Various types of bearings have different characteristics due to their different designs. Due to the variability and complexity of the spe...
"Various types of bearings have different characteristics due to their different designs. Due to the variability and complexity of the specific installation position and application situation of the bearings, there is no fixed mode for the selection of bearing types. In order to adapt to the specific installation position and application conditions of a certain host machine, it is recommended to consider the following main factors comprehensively."
Allow space
In mechanical design, the size of the shaft is generally determined first, and then the bearing is selected according to the size of the shaft. Generally, small shaft adopts ball bearing; Cylindrical roller bearing, self-aligning roller bearing and tapered roller bearing (sometimes ball bearing can also be selected) are selected for the large shaft. If the radial space of the bearing installation position is limited, the bearing with smaller radial section height shall be used. Such as needle roller bearings, some series of deep groove ball bearings, angular contact ball bearings, cylindrical roller or self-aligning roller bearings and thin-walled bearings. If the axial space of the bearing installation position is limited, the bearing with smaller width can be used.
load
The size of the load is usually the decisive factor in selecting the bearing size. Roller bearing has greater bearing capacity than ball bearing with the same overall dimension. Generally, ball bearings are suitable for light or medium loads, and roller bearings are suitable for bearing heavy loads.
In terms of load mode, deep groove ball bearing and cylindrical roller bearing can be selected for pure radial load; Thrust ball bearing and thrust cylindrical roller bearing can be selected for pure axial load; When there is radial load and axial load (combined load), angular contact ball bearing or tapered roller bearing is generally selected. If the radial load is large and the axial load is small, the deep groove ball bearing and the cylindrical roller bearing with ribs on the inner and outer rings can be selected. As there are also large shaft or shell deformation and poor installation alignment, self-aligning ball bearing and self-aligning roller bearing can be selected. If the axial load is large and the radial load is small, thrust angular contact ball bearing and four-point contact ball bearing can be selected; If self-aligning performance is also required, thrust self-aligning roller bearing can be selected.
speed
The working speed of rolling bearing mainly depends on its allowable operating temperature. Bearings with low friction resistance and less internal heat are suitable for high-speed operation. When only bearing radial load, deep groove ball bearing and cylindrical roller bearing can reach higher speed. If bearing combined load, angular contact ball bearing should be selected. The specially designed high-precision angular contact ball bearing can achieve extremely high speed. The speed of various thrust bearings is lower than that of radial bearings.
Rotation accuracy
For most machines, the bearing with a tolerance of level 0 is sufficient to meet the requirements of the host machine, but when there are strict requirements for the rotation accuracy of the shaft, such as the machine tool spindle, precision machinery and instruments, the deep groove ball bearing, angular contact ball bearing, tapered roller bearing, cylindrical roller bearing and thrust angular contact ball bearing with a higher tolerance level should be selected.
rigidity
The rigidity of rolling bearing is determined by its elastic deformation when bearing the load. Generally, this deformation is small and can be ignored. However, in some machines, such as machine tool spindle system, the static stiffness and dynamic stiffness of bearing have a great impact on the characteristics of the system. Generally speaking, roller bearings have higher stiffness than ball bearings. The rigidity of various bearings can also be improved to varying degrees by proper "preloading".
Vibration and noise
The noise and vibration of the bearing itself are generally very low. However, low-noise bearings are usually used for small and medium-sized motors, office machinery, household appliances and instruments that have special requirements for noise and running stability.
Axial displacement
The most common configuration of bearings is to install a set of axially positioned "fixed bearings" at one end of the shaft, and a set of axially movable "floating bearings" at the other end to prevent jamming due to thermal expansion and contraction of the shaft. The commonly used "floating bearing" is a cylindrical roller bearing with an inner ring or an outer ring without a rib. At this time, the fit between the inner ring and the shaft or the fit between the outer ring and the housing hole can adopt an interference fit. Sometimes the non-separable deep groove ball bearing or self-aligning roller bearing can also be selected as the floating bearing, but the clearance fit between the inner ring and the shaft or the outer ring and the shell hole should be selected during installation to ensure that the inner ring or outer ring has enough freedom of axial movement.
friction torque
The friction resistance of ball bearing is smaller than that of roller bearing, and the friction resistance of radial contact bearing is smaller under pure radial load; Under pure axial load, the friction resistance of axial contact bearing is small; Under the combined load, the angular contact bearing with the bearing contact angle close to the load angle has the smallest friction resistance. Ball bearing or cylindrical roller bearing is more suitable for instruments and machinery requiring low friction torque. In addition, contact sealing should be avoided for low friction moment bearings. At the same time, it is recommended to use oil drop lubrication, oil gas lubrication or other lubrication methods that are conducive to reducing wear.
Installation and removal
The bearings with cylindrical inner holes are used in the machinery with frequent installation and disassembly. The separated angular contact ball bearings, tapered roller bearings, separable cylindrical roller bearings, needle roller bearings and thrust bearings should be preferred. The bearing with conical inner hole can be installed on the journal, or on the cylindrical journal with the help of the locking sleeve or the withdrawal sleeve, which is more convenient for installation and disassembly.
