For designers of electric motors and plant operators who use motors, key design and quality criteria are efficiency, noise and vibration levels. With small, low-capacity electric motors – such as those often found in consumer goods including washing machines, power tools and ventilators – efficiency is mostly determined by the power loss in the internal bearings.
The Schaeffler Group is therefore introducing Generation C deep-groove ball bearings that not only offer 35 per cent less friction than their predecessors, but also cut noise by 50 per cent. This means a more efficient motor, resulting in reduced energy consumption, plus the new design improvements enable the bearings to run faster while simultaneously offering a longer operating life. Reduced friction and improved energy efficiency also equate to a reduction in running costs for plant operators, and more efficient machinery with extended maintenance intervals.
In order to reduce friction by 35 per cent, Schaeffler has optimised the osculation (raceway curvature) between the balls and rings on the new bearings. This means there is less chance of misalignment between the inner and outer ring. As well as offering less friction, the bearings also generate less heat, making them suitable for higher running speeds.
Schaeffler is also modifying the seal on the bearings. The new novel HRS seal has modified double-lip geometry and is made from nitrile butadiene rubber (NBR). These have been adjusted to match the recess on the bearing inner ring. Axial contact between the inner ring and the seal means more effective protection against contamination or loss of grease, as well as less frictional torque. This results in longer grease life, thereby increasing the life and reliability of the bearing and providing improved bearing performance at higher speeds.
Venting grooves have also been added in order to improve the run-in behaviour of the bearings. In addition to the HRS seal, the bearing shield has been modified. The recesses on the bearing rings and the shield geometry are functionally adjusted to each other in such a way that the sealing efficiency is improved and grease life increased. The new design creates an axial and radial labyrinth with the shield.
This improved guidance of the rolling elements also contributes to higher performance of the bearing. The new riveted steel cage, which replaces the previous steel 'ribbon' cage, offers higher rigidity and so is suitable for higher running speeds. The riveted steel cage also reduces noise and means the bearing is less sensitive to shock loads. The manufacturing tolerance of the bearings has also been increased (to P5 Abec 5 standards), ball roundness to G5 tolerances and surface finish is improved.
Dimensions for the new bearings correspond to those of the previous bearing types, enabling easy replacement. Generation C bearings can operate in temperatures from -30 up to +120degC.
These bearings are available with outside diameters from 26mm up to 90mm. Riveted steel cages are standard, although polyamide cages are optional. P6 or P5 tolerances can be specified on ordering. Sealing options include one or two-gap seals; one or two-lip seals; or low-friction, non-contact labyrinth seals.
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