Elasto-dynamic Analysis And Dynamic Design Approach Of Ring-plate Gear Reducer With Small Tooth Number Difference

The research carried out in this thesis is aimed to solve problems of severe vibration and premature fatigue of planetary bearings occurred in the application of ring-plate gear reducer with small tooth number difference. An elasto-dynamic model and a finite element model are developed respectively to investigate the dynamics and meshing characteristics in the transmission, with which a dynamic design approach is finally presented as the guideline for its design.Firstly, the deformation compatibility condition of this over-constrained transmission system is analyzed by considering deformations of high-speed shafts, ring-plates, gears, bearings and manufacturing errors of eccentrics. Then with dynamic substructure method, an elasto-dynamic model is developed.By solving the elasto-dynamic equation set of the system, the dynamic loads and natural frequencies are obtained. It is revealed that the main reason for reducer's vibration is the parametric excitation rather than the shaking moments of paralleling mechanisms. To validate the correctness of elasto-dynamic model, a finite element model is developed in ANSYS. The results of mode analysis agree well with those of elasto-dynamic analysis. Furthermore, the experimental results of mode parameters verify the accuracy of the finite element model.Then several finite element models are developed in ANSYS to predict the multi-teeth contact in planetary gear transmission with small tooth number difference. The main conclusions are listed as followings. The 3-D completed gearing finite element model proposed in the dissertation can lead to accurate results while the segment gearing finite element models brings considerable errors. Compared with 3-D completed gearing model, the 2-D finite element model produces results with an error of 10% and the equivalent cantilever model produces results with an error of 20%. The investigations on gear width, rim thickness, grid intensity, pitch error and central distance error reveal that the former three factors have minor influence on gear meshing characteristics while the errors affect the calculating results greatly.Based on the elasto-dynamic model, the influences of parameters such as bearing stiffness, pressure angle, input speed, etc. on system dynamics are investigated. Then the key technologies in design of ring-plate gear reducer are discussed and a dynamic design approach is proposed.Finally, a novel double-ring gear reducer is proposed and a prototype is made under the guidance of dynamic design approach. The load capacity, transmission efficiency and vibration feature are investigated. The experimental data indicate that the elasto-dynamic analysis conducted in the dissertation can predict the dynamics of the system accurately.