As an important part of the bearing, the cage plays the role of guiding and separating the rolling elements. The guiding effect of the cage actually refers to the correction of the running of the rolling elements. This correction is achieved by the collision of the cage and surrounding components.
There are three general guiding methods for bearing cages: rolling element guiding, inner ring guiding, and outer ring guiding.
Roller guide:
The standard structure of general design is rolling element guidance, such as short cylindrical roller bearings, which are guided by rolling elements, and the cage and the rib surfaces of the inner and outer rings are not in contact. The rotation is unstable, so the rolling element guidance is suitable for medium speeds and medium loads, such as gearbox bearings.
The bearing cage guided by the rolling elements is located in the middle of the rolling elements. There is no contact and collision between the cage and the inner and outer rings of the bearing, and the collision between the cage and the rollers corrects the motion of the rollers, and at the same time separates the rollers at a certain equal distance.
Outer ring guide:
The outer ring is generally stationary, and the guide of the outer ring facilitates the entry of lubricating oil into the guide surface and raceway. The high-speed gearbox is lubricated by an oil mist, which is guided by the rotating inner ring to squeeze the oil out. The bearing cage guided by the outer ring is located on the side of the rolling body close to the outer ring. When the bearing is running, the bearing cage may collide with the bearing outer ring to correct the position of the cage.
The outer ring guide is generally used in the case of high speed and stable load. Take cylindrical roller bearing as an example. It only bears a fixed value of axial load. When rotating, the speed of each rolling element changes little, and the rotation of the cage nor unbalanced.
Inner ring guide:
The inner ring is generally a rotating ferrule, and provides rolling elements to drag torque during rotation. If the bearing load is unstable, or the load is light, slippage will occur.
However, the cage adopts internal guidance, and an oil film is formed on the guide surface of the cage. Due to the friction of the oil film, the friction of the oil film gives the cage a drag force in the non-load area, which increases the additional driving torque of the cage to the rolling elements, and can prevent slipping.
The bearing cage guided by the inner ring is located at the position where the rolling elements are close to the inner ring. When the bearing is running, the cage may collide with the inner ring of the bearing, thereby correcting the position of the cage.
The three cage guidance methods may appear in different types of bearings, including performance reasons, as well as the design and manufacture of the bearing itself. Engineers can choose according to their needs. But sometimes engineers have no choice. In any case, the different properties of different cage guidance methods should be noted.
The difference between the three cages is mainly manifested in: The performance difference of the bearings of the three cage guiding methods is mainly manifested in the difference of the rotational speed performance under different lubrication conditions.
All three cage types of bearings can be used for oil and grease lubrication.