Shinkansen cars runs at speeds higher than 350km/h are apprehended to experience an increase in lubricant leakage, which impedes the normal lubrication condition of axle bearings. The RTRI surveyed the oil seals currently in use and performed bench tests on them to reproduce leakages. It was clarified that the major cause of leakage is the peeling of the lip contact surface (i.e. the detachment of rubber and filler), and that fluoro-rubber is better at maintaining the seal than acrylic rubber (Figs.1 and 2 (a)). Based on these findings, the RTRI adopted fluoro-rubber and a filler to suppress premature peeling due to high-speed operation (Fig. 2(a)). Additionally, the RTRI changed the dimensions and profile of the lip part to prevent position changes caused by fluctuations in pressure at tunnel entry/exit or when two trains pass each other (Fig. 2(b)).
      A bench test of the prototype product verified that no leakage occurs even in prolonged usage (Fig. 1(b)). The lip contact face was normal and displayed no peeling after the test (Fig. 1(a)), confirming the oil seal's suitability for use in high-speed Shinkansen cars.

Fig. 1 Results of bench test

Fig. 2 Prototype

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