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How to choose the type of motor bearing

by:JNSN     2022-03-13
Bearing type selection The commonly used types of rolling bearings for motors are deep groove ball bearings, cylindrical roller bearings, spherical roller bearings, and angular contact ball bearings. The bearings at both ends of the small motor use deep groove ball bearings, the medium motor uses roller bearings at the load end (generally used in high-load conditions), and the non-load end uses ball bearings (but there are opposite cases, such as 1050kW motors). Small motors also use angular contact ball bearings. Spherical roller bearings are mainly used for large motors or vertical motors. Motor bearings require no abnormal sound, low vibration, low noise and low temperature rise. In accordance with the selection rules in the table below, the following factors are usually considered to analyze the project selection method. The installation space of the bearing can accommodate the bearing size in the bearing installation space. Since the rigidity and strength of the shaft are paid attention to when designing the shaft system, the shaft diameter is generally determined first. However, rolling bearings have a variety of size series and types, and the most suitable bearing dimensions should be selected from them. Load The magnitude, direction and nature of the bearing load [the load capacity of the bearing is represented by the basic load rating, and its value is contained in the bearing dimension table] The bearing load is full of changes, such as the size of the load, whether there is only radial load, and whether the axial load is single direction or two-way, degree of vibration or shock, etc. After considering these factors, choose the most suitable type of bearing structure. Generally speaking, the radial load of NSK bearings with the same inner diameter varies according to the series, and the rated load can be checked according to the sample. The bearing type whose speed can adapt to the mechanical speed [the limit value of the bearing speed is expressed by the limit speed, and its value is shown in the bearing dimension table] The limit speed of the bearing depends not only on the bearing type, but also on the bearing size, cage type, and accuracy grade. , load conditions and lubrication methods, etc., therefore, these factors must be considered when selecting. Bearings with the same structure with an inner diameter of 50~100mm have the highest limit speed; the rotation accuracy has the required rotation accuracy of the bearing type [the dimensional accuracy and rotation accuracy of the bearing have been standardized by GB according to the bearing type]. According to the ratio of the speed to the limit speed, the accuracy of the bearing is determined. The higher the accuracy, the higher the limit speed, and the smaller the heat generation. If it exceeds 70% of the limit speed of the bearing, the accuracy level of the bearing must be improved. Under the same radial original clearance, the smaller the heat generation, the relative inclination of the inner ring and the outer ring is analyzed. or installation error), and select a bearing type that can adapt to this use condition. If the relative inclination of the inner ring and the outer ring is too large, the bearing will be damaged due to the internal load. Therefore, a spherical roller bearing that can withstand this tilt should be selected. If the inclination is small, you can choose other types of bearing analysis item selection method. The bearing configuration shaft is supported by two bearings in the radial and axial directions. One side is the fixed side bearing, which bears both radial and axial loads. , plays the role of relative axial movement between the fixed shaft and the bearing housing. The other side is the free side, which only bears the radial load and can move relatively in the axial direction, so as to solve the problem of expansion and contraction of the shaft caused by temperature changes and the spacing error of the installed bearing. On shorter shafts, the fixed side is indistinguishable from the free side. The fixed end bearing is selected for the axial positioning and fixing of the bearing to bear the bidirectional axial load. During installation, the corresponding strength should also be considered according to the magnitude of the axial load. Generally, the ball bearing is selected as the fixed end and the free end bearing is selected to avoid factors. The expansion and contraction of the shaft caused by the temperature change during operation, and the axial position used to adjust the bearing should only bear radial load, and the outer ring and the outer casing generally adopt a clearance fit, so that the shaft can be used for axial avoidance together with the bearing during expansion and contraction. , and sometimes the mating surface of the shaft and the inner ring is used for axial avoidance. Generally, the cylindrical roller bearing is selected as the free end, regardless of the fixed end and the free end. When the bearing spacing is small and the influence of the shaft expansion and contraction is small, the axial clearance after installation is adjusted with a nut or washer. Generally, two Deep groove ball bearings or two spherical roller bearings Spherical roller bearings can be used as the support for the fixed end and the free end or regardless of the fixed end and the free end. Assembly and disassembly frequency and method of assembly and disassembly, such as regular inspection of installation and disassembly, use installation and disassembly tools when installing and disassembling. Speed u200bu200band load are two important factors. The structural form of the bearing is determined according to the comparison between the speed and the limit rotation, and the comparison between the load and the rated load, that is, the rated fatigue life. These two factors are highlighted below.
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