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Needle bearing is a roller bearing with cylindrical rollers, which are thin and long relative to their diameter.This type of roller is called a needle roller.Despite its small cross-section, the bearing still has a high load capacity. The needle roller bearing is equipped with thin and long rollers (roller diameter D≤5mm, L/D≥2.5, where L represents the length of the roller). As a result, it boasts a compact radial structure. When its inner diameter size and load capacity are equivalent to those of other types of bearings, its outer diameter is minimal, making it especially suitable for support structures where radial installation dimensions are constrained.
According to different usage scenarios, bearings without inner rings or needle roller and cage assemblies can be selected. In this case, the journal surface and housing hole surface that match the bearing directly serve as the inner and outer rolling surfaces of the bearing. To ensure load capacity and operating performance similar to those of ring-type bearings, the hardness, machining accuracy, and surface quality of the shaft or housing hole raceway surface should be similar to those of the bearing race's raceway.This type of bearing can only withstand radial loads.
In addition to the bearings listed in the catalog, which can be used for general engineering applications such as open-type stamped needle roller bearings with outer rings, closed-type stamped needle roller bearings with outer rings, inner ring needle roller bearings and non-inner ring needle roller bearings/non-inner ring cages without needles or full needle roller bearings with cages
The stamped outer ring needle roller bearing is a type of needle roller bearing featuring a thin, stamped outer ring.Its main feature is that the section height is very low and the load-bearing capacity is high.It is mainly used for bearings with compact structure, low price and bearing box inner hole that cannot be used as the rolling track of needle roller cage components.The bearing and the bearing box must be installed in an interference fit manner.If the axial positioning functions such as box shoulders and stop rings can be eliminated, then the inner bore of the bearing housing can be made extremely simple and economical.The stamped outer ring needle roller bearings installed on the shaft end are available in double-sided open and single-sided closed designs.The base end surface of the closed stamped outer ring can withstand a small axial guiding force.Stamped outer ring needle roller bearings are generally not attached to the inner ring.In situations where the shaft neck cannot be hardened or ground, the inner rings listed in the table can be used.The hardened steel outer ring of the stamped needle roller bearing and its needle cage assembly are inseparable.The free space for storing lubricant can extend the interval between replenishments.Bearing is generally designed with single row.However, the wider specifications of bearings 1522, 1622, 2030, 2538 and 3038 series are excluded, as they are equipped with two needle roller cage assemblies.The outer ring of the bearing has lubricating oil holes.According to user needs, all single-row stamped needle roller bearings with a shaft diameter greater than or equal to 7mm can be equipped with an outer ring with lubrication holes (code suffix AS1).For applications where space constraints prevent the installation of an oil seal, open-end or closed-end needle roller bearings with stamped outer rings and oil seals (3 to 5) are available.This type of bearing is equipped with a friction-type oil seal made of polyurethane or synthetic rubber, which is filled with lithium-based grease that has good rust prevention properties and is suitable for operating temperatures ranging from -20 to +100℃.The inner ring of the oil-sealed bearing is 1mm wider than the outer ring, which ensures that the oil seal works well and prevents contamination of the shaft when there is a slight displacement between the shaft and the bearing housing.The inner ring of the bearing also has lubrication holes, which can be supplemented by the outer or inner rings depending on the needs of the bearing configuration.
Solid ring needle roller bearings consist of one or two rings and a set of needles with a cage.According to different application scenarios, it can be divided into bearings with or without inner rings.Therefore, the solid ring needle roller bearing can meet the requirements of light weight, small space occupation and high transmission power.Solid ring needle roller bearings have a small volume and high load capacity.The structural type of double-ribbed (or double-lock ring) needle roller bearing with cage NA, NAV, and NKI can be installed with inner and outer rings (with lock ring, complete set of needles, and cage), respectively. It has high speed limit and is available in single-row and dual-row configurations.If the shaft cannot be used as a raceway, that is, if it is impossible or uneconomical to harden and grind the shaft, this type of needle roller bearing with an inner ring can be used.
