Convex-T type coaxial magnetic gear with Spoke structure and Halbach array

Abstract

A convex-T type coaxial magnetic gear with a Spoke structure and a Halbach array sequentially comprises an inner rotor, inner rotor permanent magnets, a magnetism adjusting ring and an outer rotor from inside to outside, the inner rotor permanent magnets are attached to the outer side of the inner rotor, outer rotor permanent magnets are embedded in the surface of the outer rotor, and Spoke type permanent magnets are embedded in the positions, between the outer rotor permanent magnets, of the outer rotor. According to the utility model, the inner rotor is arranged in a convex-T shape to form a Halbach array, so that the effective harmonic amplitude in an air gap is improved, the torque output capability is enhanced, the operation efficiency is improved, and the motor can adapt to various application scenes; according to the outer rotor, on the premise that the using amount of permanent magnet materials is not increased, the Spoke structures and the Halbach arrays of the permanent magnets of the outer rotor are combined, so that the magnetic flux gathering effect is enhanced, the air gap flux density amplitude is effectively improved, meanwhile, non-working harmonic waves are remarkably reduced, and the operation stability of a magnetic gear is further improved.

Description

Technical Field

[0001] This utility model relates to the field of magnetic gear technology, and in particular to a convex-T type coaxial magnetic gear with a Spoke structure and a Halbach array. Background Technology

[0002] To address the low-speed, high-torque requirements of wind power generation, traditional mechanical gearboxes achieve transmission through physical meshing between gears. This leads to additional energy losses, shorter lifespans, and higher generator failure rates. Traditional mechanical gears also suffer from high noise and friction, easily causing accelerated wear and potentially serious malfunctions. However, magnetic gears inherently possess the advantage of requiring no lubrication or regular maintenance. They can operate without loss of synchronization or overload, and their maintenance-free lifespan exceeds 10 years. Coaxial magnetic gears with double-layer permanent magnets and spoke structures offer even better performance. Moreover, magnetic gears not only achieve torque transmission similar to mechanical gears but also exhibit lower failure rates and higher reliability. With the development of magnetic field modulation mechanisms, a magnetic field-modulated gear design has been proposed, introducing a stationary ring between the inner and outer rotors. This allows all permanent magnets to effectively participate in torque transmission, significantly improving the utilization rate of permanent magnets. Subsequently, innovative research on CMGs has become a hot topic. By employing a Halbach array magnetization method, torque density has been increased by 13% compared to traditional permanent magnets, while overall losses have been reduced by 28%. Subsequently, a high-temperature superconducting modulated magnetic gear design with an eccentric structure and a Halbach array was proposed, achieving a torque density of 173 kN·m / m³. This high torque density provides a more reliable alternative to mechanical gearboxes.

[0003] The drawback of high-temperature superconducting modulated magnetic gears (CMGs) is that the permanent magnets are prone to detachment during high-speed rotation of the inner rotor, affecting the normal operation of the motor. Replacing the surface-mounted structure of the inner rotor permanent magnets with a Spoke structure enhances the magnetizing effect, increases the torque density of the CMG, and provides high mechanical stability at high speeds; however, this presents technical challenges in cooling. Recently, a novel motor structure employing Spoke structures for both inner and outer rotor permanent magnets has been proposed, successfully enhancing the magnetizing effect and further improving the torque density of the CMG. However, when the outer rotor permanent magnets are tangentially magnetized using a Spoke structure, flux leakage may occur at the edges, affecting torque transmission. To address this issue, a dual-flux-modulated CMG has been proposed. By adding an auxiliary flux modulator, flux leakage is reduced. Therefore, the magnetization of the Halbach array exhibits a unilateral magnetizing effect, enhancing the magnetic field in the air gap. The Spoke structure enables focused flux alignment, enhancing the effective operating harmonic amplitude, suppressing non-operating harmonics, and improving torque performance.

[0004] Previous research on magnetic gears has mainly focused on exploring the performance and applications of different topologies, but research on the design and optimization of magnetic gear systems is relatively lacking. In recent years, the use of statistical fitting methods for modeling and designing electromagnetic devices has received widespread attention. Response surface methodology is suitable for developing analytical models and can create constrained objective functions. By optimizing design parameters hierarchically according to their importance and combining this with a multi-objective genetic algorithm to optimize geometric parameters, electromagnetic characteristics such as output torque can be maximized. Summary of the Invention

[0005] The technical problem to be solved by this utility model is to provide a convex-T type coaxial magnetic gear with Spoke structure and Halbach array to replace the mechanical gearbox in the wind power generation system, aiming to improve the working efficiency of the wind power generation system based on improving the electromagnetic characteristics of the magnetic gear.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is: a convex-T type coaxial magnetic gear with Spoke structure and Halbach array, which includes an inner rotor, an inner rotor permanent magnet, a magnetic adjustment ring and an outer rotor from the inside to the outside. The inner rotor permanent magnet is attached to the outside of the inner rotor, an outer rotor permanent magnet is embedded on the surface of the outer rotor, and a Spoke type permanent magnet is embedded on the outer rotor between the outer rotor permanent magnets.

