What Are Bearings Used For?

What Are Bearings Used For?
Bearing is an important part of modern mechanical equipment.  
Its role should be support, that is, literal interpretation used to bear the shaft, but this is only a part of its role, support its essence is able to bear radial load.  You can also understand that it's used to fix the axis.  It is fixed axis so that it can only achieve rotation, and control its axial and radial movement.  
Bearing the role of a support role, namely if the transmission parts (such as: shaft) directly cooperate with hole, a driving resistance is big, and the wear big, transmission is not easy to change, and bearing is rely on rolling contact between components to support the transmission parts, so the sliding resistance is small, less power consumption, starting easily, etc.  
The main function is to support the mechanical rotating body, reduce its friction coefficient in the process of movement, and ensure its rotation accuracy.  It can be understood that it is used to fix the axis, so that it can only achieve rotation, and control its axial and radial movement.  If the shaft has no bearings it will not work at all.  Because the axis can move in any direction, and the work requires that the axis can only rotate.  
Bearings are widely used in automobiles: rear wheels, transmission, electrical components.  
Electrical: general motors, household appliances.  Instrumentation, internal combustion engine, construction machinery, railway rolling stock, loading and unloading machinery, various industrial machinery.  Machine tool spindles, agricultural machinery, high frequency motors, steam turbines, centrifuges, small car front wheels, differential pinion shafts.  
Oil pump, Roots blower, air compressor, all kinds of transmission, fuel injection pump, printing machinery, motor, generator, internal combustion engine, steam turbine, machine tool spindle, reducer, loading, unloading and handling machinery, all kinds of industrial machinery, etc.  Almost as long as it is rotating rotating are used to bearings. 
Bearing parameters  
Life  
Under a certain load, the number of revolutions or hours that the bearing experiences before pitting corrosion is called the bearing life.  
The life of a rolling bearing is defined in revolutions (or hours of operation at a given speed) : a bearing within this life shall have initial fatigue damage (spalling or defect) on any of its bearing rings or rolling bodies.  However, whether in laboratory tests or in actual use, it can be obviously seen that the actual life of bearings with the same appearance under the same working conditions is very different.  In addition, there are several different definitions of bearing "life", one of which is the so-called "working life", which means that the actual life of a bearing can be achieved before damage is caused by wear, damage is usually not caused by fatigue, but by wear, corrosion, seal damage and other reasons.  
Due to the difference in manufacturing accuracy and material uniformity, even if the same material and the same size of the same batch of bearings are used under the same working conditions, their service life is not the same.  If the statistical life is 1 unit, the longest relative life is 4 units, the shortest is 0.1-0.2 units, and the ratio between the longest and the shortest life is 20-40 times.  90% of bearings do not produce pitting corrosion, and the number of revolutions or hours experienced is called the bearing rated life.  
Rated dynamic load  
In order to compare the bearing capacity against pitting corrosion, it is stipulated that the maximum load that can be borne when the rated life of the bearing is one million revolutions (106) is the basic rated dynamic load, represented by C. 
That is, under the action of rated dynamic load C, the reliability of this bearing working for one million turns (106) without pitting failure is 90%, and the greater the C, the higher the carrying capacity.  
Bearing classification  
Sliding bearin :sliding bearing has no inner and outer rings and no rolling body. It is generally made of wear-resistant materials.  It is usually used for low speed, light load, lubricating oil filling and mechanical rotating parts which are difficult to maintain.  
knuckle bearing: the knuckle bearing contact surface of plain bearing is spherical, which is mainly suitable for swing motion, inclined motion and rotary motion.  
Rolling bearing  
Rolling bearings are divided into centripetal bearings and thrust bearings according to their load direction or nominal contact Angle.  The radial contact bearings are centripetal bearings with nominal contact angles of 0 and centripetal angular contact bearings with nominal contact angles greater than 0 to 45.  Axial contact bearings are thrust bearings whose nominal contact Angle is 90, and thrust angular contact bearings whose nominal contact Angle is greater than 45 but less than 90.  
