Design method of back iron-free squirrel cage type permanent magnet coupling

Abstract

The application belongs to the technical field of permanent magnet transmission, and discloses a design method of a back-iron-free squirrel-cage type permanent magnet coupling. The permanent magnet installed in the squirrel-cage type hub is wrapped around; one pair of magnetic pole surfaces of the permanent magnet is exposed in the air domain, torque can be synchronously transmitted, and the utilization rate of the permanent magnet is improved; the squirrel-cage type hub does not need a back-iron structure, the weight of the hub can be reduced, and the overall design size of the permanent magnet coupling can be reduced; and the squirrel-cage type hub structure is more stable, can not only absorb the impact force generated when the collision between rotors occurs, but also can be used with an aluminum sleeve to prevent the permanent magnet from being thrown out due to centrifugal force and radial adsorption force during the operation of the permanent magnet coupling; in addition, the torque, radial eccentric load, axial force, magnetic circuit topology structure, torque density and mass of the back-iron-free squirrel-cage type permanent magnet coupling can be used as optimization targets, the best parameter group is obtained through correlation analysis of key parameters, the performance iteration upgrade of the permanent magnet coupling is completed, and the back-iron-free squirrel-cage type permanent magnet coupling has high engineering universality and application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of permanent magnet transmission, and relates to a design method of a back-iron-free squirrel-cage type permanent magnet coupling. BACKGROUND

[0002] As an important component of a marine transmission system, a permanent magnet coupling plays a key role in connecting a driving end and a load end, and is the only guarantee for stable and efficient transmission of power and torque of the marine transmission system. Compared with a contact type coupling, the permanent magnet coupling can utilize the magnetic field air gap and the proportion of magnetic steel to play the functions of torque adjustment, non-contact vibration isolation, overload protection, etc. while transmitting power and torque. In the existing permanent magnet coupling configuration library, the "double-layer cylinder type" configuration has a simple structure, that is, a group of magnetic steel arrays are distributed on the inner rotor hub and the outer rotor hub respectively, and the hub adopts a "inverted trapezoidal" or "dove tail" slot design scheme to limit the degrees of freedom of the permanent magnet. At this time, the permanent magnet has only one magnetic pole surface to play a role in transmitting torque, and the magnetic field air gap between the magnetic steel arrays is usually small, which has problems such as easy radial eccentric load and insufficient torque transmission capacity. In view of the requirements of anti-eccentric load and high torque density transmission, the permanent magnet coupling configuration is iterated to a "multi-layer nested cylinder type" structure, that is, the inner rotor and the outer rotor are respectively provided with multiple hubs, the hubs of each layer are staggered and nested, and one or two groups of magnetic steel arrays are distributed on the surface to transmit torque. Taking the "six-layer nested cylinder type" structure as an example, the inner rotor and the outer rotor are respectively provided with two hubs, one group of magnetic steel arrays is distributed on the inner circle hub of the inner rotor and the outer circle hub of the outer rotor respectively, and two groups of magnetic steel arrays are distributed on the inner and outer surfaces of the outer circle hub of the inner rotor and the inner circle hub of the outer rotor respectively. Each layer of hub adopts a "dove tail" slot design scheme to limit the degrees of freedom of the permanent magnet, and the permanent magnet also has only one magnetic pole surface to play a role in transmitting torque. With the increase of the number of hubs and magnetic steel arrays, the "multi-layer nested cylinder type" structure can ensure that the magnetic field air gap between the magnetic steel arrays is not less than 1 cm under the premise of meeting the large torque transmission capacity, effectively reducing the radial eccentric load, and ensuring the stability of the transmission performance of the permanent magnet coupling. However, in order to ensure the structural stability, the use amount of hubs and magnetic steels needs to be increased, and the size of the permanent magnet coupling needs to be enlarged, thereby increasing the working burden of the sliding bearing for supporting the inner and outer rotors of the permanent magnet coupling, causing heating of the marine transmission system and wear of the sliding bearing bush. It is urgent to design a lightweight permanent magnet coupling under the premise of ensuring the magnetic field and transmission performance, reduce the manufacturing cost of the permanent magnet coupling, and improve the torque density of the permanent magnet coupling. Therefore, the development of a back-iron-free squirrel-cage type permanent magnet coupling which takes into account the quality, space utilization rate, torque density and structural stability can provide important theoretical support for the configuration optimization and performance improvement of the permanent magnet coupling.

