Development Of Magnetic Gear Compound Hub Motor

With the development of modern industry,automobile hub motor is considered as the development direction and the final development form of electric vehicle because of its own structure and control mode and other advantages.The wheel hub motor deceleration drive can not avoid the gear contact wear,vibration noise and lubrication problems caused by torque transmission because of its deceleration process equipped with mechanical gears,which affects the service life of the vehicle.In order to meet the need of high output torque density,direct drive has not been widely used because of its large volume,high cost and difficult to install.In this paper,a new type of magnetic gear composite hub motor is proposed.The main purpose of this paper is to develop the mechanical characteristics and theoretical knowledge of the main body of the magnetic gear composite hub motor.A new type of permanent magnet motor and magnetic gear compound method is used to reduce the volume and cost of hub motor,and the torque density can reach as high as 120kNm/m~3,which is much higher than that of common permanent magnet motor and existing magnetic gear compound motor.The main contents are as follows:1.According to the research on the power assembly system of electric vehicle,a new power assembly scheme is designed,which is suitable for the magnetic gear compound motor.In this scheme,the traditional gearbox,differential and other variable speed structure are removed,and the space inside the vehicle is saved.Through the modification of the JAC iEV6E electric vehicle,the power assembly parts are selected and the parameters of the power system are matched,which provides the performance index for the design of the magnetic gear compound motor.2.The structure and working principle of the magnetic gear compound motor are described,and the qualitative analysis of the magnetic gear compound motor is carried out by the analytic method.The mathematical models of permanent magnet motor and magnetic gear device are established respectively,According to the Maxwell equations,the vector magnetic potential is obtained by listing each part of Laplace equation or Poisson equation combined with boundary conditions.The output torque is obtained under the condition that the linear equation is satisfied.From the point of view of radial and tangential magnetic density of air gap,the relationship between harmonic frequency and polar logarithm is explained.3.Quantitative analysis of magnetic gear transmission device by finite element method.Firstly,the finite element model of magnetic gear is established,and the conclusion of the above analytical method of magnetic field modulation principle is analyzed and verified from the angle of air-gap flux density,and the rationality of the design of pole logarithm of the inner and outer rotor of magnetic gear is also verified.The structure of the modulation ring and the thickness of the inner and outer air gap are optimized by simulation to make the magnetic gear output the maximum torque.4.In order to realize the compound of permanent magnet synchronous motor and magnetic gear device,the thickness of transition rotor is optimized by finite element method to reduce its influence on the magnetic gear device as well as the magnetic potential of the original yoke of the magnetic gear is guaranteed to supply the excitation of the permanent magnet motor.And the performance of the composite motor is analyzed,including air-gap flux density,electromotive force,torque characteristics and so on.Finally,the composite of magnetic gear device and permanent magnet synchronous motor is formed.