A kind of stator-rotor unit combined structure, multi-stage series magnetic type axial flux permanent magnet multi-rotor motor

Abstract

The application discloses a stator-rotor unit combined structure and a multi-stage series magnetic type axial flux permanent magnet multi-rotor motor, wherein the multi-stage series magnetic type axial flux permanent magnet multi-rotor motor comprises N rotor output shafts and N stator-rotor unit combined structures arranged in an axial direction; each rotor unit is connected with a different rotor output shaft and has an independent rotating direction and speed; each stator unit comprises a plurality of stator modules, each of which has a stator core and an independent single-phase armature winding; a rotor module is provided with permanent magnets which are magnetized alternately in an axial direction, and the permanent magnets and the stator core form a magnetic flux series connection structure, thereby improving the utilization rate of the permanent magnets, reducing the size and weight of the motor, and improving the torque density and power density of the motor; the multi-stage series magnetic type axial flux permanent magnet multi-rotor motor is suitable for various multi-load systems, such as underwater vehicle propeller propulsion, unmanned aerial vehicle coaxial counter-rotating rotor wing and the like, and has improved system performance and certain fault tolerance.

Description

[0001] This invention relates to the field of novel motor design, and in particular to a multi-stage series-magnetic axial flux permanent magnet multi-rotor motor. Background Technology

[0002] The counter-rotating dual-propeller drive system cancels out the rotational torque generated by the rotating blades, and is widely used in underwater vehicle propeller propulsion and coaxial counter-rotating rotors of UAVs. Traditional implementations of this system have two approaches: one uses two independent conventional motors to drive the front and rear propellers in opposite directions, and the other uses a single high-speed motor with an external mechanical transmission to achieve counter-rotation. The former approach is bulky, costly, and difficult to control; the latter has a complex transmission structure, high mechanical losses, and low efficiency and robustness. Multi-rotor motors, with multiple independent mechanical outputs, are compact, have simple transmission, and offer good economic and environmental benefits. Utilizing multi-rotor motors to directly drive two propellers in opposite directions is a major research direction for future electric propulsion systems with counter-rotating dual propellers and various multi-load systems.

[0003] Currently, research on multi-rotor motors can be categorized into radial flux multi-rotor motors and axial flux multi-rotor motors based on the direction of magnetic flux. Compared to radial flux multi-rotor motors, axial flux multi-rotor motors offer higher torque density and power density, better meeting the application requirements of underwater vehicles. However, traditional axial flux multi-rotor motors have a large outer diameter and short axial length, limiting their application. To overcome the spatial limitations of axial flux permanent magnet multi-rotor motors, a multi-stage coaxial series structure is the only viable option. While multi-stage coaxial structures have been applied in single-load axial flux permanent magnet motors, they often involve simply stacking three-phase axial flux motors axially. Although this reduces the motor's outer diameter, it introduces problems such as magnetic coupling and cross-saturation between the three-phase windings, a risk of short circuits between phase windings, low fault tolerance, and no multi-rotor output structure design has yet emerged.

[0004] Patent 202210965315.4 discloses a single-phase multi-stage coaxial series axial flux permanent magnet motor, including a housing. Inside the housing, at least three single-phase motors are coaxially connected in series. Each single-phase motor has an independent single-phase winding, and the phase difference between adjacent single-phase motors is 120°. This motor avoids interphase mutual inductance and magnetic coupling problems, and reduces cross-saturation between windings. However, since each single-phase motor has an independent magnetic circuit, the motor structure is redundant, resulting in low utilization of permanent magnets and low torque density, further improvements are still needed. Summary of the Invention

