| In recent years,with the rapid development of the commercial vehicle industry,people’s requirements for the riding comfort of commercial vehicles have also been gradually improved.The NVH problem of commercial vehicles has increasingly become a concern of engineers and manufacturers.As one of the models with the highest sales volume in commercial vehicle enterprises,tractor is prone to torsional vibration of the power transmission system due to its front and rear engine,large output torque,long transmission distance and other characteristics,Therefore,it is necessary to carry out simulation analysis and experimental research on the torsional vibration of the transmission system of this type of vehicle.The specific research work of this paper is as follows:(1)The excitation source of the torsional vibration of the transmission system is analyzed,in which the detailed theoretical analysis is focused on the engine excitation mode.At the same time,the vehicle transmission system is simplified into a 22 degree of freedom vibration model and a 16 degree of freedom forced vibration model using the concentrated mass method.The method to obtain the parameters of the main components in the model is established,and the corresponding dynamic equation is established,and the inherent characteristics of the equation are theoretically analyzed;(2)Organize a real vehicle test,use the LMS.Test.Lab signal acquisition and processing system,and measure the torsional vibration of the transmission system of the test vehicle through a road test.The test equipment includes a magnetoelectric speed sensor,a Hall speed sensor,a three-dimensional vibration acceleration sensor,and an acoustic microphone.The measurement points include rotation speed measurement points such as the engine flywheel,transmission input shaft,and transmission output shaft,as well as vibration acceleration measurement points such as the driver’s seat rail,transmission housing,and noise measurement points at the driver’s right ear.The test conditions include starting,full throttle acceleration,coasting,and Tip in/out.The results show that the test vehicle exhibits torsional vibration of the transmission system under acceleration conditions in common gears,and the resonance speed falls within the common speed range;(3)The structural parameters of the main rotating parts of the transmission system were obtained through theoretical calculation,3-digit modulus measurement and finite element simulation.The free vibration and forced vibration simulation models of the transmission system torsional vibration in the eighth gear were established using Amesim software.The simulation results were compared with the test results,and the accuracy of the simulation model was verified.The results showed that the engine speed of the test vehicle was close to 1255 rpm,That is to say,when the third order excitation frequency is close to 62.75 HZ,the fifth order mode of the transmission system is excited,which causes the torsional vibration of the transmission system,and the torsional vibration of the driven part of the clutch and the transmission is the main form;(4)The influence of the key parameters of the transmission system,including the torsional stiffness of the clutch torsional damper,damping torque,half axle torsional stiffness,transmission moment of inertia and rear axle moment of inertia,on the torsional vibration of the transmission system was investigated,and an optimization scheme for the torsional vibration of the transmission system of the test vehicle was developed: reduce the torsional stiffness of the torsional damper by 20%,increase the damping torque of 10 Nm,and reduce the torsional stiffness of the middle and rear axle half shafts by 30%,The results show that the improved scheme achieves ideal results in both frequency avoidance and amplitude reduction compared with the original scheme,and the feasibility of the improved scheme is verified. |
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