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The assembly of rolling bearing is an operation often done by fitters in assembly and repair, and the adjustment and pre tightening of rolling bearing clearance is an important link in the assembly of rolling bearing.
Accurately grasping the process concept of clearance adjustment and pre tightening and correctly using this process method in the assembly work is the guarantee of the quality of bearing assembly work.
The clearance of rolling bearing refers to the large amount of radial or axial movement of another ring when one ring is fixed, so the clearance is divided into radial clearance and axial clearance.
When assembling the rolling bearing, the clearance shall not be too large or too small. Too large clearance will reduce the number of rolling elements bearing load at the same time and increase the load of a single rolling element, so as to reduce the rotation accuracy of the bearing and reduce the service life;
If the clearance is too small, the friction will increase, the heat generated will increase, and the Clearance Of Rolling Bearing wear will be intensified, which can also reduce the service life of the bearing. Therefore, many bearings must strictly control and adjust the clearance during assembly.
When the bearing outer ring and the bearing inner ring are assembled, a preload is generated to eliminate the axial contact between the Clearance Of Rolling Bearing bearing outer ring and the bearing inner ring.
Preloading can improve the stiffness and rotation accuracy of the bearing in the working state. For bearings with large load and high rotation accuracy requirements, most of them work in the state of no clearance or even a small amount of interference. In this case, it is necessary to pre tighten the bearing during assembly.
Clearance adjustment and pre Clearance Of Rolling Bearing tightening are usually completed by making the inner ring of the bearing make an appropriate axial relative displacement to the outer ring.
it is not difficult to see that the bearing capacity and rotation accuracy of the bearing can be improved and the service life of the bearing can be improved by adjusting the clearance of the rolling bearing. But at the same time, it will aggravate the bearing friction and increase the calorific value.
Therefore, good lubrication and heat dissipation must be ensured while Clearance Of Rolling Bearing adjusting the clearance or preload. If the adjustment is improper or the lubrication is poor, the bearing wear will be intensified and the service life will be reduced.
Therefore, to correctly adjust and pre tighten the clearance of rolling bearing, we should also pay attention to the following problems.
1. Assembly technical requirements are the fundamental basis for selecting assembly process Clearance Of Rolling Bearing methods
Adjusting the clearance of rolling bearing can effectively improve the rotation accuracy of bearing, improve the bearing capacity of bearing, prolong the service life of bearing, and effectively reduce vibration and noise, but not all rolling bearings need to adjust the clearance during assembly.
Pre tightening can improve the rigidity and rotation accuracy of the bearing, but at the same time, it will aggravate the friction, destroy the Clearance Of Rolling Bearing lubricating oil film and produce a lot of heat. Therefore, the pre tightened bearing must be forced lubricated and cooled.
This process method is only used when the requirements for bearing rigidity and rotation accuracy are very high. It is a special process method, In practice, it is only used in the assembly of machine tool spindle, and the bearing assembly of other transmission mechanisms is almost invisible.
Whether to adjust and pre tighten the clearance in the assembly of rolling bearing shall be determined according to the assembly technical requirements proposed in the technical documents. Specifically, in the assembly technical requirements, generally,
for bearings with high speed, heavy load or high rotation accuracy, there will be requirements to adjust the bearing clearance or preload. On the contrary, the bearing clearance will be maintained and only axial fixation can be made during assembly. In terms of bearing types, the clearance of tapered roller bearing,
angular contact bearing and thrust bearing needs to be adjusted; For the radial ball bearing with low speed and light load, in most cases, the clearance does not need to be adjusted, but only fixed axially.
2. The requirements of clearance adjustment and pre tightening shall be met under the condition of heat balance
The actual ideal working clearance of rolling bearing is the clearance adjusted after the temperature rise of bearing is stable. Therefore, the adjustment of bearing clearance should be carried out in two stages:
first, adjust the bearing clearance at room temperature according to relevant operation specifications and technical requirements until the clearance is appropriate and rotate by hand, which should feel flexible;
Then, loosen the adjusting mechanism properly (to prevent the sudden locking of the bearing due to the increase of temperature during commissioning), and conduct the idling test. The idling time from low speed to high speed shall not exceed 2 hours, and the idling time at high speed shall not be less than 30 minutes.
The bearing shall operate flexibly, have low noise and the working temperature shall not exceed 50 ℃, and then reset and lock the adjusting mechanism.
3. Maintain good lubrication
Good lubrication can not only reduce friction, but also cool bearings and shaft parts. After the clearance of rolling bearing is adjusted, the friction will be intensified, and the heat generated will increase the temperature of the whole transmission system.
If the heat cannot be dissipated in time, these heat will change the size of transmission parts, thus affecting the change of rolling bearing clearance, generating more heat and forming a vicious circle. Therefore, for the rolling bearing with clearance adjustment, it is necessary to maintain good lubrication to reduce friction.
More importantly, the continuously circulating lubricating oil is used to take away a large amount of heat, control the rise of temperature and realize the heat balance of the transmission system.
Special attention should also be paid to: before the idling test, it is necessary to check whether the oil supply of all parts of the lubrication system is normal, especially the pre tightened bearing parts. It is more necessary to pay special attention to the sufficient supply of lubricating oil and good working condition.
In short, the correct assembly and rational use of the rolling bearing according to the process,
and the careful implementation of the adjustment and pre tightening process of the clearance of the rolling bearing are effective means to improve the rotation accuracy and bearing capacity of the bearing and reduce the vibration and noise of the transmission system.
In addition to meeting the general technical requirements of the rolling bearing assembly, the influence of the bearing temperature rise and lubrication on the adjustment work should also be considered,
In addition, after the idling test, careful inspection and secondary adjustment should be carried out. The patient and meticulous working attitude is also an indispensable good quality for assembly and maintenance fitters.