The Schaeffler Group has developed a totally new bearing concept - the tube roller bearing - a cylindrical roller bearing that prevents slippage in low radial load applications such as wind turbine gearboxes.
By replacing a standard roller set on a conventional cylindrical roller bearing with tube rollers that have slightly larger diameters, the Schaeffler Group has developed a brand new bearing concept, the FAG tube roller bearing, which prevents bearing slippage in very low radial load applications. If left undetected, this slippage can result in bearing damage and possible bearing failure.
The new bearings are currently undergoing field and endurance tests with Schaeffler customers in various industrial applications, including hot rolling mills, wind turbine gearboxes and paper mills.
In conventional cylindrical roller bearings, under low load conditions, the rolling elements do not roll correctly but start to ‘slip’. The roller set and cage rotate, in some cases at lower than nominal speed. This can lead to damage due to slippage. Under high load, the rolling elements run correctly again and the cage rotates at its nominal speed.
On display at The Schaeffler Group’s stand at this year’s Hanover Fair, the new tube roller concept was demonstrated to visitors using a standard cylindrical roller bearing with brass housing. The roller set consisted of 12 rolling elements, nine of which were standard solid rolling elements, with the other three replaced with the new tube rollers, equally spaced around the bearing raceway. These tube rollers have a slightly larger diameter (around one micrometer) than the standard rollers and are also bored through the centre, which ensures reduced stiffness during operation and prevents peak loads.
The larger diameter of the three tube rollers produces a slight preload in the bearing. Under very low load conditions, the tube rollers therefore support the load and drive the cage. Slippage of the roller set and any resulting damage is therefore avoided.
If the bearing is subjected to higher radial loads, the three tube rollers undergo elastic deflection and the forces are spread onto the rolling elements in the load zone.
The tube roller bearing is a design concept unique to the Schaeffler Group. Compared to axially preloaded bearing solutions, the new bearing also enables simplified designs and easier assembly and installation. The bearings are also interchangeable with standard cylindrical roller bearings.