Schaeffler is introducing the FAG tube roller bearing that incorporates three tube rollers to enable the bearing to rotate without slippage under all load conditions - and with no adverse impact on the bearing's load rating and rating life.
Any slippage in a rolling bearing will reduce performance and life, and overloading and underloading are the primary causes. This is because rolling bearings are designed with a minimum load requirement in order to function optimally. If this minimum load is not met, slippage occurs and results in surface damage such as increased wear or smearing, particularly in critical lubrication conditions.
In wind turbines, rolling bearings have to meet special performance requirements. The bearings must be designed to withstand extremely low and high loads that act on the bearing during calm or strong wind conditions. The risk of damage to a bearing increases significantly when the roller set of a rolling bearing with high slippage is suddenly subjected to extremely high acceleration forces. For this reason, Schaeffler has developed the tube roller bearing that is claimed to eliminate the problem of slippage.
The FAG tube roller bearing is a conventional cylindrical roller bearing that incorporates three cylindrical rollers with a slightly increased diameter. These three rollers are hollow and carry a support roller in the inner bore. The tube rollers 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 in a conventional rolling bearing.
To ensure that the roller is less rigid (more flexible) at higher loads, the support roller in the inner bore of the tube roller has a slight clearance; 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.
The tube roller bearing is not available from Schaeffler's standard catalogue but is custom-designed for each application. Initial prototypes have already been manufactured and tested. Pilot applications in wind turbine gearboxes are planned for the end of 2010.
For more information on Schaeffler's tube roller bearing, please call the marketing department on +44 (0)0121 313 5870 or email .