10. Oil for axle-box for Shinkansen with excellent low-temperature performance and maintainability

Currently, only one brand of oil is used to lubricate the axle journal bearings of Shinkansen trains. However, there were concerns that this oil would not cope when the Shinkansen network was expanded into extremely cold regions, due to a lack of low-temperature performance.
The lubricating oil developed by the RTRI in the past (“Axlube”), made using synthetic oil for enhanced low-temperature performance, has not been adopted because it turns red over time, making it difficult to distinguish this color change from the presence of abrasion debris, which is a problem for maintenance.
To solve these problems, we developed a new oil for axle-box for Shinkansen (developed oil) that offers both excellent low-temperature performance and maintainability.

The developed oil utilizes a highly refined mineral oil as a base oil and includes additive substances that inhibit reddening.
The developed oil has a lower pour point than the current oil and is verified to retain its fluidity even at temperatures below -40°C (Fig. 1).

Outdoor exposure tests have also confirmed that the developed oil is capable of inhibiting reddening caused by using Axlube (Fig. 2).

We verified the durability of the developed oil by conducting a bench test with real axle journal bearings operating for the equivalent of 800,000 km of travel.
At the end of testing under these conditions, no abnormalities were found in the properties of the oil or the test bearings, confirming the oil’s outstanding durability (Fig. 3).
The base oil and additives that make up the developed oil are general-purpose products that are employed widely in oils for other applications.
This helps to keep costs down and ensure a stable supply of raw materials.

The developed oil is expected to be deployed on Shinkansen vehicles that use oil bath lubrication after its durability is confirmed on operational vehicles.