Abstract:
A self aligning bearing assembly comprising an inner ring and an outer ring, and two rows of rolling elements of equal length 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 disposed 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 feet 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. 
       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 equal length rolling elements disposed between an 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 inner ring  2  having inner races  2 A and  2 B on a radially inner circumferential surface, outer ring  3  having outer races  3 A and  3 B on a radially outer circumferential surface, first row rolling elements  1 A disposed in cage  4 A, second row rolling elements  1 B disposed in cage  4 B, each row,  1 A and  1 B, separated by floating spacer  7 . Floating spacer  7  may be inner ring or outer ring guided, however, in the embodiment shown, spacer  7  is inner ring guided. Outer ring  3  is shown with lubrication hole  8 , however, it is also contemplated in the present invention that no lubrication holes can be present in outer ring  3 . Rolling elements  1 A and  1 B are shown as spherical rollers, however, the present invention contemplates the use of other rolling elements. In addition, rolling elements  1 A and  1 B are shown as of equal length. 
         [0011]    In one example embodiment, first row rolling elements  1 A operate at contact angle α1 and second row rolling elements  1 B 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  1 B are better accommodated to support increased thrust loads, for example, from a wind turbine rotor. In this configuration, first row rolling elements  1 A 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. 
         [0012]    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. 
         [0013]    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. 
         [0014]    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 
       [0015]      1 A First Row Rolling Elements 
         [0016]      1 B Second Row Rolling Elements 
         [0017]      2  Inner Ring 
         [0018]      2 A First Row Inner Race 
         [0019]      2 B Second Row Inner Race 
         [0020]      3  Outer Ring 
         [0021]      3 A First Row Outer Race 
         [0022]      3 B Second Row Outer Race 
         [0023]      4 A First Row Cage 
         [0024]      4 B Second Row Cage 
         [0025]      7  Spacer 
         [0026]      8  Lubrication Hole 
         [0027]      10  Bearing Assembly 
         [0028]    α1 First Row Contact Angle 
         [0029]    α2 Second Row Contact Angle