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When selecting bearing clearance, the following aspects should be considered:
1. Working conditions of bearing, such as load, temperature, speed, etc;
2. Requirements for bearing performance (rotation accuracy, friction torque, vibration and noise);
3. When the bearing is in interference fit with the shaft and housing hole, the bearing clearance decreases;
4. When the bearing works, the temperature difference between the inner and outer rings leads to the Aspects reduction of bearing clearance;
5. Due to the different expansion coefficients of shaft and shell Aspects materials, the bearing clearance decreases or increases.
6. According to the application experience, the suitable working clearance of ball bearing is close to zero; Roller bearings shall have a Aspects small amount of working clearance. In the parts requiring good support rigidity, the bearing is allowed to have a certain amount of preload.
In particular, it is pointed out that the so-called working clearance refers to the clearance of the bearing under actual operating conditions. There is also a clearance called original clearance, which refers to the Aspects clearance before the bearing is installed.
The original clearance is greater than the installation clearance. Our choice of clearance is mainly to select the Aspects appropriate working clearance. Valve inlet pump
basic group (group 0), small clearance auxiliary group (groups 1 and 2) and large clearance auxiliary group (groups 3, 4 and 5). During selection, under normal working conditions, the basic group should be preferred, so that the bearing can get appropriate working clearance.
When the basic group cannot meet the use requirements, the auxiliary Aspects group clearance shall be selected. The large clearance auxiliary group is applicable to the occasions where the interference fit is adopted between the bearing and the shaft and the shell hole,
the temperature difference between the inner and outer rings of the v bearing is large, the deep groove ball bearing needs to bear large axial load or improve the centering performance, and it is required to increase the limit speed and reduce the bearing friction torque;
The small clearance auxiliary group is suitable for occasions requiring high Aspects rotation accuracy, strictly controlling the axial displacement of the housing hole, and reducing vibration and noise.
Clearance is an important factor for the normal operation of rolling bearing, which is divided into axial clearance and radial clearance. Selecting proper clearance can make the load distribute reasonably among the bearing rolling elements;
It can limit the axial and radial displacement of the shaft (or shell) and ensure the rotation accuracy of the shaft; It can make the bearing work normally at the specified temperature;
Reducing vibration and noise is conducive to improving the service life of bearings. Therefore. When selecting bearings, appropriate bearing clearance must be selected.
The microstructure overheating after quenching can be observed from the rough mouth of bearing parts. However, the microstructure must be observed to determine the degree of overheating. If coarse acicular martensite appears in the quenched structure of GCr15 steel,
it is quenched superheated structure. The cause may be the overall overheating caused by too high quenching heating temperature or too long heating and holding time; It may also be due to the serious banded carbide in the original structure and the formation of local martensite acicular coarseness in the low-carbon region between the two bands, resulting in local overheating.
The retained austenite in the superheated structure increases and the dimensional stability decreases. Due to the overheating of quenching structure and the coarseness of steel crystal, the toughness of parts will be reduced, the impact resistance will be reduced, and the service life of bearings will also be reduced. Serious overheating may even cause quenching cracks.