Maintenance and repair methods for reducing NTN imported bearing noise

Maintenance and repair methods for reducing NTN imported bearing noise

• In severe cases, metal peeling and large-area random scratches occur on the contact surface; In general, the mechanical damage of IKO imported bearing refers to the appearance of groove marks at different levels on the alloy surface of bearing bush. Contact surface damage and ablation exist at the same time. The main reason for bearing mechanical damage is that the bearing surface is difficult to form oil film or the oil film is seriously damaged.Maintenance and repair methods for reducing NTN imported bearing noise
• Plastic deformation and cold work hardening occur on the outer surface layer, and IKO imported bearing is under the repeated action of cylinder pressure (impact load). The deformation capacity is lost locally, and the grain is gradually formed and continuously expanded. Then, with the falling off of wear debris, the loaded outer layer forms a hole. Generally, when the bearing bush is pitted, the pit first appears, and then the pit gradually expands and causes the cracking of the alloy layer interface. Maintenance and repair methods for reducing NTN imported bearing noise
• The crack extends along the parallel direction of the interface until it peels off. This kind of damage is mostly caused by overload, excessive bearing clearance, or unclean lubricating oil and foreign matters mixed in it. Therefore, when using, attention should be paid to prevent the bearing from overload and do not run at too low or too high speed; Adjust the engine to a stable state at idle speed; Ensure the normal bearing clearance and prevent the engine speed from being too high or too low; Check and adjust the working condition of the cooling system to ensure that the working temperature of the engine is appropriate.Maintenance and repair methods for reducing NTN imported bearing noise
• The chemical impurities (acid oxides, etc.) in the lubricating oil oxidize the bearing alloy to form acidic substances. The corrosion area of the bearing alloy is generally impure lubricating oil. Cause the bearing alloy to fall off locally and form irregular small cracks or pits. The main causes of bearing alloy corrosion are improper selection of lubricating oil, poor corrosion resistance of bearing data, or rough engine operation and high temperature.
• Local high temperature is formed, and there is a small convex metal surface in direct contact between the journal and the IKO bearing friction pair. In case of lack of lubrication and poor cooling, the bearing alloy will be blackened or partially burned. This fault is often caused by too tight fit between journal and bearing; Lack of lubricating oil pressure is also easy to burn the bearing.Maintenance and repair methods for reducing NTN imported bearing noise
•   Use standard charging capacity. Each heating furnace 40 is quenched to avoid the shortage of quenched IKO bearing parts and the insulation defects of lack of time stacking. The same is true in the aging process, so that the holding time of the workpiece is sufficient.Maintenance and repair methods for reducing NTN imported bearing noise
•  quenching, quenching oil is dispersed into oil for cooling to prevent too many workpieces from cooling too slowly, resulting in changes in microstructure and properties, which is not enough to reduce workpiece defects. Completely dispersed into oil cooling, due to a small part of the oil, heating oil, post workpiece processing and excellent performance.Maintenance and repair methods for reducing NTN imported bearing noise
•  Using the improved technical measures, the heat treatment quality of IKO bearing parts is good, the hardness index of the workpiece meets the technical requirements, and the production is stable and normal.Maintenance and repair methods for reducing NTN imported bearing noise
• IKO bearing precision parts meet the above requirements. If it is not often, the installation accuracy of IKO bearing is larger than several times after the original error, and even more than 10 times of the error can not become an accurate IKO bearing at all, because the part of competition error can not be simply added to IKO bearing error, but increases in multiple different expansion.
• In order to ensure higher actual results, the shaft and seat hole shall match the surface of IKO bearing, and the roughness shall be as small as possible. In these measurements, IKO bearings and cylindrical holes, as well as the assembly chamfers on both sides of the corresponding shafts and holes, near the surface, indicate the direction of the large deviation of the two marks. Maintenance and repair methods for reducing NTN imported bearing noise
• Therefore, in the actual assembly, the large deviation of both sides matches the same aligned position, so that after assembly, both sides partially offset the deviation After the NTN bearing is pressed into the bearing, it shall rotate flexibly without blocking feeling. If there is obvious inflexible rotation, it indicates that the size of the shaft is too large and the tolerance should be reduced.Maintenance and repair methods for reducing NTN imported bearing noise
•  If the NTN bearing rotates by hand after being pressed into the shaft, there is an obvious “rusty” feeling, it may be that the tolerance of the shaft is too large or the roundness of the shaft is not good. Therefore, when controlling the tolerance of shaft and bearing chamber, it is also necessary to control the roundness. At present, many domestic manufacturers only control the tolerance, not the roundness.Maintenance and repair methods for reducing NTN imported bearing noise
• Because NTN bearing is a high-precision product, if it is not assembled properly, it is easy to damage the NTN bearing channel, resulting in bearing damage. The bearing shall be equipped with a special mold during assembly, which cannot be knocked at will. When pressing the shaft, only the small ring can be stressed, and when pressing the large ring, only the large ring can be stressed. Pneumatic or hydraulic pressure is required during assembly. Maintenance and repair methods for reducing NTN imported bearing noise
• During press assembly, the upper and lower molds shall be outside the horizontal state. If there is inclination, the bearing channel will be damaged due to stress and the NTN bearing will produce conduction sound.Maintenance and repair methods for reducing NTN imported bearing noise
• When the NTN bearing is installed on the rotor for dynamic balance, it is easy to enter the iron filings generated during dynamic balance into the bearing, so it is necessary to perform dynamic balance before installing the bearing.
