The frictional moment of rolling bearings can be easily compared with that of plain bearings. The frictional moment of rolling bearings can be obtained from their bore diameter, using the following equation :
The friction coefficient is greatly dependent on bearing type, bearing load, rotation speed and lubrication, etc.
Reference values for the friction coefficient during stable operation under normal operating conditions are listed in Table 8-1.
For plain bearings, the value is normally 0.01 to 0.02 ; but, for certain cases, it is 0.1 to 0.2.
Table 8-1 Friction coefficient μ
|Bearing type||Friction coefficientμ|
|Deep groove ball bearing||0.0010～0.0015|
|Angular contact ball bearing||0.0012～0.0020|
|Self-aligning ball bearing||0.0008～0.0012|
|Cylindrical roller bearing||0.0008～0.0012|
|Full complement type needle roller bearing||0.0025～0.0035|
|Needle roller and cage assembly||0.0020～0.0030|
|Tapered roller bearing||0.0017～0.0025|
|Spherical roller bearing||0.0020～0.0025|
|Thrust ball bearing||0.0010～0.0015|
|Spherical thrust roller bearing||0.0020～0.0025|