Abstract:
A self aligning bearing assembly comprising a split inner ring and a split outer ring, and two rows of rolling elements arranged at different contact angles, for supporting a main shaft of a wind turbine.

Description:
TECHNICAL FIELD 
       [0001]    Example aspects described herein relate to bearing assemblies, particularly of self-aligning bearings for wind turbine applications. 
       BACKGROUND 
       [0002]    Bearing assemblies are typically circular in shape, and generally comprise rolling elements sandwiched between raceways in bearing rings. Rolling elements take many forms, including spherical balls, rollers or various other configurations, such as cone-shaped tapered rollers or barrel-shaped spherical rollers. 
         [0003]    Bearings are widely used in wind power generation, particularly in the nacelle of the turbine, to support components in the gearbox and the main shaft of the wind turbine, which, typically the blade rotor assembly is mounted on. In large size wind turbines, the nacelle can be dozens of meters high above the ground, thus maintaining the bearings supporting the main shaft of the blade rotor assembly can involve substantial labor, costs and often the use of specialized equipment, such as large cranes. 
         [0004]    Both radial and thrust loads are generated during power generation cycles in a wind turbine, as a result of the action of the wind on the blade rotors and, in turn, the main shaft. The main shaft bearing, must, therefore, be able to support both radial and axial (or thrust) loads. 
         [0005]    Various bearing assemblies are disclosed for rotatably supporting the main shaft of the wind turbine, for example, U.S. Pat. No. 7,918,649 discloses a double row spherical roller assembly with one row having rollers of different lengths from every roller of the other row. A disadvantage of such assemblies is that an entire bearing assembly must be lifted and mounted in place on the main shaft of the wind turbine. 
       SUMMARY OF THE INVENTION 
       [0006]    A new design for a bearing assembly for a wind turbine is disclosed. In one example embodiment of the invention, the bearing comprises two rows of rolling elements disposed between an axially split inner ring and an axially split outer ring, the rolling elements retained by a cage. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0007]    The above mentioned and other features and advantages of the embodiments described herein, and the manner of attaining them, will become apparent and be better understood by reference to the following description of at least one example embodiment in conjunction with the accompanying drawings. A brief description of those drawings now follows. 
           [0008]      FIG. 1  is a cross sectional view of a bearing assembly according to one example embodiment herein described. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0009]    Identically labeled elements appearing in different ones of the figures refer to the same elements but may not be referenced in the description for all figures. The exemplification set out herein illustrates at least one embodiment, in at least one form, and such exemplification is not to be construed as limiting the scope of the claims in any manner. Radially inward directions are from an outer radial surface of the cage, toward the central axis or radial center of the cage. Conversely, a radial outward direction indicates the direction from the central axis or radial center of the cage toward the outer surface. Axially refers to directions along a diametric central axis. 
         [0010]      FIG. 1  is a cross sectional view of bearing assembly  10  according to one example embodiment of the invention. Bearing assembly  10  comprises split inner ring  1  having inner races  1 A and  1 B, split outer ring  2  having outer races  2 A and  2 B, first row rolling elements  11  disposed in cage  4 A , second row rolling elements  12  disposed in cage  4 B, each row,  11  and  12 , separated by floating spacer  5 . Floating spacer  5  may be inner ring or outer ring guided. Rolling elements  11  and  12  are shown as spherical rollers, however, the present invention contemplates the use of other rolling elements. In addition, rolling elements  11  and  12  are shown as of equal length, though different length rollers are also contemplated by the present invention. 
         [0011]    Split inner ring  1  comprises two circumferential sections or segments  13  and  14  joined by joining bolts  3 A, forming a continuous ring when joined. Split outer ring  2  comprises two circumferential sections  15  and  16  joined by joining bolt  3 B, forming a continuous ring when joined. When split inner ring  1  and split outer ring  2  are assembled, races  1 A,  1 B,  2 A and  2 B form smooth, continuous races for rolling elements  11  and  12 , respectively. 
         [0012]    In one example embodiment, first row rolling elements  11  operate at contact angle al and second row rolling elements operate at contact angle α2, where α1 and α2 are different from each other. In the embodiment shown at  FIG. 1 , α2 is greater than α1, and therefore, second row rolling elements  12  are better accommodated to support increased thrust loads, for example, from a wind turbine rotor. In this configuration, first row rolling elements  11  would be mounted toward the rotor blades (not shown) of the wind turbine and second row rolling elements would be mounted toward the gearbox side (not shown) of the wind turbine. 
         [0013]    In the foregoing description, example embodiments are described. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense. It will, however, be evident that various modifications and changes may be made thereto, without departing from the broader spirit and scope of the present invention. 
         [0014]    In addition, it should be understood that the figures illustrated in the attachments, which highlight the functionality and advantages of the example embodiments, are presented for example purposes only. The architecture or construction of example embodiments described herein is sufficiently flexible and configurable, such that it may be utilized (and navigated) in ways other than that shown in the accompanying figures. 
         [0015]    Although example embodiments have been described herein, many additional modifications and variations would be apparent to those skilled in the art. It is therefore to be understood that this invention may be practiced otherwise than as specifically described. Thus, the present example embodiments should be considered in all respects as illustrative and not restrictive. 
       LIST OF REFERENCE SYMBOLS 
       [0000]    
       
           1  Split Inner Ring 
           1 A First Row Inner Race 
           1 B Second Row Inner Race 
           2  Split Outer Ring 
           2 A First Row Outer Race 
           2 B Second Row Outer Race 
           3  Joining Bolts 
           3 A Inner Ring Joining Bolts 
           3 B Outer Ring Joining Bolts 
           4 A First Row Cage 
           4 B Second Row Cage 
           5  Floating Spacer 
           10  Bearing Assembly 
           11  First Row Rolling Elements 
           12  Second Row Rolling Elements 
           13  Split Inner Ring First Section 
           14  Split Inner Ring Second Section 
           15  Split Outer Ring First Section 
           16  Split Outer Ring Second Section