[0003] For the no back iron type squirrel cage permanent magnet coupling, Huang Zhunen, Han Libiao, etc. in the patent "a cylinder type permanent magnet coupling" (CN 109361306 A) use permanent magnet, permanent magnet tray and sleeve structure to design a permanent magnet coupling which can isolate the vibration of load end and driving end. The labyrinth groove on the permanent magnet tray can effectively isolate metal dust. However, the space utilization of this structure is low, it cannot realize axial displacement compensation, and the synchronous transmission between rotors depends on the positioning shaft. Due to the limited size of the ring hole matched with it, overload protection cannot be realized. In 2024, Sun Wei of Shenyang University of Technology in his master's degree thesis "structure design and offset analysis of permanent magnet coupling" aimed to improve the transmission performance of permanent magnet coupling, constructed a torque transmission analytical model, and based on the traditional structure, proposed double layer, three layer and four layer permanent magnet innovative structure, and optimized the key design parameters. However, the paper only carries out principle research and does not mention the specific implementation route of the installation method of permanent magnet in the innovative structure and the design of hub structure, and the permanent magnets on the same hub are closely attached, which cannot realize the magnetic circuit topology and torque adjustment. Therefore, it is necessary to design a no back iron type squirrel cage permanent magnet coupling. SUMMARY

[0004] The present application is to make up for the shortcomings of the prior art, and a no back iron type squirrel cage permanent magnet coupling is invented. The purpose is to meet the design requirements of lightweight, small size and high torque density, to use COMSOL simulation software to build a no back iron type squirrel cage permanent magnet coupling magnetic field and transmission performance analysis model, to optimize the existing configuration characteristics and process, to reduce the quality and manufacturing cost while improving the torque density, and finally to complete the design, processing and assembly, and to serve in complex operating environments such as low speed, heavy load and limited operating space, to provide important technical support for the optimization of magnetic field and transmission performance of permanent magnet coupling.

[0005] The technical scheme of the present application is as follows:

[0006] A design method of a no back iron type squirrel cage permanent magnet coupling, the design steps are as follows:

[0007] First step, determine the configuration and key parameters of the no back iron type squirrel cage permanent magnet coupling;

[0008] The inner rotor and the outer rotor are respectively provided with two hubs, and there are four layers in total; dovetail-shaped notches are formed on the inner layer hub of the inner rotor and the outer layer hub of the outer rotor, and a group of magnetic steel arrays are distributed in the dovetail-shaped notches of the inner layer hub of the inner rotor and the outer layer hub of the outer rotor; the outer layer hub of the inner rotor and the inner layer hub of the outer rotor are of a squirrel-cage structure, and inverted-trapezoidal notches are arranged to penetrate the inner and outer surfaces of the outer layer hub of the inner rotor and the inner layer hub of the outer rotor, so that the pair of magnetic pole surfaces of the permanent magnet are all exposed in the magnetic field air gap, and only the non-magnetic pole surface is in contact with the hub; part of the area between the dovetail-shaped notches, between the inverted-trapezoidal notches, and at the end faces of the inner layer hub of the inner rotor, the outer layer hub of the outer rotor, the outer layer hub of the inner rotor and the inner layer hub of the outer rotor is reserved for limiting the tangential and axial degrees of freedom of the permanent magnet and connecting the end cover; when the permanent magnet is completely embedded in the outer layer hub of the inner rotor and the inner layer hub of the outer rotor, the pair of magnetic pole surfaces of the permanent magnet are coplanar with the inner and outer surfaces of the outer layer hub of the inner rotor and the inner layer hub of the outer rotor respectively, and the radial degree of freedom of the permanent magnet is limited by the non-magnetic aluminum sleeve;

[0009] The key parameters that determine the torque transmission capacity of the non-back iron type squirrel-cage permanent magnet coupling include the radial magnetic field air gap airgap_r, the permanent magnet length PM_l, the outer rotor inner layer permanent magnet thickness PM_t_1o, the outer rotor outer layer permanent magnet thickness PM_t_2o, the inner rotor inner layer permanent magnet thickness PM_t_1i, the inner rotor outer layer permanent magnet thickness PM_t_2i, the permanent magnet residual magnetic flux density Br, the number of permanent magnets PM_num and the boss width tutai_a.

[0010] Second step, construct the magnetic field and transmission performance analysis model of the non-back iron type squirrel-cage permanent magnet coupling;

[0011] Import the key parameters into the COMSOL software and construct the three-dimensional model of the non-back iron type squirrel-cage permanent magnet coupling, then give the material properties of each structure of the non-back iron type squirrel-cage permanent magnet coupling and determine the magnetization model of each structure of the non-back iron type squirrel-cage permanent magnet coupling, and then solve the transmission torque of each layer of magnetic steel array of the non-back iron type squirrel-cage permanent magnet coupling after refining the grid of the three-dimensional model of the non-back iron type squirrel-cage permanent magnet coupling.

