Patent Publication Number: US-2011052403-A1

Title: Wind-turbine blade

Description:
RELATED APPLICATIONS 
     The present application is national phase of International Application Number PCT/JP2009/064879, filed Aug. 26, 2009, and claims priority from Japanese Application Number 2008-227372 filed Sep. 4, 2008. 
    
    
     TECHNICAL FIELD 
     The present invention relates to wind-turbine blades. 
     BACKGROUND ART 
     In recent years, wind turbine generators have increased in size for enhancing their electricity generation efficiency and for generating more electricity. An increase in the size of wind turbine generators has caused a corresponding increase in the size of wind-turbine blades; for example, the blade length is 40 meters or more. 
     Such large blades cause various kinds of difficulties, such as a difficulty in fabricating each blade as a single unit and a difficulty in transportation since it is difficult to ensure roads, transporter vehicles, and the like. 
     In order to overcome such difficulties, examples of wind-turbine blades that are divided into segments in the longitudinal direction have been proposed, as in Patent Literatures 1 to 3. 
     In the example discussed in Patent Literature 1, the divided structure is designed so as to ensure sufficient strength with the skin alone. In the example discussed in Patent Literature 2, the divided structure is designed so as to significantly reduce the time and labor required for the connecting process. In the example discussed in Patent Literature 3, the divided structure is designed so as to have strength sufficient to be able to withstand actual usage without leading to an increase in weight. 
     CITATION LIST 
     Patent Literature 
     {PTL  1 } Japanese Unexamined Patent Application, Publication No. 2004-11616 
     {PTL  2 } Japanese Unexamined Patent Application, Publication No. 2005-147086 
     {PTL  3 } Japanese Unexamined Patent Application, Publication No. 2005-240783 
     SUMMARY OF INVENTION 
     Technical Problem 
     In Patent Literatures 1 to 3, the divided areas are open. With regard to wind-turbine blades, the fabrication site and the installation site thereof are distant from each other, and the installation site is nearly always located where the force of wind is strong. 
     Therefore, during transportation of the wind-turbine blades, dust, sand, dirt, and the like may enter through the openings in the divided areas. A large amount of such dust, sand, dirt, and the like can have an adverse effect on the rotation of the wind-turbine blades, reducing the electricity generation efficiency and causing breakage. The process for removing such dust, sand, dirt, and the like is troublesome and time-consuming. 
     Although the examples discussed in Patent Literatures 1 to 3 are given various designs for improvement, the maintainability thereof, such as the ease of assembly and disassembly, is still insufficient and requires further improvement. 
     In view of the circumstances described above, the present invention provides a wind-turbine blade that prevents foreign matter from entering the inside thereof during transportation and that can be efficiently assembled in good condition. 
     Solution to Problem 
     In order to solve the aforementioned problems, the present invention provides the following solutions. 
     An aspect of the present invention provides a wind-turbine blade that includes a skin that forms a long and hollow shape, and a spar that extends in the longitudinal direction and reinforces the skin from the inside thereof. In the wind-turbine blade, the spar is divided into multiple spar segments in the longitudinal direction, and the spar segments adjacent to each other have connection sections that are connected to each other. The skin is divided into a connection-section skin, located at a position corresponding to the connection sections, and a main-body skin. An opening formed in the main-body skin is blocked off by a blocking plate. 
     The wind-turbine blade according to this aspect is fabricated in units of the divided main-body skin and the spar segments. In other words, since the wind-turbine blade is fabricated in the form of longitudinally divided parts, a high-quality wind-turbine blade can be readily fabricated at low cost, as compared with that fabricated as a single unit. 
     Since the wind-turbine blade is transported in fabricated units, transporter vehicles can be readily procured and the selection of roads is facilitated. Since this allows for efficient transportation, the transportation time can be shortened, and cost reduction can be achieved. 
     Because the opening formed in the main-body skin is blocked off by the blocking plate, dust, sand, dirt, and the like are prevented from entering the hollow interiors during transportation. Therefore, since a process for removing dust, sand, dirt, and the like becomes unnecessary during assembly of the wind-turbine blade, the time required for such a process can be eliminated. 
     The assembly process of the wind-turbine blade at the installation site is performed by connecting the connection sections of the spar segments to each other while the connection-section skin to be located at the position corresponding to the connection sections is placed separately. Since the connection-section skin is open in this manner, the connection sections are readily accessible. Therefore, the connection sections can be readily and efficiently connected within a short time. 
     In the aforementioned aspect, the connection sections may be connected by a connecting member that lies astride the spar segments opposed to each other so as to connect the spar segments. 
     Accordingly, since the structure of the spar segments can be simplified, the fabrication process can be facilitated. 
     In the aforementioned aspect, the connection sections may be connected by overlapping with each of the spar segments opposed to each other. 
     Accordingly, since an additional member for joining the spar segments is not required, an increase in cost can be suppressed. 
     In the aforementioned aspect, an electrically-conductive cable extending in the longitudinal direction is preferably divided into segments that are connectable to each other at the position corresponding to the connection sections. 
