| Torsional vibration of crankshaft system is a major factor affecting the NVH performance of the engine.Furthermore,as the crankshaft torsional vibration damper(TVD)is the key structure connecting the crankshaft system and the front end accessory drive(FEAD)system,its’ damping effect is of vital importance to control the torsional vibration of crankshaft system and to improve the working condition of the FEAD system.The crankshaft system which has an excellent torsional vibration performance could greatly improve the NVH performance of the engine,the engine’s power output would be smoother,and the components of the crankshaft system would have a longer service life.In this paper,the single-stage rubber TVD of crankshaft which had been widely used on gasoline engines was studied.The research combined the methods of theoretical calculations,dynamics simulations and experimental verification,and the damping effect of TVD with bearing and non-bearing structures as well as resonance and optimum parameters design method were in-depth investigated.First,the damping effect when TVD applied different structure forms and design parameters were preliminary compared by theoretical calculations applied crankshaft system lumped parameter model.The calculation contained the circumstance of considering rubber layer’s damping or not,derived the frequency-response formula of torsional vibration system,calculated the relations between setting ratio and damping ratio when applied the resonance design as well as the parameters of optimum setting ratio and optimum damping ratio,and analyzed the influence of mass ratio,frequency ratio and damping ratio on amplitude amplification factor.Then,the flexible multi-body dynamics co-simulation model of a 1.0T three-cylinder gasoline engine was established based on multi-body dynamics theories combined with finite element method(FEM).The simulation model contained the crankshaft system,the FEAD system and the timing drive system,and the EHD(elastic hydraulic lubrication)main bearing models were introduced to considering the influence of lubrication on simulation results.The simulations analyzed the torsional vibration results of crankshaft system as well as the transversal vibration amplitudes and relative slippage results of the FEAD belt.While the multi-body dynamic simulation models were modeling,the experiments of structures free modal test,the crankshaft torsional bench test and the engine 5-points and near-field noise test were conducted to verify the computation accuracy of simulation models.The experimental results all kept a high consistency with the simulation results,ensured the accuracy of the simulation models.The results showed that the theoretical calculation results kept a high consistency with dynamic simulation results and experiment results.When the TVD applied the same structure form,the TVD with optimum parameters design could reduce the torsional vibration amplitude and improve the working conditions of the FEAD system more effectively compared with the resonance design,and the resonance design is more inclined to significantly reduce the torsional vibration amplitude in a certain speed range of the crankshaft system.When TVD adopted the resonance design,the damping effect on crankshaft torsional vibrations of non-bearing TVD was obviously better than bearing structure TVD,and when TVD adopted the optimum parameters design,the damping effect of two kinds of structures was almost the same,but on the resonance orders,the damping effect of non-bearing TVD did better than bearing TVD.However,no meter the TVD adopted which kind of design parameters,the non-bearing TVD ‘s damping effect on the belt transversal vibration and relative slippage of FEAD system performed better than bearing TVD.The conclusions and research method of the paper would provide manufactures important suggestions and theoretical foundations while developing and improving the similar products. |
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