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Selection method of motor bearing type

by:JNSN     2021-12-26
The bearing type is the deep groove ball bearing, cylindrical roller bearing, spherical roller bearing, angular contact ball bearing. Small motors use deep groove ball bearings at both ends of the bearings, medium-sized motors use roller bearings on the load end (usually used for high load conditions), and ball bearings on the non-load end (but the opposite is also true, 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 noise, low vibration, low noise, and low temperature rise. In accordance with the selection rules in the following table, the following factors are usually considered to analyze the project selection method. The bearing installation space can accommodate the bearing size in the bearing installation space. Because the rigidity and strength of the shaft are emphasized when designing the shaft system, the shaft diameter is generally determined first. However, rolling bearings have a variety of size series and types, from which the most appropriate bearing dimensions should be selected. Load The size, direction and nature of the bearing load [The load capacity of the bearing is expressed by the basic load rating, and its value is shown in the bearing size table] The bearing load is rich in changes, such as the size of the load, whether there is only radial load, and axial load. Or is it two-way, the degree of vibration or shock, etc. After considering these factors, choose the most suitable type of bearing structure. Generally speaking, the radial load of the bearing 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 indicated by the limit speed, and the value is shown in the bearing size table] The limit speed of the bearing is not only dependent on the bearing type, but also limited by the bearing size, cage type, and accuracy class , Load conditions and lubrication methods, etc. Therefore, these factors must be considered when selecting. Bearings with the same structure have the highest limiting speed with an inner diameter of 50~100mm; the type of bearing with the required rotation accuracy of rotation accuracy [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, the lower the heat generation, which exceeds 70% of the limit speed of the bearing. The accuracy level of the bearing must be improved. The higher the dimensional accuracy, the less the original clearance will be affected after the shaft is matched. Under the same radial original clearance, the smaller the heating, the relative tilt analysis of the inner ring and the outer ring causes the relative tilt of the inner ring and the outer ring of the bearing (such as the deflection of the shaft caused by the load, the poor accuracy of the shaft and the housing) Or installation error), and choose a bearing type that can adapt to this use condition. If the relative tilt between the inner ring and the outer ring is too large, the bearing will be damaged due to internal load. Therefore, a spherical roller bearing that can withstand this inclination should be selected. If the tilt is small, you can choose other types of bearing analysis project 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 box. The other side is the free side, which only bears radial load, and can move relative to the axial direction, so as to solve the problem of shaft expansion and contraction caused by temperature changes and the interval error of installing bearings. On shorter shafts, there is no difference between the fixed side and the free side. The fixed-end bearing is used for the axial positioning and fixing of the bearing to bear the bidirectional axial load. When installing, the corresponding strength needs to be considered according to the size of the axial load. Generally, the ball bearing is selected as the fixed end and the free-end bearing is used for avoidance. The expansion and contraction of the shaft caused by temperature changes during operation and the adjustment of the axial position of the bearing should be selected to only bear radial load and generally use a clearance fit between the outer ring and the housing, so that the shaft can be expanded and contracted together with the bearing for axial avoidance , Sometimes the mating surface of the shaft and the inner ring is also used for axial avoidance. Cylindrical roller bearings are generally selected as the free end regardless of the fixed end and the free end. When the bearing spacing is small and the effect of shaft expansion and contraction is not large, the axial clearance after installation is adjusted with a nut or a washer. Generally, two are selected. Deep groove ball bearings or two spherical roller bearings spherical roller bearings can be used as a support when the fixed end and the free end or the fixed end and the free end are not divided. The frequency and method of assembly and disassembly, such as regular inspections of installation and disassembly, require the use of installation and disassembly tools. Speed u200bu200band load are two important factors. The structure of the bearing is determined based on the comparison between the speed and the limit revolution, and the comparison between the load and the rated load, that is, the rated fatigue life. The following focuses on these two factors.
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