Type construction and type selection
1) The machine has various working conditions. In order to meet these specific use requirements, different types of bearings are needed to ensure the actual needs. According to the shape of the rolling element, the rolling bearing can be roughly divided into a ball bearing and a roller bearing; according to the main direction of the load, it can be divided into a radial bearing and a thrust bearing. Table 1 compares the general characteristics of ball bearings and roller bearings. Table 1 Comparison of general characteristics of ball bearing and roller bearing According to the national standard GB/T272-93, the commonly used types of rolling bearings can be found in the database.
2) Selection of rolling bearing type There are many types of rolling bearing. When selecting, consider the following factors to select.
1. Size, direction and nature of the load: Ball bearings are suitable for withstanding light loads and roller bearings are suitable for heavy and impact loads. When the rolling bearing is subjected to pure axial load, thrust bearing is generally used; when the rolling bearing is subjected to pure radial load, deep groove ball bearing or short cylindrical roller bearing is generally used; when the rolling bearing is subjected to pure radial load, there is still little For axial load, deep groove ball bearings, angular contact ball bearings, tapered roller bearings and self-aligning balls or spherical roller bearings are available. When the axial load is large, angular contact with large contact angle can be selected. Ball bearings and tapered roller bearings, or the combination of radial and thrust bearings, are particularly suitable for very high axial loads or especially for large axial stiffness.
2. Allowable speed: There are large differences depending on the type of bearing. In general, bearings with low friction and low heat generation are suitable for high speeds. The design is designed to work with rolling bearings below their limit speed.
3. Rigidity: When the bearing is under load, the bearing ring and the rolling element will be elastically deformed at the contact point. The deformation amount is proportional to the load, and the ratio determines the rigidity of the bearing. Generally, the rigidity of the bearing can be improved by pre-tightening of the bearing; in addition, in the design of the bearing support, the bearing rigidity can be improved by considering the combination and arrangement of the bearings.
4. Self-aligning performance and installation error: After the bearing is loaded into the working position, the installation and positioning are often poor due to manufacturing errors. At this time, the bearing is often subjected to excessive load due to deflection and thermal expansion of the shaft, causing early damage. Self-aligning bearings can overcome the defects caused by installation errors and are suitable for such applications.
5. Installation and disassembly: Tapered roller bearings, needle roller bearings and tapered roller bearings, etc., belong to the type of bearings that can be separated inside and outside the ring (so-called separate bearings), easy to install and disassemble.