Axial flux permanent magnet synchronous motor

Abstract

The application discloses an axial flux permanent magnet synchronous motor, which comprises a mirror frame and a base arranged on a rotating shaft, the base is provided with a PCB winding stator, the PCB winding stator is arranged on the rotating shaft, the mirror frame is arranged above the PCB winding stator, and the mirror frame is provided with an annular rotor at one end opposite to the PCB winding stator; under the action of a magnetic field generated by the PCB winding stator, the annular rotor drives the mirror frame to rotate around the rotating shaft; wherein the PCB winding stator comprises at least two layers of PCB coil layers, each layer of the PCB coil layers comprises a plurality of windings distributed in the circumferential direction of the rotating shaft, each winding comprises a radial conductor extending in the radial direction and an end conductor connected with the radial conductor; wherein the radial conductors of any two adjacent PCB coil layers are arranged in space staggeredly; and the end conductors of any two adjacent PCB coil layers are arranged in the thickness direction of the coil layer in an overlapped mode. The axial flux permanent magnet synchronous motor has a high effective number of turns.

Description

Technical Field

[0001] This application relates to the field of motor technology, and in particular to an axial flux permanent magnet synchronous motor. Background Technology

[0002] Axial flux permanent magnet synchronous motors (also known as disc motors) have attracted widespread attention due to their compact structure and high power density. Especially in coreless or quasi-coreless structures, the elimination of the cogging effect in the stator core inherently provides the advantage of cogging torque, enabling smooth control and low-vibration operation. These motors have significant application value in robotics, precision instruments, aerospace, and micro-drive systems.

[0003] In coreless axial flux motors, the manufacturing process of the stator windings is crucial to determining motor performance and production feasibility. Printed circuit board (PCB) winding technology has been introduced as an alternative to wound windings (such as those using self-adhesive enameled wire wound and potted for fixation). PCB windings utilize mature printed circuit board manufacturing processes, enabling precise positioning of coil shapes (such as circular, trapezoidal, and rhomboid shapes) and dimensions, offering significant advantages such as design flexibility, high process consistency, compact structure (small thickness), and high mechanical strength. However, existing PCB winding designs still face challenges in achieving high effective turns. Summary of the Invention

[0004] To address the technical problems existing in the prior art, this application proposes an axial flux permanent magnet synchronous motor. The radial conductors of adjacent PCB coil layers of the motor are radially staggered, so that the induced voltage phase of each layer is basically consistent. After being superimposed in phase through end overlap and series connection, the total number of turns and back EMF are effectively increased, and the torque density is enhanced. At the same time, the end overlap design shortens the interlayer connection path, reduces winding resistance and copper loss, and improves motor efficiency. The overall structure is compact, the axial dimension is short, and it is conducive to obtaining a more sinusoidal back EMF waveform, which is suitable for FOC smooth control.

[0005] This application provides an axial flux permanent magnet synchronous motor, including a mirror frame and a base mounted on a rotating shaft. A PCB winding stator is disposed on the base and mounted on the rotating shaft. The mirror frame is positioned above the PCB winding stator. An annular rotor is disposed at the end of the mirror frame opposite to the PCB winding stator. Under the action of the magnetic field generated by the PCB winding stator, the annular rotor drives the mirror frame to rotate around the rotating shaft. The PCB winding stator includes at least two PCB coil layers. Each PCB coil layer includes multiple windings distributed circumferentially along the rotating shaft. Each winding includes a radially extending radial conductor and an end conductor connecting the radial conductor. The radial conductors of any two adjacent PCB coil layers are spatially staggered. The end conductors of any two adjacent PCB coil layers overlap in the coil layer thickness direction. Furthermore, adjacent coil windings located on different layers are connected in series via the end conductors.

[0006] Optionally, the magnets distributed circumferentially along the axis of rotation in the annular rotor constitute a Halebeck array; the Halebeck array is formed by assembling multiple unmagnetized magnetic blanks with different easy magnetization directions into a ring, and then magnetizing the whole in one go using a special fixture.

[0007] Optionally, the annular rotor includes a first magnet and a second magnet of different shapes arranged adjacent to each other, wherein the first magnet is used to generate a horizontal magnetic field and the second magnet is used to generate an axial magnetic field.