     Accordingly, since the electrically-conductive cable can be set over the entire length of the wind-turbine blade, deterioration of the lightning protection performance can be suppressed. 
     In the aforementioned aspect, the wind-turbine blade may further include a reinforcement member extending in the longitudinal direction and located at a leading-edge side and/or a trailing-edge side of the spar, and the reinforcement member may be divided into segments connectable to each other at the position corresponding to the connection sections. 
     Accordingly, since the reinforcement member extending in the longitudinal direction and located at the leading-edge side and/or the trailing-edge side of the spar is provided, the ability of the wind-turbine blade to resist a torsion load can be increased. 
     In the aforementioned aspect, the connection sections may be configured to be joint plates formed substantially integrally with the spar segments. 
     Accordingly, since this eliminates the need for forming a connection structure in the actual spar segments, the spar segments can be readily fabricated. 
     The spar segments and the joint plates are preferably attached so that, for example, they constitute a single unit in terms of strength via the blocking plate. 
     In the aforementioned configuration, the joint plates may include a plurality of joint plates provided in the chord direction of the blade. 
     Accordingly, the strength of the joint sections can be increased. 
     In the aforementioned configuration, it is preferable that at least one of the joint plates be attached such that the thickness direction thereof is substantially orthogonal to the chord direction. 
     Accordingly, since the width direction of the joint plate is aligned with the chord direction, the ability of the wind-turbine blade to resist a torsion load can be increased. 
     ADVANTAGEOUS EFFECTS OF INVENTION 
     According to the present invention, the wind-turbine blade is fabricated in units of the divided main-body skin and the spar segments. In other words, since the wind-turbine blade is fabricated in the form of longitudinally divided parts, a high-quality wind-turbine blade can be readily fabricated at low cost, as compared with that fabricated as a single unit. 
     Since the wind-turbine blade is transported in fabricated units, transporter vehicles can be readily procured and the selection of roads is facilitated. Since this allows for efficient transportation, the transportation time can be shortened, and cost reduction can be achieved. 
     Because the opening formed in the main-body skin is blocked off by the blocking plate, dust, sand, dirt, and the like are prevented from entering the hollow interiors during transportation. Therefore, since a process for removing dust, sand, dirt, and the like becomes unnecessary during assembly of the wind-turbine blade, the time required for such a process can be eliminated. 
     The assembly process of the wind-turbine blade at the installation site is performed by connecting the connection sections of the spar segments to each other while the connection-section skin to be located at the position corresponding to the connection sections is placed separately. Since the connection-section skin is open in this manner, the connection sections are readily accessible. Therefore, the connection sections can be readily and efficiently connected within a short time. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a side view illustrating the overall schematic configuration of a wind turbine generator according to a first embodiment of the present invention. 
         FIG. 2  is a perspective view illustrating a wind-turbine blade according to the first embodiment of the present invention. 
         FIG. 3  is a partial perspective view illustrating the configuration of connection sections according to the first embodiment of the present invention. 
         FIG. 4  is a plan view illustrating a wind-turbine blade according to a second embodiment of the present invention. 
         FIG. 5  is a partial plan view illustrating connection sections according to the second embodiment of the present invention. 
         FIG. 6  is a partial cross-sectional view illustrating the connection sections according to the second embodiment of the present invention. 
         FIG. 7  is a partial plan view illustrating an alternative example of connection sections according to the second embodiment of the present invention. 
         FIG. 8  is a partial cross-sectional view illustrating the alternative example of the connection sections according to the second embodiment of the present invention. 
         FIG. 9  is a plan view illustrating a wind-turbine blade according to a third embodiment of the present invention. 
         FIG. 10  is a partial plan view illustrating connection sections according to the third embodiment of the present invention. 
         FIG. 11  is a perspective view illustrating connection sections of a wind-turbine blade according to a fourth embodiment of the present invention. 
         FIG. 12  is a perspective view illustrating a connected state of the connection sections of the wind-turbine blade according to the fourth embodiment of the present invention. 
         FIG. 13  is a perspective view illustrating connection sections of a wind-turbine blade according to a fifth embodiment of the present invention. 
         FIG. 14  is a cross-sectional view taken along line X-X in  FIG. 13 . 
         FIG. 15  is a cross-sectional view taken along line Y-Y in  FIG. 13 . 
         FIG. 16  is a partial cross-sectional view illustrating a connected state between a blade-root-side center joint plate and a blade-tip-side center joint plate according to the fifth embodiment of the present invention. 
         FIG. 17  is a partial cross-sectional view illustrating a connected state between the blade-root-side center joint plate and a blade-tip-side center joint plate of an alternative example according to the fifth embodiment of the present invention. 
         FIG. 18  is a perspective view illustrating an alternative example of a blade-root-side center joint plate according to the fifth embodiment of the present invention. 
         FIG. 19  is a perspective view illustrating an alternative example of connection sections according to the fifth embodiment of the present invention. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the drawings. 
     First Embodiment 
     A wind turbine generator  1  according to a first embodiment of the present invention will now be described with reference to  FIGS. 1 to 3 . 
