Transmission Properties Analysis Of External Magnetic Gears

Non-contact is the transmission method of magnetic gear.Magnetic gears are driven by magnetic pole coupling.Due to the physical contact transmission mode of conventional mechanical gears,vibration noise and wear failure occur.This problem can be solved by non-contact transmission mode.Magnetic gear has good application prospects in industry and aviation.However,the development of magnetic gears is currently limited,mainly due to insufficient torque.Compared to internal meshing magnetic gears,there are fewer studies on external meshing magnetic gears.It is because the torque and transmission stability of the external meshing magnetic gear are not as good as the internal meshing magnetic gear.However,external meshing magnetic gears have their special advantages.For example,cross-axis magnetic gears can achieve a 90° staggered transmission direction space through a primary transmission.It cannot be replaced by internal meshing magnetic gears and mechanical gears.Therefore,it is necessary to study how to increase the torque of the external meshing magnetic gear.The paper will focus on two types of external meshing magnetic gears(parallel-axis magnetic gears and cross-axis magnetic gears).Based on the literature review,it was established that a finite element model in the electromagnetic field of these two external magnetic meshing gears.Finite element modeling and simulation were performed in a static magnetic field and transient magnetic field to study the structure and transmission characteristics of these two magnetic gears.Then the factors that affect the magnitude of the gear torque were found,analyzed and verified.Finally,the gear structure was optimized based on the response surface method and the gear parameters that maximize the torque were found.The parallel-axis magnetic gear was analyzed by finite element simulations.It is found that the factors that affect the maximum output torque of gears included gear diameter,gear clearance,number of magnetic poles,thickness of magnetic ring,and aspect ratio.These five factors were used to design a simulation test using the control variable method.The regular pattern of each factor and the maximum output torque change was: the torque had a positive growth relationship with the aspect ratio and gear diameter;the torque had a negative growth relationship with the gear clearance and the number of magnetic poles;the torque had a negative growth relationship with the gear clearance and the number of magnetic poles.When the thickness of the magnetic ring was between 1mm and 3mm,the torque increased with the thickness.When the thickness was 3mm ? 5mm,the thickness increased and the torque decreased,but not much.The larger the gear diameter,the larger the torque decreased or increased.Finite element simulation analysis was performed on the cross-axis magnetic gear.In addition to the five parameters of the parallel-axis magnetic gear,a helix angle parameter was added.Through the static magnetic field and transient magnetic field simulation analysis,the relationship between the gear factors and the maximum output torque was: the torque had a positive growth relationship with the thickness of the magnetic ring,the aspect ratio,and the gear diameter;the torque had a negative growth relationship with the gear clearance and the number of magnetic poles;the maximum torque was obtained when the gear helix angle was 45 °;the larger the gear diameter,the larger the torque variation.Then,the effects of the structural parameters of the two magnetic gears on the torque was compared and analyzed.It was found that the torque of the parallel-axis magnetic gear was greater than the torque of the cross-axis magnetic gear as the same size and they have different effects on torque.Next,a cross-axis magnetic gear test bench was built to measure the maximum output torque value when the gear clearance changed,and the results were compared with the simulation results to verify the correctness of the simulation results.It had been found out that the reasons for the differences between the actual test results and the simulation results,as well as problems that may occur in practical application,and appropriate solutions to the problems were given.Finally,the response surface method was used to optimize the structural parameters of the parallel-axis magnetic gear and the cross-axis magnetic gear.The simulation data and the objective optimization function were used to establish the response surface,and the optimization function,the optimal parameter combination of each magnetic gear,and the maximum torque were obtained.