Ohta Hiromitsu

This paper shows the vibration characteristics of a sliding bearings. Especially, the self-excited vibration to be called as oil whirl generated in sliding bearing is studied in the current paper. Three methods like trajectory analysis, tracking analysis and frequency analysis of shaft vibration are analyzed to clarify the vibration characteristics of oil whirl. The oil whirl in a sliding bearing is a characteristic self-oscillation, which occurs at a rotation speed less than the twice of the critical speed of the experimental system. In addition, when oil whirl and shaft unbalance are simultaneously generated in a sliding bearing, the frequency response in all domains of frequency is suddenly become larger compared to that in the case of the only oil whirl. It seems that simultaneous development of oil whirl and shaft unbalance generate the large damage to the rotary machinery system. Furthermore, the amount of whirling to the shaft generated by the oil whirl are identified large in the horizontal, vertical and axial directions of sliding bearing. Particularly, the amount of whirling in the horizontal direction is identified larger, because, there is no suppression as gravity and structural barrier in this direction like that in the vertical and in the axial directions.