15. Cylindrical roller bearings with ribs for conventional line electric railcar gear unit and its performance evaluation

Tapered roller bearings, which are often used as pinion bearings for gear units in conventional line electric railcars, are a burden on maintenance work because strict adjustment of the end play value (the total axial clearance of the bearings, hereafter "EP value") is essential to prevent damage.
In response, to achieve both reduced maintenance effort and improved reliability, we developed a pinion support structure (Figure 1: proposed structure) that uses cylindrical roller bearings with ribs as pinion bearings. This structure allows for a greater range of adjustment for the EP value.

Unlike the conventional structure, the proposed structure does not change the bearing's radial clearance (the clearance perpendicular to the axis) even if the EP value changes.
This allows the upper limit of the EP value to be increased from 0.16 mm in the conventional structure to 0.30 mm (lower limit: 0.10 mm). This expansion of the permissible range for the EP value reduces the need for adjustment work that involves disassembling the gear unit.
The proposed structure can be implemented without the need for new construction or significant modifications to the gear unit. It only requires replacing the conventional pinion shaft and bearing housings.

Additionally, we conducted rotation tests under operational load conditions with the bearing alone for the proposed structure.
We confirmed that the temperature and vibration acceleration, which are indicators of bearing heat generation and lubrication condition, are equivalent to or lower than those of the conventional structure (Figure 2).