Research And Optimization Of Permanent Magnet Slip Clutch

Comfort is the common pursuit of passengers,drivers and technicians.The performance of the connecting components between the engine and the transmission has a large impact on the shifting smoothness,while at the same time requiring the component to have a high transmission efficiency.Comprehensive improvement of transmission efficiency and shift quality is the pursuit of this part in design.The currently used torque converters,dual clutches and multi-plate wet clutches have achieved high results in these two aspects.However,some components have advantages in terms of efficiency;some components have small shifting impact when shifting gears;some have advantages in two aspects,but there is a risk of power interruption.In order to improve the shifting quality and transmission efficiency,a new type of transmission mechanism is provided between the engine and the transmission,with a coupling working mode and a slipping transmission mode to cooperate with the friction clutch or other transmission mechanism to achieve uninterrupted power conversion.It has high theoretical significance and application value for realizing permanent magnet stepless speed change transmission.The main research contents of this paper were as follows:Firstly,by using field theory and static magnetic field theory,the magnetic circuit analysis of permanent magnet slip clutch was carried out,and the scheme of sparse arrangement of permanent magnets,superimposed permanent magnet scheme and permanent magnet with eccentric arc were proposed,and the simulation calculation and experimental verification were carried out.In the comparative analysis of the results of these three schemes,it was found that the magnetic field force between the two permanent magnets would have a sudden change in the direction of the force at a certain position.Combined with Biot-Savart Law and Ampere circuital theorem,it was found that the permanent magnets had a critical position when arranged with large gaps,and the direction of the magnetic field forces on both sides of the permanent magnet changed.Therefore,it could be explained that the magnetic torque characteristics of the permanent magnet sparse arrangement and the superimposed permanent magnets would be abrupt,and it was the intrinsic reason that the eccentric arc permanent magnet scheme could obtain the continuous stable magnetic torque characteristics.Based on the analysis of the magnetic torque law and the influencing factors transmitted by the axial flux permanent magnet coupling,the fan-shaped permanent magnets in the drive disk were sparsely arranged,and designed the new structure with eccentric arc instead of fanshaped permanent magnet.According to calculating the magnetic field force and analyzing the positional relationship between the magnitude and direction of the magnetic field and the permanent magnet in the three-dimensional space,the fan angle of the permanent magnet in the drive disk and the output disk was limited to 150°,and the relative installation of the symmetry axis staggered by 45° was determined.The position obtained a magnetic torque characteristic in which the output magnetic torque value fluctuated less in a range of relative rotation angles at which the drive disk was rotated by 90° with respect to the output disk.Secondly,a novel method for a critical position between permanent magnets was proposed.Based on finding the critical position,combined with Biot-Savart Law and Ampere circuital theorem,the influence of the volume distribution of permanent magnets on the two sides of the critical position on the magnetic field force and magnetic torque was analyzed.An eccentric arc permanent magnet scheme was designed.This scheme needed to avoid the critical position when designing the sector-shaped permanent magnet on the drive disk and the profiled permanent magnet fan angle on the output disk,that was,when the drive disk rotated within the range of 0o-90° with respect to the output disk,a critical position could not occur in the circumferential direction.In order to obtain a stable magnetic torque,the special-shaped permanent magnet in the output disk needed to utilize the critical position so that the critical position continuously changed in the radial direction to meet the design purpose.The simulation calculation was carried out using MAGNET software to verify the existence of the critical position and the law of the magnetic force near the critical position.Thirdly,the relationship between the parameters of the two permanent magnets and the critical position was analyzed,and the method of obtaining the stable magnetic torque-relative corner characteristics was proposed.The thickness of the silicon steel sheet,the thickness of the air gap,the relative position parameters of the permanent magnet,the starting position and the ending position of the relative rotation angle,the positional parameters of the center of the eccentric arc and the radius size were determined by simulation.The magnetic torque under the motion state was calculated by MAGNET software,and the stable magnetic torque characteristics was obtained by torque simulation calculations.On this basis,the influence of relative rotational speed on the magnetic torque law was analyzed,and the distribution of magnetic flux and magnetic field lines of the silicon steel sheet and air gap was studied.The magnetic induction intensity distribution and magnetic force line state of critical position with relative rotation angle of 0°,45°and 90° were obtained,and the inner law of stable magnetic torque-relative angle was found out.Therefore,a new scheme for quickly designing permanent magnet structures was proposed by using equivalent area.Based on analyzing the simulation and experimental results,combining the Biot-Savart theorem and the Ampere circulation theorem,the equivalent area model data to the magnetic torque-relative rotation angle characteristic data was mapped by using BP neural network,and a trained network model was obtained.The magnetic torque characteristics could quickly be obtained according to the structure parameters of the magnet,which provided a means to shorten the design time of the permanent magnet slip transmission mechanism.The optimized profiled permanent magnet parameters were obtained by using genetic algorithm extreme value optimization.Finally,the combinations of PLA,aluminum alloy,silicon steel sheet and permanent magnet material were used to complete the structural design,and the torque test device of permanent magnet slip clutch was fabricated.The magnetic torque-relative angle characteristics were measured to verify the correctness of the simulation calculation.Through in-depth study of the magnetic field distribution at the critical position,the optimized system structural parameters were obtained.Because the mechanism has slip transmission mode,coupling transmission mode and a characteristic of non-contact transmission,it can acquire the high transmission efficiency of the vehicle and the better shifting comfort requirement,and has predictable application research value.