A high current density axial flux motor coreless stator and axial flux motor

Abstract

This invention provides a coreless stator for a high current density axial flux motor and an axial flux motor. The coreless stator of the high current density axial flux motor includes at least one stator winding layer, which includes several circumferentially spaced and independent conductive coil units. In each stator winding layer, several conductive coil units are processed on a conductive substrate using a subtractive process. Each conductive coil unit includes a planar working portion extending straight in a radial plane, an outer transition line portion connected to the outer end of the planar working portion, and an inner transition line portion connected to the inner end of the planar working portion. At least one of the outer transition line portion and the inner transition line portion is bent wholly or partially relative to the planar working portion, thereby forming a three-dimensional transition line portion. This directly releases the radial plane space occupied by the outer transition line portion and the inner transition line portion, thereby significantly increasing the radial width and total area of ​​the effective electromagnetic working area and achieving a significant improvement in torque and power density.

Description

Technical Field

[0001] This invention relates to the field of motor technology, and in particular to a coreless stator for a high current density axial flux motor, and an axial flux motor equipped with the coreless stator of the high current density axial flux motor. Background Technology

[0002] Axial flux motors, with their inherent advantages of short axial dimensions and high power density, have shown great application potential in space- and weight-sensitive fields such as high-end electric motorcycles, drones, and precision servo systems. Among them, the single-stator dual-rotor axial flux motor, due to its symmetrical magnetic circuit and higher thrust density, has become one of the mainstream topologies for achieving ultimate performance. This is in pursuit of high efficiency and high response speed.

[0003] Prior art 1: The coreless disc-winding axial magnetic field brushless motor disclosed in Chinese invention patent CN102255403B has a stator winding that constitutes a coreless stator. This stator winding consists of multiple coils connected end to end and arranged in a ring, and the coils are made of wire. However, the stator winding of this structure has the following defects.

[0004] 1. The coil is made of wire, which is relatively soft and lacks support. As a result, the stator winding is also relatively soft and is very easy to deform during subsequent processing, which leads to unstable motor performance. At the same time, the stator winding needs to be injection molded and coated to give it a certain support strength, which increases the processing steps and production costs of the stator winding, and also prolongs the processing cycle of the stator winding.

[0005] 2. The thickness of the stator winding is limited by the thickness of the coil wire, which makes it impossible to flexibly control the thickness of the stator winding and thus cannot well meet the different needs of customers for motors.

[0006] 3. The stator winding has a planar structure, including a working region in the middle, an inner transition connection region at the inner edge, and an outer transition connection region at the outer edge. The working region is responsible for generating effective tangential electromagnetic force, while the inner and outer transition connection regions are responsible for connecting the coils in series or parallel according to a specific phase sequence. Therefore, both the inner and outer transition connection regions have transition lines. In existing planar stator windings, the inner and outer transition connection regions are kept in the same radial plane as the working region, which is a purely planar wiring method. This planar transition line structure has a significant technical drawback: the planar transition lines will significantly encroach on the valuable radial space of the stator winding.

[0007] Specifically, to complete the electrical connection from one coil to another on a plane, the transition line needs to wind around the inside or outside of the working area. On the one hand, this directly increases the overall outer diameter of the stator winding or reduces the usable inner diameter space. On the other hand, in applications where the total diameter of the motor (i.e., the installation size) is strictly limited, such as in constrained hub space or compact housing designs, the outer diameter of the stator winding is also limited. In this case, the radial dimension occupied by the planar transition line will force a significant compression of the radial dimension of the effective working area. According to the basic principle that motor torque and power density are proportional to the area of ​​the working area, this directly leads to a decrease in the motor's torque output capability and power density, failing to meet the requirements of high-performance applications. Furthermore, in an axial flux motor with a single stator and dual rotor structure, the effective working area of ​​the magnetic field generated by the permanent magnets on both rotor discs should ideally correspond completely radially to the working area of ​​the stator coil. However, the planar transition line is located radially outside the working area, but it cannot be effectively used to cut the main flux, resulting in a leakage magnetic field in the space where it is located. This not only wastes the magnetic field of the permanent magnets, but may also bring additional eddy current losses. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a coreless stator for a high current density axial flux motor, which can maximize the area of ​​the effective working area under strict radial dimension constraints, thereby improving space utilization and electromagnetic performance.

[0009] To achieve the above objectives, the present invention provides a coreless stator for a high current density axial flux motor, comprising at least one stator winding layer, wherein the stator winding layer comprises several circumferentially spaced and mutually independent conductive coil units;

[0010] In each stator winding layer, several conductive coil units are processed on a conductive substrate by a subtractive process, and there is a gap between two circumferentially adjacent conductive coil units after the subtractive process.

[0011] The conductive coil unit includes a planar working portion extending straight in a radial plane, an outer transition line portion connected to the outer end of the planar working portion, and an inner transition line portion connected to the inner end of the planar working portion. The two ends of the conductive coil unit are a first terminal and a second terminal, respectively. At least one of the outer transition line portion and the inner transition line portion is bent entirely or partially relative to the planar working portion, thereby forming a three-dimensional transition line portion. The bending angle of the three-dimensional transition line portion relative to the planar working portion is 70° to 110°.

[0012] Each of the stator winding layers has an effective electromagnetic working area consisting of a planar working section composed of several conductive coil units.

[0013] Furthermore, the bending angle of the three-dimensional transition line relative to the planar working part is 90°.

[0014] Furthermore, the conductive coil unit is a hollow wire type, including a multi-turn concentric coiled conductor ring formed by a subtractive process, and a hollow groove formed in the inner ring of the multi-turn concentric coiled conductor ring. There is a gap formed by a subtractive process between adjacent inner and outer rings of the multi-turn concentric coiled conductor ring. The hollow groove is used to construct a low magnetic reluctance main magnetic circuit.

[0015] The multi-turn concentric coiled conductor ring includes several radially extending flux-cutting segments, several circumferentially extending outer and inner transition connecting segments, and several arc connecting segments. The flux-cutting segments are spaced apart circumferentially, and the outer and inner transition connecting segments are spaced apart radially. The flux-cutting segments, outer and inner transition connecting segments are sequentially connected by the arc connecting segments. The flux-cutting segments constitute the planar working part, the outer transition connecting segments and some arc connecting segments constitute the outer transition line part, and the inner transition connecting segments and some arc connecting segments constitute the inner transition line part.

