Non-contact Measuring System for Surface Wear Dent of Journal Bearing

在长期使用的轴颈轴承表面上经常会发现磨损凹痕，这些凹陷形状是因为轴颈与轴承表面直接金属对金属接触，而在启动或关闭操作期间，流体动力油膜仍然太薄。一旦形成磨损坑，油膜的形状就会发生变化，最小油膜厚度可能会减小，从而危及轴承的咬合。此外，转子动力学系数将发生变化，在达到额定转速之前，引起支承在轴承中的转子的自激振动。因此，必须精确测量轴承表面上的磨损凹痕轮廓，以估计轴承性能的退化。本课题旨在研制一种新型的、实用的、方便快捷的大直径滑动轴承表面磨损凹痕检测系统，其检测精度可达微米级。涡流式间隙传感器用于检测传感器与轴承表面之间的距离。传感器安装在旋转臂上，旋转臂又固定在梁上。梁可以在线性致动器中移动。因此，传感器可以在周向以及轴向方向上扫描轴承表面。所采集的距离数据在小型计算机中进行实时在线处理，并通过安装在计算机中的计算机程序自动计算出磨痕轮廓。该程序是新开发和编码的。结果以图形和数字显示在监视器屏幕上。该系统用于测量模型滑动轴承表面人工加工的各种磨损凹痕，并证明其功能令人满意的精确测量。

Wear dents are often found on the surfaces of journal bearings in use for long, and these concave shapes are made because journals, make direct metal-to-metal contact with bearing surfaces while hydrodynamic oil films remain too thin during start-up or shut-down operation. Once the wear dent is formed, the oil film changes its shape, and the minimum oil film thickness may decrease, endangering bearing into seizure. Furthermore the rotordynamic coefficients would change, causing a self-excited vibration of rotor supported in the bearings before rated speeds are reached. Consequently, wear dent profiles on the bearing surfaces must be measured precisely to estimate the degradation of the bearing performance. However there exists no suitable measuring system available on the sites where bearings are installed.This research project aimed to develop a new handy measuring system for practical use that can easily and rapidly detect surface wear dents of journal bearings of large diameter with the resolution of some micrometer. A gap sensor of eddy-current type is used to detect the distance between the sensor and the bearing surface. The sensor is mounted on a rotating arm which, in turn, is fixed on a beam. The beam can move in a linear actuator. Thus the sensor can scan the bearing surface in the circumferential and also axial directions. The distance data collected are real-time processed on-line in a small-size computer, and wear dent profiles are calculated automatically by means of a computer program installed in the computer. The program was newly developed and coded. The results are presented graphically and numerically on a monitor screen. This system was used to measure various wear dents machined artificially on the surfaces of model journal bearings, and proved to function satisfactorily with precise measurements.