Preload of high-precision cross roller bearing means that after the bearing is loaded into the bearing seat and shaft, certain measures are taken to make the rolling body and inner and outer ring of the bearing produce a certain amount of pre-deformation, so as to keep the inner and outer ring in a state of compression.
YOGIE specializes in the production of cross roller bearing manufacturers for the majority of customers professional analysis of the cross roller bearing pre-tightening mode and role.
The purpose of cross roller bearing pretightening is to increase the rigidity of the bearing;
Reduce vibration and noise;
To prevent the sliding of the rolling body relative to the inner and outer ring raceway caused by the inertia moment.
Bearing configurations shall have positive or negative working clearances depending on application.
In most cases, the working clearance is positive, that is, when the bearing is in operation, there is a certain residual clearance, although it may be very small clearance.
On the other hand, there are many applications where a negative working clearance, or negative preload, is required to improve the rigidity or rotational accuracy of the bearing configuration.
For example, spindle bearing of machine tool, YRT rotary table bearing of CNC machine tool, thin wall cross roller bearing of robot arm, pinion bearing of automobile transmission shaft, small motor bearing, or bearing configuration for reciprocating movement, etc.
In some applications, if the imported bearings are not or only bear a small load and operate at a high speed, they should be preloaded on the bearing configuration, for example, by springs.
In this case, the preload is intended to provide a minimum load to the bearing to prevent damage to the imported bearing due to the sliding of the rolling body.
Precompact form
Preload may be radial or axial depending on the bearing type.
For example, cylindrical roller bearings can only be preloaded in the radial direction due to their design, while thrust ball bearings and thrust cylindrical roller bearings can only be preloaded in the axial direction.
Single-row angular contact ball bearings and tapered roller bearings are generally subjected to axial pretightening and are usually paired with another imported bearing of the same type in a back-to-back or face-to-face manner.
Deep groove ball bearings are usually preloaded in the same axial direction. For the purpose of pretightening, radial internal clearances with larger than ordinary groups should be used so that they can have a contact Angle greater than zero as angular contact ball bearings.
Preload is generally adjusted during installation at ambient temperature (or set according to this temperature). If the temperature rise of the shaft is greater than that of the bearing seat during operation, the preload will increase.
And the face to face configuration increases the preload more than the back to back configuration.
When the shaft is expanded by heat, the shaft diameter increases (radial expansion) and also expands (axial expansion).
Under the influence of radial expansion, the clearance of the bearing configuration will decrease, that is, the pre-tightening will increase.
For face-to-face bearing configurations, under the influence of axial expansion, the preload will be further increased, but the preload of back-to-back bearing configurations will be reduced accordingly.
In the back-to-back bearing configuration, if there is a given distance between the bearings and the bearing and related parts have the same thermal expansion coefficient, the influences of radial expansion and axial expansion on the preload will offset each other, so the preload will not change.
