Double Row Miniature Cylindrical Roller Bearings Nu And Nj Bearing NU1038M

Jatec NU1038M Product introduction

Short cylindrical bearings

Cylindrical rollers and raceways are linear contact bearings. Large load capacity, mainly bearing radial load. The friction between the rolling element and the ferrule flange is small, which is suitable for high-speed rotation. According to whether the ring has a flange, it can be divided into NU, NJ, NUP, N, NF and other single row cylindrical roller bearings, and NNU, NN and other double row cylindrical roller bearings. The bearing is a separable structure for the inner and outer rings.

Cylindrical roller bearings with no flange in the inner or outer ring can be used as free end bearings because the inner and outer rings can be moved relative to each other in the axial direction. Cylindrical roller bearings with double flanges on one side of the inner and outer rings and single flanges on the other side can accommodate a certain degree of axial load in one direction. Generally, steel stamping cages are used, or copper alloy turned solid cages. However, some use polyamide forming cages.

peculiarity

1. The roller and the raceway are line contact or repair line contact, with large radial bearing capacity, suitable for bearing heavy loads and shock loads.

2. The friction coefficient is small, suitable for high speed, and the limit speed is close to deep groove ball bearings.

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

4. The processing requirements for the shaft or housing bore are high, and the relative deflection of the axis of the outer ring after bearing installation should be strictly controlled to avoid contact stress concentration.

5. The inner or outer ring can be separated for easy installation and removal

Product features

The cylindrical rollers are in linear contact with the raceways and have a large radial load capacity. It is suitable for heavy loads and shock loads, as well as high-speed rotation.

Cylindrical roller bearing raceways and rolling elements are geometrically shaped. After the improved design, with high load carrying capacity, the new structural design of the flange and 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 flange, and improves the performance of the bearing.

structure

1. The outer ring without flange N0000 type and the inner ring without flange NU0000 type, cylindrical roller bearings can accept large radial loads, high limit speed, do not bind the axial displacement of the shaft or shell, and cannot accept axial loads.

2. Cylindrical roller bearings with flanges in the inner and outer rings NJ0000 and NF0000 can bind the axial displacement in one direction of the shaft or shell, and can accept small unidirectional axial loads. NU0000+HJ0000, NJ0000+HJ0000 and NUP0000 bearings can bind the axial displacement in both directions of the shaft or housing in the axial clearance field of imported bearings, and can accept small axial loads in both directions].

Cylindrical roller bearing category

Cylindrical roller bearings are separable bearings that are easy to mount and dismount. Cylindrical roller bearings can withstand large radial loads and are suitable for use at high speeds.

These bearings allow a small angular error (inclination) between the inner and outer ring axes, only 2′~4′. Therefore, the machining accuracy of the shaft and bearing housing is relatively high, otherwise, it is easy to have uneven loads or stress concentrations in the raceway contact parts. However, the modification of the roller or raceway contact busbar can reduce the occurrence of stress concentrations.

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 installed. Bearings of different structures are also manifested in the position design of the flange. Among them, cylindrical roller bearings commonly used are in the following forms:

Single row cylindrical roller bearings: Single row cylindrical roller bearings are separable bearings for easy mounting and dismounting, both rings can be tightly fitted, and the modified contact line between the roller and raceway can reduce stress concentration.

Double row cylindrical roller bearings: Double row cylindrical roller bearings are swimming bearings whose separability makes mounting and dismounting convenient. Both ferrules can be fitted snugly. Double row cylindrical roller bearings hardly allow for tilt angles.

Single row bearings

Single row cylindrical roller bearings

N, NU type

N-type bearings have no flanges on the outer ring and flanges on both sides of the inner ring. Displacement between shafts relative to housings in both axial directions can be allowed. Bearings of type NU have flanges on both sides of the outer ring and no flanges on the inner ring. It is also possible to allow displacement between shafts relative to housings in both axial directions. Therefore, this type of construction is suitable for use as a moving end bearing.

NJ, NF type

NJ type bearings have flanges on both sides of the outer ring and flanges on one side of the inner ring. It can withstand a certain amount of unidirectional axial load. The NF type has a flange on one side of the outer ring and a flange on both sides of the inner ring. It can also withstand a certain amount of unidirectional axial load. This type of construction is therefore suitable for use as one-direction axial positioning bearings.

NUP, NFP type

Bearings of type NUP have flanges on both sides of the outer ring, single flanges on one side of the inner ring, and separable flat rings on the other side. It can withstand a certain amount of axial load in both directions.

