Common sense of rolling bearing use

Whether the rolling bearing can be selected correctly in the selection method and steps will have good working performance and prolong the service life of the main engine; It plays a very important role in shortening maintenance time, reducing maintenance cost and improving machine operation rate. Therefore, both design and manufacturing units and maintenance and use units must attach great importance to the selection of rolling bearings, and the whole selection procedure is shown in figure 1 1.

Generally speaking, the steps of selecting bearings can be summarized as: 1. According to the working conditions of the bearing (including load direction and load type, rotating speed, lubrication mode, coaxiality requirements, positioning or non-positioning, installation and maintenance environment, ambient temperature, etc.). ), select the basic type, tolerance grade and clearance of the bearing; 2。

According to the working conditions, stress and service life requirements of the bearing, the bearing model is determined by calculation, or the bearing model is selected according to the service requirements, and then the service life is checked; 3。 Check the rated load and limit speed of the selected bearing.

The main factors to be considered in selecting bearings are limit speed, required life and bearing capacity, and other factors are helpful to determine the final scheme of bearing type, structure, size, tolerance level and clearance calculation. 1。

The selection of various rolling bearings has its own characteristics and is suitable for different uses of various machinery. When selecting a bearing type, the following factors should generally be considered.

Generally speaking, thrust bearing and angular contact bearing are selected for bearing thrust load, ball bearing is usually selected for high-speed application, and roller bearing is selected for bearing larger radial load. In a word, the selector should choose the appropriate type from different manufacturers and numerous bearing products.

In mechanical design, the size of the shaft is generally determined first, and then the rolling bearing is selected according to the size of the shaft. Usually, ball bearings are used for small shafts and roller bearings are used for large shafts.

However, when the bearing is limited in the diameter direction of the machine, needle bearing, ultra-light and ultra-light series ball or roller bearing are selected; When the axial position of the bearing is limited, narrow or ultra-narrow series of ball or roller bearings can be selected. The size, direction and nature of the load on the bearing are the most important factors in selecting the bearing.

Roller bearings are used to bear heavy loads, ball bearings are used to bear light or medium loads, and bearings with carburized steel or bainite quenching can bear impact and vibration loads. In the load direction, deep groove ball bearing, cylindrical roller bearing or needle roller bearing can be selected when bearing pure radial load.

When bearing small pure axial load, thrust ball bearing can be selected; When bearing a large pure axial load, the thrust roller bearing can be selected. When the bearing bears the combined radial and axial loads, angular contact ball bearings or tapered roller bearings are generally selected.

For cantilever support structures, tapered roller bearings or angular contact ball bearings are often used in pairs. Self-aligning performance of bearings When the center line of an important official is different from the center line of the bearing seat, there is an angle error, or the distance between the two bearings of the shaft is large, resulting in less rigidity of the shaft and easy bending or tilting under stress, self-aligning ball bearings or self-aligning roller bearings and outer ball bearings with good self-aligning performance can be selected.

This kind of bearing can keep normal operation when the shaft is slightly tilted or bent. The self-aligning performance of bearing is related to its allowable misalignment. The larger the misalignment value, the better the self-alignment performance.

See table 1 1 for the allowable deviation of various bearings. Stiffness of a rigid bearing refers to the force required for unit deformation of the bearing. The elastic deformation of rolling bearings is very small, which can be ignored in most machines, but in some machines, such as the spindle of machine tools, bearing stiffness is an important factor, and generally cylindrical and tapered roller bearings should be selected.

Because these two kinds of bearings are in point contact with the raceway when loaded, their rigidity is poor. In addition, various bearings can also achieve the purpose of increasing the support stiffness by pre-tightening.

For example, angular contact ball bearings and tapered roller bearings, in order to prevent shaft vibration and increase support stiffness, a certain axial force is often applied in advance during installation to make them press each other. It is especially pointed out here that the pre-tightening amount should not be too large.

If it is too large, it will increase the friction and temperature rise of the bearing and affect the service life of the bearing. Speed of bearing Each bearing model has its own limit speed, which is determined by physical characteristics such as size, type and structure. The limit speed refers to the highest working speed of the bearing (usually r∕min). If it exceeds this limit, the bearing temperature will rise, the lubricant will dry up, and even the bearing will be stuck.

