Investigation on Dynamic Oil-film-formation and Pitting in Spur Gear : 3rd Report, Comparison of the State of Oil-film-formation between an Integral Gear Ratio and a Hunting One

Abstract

Authors have carried out running tests of hobbed spur gears, measuring the dynamic root strain and the electrical resistance between meshing teeth. Compared with the case of integral gear ratio (1/1) where elastohydrodynamic films grow rapidly built up during running owing to an improvement of conformity between micro-geometries of meshing teeth, it is verified, in the case of hunting gear ratio (27/25), EHD film is hard to build up since severe asperity contacts repeatedly take place due to the replacement of meshing teeth. Therefore, surface durabi1ity for pitting in hunting gear ratio becomes considerably lower than in integral one. It is also shown that the state of EHD film formation and durability for pitting in hunting gear ratio are noticeably affected by combinations of gear materials and by surface roller finishing by which asperities of the tooth flanks are depressed.