[0005] The purpose of this invention is to address the aforementioned problems of existing axial flux permanent magnet multi-rotor motors by disclosing a multi-stage series-connected axial flux permanent magnet multi-rotor motor. This motor contains multiple output shafts and stator / rotor units, with the magnetic circuits connected in series in the axial space. This improves the utilization rate of permanent magnets, reduces motor size and weight, and increases torque density. Compared to existing axial flux multi-rotor motors, the multi-rotor motor proposed in this invention has a smaller outer diameter, higher performance, and a certain degree of fault tolerance. It is suitable for various multi-load systems, such as underwater vehicle propeller propulsion and coaxial counter-rotating rotors of unmanned aerial vehicles.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] In a first aspect, the present invention discloses a stator-rotor unit combination structure, comprising axially arranged stator units and rotor units; the stator unit comprises M (M=2,3,4…) stator modules, and the rotor unit comprises two outer rotor modules and M-1 inner rotor modules; wherein the M-1 inner rotor modules and the M stator modules are alternately superimposed between the two outer rotor modules; each stator module has a stator core and an independent armature winding, and the phase difference between the armature windings of two adjacent stator modules is (360 / M)°. Electrical angle; the outer rotor module has a rotor core, an outer rotor permanent magnet and an outer rotor fixing disk, with the outer rotor permanent magnet arranged on one side of the rotor core; the inner rotor module consists of multiple inner rotor permanent magnets arranged in a single layer and fixed by the inner rotor fixing disk; in the same rotor unit, adjacent permanent magnets in the same rotor module have opposite magnetization directions; the permanent magnets at the same position in different rotor modules have the same axial magnetization direction, and through the stator core and rotor core, they form a magnetic flux series path with the adjacent permanent magnets in the entire axial space of the stator and rotor unit combination.

[0008] In some embodiments, in the same rotor unit, the number of permanent magnets on each outer rotor module and the number of iron cores on each inner rotor module are the same as those on the stator module, which are 2K (K=1,2,3,4,5…).

[0009] In some embodiments, the stator core of the stator module adopts a yokeless structure, and the armature winding adopts a concentrated winding, a distributed winding, or a loop winding; the armature winding coils in the same stator module can be connected in series or in parallel, or connected to the power supply device respectively.

[0010] In some embodiments, in the outer rotor module, the outer rotor permanent magnet is surface-mounted on one side of the rotor core; in the inner rotor module, the inner rotor fixing disk is made of non-magnetic material, the inner rotor permanent magnet has a protruding structure corresponding to the groove in the inner rotor fixing disk, and the inner rotor permanent magnet is embedded in the inner rotor fixing disk.

[0011] Secondly, the present invention discloses a multi-stage series magnet type axial flux permanent magnet multi-rotor motor, including N (N=1,2,3…) rotor output shafts and N stator and rotor unit combination structures arranged axially as described above; wherein, the outer rotor fixing disk in the outer rotor module is used to connect with the rotor output shaft.

[0012] In some embodiments, the innermost rotor output shaft is a solid shaft, while the remaining rotor output shafts are hollow shafts. The rotor output shafts are coaxially arranged by bearing connections. Each rotor output shaft is rigidly connected to a different rotor unit, and each rotor output shaft has an independent rotational speed and direction.

[0013] In some embodiments, the rotor core and stator core may be formed by stacking and casting silicon steel sheets, and the inner rotor fixing disk and the outer rotor fixing disk may be formed by epoxy resin casting.

[0014] In some embodiments, the N stator-rotor unit combination structures each have M1, M2…M N Each stator module in the stator-rotor unit assembly has 2K1, 2K2, 2K3…2K modules. N (K1,K2,K3…K N =1,2,3…) permanent magnets; the armature windings on two adjacent stator modules in the same stator-rotor unit combination are 360° out of phase by (M1,M2…M…M…) N Electrical angle.

[0015] In some embodiments, when the armature windings of multiple stator units share a single inverter drive, each rotor output shaft can rotate in the same or opposite direction. When the armature windings in different stator units are connected in series and parallel, the corresponding phase sequence of the armature windings of different stator units is reversed in series and parallel, or the phase sequence of two phases of the stator unit armature windings is exchanged and connected in series or parallel with other stator unit armature windings to achieve reverse rotation. At the same time, changing the number of permanent magnets on the rotor module and the number of iron cores on the stator module in each stator-rotor unit combination (2K) can respectively achieve different speed rotation of each rotor output shaft. When the armature windings of different stator units are connected to different power supply devices, the output direction and speed of each rotor output shaft can be adjusted independently.

