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KOYO Bearing Damage Investigation and Countermeasures

Writer: Eric Bearing Limited

Koyo imported bearing fatigue failure is a failure surface form, mainly manifested as fatigue crack initiation, expansion and fracture process, the metal produced by the long-term impact of the load failure generated under alternation. The cracks are in two ways:

1. From the surface, this is KOYO imported bearings during rolling contact, due to the external load caused by the periodic deformation of the plastic deformation on the working surface and the contact stress on the hardened surface of the strain, and finally developed from a small crack The inner surface, the formation of surface cracks between the two, due to the introduction of lubricant on the working surface, the opening force, severely hit the wall, forcing the crack to move forward;

2. From the surface layer, under repeated pressure, the contact of the surface initially generates a crack at a certain depth in the place where the surface is exposed, and the angle along the surface direction to a certain depth, from behind the surface of the contact surface, and beyond The surface and eventually form an etch peel, leaving a horse pit.

From the surface of KOYO imported bearings, it is still from the cracks in the surface layer. These two goals (part carburization, quenching and other surface heat treatment, if there are uneven hardness, structure, and non-uniform internal stress and other disadvantages, then The contact stress is generally caused by the effect of the opposite underground cracks. If the surface quality of the parts is poor, there is a defect (oxidation, decarburization), poor friction or lubrication, and cracks from the surface.   KOYO 6304 bearings online , pls click here :

The methods for controlling the raceway sound are: select low-noise KOYO imported bearings, that is, bearings with low ripple, and carefully select the conditions of use. The sound of the raceway often affects the noise of the entire machine. Reducing the sound of the raceway can reduce the noise of the whole machine.

Bearings can have a very long life under the correct use. If damage occurs prematurely, it may be caused by wrong selection, improper use or poor lubrication.

Therefore, when installing bearings imported from KOYO, we need to record the type of machine, the installation location, the use conditions and the surrounding fit. Summarize the type of bearing damage through research and the environment in which the problem occurs to avoid the recurrence of similar situations.

Technical analysis of industrial koyo cylindrical roller bearings

In order to maintain the original performance of the cylindrical roller bearing in good condition for as long as possible, maintenance, inspection and repair are required to prevent accidents before they occur, ensure the reliability of operation, and improve productivity and economy. Maintenance should be performed regularly in accordance with the operating standards of the machine's operating conditions. The contents include monitoring the running status, replenishing or replacing lubricants, and regular disassembly inspections. As maintenance items during operation, there are rotation sound, vibration, temperature, lubricant state, etc. of KOYO bearings.

Bearing cleaning: When disassembling the cylindrical roller bearing for maintenance, first record the appearance of the KOYO bearing, confirm the remaining amount of lubricant, and after sampling the lubricant for inspection, wash the bearing. As a cleaning agent, gasoline and kerosene are generally used.

The removed bearings are divided into coarse cleaning and fine cleaning, and put them in the container respectively. Put the bottom of the metal mesh pad first so that the bearing does not directly contact the dirt of the container. During rough cleaning, if the cylindrical roller bearing is rotated with dirt, it will damage the rolling surface of the bearing, so care should be taken. In the coarse cleaning oil, use a brush to remove grease and adhesions. After it is roughly clean, transfer to fine washing.

The cracking and peeling of the bearing is caused by the fatigue damage of the contact surface of the KOYO bearing under the cyclic load, so in order to improve the service life of the bearing, the bearing steel must have a high contact fatigue strength.

Hardness is one of the important qualities of cylindrical roller bearings and has a direct impact on contact fatigue strength, wear resistance, and elastic limit. The hardness of cylindrical roller bearing steel in use should generally reach HRC61~65, so that KOYO bearings can obtain higher contact fatigue strength and wear resistance.

The cage is made of nylon 46, which reduces the sliding friction between the balls and the cage. In addition, the uneven shape in the rotation direction is eliminated, thereby reducing the stirring loss. In addition, by adopting a shape that reduces stress during assembly, assembly performance is ensured. The loss torque on a single cage is reduced by 30-40%, and the overall loss torque of the cylindrical roller bearing is reduced by 50-65%. The company speculates that Prius increased the fuel efficiency of the 10 mode and 15 mode from the previous 35.5km/L to 38.0km/L. About 1-2% of the improved fuel efficiency is obtained by using this type of bearing.

In the production process of KOYO bearing parts, there are many cold and hot processing procedures. In order to meet the requirements of large quantities, high efficiency and high quality, cylindrical roller bearing steel should have good processing performance. For example, cold and hot forming performance, cutting performance, hardenability, etc.

The important role of overhaul of KOYO one-way bearing

KOYO bearings show the characteristics of late failure to serious failure (usually bearing damage such as shaft holding, burns, sand frame spalling, raceway, bead wear, etc.). The time is not more than one week. The larger the equipment capacity, the faster the speed. The shorter the interval. Therefore, in the actual bearing fault diagnosis, once the late fault characteristics are found, the one-way bearing should be decisively determined to be faulty, and maintenance should be arranged as soon as possible.

The manufacturing of KOYO bearings generally goes through multiple processes such as forging, heat treatment, turning, grinding and assembly. The rationality, advancement and stability of each processing technology will also affect the life of the one-way bearing. Heat treatment and grinding processes that affect bearing quality often have a more direct relationship with bearing failure. In recent years, the study of the degeneration layer on the bearing working surface indicates that the grinding process is closely related to the quality of the bearing surface.

1. The KOYO bearing has been damaged and should be replaced immediately.

2. Bearing grease is too little, too much or there are impurities such as iron filings. The capacity of one-way bearing grease should not exceed 70% of the total volume, and those with impurities should be replaced.

3. The shaft and bearing fit too tightly or too loosely. If it is too tight, it should be re-grinded, and if it is too loose, the shaft should be set.

4. The bearing and end cover are too tight or too loose. The bearing chamber is processed when it is too tight, and a steel sleeve is inserted in the end cover when it is too loose.

5. Poor assembly of the motor end cover or bearing cover. Install the end cap or bearing cap stop, install it flat, and tighten the screws.

6. The belt is too tight or the coupling is poorly assembled. Adjust the belt tension and correct the coupling.

7. There is too little lubricating oil in the one-way bearing, there are impurities or the oil ring is stuck. Should refuel, replace with new oil, repair or replace the oil ring.

After a period of exercise, the vibration and noise maintain a certain level, and the frequency spectrum is very single, with only one or two times the frequency. The frequency spectrum above three times the power frequency rarely occurs, and the one-way bearing is very stable, entering a stable working period. After continuing to operate, it entered the later period of use, bearing vibration and noise began to increase, and sometimes there were abnormal sounds, but the change in vibration increased slowly. At this time, the koyo bearing kurtosis value began to suddenly reach a certain value. We believe that at this time the bearing appears as an initial failure.

The primary duty of KOYO bearing service life analysis is to find out the primary elements that constitute bearing failure based on a large amount of background data, analysis data and failure pattern, so as to propose targeted improvement measures and delay the retirement of one-way bearings. Avoid sudden early failure of KOYO bearings.