Abstract:
A power-generating wind turbine has a plurality of streamline-wing-shaped blades provided every predetermined angle around a rotation shaft, and the blades have lift coefficients of 1.0 or larger. Apertures are provided within a range of 55 to 95% from a front rim for a length of a chord on a rear face being the rotation shaft side to the chord. Thus, the turbine can be activated with a gentle breeze by drag on the apertures. Since the apertures are provided at a position of 55 to 95% for the chord length distant from the front rim of the rear face of the blade, in a high wind speed region where the turbine rotates by the lift of the blades, less disturbance of the wind flow is observed on the rear faces to be resistance, and thus high rotation torque can be obtained.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a power-generating wind turbine and a method of manufacturing the same. 
         [0002]    In the wind power generation of the vertical shaft and vertical airfoil type, the rotation of blades for wind power generation by wind force is effected by the use of not only drag force being a wind force for pressing the blades but also lift force produced on the blades by the rotation thereof, thereby accomplishing intended power generation. 
         [0003]    A Savonius wind turbine of the configuration emphasizing a wind receiving area is generally known as being useful in the wind power generation utilizing drag forces. The blades thereof can be rotated by a slight breeze of about 1 m/sec wind speed. However, no rotary torque during rotation exceeding the wind speed can be obtained. On the other hand, a gyro-mill wind turbine based on the same airfoil configuration as in aircraft is generally known as being useful in the wind power generation utilizing lift forces. However, the blades thereof cannot be rotated by a slight breeze produced during rotation. 
         [0004]    Taking these problems into account, it was proposed to use a gyro-mill wind turbine which obtains drag forces at rotation start-up through cutting out a portion of the inner face side of the blades having the same airfoil shape as in aircraft so that it can be rotated by a slight breeze (see, for example, patent reference 1). 
         [0005]    Patent reference 1: Japanese Patent No. 3451085. 
       SUMMARY OF THE INVENTION 
       [0006]    In the above wind turbine, the problem of wind turbulence occurring during rotation could not be solved because of the cutout of a portion of the inner face side of the blades. Consequently, the lift force is decreased, thereby lowering its proper rotary torque. Therefore, a high electricity-generating capacity being an object of wind power generation could not be attained. 
         [0007]    In the conventional wind power generator of the vertical shaft and vertical airfoil type, as the blade having the same airfoil shape as in aircraft, use is made of one obtained by bending a thin sheet of an aluminum alloy. This poses the problem of, because of the difficulty in ensuring the uniformity of the shape of the front-edge portion of the blade, rendering the air flow turbulent, and invites the danger of poor strength, distortion or the like. 
         [0008]    Therefore, it is an object of the present invention to provide a power-generating wind turbine that can be actuated by a slight breeze and can suppress any turbulence of wind by rotation, thereby realizing an excellent power generation efficiency. 
         [0009]    According to the present invention, there is provided a power-generating wind turbine comprising a vertical rotating shaft and, provided at given angular intervals around the rotating shaft within a plane orthogonal to the vertical rotating shaft, a plurality of blades, each of these blades having the shape of a streamlined airfoil exhibiting a lift coefficient of 1.0 or higher, wherein the face of the airfoil on the side of the rotating shaft with respect to a chord of the airfoil is provided with an opening portion in a region of 55 to 95% of the length of the chord from its front edge. 
         [0010]    Further, according to the present invention, the area of the opening portion is in the range of 30 to 5% of the area of the face of the airfoil on the side of the rotating shaft. 
         [0011]    Further, according to the present invention, the face of the airfoil on the side of the rotating shaft is provided with a plurality of opening portions. 
         [0012]    Further, according to the present invention, the opening portion comprises a member thinner than that of a front portion of the blades. 
         [0013]    Moreover, according to the present invention, there is provided a method of manufacturing the blades defined in claim  1 , comprising forming at least a portion of each of the blades by extrusion of an aluminum alloy. 
         [0014]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein the front portion of each of the blades is formed by extrusion of an aluminum alloy. 
         [0015]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein the front portion has a hollow portion, and wherein the coupling portion at its end portion is provided with a tier portion corresponding to the thickness of the rear-side member and a front side of the rear-side member is disposed on the tier portion. 
         [0016]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein the front portion is provided with a coupling portion configured to couple a rear-side member to the front portion. 
         [0017]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein rear-side member has a thickness smaller than that of the front portion. 
         [0018]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein the coupling portion is formed by extrusion of an aluminum alloy. 
         [0019]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein there is provided coupling means for coupling the front portion to the coupling portion. 
