Research On Axial-flux Permanent-magnet Linear Machine For Hybrid Electric Vehicles

In the field of hybrid electric vehicles,the new power generation system uses a combination of free piston internal combustion engines and linear motors,which has outstanding advantages in energy utilization and environmental protection.Among them,the system has higher requirements for the quality of the linear motor mover and thrust fluctuations.Based on the practical application background of hybrid electric vehicles,the design and optimization,thrust fluctuation,thermal field analysis and mechanical strength of the tubular permanent magnet linear motor are studied in this paper.The main work is as follows:Firstly,the electromagnetic scheme of tubular permanent magnet linear motor is designed and optimized.The structure of permanent magnets in axial magnetizing mode is determined,and the matching structure of 12-slot 14-pole is selected to design the initial electromagnetic scheme of the motor.The effects of different external diameters of motor and the radial and axial lengths of permanent magnets on the motor performance are compared,the initial electromagnetic scheme is optimized,and the electromagnetic performance of the motor before and after the optimization is compared.Secondly,the generation of no-load detent force and the suppression scheme of load thrust fluctuation in tubular permanent magnet linear motor are studied.The magnitude of the detent force and fluctuation of the basic scheme are analyzed,the end effect and the cogging effect which cause the thrust fluctuation of the motor are analyzed,and the key structural parameters are determined.The finite element was used to verify and analyze the various suppression methods proposed,and the suppression effects of various schemes were compared.The results show that the method of changing the structural parameters of the side teeth of the motor has high feasibility and good effect;the method of adding a sawtooth magnetic block can well ensure that the average thrust of the load is as undisturbed as possible.Thirdly,the temperature rise distribution of the motor under rated operating conditions is analyzed and studied.The heat rate of the linear motor and the thermal conductivities of each part of the motor are calculated,and the method of solving the heat transfer coefficient at the boundary of each part of the motor is analyzed and explained.A two-dimensional thermal field solution model of the linear motor is established.Through repeated iterative calculations,the heat transfer coefficients of each part of the motor are solved,and the thermal rise of the motor under rated conditions is simulated.On this basis,the influence of different water flows on the thermal rise of the motor and the influence of thermal rise on the performance of themotor are analyzed.Finally,the mechanical strength of the tubular permanent magnet linear motor is analyzed and checked.The type and size of the load that the motor bears are analyzed,and the stress distribution when the motor is subjected to various loads is analyzed.Through finite element simulation,the stress distribution and strain of the tubular linear motor mover at the peak working point are analyzed.The stress distribution of hollow shaft and solid shaft is compared and analyzed,and the optimal shaft structure which meets the requirement of mechanical strength is selected.