Bearing is called a special unit, which is part of the support to support the shaft and designed to rotate or roll the latter without loss of friction energy. There are several varieties of such structural elements. In this case, the size of the bearings in most cases are regulated by GOST.
Varieties
Nodes of this type are used in industry and other sectors of the economy very widely. There are hydrostatic, gas-static, magnetic and other groups of bearings. However, the most common varieties are sliding and rolling units. According to the perceived load, both of these groups are divided into:
radial;
persistent;
angular contact.
Rolling bearings
The main elements of nodes of this type are balls or rollers located at a certain distance from each other in a special cage called a separator. During the operation of the bearing, they roll along the treadmills of two rings, one of which is static in most cases. Nodes of this type are used in industry most often. The fact is that, in comparison with plain bearings, they have a number of advantages. These include primarily small friction and low lubricant consumption. Simplicity of operation and installation is also what distinguishes these bearings. Standards (their sizes are regulated by GOST) of such nodes are presented in special tables. Therefore, finding a suitable bearing in one case or another will not be difficult. A node of this type can be matched to absolutely any typical design.
Sensitivity to vibration and shock loads is the only drawback that distinguishes these bearings. Standards for their manufacture must be followed. Otherwise, they will not last too long.
Types of rolling bearings
In addition to the perceived load, nodes of this type are classified into groups according to the following criteria:
The shape of the rolling elements. In this regard, distinguish between ball and roller bearings. The rolling bodies of the latter type can be conical, cylindrical, needle-shaped, twisted, barrel-shaped, etc.
By the ability of self-determination. In this case, spherical and non-self-aligning bearings are distinguished.
By the number of rolling bodies. There are single row and double row bearings.
In size. All bearings manufactured to date on this basis are divided into several series.
Depending on the series with the same inner diameter, the width of the bearing and its outer D can vary. Rolling bearings can be used when assembling cars, bicycles, windmills, etc.
Dimensions
The dimensions of nodes of this type are determined by GOST 3478-79. When observed, very strong and durable bearings are obtained. These standards apply to all varieties of rolling units, with the exception of special-purpose models that have a special design. In the latter case, the nodes can be made in a variety of sizes, the most suitable for a particular design.
You can find out the standard sizes of bearings for each series, as already mentioned, from the special tables that indicate the outer and inner diameters, the smallest limit dimensions (Rmin), as well as the nominal width of the inner and outer rings (B). As an example, below is a table for a series of bearings of diameters 8 (abbreviated).
d | D | Size B for Series | Rmin |
7 | 1 | 2 | 3 | 4 | 5 | 6 |
0.6 | 2.5 | - | 1 | - | 1.4 | - | - | - | 0.05 |
1.5 | 4.0 | - | 1.2 | 1.7 | 2 | - | - | - | 0.05 |
3 | 7 | - | 2 | 2.5 | 3 | - | - | - | 0.10 |
7 | fourteen | - | 3.5 | 5 | 6 | - | - | - | 0.15 |
20 | 32 | 4 | 7 | eight | ten | 12 | 16 | 22 | 0.3 |
200 | 250 | 16 | 24 | thirty | 37 | 50 | 67 | 90 | 1 for series 7, 1.5 - for series 1-6 |
More detailed tables can be found in the specialized literature. There are also bearing standards in Compass, a graphical editor for computer-aided design (in the design library). There are tables for different diameters of nodes.
Accuracy classes
Thus, the standard sizes of rolling bearings can be found from special tables. However, in some cases, some deviations in dimensions from GOST are allowed. According to the accuracy class, rolling bearings are divided into:
normal "0";
high accuracy "6";
high "5";
especially high "4";
superhigh "2".
Units designed for different designs may have strictly defined tolerances. So, for example, the standards of bearings for a bicycle (608 type) are as follows:
ball tolerances - 0 / -0.005;
internal track - + 0.0001 / -0.0003;
external track - + 0.0001 / -0.0005.
Designations
The standards of rolling bearings in their manufacture are followed. In order for the consumer to see what kind of unit is in front of him and for what purposes it can be used, special markings are used. Rolling bearings are usually marked with an engraved set of numbers. Sometimes standard markings include letters. Wherein:
The first number or letter indicates the type of bearing.
The following two numbers indicate the series of the node. The first indicates a group of width or height, the second indicates a group of diameter.
The last two digits are the hole diameter code. If you multiply it by 5, you can get the value of d in mm.
Standard sizes of bearings 66414 (fits in this case are selected according to GOST 3325-85), for example, such:
d - 70 mm;
D - 180 mm;
width - 42 mm;
weight - 5.74 kg.
Plain bearings
Knots of this type consist of two main elements: a strong body and a liner, between which there are special lubricants. The main advantages of such bearings include primarily small diameters, as well as the ability to make them detachable and used for shafts of very complex design. The disadvantages of the nodes of this variety are considered not too long service life and the need for expensive lubricants.
Types of Plain Bearings
Currently there are nodes in this group:
high speed;
detachable (used, for example, in crankshafts) ;
precision machines, precisely guiding shafts and enabling clearance adjustment;
cheap low-speed mechanisms;
designed to work in special conditions (water, aggressive environments).
Depending on the operating mode, this type of bearing may have fluid or semi-fluid friction. In the first case, the working surfaces of the housing and shaft are separated by a rather thick layer of oil. In semi-liquid friction, the boundary friction is added to the fluid (through the thinnest oil film formed by molecular bonds).
Dimensions of plain bearings
The dimensions of the nodes of this group are determined by GOST 2795. Data from special tables is also something that must be taken into account when making such bearings. Standards in this case apply to such parameters as:
The table below (abbreviated) presents the standard sizes of plain bearings in different rows.
d | D for rows | L for rows |
1 | 2 | 1 | 2 | 3 | 4 |
1 | 3 | | 1 | 2 | | |
nine | fourteen | 12 | 6 | ten | fourteen | |
25 | 32 | thirty | 20 | 25 | thirty | 35 |
Design features and materials
The standards of plain bearings are thus strictly defined by GOST. There are some requirements for the quality of the materials used for their manufacture. The plain bearing housing , as already mentioned, can be solid or split. In the latter case, special studs or bolts are used to connect the parts. The plain bearing shell is in the form of a sleeve. In an integral unit, it can be made of two halves. On shafts subject to deformation, usually self-aligning plain bearings are mounted.
For the manufacture of nodes of this type, the following materials can be used:
In some cases, but of course, very rarely, bushings are made of wood or even chipboard.
Primary requirements
Thus, the bearings standards (or rather, their observance) allow us to produce the highest quality, durable and with excellent performance characteristics. The requirements for the nodes of this group are as follows:
The materials and design of the plain bearings must be such as to ensure a minimum coefficient of friction between the housing and the sleeve.
The strength and rigidity of the node must be such that it can withstand any necessary loads.
Maximum simplicity of bearing design is appreciated. When installing it, there should not be any difficulties.
Bearings should be made in such a way that their surface has sufficient area to remove the heat generated during operation.
How do
They produce sliding and rolling bearings at specialized large enterprises, which usually include two main workshops: thermal and mechanical. Assembly lines of such plants most often operate in automatic mode. In addition to them, modern spraying machines are also installed in the workshops.
In our country, the nodes most popular are those produced at domestic factories, as well as in Switzerland (SKF). SKF bearing standards are the same as in Russian.