Bearing type selection process and bearing basic code introduction

Bearing type selection process and bearing basic code introduction
Rolling bearing selection process

With the development of industry, the use of bearings is more and more extensive, and still in the continuous development, has become one of its important mechanical components, bearing varieties, different use requirements on the choice of bearings are also different, the shaft selection of the correct or not decide the bearing's ability to action of the high and low, how to choose the most suitable bearings in a variety of bearings is often very difficult.

Speed

Under certain load and lubrication conditions, the maximum speed allowed for rolling bearings is called the limiting speed of the bearing. Speed and bearing type, size, precision, clearance, cage material and structure, lubrication, lubricant nature and amount, load size and direction and heat dissipation conditions and other factors.

Limit speed of various bearings see the parameters of various types of bearing specifications table, the values in the table are in the grease lubrication and oil lubrication conditions to determine. Applicable to the equivalent dynamic load P ≤ 0.1C; lubrication and cooling conditions are normal; radial bearings bear only radial load; thrust bearings bear only axial load rigid housing and shaft conditions of the 0 level of the work of differential bearings.

When the actual working conditions are different from the above, for example, when the bearing is subjected to heavy load (P>0.1C) or combined load, the maximum permissible working speed can be calculated according to the following formula:

Nmax≤f1f2nlim

In the formula

Nmax - the actual working conditions of the bearing speed, r/min

f1 - load factor, for consideration when the bearing in the equivalent load P> 0.1C conditions, due to increased contact stress, increased heat generation, lubrication conditions deteriorate, resulting in low limit speed listed correction parameters.

f2 - load distribution coefficient. To consider when the bearing in the combined load, so that the number of loaded rolling elements increased, rolling elements and raceway friction surface increases, friction conditions and lubrication conditions deteriorate, resulting in the listed limit speed reduction of the correction parameter.

Nlim--Limit rotational speed of the bearing, r/min

If the actual working speed of the bearing exceeds the permissible maximum working speed, it is necessary to take certain improvement measures, such as improving the lubrication method, setting up an effective cooling system, improving the precision of the bearing, appropriately increasing the clearance of the bearing, switching to a special bearing material and a special structure of the cage and so on.

According to the bearing speed selection bearing type, can refer to the following points:

(1) Ball bearings have higher limiting speed and rotational accuracy than roller bearings, and ball bearings should be preferred for high speed.

(2) the smaller the contact angle of the bearing, the better the conditions of its collar to withstand the inertia of the rolling body centrifugal force, so the ultimate speed of the thrust bearing is lower than the centripetal bearing, and single row centripetal bearings are better than the double row self-aligning bearings, when the working speed is high, if axial load is not too big, can be used to withstand pure axial load angular contact ball bearings.

(3) high speed, it is appropriate to use the same inner diameter, outer diameter smaller bearings, when its bearing capacity is not enough, can be used in a wide series of bearings or two bearings and mounted together. 

(4) entity keep frame than the stamping keep frame allows higher speeds
The basic code is used to indicate the inner diameter, diameter series, width series and type of bearings, generally up to five digits, first divided into the following
(1) bearing diameter with the basic code right from the first two figures. For commonly used inner diameter d = 20 ~ 480mm bearing inner diameter is generally a multiple of 5, the two digits indicate the size of the bearing inner diameter is 5 divided by the quotient, such as 04 said d = 20mm; 12 said d = 60mm and so on. For the inner diameter of 10mm, 12mm, 15mm and 17mm bearings, the inner diameter code for 00, 01, 02 and 03. For the inner diameter of less than 10mm and greater than 500mm bearings, the inner diameter of the method of expression of other provisions, can refer to GB/T272-93.

(2) bearing diameter series (i.e., the same structure, the same inner diameter of the bearing in the outer diameter and width of the changes in the series) with the basic code right from the third digit. For example, for centripetal bearings and centripetal thrust bearings, 0,1 means extra light series; 2 means light series; 3 means medium series; 4 means heavy series. The size comparison between each series is shown in the figure below. Thrust bearings in addition to 1 indicates the special light series, the rest of the representation with the centripetal bearings consistent.

(3) bearing width series (i.e., structure, inner diameter and diameter series are the same bearing width changes in the series) with the basic code right from the fourth digit. When the width of the diameter series of comparison as 0 series (normal series), the majority of bearings in the code may not mark the width of the series code 0, but for spherical roller bearings and tapered roller bearings, the width of the series code 0 should be marked. Diameter series code and width series code collectively referred to as size series code.

(4) bearing type code with basic code first digit from the left.

(5) bearing type number:
0 indicates double row angular contact ball bearings

1 for spherical ball bearings

2 means spherical roller bearings and thrust spherical roller bearings

3 means tapered roller bearings

4 indicates double row deep groove ball bearings

5 indicates thrust ball bearings

6 indicates deep groove ball bearings

7 indicates angular contact bearings

8 indicates thrust cylindrical roller bearings

9 indicates single row tapered roller bearings

N denotes cylindrical roller bearings with outer ring and non-blocked edges

NU denotes cylindrical roller bearings with inner ring and non-blocking edge

NJ indicates cylindrical roller bearings with single-edge inner ring.

NUP denotes cylindrical roller bearings with a single inner ring and a flat retaining ring on the other side.

NN means double row cylindrical roller bearings.

U indicates external spherical bearings

QJ indicates four-point contact ball bearings
2. Posterior designation

Bearing after the code is with letters and numbers and other representations of the structure of bearings, tolerances and special requirements of the material and so on. The content of the rear code is a lot, the following is a few commonly used code.

(1) the internal structure of the code is the same type of bearing different internal structure, with a letter followed by the basic code. For example: contact angle of 15 °, 25 ° and 40 ° angular contact ball bearings with C, AC and B respectively, the internal structure of the different.

(2) bearing tolerance level is divided into 2 level, 4 level, 5 level, 6 level, 6X level and 0 level, a total of 6 levels, in order from the high level to the low level, its code were /PZ, /P4, /PS, /P6, /P6X and /P0. Tolerance level, 6X level applies only to the tapered roller bearings; 0 level of the ordinary level, in the bearing code is not marked.

(3) commonly used bearing radial clearance series is divided into 1 group, 2 groups, 0 groups, 3 groups, 4 groups and 5 groups, a total of 6 groups, radial clearance in order from small to large. 0 groups of clearance is commonly used clearance groups, in the bearing code is not marked out, the rest of the clearance groups in the bearing code were used /C1, /C2, /C3, /C4, /C5 said.

3. Front code

The front code of the bearing is used to indicate the sub-parts of the bearing, expressed in letters. For example, L indicates that the separable bearing can be separated from the ring; K indicates that the bearing rolling body and keep frame components and so on.

The actual application of rolling bearing type is a lot of, the corresponding bearing code is also more complex. The above code is the most basic and commonly used part of the bearing code, familiar with this part of the code, you can identify and check the commonly used bearings.