Double-stator skew magnetization axial flux permanent magnet motor and driving method

Abstract

This invention relates to the field of micro motor technology, specifically proposing a dual-stator obliquely magnetized axial flux permanent magnet motor and its driving method. The permanent magnet motor includes a rotatable rotor assembly and two stator assemblies symmetrically arranged on both axial sides of the rotor assembly. The rotor assembly includes obliquely magnetized permanent magnets. The stator assembly includes a first coil and a second coil that are concentrically arranged, wound in opposite directions, and connected in parallel. Its advantages are: The dual-stator obliquely magnetized axial flux permanent magnet motor disclosed in this invention adopts a dual-stator structure combined with a dual-coil reverse-wound parallel design. When energized, the two coils can generate a superimposed magnetic field in the same direction, significantly improving the air gap magnetic flux density and torque density. The rotor assembly uses obliquely magnetized permanent magnets, and the axial components of the permanent magnets on both sides cancel each other out, reducing the axial force on the bearings and extending the motor's lifespan.

Description

Technical Field

[0001] This invention relates to the field of micro drive motor technology, specifically to a dual-stator obliquely magnetized axial flux permanent magnet motor. Background Technology

[0002] Miniature drive motors are miniaturized electromagnetic actuators that can be used in low-to-medium power applications such as home appliances, automotive micro motors, and general industrial drives to provide rotational power or linear drive.

[0003] Common micro drive motors include brushed DC motors and brushless DC motors. With the rapid development of industrial automation and new energy vehicles, higher demands are placed on the power density, operational stability, and service life of drive motors. However, existing micro drive motors suffer from several problems. For example, brushed DC motors are characterized by high noise, short lifespan, spark interference, and poor precision. While brushless DC motors are widely used, their torque density still has room for improvement in scenarios requiring high power density, and the traditional radial flux structure limits further miniaturization. Due to these shortcomings of traditional drive motors, axial flux permanent magnet motors have become a research hotspot in the field of drive motors in recent years due to their compact structure and high power density. However, existing axial flux permanent magnet motors mostly use a single stator and single winding structure, which has the following drawbacks: First, the magnetic field distribution is asymmetrical, causing magnetic pull fluctuations during operation, leading to noise and vibration; second, the magnetic field strength generated by a single winding is limited, resulting in insufficient torque output capability; third, the rotor permanent magnets are radially or circumferentially magnetized, which easily generates axial components in the axial flux structure, increasing bearing load and affecting motor lifespan. Summary of the Invention

[0004] To overcome the problems of asymmetrical magnetic field distribution, limited torque output capability, and large axial load in existing axial flux permanent magnet motors, this invention proposes a dual-stator obliquely magnetized axial flux permanent magnet motor, which is suitable for low-to-medium power applications such as home appliances, automotive micro motors, and general industrial drives. Specifically, it includes the following technical solutions.

[0005] A dual-stator obliquely magnetized axial flux permanent magnet motor includes a housing, a rotatable rotor assembly, and two stator assemblies symmetrically arranged on both sides of the rotor assembly. The rotor assembly includes obliquely magnetized permanent magnets. The stator assembly includes a first coil and a second coil. When energized, the first coil and the second coil can generate a magnetic field superimposed in the same direction to drive the permanent magnets to rotate the rotor assembly.

[0006] Firstly, this invention employs a dual-stator, single-rotor structure. Compared to single-stator, single-rotor drive motors, the magnetic field distribution is symmetrical, eliminating significant magnetic pull fluctuations and resulting in more stable torque output. Secondly, the stator assembly utilizes a concentric dual-coil design. The counter-winding concentric coils generate a superimposed magnetic field between the two coils. When the permanent magnet is positioned within this superimposed magnetic field, a greater torque output can be achieved compared to a single coil, overcoming the size limitations of micro-drive motors to some extent and increasing the product's torque density. The magnetization direction of the permanent magnet is set at a specific angle (45°-60°) to the axial direction, allowing the permanent magnet to simultaneously generate tangential and axial components in the air gap magnetic field. Combined with the symmetrical topology of the dual-stator, the axial components of the permanent magnets on both sides cancel each other out, reducing the axial load on the bearings, lowering frictional losses, and improving the motor's service life.

[0007] Furthermore, the stator assembly includes an end cover, a coil support, a first coil, a second coil, and a bearing; the end cover is fixedly connected to the coil support, the bearing is pressed against the middle of the end cover, and the first coil and the second coil are mounted on the coil support; the first coil and the second coil are concentrically arranged, wound in opposite directions, and connected in parallel.

