Optimization of planetary gears and effects of thin-rimed gear on fillet stress

Abstract

Planetary gears take a very significant place among the gear transmissions, and they are widely used in military and civil industry applications such as marine vehicles, aircraft engines, helicopters and heavy machinery. Planetary gears are complex mechanisms which can be decomposed into external and internal gears with the corresponding interaction, which requires geometrical conditions in order to perform the mounting and an appropriate meshing of the gears during their work. Planetary gears have a number of advantages as compared to the transmission with fixed shafts such as a compact design, with co-axial shafts, high power density and higher efficiency, which is achieved by reducing gear weight using thin-rimed gears. The purpose of this paper is to present the optimization model for the planetary gears, where the objective function is the weight of gears, and functional constraints imposed upon their respective structural design. Hence, the objective is to minimize rim thickness of the gear in order to achieve high-performance power transmission and minimize weight. This paper presents the results of an investigation with finite element analysis (FEM) into the effects of thin-rimmed gear geometry on the root fillet stress distribution.