[0012] Third step, optimize the structure of the non-back iron type squirrel-cage permanent magnet coupling considering the processing and assembly process;

[0013] In combination with the processing and assembly process requirements, the structure of the non-back iron type squirrel-cage permanent magnet coupling is optimized by means of SOLIDWORKS software, including splitting the structure, reserving the stopper, adding the boss, and setting the chamfer and round corner;

[0014] First, the inner rotor is divided into an inner rotor end cover, a distance block, an inner rotor inner layer hub, an inner rotor inner layer magnetic steel array, an inner rotor gland, an inner rotor inner layer aluminum sleeve, an inner rotor outer layer hub, an inner rotor outer layer magnetic steel array, and an inner rotor outer layer aluminum sleeve; then the outer rotor is divided into an outer rotor gland, an outer rotor outer layer magnetic steel array, an outer rotor outer layer hub, an outer rotor outer layer aluminum sleeve, an outer rotor inner layer magnetic steel array, an outer rotor inner layer aluminum sleeve, an outer rotor inner layer hub, and an outer rotor end cover; after that, a boss is additionally provided at the connection between the inner rotor end cover and the inner rotor inner layer hub and the inner rotor outer layer hub, and at the connection between the outer rotor end cover and the outer rotor outer layer hub and the outer rotor inner layer hub; all the structural edges in the back-iron-free squirrel-cage type permanent magnet coupling are provided with round corners and chamfers; the inner rotor end cover is provided with an axial jackscrew hole, and the outer rotor gland and the outer rotor end cover are provided with radial jackscrew holes, so as to facilitate the adjustment of the radial magnetic field air gap between the inner rotor and the outer rotor during assembly until the radial magnetic field air gap is uniformly distributed in the circumferential direction.

[0015] Fourth step, calculate the minimum allowable diameter of the connecting piece in combination with the maximum torque value;

[0016] After the inner rotor and the outer rotor are divided, the inner rotor and the driving end, the outer rotor and the load end, the inner rotor end cover and the inner rotor inner layer hub, the inner rotor end cover and the inner rotor outer layer hub, the outer rotor end cover and the outer rotor outer layer hub, and the outer rotor end cover and the outer rotor inner layer hub are connected by screws and cylindrical pins respectively; during torque transmission, the screws only play a connecting and fastening role by default, and the torque is entirely borne by the cylindrical pins as connecting pieces; the cylindrical pin connection strength calculation formula is:

[0017]

[0018] Wherein: τ is the actual shear stress of the cylindrical pin, MPa; F is the actual shear force borne by the cylindrical pin, N; d is the diameter of the cylindrical pin, mm; Z is the number of cylindrical pins, τ p is the allowable shear stress of the cylindrical pin, τ p = 80 MPa;

[0019] After transformation, the minimum allowable diameter calculation formula of the cylindrical pin is:

[0020]

[0021] Wherein, i is the number of the position of the cylindrical pin, i = 1, 2, 3, 4, 5, i = 1 represents the inner rotor end cover interface, i = 2 represents the inner rotor end cover and the inner rotor inner hub connection, i = 3 represents the inner rotor end cover and the inner rotor outer hub connection, i = 4 represents the outer rotor end cover and the outer rotor inner hub connection, i = 5 represents the outer rotor end cover and the outer rotor outer hub connection, the torque transmitted at the outer rotor end cover interface is consistent with that at the inner rotor end cover, and the same cylindrical pin is used; d i is the minimum allowable diameter of the cylindrical pin used at i, T i is the actual torque borne by the cylindrical pin at i, Z i is the number of cylindrical pins used at i; R i is the rotary radius of the cylindrical pin used at i.

[0022] Fifth step, complete the processing and assembly of the back iron-free squirrel cage type permanent magnet coupling;

