Abstract:
A two-row tapered roller bearing includes an outer ring ( 1 ) having an outer diameter of at least one meter, a first inner ring ( 2 ) and a second inner ring ( 3 ) that is disposed axially adjacent the first inner ring ( 2 ). A first set of conically-formed roller bodies ( 4 ) roll between the outer ring ( 1 ) and the first inner ring ( 2 ) and a second set of conically-formed roller bodies ( 5 ) are disposed axially adjacent the first roller bodies ( 4 ) and roll between the outer ring ( 1 ) and the second inner ring ( 3 ). A first sealing ring ( 11 ) is disposed axially adjacent the outer ring ( 1 ), is connected with the outer ring ( 1 ) and slips on a slip surface ( 16 ) of the first inner ring ( 2 ) in a contacting manner.

Description:
CROSS-REFERENCE 
     This application claims priority to German patent application no. 10 2009 014 923.6, filed Mar. 25, 2009, which is incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present invention generally relates to roller bearings having relatively large diameters, e.g., greater than one meter. Preferred roller bearings include two-row tapered roller bearings that may be utilized, e.g., to support a rotor shaft of a wind turbine. 
     KNOWN ART 
     Although bearings having an outer ring with a diameter of greater than one meter are generally known as large diameter bearings, other criteria and, e.g., other diameter-values could also be consulted for the definition of large diameter bearings. Generally speaking, bearings disclosed herein are considerably larger than bearings which have an outer diameter of a few centimeters and are utilized in typical everyday applications, such as e.g., in passenger cars. 
     When designing large diameter bearings, a pure upscaling of the bearing geometry starting from a known “small” bearing is normally not feasible, because different criteria require special consideration for large diameter bearings than for small diameter bearings, such as e.g., weight, the material(s) utilized to produce the bearing, the assembly cost, repair options, etc. For example, DE 10 2004 058 905 A1 discloses a large diameter bearing having an inner ring and an outer ring that are each composed of a plurality of segments in the circumferential direction. Due to the segmentation of the rings, it is possible to replace a damaged bearing without having to remove the shaft that is rotatably supported by the bearing. 
     SUMMARY 
     In one aspect of the present teachings, a high-quality and reliable large diameter bearing is disclosed that reduces material usage requirements. 
     In another aspect of the present teachings, a two-row tapered roller bearing may include an outer ring having an outer diameter of at least one meter, more preferably at least 1.5 meters. The bearing may further include a first inner ring disposed axially adjacent a second inner ring. Furthermore, the tapered roller bearing preferably includes a first set of first roller bodies, which are preferably conically-shaped and roll between the outer ring and the first inner ring, and second set of second roller bodies, which are also preferably conically-shaped, are disposed axially adjacent the first roller bodies and roll between the outer ring and the second inner ring. A first sealing ring is preferably connected with the outer ring on one axial side of the outer ring and is disposed so as to slip on or along a slip surface of the first inner ring in a contacting manner. More preferably, the entire first sealing ring is disposed axially adjacent to the outer ring. 
     According to this aspect of the present teachings, the outer ring can have a relatively narrow width in the axial direction, thereby reducing material requirements for the production of the tapered roller bearing while still ensuring a reliable sealing of the tapered roller bearing. A weight reduction also results from the material savings. In view of the larger diameter of the outer ring, a reduction of the axial width of the outer ring affects the achievable material savings substantially more with regard to the outer ring than the inner rings. Designs according to this aspect of the present teachings also have the advantage of reducing the risk of damaging the sealing ring(s) during the assembly of the tapered roller bearing. 
     The first inner ring and the second inner ring can be integrally formed as a common ring part. However, it is preferred that the two inner rings are formed as two separate parts, which provides, e.g., advantages during the assembly of the tapered roller bearing. 
     In another aspect of the present teachings, a second sealing ring can be provided axially adjacent the outer ring and can be connected, e.g., fixedly connected, with the outer ring. The second sealing ring is preferably disposed so as to slip on a slip surface of the second inner ring in a contacting manner. In such an embodiment, it is possible to completely seal the interior of the tapered roller bearing. 