       FIG. 1  is a side view illustrating the overall schematic configuration of the wind turbine generator  1 . 
     As shown in  FIG. 1 , the wind turbine generator  1  includes a tower  3  standing upright on a foundation  11 , a nacelle  5  disposed on the top of the tower  3 , a hub  7  provided in the nacelle  5  in a rotatable manner about a rotation axis extending substantially in the horizontal direction, and multiple, e.g., three, wind-turbine blades  9  attached to the hub  7  so as to extend radially around the rotation axis thereof. 
     The force of wind striking the wind-turbine blades  9  in the rotation-axis direction of the hub  7  is converted to power that rotates the hub  7  about the rotation axis. 
     An anemometer  13  that measures the ambient wind speed value, an anemoscope  15  that measures the wind direction, and a lightning rod (not shown) are provided on the top of the nacelle  5 . 
     Although not shown, a generator linked with the hub  7  via a gear box that is coaxial therewith is disposed inside the nacelle  5 . Specifically, the generator is driven by increasing the speed of rotation of the hub  7  using the gear box so that generator output power can be obtained by the generator. 
       FIG. 2  is a perspective view illustrating one of the wind-turbine blades  9  in the process of being assembled. 
     The wind-turbine blade  9  includes a long and hollow skin  14  that defines the shape of the blade and multiple, e.g., two, main spars (spars)  16  extending longitudinally through the interior of the skin so as to reinforce the strength of the skin  14 . 
     The wind-turbine blade  9  is divided into two segments, i.e., a blade-root-side wind-turbine blade  17  and a blade-tip-side wind-turbine blade  19 , in the longitudinal direction. 
     The skin  14  is constituted of a blade-root-side skin (main-body skin)  21 , a blade-tip-side skin (main-body skin)  23 , and a connection-section skin  25 . 
     The blade-root-side skin  21 , the blade-tip-side skin  23 , and the connection-section skin  25  are each formed of two halves, i.e., a back skin and a front skin. In order to differentiate between the back skin and the front skin in the following description, the blade-root-side skin  21 , the blade-tip-side skin  23 , and the connection-section skin  25  will be given a suffix “a” or “b” after their reference numerals. A suffix “a” denotes a back skin, whereas a suffix “b” denotes a front skin. 
     A joint between the back skins and the front skins forms a leading edge  27  and a trailing edge  29  of the wind-turbine blade  9 . 
     The blade-root-side skin  21 , the blade-tip-side skin  23 , and the connection-section skin  25  are composed of fiberglass-reinforced plastic or carbon-fiber-reinforced plastic. Alternatively, the material thereof may be, for example, carbon-fiber-reinforced plastic, or another material may be used. Using carbon-fiber-reinforced plastic, which has great strength and high rigidity, makes it possible to readily cope with an increase in the size of the wind-turbine blade  9 . 
     The main spars  16  are each divided into two segments, i.e., a blade-root-side main spar (spar segment)  31  and a blade-tip-side main spar (spar segment)  33 , in the longitudinal direction. 
     Regarding the pair of blade-root-side main spars  31  and the pair of blade-tip-side main spars  33 , each main spar has an angular U-shape in cross section, and each pair is attached such that openings thereof face each other. 
     The blade-root-side main spars  31  and the blade-tip-side main spars  33  are composed of fiberglass-reinforced plastic. Alternatively, the material thereof may be, for example, carbon-fiber-reinforced plastic, or another material may be used. 
     Blade-root-side reinforcement layers  35  are interposed between the blade-root-side main spars  31  and the blade-root-side skin  21 . The blade-root-side reinforcement layers  35  are composed of fiberglass-reinforced plastic and are integrally formed with the blade-root-side skin  21  and the blade-root-side main spars  31 . 
     Blade-tip-side reinforcement layers  37  are interposed between the blade-tip-side main spars  33  and the blade-tip-side skin  23 . The blade-tip-side reinforcement layers  37  are composed of fiberglass-reinforced plastic and are integrally formed with the blade-tip-side skin  23  and the blade-tip-side main spars  33 . Alternatively, the material of the blade-root-side reinforcement layers  35  and the blade-tip-side reinforcement layers  37  may be, for example, carbon-fiber-reinforced plastic, or another material may be used. 
     The blade-tip side of the blade-root-side wind-turbine blade  17  is provided with an opening  39 . The opening  39  is blocked off by a blanking plate (blocking plate)  41  composed of fiberglass-reinforced plastic. 
     The blade-root side of the blade-tip-side wind-turbine blade  19  is provided with an opening  43 . The opening  43  is blocked off by a blanking plate (blocking plate)  45  composed of fiberglass-reinforced plastic. 
     The blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  each have an electrically-conductive cable  47  attached thereto and extending in the longitudinal direction thereof. The material of the blanking plates  41  and  45  may alternatively be, for example, carbon-fiber-reinforced plastic, or another material may be used. 
     The electrically-conductive cables  47  protrude outward from the respective blanking plates  41  and  45  and have connection terminals  49  attached to protruding ends thereof. 
