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Cylindrical roller bearing

January 16, 2020

The rolling elements are radial rolling bearings of cylindrical rollers. The internal structure of the cylindrical roller bearing adopts rollers arranged in parallel. Spacers or spacers are installed between the rollers, which can prevent the tilting of the rollers or friction between the rollers, and effectively prevent the increase of rotational torque.

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 collar of the ferrule is small, which is suitable for high-speed rotation. Depending on whether the ring has ribs, 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, NN. The bearing has a separable inner and outer ring structure.
Cylindrical roller bearings with no ribs on the inner or outer ring, the inner and outer rings can move relatively in 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. Steel stamped cages or copper alloy solid cages are generally used. However, some use polyamide molding cages.
Features edit
1. Roller and raceway are in line contact or repaired line contact, with large radial bearing capacity, suitable for bearing heavy load and impact load.
2. The friction coefficient is small, suitable for high speed, and the limiting 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 of the shaft and the housing caused by thermal expansion or installation error, and can be used as free end support.
4. The machining requirements for the shaft or seat hole are high. The relative deflection of the outer ring axis after the bearing is installed must be strictly controlled to avoid causing contact stress concentration.
5. The inner or outer ring can be separated for easy installation and removal [1].
Product feature editing
Cylindrical rollers are in linear contact with the raceways and have a large radial load capacity. It is suitable for both heavy and shock loads and high-speed rotation.
Cylindrical roller bearing raceways and rolling bodies are geometrically shaped. After the improved design, it has a higher load carrying capacity. The new structural design of the flange and roller end faces 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 flange. Bearing performance.
Structure editing
Bearing construction type
Bearing construction type
1. Outer ring without rib N0000 and inner ring without rib NU0000. Cylindrical roller bearings. These bearings can accept large radial loads, high limiting speeds, do not restrict axial displacement of the shaft or housing, and cannot accept axial Load.
2. NJ0000 and NF0000 cylindrical roller bearings with ribs on the inner and outer rings can restrain axial displacement of the shaft or housing in one direction, and can accept small unidirectional axial loads. NU0000 + HJ0000, NJ0000 + HJ0000 and NUP0000 bearings can restrain axial displacement of the shaft or housing in the axial clearance field of imported bearings, and can accept small bidirectional axial loads [2].
Cylindrical roller bearing category edit
Four-row cylindrical roller
Four-row cylindrical roller
Cylindrical roller bearings are separate bearings, which are very easy to install and remove. Cylindrical roller bearings can withstand large radial loads and are suitable for use at high speeds.
This type of bearing allows the angular error (inclination) between the axis of the inner ring and the axis of the outer ring to be 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 is likely to occur at the contact portion of the raceway. However, after the roller or raceway contact bus bar is modified, the occurrence of stress concentration can be reduced.
Cylindrical roller bearings can be divided into single-row, double-row, and multi-row cylindrical roller bearings according to the number of rows of mounted rolling elements. Different structural bearings are also shown in the design of the position of the ribs. The commonly used cylindrical roller bearings have the following forms:
Single-row cylindrical roller bearings: Single-row cylindrical roller bearings are separable bearings for easy installation and removal. Both ferrules can be tightly fitted. The contact line between the modified roller and raceway can reduce stress concentration.
Double-row cylindrical roller bearings: Double-row cylindrical roller bearings are movable bearings, and their separability makes installation and removal very convenient. Both ferrules can be fitted tightly. Double-row cylindrical roller bearings are almost never allowed to have a tilt angle.
Single row bearing
Single row cylindrical roller bearing
Single row cylindrical roller bearing
N, NU type
N-type bearings have no ribs on the outer ring and ribs on both sides of the inner ring. Displacement between the shaft and the bearing housing in both axial directions can be allowed. NU type bearings have 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 moving end bearing.
NJ, NF type
NJ 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. The outer ring of the NF type has ribs on one side and the inner ring has ribs on both sides. Can also bear a certain amount of unidirectional axial load. Therefore, this type of structure is suitable for use as a unidirectional axial positioning 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 retaining ring on the other side. Can withstand a certain amount of bidirectional axial load.
