Contact forces between roller and cage pocket in cylindrical roller bearings (Consideration based on dynamic behavior between roller and cage)

When rolling bearings are used under light loads and high rotational speeds, their life may be determined by cage wear rather than raceway flaking. Under these operating conditions, the life and reliability of the bearings can be improved by reducing cage wear. To reduce cage wear, it is necessary to measure and analyze the contact forces acting on the cage due to the interactions between the roller and the cage pocket. In this paper, a measurement system capable of measuring “the contact forces between the roller and the cage pocket” and “the cage center displacement” at the same time has been constructed. Measurements have been conducted using this system for a cylindrical roller bearing at various rotational speeds. As a result of measuring the contact forces, it has been found that “the force to accelerate the cage” is generated continuously in the load zone of the bearing, while “the force to decelerate the cage” is generated intermittently in the non-load zone of the bearing. Since the contact forces are not constant during one rotation of the cage, the impulses due to the interactions have been calculated to evaluate not only the contact force but also the contact time. Results indicate that the impulses per rotation of the cage caused by each force show a tendency to decrease up to 2000 min-1 of rotational speed and not to almost change at higher speeds. In addition, it has been found that the cage center displacement measured becomes a constant velocity circular motion when the rotational speed exceeds 2000 min-1. These findings suggest that the contact between the roller and the cage can be easily modeled when the rotational speed exceeds 2000 min-1. The analysis based on this model created is in general agreement with the impulses obtained from the measurement results.