[0016] Compared with the prior art, the beneficial effects of the present invention are:

[0017] 1. In this invention, multiple stator unit armature windings can share a single inverter drive to achieve the same or opposite rotation of each rotor output shaft. Furthermore, by changing the motor structure, the same speed or different speeds can be achieved. The single-port control system is simple and easy to implement.

[0018] 2. In this invention, each stator module is wound with only a single-phase winding. Since each stator winding is independent of the others, the problem of short circuit between windings is avoided, giving the motor a certain fault tolerance. Each stator module is axially arranged, and the adjacent stator modules are separated by an electrical angle of (360 / M)°, forming a rotating magnetomotive force. The torque waves obtained by each rotor module in the same rotor unit are superimposed to obtain the required torque.

[0019] 3. The magnetic flux series structure used in this invention allows the magnetic flux to flow through two adjacent columns of permanent magnets to form N series magnetic circuits in the entire axial space of the motor. Each stator unit and rotor unit combination, compared with the existing multi-stage coaxial axial flux motor, reduces the amount of permanent magnets and iron cores, shortens the axial length of the motor and the overall mass of the motor, and reduces the iron loss of the motor while keeping the motor performance basically unchanged, thereby achieving higher permanent magnet utilization and torque density.

[0020] 4. Compared with traditional three-phase axial flux permanent magnet motors, the motor has higher torque density and power density, and smaller outer diameter; compared with existing multi-stage coaxial axial flux permanent magnet motors, the motor's torque density and power density have also been further improved, and the axial length has been reduced, making it applicable to more installation scenarios. Attached Figure Description

[0021] The accompanying drawings, as part of this invention, are provided to further illustrate the invention. The illustrative embodiments and descriptions of the invention are used to explain the invention, but do not constitute an undue limitation thereof. Clearly, the drawings described below are merely some embodiments, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0022] In the attached diagram:

[0023] Figure 1 This is a schematic diagram of the stator and rotor unit combination structure of the present invention;

[0024] Figure 2 This is a schematic diagram of the stator unit structure of the present invention;

[0025] Figure 3 This is a perspective view of the stator module structure of the present invention;

[0026] Figure 4 This is a schematic diagram of the rotor unit structure of the present invention;

[0027] Figure 5 This is a schematic diagram of the inner rotor module structure of the present invention;

[0028] Figure 6 This is a schematic diagram of the main magnetic circuit of the stator and rotor unit combination structure of the present invention;

[0029] Figure 7 This is a three-dimensional schematic diagram of the multi-stage series magnet type axial flux permanent magnet multi-rotor motor of the present invention;

[0030] Figure 8 This is a side view schematic diagram of the multi-stage series magnet type axial flux permanent magnet multi-rotor motor of the present invention;

[0031] The markings in the diagram are: 1-stator module, 11-stator core, 12-armature winding, 2-outer rotor module, 21-rotor core, 22-outer rotor mounting plate, 23-outer rotor permanent magnet, 3-inner rotor module, 31-inner rotor mounting plate, 32-inner rotor permanent magnet, 4-first rotor output shaft, 5-second rotor output shaft.

[0032] It should be noted that these accompanying drawings and textual descriptions are not intended to limit the scope of the invention in any way, but rather to illustrate the concept of the invention to those skilled in the art by referring to specific embodiments. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below with reference to the accompanying drawings. The following embodiments are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0034] In the description of this invention, it should be noted that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0036] The purpose of this invention is to address the aforementioned problems of existing multi-rotor motors by disclosing a stator-rotor unit combination structure that connects the magnetic circuits in series throughout the axial space of the motor, thereby improving the utilization rate of permanent magnets, reducing the outer diameter and weight of the motor, and increasing the torque density of the motor.

