid to the one-segment coil 45 wound around one tooth portion 42, the wiring of the coil 45 is connected to the main wiring portion 45A passed through three slits 43 arranged in the axial direction and the circumferential direction of the tooth portion 42. The coil end portion 45B protrudes outward from the end surface of the stator core 41 in the axial direction. The two coils 45 wound around the two tooth portions 42 adjacent to each other in the axial direction are wound with wires in opposite directions, and reverse current flows.

  The coil end portion 45B has the same configuration as the coil end portion 25B of the first embodiment and exerts the same action. However, the direction of the current flowing in one (upper side in FIG. 10) and the other (lower side in FIG. 10) coil end part 45B in the axial direction is the same.

  The main wiring portion 45 </ b> A of the coil 45 generates radial magnetic fluxes Φ <b> 11 and Φ <b> 12 from the inner peripheral surface of the tooth portion 42 when a current flows. Since the two coils 45 adjacent in the axial direction are wound in opposite directions, the magnetic flux Φ11 generated on one side of the gap 41h and the magnetic flux Φ12 generated on the other side are in opposite directions. The coil end portion 45B of the coil 45 generates magnetic fluxes Φ21 and Φ22 in the axial direction when a current flows. Since the direction of the current flowing through the coil end part 45B on one side (upper side in FIG. 10) and the coil end part 45B on the other side (lower side in FIG. 10) is the same, the magnetic fluxes Φ21 and Φ22 in the same direction are generated from both. appear.

  The rotor 30 is configured by connecting a motor shaft 39, a first rotor element 31, and a second rotor element 35, and is rotatably held around a rotation axis O1.

  The first rotor element 31 is arranged with a gap in the radial direction from the inner peripheral surface of the stator core 41, receives the magnetic flux in the radial direction from the stator core 41, and generates torque by electromagnetic force. The first rotor element 31 includes a plurality of permanent magnets 31a and a holding body 31b that holds them. The plurality of permanent magnets 31a are respectively provided in (n × 2) sections that are n-divided (n is an even number) in the circumferential direction and divided into two in the axial direction in the holding body 31b. The plurality of permanent magnets 31a arranged side by side in the circumferential direction are arranged so that the north and south poles are alternately directed in the radial direction, and the two permanent magnets 31a arranged in the axial direction are opposite to each other. It arrange | positions so that the polarity of direction may face a radial direction.

  The second rotor element 35 is configured in the same manner as the second rotor element 15 of the first embodiment except that the polar directions of the plurality of permanent magnets 35a are different. The pair of permanent magnets 35a facing each other on one end side and the other end side in the axial direction are arranged such that the magnetic poles facing the stator 40 are opposite to each other.

  According to the rotary electric motor 1 </ b> A configured as described above, a three-phase current is passed through the coil 45 and torque is generated in the rotor 30. Specifically, radial magnetic fluxes Φ11 and Φ12 generated by the current in the main wiring portion 45A of the coil 45 act to generate torque in the first rotor element 31. Furthermore, axial magnetic fluxes Φ21 and Φ22 generated by the current of the coil end portion 45B act to generate torque in the second rotor element 35. These are added together and torque is output to the motor shaft 39.

  Here, the stator 40 has core portions 41u and 41d that are divided into two in the axial direction, and the winding direction of the coil 45 is different around the two tooth portions 42 arranged in the axial direction. Current flows. Accordingly, when focusing on the pair of coil end portions 45B facing each other in the axial direction, the magnetic flux Φ21 generated by one coil end portion 45B and the magnetic flux Φ22 generated by the other coil end portion 45B cancel each other. There is nothing to do. And in the some coil end part 45B located in a line with the circumferential direction, the magnetic circuit of the high magnetic flux density which the magnetic flux continued between these can be formed. Accordingly, a large torque can be obtained from the second rotor element 35 by the magnetic fluxes Φ21 and Φ22 of the coil end portion 45B. Therefore, the rotary electric motor 1A of the second embodiment can achieve a higher output density than the rotary electric motor 1 of the first embodiment.

  In the second embodiment, the stator core 41 has been described as an integral configuration that is connected in a ring shape. However, the stator core 41 may be divided into a plurality of parts in the circumferential direction, the axial direction, or both. And after winding a coil around each element of the divided stator core 41, the divided stator core 41 may be combined to manufacture one stator 40. By such a manufacturing method, the workability of the winding process of the coil 45 including the coil end portion 45B that bends in the radial direction is improved, and the winding process can be simplified.

(Modification 1)
FIG. 12 is a diagram illustrating a first example (A) and a second example (B) of the first rotor element according to the second embodiment.

