Automotive News
16/11/2010
Extremely Long Life Pinion Shaft Developed for Use in Automatic Transmissions
Longer service life for more compact, lighter weight transmissions
NSK has developed a new Ultra Long Life Pinion Shaft (made from the original NSK material SHX3) for use in the planetary mechanisms of automatic transmissions (ATs). The new pinion shaft features a significantly longer service life than existing products. The increase in service life enables reductions of 20% in both size and weight when operating under the same conditions. The product is also suitable for more demanding operating environments. The new pinion shaft enables greater efficiency in transmission mechanisms used in ATs, hybrid electrical vehicles (HEVs) and continuously variable transmissions (CVTs). NSK is targeting sales of ¥2 billion by 2015.
Information on product development
In recent years, there has been continuous demand for more compact and lightweight bearings used in transmissions as a way to improve fuel efficiency. There has also been demand for the use of low viscosity AT fluids with lower agitation resistance, which lead to lower friction loss. Another challenge is meeting the requirements of demanding transmission operating conditions. This includes the very sparse bearing lubrication that occurs when the oil pump shuts down during travel in the electric motor only mode in HEVs. Other demands include the need for a wider gear range as a way to reduce gear shifting shock, as well as the need for improved efficiency of power transmission in ATs, which require AT bearings capable of operating at higher RPMs.
The new Extremely Long Life Pinion Shaft was developed by applying a special heat treatment to the original NSK material SHX3. The process enables improved durability and fatigue strength, while reducing heat deformation curvature. The result is a 2.5 times longer service life than that of existing pinion shafts.
Product features
1. Decrease of 20% in size and weight compared with existing products
Significantly extended service life enables size and weight reductions of 20% compared with existing products.
2. Well-suited for more demanding operating environments
The new pinion shaft can be used in operating conditions far more demanding than that of conventional products.
- Operating with sparse lubrication: capable of operating at a minimum lubrication of 50 cc/min.
(compared with a conventional minimum of 100 cc/min.)
- Improved durability: capable of operating at a maximum temperature of up to 150°C
(compared with a conventional maximum of up to 120°C).
- Operation at high speeds: adoption of the cage and roller design increases maximum RPM capability to 3 times
that of a full-complement roller bearing (12,000 rpm→38,000 rpm).
Product benefits
In addition to its more compact, lightweight design, the new pinion shaft works with lower viscosity AT fluids that offer lower agitation resistance. The ability to operate under sparse lubrication conditions allows the use of smaller oil pumps and improved fuel efficiency. The new pinion shaft also supports the higher RPMs required for wider gear range ATs, HEVs and CVTs.