A PCB stator axial flux motor

Abstract

This invention provides a PCB stator axial flux motor, relating to the field of motor technology, to solve the technical problems of poor heat dissipation, high risk of motor rubbing, and high magnetic reluctance in existing PCB axial motors. The PCB stator axial flux motor includes a shaft system assembly and at least one unit group. The shaft system assembly includes a motor shaft. Each unit group includes a rotatable rotor assembly and two fixed stator assemblies. The rotor assembly includes a rotor yoke and several permanent magnets. The rotor yoke is mounted on the motor shaft. Several permanent magnets are equidistantly distributed circumferentially on both the upper and lower end faces of the rotor yoke. The two stator assemblies are located on the upper and lower sides of the rotor assembly, respectively. Each stator assembly includes a PCB board and winding coils mounted on the PCB board, which is mounted on the motor shaft. The uppermost and lowermost stator assemblies are provided with connection structures for connecting to the motor housing.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electric machines, in particular to a PCB stator axial flux motor. BACKGROUND

[0002] Under the background of the acceleration of the upgrading of high-end fields such as medical treatment, aviation, low-altitude flight, industrial equipment and robot joints to "miniaturization integration, high power density and high precision control", the core power components put forward strict requirements on the performance boundary of the electric machine. The minimally invasive surgery robot in the medical field needs to output stable torque in a millimeter level space to ensure the operation precision, the low-altitude flight equipment such as unmanned aerial vehicles and light aviation auxiliary systems have very high requirements on the lightness and endurance adaptability of the electric machine, and the robot joint relies on the flat structure and rapid dynamic response of the electric machine to realize flexible movement with multiple degrees of freedom. The traditional radial flux motor gradually cannot meet the core needs of these scenes due to the limitations of large axial size, limited torque density, low space utilization and the like.

[0003] The axial flux motor becomes the key technical direction for breaking through the above bottleneck due to the unique structure that the air gap magnetic field is parallel to the axis of the electric machine, and the integration of the PCB technology further promotes the adaptability of the axial flux motor in the high-end field. By directly printing the winding on the PCB board, the axial flux motor can omit the complex structure of the traditional iron core and copper wire winding, and the copper consumption is reduced by more than 66 %, which not only greatly reduces the weight to adapt to the load limit of the aviation equipment, but also eliminates the cogging effect by relying on the high-precision layout of the PCB winding, so that the torque fluctuation is controlled at a very low level, and the requirement of the minimally invasive surgery robot for "undisturbed" movement is met. In addition, the excellent thermal stability and integration characteristics of the PCB can realize the integrated design of the electric machine and the equipment control system, and prolong the endurance time of the flight equipment.

[0004] Chinese patent CN103001426A discloses a printed circuit board coreless disc type motor, which is characterized in that a stator disc is arranged between two rotor discs, permanent magnets are arranged on the two rotor discs, and the stator disc is formed by axially stacking at least two printed circuit boards. After the above structure is adopted, the motor has the advantages of light weight, small size and low manufacturing cost. However, the arrangement scheme of the intermediate stator and the two end rotors still has the problems of long stator heat dissipation path and poor heat dissipation effect, and the cantilever effect of the rotor leads to poor stator flatness and high motor sweep risk. Meanwhile, the PCB has low magnetic permeability, and the equivalent air gap needs to be stacked with the thickness of the PCB, which leads to increased magnetic resistance and difficult power density improvement, and the small number of layers of the PCB winding coil limits the application of the motor in the conditions of high power, high precision and small size. SUMMARY

[0005] In view of the defects of the prior art, the purpose of the present application is to provide a PCB stator axial flux motor to solve the technical problems of poor heat dissipation effect, high risk of motor sweep bore and high magnetic resistance in the prior art.

[0006] To solve the above technical problems, the present application provides a PCB stator axial flux motor, comprising:

[0007] A shafting assembly comprising a motor shaft;

[0008] At least one unit group, each unit group comprising one rotatable rotor assembly and two fixed stator assemblies, the rotor assembly comprising a rotor yoke and a plurality of permanent magnets, the rotor yoke being arranged on the motor shaft, the upper and lower end faces of the rotor yoke being circumferentially equidistantly distributed with a plurality of permanent magnets, the two stator assemblies being located on the upper and lower sides of the rotor assembly, each stator assembly comprising a PCB board and a winding coil arranged on the PCB board, the PCB board being arranged on the motor shaft;

[0009] The stator assemblies located at the uppermost end and the lowermost end are each provided with a connecting structure for connecting with the motor housing.

