The three cylindrical rollers in Schaeffler’s FAG tube roller bearing have a hollow design and are supported by a support roller in the inner bore. These rollers with a slightly increased diameter generate preload in the bearing and drive the bearing cage, and therefore the entire roller set, at low loads. At higher loads, the bore of the cylindrical rollers ensures sufficient deflection of the larger rollers so that that they are not overloaded. This means that the load is evenly distributed to all the rolling elements, similar to a conventional rolling bearing.
The support roller in the inner bore of the tube roller has a slight clearance to ensure that the roller is less rigid (more flexible) at higher loads. At the same time, this also prevents excessive deflection of the tube roller. Together, the tube roller and support roller provide increased fatigue strength to the bearing, which results in a rigid rolling element that withstands peak load conditions.
Initial prototypes have already been manufactured and tested. Pilot applications in wind turbine gearboxes are planned for the end of 2010.