The NFP type bearing has a (fixed) single rib on one side of the outer ring, and a separable flat retaining ring on the other side. Can also bear 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 two axial directions. Therefore, it is suitable for use as a fixed-end bearing.
NH (NJ + HJ) type
The NH type bearing is a structure obtained by combining the NJ type bearing and the HJ type oblique 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 entire inner ring width of the NJ type bearing to maintain a closer fit with the shaft. And NH type bearings are more convenient for installation and removal.
NH type bearings can limit the displacement of the shaft relative to the bearing seat in two axial directions. Therefore, it is suitable for use as a fixed-end bearing.
Double row bearing
Double-row cylindrical roller bearings
Double-row cylindrical roller bearings
Double-row cylindrical roller bearings have two structures: cylindrical bore and conical bore (post bearing code plus K). This type of bearing has the advantages of compact structure, high rigidity, large bearing capacity, and small deformation after load. It is especially suitable for machine tool spindle support. The conical inner hole can also play a role of adjusting the clearance in a small amount, and can simplify the structure of the positioning device and facilitate the installation and disassembly. Commonly used double-row cylindrical roller bearings have the following forms:
NN, NNU type
NN type bearings have no ribs on the outer ring, and there are ribs on both sides of the inner ring and a middle rib on the middle. It can allow displacement in two directions in the axial direction between the shaft and the bearing seat.
NNU bearings have ribs on both sides of the outer ring and middle ribs in the middle, and no ribs on the inner ring. It can allow displacement in two directions in the axial direction between the shaft and the bearing seat. Therefore, this type of structure is suitable as a moving end bearing. The cages of this type of bearings are mostly made of car-made solid cages.
NNF type
NNF type bearings are double row full complement cylindrical roller bearings. The bearing consists of an outer ring with a middle rib and two inner rings with a double rib. The rollers are guided by the ribs of the inner ring, and the two inner rings are fixed together by a fastening ring. In addition to bearing large radial and axial loads, this structure can also bear overturning moments, so it is often used as a fixed-end bearing.
NNF bearings adopt contact seals on both sides. The bearing is filled with grease. The working temperature of the grease is -50 ° C to + 110 ° C. However, due to the limitation of the sealing material, the working temperature of the bearing is limited to -40 ° C to + 80 ° C. Under good operating conditions, NNF bearings with seals do not need to be maintained. If the bearings are exposed to water vapor or polluted the environment for a long time, and they are running at medium and high speeds, they can be adjusted through the oil grooves and holes on the outer ring The bearings are relubricated.
Four-row bearing
Four-row cylindrical roller bearings
Four-row cylindrical roller bearings
Four-row cylindrical roller bearings are mainly used in cold rolling, hot rolling mills, billet rolling mills and other rolling mill machinery. The bearings have a separate structure. The bearing rings and rolling element components can be easily separated. Installation and disassembly are very convenient.
FC type
The FC type bearing is composed of two outer rings and one inner ring. Each side of the outer ring has a rib on the two sides and a middle rib on the middle. There is no rib on the inner ring.
FCD type
FCD bearings are actually a combination of two NN bearings.
FC and FCD bearings can allow axial displacement in two directions between the shaft and the bearing housing. Therefore, this type of structure is suitable as a moving end bearing. The cage of this type of bearing mostly uses the car body 13:58.
Editing accuracy class
Cylindrical roller bearings can be divided into PO, P6, P5, P4, P2 according to the accuracy level. The accuracy levels are ordered from low to high.
Method for adjusting radial clearance of cylindrical roller bearings
The commonly used methods for adjusting the radial clearance of a full complement cylindrical roller bearing are as follows [3]:
1. The backlash of cylindrical and elliptical bearing pads can be adjusted by manual grinding scraping or scraping after turning with padding in the bearing.
2. The top clearance of the cylindrical and oval bearing pads can be adjusted manually by scraping or padding the bearing mid-face when the situation permits.
3. For multi-oil wedge-type bearing pads, scraping and adjusting the bearing pad clearance is not allowed in principle. If the clearance is not suitable, a new bearing pad should be replaced.