     The blade-root-side main spars  31  and the blade-root-side reinforcement layers  35  protrude outward from the blanking plate  41 . The blade-root-side reinforcement layers  35  protrude further outward than the blade-root-side main spars  31  and each have a thin-walled portion  51  formed to have a thin wall by scraping off the inner side of an end portion of the blade-root-side reinforcement layer  35 . Multiple through-holes  53  spaced apart in the blade-width direction are formed in two rows in each thin-walled portion  51 . 
     Multiple through-holes  55  spaced apart in the blade-height direction are formed in two rows in an end portion of the side surface of each blade-root-side main spar  31 . 
     The blade-tip-side main spars  33  and the blade-tip-side reinforcement layers  37  protrude outward from the blanking plate  45 . The blade-tip-side reinforcement layers  37  protrude further outward than the blade-tip-side main spars  33  and each have a thin-walled portion  57  formed to have a thin wall by scraping off the outer side of an end portion of the blade-tip-side reinforcement layer  37 . Multiple through-holes  59  spaced apart in the blade-width direction are formed in two rows in each thin-walled portion  57 . 
     Multiple through-holes  61  spaced apart in the blade-height direction are formed in two rows in an end portion of the side surface of each blade-tip-side main spar  33 . 
     The disposed position of the through-holes  55 , the disposed position of the through-holes  53  (through-holes  59 ), and the disposed position of the through-holes  61  are shifted from each other in the longitudinal direction of the wind-turbine blade  9 . 
     A portion, protruding outward from the blanking plate  41 , of the blade-root-side main spars  31  and the blade-root-side reinforcement layers  35  and a portion, protruding outward from the blanking plate  45 , of the blade-tip-side main spars  33  and the blade-tip-side reinforcement layers  37  each constitute a connection section  50 . When in a connected state, the thin-walled portions  51  and the thin-walled portions  57  overlap with each other so that the through-holes  53  and the through-holes  59  communicate with each other. 
     In this state, the blade-root-side main spars  31  and the blade-tip-side main spars  33  are positioned with a gap interposed therebetween. Connecting plates (connecting members)  60  composed of fiberglass-reinforced plastic for joining the blade-root-side main spars  31  and the blade-tip-side main spars  33  are provided. The connecting plates  60  are provided with through-holes  58  that correspond to the through-holes  55  of the blade-root-side main spars  31  and through-holes  62  that correspond to the through-holes  61  of the blade-tip-side main spars  33 . The material of the connecting plates  60  may alternatively be, for example, carbon-fiber-reinforced plastic, or another material may be used. 
     A fabrication process and an assembly process of each of the wind-turbine blades  9  having the above-described configuration will now be described. 
     The blade-root-side skin  21 , the blade-tip-side skin  23 , and the connection-section skin  25  are each fabricated as two halves, i.e., the back skin and the front skin. 
     The blade-root-side main spars  31 , the blade-tip-side main spars  33 , the blanking plates  41  and  45 , and the connecting plates  60  are fabricated. 
     The blade-root-side wind-turbine blade  17  is fabricated by combining the two halves, i.e., the back skin and the front skin, of the blade-root-side skin  21 , the blade-root-side main spars  31 , the blanking plate  41 , and the electrically-conductive cable  47 . 
     The blade-tip-side wind-turbine blade  19  is fabricated by combining the two halves, i.e., the back skin and the front skin, of the blade-tip-side skin  23 , the blade-tip-side main spars  33 , the blanking plate  45 , and the electrically-conductive cable  47 . 
     Since the blade-root-side wind-turbine blade  17  or the blade-tip-side wind-turbine blade  19  is fabricated as one of the longitudinally divided parts in this manner, a high-quality blade-root-side wind-turbine blade  17  or blade-tip-side wind-turbine blade  19  can be readily fabricated at low cost, as compared with that fabricated as a single unit. 
     In other words, the molds used for fabricating the blade-root-side skin  21 , the blade-tip-side skin  23 , the blade-root-side main spars  31 , and the blade-tip-side main spars  33  can be made compact. Since this allows for high quality control, the quality is enhanced. In addition, since the number of rejects caused by fabrication errors is reduced, the production yield rate is enhanced. Moreover, the space required for the fabrication can be made smaller. 
     The blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , the connection-section skin  25 , and the connecting plates  60  that have been fabricated are transported to an installation site of the wind turbine generator  1 . 
     At this time, since the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  each have a size and a weight that are substantially half of those of a single-piece wind-turbine blade  9 , transporter vehicles can be readily procured and the selection of roads is facilitated. Since this allows for efficient transportation, the transportation time can be shortened, and cost reduction can be achieved. 
     Since the openings  39  and  43  of the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are respectively blocked off by the blanking plates  41  and  45 , dust, sand, dirt, and the like are prevented from entering the hollow interiors, formed by the blade-root-side skin  21  and the blade-tip-side skin  23 , during transportation. 
     Therefore, since a process for removing dust, sand, dirt, and the like becomes unnecessary during assembly of the wind-turbine blade  9 , the time required for such a process can be eliminated. 
