The bearing in the bearing exhibition is a component used to support the shaft, guide the rotational movement of the shaft, and bear the load transmitted from the shaft to the frame. Bearing is a widely used and strict supporting and basic part in the mechanical industry. It is not only the supporting element of the rotating shaft or movable part of all kinds of machinery, but also the supporting element to rotate the main engine by relying on the rolling of the rolling body. It is called mechanical joint. Bearing is an important and indispensable basic component in contemporary machinery. Although its rise has only a history of more than 100 years, due to its relationship with the national economy and the people's livelihood, countries all over the world spare no effort to develop their own bearing industry. With superb modern science and technology, more than 100000 kinds of bearing production varieties have been produced, with excellent quality and excellent performance, which has made outstanding contributions to the development of the world machinery industry and other industries and the progress of human society.
1, These factors must be considered in the selection of most mechanical bearings
"Various types of bearings have different characteristics due to different designs. Due to the variability and complexity of the specific installation position and application occasions of the bearing, there is no fixed mode to follow in the selection of bearing type. In order to adapt to the specific installation position and application conditions of a certain host machine, it is recommended to comprehensively consider the following main factors."
Allowable 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, the 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 main shaft. If the radial space of the bearing installation position is limited, the bearing with small 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-wall bearings. If the axial space of the bearing installation part is limited, the bearing with smaller width can be used.
Bearing load
Load size load size is usually the decisive factor in the selection of bearing size. The bearing capacity of roller bearings is larger than that of ball bearings with the same overall dimensions. Generally, ball bearings are suitable for light or medium loads, and roller bearings are suitable for heavy loads.
Load mode pure radial load can choose deep groove ball bearing and cylindrical roller bearing. Thrust ball bearing and thrust cylindrical roller bearing can be selected for pure axial load. When there are 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, deep groove ball bearings and cylindrical roller bearings with retaining edges on the inner and outer rings can be selected. In case of large deformation of shaft or shell 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, the thrust angular contact ball bearing can be selected. If the four point contact ball bearing also requires centering performance, the thrust self-aligning roller bearing can be selected.
speed
The working speed of rolling bearing mainly depends on its allowable operating temperature. The bearing with low friction resistance and less internal heating is suitable for high-speed operation. When bearing only radial load, deep groove ball bearing and cylindrical roller bearing can achieve high 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 bearings with Class 0 tolerance are sufficient to meet the requirements of the main engine, but when there are strict requirements on the rotation accuracy of the shaft, such as machine tool spindle, precision machinery and instruments, deep groove ball bearings, angular contact ball bearings, tapered roller bearings, cylindrical roller bearings and thrust angular contact ball bearings with higher tolerance levels shall be selected.
rigidity
The rigidity of rolling bearing is determined by its elastic deformation when bearing load. Generally, this deformation is very 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 through appropriate "pre tightening".
Noise and vibration
The noise and vibration of the bearing itself are generally very low. However, for small and medium-sized motors, office machinery, household appliances, instruments and other machinery with special requirements for noise and running stability, low-noise bearings are usually selected.
Axial movement
The most common configuration of the bearing is to install a set of axially positioned "fixed bearing" at one end of the shaft and a set of axially movable "floating bearing" at the other end to prevent jamming due to thermal expansion and cold contraction of the shaft. The frequently used "traveling bearing" is a cylindrical roller bearing without retaining edge on the inner ring or outer ring. 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 interference fit. Sometimes, the non separable deep groove ball bearing or self-aligning roller bearing can also be selected as the traveling bearing, but during installation, the clearance fit shall be selected for the fit between the inner ring and the shaft or the outer ring and the shell hole, so as to ensure that the inner ring or outer ring has enough freedom of axial movement.
The friction resistance of ball bearing is smaller than that of roller bearing. When pure radial load is applied, the friction resistance of radial contact bearing is smaller; Under pure axial load, the friction resistance of axial contact bearing is small; Under combined load, the friction resistance of angular contact bearing with similar bearing contact angle and load angle is the smallest. Ball bearing or cylindrical roller bearing is more suitable for instruments and machines requiring low friction torque. In addition, contact sealing should be avoided for low friction torque bearings. At the same time, it is recommended to use drip lubrication, oil-gas lubrication or other lubrication methods conducive to wear reduction.
Bearings with cylindrical inner holes are used in machines with frequent installation and disassembly. Separate 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 tightening sleeve or retracting sleeve, which is very convenient for installation and disassembly.