The speed range required in the application helps to decide which type of bearing to use. Figure 12 shows the typical speed range of most common bearings. D is the bearing size, which usually refers to the middle diameter of the bearing. When selecting bearings, use the average value of bearing inner diameter and outer diameter in mm. ..

Multiplying the pitch circle diameter d by the shaft speed (unit r/min) to get the limit speed coefficient (DN), which is very important in selecting the bearing type and size. The catalogues of most bearing manufacturers provide the limit speed values of their products. Practice has proved that it is best to work at 90% limit speed.

The limit speed of grease lubricated bearings is lower than that of oil lubricated bearings, and the oil supply mode of bearings has an influence on the achievable limit speed. Table 12 provides the limit speed correction coefficient (k) of several bearing lubrication forms.

It must be noted that for grease lubricated bearings, the limit speed is generally only 80% of the limit speed when the bearing adopts high-quality circulating oil system, but for oil mist lubrication system, the limit speed is generally 50% higher than that of the same basic lubrication system. The design and structure of the cage also affect the limit speed of the bearing, because the rolling elements are in sliding contact with the surface of the cage. Using expensive, reasonably designed cages made of high-quality low-friction materials can not only isolate the rolling elements, but also help to maintain the lubricating oil film in the sliding contact area.

However, low-cost cages, such as stamping cages, usually only keep the rolling elements separated. Therefore, they are prone to accidents and interfere with sliding contact, resulting in lower speed limit.

Generally speaking, deep groove ball bearings, angular contact bearings and cylindrical roller bearings should be selected for high-speed work occasions; Tapered roller bearings can be used in low-speed working occasions. The limit speed of tapered roller bearings is generally around deep groove ball bearings.

2. Some knowledge about bearings,

Rolling bearing is a precision mechanical element that transforms sliding friction between running shaft and shaft seat into rolling friction, thus reducing friction loss.

Rolling bearings are generally composed of outer ring, inner ring, rolling body and cage. Rolling bearings are generally composed of inner ring, outer ring, rolling body and cage. The function of the inner ring is to cooperate with the shaft and rotate with the shaft. The function of the outer ring is to cooperate with the bearing seat and play a supporting role; Rolling elements are evenly distributed between the inner ring and the outer ring through the cage, and their shape, size and quantity directly affect the service performance and life of rolling bearings; The cage can make the rollers evenly distributed, prevent the rollers from falling off and guide the rollers to rotate and lubricate.

3. Basic knowledge of bearings

Let me give you an answer! The first question: the 50222M you gave is wrong.

And the holder indicates that the method is wrong. It should be 502222H, the code name is the code name of the old Soviet Union, which means: 1, type cylindrical roller bearing 2, no outer ring deformation 3, size series 2 4, inner diameter 1 10mm 5, and h stands for brass solid cage.

RN222M and 502222M are the same bearing model. Only RN222M is the standard code currently used.

Meaning: R is a prefix code, indicating a bearing without a detachable inner ring or outer ring. That is, what is and is not.

N stands for cylindrical roller bearing 2 stands for diameter series code 2 22 stands for inner diameter 1 10mm stands for brass solid cage. Second question: 1, characteristics of deep groove ball bearing 1. 1 Structurally, deep groove ball bearing has a continuous raceway for each turn, and the cross section of the raceway is about three-thirds of the circumference of the ball. It is mainly used to bear radial load, but it can also bear certain axial load.

1.2 has the property of angular contact ball bearing when the radial clearance of the bearing increases, and can bear the axial load alternating in two directions. 1.3 Low friction and high speed.

1.4 has simple structure, low manufacturing cost and high manufacturing accuracy. Generally, 1.5 adopts stamping wave cage, and the bearing with inner diameter greater than 200mm or running at high speed adopts lathe solid cage.

There are more than 60 improved structures of deep groove ball bearings. 2. Angular contact ball bearing can bear both radial load and axial load. The higher the rotating speed, the greater the contact angle and the higher the axial bearing capacity.

Single row bearing can only bear axial load in one direction, and it will cause additional axial force when it bears radial load. And can only limit the axial displacement of the shaft or the housing in one direction.

