Elasto-Static Analysis Of Three-Ring Gear Reducer In Consideration Of Gear-Coupler Deformations

The Three-Ring gear reducer (TRGR), invented by a Chinese engineer in 1985,is a novel type of planetary transmission devices with few tooth differences. It hasnumerous advantages over common reducers, such as large transmission ratio, highloading capacity, compact volume, low fabricating cost and wide adaptability.The gear-coupler is the key element of the TRGR, which acts as theconnecting-rod of the parallelogram mechanism and meshes with the external gear ofthe output shaft. In this thesis, the finite element model of the gear-coupler isestablished by utilizing the ANSYS software for the symmetrical TRGR featuring aphase difference of 120 degrees. The displacements, stresses and elastic deformationsof three gear-couplers are calculated in a whole motion cycle of the TRGR. Results ofcomputer simulation reveal that both longitudinal and lateral deformations of thegear-couplers will greatly affect the kinematic and dynamic performance of the TRGR.Therefore, it is necessary to take into account elastic deformations of thegear-couplers in the analysis and design of the TRGR.The TRGR is in fact an over-constrained mechanism whose actual loading statecannot be analyzed by rigid-body mechanics. Herein, an improved elasto-static modelof the TRGR is formulated by considering elastic deformations of the elements suchas high-speed shafts, gear-couplers, meshing teeth and planetary bearings. Inconjunction with the ANSYS based finite element analysis of the gear-couplers, theactual loading state of the TRGR is finally achieved. It is proved that the rating life ofplanetary bearings will be shortened as a result of elastic deformations of thegear-couplers. This conclusion may be used for series-design of the TRGR.Finally, optimal design of the gear-couplers is investigated based on finiteelement analysis and elasto-static analysis. Several structure modification methods areproposed which include enlarging edge sizes, drilling holes and cutting arcs. Bycomparing the rating life of planetary bearings, maximum stresses of gear-couplersand shaking forces of high-speed shafts, some suggestions are put forward forimproving general performance of the TRGR.