[0008] Optionally, the first magnet is a strip-shaped structure, and the second magnet is a trapezoidal structure with rounded ends.

[0009] Optionally, the surface of the magnet is coated with an insulating varnish layer, and the magnet is spliced ​​in sections to cut off the eddy current path.

[0010] Optionally, the annular rotor further includes an annular mounting groove, in which the magnet is disposed circumferentially and fixed by epoxy resin structural adhesive.

[0011] Optionally, the annular mounting groove is made of a non-magnetic material.

[0012] Optionally, the magnet is made of sintered neodymium iron boron.

[0013] Optionally, the annular rotor includes a U-shaped back iron yoke and an axially magnetized annular magnet. The U-shaped back iron yoke includes a cylindrical inner edge and an outer edge, which are connected by a base plate. The inner edge, the outer edge, and the base plate form a U-shaped groove for accommodating the annular magnet.

[0014] Optionally, the winding is trapezoidal in shape, with rounded ends at both ends.

[0015] Optionally, the winding of the PCB winding stator is fixed on the PCB board, and a through hole is provided on the PCB board near the end spokes, through which the conductors of adjacent windings of different layers are connected in series.

[0016] Optionally, the relative starting position of the annular rotor and the PCB winding stator is set such that the pole line of the annular rotor is aligned with the mechanical center of any winding in the PCB winding stator in the circumferential direction, so that the back electromotive force generated by the winding at this starting position is at its maximum value.

[0017] Optionally, the axial flux permanent magnet synchronous motor further includes a Hall sensor, which is mounted on the PCB winding stator or base, and the sensing position of the Hall sensor is aligned with the pole line in the circumferential direction to detect the zero-crossing point of the magnetic field when the pole line passes through.

[0018] Optionally, the relative starting position of the annular rotor and the PCB winding stator is set such that the magnetic pole center line of the annular rotor is aligned with the mechanical center of any winding in the PCB winding stator in the circumferential direction, so that the back electromotive force generated by the winding at this starting position is zero.

[0019] The radial conductors of adjacent PCB coil layers of the axial flux permanent magnet synchronous motor proposed in this application are radially staggered, so that the induced voltage phase of each layer is basically consistent. After being superimposed in phase through end overlap, the total number of turns and back EMF are effectively increased, and the torque density is enhanced. At the same time, the end overlap design shortens the interlayer connection path, reduces winding resistance and copper loss, and improves motor efficiency. The overall structure is compact, the axial dimension is short, and it is conducive to obtaining a more sinusoidal back EMF waveform. Attached Figure Description

[0020] The preferred embodiments of this application will now be described in further detail with reference to the accompanying drawings, wherein: Figure 1 This is a three-dimensional structural diagram of an axial flux permanent magnet synchronous motor according to an embodiment of this application; Figure 2 yes Figure 1 The structure shown is a cross-sectional view along AA; Figure 3 This is a schematic diagram of the structure of a PCB winding stator according to an embodiment of this application; Figure 4 yes Figure 3 The structure shown is a cross-sectional view along BB; Figure 5 yes Figure 3The diagram shows a portion of the PCB winding stator after being cut along arc C. Figure 6 yes Figure 5 Enlarged view of point E in the structure shown; Figure 7 This is a three-dimensional structural schematic diagram of the annular rotor of an axial flux permanent magnet synchronous motor according to an embodiment of this application; Figure 8 yes Figure 7 Exploded view of the structure shown; Figure 9 This is a three-dimensional structural schematic diagram of the annular rotor of another axial flux permanent magnet synchronous motor according to an embodiment of this application; Figure 10 yes Figure 9 A schematic diagram of the magnet arrangement in the rotor structure shown. Figure 11 This is a three-dimensional structural schematic diagram of another axial flux permanent magnet synchronous motor according to an embodiment of this application; Figure 12 yes Figure 11 The structure shown is a cross-sectional view along DD; Explanation of reference numerals in the attached figures: 10. Axial flux permanent magnet synchronous motor; 100. Shaft; 101. Frame; 102. Base; 210. Bearing; 103. PCB winding stator; 1032. First layer coil; 1033. Second layer coil; 1034. Third layer coil; 1035. Fourth layer coil; 1036. Fifth layer coil; 1037. Sixth layer coil; 104. Annular rotor; 106. Winding; 107. End conductor; 1 16. PCB coil layer; 108. Radial conductor; 109. Via; 121. U-shaped back iron yoke; 122. Ring magnet; 123. Inner edge; 124. Outer edge; 130. PCB board; 131. Core board; 132. Prepreg; 300. Mirror; 400. Electrical connector; 610. Helbeck array magnet; 620. Ring mounting slot; 1042. First magnet; 1043. Second magnet. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0022] In the following detailed description, reference can be made to the accompanying drawings, which form part of this application and illustrate specific embodiments of the present application. In the drawings, similar reference numerals describe substantially similar components in different figures. Specific embodiments of the present application are described in sufficient detail below to enable those skilled in the art to implement the technical solutions of the present application. It should be understood that other embodiments may also be utilized, or structural, logical, or electrical changes may be made to the embodiments of the present application.

