When the machine is running, according to the load acting on the cylindrical roller bearing relative to the rotation of the ring, the load on the ring can be divided into the following three types:
1. Partial load
The composite radial load acting on the cylindrical roller bearing is relatively static with the ring, that is, the direction of the load always acts on the local area of the ring raceway, which is the nature of the load that the ring bears. (The outer ring of the driven wheel of the car).
2. Cycle load
The composite radial load acting on the cylindrical roller bearing rotates relative to the ferrule, that is, the load sequentially acts on the entire circumference of the raceway of the ferrule, which is the nature of the load that the ferrule bears. (Inner ring of the driven wheel of the car).
3. Swing load
The composite radial load acting on the cylindrical roller bearing and the bearing ring oscillate relative to each other in a certain area, that is, its load vector often changes and acts on the local circumference of the ring raceway. The nature of the load.
Examples of swing load:
The bearing bears a radial load with a constant direction and a smaller rotating radial load. The combined radial load of the two changes in magnitude and direction. However, the composite radial load only swings in a section of the raceway of the non-rotating ferrule, and the nature of the load borne by the ferrule is the swing load.
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Selection principle of force and cooperation
1. Generally, an interference fit or a tighter transition fit should be selected for the matching between the cyclically loaded ferrule and the shaft (or housing hole). The size of the interference should not make the ferrule fit the shaft or the housing hole The principle of creeping phenomenon on the surface.
2. For the fit between the ferrule bearing the local load and the housing hole or shaft, a looser transition fit or a smaller clearance fit should be selected to allow the frictional moment between the raceways of the ferrule to drive the index and extend the cylindrical roller The service life of the bearing.
3. For the ferrule bearing the swing load, its fit tightness is between the cyclic load and the local load.
The influence of load on the size of the selected fit
The minimum interference between the cylindrical roller bearing ring and the shaft or housing hole is determined by the load.
When subjected to a heavier load or impact, the cylindrical roller bearing will cause greater deformation, reducing the actual interference between the joint surfaces and increasing the actual clearance inside the bearing. At this time, in order to make the cylindrical roller bearing operate normally , A larger interference fit should be selected. Similarly, with lighter loads, smaller interference fits can be selected.
For cylindrical roller bearings with large loads and high rotation accuracy requirements, in order to eliminate the effects of elastic deformation and vibration, clearance fits should be avoided.
For cylindrical roller bearings with light loads and higher rotation accuracy requirements, smaller clearance fits are often used.
The larger the size of the cylindrical roller bearing, the tighter the selected fit.
Hollow journals are better than solid journals, thin-walled shells are better than thick-walled shells, and light alloy shells are tighter than steel or cast iron shells.
The split shell has a looser fit than the integral shell, so as to prevent interference from clamping the outer ring of the bearing or even jamming the shaft.
In order to facilitate installation and disassembly, especially for heavy machinery, a loose fit should be used.
When the inner or outer ring of the bearing is required to move in the axial direction, the inner ring and the shaft or outer ring and the housing hole should be fitted with a looser fit.
Because the interference fit reduces the radial clearance of the cylindrical roller bearing, for example, when one of the two rings of the cylindrical roller bearing needs to use an extra large interference fit, the radial clearance should be larger than that of the basic group. Bearings.
The working temperature of cylindrical roller bearings is generally lower than 100°C. For bearings that work at high temperatures, the selected fit should be modified.