  The rotary electric motor of Modification 1 of Embodiment 2 includes a first rotor element 33 of 12 (B) instead of the first rotor element 31 (FIG. 12 (A)) of Embodiment 2 described above. The The first rotor element 33 is configured by connecting two sets of cage rotors 33u and 33d arranged in the axial direction. Each cage rotor 33u, 33d has two end rings 33a and a plurality of conductive bars 33b. The end ring 33a and the conductive bar 33b are conductors and are joined so that a current flows between them. The two sets of squirrel-cage rotors 33u and 33d are arranged so that the side surfaces in the radial direction are surrounded by the two core portions 41u and 41d corresponding to the two core portions 41u and 41d of the stator 40. The two sets of squirrel-cage rotors 33u and 33d are connected so as not to conduct each other.

  In the rotary electric motor according to Modification 1 of Embodiment 2, one cage rotor 33u receives the magnetic flux Φ11 generated from the core portion 41u of the stator core 41, and the other cage rotor 33d receives the magnetic flux Φ12 generated from the core portion 41d. Receive. Then, when an induced current flows through the cage rotors 33u and 33d, a torque corresponding to the slip is generated in the first rotor element 33. At the same time, torque is generated in the second rotor element 35 by the magnetic fluxes Φ21 and Φ22 in the axial direction generated by the current of the coil end portion 45B. Then, a torque obtained by adding these is output to the motor shaft 39.

  In addition, also in 1 A of rotary electric motors of Embodiment 2, and its modification 1, the 2nd rotor element 35 may be substituted to the 2nd rotor element 17 shown to FIG. 9 (B).

  Also in these modified examples, the output density of the rotary motor can be made higher than that of the rotary motor 1 of the first embodiment and the modified examples 1 to 4 thereof.

<Application example>
The rotary motor 1 of the first embodiment described above, the rotary motors of the first to fourth modifications thereof, the rotary motor 1A of the second embodiment and the rotary motor of the second modification are motors of various industrial machines or industrial applications. Applicable to vehicle motors. Specifically, the rotary electric motor described above is applied to various motors of injection molding machines, travel motors provided in hybrid excavators, turning motors and assist motors of generators, turning motors provided in robots, joint drive motors, and the like. it can.

  The embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment. For example, in the above-described embodiment, wiring having a circular cross section is illustrated as the wiring of the coils 25 and 45. However, the wiring of the coils 25 and 45 may be a flat wire whose cross section is flatter than a circular shape, for example. Even if a flat wire is used, the degree of integration of the wiring of the coils 25 and 45 can be improved without deteriorating the formability of the coil end portions 25B and 45B that bend in the radial direction. In the above embodiment, the coil end portions 25B and 45B are bent outward in the radial direction. However, the coil end portions 25B and 45B may be bent inward in the radial direction. In addition, the details shown in the embodiments can be changed as appropriate without departing from the spirit of the invention.

1, 1A Rotary motor 10, 30 Rotor 11, 13, 31, 33 First rotor element 11a, 31a Permanent magnet 13a, 33a End ring 13b, 33b Conductive bar 15, 17, 35 Second rotor element 15a, 35a Permanent magnet 17a1 17a2 End ring 17b Conductive bar 19, 39 Motor shaft 20, 40 Stator 21, 41 Stator core 41u, 41d Core part 41h Gap part 22, 42 Tooth part 23, 43 Slit 25, 45 Coil 25A, 45A Main wiring part 25B, 45B Coil end Φ1, Φ11, Φ12 Radial magnetic flux Φ2, Φ21, Φ22 Axial magnetic flux

Claims (4)

A stator core;
A rotor having a first rotor element arranged in a radial direction of the stator core and receiving a magnetic force, and a second rotor element arranged in an axial direction of the stator core and receiving a magnetic force;
A coil wound around the stator core so that a magnetic flux penetrates in a radial direction from an end surface of the stator core facing the first rotor element, and having a coil end portion outward from an end surface in the axial direction of the stator core;
With
The coil end portion bends in a radial direction and overlaps with the second rotor element as viewed from the axial direction.
Rotating motor. A termination core that is a magnetic body and is disposed on the inner periphery of the coil end portion so as to face the second rotor element;
The stator core and the terminal core are separated via a non-magnetic material;
The rotary electric motor according to claim 1. The first rotor element has a permanent magnet or a conductive bar and an end ring;
The second rotor element comprises a conductive bar and an end ring;
The rotary electric motor according to claim 1 or 2. The first rotor element comprises a conductive bar and an end ring;
The second rotor element has a permanent magnet or a conductive bar and an end ring.
The rotary electric motor according to claim 1 or 2.

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