NSK Develops Low-Maintenance High-Reliability Gearbox Bearings

NSK technology achieves extended maintenance intervals reducing total life cycle costs

Building on a long history of success in the railway industry, NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President & CEO: Toshihiro Uchiyama) has developed new high reliability gearbox bearings integrating advanced technologies that further increase reliability over previous models.

This includes new bearings for large and small gears (pinion shafts, etc.) in rolling stock gearboxes. The bearings for small gear shafts deliver a completely new level in value through even higher reliability and reductions in specialized maintenance requirements. The bearings for large gear shafts offer even higher reliability and the standard lineup has been expanded to offer a greater range of sizes to meet diverse customer needs.

High reliability is indispensable for gearbox bearings, which are subjected to severe conditions with frequent shocks and vibrations. The new bearings feature a suite of NSK technologies that significantly enhance the ease of handling (small gear bearings only), extend maintenance intervals, and contribute to a reduction in total life cycle costs.

Major rail operators in over 20 countries worldwide trust NSK railway bearings with a proven record of quality and reliability built on over 100 years of expertise in bearings, materials, and tribology. NSK has been generating significant momentum in the railway industry, and is moving to double sales by fiscal 2026 (compared to fiscal 2018).

Development is driven by NSK Vision 2026: “We’re Setting the Future in Motion,” which represents the company’s determination to create new value in mobility contributing to the development of a more prosperous society and enhancing value for all stakeholders, from employees and their families to the end user.

Development Background

Trends in the railway industry emphasize strict management and reductions in total life cycle costs. Gearboxes bearings are subjected to some of the most severe operating conditions amongst railway components, resulting in significant demand for even higher reliability products.

The gearbox transmits force generated by the traction motor to the wheelset (wheel-axle assembly), and is directly connected to the axle shaft. The structure results in gearbox bearings being subjected to intense shocks and vibrations arising from the wheels clattering along the tracks. The severe operating conditions demand regular bearing maintenance, which has spurred demand for solutions that contribute to extending maintenance intervals and reducing the overall burden of maintenance work.

Mounting and maintaining tapered roller bearings, which have often been used to support pinion shafts, requires labor-intensive end play clearance adjustment by expert maintenance engineers. This results in significant time and labor costs that increase total lifecycle cost for railway operators.

In light of these needs, NSK has developed new bearings integrating advanced technologies. Products features are detailed below.

1. Features of Bearings for Small Gears (Pinion Shafts, etc.)

i. Low-maintenance design (time and labor savings)

Using a combination of the new cylindrical roller bearings and four-point-contact ball bearings eliminates the need for end play clearance adjustment, simplifying mounting and maintenance. NSK ships these bearings with preset clearance, making it easy to achieve highly optimized results just by mounting.

ii. Significantly Increased Cage Strength

Gearbox bearings are subjected to intense shocks and vibrations from the tracks, so cage strength is vital to ensuring high reliability operation. Drawing on vast experience designing bearings for railway applications, NSK has developed a special ring-guided cage with optimized pockets employing “R-shaped corners.” The novel design reduces stress in the cage structure by 75%.

iii. Enhanced Suppression of Bearing Creep

The inner ring is specially heat treated to ensure dimensional stability even under conditions of extended use at high temperatures. Extremely high dimensional stability delivers excellent anti-creep performance, preventing the bearing from shifting along the shaft.

2. Expanded Lineup of Bearings for Large Gears (Shafts)

Due to increasing demand, NSK is expanding number of sizes offered in the standard lineup of high reliability tapered roller bearings for large gears. Makers of rolling stock can quickly and easily integrate these widely tested standard models into new designs. All models feature high reliability design.

3. Overview of Standard Lineup of Bearings For Small/Large Gears in Rolling Stock

NSK supplies products for both high speed and low speed rolling stock applications. All rail products feature NSK’s high reliability technologies and design. Please contact us for availability in other sizes and specifications.

4. Customer Benefits of New Bearings

A suite of NSK technologies significantly enhance the ease of handling, extend maintenance intervals (reduce maintenance burden), and contribute to a reduction in total life cycle costs.