Fixed end bearing of motor


Fixed end bearings use radial bearings that can withstand combined (radial and axial) loads. These bearings include: deep groove ball bearing, double row or matched single row angular contact ball bearing, self-adjusting ball bearing, spherical roller bearing, matched tapered roller bearing, NUP type cylindrical roller bearing or NJ type cylindrical roller bearing with HJ angle ring.


For the selection of the fixed end of motor bearing support (referred to as motor fixed end), the following factors shall be considered:


(1) The precision control requirements of the towed equipment;


(2) The load property of motor drive;


(3) Bearing or bearing combination must be able to bear certain axial force.


In the medium and small motors, deep groove ball bearings are more preferred as fixed end bearings of motor.


Deep groove ball bearing is the most common rolling bearing. When deep groove ball bearing is applied, the support system of motor bearing is very simple and convenient for maintenance. Deep groove ball bearing is mainly used to bear radial load, but when the radial clearance of the bearing is increased, it has the characteristics of angular contact ball bearing, and can bear the combined radial and axial loads; When the speed is high and thrust ball bearing is not suitable, it can also be used to bear pure axial load. Compared with other types of bearings with the same size and specification, the advantages of these bearings are small friction coefficient, high limit speed, and their disadvantages are not shock resistant and unsuitable for heavy load.


After the deep groove ball bearing is installed on the shaft, the radial fit of the shaft or shell can be limited within the axial clearance range of the bearing. In radial direction, the interference fit is adopted between the bearing and the shaft, and the small interference fit is adopted for the bearing and the bearing housing or the shell of the end cover. The final goal of this kind of matching is to ensure that the working clearance of the bearing is zero or slightly negative during the operation of the motor, so that the bearing has better performance. In axial direction, the axial fit between the positioning bearing and the associated parts shall be determined according to the specific conditions of the floating end bearing system. The bearing inner ring is limited by the bearing position limit step (shoulder) and bearing ring on the shaft. The outer ring of the bearing is controlled by the matching tolerance between the bearing and the bearing chamber, the height of the inner and outer cover of the bearing and the length of the bearing chamber.


Motor floating end bearing


The floating end of motor is also called free end, which is relative to the fixed end; Generally, the floating end is selected at the non drive end, but in the case of high motor load requirements and the axial matching dimension requirements with load equipment are not high, the floating end will be selected at the drive end.


When the bearing support system of motor is double support point and double bearing structure, the drive end is also used as floating end when the radial load is large. Especially for low-voltage and high-voltage motors, the cylindrical roller bearing at the floating end can meet the requirements of larger radial load.


The roller of cylindrical roller bearing is in line contact or repair line contact with the raceway, and the radial bearing capacity is large. It is suitable for bearing heavy load and impact load. The inner ring or outer ring can be separated for easy installation and disassembly. The friction coefficient of the series bearings is small, which is suitable for the operation condition of high speed and limit speed approaching deep groove ball bearing. The n-type and nu type cylindrical roller bearings are commonly used in the motor. The bearing inner and outer rings can move axially, and can adapt to the change of the relative position between the shaft and the shell caused by thermal expansion or installation error, and can be used as free end support. However, the bearing has high requirements for the processing of shaft or bearing chamber hole. The relative deviation of the inner and outer ring axis after bearing installation should be strictly controlled to avoid the contact stress concentration.


Compared with the fixed end bearing, in order to meet the axial displacement requirements of rotor part in the motor operation, according to the different bearing selection, the axial clearance requirements of outer ring and inner and outer cover of bearing are different.


(1) When the floating end adopts the bearings with internal and external rings that can be separated, the fixed end is selected at the non driving end for the two bearing structure motors; The outer ring of fixed end and floating end bearing and the inner and outer cover of bearing are matched with axial no gap.


(2) When the floating end adopts the non separable bearing, that is, the ball bearing structure is common at both ends of the small and medium-sized motor. Considering the influence on the installation accuracy of the driving equipment, the driving end is the fixed end, the inner ring of the floating end bearing should be limited, and there is axial clearance between the outer ring and the inner and outer cover of the bearing; At the same time, in order to ensure the axial fit displacement requirements of the motor, the radial fit between the outer ring and the bearing chamber is not easy to be too tight.


The actual bearing configuration should match the operation condition of the motor, including the specific parameters such as clearance, heat resistance performance and precision in the selection of motor bearings, and the radial matching relationship between the bearing and the bearing chamber.


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