2014 年 55 巻 4 号 p. 229-234
A long-life gear oil for electric railway trains was developed to reduce the workload and cost of gear unit maintenance. A semi-synthetic base oil, a mixture of polyalphaolefin (PAO) and highly purified mineral oil, was used in the developed gear oil in order to improve high temperature oxidation stability. The composition of additives was also modified to enhance oxidation stability. In an accelerated oxidation test (Indiana stirring oxidation test at 135 ℃/96 hours), the developed gear oil demonstrated sufficient oxidation stability to enable an electric train to run 1,200,000 km without an oil change. Reliability at low temperatures was also shown to be better compared with existing gear oils, because the viscosity at low temperatures and the pour-point was reduced by virtue of the semi-synthetic base oil.
