| Heavy vehicle has become the main force of road transportation.Because of the Government regulations and market competition,the requirements for fuel economy and ride comfort of heavy vehicle are getting higher and higher.So the research on the ride comfort of heavy vehicle appears to be very important.Heavy vehicle generally has large load,big wheelbase and long body,the frame’s bending vibration is significantly pronounced.Therefore,it is necessary to consider frame’s elastic when establishing the ride comfort model of heavy vehicle.The transmission shaft is an important part of heavy vehicle powertrain system,and that heavy vehicle drives for a long time with bad road conditions is easy to cause transmission shaft failure and reduce the vehicle’s NVH performance.So designers hope to optimize transmission shaft parameters in the level of vehicle vibration.This paper foucs on the vibration of heavy vehicle.Based on vibration theory and using the methods of theory,simulation and experiment,focusing on four aspects: vibration mechanism and optimal matching of transmission shaft,vehicle vibration model,model experimental verification.The main contents are as follows:(1)Vibration mechanism analysis of transmission shaft.The various motivators and transfer paths of transmission shaft vibration are studied,and the formula of the centrifugal force of transmission shaft is derived.The characteristic of unequal velocity of single cross universal joint is analyzed.The equal-speed transmission of double and triple universal joints is discussed by theoretical deduction and ADMAS.It has engineering practical value in the vehicle arrangement of transmission shaft.(2)Establishment of elastic vibration model of heavy vehicle.The conventional 6-DOF rigid model is firstly established.Based on elastic beam theory,the synthesis between elastic bending vibration and rigid motion of frame is carried out.The formula of modal mass and stiffness are derived,and 8-DOF elastic model of two-axle heavy vehicle is established.The elastic model and rigid model are compared by MATLAB/Simulink,and the results show that it is necessary to regard the frame as an elastic body when researching heavy vehicle.(3)Research on optimal matching of transmission shaft.According to vehicle arrangement and centrifugal force of transmission shaft,the 8-DOF elastic model of heavy vehicle with transmission shaft’s centrifugal force is established.The four transmission shaft’s parameters and three vehicle arrangement’s parameters are presented.The orthogonal test is used to analyze the seven parameters one by one in vehicle vibration level,and the test results are analyzed by the intuitive analysis and variance analysis.The results show that: 1)The main reduction ratio,assembly error,transmission shaft length and residual unbalance are the main factors that affect vehicle vibration,which need to be considered in the vehicle layout design.2)The optimal combination of various parameters,which provides a theoretical method for the rational matching of the transmission shaft’s parameters and has the engineering value.(4)Experimental verification for model.Five kinds of transmission shafts were tested on the bench,and the transmission shaft’s parameters are introduced into the 8-DOF elastic model of heavy vehicle with centrifugal force of the transmission shaft for orthogonal test.The bench experimental data is compared with the orthogonal tests’.The comparison results show that the vibration trend of experiment and simulation is consistent,which verifies the reliability of the model established in this paper. |
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