[0023] Figure 1 This is a three-dimensional structural diagram of an axial flux permanent magnet synchronous motor according to an embodiment of this application. Figure 2 yes Figure 1 The structure shown is a cross-sectional view along AA. (Combined with...) Figure 1-2 As shown, the axial flux permanent magnet synchronous motor 10 includes a lens frame 101 and a base 102 passing through a rotating shaft 100. A PCB winding stator 103 is disposed on the base 102 and passes through the rotating shaft 100. The lens frame 101 is disposed above the PCB winding stator 103. An annular rotor 104 is disposed at the end of the lens frame 101 opposite to the PCB winding stator 103. When the PCB winding stator 103 is energized, it generates an alternating magnetic field. Under the action of the magnetic field generated by the PCB winding stator 103, the annular rotor 104 drives the lens frame 101 to rotate around the rotating shaft 100. In some embodiments of this application, a bearing 210 is provided between the lens frame 101 and the rotating shaft 100.

[0024] Figure 3 This is a schematic diagram of the structure of a PCB winding stator according to an embodiment of this application. Figure 4 yes Figure 3 The structure shown is a cross-sectional view along BB. Combined with... Figure 3-4 As shown, the PCB winding stator 103 includes multiple PCB coil layers. Specifically, the PCB winding stator 103 may include six coil layers, namely, a first coil layer 1032, a second coil layer 1033, a third coil layer 1034, a fourth coil layer 1035, a fifth coil layer 1036, and a sixth coil layer 1037.

[0025] In some embodiments of this application, optionally, the windings of the PCB winding stator 103 are disposed on a PCB board 130 (i.e., a multilayer printed circuit board substrate). The windings of each layer of the PCB winding stator 103 are fixed to different layers of the PCB board using PCB technology. Through-holes 109 are provided on the PCB board 130 near the end conductors 107. Windings of adjacent different layers are connected in series by conductors passing through the through-holes 109, such as bare copper wires or copper-plated layers. Specifically, the through-holes can be through-holes, blind vias, or buried vias, preferably through-holes which are simple to manufacture and low in cost. This connection method fully utilizes mature PCB technology, ensuring the reliability and consistency of the connection.

[0026] In some embodiments of this application, optionally, the PCB board 130 includes a core board 131 and prepreg sheets 132. The core board 131 serves as the basic structure of the PCB board 130. The copper wires of the PCB winding stator 103 are laid on the upper and lower surfaces of the core board, and each core board with copper laid is connected by several prepreg sheets to form a multilayer PCB structure. For a 2-layer board, only one core board is needed, with no prepreg sheets in between. For a 4-layer board, one core board and at least two prepreg sheets, or two core boards and at least one prepreg sheet, are needed. For a 6-layer board, two core boards and at least three prepreg sheets, or three core boards and at least two prepreg sheets, are needed. See also Figure 4 As shown, in this embodiment, the PCB board of the PCB winding stator 103 has two core boards 131 and three prepregs 132. In some embodiments of this application, the prepregs can optionally be used as core boards, but only a small number can be used in a single PCB board.

