Influence of Preloading Method of Cylindrical Roller Bearing

Time：2020.08.07  Source：Roller Bearings Suppliers

There are two ways of axial preload for cylindrical roller bearings, one is constant pressure preload, and the other is positioning preload. Under constant pressure preload, the radial stiffness of the bearing increases slightly with the increase of speed, but the axial and angular stiffness decrease rapidly. Under positioning preload, the radial, axial and angular stiffness of the bearing all increase rapidly with the increase of speed, but the increase in axial and angular stiffness is relatively gentle.

1. The influence of preload

With the increase of preload, the radial, axial and angular stiffness of cylindrical roller bearings increase slightly, but the effect is small. Compared with positioning preload, this effect is more significant for constant pressure preload. This is because the increase in the pre-tightening load increases the contact angle of the inner and outer rings, and at the same time increases the contact load, thereby increasing the radial, axial and angular stiffness. 

However, the change in contact load and contact angle caused by the preload load is smaller than the change caused by the speed and displacement of the parts. Therefore, the impact on the stiffness of the cylindrical roller bearing is limited. This is also the reason why the change under positioning preload is smaller than that under constant pressure preload. WSBC NJ313EM bearings online, if you interested, pls click here to learn more :

2. The influence of the radius of curvature of the groove

As the radius of curvature of the inner and outer ring channels increases, the radial, axial and angular stiffnesses decrease, but this effect is small. Only the stiffness changes under positioning preload are slightly more pronounced. This is due to the channel curvature. The increase in radius increases the amount of contact deformation. Therefore, when selecting the radius of curvature of the channel, its effect on stiffness can be ignored.

3. The effect of the number of balls

Under positioning preload, the increase in the number of balls will slightly increase the radial, axial and angular stiffness. The increase in the number of balls increases the stiffness, but under the same preload load, the increase in the number of balls will reduce the contact load. The result of their combined effect can increase the stiffness of the cylindrical roller bearing, but less.

Under constant pressure preloading, the increase in the number of balls causes the radial stiffness to increase significantly, while the axial and angular stiffness decreases when the speed increases to a certain value, but the change is small. This is because under constant pressure preloading, the increase in the number of balls reduces the contact load of the inner ring, but at the same time reduces the contact angle of the inner ring. Their combined effect makes the radial stiffness of the cylindrical roller bearing increase significantly, while the axial and The angular stiffness is slightly reduced.

Therefore, when the number of balls increases, the preload load should be increased accordingly. Only when the contact load is the same, the increase in the number of balls can increase the stiffness of the cylindrical roller bearing.

4. The shadow of the ball diameter

Under positioning preload, the diameter of the ball increases, and the radial, axial and angular stiffness increase slightly. The increase of the ball diameter increases the centrifugal force of the ball, reduces the contact angle of the outer ring, and increases the contact angle of the inner ring, but at the same time increases the contact load of the inner and outer rings. 

As a result of their combined action, the stiffness of the cylindrical roller bearing increases. Since the change of centrifugal force under positioning preload has little influence on the contact load, the change of ball diameter has little influence on the stiffness. WSBC NJ314EM bearing online, if you interested, pls click here to learn more:

Under constant pressure preload, the radial stiffness of the ball diameter increases, while the axial and angular stiffness decrease, but the effect is small. This is because the increase of the ball diameter increases the centrifugal force of the ball, the contact angle of the inner and outer rings decreases, the contact load of the outer ring increases, and the contact load of the inner ring remains basically unchanged, so the radial stiffness increases, while the axial and angular stiffness decrease slightly. 

Therefore, reducing the ball diameter not only improves the speed performance, but also does not reduce the stiffness performance. This also proved theoretically that reducing the diameter ball is one of the current development trends of spindle bearings.

5. Influence of initial contact angle

Under positioning preload, the increase of the initial contact angle significantly reduces the radial stiffness, and the axial and angular stiffness increase significantly. This is because the initial contact angle increases, the radial component of the contact stiffness decreases, and the axial component increases. At the same time, the contact load decreases under the same preload.

Under constant pressure preloading, the increase of the initial contact angle significantly reduces the radial stiffness; at low speed, the axial and angular stiffness increase, and at high speed, there is basically no change. This is because the inner and outer rings allow axial displacement under constant pressure preload. 

In order to maintain the balance of force, the contact angle of the outer ring is almost close to 0, and the initial contact angle has little effect on the contact angle of the outer ring. Similarly, the initial contact angle increases, and the contact load decreases under the same preload.

Therefore, increasing the initial contact angle of a cylindrical roller bearing under positioning preload can increase the axial and angular rigidity, while increasing the initial contact angle under constant pressure preloading can not only increase the axial and angular rigidity, but reduce the radial rigidity.