Abstract:
A frame for supporting equipment arranged in a hub of a wind turbine is fixed to the hub at one end and flexibly connected to the hub at another end. The variation of the relative position between the hub and the frame caused by the deformation of the hub associated with a rotation of the wind turbine or the like is absorbed by the flexible connection. A wind turbine whose frame in the hub has high durability against the rotation can be provided.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a continuation application of International Application No. PCT/JP2010/058211, filed on May 14, 2010. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a structure of a wind turbine. 
     BACKGROUND ART 
     A wind turbine for wind turbine generator has been used.  FIG. 1  shows an example of a configuration of the wind turbine. A tower  2  is fixed vertical to the ground. A nacelle  3  is supported on the tower  2 . A hub  5  is rotatably supported by the nacelle  3  in a horizontal direction via a main shaft  4 . The hub  5  is covered with a cover  6 . Blades  7  are attached to the hub  5 . 
     At power wind generation, the pitch angle of the blade  7  is controlled so as to efficiently convert wind power to torque. When the blade  7  receives wind, the main shaft  4  rotates. The rotation is accelerated by a gear box  8 . The accelerated rotation causes a generator  9  to generate electric power. 
     Patent Document 1 is cited as a reference technique relating to the configuration of a hub. 
     CITATION LIST 
     Patent Document 
     
         
         Patent Document 1: Japanese Patent Application Publication JP 2008-128135 A 
       
    
     SUMMARY OF INVENTION 
     A certain weight of mechanical equipment such as equipment for pitch driving/control for the blade  7  is disposed within the hub  5 . Since the hub  5  rotates about the main shaft  4  which is substantially horizontally oriented, a frame that mounts the equipment thereon is subjected to repetitive loads accompanied with the rotation. Furthermore, the hub  5  is slightly deformed by the rotation and wind loads applied to the blade. Thus, the frame in the hub  5  is required to be durable to such deformation. Especially with an increase in the size of the wind turbine in these years, it is assumed that the configuration of the frame subjected to the influence of such deformation will become more important. There is a demand for the frame that supports equipment disposed in the hub and is highly durable to rotation. However, when the frame with rigid structure is merely manufactured, the structure needs to be able to support loads applied to the hub, disadvantageously resulting in an increase of weight and size. 
     According to an aspect of the present invention, a wind turbine converts a wind power into a torque by a blade attached to a hub. The wind turbine includes a frame for supporting equipment disposed in the hub, a fixation part for fixing one end of the frame to the hub and a connection part for connecting another end of the frame to the hub with a flexible connection. 
     According to another aspect of the present invention, at the connection part, the frame is flexibly connected to the hub in a pivotal direction. 
     According to still another aspect of the present invention, a connection part includes: a flange fixed to a wall of the hub and having a hole; and a spherical bearing fixed inside the hole. The frame includes a pin connected to an end of the frame on a side of the connection part. The connection part forms the flexible connection in the pivotal direction by supporting the pin by the spherical bearing. 
     According to still another aspect of the present invention, the hole penetrates the flange. A through hole is formed in the wall of the hub at the connection part. The flange is attached to an external surface of the hub to cover the through hole. An end of the structural beam on the side of the connection part is disposed inside the through hole. 
     According to still another aspect of the present invention, the flange is fixed to an internal surface of the hub. The flange includes a recess portion that encloses one end of the structural beam on a side of the connection part. 
     According to still another aspect of the present invention, a gap is formed between the structural beam and the flange. 
     According to still another aspect of the present invention, the spherical bearing is a radial bearing. The connection part forms a flexible connection in a longitudinal direction of the frame by the pin being slidably connected to the spherical bearing in a thrust direction. 
     According to still another aspect of the present invention, the frame is connected to the hub flexibly in a longitudinal direction of the frame at the connection part. 
     According to still another aspect of the present invention, equipment includes an accumulator of a hydraulic system for changing a pitch of the blade attached to the hub or a control board for controlling an operation of the wind turbine. 