     The blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , the connection-section skin  25 , and the connecting plates  60  that have been transported in this manner are combined in the following manner. 
     The blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are set at a position at which the blade-root-side reinforcement layers  35  overlap the blade-tip-side reinforcement layers  37  and the through-holes  53  and the through-holes  59  communicate with each other. In this state, the blade-root-side reinforcement layers  35  and the blade-tip-side reinforcement layers  37  are joined using bolts and nuts. 
     Subsequently, the connecting plates  60  are set such that the through-holes  58  thereof are aligned with the through-holes  55  in the end portions of the blade-root-side main spars  31  and the through-holes  62  are aligned with the through-holes  61  in the end portions of the blade-tip-side main spars  33 . In this state, the connecting plates  60  are joined to the blade-root-side main spars  31  and the blade-tip-side main spars  33  using bolts and nuts. Consequently, the blade-root-side main spars  31  and the blade-tip-side main spars  33  are integrated with each other. 
     Since the connecting plates  60  lie astride the blade-root-side main spars  31  and the blade-tip-side main spars  33  so as to connect them, the shape of the blade-root-side main spars  31  and the blade-tip-side main spars  33 , in other words, the structure thereof, can be simplified. Consequently, the blade-root-side main spars  31  and the blade-tip-side main spars  33  can be readily fabricated. 
     The connection terminals  49  of the electrically-conductive cables  47  in the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are connected to each other. 
     Thus, since the electrically-conductive cables  47  can be set over the entire length of the wind-turbine blade  9 , deterioration of the lightning protection performance of the wind-turbine blade  9  can be suppressed. 
     Since the connection-section skin  25  is removed in this manner, the connection sections  50  are readily accessible. Therefore, the blade-root-side reinforcement layers  35  and the blade-tip-side reinforcement layers  37 , the blade-root-side main spars  31  and the blade-tip-side main spars  33 , and the electrically-conductive cables  47  can be readily and efficiently connected to each other within a short time. 
     Furthermore, since the joint position of the blade-root-side main spars  31 , the joint position of the blade-tip-side main spars  33 , and the joint position between the blade-root-side reinforcement layers  35  and the blade-tip-side reinforcement layers  37  are shifted from each other in the longitudinal direction of the wind-turbine blade  9 , the joining process is facilitated. 
     Finally, the two halves, i.e., the back skin and the front skin, of the connection-section skin  25  are disposed so as to cover the connection sections  50  and are bonded to each other using an adhesive, thereby completing the assembly process of the wind-turbine blade  9 . 
     After assembling a predetermined number of, e.g., three, wind-turbine blades  9  in this manner, these wind-turbine blades  9  are attached to predetermined positions of the hub  7 . 
     Although the joining process is performed using bolts and nuts in this embodiment, the joining process may alternatively be performed by riveting or by using an adhesive. 
     Supposing that the joining process is performed by using an adhesive, the possibility of corrosion or the like can be suppressed since all of the components constituting the wind-turbine blades  9  are composed of fiberglass-reinforced plastic. 
     Second Embodiment 
     Next, a wind-turbine blade  9  according to a second embodiment of the present invention will be described with reference to  FIGS. 4 to 6 . 
     In this embodiment, since the configurations of a main spar  16  and the joint structure are different from those in the first embodiment, the following description will mainly be directed to these differences, and redundant descriptions of sections that are the same as those in the first embodiment described above will be omitted. Components that are the same as those in the first embodiment will be given the same reference numerals. 
     In this embodiment, a single hollow main spar  16  having a rectangular shape in cross section is provided. Connection sections  50  are provided with a connecting member  63  that joins a blade-root-side main spar  31  and a blade-tip-side main spar  33  to each other. The connecting member  63  has a substantially rectangular parallelepiped shape that is hollow, and is configured to receive the blade-root-side main spar  31  and the blade-tip-side main spar  33  into the hollow section thereof.
         In this embodiment, a blade-root-side wind-turbine blade  17 , a blade-tip-side wind-turbine blade  19 , a connection-section skin  25 , and the connecting member  63  are fabricated, as in the first embodiment.       

     Since the advantages in this case are the same as those in the first embodiment, redundant descriptions thereof will be omitted. 
     The wind-turbine blade  9  is assembled in the following manner using the blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , the connection-section skin  25 , and the connecting member  63  brought to the installation site of the wind turbine generator  1 . 
     The blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are disposed such that the connection sections  50  thereof face each other. An adhesive is applied to the joint section of the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17  and to the joint section of the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19 . 
     The adhesive is also applied to the inner side of the connecting member  63 , which is then attached to the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17 . Then, the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19  is attached to the connecting member  63 , whereby the blade-root-side main spar  31  and the blade-tip-side main spar  33  are in a joined state, as in  FIG. 6 . When the adhesive dries, the joining process is completed. 
     Since only an end of the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17  and an end of the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19  need to be attached to the connecting member  63 , the assembly process of the wind-turbine blade  9  is facilitated. 
