Abstract:
A wind turbine generator includes: a main shaft; a generator having a rotor and a stator; and a sleeve coupled to the rotor and inserted onto the main shaft. The stator includes: stator magnetic poles arrayed circumferentially of the main shaft; and first and second stator plates rotatably coupled to the main shaft to support the stator magnetic poles. The rotor includes: rotor magnetic poles and at least one magnetic pole supporting structure coupled to the main shaft to support the rotor magnetic poles and provided between the first and second stator plates such that the rotor and stator magnetic poles are detachable from the sleeve. Positions at which the rotor and stator magnetic poles are detachable from the sleeve are closer to the main shaft from a closer end of the main shaft to the generator.

Description:
RELATED APPLICATIONS 
     The present application is national phase of, and claims priority from, International Application Number PCT/JP2010/051112, filed Jan. 28, 2010, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     TECHNICAL FIELD 
     The present invention relates to a wind turbine generator, in particular, to a generator structure in the wind turbine generator. 
     BACKGROUND ART 
     One known structure as a coupling structure between a main shaft and a generator rotor in the wind turbine generator is a structure where the generator rotor is coupled to a cylindrical sleeve and the sleeve is fastened to the main shaft. Such a structure is disclosed, for example, in International Publication Pamphlet WO2007/111425A1 (Patent Literature 1). Patent Literature 1 discloses a coupling structure where a rotor bearing (corresponding to a sleeve in the present application) to which a generator rotor is joined is fastened to a main shaft by shrink disk (corresponding to a shrink fit in the present application). In the coupling structure, the shrink disk is positioned between a generator and a bearing, where the rotor bearing is fastened to the main shaft. The shrink click includes a fixed disk and a movable disk and the fixed disk and the movable disk are coupled to each other by a bolt. The bolt is inserted in parallel with a central axis of the main shaft. When the bolt is fastened, the movable disk is pushed to the fixed disk so that an inner diameter of the shrink disk is reduced and the rotor bearing is fastened to the main shaft. 
     One problem in the structure where the sleeve is fastened to the main shaft is a difficulty in work operations for unfastening the sleeve from the main shaft and inserting the sleeve onto the main shaft. In order to secure fastening strength, it is preferable that the clearance between the sleeve and the main shaft is narrow. From such a viewpoint, the clearance between the sleeve and the main shaft is typically adjusted to about 0.1 mm. However, a narrow clearance between the sleeve and the main shaft makes it difficult to perform work operations for detaching the sleeve from the main shaft and inserting the sleeve onto the main shaft. 
     This problem is especially important when generator replacement is required after the wind turbine generator is installed. After the installation of the wind turbine generator is completed, it is very difficult to perform work operations such as detaching the sleeve from the main shaft over the tower and inserting the sleeve onto the main shaft. For example, in a wind turbine generator with an output of 5 MW class, the weight of the generator exceeds 100 tones. When wind turbine generator replacement is performed over the tower, the replacement must be performed while the generator is hoisted by a crane; however, it is significantly difficult to perform work operations for detaching the sleeve from the main shaft and inserting the sleeve onto the main shaft, while a heavy generator is being hoisted by a crane. 
     CITATION LIST 
     Patent Literature
     Patent Literature 1: International Publication Pamphlet WO2007/111425 A1   

     SUMMARY OF INVENTION 
     Therefore, an object of the present invention is to provide a technique for facilitating generator replacement in a wind turbine generator. 
     In one aspect of the present invention, a wind turbine generator is provided with: a main shaft which supports a wind turbine rotor; a main bearing which rotatably supports the main shaft; a generator provided with a generator rotor and a stator; and a sleeve coupled to the generator rotor and is inserted onto the main shaft. The stator is provided with: stator magnetic poles arrayed in the circumferential direction of the main shaft; and first and second stator plates which are coupled to the main shaft relatively rotatably thereto to support the stator magnetic poles and arranged in the axial direction of the main shaft. The generator rotor is provided with: rotor magnetic poles arrayed in the circumferential direction; and at least one magnetic pole supporting structure coupled to the main shaft to support the rotor magnetic poles and provided between the first and second stator plates. The first and second stator plates and the rotor magnetic pole supporting structure are configured such that the rotor magnetic poles and the stator magnetic poles are detachable from the sleeve. With respect to the first and second stator plates and the rotor magnetic pole supporting structure, positions at which the rotor magnetic poles and the stator magnetic poles are detached from the sleeve are closer to the main shaft as reduction of distances from a closer end of the main shaft to the generator. 
