Thermal Performance of a Ball Bearing System Operating at High Speed with a Circulating Oil Lubrication Module

Bearings are common components used in the transmission system of tool machinery and linear drive equipment. With increasing demand for higher efficiency and faster production under the required accuracy, the control of bearing temperature rise under high operational speed becomes a critical issue. The improper control of temperature rise can lead to the thermal deformation and life reduction of the machinery. Conventionally, a circulating oil lubrication system is utilized with journal bearings. In this study, a similar lubrication system was adopted for the ball bearing with a retrofit design. Three control factors, i.e., rotational speed, bearing preload, and the viscosity of the lubricant used, were chosen to study their effects on the temperature performance of the proposed lubrication system. Experimental measurements showed that the lubrication system was able to lower the temperature rise of the bearing considerably compared with its unlubricated counterpart, especially at high rotational speeds. Even with the enhanced cooling from the oil circulation system, temperature rise still increased with rotational speed. However, with increased preload, the temperature rise first dropped and then increased owing to the different contact characteristics of the balls and rings of the bearing. A fitted function for the temperature rise of the bearing under different operational conditions was demonstrated to have a prediction accuracy within 3%. Therefore, the retrofitted bearing oil cooling system should be applicable in the design of high-speed machinery for industry.