The extension of maintenance periodicity is a desirable target for the traction motor of railway rolling stock, and achieving such a goal necessitates extending the life of bearing grease. The lubrication behavior of grease contained in the conventional grease-sealing structure (or grease pocket) was analyzed, a remodeled structure was then proposed that has a larger channel to supply lubricant to the bearings more effectively. To confirm the effect of this pocket, it was applied for the bearings of Shinkansen traction motors (Fig. 1) and implemented a bench test on the bearings by simulating actual service conditions. The test verified that the new grease pocket would extend the life of grease by a factor of two or more on the ball bearing side, and by a factor of 1.3 or more on the roller bearing side (Fig. 2). The actual disassembly inspection of bearing is implemented at a periodicity to match the conditions of ball bearing whose life is shorter than those of roller bearing. The remodeled grease pocket thus is expected to double the life of grease and therefore the inspection periodicity of traction motors. The remodeled grease pocket was also applied to traction motors on narrow-gauge test cars, and running tests was implemented to confirm its reliability.

This structure is applicable to the traction motors of Shinkansen trains as well as to those of narrow-gauge trains.