Bearing cage materials mainly include stamped steel, machined steel, stamped brass, machined brass, polymeric materials, etc.
Stamping steel material has high strength and can reduce friction and wear through surface treatment; Cutting steel materials are usually used for oversize bearings or not suitable for brass cages; Stamped brass materials are generally used for some small and medium-sized bearings; Cutting brass material is usually not affected by bearing lubricant and can be cleaned with ordinary lubricant. Brass should not be used at working temperature above 250 ℃; Compared with metal cages, polymer materials (nylon 66, nylon 46, etc.) have the advantages of better toughness, more wear resistance, impact resistance, acid resistance, corrosion resistance, etc.
Bearing cage
The bearing cage is mainly divided into three types: punch cage, solid cage and strut cage.
1. The stamping cage has the advantages of light weight, large internal space and convenient lubricant addition;
2. Generally, the solid cage is allowed to rotate at a higher speed. When the bearing moves in the form of motion other than rotation at the same time, especially at high speed, the machined metal cage should also be used;
3. The column cage adopts a pin through the roller with holes, and the two ends of the pin are fixed on the washer. It has the characteristics of light weight and can accommodate more rollers. It is generally used for large roller bearings.
There are three ways to guide the bearing cage: roller guide, inner ring guide and outer ring guide.
Rolling body guide:
The standard structure of general design is rolling body guidance, such as short cylindrical roller bearing, which adopts rolling body guidance. The cage does not contact the retaining surface of the inner and outer rings. The cage can be universal, but when the rolling body speed increases at high speed, the rotation is unstable. Therefore, the rolling body guidance is suitable for medium speed and medium load, such as gear box bearing. The bearing cage guided by the rolling element is located in the middle of the rolling element. There is no contact and collision between the cage and the inner and outer rings of the bearing. The collision between the cage and the roller corrects the roller movement, and separates the rollers at a certain equal distance.
Outer circle guide:
The outer ring is generally stationary, and the guide of the outer ring is convenient for lubricating oil to enter the guide surface and raceway. The high-speed gearbox is lubricated by oil mist, and the oil will be squeezed out by the guide of the rotating inner ring. 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 bearing outer ring to correct the cage position. The outer ring guide is generally used under the condition of high speed and stable load. Take the cylindrical roller bearing for example, it only bears a fixed axial load. When rotating, the rotational speed of each rolling element changes little, and the rotation of the cage will not be unbalanced.
Inner circle guide:
The inner ring is generally a rotating ring, and provides the rolling element to drag the moment when rotating. If the bearing load is unstable or light, it will slip. When the cage is guided internally, an oil film is formed on the guide surface of the cage. Because the friction of the oil film gives the cage a drag force in the inner circle of the non-load zone, which increases the additional driving torque of the cage to the rolling body, and can prevent slipping. The bearing cage guided by the inner race is located near the inner race of the rolling body. When the bearing is running, the cage may collide with the inner race of the bearing, thus correcting the cage position.
The cage can evenly and orderly distribute the inner ring, outer ring and rolling element, and a slight error can easily shorten the service life of the bearing, or even damage it.
The bearing cage is damaged due to:
1. Insufficient bearing lubrication
During the use of the bearing, the lubricating oil or grease was not added in time, and the model of the lubricating oil or grease used was incorrect.
2. Impact load of bearing
The intense vibration in the impact load will cause the impact between the rolling body and the cage.
3. Bearing cleanliness
The bearing is not well sealed in the bearing box, and dust will enter, which will cause friction between the rolling element and the cage, thus damaging the cage.
4. Installation problems
If the bearing is installed incorrectly, the cage will be damaged during installation.
5. Bearing creep phenomenon
Creep refers to the sliding phenomenon of the ferrule. In the case of insufficient interference of the mating surface, the load point moves to the surrounding direction due to the sliding, resulting in the deviation of the ferrule from the axis or the shell to the circumferential direction
6. Abnormal load of bearing cage
Inadequate installation, inclination, excessive interference, etc. are easy to cause clearance reduction, increase friction heat generation, surface softening, and premature abnormal peeling. With the expansion of the peeling, the peeling foreign matter enters the cage pocket hole, resulting in the cage operation retardation and additional load, which aggravates the wear of the cage. Such a deteriorating cycle may cause cage fracture.
7. Material defect of bearing cage
Cracks, large heterogeneous metal inclusions, shrinkage holes, bubbles and riveting defects, lack of nails, cushion nails or gaps on the joint surface of the two halves of the cage, serious riveting injuries, etc. may cause cage fracture.
8. Invasion of hard foreign matters in bearings
The invasion of foreign hard foreign matters or other foreign matters aggravates the wear of the cage. Solve the above reasons, and the bearing life will be very long. The reason for many bearing damage is not that the bearing life is expired, but that caused by many external environments, such as insufficient lubrication, dust entry, installation error, excessive load, high temperature, and incorrect coupling.
9. Other reasons
The misalignment of the coupling results in bearing deflection and uneven stress; The belt is installed too tight; Environmental problems and so on may damage the bearing or cage.