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needle bearing

January 16, 2020

Needle bearing is a kind of roller bearing with cylindrical roller. The roller is thin and long relative to its diameter. This roller is called a needle roller. Although it has a smaller section, the bearing still has a higher load bearing capacity. The needle roller bearing is equipped with thin and long rollers (roller diameter D ≤ 5mm, L / D ≥ 2.5, l is roller length). Therefore, the radial structure is compact. When its inner diameter and load capacity are the same as other types of bearings, the outer diameter is the smallest, especially suitable for the support structure with limited radial installation size.
According to the different occasions of use, the bearing or needle roller and cage assembly without inner ring can be selected. At this time, the journal surface and shell hole surface matching with the bearing are directly used as the inner and outer rolling surfaces of the bearing. In order to ensure that the load capacity and operation performance are the same as that of the bearing with ferrule, the machining accuracy and surface quality of the surface of the raceway of the shaft or outer shell hole should be similar to that of the raceway of the bearing ferrule. This bearing can only bear radial load.

In addition to the listed in the catalog, it can be used for general engineering bearings, such as: open stamped outer ring
Needle bearing
Needle bearing
Needle roller bearings (1), closed drawn needle roller bearings with outer ring (2), needle roller bearings with inner ring (3) and needle roller bearings without inner ring / needle bearing without cage without cage (4), yes Cages and cageless full roller bearings (5) SKF can also supply various types of needle roller bearings, 1, needle roller cage assemblies 2, needle roller bearings without ribs 3, self-aligning 4, combined rollers Needle / ball bearing 5, combined needle / thrust ball bearing 6, combined needle / cylindrical roller thrust bearing. [1]
Stamped outer ring
Drawn cup needle roller bearings are needle bearings with a thin stamped outer ring. Its main feature is its low section height and high load capacity. It is mainly used for bearing configuration with compact structure and low price, and the inner hole of the bearing box cannot be used as the raceway of the needle cage assembly. The bearings and bearing housings must be installed in an interference fit. If axial positioning functions such as box shoulders and retaining rings can be omitted, then the bore in the bearing box can be made extremely simple and economical. Drawn cup needle roller bearings mounted on the shaft end are open on both sides and closed on one side. The base end face of the closed drawn outer ring can withstand small axial guiding forces. Drawn cup needle roller bearings generally do not have an inner ring. Where the journal cannot be hardened and ground, the inner ring listed in the table can be used. The hardened steel outer ring of the drawn cup needle roller bearing is inseparable from the needle roller cage assembly. Free space for lubricant storage can extend the relubrication interval. The bearings are generally designed in a single row. Except for the wider bearing series 1522, 1622, 2030, 2538 and 3038, which are equipped with two needle cage assemblies. The bearing outer ring has a lubricant hole. According to user requirements, all single-row drawn needle roller bearings with a shaft diameter of 7 mm or more can be equipped with an outer ring with a lubrication hole (code suffix AS1). Drawn cup needle roller bearings with oil seals Where oil seals cannot be installed due to space constraints, oil drawn cup needle roller bearings with open ends or closed ends can be provided (3 to 5). This type of bearing is equipped with a friction oil seal of polyurethane or synthetic rubber, which is filled with lithium-based grease with good anti-rust performance, suitable for operating temperature -20 to + 100 ° C. The inner ring of the oil-sealed bearing is 1mm wider than the outer ring. This allows the bearing to ensure that the oil seal works well when the shaft has a small displacement relative to the bearing box to prevent the bearing from being contaminated. The bearing inner ring also has lubrication holes, which can be relubricated by the outer ring or the inner ring according to the needs of the bearing configuration. [1]
Solid ferrule
The solid ring needle bearing is composed of one or two rings and a needle set with a cage. Depending on the application, it can be divided into bearings with or without an inner ring. Therefore, the solid ring needle roller bearings can meet the requirements of light weight, small space occupation and large transmission power. The solid ring needle roller bearing has a smaller volume and a higher bearing capacity. Structure type Outer ring double rib (or double lock ring) needle roller bearings with cage NA, NAV, NKI can be installed with inner ring and outer ring (with lock ring, full set of needle rollers and cages), high authority speed, There are two types of single-row and double-row. If the shaft cannot be used as a raceway, that is, if it is impossible or uneconomical to grind the shaft for grinding, this type of needle roller bearing with inner ring can be used. [1]
Features NA and NKI bearings are RNA and NK needle roller bearings without inner ring. This type of bearing has no inner ring and is suitable for supporting structures with restricted radial installation dimensions. The journal matching the bearing is used as the rolling surface directly. The shaft as the raceway surface must be hardened and ground, and only when it is processed to an appropriate size and shape accuracy, the entire set of needle bearings can have a higher life and running accuracy. At the same time, because there is no inner ring, the diameter of the shaft can be appropriately enlarged, which also increases rigidity. [1]
Combinatorial editing
The combined needle roller bearing is a bearing unit composed of a radial needle roller bearing and a thrust bearing component. It has a compact structure, small volume, high rotation accuracy, and can withstand a certain axial load while bearing a high radial load. And the product structure is diverse, adaptable and easy to install. Combined needle roller bearings are widely used in machine tools, metallurgical machinery, textile machinery and printing machinery, and can make mechanical system designs very compact and smart. [1]
