Rolling noise analysis of NTN bearings

     The rolling sound is due to the rolling of the rolling elements in the raceway when the NTN bearing rotates to excite a smooth and continuous noise, which only attracts attention when its sound pressure level or tone is extremely large. In fact, the sound energy excited by the raceway sound is limited. For example, under normal conditions, the quality of the 6203NTN bearing raceway is 25~27dB. This type of noise is the most typical of single row deep groove ball NTN bearings that can withstand radial loads. It has the following characteristics:
a. Noise and vibration are random;
b. The vibration frequency is above 1 kHz;
c. Regardless of the change in the rotational speed, the main frequency of the noise is almost constant and the sound pressure level increases as the rotational speed increases;
d. When the radial clearance increases, the sound pressure level increases sharply;
e. NTN bearing housing rigidity increases, the lower the total sound pressure level, even if the speed increases, its total sound pressure level does not increase much;
f. The higher the viscosity of the lubricant, the lower the sound pressure level, but for grease lubrication, the viscosity and shape of the soap fiber can affect the noise value.
The source of the rolling sound is caused by the natural vibration of the ferrule after the load. Due to the elastic contact of the ferrule and the rolling body, a nonlinear vibration system is formed. When the lubrication or machining accuracy is not high, the natural vibration associated with this elastic characteristic is excited, and when it is transmitted to the air, it becomes noise. It is well known that even with the most advanced manufacturing techniques used to process NTN bearing parts, there are always small geometric errors in the working surface, which causes small fluctuations between the raceway and the rolling elements to excite the natural vibration of the vibration system.
Although the rolling noise of the NTN bearing is unavoidable, the working surface of the part can be processed with high precision, the NTN bearing is correctly selected and the NTN bearing is accurately used to reduce noise and vibration.

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How INA oil film bearings work

     INA oil film bearing is a radial sliding bearing with lubricating oil as the lubricating medium. Its working principle is: during the rolling process, due to the rolling force, the roller journal is forced to move, INA oil film bearing center and shaft The center of the neck is eccentric, so that the gap between the INA oil film bearing and the journal forms two regions, one is called the divergent zone (the gap gradually increases along the direction of the journal rotation), and the other is called the convergence zone (the direction of rotation along the journal) slowing shrieking). When the rotating journal brings the viscosity of the lubricating oil from the dispersing zone into the convergent zone, the bearing clearance changes from large to small along the direction of the journal rotation, forming an oil wedge to generate pressure in the lubricating oil. The combined force of the pressure at each point in the oil film along the rolling direction is the bearing capacity of the INA oil film bearing. When the rolling force is greater than the bearing capacity, the eccentricity between the center of the journal and the center of the INA oil film bearing increases. In the asymmetry zone, the bearing clearance becomes steeper along the direction of rotation of the journal, the minimum oil film thickness becomes smaller, the pressure inside the oil film becomes larger, the bearing capacity becomes larger, and the bearing center is not balanced, the center of the journal is no longer offset, and the INA oil film The bearing and the journal are completely separated by the lubricating oil, which theoretically forms a full fluid lubrication.
    From the working principle of INA oil film bearings, one of the most important parameters in the INA oil film bearing system is the minimum oil film thickness. If the minimum oil film thickness value is too small, and the metal impurity particles in the lubricating oil are too large, and the outer size of the metal particles is numerically larger than the minimum oil film thickness, the metal particles accompany the lubricating oil through the minimum oil film thickness as if causing metal contact. When it is serious, it will burn tiles. In addition, if the minimum oil film thickness value is too small, when there is an accident such as steel pile, it is easy to cause metal contact between the journal and the INA oil film bearing to cause burnt tile. The minimum oil film thickness value is related to the structural size and material of the INA oil film bearing, the machining accuracy of the related parts, the mounting accuracy of the INA oil film bearing system, the size of the lubricating oil and the rolling force. How INA oil film bearings work

