Slewing bearings are mainly used in lifting, construction machinery and other large-scale engineering machinery and equipment. They mainly bear axial force and overturning moment. However, in many cases, overturning moment is the main load of the bearing. Under the action of the overturning moment, the angular deformation of the bearing will greatly affect the stiffness and working accuracy of the entire machine. Therefore, it is necessary to analyze the relationship between the moment load bearing and the deformation of the turntable bearing.
The role and requirement of bearing clearance is to ensure that the bearing can run flexibly and without hindrance, but it is also required to ensure that the bearing runs smoothly. According to the state of the bearing, the clearance can be divided into three general existence states: original clearance, installation clearance and working clearance.
The size of the clearance (called the working clearance) during operation has an impact on the performance of the slewing bearing and slewing ring, as well as the precise rolling fatigue life, temperature rise, noise, and vibration. When selecting the bearing clearance, it is generally appropriate to make the working clearance zero or slightly positive. Because it is actually installed in the machine, the slewing bearing has to bear a certain load to rotate, and there is also the amount of elastic deformation caused by the matching of the bearing and the load. And, considering the factors of thermal expansion (load), enough clearance is reserved, and proper installation clearance will help the normal operation of the rolling bearing. If the clearance is too small, the temperature of the rolling bearing will increase, and it will not work normally, and the rolling elements will be stuck; if the clearance is too large, the equipment will vibrate and the rolling bearing will be noisy.
The choice of working clearance is determined by the application conditions (load, speed, design parameters) and expected working conditions (lifetime, rigidity, low heat generation, ease of maintenance, etc.). However, in most applications, we cannot directly adjust the working clearance, which requires us to calculate the corresponding clearance value after installation based on the analysis and experience of the application.
1, the selection principle of bearing clearance
①With tighter fit, the temperature difference between the inner and outer rings is large, the friction torque needs to be reduced, and the deep groove ball bearing bears a larger axial direction
For load or occasions where the self-aligning performance needs to be improved, a large clearance group should be used.
②When the rotation accuracy is high or the axial displacement needs to be strictly limited, a small clearance group should be used.
2. Factors related to clearance: the fit of the inner ring of the bearing and the shaft; the fit of the outer ring of the bearing and the housing hole; the influence of temperature.
3. How to adjust the axial clearance
①Use the nut installed on the bearing housing to push the gland pressed on the outer ring of the bearing for adjustment.
②Adjust the thickness of the gasket between the bearing cap and the base to adjust.