2010

Rotational Torque of Thrust Needle Roller Bearings Reduced by 50%March 31, 2010

The reduction of internal energy loss in engines and transmissions is necessary to reduce CO2 emissions, and for improved fuel economy. NTN Corporation (hereafter NTN) has developed a ‘Low torque thrust needle roller bearing’ with rotational torque reduced by 50% for transmissions of gasoline or hybrid cars.

This development focused on two factors that generate rotational torque in a thrust needle roller bearing. The first factor is friction loss generated by the sliding of the rollers on the raceway surface caused by the difference of roller's running distances at the inner and outer circumferences of the bearing. Using full crowned rollers attained reduction of friction loss on the raceways for this condition. Full crowned rollers shorten the contact length of the rollers in the axial direction and reduce the contact distances at the inner and outer circumferences of the bearing. The second factor is friction loss caused by contact of the cage that guides the rollers. Focusing on the outside ends of the rollers that contact the cage, friction loss was minimized by making the roller end surface into a circular arc shape and smoothing the contact surface of the cage with improved processing accuracy. As a result, the rollers contact the cage at the center of roller end surfaces where the circumferential speed of rollers is slow.

This new product is effective to reduce bearing temperature rise during operation because of reduced friction from the losses mentioned above.

NTN will continue to develop products that are more efficient, in order to construct an eco-friendly automotive society.

Features

Bearing rotational torque:…Reduced by 50% [Compared with NTN's conventional product]
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Use of full crowned roller
Roller end face: Circular arc shape
Cage O.D. pocket surface: Smoothed shape