1.Allowable deviation of inner and outer rings of deep groove ball bearings
Rolling bearings have extremely high machining accuracy, and in order to maintain this accuracy, it is necessary to ensure the machining and installation accuracy of the installed shaft and bearing seat. However, in practical use, the machining accuracy of the components around the bearing is limited, and when the shaft bends under external loads, the inner and outer rings of the bearing will tilt. The allowable deviation is generally between 0.0006~0.003 rad (2 '~10), but it depends on the size of the deep groove ball bearing, the internal clearance during operation, and the load.
2. The influence curve of the inclination of the inner and outer rings of deep groove ball bearings on the bearing life
This section will introduce the relationship between inner/outer ring deviation and fatigue life. We have selected four different sizes of bearings from the 62 series ball bearings and the 63 series deep groove ball bearings as examples.
Let the non tilted fatigue life be L θ=0, and the tilted fatigue life also be L θ. Calculate the effect of tilt on fatigue life using L θ=0/L0.
To represent general operating conditions, the radial load Fr (N) and axial load Fa (N ") are set to approximately 10% (standard load) and 1% (light preload) of the rated dynamic load Cr (N) of the bearing, respectively, and used as load conditions for calculation. Using standard radial clearance, the shaft fit is set to i5. In addition, the factor of reduced internal clearance caused by inner ring expansion is also considered.
In addition, assuming a temperature difference of 5 ℃ between the inner and outer rings during operation, calculate L0=0/L0 for the maximum, minimum, and average effective clearances.
When the tilt range is between 0.0006-0.003 rad (2-10 '), the fatigue life is reduced by 5% -10% or less, so the effect is not significant.
However, when the tilt exceeds a certain limit, the fatigue life will rapidly decrease. Therefore, attention should be paid to this aspect.
When the clearance is small, slight tilting has almost no effect and will not have a significant impact. But as the tilt increases, the fatigue life will significantly decrease. As mentioned earlier, it is necessary to minimize installation errors when using bearings.
3.Calculation Example
Deep groove ball bearing 6202, bearing torque load, calculate its tilt angle and contact angle. Assuming the radial clearance is such that the original contact angle is 0 ° and all other conditions are 0,
Ball diameter D: 6.35mm
Number of balls Z: 7
Steel ball joint diameter Dmw: 46mm
The ratio of channel radius to ball diameter: inner circle fi=0.515, outer circle fe=0.52
Torque load M: 15Nm (15000N * mm)
3.1. The tilt angle caused by a 15000N.mm torque is 0.004584rad
3.2. The tilt angle caused by a 2900N.mm torque is 0.003009rad
