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Self-aligning roller bearings feature double-row rollers, with one common spherical raceway on the outer ring and two raceways on the inner ring angled relative to the bearing axis. This ingenious design gives them self-aligning properties, making them less susceptible to errors in the shaft-bearing housing angle or shaft bending. They are suitable for applications where angular errors are caused by installation errors or shaft deflection. In addition to radial loads, these bearings can withstand bidirectional axial loads.

Self-aligning roller bearings are available with either cylindrical or tapered bores. The tapered bores have taper ratios of 1:30 and 1:12. These tapered bore bearings, when used with adapter sleeves or withdrawal sleeves, allow for convenient and quick assembly onto plain or stepped machine shafts.

Self-aligning roller bearings have two rows of rollers and primarily bear radial loads, but can also withstand axial loads in either direction. They have high radial load capacity and are particularly suitable for heavy-duty or vibratory loads, but cannot withstand pure axial loads. This type of bearing has a spherical raceway on the outer ring, resulting in excellent self-aligning performance and the ability to compensate for coaxiality errors.

It features two rows of symmetrical spherical rollers. The outer ring has a common spherical raceway, while the inner ring has two raceways inclined at an angle to the bearing axis. This provides excellent self-aligning performance, allowing the bearing to function normally even when the shaft is subjected to bending or misalignment during installation. The self-aligning capability varies depending on the bearing size series, but the generally permissible self-aligning angle is 1~2.5 degrees. This type of bearing has a high load capacity, capable of withstanding both radial and bidirectional axial loads. It also exhibits good impact resistance. Generally, self-aligning roller bearings have a lower permissible operating speed.

Self-aligning roller bearings are classified into two different structures based on the roller cross-sectional shape: symmetrical spherical roller bearings and asymmetrical spherical roller bearings. Asymmetrical self-aligning roller bearings are an earlier product, primarily used for main engine maintenance. They are rarely used in new main engine designs. Their internal structure has undergone comprehensive design improvements and parameter optimization, allowing them to withstand greater axial loads compared to earlier self-aligning roller bearings. These bearings operate at lower temperatures, thus meeting higher speed requirements. Based on the presence or absence of inner ring flanges and the type of cage used, they are further divided into type C and type CA. Type C bearings are characterized by an inner ring without flanges and a stamped steel cage, while type CA bearings are characterized by flanges on both sides of the inner ring and a machined solid cage. To improve bearing lubrication, self-aligning roller bearings with annular oil grooves and three oil holes on the outer ring are available, indicated by the bearing designation /W33.

Self-aligning roller bearings with inner ring oil holes can also be supplied according to customer requirements. For ease of installation, removal, and replacement, self-aligning roller bearings with tapered inner bores are also available, with a taper of 1:12, indicated by the suffix “K”. Bearings with a taper of 1:30 inner bore are also available to meet special customer requirements, with the suffix “K30”.

Bearings with tapered inner bores can be directly mounted on tapered journals using a lock nut, or mounted on cylindrical journals using a locknut or withdrawal sleeve. To ensure that the bearing does not experience harmful slippage between the raceway and rollers due to centrifugal force during high-speed operation,

the bearing should withstand a certain minimum radial load, the magnitude of which can be estimated by the following formula:

Fr = 0.02C
Where:

Fr — Minimum radial load N

C — Basic rated dynamic load of the bearing N
Equivalent dynamic load

P = Fr + Y1Fa (when Fa/Fr < 0)

P = 0.67Fr + Y2Fa (when Fa/Fr < 0)

Where:

P — Equivalent dynamic load N

Y1 & Y2 — Axial dynamic load coefficient

Equivalent static load

P0 = Fr + Y0Fa
Where:

P0 — Equivalent static load N

Y0 — Axial static load coefficient

Applications:
Mainly applicable cages: Stamped steel reinforced cage (suffix E, rarely seen in China). Stamped steel cage (suffix CC), glass fiber reinforced polyamide 66 cage (suffix TVPB), machined brass two-piece cage (suffix MB). Machining brass integral cage (suffix CA), stamped steel plate cage for vibration applications (suffix JPA). Brass cage for vibration applications (suffix EMA). The same structure may have different markings on the bearing.

Main applications: papermaking machinery, speed reducers, railway vehicle axles, rolling mill gearbox bearing housings, rolling mill rollers, crushers, vibrating screens, printing machinery, woodworking machinery, various industrial speed reducers, vertical self-aligning bearings with mounting brackets. [2]

Installation Self-aligning roller bearings are bearings with drum-shaped rollers assembled between an inner ring with two raceways and an outer ring with spherical raceways. The curvature center of the outer ring raceway surface coincides with the bearing center, so it has the same self-aligning function as an automatic self-aligning ball bearing. When the shaft or housing deflects, it can automatically adjust the load and axial load in two directions. It has a large radial load capacity and is suitable for heavy loads and impact loads. Bearings with tapered inner ring diameters can be directly installed. Or, a locking sleeve or a disassembly sleeve can be used to install it on a cylindrical shaft. Cages are made of stamped steel, molded polyamide, or machined copper alloy. For self-aligning bearings, an intermediate mounting ring is used to prevent the outer ring from tilting and rotating when the bearing with a shaft is installed into the housing bore. It should be noted that some sizes of self-aligning ball bearings have balls that protrude from the side of the bearing, so the intermediate mounting ring should be recessed to prevent damage to the balls. Most bearings are installed using mechanical or hydraulic press-fitting. [3] For separable bearings, the inner and outer rings can be installed separately, simplifying the installation process, especially when both the inner and outer rings require an interference fit. When installing a shaft with the inner ring already installed into a bearing housing containing the outer ring, it is essential to check that the inner and outer rings are correctly aligned to avoid scratching the bearing raceways and rolling elements. If cylindrical and needle roller bearings use inner rings without flanges or with flanges on one side, it is recommended to use mounting sleeves. The outer diameter of the sleeve should be equal to the inner ring raceway diameter F, and the machining tolerance should be d10. Stamped outer ring needle roller bearings are best mounted using a mandrel.

Clearance: For the axial clearance of self-aligning roller bearings, it can be adjusted using adjusting nuts on the journal, adjusting shims, and threads in the bearing housing bore, or by using preload springs. The size of the axial clearance depends on the bearing arrangement during installation, the distance between bearings, and the materials of the shaft and bearing housing, and can be determined according to the working conditions. For high-load, high-speed self-aligning roller bearings, the effect of temperature rise on axial clearance must be considered when adjusting the clearance, and the reduction in clearance caused by temperature rise must be estimated. In other words, the axial clearance should be adjusted to be slightly larger. For low-speed bearings and bearings subjected to vibration, zero-clearance installation or preload installation should be adopted. The purpose is to ensure good contact between the rollers and raceways of the self-aligning roller bearing, uniform load distribution, and prevention of damage to the rollers and raceways from vibration and impact. After adjustment, the size of the axial clearance is checked with a dial indicator. The method is to first fix the dial indicator on the machine body or bearing housing, so that the dial indicator contact touches the smooth surface of the shaft, and push the shaft left and right along the axis. The maximum swing of the indicator needle is the axial clearance value.