| The vibration and noise of powertrain is the main source of vehicle vibration and noise,and the mount is the main component of the powertrain to connect the body or the frame.It’s vibration isolation performance has significant influence on the vehicle NVH(noise,vibration and harshness)performance.Reasonable matching mounting system is a key point in the NVH performance development.In this paper,the powertrain mounting system of a plug-in hybrid vehicle is taken as the research object.The main contents of the paper are as follows:(1)The vibration model and the differential equation of the mounting system are established in a hybrid electric vehicle.Then,the energy decoupling theory of a powertrain mounting system is discussed.The natural frequencies and decoupling rate are calculated based on the mounts stiffness of a traditional fuel vehicle on the same platform.The calculate results show that the decoupling rate is too low.Finally,the decoupling rate is regarded as the optimization goal with the restricted natural frequencies range and variable mount stiffness,and the mounting stiffness parameters are optimized through the SQP algorithm of fmincon function in the MATLAB optimization toolbox.(2)The mounts with the optimized mounts stiffness value are fabricated and installed in the vehicle for idling test.The overall vibration amplitudes of the steering wheel and the seat rail are less than 0.06m/s2,and the sound pressure levels of the interior noise are less than 39 dB(A).The overall vibration and noise levels meet the target value requirement whether the air conditioner is on or not in the pure electric mode.The overall vibration amplitude of the seat rail is 0.066m/s2,which is less than 0.1m/s2 of the target value.The sound pressure levels of the interior noise are less than 46.5 dB(A)of the target value whether the air conditioner is on or not in the extended-range mode.However,the steering wheel vibration is too large to meet the target value requirements whether the air conditioner is on or not.It was found that the left mount vibration isolation is insufficient,the steering wheel modal frequency is closed to the engine’s second order excitation frequency.The steering wheel vibration is optimized by adjusting the left mount stiffness and the idling speed of the engine.(3)It is found that the interior noise is too large to satisfying the target value requirement and accompanied with booming noise at the multiple rotating speeds during the wide open throttle accelerating in extended-range mode via test analysis in pure electric mode,extended-range mode,hybrid mode.The comparisons between the theoretical calculation and the test results of the mount displacement demonstrate that the operating points of the right mount and the rear mount are located in the non-linear region during the wide open throttle accelerating conditions,resulting in the insufficient of the vibration isolation.Finally,The operating point of the mounts are located in the linear region via the optimization of the mount displacement and the torque strut stiffness,which improve the mount vibration isolation,reduce the interior noise level and eliminate the booming noise. |