         [0020]    Further, according to the present invention, there is provided the manufacturing method as mentioned above, wherein the coupling means includes a fitting portion provided on one of the front portion and the coupling portion and a fitting receiving portion provided on the other thereof. 
         [0021]    By virtue of the above arrangement of constituent elements, the wind turbine can be actuated even with a slight breeze due to the drag force at the opening portion. In a zone of high wind speed in which the wind turbine is rotated by the lift force of the blades, as the face of the blades on the side of the rotating shaft is provided with the opening portion in a region of 55 to 95% of the length of the chord set distant from its front edge, any turbulence of wind flow on the face on the side of the rotating shaft that causes resistance can be suppressed, thereby realizing a high rotary torque. 
         [0022]    Further, by virtue of the above arrangement of constituent elements, the ratio of the area of opening portion is small, thereby realizing enhanced suppression of any wind flow turbulence. 
         [0023]    Further, by virtue of the above arrangement of constituent elements, there are provided a plurality of opening portions, thereby realizing efficient capturing of wind at start-up. 
         [0024]    Further, by virtue of the above arrangement of constituent elements, the front portion exposed to an intense wind resistance can have a large thickness, thereby ensuring desirable strength of the front portion, while the material of the opening portions can have a small thickness, thereby contributing to weight reduction. 
         [0025]    By virtue of the above arrangement of constituent elements relating to the manufacturing method, uniform thickness and shape can be ensured by extrusion forming of an aluminum alloy. 
         [0026]    Further, by virtue of the above arrangement of constituent elements, desirable strength and uniform shape can be ensured for the front portion exposed to an intense wind resistance. 
         [0027]    Further, by virtue of the above arrangement of constituent elements, enhanced strength can be realized by including a hollow portion. 
         [0028]    Further, by virtue of the above arrangement of constituent elements, a rear-side member can be coupled to a coupling portion. 
         [0029]    Further, by virtue of the above arrangement of constituent elements, the thickness of the rear-side member can be reduced, thereby attaining weight reduction. 
         [0030]    Further, by virtue of the above arrangement of constituent elements, desirable strength and uniform configuration can be ensured for the coupling portion. 
         [0031]    Further, by virtue of the above arrangement of constituent elements, a front side of the rear-side member can be disposed on a tier portion, thereby avoiding the occurrence of any level difference between the front portion and the rear-side member 
         [0032]    Further, by virtue of the above arrangement of constituent elements, the front portion and the coupling portion can be coupled to each other by coupling means. 
         [0033]    Further, by virtue of the above arrangement of constituent elements, the front portion and the coupling portion can be coupled to each other by fitting of a fitting portion to a fitting receiving portion. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a front view of a wind turbine according to Example 1 of the present invention. 
           [0035]      FIG. 2  is a rear view of a blade according to Example 1 of the present invention. 
           [0036]      FIG. 3  is a plan view of a wind turbine according to Example 1 of the present invention. 
           [0037]      FIG. 4  is a cross-section view of a blade according to Example 1 of the present invention. 
           [0038]      FIG. 5  is a rear view of main portions of a blade according to Example 1 of the present invention. 
           [0039]      FIG. 6  is a cross-section view of main portions of a blade according to Example 1 of the present invention. 
           [0040]      FIG. 7  is a cross-section view of main portions of a blade according to Example 2 of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0041]    Preferred embodiments of the present invention will be described in detail below with reference to the appended drawings. It should not be construed that the following embodiments limit the claimed subject matter of the present invention. Further, all the constituent elements described below are not necessarily essential elements of the present invention. The Examples describe the realization of a hitherto unknown novel power-generating wind turbine and the particulars of the power-generating wind turbine. 
       EXAMPLE 1 
       [0042]    One embodiment of the present invention will be described below with reference to the appended drawings.  FIGS. 1 to 6  illustrate Example 1 of the present invention. Referring to the drawings, a wind turbine  1  of the vertical shaft type is provided at its center with a vertically erected rotating shaft  2 . A plurality of blades  3  are disposed around the rotating shaft  2  at equal intervals in the circumferential direction thereof. In this instance, three blades  3 , 3 , 3  are disposed in parallel relationship to the rotating shaft  2 . Namely, the blades  3  are disposed at equal angular intervals (in this Example, 120° intervals) along the circumferential direction of identical radius within a plane orthogonal to the rotating shaft  2 . 
         [0043]    Each of the blades  3  is fixed to an end portion of an arm  4  radially extending from the rotating shaft  2  with a given angle to a support beam  4 . A plurality of arms  4  are provided in the longitudinal direction of the blades  3 . In this instance, two arms are provided. 