[0037] A stator-rotor unit combination structure includes axially arranged stator units and rotor units; the stator unit includes M (M=2,3,4…) stator modules, and the rotor unit includes two outer rotor modules and M-1 inner rotor modules; wherein, the M-1 inner rotor modules and the M stator modules are interleaved and superimposed between the two outer rotor modules; each stator module has a stator core and an independent armature winding, and the phase difference between two adjacent armature windings is (360 / M)° electrical angle, forming a rotating magnetomotive force; The outer rotor module has a rotor core, an outer rotor permanent magnet, and an outer rotor fixing disk. The outer rotor permanent magnet is arranged on one side of the rotor core. The inner rotor module has multiple inner rotor permanent magnets arranged in a single layer and fixed by the inner rotor fixing disk. In the same rotor unit, the magnetization directions of adjacent permanent magnets in the same rotor module are opposite. The magnetization directions of permanent magnets at the same position in different rotor modules are consistent in the axial direction. Through the stator core and the rotor core, they form a magnetic flux series path with the permanent magnets at adjacent positions in the entire axial space of the stator and rotor unit combination.

[0038] In a further proposed scheme, within the same rotor unit, the number of permanent magnets on each outer rotor module and inner rotor module is the same as the number of iron core teeth on the stator module, both being 2K (K=1,2,3,4,5…).

[0039] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the embodiment, the motor has M=3 and K=5, that is, there are ten permanent magnets arranged on one rotor module and ten windings on one stator module.

[0040] like Figure 1 As shown, this embodiment discloses a stator-rotor unit combination structure, including a stator unit and a rotor unit. Figure 2 As shown, the stator unit consists of three stator modules 1 with identical structures, each stator module having the following structure: Figure 3 As shown, it includes a stator core 11 and independent armature windings 12. The stator core 11 adopts a yokeless structure. The phase difference between two adjacent armature windings 12 is 120° electrical degrees. The windings in the same stator module 1 can be connected in series or in parallel. The three stator windings are A-phase winding, B-phase winding, and C-phase winding, respectively, and three-phase current is passed through them. Since the three stator windings are independent of each other, the short circuit problem between windings is avoided, so that the motor has a certain fault tolerance.

[0041] like Figure 4 As shown, the rotor unit includes two outer rotor modules 2 and two inner rotor modules 3. The outer rotor module 2 includes a rotor core 21, an outer rotor permanent magnet 23, and an outer rotor mounting plate 22. The outer rotor permanent magnet 23 is surface-mounted to one side of the rotor core 21. The structure diagram of the inner rotor module is shown below. Figure 5As shown, the motor includes an inner rotor mounting plate 31 and inner rotor permanent magnets 32. The inner rotor mounting plate 31 is made of a non-magnetic material, reducing the weight of the motor. Each inner rotor permanent magnet 32 ​​has a protruding structure during manufacturing, and the corresponding inner rotor mounting plate 31 has grooves for fixing the inner rotor permanent magnets 32. The four rotor modules of the motor are coaxially mounted.

[0042] Figure 6 This is a magnetic circuit diagram of the stator-rotor unit combination structure of the present invention. All permanent magnets in the present invention are axially magnetized. As can be seen in the diagram, in the inner rotor module 3 and the outer rotor module 2, adjacent permanent magnets in the same rotor unit have opposite magnetization directions; permanent magnets at the same position in different rotor units have the same axial magnetization direction, forming a magnetic flux series path with adjacent permanent magnets throughout the entire axial space of the motor through the stator core 11, the air gap, and the rotor core 21. Compared with the traditional multi-stage coaxial axial flux permanent magnet motor structure, the present invention shortens the axial length of the motor, improves the utilization rate of permanent magnets, and increases the torque density and power density of the motor.

[0043] In different embodiments, the present invention can optimize numerous parameters. While keeping other structures unchanged, the armature winding can also adopt a distributed winding and a loop winding structure, which can improve the air gap magnetic flux density amplitude and sinusoidal intensity, and simplify the motor winding process. Other parameters that can be optimized include the axial length of the stator and rotor cores and permanent magnets, the inner and outer diameters of the motor, the materials used for each component, and the pole arc coefficient of the permanent magnets. Therefore, the design is flexible in terms of volume and weight, and there is a large space for structural optimization.

