A TEST RIG TO ASSESS FLUID SEALING IN VERTICAL HYDRODYNAMIC JOURNAL BEARINGS

摘要

Many of the latest hard-disk drives produced in recent years utilize fluid bearing technology. This is due to the significant advantages of fluid bearings over ball bearings such as: low acoustic noise that allows higher spindle speed, higher spindle speed that leads to faster data access, less non repeatable run-out (NRRO) that leads to higher track density, better shock performance, better fatigue performance that lead to higher life expectancy, and better stiffness and dynamic stability due to the elimination of the half-frequency whirl phenomenon in high speed operations. A test rig has been designed and fabricated to assess the fluid sealing capability of some vertical hydrodynamic journal bearings with herringbone groove patterns on the shafts. Tests have been performed on five different shafts at rotational speeds ranging from 203 rpm to 2110 rpm. They consist of one plain shaft, two symmetrical herringbone grooved shafts with different diameters (46.0 mm and 46.2 mm) and two asymmetrical pattern herringbone grooved shafts with different groove ratios. From the leakage rates measured, the asymmetrical groove patterns have better pumping sealing effect than the others. The pressure profiles show that the maximum pressure increases with rotational speed but decreases with increasing clearance between the shaft and the sleeve.