         [0044]    The casing of each of the blades  3  is formed of a thin sheet of a material, for example, a light metal, such as an aluminum alloy or a titanium alloy, or a composite material, such as a fiber-reinforced plastic (FRP). Each of the blades  3  has the shape of a streamlined airfoil exhibiting a lift coefficient of 1.0 or higher, preferably 1.0 to 1.4. It is especially preferred for the shape to be that used in the main wing of a light aircraft with nonsymmetrical airfoils (aircraft whose takeoff weight is 5700 kg or less), for example, the 4-digit airfoil shape, RAF airfoil shape or Gottingen airfoil shape. The face with greater bulge of the airfoil shape (face on the outer circumferential side) constitutes the obverse face  5  of the blade  3 , while the face with less bulge of the airfoil shape (face on the inner circumferential side) constitutes the reverse face  6  of the blade  3 . This reverse face is the face on the side of the rotating shaft. 
         [0045]    Each of the blades  3  thereinside is provided with a coupling member  7  for coupling the side of obverse face  5  and the side of reverse face  6  to each other. This coupling member  7  is formed of the same thin sheet of material as in the casing of each of the blades  3 . This coupling member  7  prevents any deformation of the blade  3  at its rotation. In the drawing, numeral  8  denotes a power generator  8  coupled at its superior portion to the rotating shaft  2 . This power generator  8  is mounted on a pole  9 . 
         [0046]    In this Example, the front portion  11  of each of the blades  3  is formed of an extrudate of an aluminum alloy. This front portion  11  is integrally provided with a hollow portion  12  positioned on the side in front of the coupling member  7  and with an obverse face coupling portion  13  and a reverse face coupling portion  14  both extending from the coupling member  7  to the rear side. In these, the same cross section continues in the longitudinal direction by virtue of extrusion forming. The obverse face coupling portion  13  at its rear end side is provided with an obverse face attaching portion  16  of inside recessed tier portion  15 . The reverse face coupling portion  14  at its rear end side is provided with a reverse face attaching portion  18  of inside recessed tier portion  17 . An obverse cover member  19  of a sheet thinner than the front portion  11  is fixed to the external face of the obverse face attaching portion  16  by rivets  20  as fixing means. A reverse cover member  21  of a sheet thinner than the front portion  11  is fixed to the external face of the reverse face attaching portion  18  by rivets  20 . The tier portions  15 , 17  are so constructed that no level difference is made on the obverse face  5  and the reverse face  6 . The obverse face coupling portion  13  and reverse face coupling portion  14  at the rear ends thereof are provided with folded edge portions  13 A, 14 A which have been approximately vertically folded toward the internal side. These obverse cover member  19  and reverse cover member  21  constitute rear-side members. 
         [0047]    In the drawing, numeral  22  denotes a plurality of screw holes provided in the front portion  11 . The screw holes are provided in the hollow portion  12 . The screw holes are provided at two positions at both end corner portions of the coupling member  7  and two positions on the front side. 
         [0048]    Each of the blades  3  is provided with an arm support member  31  correspondingly to the attaching position of the arm  4 . This arm support member  31  has a nearly ▭-shaped cross section, comprising a center portion  31 A and, arranged on its both sides, side portions  31 B, 31 B. The center portion  31 A is arranged along the internal faces of the obverse face coupling portion  13  and obverse cover member  19  and is fixed to the obverse cover member  19  by means of a plurality of rivets  20 , and the side portions  31 B, 31 B at the front sides thereof are fixedly disposed between the obverse face coupling portion  13  and the reverse face coupling portion  14 . The arm support member  31  is provided on the side of the center portion  31 A with a receiving groove portion  131 A configured to have the folded edge portion  13 A fitted therein. Further, the arm support member  31  on an edge of the side portion  31 B is provided with a receiving groove portion  131 B configured to have the folded edge portion  14 A fitted therein. Still further, the arm support member  31  on its front side is fixed to the coupling member  7  by means of screws  32  as a fixing member. 
         [0049]    Moreover, the reverse face coupling portion  13  is provided with an insertion hole  33  correspondingly to the attaching position of the arm  4 , and an arm receiving member  34  is inserted through the insertion hole  33 . A distal end of the arm  4  is inserted through the arm receiving member  34 , and the distal end is fitted in the space between the side portions  31 B, 31 B. In each of the blades  3 , a plurality of bolts  35  are inserted through the side portions  31 B, 31 B and the arm receiving member  34  and screwed in nuts  35 A. Thus, the arm receiving member  34  is fixed to the blade  3 . The arm  4  is externally fitted in the portion of the arm receiving member  34  protruding from the blade  3 , and the arm  4  is fixed to the arm receiving member  34  by means of the plurality of bolts  35  and nuts  35 A. The arm receiving member  34  is formed of an extrudate of aluminum alloy with a solid core. Accordingly, the arm support member  31 , the arm receiving member  34  and the bolts  35  and nuts  35 A constitute arm fixing means  36  for fixing the arm  4  to the blade  3 . 
