Introduction to the construction of rolling bearings and the role of each part in the bearing

Rolling bearing is a rolling bearing developed on the basis of plain bearings. Its working principle is to replace sliding friction with rolling friction. It is generally composed of two ferrules, a set of rolling elements and a cage. The versatility, standardization and serialization of mechanical basic 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 - usually called four large pieces. For sealed bearings, add lubricant and seals (or dust caps) - also known as six large pieces. The various bearing type names are mostly named according to the name of the rolling element. The role of various parts in the bearing is: for radial bearings, the inner ring usually fits tightly with the shaft and runs with the shaft. The outer ring usually transitions with the bearing housing or the mechanical housing bore. Fit, 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 the weigh ring that fits tightly with the shaft and moves together, and the bearing ring or the mechanical housing hole is a transition fit and supports the seat ring. 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.

What are the classifications of bearings?

Deep groove ball bearings The most representative rolling bearings are versatile and can withstand radial loads and bidirectional axial loads. Suitable for high-speed rotation and low-noise, low-vibration applications. Sealed bearings with steel dust caps or rubber seals are pre-filled with a proper amount of grease. Bearings with snap rings or flanges on the outer ring are easy to shaft. Positioning, and easy to install inside the casing. The maximum load type bearing is the same size as the standard bearing, but there is a loading groove in the inner and outer rings, which increases the number of balls and increases the rated load. Self-aligning ball bearings Spherical roller bearings are fitted with drum rollers between the inner ring with two raceways and the outer ring with spherical races. . The center of curvature of the raceway surface of the outer ring is identical to the center of the bearing, so it has the same self-aligning function as the self-aligning ball bearing. When the shaft and outer casing are deflected, the axial load in both directions can be automatically adjusted. The radial load capacity is large, and it is suitable for heavy load and impact load. The inner ring inner diameter is a tapered bore bearing that can be mounted directly. Or use the adapter sleeve and the removal cylinder to mount on the cylindrical shaft. The cage uses a steel stamping cage, a polyamide forming cage and a copper alloy cage. Needle roller bearings Solid needle roller bearings The basic structure of inner ring bearings is the same as that of NU type cylindrical roller bearings, but due to the use of needle rollers The volume can be reduced, and can withstand large radial loads. Without inner ring bearings, the mounting surface of the shaft with appropriate accuracy and hardness should be used as the raceway surface. Thrust Needle Roller Bearings Separate Bearings Consisting of raceway ring and needle roller and cage assembly, it can be combined with stamped thin raceway (W) or a combination of cut and processed thick raceway rings (WS). Non-separable bearings are integral bearings consisting of precision stamped raceway rings and needle and cage assemblies. Can withstand one-way axial load of this type of bearing. The small footprint is conducive to the compact design of the machine. Most of them only use the needle roller and cage assembly, and the mounting surface of the shaft and the casing is used as the raceway surface. Tapered Roller Bearings This type of bearing is equipped with a truncated roller and the roller is guided by a large rib on the inner ring. The apexes of the conical surfaces of the inner ring raceway surface, the outer ring raceway surface, and the roller rolling surface are designed to intersect at a point on the bearing center line. Single row bearings can withstand radial loads and one-way axial loads. Double row bearings can withstand radial loads and biaxial axial loads and are suitable for heavy and shock loads. Cylindrical Roller Bearings Cylindrical roller bearings can be classified into single-row, double-row and multi-row cylindrical roller bearings depending on the number of rows of rolling elements used in bearing assembly. Among them, a single row cylindrical roller bearing with a cage is used. In addition, there are cylindrical roller bearings of other constructions such as single or double row full complement rollers. Single row cylindrical roller bearings According to the ferrule ribs, it is divided into N type, NU type, NJ type, NF type and NUP type. Cylindrical roller bearings have a large radial load capacity and can withstand a certain one-way or two-way axial load depending on the structure of the ferrule rib. NN type and NNU double row cylindrical roller bearings are compact in structure, strong in rigidity, large in carrying capacity, and small in deformation after load, and are mostly used for the support of machine tool spindles. 