May 17, 2006

NTN Develops "High Load Capacity Cylindrical Roller Bearings
for Wind Turbines"

<Provides high reliability with 1.5 times the rating life of current products>

The NTN Corporation (NTN) has developed high load capacity cylindrical roller bearings appropriate for supporting the intermediate shaft and output shaft of gearbox for wind turbines.

Gearbox for wind turbines are installed in high places, which makes maintenance difficult. Therefore, high reliability and long service life are required for the bearings for gearbox. In addition, in recent years wind turbine designs are moving toward higher output and larger size, with the objective of improving the power generation efficiency. Therefore, the need is increasing for bearings with high load capacity.

Conventionally, "full complement cylindrical roller bearings" are used on the input shafts of gearbox in wind turbines as high load capacity bearings. Compared to bearings with cages, they have more rollers and longer rated life. However, because the adjoining rollers in full complement roller bearings contact each other, damage such as scuffing and smearing (*1) occur easily, so their application is restricted to locations rotating at low speed.

On the other hand, for the output shaft and intermediate shaft of gearbox, which rotate at medium to high speed, "cylindrical roller bearings with cages" are used. Although bearings with cages have superior performance at higher speeds, they have fewer rollers and therefore, it is difficult to meet the demand for longer service life with such bearings.

That is why instead of the conventional cage, NTN has now developed a "rolling element separator" to increase the load capacity without impacting the high speed performance. The end result is a cylindrical roller bearing with 1.5 times the rating life compared with a conventional bearing with cage.

(*1)	This is type of surface damage occurring on the rolling surface. It is an aggregation of minute seizing.

[Features]

1. Longer service life
   • By containing nearly as many rollers as a full complement roller bearing, these new bearings increase the load capacity and achieve a rating life 1.5 times of that for conventional bearings with cages.
2. Higher speed
   • These bearings prevent contact between adjoining rollers as occurs in full complement roller bearings. And, by optimizing the shape and guidance method of the separators, allowable speeds equivalent to those for bearings with cages are achieved.
3. Improved handling
   • Since the rollers do not fall out even if the inner ring is removed, the inner ring and outer ring sub-assemblies can be handled separately; therefore, installation into the final equipment is easier.

[Applications]

Gearbox for wind power generators and other gearbox for industrial machinery and construction machinery

This product will be exhibited at the "WindEnergy 2006" international exhibition
of wind turbines to be held in Hamburg, Germany May 16 through 19.

[Product photograph]
High load capacity cylindrical roller bearings for wind turbines

[Advantages]

• Without changing the envelope dimensions,
  1.5 times the rating life of conventional bearings is achieved.
  ⇒ Contributes to longer machinery service life and allows for more compact designs.
• Attains allowable speeds equivalent to those for bearings with cages.
  [with oil lubrication]
  ⇒ Can also be used in high-speed position.
• The inner ring and outer ring sub-assemblies can be separated.
  ⇒ Easy installation of bearing assembly.

[How it works]

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