     In one embodiment, the first stator plate is positioned farther from the end of the main shaft closer to the generator than the second stator plate, the first stator plate includes a first plate member coupled to the sleeve and a second plate member coupled to the stator magnetic poles and detachable from the first plate member, while the rotor magnetic pole supporting structure includes a first supporting member coupled to the sleeve and a second supporting member coupled to the rotor magnetic poles and detachable from the first supporting member, and the second stator plate includes a third plate member coupled to the sleeve and a fourth plate member coupled to the stator magnetic poles and detachable from the third plate member. In this case, it is preferable that an end of the second plate member closer to the sleeve is separated farther from the main shaft than an end of the first supporting member closer to the rotor magnetic poles, and an end of the second supporting member closer to the sleeve is separated farther from the main shaft than an end of the third plate member closer to the stator magnetic poles. 
     It is preferable that at least one of the first and second stator plates is provided with an opening at a position corresponding to a position where the rotor magnetic poles are separated from the sleeve in the rotor magnetic pole supporting structure. 
     It is preferable that, when the at least one rotor magnetic pole supporting structure includes a plurality of rotor magnetic pole supporting structures arrayed in the axial direction of the main shaft, positions where the rotor magnetic poles are detached from the sleeve are closer to the main shaft according to reduction of distances from the end of the main shaft in each of the plurality of rotor magnetic pole supporting structures. 
     In an embodiment, it is preferable that the first stator plate and the rotor magnetic pole supporting structure are provided to oppose each other, and the first stator plate and the rotor magnetic pole supporting structure are each provided with an attachment structure for attaching a temporary fixing tool which temporarily fixes the first stator plate and the rotor magnetic pole supporting structure. In this case, the temporary fixing tool may include a wedge or a rod-shaped member and the attachment structures may be openings into which the temporary fixing tool is inserted. 
     It is preferable that, when an opening used for maintenance work is provided through at least one of the first and second stator plates, a maintenance method for the wind turbine generator includes: a step of performing a work operation for fastening a first supporting member coupled to the sleeve of the rotor magnetic pole supporting structure and a second supporting member coupled to the rotor magnetic pole or a work operation for detaching the second supporting member from the first supporting member, within a protective tube. 
     The present invention facilitates a replacement of a generator in a wind turbine generator. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram schematically showing a structure of a wind turbine generator in an embodiment of the present invention; 
         FIG. 2A  is a diagram showing a structure of a generator in an embodiment of the present invention in detail; 
         FIG. 2B  is a diagram showing in detail a structure of a portion where a generator rotor and a stator are coupled to a sleeve in an embodiment of the present invention; 
         FIG. 2C  is a diagram showing a state where the generator rotor and the stator have been separated from the sleeve; 
         FIG. 2D  is a diagram showing a structure of a generator in another embodiment of the present invention in detail; 
         FIG. 3  is a diagram showing a preferred procedure for fastening a bolt within the generator; 
         FIG. 4  is a diagram showing a preferred procedure for fastening the bolt within the generator; and 
         FIG. 5  is a diagram showing a preferred procedure for fastening the bolt within the generator. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  is a diagram schematically showing a structure of a wind turbine generator  1  in one embodiment of the present invention. The wind turbine generator  1  of this embodiment is provided with a tower  2 , a nacelle base plate  3 , a main shaft  4 , bearings  5  and  6 , bearing housings  7  and  8 , and a generator  9 . The nacelle base plate  3  is rotatably attached on the top of the tower  2  to allow yaw rotation. The main shaft  4  is rotatably supported by the two bearings  5  and  6 , and the bearings  5  and  6  are fixed on the nacelle base plate  3  with the bearing housings  7  and  8 . One end of the main shaft  4  is coupled with a wind turbine rotor (not shown), while the other end thereof is coupled with the rotor of the generator  9 . In the wind turbine generator  1  of this embodiment, the main shaft  4  is shared by the wind turbine rotor and the generator rotor, so that the wind turbine generator  1  of this embodiment is configured as a so-called direct drive wind turbine generator. 
