Root Stresses of Thin-Rimmed Spur Internal Gears of Higher Pressure Angle with Asymmetric Web Arrangemcnts.

Abstract

This paper presents a study on root stresses of thin-rimmed spur internal gears of higher pressure angle (α0=27°, α0: standard pressure angle) with asymmetric web arrangements for planetary gear units of automatic transmissions of automobiles, caterpillar drives of construction machinery and so on. Tooth deflections of thin-rimmed spur internal gears with asymmetric web arrangements due to a concentrated load in the normal direction of the tooth surface were calculated by the three-dimensional finite-element method (3 D-FEM). On the basis of the calculated results, approximate equations for the influence function of tooth deflection were derived. The load sharing factor and the load distributions on contact lines were calculated using the approximate equations and Kubo and Umezawa's method. Root stresses of thin-rimmed spur internal gear pairs in mesh were calculated by means of 3 D-FEM, and the maximum root stress and its position were examined. Root stresses of the thin-rimmed spur internal gear of higher pressure angle with asymmetric web arrangements were determined by being compared with those of thick-rimmed or solid internal gears and with those of thin-rimmed spur internal gears of α0=20° with asymmetric web arrangements.