Study On The Effect Of Geometric Eccentricity Error On Gear Mesh Stiffness And Dynamic Response

Nowadays,the NVH performance of automotive has been highly regarded.The dynamic responses of gearbox and engine,which are the main excitation source of automotive NVH performance,have been research topics of auto makers and research institutions.Since gear drive is the primary transmission in MT(Manual Transmission),the dynamic vibration response of gear system has great impact on the NVH performance of MT even vehicle.Geometric eccenticity error is one of the main errors during the process of MT and gears.As an internal excitation,the geometric eccentricity error not only effect the gear system with cam and mass eccentricity,but also effect the gear mesh stiffiness.Although many of scholars have studied dynamic model of gear system with geometric eccentricity error,few of them focus on the effect of geometric eccenticty error on gear mesh stiffiness.In this paper,we focused on the effect of geometric eccentricity error on gear mesh stiffiness and calculate the mesh stiffiness.After substituting the mesh stiffiness of geometric eccentric gear into the dynamic model,we obtained a more accurate dynamic model of gear system with geometric eccentric error.The achievements in this paper can be summarized as follows:1.Based on the literatures of gear mesh stiffiness,we proposed a moled to calculate the gear mesh stiffiness of gear system with geometric eccentricity error.The model was composed by four modules which include: transformation module of coner rotated about the geometric center,calcutaion module of start and finish angle during meshing,estimation module of mesh interval and calculation module of complementary angle of engagement force.We could calculate the mesh stiffiness of gear system with geometric eccentricity error quickly by these four modules.Compared with the mesh stiffiness of standard gear system,the stiffiness of gear system with geometric eccentricity error has two kinds of modulation: amplitude modulation(AM)and frequency modulation(FM).2.We modeled the dynamic model of gear system with geometric eccentricity error.In the model,the cam effect and mass eccentricity effect were considered.Futher more,two dynamic models are modeled,one considered coupling terms and the other one did not consider the coupling terms.The model with coupling terms were solved by Runge-Kutta method and the one without coupling terms were solved by Newmark-b method.After comparsion,we found that the couping terms make no difference to the location of the peak in frequency spectrum of the dynamic vibration response and the astringency of Newmark-b is much stronger than that of Runge-Kutta.3.After substituting the mesh stiffiness of gear system with geometric eccentricity error into the dynamic model,we solved the model and obtained the dynamic vibration response of gear system with geometric eccentricity error.By analyzing the the frequency spectrum of dynamic vibration response,we got the characteristic of gear system with geometric eccentricity error in frequency spectrum.Firstly,there exis sidebands around the mesh frequency and defect frequency peak in low frequency region.The bandwiths of sidebands are equal to the defect frequency.Secondly,because of the FM of mesh stiffiness of gear system with geometric eccentricity error,there exist other sidebands that surrounds the mesh frequency and the bandwiths of these sidebands are equal to the 2 or more times of the defect frequency.This phenomenon was rarely mentioned in the studies on the gear system with geometric eccentricity error.4.We also tested the NVH performance of MT of automotive in the powertrain NVH Test Lab of China automotive technology and research center.We analyzed the accelerated process of MT by order method.We found that there exist evident AM and FM phenomena in 3D waterfall of the MT.The phenomena qualitatively verify the AM and FM characteristic of gear system with geometric eccentricity error.