The design of various modern machines includes many nodes with rotating parts. These are all kinds of levers, wheels, drums. The friction between the parts that occurs in such units can lead to the destruction of materials and the rapid failure of the machine. To prevent this from happening, the rotating elements are connected by bearings.
Details of this type can have a different configuration, size, principle of operation. Design features of such products are reflected in their labeling. Deciphering bearings according to such designations is an extremely simple matter.
Two main varieties
All products of this type currently used in various mechanisms can be divided into three large groups. Bearings are installed in rotating units:
All these varieties of products are widely in demand and can be used both in industrial units, and in machine tools, cars, etc.
Plain bearings
In parts of this type, friction is reduced by lubrication. Such bearings may consist of:
- housing with a hole and a sleeve pressed into it;
- from the detachable case and two tabs.
They make such bearings from different materials. Their case is usually made of steel. The sleeve or tabs are most often made of bronze or other similar alloys. Thanks to this design, the friction between the bearing parts is significantly reduced. In order to completely reduce it to nothing, grooves are made in the inserts of products of this type into which oil is poured. When the shaft rotates, the latter is pulled under the metal. As a result, an oil film is formed. She lifts the shaft and it is no longer in contact with the liner.
The main advantages and disadvantages
Plain bearings are slightly simpler to manufacture than rolling bearings. They can be used in a variety of nodes. For example, such bearings are often used for electric motors.
The advantages of plain bearings, among other things, include the following advantages:
- silent operation;
- possibility of use in heavily loaded nodes.
In addition, the advantage of bearings of this type is that they eliminate the reels very well.
But the products of this variety, of course, have their drawbacks. The main disadvantage of such bearings is the difficulty in maintenance. In order for such a part to serve for a long time and perform its functions well, it is placed in an oil bath or pumps are used to constantly supply the latter.
Also disadvantages of plain bearings are:
- the inability to use in very hot nodes (oil may ignite);
- the need to use expensive non-ferrous metals in the design;
- increased starting factors;
- increased dimensions in axial direction.
Rolling bearings
Such products are currently more popular than plain bearings. Non-ferrous metals in such details can also be used, but usually they are still made entirely of steel. Friction in products of this type is reduced due to the presence of metal balls, rollers, cones or, for example, needles in their design. Such elements are placed in rolling bearings in the grooves between the housing and the fixed support.
The advantages of this type of product are as follows:
- low costs of overcoming friction (several thousandths of the load on the shaft);
- ease of maintenance.
The oil in such bearings is usually changed only during the next repair of the unit. The disadvantages of products of this type include primarily the fact that they cannot bear large axial loads. If the pressure is too strong, the rollers or balls in this type of bearing can easily break.
Needle products
This type of detail combines the advantages of rolling and plain bearings. In this case, thin long cylindrical needles are installed between the body and the fixed shaft. When the assembly rotates slowly, such a bearing works according to the ball principle. That is, the needles on which the body rolls are responsible for reducing friction in it.
At high speeds, a product of this type begins to act as a plain bearing. That is, the needles in it stop rolling and begin to move in a continuous mass with a separate layer of oil.
Despite the fact that such parts are, in fact, a combined type, in the classification they are usually referred to as a group of rolling bearings. They are most often used where large or variable loads occur in the nodes. It can be, for example, aircraft engines, giant rolling machines, etc.
Classification of rolling bearings
Such products can be divided into groups according to the following criteria:
- in the direction of perceived load;
- depending on the size ratio;
- by dimensional accuracy and rolling;
- in the form of rolling bodies.
Also, these products can be classified by the method of manufacture of the separators. The properties of such parts are reflected in their marking. The decoding of rolling bearings includes, for example, characteristics such as series, type, accuracy class.
Groups in the direction of perceived load
In this regard, rolling bearings can be:
- radial
- persistent;
- angular contact.
Products of the first variety are the most popular and are used very widely. Radial bearings perceive mainly the load directed perpendicular to the axis of the shaft.
Persistent products in industry, automotive are somewhat less common. Such bearings generally only absorb axial load. Most often, products of this variety are used in metallurgy and mechanical engineering.
Axial radial bearings are capable of absorbing both axial and radial loads. There are at least two rows of rolling bodies in such products - in perpendicular planes.
