Torsional Vibration Analysis Of Motor Powertrain Shaft System Based On AVL Excite PU

Powertrain system is an important excitation source to vehicle vibration and noise.With the improvement of vehicle comfort requirements,reducing vibration and noise has become a hot issue.Due to the periodic excitation torque in the working process of engine,torsional vibration occurs during the crankshaft rotation.Torsional vibration not only affects the stability of the engine,but also induces the gear system vibration and noise of the transmission.At present,most of the crankshaft torsional vibration research is based on the independent engine shaft model,the interaction between engine and gearbox is seldom involved.This paper researches the powertrain torsional vibration characteristic of the shafting,firstly simplifies powertrain shafts equivalent model by lumped parameter method,and then established joint model of a four-cylinder gasoline engine and a five-speed manual gearbox in multi-body dynamics software AVL Excite PowerUnit.The paper analyses vibration and natural frequency of the crankshaft,calculates torsional angle displacement in the front end and the flywheel end of crankshaftand analyses vibration of shafting and gear transmission.Compared the torsion angle displacement with an independent engine model.The results show that the torsional angle of the crankshaft in the powertrain system is smaller than that of the engine model and the gearbox has a certain attenuation effect on the torsional vibration of the crankshaft.In this paper,the influence of dual mass flywheel on the torsional vibration of the engine and the gearbox shafting is investigated in the powertrain model.The results show that the dual mass flywheel can effectively reduce the torsional vibration amplitude and velocity fluctuation of the crankshaft output,decrease shafts' natural frequency and it also reduces the torsional vibration of gearbox,but it can't improve the torsional vibration of the crankshaft front end.Cylinder deactivation is a kind of technology to improve the economy of engine under small and medium load.This paper calculates the torsional angle displacement and gear system vibration of the both ends of cylinders' pause scheme and middle two cylinders' pause.Cylinder deactivation makes the torsional amplitude increase 2-3 times,1 harmonic becomes the main vibration harmonic.From the perspective of crankshaft torsional vibration,both ends of cylinders' pause scheme is better than the middle two cylinders' pause.Free gear's angle acceleration changed rapidly after cylinder deactivation.