The Methods Of Calculation And Experiment Investigation For The Performance Of An Automatic Tensioner On Accessory Drive System

The engine front end accessory drive system(EFEADS)is an important system in the automobile.The power is transmitted from the crankshaft of the engine to each accessory through a transmission belt in order to ensure the operation of each accessory.At present,a serpentine belt is widely used for power transmission.Serpentine belt transmission has some advantages,such as a larger transmission power,and more compact layout structure.However,there are some disadvantages,such as a fluctuation of belt tension and belt slip.Thus an automatic tensioner is applied to maintaining the belt tension,reducing the belt slip and reducing the system vibration.But now,there is few research on the mechanism theory of automatic tensioners inside China,especially the method of calculating the performance of the automatic tensioner.With the development of automobiles,it is urgent to establish a calculating method for the performance of the tensioner to improve the design level of automatic tensioners,to shorten the design period and cost of development.In this paper,taking an automatic tensioner of engine front end accessory drive system as the research object,the working principle and main design flow of automatic tensioner are described,The analytic model and finite element model of the Quasi-static hysteresis characteristic for the tensioner are established.The computing accuracy of the model is verified by test,then the hysteresis model of the automatic tensioner under dynamic excitation is established and verified by relevant experiments.The main work of this paper is as followings:(1)The working principles and main design flow of the automatic tensioner are described.The design parameters of the automatic tensioner are obtained in the design software of the engine front end accessory drive system.The mechanism of friction torque of tensioner is analyzed and an analytic model of output torque is proposed.Based on the analytic model,the calculating method of quasi-static hysteresis characteristic curve of automatic tensioner is obtained,and the reliability of the analytic model is verified by the quasi-static torque test.(2)The finite element model of the automatic tensioner is established,and the force nephogram and contact nephogram of each part of the automatic tensioner are obtained.The reliability of the finite element model is verified by comparing the samples after a durablility test,and the hysteresis characteristic curve calculated by the finite element model is obtained and verified by quasi-static torque test.Its precision is higher than that of analytic model,then the influence of design parameters of damping mechanism on damping torque is discussed.(3)On the basis of quasi-static hysteresis characteristic model,the analytic model under dynamic excitation is established.And the calculating formula of hysteresis curve under dynamic excitation is derived,the accuracy of the model is verified by dynamic test.The influence of the transition region coefficient on the hysteresis characteristic is analyzed,and the influence of different excitation frequency,amplitude and initial working position on the hysteresis characteristic curve is investiagtied.The comparison between the calculated value and the experimental value is given,and it shows a good correlation.