A proposal of grease pocket structure in consideration of base oil migration

The periodicity of motor disassembling maintenance is now determined by the durability of the sealed grease whose lifetime is the shortest among all bearing parts and materials, which should be lengthened further. We discussed the structure of the grease pocket and have shown that the efficiency of grease lubrication depends on the shape of grease pocket, which should be modified appropriately. We performed laboratory tests with small grease-pocket models of different shapes to find that a grease pocket structure to improve oil circulation is obtained by (1) increasing the depth of a ring-shaped grease pocket (main-GP), and (2) expanding the outer space of the grease pocket (sub-GP) upward and downward. Based on the test findings, we designed, manufactured, and tested full-size grease pocket models with a bearing rotating test machine to prove that the oil component of the grease in the sub-GP migrates in a larger quantity than when a conventional grease pocket in used. It is expected, therefore, that the proposed grease pocket structure extends the lifetime of the grease and improves the durability of bearings.