A Study on Friction of Journal Bearing under Dynamic Load

1.目的：多缸内燃机常用滑动轴承。它们在非常重的动态载荷下运行。另一方面，它们的摩擦损失应该是低的。压力分布是讨论动载作用下轴承所有特性的最重要的量值，很少有研究涉及到这一点。帕特里克只同时测量了它们的摩擦力。本研究正是在这样的背景下开展的，目的是为了弄清轴颈轴承的动态特性。方法：试验台的设计和建造使径向轴承的所有基本和重要的量，即压力分布、轴承载荷、轴颈中心轨迹、油温、摩擦力矩和油流量都可以同时检测。数据处理由在线的微型计算机系统完成，实验中始终测量负压。最大值为-0.35MPag。用气液两相流体动力润滑理论对负压进行了解释。对压强分布、摩擦力矩和桩体流量进行了理论计算，并与实验结果进行比较。结论：(1)负压分布形态取决于加载方式。在高频载荷作用下，油膜破裂区对应的平压区的水平约为绝对真空。(2)两相理论可以解释实验测量的负压。然而，它高估了摩擦力矩的值。因此，应该从这个角度来完善这一理论。(3)静载荷下摩擦损失实测值与理论值基本吻合，而动态载荷下由于测量系统的不完善而得不到可靠的结果。(4)油流的理论计算结果与实验结果吻合较好。

1. Objective: Journal bearings are usually used in multi-cylinder internal combustion engines. They are operating under very heavy dynamic load. On the other hand, their frictional loss should be low. Few studies have been presented which had dealt with pressure distribution, that is most important quantity for discussing all of bearing characteristics, under dynamic loading. Patrick had only measured simultaneously the frictional force in them. On this background, this study was carried out in order to make clear the dynamic characteristics of journal bearings.2. Approach: The test rig was designed and constructed so that all of basic and important quantity of journal bearing, namely pressure distribution, load of bearing, journal center orbit, oil temperature, frictional torque and oil flow rate, are simultaneously detectable. Data processing was carried out by on-line mini-computer system.Experimentally negative pressure was always measured. The maximum value is -0.35MPag. The liquid-gas two phase hydrodynamic lubrication theory was used to expound those negative pressure. Comparison was made between theoretical results and experimental one on pressure distribution, frictional torque and pil flow rate.3. Conclusings: (1) The shape of negative pressure distribution depends upon the loading pattern. The level of flat pressure region corresponding to oil film ruptured region is about absolute vacuum under high frequency of load. (2) The two-phase theory can explain negative pressure measured experimentally. However, it over-estimates value on the frictional torque. So, the theory should be improved from this point of view. (3) Measured values of frictional loss agreed qualitatively with theoretical results under static loading, whereas no reliable results were obtained under dynamic conditions by means of an imperfection of the measuring system. (4) Good agreement was obtained between the theoretical and the experimental results for oil flow.