Study On The Torsional Vibration And Abnormal Noise Of The Driveline Of A Medium Truck

With the rapid development of the automotive industry,commercial vehicle users are paying more and more attention to the vehicle vibration and noise performance,which means that the vehicle for each subsystem of the NVH performance requirements of the entire vehicle are more stringent.The power transmission system is one of the most important components of the whole vehicle.It is responsible for transmitting the engine torque to the driving wheel,which is prone to orsional vibration during operation.This paper studies the abnormal sound caused by torsional resonance of power transmission system with market feedback.In this paper,a certain type of truck with acceleration abnormal sound is studied.The goal is to find the cause of the problem through the combination of simulation and experiment,and propose effective improvement measures and real vehicle verification.The main contents of this paper are as follows:First,relevant subjective evaluations and objective measurements were made for market complaints,and the problem phenomena and NVH performance related parameters were confirmed.Through the analysis of objective data,the abnormal sound comes from the torsional vibration of the power transmission system.Secondly,based on the existing three-dimensional model of the design department,the multi-body dynamic model of the vehicle transmission system is established,and the transmission shafts and semi-axles with low torsion stiffness are treated flexibly.Finally,the rigid-flexible combination model of the whole power transmission system is established and the modal calculation is carried out on the model.By comparing the test results with the simulation results and searching the knocking position,the cause of the abnormal sound is finally confirmed: under accelerated driving condition,the ignition excitation frequency of the engine at a certain speed is close to or coincides with the torsional natural frequency of the transmission system,resulting in torsional resonance.When the speed fluctuation of the input shaft of the gearbox increases,the lock pin and the outer ring of the synchronizer are knocked,and the vibration is transmitted to the transmission shaft and transmitted to the air in the form of noise.Thirdly,the influence of clutch stiffness and hysteretic damping on torsional vibration is analyzed by the multi-body dynamic model,and the inherent characteristics of transmission shaft under different states are compared by the method of objective measurement.Based on the simulation and comparative test,suggestions are given: reducing the main stiffness of the clutch plate;increasing the hysteretic damping to 100Nm;increasing the damping material inside the drive shaft.Finally,the improvement measures were carried out on the test sample car,and the test measurement and subjective evaluation under the same working condition are made.Finally,it was confirmed that the abnormal sound declaration was obviously reduced and acceptable.The torsional vibration of the transmission system was significantly reduced.In summary,this paper conducts a subjective and objective evaluation of vehicles with abnormal noise in the market,confirms the nature of the problem,and identifies the reasons.The multi-body dynamic model with rigid and flexible combination is established,and the free mode analysis is carried out.The stiffness and hysteretic damping of the clutch are optimized,and the improvement suggestions are given.By comparing the transmission shaft test with different filling states,the best scheme of NVH performance is put forward.Finally,the improvement scheme is verified on the test vehicle.The solution of this problem not only alleviates users’ complaints and saves the company’s reputation,but also provides an effective reference for other companies to deal with similar problems of vehicles.