•  In order to facilitate assembly, some manufacturers apply some oil or grease in the NTN bearing chamber for lubrication effect during assembly, but it is often difficult for operators to control the amount. If there is a large amount of oil or grease in the bearing chamber, it is easy to enter the bearing along the shaft when the bearing rotates. The bearing chamber shall not be coated with oil or grease. If it must be coated, it shall be controlled and there shall be no accumulation in the NTN bearing chamber.
• The service life of NTN bearing is closely related to manufacturing, assembly and use. It must be done well in each link in order to make the bearing in the running state and prolong the service life of the bearing.
• The additional sealing device supported by the NTN bearing can effectively make the bearing work normally without being invaded by external dirt, but this additional sealing device will increase the axial dimension of the mechanical mechanism and bring inconvenience to the use and installation of the bearing. Maintenance and repair methods for reducing NTN imported bearing noise
• At the same time, the sealing function of the additional sealing device is often affected by the machining accuracy and geometric tolerance of the matching parts of the journal and shell. Therefore, in the parts with compact structure and strict sealing requirements, If the motor supports NTN bearings, deep groove ball bearings with seals have been used in large quantities.
• Sealing can prevent the invasion of external foreign matters. Foreign matters entering the bearing, especially metal foreign matters, often cause abrasive wear in the working raceway of the bearing, affect the service accuracy of the bearing and shorten the service life of the bearing. Maintenance and repair methods for reducing NTN imported bearing noise
• Any harmful gas and water entering the NTN bearing will not only cause the corrosion of bearing parts, but also affect the physical and chemical functions of NTN bearing lubricant, Destroy the lubricating oil film and accelerate the aging of the lubricant. The sealing device can also prevent lubrication loss and reduce environmental pollution.Maintenance and repair methods for reducing NTN imported bearing noise
• Generally, sealing is essential for NTN bearings. If a bearing is directly exposed to the working environment without any sealing device, it is often harmful.
• NTN bearings have a certain internal clearance, but sometimes when the bearing is installed or the bearing group assembled in pairs is used, the preload is often applied to the bearing to produce a certain pre deformation between the moving elastic body and the inner and outer rings, so as to achieve the required working purpose. Maintenance and repair methods for reducing NTN imported bearing noise
• At this time, NTN bearing will operate under the condition of negative clearance. Negative clearance is one of the characteristics of dynamic bearing, and any kind of sliding bearing must work with clearance. Use vibration absorbing equipment.Maintenance and repair methods for reducing NTN imported bearing noise
• Good results can be obtained by using vibration absorption or vibration isolation devices to reduce NTN bearing noise or isolate NTN bearing noise, but this often costs a lot in economy. Sometimes, the mechanism becomes larger, the heat dissipation conditions become worse, or it is easy to rust. It should be fully considered in use. This method can be used only after other measures are taken and the low noise index can not be reached.
• Another example is to add an intermediate sleeve between the NTN bearing and the seat hole, which can attenuate the vibration force transmitted by the rotating system to the NTN bearing seat, but this requires proper allocation, otherwise the opposite effect may occur.Maintenance and repair methods for reducing NTN imported bearing noise
• Here, glass fiber or foam plastics are used to eliminate high frequency noise. The inner surface with small holes is used to eliminate the low frequency noise, while the thick steel plate on the outer surface is used to isolate the noise.Maintenance and repair methods for reducing NTN imported bearing noise
• Method of changing speed of corresponding parts of main engine
• In order to reduce the noise of the oil pump system,
• The noise of rolling NTN bearing is not very sensitive to load, but it is very sensitive to speed. If conditions permit, the same working purpose is achieved by reducing speed and increasing torque, but the noise is reduced.
• Methods of using chemical additives
• Adding some chemical additives to the lubricant of NTN bearing can reduce the noise of NTN bearing and reduce the noise of NTN bearing by 3.9 ~ 9.2db from the original basis. It is suitable for use in micro or small NTN bearing.
• Generally, if NTN bearings are used correctly, they can be used until the fatigue life is reached. However, there will be accidental and premature damage, which can not be resistant to use. This early damage, as opposed to fatigue life, limits the use of quality known as failure or accident. Most of them are caused by careless installation, use and lubrication, foreign matters invading from the outside, and insufficient research on the thermal effects of shafts and shells.Maintenance and repair methods for reducing NTN imported bearing noise
• As for the damage state of NTN bearing, for example, the clamping of the ring retaining edge of roller bearing can be considered as the reason. These reasons can also coincide with insufficient lubricant, unsuitable, defects of oil supply and drainage structure, intrusion of foreign matters, installation error of NTN bearing and excessive deflection of shaft.Maintenance and repair methods for reducing NTN imported bearing noise
• If it is not detachable, it will be more troublesome! Use destructive methods. Use a precision screwdriver to reach into the seam of the side cover and pry the side cover up. Don’t doubt it. That’s it, but the side cover can’t be installed back! Well, throw it away! Remember, just dismantle one side and destroy both sides!Maintenance and repair methods for reducing NTN imported bearing noise
• Therefore, only investigating NTN bearing damage, it is difficult to know the real cause of the damage. However, if we know the use machinery and conditions of NTN bearing, the structure around NTN bearing, the situation before and after the accident, and combined with the damage state of NTN bearing and several causes, we can prevent the recurrence of similar accidents.Maintenance and repair methods for reducing NTN imported bearing noise