     The first slip surface is preferably cylinder-shaped, which ensures well-defined slippage conditions for the sealing ring with axial tolerances. It is particularly advantageous when the first slip surface is formed at, on or near a shoulder of the first inner ring. The first inner ring and/or the second inner ring is preferably produced from a suitable, i.e. sufficiently hard, material and is manufactured with high precision. More preferably, the first slip surface and/or the second slip surface is ground in a twist-free or directionality-free manner, i.e. the first and/or second slip surface preferably has a non-directional surface finish, which ensures a high surface quality with very small shape- and mass deviations, as well as flawless rotation while minimizing wear over the service life of the roller bearing. 
     The first sealing ring can be attached to a first retaining ring. The first retaining ring can be attached to the outer ring. Such an embodiment provides a reliable seating of the first sealing ring at a relatively low cost. More preferably, the first retaining ring can be attached to the outer ring by screws that further serve to attach the outer ring in an installation environment. This particularly preferred embodiment has the advantage that no additional screws are necessary for the attachment of the first sealing ring. 
     In a further aspect of the present teachings, the first sealing ring and the first retaining ring may be integrally formed. In this case, it is possible to reduce the number of individual components that must be handled during assembly or repair. In addition or in the alternative, the first sealing ring and the first retaining ring can be comprised of the same material, which provides an especially efficient and cost-effective embodiment for realizing the first sealing ring. In addition, a sealing ring formed in such a manner can also include axially-oriented bores configured for the attachment of the sealing ring to the outer ring, e.g., via screws or bolts. 
     In a further aspect of the present teachings, the first sealing ring can include at least one sealing lip and/or the second sealing ring can include at least one sealing lip. The sealing lip(s) can be produced, e.g., by a machine-cutting operation, by injection molding or by vulcanization. 
     In a further aspect of the present teachings, the outer ring and/or the first inner ring and/or the second inner ring can be formed as a ring that is closed and/or continuous in the circumferential direction. In such an embodiment, a high mechanical stability and a good rolling behavior of the roller bodies on the tracks can be achieved. 
     In a further aspect of the present teachings, the first roller bodies can be disposed in a first cage and/or the second roller bodies can be disposed in a second cage. More preferably, the first cage and/or the second cage can be formed in a segmented or discontinuous manner in the circumferential direction, which reduces the danger of a mechanical overstressing of the cage and facilitates the expected thermal expansion. 
     In a further aspect of the present teachings, the first sealing ring and/or the second sealing ring can be manufactured, e.g., from polyurethane or polytetrafluoroethylene. These materials are particularly suitable when a high shape-stability is desired. 
     The tapered roller bearing can include grease as a lubricant. A reliable lubrication can be achieved thereby. 
     In a further aspect of the present teachings, the tapered roller bearing can be formed as a component of a wind turbine and/or may be utilized to rotatably support a rotor shaft utilized in a wind turbine. 
     The invention will be further explained in the following with the assistance of the exemplary embodiments illustrated in the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an exemplary embodiment of a first representative tapered roller bearing in a cross-sectional illustration. 
         FIG. 2  shows the sealing ring of the tapered roller bearing illustrated in  FIG. 1  in a cross-sectional illustration. 
         FIG. 3  shows a further exemplary embodiment of a second representative tapered roller bearing in a cross-sectional illustration. 
         FIG. 4  shows a further exemplary embodiment of a third representative tapered roller bearing in a cross-sectional illustration. 
         FIG. 5  shows the sealing ring of the tapered roller bearing illustrated in  FIG. 4  in a cross-sectional illustration. 
         FIG. 6  shows a representative wind turbine having a rotor shaft rotatably supported by tapered roller bearings according to the present teachings. 1    1   FIG. 6  and text in italics added to satisfy USPTO drawing requirements. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Each of the additional features and teachings disclosed below may be utilized separately or in conjunction with other features and teachings to provide improved roller bearings and/or wind turbines, as well as methods for designing, constructing and using the same. Representative examples of the present invention, which examples utilize many of these additional features and teachings both separately and in combination, will now be described in further detail with reference to the attached drawings. This detailed description is merely intended to teach a person of skill in the art further details for practicing preferred aspects of the present teachings and is not intended to limit the scope of the invention. Therefore, combinations of features and steps disclosed in the following detail description may not be necessary to practice the invention in the broadest sense, and are instead taught merely to particularly describe representative examples of the present teachings. 
