Section 1 Basic structure of rolling bearings
Rolling bearings developed on the basis of sliding bearings, whose working principle is to replace sliding friction with rolling friction, are generally composed of two rings, a set of rolling elements and a cage, which are highly versatile, standardized and serialized. High mechanical base pieces. Due to the different working conditions of various machines, various requirements are put forward for rolling bearings in terms of load capacity, structure and performance. For this reason, rolling bearings require various structures. However, the most basic structure is composed of inner ring, outer ring, rolling elements and cage.The functions of various parts in the bearing are:
For radial bearings, the inner ring usually has a tight fit with the shaft and runs together with the shaft, and the outer ring usually forms a transition fit with the bearing seat or the mechanical housing hole to play a supporting role. However, in some occasions, the outer ring is also running, and the inner ring is fixed to act as a support, or both the inner ring and the outer ring are running at the same time. For thrust bearings, it is called the shaft ring that fits tightly with the shaft and moves together, and it is called the seat ring that is in transition fit with the bearing seat or the hole of the mechanical housing and plays a supporting role. The rolling elements (steel balls, rollers or needle rollers) are usually evenly arranged between the two rings by means of cages in the bearing for rolling motion. Its shape, size and quantity directly affect the load capacity and performance of the bearing. In addition to separating the rolling elements evenly, the cage can also guide the rolling elements to rotate and improve the internal lubrication performance of the bearing.
Section 2 Classification of Rolling Bearings
1. Classification by rolling bearing structure type
(1) Bearings are divided into:
1) Radial bearings - mainly used for rolling bearings that bear radial loads, and their nominal contact angles range from 0 to 45. According to the different nominal contact angles, it is further divided into: radial contact bearings - radial bearings with a nominal contact angle of 0; radial angular contact bearings - radial bearings with a nominal contact angle greater than 0 to 45.
2) Thrust bearings - mainly used for rolling bearings bearing axial loads, and their nominal contact angles are greater than 45 to 90. According to the nominal contact angle, it is divided into: Axial contact bearings - thrust bearings with a nominal contact angle of 90°; thrust angular contact bearings - thrust bearings with a nominal contact angle greater than 45° but less than 90°.(2) Bearings are classified according to the type of rolling elements:
1) Ball bearings - the rolling elements are balls:
2) Roller bearings - the rolling elements are rollers. According to the types of rollers, roller bearings are divided into: Cylindrical roller bearings ---- bearings whose rolling elements are cylindrical rollers, the ratio of the length to diameter of cylindrical rollers is less than or equal to 3; needle roller bearings ---- The rolling element is a needle roller bearing, the ratio of the length to the diameter of the needle roller is greater than 3, but the diameter is less than or equal to 5mm; tapered roller bearing ---- the rolling element is a tapered roller bearing; spherical roller bearing one by one The rolling elements are spherical roller bearings.
(3) Bearings can be divided into:
1) Self-aligning bearing--the raceway is spherical, which can adapt to the angular deviation and angular motion between the axis lines of the two raceways;
2) Non-aligning bearings (rigid bearings) ---- bearings that can resist the offset of the axis line angle between the raceways.
(4) According to the number of rows of rolling elements, bearings are divided into:
1) Single row bearings - bearings with one row of rolling elements;
2) Double row bearings - bearings with two rows of rolling elements;
3) Multi-row bearings - bearings with more than two rows of rolling elements, such as three-row and four-row bearings.
(5) According to whether the parts can be separated, the bearings are divided into:
1) Separable bearings - bearings with separable parts;
2) Non-separable bearings ---- after the final assembly of the bearings, the rings cannot be separated freely at will.
(6) Bearings can be divided into various structural types according to their structural shape (such as whether there is a filling groove, whether there is an inner and outer ring and the shape of the ferrule, the structure of the rib, and even whether there is a cage, etc.).
2. Classification according to the size of rolling bearings Bearings are divided into:
(1) Miniature bearings - bearings with a nominal outer diameter of 26mm or less;
(2) Small bearings - bearings with a nominal outer diameter ranging from 28 to 55mm;
(3) Small and medium-sized bearings - bearings with a nominal outer diameter ranging from 60-115mm;
(4) Medium and large bearings - bearings with a nominal outer diameter ranging from 120-190mm
(5) Large bearings - bearings with a nominal outer diameter ranging from 200-430mm;
(6) Extra-large bearings - bearings with a nominal outer diameter of 440mm or more.
Section 3 Basic Production Process of Rolling Bearings
Due to the different types, structural types, tolerance levels, technical requirements, materials and batches of rolling bearings, the basic production process is not exactly the same.
