Powerful Spherical Roller Bearings
Product Introduction
Spherical roller bearings incorporate a large number of long, symmetrical, and large-diameter rollers, allowing them to withstand heavy concentrated loads. The unique raceway geometry and optimal surface finish of Type C and CA bearings minimize friction. Compared to traditional spherical roller bearings, these designs operate at lower temperatures, support heavier axial loads, and achieve higher speeds. HRB spherical roller bearings are available with cylindrical or tapered bores. Bearings of series 240 and 241 have a tapered bore with a taper of 1:30 (suffix code K30), while other bearings feature a tapered bore with a taper of 1:12 (suffix code K).
Design
Type C and EC Designs
These bearings feature symmetrical rollers and a stamped steel cage. The guide ring is centered on the inner ring. Type EC bearings incorporate reinforced rollers for increased load capacity. Type C bearings employ optimized surface finishing on rollers and raceways to improve roller guidance and reduce friction.
Type CA and ECA Designs
These bearings feature symmetrical rollers and flanges on the inner ring. The guide ring is positioned between the two rows of rollers and centered on the inner ring. The cage is a one-piece machined brass or steel design. Type CA and ECA bearings utilize the same surface finishing as Type C bearings. Type ECA bearings incorporate reinforced rollers for enhanced load capacity.
Oil Grooves and Holes
For effective lubrication, standard HRB spherical roller bearings include annular oil grooves and three oil holes on the outer ring, except for Type C bearings with an outer diameter below 150 mm or 180 mm (varies by series) and all series 213 bearings. The suffix code W33 denotes bearings (Types C, EC, CA, and ECA) with oil grooves and holes on the outer ring.
Angular Misalignment
The design of spherical roller bearings enables self-alignment, allowing them to compensate for angular misalignment between the inner and outer rings. Under normal load and operating conditions, the permissible misalignment values during inner ring rotation are provided in the table on the right.
Tolerances
Spherical roller bearings with cylindrical or tapered bores are manufactured with standard (normal) tolerances, as listed in Table 9.4.
Internal Clearance
Standard spherical roller bearings are supplied with normal radial internal clearance. However, most applications require bearings with C3 clearance, and some even require larger C4 clearance. Certain sizes are available with C2 clearance (smaller than normal). The limits for various clearance grades are listed in Tables 5.25 and 5.26 (Pages 67–68) and comply with ISO 5753:1981. These values apply to unloaded bearings in an unmounted state.
Effect of Operating Temperature on Bearing Materials
Standard spherical roller bearings undergo special heat treatment, ensuring no significant dimensional changes occur at operating temperatures exceeding +200°C.
Minimum Load
To ensure satisfactory operation, bearings must be subjected to a minimum load. Spherical roller bearings are no exception. Without sufficient load, inertial forces of the rollers and cage, along with lubricant friction, may adversely affect rolling behavior at high speeds, potentially causing destructive sliding between rollers and raceways. The minimum required radial load can be estimated using the formula:
F_{rm} = 0.02C_r
Where:
· F_{rm}: Minimum radial load (N)
· C_r: Basic dynamic load rating (N)
The weight of supported components combined with external forces often exceeds the minimum load requirement. If not, supplemental radial loads (e.g., increased belt tension or idle torque) must be applied.
Dynamic Equivalent Bearing Load
· When \frac{F_a}{F_r} \leq e:
P = F_r + Y_1 F_a
· When \frac{F_a}{F_r} > e:
P = 0.67F_r + Y_2 F_a
The calculation coefficients e, Y_1, and Y_2 for each bearing are provided in the bearing tables.
Static Equivalent Bearing Load
P_0 = F_r + Y_0 F_a
The calculation coefficient Y_0 for each bearing is provided in the bearing tables."