[0027] See also Figure 3 As shown, each PCB coil layer includes multiple windings 106 distributed circumferentially along the axis of rotation 100. Taking one winding as an example, each winding 106 includes a radially extending radial conductor 108 and an end conductor 107 connecting the radial conductor. In some embodiments of this application, the winding 106 is optionally trapezoidal in shape, and the two ends of the trapezoidal shape (i.e., the ends located on the inner diameter side and the outer diameter side) are rounded. Specifically, this winding is evolved from a trapezoidal winding, replacing its originally sharp ends with rounded arcs. This design retains the advantages of trapezoidal windings, such as large winding coefficient and high flux linkage, while overcoming the disadvantages of trapezoidal windings, such as long ends, high copper loss, and easy heat accumulation. The rounded ends shorten the length of the end conductor, reduce copper loss, improve heat dissipation, and increase the service life of the PCB winding.

[0028] Figure 5 yes Figure 3 The diagram shows a partial PCB winding stator structure after being cut along arc C. Figure 6 yes Figure 5 A magnified view of point E in the structure shown. Combined with... Figure 3 , Figure 5 and Figure 6 As shown, the radial conductors 108 of any two adjacent PCB coil layers 116 are spatially offset. This offset design allows the upper and lower radial conductors to induce voltages at slightly different positions under the same magnetic pole, but with essentially the same phase. See also... Figure 4 As shown, the end conductors 107 of any two adjacent PCB coil layers 116 overlap in the coil layer thickness direction (i.e., axial direction) (e.g.) Figure 4 The upper and lower end conductors are aligned vertically; and adjacent coil windings located on different layers are connected in series via end conductors 107. Specifically, the end conductors 107 of adjacent layers are connected via vias 109 or through direct contact. In this embodiment, the via 109 is a through-hole that penetrates the entire PCB board. As the PCB winding stator is part of the structure on the PCB board, the via 109 also penetrates multiple PCB coil layers, thereby enabling electrical connection between the various PCB coil layers.

[0029] The axial flux permanent magnet synchronous motor proposed in this application embodiment makes the induced voltages of each layer add up in phase, and the total effective number of turns is equal to the sum of the number of radial conductors in each layer. This achieves high back EMF and high torque density in a compact axial space. At the same time, the end overlap makes the connection path the shortest, effectively reducing winding resistance and copper loss.

[0030] Figure 7 This is a three-dimensional structural schematic diagram of the annular rotor of an axial flux permanent magnet synchronous motor according to an embodiment of this application. Figure 8 yes Figure 7 An exploded view of the structure shown. Combined with... Figure 2 , Figure 7 and Figure 8 As shown, the annular rotor 104 of the axial flux permanent magnet synchronous motor 10 of this application embodiment adopts a Halbach array magnet structure. Specifically, the magnets distributed circumferentially along the shaft 100 in the annular rotor 104 constitute a Halbach array. This Halbach array is formed by the following process: First, multiple magnetic blanks with different easy magnetization directions (e.g., magnetic blanks for generating tangential magnetic fields and magnetic blanks for generating axial magnetic fields) are provided, and these magnetic blanks are assembled into a complete ring in a pre-set magnetization direction in a non-magnetic state; then, the assembled magnetic blank assembly is placed in a special fixture, and a specific magnetizing magnetic field is applied using a one-time overall magnetization process, so that each magnetic blank is magnetized along its respective easy magnetization direction, thereby forming a complete Halbach array. This method of assembling first and then magnetizing as a whole avoids the problem of magnetization history caused by step magnetization and ensures the accuracy of the magnetic field waveform.

[0031] Further, see Figure 8 As shown, the annular rotor 104 in this embodiment includes a first magnet 1042 and a second magnet 1043 of different shapes arranged adjacent to each other. The first magnet 1042 generates a horizontal (i.e., tangential) magnetic field, with its magnetization direction tangential; the second magnet 1043 generates an axial magnetic field, with its magnetization direction axial. This alternating arrangement produces a unilateral magnetic focusing effect, significantly enhancing the magnetic field on the working air gap side.

[0032] In some embodiments of this application, the first magnet 1042 may optionally be a strip-shaped (or tile-shaped) structure; the second magnet 1043 may be a trapezoidal structure with rounded ends, so as to better adapt to the geometry of the annular rotor and optimize the magnetic field distribution.