[0016] Furthermore, the conductive coil unit is a single-wire type, including a single conductor strip. The single conductor strip includes a magnetic flux cutting segment extending radially, an outer transition connection segment connected to the outer end of the magnetic flux cutting segment, and an inner transition connection segment connected to the inner end of the magnetic flux cutting segment. The magnetic flux cutting segment constitutes the planar working part, the outer transition connection segment constitutes the outer transition line part, and the inner transition connection segment constitutes the inner transition line part.

[0017] Furthermore, the magnetic flux cutting segment extends radially in a straight line or in a meandering manner.

[0018] Furthermore, several conductive coil units in the same stator winding layer are fabricated on the same conductive substrate;

[0019] The processing method of the stator winding layer includes the following steps in sequence:

[0020] A1. Select a flat plate as the conductive substrate, and the flat plate has a through hole that runs through the center in the middle.

[0021] A2. Several conductive coil units are fabricated on the flat plate using a subtractive manufacturing process;

[0022] A3. Using a bending process, the outer transition lines and / or inner transition lines of several conductive coil units are bent along the pre-designed boundary lines at 70° to 110°.

[0023] Furthermore, several conductive coil units in the same stator winding layer are fabricated on the same conductive substrate;

[0024] The processing method of the stator winding layer includes the following steps in sequence:

[0025] B1. Select an L-shaped plate or a U-shaped plate as the conductive substrate. The L-shaped plate or the U-shaped plate has a through hole pre-processed in the middle. The outer or inner circumference of the L-shaped plate is integrally pre-fabricated with a bending part through a bending process. The outer and inner circumferences of the U-shaped plate are integrally pre-fabricated with a bending part through a bending process. The bending angle of the bending part is 70° to 110°.

[0026] B2. Several conductive coil units are processed on the L-shaped plate or the U-shaped plate using a subtractive manufacturing process, wherein the outer transition line and / or inner transition line of the conductive coil unit are wholly or partially provided on the bending portion.

[0027] Furthermore, the conductive substrate is a copper plate, an aluminum plate, or a silicon steel plate, and the subtractive material process is laser etching.

[0028] Furthermore, the stator winding layer has multiple layers, which are axially stacked and fixed.

[0029] In the multi-layered stator winding, the bending direction of the three-dimensional transition line portion of all stator winding layers is consistent; or, the bending direction of the three-dimensional transition line portion of a portion of the stator winding layers is consistent and opposite to the bending direction of the three-dimensional transition line portion of the remaining stator winding layers.

[0030] Furthermore, at least a portion of the conductor in the three-dimensional transition line extends axially and forms a flux-assisted cutting segment.

[0031] This application also provides an axial flux motor, including a motor housing, a motor shaft rotatably mounted in the motor housing, a first rotor disk and a second rotor disk rotatably mounted in the motor housing and fixed to the outer periphery of the motor shaft, and a coreless stator of the high current density axial flux motor as described above. The first rotor disk and the second rotor disk each include a plurality of circumferentially spaced permanent magnets. The polarities of two circumferentially adjacent permanent magnets and two axially facing permanent magnets are opposite. The coreless stator of the high current density axial flux motor is assembled between the first rotor disk and the second rotor disk. The planar working part is axially facing the permanent magnets, and the three-dimensional transition line is partially distributed on the outer periphery and / or inner periphery of the permanent magnets.

[0032] As described above, the high current density axial flux motor coreless stator and axial flux motor of the present invention have the following beneficial effects.

[0033] 1. Optimized Radial Space Utilization for Enhanced Power Density: This application revolutionizes the traditional coreless stator layout. It designs the coreless stator of a high-current-density axial flux motor with a spatial layout. By bending at least one of the outer and inner transition lines, either wholly or partially, into the axial space, a three-dimensional transition line is formed that occupies almost no radial plane space, directly freeing up the radial plane space traditionally occupied by the outer and inner transition lines. Thus, even with strict limitations on the total outer diameter or installation space of the axial flux motor, this freed radial plane space is entirely allocated to the planar working section, expanding it. The planar working section is the effective electromagnetic working area responsible for generating effective tangential electromagnetic force; therefore, this application significantly increases the radial width and total area of ​​the effective electromagnetic working area. According to the basic principles of motors, torque output is proportional to the effective working area. Therefore, this application can achieve a significant increase in torque and power density within the same external dimensions, improving them by 10%-30%, thus solving the performance bottleneck of traditional axial flux motors under small-size constraints.

[0034] 2. Improved magnetic field utilization and reduced magnetic leakage: In axial flux motors with a single stator and dual rotor configuration, the radial magnetic field generated by the permanent magnet is mainly concentrated in the corresponding area of ​​the planar working section. This application bends the three-dimensional transition line, causing it to almost completely avoid the radial path region of the main magnetic flux, reducing interference from the three-dimensional transition line to the external magnetic circuit. Simultaneously, the radial planar space freed up by the three-dimensional transition line is used to expand the planar working section, allowing more permanent magnet area to align with the effective electromagnetic working area of ​​the conductive coil unit, improving the utilization rate of the permanent magnet flux, enabling more magnetic field to participate in effective torque generation, and enhancing electromagnetic performance.

[0035] 3. Enhanced structural compactness and integration: The design of the three-dimensional transition line section makes the radial profile of the coreless stator of the high current density axial flux motor more compact, which is particularly beneficial for realizing ultra-thin, high diameter-to-width ratio disc motor structures. At the same time, the axial or near-axial arrangement of the three-dimensional transition line section provides more flexible radial layout space for the cooling channels (such as axial air ducts or liquid cooling plate interfaces) integrated between the stator and rotor or within the stator itself in the disc motor.

