NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President and CEO: Norio Otsuka) today announced that it has developed an inner race diamond-like carbon-coated(DLC) cylindrical roller bearing for high efficiency turbo chillers used in large-scale air conditioners in office buildings and factories. The application of DLC coating improves the skidding resistance* of cylindrical roller bearings, making such bearings suitable for application to turbo chiller compressors used in high-speed, light-load conditions, and also achieving a higher level of reliability and a lower level of bearing friction loss. NSK plans to expand sales of this product, which promotes higher reliability and better energy savings, in and outside Japan, and it is targeting 200 million yen in sales in 2018.
||Skidding is a phenomenon that occurs when slipping happens between the outer and inner raceway surface and the roller's rolling contact surface due to the drive of the roller transmitted from the bearing's inner raceway being inhibited by agitation resistance in the lubrication oil.
In Japan air conditioning accounts for about 30 percent of consumer energy consumption (heat source systems) and as such, is responsible for a great deal of power and fuel consumption. As a result, the demand for turbo chillers that are highly energy efficient is increasing. Further, there is a demand for higher levels of reliability in large-scale applications.
NSK introduced angular ball bearings as roller bearings for turbo chillers (compressors) in 2000. Replacing conventional sliding bearings with these angular contact ball bearings resulted in a huge improvement in energy efficiency (energy savings).
In addition, only angular contact bearings with a position-preload were deployed to address the issue of the skidding resistance required for roller bearings used for turbo chiller compressors. Those bearings ended the trend toward multiple bearing configurations, but that approach in turn reached the limit of friction loss reduction.
In response, NSK has added a new member to its lineup for turbo chiller compressors. The new bearing is a DLC-coated cylindrical roller bearing that has greater reliability, less friction loss, and requires less space and resources than the conventional angular contact ball bearing.