1. The processing process of the main parts of various bearings:
1. The processing process of the ferrule: The processing of the inner ring and the outer ring of the bearing is different according to the raw material or the blank form. Among them, the process before turning can be divided into the following three types. The whole processing process is: bar or tube (Some bars need to be forged, annealed, and normalized)----turning----heat treatment----grinding----finishing or polishing----parts final inspection---- Anti-rust----storage----(to be assembled>
2. The processing process of steel balls, the processing of steel balls also varies according to the state of raw materials. Among them, the process before frustrating or polishing can be divided into the following three types, and the process before heat treatment can be divided into the following Two kinds, the whole processing process is: cold stamping of bar or wire (some bars need ring punching and annealing after cold stamping)----frustration, rough grinding, soft grinding or light ball----heat treatment- ---Hard Grinding--Finish Grinding--Finish Grinding or Grinding--Final Inspection Grouping--Rust Prevention, Packaging--Storage <to be assembled>.3. The processing process of the roller The processing of the roller is different according to the different raw materials. The process before heat treatment can be divided into the following two types. The whole processing process is: bar turning or wire rod ringing after cold heading and soft grinding ----heat treatment----string soft point----coarse grinding outer diameter----rough grinding end face----finish grinding end face----fine grinding outer diameter----finish grinding outer diameter ----final inspection grouping----rust prevention, packaging----storage (to be assembled and assembled).
4. The processing process of the cage The processing process of the cage can be divided into the following two categories according to the design structure and raw materials:
(1) Sheet → cutting → blanking → stamping → shaping and finishing → pickling or shot blasting or string light → final inspection → rust prevention, packaging → storage (to be assembled)
(2) The processing process of the solid cage: The processing of the solid cage varies according to the raw material or the roughness. Among them, it can be divided into the following four blank types before turning. The whole processing process is: bar, Pipe material, forging, casting----car inner diameter, outer diameter, end face, chamfering----drilling (or drawing, boring)----pickling----final inspection---- Anti-rust, packing----warehousing (to be assembled and assembled).
Second, the assembly process of rolling bearings:
Rolling bearing parts such as inner rings, outer rings, rolling elements and cages, etc., after passing the inspection, enter the assembly workshop for assembly. The process is as follows:
Parts demagnetization, cleaning → inner and outer rolling <groove> channel size grouping and sorting → fitting → clearance inspection → riveting cage → final inspection → demagnetization, cleaning → rust prevention, packaging → finished product warehouse (packing, shipping >.
Section 4 Characteristics of Rolling Bearings
Compared with sliding bearings, rolling bearings have the following advantages:
1. The friction coefficient of the rolling bearing is smaller than that of the sliding bearing, and the transmission efficiency is high. Generally, the friction coefficient of sliding bearings is 0.08-0.12, while that of rolling bearings is only 0.001-0.005;
2. Rolling bearings have achieved standardization, serialization and generalization, are suitable for mass production and supply, and are very convenient to use and maintain;
3. Rolling bearings are made of bearing steel and undergo heat treatment. Therefore, rolling bearings not only have high mechanical properties and long service life, but also can save expensive non-ferrous metals used in the manufacture of sliding bearings;
4. The internal clearance of the rolling bearing is very small, and the processing precision of each part is high, so the running precision is high. At the same time, the rigidity of the bearing can be increased by preloading. This is very important for precision machinery;
5. Some rolling bearings can bear radial load and axial load at the same time, so the structure of the bearing support can be simplified;
6. Due to the high transmission efficiency and low heat generation of rolling bearings, the consumption of lubricating oil can be reduced, and the lubrication maintenance is relatively easy;
7. Rolling bearings can be easily applied to uranium in any orientation in space.
However, everything is divided into two, and rolling bearings also have certain disadvantages, mainly:
1. The load-bearing capacity of rolling bearings is much smaller than that of sliding bearings of the same volume, so the radial dimension of rolling bearings is large. Therefore, sliding bearings are often used in occasions that bear heavy loads and require small radial dimensions and compact structures (such as internal combustion engine crankshaft bearings);
2. The vibration and noise of rolling bearings are relatively large, especially in the later period of use. Therefore, rolling bearings are not suitable for occasions that require high precision and vibration is not allowed. Generally, sliding bearings are better.
3. Rolling bearings are particularly sensitive to foreign matter such as metal shavings. Once foreign matter enters the bearing, it will generate intermittent large vibration and noise, which will also cause early damage. In addition, rolling bearings are also prone to early damage due to metal inclusions and impurities. Even if early damage does not occur, the life of rolling bearings has a certain limit. In short, the life of rolling bearings is shorter than that of sliding bearings.
However, compared with sliding bearings, rolling bearings have their own advantages and disadvantages, and each occupies certain applicable occasions. Therefore, the two cannot completely replace each other, and each develops in a certain direction and expands its own field. However, due to the outstanding advantages of rolling bearings, there is a tendency for latecomers to prevail. At present, rolling bearings have developed into the main support type of machinery, and their applications are becoming more and more extensive.