Common Failure Mode And Solution Of Fan Gearbox Bearing
Plannet Carrier Bearings
Common Faiure Mode:
The selection and application of the planetary carrier is related to the design of the
spindle. At present, the common planetary carrier is full of roller cylindrical roller bearings.
If the spindle bearings use spherical roller bearings, whether it is a single spherical roller
bearings 3 point bearing design or two spherical roller bearings 4 point bearing design, as the
spherical roller bearings and radial the presence of the play.
When the fan in the brake or other axial load alternation in the direction of the situation,
the spindle and the rear of the planet carrier in the axial direction may be moving. At this
time, if the use of cylindrical roller bearings as a carrier bearing, because of its inner and
outer ring in the axial direction of a certain relative displacement space, so the axial direction
from the spindle will be transmitted to the carrier of the cylindrical roller bearings, and if the
amount of movement is large enough, then the cylindrical roller bearings will cause an impact.
Moreover, because the ring gear and the gear box is intergrated into one, so the planetary wheel
and the planet carrier with the axial movement will also cause the planet wheel wear surface.
Timken recommends the use of single row tapered roller bearings across the tapered roller
bearings through the preload to solve the spindle axial movement on the impact of the planetary
wheel. And the preloaded tapered roller bearing area is optimized to reduce the raceway stress,
improve the rigidity of the planetary gear train, and can withstand the external transimission
into the gear box carrier side of the additional axial force.
A common planetary wheel bearing is composed of a pair of double row cylindrical roller
bearings. In the case of an insufficient amount of interference between the bearing outer ring
and the inner bore of the planetary gear or due to the deformation of the gear so that the contact
area between the two is reduced, there may be an outer ring race and wear.
For the planetary gear design, due to the planetary wheel and the ring gear and the sun wheel
at the same time when the same size by the same direction, the opposite direction of the axial
force, the resulting overturning moment makes the outer two rows of roller bearing a larger. The
middle two rows of rollers are smaller. The uneven distribution of the load between the four rows
of rollers makes the actual service life different, and under the premise of the same design
life, the outer two columns will appear fatigue in advance.