Choosing the bearing clearance, should consider the following aspects: 1.
Bearing working conditions, such as load, temperature, speed, etc. ;
2.
On the properties of bearing use requirements (
Rotating accuracy, friction torque, vibration and noise)
;
3.
Bearing and shaft and the shell hole for fit to the bearing clearance decreased;
4.
Bearing is working, the difference in temperature between inside and outside ring lead to bearing clearance decreased;
5.
Because the coefficient of expansion of shaft and the shell material is different, lead to bearing clearance decrease or increase.
According to the experience of the use, the ball bearing is the most suitable work clearance is zero;
Roller bearings with a small amount of work clearance shall be maintained.
In required supporting rigid good parts, FAG bearings allow prestressing force has a certain value.
Here in particular, the so-called work clearance, is refers to the bearing in the actual operation conditions of clearance.
There is a clearance is called the original clearance, is refers to the clearance of the bearing before installation.
The original clearance than installation clearance.
Our choice of clearance, the main work is to choose the appropriate clearance.
The clearance value of national standard is divided into three groups: a basic group (
0 group)
, small clearance assisted group (
Group 1, 2)
And the big clearance aided group (
Group 3, 4, 5)
。
When the choice, under normal working conditions, appropriate priority choose basic group, then can make the bearing work properly for clearance.
When basic group cannot satisfy the use requirement, should choose auxiliary clearance.
Big clearance auxiliary group applies to bearing and shaft and the shell hole USES the interference fit, the bearing inner and outer circle temperature difference is bigger, deep groove ball bearings under high axial load or need improve heart function, heart and NSK bearings for higher limit speed and reduce the friction torque, etc;
Small clearance auxiliary set higher requirements applicable to the rotation of the precision, to strictly control the shell hole axial displacement, and the need to reduce vibration and noise.
1 bearing fixed after determine the type and model of the bearing, must also be correct for the combination of the rolling bearing structure design, to guarantee the normal work of the TIMKEN bearings.
The combination of the bearing structure design including: 1)
Shaft bearing structure side;
2)
Bearings and related parts;
3)
Bearing lubrication and sealing;
4)
Improve the stiffness of the bearing system.
1.
Both ends fixed (
Unidirectional fixed at both ends)
Short axis of normal operating temperature (
Span L<
400mm）
, on both ends of the one-way fulcrum often USES fixed way, each bearing a under the direction of the axial force.
As shown in figure, to allow the shaft work there is a small amount of thermal expansion, bearing installation, axial clearance shall be maintained zero.
25mm-
0.
4毫米(
Don't have to draw the clearance is small, chart)
, the interval used pads or adjusting screw to adjust.
Features: limit shaft two-way movement.
Working is suitable for the temperature change is the axis.
Note: consider thermal elongation, leave compensation gap between bearing cover and the outer end face c, c = 0.
2 to 0.
3mm。
Bidirectional fixed at one end, side swimming when the shaft is longer or work at high temperature, thermal expansion of the axis shrinkage is larger, should adopt the fulcrum of bidirectional fixed at one end, the end winding structure, as shown in figure.
Fixed comprised of a single two-way under axial force bearing or bearing group, while swimming end guarantee axis telescopic can swim free.
To avoid loose, winding bearing inner ring and shaft axial fixation (
The elastic ring) is often used to
。
Swimming protection for cylindrical roller bearings, KOYO bearing outer ring with axial fixed frame, by swimming between roller and ring to ensure that the free expansion of shaft.
Characteristics: a fulcrum bidirectional fixed and the other a fulcrum for the axial winding.
Swim deep groove ball bearing as a fulcrum, bearing outer ring and the end cover for clearance.
Cylindrical roller bearing swimming as a fulcrum, bi-directional bearing outer ring should be fixed.
Applicable: the long axis with higher temperature.