If installed in pairs, make the outer rings of a pair of bearings face each other, that is, the wide end faces the wide end face and the narrow end faces the narrow end face. In this way, additional axial force can be avoided, and the shaft or housing can be limited within the axial clearance range in two directions.

There are more than 70 improved structures for angular contact ball bearings. 2. 1 There are three kinds of nominal contact angles:15, 25 and 40. The larger the contact angle, the higher the axial bearing capacity.

The contact angle of high-precision and high-speed bearings is usually 15, which will increase under the action of axial force. 2.2 Generally, the inner ring or the outer ring is locked, and the inner and outer rings are inseparable.

After the outer ring is heated and expanded, it is assembled with the inner ring, roller and cage assembly. The number of balls loaded is more than that of deep groove ball bearings, and the rated load is the largest among ball bearings, with strong rigidity and smooth operation.

2.3 The radial clearance can be adjusted by mutual displacement of the inner and outer rings. They are usually used in pairs, and the preload is used to improve the rigidity of bearings.

3. Characteristics of cylindrical roller bearing 3. 1 The roller is in contact with the raceway line and has large radial bearing capacity, which is suitable for bearing heavy load and impact load. 3.2 Low friction coefficient, suitable for high speed, and the limit speed is close to the deep groove ball bearing.

3.3 N type and NU type can move axially, adapt to the change of relative position between shaft and shell caused by thermal expansion or installation error, and can be used as free end support. The inner ring or the outer ring can be separated, which is convenient for installation and disassembly.

3.4 The processing requirements for shaft and seat hole are high, so the relative deflection of inner and outer ring axes after bearing installation should be strictly controlled to avoid contact stress concentration. 3.5 Double-row cylindrical roller bearing with inner hole taper of 1: 12, with adjustable radial clearance and high radial stiffness, is suitable for machine tool spindle.

4. Tapered roller bearings are separated bearings. The inner ring and outer ring of the bearing have tapered raceways, and the rollers are frustum-conical. The roller is in contact with the raceway line, which can bear larger combined radial and axial loads and pure axial loads.

The larger the contact angle, the higher the axial bearing capacity. The design of tapered roller should extend the contact line between roller and inner and outer raceway, and then intersect at the same point on the bearing axis to realize pure rolling.

The newly designed tapered roller bearing adopts reinforced structure, with larger roller diameter, longer roller length and more rollers. The bearing capacity and fatigue life can be significantly improved by using convex rollers. The contact between the big end face of the roller and the big flange is spherical and conical, which improves the lubrication.

This kind of bearing can be divided into single row, double row and four rows of tapered roller bearings according to the number of roller rows installed. This kind of bearing is also made of British series products.

5. The thrust ball bearing is a separable bearing with a contact angle of 90, which can be installed separately and can only bear axial load. The limit speed is low.

The steel ball is squeezed out of the raceway by centrifugal force, which is easy to scratch, but it is not suitable for high-speed operation. One-way bearing can bear one-way axial load and two-way bearing can bear two-way axial load.

Spherical race thrust ball bearing has self-aligning performance, which can eliminate the influence of installation error. 6. The thrust cylindrical roller bearing is characterized by a separate bearing.

It can bear unidirectional axial load and cannot limit the radial displacement of the shaft. The bearing has high rigidity, small occupied space, large axial bearing capacity and low sensitivity to impact load.

Suitable for low rotation speed, often used in working occasions where thrust ball bearings are not suitable. It is not allowed to tilt the axis of the shaft and the shell during installation.

7. The thrust self-aligning roller bearing is characterized by a separate bearing, and its load line forms a certain angle with the bearing axis, which has a large axial bearing capacity, and can bear a certain radial load while bearing an axial load. The self-aligning rollers of this bearing are arranged obliquely, and the raceway surface is spherical, which has self-aligning performance, so a certain inclination of the shaft is allowed.

Can be used in extremely heavy load occasions, allowing a higher speed. When in use, oil lubrication is generally used.

8. Features of self-aligning ball bearings 8. 1 The raceway surface of the outer ring is spherical and has self-aligning performance. This kind of bearing is suitable for the case that the shaft and the seat hole are not concentric due to machining, installation and shaft bending.

The adjusted deflection angle can be within 3. 8.2 The bearing contact angle is small, almost unchanged under the action of axial force, and the axial bearing capacity is small.

