发动机是机车的“心脏”，其主要零件如气缸套、活塞环、曲轴和轴瓦等，虽其配合表面具有较高的精度和表面光洁度，但放大观察，零件表面仍有凹凸不平的加工印痕，这就使摩擦表面间的实际接触面积减少，各接触点的受力增大。如果新车或大修后的机车直接投入负荷运转，零件接触 Engine is the locomotive’s “heart”, its main parts such as cylinder liner, piston ring, crankshaft and bearing, although with the surface with high precision and surface finish, but the magnification of observation, parts surface is still uneven processing imprint, This reduces the actual area of ​​contact between the friction surfaces and increases the force at each contact point. If the new car or overhaul the locomotive directly into the load operation, parts contact