1. The inner and outer rings are not at the same rotation center, resulting in shaft deflection Shaft deflection is a common phenomenon in actual running bearings, and the deflection of the axis line is one of the main reasons for the failure of thrust bearings. The reasons for the misalignment between the bearing and the shaft are: (1) shaft tilt; (2) rotor installation error; (3) rotor manufacturing error; (4) thermoelastic deformation of the shaft, rotor and bearing during operation. The shaft deflection causes the oil film thickness, pressure distribution, and pad surface temperature of each tile to be different, which has a great influence on the oil film thickness and pressure distribution, but has little effect on the temperature distribution of the pad surface; the shaft deflection causes unevenness in the bearing The fluid dynamic pressure of the shaft causes the oil film force fluctuation on the shaft. As the degree of deflection increases, the fluctuation of the oil film force becomes more serious; in the state of full oil lubrication, a slight change in the deflection angle will cause obvious changes in the minimum oil film thickness and maximum pressure , but the maximum temperature of the tile surface changes little. To sum up, the shaft deflection causes the oil film thickness in the bearing to be uneven, which may cause the oil film to break and cause the bearing to fail. During installation, in order to maintain concentricity as much as possible, the best way is to adopt the shell with integral structure, and bore out two holes for installing the bearing at one time. If bearings of different sizes are installed on one shaft, the bearing holes on the casing should still be bored out at one time, and the bushing can be used to install bearings with smaller sizes. When the two bearing holes are divided into two shells, the two shells should be combined for boring. 2. The installation is not in place, there is deviation or it is not installed in the bearing position, resulting in too small bearing clearance During operation, the temperature of the shaft is generally higher than that of the outer ring, and the axial and radial thermal expansion of the shaft will be greater than the thermal expansion of the housing. If the bearing clearance is too small, it may cause seizure. 3. Too tight fit between the rotating ring and the fixed ring The selection of the type of bearing fit should be determined according to the type and size of the bearing, the magnitude and direction of the load, and the nature of the load. The correctly selected bearing fit should ensure the normal operation of the bearing and prevent the relative rotation between the inner ring and the shaft, the outer ring and the housing hole during operation. Generally speaking, when the direction of the working load is constant, the rotating ring has a tighter fit than the fixed ring, because the rotating ring bears the rotating load, while the non-moving ring bears the local load. When the speed is higher, the load is larger and the vibration is stronger, the tighter fit should be selected. A tighter fit should also be used when the bearing is mounted on a thin-walled housing or hollow shaft. However, too tight fit is unfavorable. At this time, the internal clearance of the bearing may be reduced or even completely disappeared due to the elastic expansion of the inner and outer rings and the contraction of the outer ring, or it may be due to the irregularity of the mating shaft and the surface of the seat hole. Irregular deformation of the inner and outer rings of the bearing caused by the shape or uneven rigidity will destroy the normal operation of the bearing. A tight fit can also make assembly and disassembly difficult, especially with heavy machinery. 4. During the installation process, the pre-tightening force is too large The pretightening force is to use the external force applied during the assembly process to give the bearing an appropriate pretightening load. If the pretightening force is too small, there will be a gap when the bearing is working, resulting in a decrease in support stiffness and rotation accuracy, causing vibration and noise. Excessive pre-tightening force will increase the friction between the rolling elements and the raceway of the inner and outer rings, and the temperature will rise too fast during operation, which will reduce the transmission efficiency and reduce the bearing life. Only by applying proper pre-tightening force can the axial clearance be eliminated, the reverse error reduced, the rotation accuracy of the shaft system improved, and the vibration and noise reduced. Give the bearing an appropriate preload, even if the relative position of the bearing changes slightly after a certain period of operation, the pre-applied load can still keep the position of the inner and outer rings of the bearing stable, so the control of the preload during installation is very important.  

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