Tapered roller bearings
Tapered roller bearings have tapered inner and outer ring raceways and tapered rollers. They are designed to accommodate combined loads, i.e. simultaneously acting radial and axial loads. The projection lines of the raceways meet at a common point on the bearing axis (fig. 1) to provide true rolling and low friction. The axial load carrying capacity of tapered roller bearings increases with increasing contact angle α. The size of the angle is related to the calculation factor e (→ product tables): the larger the value of e, the larger the contact angle. A single row tapered roller bearing is typically adjusted against a second tapered roller bearing.
Single row tapered roller bearings are separable (fig. 2), i.e. the inner ring with roller and cage assembly (cone) can be mounted separately from the outer ring (cup).
The factors that influence SKF bearing performance and service life include but are not limited to the following:
Roller end / flange contact area
The geometry and surface finish of the roller ends and the area on the flange that makes contact with the roller ends (fig. 3
) have been optimized to promote and maintain the formation of a lubricant film. This reduces friction and frictional heat as well as flange wear. The bearings can better maintain preload and run at reduced noise levels.
To extend service life under misalignment or heavy load conditions, SKF tapered roller bearings have either crowned raceways or a logarithmic profile to prevent stress peaks at the roller ends. The logarithmic profile is designed to optimize load distribution along the rollers.
Consistency of profiles and roller size
The rollers used in SKF tapered roller bearings are made to such close tolerances that they are virtually identical. These extremely close tolerances, together with the precision of the raceway profiles, provide optimal load distribution over the rollers to reduce noise and vibration levels and enable preload to be set more accurately.
Tapered roller bearings typically have a running- in period. During the running-in period, a conventional design tapered roller bearing experiences a significant amount of friction, resulting in wear, which can be noticed as a temperature spike (diagram 1
). With current SKF tapered roller bearing designs, friction, wear and frictional heat are significantly reduced, provided the bearings are mounted and lubricated correctly.
The SKF assortment of standard tapered roller bearings comprises:
single row tapered roller bearings (fig. 4)
matched single row tapered roller bearings (fig. 5)
double row tapered roller bearings (fig. 6)
four-row tapered roller bearings (fig. 7)
hub units based on tapered roller bearings for industrial, automotive, railway and off-highway applications (→ contact SKF)