Abstract
Floating bush journal bearings are widely used to support small-sized high-speed rotating machinery. When the shaft rotational speed exceeds a stability threshold speed, the bearing shows self-excited vibration. However, the vibration could be disappeared when the speed further increases and the bush rotational speed levels off. The phenomenon can be explained qualitatively by applying the hydrodynamic lubrication model with the axial oil film rupture being considered. However, the predictions are in quantitatively poor agreement with the measurements. Therefore, one of the authors aims to improve the model based on the phenomenon observed experimentally by using a test apparatus of a cylindrical bearing that corresponds to a high-speed floating bush journal bearing. In this report, the bush driving torque due to oil film viscous force is measured with the experimental apparatus that the oil feeding system is a little modified and is related to the oil film width reduction phenomenon observed in the previous report. The results imply that they are related to each other. The effect of oil supply pressure is also investigated on the bush driving torque. It is found that the torque measured under the lowest oil supply pressure is in qualitative agreement with the numerical predictions.