[0036] 4. Each stator winding layer is processed into several conductive coil units on a conductive substrate using a subtractive process. This allows for flexible and controllable thickness control of each stator winding layer, enabling flexible and controllable thickness control of the coreless stator of the high current density axial flux motor, which can better meet the different needs of customers for the motor. At the same time, each stator winding layer has its own certain support strength, and the bending structure formed by the three-dimensional transition line further increases the structural strength of the stator winding layer. Subsequent injection molding and overmolding are not required, which shortens the processing cycle and reduces processing costs. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of a coreless stator for a high current density axial flux motor according to the present application;

[0038] Figure 2 This is a schematic diagram of the structure of the coreless stator of the high current density axial flux motor of this application;

[0039] Figure 3 This is a schematic diagram of the structure of the coreless stator of the high current density axial flux motor of this application;

[0040] Figure 4 This is a schematic diagram of the structure of the coreless stator of the high current density axial flux motor of this application;

[0041] Figure 5 for Figures 1 to 4 Cross-sectional view;

[0042] Figure 6 This is a schematic diagram of the structure of the coreless stator of the high current density axial flux motor of this application;

[0043] Figure 7 for Figure 6 Side view;

[0044] Figure 8 for Figure 6 The main view;

[0045] Figure 9 for Figure 6 Cross-sectional view;

[0046] Figure 10 This is a schematic diagram of the structure of the coreless stator of the high current density axial flux motor of this application;

[0047] Figure 11 for Figure 10 Cross-sectional view;

[0048] Figure 12 A schematic diagram showing the fabrication of a flat conductive substrate into a stator winding layer using a subtractive manufacturing process.

[0049] Figure 13 To be Figure 12 A schematic diagram of the outer transition line being bent into a three-dimensional transition line;

[0050] Figure 14 To be Figure 12 A schematic diagram of the inner transition line being bent into a three-dimensional transition line;

[0051] Figure 15 To be Figure 12A schematic diagram showing that both the outer and inner transition lines are bent into three-dimensional transition lines;

[0052] Figures 16 to 18 for Figure 12 A schematic diagram showing that the middle conductive coil unit uses other line types;

[0053] Figure 19 This is a cross-sectional view of the conductive substrate of the L-shaped plate.

[0054] Figure 20 To use subtractive manufacturing process Figure 19 A schematic diagram of a conductive substrate being processed into a stator winding layer;

[0055] Figure 21 for Figure 20 A schematic diagram showing that the middle conductive coil unit uses other line types;

[0056] Figure 22 This is a cross-sectional view of another embodiment of the conductive substrate of the L-shaped plate;

[0057] Figure 23 To use subtractive manufacturing process Figure 22 A schematic diagram of a conductive substrate being processed into a stator winding layer;

[0058] Figure 24 for Figure 22 A schematic diagram showing that the middle conductive coil unit uses other line types;

[0059] Figure 25 This is a cross-sectional view of the conductive substrate of the U-shaped plate.

[0060] Figure 26 To use subtractive manufacturing process Figure 25 A schematic diagram of a conductive substrate being processed into a stator winding layer;

[0061] Figure 27 for Figure 25 A schematic diagram showing that the middle conductive coil unit uses other line types;

[0062] Figure 28 This is a schematic diagram of a multilayer stator winding laminated assembly.

[0063] Figure 29 This is a schematic diagram of the single-stator dual-rotor configuration in the axial flux motor of this application.

[0064] Component labeling description: Stator winding layer 10, conductive coil unit 20, planar working part 21, outer transition line part 22, inner transition line part 23, first terminal 24, second terminal 25, multi-turn concentric coiled conductor ring 26, hollow slot 27, magnetic flux cutting section 28, outer transition connection section 29, inner transition connection section 210, arc connection section 211, single conductor strip 212, magnetic flux auxiliary cutting section 213, radial straight edge 214, wavy curved edge 215, three-dimensional transition line part 30, L-shaped plate 41, U-shaped plate 42, bending part 43, first rotor disk 51, second rotor disk 52, permanent magnet 53, first air gap 54, second air gap 55, etched groove 60, radial planar part 71, forward flange part 72, reverse flange part 73. Detailed Implementation

[0065] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0066] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and objectives of the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0067] It should also be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on the other component or may be connected to an intermediary component. When a component is referred to as being "connected to" another component, it can be directly connected to the other component or indirectly connected to the other component through an intermediary component.

[0068] Furthermore, the use of terms such as "first" and "second" in this application is for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Additionally, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. When the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed in this application.

[0069] This application relates to a coreless stator for a high current density axial flux motor, and an axial flux motor incorporating the coreless stator of the high current density axial flux motor, wherein the axial flux motor adopts a single stator dual rotor configuration. Furthermore, for ease of description, in the following embodiments, the axial direction of the motor shaft of the axial flux motor is defined as the left-right direction.

[0070] The axial flux motor involved in this application includes a motor housing, a motor shaft, a first rotor disk 51, a second rotor disk 52, and a coreless stator for a high current density axial flux motor; the motor shaft is rotatably mounted in the motor housing via bearings; as Figure 29 As shown, the first rotor disk 51 and the second rotor disk 52 are arranged opposite each other along the axial direction of the motor shaft. Both the first rotor disk 51 and the second rotor disk 52 are rotatably mounted in the motor housing and fixed to the outer periphery of the motor shaft. The coreless stator of the high current density axial flux motor is assembled between the first rotor disk 51 and the second rotor disk 52. A first air gap 54 is provided between the first rotor disk 51 and the coreless stator of the high current density axial flux motor, and a second air gap 55 is provided between the second rotor disk 52 and the coreless stator of the high current density axial flux motor. Thus, the coreless stator of the high current density axial flux motor, the first rotor disk 51, and the second rotor disk 52 constitute a single-stator dual-rotor configuration of the axial flux motor. Both the first rotor disk 51 and the second rotor disk 52 include several circumferentially spaced permanent magnets 53. In the first rotor disk 51, the polarities of two circumferentially adjacent permanent magnets 53 are opposite, that is, the several permanent magnets 53 of the first rotor disk 51 are spaced apart in the manner of N pole, S pole, N pole, S pole, etc. In the second rotor disk 52, the polarities of two circumferentially adjacent permanent magnets 53 are opposite, that is, the several permanent magnets 53 of the second rotor disk 52 are spaced apart in the manner of N pole, S pole, N pole, S pole, etc. In the first rotor disk 51 and the second rotor disk 52, the polarities of two permanent magnets 53 facing each other axially are opposite, that is, the N pole permanent magnet 53 of the first rotor disk 51 and the S pole permanent magnet 53 of the second rotor disk 52 are facing each other axially, and the S pole permanent magnet 53 of the first rotor disk 51 and the N pole permanent magnet 53 of the second rotor disk 52 are facing each other axially.

