The rolling elements are radial rolling bearings with cylindrical rollers. The internal structure of cylindrical roller bearing adopts rollers arranged in parallel, and spacers or spacers are installed between the rollers, which can prevent the inclination of the rollers or the friction between the rollers, and effectively prevent the increase of the rotational torque. [1]
Chinese Name: Cylindrical Roller Bearing. Foreign Name: Alias: English Name: Cylindrical Roller Bearing Bearing Application: Large and Medium Motors, Locomotives and Vehicles Main Function: Reduce Friction
Introduction
Cylindrical roller bearing
Cylindrical rollers and raceways are linear contact bearings. Load capacity, mainly bear radial load. The friction between the rolling element and the rib of the ring is small, which is suitable for high-speed rotation. According to whether the ring has ribs or not, it can be divided into single row cylindrical roller bearings such as NU, NJ, NUP, N, NF, and double row cylindrical roller bearings such as NNU and NN. The bearing is a structure in which the inner ring and the outer ring can be separated.
Cylindrical roller bearings without ribs on the inner or outer ring, the inner and outer rings can move relative to the axial direction, so they can be used as free end bearings. Cylindrical roller bearings with double ribs on one side of the inner ring and outer ring and a single rib on the other side of the ring can withstand a certain degree of axial load in one direction. Generally, a steel stamping cage is used, or a copper alloy turning solid cage is used. However, there are also part of the use of polyamide forming cage.
Bearing Features
1. The roller and the raceway are in line contact or trimmed line contact, and the radial bearing capacity is large, which is suitable for bearing heavy loads and impact loads.
2. The friction coefficient is small, suitable for high speed, and the limit speed is close to that of deep groove ball bearings.
3. The N and NU types can move axially, and can adapt to changes in the relative position of the shaft and the housing caused by thermal expansion or installation errors, and can be used as free end supports.
4. The processing requirements for the shaft or seat hole are high. After the bearing is installed, the relative deflection of the outer ring axis should be strictly controlled to avoid contact stress concentration.
5. The inner ring or outer ring can be separated for easy installation and removal.
product features
The cylindrical roller is in line contact with the raceway and has a large radial load capacity. Suitable for both heavy loads and shock loads, as well as high-speed rotation.
Cylindrical roller bearing raceways and rolling elements are geometric. After the improved design, it has higher bearing capacity. The new structural design of the rib and the 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. performance of bearings.
Structural classification
Structural type
1. N0000 type without ribs on the outer ring and NU0000 type without ribs on the inner ring. Cylindrical roller bearings can accept large radial loads, have a high limit speed, do not bind the axial displacement of the shaft or housing, and cannot accept axial load.
2. Cylindrical roller bearings NJ0000 and NF0000 with ribs on both the inner and outer rings can restrain the axial displacement of the shaft or housing in one direction, and can accept a small one-way axial load. NU0000+HJ0000, NJ0000+HJ0000, NUP0000 bearings can restrain the axial displacement of the shaft or housing in both directions within the axial clearance area of the imported bearing, and can accept small bidirectional axial loads.
Bearing category
Cylindrical roller bearings are separable bearings, which are very convenient to install and disassemble. Cylindrical roller bearings can withstand large radial loads and are suitable for use in high-speed operation.
This type of bearing allows the angle error (inclination) between the axis of the inner ring and the axis of the outer ring to be very small, only 2' to 4'. Therefore, the machining accuracy of the shaft and the bearing seat is relatively high. Otherwise, uneven load or stress concentration will easily occur at the contact part of the raceway. However, the occurrence of stress concentrations can be reduced by modifying the contact busbars of the rollers or raceways.
Cylindrical roller bearings can be divided into different structures such as single-row, double-row and multi-row cylindrical roller bearings according to the number of rows of rolling elements installed. Different structural bearings are also reflected in the design of the position of the rib. Among them, the commonly used cylindrical roller bearings have the following forms:
Single-row cylindrical roller bearings: Single-row cylindrical roller bearings are separable bearings, which are easy to install and disassemble. Both rings can be tightly fitted, and the contact line between the roller and the raceway can be corrected to reduce stress concentration.
