October 19, 2011
NSK Ltd.
Public Relations Department
NSK Develops Anti-Electrical Corrosion New Material Ceramic Ball Bearing for Fan Motors
New Ceramic Balls Improve Productivity
Tokyo, Japan, October 18, 2011 – NSK Ltd. (NSK; Headquarters: Tokyo, Japan; President and CEO: Norio Otsuka) today announced that it has developed a ceramic ball bearing made of a new material that prevents galvanic corrosion as a bearing for fan motors used in devices such as air conditioners. Quietness is maintained in the new product for a long time by preventing bearing damage from electrical corrosion that occurs due to the effects of inverter control devices. NSK is aiming for annual sales of the new product of 3 billion yen by fiscal 2013.
Fan motors are widely used in products such as air conditioners, clean room equipment, air cleaners, and ventilation systems. In recent years, the shift to inverter-controlled motors has progressed in order to save energy on top of having quiet fan motors. With invert control, however, voltage variation causes current to infrequently flow through the inside of the bearing, resulting in damage called electrical corrosion*1, which may lead to increasing noise from the bearing. Silicone nitride ceramic balls have conventionally been used as a countermeasure to electrical corrosion. NSK has now developed an anti-electrical corrosion bearing that is perfect for fan motors and that uses ceramic balls made of a new material with higher productivity.
*1 When electric current passes through a bearing, arcing and burning occur through the thin oil film at points of contact between the race and rolling elements. The points of contact are melted locally to from “fluting” or groove-like corrugations which are seen by the naked eye. The magnification of these grooves will reveal crater-like depressions which indicate melting by arcing.
Product features
- Prevention of electrical corrosion
- Current flowing through the inside of the bearing is interrupted by using ceramic, which is an insulator, for the rolling element, thereby preventing damage inside the bearing from electrical corrosion.
- Long life
- The new material ceramic balls reduce friction inside the bearing, providing long bearing life (sound, grease).
- High productivity for ceramic balls achieved by using a new material
- Productivity for balls was increased, compared to the currently used silicone nitride ceramic, by using an oxide-based new material ceramic.
Product benefits
The new product will help improve the reliability of fan motors through the following two points:
- Inhibition of increasing fan motor noise for a long time
- Prevention of false brinelling*2 damage that occurs due to vibration during transportation
*2 False brinelling: A phenomenon in which friction is generated at the contact area between the race and rolling element due to vibration and oscillation.
Development Concept
Countermeasures to electrical corrosion in bearings
Prevent sparks caused by current passing through the bearing
Interrupt current using ceramic balls as insulators
Electrical corrosion prevented
There are productivity disadvantages with currently used silicone nitride ceramic
Productivity is better with oxide ceramics than silicone nitride, but mechanical strength is an issue
NSK developed a new material ceramic that combines a bearing life (sound, grease) that is better than current (silicone nitride ceramic) products with good productivity
Performance Assessment Results
Electrical corrosion test results
Anti-electrical corrosion performance of the new material balls
the same as silicone nitride balls
False brinelling test results
Compared to silicone nitride balls, the new material balls show improved resistance to false brinelling that occurs with vibration induced from outside due to things such as long transportation time.