       FIG. 2A  is a sectional view showing the structure of the wind turbine generator  1  in this embodiment, especially, the structure of the generator  9  in detail. The generator  9  is provided with a generator rotor  11  and a stator  12 . The generator rotor  11  is coupled to a sleeve  21 , and the sleeve  21  is fastened onto the main shaft  4  by a hydraulic shrink fit  25  so that the generator rotor  11  is coupled to the main shaft  4 . The hydraulic shrink fit  25  is provided with a fixed ring  25   a  and a movable ring  25   b . When hydraulic fluid (typically, hydraulic oil) is supplied to a port provided in the hydraulic shrink fit  25 , the movable ring  25   b  is moved so that the inner diameter of the hydraulic shrink fit  25  is reduced to fasten the sleeve  21  to the main shaft  4 . It is advantageous that the hydraulic shrink fit  25  is provided within the generator  9 , because this reduces the bowing of the main shaft  4  by reducing the distance between the bearing  6  and the generator  9 . 
     In addition, an end plate  22  is used to prevent displacement of the sleeve  21  in the axial direction (the direction parallel to the center line of the main shaft  4 ; the same goes for the following). Specifically, the end plate  22  is attached to bridge the end of the sleeve  21  and the end of the main shaft  4 , and the sleeve  21  is sandwiched between the a bearing fixing ring  20  and the endplate  22 , the bearing fixing ring  20  fixing the bearing  6 . This suppresses the movement of the sleeve  21  in the axial direction. 
     As described below in detail, the generator  9  has a dividable structure in this embodiment, so that the generator  9  can be replaced without detaching the sleeve  21  from the main shaft  4 . The fact that the generator  9  can be replaced without detaching the sleeve  21  from the main shaft  4  has an advantage that the generator replacement is facilitated. The structure of the generator  9  will be explained below in detail. 
     The generator rotor  11  is provided with field magnets  13  functioning as rotor magnetic poles, a back plate  14  supporting the field magnets  13 , and rotor plates  15  and  16  for supporting the back plate  14 . The rotor plate  16  includes a plurality of plate members  16   a  and  16   b . The rotor plate  15  is fastened to a flange  21   a  of the sleeve  21  by bolts  31 . On the other hand, the plate member  16   a  of the rotor plate  16  is fastened to the sleeve  21  by bolts  32   a , and the plate member  16   b  is fastened to the plate member  16   a  by bolts  32   b . Here, it should be noted that a plurality of bolts  31 ,  32   a , and  32   b  are actually arrayed in circumferential direction, although only one of the bolts  31 , one of the bolts  32   a , and one of the bolts  32   b  are shown in the illustration. 
     On the other hand, the stator  12  is provided with a stator winding  17  functioning as stator magnetic poles and stator plates  18  and  19  supporting the stator winding  17 . The stator plate  18  includes a plurality of plate members  18   a  and  18   b , and the stator plate  19  similarly includes a plurality of plate members  19   a  and  19   b . A generator bearing  23  is fixed to the inner end of the plate member  18   a  of the stator plate  18 , and the plate member  18   b  is fastened to the outer end of the plate member  18   a  by bolts  33 . Similarly, a generator bearing  24  is fixed to the inner end of the plate member  19   a  of the stator plate  19 , and the plate member  19   b  is fastened to the outer end of the plate member  19   a  by bolts  34 . In such a structure, the generator  9  is also supported by the main shaft  4  with the generator bearings  23  and  24 . This structure is effective for dispersing the mechanical load caused by the weight of the generator  9 . Here, it should be noted that a plurality of bolts  33  and  34  are arrayed in the circumferential direction, although only one of the bolts  33  and one of the bolts  34  are shown in the illustration. 
     Here, it should be noted that the bolts  33  fastening the plate members  18   a  and  18   b  of the stator plate  18 , the bolts  31  fastening the flange  21   a  of the sleeve  21  and the rotor blade  15 , the bolts  32   b  fastening the plate members  16   a  and  16   b  of the rotor plate  16 , and the bolts  34  fastening the plate members  19   a  and  19   b  of the stator plate  19  are arranged such that their distances from the central axis of the main shaft  4  are increased as the separations from the end of the main shaft  4  on the side of the generator  9 . That is, such an arrangement is adopted that the positions of fastening fixtures for coupling the field magnets  13  and the stator winding  17  to the sleeve  21  from the central axis of the main shaft  4  are farther from the end of the main shaft  4 , as the distances thereof are farther. 