[0071] like Figures 1 to 4 , Figure 6 and Figure 10 As shown in any view, the coreless stator of the high current density axial flux motor of this application includes at least one stator winding layer 10, and each stator winding layer 10 includes several circumferentially spaced and independent conductive coil units 20. In each stator winding layer 10, several conductive coil units 20 are processed on a conductive substrate by a subtractive process. Two circumferentially adjacent conductive coil units 20 do not overlap, and there is a gap between them formed by the subtractive process. The gap is filled with fixing adhesive, and the several conductive coil units 20 are fixed to form a stator winding layer 10. Specifically, the conductive coil unit 20 includes a planar working portion 21, an outer transition line portion 22 connected to the outer end of the planar working portion 21, and an inner transition line portion 23 connected to the inner end of the planar working portion 21. The two ends of the conductive coil unit 20 are a first terminal 24 and a second terminal 25, respectively. The first terminal 24 is the end of the outer transition line portion 22, and the second terminal 25 is the end of the inner transition line portion 23. The planar working portion 21 extends straight in a radial plane, and each stator winding layer 10 has an effective electromagnetic working area composed of the planar working portions 21 of several conductive coil units 20. At least one of the outer transition line portion 22 and the inner transition line portion 23 is bent entirely or partially relative to the planar working portion 21, thereby forming a three-dimensional transition line portion 30. The bending angle of the three-dimensional transition line portion 30 relative to the planar working portion 21 is 70° to 110°, causing the three-dimensional transition line portion 30 to be axially bent or nearly axially bent. The transition line in the three-dimensional transition line portion 30 is a three-dimensional transition line.

[0072] After the coreless stator of the aforementioned high current density axial flux motor is installed between the first rotor disk 51 and the second rotor disk 52, the three-dimensional transition line portion 30 obtained by bending the outer transition line portion 22 is distributed on the outer periphery of the permanent magnet 53, and the three-dimensional transition line portion 30 obtained by bending the inner transition line portion 23 is distributed on the inner periphery of the permanent magnet 53. The permanent magnet 53 is circumferentially opposite to the planar working part 21. This application innovates the layout of the traditional coreless stator, reconstructs the spatial layout of the outer transition line and / or inner transition line, and designs the coreless stator of the high current density axial flux motor as a spatial layout. By bending at least one of the outer transition line portion 22 and the inner transition line portion 23 wholly or partially into the axial space, a three-dimensional transition line portion 30 that hardly occupies the radial plane space is formed, directly releasing the radial plane space occupied by the outer transition line portion 22 and the inner transition line portion 23 in the traditional structure. Thus, when the total outer diameter or installation space of the axial flux motor is strictly limited, all the freed radial planar space is allocated to the planar working section 21, expanding the planar working section 21. The planar working section 21 is the effective electromagnetic working area responsible for generating effective tangential electromagnetic force. That is, this application significantly increases the radial width and total area of ​​the effective electromagnetic working area. According to the basic principle of motors, torque output is proportional to the effective working area. Therefore, this application can optimize the use of radial space to the extreme within the same external dimensions, achieving a significant improvement in torque and power density, which can be increased by 10%-30%, solving the pain point of insufficient performance of traditional axial flux motors under small size constraints.

[0073] In a single-stator, dual-rotor axial flux motor, the radial magnetic field generated by the permanent magnet 53 is mainly concentrated in the corresponding area of ​​the planar working section 21. This application bends the three-dimensional transition line 30, causing it to almost completely avoid the radial path region of the main magnetic flux, reducing interference from the three-dimensional transition line 30 to the external magnetic circuit. Simultaneously, the radial planar space freed up by the three-dimensional transition line 30 is used to expand the planar working section 21, allowing more of the permanent magnet 53 area to align directly with the effective electromagnetic working area of ​​the conductive coil unit 20, improving magnetic field utilization, increasing the utilization rate of the permanent magnet 53's magnetic flux, enabling more magnetic field to participate in effective torque generation, reducing leakage flux, and improving electromagnetic performance. The design of the three-dimensional transition line 30 makes the radial profile of the coreless stator of the high-current-density axial flux motor more compact, particularly beneficial for achieving an ultra-thin, high-diameter-to-width-ratio disc motor structure, enhancing structural compactness. The three-dimensional transition line section 30 is arranged axially or nearly axially. The inner ring area of ​​the three-dimensional transition line section 30 provides more flexible radial layout space for the cooling channels (such as axial air ducts or liquid cooling plate interfaces) integrated between the stator and rotor or the stator itself in the disc motor, thereby enhancing the structural integrity.

[0074] In this application, each stator winding layer 10 is processed into several conductive coil units 20 on a conductive substrate through a subtractive process. This allows for flexible and controllable thickness of each stator winding layer 10, making the thickness of the coreless stator of the high current density axial flux motor also flexible and controllable, which can better meet the different needs of customers for the motor. At the same time, each stator winding layer 10 has its own certain support strength, and the bending structure formed by the three-dimensional transition line 30 further increases the structural strength of the stator winding layer 10. Subsequent injection molding and overmolding are not required, which shortens the processing cycle and reduces processing costs.

[0075] Preferably, such as Figures 1 to 4 , Figure 6 and Figure 10 As shown in any view, the bending angle of the three-dimensional transition line portion 30 relative to the planar working portion 21 is 90°, so that the three-dimensional transition line portion 30 is axially bent and distributed in the axial space, without occupying the radial space at all, thereby maximizing the torque and power density.

