Wear Analysis Of A Camshaft And Roller Tappet Of An Engine

Valve mechanism is to achieve the engine cylinder working process of the key institutions,through the valve mechanism can be achieved in the cylinder charge replacement,to ensure that the engine to complete the four stroke of the working cycle.Therefore,the design of the gas distribution mechanism directly affects the engine dynamics,economy and reliability.The cam-tappet friction pair is one of the very important friction pairs of the engine.Through the analysis of the wear failure of the cam-tappet roller friction pair of the valve body,it is found that the cause of the wear and the rectification and optimization measures can improve the reliability of the engine And durability indicators.In this paper,an engine in the actual operation,the valve out of the exhaust cam-tappet roller friction pair wear failure as the research direction.Based on the Excite Timing Drive calculation software,the engine valve train is modeled,and the kinematics and kinetic characteristics of the engine air distribution mechanism are simulated and analyzed.Combined with the experimental verification,it can provide reference for the analysis of fatigue wear performance and the improvement of structural parameters of various components of valve train.Based on the analysis of wear theory and the simulation analysis of gas distribution mechanism,in order to solve the wear failure of cam-tappet roller friction pair,this paper proposes the following corrective measures:optimizing material selection and heat treatment process;reducing the weight of exhaust rocker,Reduce the inertia of the valve and reduce the contact stress between the cam and the tappet roller;reduce the valve spring preload;improve the lubrication conditions,increase the amount of lubricating oil to prevent dry grinding;improve the processing accuracy,fine inspection process;Redesign an FB2 exhaust cam profile.According to the improvement of the structure and parameters of the rocker arm,roller and valve spring of the valve train,the kinematics and kinetic model of the original air distribution mechanism are changed accordingly,and the newly designed FB2 cam profile is simulated and analyzed-Compared with the calculation scheme of the original machine,the new scheme can meet the requirements of the engine inflatable performance,the valve mechanism is working smoothly,and the contact stress of the cam-tappet roller friction pair is reduced.Among them,the full impact coefficient of the engine inflatable efficiency increased from 0.445 to 0.528.And the contact stress of the cam-tappet roller friction pair decreased from 1272.5MPa to 983.47MPa.The improved valve train and cam profile are tested on the engine for 8,000 hours of continuous operation.The cam-tappet roller friction pair does not exhibit wear failure,and the program is to be verified in subsequent tests.