Effect of Oil Film Parameter on Vibration Acceleration and Electrical Pitting of Small Ball Bearing

The authors have studied the current density and voltage at which electrical pitting occurs in a small ball bearing. Some current-applying bearing tests in previous studies showed an interesting tendency for the vibration of bearings to increase when they were lubricated with a thicker oil film. In this study, the oil film parameter is intentionally changed, and its effects on the generation of pitting and vibration acceleration are experimentally investigated. Ball bearing endurance tests involving 500 h of operation were performed by applying a direct electric current with various rotational speeds, and with various base oil viscosities of grease and surface roughness of the raceway. The test results clarified that electrical pitting appeared more clearly and the vibration due to damage became severer with increasing oil film parameter. Although a larger oil film parameter is generally advantageous for increasing bearing life, it is undesirable from the standpoint of preventing electrical pitting