Comparative investigation of worm and spiroid gears with cylindrical worms

Abstract

The paper gives a thorough comparative evaluation of two close worm-type mechanisms – worm and spiroid gears – provided they have equal dimensions. Evaluation is made in accordance with layout, geometric and kinematic, force and accuracy characteristics. Quantitative parameters of the spiroid gearing as compared to the worm one are obtained. In particular, numerical analysis of a spiroid gear gave the backgrounds for applying steel as the material of gearwheel rims; its decreased loading in tooth pairs (increased static strength of the gear) and lower sensitivity to errors of the gearwheel axial arrangement are shown; and its preferability of application for small gear ratios is substantiated. Better conditions of providing smooth operation are specific for all groups of parameters: geometry and kinematics, forces, stress, and accuracy. A worm gear is featured by comparatively low contact stresses, minor forces in meshing, and less sensitivity to errors of the worm pitch. The obtained results are, therefore, contradictory; they indicate that each of these gears can be preferable in specific design, production and operation conditions. It is also shown that contact localization provides more stable accuracy characteristics that are less dependent on the degree of mounting errors in most cases.