Feature Enclosures & air movers
Smaller bearings, dramatic leaps in performance
The Schaeffler Group launches THREE innovative, needle roller bearings designs which provide dramatic new downsizing options for design engineers
1. X-life machined needle roller bearings ‘version D’ ‘Version D’ benefits from a new profiled steel cage using a newly-developed Schaeffler technique to provide a signif- icantly higher load carrying capacity. The number of needle rollers and the length of needle rollers are increased without increasing the overall dimen- sions of the bearing. In this way, by using more rolling elements and by extending their load- bearing length, the new X-life needle roller bearings version D offer an increase in load ratings of up to 25%.
X-life Version D Load rating Bearing size Weight Friction
+25% -15% -20% -30%
This means that bear-
ings installed in the same mounting space can be subjected to significantly higher loads without increasing the physical size of the bearings. Conversely, the new X-life needle roller bearings version D create new opportunities for designers to downsize bearings, i.e. reduce the size of machines and systems while still achieving the required bearing performance. For example, the new X-life NK20/16- D-XL needle roller bearing with a 20mm diameter bore and a 16mm width offers a higher load carrying capacity than the X-life NK26/16-XL needle roller bearing, which has a larger bore diame- ter of 26mm. If the new bearing is used for downsizing, the section height of the bearing can be reduced by 15%, the weight by 20% and friction by 30%, whilst still providing the same load carrying capacity.
Schaeffler’s new range includes five bearing sizes ranging from 14mm to 70mm enveloping circle diameter.
2. X-life needle roller bearing TWin Cage: 25% less friction The new machined needle roller bear- ings with TWin Cage 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 the new TWin Cage operating at 4,000rpm is 25W-30W less than a bearing with a 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 addi- tion, the new bearings operate with reduced heat generation, resulting in increased grease operat- ing life and therefore longer lubrication inter- vals. The accuracy of the application also improves due to reduced fluctua- tions in temperature. There is an improve- ment in bearing kinematics due to optimum load distribu- tion on both rows of needle rollers. Tests at Schaeffler have shown that bearings with a TWin Cage benefit from a significantly increased operating life.
3. Slimline drawn cup bearings: less friction, improved efficiency Currently, the smallest section height available from most other bearing suppliers is around 2.5mm. The radial section height of the new Schaeffler Slimline drawn cup bearings is just 1.5mm for drawn cup needle roller
10
The Slimline drawn cup needle roller bearing has a radial section height of just 1.5mm
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
Slimline drawn cup bearing
Slimline Friction
Section height -60% 1.5mm
bearings with diame- ters from 15 to 50mm. The new Slimline drawn
cup needle roller bearings are equiva- lent to plain bearings in terms of their external dimensions, which makes them ideal for replacing plain bear- ings, particularly in automotive appli- cations such as automatic transmission systems and gearboxes.
The great advantage of Slimline drawn cup needle roller bearings is that friction is reduced 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. For example, plain bearings in automatic transmissions must always receive a direct, adequate supply of oil from inside the transmission for the system to operate reliably. This requires significant machining time and costs, as the shaft has to be provided with hori- zontal and vertical holes for the oil feed. In contrast, a fine oil mist is sufficient for Schaeffler Slimline drawn cup needle roller bearings to operate reliably. Complex oil feed systems are no longer required and any oil pumps within the system can be replaced with smaller, more cost effective units.
X-life TWin Cage Friction
-25%
X-life TWin Cage needle roller bearings
Plain bearings also require a load-bearing lubricant film for reliable operation. The reduced frictional torque of a rolling bear- ing 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 transmis- sion 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. Schaeffler (UK)
e-mail:
info.uk@
schaeffler.com
www.schaeffler.co.uk Enter 206
OCTOBER 2011 Design Solutions 1971-2011
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