Section 1 Basic Structure of Rolling Bearings
The rolling bearing developed on the basis of plain bearings is based on rolling friction instead of sliding friction. Generally, the two ferrules, a set of rolling elements and a cage are highly versatile, standardized and serialized. High mechanical foundation parts. Due to the different working conditions of various machines, various requirements are imposed on the rolling bearing in terms of load capacity, structure and performance. For this reason, rolling bearings require a wide variety of structures. However, the most basic structure consists of the inner ring, the outer ring, the rolling elements and the cage.
The role of various parts in the bearing is:
For a radial bearing, the inner ring usually fits tightly with the shaft and operates with the shaft. The outer ring is usually in a transitional fit with the bearing housing or the mechanical housing bore for support. However, in some cases, there is also an outer ring running, the inner ring is fixed to support or the inner ring and the outer ring are simultaneously operated. For a thrust bearing, a shaft ring that fits tightly with the shaft and moves together, and a bearing ring that is in a transitional fit with the bearing housing or the mechanical housing bore and serves as a support. The rolling elements (steel balls, rollers or needles) are normally arranged in the bearing between the two ferrules by means of a cage for rolling motion. The shape, size and number of the bearings directly influence the load capacity and performance of the bearing. In addition to the uniform separation of the rolling elements, the cage can also function to guide the rotation of the rolling elements and improve the lubrication performance inside the bearing.
Section 2 Classification of rolling bearings
1. Classified by rolling bearing structure type
(1) Bearings are classified according to their load direction or nominal contact angle:
1) Radial bearings - mainly used for rolling bearings bearing radial loads, with nominal contact angles from 0 to 45. According to the nominal contact angle, it is divided into: radial contact bearing----the radial bearing with the nominal contact angle of 0: the radial angular contact bearing---the radial bearing with the nominal contact angle greater than 0 to 45.
2) Thrust bearings - mainly used for rolling bearings bearing axial loads, with nominal contact angles greater than 45 to 90. According to the different nominal contact angles, they are further 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 bearing ---- rolling element is the ball:
2) Roller bearing----The rolling element is a roller. Roller bearings are divided into: roller bearings----rolling elements are cylindrical roller bearings. The ratio of 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 5 mm; the tapered roller bearing----the rolling element is the bearing of the tapered roller; the spherical roller bearing one by one The rolling elements are bearings of spherical rollers.
(3) Bearings can be adjusted according to their work, divided into:
1) Self-aligning bearing----the raceway is a spherical shape, which can adapt to the angular deviation and angular movement between the two raceway axis lines;
2) Non-aligning bearings (rigid bearings)----bearings that can offset the axial angle between the raceways.
(4) Bearings are divided into: according to the number of rows of rolling elements:
1) Single row bearings----bearings with a 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) Bearings can be separated according to their components and are divided into:
1) separable bearings---bearings with separable parts;
2) Non-separable bearings----bearings that cannot be freely separated after the final assembly.
(6) The bearing can be divided into various structural types according to its structural shape (if there is no filling groove, whether there are inner and outer rings and the shape of the ferrule, the structure of the rib, or even the cage).
2. Classification according to the size of rolling bearings Bearings are divided into: according to their outer diameter size:
(1) Miniature bearings----bearings with a nominal outside diameter range of 26 mm or less;
(2) Small bearings----bearings with a nominal outer diameter range of 28-55mm;
(3) Small and medium-sized bearings----bearings with a nominal outer diameter range of 60-115mm;
(4) Medium and large bearings----bearings with nominal outer diameters ranging from 120-190mm
(5) Large bearings----bearings with a nominal outer diameter range of 200-430mm;
(6) Extra large bearings----bearings with a nominal outer diameter range of 440mm or more.
The basic production process of the third section rolling bearing
Due to the type of rolling bearing, structural type, tolerance class, technical requirements, materials and batches, the basic production process is not exactly the same.
First, the processing of the main parts of various bearings:
1. The processing of the ferrule: The processing of the inner and outer rings of the bearing varies according to the raw material or the form of the blank. The process before the machining can be divided into the following three types. The whole processing process is: bar or pipe material (Some bars need to be forged and annealed, normalized)----Car processing----heat treatment----grinding----finishing or polishing----final inspection of parts---- Anti-rust----into the warehouse----(to be combined with the package)
2. The processing of the steel ball, the processing of the steel ball also varies according to the state of the raw material, wherein the process before the frustration or the photosphere can be divided into the following three types, the process before the heat treatment, and can be further divided into the following Two kinds, the whole processing process is: bar material or wire cold punching (some bars need to be punched and annealed after cold pressing)----frustration, rough grinding, soft grinding or light ball----heat treatment- --- Hard grinding----fine grinding----finishing or grinding----final inspection group----rust prevention, packaging----into the warehouse.