         [0050]    Each of the blades  3  at both end portions in the longitudinal direction thereof is provided with lid plates  41  configured to close the end portions. Each of the lid plates  41  is fixed by a fixing member  42  having a nearly L-shaped cross section. One side piece  42 A of the fixing member  42  is fixed to the internal face of the blade  3  by rivets  20 . Another side piece  42 B of the fixing member  42  is fixed to the lid plate  41  by rivets  20 . The front side of the lid plate  41  is fixed by inserting screws not shown through the lid plate  41  and engaging the screws to the screw holes  22 . 
         [0051]    The fixing member  42  at its one side piece is provided with a receiving groove portion  131 A configured to have the folded edge portion  13 A fitted therein. Further, the arm support member  31  on an edge of the side portion  31 B is provided with a receiving groove portion  131 B configured to have the folded edge portion  14 A fitted therein. 
         [0052]    Each of the blades  3  in its reverse face  6  is provided with a plurality of opening portions  51 , 51  . . . The plurality of opening portions  51 , 51  . . . are provided in a region of 55 to 95%, preferably 75 to 95% of the interspace between a front edge  52  and a rear edge  53  from the front edge  52 , depending on the aerodynamic characteristics of the airfoil. The total area of these opening portions  51 , 51  . . . is in the range of 30 to 5%, preferably 20 to 5%, of the area of the reverse face  6 . Consequently, the blade  3  can have an airfoil shape ensuring a low Reynolds number and a high lift coefficient, and can have a structure such that the air flow turbulence on the side of the reverse face  6  is reduced in a zone of high wind speed. 
         [0053]    The chord  54  of each of the blades  3  is mounted with an angle of 0 to 5° with respect to the direction of the wind to the blade  3  (the direction of a normal line to the direction of rotation T). In the drawing, W represents the direction of wind blowing. 
         [0054]    Therefore, at the actuation in a zone of low wind speed, when the plurality of blades  3  catch wind, the wind drag from the rear side is increased by virtue of the opening portions  51  positioned in rear areas of the blades  3 . This air drag produces an actuation torque for the forward rotation of the blades  3 . 
         [0055]    In contrast, in a zone of high wind speed exhibiting a peripheral speed ratio of 1 or greater, the blades  3  are rotated by the lift force produced thereon. In that instance, as the opening portions  51  are positioned in rear areas of the blades  3 , any turbulence of air flow along the reverse face  6  from the front edge  52  toward the rear edge  53  can be suppressed to thereby produce a high rotary torque. 
         [0056]    In this Example, as apparent from the above, there is provided a power-generating wind turbine comprising a rotating shaft  3  and, provided at given angular intervals around the rotating shaft  3  within a plane orthogonal to the rotating shaft  3 , a plurality of blades  3 , each of these blades  3  having the shape of a streamlined airfoil exhibiting a lift coefficient of 1.0 or higher, wherein the face of the airfoil on the side of the rotating shaft with respect to a chord  54  of the airfoil, namely, a reverse face  6  is provided with an opening portion  51  in a region of 55 to 95% of the length of the chord from its front edge  52 . Therefore, the wind turbine can be actuated even with a slight breeze due to the drag force at the opening portion  51 . In a zone of high wind speed in which the wind turbine is rotated by the lift force of the blades  3 , due to the opening portion  51  provided in a position of 55 to 95% of the length of the chord set distant from the front edge  52  of the reverse face  6  of the blades  3 , any turbulence of the wind flow on the reverse face  6  that causes resistances can be suppressed, thereby realizing a high rotary torque. 
         [0057]    Further in this Example, as apparent from the above, the area of the opening portion  51  is in the range of 30 to 5% of the area of the face on the side of the rotating shaft, namely, the reverse face  6 . Therefore, there can be realized enhanced suppression of any wind flow turbulence. 
         [0058]    Further in this Example, as apparent from the above, there are provided a plurality of opening portions  51 . Therefore, efficient capturing of wind can be attained at start-up. 
