Research On Design And Application Of Asymmetric Damping Automatic Tensioner

In this paper,an asymmetric damping automatic tensioner in an engine front end accessory drive system is the research object,and the passage-based calculation formula of the friction torque is established,and the mathematical model calculated by asymmetric damping tensioner hysteresis characteristics is established.The hysteresis test of the tensioner is carried out to verify the correctness of the analytical model.Then,a method to check the overall strength of the tensioner is given to further analyze the life of the tensioner in the working range.The motion model of the accessory system is established and solved to obtain the numerical solution.Finally,the experimental test is conducted and the results are compared to verify the correctness of the model.The main work of the thesis is as follows:(1)The structure and working principle of the asymmetric damping automatic tensioner in the engine front end accessory drive system are introduced.The friction torque of the damper film friction surface is analyzed,and the analysis model of the asymmetric damping automatic tensioner hysteretic torque calculation is established,and the tensioner quasi-static torque test is performed,and the reliability of the model is verified.The error between the calculation results and the test results is analyzed,and an asymmetric factor and damping is used to describe the hysteresis characteristics of the tensioner,and the proposed method is advantageous to predict the hysteresis characteristics of the automatic tensioner.A hysteresis model for dynamic excitation of the tensioner is established,and dynamic excitation tests are carried out to verify the correctness of the model.The relationship between the dynamic hysteresis torque and the swing angle of the tensioning arm is obtained.(2)The three-dimensional model of the asymmetric damping tensioner is established,and the model is simplified.The finite element model of the asymmetrical damper tensioner is established with a simplified part: Tensioning arm,base,bushing,shaft.The boundary parameters of the finite element model are determined according to the operating conditions of the tensioner,which solves the problem of complex frictional contact and non-convergence in the existing method to simulate the torsion process of the tensioner.The efficiency of analyzing the tensioner can be greatly improved.By setting the contact pairs and constraints of each component,the tensioner is checked for strength,and the change of the stress in the key components with the angular displacement of the spring is analyzed.(3)Based on the hysteresis model of the tensioner,a dynamic model of the accessory drive system with an asymmetric damped tensioner is established,and the dynamic response solution method is given.The dynamic response results of the system under various speed conditions are analyzed,and the validity of the results is verified through experiments;compared with the dynamic response results of the symmetrical damping tensioner,the influence and effect of asymmetric damping on the dynamic response of the system are analyzed.