The outer ring of the NFP type has a (fixed) single flange on one side, while a separable flat ring on the other side and a flange on both sides of the inner ring. It can also withstand a certain amount of bidirectional axial load. These structural bearings limit the displacement of the shaft relative to the housing in both axial directions. It is therefore suitable for use as a fixed end bearing.

NH (NJ+HJ) type

NH type bearings are the structure of NJ type bearings combined with HJ type diagonal retaining rings. Due to the short inner ring of NUP type bearings, and the fact that the flat ring is not fixed, it is inconvenient to use, while NH type bearings can use the width of the entire inner ring of NJ type bearings to maintain a closer fit with the shaft. And NH type bearings are easier to mount and dismount.

NH type bearings limit the displacement of the shaft relative to the housing in both axial directions. It is therefore suitable for use as a fixed end bearing.

Double row bearings

Double row cylindrical roller bearings are available in two configurations: cylindrical bore and tapered bore (bearing post-code plus K). This type of bearing has the advantages of compact structure, large rigidity, large load carrying capacity and small deformation after load, and is especially suitable for machine tool spindle support. The conical inner bore can also play a role in slightly adjusting the clearance, and can simplify the structure of the positioning device and facilitate installation and removal. Commonly used double row cylindrical roller bearings are available in the following forms:

NN and NNU type

Bearings of type NN have no flanges on the outer ring, flanges on both sides of the inner ring, and middle flanges in the middle. Displacement in both directions in the axial direction between shafts relative to housings can be allowed.

The outer ring of NNU type bearings has flanges on both sides and a middle flange in the middle, and the inner ring has no flange. Displacement in both directions in the axial direction between shafts relative to housings can be allowed. Therefore, this type of construction is suitable for swimming end bearings. The cages of this type of bearing mostly use turn-based solid cages.

NNF type

NNF type bearings are double row full complement cylindrical roller bearings consisting of one outer ring with a middle flange and two with a double flange inner ring. The rollers are guided by the flange of the inner ring, and the two inner rings are fastened together with fastening rings. In addition to large radial and axial loads, the structure can also withstand overturning moments, so it is often used as a fixed end bearing.

NNF type bearings are sealed in contact on both sides. The bearings are filled with grease that operates at temperatures ranging from -50°C to +110°C, but due to the limitation of the sealing material, the operating temperature of the bearings is limited to between -40°C and +80°C. In the case of good working conditions, the NNF bearings with seals do not need to be maintained, if the bearings are exposed to water vapor or polluted environment for a long time, and are running at medium and high speeds, the bearings can be re-lubricated through the lubricating oil groove and lubricating oil holes on the outer ring.

Four-row bearings

Four-row cylindrical roller bearings are mainly used in cold and hot rolling mills, billet mills and other rolling mill machinery, the bearings are separated structure, bearing rings and rolling element assemblies can be easily separated, therefore, the bearing cleaning, inspection or installation and disassembly are very convenient.

FC type

FC design bearings consist of two outer rings and an inner ring, each with flanges on both sides and a middle flange in the middle, and no flange in the inner ring.

FCD type

FCD type bearings are actually a combination of two NN type bearings.

FC and FCD bearings allow displacement in both axial directions between shafts relative to housings. Therefore, this type of construction is suitable for swimming end bearings. The cages of this type of bearing are mostly made of 13:58 vehicle body.

Accuracy class

Cylindrical roller bearings can be divided into PO, P6, P5, P4, P2 according to the accuracy class.

Method for radial clearance adjustment of cylindrical roller bearings

Common methods for adjusting radial clearance of full complement cylindrical roller bearings are as follows

1. For cylindrical and oval bearings, the backlash can be adjusted by manual scraping or the method of polishing and scraping after faceted padding in the bearing.

2. For cylindrical and oval bearings, the top clearance can be adjusted by manual scraping or pad the bearing when the situation permits.

3. For multi-oil wedge fixed bearings, in principle, it is not allowed to scrape and adjust the bearing gap, and the new tile should be replaced when the gap is not suitable.

4. For multi-oil wedge tiltable bearings, it is not allowed to scrape the tiles, and the tiles should be replaced when the gap is not suitable. For tiles with adjustable thickness, the amount of tiles can be adjusted by adding stainless steel pads under the adjustment block behind the tile, or by reducing the thickness of the adjustment block. Note that for multi-oil wedge tiltable bearings, the thickness error between the same group of tiles should be less than 0.01mm.

