Issues to Be Considered in Rolling Bearing Combination Design

Except for the rod end joint bearing and spherical plain bearings, there is rolling bearing. In order for the bearing to run well in the equipment, it is necessary to choose the appropriate bearing type and size, and at the same time, the bearing should be designed correctly to achieve a good fit between the bearing and its surrounding parts. In addition, it is necessary to reasonably fix the axial position of the bearing, ensure coordination between the bearing and other parts, adjust the gap, and solve many problems such as lubrication, assembly and disassembly.

 

 

Fixing of Rolling Bearings

After selecting the type and model of the bearing, the combined structure design of the rolling bearing must be correctly carried out to ensure the normal operation of the bearing. The design of the combined structure of the bearing includes four aspects, the structure of the bearing end of the shafting, the coordination of the bearing and related parts, the lubrication and sealing of the bearing and the improvement of the rigidity of the bearing system.

 

1. Both Ends Fixed in One Direction

For short shafts at ordinary operating temperatures, the fulcrum is often fixed in one direction at each end, and each bearing bears an axial force in one direction. In order to allow a small amount of thermal expansion when the shaft is working, there should be an axial gap of 0.25mm-0.4mm when the bearing is installed. The gap is very small. It is not necessary to draw it on the structural drawing. The amount of gap is usually adjusted by spacers or adjusting screws. The characteristic of this fixing method is to limit the two-way movement of the shaft, which is suitable for the shaft with little change in working temperature. However, it is necessary to pay attention to the thermal elongation, leaving a compensation gap between the bearing cover and the outer end surface, which is 0.2 to 0.3mm.

 

2. One End Is Fixed in Both Directions and One End Is Moving

When the shaft is long or the working temperature is high, the thermal expansion and contraction of the shaft is large, and a fulcrum structure with one end fixed in two directions and one end moving should be adopted. The fixed end is subjected to a two-way axial force by a single bearing or bearing group, while the moving end ensures that the shaft can freely move when it is telescopic. In order to avoid loosening, the inner ring of the floating bearing should be fixed axially with the shaft, and an elastic retaining ring is often used. When a cylindrical roller bearing is used as a fulcrum, the outer ring of the bearing should be axially fixed with the machine base, and the free movement of the shaft can be ensured by the movement between the roller and the ring. The characteristic of this fixing method is that one fulcrum is fixed in both directions, and the other fulcrum is used for axial movement. If the deep groove ball bearing is used as the fulcrum, the outer ring of the bearing and the end cover will have clearance, and if the cylindrical roller bearing is used as the fulcrum, the outer ring of the bearing should be fixed in both directions. This fixing method is suitable for long axis with large temperature change.

 

 

Adjustment of Bearing Combination

There are three steps to adjust the bearing combination.

 

1. Adjustment of Bearing Clearance

There are two steps to adjust it. The first step is to adjust the gasket thickness of the bearing cover and the machine base, and the second step is to adjust the movement of the bearing outer ring gland with screws.

 

2. Bearing Preload

The purpose of bearing preload is to improve accuracy, stiffness and reduce vibration. According to the preload force requirements of the bearing during installation, a certain axial force is maintained in the bearing to ensure a certain clearance,

 

3. Adjustment of Bearing Assembly Position

The purpose of this step is to make the parts on the shaft including gears and pulleys have accurate working positions.

 

 

The Coordination of Rolling Bearings

The base hole is used for the cooperation between the bearing inner ring hole and the shaft. The outer shaft of the bearing and the hole of the bearing seat adopt the base shaft system.

 

 

Assembly and Disassembly of Rolling Bearings

The usual design life of rolling bearings is inconsistent with the whole machine, and it needs to be replaced multiple times during use. When the parts with the bearing are damaged, the bearings need to be disassembled. When disassembling the bearings, the disassembly force should not be transmitted through the rolling elements to prevent plastic deformation of the rolling elements.

 

Special tools are usually used for disassembling rolling bearings. The design of the shafting structure should allow enough space for the use of the tools. These data can be found in the rolling bearing manual.

 

 

Hopefully, this passage can help you learn more about rolling bearings.