[0033] Further, see also Figure 8 As shown, the annular rotor 104 in this embodiment further includes an annular mounting groove 620 (which can be integrally formed from metal or plastic). The first magnet 1042 and the second magnet 1043 of the annular rotor are arranged circumferentially in the groove along the annular mounting groove 620 and are integrally potted and fixed by epoxy resin structural adhesive. This overcomes the mutual repulsion between the magnets and prevents the risk of falling off during high-speed rotation. In some embodiments of this application, the annular mounting groove 620 is optionally made of a non-magnetic material, such as stainless steel, titanium alloy, or engineering plastics such as PEEK. Non-magnetic materials ensure that they will not interfere with the magnetic field generated by the Hellbeck array and will not form a magnetic short circuit. In addition, the surface of the Hellbeck array magnet 610 in this embodiment is coated with an insulating varnish layer (not shown separately in the figure), and the magnet itself is spliced ​​in a modular manner (i.e., composed of multiple independent magnetic blocks). This modular structure can effectively cut off the eddy current path and reduce eddy current loss and heat generation. Furthermore, in some embodiments of this application, the Heilbeck array magnet 610 is preferably made of sintered NdFeB, and further, a grade with a temperature resistance rating of 160°C or higher, such as N45SH or N45UH, is used to ensure the stability of magnetic properties at high temperatures.

[0034] In this embodiment, when a three-phase sinusoidal current (using FOC control strategy) is applied to the PCB winding stator, a rotating magnetic field is generated. This rotating magnetic field interacts with the strong focusing magnetic field generated by the Hellbeck array on the annular rotor, producing electromagnetic torque and driving the annular rotor along with the mirror frame to rotate around the axis. Since the coreless structure of the PCB winding eliminates cogging torque, and the Hellbeck array provides a highly sinusoidal air gap magnetic field, combined with FOC control, extremely low torque ripple, high efficiency, and smooth speed control can be achieved.

[0035] Figure 9 This is a three-dimensional structural diagram of the annular rotor of another axial flux permanent magnet synchronous motor according to an embodiment of this application. Figure 10 yes Figure 9 A schematic diagram showing the magnet arrangement of the rotor structure. (Combined with...) Figure 2 , Figure 9 and Figure 10 As shown, the annular rotor 104 includes a U-shaped back iron yoke 121 and an axially magnetized annular magnet 122. The U-shaped back iron yoke 121 is made of a magnetically conductive material (e.g., electrical pure iron, cold-rolled steel, galvanized steel, low-carbon steel, stainless iron, or SMC soft magnetic material). The U-shaped back iron yoke 121 includes a cylindrical inner edge 123 and a cylindrical outer edge 124, which are connected by a base plate (not shown in the figure). The inner edge 123, the outer edge 124, and the base plate together form a U-shaped groove for accommodating the annular magnet 122. The annular magnet 122 is a multi-pole axially magnetized integral magnetic ring. The N pole and S pole of the annular magnet 122 are alternately distributed along the circumference of the annular magnet, and the magnetization direction of adjacent N poles is opposite to that of the S pole.

[0036] The U-shaped back iron structure of this application embodiment can effectively suppress end magnetic leakage: the inner and outer edges act like two walls, forcing magnetic lines of force to pass through the coil area more axially, significantly improving the air gap magnetic flux density and magnetic utilization rate. Simulation verification shows that compared with a flat back iron, this structure can increase the average magnetic flux density of the working air gap by more than 100%, while reducing the harmonic distortion rate.

[0037] In some embodiments of this application, optionally, the relative starting position of the annular rotor and the PCB winding stator is set such that the pole line of the annular rotor is aligned with the mechanical center of any winding in the PCB winding stator in the circumferential direction, so that the back EMF generated by the winding at this starting position is at its maximum value.

[0038] In some embodiments of this application, the axial flux permanent magnet synchronous motor may optionally include a Hall sensor, which is mounted on the PCB winding stator or base, and the sensing position of the Hall sensor is aligned with the pole line in the circumferential direction to detect the zero-crossing point of the magnetic field when the pole line passes through.

[0039] In some embodiments of this application, optionally, the relative starting position of the annular rotor and the PCB winding stator is set such that the magnetic pole center line of the annular rotor is aligned with the mechanical center of any winding in the PCB winding stator in the circumferential direction, so that the back electromotive force generated by the winding at this starting position is zero.

