Numerical Analysis of a Coupled Porous Journal and Thrust Bearing System

Abstract

A numerical model has been developed to analyze both static and dynamic characteristics of a coupled porous journal and thrust bearing system that is used to support a rotating shaft in a magnetic hard disk drive. The analyzed system is composed of a porous sleeve, a herringbone-grooved solid thrust plate and a flanged shaft, where the bottom end is closed to form a cantilever spindle. The inner surface and the bottom face of the porous sleeve operate as a herringbone-grooved journal and thrust bearing, respectively. The model is based on the narrow groove theory for the bearing oil film, and Darcy’s law for the internal flow in the porous sleeve. The pressure distribution, static equilibrium position of the shaft and dynamic coefficients are obtained under a given external axial load. There exists a window of permeability of the porous sleeve that presents significant advantage to prevent the creation of a sub-ambient condition and to maintain a large thrust bearing film thickness at the expense of some loss of dynamic performance.