| Planetary gear trains (PGT) have been widely applied in aircrafts, ships, artilleries, automobiles and a variety of industrial machines due to their large transmission ratio, compact volume and high loading capacity. In some cases vibration and noise of PGT will have a great influence on reliability and life-span of the system. To achieve load sharing and vibration suppression, flexible ring gears are usually made use of in high-speed PGT. To highlight the importance of ring gear flexibility to dynamic performance of the system, a novel elastodynamic model of spur PGT is presented in this thesis. Some achievements obtained are as the follows:1. The stress and elastic deformation of the ring gear are investigated, which is connected to the gearcase by straight splines. The rim thickness to tooth depth ratio is defined as flexibility of the ring gear. A finite element model of the ring gear is established by means of Pro-E and Ansys. Equally-spaced linear springs are utilized to describe fitting status of the ring gear. The meshing teeth are loaded according to the contact ratio and the load sharing coefficient. The influence of flexibility and fitting status on stress and elastic deformation of the ring gear are analyzed.2. The transverse-torsional model of spur PGT is checked carefully and the expression of planet gear acceleration and those of relative displacements between the members are corrected. Moreover, a modified transverse-torsional model of spur PGT is established in the rotating Cartesian coordinates and compared with the transverse-torsional model.3. On the basis of the modified transverse-torsional model, a novel elasto- dynamic model of spur PGT is presented in which elastic deformation of the ring gear is taken into account. The flexible ring gear is treated as the combination of finite rigid segments and linear springs. Additionally, the complex mode closed-form solution is utilized to acquire steady dynamic response of the system.4. To validate the proposed elastodynamic model in consideration of ring gear flexibility, the natural characteristics is analyzed for spur PGT whose ring gear is completely fixed, radial floated or rotated. The influences of ring segment number and stiffness of connected linear springs on natural frequencies of the system are analyzed. |