According to the shape of the rolling body can be divided into ball bearings and roller bearings.  Roller bearings are divided into cylindrical roller bearings, needle roller bearings, tapered roller bearings and self-aligning roller bearings.  
According to its work can be divided into self-aligning bearings ---- raceway is spherical, can adapt to the angular deviation and angular motion between two raceway axis line bearings and non-self-aligning bearings (rigid bearings)---- can resist the angular deviation between raceway axis line bearings.  
According to the column number of the rolling body, it is divided into single row bearings, double row bearings and multiple row bearings.  
According to its components (rings) can be separated into separable bearings and non-separable bearings.  
According to its structure shape (such as whether there is a filling groove, whether there is an inner ring, outer ring and the shape of the ring, the structure of the guard edge, and even whether there is a cage, etc.) can also be divided into a variety of structural types.  
Its outer diameter size is divided into miniature bearings (<26mm), small bearings (28-55mm), small and medium bearings (60-115), medium and large bearings (120-190mm), large bearings (200-430mm) and very large bearings (>440mm).  
According to the application field, it can be divided into motor bearings, rolling mill bearings and main bearings.  
According to the material is divided into ceramic bearings, plastic bearings and so on.  
Deep groove ball bearing

Deep groove ball bearing is the most representative rolling bearing.  Compared with other types of bearings of the same size, this kind of bearing has small friction coefficient, high limit speed, simple structure, low manufacturing cost, high precision, no need for regular maintenance, and large size range, many forms, is the most widely used type of bearing.  It mainly bears radial load, but also can bear certain axial load.  When it only bears radial load, the contact Angle is zero.  
Deep groove ball bearings installed on the shaft, in the axial clearance range of the bearing, can limit the axial displacement of the shaft or the shell in two directions, so it can be used for axial positioning in both directions.  When deep groove ball bearings have large radial clearance, they have the performance of angular contact bearings and can bear large axial loads.  Deep groove ball bearings have more advantages than thrust ball bearings under high speed operation conditions with large axial loads.  In addition, this kind of bearing also has a certain self-aligning ability, when it is tilted 2 '~ 10' relative to the shell hole, it can still work normally, but it has a certain influence on the bearing life. 
Angular contact ball bearing  
Generally known as 36, 46 type bearings represented by six types of bearings, angular contact is generally 15 degrees, 25 degrees, 45 degrees and so on.  

The self-aligning ball bearing is a bearing equipped with spherical ball bearings between the inner ring of two raceways and the outer ring of a spherical raceway.  The center of curvature of the raceway surface of the outer ring is consistent with the center of the bearing, so it has the same aligning function as the automatic aligning ball bearing.  When the shaft and shell are bent, it can be adjusted automatically without increasing the bearing burden.  Self-aligning roller bearings can bear radial loads and axial loads in two directions.  Self-aligning ball bearings have large radial load capacity and are suitable for heavy load and impact load.  The inner diameter of the inner ring is the bearing with taper hole, which can be installed directly.  Or the use of fixed sleeve, disassembly cylinder installed on the cylindrical shaft.  Cage using steel plate stamping cage, polyamide forming.  
Self-aligning ball bearings are suitable for bearing heavy loads and impact loads, precision instruments, low noise motors, automobiles, motorcycles, metallurgy, rolling mills, mines, petroleum, paper making, cement, sugar pressing industries and general machinery, etc.  
Thrust ball bearing
Thrust ball bearings are divided into one-way and two-way.  They can only withstand axial loads, never any radial loads.  
Thrust bearing is divided into two parts: tight ring and loose ring.  The tight ring is fastened with the shaft sleeve, and the living ring is supported on the bearing seat.  The ring and rolling body are usually made of rolling bearing steel with high strength and good wear resistance. After quenching, the surface hardness should reach HRC60 ~ 65.  The cage is mainly made of soft steel, and can also be made of copper alloy laminated bakelite or plastic.  