Size classification
In this regard, several groups of similar products are also distinguished. Depending on the aspect ratio of the inner and outer rings, the classification of bearings is as follows:
- especially light;
- lungs;
- wide lungs;
- medium;
- medium-wide.
Also in the nodes and mechanisms can be used heavy products of this type. Below is a table of sizes of single row ball bearings.
Depending on the series, in this case, with the same diameter of the inner ring, the diameter of the outer or its width can vary. The width of the rolling bearings are classified as:
- particularly narrow;
- narrow
- normal
- wide;
- especially wide.
The above table for ball bearings sizes shows the parameters for light and medium series products.
Accuracy Classification
Rolling bearings are installed in the nodes, on which the effective operation of the whole mechanism as a whole depends. At the same time, such products are manufactured in compliance with the standards provided by GOST. Rolling bearings in terms of accuracy can be classified by:
- size;
- rotation parameters.
In the first case, the quality of the product is determined by the deviations of the external and internal diameters, as well as the width of the rings. Rotation accuracy is measured by the degree of runout in the radial and lateral directions. At present, the following classes of rolling bearings are distinguished in this regard:
- 0 - normal with beating of the inner ring (up to 20 microns);
- 6 - increased accuracy with beating (up to 10 microns);
- 5 - high precision with runout (up to 5 microns);
- 4 - especially high accuracy (up to 3 microns);
- 2 - ultra-high accuracy (up to 2.5 microns).
Coarse rolling bearings of class 7 and 8 are also manufactured by industry, with runout over 20 microns. The price of such products is determined mainly by the accuracy class of rotation. The higher it is, the more expensive the bearing is.
Classification according to the shape of the rolling elements
Depending on the shape, details may also vary. Most often in the industry and automotive industry ball bearings are used. GOST defines both their size and accuracy class. Such products are considered the simplest to manufacture and fastest. These bearings allow, among other things, quite a large angular velocity. Their main advantage is low cost. The disadvantages of bearings of this type include the fact that they cannot bear a significant load.
Roller products are characterized by increased carrying capacity and are able to withstand shock loads. However, such products completely prevent distortion of the shaft. In this case, the rollers begin to work along the edges, which leads to rapid wear of the bearing. Details of this type can be worked out several times longer than ball.
Products with twisted rollers are very undemanding to assembly accuracy. They are used in those cases when radial loads of shock type arise in the assembly. The sizes of bearings of this variety are usually small.
Tapered roller bearings are used in those units where both radial and one-sided axial loads act simultaneously. Install them at medium and low shaft speeds. Such products are used mainly in the same cases as angular contact ball bearings. GOST, of course, determines the dimensions of such parts.
Self-aligning bearings are used when the skew of the rings can reach 2-3 degrees. Among other things, such products allow a slight axial load.
The design of the simplest bearings has only one row of rolling elements. But in industry, more complex products of this type can also be used - 2-4 rows.
Sometimes in various kinds of units and mechanisms, rolling bearings of a special design can also be installed - ringless. For such products, the rolling bodies are located directly between the housing and the shaft. The disadvantage of such designs is, of course, considered primarily the complexity of assembly and disassembly.
Decryption
The interpretation of the rolling bearings is important to determine its characteristics. In order for the consumer to be able to purchase exactly the bearing he needs, such products are designated by manufacturers in a special way. In the labeling of such products there are always several numbers by which it is possible to determine its class and series.
The decoding of the rolling bearings is carried out, according to the regulations, from right to left. The first and second figures indicate the inner diameter of the product. To determine the actual size, this number just needs to be multiplied by 5.
Focusing on the third digit, you can find out the outer diameter of the bearing, that is, its series. The latter are designated as:
- ultralight - 8 or 9;
- especially easy - 1 or 7;
- easy - 2 or 5;
- average - 3 or 6;
- heavy - 4.
On the fourth digit on the right in the marking, you can decipher the type of rolling bearing:
- 0 - radial single-row ball;
- 1 - radial ball double row;
- 2 - radial with cylindrical short rollers;
- 3 - double-row radial roller;
- 4 - needle;
- 5 - radial with twisted rollers;
- 6 - angular contact ball;
- 7 - angular contact roller conical;
- 8 - persistent ball;
- 9 - persistent roller.
