Analysis And Improvement Of HEV Powertrain Mounting System

With the progress of the society and the development of technology,people's demand for a better vehicle ride comfort has been growing dramatically. And the vibration and noise performance have been the important standard to measure whether the vehicle is good or not. As the main excitation source of the vehicle,the powertrain have a crucial influence on the vehicle NVH performance. The powertrain mounting system with a reasonable design not only can obviously lower the vibration transmissibility from the powertrain to the frame and reduce the noise ,but also can improve the stress and motion state between the powertrain and the frame and reduce the movement interference among parts , thus lengthening the powertrain and components service life.Based on vibration theory,multi-rigid-body dynamic theory and test technology,a domestic HEV powertrain mounting system was studied in this thesis according to the problems occurred in actual operation such as vibration,noise and components damage etc. The main contents includes:1) According to the HEV powertrain model parameters,the powertrain mounting system rigid dynamical model and mathematical model were established by using CATIA,ADAMS and MATLAB. It showed that the mounting system natural frequency was low through modal analysis. In other words,the mounting system was soft that it would lead to a big powertrain relative displacement,and it matched well with the actual problems.2) An improved program was proposed for the original mounting system. Considering that the variation of the mounting parameters had an effect on the mounting system modal results,and on the basis of increasing natural frequency,with the energy decoupling rate as the target,the improved program was optimized with the 6σrobust optimization method by ISIGHT and MATLAB. The results showed that the optimization object can still keep high robustness when the design variables had a±10% variation around their nominal values.3) To solve the HEV noise problem,and on the basis of the powertrain mounting improved program,it was proposed that the bevel gears in the ancillary box of the transmission need to be grinded in order to improve their engaging status,thus reducing the braking squealing noise caused by the bevel gear engagement. 4) Using the testing device,the improved program of the powertrain mounting system was analyzed through road test experiments which including angle testing,vibration testing and noise testing. The performance of the improved program was analyzed and evaluated according to the testing results. It showed that the vibration isolation performance basically remained stable,while the relative angular displacement and noise performance had a better improved effect which met with the expected purpose. The improved program can solve the HEV problems occurred in actual operation,and now it has been put in practical application.