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Generally, lubricating grease, oil rope and oil dripping are used for lubrication. The shaft diameter and bearing surface can not get enough lubricant, and the liquid oil film is discontinuous. The utility model has the advantages of simple structure, large friction coefficient and large wear.
a. Integral type
The clearance between shaft and bearing bush 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 assembly and disassembly.
b. Subdivision
The clearance between shaft and bearing bush can be adjusted and the installation is simple. This method is often used when it is difficult to assemble and disassemble the machine.
c. The bearing bush can swing properly in the bearing seat to adapt to the deflection caused by the bending of the shaft. It is used when the transmission shaft is skewed, in which the articulated bearing is suitable for bearing radial load at the joint of swinging rods.
Because of the lack of liquid friction, the common plane thrust sliding bearing is in the state of incomplete fluid lubrication, which needs to be used together with the radial bearing. Used for bearing axial force.
It is porous, and the oil is stored in the pores. It can automatically lubricate without adding lubricating oil for a long time to ensure normal operation. However, due to its soft material, it has low load bearing capacity. It is used under light load, low speed and difficult to refuel.
Compared with metal bearings, plastic bearings are light and easy to maintain. It has good chemical stability, high wear resistance and fatigue strength, and has vibration damping, sound absorption, self lubrication, insulation and self extinguishing. However, the thermal expansion coefficient is large, the thermal conductivity is low, the moisture absorption is large, and the strength and dimensional stability are not as good as metals. For places with low speed or good heat dissipation, the working temperature should not exceed 65 ℃ and the instantaneous working temperature should not exceed 80 ℃.
It can absorb vibration and impact force and has good wear and corrosion resistance in the environment with impurities, but its unit strength is lower than that of metal and poor heat resistance. It is not suitable for use in the environment of high temperature and contact with oil or organic solvents. Bearings used in ship shaft tubes must work in vibration damping and corrosive environment.
Wood bearing is light and cheap, can absorb impact, has little sensitivity to shaft deflection, but has low strength, poor thermal conductivity, moisture resistance and wear resistance. It is used for vibration reduction under light load, such as circular rake bearing of agricultural machinery, bearing of large ore conveying pump, etc.
The journal is completely separated from the bearing working surface by oil film. The dynamic pressure bearing must have: ① the bearing has sufficient speed; ② There is enough oil supply and the lubricating oil has a certain viscosity; ③ Proper clearance shall be provided between the journal and the working surface of the bearing. Multi oil wedge hydrodynamic bearing can meet the requirements of high-precision rotation of shaft and has long service life. It is used for high-speed and high-precision machinery, such as bearings of centrifugal compressors.
The journal and bearing are completely separated by the bearing oil film of a certain pressure supplied from the outside. The formation of the oil film is not limited by the relative sliding speed, and has a large bearing capacity at various speeds (including zero speed). The shaft has good stability, can meet the requirements of high-precision rotation of the shaft, small friction coefficient, high mechanical efficiency and long service life.
Gas dynamic pressure and static pressure bearings, using air or other gases as lubricants, have small friction coefficient and high mechanical efficiency, which can meet the requirements of operation. Gas bearing is used as gyro rotor and TV recorder bearing.
(plastic, carbon graphite bearing) Operate without lubricating oil or grease. Less application.
(1) Solid lubricated bearing
It is lubricated with solid lubricants such as graphite, molybdenum disulfide, phthalocyanine dye and polytetrafluoroethylene. It is used under special working conditions such as extremely low temperature, high temperature, high pressure, strong radiation, space, vacuum and so on.
(2) A. magnetic fluid bearing uses magnetic fluid as lubricant;
b. Electrostatic bearing {uses electric field to suspend the shaft;
c. Magnetic bearings {use a magnetic field to suspend the shaft.
It is mostly used in high-speed machinery and instruments.