[0040] Regarding the relative starting positions of the rotor and stator coils, two basic concepts need to be clarified first: the pole line and the magnetic pole center line. Regardless of whether the rotor uses a Halebeck array magnet (composed of multiple magnet blanks with different magnetization directions, where the center of the horizontal magnet corresponds to the peak air gap magnetic flux density and the center of the vertical magnet corresponds to the zero air gap magnetic flux density) or an axially magnetized integrated toroidal magnet (i.e., a conventional multi-pole magnetized ring with alternating poles), the rotor's air gap magnetic field exhibits a periodic alternation of N and S poles. The pole line refers to the boundary line between adjacent N and S poles. At this position, the air gap magnetic flux density is exactly zero, and the magnetic field direction reverses, thus it is also the position with the largest rate of change of the magnetic field. For a Halebeck array, the pole line is located on the center line of the vertical magnet (axially magnetized block); for an axially magnetized toroidal magnet, the pole line is located at the boundary between two adjacent magnetic poles of opposite polarity. The magnetic pole centerline refers to the geometric center axis of each N or S pole, where the air gap magnetic flux density reaches its maximum positive or negative value, and the magnetic field direction is most stable. For a Hellbeck array, the magnetic pole centerline is located on the center line of the horizontal magnet (tangentially magnetized magnet), while for an axially magnetized toroidal magnet, the magnetic pole centerline is located at the center of each pole. Within a complete cycle of a magnetic pole pair (one N pole and one S pole), the magnetic pole centerline and the inter-pole line are spaced 90° electrically (22.5° mechanically for an 8-pole motor), and together they form the reference for rotor magnetic field positioning.

[0041] For the first initial position scheme: the pole line of the annular rotor is aligned circumferentially with the mechanical center of any winding in the PCB winding stator, maximizing the back EMF generated by that winding at the initial position. When the pole line coincides with the mechanical center of the winding, the two radial conductors (effective sides) of the winding are each half-covered by an N pole and a S pole, respectively. Therefore, the net magnetic flux through the winding is zero, but the rate of change of magnetic flux with rotor angle (dψ / dθ) reaches its peak. According to Faraday's law of electromagnetic induction e=-ω·dψ / dθ, the amplitude of the back EMF is proportional to the rate of change of magnetic flux at a given speed. Therefore, the back EMF generated at this initial position is at its maximum value (peak or trough). This scheme is suitable for square wave controlled brushless DC motor (BLDC) drives, especially in low-cost applications using a six-step commutation method and relying on Hall sensors for position detection. Because the back EMF amplitude is largest at the initial position, the controller can easily achieve commutation by detecting the zero-crossing point of the back EMF, or by using this position as the electrical zero-degree reference point when installing the Hall sensor, thus obtaining a clear and reliable commutation moment. The advantages of this scheme are: the strong and steep back EMF signal at startup is easy for the controller to capture, improving startup reliability; the maximum back EMF point coincides with the zero-crossing point of the magnetic field (inter-pole line), providing a precise physical reference for Hall sensor installation and simplifying the commutation logic; the control algorithm is simple, with low requirements for microcontroller performance, effectively reducing the overall cost of the drive system.

[0042] In some embodiments of this application, the axial flux permanent magnet synchronous motor optionally includes a Hall sensor. The Hall sensor is mounted on the PCB winding stator or base, and its sensing position is aligned with the pole line in the circumferential direction to detect the zero-crossing point of the magnetic field when the pole line passes through. Since the air gap magnetic flux density is zero and the magnetic field direction is reversed by 180° at the pole line, this position is the steepest point of magnetic field change. When the rotor rotates and the pole line passes through the sensing area of ​​the Hall sensor, the Hall output signal will produce a fast and clean level transition (e.g., from high level to low level or vice versa). The controller detects this transition signal and can accurately determine that the rotor has reached the mechanical position of the pole line, thereby performing commutation or calculating the rotational speed accordingly. Typically, three Hall sensors can be installed at 120° electrical angles in the circumferential direction to obtain six different position code combinations, covering the complete commutation cycle of 360° electrical angle. The advantages of this scheme are as follows: by utilizing the inherent characteristics of the magnetic field zero-crossing point at the pole line, the Hall sensor outputs a steep transition signal with low jitter and strong anti-electromagnetic interference capability, and can work stably even in a high-frequency PWM harmonic environment; it can obtain accurate rotor position without the need for complex position observers or angle interpolation algorithms, making it particularly suitable for motor drive systems that are cost-sensitive and have certain requirements for commutation accuracy; at the same time, the physical installation position of the Hall sensor is fully compatible with the above-mentioned starting position setting, the hardware structure is unified, and different control strategies can be adapted through software configuration alone, enhancing the platform capability of the product.