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 The bearing is equipped with a spherical roller between the outer race of the spherical raceway and the inner race of the double raceway. According to the internal structure, it is 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 self-aligning performance, so the shaft misalignment caused by the deflection or misalignment of the shaft or the outer casing can be automatically adjusted. Can withstand radial loads and bidirectional axial loads. In particular, it has a large radial load capacity and is suitable for withstanding heavy loads and shock loads. Tapered bore bearings can be attached to and removed from the shaft by using fasteners or withdrawal sleeves. Spherical roller bearings can withstand large radial loads while also withstanding certain axial loads. The outer ring raceway of this type of bearing is spherical, so it has the function of self-aligning. When the shaft is bent or tilted so that the center line of the inner ring and the center line of the outer ring are inclined no more than 1°~2.5°, the bearing can still work. . Thrust Roller Bearings Thrust Roller Bearings include thrust spherical roller bearings, thrust cylindrical roller bearings and thrust tapered roller bearings. A thrust spherical roller bearing can withstand both axial and radial loads, but the radial load must not exceed 55% of the axial load. Another important feature of this type of bearing is its self-aligning performance, which makes it less sensitive to different degrees of heart and shaft deflection. Just load P and P. No more than 0.05C, and the shaft rotates, the bearing allows a certain range of centering angle. The small number & #20540; is suitable for large bearings, and allows the centering angle to be reduced when the load is increased. Spherical Bearings Spherical bearings are preferred for applications where equipment and components are required, such as in agricultural machinery, transportation systems or construction machinery. It is mainly used to bear radial and axial combined loads mainly based on radial load. Generally, it is not suitable to bear axial load alone. Such bearings can be installed with inner ring (with full set of rollers and retainers) and outer ring. This type of bearing does not allow the shaft to be tilted relative to the housing, creating additional axial forces under radial load. The axial clearance of the bearing has a great relationship with the normal operation of the bearing. 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, pre-interference can be installed to increase the rigidity of the bearing. Joint Bearings Joint bearings are lubricated and self-lubricating. Joint bearings are a special type of plain bearing. Its structure is simpler than rolling bearings. It is mainly composed of an outer ring with an inner spherical surface and can withstand large loads. It can withstand radial loads according to the inner ring with outer spherical surface and its different type and structure. , axial load or combined load of radial and axial simultaneously. Generally used for low-speed oscillating motion (ie, angular transport, or tilting motion within a certain range of angles (ie, aligning motion), because the sliding surface is spherical), the center of the bearing shaft and the shaft hole are not different. Larger bearings can still work normally. Linear motion ball bearings are mainly used in linear reciprocating parts of mechanical equipment. They have the advantages of small friction, flexible movement 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 Bearings Angular contact ball bearings can withstand both radial and axial loads, as well as with pure axial loads. The ability of this type of bearing to withstand axial loads is determined by the contact angle, the contact angle is large, and the ability to withstand axial loads is high. Pressure Bearings Pressure bearings are separate bearings and are classified into one-way pressure balls and two-way pressure ball bearings according to their construction. One-way pressure bearings can withstand axial loads in one direction, and two-way pressure bearings can withstand axial loads in both directions. None of them can withstand radial loads

