Influence of Profile Modification and Lubricant Viscosity on Scoring of Helical Gears

Abstract

Scoring limit of helical gears made of carburized steel is investigated experimentally. Gear testing machine used for the tests is a closed power circuit type and designed for operation up to 23,000 rpm. All tests are made with pairs of 14 and 141-tooth gears of 3-module, 20-deg normal pressure angle, 29.066-deg helix angle, and 30-mm face width. The effect of profile modification on the scoring limit is investigated, and the effects of lubricant viscosity and location of oil supply nozzle are investigated in connection with the effect of profile modification. Three kinds of lubricants of various viscosity ordinarily used in a gear system are tested (lubricant viscosity: 32, 53, 70 cSt at 40 C). Load carrying capacity of the lubricant of the highest viscosity is higher by 25 percent than that of the lowest one. But the effect of modification is much larger than that of lubricant viscosity.