     Moreover, the various features of the representative examples and the dependent claims may be combined in ways that are not specifically and explicitly enumerated in order to provide additional useful embodiments of the present teachings. In addition, it is expressly noted that all features disclosed in the description and/or the claims are intended to be disclosed separately and independently from each other for the purpose of original disclosure, as well as for the purpose of restricting the claimed subject matter independent of the compositions of the features in the embodiments and/or the claims. It is also expressly noted that all value ranges or indications of groups of entities disclose every possible intermediate value or intermediate entity for the purpose of original disclosure, as well as for the purpose of restricting the claimed subject matter. 
       FIG. 1  shows a first exemplary embodiment of a tapered roller bearing according to the present teachings. The tapered roller bearing is formed with two rows of roller bodies and includes an outer ring  1  having two conical tracks. Furthermore, the tapered roller bearing includes two inner rings  2  and  3  disposed axially adjacent each other and each having a conical track. The outer ring  1  and the two inner rings  2 ,  3  are formed as continuous rings closed in the circumferential direction in the illustrated exemplary embodiment. However, it is also possible to utilize segmented rings, i.e. rings that include discontinuous segments that abut in the circumferential direction. 
     Conically-shaped roller bodies  4  roll on the conical track of the inner ring  2  and on the adjacent conical track of the outer ring  1 . Conically-shaped roller bodies  5  roll on the conical track of the inner ring  3  and on the adjacent conical track of the outer ring  1 . The roller bodies  4  are disposed in a cage  6  and the roller bodies  5  are disposed in a cage  7 . The cages  6  and  7  are formed in a segmented manner in the illustrated exemplary embodiment, i.e. the cages  6 ,  7  are discontinuous, but abutting, in the circumferential direction. For example, the individual cage segments can be disposed one after another in the circumferential direction, as is disclosed in DE 102 46 825 A1, which is incorporated herein by reference. The cages  6 ,  7  or cage segments thereof can be made of plastic. However, it is noted that the cages  6 ,  7  can also be formed in a continuous manner in the circumferential direction. 
     A retaining ring  8  is attached to the outer ring  1  on one axial side using screws  10  and a retaining ring  9  is attached to the other axial side using screws  10 . The retaining rings  8 ,  9  can be manufactured, e.g., from metal or plastic. High-quality roller bearing steel is not necessary for the sealing ring-retaining function. 
     A sealing ring  11  is attached to the retaining ring  8  using a clamping ring  12 . The sealing ring  11  can be formed as a radial shaft seal. A sealing ring  11  formed in such a manner is depicted in  FIG. 2  in a cross-sectional illustration. 
     As can be derived in more detail from  FIG. 2 , the sealing ring  11  has a dust lip  13  and a sealing lip  14 . The sealing lip  14  is urged radially inwards by a spring  15  (e.g., a garter spring) and lies in contact on the slip surface  16  that is formed on a shoulder  17  of the inner ring  2  (see also  FIG. 1 ). 
     A sealing ring  18  is attached to the retaining ring  9  using a clamping ring  19 . The sealing ring  18  is formed in an analogous manner to the sealing ring  11  and lies in contact on the slip surface  20  that is formed on the shoulder  21  of the inner ring  3 . 
     The inner rings  2 ,  3  may comprise uniformly-hardened steel or only the areas of the tracks and the slip surfaces  16 ,  20  may be hardened steel. The slip surfaces  16 ,  20  are preferably manufactured with high precision and are, e.g., mechanically-ground in a twist-free or directionality-free manner. As utilized herein, the terms “twist-free” and/or “directionality-free” are intended to mean that the slip surfaces  16 ,  20  do not have any microscopically small structures that cause a fluid (e.g., lubricant) stream to be generated in the axial direction under the sealing lip  14  when the inner rings  2 ,  3  rotate. 2  The use of twist-free or directionality-free slip surfaces  16 ,  20  enable a reliable sealing to be achieved with low friction and such that the wear of the sealing lips  14  of the sealing rings  11 ,  18  is minimized.  2 Definition added to ensure proper interpretation of “directionality-free” (i.e. drallfrei). 