[0044] This invention is applicable to three-phase or multi-phase motor topologies, such as five-phase motors and six-phase motors. It can be achieved simply by adjusting the number of stator modules and rotor modules along the axial direction, as well as the electrical angle difference between adjacent stator modules. In applications with long axial lengths, three-phase motors in multiple embodiments can be connected in series coaxially to obtain greater output power and output torque.

[0045] The following are application examples of the above embodiments regarding the stator-rotor unit combination structure:

[0046] To address the aforementioned problems of existing multi-rotor motors, this invention discloses a multi-stage series-magnetic axial flux permanent magnet multi-rotor motor. It adopts a multi-stage coaxial series-magnetic structure, which connects the magnetic circuits in series throughout the axial space of the motor, thereby improving the utilization rate of permanent magnets, reducing the outer diameter and weight of the motor, and increasing the torque density of the motor.

[0047] A multi-stage series-magnetic axial flux permanent magnet multi-rotor motor includes N (N=1,2,3…) rotor output shafts and N stator and rotor unit combinations arranged axially. Each stator unit includes M (M=2,3,4…) stator modules, each with a stator core and an independent armature winding. The phase difference between adjacent armature windings is (360 / M)° electrical angle. Each rotor unit includes two outer rotor modules and (M-1) inner rotor modules. Each outer rotor module has a rotor core, an outer rotor mounting plate, and outer rotor permanent magnets, with the outer rotor permanent magnets arranged on one side of the rotor core. Each inner rotor module has multiple inner rotor permanent magnets arranged in a single layer, fixed by the inner rotor mounting plate. In the same rotor unit, adjacent permanent magnets in the same rotor module are magnetized in opposite directions, while permanent magnets at the same position in different rotor modules are magnetized in the same direction. Through the motor core and adjacent permanent magnets, N series-magnetic paths are formed throughout the entire axial space of the motor.

[0048] In a further design, the innermost rotor output shaft is a solid shaft, while the remaining rotor output shafts are hollow shafts. The rotor output shafts are coaxially arranged via bearing connections. Each rotor output shaft is rigidly connected to a different rotor unit, and each rotor output shaft has independent rotational speed and direction. The number of permanent magnets on each rotor module within the same rotor unit is the same as the number of iron cores on the corresponding stator module. The number of permanent magnets on the rotor modules in the N rotor units are 2K1, 2K2, 2K3…2K… N (K1,K2,K3…K N =1,2,3…) items.

[0049] A further solution involves allowing independent adjustment of the output direction and speed of each rotor output shaft when the armature windings in different stator units are connected to different power supply devices. When the armature windings in different stator units are connected in series or parallel, this can be achieved by reversing the phase sequence of the corresponding phases of the armature windings, or by exchanging the phase sequence of two phases of one stator unit's armature winding with other stator unit armature windings in series or parallel. Simultaneously, the phases 2K1, 2K2, 2K3…2K can be changed. N This allows each rotor output shaft to rotate at a different speed.

[0050] A further proposed solution is that the multi-stage series-magnetic axial flux permanent magnet multi-rotor motor can be used as both a motor and a generator.

[0051] The present invention will be further described below with reference to the accompanying drawings and embodiments. The embodiment motor has N=2, M=3, K1=5, K2=5, that is, a three-phase dual-rotor output structure, and each rotor module has ten permanent magnets arranged on it, and each stator module has ten stator cores.

[0052] like Figure 7 , Figure 8 As shown, this embodiment discloses a multi-stage series magnet type axial flux permanent magnet multi-rotor motor, including a first rotor output shaft 4 and a second rotor output shaft 5, as well as two sets of stator and rotor unit structures arranged axially; the first rotor output shaft 4 is a hollow shaft, and the second rotor output shaft 5 is installed in the first rotor output shaft 4 through bearings and is arranged coaxially with the first rotor output shaft 4.