[0043] For the second starting position scheme: the center line of the magnetic poles of the annular rotor is aligned circumferentially with the mechanical center of any winding in the PCB winding stator, making the back EMF generated by that winding zero in the starting position. When the center line of the magnetic poles coincides with the mechanical center of the winding, the two radial conductors of that winding are completely covered by the same magnetic pole (the entire N pole or the entire S pole). At this time, the magnetic flux through the winding reaches its maximum value (positive maximum or negative maximum), but the rate of change of the magnetic flux linkage with the rotor angle, dψ / dθ, is 0, so the back EMF is zero. This position corresponds exactly to the zero-crossing point in the sinusoidal air gap magnetic field waveform, which is completely consistent with the electrical zero-degree angle defined in Field Oriented Control (FOC) (usually, the position where the axis of the rotor magnetic poles—the D-axis—coincides with the axis of the A-phase winding is defined as 0° electrical angle). Therefore, this starting position scheme is particularly suitable for sinusoidal wave driven FOC vector control. In systems using encoders or rotary transformers as position sensors, the position can be directly calibrated as the electrical angle zero point during assembly without additional phase offset compensation. In systems using sensorless FOC (which estimates rotor position using a back EMF observer or high-frequency injection method), the controller can automatically find the zero point through a pre-positioning algorithm. Furthermore, since the back EMF is zero at the initial position, current surges or malfunctions caused by non-zero back EMF at zero speed are avoided.

[0044] The beneficial effects of this scheme are as follows: it naturally matches the coordinate system of the FOC control model, simplifying angle calculations in Park and inverse Park transformations and reducing the complexity of the control software; it achieves theoretically zero torque pulsation across the entire speed range (especially at extremely low and zero speeds), resulting in extremely smooth motor operation and significantly reduced vibration and noise; simultaneously, due to the good linearity of the back EMF waveform near zero, it is beneficial for high-precision servo positioning and low-speed crawling control, making it particularly suitable for high-end applications with stringent requirements for dynamic response and quiet operation, such as robot joints, UAV gimbals, and medical devices. It is worth noting that the two starting position schemes defined in claims 12 to 14 differ by a 90° electrical angle (for an 8-pole motor, the mechanical angle difference is 22.5°), both of which are compatible with the aforementioned Heilbeck array rotor or axially magnetized annular magnet rotor of this application. In actual products, one can be flexibly selected according to the control mode (BLDC square wave or FOC sine wave) of the target application, thereby achieving adaptation of the same mechanical structure to different drive algorithms.

[0045] Figure 11 This is a three-dimensional structural schematic diagram of another axial flux permanent magnet synchronous motor according to an embodiment of this application. Figure 12 yes Figure 11 The structure shown is a cross-sectional view along DD. Figure 11 The axial flux permanent magnet synchronous motor shown is with Figure 1 The axial flux permanent magnet synchronous motors shown are similar in main structure to those shown. Specifically... Figure 11 The motor also includes a rotating shaft 100, bearing 210, base 102, frame 101, PCB winding stator 103, and annular rotor 104, and the assembly relationship of the above components is as follows: Figure 1 The motors shown are the same. Figure 11 The motor shown is Figure 1 The main difference between the motors shown lies in the structure of the eyeglass frame: Figure 11 In the motor shown, the mirror frame 101 is cylindrical, and the reflector 300 is only provided on one side of the cylinder. Figure 1 In the motor shown, the frame 101 has a square structure, and reflectors 300 are arranged around all four sides of this square structure. Additionally, in Figure 11 The illustrated motor also includes an electrical connector 400 for electrical connection to an external structure. The electrical connector 400 may also be provided... Figure 1 The same position of the axial flux permanent magnet synchronous motor shown can achieve the same function.

