Bearings are crucial components in mechanical equipment. Their main function is to support rotating mechanical parts and reduce the coefficient of friction of mechanical loads during transmission.
Bearings are classified into radial bearings and thrust bearings according to their load-bearing direction or nominal contact angle.
According to the type of rolling element, they are divided into: ball bearings and roller bearings.
Based on whether they can be self-aligned, they are divided into: self-aligning bearings and non-self-aligning bearings (rigid bearings).
Based on the number of rows of rolling elements, bearings are classified as: single-row bearings, double-row bearings, and multi-row bearings.
Based on whether the components can be separated, bearings are divided into: separable bearings and non-separable bearings.
In addition, there are classifications based on structural shape and size.
This article mainly shares the characteristics, differences, and corresponding applications of 13 common bearings.
1. Angular contact ball bearings
There is a contact angle between the bearing ring and the ball. The standard contact angles are 15°, 30°, and 40°. The larger the contact angle, the greater the axial load capacity; the smaller the contact angle, the more conducive it is to high-speed rotation. Single-row bearings can withstand radial loads and unidirectional axial loads. Structurally, two single-row angular contact ball bearings with back-mounted assembly share the inner and outer rings and can withstand radial loads and bidirectional axial loads.
Main uses:
Single-row: machine tool spindles, high-frequency motors, gas turbines, centrifugal separators, front wheels of small cars, and differential pinion shafts.
Double-row: oil pumps, Roots blowers, air compressors, various transmissions, fuel injection pumps, printing machinery.
II. Self-aligning ball bearings
Double-row steel balls and an outer ring raceway with an inner spherical surface allow for automatic adjustment of misalignment caused by shaft or housing deflection or eccentricity. Tapered bore bearings can be easily mounted on shafts using fasteners and primarily bear radial loads.
Main applications: drive shafts for woodworking machinery and textile machinery; vertical self-aligning bearings with mounting brackets.
III. Self-aligning roller bearings
This type of bearing has spherical rollers installed between the outer ring with a spherical raceway and the inner ring with a double raceway. According to the different internal structures, it is divided into four types: R, RH, RHA and SR. Since the arc center of the outer ring raceway is consistent with the bearing center, it has self-aligning performance. Therefore, it can automatically adjust the misalignment of the shaft caused by the deflection or misalignment of the shaft or housing, and can withstand radial loads and bidirectional axial loads.
Main applications: papermaking machinery, speed reducers, railway vehicle axles, rolling mill gearbox seats, rolling mill roller conveyors, crushers, vibrating screens, printing machinery, woodworking machinery, various industrial speed reducers, and vertical self-aligning bearings with mounting brackets.
IV. Thrust self-aligning roller bearings
In this type of bearing, the spherical rollers are arranged at an angle. Because the raceway surface of the seat ring is spherical, it has self-aligning properties, so it can allow the shaft to have some tilt. It has a very large axial load capacity and can also bear some radial load while bearing axial load. It is generally lubricated with oil during use.
Main applications: hydroelectric generators, vertical electric motors, marine propeller shafts, reducers for rolling mill screws, tower cranes, coal mills, extruders, forming machines.
V. Tapered Roller Bearings
These bearings are equipped with frustum-shaped rollers, guided by the large flange of the inner ring. The design ensures that the vertices of the conical surfaces of the inner ring raceway, outer ring raceway, and rolling surface of the rollers intersect at a single point on the bearing's centerline. Single-row bearings can withstand radial and unidirectional axial loads, while double-row bearings can withstand radial and bidirectional axial loads, making them suitable for heavy loads and impact loads.
Main applications: Automobiles: front wheels, rear wheels, transmissions, differential pinion shafts. Machine tool spindles, construction machinery, large agricultural machinery, railway vehicle gear reduction devices, rolling mill roll necks and reduction devices.
VI. Deep Groove Ball Bearings
Structurally, each ring of a deep groove ball bearing has a continuous groove raceway with a cross-section approximately one-third of the circumference of the ball's equator. Deep groove ball bearings are primarily used to bear radial loads, but can also withstand certain axial loads.
When the radial clearance of a bearing increases, it exhibits the characteristics of an angular contact ball bearing, capable of withstanding alternating axial loads in two directions. Compared to other types of bearings of the same dimensions, this type of bearing has a lower coefficient of friction, higher limiting speed, and higher precision, making it the preferred bearing type for users.