[0010] After adopting the above structure, the PCB stator axial flux motor has the following advantages: the two stator assemblies form a double-stator structure, and the permanent magnets are arranged on the upper and lower end faces of the rotor yoke to form a double-rotor structure, thus forming a topology structure of double-rotor in the middle and double-stator on the outside, the magnetic field starts from the outer stator assembly, passes through the physical air gap to reach the middle rotor assembly, and then returns to the adjacent outer stator assembly through another physical air gap, the magnetic path is relatively short and direct, and there is no additional complex magnetic path structure or air gap superposition, so that the equivalent air gap is equal to the actual physical air gap, compared with some single-stator structure or other complex topology structure, there is no case of increased equivalent air gap caused by magnetic path detour or multiple air gaps in series, thus the magnetic resistance is reduced, and the two stator assemblies can both form a rotating magnetic field, which can improve the electrical load of the motor and enable the motor to output large torque in a very small volume; in addition, the stator assemblies located at the uppermost end and the lowermost end can be connected with the motor housing through the connecting structure, improving the stability of the overall structure, the flatness error of the PCB board can be controlled within ±0.05 mm, the risk of sweep bore is avoided, and the heat generated by the stator assemblies can be directly dissipated to the surrounding environment through the motor housing, reducing the transmission distance and thermal resistance of the heat inside the motor, and greatly shortening the heat dissipation path compared with the structure of the middle stator.

[0011] As an improvement, several permanent magnets are symmetrically distributed on the upper and lower end faces of the rotor yoke, and two stator assemblies are symmetrically distributed on the upper and lower sides of the rotor assembly; with this structure, when the motor is running, electromagnetic force will be generated between the two stator assemblies on the outside and the rotor assembly in the middle. Since the electromagnetic force of the two stator assemblies on the rotor assembly is equal in size and opposite in direction in the axial direction, it is counteracted, so that the rotor assembly is not subjected to the net electromagnetic force in the axial direction. Therefore, the motor shaft does not need to bear the additional load caused by the axial electromagnetic force, which can reduce mechanical loss and avoid shaft vibration caused by the cantilevered rotor when the stator is in the middle. The symmetry design of the topology structure makes the electromagnetic force and mechanical force also present a symmetric distribution characteristic in the whole system. This symmetry makes the motor shaft not subjected to additional bending moment and torque caused by structural asymmetry during operation, thereby further ensuring that the motor shaft only needs to support its own weight to maintain a stable working state.

[0012] As an improvement, each PCB board includes several mutually laminated wiring layers, and each winding coil includes several lines respectively arranged on the wiring layers; with this structure, the multi-layer PCB winding design can be more closely integrated inside the motor, improving the space utilization of the motor, optimizing the transfer and diffusion of heat between layers, and further improving the heat dissipation efficiency of the motor. In addition, more wiring layers can arrange more conductors in the same volume, thereby increasing the number of turns of the winding coil and improving the output power of the motor, effectively improving the power density of the motor, so that the motor can output large torque in a very small volume.

[0013] As an improvement, the number of wiring layers in each PCB board is 4-32.

[0014] As an improvement, the shaft system assembly further includes at least one shaft shoulder and at least one fixing disc, the number of shaft shoulders and fixing discs is the same as that of the rotor yoke, the shaft shoulder is arranged on the motor shaft, the bottom end of the shaft shoulder is provided with a mounting groove penetrating through the outer wall of the shaft shoulder in the radial direction, the fixing disc is sleeved on the motor shaft and abuts against the bottom end of the shaft shoulder, and the rotor yoke is connected in the mounting groove.

[0015] As an improvement, the number of unit groups is 2-10, and several unit groups are spaced apart along the axial direction of the motor shaft; with this structure, the power and torque of the motor can be flexibly expanded by stacking unit groups, the power density is improved in steps while maintaining the axial flat structure, and the customizable demand of different equipment for power output is met.

[0016] As an improvement, the magnetization directions of the circumferentially adjacent permanent magnets are opposite.

[0017] As an improvement, all permanent magnets are made of ferrite material or neodymium-iron-boron material; with this structure, performance and cost are taken into account; ferrite is suitable for low-cost and corrosion-resistant scenarios; neodymium-iron-boron provides high magnetic energy product, which helps to improve power density and meet the pursuit of lightweight and high efficiency of high-end equipment.