[Chinese bearing net] 4/6/2011 Author: China Bearing Network
     INA oil film bearing is a radial sliding bearing with lubricating oil as the lubricating medium. Its working principle is: during the rolling process, due to the rolling force, the roller journal is forced to move, INA oil film bearing center and shaft The center of the neck is eccentric, so that the gap between the INA oil film bearing and the journal forms two regions, one is called the divergent zone (the gap gradually increases along the direction of the journal rotation), and the other is called the convergence zone (the direction of rotation along the journal) slowing shrieking). When the rotating journal brings the viscosity of the lubricating oil from the dispersing zone into the convergent zone, the bearing clearance changes from large to small along the direction of the journal rotation, forming an oil wedge to generate pressure in the lubricating oil. The combined force of the pressure at each point in the oil film along the rolling direction is the bearing capacity of the INA oil film bearing. When the rolling force is greater than the bearing capacity, the eccentricity between the center of the journal and the center of the INA oil film bearing increases. In the asymmetry zone, the bearing clearance becomes steeper along the direction of rotation of the journal, the minimum oil film thickness becomes smaller, the pressure inside the oil film becomes larger, the bearing capacity becomes larger, and the bearing center is not balanced, the center of the journal is no longer offset, and the INA oil film The bearing and the journal are completely separated by the lubricating oil, which theoretically forms a full fluid lubrication.
    From the working principle of INA oil film bearings, one of the most important parameters in the INA oil film bearing system is the minimum oil film thickness. If the minimum oil film thickness value is too small, and the metal impurity particles in the lubricating oil are too large, and the outer size of the metal particles is numerically larger than the minimum oil film thickness, the metal particles accompany the lubricating oil through the minimum oil film thickness as if causing metal contact. When it is serious, it will burn tiles. In addition, if the minimum oil film thickness value is too small, when there is an accident such as steel pile, it is easy to cause metal contact between the journal and the INA oil film bearing to cause burnt tile. The minimum oil film thickness value is related to the structural size and material of the INA oil film bearing, the machining accuracy of the related parts, the mounting accuracy of the INA oil film bearing system, the size of the lubricating oil and the rolling force.

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Motor assembly and disassembly steps and methods

      Before disassembly, the site should be cleaned, tools should be prepared, and the joints, end caps and casings, bearing caps and end caps should be marked to avoid mistakes during assembly. The general steps for removing the motor are as follows:

      1. Remove the belt or disconnect the coupling pin of the coupling;

      2. Remove the power wiring and grounding wire in the junction box;

      3. Remove the pulley or coupling;

      4. Remove the foot nut and washer;

      5. Remove the front bearing cover;

      6. Remove the front end cover;

      7. Remove the fan blade cover;

      8. Remove the blades;

      9. Remove the rear bearing cover;

      10. Remove the rear end cover;

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Method of disassembling a bearing cap of an electric motor

       1. The bearing cover is very easy to remove. Just remove the screws that fix the bearing cover and remove the front and rear bearing covers. The front and rear bearing covers should be marked with a mark to avoid mis-assembly before and after assembly.

       2. The assembly method of the bearing cover is: insert the outer cover through the rotating shaft outside the end cover, insert a screw, hold the screw with one hand, turn the shaft with one hand, and then turn the bearing inner cover to the outer cover. When the screw holes are aligned, the screws can be inserted into the screw holes of the inner cover and tightened. Finally, the other two screws are also tightened.

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Causes of damage to the clutch release bearing

