brief introduction
Cylindrical roller bearing
The cylindrical roller and raceway are linear contact bearings. Large load capacity, mainly bearing radial load. The friction between the rolling element and the ring flange is small, so it is suitable for high-speed rotation. According to whether the ring has rib or not, it can be divided into single row cylindrical roller bearings such as Nu, NJ, NUP, N and NF, and double row cylindrical roller bearings such as NNU and NN. The inner ring and outer ring of the bearing can be separated.
Cylindrical roller bearing with no rib in inner ring or outer ring, its inner ring and outer ring can move relative to each other in axial direction, so it can be used as free end bearing. The cylindrical roller bearing with double rib on one side of inner ring and outer ring and single rib on the other side can bear a certain degree of axial load in one direction. Generally use steel stamping cage, or copper alloy car solid cage. However, some cages are formed by polyamide.
characteristic
1. The roller and raceway are in line contact or repair line contact, with large radial bearing capacity, suitable for bearing heavy load and impact load.
2. Small friction coefficient, suitable for high speed, the limit speed is close to deep groove ball bearing.
3. Type N and type Nu can move axially to adapt to the change of relative position between shaft and shell caused by thermal expansion or installation error, and can be used as free end support.
4. The machining requirements of shaft or seat hole are high. After the bearing is installed, the relative deflection of outer ring axis should be strictly controlled to avoid contact stress concentration.
5. The inner ring or outer ring can be separated to facilitate installation and disassembly.
Product features
The cylindrical roller is in line contact with the raceway and has large radial load capacity. It is not only suitable for bearing heavy load and impact load, but also suitable for high-speed rotation.
The raceway and rolling element of cylindrical roller bearing are geometric. After the improved design, it has higher bearing capacity. The new structural design of the rib and roller end face not only improves the axial bearing capacity of the bearing, but also improves the lubrication conditions of the contact area between the roller end face and the rib, and improves the service performance of the bearing.
structure
1. N0000 with no rib on the outer ring and nu0000 with no rib on the inner ring are cylindrical roller bearings. This kind of bearing can accept larger radial load, high limit speed, no binding of axial displacement of shaft or shell, and can not accept axial load.
2. Nj0000 and nf0000 cylindrical roller bearings with both inner and outer rings can restrain the axial displacement of the shaft or shell in one direction, and can accept small one-way axial load. Nu0000 + hj0000, nj0000 + hj0000 and nup0000 bearings can restrain the axial displacement in both directions of the shaft or shell in the axial clearance field of the imported bearing, and can accept smaller bidirectional axial load.
Classification of cylindrical roller bearings
Cylindrical roller bearing is a kind of separate bearing, which is very convenient for installation and disassembly. Cylindrical roller bearing can bear large radial load and is suitable for high speed operation.
The angle error (inclination) between the inner ring axis and the outer ring axis is very small, only 2 ′ ~ 4 ′. Therefore, the machining accuracy of shaft and bearing seat is relatively high, otherwise, uneven load or stress concentration is easy to appear in the contact part of raceway. However, the stress concentration can be reduced by modifying the contact bus of roller or raceway.
Cylindrical roller bearings can be divided into single row, double row and multi row cylindrical roller bearings according to the number of rows of rollers. Different structure bearings are also shown in the design of rib position. The commonly used cylindrical roller bearings are as follows:
Single row cylindrical roller bearing: single row cylindrical roller bearing is separable bearing, easy to install and disassemble, two rings can adopt tight fit, the contact line between roller and raceway can reduce stress concentration.
Double row cylindrical roller bearing: double row cylindrical roller bearing belongs to floating bearing, its separability makes installation and disassembly very convenient. Both ferrules can be tight fit. Double row cylindrical roller bearings are almost not allowed to have an inclination angle.
Single row bearing
N. Nu type
The outer ring of n-type bearing has no rib, and both sides of inner ring have rib. The axial displacement between the shaft and the bearing pedestal can be allowed. Nu type bearing has rib on both sides of outer ring and no rib on inner ring. The axial displacement between the shaft and the bearing pedestal can also be allowed. Therefore, this kind of structure is suitable for use as a floating end bearing.
