The Optimization Research On Radial Dynamic Characteristics Of The Internal Combustion Engine Camshaft

The vibration and noise produced during the normal operation of the valve train are the important factors that affect the performance of NVH,so it is an important research topic to weaken the vibration and noise radiation of the valve train system.Camshaft as an important part of the valve mechanism,function is to open the valve timing,and the dynamic characteristic of the camshaft has important influence on the dynamic characteristics of the valve,so it is important to study the optimization of the radial dynamic characteristics of the camshaft.The main work and conclusions of this paper are as follows:Design and build the dynamic characteristic test bench for the valve mechanism,installing three acceleration sensor on the valve disk,laser displacement sensor installed on the valve rod,collected the signal of dynamic characteristics of valve.Mounting strain gauges on the valve end of the rocker arm collected the load signal of the valve end of the rocker arm.Design the static calibration experiment of the valve train is to establish the corresponding relationship between the load and the strain voltage.Design a simple cam profile measuring experiment,collecting cam profile data.A one dimensional dynamic model of valve train mechanism was established by AVL software,the key parameters of the model were established by the experimental measurement and finite element method,the damping coefficient of the system and the friction coefficient between the parts are the empirical value of the software is recommended,the calculation results are compared with the experimental results,the model can be used for the simulation analysis.Using the model to calculate the radial force of 5 bearings,through the comparison and analysis,establish the fourth bearing as camshaft radial dynamic characteristics optimization research object.Using one dimensional dynamic model,the optimization of the radial dynamic characteristics of the camshaft is carried out from 3 aspects: the width of the bearing,the radial clearance of the bearing and the dynamic viscosity of lubricating oil.Increasing the dynamic viscosity of lubricating oil can reduce the maximum radial and radial vibration velocity of the camshaft.When the internal combustion engine is running at low and medium speed conditions,increasing the dynamic viscosity of the lubricating oil will increase the maximum radial force of the bearing;When running at high speed,increasing the dynamic viscosity of the lubricating oil can reduce the maximum radial force of the bearing.Increasing the radial clearance of bearings with the radial clearance increases the maximum radial and radial movement of the camshaft.The internal combustion engine runningat low and medium speed conditions,due to the inability to form a good lubrication condition,the smaller the radial clearance of the bearing,the greater the radial force of the camshaft;Running in high speed condition,the bearing clearance is bigger and bigger,the camshaft radial vibration is fiercer,the camshaft maximum radial force will increase.Increasing the width of the bearing seat can reduce the maximum radial and radial vibration velocity of the cam shaft.When the internal combustion engine running at low and medium speed conditions,increasing the bearing seat width will increase the radial bearing capacity,but in high speed operation,increase the bearing block width can reduce the bearing block radial force.Research on the influence factors of the radial dynamic characteristics of the cam shaft by the design of the orthogonal experiment,we know that the largest impact on the camshaft maximum radial displacement is bearing radial clearance,the second is the bearing seat width,minimal impact is power lubrication oil viscosity;The largest impact on the maximum radial vibration speed of the camshaft is the width of the bearing seat,the second is the dynamic viscosity of the lubricating oil,and the least influence is the radial clearance of the bearing;The largest impact on the maximum radial force of bearing is bearing radial clearance,the second is the width of the bearing seat,and the minimum influence is the dynamic viscosity of the lubricating oil.Based on orthogonal experiment results,by optimizing the bearing block width,bearing block with radial clearance and lubrication oil dynamic viscosity of three parameters,compare the new scheme with the original scheme,We know that the maximum radial displacement is reduced by11.6%,the maximum radial vibration velocity is decreased by 21.3%,and the maximum radial force of the bearing is decreased by 1.09%.