Unitized Thrust Needle Bearings for Eccentric Applications
(Service life 4 times longer in torque converter applications!)
NTN Bearing Corporation has developed a unitized type thrust needle bearing to meet demands for a long-life thrust needle bearing in eccentric, or off-centering, applications such as torque converters.
The centerlines of the engine and torque converter axis where the thrust bearings are used can be somewhat eccentric, or off-center. When the thrust bearing is exposed to this eccentricity, the bent lip sections of the bearing raceways make contact with the bearing cage causing heat, friction, and potentially catastrophic bearing damage. Consequently, the industry needs a thrust bearing for these applications that satisfies the following 2 points:
| (1) | The bearing must have a long service life and allow large eccentricities during operation (up to 0.5 mm). |
| (2) | The bearing must be one unitized, or integrated, raceway and cage assembly. |
Up to this point, conventional bearings have had either a separated structure (separable raceways with no lips) that allows large eccentricities, or a unitized (one-piece) structure that does not allow large eccentricities. Satisfying both of the above conditions was impossible until now.
Our newly developed product not only has a unitized structure but also features the following 3 points that help give it a service life 4 times longer than our conventional bearing while operating with eccentricities up to 0.5 mm:
| (1) | Radial internal clearance (gap between the bearing raceways and cage) set larger than eccentric amount. |
| (2) | A V-type hardened cage with shape, thickness, and hardness optimized by FEA analysis. |
| (3) | Large oil gates were incorporated to aid lubrication flow through the bearing in an effort to prevent damaging or scuffing on the raceway surfaces due to insufficient lubrication. |
We made our new needle bearing in one unitized piece (no separation of the cage and races) by using raceway structures with curved lip sections as well as staked sections. We designed it to have a minimum number of components to hold down the cost while allowing for the assembly into the customer application to be easier. Mass production and supply of this new bearing for use in torque converters has already begun.
This new bearing is also ideal for automatic transmission applications requiring a cage with higher strength and a bearing with extended service life.
[Features]
| (1) | Longer service life: 4 times that of conventional product (in-house test conditions with eccentric amount of 0.5 mm)
[Due to increased radial internal clearance, increased cage strength, and improved lube flow] |
| (2) | Unitized structure allows for easy assembly into customer application |
[How We Solved This Technical Challenge]
| (1) | Set radial internal clearance between the cage and races to at least 1 mm (0.5 mm eccentricity allowed during installation) |
| (2) | Designed a V-type hardened cage with shape, thickness, and hardness optimized by FEA analysis. |
| (3) | Established lubrication flow to interior of bearing (formed oil gates in outer ring lip section) |
| (4) | Integrated the outer ring and cage into one piece (O/R curved lip and I/R staked sections) |
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