Sizes from 1.5 mm to 8.6 meters Bearings vary greatly in size from small to large. In Tokyo, Japan, Minebea Co., Ltd. announced that its steel ball was awarded the Guinness World Record title for the smallest commercial steel ball bearing, with the outer diameter of the steel ball certified by a representative from Guinness World Records Co., Ltd. to be only 1.4978 mm. The dimensions of this record-breaking bearing are 1.5 mm outer diameter, 0.5 mm inner diameter, and six steel balls within a length of 0.65 mm wide. Its compactness and precision meet JIS codes. It is used in the fields of micro motors and watches.
In July 2019, China Railway Construction Heavy Industry Group Co., Ltd. (hereinafter referred to as "China Railway Construction Heavy Industry") established the 197 Research and Design Institute, determined to overcome the key technologies of shield machine main bearings. Four years later, the world's largest diameter, heaviest single body, and highest load-bearing shield machine main bearing with a diameter of 8.61 meters and a weight of 62 tons was launched. The dental drill (commonly known as a dental handpiece) used by dentists at 400,000 revolutions per minute is equipped with a bearing that can rotate at ultra-high speed. These are two ultra-precision bearings with an inner diameter of 3.0mm, an outer diameter of 6.0mm, and a width of 2mm, and a steel ball diameter of 1.0mm. They can rotate at an amazing speed of "400,000 revolutions per minute", greatly reducing the vibration of the dental handpiece, thereby greatly alleviating the pain of the patient during treatment. The steel ball rotates at 160 meters per second. The main shaft bearings of the jet engine V2500 of international airliners have a rolling speed of 160 meters per second, equivalent to 580 kilometers per hour. It is precisely because of the use of high-performance high-speed bearings that the engine can operate safely for a long time and send passengers safely to all parts of the world. Amplitude below 100 nanometers "The accuracy of the machine depends on the rotation accuracy of the bearing", which is no exaggeration. The two ends of the rotating shaft are supported by two bearings. If the axis shakes greatly, the mechanical performance cannot be improved. Metal processing WeChat, the content is good and worth paying attention to. The amplitude of the axis of the computer external storage device, that is, the "hard disk", which uses ultra-precision bearings, is less than 100 nanometers (1 nanometer = 1/1000000 mm). The key to achieving such ultra-high precision is the precision of rolling elements such as "steel balls" and "rollers". Bearings are also indispensable for space development. Weather forecasts, satellite broadcasting and television signals, and car satellite positioning information are all provided by artificial satellites flying around the earth. Satellites are equipped with gyroscopes that maintain the satellite's attitude and heading, and ultra-precision bearings are installed in the gyroscopes. This type of bearing can work continuously in space for 15 years. The bearings in the liquid fuel pumps of the world's aerospace rockets at -253 degrees to +500 degrees are the bearings with the lowest operating temperature. This type of bearing works in liquid hydrogen at -253 degrees Celsius. The bearings used in high-temperature environments are typically represented by special high-performance bearings in medical CT scanners. In X-ray vacuum tubes with temperatures as high as 300 to 500 degrees Celsius, bearings can also continue to operate and play a role in protecting our health.
The world of bearings from the shape "Self-aligning ball bearings" Self-aligning roller bearings are bearings with drum rollers installed between the inner ring with two raceways and the outer ring with spherical raceways. The center of curvature of the outer ring raceway is consistent with the center of the bearing, so it has the same self-aligning function as the self-aligning ball bearing. Metal processing WeChat, the content is good and worth paying attention to. When the shaft and the housing are bent, the load and the axial load in two directions can be automatically adjusted. The radial load capacity is large and it is suitable for heavy loads and impact loads. The inner ring inner diameter is a tapered hole bearing, which can be installed directly. Or use a clamping sleeve and a disassembly cylinder to install it on a cylindrical shaft. The cage uses a steel plate stamping cage, a polyamide forming cage, and a copper alloy machined cage. "Needle roller bearing" solid needle roller bearing The basic structure of the inner ring bearing is the same as that of the NU type cylindrical roller bearing, but because of the use of needle rollers, the volume can be reduced and it can withstand large radial loads. The inner ring bearing should use the mounting surface of the shaft with appropriate accuracy and hardness as the raceway surface. Thrust needle roller bearing separable bearings are composed of a raceway ring, a needle roller and a cage assembly, and can be combined with a stamped thin raceway ring (W) or a cut thick raceway ring (WS) at will. Non-separable bearings are integral bearings consisting of precision stamped raceways, needle rollers and cage assemblies. This type of bearing can withstand unidirectional axial loads. It occupies a small space, which is conducive to the compact design of the machine. Most of them only use needle rollers and cage assemblies, and use the mounting surfaces of the shaft and the housing as raceway surfaces. "Tapered roller bearings" This type of bearing is equipped with truncated cone-shaped rollers, which are guided by the large ribs of the inner ring. The design makes the vertices of the conical surfaces of the inner ring raceway surface, the outer ring raceway surface and the roller rolling surface intersect at a point