Development of next-generation ultra-low friction torque tapered roller bearings
JTEKT developed a next-generation product that boasts world’s number one low friction torque performance among the tapered roller bearings that are used for support of differential pinions and such components or inside the automotive transmissions. We are going to proceed with the proposal of this product as a product that contributes to the low fuel consumption and high efficiency of automobiles toward especially automotive manufacturers around the world.
1.Product Overview
• Compared with our standard low friction torque tapered roller bearing LFT-II which has the same size, this bearing is able to reduce a maximum of 50% or more losses.
• Compared with our LFT-III which has the world’s number one low friction torque (volume production product), this bearing is able to reduce approximately 30% losses.
• Through the employment to pinion support of differential unit contributes to the improvement of vehicle fuel efficiency by 2.5%.
2.Detailed description
Tapered roller bearings (hereinafter TRB) are employed on lubrication of automotive driveline components such as transmissions and differentials. However, since the rollers of TRB have a pumping function due to its inclination, there was an issue that the agitation loss of lubricants applied to sections (such as differential drive pinion shaft support) with high lubrication viscosity, high lubrication amount, or high rotation becomes large.
JTEKT put a special focus on the reduction of the agitation loss of the lubricant and in 2006, developed and commercialized the “Ultra-low torque TRB (LFT-III)” which suppresses the lubricant amount that flows into the bearings and achieves torque reduction largely. LFT-III has been largely contributing to the automobile fuel efficiency.
To meet the demands for further automobile low fuel consumption, we pursued a thorough reduction of the agitation loss and have developed “next-generation ultra-low friction TRB (LFT-IV)” this time.
The developed product employs a resin cage that has high design flexibility. Through the oil flow analysis using CAE to aim for the optimization of the cage shape, we have succeeded in reducing more amount of oil that flows into the bearings.
As a result, LFT-IV reduces a maximum of 50% or more loss than our equivalent size bearing, the standard low friction torque TRB (LFT-II). The adoption of a resin cage made it possible to obtain results such as the reduction of the sliding resistance between the cage and rollers, weight reduction of the cage, and improvement of anti-seizure performance (the generation of non-lubricated seizure is three times longer than the conventional ones), and also responding to the low viscosity and oil amount reduction of the lubricant of the future drive units to contribute to the improvement of fuel efficiency as a whole.
3.Product photo
4.Information relating to production
| 1.Start of production | Year 2018 |
|---|---|
| 2.Sales target | 600,000 set/year (based on plan for 2020) |
| 3.Production plant | Kagawa Plant and Kokubu Plant |
| 4.Others | Supporting various vehicle types from Japanese Kei-car (small vehicle) to pick-up trucks.
Price and capital investment are under examination now. |
5.Reference: Advance in the generations of LFT series
| Torque reduction (vs. standard) |
|||
| Equivalent size | Include effects from size reduction |
||
| LFT-I | Optimization of inner ring rib/roller contact area shape and roughness | -10% | -10% |
| LFT-II | Special crowing of inner/outer ring raceways | -20% | -20% |
| LFT-III | Optimization of inner specifications, flow rate control of lubricant (Longer life -> smaller size through special heat treatment) |
-50% | (-80%) |
| LFT-IV | Optimization of cage shape and material, further oil flow rate control | -65% | (-86%) |
* LFT is the abbreviation for Low Friction Torque, and is a registered trademark of JTEKT Corporation.