[0076] Furthermore, the conductive substrate has a certain thickness, which can be a copper plate, an aluminum plate, or a silicon steel plate. In this application, a copper plate is used for the linear design of the conductive coil unit 20, and laser etching is used as a subtractive process to complete the processing of the conductive coil unit 20. This allows the coreless stator of the high current density axial flux motor to adopt an integrated molding method of "design as manufacturing," where the design drawing is the finished product. This fundamentally eliminates inconsistencies caused by secondary assembly, poor soldering, or connections, ensuring high precision and consistency of the winding electrical parameters, while significantly improving the mechanical integrity and reliability of the structure. After laser etching of the copper plate, etching grooves 60 representing the etching path are formed on the copper plate. The etching grooves 60 penetrate the copper plate along its thickness direction. The remaining copper plate portion after laser etching and subtraction constitutes the current-carrying conductors of several orderly arranged conductive coil units 20.

[0077] Furthermore, the distribution of the three-dimensional transition line portion 30 on the stator winding layer 10, the line type of the conductive coil unit 20, and the number of layers in the stator winding layer 10 can be designed in various ways, and can be designed accordingly according to actual needs, thereby enabling multiple embodiments of the coreless stator of the high current density axial flux motor. The following provides a preferred embodiment of the coreless stator of the high current density axial flux motor.

[0078] Example 1: Coreless stator for a high current density axial flux motor.

[0079] like Figure 1As shown, the stator winding layer 10 has two layers. Each stator winding layer 10 has its outer transition line portion 22 bent at 90° relative to the planar working portion 21, resulting in a three-dimensional transition line portion 30 distributed on the outer periphery of the planar working portion 21. The three-dimensional transition line portions 30 of the two stator winding layers 10 are stacked opposite each other in the axial direction. The opposite stacking means that the bending directions of the three-dimensional transition line portions 30 on the left and right sides are opposite, that is, the three-dimensional transition line portion 30 of the left stator winding layer 10 bends to the left, and the three-dimensional transition line portion 30 of the right stator winding layer 10 bends to the right.

[0080] In the first embodiment of the high current density axial flux motor with a coreless stator, the conductive coil unit 20 is a hollow wire type. For example... Figure 12 As shown, the hollow linear conductive coil unit 20 includes a multi-turn concentric coiled conductor ring 26 formed by a subtractive process, and a hollow groove 27 formed in the inner ring of the multi-turn concentric coiled conductor ring 26. There is a gap formed by the subtractive process between adjacent inner and outer rings of the multi-turn concentric coiled conductor ring 26; this gap is also the aforementioned etching groove 60. The hollow groove 27 is used to construct a low-resistivity main magnetic circuit. After laser etching the copper plate according to the hollow linear shape, several circumferentially arranged conductive coil units 20 are obtained, and regular, axially penetrating gaps are naturally formed between adjacent conductive coil units 20, and regular, axially penetrating hollow grooves 27 are naturally formed on the inner circumference of each conductive coil unit 20. After the coreless stator of the high current density axial flux motor is installed between the first rotor disk 51 and the second rotor disk 52, the gap and hollow slot 27 provide an unobstructed direct channel for the axial flux, allowing the axial magnetic lines of force to pass through perpendicularly and reach the S-pole permanent magnet 53 almost unimpeded. This actively constructs an ideal physical channel for the magnetic flux, allowing the magnetic lines of force between the two rotors to form a complete low magnetic reluctance closed magnetic circuit. It actively guides and optimizes the magnetic flux path, ensuring the formation of a complete and efficient closed magnetic circuit in the single stator dual rotor configuration, and greatly reducing magnetic leakage and magnetic circuit distortion.

[0081] like Figure 12As shown, each turn of the multi-turn concentric coiled conductor ring 26 is roughly rectangular. The multi-turn concentric coiled conductor ring 26 includes several magnetic flux cutting segments 28 that extend radially, several outer transition connecting segments 29 and inner transition connecting segments 210 that extend circumferentially, and several arc connecting segments 211. The magnetic flux cutting segments 28 are spaced apart circumferentially, and the outer transition connecting segments 29 and the transition connecting segments are spaced apart radially. The magnetic flux cutting segments 28, the outer transition connecting segments 29, and the inner transition connecting segments 210 are connected sequentially by the arc connecting segments 211. The magnetic flux cutting segments 28 constitute the planar working part 21, the outer transition connecting segments 29 and the partial arc connecting segments 211 constitute the outer transition line part 22, and the inner transition connecting segments 210 and the partial arc connecting segments 211 constitute the inner transition line part 23. The arc-shaped connecting segments 211 are distributed at the corners of the rectangular ring, forming a rounded corner transition. Of course, the corners of the rectangular ring can also be transitioned at right angles, in which case the arc-shaped connecting segments 211 are omitted, and several magnetic flux cutting segments 28, several outer transition connecting segments 29, and several inner transition connecting segments 210 are connected in sequence.

[0082] like Figure 12 As shown, in the hollow-shaped conductive coil unit 20, the flux-cutting segment 28 extends radially in a straight line, and the sides of the flux-cutting segment 28 on both sides in the circumferential direction are radial straight edges 214. Of course, in other embodiments, by changing the hollow shape of the conductive coil unit 20, the stator winding layer 10 can be set to other polygonal, irregular, or other hollow-shaped topologies, for example, as... Figure 16 As shown, if the magnetic flux cutting segment 28 is set to extend radially in a meandering manner, then the sides of the magnetic flux cutting segment 28 on both sides in the circumferential direction are wavy curved edges 215, which are hollow lines of irregular shape.

[0083] Example 2 of a coreless stator for a high current density axial flux motor.

[0084] The difference between Embodiment 2 of the high current density axial flux motor coreless stator and Embodiment 1 is that the number of stacked layers of the stator winding layer 10 is increased. For example... Figure 2As shown, the stator winding layer 10 has six layers. The three stator winding layers 10 on the left are stacked in opposite directions, that is, their respective three-dimensional transition lines 30 are bent to the left. The three stator winding layers 10 on the right are stacked in the forward direction, that is, their respective three-dimensional transition lines 30 are bent to the right. Then, the three stator winding layers 10 on the left and the three stator winding layers 10 on the right are stacked in opposite directions. Therefore, the bending direction of the three-dimensional transition lines 30 of the stator winding layers 10 on the left is the same, the bending direction of the three-dimensional transition lines 30 of the stator winding layers 10 on the right is the same, and the bending direction of the three-dimensional transition lines 30 of the stator winding layers 10 on the left is opposite to the bending direction of the three-dimensional transition lines 30 of the stator winding layers 10 on the right. The resulting high current density axial flux motor coreless stator embodiment two is also a forward and reverse stacking structure.

