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 retaining edge of the ferrule is small, which is suitable for high-speed rotation. According to whether the ferrule has retaining edge 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 bearing is a separable structure of inner ring and outer ring.

Cylindrical roller bearing with inner ring or outer ring without retaining edge, whose inner ring and outer ring can move relatively axially, can be used as free end bearing. A cylindrical roller bearing with double retaining edges on one side of the inner ring and the outer ring and a single retaining edge on the other side can bear a certain degree of axial load in one direction. Generally, steel plate stamping cage or solid cage made of copper alloy are used. However, some use polyamide shaped cages.

Feature editing and broadcasting

1. The roller and raceway are in line contact or repair line contact, with large radial bearing capacity, which is suitable for bearing heavy load and impact load.

2. Low friction coefficient, suitable for high speed, and the limit speed is close to the deep groove ball bearing.

3. N-type and nu type can move axially, can adapt to the change of the relative position between the shaft and the shell caused by thermal expansion or installation error, and can be used as free end support.

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 to facilitate installation and disassembly [1].

Editing and broadcasting of 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 in geometric shape. After the improved design, it has high bearing capacity. The new structural design of retaining edge and roller end face not only improves the axial bearing capacity of the bearing, but also improves the lubrication conditions in the contact area between roller end face and retaining edge, and improves the service performance of the bearing.

Structure editing and broadcasting

Bearing structure type

Bearing structure type

1. N0000 type without flange in outer ring and nu0000 type without flange in inner ring. Cylindrical roller bearing can accept large radial load, high limit speed, does not restrict the axial displacement of shaft or shell, and cannot accept axial load.

2. Cylindrical roller bearings nj0000 and nf0000 with retaining edges on the inner and outer rings can bind the axial displacement of the shaft or shell in one direction and accept small unidirectional axial load. Nu0000 + hj0000, nj0000 + hj0000 and nup0000 bearings can bind the axial displacement of the shaft or shell in the axial clearance field of the imported bearing, and can accept small two-way axial load [2].

Editing and broadcasting of cylindrical roller bearing categories

Four row cylindrical roller

Four row cylindrical roller

Cylindrical roller bearing is a 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.

This kind of bearing allows the angular error (inclination) between the inner ring axis and the outer ring axis to be very small, only 2 ′～ 4 ′. Therefore, the machining accuracy of the shaft and bearing seat is relatively high, otherwise, it is easy to have uneven load or stress concentration at the contact part of the raceway. However, the occurrence of stress concentration can be reduced by correcting 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 rolling elements. Different structural bearings are also reflected in the position design of the retaining edge. Cylindrical roller bearings are commonly used in the following forms:

Single row cylindrical roller bearing: single row cylindrical roller bearing is a separable bearing, which is convenient for installation and disassembly. Both rings can adopt tight fit. The contact line between the corrected roller and the raceway can reduce the stress concentration.

Double row cylindrical roller bearing: double row cylindrical roller bearing belongs to traveling bearing, and its separability makes installation and disassembly very convenient. Both ferrules can be tight fit. Double row cylindrical roller bearings are hardly allowed to have inclination angles.

Single row bearing

cylindrical roller bearing 

cylindrical roller bearing 

N. Nu type

The outer ring of n-type bearing has no retaining edge, and there are retaining edges on both sides of the inner ring. The displacement of the shaft relative to the bearing seat in both axial directions can be allowed. Nu type bearing has retaining edges on both sides of the outer ring and no retaining edge on the inner ring. The displacement of the shaft relative to the bearing seat in both axial directions can also be allowed. Therefore, this kind of structure is suitable for use as a swimming end bearing.

NJ, NF type

Both sides of the outer ring of NJ type bearing are provided with retaining edges, and one side of the inner ring is provided with retaining edges. It can bear a certain amount of unidirectional axial load. NF type outer ring has a retaining edge on one side and a retaining edge on both sides of the inner ring. It can also bear a certain amount of unidirectional axial load. Therefore, this kind of structure is suitable for single direction axial positioning bearing.

NUP, NFP type

NUP type bearings have retaining edges on both sides of the outer ring, one side of the inner ring has (fixed) single retaining edge, and the other side is a separable flat retaining ring. It can bear a certain amount of bidirectional axial load.

One side of NFP bearing outer ring is provided with (fixed) single retaining edge, while the other side is a separable flat retaining ring with retaining edges on both sides of the inner ring. It can also bear a certain amount of bidirectional axial load. This kind 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 structure of the rear diagonal bearing is a combination of the NH type and the NJ type. Because the inner ring of NUP bearing is short and the flat retaining ring is not fixed, it is inconvenient to use, while NH bearing can use the width of the whole inner ring of NJ bearing to maintain a closer fit with the shaft. Moreover, NH bearing is more convenient for installation and disassembly.

NH type 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.

Double row bearing

Double row cylindrical roller bearing

Double row cylindrical roller bearing

Double row cylindrical roller bearings have two structures: cylindrical inner hole and conical inner hole (bearing post 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 slightly adjusting the clearance, simplify the structure of the positioning device and facilitate 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 retaining edge, there are retaining edges on both sides of the inner ring, and there is a middle retaining edge in the middle. The shaft can be allowed to produce displacement in two directions in the axial direction relative to the bearing seat.

Both sides of the outer ring of NNU bearing have retaining edges, the middle retaining edge is in the middle, and the inner ring has no retaining edge. The shaft can be allowed to produce displacement in two directions in the axial direction relative to the bearing seat. Therefore, this kind of structure is suitable for swimming end bearing. The cage of this type of bearing mostly adopts turning solid cage.

