Car clutch in the fully engaged and engaging state all will produce judder phenomenon.They performed low-frequency vibration in the front-rear direction.The low-frequency judder destroys not only the smoothness of the clutch work but also seriously affect the vehicle transmission system and vehicle vibration characteristics,while increasing the clutch wear and reduce the clutch life.Clutch judder is caused by piecewise linear spring of torsional vibration damper and the nonlinear of friction.Clutch judder is widespread and urgent to solve in practical application of the project,which is highly concerned by the academia and the engineering community.This paper,for a vehicle model,mainly analyzes and optimizes the clutch judder problem generated during the two conditions of fully engaged state and engaging state from the perspective of clutch parameter design.Firstly,based on the whole vehicle power transmission system,the main transmission components were simplified and parameterized according to the equivalent simplification principle and the relevant calculation formula.The two dynamic models of the clutch in the fully engaged state and engaging state were established respectively by Ritz method.Secondly,according to the piecewise linear dynamic model under the clutch fully engaged condition,the jumping phenomenon and the dynamic characteristics near the working point of the clutch are analyzed qualitatively by the phase plane method.Besides,the frequency response characteristic is obtained by the KB method of nonlinear vibration theory,and the instability phenomenon of the clutch after full engagement is quantitatively analyzed.The influence of main parameters,such as engine excitation amplitude,piecewise linear spring stiffness switching point and damping coefficient,on the amplitude-frequency response and stability of the clutch system are studied in this article.In order to study the clutch judder caused by friction,several models that commonly used aiming at the dynamic model under engaging state are established.The influence of multiple parameters on clutch friction judder and the self-excited vibration mechanism caused by friction are analyzed qualitatively by using phase plane method,limit cycle theory and energy method.The numerical analysis of clutch engagement is carried out by using Runge-Kutta method.The influence of main parameters,gradient of friction coefficient,friction coefficient,damping coefficient and stiffness on clutch friction judder are studied in this article too.Finally,this paper focuses on two judder problems which includes the clutch is fully engaged and under engaging process.The basic parameters of the clutch system are optimized based on theirinfluence law on clutch vibration.The results are correspondingly verified by simulation method in MATLAB software and the clutch judder is reduced.All of those provide an important reference for the basic design of the clutch. |