NJ, NF
NJ bearing has rib on both sides of outer ring and one side of inner ring. It can bear a certain amount of one-way axial load. NF type outer ring has rib on one side and inner ring has rib on both sides. It can also bear a certain amount of one-way axial load. Therefore, this kind of structure is suitable for single direction axial positioning bearing.
NUP, NFP
NUP type bearing has rib on both sides of outer ring, single rib on one side of inner ring and separable flat ring on the other side. It can bear a certain amount of bidirectional axial load.
One side of NFP bearing outer ring is provided with (fixed) single rib, while the other side is provided with separable flat retaining ring, and both sides of inner ring are provided with rib. It can also bear a certain amount of bidirectional axial load. This kind of structural bearing can limit the axial displacement of the shaft relative to the bearing seat in both directions. Therefore, it is suitable to be used as a fixed end bearing.
NH (NJ + HJ) type
NH type bearing is a combination of NJ type bearing and HJ type oblique retaining ring. Because the inner ring of NUP bearing is short, and the flat retaining ring is not fixed, it is inconvenient to use. NH bearing can use the width of the whole inner ring of NJ bearing to keep a closer fit with the shaft. Moreover, NH bearing is more convenient in installation and disassembly.
NH type bearing can limit the axial displacement of the shaft relative to the bearing seat in both directions. Therefore, it is suitable to be used as a fixed end bearing.
Double row bearing
Double row cylindrical roller bearing has cylindrical bore and conical bore (bearing code plus K). This kind of bearing has the advantages of compact structure, high rigidity, large bearing capacity and small deformation after being loaded. It is especially suitable for machine tool spindle support. The conical inner hole can also play the role of micro adjusting the clearance, and can simplify the structure of the positioning device, which is convenient for installation and disassembly. The commonly used double row cylindrical roller bearings have the following forms:
NN, NNU type
The outer ring of NN bearing has no rib, the inner ring has rib on both sides, and the middle rib. The shaft can be allowed to produce displacement in two directions in the axial direction relative to the bearing pedestal.
NNU bearing has rib on both sides of the outer ring, middle rib in the middle and no rib in the inner ring. The shaft can be allowed to produce displacement in two directions in the axial direction relative to the bearing pedestal. Therefore, this kind of structure is suitable for moving end bearing. The cage of this type of bearing is mostly made of solid cage.
Nnf type
Nnf bearing is a double row full loaded cylindrical roller bearing, which consists of one outer ring with middle rib and two inner rings with double rib. The roller is guided by the rib of the inner ring, and the two inner rings are fixed together with fastening rings. The structure can not only bear large radial load and axial load, but also can bear overturning moment, so it is often used as fixed end bearing.
Both sides of nnf bearing adopt contact seal. The bearing is filled with grease, and the working temperature of the grease is - 50 ℃ to + 110 ℃. However, due to the limitation of sealing materials, the working temperature of the bearing is only between - 40 ℃ and + 80 ℃. Under good working conditions, the nnf bearing with seal does not need maintenance. If the bearing is in water vapor or polluted environment for a long time and operates at medium and high speed, the bearing can be lubricated through the lubricating oil groove and lubricating oil hole on the outer ring.
Four row bearing
The four row cylindrical roller bearing is mainly used in cold rolling mill, hot rolling mill, blooming mill and other rolling mill machinery. The bearing is a separate structure, and the bearing ring and rolling element components can be easily separated. Therefore, the cleaning, inspection, installation and disassembly of the bearing are very convenient.
FC type
FC bearing is composed of two outer rings and one inner ring. Each outer ring has a rib on both sides, a middle rib in the middle and no rib in the inner ring.
FCD type
FCD bearing is actually composed of two NN bearings.
FC type and FCD type bearings can allow axial displacement in two directions between the shaft and the bearing pedestal. Therefore, this kind of structure is suitable for moving end bearing. The cage of this type of bearing mostly adopts turning solid 13:58.
Accuracy class
Cylindrical roller bearings can be divided into Po, P6, P5, P4 and P2 according to the accuracy level. The accuracy level is ranked from low to high.
Method of adjusting radial clearance of cylindrical roller bearing
The common methods for adjusting the radial clearance of fully loaded cylindrical roller bearings are as follows:
1. For cylindrical and oval bearing shells, the side clearance can be adjusted by hand grinding and scraping or by scraping after the bearing split surface is padded and turned.