Nnf type

Nnf bearing is a double row full loaded cylindrical roller bearing. The bearing consists of one outer ring with middle retaining edge and two inner rings with double retaining edge. The roller is guided by the retaining edge of the inner ring, and the two inner rings are fixed together with fastening rings. In addition to bearing large radial load and axial load, the structure can also bear overturning moment. Therefore, it is often used as fixed end bearing.

Both sides of nnf bearing adopt contact seal. The bearing is filled with grease. The working temperature of the grease is - 50 ℃ to + 110 ℃, but due to the limitation of sealing materials, the working temperature of the bearing is limited to - 40 ℃ to + 80 ℃. Under good operating 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 supplemented and lubricated through the lubricating oil groove and lubricating oil hole on the outer ring.

Four row bearing

Four row cylindrical roller bearing

Four row cylindrical roller bearing

Four row cylindrical roller bearings are mainly used in cold rolling mill, hot rolling mill, billet opener and other rolling mill machinery. The bearings are of separate structure, and the bearing rings and rolling element components can be easily separated. Therefore, the cleaning, inspection, installation and disassembly of the bearings are very convenient.

FC type

FC type bearing is composed of two outer rings and one inner ring. There are retaining edges on both sides of each outer ring, a middle retaining edge in the middle, and there is no retaining edge 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 seat. Therefore, this kind of structure is suitable for swimming end bearing. The cage of this type of bearing mostly adopts turning solid 13:58.

Accuracy level editing and broadcasting

Cylindrical roller bearings can be divided into Po, P6, P5, P4 and P2 according to the accuracy grade The accuracy level is sorted from low to high.

Method of adjusting radial clearance of cylindrical roller bearing

The common methods to adjust the radial clearance of fully loaded cylindrical roller bearings are as follows [3]:

1. The side clearance of cylindrical and oval bearing shells can be adjusted by manual grinding and scraping or by adding pad on the bearing split and scraping after turning.

2. The top clearance of cylindrical and oval bearing shells can be adjusted by manual grinding and scraping or adding pad to the bearing split when circumstances permit.

3. In principle, it is not allowed to scrape and adjust the clearance of multi oil wedge fixed bearing bush. If the clearance is inappropriate, replace it with a new one.

4. For multi oil wedge tilting bearing bush, it is not allowed to scrape the pad. If the clearance is not appropriate, replace the pad. 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. Note that for the multi oil wedge tilting bearing bush, the thickness error between the same group of pads shall be less than 0.01mm.

Application editing broadcast

Large and medium-sized motors, rolling stock, machine tool spindles, internal combustion engines, generators, gas turbines, reduction boxes, rolling mills, vibrating screens, hoisting and transportation machinery, etc.

Attention problems editing and broadcasting

Vibration

In normal use, vibration is very sensitive to bearing damage. Peeling, indentation, corrosion, crack, wear and so on will be reflected in bearing vibration measurement. Therefore, the vibration can be measured by using a special bearing vibration meter (frequency analyzer, etc.), and the specific situation of abnormality 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. Therefore, it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment standard.

Temperature aspect

The use of high temperature often indicates that the cylindrical roller bearing has been in an abnormal condition. High temperature is also harmful to the lubricant of the bearing. Sometimes bearing overheating 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 bearings include insufficient or excessive lubrication, impurities in the bearing raceway, high limit speed, long-term overload operation of the bearing, etc.

Maintenance editing broadcast

disassemble

The bearing is disassembled for regular maintenance and replaced. After disassembly, if the bearing continues to be used or the condition of the bearing needs to be checked, the disassembly shall be carried out with the same care as during installation. Pay attention not to damage all parts of the bearing, especially the disassembly of the interference fit bearing, which is difficult to operate.

It is also very important to design and make disassembly tools according to needs. During disassembly, the disassembly method and sequence shall be studied according to the drawings, and the matching conditions of the bearing shall be investigated to ensure the safety of the disassembly operation.

For the disassembly of the outer ring, the outer ring with interference fit shall be provided with several outer ring extrusion screws on the circumference of the shell in advance, and the screws shall be tightened equally while being disassembled. These screw holes are usually covered with blind plugs, tapered roller bearings and other separate bearings. Several cuts are set on the cover shoulder of the shell. Use cushion blocks, disassemble with a press, or knock gently.

The disassembly of the inner ring can be pulled out with a press, which is the simplest. At this time, pay attention to make the inner ring bear its pulling force. Moreover, most of the pulling fixtures shown are also used. No matter what kind of fixture, it must be firmly clamped on the side of the inner ring. Therefore, it is necessary to consider the size of the shaft shoulder, or study the processing of the upper 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 set in the bearing to make it easy to pull out. For the bearing with large width, the 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. It is a method of drawing after heating part in a short time to expand the inner ring. Induction heating is also used where a large number of such bearing inner rings need to be installed.

clean

When removing the bearing for inspection, first make appearance records by photography and other methods. In addition, confirm the amount of remaining lubricant and sample the lubricant before cleaning the bearing.

a. The cleaning of bearings is divided into rough cleaning and fine cleaning, and a metal grid can be placed at the bottom of the container.

b. During rough cleaning, 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 to the rolling surface due to foreign matters.

c. During fine cleaning, rotate the bearing slowly in oil and carry out it carefully.

The commonly used cleaning agent is neutral water-free diesel oil or kerosene, and sometimes warm lye is used as needed. No matter what kind of cleaning agent you use, always filter it and keep it clean.

After cleaning, apply antirust oil or antirust grease on the bearing immediately.