Enabling more energy efficient systems due to downsizing and reduced friction, the three new high precision roller bearings, introduced by The Schaeffler Group, include the X-life machined needle roller bearing version D; the X-life machined needle roller bearing with TWin Cage; and a slimline drawn cup needle roller bearing, which has a radial section height of 1.5mm.
Benefiting from a new profiled steel cage, the X-life machined needle roller bearings version D offers an increase in load ratings of up to 25%. The number of needle rollers and the length of needle rollers can be increased without increasing the overall dimensions of the bearing. The X-life NK20/16-D-XL with a 20mm diameter bore and a 16mm width, for example, offers a higher load carrying capacity than the X-life NK26/16-XL needle roller bearing, which has a larger bore diameter of 26mm. In addition to the new X-life NK20/16-D-XL needle roller bearing, the new range also includes the NK55/25-D-XL, as well as three additional sizes: the NK14/16-D-XL, the NK28/16-D-XL and the NK37/20-D-XL.
Together, these five bearing sizes offer numerous downsizing options for radial needle roller bearings, i.e. the enveloping circle diameter of the new bearings ranges from 14 up to 70mm. The new machined needle roller bearings with TWin Cage are manufactured in plastic and provide higher efficiency as a result of lower friction. Rather than a single long length needle roller, this new bearing uses two short needle rollers, which are inserted next to one another in a single cage pocket. This unique combination of cage and rolling elements reduces friction by up to 25% compared to conventional needle roller bearings. For example, the power loss due to friction of an X-life NK45/20-TV-XL machined needle roller bearing with new TWin Cage operating at 4,000rpm is 25W-30W less than a bearing with conventional plastic cage. This means that the use of only one needle roller bearing with a TWin Cage saves a similar amount of energy to that required to operate a light bulb.
In addition, the new bearings operate with reduced heat generation, resulting in increased grease operating life and therefore longer lubrication intervals. The accuracy of the application also improves due to reduced fluctuations in temperature. The new slimline drawn cup needle roller bearing also makes a significant contribution towards lowering friction and improving energy efficiency. The radial section height of the new bearings is just 1.5 mm. For a drawn cup needle roller bearings with diameters from 15-50mm, a section height of 1.5mm is the current limit in terms of how small the bearing and cage can be manufactured. Currently, the smallest section height available from most other bearing suppliers is around 2.5mm. This means the new slimline drawn cup needle roller bearings are equivalent to plain bearings in terms of their external dimensions, which makes them ideal for replacing plain bearings, particularly in automotive applications such as automatic transmission systems and gearboxes. Other advantages of slimline drawn cup needle roller bearings are that they reduce friction by up to 60% compared to conventional plain bearings. They also help to simplify any adjacent structures or components and increase the accuracy and reliability of the system. A fine oil mist is sufficient for these bearings’ reliable operation as opposed to the need for the plain bearings to receive direct, adequate supply of oil from inside the transmission. Thus, complex oil feed systems are no longer required, whilst any oil pumps within the system can be replaced with smaller, more cost effective pumps.
For reliable operation, plain bearings also require a load-bearing lubricant film. The reduced frictional torque of a rolling bearing compared to a sliding lubricant film or layer results in reduced breakaway torque during start up. This means that slimline drawn cup needle roller bearings offer higher operational reliability, for example, in start-stop applications. In addition, the transmission oil will not be contaminated by fine wear debris from the sliding layer found in plain bearings. The oil therefore remains cleaner if slimline drawn cup needle roller bearings are used. At the same time, accuracy also increases because the bearing clearance on the shaft also increases due to abrasion or wear in the plain bearings. The high accuracy of a drawn cup needle roller bearing throughout its operating life contributes to reduced clearance of the gear teeth, which in turn increases the reliability and operating life of the transmission system.