It mainly bears radial load, while bearing radial load, it can also bear a small amount of axial load, and the limit speed is lower than that of deep groove ball bearings. 9. Characteristics of four-point contact ball bearings The separable structure can bear radial load and bidirectional axial load, and can limit axial displacement in both directions, but it takes up less axial space than the current double-row angular contact ball bearings.

A single bearing can be replaced by a front assembly or a rear assembly for angular contact ball bearings. Because it is a double half inner ring (or outer ring), the number of balls increases and the bearing capacity is large.

Four-point contact ball bearings are suitable for axial and radial coupling under pure axial load or axial load.

4. Classification of rolling bearings

Generally speaking, the steps of selecting bearings can be summarized as: 1.

According to the working conditions of the bearing (including load direction and load type, rotating speed, lubrication mode, coaxiality requirements, positioning or non-positioning, installation and maintenance environment, ambient temperature, etc.). ), select the basic type, tolerance grade and clearance of the bearing; 2。 According to the working conditions, stress and service life requirements of the bearing, the bearing model is determined by calculation, or the bearing model is selected according to the service requirements, and then the service life is checked; 3。

Check the rated load and limit speed of the selected bearing. The main factors to be considered in selecting bearings are limit speed, required life and bearing capacity, and other factors are helpful to determine the final scheme of bearing type, structure, size, tolerance level and clearance calculation.

1。 The selection of various rolling bearings has its own characteristics and is suitable for different uses of various machinery.

When selecting a bearing type, the following factors should generally be considered. Generally speaking, thrust bearing and angular contact bearing are selected for bearing thrust load, ball bearing is usually selected for high-speed application, and roller bearing is selected for bearing larger radial load.

In a word, the selector should choose the appropriate type from different manufacturers and numerous bearing products. ? In mechanical design, the size of the shaft is generally determined first, and then the rolling bearing is selected according to the size of the shaft.

Usually, ball bearings are used for small shafts and roller bearings are used for large shafts. However, when the bearing is limited in the diameter direction of the machine, needle bearing, ultra-light and ultra-light series ball or roller bearing are selected; When the axial position of the bearing is limited, narrow or ultra-narrow series of ball or roller bearings can be selected.

? The size, direction and nature of the load on the bearing are the most important factors in selecting the bearing. Roller bearings are used to bear heavy loads, ball bearings are used to bear light or medium loads, and bearings with carburized steel or bainite quenching can bear impact and vibration loads.

In the load direction, deep groove ball bearing, cylindrical roller bearing or needle roller bearing can be selected when bearing pure radial load. When bearing small pure axial load, thrust ball bearing can be selected; When bearing a large pure axial load, the thrust roller bearing can be selected.

When the bearing bears the combined radial and axial loads, angular contact ball bearings or tapered roller bearings are generally selected. ? Self-aligning performance of bearings When the center line of an important official is different from the center line of the bearing seat, there is an angle error, or the distance between the two bearings of the shaft is large, resulting in less rigidity of the shaft and easy bending or tilting under stress, self-aligning ball bearings or self-aligning roller bearings and outer ball bearings with good self-aligning performance can be selected.

This kind of bearing can keep normal operation when the shaft is slightly tilted or bent. The self-aligning performance of bearing is related to its allowable misalignment. The larger the misalignment value, the better the self-alignment performance.

See table 1 1 for the allowable deviation of various bearings. Stiffness of bearing Stiffness of bearing refers to the amount of force required for bearing to produce unit deformation. The elastic deformation of rolling bearings is very small, which can be ignored in most machines, but in some machines, such as the spindle of machine tools, bearing stiffness is an important factor, and generally cylindrical and tapered roller bearings should be selected.

Because these two kinds of bearings are in point contact with the raceway when loaded, their rigidity is poor. In addition, various bearings can also achieve the purpose of increasing the support stiffness by pre-tightening.

For example, angular contact ball bearings and tapered roller bearings, in order to prevent shaft vibration and increase support stiffness, a certain axial force is often applied in advance during installation to make them press each other. It is especially pointed out here that the pre-tightening amount should not be too large.

If it is too large, it will increase the friction and temperature rise of the bearing and affect the service life of the bearing. ? Speed of bearing Each bearing model has its own limit speed, which is determined by physical characteristics such as size, type and structure. The limit speed refers to the highest working speed of the bearing (usually r∕min). If it exceeds this limit, the bearing temperature will rise, the lubricant will dry up, and even the bearing will be stuck.

