2014
Development of “Long-life Needle Roller Bearing Unit” for Reduction Gear BoxJanuary 8, 2014
[More than 10-fold operating life compared to conventional products with contaminated lubrication!]
NTN Corporation (hereafter, NTN) has developed the “Long-life Needle Roller Bearing Unit” that improves operating life more than 10-fold by applying a special heat treatment to the “rollers” of the bearing rolling element and changing the design of parts, and combining a grooved thrust washer and shaft with optimized surface roughness and hardness.
Needle roller and cage assembly bearings are ordinarily used in the planetary reducer of the final and swing drive of construction machinery such as hydraulic excavators. Bearings used in these parts need to be able to withstand heavy loads, and contamination such as abrasion powder from the planetary gears easily mixes in with the bearing track surface through lubrication oil. The bearings are subjected to extremely harsh conditions, and a long bearing operating life has been an ongoing issue.
The newly developed “Long-life Needle Roller Bearing Unit” is a unit product that combines the bearing (rollers and cage) with a shaft and thrust washer. The rollers and shaft have been treated with NTN's proprietary special heat treatment, and a newly designed roller crowning shape*1 helps to limit edge stresses*2 due to tolerance during bearing installation. Changes to the cage pocket shape help to improve the flow of lubricant and reduce the amount of contamination becoming trapped between the roller and cage contact areas. These improvements help to increase operating life more than 10-fold over conventional products with contaminated lubrication. Assembly with a planetary reducer features a thrust washer installed on the bearing side, and the use of grooved thrust washer improves lubricant flow as well as discharge of contaminants to further improve the operating life.
NTN will market the “Long-life Needle Roller Bearing Unit” extensively as a product to contribute to improvements to reliability of various reducers, including those used in construction machinery.
| *1 | “Crowning shape”: cylindrical shape where the diameter of rollers gradually becomes smaller on a micron scale in the direction of the edges |
| *2 | “Edge stress”: pressure focused on the edges of rollers. A higher edge stress generates more wear and reduces the operating life. |
Features
| More than 10-fold operating life with contaminated lubrication (compared to conventional products) | ||
| - | Unitization of the bearing, shaft and thrust washer | |
| - | Application of special heat treatment to rollers and shaft for a longer operating life with contaminated lubrication | |
| - | Improved roller crowning shape to limit edge stress due to bearing installation tolerance | |
| - | Optimal design for the cage pocket shape to reduce trapping contaminants | |
| - | Added thrust washer discharge groove to improve discharging contaminants (oil discharge quantity: 6-times conventional method) | |
Inquiries about this release
Product photo
Applicable parts
Hydraulic excavator
External photo of bearing unit(planetary reducer)