Features NA, NKI type bearings without inner rings are RNA, NK type needle roller bearings.This type of bearing has no inner ring and is suitable for supporting structures with limited radial installation dimensions. The journal that matches the bearing directly serves as a rolling surface.As the shaft of the raceway surface, it is necessary to harden and grind the hardware. Only when it is processed to an appropriate size and shape accuracy can the entire needle roller bearing achieve high life expectancy and operational precision.At the same time, due to the absence of an inner ring, the diameter of the shaft can also be appropriately increased, thereby increasing its rigidity.
The combined needle roller bearing is a bearing unit composed of radial needle roller bearings and thrust bearing components. It has compact structure, small volume, high rotation accuracy, and can withstand both high radial loads and certain axial loads.And the product structure is diverse, adaptable and easy to install.Combined needle roller bearings are widely used in various mechanical equipment such as machine tools, metallurgical machinery, textile machinery and printing machinery. They can make the design of mechanical systems very compact and smart.
The thrust bearing consists of a thrust cage assembly with needle rollers or cylindrical rollers or balls, and a thrust washer.The needle rollers and cylindrical rollers are held and guided by the thrust cage.When used with different series of DF thrust bearing washers, many different combinations can be provided for the configuration of the bearings.Due to the use of high-precision cylindrical rollers (needles) that increase contact length, this bearing can achieve high load capacity and stiffness in a small space.Another advantage is that if the surfaces of adjacent parts are suitable for use as raceway surfaces, gaskets can be omitted, resulting in a compact design. The cylindrical surfaces of the DF thrust needle roller bearing and thrust cylindrical roller bearing used to form the modified surface reduce edge stress and improve service life.
The installation of full needle roller bearings is usually carried out using auxiliary sleeves.At this time, the auxiliary roller or sleeve holds the needle rollers so that they do not fall out. The journal lifts up the needle rollers with its own chamfer. As the needle bearing moves slowly inward on the journal, the auxiliary roller or sleeve gradually withdraws until it is installed in the working position.The outer diameter of the auxiliary roller and sleeve should be 0.1-0.3mm smaller than that of the shaft.During installation, first apply lubricating grease to the inner surface of the bearing outer ring and place needle rollers against it (leaving a gap when placing the last roller). Next, push an auxiliary roller or sleeve that replaces the journal or bearing inner race into the hole in the outer ring. Align its end face with the mounting shaft end face or the end face of the bearing inner race already mounted on the shaft. Then use a press or hammer to apply pressure.The needle roller bearing can also be installed by applying a thin layer of lubricating oil on the outer diameter of the auxiliary sleeve, inserting it into the outer ring of the bearing, forming an annular hole between the auxiliary sleeve and the outer ring of the bearing, and then installing the needle rollers in the annular hole.After installing the needle roller, push out the auxiliary sleeve with a working shaft.For needle roller bearings without inner or outer rings, during installation, a thin layer of grease can be applied to the rolling surface of the shaft or housing hole. Then, the needles are sequentially placed against the grease at the mounting location.When placing the last needle roller, a gap should be left, and the size of the gap is preferably 0.5mm on the circumference of the needle bearing.The last needle roller cannot be forced into the bearing, or one less needle roller should not be installed. This is because when it's forced in, the bearing will become stuck and unable to rotate;When the load is too small, the clearance will be too large and it may cause the needle rollers to twist or break during operation.For needle roller bearings with only a stamped outer ring, due to the thin wall of the outer ring, it is not recommended to install them by hand hammering. Instead, they should be pressed in using a press machine.Because the pressure is uneven when hammering, it is easy to cause local deformation of the outer ring of the needle roller bearing.
