There are usually three ways of guiding the bearing cage: rolling element guiding, inner ring guiding and outer ring guiding.

As an important part of the bearing, the cage plays the role of guiding and separating the rolling element, so as to reduce the friction heat of the bearing, optimize the load distribution of the rolling element and improve the lubrication.

The guiding role of the cage actually refers to the correction of the running trajectory of the rolling element, which is achieved by the collision between the cage and the surrounding parts. Three cage guidance methods may appear in different types of bearing structure design, which have bearing performance needs, but also have the bearing itself design, manufacturing and economic reasons.

1 Rolling element guidance

The most common guide structure for bearings is the rolling element guide. The bearing cage guided by the rolling body is located in the middle part of the rolling body, and the cage and the inner and outer rings of the bearing do not contact and collide. The collision between the cage and the roller in rotating operation automatically corrects the movement of the rolling body, and at the same time, the rolling body is separated in a certain equal spacing position.

Using rolling body guidance, the cage and the inner and outer ring of the guard surface are not in contact, the guide contact surface is small, the cage can withstand less impact capacity. When the bearing speed is very high or the rolling speed increases, the rotation will be unstable.

The contact surface clearance of the rolling body guided by the cage is large, and it is easy to be affected by impact and vibration load. Therefore, although the rolling body guiding is the most common cage guiding method, it is only suitable for the design of medium speed and medium load structure, but also suitable for the general working environment such as low vibration and low acceleration.

2 Outer guide

The bearing cage guided by the outer ring is located on the side of the rolling body near the outer ring. When the bearing is running, the bearing cage may collide with the outer ring, thus correcting the position of the cage. The outer ring guide has higher guiding accuracy than the rolling body guide, and the outer ring guide is generally suitable for high speed, vibration and acceleration.

Because it is the shoulder guide, in order to ensure the guiding accuracy and reduce the friction coefficient between the cage and the shoulder, the shoulder needs to be ground, and oil lubrication is the best lubrication method.

The contact surface of cage outer ring is larger than that of rolling body, and the contact stress is reduced under the same load. It can design smaller clearance of the guide contact surface, and the cage life will be better than the rolling element guide and the inner ring guide under the impact and vibration load conditions.

For this reason, the guiding design of the outer ring cage is commonly used in the bearing high-speed working conditions or the impact load and vibration load.

3 Inner ring guide

The bearing cage guided by the inner ring is located at the position of the rolling body close to the inner ring. When the bearing is running, the cage may collide with the shoulder position of the inner ring stop, so as to correct the position of the cage, so as to achieve the purpose of isolating the rolling body and guiding the normal rotation of the rolling body.

In order to ensure the guiding accuracy and reduce the coefficient of friction between the cage and the shoulder, the inner ring shoulder also needs grinding, and the higher processing accuracy is very necessary. The inner ring guiding lubrication method can be oil lubrication or grease lubrication.

The common bearing working condition is that the bearing outer ring is static, the inner ring is generally rotating ring, when the shaft and the inner ring rotate there is a dragging torque to drive the rolling body to rotate, if the bearing load is unstable or the load is light, there will be skid phenomenon. When the cage inner ring is used to guide, an oil film is formed on the guiding surface of the cage. The friction of the oil film drags power to the cage in the non-load area, thereby increasing the additional driving torque of the cage on the rolling body, which can prevent skidding and reduce wear.

Inner ring guidance is common in medium and heavy series bearings, large bearings or solid mechanism cage designs and conditions.

4 Cage guide clearance and pocket clearance control

Rolling bearings are widely used, and cage clearance directly affects bearing lubrication, oil film, heat, noise and cage stability. If the cage clearance is not well controlled, it will not only cause instability of the bearing cage and the rolling body, but also lead to a rapid increase in the collision force and friction of the bearing ring, eventually leading to the damage of the cage. Reduce the service life of bearings.

Cage clearance factors affecting the normal use of rolling bearings are mainly reflected in the cage hole clearance and cage guide clearance design is reasonable. If the cage guide clearance is given, increasing the hole clearance will make the stability of the cage worse, and the inner ring guide is more likely to make the cage unstable than the outer ring guide.

Both guide clearance and pocket clearance affect the wear of cage and steel ball, but the influence of guide clearance on cage wear is more significant than that of pocket clearance. When the guide clearance is small, the wear of the cage guide surface is serious. With the increase of the guide clearance, the wear of the cage guide surface is gradually reduced. At the same time, the guide gap affects the cage hole wear, when the guide gap design is not reasonable, will aggravate the cage hole wear; On the contrary, the wear degree of cage guide surface and hole decreases gradually with the increase of hole clearance.

The factors affecting the stable operation of the cage include load, speed, cage clearance, channel curvature, etc. Generally, the increase of axial load has little effect on the stability of cage. The increase of radial load will reduce the stability of cage. The movement of cage tends to be stable after the speed increases. The increase of clearance between cage and guide surface and rolling element will destroy the stability of cage.