     According to the present invention, a wind turbine having a frame that supports equipment disposed in the hub and is highly durable to rotation. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The above-mentioned objects and other objects, effects and features of the present invention will become more apparent from description of an embodiment in combination with accompanying drawings, in which: 
         FIG. 1  shows a configuration of a wind turbine; 
         FIG. 2  is a sectional view of a hub when viewed from a side; 
         FIG. 3  is a front view of the hub; 
         FIG. 4  is a schematic view of a supporting structure of a structural beam; 
         FIG. 5  is a schematic view of a supporting structure of the structural beam; 
         FIG. 6  shows details of a connection part; 
         FIG. 7A  shows details of a fixation part; 
         FIG. 7B  shows details of the fixation part; and 
         FIG. 8  shows details of the connection part. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Some embodiments of the present invention will be described referring to the attached drawings. A wind turbine in the present embodiment has a configuration shown in  FIG. 1 .  FIG. 2  is a sectional view of the hub  5  of the wind turbine  1  when viewed from a side.  FIG. 3  is a diagram of the hub  5  when viewed from the front, that is, an opposite side to the nacelle  3 . In an example shown in  FIG. 3 , the blades  7  are attached to respective of blade roots  17  provided at three sections in the circumference of the hub  5 . 
     A structural beam  10  as a frame for mounting equipment thereon is installed in the hub  5 . Various supporting structures such as beams made of square steel, I-steel and aluminum alloy can be adopted as the structural beam  10 . The structural beam  10  in the present embodiment is made of H-steel. In an example shown in  FIG. 2 , the structural beam  10  extends in substantially parallel with the main shaft  4 . A fixation part  12 B as a rear part of the structural beam  10 , that is, an end on the side close to the nacelle  3  is rigidly connected to the hub  5  via a fixation member  11 . A front part of the structural beam  10 , that is, a side close to the front end of the hub  5  is flexibly connected to the hub  5  at a connection part  12 A. The structural beam  10  may be disposed within the hub  5  in any fashion. In the example shown in  FIG. 3 , three structural beams  10  and hydraulic cylinders not shown are alternately disposed about the rotational center of the hub  5  and in substantially parallel with the main shaft. Such configuration constitutes a semi-flexible frame. 
     The structural beam  10  can support various equipment. For example, a control board for controlling operations of the wind turbine, and a PLC (Programmable Logic Controller) for controlling the pitch and various sensors and a battery in the case of the wind turbine that electrically control the pitch may be mounted on the structural beam  10 . In the present embodiment, an accumulator  14  of the hydraulic system for changing the pitch of the blade  7  attached to the hub  5  is installed on each of the three structural beams  10  correspondingly to each of the blades  7 . 
       FIG. 4  is a schematic view of the supporting structure of the structural beam  10  in the present embodiment. One end of the structural beam  10  is rigidly connected to the hub  5  at the fixation part  12 B and the other end of the structural beam  10  is flexibly connected to the connection part  12 A. With such structure, when the hub  5  is distorted due to the self-weight or the wind pressure at rotation of the wind turbine, the distortion is absorbed by the connection part  12 A with flexible structure. For this reason, the stress applied to the structural beam  10  by the distortion of the hub  5  is suppressed. In comparison with a strong member with rigid structure having enough large strength to prevent influence of the distortion of the hub  5 , this structure can support various equipment in the hub  5  with a lighter weight. 
       FIG. 1  to  FIG. 3  illustrate the example of an upwind-type wind turbine in which one end of the structural beam  10  is rigidly connected at the rear part of the hub  5  (leeward side) and the other end of the structural beam  10  is flexibly connected to the front part of the hub  5  (windward side). However, for applying to wind turbines having other structures, the supporting structure shown in  FIG. 4  in which one end is rigidly connected and the other end is flexibly connected can achieve similar effects. For example, even when the structural beam  10  is disposed in a longitudinal direction as a direction diagonal to the direction of back and forth of the hub  5 , as long as one end and the other end of the structural beam  10  are rigidly connected to and flexibly connected to the hub  5 , respectively, the stress applied to the structural beam  10  can be suppressed. Also in the case of the downwind-type wind turbine, even when the structural beam  10  is disposed in any direction, the similar effects can be obtained. 