Application scenarios

Large and medium-sized electric motors, rolling stock, machine tool spindles, internal combustion engines, generators, gas turbines, gearboxes, rolling mills, vibrating screens and lifting and transportation machinery.

Pay attention to the problem

Vibration aspect

In ordinary use, vibration is quite sensitive to bearing damage, and peeling, indentation, rust, cracks, wear, etc. will be reflected in the bearing vibration measurement. Therefore, the magnitude of the vibration can be measured by using a special bearing vibration measuring device (frequency analyzer, etc.), and the specific situation of the abnormality can be inferred from the frequency distribution. The measured values vary depending on the conditions under which the bearings are used or the sensor mounting position, so it is necessary to analyze and compare the measured values of each machine in advance to determine the judgment criteria.

Temperature-wise

High temperatures often indicate that cylindrical roller bearings have been in an abnormal condition. High temperatures are also harmful to the lubricants of bearings. Sometimes bearing overheating can be attributed to the bearing lubricant. Long-term rotation of bearings at temperatures above 125°C will reduce bearing life. The causes of high temperature bearings include: insufficient or excessive lubrication, impurities in the bearing raceway, too high limit speed, long-term overload of the bearing, etc.

Maintenance

The dismounting of the bearings is carried out at regular intervals and when the bearings are replaced. After disassembly, if it continues to be used, or if it is necessary to check the condition of the bearing, the disassembly should be carried out as carefully as when mounted. Pay attention not to damage the bearing parts, 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. In the disassembly, study the disassembly method, sequence, and the matching conditions of the bearing according to the drawings to obtain the foolproof disassembly operation.

To disassemble the outer ring of the interference fit, several outer ring screws for extrusion screws are set on the circumference of the shell in advance, and the screws are tightened equally on one side and disassembled at the same time. These screw holes are usually covered with blind plugs, tapered roller bearings, etc. separating bearings, several cuts are made in the shoulder of the shell, and the pads are used to disassemble with a press, or gently tapped.

The removal of the inner ring can be easiest with a press. At this time, care should be taken to let the inner ring withstand its pulling force. In addition, the pull-out fixture shown is also mostly used, and regardless of the fixture, it must be firmly stuck on the side of the inner ring. For this purpose, it is necessary to consider the size of the shaft shoulder or study the machining of the upper groove at the shoulder in order to use the pull fixture.

The inner ring dismounting of large bearings adopts the hydraulic method. Oil pressure is applied by placing oil holes in the bearings to make it easy to pull. Bearings with large widths are disassembled using the hydraulic method and pulling fixtures.

The inner ring dismounting of cylindrical roller bearings can be carried out using the induction heating method. A method of heating a local area in a short period of time to expand the inner ring and then pulling out. Induction heating is also used where a large number of such bearing inner rings need to be mounted.

When removing the bearing for inspection, first make a record of the appearance 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 carried out in rough washing and fine cleaning, and a metal grid frame can be placed at the bottom of the container used.

b. When rough washing, use a brush or other to remove grease or sticky in oil. At this time, if the bearing is rotated in oil, pay attention to the damage to the rolling surface due to foreign matter.

c. During fine cleaning, slowly rotate the bearing in oil, which must be carried out carefully.

The cleaning agents commonly used are neutral, do not contain water, diesel or kerosene, and sometimes warm lye is used as needed. Regardless of the cleaning agent used, it must be filtered frequently to keep it clean.

Immediately after cleaning, apply anti-rust oil or anti-rust grease to the bearings.

Internal control size chart

Notes

Deep groove ball bearings, the bearing load is too small during operation, which will cause sliding between the ball and the raceway, which will become the cause of abrasion. In particular, large deep groove ball bearings with high ball and cage weights have this tendency. In many cases, the bearing will be corroded, and there are many reasons for bearing rust, and the most common in our daily life are mainly the following factors:

1) Due to poor sealing device, it is invaded by moisture, dirt, etc.;

2) The bearing is not used for a long time, exceeds the rust-proof period, and lacks maintenance.

3) The roughness of the metal surface is large;

4) Contact with corrosive chemical medium, bearing cleaning is not clean, the surface is dirty, or contact with sweaty hands on the bearing, after the bearing is cleaned, it is not packaged or installed in time, long-term exposure to the air, and is attacked and contaminated by air moisture;

5) Ambient temperature and humidity and contact with various environmental media; The rust inhibitor fails or the quality does not meet the requirements.