bearings online
bearings online
Author :Admin | Publish Date:2013-04-09 10:11:07
Historically, the tapered roller [bearings online]
has been the primary bearing option for axle and differential applications
thanks to its robustness, the lack of alternatives, and low efficiency targets
of the past. However, the use of tapered roller bearings comes at the expense of
much higher sliding friction. The need to maximize fuel economy has opened the
door to modern technologies that can deliver lower friction and higher
efficiency.
The tandem bearing is a two-row angular contact ball bearing, with each row
having a contact angle in the same direction. This arrangement of ball rows
enables high stiffness and rigidity. Because the tandem utilizes ball bearings,
rolling resistance comes from rolling friction between the balls and the grooved
raceways they roll against. In comparison, a tapered roller bearing’s rolling
resistance comes from a combination of rolling friction and sliding friction,
most of which comes from the sliding motion between the end of the roller and
the raceway support lip that it slides against. This results in much greater
sliding friction. The end result means tandem ina
bearings have about half the friction of tapered roller bearings, which
allows tandems to run with higher overall efficiency and lower operating
temperatures when compared with a taper bearing.
Another challenge that Schaeffler had to address with the tandem bearings
on line was to choose an appropriate plastic material for the bearing cages. The
requirements upon these cages were somewhat challenging. The plastic needed
adequate stiffness to retain the ball bearings yet it also had to be flexible to
facilitate loading of the balls into the bearing pockets. In addition, the
polymer needed to withstand hypoid gear oil at temperatures of up to 150°C
(302°F). Finally, it needed to be dimensionally stable in support of the
differential and pinion assembly process. Schaeffler selected Stanyl from DSM
Engineering Plastics for the cages, thanks to the material’s proven performance
in other Schaeffler bearing applications.
Stanyl is a high-performance polyamide with a wide versatility and a unique
set of properties, including high mechanical property retention and excellent
resistance to wear and friction. DSM offers Stanyl in a wide variety of grades
including unfilled (non-reinforced) as well as grades containing glass fiber,
mineral, lubricants, and/or flame retardants.
Indentation marks in rolling bearing raceways are known to be a source of
surface damage, resulting in shorter bearing service life. SKF bearing life calculation has taken account of this for
many years using the ηc contamination factor. Recently, SKF has developed
advanced models and conducted experiments to predict the interaction of
scratches and indentations, and the lubricant present in the raceways. This
article explores in detail these interactions and the effect of sliding, to give
a unique insight into the way the damage process takes place.
34BWD04BCA70
35BD219T12DDU
35BD5220AT1XDDUM3C01
Prev:miniature bearings Next:bearings online