Research On The Nonlinear Dynamics And Noise Performance Of Timing Gear System Of Diesel Engine

The dynamic characteristics and NVH performance of diesel engine timing gear system have a very important influence on diesel engine power,reliability and comfort.The timing gear system is complex,and the influence factors are more,which show the nonlinear characteristics and coupling effect.Therefore,the research on the dynamic characteristics and NVH characteristics of the timing gear system has attracted much attention.In this paper,based on the simplified diesel engine timing gear rotor system,the dynamic characteristics of the system were solved by numerical calculation method,and the timing gear system noise control methods were explore.The main research contents are as follows.Based on the principle of gear meshing,a gear meshing equivalent physical model and mathematical model of Elastohydrodynamic lubrication were built.The lubrication state of the meshing process of involute spur gear was calculated by the multigrid method.The effects of different meshing position,gear transmission ratio,gear modulus,gear pressure angle,gear speed and roughness on the oil film pressure and oil film thickness were analyzed.The 5 degree of freedom quasi-dynamic model of rolling bearing load distribution was derived.Considering the time varying characteristics of the tooth backlash and meshing stiffness,the effect of the oil film transient extrusion and the friction torque in the mixed lubrication condition,the friction dynamic model of the gear was established.Based on the finite element theory,the multi-body dynamics model of the diesel engine timing gear system was established by coupling the subsystem model with six degrees of freedom space beam element.The nonlinear dynamic behavior of the positive time gear system was solved by numerical iteration method.Study on timing noise of gear transmission system classification,dynamic excitation,gear howling and mechanism of impact noise and low noise design,and the theoretical method of analyzing the subjective and objective evaluation of sound quality.A support vector machines was adopted to establish a diesel engine noise quality prediction model,and the accuracy of the prediction model was verified with the noise test samples.Based on the prediction model,the influence weight of objective evaluation of sound quality parameters on the results of subjective evaluation was analyzed and calculated.In this study,a comprehensive evaluation method of sound quality was proposed focusing on solving the multi-factor,multi-condition problem,and reducing time and difficulty of subjective jury test at the same time.The comprehensive evaluation model of diesel engine sound quality was developed based on hierarchy analysis,UDS and subjective perception analysis.An improved AHP was developed by introducing a new method calculating the relative weight based on evaluators’ preference order instead of the traditional 1~9 scales method,which reduces subjective liberty and difficulty of the consistency of the judgment matrix meeting the requirement,and the requirements of evaluators’ specialized knowledge.The interaction of fixed gear and gear meshing,loading gear mechanism and shear type time-varying gear meshing stiffness calculation method and variation analysis model was established based on scissor gear transmission system of two translational and torsional vibration dynamic model and inherent characteristics.The influence of stiffness parameters on the system’s inherent characteristics was studied.The nonlinear dynamic characteristics of the scissor gear transmission system contained friction,backlash,time-varying meshing stiffness and transmission error are studied.The effect of scissor gear on the noise performance of diesel engine is analyzed by means of noise testAcoustic source localization test camera on the front end of a diesel engine.The results show that the middle parts cover gear room was the most concentrated area in front of the noise energy.Study on noise reduction principle of sound absorption structure and its application in noise reduction of gear cover.Based on the multi objective optimization method,the optimization design of the low noise structure of the gear room cover was carried out,which provided a reference for the noise control of the timing gear system.