3. The processing of the roller during the processing of the roller varies according to the raw materials. The process before the heat treatment can be divided into the following two types. The whole processing process is as follows: bar processing or wire cold rolling, string ring and soft grinding ----Heat treatment----string soft point----grinding outer diameter----grinding end face----finishing end face----fine grinding outer diameter----finishing outer diameter ---- Final inspection group----rust prevention, packaging----into the warehouse (to be combined with the package).
4. Processing of the cage The processing of the cage can be divided into the following two categories depending on the design structure and raw materials:
(1) Sheet → shear → punching → stamping forming → shaping and finishing → pickling or shot peening or stringing → final inspection → rust prevention, packaging → storage (to be combined)
(2) Processing of the solid cage: The processing of the solid cage varies according to the raw materials or the gross damage. The following four types of blanks can be divided into the following processing: The bar is Pipe, forgings, castings----car inner diameter, outer diameter, end face, chamfering----drilling (or pulling, boring)----pickling----final inspection---- Anti-rust, packaging----into the warehouse.
Second, the assembly process of rolling bearings:
Rolling bearing parts such as inner ring, outer ring, rolling element and cage, etc., after passing the inspection, enter the assembly workshop for assembly, the process is as follows:
Parts demagnetization, cleaning → internal and external rolling <ditch> road size grouping → combination set → check clearance → riveting cage → final inspection → demagnetization, cleaning → rust prevention, packaging → into the finished product warehouse (boxing, shipping 〉.
Section 4 Characteristics of Rolling Bearings
Rolling bearings have the following advantages over plain bearings:
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 a sliding bearing is 0.08-0.12, and the friction coefficient of a rolling bearing is only 0.001-0.005;
2. Rolling bearings have been standardized, serialized and generalized, suitable for mass production and supply, and easy to use and maintain;
3. The rolling bearing is made of bearing steel and is heat treated. Therefore, the rolling bearing not only has high mechanical properties and long service life, but also can save the expensive expensive non-ferrous metal used for manufacturing the sliding bearing;
4. The internal clearance of the rolling bearing is small, and the machining accuracy of each part is high, so the running accuracy is high. At the same time, the rigidity of the bearing can be increased by a preloading method. This is very important for precision machinery;
5. Some rolling bearings can withstand both radial and axial loads, thus simplifying the structure of the bearing support;
6. Because the rolling bearing has high transmission efficiency and less heat generation, it can reduce the consumption of lubricating oil, and the lubrication maintenance is more trouble-free;
7. Rolling bearings can be easily applied to uranium in any orientation in space.
However, everything is divided into two, rolling bearings also have certain shortcomings, mainly:
1. The ability of a rolling bearing to withstand a load is much smaller than that of a plain bearing of the same volume, and therefore the radial dimension of the rolling bearing is large. Therefore, in the case of heavy load and where the radial size is small and the structural requirements are compact (such as crankshaft bearings for internal combustion engines), sliding bearings are often used;
2. The rolling bearing has large vibration and noise, especially in the later stage of use. Therefore, in the case where the precision is high and vibration is not allowed, the rolling bearing is difficult to perform, and the sliding bearing is generally better.
3. Rolling bearings are particularly sensitive to foreign objects such as metal chips. Once foreign matter enters the bearing, intermittent vibration and noise will occur, which will cause early damage. In addition, rolling bearings are prone to early damage due to metal clip impurities. Even if early damage does not occur, the life of the rolling bearing has a certain limit. In short, the life of a rolling bearing is shorter than that of a plain bearing.
However, compared with sliding bearings, rolling bearings have their own advantages and disadvantages, each of which occupies a certain application. Therefore, the two cannot be completely replaced with each other, and each develops in a certain direction to expand its field. However, due to the outstanding advantages of rolling bearings, there is a tendency for latecomers to stay. At present, rolling bearings have developed into the main support type of machinery, and the application is becoming more and more extensive.
没有评论:
发表评论