[0008] Furthermore, the resistances of the first coil and the second coil are equal, and the first coil is located outside the second coil. Since the first coil and the second coil are connected in parallel, when the resistances of the first coil and the second coil are equal, the current flowing through them is equal. By controlling the number of turns of the first coil and the second coil, the magnitudes of the magnetic forces generated by the first coil and the second coil can be made different, which facilitates the analysis of the force.

[0009] Furthermore, the end cap includes an integrally formed cover plate, a square boss on the cover plate, and an annular boss protruding from the square boss; the inner wall of the annular boss is connected to the bearing, and the outer wall is connected to the coil bracket. The end cap serves both to seal the upper and lower end faces of the drive motor and to connect the two stator assemblies, thereby improving the overall structural stability of the product.

[0010] Furthermore, the coil bracket is injection molded from insulating material and includes a base adapted to the square boss and an annular baffle protruding from the base; a positioning hole is provided in the center of the base; the first coil is located outside the annular baffle, and the second coil is located inside the annular baffle. The coil bracket is used for positioning, separating, and installing the first and second coils. It should be noted that after the coils are installed, they can be connected to external cables via leads, with the wire ends fixed by soldering, and the connection points can be protected with heat-shrinkable insulating tubing.

[0011] Furthermore, the rotor assembly includes a shaft, permanent magnets, a rotor support, and washers; the shaft is located at the center of the rotor support, the permanent magnets are mounted on the rotor support, and the washers are fitted onto both axial sides of the shaft. The rotor assembly has an overall axisymmetric structure, with the permanent magnets symmetrically arranged around the rotor support. The washers are used to reduce friction between the rotor assembly and the stator assembly.

[0012] Furthermore, the rotor assembly includes four fan-shaped neodymium iron boron permanent magnets. Each permanent magnet has the same shape and size, and is magnetized obliquely. The four permanent magnets are evenly arranged along the circumference, with adjacent permanent magnets magnetized in opposite directions. Oblique magnetization means that the magnetization direction of the permanent magnet is at a certain angle to both the axial and radial directions of the shaft, such as an angle of 45-60 degrees with the axial direction and an angle of 30-45 degrees with the radial direction. Identical arrangement means that in the rotor support, the permanent magnets are arranged with the upper left as the S or N pole and the lower right as the N or S pole.

[0013] Furthermore, the inner side of the rotor support forms mounting positions for four permanent magnets through a partition, and a cylindrical boss is provided in the middle. In a specific embodiment, there may be multiple permanent magnets. The permanent magnets should be arranged in the same way as much as possible and be subjected to balanced forces in the stator assembly. Force balance means that the axial forces received by the rotor assembly cancel each other out, and rotation is achieved only by tangential forces.

[0014] Furthermore, the two stator assemblies are fastened to both ends of the housing, together forming a receiving space for accommodating the rotor assembly. The housing, used for protection, may be made of steel or aluminum and is mainly used to enclose the rotor assembly.

[0015] A driving method for a dual-stator obliquely magnetized axial flux permanent magnet motor is disclosed. This method drives the motor by simultaneously inputting PWM signals to the first and second coils of the two stator components via a pulse power supply. The motor's speed and torque are controlled by adjusting the duty cycle or frequency of the PWM signals. By controlling the on / off state of the pulse power supply, the stator components can be energized or de-energized. Fine control allows for adjusting the duty cycle or frequency of the PWM signals to regulate the motor's speed and torque.

[0016] According to any of the above embodiments, the present invention has at least the following beneficial effects: The dual-stator obliquely magnetized axial flux permanent magnet motor disclosed in this invention adopts a dual-stator structure combined with a dual-coil reverse-winding parallel design. When energized, a superimposed magnetic field in the same direction can be generated between the two coils, significantly improving the air gap magnetic flux density and increasing the torque density. The rotor assembly uses obliquely magnetized permanent magnets, and the axial components of the permanent magnets on both sides cancel each other out, reducing the axial force on the bearings and extending the motor life. The use of a symmetrically arranged dual-stator structure balances the magnetic pull on both sides of the rotor, eliminating axial magnetic pull fluctuations and reducing vibration and noise. Attached Figure Description

[0017] Figure 1 This is an overall schematic diagram of the dual-stator obliquely magnetized axial flux permanent magnet motor of the present invention.