[0053] Each stator and rotor unit combination structure is as follows: Figure 1 As shown, each unit includes a stator unit and a rotor unit. The two rotor units are rigidly connected to the first rotor output shaft 4 and the second rotor output shaft 5, respectively. The structure of each stator unit is as follows: Figure 2 As shown, it consists of three identical stator modules 1, each with the following structure: Figure 3 As shown, it includes a stator core 11 and independent armature windings 12. The stator core 11 adopts a yokeless structure, and the phase difference between two adjacent windings is 120° electrical angle. The winding coils in the same stator module 1 can be connected in series or in parallel. The armature windings in the three stator modules 1 are phase A winding, phase B winding, and phase C winding, respectively, and three-phase current is passed through them. Since the three stator windings are independent of each other, the short circuit problem between windings is avoided, so that the motor has a certain fault tolerance.

[0054] The rotor unit in the motor in the embodiment is as follows Figure 4 As shown, each rotor unit includes two outer rotor modules 2 and two inner rotor modules 3. The outer rotor module 2 includes a rotor core 21, an outer rotor mounting plate 22, and an outer rotor permanent magnet 23. The outer rotor permanent magnet 23 is surface-mounted to one side of the rotor core 21 and then connected to the rotor output shaft via the outer rotor mounting plate 22. The structure diagram of the inner rotor module is shown below. Figure 5 As shown, the motor includes an inner rotor fixing disk 31 and an inner rotor permanent magnet 32. The inner rotor fixing disk 31 is made of non-magnetic material, which reduces the weight of the motor. The inner rotor permanent magnet 32 ​​has a protruding structure during manufacturing, and the corresponding inner rotor fixing disk 31 has a groove for fixing the inner rotor permanent magnet 32.

[0055] Figure 6This is a diagram showing the main magnetic circuit of a single stator and rotor unit in the multi-stage series-magnetic axial flux permanent magnet multi-rotor motor of this invention. In this invention, all permanent magnets in the motor are axially magnetized. As shown in the diagram, in the inner rotor module 3 and the outer rotor module 2, adjacent permanent magnets in the same rotor module have opposite magnetization directions; permanent magnets at the same position in different rotor modules have the same axial magnetization direction, forming a series magnetic flux path with adjacent permanent magnets throughout the entire axial space of the motor via the stator core 11 and the rotor core 21. Compared to the traditional multi-stage coaxial axial flux permanent magnet motor structure, this invention shortens the axial length of the motor, improves the utilization rate of permanent magnets, and increases the torque density and power density of the motor.

[0056] In different embodiments, the present invention can optimize numerous parameters. While keeping other structures unchanged, the armature winding can also adopt a distributed winding and a loop winding structure, which can improve the air gap magnetic flux density amplitude and sinusoidal intensity, and simplify the motor winding process. Other parameters that can be optimized include the axial length of the stator and rotor cores and permanent magnets, the inner and outer diameters of the motor, the materials used for each component, and the pole arc coefficient of the permanent magnets. Therefore, the design is flexible in terms of volume and weight, and there is a large space for structural optimization.

[0057] This invention is applicable to three-phase or multi-phase motor topologies, such as five-phase motors and six-phase motors. It can be achieved simply by adjusting the number of stator modules M and the electrical angle difference between adjacent stator modules. This invention is also applicable to multi-load applications, which can be achieved simply by adjusting the number of shafts N and the number of axially arranged stator and rotor unit structures.

[0058] Numerous specific details are set forth in the specification provided herein. However, it will be understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures, and techniques have not been shown in detail so as not to obscure the understanding of this specification.

[0059] Furthermore, those skilled in the art will understand that although some embodiments described herein include certain features found in other embodiments but not others, combinations of features from different embodiments are also within the scope of protection of this invention and form different embodiments. For example, in the embodiments described above, those skilled in the art can use them in combination based on known technical solutions and the technical problems to be solved by this application.