[0007] Preferably, the inner rotor permanent magnets are arranged in an alternating convex-T pattern.

[0008] Preferably, an inner air gap is provided between the adjusting magnetic ring and the inner rotor permanent magnet, and an outer air gap is provided between the adjusting magnetic ring and the outer rotor.

[0009] Preferably, the adjusting ring is made of alternating magnetic silicon steel blocks and epoxy resin.

[0010] Preferably, the number of pole pairs of the outer rotor is 17.

[0011] This invention provides a convex-T type coaxial magnetic gear with a Spoke structure and a Halbach array, which has the following advantages:

[0012] 1. This utility model improves the effective harmonic amplitude in the air gap by using a convex-T-shaped arrangement of the inner rotor to form a Halbach array, thereby enhancing the torque output capability, improving operating efficiency, and adapting to various application scenarios.

[0013] 2. Without increasing the amount of permanent magnet material used, the Spoke structure and Halbach array combination of the permanent magnet of the outer rotor enhance the magnetic flux concentration effect, effectively improve the air gap magnetic flux density amplitude, and significantly reduce non-working harmonics, thereby further improving the running stability of the magnetic gear.

[0014] 3. By combining multi-objective optimization design, the convex-T coaxial magnetic gear with Spoke structure and Halbach array of the present invention has increased the output torque by 45.43% and 23.69% respectively compared with the traditional type and conventional Halbach array magnetic gear. Attached Figure Description

[0015] The present invention will be further described below with reference to the accompanying drawings and embodiments:

[0016] Figure 1a This is a schematic diagram of the topology of a traditional magnetic gear;

[0017] Figure 1b This is a schematic diagram of the topology of a conventional Halbach array magnetic gear.

[0018] Figure 1c It is a structural diagram of the utility model;

[0019] Figure 2 This is a schematic diagram showing the dimensional parameters of this utility model;

[0020] Figure 3a This is a schematic diagram illustrating the influence of design parameter 'a' on torque performance of this utility model.

[0021] Figure 3b This is a schematic diagram illustrating the influence of design parameter c on torque performance of this utility model.

[0022] Figure 4a This is a schematic diagram of the response surface between the design parameters b and d and the output torque of this utility model.

[0023] Figure 4b This is a schematic diagram of the response surface of the design parameters b and d of this utility model to the torque pulsation of the external rotor.

[0024] Figure 4c This is a schematic diagram of the response surface of the design parameters b and d of this utility model to the torque pulsation of the inner rotor.

[0025] Figure 5a This is a schematic diagram illustrating the iterative convergence of the multi-objective genetic algorithm for output torque in this invention.

[0026] Figure 5b This is a schematic diagram of the iterative convergence of the multi-objective genetic algorithm for external air gap torque pulsation in this utility model;

[0027] Figure 5c This is a schematic diagram of the iterative convergence of the multi-objective genetic algorithm for internal air gap torque pulsation in this utility model;

[0028] Figure 6 This is a schematic diagram of the multi-objective optimization point selection of this utility model;

[0029] Figure 7a This is a schematic diagram of the magnetic field lines distribution of a conventional Halbach array magnetic gear;

[0030] Figure 7b This is a schematic diagram of the magnetic field line distribution of this utility model;

[0031] Figure 8a This is a comparative schematic diagram of the radial magnetic flux density distribution in the inner air gap of this utility model.

[0032] Figure 8b This is a comparative schematic diagram of the coaxial magnetic flux density distribution in the inner air gap magnetosphere of this utility model;

[0033] Figure 9a This is a schematic diagram comparing the radial harmonic components of the inner air gap magnetic flux density of this utility model.

[0034] Figure 9b This is a schematic diagram comparing the coaxial harmonic components of the inner air gap magnetosphere of this utility model.

[0035] Figure 10a This is a comparative schematic diagram of the radial magnetic flux density distribution in the outer air gap of this utility model;

[0036] Figure 10b This is a comparative schematic diagram of the coaxial magnetic flux density distribution in the outer air gap of this utility model;

[0037] Figure 11a This is a schematic diagram comparing the radial harmonic components of the external air gap magnetic flux density of this utility model;

[0038] Figure 11b This is a schematic diagram comparing the directional harmonic components of the external air gap magnetosphere of this utility model;

[0039] Figure 12 This is a schematic diagram comparing the output torque of the magnetic gear of this utility model. Detailed Implementation

[0040] like Figure 1c As shown, a convex-T coaxial magnetic gear with a Spoke structure and a Halbach array includes, from the inside to the outside, an inner rotor 1, an inner rotor permanent magnet 2, a magnetic adjustment ring 3, and an outer rotor 4. The inner rotor permanent magnet is attached to the outside of the inner rotor 1, an outer rotor permanent magnet 5 is embedded on the surface of the outer rotor 4, and a Spoke-type permanent magnet 6 is embedded on the outer rotor 4 between the outer rotor permanent magnets 5.