         [0059]    Further in this Example, as apparent from the above, the reverse cover member  21  as a member of the opening portion  51  is thinner than the front portion  11  of each of the blades  3 . Therefore, the strength of the front portion  11  can be secured by increasing the thickness of the front portion  11  exposed to an intense resistance of wind. Weight reduction can be attained by decreasing the thickness of the member of the opening portion  51 . 
         [0060]    In this Example, as apparent from the above, the method of manufacturing the blades defined in claim  1  comprises forming at least a portion of each of the blades  3  by extrusion of an aluminum alloy. Therefore, uniform thickness and shape can be ensured by extrusion forming of an aluminum alloy. 
         [0061]    Further in this Example, as apparent from the above, the front portion  11  of each of the blades  6  is formed of an extrudate of an aluminum alloy. Therefore, desirable strength and uniform shape can be ensured for the front portion  11  exposed to an intense wind resistance. 
         [0062]    Further in this Example, as apparent from the above, the front portion  11  is provided with a hollow portion  12 . Therefore, higher strength can be realized by including the hollow portion  12 . 
         [0063]    Further in this Example, as apparent from the above, the front portion  11  is provided with obverse face and reverse face coupling portions  13 , 15  for coupling an obverse cover member  19  and a reverse cover member  21  as rear-side members. Therefore, the obverse cover member  19  and reverse cover member  21  can be coupled to the obverse face and reverse face coupling portions  13 , 15 . 
         [0064]    Further in this Example, as apparent from the above, the obverse cover member  19  and reverse cover member  21  as rear-side members are thinner than the front portion  11 . Therefore, weight reduction can be attained by reducing the thicknesses of the obverse cover member  19  and reverse cover member  21 . 
         [0065]    Further in this Example, as apparent from the above, the coupling portions  13 , 15  are formed by extrusion of an aluminum alloy. Therefore, desirable strength and uniform shape can be ensured for the coupling portions  13 , 15 . 
         [0066]    Further in this Example, as apparent from the above, the coupling portions  13 , 15  at end portions thereof are provided with tier portions  15 , 17  corresponding to the thicknesses of the obverse cover member  19  and reverse cover member  21  as rear-side members, and the front sides of the obverse cover member  19  and reverse cover member  21  are disposed on the tier portions  15 , 17 . Therefore, the occurrence of any level difference between the front portion  11  and each of the obverse cover member  19  and the reverse cover member  21  can be avoided. 
         [0067]    As a further effect of this Example, the front portion  11  is provided with screw holes  22 , so that lid plates  41  or the like can be easily attached to the end portions by means of screws. 
       EXAMPLE 2 
       [0068]      FIG. 7  illustrates Example 2 of the present invention. Like elements are identified by like numerals or marks through Examples 1 and 2, and repetition of detailed descriptions will be avoided. In this Example, the front portion  11  is composed of a hollow portion  12  and, disposed separate from the hollow portion  12 , a divided part  61 . This divided part  61  has a nearly ▭-shaped configuration in which the front ends of the obverse face coupling portion  13  and reverse face coupling portions  14  are coupled together by means of a rear coupling member  62  of sheet form. A fitting groove  7 A is provided in the above coupling member  7 , and a fitting portion  62 A configured to fit in the fitting groove  7 A is provided in the rear coupling member  62 . These fitting groove  7 A as a fitting receiving portion and fitting portion  62 A constitute coupling means  63 . Both the front portion  11  and the divided part  61  are formed of an extrudate of an aluminum alloy. In the hollow portion  12 , the screw holes  22  are provided at two locations at both end corner portions of the coupling member  7 , two locations on the center side and two locations on the front side. 
         [0069]    Therefore, the hollow portion  12  and the divided part  61  are coupled and unified together by fitting the fitting portion  62 A in the fitting groove  7 A and shifting the divided part  61  in the longitudinal direction thereof toward the hollow portion  12 . 
         [0070]    In this Example, as apparent from the above, the coupling means  63  for coupling together the front portion  11  and the coupling portions  13 , 15  is integrally provided, so that the front portion  11  can be coupled to the divided part  61  including the coupling portions  13 , 15  by the coupling means  63 . 
         [0071]    Further in this Example, as apparent from the above, the coupling means  63  is provided with the fitting portion  62 A disposed at one of the front portion  11  and the divided part  61  including the coupling portions  13 , 15  and with the fitting groove  7 A as a fitting receiving portion disposed on the other thereof, so that the front portion  11  and the coupling portions  13 , 15  can be coupled together by the fitting of the fitting portion  62 A in the fitting groove  7 A. 
         [0072]    The present invention is in no way limited to these Examples, and various modifications thereof can be implemented.