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Product/technological information
11. Friction Torque
Friction Torque(reference)
The friction torque of a rolling bearing changes according to the bearing load and lubrication conditions. Furthermore, when grease is used as the lubricant, grease resistance is added to the bearing’s friction torque. If the bearing’s load is normal (Cr/P＞12 and Fa/Fr＜0.2) and the bearing is well lubricated (oil lubrication), the bearing’s friction torque during operation can be obtained by the following equation:
M=μ×Pr×d/2
M=Friction torque(N・mm)
μ=Coefficient of friction
Pr=Radial load(N)
d=Bearing bore diameter(mm)
| Bearing Type | Coefficient of friction:μ |
|---|---|
| Deep groove ball bearing | 0.0013 |
| Angular contact ball bearing | 0.0015 |
| Thrust ball bearing | 0.0011 |
Temperature Increase
When the bearing is used, its temperature increases due to rotational friction and the grease’s agitation resistance. In general, the temperature increases rapidly at the beginning of operation, but the temperature eventually becomes steady due to factors such as the dissipation of heat from the shaft and the housing, and the cooling effect achieved by the lubrication. If the temperature increase continues for a long period of time, this will result in a shorter life owing to factors such as decreased bearing clearance, decreased rotational accuracy, and degraded lubricant.
Therefore, when such a state is detected, you must review and reconsider the selected bearing specifications, the setup and structure around the bearing, the lubricant and lubrication method, and other factors.