Keep frame (that is, bearing keep frame, also known as bearing keeper), refers to partly wrapped all or part of the rolling body, and with the movement of the bearing parts, to isolate the rolling body, usually also guide the rolling body and will keep it in the bearing.
Rolling bearing in the work, especially the load complex and high-speed rotation, bearing keeper to withstand a large centrifugal force, shock and vibration, bearing keeper and rolling body between the existence of large sliding friction, and generate a lot of heat. The result of the combined effect of force and heat can lead to cage failure, which can cause serious bearing keeper burns and fractures. Therefore, the bearing keeper material is required to have good thermal conductivity, good wear resistance, small friction coefficient, small density, certain strength and toughness of the fit, good elasticity and stiffness. The expansion coefficient is similar to that of the rolling body. As well as good processing process performance. In addition, the cage is also subject to chemical media, such as lubricants, lubricant additives, organic solvents and coolants, etc.
Commonly used cage according to the type of material divided into metal cage and non-metallic cage. In addition, there are composite material cages. Special purpose bearing cage should also meet the requirements of special working conditions. Such as high temperature resistance, corrosion resistance, self-lubrication (used in vacuum) or non-magnetic, etc.
Due to high strength, good toughness, easy processing and other characteristics, steel cage material in rolling bearings are commonly used. Often 08 and 10 high-quality carbon steel sheet cold stamping and become. In addition, can also be used according to the needs of other mechanical processing methods to obtain. Commonly used steel cage materials are also 20, 30, 45, 0Cr18Ni9, 1Cr18Ni9Ti, 40CrNiMo, ML15, ML20, etc.. Steel cages are generally heat treated to eliminate stress and restore plasticity. Including high temperature tempering, recrystallization annealing, etc. In order to reduce the coefficient of friction of steel cages, the finished cage must be surface treated if necessary.
Unlike steel, non-ferrous metals have their own special properties, for example, aluminium alloy has the characteristics of low density, good thermal conductivity and good corrosion resistance; copper alloy has the characteristics of good thermal conductivity, small coefficient of friction, good formability and high temperature; zinc aluminium alloy has the advantages of low cost, small density and excellent performance.
Non-metallic bearing keeper materials are mainly polymers and their composite materials, including nylon, phenolic tape, polytetrafluoroethylene, etc. Polymer materials have good strength and elasticity matching. Good sliding properties make the polymer cage in the relative motion with the lubricated rolling element surface only a small friction, which can make the bearing heat and wear to a minimum. In conditions of lubricant deficiency, the polymer cage still has excellent kinematic properties. This ensures that the bearing can continue to operate for a period of time without damage. Due to the low density of polymers, cages made from them have a low inertia.
In addition to the pure material used in the manufacture of cages, the polymer material is also modified. Other materials are used for filling or reinforcement.
For engineering plastic cages, the performance of each manufacturer varies slightly, but is largely similar. This type of cage is light in weight and suitable for high speed applications. And the failure mode of this cage is not sudden bursting, so it is more suitable for some occasions where sudden stoppage is not allowed. However, for mining machinery, this type of cage is not suitable for use due to safety considerations, because its damage does not occur suddenly, but is completely damaged as the temperature rises gradually to a certain level, which can be dangerous for explosive situations. At the same time this type of cage has a temperature limit, generally -40 to 120°C.
For brass cages, there is basically no hindrance, but they are not suitable for environments with ammonia. Generally small bearings do not use brass cages.
For steel bearing keeper, there are also no restrictions, but steel bearing keeper are not used for large bearings.