[0018] Figure 2 This is an exploded view of the structure of the dual-stator obliquely magnetized axial flux permanent magnet motor of the present invention.

[0019] Figure 3 This is a schematic diagram of the structure of the housing of the present invention.

[0020] Figure 4 This is a schematic diagram of the stator assembly of the present invention.

[0021] Figure 5 This is an exploded view of the stator assembly of the present invention.

[0022] Figure 6 This is a schematic diagram of the end cap structure of the present invention.

[0023] Figure 7 This is a schematic diagram of the coil support structure of the present invention.

[0024] Figure 8 This is a schematic diagram of the rotor assembly of the present invention.

[0025] Figure 9 This is an exploded view of the rotor assembly of the present invention.

[0026] Figure 10 This is a schematic diagram of the rotor support structure of the present invention.

[0027] Figure 11 This is a cross-sectional structural diagram of the invention.

[0028] Figure 12 This is a schematic diagram of the connection between the end cap and the coil support.

[0029] in:

[0030] 100—Housing; 200—First stator assembly; 300—Second stator assembly; 400—Rotor assembly;

[0031] 101—Through hole;

[0032] 201—End cap; 202—Coil support; 203—Coil; 204—Bearing;

[0033] 2011—Cover plate; 2012—Square boss; 2013—Annular boss;

[0034] 2021—Base; 2022—Annular baffle; 2023—Positioning hole;

[0035] 401—Shaft; 402—Permanent magnet; 403—Rotor support; 404—Washer;

[0036] 4031—Mounting position; 4032—Cylindrical boss. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0038] A dual-stator obliquely magnetized axial flux permanent magnet motor, the overall structure of which is as follows: Figure 1 and Figure 2 As shown, the assembly includes a housing 100, a first stator assembly 200, a second stator assembly 300, and a rotor assembly 400. The first stator assembly 200 and the second stator assembly 300 are respectively fastened to the upper and lower end faces of the housing 100, forming an internal space to accommodate the rotor assembly 400. The first stator assembly 200 and the second stator assembly 300 are symmetrically spaced on the upper and lower sides of the rotor assembly 400. When energized, the coils of the first stator assembly 200 and the second stator assembly 300 generate a magnetic field, and the rotor assembly 400 rotates under the action of this magnetic field, driving the shaft 401 to output torque. More specifically, the shaft 401 can pass upward through the first stator assembly 200, or downward through the second stator assembly 300, or simultaneously through both the first stator assembly 200 and the second stator assembly 300.

[0039] In a specific embodiment, the structure of the housing 100 is as follows: Figure 3 As shown, the housing is a square shell with openings at the top and bottom. A through hole 101 is provided on one side of the shell for an external power cable (not shown in the drawing) to pass through. The shape of the through hole 101 matches the external power cable, preferably being circular. The shell 100 mainly mates with the end caps of the first stator assembly 200 and the second stator assembly 300, serving as the outer surface for accommodating the space and providing mechanical protection against collisions. In this invention, the shell and other components such as end caps, outer shells, shafts, bearings, and screws are all made of non-magnetic materials, such as aluminum alloy, stainless steel 201, 304, 316, or injection-molded materials.

[0040] The structure of the first stator assembly 200 is as follows: Figure 4 and Figure 5As shown, the assembly includes an end cap 201, a coil support 202, a coil 203, and a bearing 204. The bottom surface of the coil support 202 is fixed to the end cap 201, and its top surface is fixedly connected to the coil 203, providing a mounting position for the coil 203. The bearing 204 is located in the middle of the coil 203 and is pressed into the end cap 201. In both the first stator assembly 200 and the second stator assembly 300, two concentrically arranged circular coils 203 are used. The two coils 203 are connected in parallel, and the winding directions of the two coils are opposite. When energized, a magnetic field with the same direction is generated on the outside of the smaller second coil and the inside of the larger first coil, which can obtain a larger magnetic field than a single coil in a limited space. To make full use of the limited space inside the housing, preferably, the resistance values ​​of the first coil and the second coil are equal, and the resistance deviation can be controlled within ±5%. When energized, according to the right-hand screw law, the magnetic field generated inside the large coil points upward toward the rotor assembly, the magnetic field generated inside the small coil points downward, and the magnetic field generated outside the small coil points in the opposite direction toward the rotor assembly. At this time, a superimposed magnetic field pointing toward the rotor assembly is generated inside the large coil and outside the small coil. By placing the permanent magnet of the rotor assembly in this magnetic field, a higher torque output can be obtained.

