How to measure the bearing clearance and how to ensure the accuracy of the clearance measurement are the problems often encountered by many users in measuring the bearing clearance. Here are some measurement methods, aspects to pay attention to and some measurement skills of Japanese NTN bearings.
Bearing clearance refers to the movement amount of the bearing when one side of its inner ring or outer ring is fixed when it is not installed in the shaft or bearing housing, and then the unfixed side moves radially or axially. Five points for correct installation and adjustment of low noise NTN bearings
Generally speaking, the duration of bearing rotation is long, the stop is slow, and the flexibility is good. On the contrary, if the rotation time is short and the stop is sudden, the flexibility is not good. According to the moving direction, it can be divided into radial clearance and axial clearance. Five points for correct installation and adjustment of low noise NTN bearings
The measurement of the radial clearance of the whole set of bearings is not easy. The measuring force causes the elastic deformation of the ferrule and the rolling element itself and its contact. The amount of deformation is a multi factor causing the measurement error, which is related to the measuring force, the contact state and the position of the rolling element. Five points for correct installation and adjustment of low noise NTN bearings
The rotation flexibility of Japanese NTN bearings is generally checked at the horizontal position. Usually fix the inner ring (or hold the inner ring by hand) and rotate the outer ring by hand to check whether there is abnormal sound and blockage during bearing rotation. Five points for correct installation and adjustment of low noise NTN bearings
Due to different structural types and sizes of bearings, there should be different requirements for their rotation flexibility. For example, single row centripetal ball bearings and single row centripetal thrust ball bearings are relatively light when rotating due to the small contact area between the rolling element and the ferrule.
while double row centripetal spherical bearings and thrust roller bearings are less light when checking their rotation flexibility due to the large contact area between the rolling element and the raceway and the small weight of the outer ring. Five points for correct installation and adjustment of low noise NTN bearings
For extra large bearings, there should be no jamming when rotating them, and the rotating sound is generally not checked. For tapered hole bearing, the following methods can be used to supplement and check the rotation flexibility of the bearing. The specific operations are as follows: press the tapered hole bearing into the mandrel until a certain radial preload is added. Five points for correct installation and adjustment of low noise NTN bearings
Under this preload, when a ferrule rotates, the rolling element should rotate. If the rolling element slides instead of rotates, it means that there are too many geometric defects of the ferrule or the size of the rolling element is uneven, and the rotation flexibility of the bearing is poor.
Five points for correct installation and adjustment of low noise NTN bearings
In the case of close fit between the bearing ring and the bearing seat or transmission shaft, the bearing ring may be deformed by matching with the shape of adjacent components. If deformation occurs, vibration may occur during operation. Therefore, it is important to machine the bearing pedestal and drive shaft to the required tolerances.Five points for correct installation and adjustment of low noise NTN bearings
The bearing is excited by the change of the number of loaded rolling elements. When a radial load is loaded on a bearing, the number of loaded rolling elements will change slightly during operation, that is to say, it will cause the shift of load direction. In this case, it is inevitable to reduce the vibration of the roller by preloading the roller (but it is not applicable to all rolling bearings).Five points for correct installation and adjustment of low noise NTN bearings
The bearing is partially damaged. A small number of bearing raceways and rolling elements may be damaged due to incorrect operation or installation. In operation, rolling damaged bearing components will produce specific vibration frequencies. Vibration frequency analysis can identify damaged Japanese NTN bearing components.
As we all know, NTN imported bearings are precision parts and require considerable caution in use, that is, high-performance bearings are used. If they are not used properly, they can not achieve the expected performance effect, and it is easy to damage NTN imported bearings. Five points for correct installation and adjustment of low noise NTN bearings
Most bearings are broken for many reasons – exceeding the original estimated load, ineffective sealing, too small NTN inlet bearing clearance caused by too tight fit, etc. Any of these factors has its special damage type and will leave special damage traces.Five points for correct installation and adjustment of low noise NTN bearings
Therefore, by examining the damaged bearing, we can find the possible causes in most cases. Generally speaking, one third of the NTN imported bearing damage is due to fatigue damage, the other one third is due to poor lubrication, and the other one third is due to pollutants entering the bearing or improper installation and treatment.