     More specifically, as shown in  FIG. 2B , the position of the closer end of the plate member  18   b  of the stator plate  18  to the sleeve  21  is farther from the central axis of the main shaft  4  than the positions of the closer ends of the flange  21   a , the plate member  16   a  of the rotor plate  16 , the plate member  19   a  of the stator plate  19  to the stator winding  17 . Further, the position of the closer end of the rotor plate  15  to the sleeve  21  is farther from the central axis of the main shaft  4  than the positions of the closer ends of the plate member  16   a  of the rotor plate  16  and the plate member  19   a  of the stator plate  19  to the stator winding  17 . Furthermore, the position of the closer end of the plate member  16   b  of the rotor plate  16  to the sleeve  21  is farther from the central axis of the main shaft  4  than the position of the closer end of the plate member  19   a  of the stator plate  19  to the stator winding  17 . Here, it should be noted that the flange  21   a  and the plate member  16   a  are members coupled to the sleeve  21  to remain when the field magnets  13  are detached from the sleeve  21  in the rotor magnetic pole supporting structure supporting the field magnets  13 , and the plate member  19   a  of the stator plate  19  is a member coupled to the sleeve  21  to remain when the stator winding  17  is detached from the sleeve  21 . 
     As shown in  FIG. 2C , the use of the above-mentioned structure allows the field magnets  13  of the generator rotor  11  and the stator winding  17  of the stator  12  to be detached without detaching the sleeve  21  from the main shaft  4  in the wind turbine generator  1  of this embodiment, when maintenance work is performed. Specifically, by unfastening and removing the bolts  33  and  34 , the stator winding  17  can be detached together with the plate members  18   b  and  19   b . Similarly, by unfastening and removing the bolts  31  and  32   b , the field magnets  13  can be detached together with the back plate  14 , the rotor plate  15 , and the plate member  16   b . Here, the use of the structure shown in  FIG. 2B  avoids the interference between members during detaching work of the generator  9 . 
     On the contrary, the stator winding  17  can be reattached through attaching the stator winding  17  to the plate members  18   a  and  19   b  and fastening the bolts  33  and  34  to the plate members  18   a  and  19   b . Further, the field magnets  13  can be reattached through attaching the field magnets  13  to the back plate  14  and attaching the rotor plate  15  and the plate member  16   b  to the back plate  14  by fastening the bolts  31  and  32   b . As thus described, replacement of most important configuration members (the field magnets  13 , the stator winding  17 ) can be performed without detaching the sleeve  21  from the main shaft  4  in the wind turbine generator  1  of this embodiment. 
     In addition, it is preferable for facilitating the work that the members detached together with the field magnets  13  and the stator winding  17  are positioned nearer to the end of the main shaft  4  than the members which remain together with the sleeve  21 . With respect to the stator plate  18 , for example, the plate member  18   b , which is detached together with the stator winding  17 , is fastened to a face of the plate member  18   a , which remains together with sleeve  21 , the face being closer to the end of the main shaft  4 . As for the rotor plate  15 , which is detached together with the field magnet  13 , the rotor plate  15  is fastened to a face of the flange  21   a  of the sleeve  21 , the face being closer to the end of the main shaft  4 . As for the rotor plate  16 , the plate member  16   b , which is detached together with the field magnets  13 , is fastened to a face of the plate member  16   a , which remains together with the sleeve  21 , the face being closer to the end of the main shaft  4 . As for the stator plate  19 , finally, the plate member  19   b , which is detached together with the stator winding  17 , is fastened to a face of the plate  19   a , which remains together with the sleeve  21 , the face being closer to the end of the main shaft  4 . Such a structure preferably facilitates work operations for detaching the field magnets  13  and the stator winding  17 . 
     Here, work operations for fastening the rotor plate  15  by the bolt  31  and for fastening the plate members  16   a  and  16   b  of the rotor plate  16  by the bolts  32   a  and  32   b  are performed within the generator  9 . In the same way, work operations for detaching the bolt  31  from the rotor plate  15  and for detaching the bolts  32   a  and  32   b  from the plate members  16   a  and  16   b  are performed within the generator  9 . When a foreign matter enters the generator  9  in these work operations, this may cause damage of the generator  9 . 
     In order to avoid damage of the generator  9  due to entry of a foreign matter, it is preferable that work operations for fastening the bolts  31 ,  32   a , and  32   b  or detaching them are performed within a protective tube inserted from the stator plate  18  or  19 .  FIGS. 3 to 5  are conceptual diagrams showing a procedure of performing fastening of the bolts  31  within a protective tube  41 . 