[0018] As an improvement, the permanent magnets are distributed in the form of Halbach array; with this structure, the magnetic field can be concentrated on the air gap side, enhancing the air gap flux density and reducing the rotor backside leakage, further improving the power density and motor efficiency.

[0019] As an improvement, the connecting structure is a metal frame on the PCB board; with this structure, the metal frame is used as the connecting structure, not only strengthening the connection stability of the stator assembly and the motor shell, but also improving the heat dissipation path of the stator assembly and improving the heat dissipation effect by using the high thermal conductivity of metal. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structure diagram of a unit group on the motor shaft in the application.

[0021] Figure 2 is a structure diagram of a unit group on the motor shaft in the application. Figure 1

[0022] Figure 3 is a sectional view of a unit group on the motor shaft in the application.

[0023] Figure 4 is an exploded structure diagram of a unit group on the motor shaft in the application.

[0024] Figure 5 is a structure diagram of a shafting assembly in the application.

[0025] Reference signs: 1, shafting assembly; 11, motor shaft; 12, shaft shoulder; 13, fixed disc; 2, rotor assembly; 21, rotor yoke; 22, permanent magnet; 3, stator assembly; 31, PCB board; 32, winding coil; 4, mounting groove. DETAILED DESCRIPTION

[0026] The application will be described in detail below in combination with the drawings.

[0027] As an improvement, all permanent magnets are made of ferrite material or neodymium-iron-boron material; with this structure, performance and cost are taken into account; ferrite is suitable for low-cost and corrosion-resistant scenarios; neodymium-iron-boron provides high magnetic energy product, which helps to improve power density and meet the pursuit of lightweight and high efficiency of high-end equipment. Figures 1 to 5 ​As shown in the figure, a PCB stator axial flux motor includes a shafting assembly 1 and at least one unit group, the shafting assembly 1 includes a motor shaft 11, each unit group includes a rotatable rotor assembly 2 and two fixed stator assemblies 3, the rotor assembly 2 includes a rotor yoke 21 and a plurality of permanent magnets 22, the rotor yoke 21 is arranged on the motor shaft 11, and the upper and lower end faces of the rotor yoke 21 are circumferentially equidistantly distributed with a plurality of permanent magnets 22, specifically, the shafting assembly 1 further includes at least one shaft shoulder 12 and at least one fixed disc 13, the number of the shaft shoulder 12 and the fixed disc 13 is the same as that of the rotor yoke 21, such as Figure 3 As shown in the figure, the shaft shoulder 12 is arranged on the motor shaft 11, the bottom end of the shaft shoulder 12 is provided with a mounting groove 4 penetrating through the outer wall of the shaft shoulder 12 in the radial direction, the fixed disc 13 is sleeved on the motor shaft 11 and abuts against the bottom end of the shaft shoulder 12, and the rotor yoke 21 is connected in the mounting groove 4.

[0028] Specifically, the shaft shoulder 12 and the fixed disc 13 are both circular in cross-section and coaxially arranged with the motor shaft 11, the mounting groove 4 is also annular, when the rotor yoke 21 is mounted, the rotor yoke 21 is first mounted into the mounting groove 4, and then the fixed disc 13 is mounted, and the inner circumferential wall of the rotor yoke 21 is attached to the inner wall of the mounting groove 4, and the upper and lower end faces of the rotor yoke 21 are respectively attached to the mounting groove 4 and the fixed disc 13. The fixed disc 13 and the shaft shoulder 12, the motor shaft 11 can adopt the existing connection mode, such as pasting.

[0029] As shown in the figure Figure 1 and Figure 3 The two stator assemblies 3 are respectively located on the upper and lower sides of the rotor assembly 2, each stator assembly 3 includes a PCB board 31 and a winding coil 32 arranged on the PCB board 31, and the PCB board 31 is arranged on the motor shaft 11; the stator assembly 3 adopts a stator coreless structure design, the winding coil 32 is arranged in a plane, and the winding coil 32 is arranged on the surface or inside of the PCB board 31 for generating a magnetic motive force, in the embodiment, the winding coil 32 is distributed on the PCB board 31 according to the corresponding motor phase sequence; in the embodiment, an axial through hole is arranged at the center of the PCB board 31, a bearing is arranged in the axial through hole and connected with the motor shaft 11, the stator assembly 3 is fixed, and the motor shaft 11 and the rotor assembly 2 rotate relative to the stator assembly 3.