[0023] The inner rotor inner layer magnetic steel array and the inner rotor inner hub are matched through dovetail-shaped notches, one side is connected with the inner rotor gland through a screw, and the other side is matched with the distance block through a stopper, and is connected with the inner rotor end cover through a screw and a cylindrical pin; the inner rotor outer hub is matched with the inner rotor outer layer magnetic steel array through an inverted trapezoidal notch, and then is connected with the inner rotor end cover through a screw and a cylindrical pin; the inner rotor inner layer aluminum sleeve and the inner rotor outer layer aluminum sleeve are respectively sleeved on the inner surface and the outer surface of the inner rotor outer hub, and the inner rotor is assembled; the outer rotor inner hub is matched with the outer rotor inner layer magnetic steel array through an inverted trapezoidal notch, and then is connected with the outer rotor end cover through a screw and a cylindrical pin; the outer rotor outer layer magnetic steel array and the outer rotor outer hub are matched through dovetail-shaped notches, one side is connected with the outer rotor gland through a screw, and the other side is connected with the outer rotor end cover through a screw and a cylindrical pin; the outer rotor inner layer aluminum sleeve and the outer rotor outer layer aluminum sleeve are respectively sleeved on the inner surface and the outer surface of the outer rotor inner layer hub, and the outer rotor is assembled; the inner rotor and the outer rotor are folded, the axial jackscrew on the inner rotor end cover is adjusted until the outer end surface of the inner rotor end cover is coplanar with the outer end surface of the outer rotor gland, the radial jackscrew on the outer rotor gland and the outer rotor end cover is used to adjust the magnetic field air gap, and at the same time, it is ensured that the interfaces reserved for the inner rotor end cover and the outer rotor end cover correspond to each other along the axial direction and keep consistent with the magnetization direction of the permanent magnets distributed along the radial direction of the back iron-free squirrel cage type permanent magnet coupling, and the axial jackscrew and the radial jackscrew are locked.

[0024] Further, the torque, the radial eccentric load, the axial force, the magnetic circuit topology, the torque density and the mass of the back iron-free squirrel cage type permanent magnet coupling can be used as optimization targets, the best key parameter group is obtained through correlation analysis of key parameters, and the performance iteration upgrade of the back iron-free squirrel cage type permanent magnet coupling is completed.

[0025] Further, the inner rotor inner layer hub, the inner rotor outer layer hub, the outer rotor outer layer hub and the outer rotor inner layer hub are made of 45 steel and are formed by wire cutting processing; the permanent magnet is made of neodymium iron boron N50; the inner rotor inner layer aluminum sleeve, the inner rotor outer layer aluminum sleeve, the outer rotor outer layer aluminum sleeve and the outer rotor inner layer aluminum sleeve are made of 6061 aluminum alloy.

[0026] The no-back iron type squirrel cage permanent magnet coupling has the following advantages: the permanent magnet installed in the squirrel cage hub is wrapped around, most of the magnetic force lines flow through the air domain from the magnetic pole surface according to the parallel magnetic circuit principle, the local lateral diffusion magnetic force lines are collected by the hub and finally converge to the magnetic pole surface, the air domain magnetic field strength is further strengthened; one pair of magnetic pole surfaces of the permanent magnet are exposed in the air domain, the torque can be synchronously transmitted, the utilization rate of the permanent magnet is improved; the squirrel cage hub does not need a back iron structure, the weight of the hub can be reduced and the overall design size of the permanent magnet coupling can be reduced; moreover, the squirrel cage hub structure is more stable, not only can absorb the impact force generated when the rotors collide, but also can be used with the aluminum sleeve to prevent the permanent magnet from being thrown out due to centrifugal force and radial adsorption force during the operation of the permanent magnet coupling; in addition, the torque, the radial eccentric load, the axial force, the magnetic circuit topology, the torque density and the mass of the no-back iron type squirrel cage permanent magnet coupling can be used as optimization targets, the best parameter group is obtained through correlation analysis of the key parameters, and the performance iteration upgrade of the permanent magnet coupling is completed. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a no-back iron type squirrel cage permanent magnet coupling design flow chart;

[0028] Figure 2 It is a no-back iron type squirrel cage permanent magnet coupling structure composition diagram;

[0029] Figure 3 It is a no-back iron type squirrel cage permanent magnet coupling torque transmission curve diagram;

[0030] Figure 4 It is a no-back iron type squirrel cage permanent magnet coupling structure side view;

[0031] Figure 5 It is a no-back iron type squirrel cage permanent magnet coupling structure front view;

[0032] In the figure, 1 is an inner rotor end cover, 2 is a distance block, 3 is an inner rotor inner layer hub, 4 is an inner rotor inner layer magnetic steel array, 5 is an inner rotor gland, 6 is an inner rotor inner layer aluminum sleeve, 7 is an inner rotor outer layer hub, 8 is an inner rotor outer layer magnetic steel array, 9 is an inner rotor outer layer aluminum sleeve, 10 is an outer rotor gland, 11 is an outer rotor outer layer magnetic steel array, 12 is an outer rotor outer layer hub, 13 is an outer rotor outer layer aluminum sleeve, 14 is an outer rotor inner layer magnetic steel array, 15 is an outer rotor inner layer aluminum sleeve, 16 is an outer rotor inner layer hub, and 17 is an outer rotor end cover. DETAILED DESCRIPTION

[0033] The specific embodiments of the present application are further illustrated in the following with reference to the accompanying drawings and technical solutions.