How to protect it and prolong its service life, the following matters should be paid attention to when using the bearing:Five points for correct installation and adjustment of low noise NTN bearings
The installation and adjustment of low-noise NTN bearing can also follow the grouping method of long-life bearing, so that the matching interference is more consistent, and the clearance of NTN bearing is also more consistent. Five points for correct installation and adjustment of low noise NTN bearings
It is hoped that the matching interference will take a smaller value within the possible range, so as to ensure that the deformation of NTN bearing raceway is small, and the noise caused by the passage of rolling element will be reduced.Five points for correct installation and adjustment of low noise NTN bearings
The clearance has a great influence on the noise. The ideal state is that when the NTN bearing is in the high temperature state of operation, the clearance value is just zero. The methods to judge the excessive clearance are: the axial displacement of the bearing in the static state, the reciprocating amplitude is large, and a large and turbid noise is emitted during operation.Five points for correct installation and adjustment of low noise NTN bearings
If there is an annoying shriek during operation, it indicates that the preload of NTN bearing is too large and the bearing has too large pre interference. The preload should be slightly relaxed. If the clearance is too large, the two bearing rings can be slightly offset along the axial direction: it not only reduces the clearance, but also increases the axial rigidity and reduces the bearing noise.Five points for correct installation and adjustment of low noise NTN bearings
When the rolling element enters the no-load area, it will slip or move left and right, which will not only increase the noise, but also cause wear. Small clearance and large axial stiffness can eliminate this phenomenon. However, the clearance should not be too small, so as not to cause excessive temperature and shorten service life.
Sometimes, due to the large working temperature range of the main engine or the large dispersion of the size between the shaft and the bearing seat hole, it is impossible to obtain a more appropriate clearance at one time. In this case, the elastic constant pressure preloading method can be adopted for the outer ring of NTN bearing.Five points for correct installation and adjustment of low noise NTN bearings
Koyo imported bearing, in most cases, working state: use appropriate clearance. According to different uses, and in the assembly bearing, the bearing is advanced to make the internal stress and make the negative bearing clearance used. This method is called using preload. More suitable, such as angular contact ball bearings, tapered roller bearings, two family bearings, bearing clearance, can be adjusted.
Main purpose of preloading: the main purpose of preloading can be proved by some representative examples:Five points for correct installation and adjustment of low noise NTN bearings
In the correct direction and radial position, the axial direction determines the shaft and suppresses the runout of the shaft.Five points for correct installation and adjustment of low noise NTN bearings
Increase the rigidity of the bearing. Machine tool spindle bearing, bicycle and small agent bearing, gear differential.
To prevent the axial direction of vibration and resonance of different sounds. Small motor bearings.
Suppresses scrolling, rotating slides, sliding and rotating revolution slides. High speed rotating center thrust bearing, thrust ball bearing.Five points for correct installation and adjustment of low noise NTN bearings
Ring and keep rolling in the correct position. Thrust ball bearing, thrust spherical roller bearing, and horizontal shaft.Five points for correct installation and adjustment of low noise NTN bearings
Preloading method: the pre positioning of load is the preloading method that the relative position of Koyo imported bearing shaft will not change in use. Here is an example:
In order to implement the difference before the adjustment of the width between preloads or the fastening method after the axial clearance of bearings.Five points for correct installation and adjustment of low noise NTN bearings
Adjust the size of the pad, gasket and bearing preload to make way.Five points for correct installation and adjustment of low noise NTN bearings
The method adopted after tightening the screw and nut clearance with adjustable shaft direction. In this case, adjust the friction torque on the hand side with an appropriate preload to determine the start.Five points for correct installation and adjustment of low noise NTN bearings
The so-called constant pressure preload is the use of coil springs and Belleville springs to give the load-bearing of appropriate preparation methods. When in use, even if the relative position of the Koyo inlet bearing changes, the preloading method. When in use, it will even change its relative position, and the preload can be maintained at a certain level.Five points for correct installation and adjustment of low noise NTN bearings
After draining the old engine oil, if possible, the bearings lubricated with engine oil should be filled with fresh engine oil and let the machine rotate at low speed for a few minutes. Make the oil collect residual pollutants as much as possible, and then drain the oil. Note: the engine oil is filtered before use.
