Analysis of a Hydrodynamic Bearing of a HDD Spindle Motor Due to Elevated Temperature

This paper presents a method to investigate the characteristics of a hydrodynamic bearing of a HDD spindle motor due to elevated temperature considering the variation of the clearance as well as the lubricant viscosity. Iterative finite element analysis of the heat conduction and the thermal deformation is performed to determine the viscosity and clearance of a hydrodynamic bearing due to elevated temperature until the temperature of the bearing area converges. Proposed method is verified by comparing the calculated temperature with the measured one in elevated surrounding temperature as well as in room temperature. This research shows that elevated temperature changes the clearance as well as the lubricant viscosity of the hydrodynamic bearing of a HDD spindle motor. Once the viscosity and the clearance of a hydrodynamic bearing of a HDD spindle motor are determined, finite element analysis of the Reynolds equation is performed to investigate the static and dynamic characteristics of a hydrodynamic bearing of a HDD spindle motor due to elevated temperature. It also shows that the variation of clearance due to elevated temperature is another important design consideration to affect the static and dynamic characteristics of a hydrodynamic bearing of a HDD spindle motor