Angular contact ball bearings are more complex than deep groove ball bearings, mostly in pairs, and require preloading. Installed well, can make the host work accuracy, bearing life greatly
improved; otherwise, not only the accuracy of less than the
requirements, life will be affected.
Installation form
Angular contact ball bearings in the form of installation, back to back, face to face and arranged in three series. The
contact angle of the bearing is diffused along the axis of rotation to
increase its radial and axial support angle rigidity and resistance to
deformation. The face-to-face (the narrow end face of the two bearings
is opposite) When installed, the contact angle of the bearing converges towards the axis of rotation, and its bearing angle is less rigid. As
the inner ring of the bearing extends out of the outer ring, when the
outer ring of the two bearings is pressed together, the original gap of
the outer ring is eliminated to increase the preload of the bearing; the
series arrangement (the wide end face of the two bearings is in one
direction) , Bearing contact angle parallel and parallel, can make the two bearings to share the same direction of the work load. However, in this form of installation, in order to ensure the axial
stability of the installation, two pairs of rows of bearings must be
installed at both ends of the shaft.
Acquisition of preload
The
preload can be done by grinding the end face of a collar in the bearing
or by using two different thickness spacers between the inner and outer
rings of the pair of bearings to clamp the bearings together so that
the ball and race Close contact and get.
The
size of the preload has a great impact on the bearing life. According
to the information, when the bearing is equipped with 0.012mm
interference, the service life is reduced by 38% and the service life is
reduced by 50% when 0.016mm Bearing
assembly with 0.004mm gap, the service life decreased significantly,
with 0.008mm gap, the service life decreased by 70%. Therefore, it is important to make a reasonable choice of the size of the preload. General high speed should choose a small preload, low speed should use large preload. At the same time, the preload should be slightly greater than or equal to the axial working load.
Preload calculation
When the preload is selected, the minimum preload is calculated as follows:
Aomin = 1.58tgaR ± 0.5A (N)
The radial load acting on the bearing (N)
Axial load acting on the bearing (N)
The angle between the straight line passing through the ball and the
raceway contact point and the straight line passing through the center
plane of each ball (ie, the nominal contact angle):
7000C a = 15 °
7000AC a = 25 °
7000B a = 40 °
Each bearing in the pair of bearings is calculated according to this type. Where
"+" for the axial working load to reduce the original pre-profit value
of that one bearing; "for the axial working load so that the original
increase in the value of the former bearing a bearing. The minimum preload of the bearing is the maximum of the two values
obtained by the two bearings (according to the assembly experience,
typically about 50N preload).
Adjustment of preload
Air run test. Angular
contact ball bearings after passing the assembly inspection, to work
speed for the air running test, the time not less than 2h, the
temperature should not exceed 15 ℃.
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