[0041] More specifically, end cap 201, as Figure 6 As shown, the device is made of steel or aluminum and includes an integrally formed cover plate 2011, a square boss 2012, and an annular boss 2013. The square boss 2012 is located above the cover plate 2011, and its perimeter is smaller than that of the cover plate 2011 to form a snap-fit ​​opening for the housing 100. Connecting holes for matching bolts are provided at the four rounded corners, and the annular boss 2013 protrudes from the surface in the center. The outer wall of the annular boss 2013 is used for positioning the coil support 202, and the inner wall is used for mounting the bearing 204. The end cover 201 is used to completely enclose the upper or lower end face of the axial flux permanent magnet motor.

[0042] Coil bracket 202 Figure 7 As shown, the device is integrally injection molded from insulating plastic material, including a base 2021 whose shape matches the square boss 2012, and an annular baffle 2022 protruding from the base 2021. A positioning hole 2023 is provided at the center of the base 2021. The coil support 202 is fitted onto the outer wall of the annular boss 2013 through the positioning hole 2023, and the square boss 2012 is bonded to the bottom of the base 2021. The annular baffle 2022 is used to separate the two coils; the larger coil is bonded to the outside of the annular baffle 2022, and the smaller coil is bonded to the inside of the annular baffle 2022. It should also be noted that, as... Figure 12 As shown, the coil bracket 202 and the end cap 201 can be designed as an integrated unit, in which case the coil bracket 202 and the end cap 201 are fixedly connected.

[0043] During the assembly of the first stator assembly 200, the bearing 204 is first pressed into the annular boss 2013 of the end cover 201, then the positioning hole 2023 of the coil bracket 202 is aligned with the outer wall of the annular boss 2013, then the coil bracket 202 is glued to the square boss 2012, and finally the two coils are glued to both sides of the annular baffle 2022 of the coil bracket 202.

[0044] The first stator assembly 200 and the second stator assembly 300 have the same structure, differing only in their positions, and will not be described again here. It should also be noted that the magnetic field generated inside the large coil of the second stator assembly 300 points towards the rotor assembly, while the magnetic field generated inside the small coil points away from the rotor assembly 400.

[0045] The structure of rotor assembly 400 is as follows Figure 8 and Figure 9 As shown, the assembly includes a rotating shaft 401, a permanent magnet 402, a rotor support 403, and washers 404. The rotating shaft 401 is located at the center of the rotor support 403, with both ends passing through the end faces of the rotor support 403 and fixedly connected to it. More specifically, the rotating shaft 401 and the rotor support 403 are integrally molded by injection molding. The permanent magnet is symmetrically mounted on the rotor support 403. Two washers 404 are fitted onto the outside of the rotating shaft 401 and are located on the upper and lower sides of the rotor support 403, respectively.

[0046] In a specific embodiment, such as Figure 9 As shown, the rotor assembly 400 includes four fan-shaped neodymium iron boron permanent magnets, all identical in shape and size. Each permanent magnet is magnetized at an angle, meaning the magnetization direction forms a certain angle with either the axial or radial direction. More specifically, the angle between the permanent magnet and the axial direction can be 45-60 degrees, and the angle with the radial direction can be 30-45 degrees. The permanent magnets are fixed in the rotor support 403, and the gaps between each permanent magnet are uniform in size and filled with a non-magnetic material.

[0047] The structure of rotor support 403 is as follows Figure 10 As shown, four permanent magnet mounting positions 4031 are formed around the inner side of the housing by partitions. A cylindrical boss 4032 for mounting the rotating shaft 401 is provided in the middle. A through hole is provided in the middle of the cylindrical boss 4032 for mounting the rotating shaft 401. The upper and lower end faces of the cylindrical boss 4032 are used to hold the washer 404.

[0048] During the assembly of rotor assembly 400, the rotor bracket 403 and shaft 401 are first injection molded into a single unit. Then, four permanent magnets are bonded and fixed to the rotor bracket 403, and the gaps are filled with non-magnetic material. Finally, washers are fitted onto the upper and lower ends of shaft 401, completing the assembly. During the overall product assembly, the shaft 401 of rotor assembly 400 is first inserted into the bearing of one of the stator assemblies. Then, the housing 100 is fastened to the stator assembly. Finally, the bearing of the other stator assembly is fitted onto the other end of shaft 401, and the two stator assemblies are secured with four bolts, completing the overall product assembly.

