| Automobile retarders are important for improving the stability of braking performance.Large passenger trucks must be equipped with corresponding retarders to ensure safe driving.At present,the commercial retarder is mainly an electromagnetic retarder that is hierarchically braked,consumes electric energy,and has a large volume.The permanent magnet retarder does not consume electric energy,which is advantageous for miniaturization and can be fitted to more small and medium-sized vehicles.Under the condition of stepless braking,it can better adapt to various road conditions.The permanent magnet retarder is of great significance for the safe operation of all types of vehicles.Therefore,it is necessary to carry out research on related technologies and characteristics of permanent magnet stepless retardation.Firstly,the working mechanism of the permanent magnet retarder is studied.It is necessary to stagger the magnetic poles on the rotor of the retarder,the rotor is connected to the automobile transmission shaft,and the copper stator is fixed on the axle.When the torque is required,the rotor is combined with the stator through the operating mechanism,and the relative motion causes the conductor to cut the magnetic field,thereby generating the motion resistance,that is the braking torque.It is proposed to realize the stepless change of braking torque by continuously changing the relative position of the stator and the rotor in the axial direction.The overall structural design of the retarder was carried out,and the cooling scheme for water cooling in the stator was determined.Secondly,the magnetic induction theory is used to calculate the braking power and braking torque of the retarder,and the causes of the braking torque are analyzed.According to the magnetoresistance analysis and considering the reliability of stator and rotor assembly and operation,the air gap between the stator and the rotor is determined in combination with the heat dissipation requirement.The optimization research of the stator structure design is carried out,and the weight reduction is realized under the guaranteed functional conditions.The research determines the number of suitable magnet blocks on the stator,and studies the structural size optimization of the single permanent magnet with the braking torque as the constraint,and solves it with MATLAB software.Thirdly,the research on the theory of permanent magnet retarder braking is carried out,and the theoretical description of the eddy current field of permanent magnet retardedbraking is analyzed.The finite element analysis model of the permanent magnet retarder brake is established,and the influence of different structural parameters on the air-gap magnetic density is studied.The variation curve is drawn and the curve is optimized according to the curve.Finally,the finite element analysis model of the retarder is used to further study the influence of the main structural parameters of the retarder on the braking torque.The influence of the change of the permanent magnet spacing and the logarithm of the permanent magnet group on the braking torque,and draw the corresponding relationship curve to determine the more optimized structure size.The relationship between the braking torque of the rotor and the axial movement of the stator is studied.The braking torque has a good linear relationship with the axial displacement.It can achieve good stepless braking by continuously changing the axial displacement of the rotor.Through theoretical analysis and simulation research,the proposed permanent magnet stepless retarder can achieve the expected braking effect,optimized to achieve a more compact structure,and the axial movement of the stator can achieve the braking torque linear stepless control.The retarder has a good application prospect. |
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