When replacing the grease of the bearing lubricated with grease, the Joe remover used shall avoid the contact of cotton with any part of the bearing. Because these residual fibers may wedge between rolling parts and cause damage, especially in the application of small bearings.Five points for correct installation and adjustment of low noise NTN bearings
When inspecting Koyo imported bearings, never expose the bearings to pollutants or moisture. If the work is interrupted, cover the machine with oil paper, plastic sheet or similar materials.
Tile surface corrosion: abnormal concentration of non-ferrous metal elements is found by spectral analysis; Submicron wear particles with many non-ferrous metal components appear in ferrography; The water content and acid value of lubricating oil exceed the standard.Five points for correct installation and adjustment of low noise NTN bearings
Journal surface strain: there are ferrous cutting abrasive particles or black oxide particles in the ferrogram, and there is tempering color on the metal surface.
Journal surface corrosion: the spectral analysis found that the concentration of iron was abnormal. There were many submicron particles of iron in the ferrogram, and the water content or acid value of lubricating oil exceeded the standard.
Surface strain: cutting abrasive particles are found in the Ferrograph, and the abrasive particles are composed of non-ferrous metals.
Fretting wear of tile back: abnormal iron concentration is found by spectral analysis. There are many iron components, submicron wear particles, abnormal moisture and acid value of lubricating oil in the ferrogram.Five points for correct installation and adjustment of low noise NTN bearings
Under the condition of liquid lubrication, the sliding surface is separated by lubricating oil without direct contact, which can also greatly reduce the friction loss and surface wear, and the oil film also has a certain vibration absorption ability
Koyo bearing faults are often due to a variety of factors, all the design and manufacturing process factors and bearing faults, their analysis is not easy to determine. Under normal circumstances, in general, you can consider and analyze factors and internal factors.Five points for correct installation and adjustment of low noise NTN bearings
The main factors used for adjustment are installation, use and maintenance, maintenance and repair, which meet the technical requirements. The installation condition is one of the factors for using Koyo bearings. It is the primary factor of the load-bearing force that often causes the state change between various parts of the incorrect installation package, and the operation in abnormal state and early failure.
Monitor and inspect the contact load, speed, temperature, vibration, noise and lubrication status of the operating bearing according to the technical requirements of bearing installation, use, maintenance and maintenance. If any abnormality is found, find the cause immediately and adjust it back to normal. In addition, the quality of oil and surrounding media and atmosphere are also very important for analysis and testing.Five points for correct installation and adjustment of low noise NTN bearings
The chamfer of the bearing does not determine the quality of the bearing, but reflects the processing method of the bearing. The chamfering is black, which means that after quenching and other heat treatment, the hardness of the bearing can be improved. Some people think that the chamfering is black, which is not good-looking and is not completely processed. This is a misunderstanding.Five points for correct installation and adjustment of low noise NTN bearings
The integrated cage is better than the two bodies. Although the new technology uses the integrated cage, it only saves materials, and its performance on rotation is worse than that of the two bodies. The chamfering of Koyo bearing does not determine the quality of the bearing, while some people think that the chamfering is black and not good-looking, which is a misunderstanding.Five points for correct installation and adjustment of low noise NTN bearings
There are three main factors that determine the quality of bearing design and manufacturing process.Five points for correct installation and adjustment of low noise NTN bearings
First of all, the structural design and advanced at the same time, there will be a longer Koyo bearing life. Bearing manufacturing will go through multiple processes of forging, heat treatment, turning, grinding and assembly. The rationality, advanced nature and stability of the treatment will also affect the service life of the bearing.Five points for correct installation and adjustment of low noise NTN bearings
