There are two ways of bearing axial pre-tightening force, one is constant pressure pre-tightening force, and the other is positioning pre-tightening force. Under constant pressure preload, the radial stiffness of the bearing increases slightly with the increase of speed, while 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 the preload, the radial, axial and angular stiffness of the bearing 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 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 bearing is limited. This is also the reason why the change under positioning preload is smaller than that under constant pressure preload.
2. The influence of the radius of curvature of the channel
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 curvature of the channel. The increase in radius increases the amount of contact deformation. Therefore, when choosing the radius of curvature of the channel, its influence on the stiffness can be ignored.
3. The influence of the number of balls
Under positioning preload, the increase in the number of balls causes a slight increase in 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 action can increase the stiffness of the bearing, but less.
Under constant pressure preloading, the increase in the number of balls causes a significant increase in the radial stiffness, but when the speed increases to a certain value, the axial and angular stiffness decreases, 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 rigidity of the bearing increase significantly, while the axial and angular rigidity are slightly increased. There is a reduction.
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 bearing.
4. The shadow of the ball diameter
Under positioning pretension, 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 bearing increases. Since the change of centrifugal force under positioning preload has little effect on the contact load, the change of ball diameter has little effect on the stiffness.
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 rigidity increases, while the axial and angular rigidity decreases slightly. . Therefore, reducing the ball diameter not only improves the speed performance, but also does not reduce the stiffness performance. This also proves from theory that reducing the diameter of the ball is one of the current development trends of spindle bearings.
5. The 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 under constant pressure preload, the inner and outer rings allow axial displacement. In order to maintain the balance of forces, 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 the bearing under positioning preload can increase the axial and angular rigidity, while increasing the initial contact angle under constant pressure preloading not only fails to increase the axial and angular rigidity, but reduces the radial rigidity.
Post time: Aug-26-2021