Main applications: automobiles, tractors, machine tools, motors, water pumps, agricultural machinery, textile machinery, etc.
VII. Thrust ball bearing
A bearing consists of a washer-shaped raceway ring with raceways, balls, and a cage assembly. The raceway ring that mates with the shaft is called the shaft ring, and the raceway ring that mates with the housing is called the housing ring. Double-direction bearings mate with the shaft. Single-direction bearings can withstand unidirectional axial loads, while double-direction bearings can withstand bidirectional axial loads (neither can withstand radial loads).
Main applications: automotive steering pins, machine tool spindles.
8. Thrust Roller Bearings
Thrust roller bearings are used to bear shafts primarily under axial loads, with combined radial loads, but the radial load must not exceed 55% of the axial load. Compared to other thrust roller bearings, this type of bearing has a lower coefficient of friction, higher speed, and self-aligning capability. The rollers in the 29000 series bearings are asymmetrical spherical rollers, which reduces relative slippage between the rollers and raceways during operation. They also feature long, large-diameter rollers, a large number of rollers, and a high load capacity. Oil lubrication is typically used, with grease lubrication possible in some low-speed applications.
Main uses: hydroelectric generators, crane hooks.
9. Cylindrical roller bearings
The rollers of a cylindrical roller bearing are typically guided by two flanges of one bearing race. The cage rollers and guide race form an assembly that can be separated from the other bearing race, making it a separable bearing.
This type of bearing is relatively easy to install and disassemble, especially when interference fits are required between the inner and outer rings and the shaft and housing. These bearings are generally only used to bear radial loads; only single-row bearings with flanges on both the inner and outer rings can withstand smaller steady axial loads or larger intermittent axial loads.
Main applications: large motors, machine tool spindles, axle boxes, diesel engine crankshafts, automobiles, and transmission boxes for motors, etc.
10. Four-point contact ball bearings
It can withstand radial loads and bidirectional axial loads. A single bearing can replace a front-combined or back-combined angular contact ball bearing. It is suitable for bearing pure axial loads or combined loads with a large axial load component. When bearing axial loads in any direction, this type of bearing can form one of the contact angles. Therefore, the ring and the ball are always in two-sided three-point contact on any contact line.
Main applications: aircraft jet engines, gas turbines.
XI. Thrust Cylindrical Roller Bearings
It consists of washer-shaped raceway rings (shaft rings, seat rings), cylindrical rollers, and a cage assembly. The cylindrical rollers are machined with convex surfaces, resulting in uniform pressure distribution between the rollers and the raceway surfaces. It can withstand unidirectional axial loads, has a large axial load capacity, and strong axial rigidity.
Main uses: oil drilling rigs, iron and steel manufacturing machinery.
12. Thrust needle roller bearings
Separable bearings consist of raceway rings, needle rollers, and a cage assembly, and can be combined with either stamped thin raceway rings or machined thick raceway rings. Non-separable bearings are integral bearings consisting of precision-stamped raceway rings, needle rollers, and a cage assembly. They can withstand unidirectional axial loads. These bearings occupy less space, which is beneficial for compact machine design. They mostly use only the needle rollers and cage assembly, while the mounting surfaces of the shaft and housing are used as raceway surfaces.
Main applications: Transmission devices for automobiles, tillers, machine tools, etc.
13. Thrust tapered roller bearings
This type of bearing is equipped with frustum-shaped rollers (the large end is spherical). The rollers are accurately guided by the raceway rings (shaft ring, housing ring). The design ensures that the vertices of the conical surfaces of the raceway surfaces of the shaft ring and housing ring, as well as the rolling surfaces of the rollers, intersect at a point on the bearing centerline. One-way bearings can withstand unidirectional axial loads, while two-way bearings can withstand bidirectional axial loads.
Main uses:
One-way: Crane hook, oil drilling rig swivel.
Bidirectional: Roll neck of rolling mill.
14. Mounted spherical ball bearings
Mounted spherical roller bearings consist of two sealed spherical roller bearings and a cast (or stamped steel) bearing housing. The internal structure of spherical roller bearings is the same as that of deep groove ball bearings, but the inner ring of this type of bearing is wider than the outer ring, and the outer ring has a truncated spherical outer surface that matches the concave spherical surface of the bearing housing for self-aligning.
Main applications: mining, metallurgy, agriculture, chemical industry, textiles, printing and dyeing, conveying machinery, etc.
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