     Although the connecting member  63  for attaching thereto the end of the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17  and the end of the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19  is used in this embodiment, a narrow portion  65 , for example, may be provided at the end of the blade-root-side main spar  31 , as shown in  FIGS. 7 and 8 . 
     In this case, the adhesive is applied to the outer periphery of the narrow portion  65  and to the inner periphery of the blade-tip-side main spar  33 , and the blade-root-side wind-turbine blade  17  is moved and joined to the blade-tip-side wind-turbine blade  19  so that the blade-tip-side main spar  33  is brought into engagement with the narrow portion  65 . 
     Although the adhesive is used for the joining process in this embodiment, the joining process may alternatively be performed by using bolts, as in the first embodiment, or by riveting. 
     Third Embodiment 
     Next, a wind-turbine blade  9  according to a third embodiment of the present invention will be described with reference to  FIGS. 9 and 10 . 
     In this embodiment, since the configurations of a main spar  16  and the joint structure are different from those in the first embodiment, the following description will mainly be directed to these differences, and redundant descriptions of sections that are the same as those in the first embodiment described above will be omitted. Components that are the same as those in the first embodiment will be given the same reference numerals. 
     In this embodiment, a blade-root-side main spar  31  is formed of two blade-root-side main spar sections  31  integrated with each other at ends thereof at the blade-tip side and has a rectangular shape in cross section. A blade-tip-side main spar  33  is formed of two blade-tip-side main spar sections  33  integrated with each other at ends thereof at the blade-root side, and has a rectangular shape in cross section. 
     Connection sections  50  are provided with a connecting member  67  that joins the blade-root-side main spar  31  and the blade-tip-side main spar  33  to each other. The connecting member  67  has a substantially rectangular parallelepiped shape that is hollow and is configured to be insertable into the blade-root-side main spar  31  and the blade-tip-side main spar  33 . 
     In this embodiment, a blade-root-side wind-turbine blade  17 , a blade-tip-side wind-turbine blade  19 , a connection-section skin  25 , and the connecting member  67  are fabricated, as in the first embodiment. 
     Since the advantages in this case are the same as those in the first embodiment, redundant descriptions thereof will be omitted. 
     The wind-turbine blade  9  is assembled in the following manner using the blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , the connection-section skin  25 , and the connecting member  67  brought to the installation site of the wind turbine generator  1 . 
     The blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are disposed such that the connection sections  50  thereof face each other. An adhesive is applied to the inner side of the joint section of the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17  and to the inner side of the joint section of the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19 . 
     The adhesive is also applied to the outer periphery of the connecting member  67 , which is then inserted into the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17 . Then, the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19  is attached to the connecting member  67 , whereby the blade-root-side main spar  31  and the blade-tip-side main spar  33  are in a joined state, as in  FIG. 10 . When the adhesive dries, the joining process is completed. 
     Since only the connecting member  67  needs to be inserted into an end of the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17  and an end of the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19 , the assembly process of the wind-turbine blade  9  is facilitated. 
     Although the adhesive is used for the joining process in this embodiment, the joining process may alternatively be performed by using bolts, as in the first embodiment, or by riveting. 
     Fourth Embodiment 
     Next, a wind-turbine blade  9  according to a fourth embodiment of the present invention will be described with reference to  FIGS. 11 and 12 . 
     In this embodiment, since the reinforcement structure of the wind-turbine blade  9  is different from that in the second embodiment, the following description will mainly be directed to this difference, and redundant descriptions of sections that are the same as those in the second embodiment (and the first embodiment) described above will be omitted. Components that are the same as those in the first embodiment will be given the same reference numerals. 
     In this embodiment, a blade-root-side wind-turbine blade  17  includes a hollow and substantially cylindrical blade-root-side leading-edge reinforcement member (reinforcement member)  69  at a leading edge  27  side of a blade-root-side main spar  31  and a hollow and substantially cylindrical blade-root-side trailing-edge reinforcement member (reinforcement member)  71  at a trailing edge  29  side thereof. 
     A blade-tip-side wind-turbine blade  19  includes a hollow and substantially cylindrical blade-tip-side leading-edge reinforcement member (reinforcement member)  73  at the leading edge  27  side of a blade-tip-side main spar  33  and a hollow and substantially cylindrical blade-tip-side trailing-edge reinforcement member (reinforcement member)  75  at the trailing edge  29  side thereof. 
     A connecting member  77  that joins the blade-root-side leading-edge reinforcement member  69  and the blade-tip-side leading-edge reinforcement member  73  to each other is provided. The connecting member  77  has a substantially cylindrical shape that is hollow, and is configured to receive the blade-root-side leading-edge reinforcement member  69  and the blade-tip-side leading-edge reinforcement member  73  into the hollow section thereof. 
     A connecting member  79  that joins the blade-root-side trailing-edge reinforcement member  71  and the blade-tip-side trailing-edge reinforcement member  75  to each other is provided. The connecting member  79  has a substantially cylindrical shape that is hollow, and is configured to receive the blade-root-side trailing-edge reinforcement member  71  and the blade-tip-side trailing-edge reinforcement member  75  into the hollow section thereof. 
