The assembly of rolling bearings is a common operation in the assembly and repair work of the fitter, and the adjustment and preloading of the rolling bearing clearance is an important part of the rolling bearing assembly work. Accurately grasping the process concept of clearance adjustment and pre-tightening, and correctly applying this process in assembly work is the guarantee of the quality of bearing assembly work.
The clearance of the rolling bearing refers to the maximum amount of movement of the other ferrule in the radial or axial direction when one ferrule is fixed, so the clearance is divided into radial clearance and axial clearance.
When the rolling bearing is assembled, its play should not be too large or too small. If the clearance is too large, the number of rolling bodies that can bear the load at the same time is reduced, so that the load of the single rolling body is increased, thereby reducing the rotation precision of the bearing and reducing the service life; if the clearance is too small, the frictional force is increased, resulting in an increase The increased heat, which exacerbates wear and tear, also reduces the service life of the bearing. Therefore, many bearings must be tightly controlled and adjusted during assembly.
The pre-tightening is that when the bearing is assembled, an axial force is applied to the inner ring or the outer ring of the bearing to eliminate the bearing play and cause initial deformation of the rolling element in contact with the inner and outer rings. Preloading can improve the stiffness and rotation accuracy of the bearing under working conditions. For bearings with large load and high rotational accuracy, most of them work without clearance or even a small amount of interference. In this case, the bearings need to be pre-tensioned during assembly.
The adjustment and preloading of the clearance are usually carried out by means of a suitable axial relative displacement of the inner ring of the bearing to the outer ring.
It is not difficult to see from the above concept of the technology that the adjustment of the rolling bearing clearance can improve the bearing capacity and rotation accuracy of the bearing and improve the service life of the bearing. At the same time, the bearing friction will be intensified and the heat generation will increase. Therefore, it is necessary to ensure good lubrication and heat dissipation while adjusting the clearance or pre-tightening. If improperly adjusted or poorly lubricated, it will in turn increase bearing wear and reduce life. Therefore, the following problems must be noted in the correct adjustment and preloading of the rolling bearing clearance.
1. Assembly technical requirements are the fundamental basis for selecting assembly process methods
The adjustment of the rolling bearing clearance can effectively improve the bearing rotation precision, improve the bearing capacity of the bearing, prolong the service life of the bearing, and also effectively reduce the vibration and noise, but not all rolling bearings need to be installed during assembly. Adjustment. The pre-fastening can improve the bearing rigidity and the precision of the rotation, but at the same time, the friction is intensified, the lubricating oil film is destroyed and a large amount of heat is generated. Therefore, the pre-tightened bearing must be forcedly lubricated and cooled. This method is limited to It is a special process for the bearing rigidity and rotation precision requirements. It is only used in the machine tool spindle assembly. The bearing assembly of other transmission mechanisms is almost invisible.
Whether to adjust and pre-tighten the clearance in the rolling bearing assembly is determined according to the assembly technical requirements of the technical documents. Specifically, in the assembly technical requirements, the bearings with high requirements for high speed, heavy load or rotation accuracy are generally required to adjust the bearing clearance or preloading. Otherwise, the bearing clearance is maintained, and only the shaft is used for assembly. Just fix it. From the perspective of the type of bearing, the clearance of the tapered roller bearing, the angular contact bearing and the thrust bearing needs to be adjusted; for the general low-speed, light-load radial ball bearing, in most cases, the clearance is not required. Adjusted and only fixed axially.
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