Reasonable selection of rotary table bearings plays an important role

The rotary table commonly used in CNC machine tools has an indexing table and a CNC rotary table. When machining certain parts of CNC machine tools, in addition to the linear feed motion of the three coordinate axes X, Y and Z, sometimes there is a need to have circular motion around the three coordinate axes X, Y and Z, respectively A, B, C axis. The CNC rotary table can be used to achieve the circumferential feed motion, in addition to the indexing motion. The function of the indexing table is only to change the surface of the workpiece, and it can be used together with the automatic tool changing device to realize the multiple installations of several surfaces in one installation of the workpiece, thus greatly improving the working efficiency. The shape of the CNC turntable and the indexing table are not much different, but there are a series of features in the structure. Since the CNC rotary table can realize the feed motion, it has much in common with the feed drive mechanism of the CNC machine. The difference is that the drive mechanism realizes the linear feed motion, and the CNC rotary table realizes the circular feed motion. Rotary tables are widely used in various CNC milling machines, boring machines, various vertical vehicles, and vertical milling machines. In addition to requiring the rotary table to withstand the weight of the workpiece well, it is also necessary to ensure its rotation accuracy under load. The rotary table bearing, as the core component of the turntable, not only has a high load carrying capacity during the operation of the turntable, but also needs to have high rotation precision, high anti-overturning capability, and high rotational speed capability. 1. Thrust ball bearing + cylindrical roller bearing Thrust ball bearing can withstand a certain axial force, so the bearing is mainly used to bear the weight of the workpiece; and cylindrical roller Bearings are primarily used for radial positioning and to withstand external radial forces (eg cutting forces, milling forces, etc.). This type of design is widely used and relatively inexpensive. Since the thrust ball is a point contact bearing, its axial bearing capacity is relatively limited, and it is mainly used for small or medium-sized machine tool rotary table. In addition, the lubrication of the thrust ball is also difficult. 2.Static bearing + precision cylindrical roller bearing The hydrostatic bearing is a kind of externally supplied pressure oil, which establishes a static pressure bearing oil film in the bearing to achieve liquid lubrication. Sliding bearing. Hydrostatic bearing always works under liquid lubrication from start to stop, so there is no wear, long service life and low starting power. In addition, this bearing also has the advantages of high rotation precision, large oil film stiffness, and can suppress oil film oscillation. Precision cylindrical roller bearings have good radial bearing capacity, and the precision of the rotary table can be guaranteed due to the use of precision bearings. The rotary table designed with this type can withstand high axial forces. Some workpieces weigh more than 200t and the turntable has a diameter of more than 10m. However, this type of design also has some shortcomings. Because the hydrostatic bearing must be equipped with a special oil supply system to supply the pressure oil, the maintenance is complicated and the cost is relatively high. 3. Crossed Roller Bearings Cross roller bearings are commonly used on turntables. Crossed roller bearings are characterized by two raceways in the bearing and two rows of rollers arranged in a row. Compared with the traditional thrust bearing + radial centering bearing combination, the cross roller bearing is compact and compact, and simplifies the workbench design, thus reducing the cost of the turntable. In addition, due to the use of optimized preload, this type of bearing has a high stiffness, so the rigidity and accuracy of the turntable are also guaranteed. Thanks to the design of the two-row cross-roller, the effective span of the bearing can be significantly improved, so this type of bearing has a high anti-overturning moment. In the cross-roller bearing, it is divided into two types: the first is a cylindrical cross-roller bearing, and the second is a tapered cross-roller bearing. In general, cylindrical cross-roller bearings are less expensive than conical crossed roller bearings and are suitable for use in turntable applications where the rotational speed is relatively low. Conical crossed roller bearings use a purely rolling design of tapered rollers for high running accuracy and speed capability. Strong, reducing the advantages of shaft length and processing cost. Crossed roller bearings are suitable for all types of vertical or horizontal boring machines, as well as vertical grinding, vertical turning and large gear milling machines. In summary, the bearing, as the core component of the machine tool spindle and turntable, plays a decisive role in the performance of the machine tool. In order to be able to choose the right size and type of bearing, we need to consider a variety of working conditions, such as operating speed, lubrication, installation type, spindle stiffness, accuracy and other requirements. As far as the bearing itself is concerned, only by fully understanding its design features and the advantages and disadvantages brought about by it, can the best performance of the bearing be achieved.

