Cage Friction Measurements in High-Speed Bearings

This article presents a new test rig that was designed and developed to investigate the friction and lubrication condition of a ball and a cage of a deep groove ball bearing (DGBB) under high-speed conditions. In this test rig, the inner and outer raceway segments of a DGBB were precisely positioned using piezoelectric stages. This allowed independent control of the internal clearances between the raceways and the ball, enabling accurate representation of actual bearing geometry. The ball is mounted to a high-speed spindle motor, enabling angular rotational speeds of up to 24,000 RPM (DN^{^*} > 1M). Frictional torque was measured using a six-axis load cell to quantify the friction between a ball and a cage pocket. A high-speed camera was used to capture the lubricant distribution within a transparent cage. The computer-aided design of the DGBB cage was used to manufacture the transparent cage. Experiments were conducted to investigate the effects of speed, ball-raceway clearance, oil flow rate, and lubricant viscosity on cage friction. The cage friction exhibited a dichotomic behavior, increasing in the oil-dominant regime at lower speeds and decreasing significantly in the air-dominant regime at higher speeds. The transition between different regimes was primarily influenced by raceway clearance and oil viscosity. The results from this investigation provide a detailed description into the ability of the cage pocket to sustain effective lubrication at elevated bearing speeds.