The influence of bearing heat treatment and grinding process is often more directly related to bearing failure, which is related to product quality. In recent years, the deterioration of bearing surface layer shows that the grinding process is closely related to the bearing surface quality.Five points for correct installation and adjustment of low noise NTN bearings
The metallurgical quality of bearing materials is the main factor affecting the early failure of rolling bearings. With the progress of Metallurgical Technology (such as bearing steel, vacuum degassing, etc.), the quality of raw materials has been improved.Five points for correct installation and adjustment of low noise NTN bearings
The proportion of raw material quality factor in bearing fault analysis has decreased significantly, but it is still one of the main factors of Koyo bearing failure. Whether the selection is appropriate or not is still a bearing fault analysis that must be considered.Five points for correct installation and adjustment of low noise NTN bearings
A satisfactory Koyo bearing life begins with the correct bearing selection. From the beginning, bearing designers extended bearing life and equipment performance by selecting the right bearings for different applications. Many factors should be considered in this process, such as load, hardness, bearing life prediction, operating environment and so on.Five points for correct installation and adjustment of low noise NTN bearings
In principle, all bearings should be kept in their original packaging before installation. They need to stay in a clean, moisture-free, relatively constant temperature environment. Rolling bearings should be kept away from dust, water and corrosive chemicals.Five points for correct installation and adjustment of low noise NTN bearings
Shaking and vibration may permanently damage the mechanical properties of the bearing, so vibration must be avoided during handling and storage.Five points for correct installation and adjustment of low noise NTN bearings
Basically, all Koyo bearings must be stored horizontally, because some heavier bearings may be deformed due to their own weight after being placed vertically for a long time.Five points for correct installation and adjustment of low noise NTN bearings
Pre greased (or sealed) bearings require special care because the density of the grease will change after long-term storage. In this way, when the bearing is used again, there will be a certain degree of rotation noise. Therefore, the shelving time of this bearing should be controlled according to the principle of first in first out.
In the process of normal operation, how to properly lubricate the bearing is also an important link in bearing maintenance.Five points for correct installation and adjustment of low noise NTN bearings
Oil bath smoothing is a common smoothing method in bearings, which is suitable for the smoothing of low and medium speed bearings. Partially immerse the Koyo bearing in the groove, and the smooth oil is brought up by the rotating bearing parts and then flows back to the oil groove. The oil level should be slightly lower than the center of the low rolling element.Five points for correct installation and adjustment of low noise NTN bearings
Smooth oil dripping is suitable for bearing components that need to be supplied with smooth oil quantitatively. The oil dripping amount should be one drop every 3-8 seconds. Excessive oil will cause the bearing temperature to increase.Five points for correct installation and adjustment of low noise NTN bearings
The filtered oil is sent to the bearing after being cooled by the oil pump. Because the circulating oil can take away certain heat and cool the bearing, this method is actually used for bearing parts with high speed.Five points for correct installation and adjustment of low noise NTN bearings
Oil mist is generated by mixing the dry shrinkage air with the smooth oil through the sprayer, and the airflow can effectively cool the bearing and avoid impurity invasion in the radial bearing. This method is suitable for the smoothing of high-speed and low-temperature bearing parts.Five points for correct installation and adjustment of low noise NTN bearings
Use the oil pump to inject the low-pressure oil into the bearing through the nozzle, and the oil injected into the bearing flows into the oil groove through the other end of the bearing. When the bearing rotates at a high speed, the rolling element and the maintenance frame also cause air flow around at a relatively high rotation speed. Five points for correct installation and adjustment of low noise NTN bearings
It is difficult to send the smooth oil to the bearing by individual smooth methods. At this time, the smooth oil must be sprayed into the Koyo bearing by means of low-pressure radiation. The position of the nozzle should be placed between the inner ring and the center of the maintenance frame.Five points for correct installation and adjustment of low noise NTN bearings
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