NTN Develops Long-Service Life, High-Rigidity
"High Load Capacity Tapered Roller Bearings for Automotive Transmissions"
[Maximizing the number of rollers to attain longer service life and higher rigidity making smaller bearing sizes possible!]
NTN Bearing Corporation has developed "high load capacity tapered roller bearings" that provide longer service life and higher rigidity under severe application conditions. They are geared for use in automotive transmissions and differentials, whose usage conditions are becoming increasingly more severe.
In recent years, in order to increase fuel economy, automotive transmissions and differentials are becoming smaller, lighter and are requiring lower torque to rotate them through the use of lower viscosity lubricating oils. Therefore, the bearings used also need to become more compact and work with lower viscosity oils*. Consequently, it is necessary to raise the rigidity of these bearings and extend their service lives.
To solve these issues, the retainer position was moved further toward the outer race side of the bearing than that of a standard bearing of the same size. This made it possible to maximize the number of rollers (to about the same as a full roller type bearing) effectively increasing the basic dynamic load rating a maximum of 10% and the basic static load rating a maximum of 15%. Increasing the number of rollers also reduces the contact stress within the bearing under load and increases the rigidity of the bearing, while simultaneously extending the service life under severe lubrication conditions (lower viscosity oil).
Furthermore, applying NTN's unique FA heat treatment, which is a technology for longer service life, to these bearings makes it possible to reduce the size of the bearings and greatly reduce their rotational torque while maintaining the same long service life and high rigidity. NTN is marketing these newly developed bearings as products that contribute to greater automobile fuel economy.
| [*Smaller size and lower viscosity oil: | Generally, if the size of a bearing is reduced, shorter service life and lower system rigidity will result. If lower viscosity oil is used, an adequate oil film is not formed on the contact surface and the service life is further shortened.] |
[Features]
| (1) | Longer service life |
(Due to 10% maximum increase in dynamic load rating, 15% maximum increase in static load rating)
- Calculated service life improvement of up to 40%
- 12 times the service life (compared to standard product) in clean oil lubrication under poor oil film conditions [λ = 0.2]
- 2.2 times the service life (compared to standard product) under contaminated lubrication conditions
|
| (2) | Higher rigidity |
- Bearing rigidity improved up to 10% (compared to standard product)
|
| (3) | Compact size and lower torque (through application of FA treatment under same service life and rigidity) |
(Case example)
- Outside diameter and assembly width dimensions is reduced by 15% and
rotational torque is reduced by 30% (compared to standard product)
|
[Applications]
Automotive transmissions and differentials
[Photograph of product]
|
[Left: Standard product Right: High load capacity tapered roller bearing] |
|
|
