The Methods Of Calculation And Experiment Investigation For The Dynamic Response Of The Accessory Drive System

Engine front end accessory drive system(EFEADS)transmits the output torque of the crankshaft to accessories such as fans,air-conditioning compressors and water pumps through a flexible belt.By the way,it is equipped with an automatic tensioner which is used to quickly compensate for the change in the expansion and contraction of the belt and maintain the stability of the belt tension and improve the NVH performance of the system.However,the design and development of the existing EFEADS mostly depends on tests and human experience,and there are problems such as long cycles and high costs.Therefore,in order to effectively predict the dynamic response of EFEADS and the hysteresis characteristics of the tensioner,and provide engineering guidance for the forward development and design of the EFEADS,this paper has carried out research on the dynamic response calculation of EFEADS and the calculation of the hysteresis characteristics of the tensioner.Relevant experiments are done to verify the reliability of the model.The main work of the paper is as follows.(1)The working principle of the tensioner with spring expansion damping structure is discussed,the mechanism of the friction torque of the tensioner friction pair is analyzed.The calculation model of hysteresis characteristics under dynamic and static excitation is established and the hysteresis characteristics test and endurance test are carried out which show that the model can effectively predict the hysteresis characteristics of the tensioner.The influence of excitation frequency and amplitude on the hysteresis characteristics of the tensioner is studied,and the effect of the structure parameters of the tensioner on the sensitivity of the damping rate is studied which provides guidance for the optimization of the tensioner damping rate.(2)Considering the factors,like the load and the moment of inertia,the motion model of the driven wheels are established.The parameters such as the output torque,damping and stiffness of the tensioner are identified by its hysteresis characteristics,which are used to build the motion of the tensioner.The determination methods of equivalent viscous damping under constant average excitation and variable frequency excitation are given respectively.Taking into account parameters such as the stiffness and elongation of the belt,a calculation model of the belt tension is established,and two types of belt tension calculation methods are proposed.The multi-harmonic excitation of the crankshaft is used as the input parameter,and the solution method of dynamic response of the EFEADS is given.(3)The test method for dynamic response of EFEADS is described.Taking three-wheelbelt-single tensioner accessory system as an example,the calculation results of tensioner hysteresis characteristics,test results of belt longitudinal stiffness and layout of the accessory system are used to calculate the dynamic response of the system under constant average speed and acceleration conditions.The variation law of the response parameters such as the dynamic tension of the belt segment,hub load,and the output torque of the tensioner are analyzed.Finally,the influence of the tensioner damping ratio on the dynamic response of the system is discussed.