     In this embodiment, the blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , a connection-section skin  25 , and a connecting member  63  are fabricated, as in the first embodiment. 
     Since the advantages in this case are the same as those in the first embodiment, redundant descriptions thereof will be omitted. 
     The wind-turbine blade  9  is assembled in the following manner using the blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , the connection-section skin  25 , and the connecting member  63  brought to the installation site of the wind turbine generator  1 . 
     The blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are disposed such that the connection sections  50  thereof face each other. 
     An adhesive is applied to the joint sections of the blade-root-side main spar  31 , the blade-root-side leading-edge reinforcement member  69 , and the blade-root-side trailing-edge reinforcement member  71  of the blade-root-side wind-turbine blade  17 . 
     The adhesive is also applied to the joint sections of the blade-tip-side main spar  33 , the blade-tip-side leading-edge reinforcement member  73 , and the blade-tip-side trailing-edge reinforcement member  75  of the blade-tip-side wind-turbine blade  19 . 
     The adhesive is applied to the inner side of the connecting member  63 , which is then attached to the blade-root-side main spar  31  of the blade-root-side wind-turbine blade  17 . The adhesive is applied to the inner side of the connecting members  77  and  79 , which are then respectively attached to the blade-root-side leading-edge reinforcement member  69  and the blade-root-side trailing-edge reinforcement member  71  of the blade-root-side wind-turbine blade  17 . 
     Subsequently, as shown in  FIG. 12 , the blade-tip-side main spar  33  of the blade-tip-side wind-turbine blade  19  is attached to the connecting member  63 , the blade-tip-side leading-edge reinforcement member  73  is attached to the connecting member  77 , and the blade-tip-side trailing-edge reinforcement member  75  is attached to the connecting member  79 . When the adhesive dries, the joining process is completed. 
     In addition to the advantages of the second embodiment, since the wind-turbine blade  9  in this embodiment is provided with a reinforcement member formed of the blade-root-side leading-edge reinforcement member  69  and the blade-tip-side leading-edge reinforcement member  73  at the leading edge  27  side of the main spar  16  and a reinforcement member formed of the blade-root-side trailing-edge reinforcement member  71  and the blade-tip-side trailing-edge reinforcement member  75 , the ability of the wind-turbine blade  9  to resist a torsion load can be increased. 
     Although the adhesive is used for the joining process in this embodiment, the joining process may alternatively be performed by using bolts, as in the first embodiment, or by riveting. Furthermore, the reinforcement members  69 ,  73 ,  71 , and  75  may have a circular or rectangular shape that is hollow or solid. 
     Fifth Embodiment 
     Next, a wind-turbine blade  9  according to a fifth embodiment of the present invention will be described with reference to  FIGS. 13 to 16 . 
     In this embodiment, since the configurations of a main spar  16  and the joint structure are different from those in the first embodiment, the following description will mainly be directed to these differences, and redundant descriptions of sections that are the same as those in the first embodiment described above will be omitted. Components that are the same as those in the first embodiment will be given the same reference numerals. 
     As shown in  FIG. 14 , in this embodiment, blade-tip-side ends of blade-root-side main spars  31  are riveted to a blanking plate  41  (see  FIG. 14 ). Although not shown, blade-root-side ends of blade-tip-side main spars  33  are similarly riveted to a blanking plate  45 . 
     A center reinforcement layer  81 , a leading-edge reinforcement layer  83 , and a trailing-edge reinforcement layer  85  are tightly attached to the blade tip side of the blanking plate  41  with an adhesive (see  FIG. 15 ). 
     A blade-root-side center joint plate (joint plate)  87  is attached to the center reinforcement layer  81 , a blade-root-side leading-edge joint plate (joint plate)  89  is attached to the leading-edge reinforcement layer  83 , and a blade-root-side trailing-edge joint plate (joint plate)  91  is attached to the trailing-edge reinforcement layer  85 , such that the thickness direction thereof is oriented in the chord direction (i.e., a direction connecting the leading edge  27  and the trailing edge  29 ). 
     A blade-tip-side wind-turbine blade  19  has a similar structure to that of a blade-root-side wind-turbine blade  17  and includes a blade-tip-side center joint plate  88 , a blade-tip-side leading-edge joint plate  90 , and a blade-tip-side trailing-edge joint plate  92  that correspond to the blade-root-side center joint plate  87 , the blade-root-side leading-edge joint plate  89 , and the blade-root-side trailing-edge joint plate  91 , respectively. 
     The blade-root-side center joint plate  87 , the blade-root-side leading-edge joint plate  89 , and the blade-root-side trailing-edge joint plate  91  are formed substantially integrally with the blade-root-side main spars  31  via the center reinforcement layer  81 , the leading-edge reinforcement layer  83 , the trailing-edge reinforcement layer  85 , and the blanking plate  41 . 
     The blade-tip-side center joint plate  88 , the blade-tip-side leading-edge joint plate  90 , and the blade-tip-side trailing-edge joint plate  92  are also formed substantially integrally with the blade-tip-side main spars  33 . 