2. The top clearance of cylindrical and oval bearing shells can be adjusted by hand scraping or adding pad on the bearing split when the situation permits.
3. In principle, it is not allowed to repair and adjust the clearance of multi oil wedge fixed bearing bush. If the clearance is not appropriate, it should be replaced with a new bush.
4. For the multi oil wedge tilting bearing bush, it is not allowed to repair and scrape the pad, and the pad should be replaced when the clearance is not suitable. For tile with adjustable thickness, the amount of tile can be adjusted by adjusting the stainless steel pad on the back of the tile or reducing the thickness of the adjustment block. Pay attention to the multi oil wedge tilting bearing, the thickness error of the same group of bearing blocks should be less than 0.01mm.
application
Large and medium motors, rolling stock, machine tool spindle, internal combustion engine, generator, gas turbine, reducer, rolling mill, vibrating screen and lifting and transportation machinery, etc.
Pay attention to the problem
Vibration
In normal use, vibration is very sensitive to bearing damage, peeling, indentation, corrosion, crack, wear and so on will be reflected in the bearing vibration measurement. Therefore, by using a special bearing vibration measuring device (frequency analyzer, etc.), the vibration can be measured, and the specific situation of abnormal can be inferred from the frequency distribution. The measured values are different due to the service conditions of the bearing or the installation position of the sensor, so it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment standard.
Folding temperature
High temperature is often used to indicate that the cylindrical roller bearing is in abnormal condition. High temperature is also harmful to bearing lubricants. Sometimes overheating of the bearing can be attributed to the lubricant of the bearing. If the temperature of the bearing exceeds 125 ℃ for a long time, the service life of the bearing will be reduced. The causes of high temperature bearing include: insufficient or excessive lubrication, impurities in bearing raceway, high limit speed, long-term overload operation of bearing, etc.
Maintenance
disassemble
The disassembly of the bearing is regular maintenance, and it is carried out when the bearing is replaced. After disassembly, if you continue to use, or need to check the state of the bearing, the disassembly should be as careful as the installation. Pay attention not to damage the bearing parts, especially the disassembly of interference fit bearing, the operation is difficult.
It is also very important to design and make disassembly tools according to needs. During the disassembly, the disassembly method and sequence are studied according to the drawings, and the matching conditions of the bearings are investigated, so as to ensure the safety of the disassembly operation.
For the outer ring of interference fit, several outer ring screws are set on the circumference of the shell in advance to extrude the screw, and the screw is tightened equally while being disassembled. These screw holes are usually covered with blind plugs, tapered roller bearings and other separate bearings, and several cuts are set on the covering shoulder of the shell, which can be removed by using cushion block, press or tapping gently.
The disassembly of the inner ring can be pulled out with a press. At this time, pay attention to let the inner ring bear its pulling force. Moreover, the drawing fixture shown is mostly used, no matter what kind of fixture, it must be firmly stuck on the side of the inner ring. Therefore, we need to consider the size of the shaft shoulder, or study the processing of the groove at the shoulder, in order to use the drawing fixture.
The inner ring of large bearing is disassembled by oil pressure method. Oil pressure is applied through the oil hole of the bearing to make it easy to draw. For wide bearings, oil pressure method and drawing fixture are used together for disassembly.
The inner ring of cylindrical roller bearing can be disassembled by induction heating method. In a short period of time heating local, so that the inner ring expansion after drawing method. The induction heating method is also used when a large number of such bearing inner rings need to be installed.
clean
When the bearing is removed for inspection, the appearance record shall be made by means of photography. In addition, confirm the amount of remaining lubricant and sample the lubricant before cleaning the bearing.
a. The cleaning of the bearing is divided into rough cleaning and fine cleaning, and the metal grid can be placed at the bottom of the container in use.
b. During rough washing, use a brush to remove grease or adhesion in the oil. At this time, if the bearing is rotated in oil, pay attention to the damage of rolling surface due to foreign matters.
c. During fine cleaning, rotate the bearing slowly in the oil and carefully.
The commonly used cleaning agent is neutral water free diesel or kerosene, and sometimes warm lye is used according to the need. No matter what kind of cleaning agent is used, always filter and keep clean.
After cleaning, apply antirust oil or grease on the bearing immediately.