on the center line of the bearing. Single-row bearings can withstand radial loads and unidirectional axial loads, and double-row bearings can withstand radial loads and bidirectional axial loads, and are suitable for bearing heavy loads and impact loads. "Cylindrical roller bearings" According to the number of rows of rolling elements installed in the bearing, cylindrical roller bearings can be divided into single-row, double-row and multi-row cylindrical roller bearings. Among them, single-row cylindrical roller bearings with cages are more commonly used. In addition, there are other cylindrical roller bearings with single-row or double-row full-complement rollers. Single-row cylindrical roller bearings are divided into N, NU, NJ, NF and NUP types according to the different ribs of the ferrule. Cylindrical roller bearings have a large radial load capacity and can also withstand certain unidirectional or bidirectional axial loads according to the structure of the ribs of the ferrule. NN and NNU double-row cylindrical roller bearings have compact structure, strong rigidity, large load capacity, and small deformation after load. They are mostly used to support the spindle of machine tools. FC, FCD, FCDP four-row cylindrical roller bearings can withstand large radial loads and are mostly used in heavy machinery such as rolling mills. "Spherical roller bearings" This type of bearing has spherical rollers installed between the spherical raceway outer ring and the double raceway inner ring. According to the different internal structures, they are divided into four types: R, RH, RHA and SR. Since the arc center of the outer ring raceway is consistent with the center of the bearing, it has aligning performance, so it can automatically adjust the axis misalignment caused by the deflection or eccentricity of the shaft or housing. It can bear radial load and bidirectional axial load. In particular, it has a large radial load capacity and is suitable for bearing heavy loads and impact loads. Metal processing WeChat, the content is good and worth paying attention to. Tapered bore bearings can be assembled and disassembled on the shaft by using fasteners or withdrawal sleeves. Spherical roller bearings can bear large radial loads and certain axial loads. The outer ring raceway of this type of bearing is spherical, so it has aligning performance. When the shaft is bent or tilted by force and the inner ring center line and the outer ring center line are tilted relative to each other by no more than 1° to 2.5°, the bearing can still work.
『Thrust roller bearing』Thrust roller bearings include thrust spherical roller bearings, thrust cylindrical roller bearings and thrust tapered roller bearings. Thrust spherical roller bearings can bear axial and radial loads at the same time, but the radial load shall not exceed 55% of the axial load. Another important feature of this type of bearing is that it has automatic aligning performance, which makes it less sensitive to eccentricity and shaft deflection. As long as the loads P and P. If the angle does not exceed 0.05C and the shaft ring rotates, the bearing will allow a certain range of self-aligning angles. Small values are suitable for large bearings, and the allowable self-aligning angle will decrease when the load increases.
『External spherical bearing』External spherical bearings are preferably used in occasions where simple equipment and parts are required, such as agricultural machinery, transportation systems or construction machinery.
It is mainly used to bear radial and axial combined loads dominated by radial loads. It is generally not suitable to bear axial loads alone. This type of bearing can be installed with an inner ring (with a full set of rollers and retainers) and an outer ring separately. This type of bearing does not allow the shaft to tilt relative to the housing, and additional axial force will be generated under radial load. The size of the axial clearance of this type of bearing has a great impact on whether the bearing can work normally. When the axial clearance is too small, the temperature rise is high; when the axial clearance is large, the bearing is easily damaged. Therefore, special attention should be paid to adjusting the axial clearance of the bearing during installation and operation. If necessary, it can be pre-interference installed to increase the rigidity of the bearing.
『Joint bearing』Joint bearings are lubricating and self-lubricating. Joint bearings are a kind of sliding bearings with a special structure. Its structure is simpler than that of rolling bearings. It is mainly composed of an outer ring with an inner spherical surface. It can bear a large load. According to the inner ring with an outer spherical surface and its different types and structures, it can bear radial load, axial load or combined load of radial and axial at the same time. It is generally used for low-speed swinging motion (i.e. angular motion), and can also make tilting motion (i.e. self-aligning motion) within a certain angle range. Since the sliding surface is spherical motion, it can still work normally when the non-concentricity between the supporting shaft and the shaft shell hole is large.
『Linear bearing』Linear motion ball bearings are mainly used in the parts of linear reciprocating motion in mechanical equipment. They have the advantages of low friction, flexible motion and convenient maintenance and replacement. It is widely used in textile machinery, printing machinery, medical machinery, precision machine tools, electrical cutting machines and automatic recorders.
『Angular contact bearing』Angular contact ball bearings can bear radial loads and axial loads at the same time, or pure axial loads, and have a high limit speed. The ability of this type of bearing to bear axial loads is determined by the contact angle. The larger the contact angle, the higher the ability to bear axial loads.
