The Research On The Noise And Vibration Of The Metal Belt Type CVT

With the gradual depletion of non-renewable resources that can be explored and utilized by human on Earth and the growing problem of global warming,developing new energy technologies becomes more and more urgent,and these problems also pose even more severe challenges to the automotive industry.As the automobile exhaust emission standards in China increasing continuously,in order to meet the national standards,developing new energy vehicles seems to be a feasible and realistic solution.Limited by the current development of battery technology,the power density of the battery is difficult to increase,ideal clean energy pure electric vehicles have not yet been used widely by the vehicle market.And hybrid electric vehicles are still the first choice to improve vehicle emissions.Metal belt type continuously variable transmission(CVT),with its continuously variable speed ratio,is favored by vehicle manufacturers for its matching the engine conditions perfectly.Therefore,new energy vehicles,especially the hybrid electric vehicles carrying Metal belt type CVT have a great development prospect.What's more,with the continuous improvements of requirement in driving from modern people,the NVH quality of automobiles have also been concerned in the process of automobile designing.According to the customer response,a domestic metal belt type CVT makes a big noise while the automobiles that carrying it are backing up.Therefore,this paper intends to take the noise of this CVT as the research object.At firs t,the transmission mechanism has been analyzed and the noise source has been confirmed to be the planetary gear system that is used to shift in forward gear and reverse gear by automobile noise testing and order tracking analysis.This planetary gear system is constructed by double planetary gear,hence it increases three degree-of-freedom for the three more planetary gear,therefore it has more excitations and its noise has increased obviously while running in reverse gear.In order to decrease the gear whine of reverse gear,the tooth profile modification technology has been proposed in this paper.And the dynamic behavior of the doublestage planetary gear train,PGT has been investigated and a torsional vibration model has been established for the further optimization of the gear profile modification parameters theoretically.Considering the backlash,the dynamic model of the PGT is nonlinear,hence it's almost impossible to obtain its analytical solution by superposition method.Therefore,the fourth-order Runge-Kutta method has been proposed to solve the non-linear dynamic model,and the variance of the accelerated speed of planetary gears has been taken as the object function then genetic algorithm method has been utilized to optimize the value of gear modification.At last,it is verified that the sound quality of the CVT has been improved by automobile noise testing.