| As diesel engine's important part,whether Air distribution mechanism's design is reasonable or not will directly relate to the power and economy of the diesel engine and the stability,reliability and emission performance of the diesel engine.With the development of high speed and high power,the strengthening of the diesel engine is also increasing,and the performance requirements of the diesel engine are also increasing.Meanwhile,the gas distribution mechanism's working conditions are deteriorating,which requires the diesel engine can stably and reliably work in high speed running condition.So,higher requirements are put forward on the design of the gas distribution mechanism,and the dynamic characteristics,fatigue damage and vibration noise of the mechanism also become the focus of the research.One domestic agricultural 4-Valve Diesel engine's air distribution mechanism is taken as the research object in this paper.Based on the analysis of some relevant literatures at home and abroad,the development of the engine's air distribution mechanism is summarized and the kinematics and dynamic characteristics of the air distribution mechanism and the evaluation index of the air distribution cam are analyzed.By optimizing the cam profile,the contact stress is reduced after increasing the minimum radius of curvature and decreasing the spring stiffness.At the same time,the optimization and matching the shape and structure,space position,materials and hardness of the Cam-Column are matched and optimized.For the optimized results,a reasonable test scheme is designed and detailed test verification is carried out.Specific work is as follows:1.The cam wear phenomenon in the diesel engine is analyzed and the reason of the wear is found out.Specifically analysis is on the cam and tappet these two aspects.Using MATLAB software,combined with the original cam drawing lift table,the original cam lift,speed and acceleration curve were obtained.The results of the correlation parameters of the cam and columns such as the maximum contact stress,the fullness coefficient,the minimum radius of curvature and so on are calculated.Through the analysis of the curve and the parameters,find out the reason of the wear.2.Starting from t these three aspects of the cam and the Column's hardness and material matching,lubrication and contact stress these three aspects,the original cam valve train is analyzed and evaluated,and the improvement measures are put forward.3.While maintaining the original power performance of the diesel engine,optimally design air distribution cam profile to improve the old cam wear problems.The new cam type lines specifically make use of constant speed-constant velocity buffer and high order polynomial work section According to the calculation and analysis of the original cam profile,the data calculation and the graphic output function of the MATLAB software are used to write the corresponding program so that multiple sets of cam type line results can be got.4.Through the kinematics calculation and analysis of multiple sets of cam type line which is calculated by MATLAB software and through the analysis of performance parameters,the contrast analysis on comprehensive comparison of various type line and the original cam type line is carried on to select a set of optimal cam profile results.5.Make a reasonable test plan,do a reliability test of the optimized cam,measure the amount of wear and compare it with the original wear and tear.Observe whether the wear of the pillar is improved and whether the optimized model can meet the demand and if the demand isn't met,optimization and improvement need to continue. |
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