Assembly of bearings, and fixing methods for inner and outer rings
The main function of bearings is to support the mechanical rotating body, ensure the working position and accuracy of the shaft and its transmission components, reduce friction and wear, and withstand loads. In daily applications, bearing assembly generally requires professional operation guidance or experienced bearing engineers. Below, we will introduce several common bearing assembly methods and techniques.
Common assembly methods for bearings
1. Knocking method: When the fit fit is small, a hammer can be used to knock and install the bearing; The method is to place a copper rod, soft iron, or sleeve on the inner or outer ring of the bearing, and use a hammer to strike the copper rod symmetrically and evenly into the bearing.
2. Top pressure method: When the fit interference is large, a press can be used to press in the bearing, and the sleeve must be placed when pressing in the bearing.
3. Temperature difference method: When the interference fit is large, the temperature difference method can be used for assembly, and hot assembly method is often used in maintenance. Heating methods include electric heaters and oil bath heating, and electric heating is widely used on site.
Common problems and key links in bearing assembly
1. Preparation before hot assembly
The fitting size, diameter, protrusion, root, and chamfer of the parts should be rechecked for accuracy, and the fitting surface should be cleaned. The flat key with key components should be repaired and fixed to the shaft in advance according to the keyway of the shaft and hole. For diagonal or tangential keys, guide keys should be used to ensure the mutual position of the keyways. Before hot installation, the retaining ring, gasket and other components should be repaired and tested for accuracy. After verification, they should be assembled.
Align before hot installation, mark with engraved lines and directional indicators. The assembly surface should be coated with lubricating oil to reduce friction resistance during loading. Before hot installation, make a measuring ruler to measure and confirm whether the heated workpiece has been heated to the assembly conditions. The measuring ruler should meet the conditions of being lightweight and not easily deformed, and be able to accurately measure the thermal expansion of the measured part away from the heat source.
Rulers can be made of metal rods or plates. The actual size should be equal to the nominal size of the measured part diameter plus the maximum interference at the fitting and the minimum clearance required for assembly.
After heating the parts, the measuring ruler can freely pass through. After confirming the accuracy of the measurement results through re examination, the heating can be stopped and the hot assembly operation can be carried out.
Methods for eliminating axial clearance in hot equipment
After hot installation, due to cooling shrinkage, axial clearance often occurs at the shoulder of the axial positioning table of the wheel and shaft. Its essence is inadequate assembly and unreliable positioning. Therefore, gaps should be eliminated during hot charging. There are generally impact method, bolt tightening method, and weight pressing method.