[0060] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-described technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A stator-rotor unit combination structure, characterized in that: It includes stator units and rotor units arranged axially; The stator unit includes M stator modules, M=2,3,4…, and the rotor unit includes two outer rotor modules and M-1 inner rotor modules; wherein the M-1 inner rotor modules and the M stator modules are interleaved and superimposed between the two outer rotor modules. Each of the stator modules has a stator core and an independent armature winding, and the phase difference between the armature windings of two adjacent stator modules is (360 / M)° electrical angle. The outer rotor module has a rotor core, an outer rotor permanent magnet, and an outer rotor fixing disk, with the outer rotor permanent magnet arranged on one side of the rotor core; the inner rotor module consists of multiple inner rotor permanent magnets arranged in a single layer and fixed by the inner rotor fixing disk. In the same rotor unit, the magnetization directions of adjacent permanent magnets in the same rotor module are opposite; the magnetization directions of permanent magnets at the same position in different rotor modules are consistent in the axial direction. Through the stator core and rotor core, they form a magnetic flux series path with the permanent magnets at adjacent positions in the entire axial space of the stator and rotor unit combination.

2. The stator-rotor unit combination structure according to claim 1, characterized in that: In the same rotor unit, the number of permanent magnets on each outer rotor module and the number of iron cores on each inner rotor module are the same as those on the stator module, both being 2K, where K=1,2,3,4,5… 3. The stator-rotor unit combination structure according to claim 1, characterized in that: The stator core of the stator module adopts a yokeless structure, and the armature winding adopts a concentrated winding, distributed winding, or loop winding; the armature winding coils in the same stator module can be connected in series or in parallel, or connected to the power supply device respectively.

4. The stator-rotor unit combination structure according to claim 1, characterized in that: In the outer rotor module, the outer rotor permanent magnet is surface-mounted on one side of the rotor core; in the inner rotor module, the inner rotor fixing plate is made of non-magnetic material, the inner rotor permanent magnet has a protruding structure corresponding to the groove in the inner rotor fixing plate, and the inner rotor permanent magnet is embedded in the inner rotor fixing plate.

5. A multi-stage series-magnetic axial flux permanent magnet multi-rotor motor, characterized in that: The structure comprises N rotor output shafts and N stator and rotor units as described in any one of claims 1 to 4 arranged axially, where N = 1, 2, 3...; wherein the outer rotor fixing disk in the outer rotor module is used to connect to the rotor output shaft.

6. A multi-stage series-magnetic axial flux permanent magnet multi-rotor motor according to claim 5, characterized in that: The innermost rotor output shaft is a solid shaft, while the remaining rotor output shafts are hollow shafts. The rotor output shafts are connected by bearings to achieve coaxial arrangement. Each rotor output shaft is rigidly connected to a different rotor unit, and each rotor output shaft has an independent rotation speed and direction.

7. A multi-stage series-magnetic axial flux permanent magnet multi-rotor motor according to claim 5, characterized in that: The rotor core and stator core can be formed by stacking and casting silicon steel sheets, and the inner rotor fixing plate and the outer rotor fixing plate can be formed by epoxy resin casting.

8. A multi-stage series-magnetic axial flux permanent magnet multi-rotor motor according to claim 5, characterized in that: The N stator and rotor unit combination structures each have M1, M2...M N Each stator module in the stator-rotor unit assembly has 2K1, 2K2, 2K3…2K modules. N There are three permanent magnets, K1, K2, K3…K. N =1,2,3…;The armature windings on two adjacent stator modules in the same stator-rotor unit combination are 360° out of phase by (M1,M2…M…M…) N Electrical angle.

9. A multi-stage series-magnetic axial flux permanent magnet multi-rotor motor according to claim 5, characterized in that: When the armature windings of multiple stator units share a single inverter drive, each rotor output shaft can rotate in the same or opposite direction. When the armature windings in different stator units are connected in series and parallel, reverse rotation can be achieved by connecting the corresponding phase sequences of the armature windings of different stator units in reverse series and parallel, or by exchanging the phase sequence of two phases of the stator unit armature windings and connecting them in series or parallel with other stator unit armature windings. At the same time, changing the number of permanent magnets on the rotor module and the number of iron cores on the stator module in each stator-rotor unit combination (2K) can achieve different rotation speeds for each rotor output shaft. When the armature windings of different stator units are connected to different power supply devices, the output direction and speed of each rotor output shaft can be adjusted independently.

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