     The surface roughness of the slip surfaces  16 ,  20 , as measured according to ISO 4288-1985, preferably falls within the following ranges:
         R a  0.2 to 0.8 μm   R z  1 to 4 μm   R max  6.3 μm       

     The lower values for R a  and R z  are minimum values in order to ensure that a sufficient amount of lubricant (e.g., grease) is held on the slip surfaces  16 ,  20  to prevent damage to the sealing lip  14  during operation. In addition, the temperature rise caused by inadequate lubrication, particularly at high rotational speeds, would lead to hardening and cracking of the sealing lip  14  and thus to premature seal failure. On the other hand, if the surfaces are too rough, there will be excessive seal lip wear and seal life will be shortened. If the value R max  is exceeded, leakage may occur. 
     As mentioned above, it is also preferable that the machining operation does not leave any directionality behind on the slip surfaces  16 ,  20 , as this could lead to leakage by pumping action, depending on the direction of rotation. A suitable surface can be achieved, e.g., by plunge grinding; whole number ratios of the grinding wheel speed to the workpiece speed are preferably avoided. The grinding wheel may be dressed using a cluster head dressing tool and the smallest possible lateral feed, or a profile dressing roll without lateral feed. 
     The slip surfaces  16 ,  20  should also be free of any damage such as bruises, scratches, cracks, rust or raised sections. It is therefore important that it not only be carefully machined but also that it be properly protected until final mounting takes place. Such protection can, for instance, be provided by threading a cardboard tube over the slip surfaces  16 ,  20 , or preferably over the whole shaft. 3    3 Text in italics is not in original German text and has been taken from: http://www.skf.com/portal/skf/home/products?maincatalogue=1&amp;lang=en&amp;newlink=4 1 21v 
     Grease is not illustrated in the Figures, but may preferably be provided as a lubricant in the inner space of the tapered roller bearing, which inner space is sealed by the sealing rings  11 ,  18 . 
     In a preferred application of the tapered roller bearing illustrated in  FIG. 1 , the outer ring  1  remains stationary during operation and the two inner rings  2 ,  3  rotate relative to the outer ring  1 . Accordingly, the sealing rings  11 ,  18  remain stationary and the respective sealing lips  14  abut on the rotating slip surfaces  16 ,  20  of the inner rings  2 ,  3 . In particularly preferred embodiments, the tapered roller bearing can be utilized in a wind turbine as a rotor bearing, which embodiment will be discussed below. As was noted above, a reliable sealing over a long service life is achievable with the sealing rings  11 ,  18  in view of the high-precision construction of the slip surfaces  16 ,  20 . Furthermore, if the sealing rings  11 ,  18  become damaged during operation, they can be individually replaced. 
       FIG. 3  shows a second exemplary embodiment of a representative tapered roller bearing in a cross-sectional illustration. This exemplary embodiment differs from  FIG. 1  with respect to the attachment of the sealing rings  11 ,  18 . In addition, a grease channel  22  is illustrated in  FIG. 3 , which extends in the radial direction along the axial border of the two inner rings  2 ,  3 . Further, in  FIG. 3 , the installation environment of the tapered roller bearing is also indicated, as will be discussed further in the next paragraph. The two exemplary embodiments coincide in other respects. 
     The installation environment illustrated in  FIG. 3  is a section of a wind turbine that surrounds the tapered roller bearing. More specifically, a rotor shaft  23  and a bearing housing  24  are illustrated. The two inner rings  2 ,  3  sit on the rotor shaft  23  and rotate with it. The outer ring  1  is disposed in a bore of the bearing housing  24  and is fixedly attached to the bearing housing  24  using axially-extending screws  25 . In addition, the retaining rings  8 ,  9  are also laterally attached to the outer ring  1  by the screws  25 , so that no additional screws are necessary for the attachment of the retaining rings  8 ,  9 . The two retaining rings  8 ,  9  may be formed in a differing manner in accordance with the particular installation environment. The attachment of the sealing rings  11 ,  18  to the retaining rings  8 ,  9  by the clamping rings  12 ,  19  may be analogous to  FIG. 1 . The clamping rings  12 ,  19  may be fixedly attached to the retaining rings  8 ,  9  by the screws  26 . 
