| Automobiles have gradually been popularized into family life. Previous consumers paid more attention to the performance, fuel economy and safety. Now, the consumers put forward higher requirements for ride comfort. The vibration and noise level of the whole vehicle has a great influence on the comfort. Transmission is an important part of the automobile drivetrain system. Vibration and noise caused by transmission is one of the most important factors. Establishing the transmission gear system dynamic model and analyzing the influence of operating conditions, gear parameters and original characteristic of housing on vibration and noise characteristics of transmission have important significance to guide the design of transmission and reduce the noise of transmission.Firstly, the mechanism of the vibration and noise of transmission is studied. The mesh stiffness of helical gears and bearing stifness are calculated. Meanwhile the effects of different helical gears parameters(e.g., helix angle, face width and pressure angle) on mesh stiffness are studied. The results indicated that the helix angle and the tooth width have a great influence on time-varying stiffness fluctuation. Reasonable selection of gear parameters can reduce time-varying stiffness fluctuation.On the basis of the research on the dynamic excitation of transmission gear system, the force analysis of gear pair, shaft, bearing and other elements in the gear transmission system is carried out. Mass matrix, stiffness matrix and damping stiffness are obtained. Reference to the finite element method, the mass matrix, stiffness matrix and damping matrix of various elements are assembled. The overall dynamic equation of the transmission gear transmission system is formed. The dynamic equations were solved by the numerical method and the dynamic response of the bearing support was obtained. Based on this model, the influences of input speed, input torque and time-varying meshing stiffness on the dynamic response of the gear transmission system are studied.The finite element model of transmission housing is established in the finite element pre-processing software Hyermesh. The finite element modal frequency and modal shape of transmission housing is discussed. Consider the dynamic response of the bearing support as excitation, modal based vibration response of transmission housing was solved in LMS virtual lab software, Boundary element model of housing is established in the LMS virtual lab software. Transmission radiated noise characteristics is studied.At last, the vibration and noise characteristics are tested to evaluate the noise level. According to the characteristics of noise sources and existing work condition, the tooth modification method was put forward to improve transmission vibration and noise performance. Compared with previous experiment results, its overall noise level has been effectively controlled. |
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