Improved Load-Carrying Capacity of Crosshead-Pin Bearings by Incorporating Taper Geometry in Oil-Grooves

大型二冲程柴油机中的十字头销轴承在恶劣的润滑条件下工作，因为轴承在低速时在小角度内振荡，并且总是承受较高的向下载荷。最近的趋势是发动机更紧凑，输出更多，这提高了轴承的比负荷，从而导致润滑严重程度显著增加。因此，提高十字头销轴承的承载能力是非常重要的。在本研究中，利用动载轴承卡住试验台进行了试验，以明确间隙比和油槽几何形状对承载能力的影响。测量了油膜的电阻，以评价油膜形成的程度。主要研究结果如下：(1)在常规油槽轴承的情况下，减小间隙比可以有效地增强整个轴承瓦的挤压作用，从而降低油膜压力。这反过来又增加了承载能力。然而，当间隙比变得太低时，形成足够的流体动力楔形油膜的能力降低，从而导致承载能力降低；(2)在油槽两侧采用优化的锥形几何形状可以促进更厚的油膜，而油膜压力只有很小的增加。因此，承载能力的显著提高是可以预期的；以及(3)最大承载能力是通过锥形几何形状实现的，锥形长度为5度，锥角为0.1度。

The crosshead-pin bearing in large two-stroke diesel engines operates under severe lubrication conditions, because the bearing oscillates within a small angle at a low speed and is always subject to a high downward load. The recent trend towards more compact engines with increased output raises the bearing specific load, thereby causing the lubrication severity to increase significantly. Thus it is very important to improve the load-carrying capacity of the crosshead-pin bearing. In the present study, experiments using a dynamically loaded bearing seizure test apparatus were carried out to clarify the influences of the clearance ratio and the oil-groove geometry on the load-carrying capacity. The electrical resistance of the oil film was also measured to evaluate the extent of the oil film formation. The major results are : (1)In the case of bearings with conventional oil-grooves, a decrease in the clearance ratio is effective in enhancing squeeze action on the entirety of the bearing pads, thereby lowering the oil film pressure. This, in turn, increases the load-carrying capacity. However, when the clearance ratio becomes too low, the ability to form an adequate hydrodynamic wedge film is degraded, thereby causing the load-carrying capacity to decrease ; (2)Incorporating an optimized taper geometry on both sides of the oil-groove promotes a thicker oil film with only a small increase in the oil film pressure. Thus a significant improvement in the load-carrying capacity can be expected ; and (3)The maximum load-carrying capacity is achieved by the taper geometry of a subtended length of 5 degrees and a taper angle of 0.1 degree.