Angular contact ball bearings are convenient for customers

The rolling element of an angular contact ball bearing is a ball because it is a point contact (distinguished from the line contact of the roller bearing), so it can provide higher rotation speed, smaller heat generation and higher rotation accuracy. . In some ultra-high-speed spindle applications, hybrid bearings with ceramic balls (typically Si3N4 or Al2O3) are also used. Compared with the traditional fully hardened steel ball, the ceramic ball material itself gives the ceramic ball bearing the characteristics of high rigidity, high rotation speed, high temperature resistance and long service life, so as to meet the demand of high-end customers for machine tool bearing products. The contact angle of angular contact ball bearings is currently the contact angle of 15 and 25; usually the contact angle of 15 has a relatively high rotational speed performance, while the contact angle of 25 has a higher axial load. ability. Since the choice of preloading has a great influence on the application of precision angular contact ball bearings, for example, in high load bearing and high rigidity, medium or heavy bearing preloading is generally used; for some high speed and high precision applications, In the early selection of bearings, care must be taken to select the appropriate preload. The preload is generally divided into three types: light, medium and heavy. Generally, light preload is more common. In order to facilitate the use of customers, the world's major bearing manufacturers generally provide pre-grinded bearing end faces and preloaded bearings, which is commonly referred to as the universal pairing precision angular contact ball bearing form. This type of bearing eliminates customer preload regulation and saves installation time. In some machine applications with heavy loads and speed requirements, such as the forging of forgings, wire machines for oil pipelines, heavy duty lathes and milling machines, etc., the choice of precision tapered roller bearings is one. An ideal solution. Because the roller of the tapered roller bearing is designed for line contact, it can provide high rigidity and load to the main shaft. In addition, the tapered roller bearing is a pure rolling bearing design, which can reduce the bearing operation. Torque and heat to ensure spindle speed and accuracy. Since tapered roller bearings are capable of adjusting the axial preload (play) during installation, this allows the customer to better optimize bearing clearance throughout the life of the bearing. In addition, in some high-speed applications where the inner ring rim speed is greater than 30 m/s, some specially designed tapered roller bearings can also meet the requirements, such as TSMA bearings or Hydra-Rib hydraulic floating gears. The rib of the edge bearing TSMA bearing has a plurality of lubricating oil holes in the axial direction, which can be lubricated by circulating oil or oil mist. The centrifugal force can distribute the oil to the contact area between the roller and the rib, so that the bearing can be more fully lubricated. Increase bearing speed. The Hydra-Rib hydraulic floating rib bearing is designed to optimize the preload of the spindle system. The bearing has a floating rib that is in contact with the large end of the roller, unlike the common bearing with a fixed inner ring rib; The floating rib is positioned by the "pressure" system, which ensures that the bearing will perform at its best under all conditions and has been successfully used in domestic customers. For precision selection of tapered roller bearings, ISO P5 bearings are mainly used in conventional lathes and milling machines; for machining centers, grinding machines, etc., ISO P4 or above is usually selected. Precision bearings. In the spindle design, there are two common tapered roller bearing layouts. The first is a tapered roller bearing with a front and rear end and a face-to-face mounting that is compact, rigid and easy to install and adjust. The second is to use two tapered roller bearings to face-to-face as the front end of the main shaft, while the rear end uses a double outer ring and two single inner ring bearings (TDO) as the floating end; Floating capacity, this type of design can withstand the axial thermal expansion of the spindle well, and the rigidity is high, which ensures the accuracy of the machine. In the application of machine tool spindles, double row precision cylindrical roller bearings are also used, usually in combination with precision angular contact ball bearings or thrust bearings. These bearings can withstand large radial loads and allow for higher speeds. The two rows of rollers in the bearing are arranged in an intersecting manner. The fluctuation frequency during rotation is greatly improved compared with the single-row bearing, and the amplitude is reduced by 60% to 70%. These bearings usually come in two forms: NN30, NN30K two series bearing inner ring with ribs, outer ring can be separated; NNU49, NNU49K two series bearing outer ring with ribs, inner ring can be separated, of which NN30K and NNU49K series The inner ring is a tapered hole (taper 1:12), which cooperates with the tapered journal of the main shaft, and moves the inner ring axially to make the inner ring expand, so that the bearing clearance can be reduced or even pre-tensioned (negative clearance) status). Cylindrical bore bearings are usually hot-fitted, with an interference fit to reduce bearing clearance or preload the bearing. For NNU49 series bearings with separable inner ring, the main shaft is usually mounted on the inner ring and then the raceway is finished to improve the spindle rotation accuracy.

Learn about thin-walled isometric bearings that can be customized according to your needs.

Thin-walled isometric bearings, also known as thin-walled ferrule bearings, are highly accurate, very quiet and have a high load carrying capacity. Thin-walled ferrule bearings can be deep groove ball bearings, four-point contact bearings, angular contact ball bearings, thin-walled and other cross-section bearings are mostly square. In these series, even with larger shaft diameters and bearing bores, the cross section remains the same. These bearings are therefore referred to as equal sections. It is this feature that distinguishes thin-walled ferrule bearings in the standard ISO series from conventional bearings. Therefore, a larger cross section can be selected and a more load bearing bearing can be used without having to change the shaft diameter. Thin-walled ferrule bearings can be designed to be extremely light and require very little space. Main applications of thin-walled isometric bearings: stepper motors, medical instruments, office equipment, testing instruments, deceleration, shifting devices, robots, optical imaging equipment, rotary encoders. Advantages of thin-walled equal-section bearings: Thin-walled bearings achieve extremely thin bearing sections and also achieve miniaturization and weight reduction. The diversity of products extends the range of applications. Product characteristics of thin-walled isopy bearings: In order to obtain low friction torque, high rigidity and good rotation accuracy of bearings, steel balls with small outer diameters are used. The use of a hollow shaft ensures space for wiring and wiring. The thin-walled 6700, 6800, and 6900 series are available in various dust cover types, flanged versions, stainless steel forms, and wide format.