Thrust angular contact ball bearing
Thrust angular contact ball bearing contact Angle 60 ° commonly used thrust angular contact ball bearings are generally two-way thrust angular contact ball bearings, mainly used for precision machine tool spindle, commonly used together with the double row cylindrical roller bearing, it can be subject to bi-directional load and have high precision, good rigidity, low temperature, high speed, convenient installation
Thrust roller bearing  
It includes thrust cylindrical roller bearing, thrust tapered roller bearing, thrust needle roller bearing and thrust self-aligning roller bearing.  
Needle roller bearing

Needle roller bearings are equipped with thin and long rollers (roller length is 3 to 10 times of diameter, diameter is generally not more than 5mm), so the radial structure is compact, its inner diameter size and load capacity and other types of bearing at the same time, the smallest outer diameter, especially suitable for radial installation size limited support structure.  Needle roller bearing according to the use of different occasions, can be used without the inner ring of the bearing or needle roller and cage components, at this time to suit the bearing surface of the surface of the shaft and the shell hole directly as inner and outer rolling bearing surface, in order to ensure the load capacity and operation performance and you have the same ring bearing, axis or shell hole hardness on the surface of the raceway, machining accuracy and surface quality and bearing ring. 
 Purpose Combined needle roller bearing is a bearing unit composed of radial needle roller bearing and thrust bearing components. It is compact in structure, small in volume, high in rotation accuracy, and can bear a certain axial load while bearing a high radial load.  And the product structure is diverse, wide adaptability, easy to install. 
 Combined needle roller bearings are widely used in machine tools, metallurgical machinery, textile machinery and printing machinery and other mechanical equipment, and can make the mechanical system design is very compact and clever.  
The self-aligning roller bearing

The self-aligning roller bearing has two rows of symmetrical spherical rollers, which can mainly bear radial load, but can also bear axial load in any direction, but not pure axial load.  The raceway of the outer ring of this kind of bearing is spherical, so its self-aligning performance is good and can compensate for coaxiality error. When the shaft is bent by force or different cores are installed, the bearing can still be used normally. The self-aligning property varies with the bearing size series, and the allowable self-aligning Angle is generally 1~2.5 degrees.  In addition to bearing radial load, bearing can also bear bidirectional axial load, with good impact resistance, generally speaking, the self-aligning roller bearing is allowed to work at a low speed.  
Suitable for working under heavy load or vibration load.  
Flange bearing 
Flange bearing Outer wheel with flange flange.  It can simplify the structure of the main engine, reduce the size of the main engine, and make the bearing easier to locate.  
Pillow blocks bearing  
An assembly consisting of a centripetal bearing and a seat with a base plate for mounting screws on a supporting surface parallel to the bearing axis line.  
Composite bearing  
A rolling bearing composed of two or more bearing structures at the same time in a set of bearings. Such as needle roller and thrust cylindrical roller combined bearings, needle roller and thrust ball combined bearings, needle roller and angular contact ball combined bearings, etc.  
Linear bearing  
Linear bearings are divided into metal linear bearings and plastic linear bearings.  
Metal linear bearing is a linear motion system produced at low cost for infinite stroke and cylindrical shaft.  Because the bearing ball is in point contact with the shaft, the load is small.  The steel ball rotates with minimal friction resistance, thus achieving smooth motion with high precision.  
Plastic linear bearing is a kind of linear motion system with self-lubrication characteristics. The biggest difference between metal linear bearing and metal linear bearing is that metal linear bearing is rolling friction. Point contact is between bearing and cylindrical shaft, so it is suitable for low load and high-speed motion.  The plastic linear bearing is sliding friction, and there is surface contact between the bearing and the cylindrical shaft, so it is suitable for high load and low speed movement.  