[0049] A cross-sectional view of the dual-stator obliquely magnetized axial flux permanent magnet motor of the present invention is shown below. Figure 11 As shown, in Figure 11 The housing 100, the stator assembly end cover 201, and the coil 202 are omitted. Figure 11 As can be seen, this invention first adopts a dual-stator, single-rotor structural design, symmetrically arranging the stator assemblies on both axial sides of the rotor assembly 400. Each stator assembly employs a dual-coil design, using two concentric coils connected in opposite directions in parallel. This creates a magnetic field inside the smaller inner coil that is opposite to that of the larger inner coil. Simultaneously, a superimposed magnetic field is formed between the outer side of the smaller inner coil and the inner side of the larger inner coil, enhancing the magnetic field strength. When the projection of the permanent magnet in the axial direction falls between the two coils, the superimposed magnetic field can drive the permanent magnet, enabling it to obtain a greater torque output. Furthermore, it should be noted that the resultant axial force of the magnetic fields generated by the two stator assemblies on the rotor assembly when energized should approach zero to avoid vertical vibration of the permanent magnet. This invention uses PWM pulse signals for power supply. When a PWM signal is applied to both stator components, the coils of the stator components generate axial electromagnetic forces. These electromagnetic forces in opposite directions act together on the permanent magnets of the rotor component. Since all four permanent magnets are obliquely magnetized, the electromagnetic forces of the stator components generate a tangential component and an axial component that cancels each other out. The tangential component drives the permanent magnets to rotate, and the permanent magnets in the rotor support drive the shaft to output torque. By adjusting the duty cycle or frequency of the PWM signal, the average current of the input coils can be adjusted, achieving stepless adjustment of the motor speed and torque.

[0050] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dual-stator obliquely magnetized axial flux permanent magnet motor, comprising a housing, characterized in that, It also includes a rotatable rotor assembly and two stator assemblies symmetrically arranged on both sides of the rotor assembly along its axial direction; the rotor assembly includes a permanent magnet that is magnetized at an oblique angle; the stator assembly includes a first coil and a second coil, and when energized, a magnetic field superimposed in the same direction can be generated between the first coil and the second coil to drive the permanent magnet to rotate the rotor assembly.

2. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 1, characterized in that, The stator assembly includes an end cover, a coil support, a first coil, a second coil, and a bearing; the end cover is fixedly connected to the coil support, the bearing is pressed against the middle of the end cover, and the first coil and the second coil are mounted on the coil support; the first coil and the second coil are concentrically arranged, wound in opposite directions, and connected in parallel.

3. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 2, characterized in that, The resistance values ​​of the first coil and the second coil are equal, and the first coil is located outside the second coil.

4. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 2, characterized in that, The end cap includes an integrally formed cover plate, a square boss on the cover plate, and an annular boss protruding from the square boss; the inner wall of the annular boss is connected to the bearing, and the outer wall is connected to the coil bracket.

5. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 4, characterized in that, The coil support is injection molded from insulating material and includes a base adapted to the square boss and an annular baffle protruding from the base; a positioning hole is provided in the center of the base; the first coil is located outside the annular baffle and the second coil is located inside the annular baffle.

6. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 1, characterized in that, The rotor assembly includes a shaft, a permanent magnet, a rotor support, and washers; the shaft is located at the center of the rotor support, the permanent magnet is mounted on the rotor support, and the washers are fitted onto both axial sides of the shaft.

7. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 6, characterized in that, The rotor assembly includes four fan-shaped neodymium iron boron permanent magnets. Each permanent magnet has the same shape and size, and is magnetized at an angle. The four permanent magnets are evenly arranged along the circumference, and the magnetization directions of adjacent permanent magnets are opposite.

8. The dual-stator obliquely magnetized axial flux permanent magnet motor according to claim 7, characterized in that, The inner side of the rotor support forms mounting positions for four permanent magnets through a partition, and a cylindrical boss is provided in the middle.

9. The dual-stator obliquely magnetized axial flux permanent magnet motor according to any one of claims 1-8, characterized in that, The two stator assemblies are fastened to both ends of the housing, together forming a receiving space for accommodating the rotor assembly.

10. A driving method for a dual-stator obliquely magnetized axial flux permanent magnet motor, used to drive the permanent magnet motor according to any one of claims 1-8, characterized in that, The motor speed and torque are controlled by simultaneously inputting PWM signals to the first and second coils of the two stator components through a pulse power supply, and adjusting the duty cycle or frequency of the PWM signals.

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