Design And Performance Analysis Of Shift Mechanism Of Pure Electric Vehicle Transmission

With the support of policies and technology upgrades,pure electric vehicles usher in rapid development,more and more recognized by consumers.Because of the wide speed range of the motor and the characteristics of constant torque at low speed and constant power at high speed,the pure electric vehicle usually adopts a fixed speed ratio transmission device.But it also brought in the latter part of the lack of acceleration,driving mileage short problem.Pure electric vehicle assembly gearbox can make the motor work in the best speed range,can significantly improve the efficiency of the motor.Research shows that the two gear box can obviously improve the power and economy of electric vehicle.In this paper,a two-speed gearbox without power-off gearshift mechanism based on overrunning clutch and rear friction plate clutch is proposed to replace the synchronizer shift mechanism of traditional mechanical gearbox.According to the change of speed,the clutch has the characteristics of automatic combination and separation.The overrunning clutch is installed in the first gear,and the friction plate clutch is connected with the second gear.By using the difference of the speed between first gear and second gear,controlling the friction of the friction plate clutch the combination and the separation of the friction plate type clutch can lead to the automatic separation and combination of the overrunning clutch,thereby realizing the interruption shifting.Shift by controlling clutch will greatly simplify the transmission structure and control system.In this paper,the performance of the shifting mechanism is studied and analyzed by structural design,theoretical analysis,modeling and simulation,prototype machining and real vehicle experiment.The main contents are as follows:1.Design the shift mechanism structure scheme.The structure of the gearbox shift mechanism is discussed in detail,determine the design scheme by study the installation position of the clutch and friction plate clutch.Establish the mathematical model of gearbox shift process,analyze the principle of uninterrupted shift based on the torque phase and inertia phase.According to the requirements of the test vehicle,determine the structural parameters of the overrunning clutch,calculated contact strength by Hertz contact theory,check the contact strength by the finite element analysis software ABAQUS.2.Simulation analysis of shift mechanism.The simplified model of gearbox shaft,gear and shift mechanism is constructed by CATIA software.Built the virtual prototype model of gearbox by ADAMS and simulate the dynamic characteristics of the overrunning clutch to verify the correctness of the design parameters.The simulation of the gearbox shift process is carried out,and the simulation results show that the gearbox can realize the uninterrupted shift.3.Prototype design and real car experiment.The gearshift was designed and processed in detail so that it could be installed in a two-speed gearbox.Built the experiment of pure electric vehicle which based on d SPACE-Micro Auto Box.The experimental results are obtained by collecting the motor speed,wheel speed and transmission shaft torque signal.The experimental results show that the shift mechanism based on the overrunning clutch and the rear friction plate clutch can realize the uninterrupted shift of the two-speed transmission of the pure electric vehicle,and has good shift quality.