[0041] Preferably, the inner rotor permanent magnet 2 is arranged in an alternating convex-T pattern.

[0042] Preferably, an inner air gap is provided between the adjusting magnetic ring 3 and the inner rotor permanent magnet 2, and an outer air gap is provided between the adjusting magnetic ring 3 and the outer rotor 4.

[0043] Preferably, the adjusting ring 3 is made of alternating magnetic silicon steel blocks and epoxy resin.

[0044] Preferably, the number of pole pairs of the outer rotor is 17.

[0045] The present invention provides a convex-T type coaxial magnetic gear with a Spoke structure and a Halbach array, such as... Figure 1c As shown, the arrow indicates the magnetization direction of the permanent magnet.

[0046] The topology of traditional magnetic gears is as follows: Figure 1a As shown, it consists of two rotors and a magnetic adjusting ring, with PMs mounted on the rotor surfaces. The magnetic adjusting ring, composed of magnetic silicon steel blocks and epoxy resin, is sandwiched between the two permanent magnet rotors. Its function is to modulate the magnetic field in the two air gaps. In contrast, Figure 1b The CMG structure is a conventional Halbach array. Its inner rotor permanent magnet is divided into three segments, each magnetized at 60° intervals, while the outer rotor consists of four segments magnetized at 90° intervals. Both the inner and outer rotors are Halbach array structures. Figure 1c The improved magnetic gear topology is shown below. The inner rotor PMs (permanent magnets) are arranged in an alternating convex-T pattern. For the outer rotor PMs, the tangentially magnetized PMs and silicon steel form a Spoke-type magnetization structure, which, together with the radially magnetized PMs, forms a Halbach array structure. Compared to ordinary magnetic focusing structures, the radially magnetized PMs can further guide the direction of magnetic field lines, improving the magnetization effect. The key parameters of the magnetic gear are shown in Table 1.

[0047] Table 1 Main parameters of the magnetic gear

[0048]

[0049] Figure 2 This diagram illustrates the key dimensional parameters of the improved magnetic gear. To achieve higher output torque and lower torque ripple, an optimization method combining Response Surface Methodology (RSM) and Multi-Objective Genetic Algorithm (MOGA) was employed to analyze and optimize these key parameters. Before optimization, sensitivity analysis was used to assess the impact of design parameters on the optimization objectives, based on the proposed design criteria for the improved magnetic gear. Design parameters that significantly influenced the optimization objectives of the magnetic gear were selected for further optimization. During optimization, the overall volume, number of pole pairs of the inner and outer rotors, axial length, and outer radius were kept constant.

[0050] Figure 3a , 3bThe single-parameter scan results for variables a and c are presented. Variable a represents the top curvature of the inner rotor convex permanent magnet. Variable c represents the width of region S1, i.e., the width of the radially magnetized portion of the inner rotor permanent magnet. The graph shows that the average torque first increases and then decreases with the increase of the outer curvature a of the convex permanent magnet, but has little impact on torque ripple. An optimal value for a is easily found around 15°. To simplify the prototype manufacturing process, the circumferential dimension is determined to be half the inner curvature, i.e., 15°. Parameter c has a linear effect on the average torque, and the torque ripple is minimized at its maximum value of 8mm; therefore, a value of 8mm is chosen. A clear understanding of the influence of design variables on the optimization objective provides strong support for subsequent optimization design.

[0051] Figure 4a , 4b Figure 4c shows the response surface plots for the three optimization objectives, design variables b and d. It visually demonstrates that as b increases, the output torque Tout gradually increases, the external rotor torque ripple kripo first increases, then decreases, and then increases again, while the internal rotor torque ripple kripi first fluctuates smoothly and then increases. Conversely, as d increases, the output torque Tout gradually decreases, the external rotor torque ripple kripo gradually increases, and the internal rotor torque ripple kripi first increases and then decreases. These effects are complex and nonlinear; therefore, it is difficult to accurately determine the optimal design values ​​of the design variables through univariate analysis, and further reasonable trade-offs are needed among the three optimization objectives.