     The sealing rings  11 ,  18  are preferably formed in an analogous manner to  FIG. 2  and slip on or slidingly contact the slip surfaces  16 ,  20  of the inner rings  2 ,  3  similar to the exemplary embodiment of  FIG. 1 . Since the outer ring  1  is attached to the bearing housing  24  by screws  25 , the outer ring  1  and the bearing housing  24  do not rotate during operation and thus remain stationary. Consequently, the sealing rings  11 ,  18  attached to the outer ring  1  also remain stationary and the sealing lips  14  slip or slidingly contact on the slip surfaces  16 ,  20  of the inner rings  2 ,  3  that rotate relative to the sealing rings  11 ,  18 . 
       FIG. 4  shows a third exemplary embodiment of a representative tapered roller bearing in a cross-sectional illustration. In this embodiment, only one sealing ring  11  is shown. However, the embodiment of  FIG. 4  may be modified to include both sealing rings  11 ,  18 , wherein the not-illustrated sealing ring  18  may be formed in a manner analogous to the illustrated sealing ring  11 . 
     The tapered roller bearing illustrated in  FIG. 4  differs from  FIGS. 1 and 3  in particular with respect to the construction of the sealing ring  11 . Unlike  FIGS. 1 and 3 , the sealing ring  11  in  FIG. 4  is not clamped in the retaining ring  8 , but rather is directly fastened together with the outer ring  1  by screws  10 . This means that, in the exemplary embodiment of  FIG. 4 , the retaining ring  8  and the clamping ring  12  are omitted and a different embodiment of the sealing ring  11  is utilized than the embodiment illustrated in  FIG. 2 . 
     The construction of the sealing ring  11  utilized in  FIG. 4  will be explained in more detail with the assistance of  FIG. 5 , which shows the sealing ring  11  in a cross-sectional illustration. Analogous to  FIG. 2 , the sealing ring  11  is equipped with the dust lip  13 , the sealing lip  14  and the spring  15 . In addition, the sealing ring  11  includes bores  27  extending in the axial direction. Sleeves  28  for receiving the screws  10  are inserted into the bores  27 . In order to ensure a reliable function of the sealing ring  11  in a long-lasting manner, it is also necessary that it possesses a sufficient shape-stability. This shape-stability can be achieved by selecting an appropriate material for the sealing ring  11 . Polyurethane (PUR) and polytetrafluoroethylene (PTFE), in particular, are suitable as materials. When using these materials, the sealing ring  11  can be produced completely, i.e. inclusive of the dust lip  13  and the sealing lip  14 , from a single material. The production can take place, e.g., by lathing or another machine-cutting process. Likewise, it is also possible, however, to produce the sealing ring  11 , in particular the dust lip  13  and the sealing lip  14 , using injection molding or vulcanization. 
     As to the remaining structures, the exemplary embodiment of  FIG. 4  corresponds to the exemplary embodiments of  FIGS. 1 and 3 , wherein the grease channel  22  previously illustrated in  FIG. 3  is again present. 
       FIG. 6  shows a representative wind turbine that may utilize one or more tapered roller bearings  30  according to the present teachings to rotatably support a rotor shaft  23 . The wind turbine may optionally also include a gearbox  31  and a generator  32 , which are driven by rotor blades  33 . A bearing housing  24  may support the outer ring  1  of the tapered roller bearing  30 . 4   4   FIG. 6  and text added to satisfy USPTO drawing requirements. 
     REFERENCE NUMBER LIST: 
     
         
           1  Outer ring 
           2  Inner ring 
           3  Inner ring 
           4  Roller bearing 
           5  Roller bearing 
           6  Cage 
           7  Cage 
           8  Retainer ring 
           9  Retainer ring 
           10  Screw 
           11  Sealing ring 
           12  Clamping ring 
           13  Dust lip 
           14  Sealing lip 
           15  Spring 
           16  Slip surface 
           17  Shoulder 
           18  Sealing ring 
           19  Clamping ring 
           20  Slip surface 
           21  Shoulder 
           22  Grease channel 
           23  Rotor shaft 
           24  Bearing housing 
           25  Screw 
           26  Screw 
           27  Bore 
           28  Sleeve 
           30  Tapered roller bearing 
           31  Gearbox 
           32  Generator 
           33  Rotor blades