The input shaft speed of the wind power gearbox is generally 10~20 r/min. Due to the relatively low speed, it is often more difficult to form the oil film of input shaft bearings. The role of the oil film is to separate the two metal contact surfaces in the bearing operation, avoiding metal and metal contact directly. We can introduce a parameter λ to characterize the bearing lubrication (λ is defined as the ratio of the oil film thickness and the sum of two surface roughness).
If λ is greater than 1, indicating that the thickness of the oil film is enough to separate the two metal surfaces and the lubrication effect is good; but if λ is less than 1, the thickness of the oil film is not enough to completely separate the two metal surfaces, the lubrication effect is not ideal. In the case of poor lubrication, the bearing may be damaged. If λ is found to be less than 1, we generally improve the lubrication effect only by reducing the roughness of bearing raceway and roller.