According to the fifth and sixth figures on the right, it is possible to determine the design features of the bearing that do not have a special effect on its performance. Such products can be, for example, non-separable, have a protective washer, a groove on the outer ring, etc.
The seventh digit on the right in the marking characterizes the bearing series in width.
Of course, when buying, you can easily find out the accuracy class of such a product. Deciphering the designations of domestic bearings on this basis is also an absolutely simple matter. To the left of the considered series of numbers in the marking of such parts through the dash there is another figure. It is on it that the accuracy is determined.
Bearings of a class from 0 to 6 can be used in various kinds of assemblies. In this case, normal products of this type, marked with the number 0, are most often used. In parts operating at a high frequency, very high-quality bearings, designated 4-5, are usually used. Class 2 products are most often used in hygroscopic devices.
Designation Example
So, the decoding of the marking of ball bearings or any other is an extremely simple matter. The mark in products of this type is applied to one of the rings. On collapsible bearings, it is affixed to both parts.
Product parameters with marking, for example, 67210 will be as follows:
- diameter - 10 * 5 = 50 mm;
- 2 - light series;
- 7 - angular contact conical;
- 6 - diametrical clearance in the main row.
Deciphering the bearing by number is usually done in this way. Since nothing is indicated in the marking of this product on the left through a hyphen, its accuracy class will be zero. But for other bearings, its designation, of course, can be affixed.
Bearing classes
Such products can be divided into:
- direction of load;
- the principle of the occurrence of lift in the oil layer;
- body type.
By the first sign, such products are classified into radial and thrust. Like rolling bearings, parts of this kind can absorb radial or axial loads. In some cases, the nodes use products of this variety with combined supports. For such bearings, axial loads occur on special ridges or ends of the bearings.
Lifting classification
In this regard, distinguish plain bearings:
- hydrodynamic;
- hydrostatic.
In the first case, excess pressure in the oil layer is formed due to its penetration into the wedge gaps with the relative movement of the surfaces. Such bearings have a fairly simple design. Hydrostatic products are characterized in that the oil pressure in them is created during the operation of the pump.
Varieties by case type
The simplest bearings of this type - blind ones - have in their construction an integral pressed-in sleeve made of antifriction material. Also in the nodes can be used and detachable products of this variety. For such plain bearings, a split sleeve is installed between the cover and housing, bolted together. It is believed that products of this type are more convenient in operation.
What can be liners
This element of the design of plain bearings is most often, as already mentioned, made of bronze. However, the industry also produces such products with bushings made of steel or cast iron with an additional layer of antifriction alloy.
Lubrication Modes
In order for the sliding bearing to work long and efficiently, it is often necessary to service it almost daily. Such products need regular lubrication. The following varieties can be used for plain bearings:
- liquid mineral and synthetic oils;
- greases based on calcium sulfonate or lithium soap;
- solid - molybdenum disulfide, graphite.
Gasostatic bearings can also be used in various kinds of units and mechanisms. In such products, nitrogen or inert gases replace grease. Products of this type are usually used in lightly loaded mechanisms.
Actually, there are three modes of lubrication of sliding bearings:
- boundary;
- semi-liquid;
- liquid.
In the first case, the contact surfaces are lubricated due to an oil film formed on a fixed shaft on the trunnion surface. Boundary lubrication is considered a type of ineffective. When it is used, a large number of irregularities contact inside the bearing. In addition, when using this method, the viscosity of the oil is lost.
At the time of application of the semi-fluid lubrication method, an oil layer forms between the journal and the liner during rotation of the shaft. In this case, contact of irregularities practically does not occur in the bearing. When using this technique, the shaft pops up under the action of the lifting force of the oil.
When using the liquid lubrication technique, the bearing liner and journal are completely separated by the oil layer. Contact irregularities in this case does not occur at all. Therefore, such a lubrication technology can be considered the most effective.
Imported bearings
Products of this type are manufactured all over the world practically according to the same standard. Imported bearings for the nodes of mechanisms used at the enterprises of the Russian industry are usually as good as domestic ones. But products delivered from abroad are marked, of course, in a completely different way. . .
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