On the Lubricating Mechanism of Roller Skew in Cylindrical Roller Bearings

Abstract

Skewing is the motion of a roller as it turns about an axis normal to the roller–race interface in cylindrical roller bearings. With a special coordinate transformation technique, complete numerical solutions for the finite line elastohydrodynamic lubrication (EHL) contact formed between a roller and races were obtained to investigate the lubricating mechanism of roller skew. The effects of skew angle, rotational speed, applied load, length of the roller, and radius of the outer race on the lubricating performance of skewed roller contact in rolling bearings is discussed. In addition, in order to weaken the end concentration of the pressure due to the skewing effect, a parabolic profile modification for the roller's generatrix was carried out. A coupled solution combining skewing and tilting effects was achieved. The results showed that when the roller is skewed, the maximum pressure appears at the end parts of the roller for a roller–outer race contact but in the middle part of the roller for a roller–inner race contact. For the roller–outer race contact, a more serious skewing effect on the lubrication can be generated by a larger skew angle, higher speed, lighter load, longer roller length, and larger radius of the outer race. The skewing effect can be reduced through the profile modification for a roller's generatrix. In general, local lubricating failure may easily occur when roller skew is coupled with the tilting effect in cylindrical roller bearings.