Abstract
To prevent the failures like scuffing and pitting on tooth surface, it is necessary to decrease the flash temperature and tangential force that are proportional to friction coefficient. And to decrease the power loss of power transmission gears, it is necessary to estimate friction coefficient at tooth meshing surface. But there was no formula with high accuracy for estimation of friction coefficient under mixed lubrication condition considered a ratio of surface roughness and oil film thickness. In this paper, empirical validation of the new estimation formula of friction coefficient was carried out. In the contact zone under mixed lubrication, a combination of fluid friction and boundary friction exists. The new function of load ratio expressed as a simple function of the ratio of surface roughness and elastohydrodynamic lubrication minimum oil film thickness was verified. To evaluate the formula, two disc tests were conducted. The estimated values agreed well with the experimental results. The friction coefficient can be estimated by using the new function of load ratio constructed by the maximum height surface roughness.