[0085] Example 3: Coreless stator for high current density axial flux motor.

[0086] The difference between Embodiment 3 and Embodiment 1 of the high current density axial flux motor coreless stator lies in the wire type of the conductive coil unit 20. For example... Figure 3 and Figure 17 As shown, the conductive coil unit 20 is a single-wire type, including a single conductor strip 212. The single conductor strip 212 includes a radially extending flux-cutting segment 28, an outer transition connecting segment 29 connected to the outer end of the flux-cutting segment 28, and an inner transition connecting segment 210 connected to the inner end of the flux-cutting segment 28. The flux-cutting segment 28 forms a planar working part 21, the outer transition connecting segment 29 forms an outer transition line part 22, and the inner transition connecting segment 210 forms an inner transition line part 23. The outer transition connecting segment 29 and the inner transition connecting segment 210 can be distributed on the extension line of the flux-cutting segment 28, or they can form an angle with the flux-cutting segment 28. Figure 17 In the view shown, both the outer transition connection section 29 and the inner transition connection section 210 form an angle with the flux cutting section 28 to adapt to a specific magnetic field distribution or heat dissipation path.

[0087] like Figure 17 As shown, in the single-wire conductive coil unit 20, the flux-cutting segment 28 extends radially in a straight line, and the sides of the flux-cutting segment 28 in the circumferential direction are both radial straight edges 214. Of course, in other embodiments, by changing the single-wire type of the conductive coil unit 20, the stator winding layer 10 can be set to other single-wire topologies, for example, as... Figure 18 As shown, if the magnetic flux cutting segment 28 is set to extend radially in a meandering manner, then the sides of the magnetic flux cutting segment 28 on both sides in the circumferential direction are wavy curved edges 215, which are irregular single-line types.

[0088] In the third embodiment of the coreless stator of the high current density axial flux motor, since the conductive coil unit 20 adopts a single-wire type, the conductive coil unit 20 does not have a hollow slot 27, but there is still a gap between two adjacent single conductor strips 212, which can still construct a low magnetic reluctance closed magnetic circuit.

[0089] Example 4: Coreless stator for high current density axial flux motor.

[0090] The difference between Embodiment 4 of the high current density axial flux motor coreless stator and Embodiment 2 of the high current density axial flux motor coreless stator is as follows: Figure 4 As shown, the stator winding layer 10 has four layers. The two stator winding layers 10 on the left are stacked in opposite directions, that is, their respective three-dimensional transition lines 30 are bent to the left; the two stator winding layers 10 on the right are stacked in the forward direction, that is, their respective three-dimensional transition lines 30 are bent to the right; and the conductive coil unit 20 is adopted... Figure 17 The aforementioned single-line type.

[0091] The above-described high current density axial flux motor coreless stator embodiments one to four all feature a multi-layer stator winding layer 10 stacked in opposite directions. The stator structure obtained after the multi-layer stator winding layer 10 is stacked in opposite directions and fixed is as follows: Figure 5 As shown, its cross-section is I-shaped, including a radial plane portion 71 and a forward flange portion 72 and a reverse flange portion 73 integrally formed on the outer periphery of the radial plane portion 71. Both the forward flange portion 72 and the reverse flange portion 73 are axially extending annular structures. The radial plane portion 71 is composed of a planar working portion 21 and an inner transition line portion 23, while both the forward flange portion 72 and the reverse flange portion 73 are composed of a bent outer transition line portion 22. The stator structure with an I-shaped cross-section obtained by using forward and reverse stacking achieves a multiplication of the effective electromagnetic working area and a significant improvement in bending stiffness within a very small radial space, which is beneficial for carrying large currents and further optimizes space utilization and structural strength.

[0092] Example 5: Coreless stator for high current density axial flux motor.

[0093] like Figures 6 to 8 As shown, the stator winding layer 10 has three layers, all stacked in opposite directions, with their respective three-dimensional transition lines 30 bent to the left in the same direction. The conductive coil unit 20 of the stator winding layer 10 is hollow. Thus, the stator obtained after the three stator winding layers 10 are stacked in opposite directions and fixed is as follows: Figure 9 As shown, its cross-section is concave and opens to the left, including a radial plane portion 71 and a reverse flange portion 73 integrally formed on the outer periphery of the radial plane portion 71. The reverse flange portion 73 is an axially extending annular structure. The radial plane portion 71 is composed of a planar working portion 21 and an inner transition line portion 23. The reverse flange portion 73 is composed of a bent outer transition line portion 22.

[0094] Example 6: Coreless stator for high current density axial flux motor.

[0095] like Figure 10 As shown, the stator winding layer 10 has two layers, both stacked in the forward direction, with their respective three-dimensional transition lines 30 bent to the right in the same direction. The conductive coil unit 20 of the stator winding layer 10 is single-wire. Thus, the stator obtained after the two stator winding layers 10 are stacked and fixed in the forward direction is as follows: Figure 11 As shown, its cross-section is concave and opens to the right, including a radial plane portion 71 and a positive flange portion 72 integrally formed on the outer periphery of the radial plane portion 71. The positive flange portion 72 is an axially extending annular structure. The radial plane portion 71 is composed of a planar working portion 21 and an inner transition line portion 23. The reverse flange portion 73 is composed of a bent outer transition line portion 22.

[0096] In all six embodiments of the high current density axial flux motor without a core stator, the outer transition line 22 is bent. Of course, in other embodiments, only the inner transition line 23 may be bent, or both the outer transition line 22 and the inner transition line 23 may be bent, depending on the specific requirements of the motor.

[0097] Furthermore, such as Figures 1 to 4 , Figure 6 and Figure 10 As shown in any view, at least a portion of the conductor in the three-dimensional transition line section 30 extends axially and forms a flux-assisted cutting section 213, which can also cut magnetic lines of force and improve motor performance.

