2022 November the Four Week ITS Technical Knowledge: Factors and Countermeasures of High Noise in Ball Bearing Operation

0 Preface

There are two kinds of bearings for micro motors: rolling bearings and sliding bearings. Rolling bearings are widely used because of their high reliability, large bearing capacity, simple maintenance, close fit between bearings and shafts, and are not easy to cause friction between stator and rotor. At present, most of the household appliances industry, such as air conditioning motors, use ball bearings in rolling shafts (hereinafter referred to as bearings).

 

1669013668671683.png 

 

1 Main factors and countermeasures for bearing noise of micro motor

1.1 Assembly control

The accuracy, life and performance of bearings are affected by the correct installation of bearings. Therefore, the installation of bearings should be carried out in strict accordance with the operating standards. There are several common problems.

 

1) Improper bearing pressing

At present, the pressing method of press is widely used. Improper pressing method will cause indentation and damage on the bearing raceway. The inner ring of the bearing shall be padded with a cushion block, and the inner ring shall be pressed quietly with a press until it is in close contact with the bearing retainer ring. If the cushion block is pressed into the outer ring pad, it will cause indentation and damage on the raceway. It is absolutely prohibited.

 

2) Bearing is dirty

The bearing and operator's gloves are not clean, which will bring bad effects to the bearing. Keep the area around the bearing clean to prevent dust from invading the bearing. It is best to unpack the bearing just before installation.

 

3) Rusty bearing

When operating the bearing with bare hands, sweat on the hands will corrode the bearing and cause rust on the bearing. Operators shall wear gloves to avoid direct contact with bearings.

 

4) The bearing bears strong collision

In the process of use, the bearing will bear strong impact, which will produce scars and indentations, which will become the cause of accidents. In serious cases, it will crack and fracture. Workers shall avoid strong crack collision during operation.

 

5) Retaining ring rough contact bearing

Generally, the bearing is positioned with an open retainer ring, and the smooth surface of the retainer ring is required to contact the bearing. If the rough surface contacts the bearing, the inner and outer rings of the bearing will tilt and the noise will become greater. During operation, workers shall distinguish the smooth surface from the rough surface, and contact the smooth surface with the bearing.

 

6) Improper operation

When installing the motor, if the rotor is stacked, the journal will be bent, so that the center line of the bearing does not coincide with the axis line after assembly. In this way, every rotation of the motor, the bearing will be subject to an alternating axial force, which will make the bearing vibrate and produce abnormal noise, and the noise is large. Workers shall not stack rotors during the operation.

 

7) Operation inspection

After the installation of the motor, in order to check whether the installation is correct, it is necessary to carry out a running inspection, which can be manually rotated to confirm whether the rotation is smooth, and check whether there is poor running due to foreign matters, bearing scars, inter axle indentation, uneven rotating torque due to poor installation, poor processing of the end cover bearing chamber, and excessive torque due to too small bearing clearance, installation error, and seal friction. If there is no abnormality, the operation test can be started. This can reduce some quality accidents caused by motor burning due to installation problems, and can also reduce the repeated testing of the rear station and improve efficiency.

 

1.2 Quality of parts

1) Shaft

① The accuracy and roughness of the shaft do not meet the design requirements. In this case, the shaft can not play its performance under its influence. Precision and roughness shall be ensured during processing.

 

② If the precision of the installed shoulder of the stepped shaft is not good, the inner and outer rings of the bearing will tilt. In addition to the bearing load, the concentrated load at the end will reduce the fatigue life of the bearing, and more seriously, it will become the cause of cage damage and sintering. Ensure the accuracy of the shoulder during processing.

 

③ Generally, the motor rotates on the shaft, so small interference fit is generally adopted in the design of the shaft and bearing. If the maximum fit interference is too large, the mating surface will be significantly worn, which will damage the shaft and bearing, thus increasing the bearing noise. In addition, the noise loss powder will invade the bearing interior, which will cause bearing heating, vibration and adverse consequences. If the fit interference is too small, it will cause the shaft to vibrate in the bearing inner race and cause abnormal noise, and it should not be disassembled during maintenance. Generally, proper bearing and matching shall be selected according to the specific use requirements of the motor.

