Influence of bearing pre tightening mode and rotating speed

There are two ways of axial preload of bearing, one is constant pressure preload, the other is positioning preload. Under constant pressure preloading, the radial stiffness of the bearing increases slightly with the increase of the rotating speed, while the axial and angular stiffness decreases rapidly. The radial, axial and angular stiffness of the bearing increase rapidly with the increase of the rotating speed, but the increase of the axial and angular stiffness is relatively gentle.

Influence of preload
With the increase of preload, the radial, axial and angular stiffness of the bearing increase slightly, but the effect is very small. Compared with the fixed pressure preloading, this effect is more significant. The reason is that the increase of preload makes the contact angle of inner and outer rings increase, and also makes the contact load increase, so that the radial, axial and angular stiffness increase. However, the change of contact load and contact angle caused by preload is smaller than that caused by rotation speed and part displacement, so the influence on bearing stiffness is limited. This is also the reason why the change of the positioning preload is less than that of the constant pressure preload.
Influence of channel curvature radius
With the increase of the curvature radius of the inner and outer raceway, the radial, axial and angular stiffness decreases, but this effect is very small, only the change of the stiffness is slightly obvious under the positioning preload, which is due to the increase of the curvature radius of the raceway and the increase of the contact deformation. Therefore, the influence of the curvature radius on the stiffness of the channel can be ignored.
The influence of the number of balls
The radial, axial and angular stiffness increase slightly with the increase of the number of balls. The stiffness increases with the increase of the number of balls, but the contact load decreases with the increase of the number of balls under the same preload. When the speed increases to a certain value, the axial and angular stiffness decreases, but the change is very small. The reason is that under the condition of constant pressure preloading, although the contact load of the inner ring decreases, the contact angle of the inner ring decreases with the increase of the number of balls. Therefore, when the number of balls increases, the preload should be increased accordingly. Only when the contact load is the same, can the stiffness of the bearing be increased by increasing the number of balls.
The influence of ball path
The radial, axial and angular stiffness increase slightly with the increase of ball diameter. With the increase of ball diameter, the centrifugal force of the ball increases, the contact angle of the outer ring decreases, and the contact angle of the inner ring increases, but at the same time, the contact load of the inner ring and the outer ring increases. The change of centrifugal force has little effect on the contact load, so the change of ball diameter has little effect on the stiffness. Under constant pressure preloading, the radial stiffness increases with the increase of ball diameter, while the axial and angular stiffness decreases, but the influence is small. The reason is that the centrifugal force of the ball increases with the increase of the ball diameter, the contact angle of the inner ring and the outer ring decreases, and the contact load of the outer ring increases, while the contact load of the inner ring is basically unchanged, so the radial stiffness increases, while the axial and angular stiffness decreases slightly. Therefore, reducing the ball diameter not only improves the speed performance, but also does not reduce the stiffness performance. This also proves theoretically that reducing ball is one of the development trends of spindle bearing at present.
Influence of initial contact angle
With the increase of initial contact angle, the radial stiffness decreases significantly, while the axial and angular stiffness increases significantly. This is due to the increase of the initial contact angle, the radial component of the contact stiffness decreases, the axial component increases, and the contact load decreases under the same preload. Under the condition of constant pressure preloading, the radial stiffness decreases significantly with the increase of initial contact angle; at low speed, the axial and angular stiffness increases, while at high speed, there is no change. In order to keep the force balance, the outer ring contact angle is almost close to 0, and the initial contact angle has no effect on the outer ring contact angle. Similarly, with the increase of initial contact angle, the contact load decreases under the same preload. Therefore, the axial and angular stiffness can be improved by increasing the initial contact angle under the positioning preload, while the radial stiffness can be reduced by increasing the initial contact angle under the constant pressure preload.

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