The speed range required in the application helps to decide which type of bearing to use. Figure 12 shows the typical speed range of most common bearings. D is the bearing size, which usually refers to the middle diameter of the bearing. When selecting bearings, use the average value of bearing inner diameter and outer diameter in mm. ..

Multiplying the pitch circle diameter d by the shaft speed (unit r/min) to get the limit speed coefficient (DN), which is very important in selecting the bearing type and size. The catalogues of most bearing manufacturers provide the limit speed values of their products. Practice has proved that it is best to work at 90% limit speed.

The limit speed of grease lubricated bearings is lower than that of oil lubricated bearings, and the oil supply mode of bearings has an influence on the achievable limit speed. Table 12 provides the limit speed correction coefficient (k) of several bearing lubrication.

It must be noted that for grease lubricated bearings, the limit speed is generally only 80% of the limit speed when the bearing adopts high-quality circulating oil system, but for oil mist lubrication system, the limit speed is generally 50% higher than that of the same basic lubrication system. The design and structure of the cage also affect the limit speed of the bearing, because the rolling elements are in sliding contact with the surface of the cage. Using expensive, reasonably designed cages made of high-quality low-friction materials can not only isolate the rolling elements, but also help to maintain the lubricating oil film in the sliding contact area.

However, low-cost cages, such as stamping cages, usually only keep the rolling elements separated. Therefore, they are prone to accidents and interfere with sliding contact, resulting in lower speed limit.

Generally speaking, deep groove ball bearings, angular contact bearings and cylindrical roller bearings should be selected for high-speed work occasions; Tapered roller bearings can be used in low-speed working occasions. The limit speed of tapered roller bearings is generally about 65% of deep groove ball bearings, 70% of cylindrical roller bearings and 60% of angular contact ball bearings.

The limit speed of thrust ball bearing is low, so it can only be used at low speed. For similar bearings, the smaller the size, the higher the allowable speed.

When selecting bearings, attention should be paid to making the actual speed lower than the limit speed. ? Bearing swimming and axial displacement usually, a shaft is supported by two bearings separated by a certain distance.

In order to adapt to different degrees of thermal expansion of the shaft and the shell, bearings should be installed on the shaft.

5. How to install the rolling bearing correctly

The general assembly steps and technical requirements of common radial ball bearings, thrust ball bearings or tapered rolling bearings are as follows: (1) Wash the bearings with gasoline, and apply proper grease on the bearing rolling bodies and the runway.

(2) Check whether there is burr on the bearing seat hole or shaft, and wipe off the sludge on it. (3) When assembling, usually use a copper rod or a sleeve tool to resist the bearing ring and knock it in with a hammer.

During operation, it is necessary to beat each point circularly along the end face of the inner ring (or outer ring) of the bearing, and the impact force shall not be transmitted through the rolling body, that is, the inner ring should be beaten when it is installed on the shaft, and the outer ring should be beaten when it is installed on the box hole. Don't push too hard, keep the copper bar perpendicular to the end face, so as not to skew the bearing or damage the mating surface.

Don't hit the bearing directly with a hammer. When hitting people, if the sleeve tool used is not suitable, the gasket should be used at the same time, and the diameter and thickness of the gasket should be the same as that of the bearing steel ring.

(4) When installing the thrust rolling bearing, it should be noted that one ball disc has a smaller inner diameter and the other has a larger outer diameter. (5) Installation method of centripetal or conical rolling bearing: First, install the bearing on the shaft. At this point, the gasket should be placed on the inner steel ring, and then pressed or hammered in. Then, put the bearing into the hole of the frame, put the gasket on the outer steel ring, and then press or hammer it in. Don't misplace the cushion cover.

(6) When installing tapered rolling bearing and thrust bearing, it should not be pressed too tightly, so that the shaft can expand when the temperature changes. Do not inject too much grease into the bearing.

(7) The installed rolling bearing should not have excessive radial clearance or axial movement. When installing the bearing, pay attention to make the printed font of the ferrule face outward, so that the bearing number can be clearly and conveniently seen when using or disassembling the bearing.