The rotor part of the motor product usually needs to be supported by two sets of bearings, and the rotor is radially and axially positioned relative to the stator. According to different usage requirements, such as load, required rotation accuracy, and manufacturing cost requirements, the motor bearing configuration generally adopts: one end fixed and one end floating configuration; two ends fixed pre-adjustment configuration; two ends floating "floating" configuration, etc.
0 1One end fixed, one end floating configuration The fixed end bearing is fixed by the shaft and the end cover bearing chamber at the same time, providing radial support at one end of the shaft and playing an axial positioning role in both axial directions. The fixed end bearing must be a radial bearing that can withstand combined radial and axial loads. Deep groove ball bearings are the most commonly used in motor products. In some other equipment and machinery, double-row or paired single-row angular contact ball bearings and other bearings that can withstand combined loads are also used.For motors with three bearing structures, the bearing combination is used for positioning, that is, a radial bearing (cylindrical roller bearing with no flange on the ring) that can only bear pure radial load is combined with a deep groove ball bearing that can bear combined load. In this configuration, the other bearing, the deep groove ball bearing, is only used for axial positioning in two directions, and a certain radial degree of freedom must be left in the bearing chamber, that is, a clearance fit with the diameter direction of the bearing chamber.
The floating bearing of the motor is at the other end of the shaft and only provides radial support. Therefore, the floating bearing can be a deep groove ball bearing or a cylindrical bearing. For motors with large loads and impact loads, cylindrical roller bearings are used in most cases. In this configuration, a certain axial displacement of the shaft must be allowed so that there is no mutual force between the bearings. During the operation of the motor, when the shaft expands due to heat, axial displacement can be achieved inside certain types of bearings (cylindrical roller bearings). Axial displacement can also occur between one of the bearing rings and the parts connected to it, preferably between the outer ring of the bearing and the bearing chamber. In view of this, the choice of N-type or NU-type bearings requires designers to conduct comparative analysis and demonstration.There are many different combinations of bearing configurations for the fixed and floating ends. The following are some of the more commonly used combinations. For rigid bearing configurations, a combination that allows axial displacement to be achieved within the bearing should be used, such as: deep groove ball bearings and cylindrical roller bearings; double row angular contact ball bearings and cylindrical roller bearings; paired single row tapered roller bearings and cylindrical roller bearings. Of course, there are other combinations. For this aspect of the design, it is recommended to conduct joint analysis and selection with the bearing manufacturer.
In the above combination, the angular error between the shaft and the bearing seat must be minimized. If the application does not allow, it is recommended to use a combination of self-aligning bearings that can withstand larger angular errors. These configurations can withstand certain angular errors and axial displacements and can avoid generating internal axial forces in the shaft system.For the bearing configuration where the inner ring bears the rotating load, the change in shaft length needs to be adjusted between the bearing and its mating surface, and the axial displacement should be between the outer ring and the bearing chamber. The most commonly used combination is deep groove ball bearings and deep groove ball bearings; paired single row angular contact ball bearings and deep groove ball bearings, etc. 0 2Floating bearing arrangement The floating bearing arrangement is also a cross-positioning method and is suitable for applications where only moderate axial positioning is required or where there are other parts on the shaft for axial positioning. In this arrangement, the most important thing is that each bearing can be axially displaced. This can be between one of the bearing rings and its mating surface, but preferably between the outer ring of the bearing and the bearing chamber.
0 3Pre-adjusted bearing arrangements In a pre-adjusted bearing arrangement, the shaft is axially located in one direction by one bearing and fixed in the other direction by another bearing. This arrangement is called "cross" positioning and is usually used for short shaft lengths. All radial bearings that can withstand axial loads (in one or two directions) are suitable for this arrangement. In some cases, single-row angular contact ball bearings or tapered roller bearings are used in a cross-positioned arrangement, but some preload may be required.
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