What is an oil-free bearing? Does it really need to be lubricated?

The bearing is a component that fixes and reduces the friction coefficient of the load during the mechanical transmission process. Its main function is to support the mechanical rotating body to reduce the friction coefficient of the mechanical load during the transmission of the equipment. According to the different friction properties of moving elements, bearings can be divided into rolling bearings and sliding bearings.
In order to ensure the smooth and reliable operation of the bearing, most of the bearings are lubricated with lubricating oil. The purpose is to reduce the internal friction and wear of the bearing and prevent sticking: prolong the fatigue life of the bearing; dissipate the frictional heat or heat transferred from the outside ; At the same time the oil film also has a certain ability to absorb vibration. However, one of the biggest disadvantages of adding lubricating oil is that it needs good sealing performance, otherwise it will cause leakage, and some equipment with special requirements does not allow lubricating oil leakage, so people use other lubricating materials to replace lubricating oil and invented Oil-free bearings not only have the advantages of lubricated bearings, but also prevent environmental pollution caused by leakage.

2 classification:
Oil-free bearings mainly include gas-lubricated bearings, composite-material-lubricated bearings, and water-lubricated bearings.
1. Gas-lubricated bearings:
Gas-lubricated bearings are sliding bearings that use gas as a lubricant. The most commonly used gas lubricant is air, and nitrogen, argon, hydrogen, helium, etc. can also be used as needed. The mechanism of the gas-lubricated bearing to form a bearing gas film is the same as that of the liquid-lubricated bearing. Gas-lubricated bearings make use of gas transmission, diffusivity, viscosity and thermal conductivity, adsorption and compressibility. Make it between the friction pairs, under the action of hydrodynamic pressure effect, static pressure effect and squeeze effect, form a complete air film, which has the function of supporting load and reducing friction.

Gas-lubricated bearings are generally divided into three types: gas dynamic pressure bearings, gas static pressure bearings and gas squeeze bearings. The actual lubrication state of the bearing often exists in the form of dynamic, static pressure, dynamic, extrusion, static, extrusion, and mixed lubrication of dynamic, static and extrusion. The mechanism of the gas-lubricated bearing to form a bearing gas film is the same as that of the liquid-lubricated bearing.

2. Composite lubricated bearings

Due to the requirements of special production processes, some key equipment of industrial and mining enterprises operates under extremely harsh working conditions. Due to the heavy equipment, high ambient temperature, large dust or acidic corrosive gas in the air, etc. There are many problems to the lubrication of the equipment, and the friction and wear are serious. At present, most of them still use traditional oil and grease lubrication. In fact, these industrial and mining conditions have exceeded the scope of oil and grease lubrication. It is very prone to bite or seizure of bearings and other friction pairs. Causes severe wear and damage of parts, often resulting in equipment outages.

The composite material used in the composite lubricated bearing is a new type of extreme pressure resistant solid lubricating material, which is composed of a metal substrate and a solid lubricant paste embedded in the hole or groove of the substrate. The metal substrate bears most of the load during the friction process. After friction, the solid lubricant in the hole or groove is transferred or reversely transferred to the friction surface, and a solid transfer film with good lubrication, firm adhesion and uniform coverage is formed on the friction surface, which greatly reduces friction and wear. As the friction progresses, the embedded solid lubricant is continuously provided on the friction surface, ensuring good lubrication of the friction pair during long-term operation.

3. Water-lubricated bearings
Since the emergence of the oil resource crisis in the 1970s and people's attention to environmental protection in recent years, hydraulic transmission technology has faced severe challenges, and water-lubricated bearings have gradually been promoted and applied. Water-lubricated bearings use water as the lubrication and working medium, which not only saves a lot of oil, but also avoids environmental pollution to traditional bearings that use oil as the lubricating medium. At the same time, water has the advantages of non-polluting, wide sources, safety and flame retardancy, and is an ideal lubricating medium. It can also reduce the friction, wear, vibration, noise, non-functional consumption and other key problems of the friction pair. Therefore, the research of water-lubricated bearings has important theoretical research and application value for improving mechanical efficiency and protecting the environment, and it has become a hot spot in various countries.

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