Sliding bearing -- Characteristics and application of various sliding bearings
Time：2021-06-16
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Characteristics and application of various sliding bearings
Note:
1. fluid lubrication: the two surfaces of sliding pair are separated by a thick continuous fluid film, and the convex peak of the surface does not contact directly. Friction occurs only in the fluid interior, which is called fluid friction. At this time, the lubrication state is called fluid lubrication, also known as full lubrication.
2. no lubrication: there is no lubricant or protective film between the two surfaces of the sliding pair and the direct contact is called dry friction. In practice, there is no real dry friction. Generally speaking, dry friction bearing refers to the bearing without lubricant intervention but with natural pollution film.
3. boundary lubrication: there is a thin boundary film (adsorption film and chemical reaction film are collectively referred to as boundary membrane) between the two surfaces of sliding pair. The strength is low, and the direct contact between the convex peaks on the two surfaces cannot be avoided. However, the friction and wear conditions are greatly improved than dry friction, which is called boundary film), and the strength is low, and the direct contact between the convex peaks on the two surfaces cannot be avoided, But friction and wear are much better than dry friction, which is called boundary friction, and the lubrication state is called boundary lubrication.
4. mixed lubrication: when the two surfaces of the lubricating pair are in the mixed state of boundary friction and fluid friction, it is called mixed friction, and the lubrication state at this time is called mixed lubrication.
5. incomplete fluid lubrication: boundary lubrication or mixed lubrication is collectively referred to as incomplete fluid lubrication or incomplete fluid friction.
Characteristics and application of various sliding bearings
classification characteristic application
Bearings lubricated by incomplete fluid Radial sliding bearing Integral Generally, grease, oil rope and oil drop type are used for lubrication. The journal and bearing surface can not get enough lubricant and the liquid oil film is discontinuous. Simple structure has large friction factor and large wear The clearance between the shaft and the bearing shell cannot be adjusted, the structure is simple, and the journal can only be installed and removed from the shaft end It is generally used on machines with low speed, light load and allowable installation and removal
split The clearance between the shaft and the bearing shell can be adjusted and the installation is simple This is often used when the machine is difficult to install and dismantle
Self position type The bearing shells can be swayed in the bearing pedestal to adapt to the deflection caused by the bending of the shaft It is used for the case of deflection of transmission shaft, in which joint bearing is used to bear radial load at the joint of rod parts with swinging each other
Thrust sliding bearing The plain thrust sliding bearing is usually used in the incomplete liquid lubrication state due to the friction of liquid, and it needs to be used simultaneously with the centripetal bearing. For the occasion of bearing axial force
Powder metallurgy bearing (oil bearing) It has porosity, and the oil is stored in the pores. It can be lubricated automatically without lubricating oil for a long time, so it can ensure normal operation. However, due to its soft material, the bearing capacity is low For light load, low speed and difficult to refuel
Plastic bearing Compared with metal bearings, plastic bearings are light weight and easy to maintain. The pour stability is good, wear resistance and fatigue resistance are high, and it has the characteristics of vibration reduction, sound absorption, self lubrication, insulation and self extinguishing. But the thermal expansion coefficient is large, the thermal conductivity is low, the moisture absorption is large, the strength and dimension stability are not as good as that of metal It is used for places with low speed or good heat dissipation, the working temperature shall not exceed 65 ℃ and the instantaneous working temperature shall not exceed 80 ℃
Rubber bearing It can absorb vibration and impact force, and it is wear-resistant and corrosion-resistant in the environment with impurities, but its unit strength is lower than that of metal and poor heat resistance, which is not suitable for use in high temperature and in the environment in contact with oil or organic solvent Used in the vibration reduction and corrosion environment of the bearing in the ship shaft pipe
Wood bearing The wood bearing is light and cheap, can absorb impact, and has little deflection sensitivity to the shaft, but it has low strength, poor heat conductivity, humidity resistance and wear resistance It is used for vibration reduction of light load, such as circular disk rake bearing of agricultural machinery, bearing of large grain ore conveying pump, etc
Fluid lubricated bearing Hydrodynamic bearing The journal and the bearing working surface are completely separated by oil film. The dynamic bearing must have: ① the bearing has enough speed; ② There is enough oil supply, and the lubricating oil has a certain viscosity; ③ There is a proper clearance between the journal and the bearing working surface. The multi oil wedge dynamic bearing can meet the high precision rotation requirements of the shaft, and has a long life For high speed and high precision machinery, such as bearings of centrifugal compressors, etc
Hydrostatic bearing The bearing film of bearing journal and bearing is completely separated by the bearing film under certain pressure supplied by the outside world. The formation of oil film is not limited by relative sliding speed, and has a large bearing capacity under various speeds (including zero speed). The shaft has good stability, can meet the high precision rotation requirements of the shaft, and has small friction factor, high mechanical efficiency and long life It is mainly used for: ① the places where the oil film weight is difficult to form at low speed, such as vertical lathe, gantry horizontal milling, heavy motor, etc; ② High rotation accuracy required
Pneumatic and static pressure bearings Pneumatic pressure and static pressure bearing, using air or other gases as lubricant, have small friction factor and high mechanical efficiency, which can meet the requirements of high-speed operation Gas bearing used as gyro rotor and TV recorder bearing
Non lubricated bearing Plastic, carbon graphite bearing Run without grease or grease Less application
other Solid lubricated bearing Lubrication with solid lubricants such as graphite, molybdenum disulfide, phthalocyanin dye, polytetrafluoroethylene and so on It is used in special working conditions such as extremely low temperature, high temperature, high pressure, strong radiation, space and vacuum
Magnetic flow bearing static bearing magnetic bearing To suspend the shaft with a magnetic fluid as a lubricant, to suspend the shaft with a magnetic field It is mostly used in high speed machinery and instruments
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