Spherical Roller Thrust Bearings
In
spherical roller thrust bearings the load is transmitted from one raceway to
the other at an angle to the bearing axis. They can accommodate radial loads
in addition to the acting axial loads. They are self-aligning making them
insensitive to shaft deflection and misalignment of the shaft. Some bearing
arrangements have a number of asymmetrical rollers. They can support very
heavy axial loads and allow high-speed operation.
Some bearings have a pressed steel window-type cage, which, with the
rollers, forms a non-separable assembly with the shaft washer. All other
bearings have a machined brass or steel cage guided by a sleeve held in the
shaft washer bore. The shaft washer and cage with rollers form a
non-separable unit.
Dimensions - The boundary dimensions of spherical roller
thrust bearings are in accordance with ISO.
Tolerance - Spherical roller thrust bearings are produced
as standard to Normal tolerances. Depending on bearing size, the tolerances
for the total height of standard bearings may be 20 to 50 % and for Explorer
bearings are up to 70 % tighter than specified by ISO.
Misalignment
Spherical roller thrust ball bearings are self-aligning. They tolerate
misalignment of the shaft relative to the housing, and shaft deflections
during operation. The permissible misalignment is reduced as the load
increases.
Minimum Load - The requisite minimum axial load to be
applied to spherical roller thrust bearings can be obtained from
This needs to be adhered to if the bearings have to operate at high speeds
or are subjected to rapid changes in the direction of load.
Equivalent dynamic bearing load Normally a spherical roller thrust bearing
is arranged so that runouts in the bearing arrangement do not affect the
load distribution
P = 0,88 (Fa + 1,2 Fr) when they do, the formula is
P = Fa + 1,2 Fr
Equivalent static bearing load
For statically loaded spherical thrust bearings, provided Fr = 0,55 Fa P0 =
Fa + 2,7 Fr
If Fr > 0,55 Fa, the application engineering service should be
contacted.