[0034] The embodiment takes the output torque of 10 kN·m as a design target, and completes the design of the no-back iron type squirrel-cage permanent magnet coupling in combination with the design idea as shown in Figure 1 The specific steps are as follows:

[0035] Step 1: Determine the configuration and key parameters of the no-back iron type squirrel-cage permanent magnet coupling according to the design target;

[0036] The configuration is a no-back iron type squirrel-cage type, a Cartesian coordinate system is defined, the Z-axis is along the axial direction of the no-back iron type squirrel-cage permanent magnet coupling, the X-axis and the Y-axis are both along the radial direction of the no-back iron type squirrel-cage permanent magnet coupling and perpendicular to each other, wherein the X-axis passes through the geometric center of the permanent magnet, and the Y-axis passes through the geometric center of the boss;

[0037] Key parameter table;

[0038]

[0039]

[0040] Step 2: Build a magnetic field and transmission performance analysis model of the no-back iron type squirrel-cage permanent magnet coupling;

[0041] After importing the key parameters in COMSOL software, a three-dimensional model of the no-back iron squirrel-cage permanent magnet coupling is drawn in "Geometry"; in "Material", the NdFeB N50 attribute of the permanent magnet is given and the permanent magnet residual magnetic flux density is defined as 1.41 and the recovery permeability is defined as 1.05; the magnetic field air gap Air attribute is given and the relative permeability is defined as 1; the inner rotor end cover 1, the inner rotor inner layer hub 3, the inner rotor gland 5, the inner rotor outer layer hub 7, the outer rotor gland 10, the outer rotor outer layer hub 12, the outer rotor inner layer hub 16, the outer rotor end cover 17 Soft Iron attribute is given and the relative permeability is defined as 2500, and 45 steel is preferred in actual application; the inner rotor inner layer aluminum sleeve 6, the inner rotor outer layer aluminum sleeve 9, the outer rotor outer layer aluminum sleeve 13 and the outer rotor inner layer aluminum sleeve 15 Aluminum attribute is given and the relative permeability is defined as 1, and 6061 aluminum alloy is preferred in actual application; in the "Magnetic Field No Current" module, the magnetization direction of the permanent magnet is along the radial direction and the magnetization direction of the adjacent permanent magnets on the same hub is opposite; the magnetization model of the inner rotor end cover 1, the inner rotor inner layer hub 3, the inner rotor gland 5, the inner rotor outer layer hub 7, the outer rotor gland 10, the outer rotor outer layer hub 12, the outer rotor inner layer hub 16, the outer rotor end cover 17, the inner rotor inner layer aluminum sleeve 6, the inner rotor outer layer aluminum sleeve 9, the outer rotor outer layer aluminum sleeve 13, the outer rotor inner layer aluminum sleeve 15 and the magnetic field air gap is selected by using the constitutive relation defined by the relative permeability; six "force calculation" instructions are added, and the solution domain is selected as the inner rotor, the outer rotor, the outer rotor outer layer magnetic steel array 11 and the outer rotor inner layer magnetic steel array 14; after refining the grid of the three-dimensional model of the no-back iron squirrel-cage permanent magnet coupling, the appropriate steady-state solver is selected, the parameterization scanning is performed with az_shift as the independent variable, 0deg as the starting point, 20deg as the end point and 1deg as the step, the calculation is performed every 1deg, a total of 21 times, and the torque curve is output, as shown in Figure 3 ;

[0042] The third step is to optimize the structure of the no-back iron squirrel-cage permanent magnet coupling considering the machining and assembly process.

[0043] The inner rotor inner layer hub 3 with dovetail notches and the outer rotor outer layer hub 12 are formed by wire cutting processing, and the two sides of the inner rotor inner layer hub 3 and the outer rotor outer layer hub 12 should not have protruding structures, and a distance block 2 is designed between the inner rotor inner layer hub 3 and the inner rotor end cover 1 as a transition structure to realize axial displacement compensation and provide convenience for machining; a 5mm thick stop is designed on the inner rotor end cover 1 and the outer rotor end cover 17 for structural support and assembly positioning; the outer rotor gland 10 and the outer rotor end cover 17 are respectively matched with the outer rotor outer layer hub 12, and the connection is sunken by 25mm thick to reduce the weight; the inner rotor end cover 1, the outer rotor gland 10 and the outer rotor end cover 17 are respectively processed with top screw holes for adjusting the magnetic field air gap; the structure edges are transitioned by chamfering and rounding to prevent structural interference during assembly, and the optimized structure is as followsFigure 4 and Figure 5 As shown;