 

2) End cover bearing chamber

① The accuracy of the end cover shaft chamber is not good, and the shaft cannot play its due performance under its influence. The deformation of the end cover bearing chamber due to external load is not large, but it should be able to fully support the rigidity of the bearing. The higher the rigidity, the more favorable the bearing noise and load distribution. When the axial stiffness of the end cover is poor, the end cover often generates axial vibration and abnormal noise due to excitation. The effective way to reduce this noise is to increase the axial dynamic stiffness of the end cover.

 

② The height of the shoulder of the end cover bearing chamber shall be able to fully contact the side of the bearing race, and the chamfer radius at the root of the bearing chamber shall not exceed the chamfer radius of the bearing. Otherwise, it will tilt the inner and outer rings of the bearing, reduce the fatigue life of the bearing, and even become the cause of cage damage and sintering. This point is generally ignored in design and processing, which should be noted.

 

③ The fit between the bearing chamber and the outer diameter of the bearing is generally designed with small clearance. The fit clearance shall not be too large. If it is too large, the fit will be too loose. When the motor is running, the outer ring of the bearing will rotate in the bearing chamber of the end cover, causing the bearing sound of "empty". If the fit is too loose, "bore cleaning" will occur, and the motor will be burned. The fit clearance shall not be too small. If it is too small, the outer ring of the bearing will shrink inward, reducing the clearance between the bearing steel ball and the outer ring, causing the bearing to become noisy or hot, and it is not convenient to load and unload the end cover during assembly and maintenance. The proper bearing and fit shall be selected according to the specific situation.

 

3) Overall coordination

The misalignment of the centerline of the motor end cover bearing chamber and the end cover inner diameter, the imbalance of the rotor, the eccentricity of the stator excircle and the end cover inner diameter, and the large runout of the rotor excircle will all cause uneven air gap, cause unilateral magnetic tension, and also cause greater bearing noise. The quality of the parts shall be controlled. In addition, it is also important to select bearings correctly. If the selected bearing grade cannot meet the requirements, the bearing noise of the motor will also be affected. The appropriate bearing accuracy grade, bearing clearance, material of bearing cage and bearing lubrication method shall be selected according to the service conditions, service performance, bearing assembly method, bearing load, bearing rotation speed, environmental conditions during operation, etc. Meanwhile, the market and economy shall be considered to select the appropriate bearing.

 

More about ITS Spherical Roller Bearing:

spherical roller bearing is a bearing with drum shaped rollers assembled between the inner ring with two raceways and the outer ring with spherical raceways. spherical roller bearing has two rows of rollers, which mainly bear radial load and axial load in either direction. It has high radial load capacity, especially suitable for working under heavy load or vibration load, but can not bear pure axial load. The outer race of this kind of bearing is spherical, so its centering performance is good and can compensate the coaxiality error.

 

ITS is a company mainly engaged in high quality ball and roller bearings. Welcome all of you to contact us to know more!

 

 Spherical Roller Bearing

 

ITS main products are roller bearingsmounted unitslinear bearingsstamping bearingsplastic roller bearings and automotive hub units, which are widely used in automotive aftermarketmining & constructionagriculturemachine toolhousehold equipment, etc. ITS bearings enjoy good reputation for their steady and reliable performance through these complicated and tough application fields.

 

ITS Customer Service team has the expertise in bearing manufacturing and is available round the clock. We promise that ITS only provides top quality products with the best price and the most professional service! We sincerely invite all of you to cooperate with us.

 


2022-11-21

Find Your Product

86-512-57698171

Contact Us
ITS Bearings

The ITS team has been engaged in Manufacturing bearings and international trade for more than 20 years. We always focus on the top quality bearing markets all over the world. The guaranteed production and highly active management has brought us competitive advantage in price and service.


Leave a Message