Study on Water/Air Lubricated Hybrid Journal Bearings

Abstract

Aerostatic bearings have often been used for high-speed spindles because of its low friction and high accuracy of motion. However aerostatic bearings have disadvantages such as lower load capacity, lower bearing stiffness and damping coefficient compared with water-lubricated hydrostatic bearings. On the other hand, water-lubricated hydrostatic bearings have higher damping coefficient and larger load capacity but larger power consumption is needed at speeds. In this paper, therefore, a water/air lubricated hybrid journal bearing was proposed, which could achieve both low power consumption and larger load capacity by selecting air or water as an operating fluid according to the operating condition of a spindle. In addition, the static characteristics of the proposed bearing for an offset load are clarified theoretically and experimentally. It was confirmed that the proposed bearing was very useful for spindles for precision machine tools.