     In  FIG. 4 , it is characterized by that one end of the structural beam  10  is flexibly connected to the hub  5 , and the fixation part  12 B on a side of rigid connection may have other structures as long as it fixes the end of the structural beam  10  to the hub  5 .  FIG. 5  shows an example of such other structures. A plurality of structural beams  10 ,  10 - 1  are disposed within the hub  5 . One end of the structural beam  10 - 1  is fixed to the hub  5  at a fixation part  12 D and the other end is fixed to the hub  5  at a fixation part  12 E. One end of the structural beam  10  is fixed to a fixation part  12 C located in the middle of both ends of the structural beam  10 - 1 . The other end of the structural beam  10  is flexibly connected to the hub  5  at the connection part  12 A. Even with such structure, the stress applied to the structural beam  10  can be suppressed. 
       FIG. 6  shows details of the connection part  12 A. At the connection part  12 A, a through hole is provided on a wall  27  forming the hub  5 . On the external side of the through hole, that is, the external side of the hub  5 , a flange  13  is fixed to the wall  27  by means of bolts  18  so as to cover the through hole. The flange  13  has a substantially same center axis as the extending direction of the structural beam  10  and has a circular hole opened to the internal side of the hub  5 . Although the hole is a through hole opened to the internal side as well as the external side of the hub  5  in an example shown in  FIG. 6 , the hole does not necessarily penetrate. A spherical bearing  24  is fixed to an inner wall of the through hole by welding. 
     The structural beam  10  in the present embodiment is a so-called H-steel formed of a web  19  and a flange  20 . A pin  22  having a cylindrical shape is attached to the web  19  via a holder  21 . By pin connection connecting the structural beam  10  to the supporting member of the flexible structure via the pin  22 , the connection part  12 A which is rigidly fixed in the radial direction and flexibly connected to be free in the moment and in the axial direction within the range of distortion of the hub  5  is achieved. The longitudinal direction of the structural beam  10  is substantially same as that of the pin  22 . The pin  22  is attached so as to be rotatable about a central axis oriented in the longitudinal direction with respect to the structural beam  10 . The ability to rotate makes the connection part  12 A more flexible. The front end of the pin  22  on the front side protrudes farther than the front end of the structural beam  10  on the front side. 
     The front end of the structural beam  10  is disposed within the through hole of the wall  27 . That is, the front end of the structural beam  10  is located on a front side at a position closer to the flange  13  rather than the plane  28  formed by extending the plane formed of the inner wall surface of the wall  27  up to a position of the through hole. A gap  25  exists between the front end of the structural beam  10  and the flange  13 . In addition, a gap  26  exists between the structural beam  10  and the inner wall surface of the through hole of the wall  27 . Since the front end of the structural beam  10  is located within the thickness of the wall of the hub  5 , even when a strong force is applied to the connection part  12 A in some unexpected situation, the end of the structural beam  10  can be held in the through hole of the hub  5 . 
     The end of the pin  22  is inserted into the spherical bearing  24 . The spherical bearing  24  is a radial bearing and the pin  22  can slide in the thrust direction of the spherical bearing  24 . When the distance between the fixation part  12 B and the connection part  12 A changes due to the distortion of the hub  5 , the pin  22  slides with respect to the spherical bearing  24 . By this movement, it is possible to suppress the stress applied to the structural beam  10 . By such a configuration, the flexible connection to the hub  5  in the longitudinal direction of the structural beam  10  is realized. 
     Since each structural beam  10  is supported by the spherical bearing  24  via one pin  22  and there are the gaps  25 ,  26 , the structural beam  10  can pivot about the spherical bearing  24 . By such a configuration, the flexible connection to the hub  5  in a pivotal direction of the structural beam  10  is realized. The pin  22  is supported by the spherical bearing  24  in the radial direction in this manner, thereby achieving flexible connection of the connection part  12 A. 
     In place of the connection part  12 A shown in  FIG. 6 , the flexible connection can be realized by other structures. For example, by supporting the pin  22  in the radial direction by rubber bushing in place of the spherical bearing  24 , a flexible structure can be realized as in the case of using the spherical bearing  24 . 
