Dynamic Analysis Of Valve Train In Diesel Engine

As one of the important parts of the diesel engine,the main function of valve train is to regularly control the opening and closing of the valve,to ensure that the cylinder timely enter and exhaust in the work.This directly determines whether the diesel engine can obtain the best power performance and economy.Only after fully understanding the actual movement and stress state of each component in the valve train,the possible problems in the valve train can be accurately evaluated,so as to make targeted analysis and improvement.Therefore,it is of great significance to study the kinetic aspects of the valve train.In this paper,the valve train of 16V265 H diesel engine is used to model each component separately through Creo5.0 software,and then complete the assembly work and pretreatment work on the ANSYS Workbench platform.The connection pair,constraint and the contact pairs of the whole mechanism and the addition of the spring unit define the discrete treatment of the various components of the valve train,and finally,the establishment of the multi-body dynamic model of the valve train camshaft-rocking arm-valve system is completed.This paper analyzes the overall mode analysis of the dynamic structure of the valve train and the dynamic characteristics at 400 r/min to observe the moving state of the mechanism for five complete working cycles.The whole mechanism is divided into valve,boom and camroller contact pair,including the movement characteristics,the rocker arm and tappet,and the contact state of the cam-roller pair.Based on the transient analysis at 400 r/min,three speed conditions are set.By comparing the results of the four speeds,the influence on the stability of the valve train is explored.The results show that the opening speed of the valve increases significantly with the increasing rotation speed,as the closing speed of the valve is affected by the recovery speed of the valve spring,the amplitude of the former,and the maximum valve closure velocity gradually becomes constant,this value is the recovery speed in the free state of the valve spring;The stress state of the rocker arm and tappet increases with the increasing speed,but the maximum load is lower than the yield stress of the material and will not cause strength damage;Through the fatigue angle,the safety coefficient distribution of rocker arm and tappet is given and meets the requirements;The maximum positive pressure,friction force and penetration of the camroller contact pair will increase with the rotation speed,And the state of the contact pair also gradually becomes unstable,The instability is reflected by the increase of roller slide momentum and the occurrence of roller beating.