The Design of Rolling Bearing Mountings

90 Driving axle of a construction machineModern construction machines feature planetary gearsin the wheel hub. This yields a considerable step-downratio in a limited space, in the example shown i g =6.35. As the considerable drive torque is generated immediatelyat the wheel, a light drive shaft is sufficient.Planet wheel bearing arrangementThe planet wheel bearings must provide a high loadcarrying capacity in a limited space. This is achievedby means of assemblies where the outer ring raceway isintegrated in the planet wheel. The self-aligning sphericalroller bearing selected in the example smoothlycompensates for small misalignments resulting fromthe deflection of the cantilever bearing journal underload. This yields a uniform contact pattern for thegearing, which is indicative of an optimal gear mesh.In the example shown the internal design of sphericalroller bearing FAG 22309E.TVPB is used.Wheel mountingAs a rule, the wheel mounting on rigid axles of constructionmachines consists of two tapered roller bearingswhich are axially adjusted against each other in Oarrangement (larger spread ) and with preload. In thisway, deformations and tilting of the planetary gear areminimized and impermissible plastic deformations(brinelling marks) resulting from adverse operatingconditions avoided.The wheel bearings are tapered roller bearings FAG32021X (in accordance with DIN ISO 355:T4DC105) and FAG 32024X (T4DC120).Machining tolerancesThe rotating outer rings of the wheel mounting aresubjected to circumferential load, the stationary innerrings to point load, therefore: journal to k6; hub to N7.Lubrication, sealingRolling bearings and gearing are washed around in therevolving wheel hub by the transmission oil.Radial shaft seals protect the bearings from dirt andsplash water.90: Driving axle of a construction machine127 FAG