A Study On Modeling Method For Nonlinear Characteristic Of Driveline With Friction Clutch

As a typical automotive component,friction clutch is widely used in the driveline and can transfer or interrupt the engine torque to the driveline through a quick and easy method.Friction clutch has characteristics of simple structure,larger torque transmission,fewer cost and lower loss of power.In order to research the influence of friction clutch on the NVH(Noise,Vibration and Harshness)issues of the automotive driveline.The relevant models of clutch which take the nonlinear characteristics into consideration are proposed and relevant vehicle and bench test are carried out to study the NVH issues of the automotive driveline and clutch pedal performances.The major studies can be summarized as follow:(1)The nonlinear characteristics of axial stiffness of diaphragm spring and waveform plate are analyzed.The analytical model and the finite element model of clutch assembly are proposed.The clutch pedal effort performance test bench is designed and developed and the effectiveness of the model is validated by the experiment results.The influences of the working position of diaphragm spring,taxial compression of waveform plate and curvature of axial stiffness curve on the characteristics of clutch release force-displacement are studied.The relationship between the characteristics of clutch release force-displacement and the force versus displacement for clutch pedal are also analyzed.An improve program of the clutch base on the study results is proposed and the improve results are validated by the experiment.(2)Both the torsional stiffness and hysteresis of clutch damper have the characteristics of multi-stage.To study these nonlinear characteristics,the static torsion model is proposed to describe the clutch damper by using the hyperbolic tangent function and validated by the experiment.Gears rattle phenomenon at idle occur if clutch damper cannot attenuate or even enlarge the torsional vibration.The nonlinear dynamic model for automotive driveline transmission systems at idle is proposed.Static torsion model of clutch is taken into consideration.The dynamic response of driveline system,such as meshing force and relative displacement between geared teeth are calculated using the presented model.The influence of nonlinear characteristic of the clutch damper on gear rattle is investigated by using the developed model and calculation method.The design guidelines of clutch parameters are proposed for avoiding gears rattle at idle and validated by the experiment by comparing the baseline and revised clutch in a real automotive.Both judder and shuffle are back-forth vibration during vehicle starting which caused by the torsional oscillation of the driveline.Physical parameters which determine the nonlinear characteristics of clutch are carefully discussed,and improvement designs of the clutch for suppression of the judder and shuffle are consequently investigated.An improvement program is proposed by simulation results and validated with vehicle experiments.(3)Study the different between the static torsion and dynamic torsion of clutch damper.The experiment for dynamic characteristics of clutch damper is proposed.The dynamic stiffness and loss angle are used to describe the dynamic characteristics of clutch damper.The dynamic model of clutch damper is proposed and validated by the experiment of nature frequency.The versatility of the dynamic model is validated by the experiment of two kinds of clutch dampers which have difference in material and shape of damping cushion.(4)The test bench for studies the clutch vibration isolation performance is desgined and developed.The isolation ratio of the rotational speed oscillation is defined to evaluate the capacity of the vibration isolation performance of clutch which relies on the bench experiment result.The dynamic model of test bench is proposed by using lumped parameter method and the clutch vibration isolation performance is calculated by both static model and dynamic model.The results are validated by the experiment in the test bench.The developed models and analytical procedures proposed in this paper have guiding significance for the positive development of the clutch.