       FIGS. 7A and 7B  are a plan view and a side view of the fixation part  12 B, respectively. In this example, the fixation member  11  in  FIG. 2  is made of H-steel. The fixation member  11  is fixed to the hub  5 . A fixing end (an end on the side of the fixation part  12 B) of the structural beam  10  is fixed to the fixation member  11  by bolts and nuts  12 B- 1 ,  12 B- 2  in an area where planes of the structural beam  10  and the fixation member  11  overlap each other. The structural beam  10  is further fixed to a reinforcing metal fitting  12 B- 4  by bolts and nuts  12 B- 3 . The reinforcing metal fitting  12 B- 4  is fixed to the fixation member  11  by bolts and nuts  12 B- 5 . The structural beam  10  and the fixation member  11  are fixed to each other by the reinforcing metal fitting  12 B- 4  in a larger area where their planes overlaps with each other. 
     As shown in  FIGS. 7A and 7B , the structural beam  10  is rigidly connected at the fixation part  12 B so as not to cause shift or twist. By forming such rigid connection on one end and flexible connection at the connection part  12 A on the other end, an excessive force is not applied to a structure of the strong member that supports various equipment in the hub  5 . 
     With such configuration, when the hub  5  rotates to deform the hub  5  and structures within the hub  5 , relative displacement between the structural beam  10  and the hub  5  can be absorbed by flexible connection. Consequently, a wind turbine having a frame which can support the equipment disposed in the hub  5  and is highly durable to rotation can be realized. 
       FIG. 8  shows another example of the flexibly connected connection part  12 A. In this example, unlike the connection part  12  shown in  FIG. 6 , it is no need to form a through hole on the wall  27  of the hub  5 . The connection part  12 A has a flange  31  shown in  FIG. 8 . A flat plate part  29  of the flange  31  is fixed to an inner side surface of the wall  27  of the hub  5 . The flange  31  has a recess portion that is located on the inner side of the hub  5  with respect to the flat plate part  29  and encloses the end of the structural beam  10  on the side of the connection part  12 A. In an example shown in  FIG. 8 , the recess portion is formed of a hollow cylindrical member  30  having a central axis in the longitudinal direction of the structural beam  10 . The front end of the structural beam  10  is located at an inner position of the flange  31  to the hub  5  than a plane  28   a  formed of a front end of the cylindrical member  30 . With such configuration, as in the case shown in  FIG. 6 , even when a strong force is applied to the connection part  12 A in some unexpected situation, the end of the structural beam  10  can be held in the flange  31 . 
     Like the flange  13  in  FIG. 4 , a hole  32  for attaching the spherical bearing  24  is provided on the flat plate part  29 . A gap  33  is formed between the end of the pin  22  supported by the spherical bearing  24  and the wall  27  of the hub  5 . A gap  26   a  is formed between an inner circumferential surface of the cylindrical member  30  of the flange  31  and the structural beam  10 . A gap  25   a  is formed between the flat plate part  29  of the flange  31  and the end of the structural beam  10 , which is opposite to the flat plate part  29 . By these gaps, the flexible connection is realized, where the structural beam  10  is able to pivot at the spherical bearing  24  within a predetermined range and slide in the longitudinal direction. 
     Although the present invention has been described referring to some embodiments, the present invention is not limited to the above-mentioned embodiments and the above-mentioned embodiments can be variously modified. 
     [Explanation of Reference Numerals] 
     
         
           1  WIND TURBINE 
           2  TOWER 
           3  NACELLE 
           4  MAIN SHAFT 
           5  HUB 
           6  COVER 
           7  BLADE 
           8  GEAR BOX 
           9  GENERATOR 
           10  STRUCTURAL BEAM 
           11  FIXATION MEMBER 
           12 A CONNECTION PART 
           12 B FIXATION PART 
           13  FLANGE 
           14  ACCUMULATOR 
           15  STRUCTURAL BEAM 
           17  BLADE ROOT 
           18  BOLT 
           19  WEB 
           20  FLANGE 
           21  HOLDER 
           22  PIN 
           24  SPHERICAL BEARING 
           25 ,  25   a  GAP 
           26 ,  26   a  GAP 
           27  WALL 
           28  SURFACE FORMED BY INTERNAL DIRECTION SIDE EDGE OF HUB  5   
           29  FLAT PLATE PART 
           30  CYLINDRICAL MEMBER 
           31  FLANGE 
           32  HOLE 
           33  GAP