[0030] Each permanent magnet 22 is used to generate a magnetic field with a link of turns with the winding coil 32 of the PCB board 31, the number of permanent magnets 22 on the upper and lower sides of the rotor yoke 21 is even, the magnetization directions of the permanent magnets 22 adjacent in the circumferential direction are opposite, all the permanent magnets 22 are made of ferrite material or neodymium-iron-boron material, the ferrite is suitable for low-cost and corrosion-resistant scenes, and the neodymium-iron-boron provides high magnetic energy product, which helps to improve the power density and meet the pursuit of lightweight and high efficiency of high-end equipment, the permanent magnets 22 in the embodiment are made of neodymium-iron-boron material; each permanent magnet 22 is distributed in the form of Halbach array, in the embodiment, the shapes of all the permanent magnets 22 are flat, for example, are fan-shaped, and each permanent magnet 22 is arranged on the rotor yoke 21 in the form of a fan-shaped array.

[0031] The stator assemblies 3 located at the uppermost end and the lowermost end are each provided with a connecting structure for connecting with the motor housing, in the embodiment, the connecting structure is a metal frame provided on the PCB board 31. It should be noted that the up-down directions in the present application are all based on the state that the motor shaft 11 is vertically arranged.

[0032] In addition, a plurality of permanent magnets 22 are symmetrically distributed on the upper and lower end faces of the rotor yoke 21, and two stator assemblies 3 are symmetrically distributed on the upper and lower sides of the rotor assembly 2.

[0033] The two stator assemblies 3 form a double-stator structure, and the permanent magnets 22 are arranged on the upper and lower end faces of the rotor yoke 21 to form a double-rotor structure, so as to form a topology structure of double rotors in the middle and double stators on the outside, the magnetic field starts from the stator assembly 3 on the outside, passes through a physical air gap to reach the rotor assembly 2 in the middle, and then returns to the adjacent stator assembly 3 on the outside through another physical air gap, the magnetic path is relatively short and direct, and there is no additional complex magnetic path structure or air gap superposition, so that the equivalent air gap is equal to the actual physical air gap, compared with some single-stator structures or other complex topology structures, there is no case of increased equivalent air gap caused by magnetic path detours or multiple air gaps in series, so the magnetic resistance is reduced, and the two stator assemblies 3 can both form a rotating magnetic field, which can improve the electrical load of the motor and can make the motor output large torque in a small volume; in addition, the stator assemblies 3 located at the uppermost end and the lowermost end can be connected with the motor housing through the connecting structure, improving the stability of the overall structure, the flatness error of the PCB board 31 can be controlled to be less than or equal to ±0.05 mm, and the risk of sweeping the bore is avoided, and the heat generated by the stator assembly 3 can be directly dissipated to the surrounding environment through the motor housing, reducing the transmission distance and thermal resistance of the heat in the motor, and greatly shortening the heat dissipation path compared with the structure of the middle stator.

[0034] When the motor is running, electromagnetic force is generated between the two outer stator assemblies 3 and the middle rotor assembly 2. Since the electromagnetic force of the two stator assemblies 3 on the rotor assembly 2 is equal in size and opposite in direction in the axial direction, it is counteracted, so that the rotor assembly 2 is not subjected to the net electromagnetic force in the axial direction. Therefore, the motor shaft 11 does not need to bear the additional load caused by the axial electromagnetic force, which can reduce mechanical loss, avoid shafting vibration caused by the cantilevered rotor when the stator is in the middle, and prolong the service life of the bearing. The symmetry design of the topology makes the electromagnetic force and mechanical force also present symmetrical distribution characteristics in the whole system. This symmetry makes the motor shaft 11 not subjected to additional bending moment and torque caused by structural asymmetry during operation, thereby further ensuring that the motor shaft 11 only needs to support its own weight to maintain a stable working state. Moreover, the mass distribution of the middle rotor structure is more symmetrical, and the dynamic balance is better, which significantly reduces the mechanical noise during high-speed operation.

[0035] Each PCB board 31 includes a plurality of laminated wiring layers, each winding coil 32 includes a plurality of lines respectively arranged on a plurality of wiring layers, and the same wiring layer includes a plurality of groups of lines to form a plurality of groups of winding coils 32. Specifically, the number of wiring layers in each PCB board 31 is 4-32, and in the embodiment, the number of wiring layers in each PCB board 31 is 18.