Thrust editing
The thrust bearing is composed of a thrust cage assembly with a needle roller or a cylindrical roller or a ball and a thrust washer. Needle rollers and cylindrical rollers are held and guided by thrust cages. When used with different series of DF thrust bearing washers, many different combinations of bearing arrangements are available. Because the selection of high-precision cylindrical rollers (needle needles) increases the contact length, this bearing can obtain high load capacity and high rigidity in a small space. Another advantage is that if the surface of adjacent parts is suitable for the raceway surface, the gasket can be omitted, which can make the design compact. The cylindrical surfaces of needle rollers and cylindrical rollers used for DF thrust needle roller bearings and thrust cylindrical roller bearings are The modified surface can reduce edge stress and improve service life. [1]
Installation edit
Installation of full complement needle roller bearings, usually with an auxiliary sleeve
Needle bearing
Needle bearing
of. At this time, the auxiliary roller or auxiliary sleeve supports the needle roller so that the needle does not fall out. The journal raises the needle with its own chamfer. As the needle bearing moves slowly inward on the journal, the auxiliary roller Or the auxiliary sleeve is slowly withdrawn until it is installed in the working position. The outer diameter of the auxiliary roller and auxiliary sleeve should be 0.1-0.3mm smaller than the shaft diameter. When installing, first coat the inner surface of the bearing outer ring with grease, place the needle against the inner surface (there should be a gap when putting the last needle), and then replace the auxiliary roller that replaces the journal or bearing inner ring Or push the auxiliary sleeve into the hole of the outer ring, and align its end face with the end face of the mounting shaft or the end face of the inner ring of the bearing that has been installed on the shaft, and then use a press or a hammer to apply pressure. Needle roller bearings can also be installed by coating a thin layer of lubricant on the outer diameter of the auxiliary sleeve and inserting it into the outer ring of the bearing so that the auxiliary sleeve and the outer ring of the bearing form an annular hole. After installing the needle roller, push out the auxiliary sleeve with the working shaft. For needle roller bearings without inner ring or outer ring, when installing, you can first apply a thin layer of grease to the rolling surface of the shaft or housing hole, and then place the needle roller in close contact with the grease on the installation site. When placing the last needle, there should be a gap. The gap should be 0.5mm on the circumference of the needle bearing. The last needle roller cannot be squeezed in, or one needle is missing, because the bearing will be stuck and cannot rotate when it is squeezed hardly; when it is small, the gap is too large, which may cause the needle roller to occur during bearing operation Twist and break. For needle roller bearings with stamped outer ring, because the outer ring wall is very thin, non-needle bearings must be installed by hammering with a hand hammer. They should be pressed in with a press. Because when the hand hammer strikes, the pressure is not uniform, and it is easy to cause local deformation of the outer ring of the needle bearing. [1]
Contrast editing
1. The friction coefficient of rolling bearing is smaller than that of sliding bearing, and the transmission efficiency is high. The friction coefficient of general sliding bearings is 0.08-0.12, while the friction coefficient of rolling bearings is only 0.001-0.005; 2. 2. Rolling bearings have been standardized, serialized and generalized, suitable for mass production and supply, and very convenient to use and maintain; Rolling bearings are made of bearing steel and are heat-treated. Therefore, rolling bearings not only have high mechanical properties and long service life, but also can save the expensive non-ferrous metals used in the manufacture of sliding bearings; 4. The internal clearance of the rolling bearing is small, and the machining accuracy of each part is high, so the running accuracy is high. At the same time, the rigidity of the bearing can be increased by pre-loading. This is very important for precision machinery; 5. 5. Some rolling bearings can support both radial and axial loads, so the structure of the bearing support can be simplified; 6. 6. Because the rolling bearing has high transmission efficiency and less heat generation, it can reduce the consumption of lubricating oil and save lubrication and maintenance; 7. Rolling bearings can be easily applied to shafts in any orientation in space. [1]
Notes edit
Needle roller bearings have large bearing capacity and are suitable for supporting structures with restricted installation dimensions.
Needle bearing
Needle bearing
The surface of the journal is hardened as a rolling surface, and the bearing is press-fitted into the seat hole without axial positioning. The bearings should be filled with a suitable amount of grease before installation. Normally, no lubrication is required after assembly. BK bearings are used for the support of journals without protruding ends. The end faces are sealed to seal and can withstand small axial movements. [1]
Cause of damage edit
Needle bearing
Needle bearing
In general, 33.3% of needle roller bearings are damaged due to fatigue, 33.3% of needle roller bearings are due to poor lubrication, and 33.3% are due to contaminants entering the bearings or improper disposal of equipment. [1]
Fine dust cleans the bearing and the surrounding environment. Fine dust that is invisible to the naked eye is a powerful killer of the bearing. It can increase bearing wear, vibration and noise. When punching forms a strong punch when using the equipment, it is very likely that the needle roller bearing will be damaged or the bearing will be directly struck with a hammer, and the pressure will be transmitted through the rolling body. The impact of non-professional tool installation The use of suitable and accurate equipment can avoid the use of cloth and staple fibers. Needle roller bearings, whether in laboratory tests or in practical use, can clearly see that under the same operating conditions, the appearance of the same needle roller bearings, the actual life is very different. [1]
Disassembly method edit
Percussion