4. For oily wedge tilting bearing pads, it is not allowed to repair the pads. If the clearance is not suitable, the invar blocks should be replaced. For tiles with adjustable thickness, you can adjust the amount of tiles by adding a stainless steel pad under the tile behind the tile, or by reducing the thickness of the tile. Note that for multi-oil wedge tilting bearing pads, the thickness error between the same group of pads should be less than 0.01mm.
Application editor
Large and medium-sized electric motors, rolling stock, machine tool spindles, internal combustion engines, generators, gas turbines, reduction gearboxes, rolling mills, vibrating screens, and lifting and transportation machinery.
Attention issue edit
In terms of vibration
In normal use, vibration is very sensitive to bearing damage, and peeling, indentation, rust, crack, and wear will be reflected in bearing vibration measurement. Therefore, by using a special bearing vibration measuring device (frequency analyzer, etc.), the magnitude of vibration can be measured, and the specific situation of the abnormality can be inferred from the frequency distribution. The measured values ​​vary depending on the conditions of use of the bearing or the mounting 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.
In terms of temperature
High temperature often indicates that cylindrical roller bearings are in abnormal conditions. High temperatures are also harmful to bearing lubricants. Sometimes bearing overheating can be attributed to bearing lubricants. Long-term continuous rotation of the bearing at a temperature exceeding 125 ° C will reduce the bearing life. Causes of high-temperature bearings include: insufficient lubrication or excessive lubrication, bearing raceways containing impurities, excessive limit speeds, and long-term overload operation of bearings.
Maintenance edit
Disassembly
The bearing is disassembled for regular maintenance and is carried out when the bearing is replaced. After disassembly, if you continue to use it, or if you need to check the condition of the bearing, the disassembly must be performed with the same care as during installation. Pay attention not to damage the various parts of the bearing, especially the disassembly of the interference fit bearing, which is difficult to operate.
It is also important to design and make disassembly tools as needed. When disassembling, study the disassembly method, sequence, and investigate the matching conditions of the bearings according to the drawings to find the foolproof operation.
Removal of the outer ring with interference fit. Set several outer ring extrusion screw screws on the circumference of the shell in advance. Tighten the screws evenly while disassembling. These screw holes are usually covered with separate bearings such as blind plugs, tapered roller bearings, etc. Several cutouts are set on the housing blocking shoulder, and they are disassembled with a press using a pad or lightly tapped.
The inner ring can be disassembled easily by using a press. At this time, pay attention to the inner ring to withstand its pulling force. Moreover, the pull-out clamps shown are mostly used, and no matter what kind of clamps, they must be firmly clamped to the side of the inner ring. For this reason, it is necessary to consider the size of the shaft shoulder, or to study the groove on the shoulder so as to use the drawing clamp.
拆卸 The inner ring of large bearings is disassembled by hydraulic method. Oil pressure is provided through the oil hole provided in the bearing to make it easy to pull. For bearings with large widths, the hydraulic method is used in combination with the pull-out clamp for disassembly.
拆卸 The inner ring of cylindrical roller bearings can be disassembled by induction heating method. A method of heating the local part in a short time to expand the inner ring and then drawing. Where a large number of bearing inner rings need to be installed, induction heating is also used.
Clean
When removing the bearing for inspection, make a record of its appearance by photography or other methods. Also, check the amount of remaining lubricant and sample the lubricant before cleaning the bearing.
a. The bearing is cleaned by rough washing and fine washing, and a metal grid can be placed on the bottom of the container.
b. For rough washing, remove grease or stickies with a brush in oil. If the bearing is turned in oil at this time, take care to prevent damage to the rolling surface due to foreign matter.
c. During fine washing, slowly rotate the bearing in oil, it must be done carefully.
Generally, the cleaning agent used is a neutral non-aqueous diesel oil or kerosene. If necessary, a mild alkaline solution may be used. No matter what kind of cleaning agent is used, always filter to keep it clean.
Immediately after cleaning, apply antirust oil or antirust grease to the bearings.