In the motor shaft system, the axial load is usually supported by the bearing at the locating end. If a deep groove ball bearing is used as the locating end bearing, the entire shaft system will not be able to withstand a large axial load due to its limited axial load carrying capacity. To solve this problem, an angular contact ball bearing can be used as the locating end bearing.
Features of angular contact ball bearings:
Single-row angular contact ball bearings can usually only bear axial loads in one direction. Therefore, in motors, paired angular contact ball bearings are usually used, arranged face to face or back to back at the locating end.
Configuration of face-to-face paired angular contact ball bearings
The figure below shows a common shaft system configuration, in which face-to-face paired angular contact ball bearings are used as locating end bearings at the right shaft extension end, and deep groove ball bearings are used as non-locating end bearings at the left non-shaft extension end.
In this configuration:
The face-to-face angular contact ball bearings at the locating end are responsible for bearing the axial and radial loads of the shaft system.
The deep groove ball bearings at the non-locating end mainly bear the radial load of the shaft system.
If the radial load of the shaft system is large, the deep groove ball bearing may not be able to meet the load requirements. In this case, the deep groove ball bearing can be replaced with a cylindrical roller bearing, as shown in the figure below:
In this configuration, both ends of the inner and outer rings of the paired angular contact ball bearings, which serve as the locating ends, need to be axially locked. It should be noted that the two angular contact ball bearings must be paired, and two arbitrary single-row angular contact ball bearings cannot be randomly selected for combination. This is because the paired angular contact ball bearings use the end face dimensions to adjust the internal preload after clamping, and these dimensions are specially processed and treated. Bearing suppliers usually provide universal paired angular contact ball bearings or paired angular contact ball bearings. Universal paired angular contact ball bearings can achieve the use of any two angular contact ball bearings in pairs, while paired angular contact ball bearings are usually provided in pairs, and the paired surfaces have special markings. When installing, it should be noted that the paired angular contact ball bearings cannot be disassembled, and the mating surfaces must be installed according to the marked surfaces, otherwise it will affect the service life of the bearings.
Choice of pairing
Paired angular contact ball bearings are available in two configurations: face-to-face and back-to-back. The two configurations are similar in load capacity, but the face-to-face paired bearing set has better anti-overturning moment capacity and support rigidity. In situations where higher flexibility is required, a back-to-back angular contact ball bearing set can be selected.
Configuration of floating end bearings
In the case of angular contact ball bearings as locating end bearings, the arrangement of non-locating end bearings needs to ensure that the axial expansion and contraction of the shaft system in the hot state can be absorbed by the free axial movement of the floating end. For example, deep groove ball bearings need to be released on both sides of the bearing outer ring, and a loose fit is used between the outer ring and the bearing chamber. In order to reduce the noise of the bearing, springs can be used to apply preload to the deep groove ball bearings.
For cylindrical roller bearings as the floating end, since the inner part can achieve good axial movement, there is no need to release the outer ring of the bearing. In this case, the outer ring of the bearing needs to be tightened on both sides of the axial direction, and the fit between the outer ring of the bearing and the bearing chamber does not need to consider the need for axial movement. You can choose a general fit or a tight fit according to actual needs.
Special application
For motor manufacturers, the configuration of paired angular contact ball bearings plus radial bearings is relatively easy to implement. However, in some special fields, the cross-positioning method of one angular contact ball bearing at each end can also be used to achieve the axial load of the shaft system. This structure is more complicated, and the installation dimensions of the cross-positioned angular contact ball bearings need to be checked and calculated, and corresponding debugging is performed during installation. Therefore, this structure is usually used in complex structures such as gearboxes, and motor shafts are rarely used.
Summary
Reasonable selection and configuration of angular contact ball bearings can significantly improve the performance and reliability of the motor shaft system. Through the correct pairing method and reasonable installation method, the stable operation of the motor can be ensured under various working conditions.