The knocking force is generally applied to the inner ring of the bearing. The knocking force of the shield machine room should not be added to the rolling elements and cages of the bearing. This method is simple and easy to use, but it will easily damage the bearing. When the bearing is located at the end of the shaft, use less than A copper rod or other soft metal material with an inner diameter abuts against the shaft end, a pad is added to the lower part of the bearing, and it can be removed by lightly tapping with a hand hammer. Application of this method should pay attention to the placement of the pads should be appropriate, the focus should be correct. [1]
Hot dismantling

Used to remove tight-fit bearings. The oil can heated to about 100 ° C is poured on the bearing to be dismantled. After the bearing ring is thermally expanded, the bearing can be pulled out with a puller. [1]
Push method

 Push the bearing with a press, the work is stable and reliable, without damaging the machine and the bearing shielding machine room. Presses are manual, mechanical or hydraulic. Note: The pressing point of the press should be on the center of the shaft, and it should not be biased. [1]
Pull out method

专门 Special puller is used. When disassembling, as long as the handle is rotated, the bearing will be slowly pulled out. When disassembling the outer ring of the bearing, the corners of the puller's legs should open outwards; when disassembling the inner ring of the bearing, the two feet of the puller should be inward and caught on the end face of the inner ring of the bearing. [1]
Benefitsedit
Needle roller bearings are equipped with thin and long rollers (roller length is 3 to 10 times the diameter, straight
Needle bearing
Needle bearing
Diameter is generally not greater than 5mm), so the radial structure is compact, and its inner diameter and load capacity are the same as those of other types of bearings, and its outer diameter is the smallest, which is especially suitable for support structures with limited radial installation dimensions. Needle roller bearings are used according to different applications. The machining accuracy and surface quality should be combined with bearing rings and applications. Needle roller bearings are bearing units that combine radial needle roller bearings and thrust bearing components.