     As shown in  FIG. 3 , an opening is formed through the plate member  18   a  of the stator plate  18  at a position corresponding to the bolts  31 . The protective tube  41  is inserted into the opening in performing maintenance works. At this time, the generator rotor  11  is adjusted at such an angle that a target bolt  31  can be received in the protective tube  41 . The protective tube  41  is inserted to abut on the flange  21   a  of the sleeve  21 . At this time, in order to prevent a foreign matter from entering the protective tube  41 , it is preferable that the protective tube  41  is inserted into the opening with a cover  42  attached to the inlet of the protective tube  41 . In this embodiment, the cover  42  is detachably attached to the protective tube  41  by bolts  43   a  and  43   b . Subsequently, the cover  42  is detached from the protective tube  41  and the target bolt  31  is fastened. At this time, as shown in  FIG. 4 , the use of a dedicated fastening tool  44  with a diameter thinner than the inner diameter of the protective tube  41  for fastening the bolt  31  facilitates the work operation. This is followed by drawing out the protective tube  41  to a position where the protective tube  41  does not interfere with the rotor plate  15 , after the cover  42  is attached to the protective tube  41  again. Further, the generator rotor  11  is slightly rotated such that the protective tube  41  reaches a position corresponding to a bolt  31  to be fastened next. The bolts  31  are sequentially fastened through repetition of similar process subsequent thereto. After all the bolts  31  are fastened, the opening of the plate member  18   a  of the stator plate  18  is closed by a cover  45 , as shown in  FIG. 5 . According to the above procedure, entry of a foreign matter into the generator  9  can be avoided during the work operation. 
     Similarly, entry of a foreign matter into the generator  9  can be also avoided through performing work operations for detaching the bolts  31  within the protective tube  41 . 
     As for the bolts  32   b  of the rotor plate  16 , entry of a foreign matter can be avoided through fastening and detaching work is performed within the protective tube in the same manner as described above. In this case, an opening is formed through the plate member  19   b  of the stator plate  19  at a position corresponding to the bolt  32   b , and the protective tube is inserted into the opening to abut on the plate member  16   b.    
     The abovementioned procedure avoids entry of a foreign matter into the generator  9  in fastening the bolts  31  and  32   b . This effectively avoids damage of the generator  9 . 
     Referring back to  FIG. 2A , it is preferable that attachment structures for attaching temporary fixing tools  35  and  36  which temporarily fixes the generator rotor  11  to the stator plates  18  and  19  are provided for the wind turbine generator  1  of this embodiment. The gap between the generator rotor  11  and the stator  12  is maintained through temporarily fixing the generator rotor  11  to the stator plates  18  and  19  using the temporary fixing tools  35  and  36  so that damage of the generator  9  is prevented, when the generator  9  is transported, for example. In the structure shown in  FIG. 2A , wedges are used as the temporary fixing tools  35  and  36 . In this case, openings into which the wedges are inserted are provided through the stator plates  18  and  19 . By inserting the wedges between the generator rotor  11  and the stator  12  through the openings, the generator rotor  11  and the stator  12  can be fixed temporarily. 
     In another embodiment, as shown in  FIG. 2D , rod-shaped members such as pins may be used as the temporary fixing tools  35 A and  36 A. In this case, openings through which the rod-shaped members are inserted are provided through the stator plates  18  and  19  and the rotor plates  15  and  16 . The generator rotor  11  can be fixed temporarily by inserting the rod-shaped members into the openings provided through the stator plates  18  and  19  and the rotor plates  15  and  16 . Also, the temporary fixing tools  35  and  36  may be configured to temporarily connect the stator plates  18  and  19  and the back plates  14 . The structure for temporarily fixing the generator rotor  11  to the stator plates  18  and  19  may be configured variously. 
     Although one embodiment of the present invention are described above, the present invention should not be interpreted to be limited to the above embodiments. Various modifications which are obvious to those skilled in the art may be adopted in the implementation of the present invention. Especially, although the rotor plates  15  and  16  are used as the coupling structure for coupling the field magnet  13  and the back plate  14  to the sleeve  21  in  FIGS. 2A to 2D , it would be easily understood by those skilled in the art that the structure for coupling the field magnet  13  and the back plate  14  to the sleeve  21  may be modified variously.