Fluid dynamic bearing lubricant air extraction device

Abstract

The fluid dynamic bearings system of the invention provides a device located in a non-grooved low pressure region located at some point in the overall fluid circulation path of the fluid dynamic bearing to collect and trap any air bubbles which may be found in the fluid of the hydrodynamic bearing. More specifically, the air extraction device of the invention comprises a shallow angle V-shaped region which is located in fluid communication with but not in a grooved region of the hydrodynamic bearing. In summary, according to the present invention the hydrodynamic bearing comprises a shaft with a thrust plate at or near at least one end thereof. The thrust bearings are formed on the upper and lower surfaces of the thrust plate () and journal bearing () on the shaft or facing sleeve surface. Lubricant lies between each of these surfaces and facing surface of a sleeve () or counter-plate () which overlies the thrust bearing, and fluid lies in all these regions. In the region on the outer surface of the counter-plate distant from the shaft () and facing the counter-plate () a countersink () is formed on the axial face of the thrust plate () and end of bearing shaft with a shallow angle such that the force of surface tension forms a meniscus between the air and the lubricant along the surface of the countersink angle period. Lubricant circulation path-holes () are provided from, this countersink region to the region at the junction between the shaft and the thrust plate which also between the journal bearing and the thrust bearing. Thus the fluid can pass through these circulation holes extending from the journal and thrust plate up to the countersink region, and form a capillary seal on either side of the countersink region adjacent the thrust bearing. As an alternative, the shallow angled region may also be located on the outer diameter of the thrust plate or on the shaft adjacent the journal bearing.