[0098] Furthermore, several conductive coil units 20 in the same stator winding layer 10 can be laser-etched onto the same conductive substrate. This can be achieved by first laser-etching several conductive coil units 20 onto a flat conductive substrate to create the flat stator winding layer 10; then, according to design requirements, the laser-etched copper plate can be bent to create the required three-dimensional transition line portion 30. Alternatively, several conductive coil units 20 can be directly laser-etched onto a pre-bent L-shaped plate 41 or U-shaped plate 42 conductive substrate to obtain a stator winding layer 10 with a three-dimensional transition line portion 30. The details are described below.

[0099] Processing method one for stator winding layer 10: First, a flat copper plate is selected as the conductive substrate, and an axially through-hole is pre-machined in the middle of the plate. Second, as... Figure 12 As shown, a laser-etched flat plate is used to fabricate several conductive coil units 20. Finally, as... Figure 13 As shown, a bending process is used to bend the outer transition lines 22 of several conductive coil units 20 at a predetermined angle along a pre-designed boundary line; or, as... Figure 14As shown, a bending process is used to bend the inner transition lines 23 of several conductive coil units 20 at a predetermined angle along a pre-designed boundary line; or, as... Figure 15 As shown, a bending process is used to bend the outer transition lines 22 and inner transition lines 23 of several conductive coil units 20 along a pre-designed boundary line at a preset angle. The bending process can be a precision-controlled stamping process or a CNC bending process, strictly bending along the pre-designed boundary line. Therefore, the processing method of the stator winding layer 10 is a "graphics-post-forming" process path, which has the advantages of easy access to raw materials, low cost, and provides maximum initial flexibility for winding pattern design.

[0100] Processing method two for stator winding layer 10: First, select a prefabricated L-shaped plate 41 or U-shaped plate 42 as the conductive substrate according to the requirements of the three-dimensional transition line section 30: When a three-dimensional transition line section 30 needs to be formed on the outer periphery, select such as Figure 19 The L-shaped plate 41 shown has a bent portion 43 integrally prefabricated on its outer periphery via a bending process; when a three-dimensional transition line portion 30 needs to be formed on the inner periphery, a selection is made as follows: Figure 22 The L-shaped plate 41 shown has a bent portion 43 integrally prefabricated on its inner circumference using a bending process; when a three-dimensional transition line 30 needs to be formed on the outer circumference side, a selection such as... Figure 25 The U-shaped plate 42 shown has bends 43 integrally pre-fabricated on both its outer periphery and outer periphery using a bending process. The bending angle of the bends 43 is 70° to 110°. The bends 43 are pre-fabricated using processes such as deep drawing and precision casting. Furthermore, an axially through-hole is pre-machined in the middle of the L-shaped plate 41 or U-shaped plate 42. Then, the L-shaped plate 41 or U-shaped plate 42 is laser-etched. Since the edges of the L-shaped plate 41 or U-shaped plate 42 have bends 43 at a certain angle, the bends 43 naturally provide the conditions for arranging a one-dimensional transition line on the side facade. After processing several conductive coil units 20, the conductive coil units 20 naturally have a three-dimensional transition line portion 30. For example, laser etching... Figure 19 After the L-shaped plate 41 shown, we obtain Figure 20 The hollow linear shape shown or Figure 21 The single-wire conductive coil unit 20 shown has an outer transition line portion 22 that is entirely or partially machined on the bending portion 43, forming a three-dimensional transition line portion 30 connected to the outer periphery of the planar working portion 21. For example, laser etching... Figure 21 After the L-shaped plate 41 shown, we obtain Figure 23 The hollow linear shape shown or Figure 24 The single-wire conductive coil unit 20 shown has an inner transition line portion 23 that is entirely or partially machined on the bending portion 43, forming a three-dimensional transition line portion 30 connected to the inner periphery of the planar working portion 21. For example, laser etching... Figure 25 After the U-shaped plate 42 shown, we obtain Figure 26 The hollow linear shape shown or Figure 27 The single-wire conductive coil unit 20 shown has an outer transition line portion 22 and an inner transition line portion 23, which are integrally or partially machined on the bending portions 43 on both the inner and outer sides, forming a three-dimensional transition line portion 30 connecting the outer and inner peripheries of the planar working portion 21. Therefore, the second processing method for the stator winding layer 10 is a "pre-forming-patterning" process path. Since the three-dimensional bending structure already exists, only laser patterning on the multi-dimensional curved surface is required, with etching performed on the planar and side surfaces of the plate material. After patterning, the entire structure is formed, usually without additional bending processes. This method provides an ideal prefabrication carrier for achieving a high-quality three-dimensional transition line portion 30, and is particularly suitable for designs that pursue high torque and high integration.

[0101] Both processing methods for the stator winding layer 10 mentioned above are high-efficiency, high-consistency semi-automatic or automatic manufacturing processes, inheriting the advantages of high precision and good consistency of planar photolithography windings. The method can be selected according to actual production needs during implementation.

[0102] Furthermore, when the multi-layer stator winding layers 10 are stacked, they can be fixed by vacuum hot pressing. Each stator winding layer 10 can have a different structure, such as... Figure 28 As shown. Furthermore, when the multilayer stator winding layers 10 are axially stacked and fixed, their respective outer transition lines 22 and inner transition lines 23 can be aligned, as shown. Figure 6 and Figure 10 As shown; or, the outer transition line portion 22 and the inner transition line portion 23 are circumferentially misaligned, as shown. Figures 1 to 4 As shown, the corresponding design should be carried out according to the requirements.

[0103] In summary, this application employs copper plate photolithography subtractive manufacturing process to produce a coreless stator for a high current density axial flux motor with a three-dimensional transition line portion 30 distributed in the axial space. Under strict radial dimension constraints, this process maximizes the area of ​​the effective electromagnetic working region, improves space utilization and electromagnetic performance, and enhances magnetic field utilization.

