BENDING STRESSES OF INTERNAL SPUR GEAR

The influences of rim thickness of an internal spur gear on tensile and compressive bending stresses at tooth fillets and bottoms are discussed. The stress measurements by strain gages, the photoelasticity experiments, and stress analyses by use of the finite element method showed that the position where the maximum stress appears in an internal gear is different from that of an external gear. Especially when the rim thickness of an internal gear is thin, the maximum tensile stress appears at the center of the bottom of the tooth space, which is apart from the loaded tooth. As the rim thickness becomes thinner, the maximum compressive stress at the fillet of the loaded tooth increases sharply, while the maximum tensile stress hardly changes. As meshing proceeds, the tooth fillet and bottom stresses of a thin-rimmed internal gear alternate more strongly than those of a solid or thicker rimmed gear.