Characteristics Study Of Rubber Torsional Damper

The engine vibration is mainly caused by the torsional vibration of the crankshaft. Theperiodic alternating torque caused by cylinder pressure will promote the crankshaft fatigue，even crankshaft fracture. It also transfers vibration to the Front End Accessory Drive system(FEAD) and the transmission, which causes adverse effects. It is an effective way to reduceengine torsional vibration by matching a appropriate Torsional Vibration Damper (TVD) forthe engine.Before the design of rubber TVD, inertia and stiffness of the TVD are known in advance.In operation of adjusting the TVD stiffness, it is necessary to make a series of test samples tochoose the TVD meeting function requirements, which increases the development cycle andcost.This paper takes one certain engine for example. Modeled the crankshaft system andexplained the inertia, stiffness and damping parameters of parts in detailed. The modal shapesand torsional vibration angle of front end of the crankshaft are calculated base on AVL-excite.According to the first order natural frequency of the crankshaft system and theequivalence principle, a vibration model with two-free-degrees is established. The basicparameters of the TVD are optimized, including the inertia, torsional stiffness and dampingratio of the TVD are optimized by the application of the Dynamic Vibration Absorber (DVA)principle and optimization theory. The simulation results are close to the experimental data,which validates the modeling and calculation method presented in this paper.The test method for the static stiffness of rubber TVD is proposed. Established thecomplex stiffness model for TVD dynamic characteristics and explained the relationship ofdynamic Stiffness, loss angle and damping parameter. On the basis of Maxwell model, astandard linear model is got by paralleling it with a spring system, which can describe thecorrelation of dynamic stiffness and frequency of rubber TVD better, and also confirmed themodel parameters by experiments.The influence factors on TVD stiffness are analyzed. The factors included rubber shearmodulus, the structure parameters of TVD, which include rubber contact width, rubbercompress ratio, shape of hub and so on. Established the dynamic stiffness model of TVD, thedynamic shear modulus of rubber under compression can be obtained by scanning the TVD infrequency.According to the analysis of matching TVD for engine crankshaft system, the allowed dissipation power of rubber TVD and maximum rubber shear stress are defined which canguide the optimization for rubber TVD.