Double row cylindrical roller bearing: Double row cylindrical roller bearing belongs to the floating bearing, and its separability makes the installation and disassembly very convenient. Both ferrules can have a tight fit. Double row cylindrical roller bearings are hardly allowed to have a tilt angle.
single row bearing
N, NU type
The outer ring of the N-type bearing has no ribs, and there are ribs on both sides of the inner ring. Displacement in both axial directions between the shaft and the bearing housing can be allowed. The NU type bearing has ribs on both sides of the outer ring and no ribs on the inner ring. It is also possible to allow displacement of the shaft relative to the bearing housing in both axial directions. Therefore, this type of structure is suitable for use as a loose end bearing.
NJ, NF type
NJ type bearings have ribs on both sides of the outer ring, and ribs on one side of the inner ring. Can withstand a certain amount of unidirectional axial load. NF type has ribs on one side of the outer ring and ribs on both sides of the inner ring. It can also bear a certain amount of unidirectional axial load. Therefore, this type of structure is suitable for use as a unidirectional axial locating bearing.
NUP, NFP type
NUP type bearings have ribs on both sides of the outer ring, a (fixed) single rib on one side of the inner ring, and a separable flat rib on the other side. Can withstand a certain amount of bidirectional axial load.
The bearing outer ring of the NFP type has a (fixed) single rib on one side, and a separable flat rib on the other side, with ribs on both sides of the inner ring. It can also withstand a certain amount of bidirectional axial load. This type of structural bearing can limit the displacement of the shaft relative to the bearing seat in both axial directions. Therefore, it is suitable for use as a fixed end bearing.
NH (NJ+HJ) type
The NH type bearing is the combination of the NJ type bearing and the HJ type inclined retaining ring. Because the inner ring of the NUP type bearing is short, and the flat retaining ring is not fixed, it is inconvenient to use, while the NH type bearing can use the width of the entire inner ring of the NJ type bearing to maintain a tighter fit with the shaft. Moreover, the NH type bearing is more convenient to install and disassemble.
NH type bearings can limit the displacement of the shaft relative to the bearing seat in both axial directions. Therefore, it is suitable for use as a fixed end bearing.
Double row bearing
Double row cylindrical roller bearings have two structures: cylindrical inner hole and conical inner hole (bearing rear code plus K). This type of bearing has the advantages of compact structure, high rigidity, large bearing capacity, and small deformation after being loaded, and is especially suitable for the support of machine tool spindles. The conical inner hole can also play the role of micro-adjustment of the clearance, and can simplify the structure of the positioning device and facilitate installation and disassembly. Commonly used double row cylindrical roller bearings have the following forms:
NN, NNU type
The outer ring of the NN type bearing has no ribs, and there are ribs on both sides of the inner ring and a middle rib in the middle. Displacement in two directions in the axial direction between the shaft and the bearing housing can be allowed.
The outer ring of the NNU bearing has ribs on both sides and a middle rib in the middle, and the inner ring has no ribs. Displacement in two directions in the axial direction between the shaft and the bearing housing can be allowed. Therefore, this type of structure is suitable for the moving end bearing. The cages of this type of bearings are mostly car-made solid cages.
NNF type
NNF type bearing is a double row full complement cylindrical roller bearing. The bearing consists of one outer ring with middle rib and two inner rings with double rib. The rollers are guided by the ribs of the inner ring, and the two inner rings are held together by a clamping ring. In addition to the large radial load and axial load, the structure can also bear the overturning moment, so it is often used as a fixed end bearing.
Contact seals are used on both sides of the NNF bearing. The bearing is filled with grease, and the working temperature of the grease is -50°C to +110°C, but due to the limitation of the sealing material, the working temperature of the bearing is limited to -40°C to +80°C. In the case of good working conditions, the sealed NNF bearing does not need to be maintained. If the bearing is in a water vapor or polluted environment for a long time, and it is running at medium and high speed, it can be adjusted through the lubricating oil groove and lubricating oil hole on the outer ring. Bearings are relubricated.
Four row bearing
Four-row cylindrical roller bearings are mainly used in cold and hot rolling mills, blanking mills and other rolling mill machinery. The bearing is a separate structure, and the bearing ring and rolling element components can be easily separated. Installation and disassembly are very convenient.
