Technical requirements for the assembly of rolling bearings for Hengli motors

1. Technical requirements for assembly of rolling bearings

(1) The end faces with marked codes on rolling bearings should be installed in a visible direction for easy reference during replacement.

(2) After the bearing is installed on the shaft or in the bearing chamber, it is not allowed to have any tilting phenomenon.

(3) One of the two coaxial bearings of the Hengli motor must have room for axial movement when the shaft expands due to heat.

(4) When assembling bearings, pressure (or impact force) should be directly applied to the end face of the mating ring, and pressure transmission through rolling elements is not allowed.

(5) During the assembly process, cleanliness should be maintained to prevent foreign objects from entering the bearing.

(6) The assembled bearings should operate flexibly, have low noise, and operate at a temperature not exceeding 50 degrees Celsius

2. Assembly of rolling bearings

The assembly method of rolling bearings should be selected based on the size and interference fit of the bearing. The general assembly methods for rolling bearings include hammering, pressing with a screw or lever press, and hot installation. Under no circumstances should the bearing ring, cage, rolling element, or seal be directly struck.

The commonly used assembly methods for deep groove ball bearings are hammering and pressing. Small and medium-sized motors generally use the pressing method, where bearings are directly pressed into the shaft neck and bearing chamber using a bearing press fitting machine; The hammering method requires a copper rod to be padded with a special sleeve during hammering, and the bearing inner ring should be installed on the shaft neck with a hammer or the bearing outer ring should be installed into the end cover bearing chamber with the hammering method. If the journal size is large and the interference fit is also large, for the convenience of assembly, the hot fitting method can be used, which is to heat the bearing and then match it with the shaft at room temperature.

3. The main factors causing vibration and noise due to improper assembly of bearings and motors

(1) The size of the radial clearance of the bearing. Hengli motor bearings have a primitive radial clearance during manufacturing, which is determined by the manufacturer. After the bearing is installed in the motor, there is a certain fit tolerance between the inner and outer rings of the bearing and the bearing housing, which causes radial deformation of the bearing and reduces the clearance. Therefore, there is another working clearance during operation. Experimental studies have shown that when the working clearance is around 10um, it is the optimal value for noise. Excessive vibration will increase, while insufficient noise will increase. The difference between the working clearance and the original clearance is mainly related to the type of fit between the inner ring of the bearing and the bearing gear, as well as the machining accuracy of the bearing gear.

(2) The stiffness of the end cap and machine base. The stator, rotor, and end cover of the motor form a vibration system. Bearings and end covers with poor axial rigidity will be "tuned" to the vibration system of the motor, causing large amplitude axial vibrations that generate resonance noise to be transmitted to the end cover and the entire motor through the bearings. At the same time, the electromagnetic noise of the motor will also be transmitted to the end cover and the entire motor through the bearings.

(3) Axial movement. Due to the electromagnetic force between the stator and rotor, there are more axial electromagnetic force components and accumulated errors in processing and assembly of axial dimensions when inclined, resulting in some axial displacement during motor operation. If improper measures are taken, low-frequency "buzzing" sounds will occur, which are sometimes loud and sometimes small. Adding spring elements (such as waveform spring plates) in the axial direction can reduce buzzing noise and stabilize the sound level. It can also significantly reduce vibration. However, it should be pointed out that the expected effect can only be achieved when the bearings are qualified, other assembly conditions are correct, and the elastic components are stable.

(4) Bearing assembly. The assembly quality of Hengli motor bearings has a significant impact on motor noise, with a difference of 5-10dB When assembling, it is necessary to choose lubricating grease of appropriate specifications; Pay attention to the purity during assembly, and do not mix in impurities such as iron powder, fine sand, dust, etc; The filling amount of lubricating grease should be appropriate; When placing the bearing into the bearing chamber, push it by hand and avoid hammering. In addition, the accuracy and installation of each stop to ensure the coaxiality of the motor must also be correct, otherwise rotor misalignment will also affect the working clearance of the bearings.