[0044] Step 4: Calculate the minimum allowable diameter of the connector based on the maximum torque value;

[0045] Depend on Figure 3 It can be seen that the maximum torque of the inner and outer rotors is T1 = 10471 N·m, the maximum torque of the inner layer of the inner rotor is T2 = 2429 N·m, the maximum torque of the outer layer of the inner rotor is T3 = 7790 N·m, the maximum torque of the inner layer of the outer rotor is T4 = 5341 N·m, and the maximum torque of the outer layer of the outer rotor is T5 = 5481 N·m; the positive and negative signs in the figure represent the direction, and the torques of the inner and outer rotors are taken as the average of their maximum values; set R1 = 0.1m, R2=0.132m, R3=0.234m, R4=0.188m, R5=0.29m. When Z1=Z2=Z3=Z4=Z5=6, d1=16.7mm, d2=7mm, d3=9.4mm, d4=8.7mm, d5=7.1mm. Considering the safety factor and processing steps, it is determined that d1 is of type φ20, and d2, d3, d4, and d5 are of type φ12.

[0046] Step 5: Complete the machining and assembly of the back-iron-less squirrel-cage permanent magnet coupling;

[0047] The inner rotor inner hub 3 is connected to the inner rotor cover 5 on one side by six M8×15 socket head cap screws, and to the inner rotor end cover 1 on the other side by six M12×20 socket head cap screws and six φ12×35 internally threaded cylindrical pins; the inner rotor outer hub 7 is connected to the inner rotor end cover 1 by six M12×25 socket head cap screws and six φ12×35 internally threaded cylindrical pins; the outer rotor inner hub 16 is connected to the inner rotor end cover 1 by six M12×25 socket head cap screws and six φ12×35 internally threaded cylindrical pins. The internal threaded cylindrical pin of 0 is connected to the outer rotor end cover 17; one side of the outer rotor outer hub 12 is connected to the outer rotor cover 10 by 6 M10×30 internal hexagonal head screws, and the other side is connected to the outer rotor end cover 17 by 6 M10×30 internal hexagonal head screws and 6 φ20×45 internal threaded cylindrical pins; the remaining structural components are fitted by slots and stops; after the inner rotor and outer rotor are closed, the axial set screws and radial set screws are finely adjusted until the magnetic field air gap is uniform, and the assembly of the back iron type squirrel cage permanent magnet coupling is completed.

[0048] The no-back iron type squirrel cage type permanent magnet coupling strengthens the magnetic field strength between air gaps, improves the utilization rate of permanent magnets and the transmission torque capacity, reduces the manufacturing cost and reduces the size, further improves the structural stability and performance stability of the permanent magnet coupling; in addition, the torque, radial eccentric load, axial force, magnetic circuit topology, torque density and mass of the no-back iron type squirrel cage type permanent magnet coupling can be used as optimization targets, the best key parameter group is obtained through correlation analysis of key parameters, the performance iteration upgrade of the no-back iron type squirrel cage type permanent magnet coupling is completed, and the no-back iron type squirrel cage type permanent magnet coupling has high engineering universality and application value.