     The blade-root-side center joint plate  87  is provided with through-holes  93 , the blade-root-side leading-edge joint plate  89  is provided with through-holes  95 , and the blade-root-side trailing-edge joint plate  91  is provided with a through-hole  97 . 
     The blade-tip-side center joint plate  88  is provided with through-holes  94 , the blade-tip-side leading-edge joint plate  90  is provided with through-holes  96 , and the blade-tip-side trailing-edge joint plate  92  is provided with a through-hole  98 . 
     In this embodiment having such a configuration, the blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , a connection-section skin  25 , and the like are fabricated in a substantially similar manner to the first embodiment. 
     Since the advantages in this case are the same as those in the first embodiment, redundant descriptions thereof will be omitted. 
     The wind-turbine blade  9  is assembled in the following manner using the blade-root-side wind-turbine blade  17 , the blade-tip-side wind-turbine blade  19 , and the connection-section skin  25  brought to the installation site of the wind turbine generator  1 . 
     The blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are disposed such that the connection sections  50  thereof face each other. 
     Then, the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are set at a position at which the blade-root-side center joint plate  87 , the blade-root-side leading-edge joint plate  89 , and the blade-root-side trailing-edge joint plate  91  respectively abut on the blade-tip-side center joint plate  88 , the blade-tip-side leading-edge joint plate  90 , and the blade-tip-side trailing-edge joint plate  92 , and the through-holes  93 , the through-holes  95 , and the through-hole  97  respectively communicate with the through-holes  94 , the through-holes  96 , and the through-hole  98 . 
     In this state, the blade-root-side center joint plate  87 , the blade-root-side leading-edge joint plate  89 , and the blade-root-side trailing-edge joint plate  91  are respectively joined to the blade-tip-side center joint plate  88 , the blade-tip-side leading-edge joint plate  90 , and the blade-tip-side trailing-edge joint plate  92  by riveting, as shown in  FIG. 16 . 
     Alternatively, the joining process may be performed using bolts and nuts or by using an adhesive. 
     Since the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  are joined to each other at three positions spaced apart in the chord direction, the joining strength can be increased. 
     Furthermore, since the joint structure of the blade-root-side main spars  31  and the blade-tip-side main spars  33  does not require processing, the fabrication process thereof can be readily performed. 
     Alternatively, if sufficient strength can be obtained, the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  may be joined to each other at one or two positions in the chord direction. As a further alternative, the blade-root-side wind-turbine blade  17  and the blade-tip-side wind-turbine blade  19  may be joined to each other at four or more positions. 
     Although a single blade-root-side center joint plate  87  and a single blade-tip-side center joint plate  88  are joined to each other in an overlapping manner in this embodiment, the blade-tip-side center joint plate  88  may be constituted of two plates with a gap therebetween, which may be joined to the blade-root-side center joint plate  87  by sandwiching it from opposite sides, as shown in  FIG. 17 . 
     Furthermore, in order to increase the ability of the wind-turbine blade  9  to resist a torsion load, the blade-root-side center joint plate  87 , for example, may be provided with a reinforcement rib extending in the chord direction, as shown in  FIG. 18 . 
     Moreover, as shown in  FIG. 19 , the blade-root-side center joint plate  87  may be attached such that the thickness direction thereof is substantially orthogonal to the chord direction. 
     Accordingly, since the width direction of the blade-root-side center joint plate  87  extends parallel to the chord direction, the ability of the wind-turbine blade  9  to resist a torsion load can be increased. 
     By similarly disposing the blade-root-side leading-edge joint plate  89  and the blade-root-side trailing-edge joint plate  91  in the same direction, the ability of the wind-turbine blade  9  to resist a torsion load can be further increased. 
     It should be noted that the present invention is not limited to the above-described embodiments, and modifications are permissible so long as they do not deviate from the scope of the invention. 
     REFERENCE SIGNS LIST 
     
         
           1  wind turbine generator 
           9  wind-turbine blade 
           14  skin 
           16  main spar 
           17  blade-root-side wind-turbine blade 
           19  blade-tip-side wind-turbine blade 
           21  blade-root-side skin 
           23  blade-tip-side skin 
           25  connection-section skin 
           27  leading edge 
           29  trailing edge 
           31  blade-root-side main spar 
           33  blade-tip-side main spar 
           39  opening 
           41  blanking plate 
           43  opening 
           45  blanking plate 
           47  electrically-conductive cable 
           50  connection section 
           60  connecting plate 
           63  connecting member 
           39  blade-root-side leading-edge reinforcement member 
           71  blade-root-side trailing-edge reinforcement member 
           73  blade-tip-side leading-edge reinforcement member 
           75  blade-tip-side trailing-edge reinforcement member 
           77  connecting member 
           79  connecting member 
           87  blade-root-side center joint plate 
           88  blade-tip-side center joint plate 
           89  blade-root-side leading-edge joint plate 
           90  blade-tip-side leading-edge joint plate 
           91  blade-root-side trailing-edge joint plate 
           92  blade-tip-side trailing-edge joint plate