Peculiarities of Assembly of Bevel and Hypoid Gears with Curved Teeth

Abstract

The author provides comparative characteristics of various processes of finishing treatment of thermally reinforced curved teeth in bevel and hypoid gears. The paper analyzes the geometrical precision and roughness of teeth lateral surfaces reached by the following processes: gear lapping, gear honing, gear hobbing with the help of cutter heads having hard-alloy cutters and gear grinding. The author considers a possibility to obtain complete interchangeability of the main gear and driven wheel in bevel and hypoid gears during the use of considered processes. Gear lapping and honing are conducted after chemical and thermal treatment to obtain the 6th and 8th degree of precision under GOST 1643-81, decrease of roughness of teeth surface (up to Ra 0.6–2.0 um) and insignificant stabilizing of the spot form and location on the teeth. As gear lapping and honing correction capabilities are insignificant, that is why it is impossible to obtain completely interchangeable pairs, one needs to conduct pairing and marking of key gear parameters. Gear hobbing and grinding allow significantly increasing the precision of teeth after chemical and thermal treatment, especially on the radial beam of a gear ring (kinematic precision norm) and on pitch deviation (norm of operation smoothness). It is very important to guarantee complete interchangeability of gear and wheel teeth interfacing in the gearing unit after gear hobbing and grinding. At the assembly of fully interchangeable parts of the interface of bevel and hypoid gears the quality of teeth engagement increases while the labour intensity of the assembly becomes lower (no operations of pairing and marking of key gear parameters).