Frictional Torque & Temperature

FRICTIONAL TORQUE

Frictional torque of rolling bearings varies under changing load and lubrication conditions. When grease is used as a lubricant, the grease resistance must be added to the bearing frictional torque.

When adequate lubrication under normal loading conditions(Cr/P>12,Fa/Fr<0.2), the frictional torque of a bearing can be expressed as follows:

M= Fd/2
M:FRICTIONAL TORQUE(N.mm)
F:BEARING LOAD (N)
d:SHAFT DIAMETER(mm)
:=0.0015 COEFFICIENT OF FRICTION


TEMPERATURE INCREASE

Friction and grease resistance can increase the bearing temperature. In the initial stages of operation, the internal bearing temperature rises rapidly: as the heat dissipates to the shaft and housing and the cooling effect of the lubricant begins to take effect, the temperature stabilizes. Constant high temperatures lead to a reduction in bearing clearance, a deterioration of the running accuracy and of the lubricant and thereby a reduction in bearing life. It is important to consider the effect of temperature increases when selecting the bearing.