Bearing material  
Characteristics of bearing steel:  
First, contact fatigue strength  
Bearing under the action of periodic load, the contact surface is very easy to attack fatigue damage, that is, the emergence of cracking and peeling, which is an important damage situation of bearings.  Therefore, in order to improve the service life of bearings, bearing steel must have high contact fatigue strength.  Two, wear resistance  
When bearing tasks, not only rolling friction occurs between the ring, the rolling body and the support frame, but also sliding friction occurs, so that the bearing parts have been wearing.  In order to increase the wear of bearing parts, maintain the stability of bearing accuracy and extend the service life, bearing steel should have good wear resistance.  
Three, hardness  
Hardness is one of the important qualities of bearing quality, which has indirect influence on contact fatigue strength, wear resistance and elastic limit.  The hardness of bearing steel in use is up to HRC61~65, which enables the bearing to obtain higher contact fatigue strength and wear resistance.  
Four, rust resistance  
In order to avoid the corrosion and rust of bearing parts and finished products in the process of processing, storage and use, the bearing steel should have good rust resistance.  
Five, processing performance  
Bearing parts in the consumption process, to go through many cold and hot processing processes, in order to meet the requirements of a small amount, high efficiency and high quality, bearing steel should have good processing performance.  For example, cold and hot forming performance, cutting performance, hardenability and so on.  
lubrication  
The lubrication of rolling bearings is to reduce internal friction and wear of bearings and prevent burning and sticking;  Prolong its service life;  Discharge friction heat, cooling, prevent bearing overheating, prevent lubricating oil aging;  It can also prevent foreign matter from invading into the bearing, or prevent rust and corrosion.
The lubrication methods  
The lubrication method of bearings is divided into grease lubrication and oil lubrication.  In order to make the bearing function well.
First of all, it is necessary to choose the lubrication method suitable for the use conditions and purposes.  If only lubrication is considered, the lubricity of oil lubrication prevails.  However, grease lubrication has the advantage of simplifying the structure around bearings. The advantages and disadvantages of grease lubrication and oil lubrication are compared.  Special attention should be paid to the amount of lubrication, whether oil lubrication or grease lubrication, too little lubrication will not fully affect the bearing life, too much will produce large resistance, affect the speed.  
seal  
Bearing seals can be divided into two categories: self-sealing and external sealing.  The so-called bearing with seal is to make the bearing itself into a sealing device.  Such as bearing dust cover, sealing ring, etc.  This seal occupies very little space, is easy to install and disassemble, and the cost is relatively low.  The so-called bearing external sealing performance device is made into a sealing device with various performance inside the installation of the end cover.  Bearing external seal is divided into non-contact seal and contact seal two.  The non-contact seal is suitable for high speed and high temperature occasions, there are gap type, labyrinth type and gasket type and other different structural forms.  Contact seal is suitable for medium and low speed working conditions, commonly used with felt seal, leather bowl seal and other structural forms.  
According to the requirements of the sealing degree of bearing working condition and working environment, various sealing forms are often used comprehensively in engineering design to achieve better sealing effect.  The selection of bearing external seal should consider the following main factors:  
1.Bearing lubricants and types (grease and lubricating oil);
2.The working environment of the bearing and the size of the space occupied;  
3.Shaft support structure advantages, allowing Angle deviation;  
4.The circumferential velocity of the sealing surface;  
5.The working temperature of the bearing;  
6.Manufacturing costs.  
Stallation and maintenance  
Pay attention to the point  
From the perspective of use, the following points should be paid attention to to ensure that bearings can work reliably:  
1.improve lubrication quality, control oil pressure, temperature and flow, strengthen oil filtration.  
2.Use fuel oil and lubricating oil in accordance with the provisions.  
3.control the temperature state of the diesel generator set, working under the condition of supercooling and overheating is unfavorable.  In cold weather, the diesel engine should be preheated before starting, and turn the crankshaft by hand to make the oil enter the friction surface.  
4.bearing and journal surface quality and geometry should be strictly guaranteed.  
