Gear Rattle Prediction Based on Compliance and Deformation of Gear Contact Points 2016-01-1094
Generally, the gear rattle noise prediction models are composed of the mass and stiffness elements. The proposals are about the gear inertia or backlash and the shaft inertia or stiffness, but there are many detailed designs in the same inertia, stiffness or backlash conditions. Therefore, these proposals can’t guide detailed designs. These models only investigate the rattle in the rotating degree, and ignore rattle contribution in the radical and axial directions. Those prediction models only consider one or several factors which affect the rattle noise performance. It is difficult to predict the influence of individual factor and multi-factors coupling on the gear rattle noise in a rattle simulation model. Those factors include the shape and size of the gear tooth, the center distance and un-parallelism between the input and output shaft, the variable gear meshing stiffness, the gear backlash in three directions changing with the gear meshing position, stiffness of the input shaft, the output shaft and the transmission housing, the bearing radical clearance, the shaft deformation, the torque of the input shaft, the vehicle driving resistance, the bearing resistance, the synchronizer resistance, the gear churning resistance, and the friction torque.
To solve the problems, gear meshing forces which are product of compliance and deformation of the gear contact points are used to build gear rattle noise prediction model. Firstly, compliance is obtained through finite element method in the model. Then the deformation is calculated by involute start angle on gear base circle, the tooth root and tip involute angle, the pressure angle, and the center distance between the input and output shaft. Subsequently, the gear meshing force is obtained through compliance multiplying by the deformation of the gear contact points. Finally, the model for the gear rattle prediction is built based on the gear meshing force. This rattle prediction model can guide the detailed designs including the gear shape and size, and the center distance between the input and output shaft. Rattle performance in the radial, axial and tangential directions can be investigated in this model. The individual and combined effect of above factors can be considered in this rattle model because those factors affect the compliance or deformation of the gear contact points. The rattle noise contribution order of the unloaded gears is obtained from the model. It is coincided with test result. This indicates that the rattle model is correct and can be used to predict rattle noise. Results show that the axis and radial rattle of the unload gears contributes significantly to the rattle noise, and its influence can’t be neglected. The reverse gears have the most contribution to rattle performance. Thus, those gears are the major directions for rattle performance optimization. The prediction model provides a rapid and economic method to solve the gear rattle noise problem.