FC type
The FC type bearing consists of two outer rings and an inner ring. Each outer ring has ribs on both sides and a middle rib in the middle, and the inner ring has no ribs.
FCD type
FCD type bearing is actually a combination of two NN type bearings.
FC type and FCD type bearings can allow axial displacement in two directions between the shaft and the bearing housing. Therefore, this type of structure is suitable for the moving end bearing. The cage of this type of bearing mostly adopts the car body 13:58.
Application
Bearing use
Large and medium-sized electric motors, rolling stock, machine tool spindles, internal combustion engines, generators, gas turbines, gearboxes, rolling mills, vibrating screens, and hoisting and transporting machinery, etc.
Accuracy class
Cylindrical roller bearings can be divided into PO, P6, P5, P4, P2 according to the accuracy grade. The accuracy grades are sorted from low to high.
The method of adjusting the radial clearance of cylindrical roller bearings:
The selection of cylindrical roller bearings is quick and easy to provide, and the comprehensive radial load on the fixed load is exposed from the local ring raceway fixed ring and transmitted to the corresponding shaft or bearing. The characteristic of this load is that the radial load vector is a relatively static resultant and ring. Bearing the load ring can be used relatively loose.
The rotational load is the resultant radial load of the full complement cylindrical roller bearing ring acting on the drum rotating in the circumferential direction, and the various parts of the rotation, such as the rotational load, which are rotated by the resultant vector phase ring radial load, are borne by the rotational load. . The rotating load ring is tightly fitted, in special cases, the load, such as elective, is light or heavy, the load at low speed is only occasional, the bearing is made of hard material and the surface roughness is high, the rotating load bearing ring can also be Used loosely.
The third load swings the load or the non-directional load, the combined direction of the radial load of the load ring is uncertain, it is characterized by the effect of the radial load vector ring raceway of the combined ring, the impact load, vibration in a certain area, vibration, The load, the direction of which is swing, the roller has to bear a certain area, or the load acting on the bearing, the load value often changes. To bear the load-bearing swing, the outer ring and the circumference, the bearing, and the hole should be used in close cooperation.
The commonly used methods for adjusting the radial clearance of full complement cylindrical roller bearings are as follows:
1. For the side clearance of cylindrical and elliptical bearing bushes, it can be adjusted by manual grinding and scraping or the method of repairing and scraping after adding padding and turning in the middle of the bearing.
2. For the top clearance of cylindrical and elliptical bearing bushes, it can be adjusted by manual grinding and scraping or by adding pads to the bearing middle face when the situation permits.
3. For the fixed bearing bush with multiple oil wedges, in principle, it is not allowed to repair and adjust the bearing bush clearance. If the clearance is not suitable, the new pad should be replaced.
4. For multi-oil wedge tiltable bearing pads, scraping pads are not allowed to be repaired, and the pads should be replaced when the clearance is not suitable. For tiles with adjustable thickness, the amount of tiles can be adjusted by adding a stainless steel pad under the adjustment block behind the tile, or by reducing the thickness of the adjustment block. Note that for multi-oil wedge tiltable bearing pads, the thickness error between the pads in the same group should be less than 0.01mm.
Pay attention to the problem
Vibration
In normal use, vibration is quite sensitive to bearing damage, spalling, indentation, rust, cracks, wear, etc. will be reflected in the bearing vibration measurement. Therefore, by using a special bearing vibration measuring instrument (frequency analyzer, etc.), the magnitude of the vibration can be measured, and the specific situation of the abnormality can be inferred through the frequency distribution. The measured values vary depending on the operating 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.
temperature
A high temperature often indicates that the cylindrical roller bearing is in an abnormal condition. High temperatures are also detrimental to bearing lubricants. Sometimes bearing overheating can be attributed to the lubricant of the bearing. If the bearing is continuously rotated for a long time at a temperature exceeding 125°C, the bearing life will be reduced. The causes of high temperature bearings include: insufficient lubrication or excessive lubrication, impurities in the bearing raceway, excessively high limit speed, and long-term overload operation of the bearing.
