The rotational speed of the input shaft of the wind turbine gearbox is generally 10-20 rpm. Due to the relatively low speed, it is often difficult to form the oil film of the input shaft bearing, which is the planet carrier support bearing. The function of the oil film is to separate the two metal contact surfaces during the operation of the bearing to avoid direct contact between the metal and the metal. We can introduce a parameter λ to characterize bearing lubrication (λ is defined as the ratio of oil film thickness to the sum of the two contact surface roughnesses).
If λ is greater than 1, it means that the thickness of the oil film is enough to separate two metal surfaces and the lubrication effect is good. If λ is less than 1, it means that the thickness of the oil film is not enough to completely separate the two metal surfaces and the lubrication effect is not ideal. If the lubrication is poor, the bearing may be damaged as shown in Figure 1. Since wind turbine gearboxes generally use circulating oils with ISOVG320 viscosity, if λ is found to be less than 1, we generally can only improve lubrication by reducing the roughness of the bearing raceways and rollers.
In addition, when the gearbox is designed, the planet carrier support bearing should try to avoid the size of one end of the bearing being too small. In practical application analysis, we found that even if the service life meets the conditions, this design will result in very low linear speed of the small bearing. More impossible to form.
