Rolling bearing selection process
With the development of industry, ucp bearings are used more and more widely, and they are still developing. They have become one of the most important mechanical components. There are many kinds of bearings, and different use requirements have different choices for bearings. Shaft selection It is often difficult to choose the most suitable ucp bearing among all kinds of bearings.
Under certain load and lubrication conditions, the maximum speed allowed by rolling ucp bearings is called the bearing limit speed. The rotational speed is related to many factors such as bearing type, size, accuracy, clearance, cage material and structure, lubrication method, lubricant properties and dosage, load size and direction, and heat dissipation conditions.
The limit speed of various bearings is shown in the parameter table of various bearing specifications. The values in the table are determined under the conditions of grease lubrication and oil lubrication. It is suitable for the equivalent dynamic load P≤0.1C; the lubrication and cooling conditions are normal; the radial bearing only bears the radial load; the thrust bearing only bears the axial load under the condition of rigid bearing seat and shaft.
When the actual working conditions are different from the above, for example, when the ucp bearing is under heavy load (P>0.1C) or combined load, the allowable maximum working speed can be calculated according to the following formula:
in the formula
Nmax–the required rotational speed under the actual working conditions of the bearing, r/min
f1–load factor, in order to consider when the ucp bearing works under the condition of equivalent load P>0.1C, due to the increase of contact stress, the increase of calorific value, and the deterioration of lubricating conditions, the correction parameters for the low limit speed are listed in the table.
f2–load distribution coefficient. In order to consider when the bearing is under combined load, the number of loaded rolling elements increases, the friction surface between the rolling elements and the raceway increases, and the friction and lubrication conditions are relatively deteriorated, resulting in the reduction of the limit speed correction parameters listed in the table.
Nlim–limit speed of bearing, r/min
If the actual working speed of the ucp bearing exceeds the allowable maximum working speed, some improvement measures need to be taken, such as improving the lubrication method, setting up an effective cooling system, improving the bearing accuracy, appropriately increasing the bearing clearance, using special bearing materials and Special structure cage, etc.
When selecting the bearing type according to the bearing speed, you can refer to the following points:
- Ball ucp bearings have higher limit speed and rotation accuracy than roller bearings, and ball bearings should be preferred at high speeds.
- The smaller the contact angle of the bearing, the better the conditions for the ring to bear the inertial centrifugal force of the rolling elements, so the limit speed of the thrust bearing is lower than that of the radial bearing, and the single-row radial bearing is better than the double-row self-aligning bearing. When the working speed is high, if the axial load is not large, angular contact ball bearings can be used to bear pure axial load.
- At high speed, ucp bearings with the same inner diameter and smaller outer diameter should be selected. When the bearing capacity is not enough, wide series bearings or two bearings can be used together.
- The solid cage allows a higher rotational speed than the stamping cage.
Basic code of bearing
The basic code is used to indicate the inner diameter, diameter series, width series and type of the bearing, generally up to five digits, as follows:
1) The inner diameter of the bearing is indicated by the first and second digits from the right of the basic code. For commonly used bearings with inner diameter d=20~480mm, the inner diameter is generally a multiple of 5. These two digits represent the quotient of the inner diameter of the bearing divided by 5, such as 04 for d=20mm; 12 for d=60mm and so on. For bearings with inner diameters of 10mm, 12mm, 15mm and 17mm, the inner diameter codes are 00, 01, 02 and 03 in sequence. For ucp bearings with an inner diameter less than 10mm and greater than 500mm, the inner diameter representation method is otherwise specified, please refer to GB/T272-93.
2) The diameter series of bearings (that is, the series of changes in outer diameter and width of bearings with the same structure and the same inner diameter) are represented by the third digit from the right of the basic code. For example, for radial bearings and radial thrust bearings, 0, 1 means extra light series; 2 means light series; 3 means medium series; 4 means heavy series. The size comparison between the series is shown in the figure below. The thrust bearing is the same as the radial bearing except that 1 is used to indicate the extra light series.
3) The width series of bearings (that is, the series of changes in bearing width with the same structure, inner diameter and diameter series) are represented by the fourth digit from the right of the basic code. When the comparison of the width and diameter series is listed as 0 series (normal series), the width series code 0 may not be marked in the code for most ucp bearings, but for spherical roller bearings and tapered roller bearings, the width series code 0 should be marked. . The diameter series code and the width series code are collectively referred to as the size series code.
4) The bearing type code is represented by the first digit from the left of the basic code.
5) Bearing type number:
0 means double row angular contact ball bearing
1 means self-aligning ball bearing
2 indicates spherical roller bearings and thrust spherical roller bearings
3 means tapered roller bearing
4 means double row радиальный шарикоподшипник
5 means thrust ball bearing
6 means deep groove ball bearing
7 means angular contact bearing
8 means thrust cylindrical roller bearing
9 means single row tapered roller bearing
N means cylindrical roller bearing without outer ring rib
NU means cylindrical roller bearing without inner ring rib
NJ means inner ring single rib cylindrical roller bearing
NUP represents a cylindrical roller bearing with a single rib on the inner ring and a flat rib on the other side
NN stands for double row cylindrical roller bearing
U means outer spherical bearing（PILLOW BLOCK BEARING）
QJ stands for four-point contact ball bearing
The post code of the ucp bearing is to use letters and numbers to indicate the structure, tolerance and special requirements of materials of the bearing, etc. There are a lot of post-code names. The following are some commonly used code names.
1) The internal structure code refers to different internal structures of the same type of bearing, which are represented by letters followed by the basic code. For example, angular contact ball bearings with contact angles of 15°, 25° and 40° use C, AC and B to indicate the difference in internal structure.
2) The tolerance grades of bearings are divided into 2 grades, 4 grades, 5 grades, 6 grades, 6X grades and 0 grades, a total of 6 grades, from high grade to low grade, and their codes are /PZ, /P4, /PS, /P6, /P6X, and /P0. Among the tolerance classes, class 6X is only applicable to tapered roller bearings; class 0 is ordinary class, which is not marked in the bearing code.
3) The commonly used ucp bearing radial clearance series are divided into 1 group, 2 group, 0 group, 3 group, 4 group and 5 group, a total of 6 groups, the radial clearance is from small to large. Group 0 clearance is a common clearance group, which is not marked in the bearing code, and the rest of the clearance groups are represented by /C1, /C2, /C3, /C4, /C5 in the bearing code respectively.
The prefix code of the bearing is used to indicate the sub-components of the ucp bearing, which are represented by letters. For example, L represents the separable ring of the separable bearing; K represents the rolling body and cage assembly of the bearing, etc.
There are many types of rolling ucp bearings in practical applications, and the corresponding bearing codes are also more complicated. The code introduced above is the most basic and commonly used part of the bearing code. If you are familiar with this part of the code, you can identify and select commonly used bearings.