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Roller bearing

January 16, 2020

Roller bearing is a kind of rolling bearing, which is widely used in modern machinery. It relies on the rolling contact between the main components to support the rotating parts. Roller bearings are now mostly standardized. The roller bearing has the advantages of small starting torque, high rotation accuracy and convenient selection.
Chinese name roller bearing foreign name roller bearing industry mechanical equipment Pinyin

Rolling bearings are divided into ball bearings and roller bearings by rolling force.
Roller bearings rely on rolling contact between the main parts to support the rotating parts. Different roller bearings can withstand different radial and axial forces. When selecting a roller bearing, the choice should be made according to specific working conditions.
Roller bearings mainly include spherical roller bearings, thrust spherical roller bearings, tapered rollers and cylindrical roller bearings. [1]
Classification performance characteristics
Table 1 Types, main performances and characteristics of roller bearings
Type code Simple diagram Type name Structure code Performance and characteristics
2
 
Spherical roller bearings 20000 Because the outer surface is a spherical surface centered on the bearing's midpoint, it can automatically align itself. It is a radial bearing and allows the inclination of the inner ring to the outer ring axis ≤ 1.5 ° ~ 2.5 °. [1]
2
 
Thrust spherical roller bearings 29000
It is a radial thrust bearing, but the radial load must not exceed 55% of the axial load.
To ensure its normal operation, a certain axial preload is generally required.
The allowable deviation of the shaft ring from the seat ring axis is ≤1.5 ° ~ 2.5 °. [1]
3
 
Tapered Roller Bearings
30000 (α = 10 ° ~ 18 °)
(3000B is a tapered roller bearing with a large contact angle, α = 27 ° ~ 30 °)
It is a radial thrust bearing (type 30,000 is mainly radial load and 3000B is mainly axial load).
The outer ring can be detached, and the bearing clearance during installation. Generally used in pairs. [1]
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Cylindrical Roller Bearings
Figure 1: Outer ring without retaining ring
Figure 2: Inner ring without retaining ring
Figure 3: Single ring on the inner ring
Figure 1: N0000
Figure 2: NU0000
Figure 3: NJ0000
It belongs to radial bearing. The outer ring (or inner ring) can be separated, so it cannot bear axial load.
The roller is axially positioned by the ribs of the inner ring (or outer ring), and a small amount of axial misalignment of the inner and outer rings is allowed during operation.
The allowable deflection of the inner and outer rings is small.
These bearings can also be used without inner or outer rings. [1]
NA
 
Needle bearing NA0000
Under the same inner diameter condition, compared with other bearings of the same type, its outer diameter is the smallest, and the inner or outer ring can be separated. A little axial misalignment of the inner and outer rings is allowed during operation.
It belongs to radial bearing.
The coefficient of friction is large. [1]
Code editor
GB / T 272——1993 stipulates the bearing code representation method, and roller bearings also obey this representation method.
Figure 4 Composition of rolling bearing code
Figure 4 Composition of rolling bearing code
Please refer to Figure 4 for the composition of the code, and the entry for the rolling bearing model code. [1]
Type selection edit
When selecting bearings, the main considerations are as follows:
Bearing load
The magnitude, direction and nature of the load on the bearing are the main factors in selecting a bearing.
When the bearing is selected according to the load, compared with the point contact of the ball bearing, the main components in the roller bearing are in line contact, which is easy to bear the load and the deformation after loading is small.
When selecting a bearing according to the load direction, for pure axial loads, a thrust bearing is generally selected. Select thrust roller bearings for larger axial forces. For smaller axial forces, thrust ball bearings are used. For pure radial loads, deep groove ball bearings, cylindrical roller bearings or needle roller bearings are generally used. When bearing radial load, but also bearing small axial load, deep groove ball bearing or tapered roller bearing can be selected; when the axial load is large, angular contact ball with larger contact angle can be selected Bearings or tapered roller bearings. [1]
Bearing speed
In general, the speed does not affect the choice of bearing type, but when the speed is large, the speed should be included in the bearing selection criteria.
(1) Compared with roller bearings, ball bearings have a higher limit speed, so in the case of high speed, ball bearings are given priority.
(2) When the inner diameter is the same, the smaller the outer diameter, the smaller the rolling element, so the smaller the centrifugal force of the rolling element on the outer ring is, the more suitable it is to work at high speed. According to the properties given in Table 1, needle roller bearings are more suitable for working at high speeds. [1]
Self-aligning performance of bearings
When the centerline of the shaft does not coincide with the centerline of the bearing seat and there is an angular error, or when the shaft is bent or inclined due to the force of the shaft, the axis of the inner and outer rings of the bearing will be skewed. At this time, a self-aligning bearing or a spherical ball bearing with a seat with a certain self-aligning performance should be used.
Roller bearings are most sensitive to bearing deflection. The bearing capacity of such bearings in deflection may be lower than ball bearings. Therefore, when the shaft rigidity and the support rigidity of the bearing housing hole are low, or when there is a large deflection moment, such bearings should be avoided as much as possible. [1]
Bearing installation and removal
When the bearing seat has no split surface and components must be installed and removed in the axial direction, bearings with separable inner and outer rings (such as N0000, NA0000, 30,000, etc.) should be preferred.
Editing the lubrication method
Lubrication is of great significance to bearings. The lubricant in bearings can not only reduce frictional resistance, but also play a role in dissipating heat, reducing contact stress, absorbing vibration, and preventing corrosion.
The common lubrication methods for bearings are oil lubrication and grease lubrication. It can also be lubricated with a solid lubricant. Which lubrication method is used depends on the speed of the bearing. Generally, the dn value of the bearing (d is the inner diameter of the bearing, mm; n is the speed of the bearing, r / min) represents the speed of the bearing. Figure 5 shows the dn limit for grease and oil lubrication.