5.bearing clearance should be appropriate, the generator set is too large to produce impact, too small poor lubrication, may burn tile.  
How to ensure the reliable operation of bearings  
Generally speaking, from the point of view of use, the following points should be noted:  
1.  Bearing clearance should be appropriate, too large impact, too small poor lubrication, may burn tile;  
2.  Bearing and journal surface quality and geometry should be strictly guaranteed;  
3.  Improve lubrication quality, control oil pressure, temperature and flow, strengthen oil filtration;  
4.  Use fuel oil and lubricating oil in accordance with the regulations.  
In order to make the bearing fully play and maintain its due performance for a long time, it is necessary to do a good job of regular maintenance (regular inspection).  It is very important to improve productivity and economy to detect faults early and prevent accidents from happening through proper periodic inspection.  
The installation  
Whether the installation of bearings is correct affects the accuracy, life and performance.  Therefore, the design and assembly department should fully study the installation of bearings.  It is expected to be installed according to operating standards.  The standard items are usually as follows:  
(1) Clean the bearing and bearing related parts  
(2) Check the size and finishing of related parts  
(3) Installation  
(4) Check after installing bearings  
(5) Supply lubricant  
Maintenance  
Disassembly  
Bearing disassembly is regular maintenance, bearing replacement.  After disassembly, if you continue to use, or need to check the state of the bearing, its disassembly should be carried out as carefully as installation.  Attention should be paid to not damage the bearing parts, especially the disassembly of interference fit bearings, which is difficult to operate.  
For the interference fit outer ring, several outer ring extrusion screw screws are set on the circumference of the shell in advance, and the screws are evenly tightened while being removed.  These screw holes are usually covered with blind plugs, tapered roller bearings and other separation bearings, and several cuts are set on the shoulder of the shell block, which are disassembled with a cushion block, or disassembled with a press, or gently knocked.  
The removal of the inner ring can be easily pulled out with a press.  At this point, pay attention to the inner ring bear its pulling force.  Also, the pull-out fixture shown is mostly for use, regardless of the fixture, it must be firmly stuck to the side of the inner ring.  To this end, it is necessary to consider the size of the shaft shoulder, or study the processing of the groove at the shoulder, so as to use the drawing clamp. 
Large bearing inner ring disassembly using oil pressure method.  Oil pressure is applied through the oil hole arranged in the bearing to make it easy to draw.  For bearings with large width, oil pressure method and drawing fixture are used to carry out disassembly operation.  
Induction heating method can be used to disassemble inner ring of cylindrical roller bearings.  In a short period of time to heat the part, so that the inner ring expansion after the method of drawing.  Induction heating method is also used when a large number of such bearing inner rings need to be installed.  
cleaning  
When the bearing is removed for inspection, the appearance is recorded by photography and other methods.  In addition, confirm the amount of remaining lubricant and sample the lubricant, and then clean the bearing.  
A. The cleaning of bearings is divided into rough washing and fine washing, and a metal mesh frame can be placed at the bottom of the container in use.  
B. rough washing, in the oil with a brush to remove grease or adhesive.  At this time, if the bearing is rotated in oil, it will be noted that the rolling surface will be damaged by foreign bodies.  
C. When cleaning, slowly turn the bearing in oil, and it must be carried out carefully.  
The cleaning agent usually used is neutral water-free diesel oil or kerosene, and sometimes warm lye is used according to the need.  No matter which cleaning agent is used, always filter to keep clean.  
After cleaning, the bearing is coated with anti-rust oil or anti-rust grease immediately.  
Safekeeping  
Bearings are coated with an appropriate amount of antirust oil and packed in antirust paper when leaving the factory. As long as the packaging is not damaged, the quality of bearings will be guaranteed.  However, for long-term storage, it is advisable to store it on a shelf 30cm above the ground under the condition of humidity less than 65% and temperature of about 20℃.  In addition, the storage place should be kept away from direct sunlight or contact with cold walls.