How to lubricate high-precision FAG bearings

Answers:0   |   LastUpdateAt:2020-07-27 19:06:35  

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bellaer
Asked at 2020-07-27 19:06:35

The difficulty of lubricating high-precision FAG bearings is that the lubricant is easy to scatter, and it is not easy to adhere to the rolling surface, or it is blocked by the high-speed airflow around the FAG bearing and cannot enter the FAG bearing. The lubricant speed entering the FAG bearing is too high, sometimes FAG bearings will be damaged, such as pitting in the cage, chipping and increased friction and wear. 6313-2Z FAG bearing online

The working temperature of high-speed FAG bearings is mostly around 200 ° C, and they tend to be higher. If they are not cooled by strong force, the temperature will continue to rise, which will be detrimental to the strength and hardness of FAG bearings. Once FAG bearings lose the ability to maintain accurate shapes It will intensify the high-speed friction and cause the temperature to rise rapidly, which further leads to a decrease in the strength and hardness of the material and makes the FAG bearing fail quickly.

Because high-speed FAG bearings are very sensitive to wear and are prone to wear debris, if they are not removed from FAG bearings in time, they will also cause a vicious cycle and make FAG bearings fail quickly.

Therefore, the task of high-speed FAG bearing lubrication must effectively deliver the lubricant to the moving surface in the FAG bearing, and remove the heat from the FAG bearing, and at the same time remove the abrasive particles or dirt from the FAG bearing.

The following are the commonly used lubrication methods and effective lubricants in high-speed FAG bearings.

Jet lubrication

The jet lubrication method is to spray lubricating oil from the nozzle hole close to the FAG bearing at a speed of 10-20m / s into the FAG bearing, usually sprayed into the gap formed by the cage and the inner ring or outer ring to lubricate And the method of cooling FAG bearings.

For small ball FAG bearings with an internal diameter of 30-35mm, the dmn value limit of jet lubrication can reach 3 million, and 2.5 million for larger FAG bearings.

Double-hole or multi-hole nozzles can not only increase the oil supply, but also improve the use efficiency of lubricating oil. Multiple nozzles or nozzles on both end surfaces can improve the lubrication and cooling effect, but when the dmn value is close to 2 million Due to the influence of centrifugal inertia and wind resistance, the oil sent to the FAG bearing is only 70% or less of the nozzle flow.

Under ring lubrication

The under-ring lubrication method uses centrifugal inertia to directly spray oil toward the surface of the raceway through many small radial holes in the inner ring. A part of the oil flows axially under the inner ring to cool the inner ring. The oil entering the raceway is divided into two left and right channels to flow out, and the abrasive debris falling from the cage and other parts is washed away by the way.

The amount of oil used in this lubrication method is much less than that of oil injection lubrication. The power loss caused by the dynamic stirring of the oil is also less. The heat generation of the FAG bearing is also greatly improved. Even the inner ring temperature may be lower than the outer ring. Reduce the failure rate of FAG bearings.

This lubrication method can also be used to cool the outer ring. When both the inner and outer rings are lubricated, the allowable dmn value of FAG bearings can be further increased.

Now this under-ring lubrication method is widely used in various ultra-high-speed operation occasions. The achievable large dmn value is 3 million for large ball FAG bearings with an inner diameter of 120 to 200 mm; 2.4 million for tapered roller FAG bearings with an inner diameter of 120 mm, and 3 million for short cylindrical roller FAG bearings with combined inner rings

Double lubrication

In this method, the inner ring hole of the rolling FAG bearing and the journal form a static pressure oil film sliding FAG bearing, which greatly reduces the rotating speed of the rolling FAG bearing, thereby achieving the purpose of reducing the effect of centrifugal force. Such a double-lubricated FAG bearing can Significantly reduce the rotation speed of the inner ring of the rolling FAG bearing, thus allowing the spindle to have a higher rotation speed, which is equivalent to the dmn value of the FAG bearing can be further increased.

Oil-air lubrication method

The big advantage of the oil-air lubrication method is that it is possible to achieve a high speed of dmn value of 800,000 to 1.5 million by reducing the friction of the FAG bearing without changing the structure of the FAG bearing. For the FAG bearing with more internal sliding, this method The advantages are even more significant.

Lubricant for high-speed FAG bearings

The lubricant for high-speed FAG bearings should be considered as the lubricant for high-temperature FAG bearings, that is, synthetic oil with good performance at high temperatures, or grease based on this synthetic oil. The diester-based MIL-L-7808 oil and MIL-L-23699 oil have been widely used in FAG bearings of jet engines. 

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