[0036] For such a multi-layer stator assembly 3, during the manufacturing process, especially before the outer printed wiring is laminated together to form a whole stator assembly 3. For example, during the lamination process, the printed wiring layers can be bonded together by means of adhesive sheets. The multi-layer PCB winding design can be more closely integrated inside the motor, improve the space utilization of the motor, optimize the heat transfer and diffusion between layers, and further improve the heat dissipation efficiency of the motor. In addition, more winding layers can arrange more conductors in the same volume, thereby increasing the number of turns of the winding and improving the output power of the motor, effectively improving the power density of the motor, so that the motor can output large torque in a very small volume.

[0037] Each wiring layer of the stator assembly 3 can have the same or different winding patterns; optionally, the stator assembly 3 can have winding patterns that are mirror images of each other or slightly different in adjacent wiring layers; optionally, each PCB board 31 in each stator assembly 3 is oriented so that the winding patterns in each PCB board 31 are aligned with each other or at least partially misaligned in the axial direction.

[0038] It should be noted that the present application does not particularly limit the coil wiring method of the stator assembly 3, and any appropriate coil wiring method can be used in the present application.

[0039] The number of unit groups is 2-10, and the unit groups are distributed along the motor shaft 11 in an axial direction. The motor shaft 11 can be a stepped shaft according to requirements. In this embodiment, the stator assembly 3 with 18 wiring layers has an axial length of about 1.5 mm.

[0040] The PCB stator axial flux motor without a stator core provided by the application completely eliminates the eddy current and hysteresis loss generated by the traditional stator core in an alternating magnetic field, reduces the motor quality and size, improves the operation stability and energy conversion efficiency of the motor, reduces the noise, and expands the application under the conditions of high power, high precision, and small size.

[0041] The embodiments of the application are described in detail above in combination with the drawings, but the application is not limited to the above-described one embodiment. All other embodiments obtained by those skilled in the art without making creative efforts fall within the protection scope of the application.

Claims

1. A PCB stator axial flux motor characterized by, Comprise: A shafting assembly (1) comprising a motor shaft (11); At least one unit group, each of which comprises a rotatable rotor assembly (2) and two fixed stator assemblies (3), the rotor assembly (2) comprises a rotor yoke (21) and a plurality of permanent magnets (22), the rotor yoke (21) is provided on the motor shaft (11), the upper and lower end faces of the rotor yoke (21) are circumferentially equidistantly distributed with a plurality of permanent magnets (22), two stator assemblies (3) are located on the upper and lower sides of the rotor assembly (2), each stator assembly (3) comprises a PCB board (31) and a winding coil (32) provided on the PCB board (31), the PCB board (31) is provided on the motor shaft (11); The stator assembly (3) located at the uppermost end and the lowermost end is provided with a connecting structure for connecting with the motor housing; The shafting assembly (1) further comprises at least one shaft shoulder (12) and at least one fixing disc (13), the number of the shaft shoulder (12) and the fixing disc (13) is the same as that of the rotor yoke (21), the shaft shoulder (12) is provided on the motor shaft (11), the bottom end of the shaft shoulder (12) is provided with an installation groove (4) penetrating through the outer wall of the shaft shoulder (12) in the radial direction, the fixing disc (13) is sleeved on the motor shaft (11) and abuts against the bottom end of the shaft shoulder (12), and the rotor yoke (21) is connected in the installation groove (4).

2. The PCB stator axial flux machine of claim 1, wherein, A plurality of permanent magnets (22) are symmetrically distributed on the upper and lower end faces of the rotor yoke (21), and two stator assemblies (3) are symmetrically distributed on the upper and lower sides of the rotor assembly (2).

3. The PCB stator axial flux machine of claim 1, wherein, Each of the PCB boards (31) comprises a plurality of laminated wiring layers, and each of the winding coils (32) comprises a plurality of lines respectively provided on a plurality of wiring layers.

4. The PCB stator axial flux machine of claim 3, wherein, The number of wiring layers in each of the PCB boards (31) is 4-32.

5. The PCB stator axial flux machine of claim 1, wherein, The number of unit groups is 2-10, and a plurality of unit groups are axially spaced along the motor shaft (11).

6. The PCB stator axial flux machine of claim 1, wherein, The magnetization directions of the permanent magnets (22) adjacent in the circumferential direction are opposite.

7. The PCB stator axial flux machine of claim 1, wherein, All the permanent magnets (22) are made of ferrite material or neodymium iron boron material.

8. The PCB stator axial flux machine of claim 1, wherein, The permanent magnets (22) are distributed in the form of Halbach array.

9. The PCB stator axial flux machine of claim 1, wherein, The connecting structure is a metal frame provided on the PCB board (31).

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