The States of Oil Film Formation and Running Performance of Deep Groove Ball Bearings under Combined Loads

Abstract

Using an electric resistance method, the authors monitored continuously the state of oil film formation during operation of the type 6008 deep groove ball bearing under variously combined radial and axial loads. As lubricants, two kinds of mineral oils with nuch different viscosity grade were used. As a result of calculation, it was found that the extent of the loading zone and the increase in the normal load become remarkable in the case of a deep groove ball bearing as the axial load increases. In the running tests, it was shown that the increase of axial load has a large effect on the state of oil film formation of the deep groove ball bearing. Furthermore, it was recognized that the extent of the loading zone has a close relation to the coefficient of friction and the slip ratio of separator. When a low viscosity mineral oil was used, the load distribution had a significant effect on the state of oil film formation and on the running performance under the combined loads as compared with a higher viscosity mineral oil.