Effect of Formulation of Li Greases on Their Flow and Ball Bearing Torque

This paper describes a study on the effect of base oil type and thickener type on bearing torques with Li type greases. Using a ball bearing tribometer equipped with a torque sensor, friction torque behaviors were determined for model Li greases with different hydrocarbon type base oils. The results showed that the bearing torque changed with the formulation of the greases. For the clarification of the mechanisms, rheological parameter and film thickness of greases were evaluated, and the fluorescence technique was introduced to observe flow behaviors of the greases in and around EHL contact area by using a ball-on-disk tribometer, furthermore, thickener fiber structure was observed by an electron microscope. The abundance of grease around EHL contact area was different depending on thickener types. It is suggested that film thickness, flow behaviors, and thickener structure influence simultaneously on the bearing torque behaviors.