Claims

1. A design method for a back-iron-less squirrel-cage permanent magnet coupling, characterized in that, The design steps are as follows: The first step is to determine the configuration and key parameters of the back-iron-less squirrel-cage permanent magnet coupling; The second step is to construct an analysis model of the magnetic field and transmission performance of a back-iron-less squirrel-cage permanent magnet coupling. Key parameters were imported into COMSOL software and a three-dimensional model of the back-iron-less squirrel-cage permanent magnet coupling was constructed. Then, the material properties of each structure of the back-iron-less squirrel-cage permanent magnet coupling were assigned and the magnetization model of each structure of the back-iron-less squirrel-cage permanent magnet coupling was determined. After refining the mesh of the three-dimensional model of the back-iron-less squirrel-cage permanent magnet coupling, the transmission torque of each layer of magnet array of the back-iron-less squirrel-cage permanent magnet coupling was solved. The third step is to optimize the structure of the back iron-less squirrel cage permanent magnet coupling considering the processing and assembly technology. Based on the processing and assembly requirements, the structure of the back iron-less squirrel cage permanent magnet coupling was optimized with the help of SOLIDWORKS software, including splitting the structure, reserving a stop, adding a boss, and setting chamfers and fillets. Step 4: Calculate the minimum allowable diameter of the connector based on the maximum torque value; Step 5: Complete the machining and assembly of the back-iron-less squirrel-cage permanent magnet coupling; The specific implementation process of the first step is as follows: The inner rotor and outer rotor are each equipped with two hubs, totaling four layers. The inner hub (3) of the inner rotor and the outer hub (12) of the outer rotor are provided with dovetail-shaped slots, and a set of magnet arrays are distributed in each of the dovetail-shaped slots of the inner hub (3) of the inner rotor and the outer hub (12) of the outer rotor. The outer hub (7) of the inner rotor and the inner hub (16) of the outer rotor are squirrel-cage structures, with inverted trapezoidal slots that penetrate the inner and outer surfaces of the outer hub (7) of the inner rotor and the inner hub (16) of the outer rotor, so that the pair of magnetic pole surfaces of the permanent magnet are fully exposed in the magnetic field air gap, and only the non-magnetic pole surface is in contact with the hub. Contact; Between the dovetail-shaped slots, between the inverted trapezoidal slots, and at the end faces of the inner rotor inner layer hub (3), outer rotor outer layer hub (12), inner rotor outer layer hub (7), and outer rotor inner layer hub (16), a portion of the area is reserved to restrict the tangential and axial degrees of freedom of the permanent magnet and to connect the end caps; when the permanent magnet is fully embedded in the inner rotor outer layer hub (7) and the outer rotor inner layer hub (16), a pair of magnetic pole surfaces of the permanent magnet are coplanar with the inner and outer surfaces of the inner rotor outer layer hub (7) and the outer rotor inner layer hub (16), respectively, and the radial degrees of freedom of the permanent magnet are restricted by the non-magnetic aluminum sleeve; Key parameters determining the torque transmission capability of a back-iron-less squirrel-cage permanent magnet coupling include the radial magnetic field air gap airgap_r, permanent magnet length PM_l, outer rotor inner permanent magnet thickness PM_t_1o, outer rotor outer permanent magnet thickness PM_t_2o, inner rotor inner permanent magnet thickness PM_t_1i, inner rotor outer permanent magnet thickness PM_t_2i, permanent magnet residual flux density Br, number of permanent magnets PM_num, and boss width tutai_a.

2. The design method of the back-iron-less squirrel-cage permanent magnet coupling according to claim 1, characterized in that, The specific implementation process of the third step is as follows: First, the inner rotor is disassembled into an inner rotor end cap (1), a distance block (2), an inner rotor inner layer hub (3), an inner rotor inner layer magnet array (4), an inner rotor pressure cap (5), an inner rotor inner layer aluminum sleeve (6), an inner rotor outer layer hub (7), an inner rotor outer layer magnet array (8), and an inner rotor outer layer aluminum sleeve (9); then, the outer rotor is disassembled into an outer rotor pressure cap (10), an outer rotor outer layer magnet array (11), an outer rotor outer layer hub (12), an outer rotor outer layer aluminum sleeve (13), an outer rotor inner layer magnet array (14), an outer rotor inner layer aluminum sleeve (15), and an outer rotor inner layer hub (16). And the outer rotor end cover (17); then, at the connection between the inner rotor end cover (1) and the inner rotor inner layer hub (3), the inner rotor outer layer hub (7), the outer rotor end cover (17) and the outer rotor outer layer hub (12), the outer rotor inner layer hub (16), a boss is added; all structural edges in the back iron type squirrel cage permanent magnet coupling are rounded and chamfered; the inner rotor end cover (1) is reserved with axial set screw holes, and the outer rotor pressure cover (10) and the outer rotor end cover (17) are reserved with radial set screw holes, so as to adjust the radial magnetic field air gap between the inner rotor and the outer rotor during the assembly process until it is evenly distributed along the circumference.

