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What measures are there to prevent the roller bearings from slipping

wallpapers Tech 2021-01-18
When the bearing is working, the rollers should perform pure rolling motion on the inner and outer ring raceways. If the drive roller cage is required to have enough drag force, it can overcome its resistance. When the roller drag force is not enough to overcome the resistance, at this time, in addition to rolling, it will be accompanied by some sliding.
What are the factors that cause roller bearings to slip and scratch?
The roller bearing skidding is a necessary condition for bearing scratches, but slipping does not necessarily cause surface scratches.
 
Slip scratches are the result of the material transfer due to the interaction of the uneven metal surface after the lubricant film is destroyed. Some materials are "stained away" to form pits; while the more stained parts protrude above the original surface. In addition, some parts of the working surface are scratched, and some parts are not scratched, which is closely related to the alternating load and the degree of damage to the sleeve. In severe cases, the excessive frictional heat generated between the roller and the inner ring causes the inner ring to expand, reducing the radial clearance and causing the bearing to jam.
What measures are there to prevent roller bearings from slipping?
1. Reduce the number of rollers and reduce the diameter of the rollers
The roller is moved by the rotating ring. When the strength allows, reduce its weight to achieve the purpose of reducing inertial resistance. It becomes very important to prevent and reduce slippage. It is relatively simple to adopt this measure, and it can be achieved only by reducing its number and diameter. In aero-turbine engines, due to the small external load, contact fatigue is no longer the main damage factor of the roller. According to the conventional standard bearing size, tolerance is still large, it is generally considered that the number of rollers is reduced by 50%, and after the diameter is reduced by 25%, its contact fatigue life is still not affected. Many engines have adopted this measure, for example, the main bearing of the Spey engine is of this type, not only the rollers are obviously sparse, but also the size is small.
 
2. Choose a reasonable structure and reduce the weight of the cage
In addition to reducing its weight when the strength permits, the cage should also consider its own characteristics, for example, should avoid its resonance, high-speed rotation resistance, etc.
 
The cage guidance method is also a very important factor in high-speed bearings. If the imbalance of the cage is properly controlled, the cage is changed from outer guidance to inner guidance, which is also very beneficial for reducing slippage. Because of the outer guidance, the relative movement between the cage and the guide surface of the bearing, the oil film forms a viscous resistance, while the inner guide is the opposite, and the viscous force of the oil film between the cage and the guide surface becomes a drag force. In this way, the viscous resistance becomes the force that drags the cage to rotate. The difference between the two cannot be ignored.
 
3. Oil supply under the ring
The advantage of using an under-ring oil supply is that it takes away the heating of the bearing and minimizes the additional loss caused by stirring. Another example is to change the outer ring belt rib to the inner ring belt rib, which undoubtedly can also reduce the resistance of mixing
 

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