[0104] In summary, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0105] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A coreless stator for a high current density axial flux motor, characterized in that: It includes at least one stator winding layer (10), which includes several circumferentially spaced and mutually independent conductive coil units (20). In each of the stator winding layers (10), several conductive coil units (20) are processed on the conductive substrate by a subtractive process, and there is a gap between two circumferentially adjacent conductive coil units (20) formed by the subtractive process; The conductive coil unit (20) includes a planar working part (21) extending straight in a radial plane, an outer transition line part (22) connected to the outer end of the planar working part (21), and an inner transition line part (23) connected to the inner end of the planar working part (21). The two ends of the conductive coil unit (20) are a first terminal (24) and a second terminal (25), respectively. At least one of the outer transition line part (22) and the inner transition line part (23) is bent entirely or partially relative to the planar working part (21) and thereby forms a three-dimensional transition line part (30). The bending angle of the three-dimensional transition line part (30) relative to the planar working part (21) is 70° to 110°. Each of the stator winding layers (10) has an effective electromagnetic working area consisting of a planar working portion (21) of several conductive coil units (20).

2. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: The bending angle of the three-dimensional transition line (30) relative to the planar working part (21) is 90°.

3. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: The conductive coil unit (20) is a hollow wire type, including a multi-turn concentric coiled conductor ring (26) formed by a subtractive process, and a hollow groove (27) formed in the inner ring of the multi-turn concentric coiled conductor ring (26). There is a gap between the adjacent inner and outer rings of the multi-turn concentric coiled conductor ring (26) formed by a subtractive process. The hollow groove (27) is used to construct a low magnetic resistance main magnetic circuit. The multi-turn concentric coiled conductor ring (26) includes several magnetic flux cutting segments (28) extending radially, several outer transition connecting segments (29) and inner transition connecting segments (210) extending circumferentially, and several arc connecting segments (211). The magnetic flux cutting segments (28) are spaced apart circumferentially, and the outer transition connecting segments (29) and transition connecting segments are spaced apart radially. The magnetic flux cutting segments (28), the outer transition connecting segments (29), and the inner transition connecting segments (210) are connected sequentially by the arc connecting segments (211). The magnetic flux cutting segments (28) constitute the planar working part (21), the outer transition connecting segments (29) and the partial arc connecting segments (211) constitute the outer transition line part (22), and the inner transition connecting segments (210) and the partial arc connecting segments (211) constitute the inner transition line part (23).

4. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: The conductive coil unit (20) is a single-wire type, including a single conductor strip (212). The single conductor strip (212) includes a magnetic flux cutting segment (28) extending radially, an outer transition connection segment (29) connected to the outer end of the magnetic flux cutting segment (28), and an inner transition connection segment (210) connected to the inner end of the magnetic flux cutting segment (28). The magnetic flux cutting segment (28) constitutes the planar working part (21), the outer transition connection segment (29) constitutes the outer transition line part (22), and the inner transition connection segment (210) constitutes the inner transition line part (23).

5. The coreless stator of the high current density axial flux motor according to claim 3 or 4, characterized in that: The flux cutting segment (28) extends radially in a straight or meandering manner.

6. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: Several conductive coil units (20) in the same stator winding layer (10) are processed on the same conductive substrate; The processing method of the stator winding layer (10) includes the following steps in sequence: A1. Select a flat plate as the conductive substrate, and the flat plate has a through hole that runs through the center in the middle. A2. Several conductive coil units (20) are fabricated on the flat plate using a subtractive process. A3. Using a bending process, the outer transition line portion (22) and / or inner transition line portion (23) of several conductive coil units (20) are bent along the pre-designed boundary line by 70° to 110°.

7. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: Several conductive coil units (20) in the same stator winding layer (10) are processed on the same conductive substrate; The processing method of the stator winding layer (10) includes the following steps in sequence: B1. Select an L-shaped plate (41) or a U-shaped plate (42) as a conductive substrate. The L-shaped plate (41) or the U-shaped plate (42) has an axially through hole pre-processed in the middle. The outer or inner periphery of the L-shaped plate (41) is integrally pre-fabricated with a bending part (43) through a bending process. The outer and inner periphery of the U-shaped plate (42) are integrally pre-fabricated with a bending part (43) through a bending process. The bending angle of the bending part (43) is 70° to 110°. B2. Several conductive coil units (20) are processed on the L-shaped plate (41) or the U-shaped plate (42) using a subtractive process. The outer transition line (22) and / or inner transition line (23) of the conductive coil unit (20) are integrally or partially provided on the bending part (43).

8. The coreless stator of the high current density axial flux motor according to claim 1, 6, or 7, characterized in that: The conductive substrate is a copper plate, an aluminum plate, or a silicon steel plate, and the subtractive material process is laser etching.

9. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: The stator winding layer (10) has multiple layers, and the multiple stator winding layers (10) are axially stacked and fixed; In the multi-layered stator winding layers (10), the bending direction of the three-dimensional transition line portion (30) of all stator winding layers (10) is consistent; or, the bending direction of the three-dimensional transition line portion (30) of a portion of the stator winding layers (10) is consistent with the bending direction of the three-dimensional transition line portion (30) of the remaining portion of the stator winding layers (10) is opposite to the bending direction of the three-dimensional transition line portion (30).

10. The coreless stator of the high current density axial flux motor according to claim 1, characterized in that: At least a portion of the conductor in the three-dimensional transition line section (30) extends axially and forms a flux-assisted cutting section (213).

11. An axial flux motor, comprising a motor housing, a motor shaft rotatably mounted in the motor housing, and a first rotor disk (51) and a second rotor disk (52) rotatably mounted in the motor housing and fixed to the outer periphery of the motor shaft, wherein the first rotor disk (51) and the second rotor disk (52) each include a plurality of circumferentially spaced permanent magnets (53), wherein the polarities of two circumferentially adjacent permanent magnets (53) and two axially opposite permanent magnets (53) are opposite, characterized in that: It also includes a coreless stator for a high current density axial flux motor as described in any one of claims 1-10, wherein the coreless stator is assembled between a first rotor disk (51) and a second rotor disk (52), wherein the planar working part (21) is axially aligned with the permanent magnet (53), and the three-dimensional transition line part (30) is distributed on the outer and / or inner peripheral sides of the permanent magnet (53).

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