3. The design method of the back-iron-less squirrel-cage permanent magnet coupling according to claim 2, characterized in that, The specific implementation process of the fourth step is as follows: After the inner and outer rotors are separated, the inner rotor is connected to the drive end, the outer rotor to the load end, the inner rotor end cover (1) to the inner rotor inner hub (3), the inner rotor end cover (1) to the inner rotor outer hub (7), the outer rotor end cover (17) to the outer rotor outer hub (12), and the outer rotor end cover (17) to the outer rotor inner hub (16) respectively by screws and cylindrical pins; in the process of transmitting torque, the screws are assumed to only play a connecting and fastening role, and the torque is entirely borne by the cylindrical pins as connecting parts; the formula for calculating the connection strength of the cylindrical pins is: (1) in: τ The actual shear stress of the cylindrical pin is given in MPa. F The actual shear force borne by the cylindrical pin, in N; d The diameter of the cylindrical pin is in mm; Z This refers to the number of cylindrical pins. τ p Let be the allowable shear stress of the cylindrical pin. τ p =80MPa; After transformation, the formula for calculating the minimum allowable diameter of the cylindrical pin is: (2) in, i Number the location of the cylindrical pin. i =1,2,3,4,5 i =1 indicates the interface of the inner rotor end cover (1). i =2 indicates the connection between the inner rotor end cover (1) and the inner rotor inner hub (3). i =3 indicates the connection point between the inner rotor end cap (1) and the inner rotor outer hub (7). i =4 indicates the connection point between the outer rotor end cap (17) and the inner hub (16) of the outer rotor. i =5 indicates the connection between the outer rotor end cover (17) and the outer rotor outer hub (12). The torque transmitted at the interface of the outer rotor end cover (17) is consistent with that at the interface of the inner rotor end cover (1), and the cylindrical pins used are the same. d i for i The minimum permissible diameter of the cylindrical pin used in the location. T i for i The actual torque borne by the cylindrical pin. Z i for i Quantity of cylindrical pins used in the location; R i for i The radius of rotation of the cylindrical pin used in the location.

4. The design method of the back-iron-less squirrel-cage permanent magnet coupling according to claim 3, characterized in that, The specific implementation process of step five is as follows: The inner rotor inner layer magnet array (4) and the inner rotor inner layer hub (3) are fitted with a dovetail groove. One side is connected to the inner rotor cover (5) by screws, and the other side is fitted to the distance block (2) by a stop. It is connected to the inner rotor end cover (1) by screws and cylindrical pins. The inner rotor outer layer hub (7) is fitted with the inner rotor outer layer magnet array (8) through an inverted trapezoidal groove, and then connected to the inner rotor end cover (1) by screws and cylindrical pins. The inner rotor inner layer aluminum sleeve (6) and the inner rotor outer layer aluminum sleeve (9) are respectively fitted on the inner surface and outer surface of the inner rotor outer layer hub (7), and the inner rotor assembly is completed. The outer rotor inner layer hub (16) is fitted with the outer rotor inner layer magnet array (14) through an inverted trapezoidal groove, and then connected to the outer rotor end cover (17) by screws and cylindrical pins. The outer rotor outer layer magnet array (11) and the outer rotor outer layer hub (14) are fitted with each other. 2) The dovetail-shaped slot is used to connect one side to the outer rotor cover (10) with screws, and the other side to the outer rotor end cover (17) with screws and cylindrical pins. The inner aluminum sleeve (15) and the outer aluminum sleeve (13) of the outer rotor are respectively fitted on the inner surface and outer surface of the inner hub (16) of the outer rotor, and the outer rotor assembly is completed. The inner rotor and the outer rotor are closed, and the axial set screw on the inner rotor end cover (1) is adjusted until the outer end face of the inner rotor end cover (1) is coplanar with the outer end face of the outer rotor cover (10). The magnetic field air gap is adjusted by using the radial set screw on the outer rotor cover (10) and the outer rotor end cover (17). At the same time, the reserved interfaces of the inner rotor end cover (1) and the outer rotor end cover (17) are aligned one-to-one along the axial direction and the magnetization direction of the permanent magnets distributed radially along the back iron type squirrel cage permanent magnet coupling is consistent. The axial set screw and the radial set screw are locked.

5. The design method of the back-iron-less squirrel-cage permanent magnet coupling as described in any one of claims 1-4, characterized in that, The torque, radial off-center load, axial force, magnetic circuit topology, torque density, and mass of the back-iron type squirrel-cage permanent magnet coupling are all optimized targets. By conducting correlation analysis on key parameters, the optimal set of key parameters is obtained, and the performance of the back-iron type squirrel-cage permanent magnet coupling is iteratively upgraded.

6. The design method of the back-iron-less squirrel-cage permanent magnet coupling as described in any one of claims 2-4, characterized in that, The inner rotor inner layer hub (3), inner rotor outer layer hub (7), outer rotor outer layer hub (12) and outer rotor inner layer hub (16) are made of 45 steel and formed by wire cutting. The permanent magnet is made of neodymium iron boron N50. The inner rotor inner layer aluminum sleeve (6), inner rotor outer layer aluminum sleeve (9), outer rotor outer layer aluminum sleeve (13) and outer rotor inner layer aluminum sleeve (15) are made of 6061 aluminum alloy.

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