Scoring limit and wear rate of cylindrical worm gears (effects of local tribological conditions on tooth surface failures)

The phenomenon of scoring, which determines operating conditions of cylindrical worm gears, is studied. Using power to circulate a worm gear testing machine and by changing the test conditions, for example, assembling errors of gears, loading torque and pitch line velocity, the initial scoring limit condition of a tooth surface was confirmed. The distributions of local contact pressure, sliding velocity and oil film on the gear tooth surface were calculated by a theoretical method previously developed by us. This method can treat the effect of change in load distribution on the gear tooth surface due to mechanical deformation. We observed a good relation ship between scoring limit on the gear tooth surface and the result of contact pressure and sliding velocity which was calculated based on initial errors of gears. Furthermore, the relation ship between the phenomenon of scoring and the change of surface temperature or root stress is studied and wear rate of gear tooth surface is investigated under the conditions close to those of the scoring limit finally, useful gear designing data are presented.