[0046] In summary, the radial conductors of adjacent PCB coil layers of the axial flux permanent magnet synchronous motor proposed in this application are radially staggered, so that the phase of the induced voltage of each layer is basically consistent. After being superimposed in phase through end overlap, the total number of turns and back EMF are effectively increased, and the torque density is enhanced. At the same time, the end overlap design shortens the interlayer connection path, reduces winding resistance and copper loss, and improves motor efficiency. The overall structure is compact, the axial dimension is short, and it is conducive to obtaining a more sinusoidal back EMF waveform.

[0047] The above embodiments are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art can make various changes and modifications without departing from the scope of this application. Therefore, all equivalent technical solutions should also fall within the scope of this application.

Claims

1. An axial flux permanent magnet synchronous motor, comprising a frame and a base mounted on a rotating shaft, characterized in that, A PCB winding stator is provided on the base, the PCB winding stator is passed through the rotating shaft, the eyeglass frame is provided above the PCB winding stator, and an annular rotor is provided at the end of the eyeglass frame opposite to the PCB winding stator. Under the action of the magnetic field generated by the PCB winding stator, the annular rotor drives the eyeglass frame to rotate around the rotating shaft. The PCB winding stator comprises at least two PCB coil layers, each PCB coil layer comprising multiple windings circumferentially distributed along the rotation axis, each winding comprising a radially extending radial conductor and an end conductor connecting the radial conductor; wherein, The radial conductors of any two adjacent PCB coil layers are spatially offset; The end conductors of any two adjacent PCB coil layers overlap in the coil layer thickness direction; and, Adjacent coil windings located on different layers are connected in series via end conductors.

2. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The magnets distributed circumferentially along the axis of rotation in the annular rotor constitute a Heilbeck array; the Heilbeck array is formed by assembling multiple unmagnetized magnetic blanks with different easy magnetization directions into a ring, and then magnetizing the whole in one go using a special fixture.

3. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The annular rotor includes a first magnet and a second magnet of different shapes arranged adjacent to each other, wherein the first magnet is used to generate a horizontal magnetic field and the second magnet is used to generate an axial magnetic field.

4. The axial flux permanent magnet synchronous motor according to claim 3, characterized in that, The first magnet is a strip-shaped structure, and the second magnet is a trapezoidal structure with rounded ends.

5. The axial flux permanent magnet synchronous motor according to claim 2, characterized in that, The surface of the magnet is coated with an insulating varnish layer, and the magnet is spliced ​​in sections to cut off the eddy current path.

6. The axial flux permanent magnet synchronous motor according to claim 2, characterized in that, The annular rotor also includes an annular mounting groove, in which the magnet is arranged circumferentially and fixed with epoxy resin structural adhesive.

7. The axial flux permanent magnet synchronous motor according to claim 6, characterized in that, The annular mounting groove is made of a non-magnetic material.

8. The axial flux permanent magnet synchronous motor according to claim 2, characterized in that, The magnet is made of sintered neodymium iron boron.

9. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The annular rotor includes a U-shaped back iron yoke and an axially magnetized annular magnet. The U-shaped back iron yoke includes a cylindrical inner edge and an outer edge, which are connected by a base plate. The inner edge, the outer edge, and the base plate form a U-shaped groove for accommodating the annular magnet.

10. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The winding is trapezoidal in shape, and the two ends of the trapezoid are rounded.

11. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The PCB winding stator winding is fixed on the PCB board, and a through hole is provided on the PCB board near the end spokes. The conductors of the through hole connect the windings of adjacent different layers in series.

12. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The relative starting position of the annular rotor and the PCB winding stator is set such that the pole line of the annular rotor is aligned with the mechanical center of any winding in the PCB winding stator in the circumferential direction, so that the back electromotive force generated by the winding at this starting position is at its maximum value.

13. The axial flux permanent magnet synchronous motor according to claim 12, characterized in that, The axial flux permanent magnet synchronous motor also includes a Hall sensor, which is mounted on the PCB winding stator or base, and the sensing position of the Hall sensor is aligned with the pole line in the circumferential direction to detect the zero-crossing point of the magnetic field when the pole line passes through.

14. The axial flux permanent magnet synchronous motor according to claim 1, characterized in that, The relative starting position of the annular rotor and the PCB winding stator is set such that the magnetic pole center line of the annular rotor is aligned with the mechanical center of any winding in the PCB winding stator in the circumferential direction, so that the back electromotive force generated by the winding at this starting position is zero.

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