      Causes of damage to the clutch release bearing
1. Working conditions and stress of clutch release bearing
The separation bearing is subjected to axial load, impact load, and radial centrifugal force during high-speed rotation during use. Further, since the fork thrust and the reaction force of the separation lever are not in the same straight line, a torsional moment is also formed. Clutch release bearings have poor operating conditions, intermittent high-speed rotation and high-speed friction, high temperature, poor lubrication conditions, and no cooling conditions.
2. Reasons for damage to the clutch release bearing
The damage of the clutch release bearing has a lot to do with the driver's operation, maintenance and adjustment. The causes of the damage are as follows:
1) The operating temperature is too high to cause overheating
Many drivers often turn the clutch halfway when turning or decelerating, and some of the gears are placed on the clutch pedal. Some vehicles have too large free travel adjustment, which makes the clutch separation incomplete, in a semi-engaged and semi-detached state. The dry friction causes a large amount of heat transfer to the separation bearing. The bearing is heated to a certain temperature, and the butter melts or dilutes the flow, so that the temperature of the separation bearing is further increased, and when the temperature reaches a certain level, it burns out.
2) wear and tear without lubrication
The clutch release bearing is lubricated with butter. There are two ways to add the butter. For the 360111 release bearing, the rear cover of the bearing should be opened to fill the grease during maintenance or when the transmission is removed, and then the rear cover should be reinstalled. For the 788611K release bearing, it can be removed and placed in molten grease for digesting, and then taken out after cooling to achieve the purpose of lubrication. In actual work, the driver easily overlooks this, resulting in a lack of oil in the clutch release bearing. The amount of wear of the separated bearing in the case of no lubrication or less lubrication is often several to several tens of times the amount of wear after lubrication. As the wear increases, the temperature will also increase greatly, which makes it more vulnerable.
3) Free travel is too small or too many loads
According to the requirements, the clearance between the general clutch release bearing and the separating lever is 2.5mm, which is reflected in the free travel of the clutch pedal is 30-40mm, the free travel is too small or there is no free travel at all, which will make the separation lever and The release bearing is in a normally engaged state. According to the principle of fatigue failure, the longer the bearing working time, the more serious the damage; the more the number of loads, the more likely the separation bearing is to cause fatigue damage. Moreover, the longer the working time, the higher the temperature of the bearing, and the easier it is to burn, reducing the service life of the separation bearing.
4) In addition to the above three reasons, whether the separation lever is adjusted flat, whether the separation bearing return spring is good or not, has a great influence on the damage of the separation bearing.

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Daily judgment of rolling hardware bearings

It is understood that knowing it can be used, to understand the functionality of hardware tools, in order to use it. Bearings, you can look at its finish (or roughness) first, the quality is good, you don't have to talk about it. Looking further, you can hold the bearing in your hand and turn it hard to see if it rotates very smoothly and naturally, without noise.

    The general 6xXXX series bearings used by nsk are really easy to use, that is, the price is more than double that of domestic ones. But its life is high, compared to most domestic bearings, one can be used for the top two. So the price is still cost-effective.

    There aren't many shops selling professional bearings. You can go to the hardware store to buy them. (There are some places where you can sell auto parts, motorcycle parts, and belts.) You don't have to go to a small shop. Generally, fixed stores with such bearings will make a very eye-catching brand. When you buy, you ask them to invoice, generally do not give fakes.

    I have used Harbin in domestic bearings, and it is more affordable to buy. The quality is also good. But after a long time, the noise is a little loud and needs lubrication, otherwise it should be rusted.

    Singapore's bearings are of quality between nsk and domestic.

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Causes of corrosion of bearing products

The main causes of corrosion are as follows:

    1. In the process of producing bearings, some enterprises did not strictly carry out anti-rust treatment on the bearing parts in the processing process and the finished bearing products in accordance with the requirements of cleaning anti-rust regulations and oil seal anti-rust packaging. If the ferrule has a long turnaround time during the turnaround, the outer ring of the outer ring is exposed to corrosive liquid or gas.

    2. The quality of anti-rust lubricating oil and cleaning kerosene used by some enterprises in production cannot meet the requirements of process technology.

    3. As the price of bearing steel drops and then falls, the bearing steel material gradually declines. For example, the content of non-metallic impurities in the steel is too high (the increase in sulfur content in the steel causes the corrosion resistance of the material itself to decrease), the metallographic structure deviation, and the like. The source of bearing steel used in production companies is more complicated, and the quality of steel is even more.

    4. Some enterprises have poor environmental conditions, high levels of harmful substances in the air, and too little turnover space, making it difficult to carry out effective anti-rust treatment. Coupled with the hot weather, production workers violated anti-rust procedures and other phenomena.

    5, some enterprises' anti-rust paper, nylon paper (bag) and plastic cylinder and other bearing packaging materials do not meet the requirements of rolling bearing oil seal anti-rust packaging is also one of the factors causing corrosion.

    6. The turning allowance and grinding allowance of the bearing ring of some enterprises are small, and the oxide scale and decarburization layer on the outer circle are not completely removed.

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