Learn about thin-walled isometric bearings that can be customized according to your needs.

Thin wall isometric bearings, also known as thin-walled ferrule bearings, which are highly accurate, very quiet and load-bearing Very strong. Thin-walled ferrule bearings can be deep groove ball bearings, four-point contact bearings, angular contact ball bearings, thin-walled and other cross-section bearings are mostly square. In these series, even with larger shaft diameters and bearing bores, the cross section remains the same. These bearings are therefore referred to as equal sections. It is this feature that distinguishes thin-walled ferrule bearings in the standard ISO series from conventional bearings. Therefore, a larger cross section can be selected and a more load bearing bearing can be used without having to change the shaft diameter. Thin-walled ferrule bearings can be designed to be extremely light and require very little space. Main applications of thin-walled isometric bearings: stepper motors, medical instruments, office equipment, testing instruments, deceleration, shifting devices, robots, optical imaging equipment, rotary encoders. Advantages of thin-walled equal-section bearings: Thin-walled bearings achieve extremely thin bearing sections and also achieve miniaturization and weight reduction. The diversity of products extends the range of applications. Product characteristics of thin-walled isopy bearings: In order to obtain low friction torque, high rigidity and good rotation accuracy of bearings, steel balls with small outer diameters are used. The use of a hollow shaft ensures space for wiring and wiring. The thin-walled 6700, 6800, and 6900 series are available in various dust cover types, flanged versions, stainless steel forms, and wide format.

Detailed description of the thrust roller bearing

Thrust Roller Bearings are used to support axial and radial combined loads dominated by axial loads, but The load must not exceed 55% of the axial load. Compared with other thrust roller bearings, this type of bearing has a low friction factor, a high rotational speed, and has a self-aligning performance. The stick of the 29000 type bearing is an asymmetrical spherical roller, which can reduce the relative sliding of the roller and the raceway during operation, and has a long roller, a large diameter, a large number of rollers, a high load capacity, and is usually oil lubricated. Individual low speed conditions can be lubricated with grease. In design selection, it should be preferred; 80000 thrust cylindrical roller bearings, 90000 thrust tapered roller bearings and AXK thrust needle bearings can withstand one-way axial loads, which is more axial than thrust ball bearings. The load capacity is much larger, and the rigidity is large and the axial space is small. Thrust cylindrical roller bearings and thrust needle roller bearings are suitable for low speed applications. Thrust tapered roller bearings have a slightly higher rotational speed than thrust cylindrical roller bearings. Thrust roller bearings are divided into thrust cylindrical roller bearings, thrust spherical roller bearings, thrust tapered roller bearings, thrust needle roller bearings.  Thrust cylindrical roller bearings are mainly used in oil drilling rigs and steelmaking machinery.   Thrust spherical roller bearings These bearings are mainly used in hydroelectric generators, vertical motors, propeller shafts for ships. , tower cranes, extruders, etc.   Thrust tapered roller bearings The main uses of these bearings: one-way: crane hooks, oil rig swivel. Two-way: rolling mill roll neck.   Plane thrust bearings in the assembly mainly It can withstand axial loads and is widely used. Although the installation of the thrust bearing is relatively simple, there are often errors in the actual maintenance, that is, the tight ring and the loose ring of the bearing are not installed correctly, and the bearing is lost, and the journal is quickly worn. The tight ring is mounted on the end face of the stationary part, ie incorrect assembly. The inner ring of the tight ring and the journal are in a transitional fit. When the shaft rotates, the tight ring is driven and friction is generated with the end face of the stationary part. When the axial force (Fx) is applied, the friction torque will be greater than the inner diameter and the resistance torque will be tight. Forced rotation of the ring-to-shaft mating surface exacerbates journal wear.