[0052] Figure 5a , 5b 5c and Figure 6 These are the iterative process for seeking optimization and the final optimized feasible design, respectively. Figure 5a , 5b Figure 5c illustrates the iterative process of the magnetic gear optimization, including the iterative changes of the outer rotor output torque Tout, the outer rotor torque pulsation kripo, and the inner rotor torque pulsation kripo. As the number of iterations increases, the optimization objectives gradually converge, ultimately reaching a relatively optimal state after a fewer number of iterations (e.g., 16), demonstrating the efficiency of the optimization algorithm. The final optimized feasible design is as follows: Figure 6 As shown, during the optimization process, these candidate points constitute the optimal solution set for the optimization problem, allowing decision-makers to select the most suitable design parameters based on actual needs. The Pareto front intuitively demonstrates the ability of multi-objective optimization algorithms to balance multiple optimization objectives, reflecting the diversity and practicality of the optimization results.

[0053] Figure 7a , 7bThe magnetic field lines distribution of three different magnetic gear models (traditional, conventional Halbach, and improved) are shown. The comparison reveals that the improved model exhibits a stronger coupled magnetic field on the outer air gap side, thanks to its unique Spoke structure and Halbach array design. Compared to the traditional and conventional Halbach models, the improved model has a more uniform and denser distribution of magnetic field lines, which is beneficial for improving torque transmission efficiency and stability.

[0054] Figure 8a , 8b and Figure 9a , 9b The comparison of radial and tangential magnetic flux density waveforms and corresponding harmonic spectra of the inner air gap are presented respectively. Figure 8a , 8b It can be seen that, compared with traditional and conventional Halbach type magnetic gears, the radial and tangential magnetic flux densities of the improved magnetic gears exhibit a more sinusoidal radial waveform and a smoother tangential air gap magnetic flux density waveform, which is beneficial for reducing torque pulsation and improving torque transmission efficiency. Figure 9a , 9b According to magnetic field modulation theory, harmonic components with pole pairs of 4, 17, 25, and 38 are considered operating harmonics. Magnetic gears employing the Halbach structure (including conventional and improved Halbach types) exhibit significantly higher operating harmonic components than traditional magnetic gears, which is beneficial for efficient torque transmission in the inner air gap. Simultaneously, it significantly suppresses non-operating harmonic components such as the 12th, 20th, 28th, 33rd, 36th, and 41st poles. This suppression effect helps improve the stability of torque transmission in magnetic gears, reduces torque pulsation, and thus enhances the overall system performance.

[0055] Figure 10a , 10b and Figure 11a , 11b The radial and tangential magnetic flux density waveforms and corresponding harmonic spectra of the inner air gap are compared. Due to the synergistic effect of the Spoke structure and the Halbach array, the harmonic amplitudes of the improved model, especially those of the 17th pole pair, are higher than those of the traditional and conventional Halbach models, both in terms of tangential and radial magnetic flux density. Furthermore, the use of the Halbach structure plays a significant role in suppressing the non-operating harmonics of the improved and conventional Halbach-type CMGs, effectively reducing torque ripple.

[0056] Figure 12This paper compares the output torque of the inner and outer rotors of three different magnetic gear models (traditional, conventional Halbach, and improved), with the adjusting ring kept stationary. The high-speed inner rotor and the low-speed outer rotor rotate in opposite directions at 170 r / min and 40 r / min, respectively. The output torque of the outer rotor of the improved magnetic gear is 356.01 N·m, while the output torques of the traditional and conventional Halbach magnetic gears are 244.79 N·m and 287.82 N·m, respectively, representing improvements of 45.43% and 23.69%.

[0057] The above embodiments are merely preferred technical solutions of this utility model and should not be considered as limitations on this utility model. The protection scope of this utility model should be the technical solution described in the claims, including equivalent substitutions of the technical features described in the claims. That is, equivalent substitutions and improvements within this scope are also within the protection scope of this utility model.

Claims

1. A convex-T type coaxial magnetic gear with a Spoke structure and a Halbach array, characterized in that: From the inside out, it includes an inner rotor (1), an inner rotor permanent magnet (2), a magnetic adjustment ring (3) and an outer rotor (4). The inner rotor permanent magnet is attached to the outside of the inner rotor (1). An outer rotor permanent magnet (5) is embedded on the surface of the outer rotor (4). Spoke-type permanent magnets (6) are embedded on the outer rotor (4) between the outer rotor permanent magnets (5). The inner rotor permanent magnet (2) is arranged in a convex-T alternating pattern to form a Halbach array.

2. The convex-T coaxial magnetic gear with Spoke structure and Halbach array according to claim 1, characterized in that: An inner air gap is provided between the adjusting ring (3) and the inner rotor permanent magnet (2), and an outer air gap is provided between the adjusting ring (3) and the outer rotor (4).

3. The convex-T coaxial magnetic gear with Spoke structure and Halbach array according to claim 2, characterized in that: The adjusting ring (3) is made of alternating magnetic silicon steel blocks and epoxy resin.

4. The convex-T coaxial magnetic gear with Spoke structure and Halbach array according to claim 1, characterized in that: The number of pole pairs of the external rotor is 17.

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