What is the minimum bearing load?

Rolling bearings reduce friction in rotating machinery by using rolling friction with a lower coefficient of friction to remove as much sliding friction as possible from the system. However, even though a rolling bearing tries to reduce the total friction in the system, the individual rolling elements within the bearing still require a certain amount of friction to roll rather than slide. This internal friction is generated by applying a load to the bearing. This load can be generated internally by preloading or by an externally applied load.

For many radial bearings, a certain space is usually provided between the rolling element and the raceway to allow for thermal expansion and prevent the bearing from sticking. "This internal clearance forms the so-called loading zone and unloading zone within the bearing. With the rotation of the shaft, the rolling element enters and exits the bearing area of the outer ring. When the rolling element enters and exits the loading zone, the rolling element speed will change. If there is no minimum load on the rolling element, acceleration in and out of the load zone can be harmful.

If the rolling bearing does not meet the minimum load, a variety of situations may occur, which greatly shortens the service life of the bearing. Slippage between the rolling element and the raceway can destroy the lubricating oil film and lead to smear damage. Smearing will not only damage the rolling surface, but also cause the temperature to rise.

The load is placed on the retainer inside the bearing. Generally, the purpose of the cage is to prevent the rolling elements from touching each other. However, when the minimum load is not met, that is, when traction is not present, the cage must now drive the traction of the rolling element instead of the raceway. This creates unexplained loads placed on the cage and can lead to premature cage failure.