1. The friction coefficient of rolling bearings is smaller than that of sliding bearings, and the transmission efficiency is higher.The friction coefficient of a typical sliding bearing is 0.08-0.12, while the friction coefficient of a rolling bearing is only 0.001-0.005;2. Rolling bearings have been standardized, serialized and universalized for mass production and supply, making them very convenient to use and maintain;3. Rolling bearings are made of bearing steel and undergo heat treatment, so they not only have high mechanical properties and long service life, but also save the expensive non-ferrous metals used in manufacturing sliding bearings;4. The internal clearance of the rolling bearing is very small, and the processing accuracy of each part is high, so the running precision is high.At the same time, the rigidity of the bearing can be increased by preloading.This is very important for precision machinery;5. Some rolling bearings can withstand both radial and axial loads, thus simplifying the structure of bearing supports;6. Due to the high transmission efficiency and low heat generation of rolling bearings, it can reduce the consumption of lubricating oil and make lubrication maintenance easier;7. Rolling bearings can be easily applied to shafts in any orientation of space.
Needle roller bearings have a large load capacity and are suitable for supporting structures with limited installation dimensions. The journal surface is hardened as the rolling surface, and the bearing is press-fit into the seat hole without requiring axial positioning.Before installation, the bearing should be injected with an appropriate amount of lubricating grease. Usually, after assembly, it does not need to be lubricated again. BK type bearings are used in support without extended ends on the shaft journal, and their end faces are sealed for sealing purposes and can withstand small axial movements.
In general, 33.3% of needle roller bearing failures are due to fatigue damage, while another 33.3% are caused by poor lubrication and the remaining 33.3% are attributed to contaminants entering the bearings or improper equipment handling.
Micro dust cleaning the bearing and surrounding environment, invisible fine dust is a powerful killer of bearings, which can increase wear, vibration and noise of the bearing.When stamping equipment is used, it can lead to strong pressure that may damage the needle roller bearing or directly hit the bearing with a hammer, transferring pressure through the rolling body.The use of suitable and accurate equipment can greatly avoid the use of cloth and short fibers.Whether in laboratory tests or actual applications, it is evident that needle roller bearings with the same appearance under identical operating conditions can have significantly different lifespans.
The striking force is generally applied to the inner ring of the bearing, and the shielding room should not apply it to the rolling elements or cages. This method is simple but can easily damage the bearing. When the bearing is at the end of the shaft, use a copper rod or other soft metal material smaller than the inner diameter of the bearing to hold against the shaft end. Add cushion blocks under the lower part of the bearing, and gently tap with a hammer to remove it.When applying this method, it is important to place the cushion block in the appropriate position and focus on the correct point of application.
Used for disassembling tightly fitted bearings.First, pour the oil heated to about 100℃ into the bearing to be dismantled with an oil can. After the bearing ring expands due to heat, use a puller to pull out the bearing.
Pressing the bearing with a press machine is stable and reliable, without damaging the machine or the bearing shield room.The press can be manually operated, or it can be driven by mechanical or hydraulic pressure.Note: The pressure point of the press should be on the center of the shaft, and it must not be pressed off-center.
Use a special puller. When disassembling, simply rotate the handle and the bearing will be slowly pulled out.When disassembling the bearing outer ring, the two feet of the puller should be bent outward;When disassembling the bearing inner ring, the two feet of puller should be inward and clamped on the end face of the bearing inner ring.
Needle roller bearings are equipped with thin and long rollers (the length of the roller is 3 to 10 times its diameter, which is generally not greater than 5mm), so their radial structure is compact. When their inner diameter size and load capacity are the same as other types of bearings, they have the smallest outer diameter, making them particularly suitable for supporting structures where radial installation dimensions are limited.The processing accuracy and surface quality of needle roller bearings should be combined with the bearing rings and applications according to different usage scenarios.Needle roller bearings are a bearing unit composed of radial needle roller bearings and thrust bearing components.
--Union Trade Tech. Co.,Ltd from Baidu Encyclopedia
