NSK Ltd.
CSR Division Headquarters
Public Relations Department
NSK Develops High-Reliability, low-torque ball bearings(BELTOP8) for Continuously Variable Transmissions
Bearings help to improve fuel economy of CVTs
Tokyo, Japan, June 29, 2011 – NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President and CEO: Norio Otsuka) today announced that it has developed high-reliability, low-torque ball bearings(BELTOP8) that help to improve the fuel efficiency and reliability of belt-type continuously variable transmissions (CVTs)*1. NSK is targeting annual sales of ¥2.0 billion from the products by 2015.
*1 Belt-type CVTs are a form of transmission that changes speed continuously without employing gears. A belt is used to transmit engine power at an ideal transmission ratio according to the engine rpm.
Belt-type CVTs are increasingly being deployed in markets such as Japan and China in recent years, as they offer excellent fuel efficiency combined with smooth driving performance. There is demand to develop CVTs that offer even greater efficiency, with global prices for crude oil expected to rise and in order to meet tighter fuel efficiency standards. In addition, transmission oils are expected to become lower in viscosity and offer lean lubrication resistancein pursuit of better fuel efficiency, which will in turn necessitate bearings with higher reliability.
The new ball bearings anticipate these market needs and offer significantly less friction loss, while delivering greatly improved reliability under low-viscosity and lean lubrication conditions. NSK will seek to actively expand sales of the ball bearings to automakers in Japan and other markets.
Product features
The ball bearings deliver high reliability and reduced friction through the following features:
◆CVT-specific design for longer bearing life
Bearings for CVTs must offer low friction and meet demanding requirements for long life, rigidity and creep strength. The new bearings build on proprietary expertise that NSK has developed in the areas of special heat treatment, creep+2 prevention, and bearing design, and incorporate a fiber-reinforced plastic cage to deliver two-and-a-half times the life of existing bearings. The new bearings offer a great leap in durability for CVTs, by limiting surface damage (peeling) that occurs when bearings are used with low-viscosity oil or under lean lubrication conditions, or lubrication with foreign material contamination.
*2 Creep occurs when the outer ring is fixed and the inner ring allowed to rotate, but the fixed outer ring gradually rotates.
◆Fiber-reinforced plastic cage for lower torque
The use of a fiber-reinforced plastic cage reduces the agitation resistance of lubrication oil by as much as 30%, without significantly changing the rated capacity or size of the bearing. An offset raceway groove enables further reduction of the bearing size and weight to make CVTs more efficient.
NSK has achieved compact, lightweight and low torque applications for automobiles by leveraging its four core technologies (tribology, materials, analysis, and mechatronics). The company has been developing these technologies for over 90 years, and is continuing to create products that will improve the fuel efficiency of automobiles.
