Patent Publication Number: US-2011070520-A1

Title: Fuel cell and method for disassembling fuel cell

Description:
TECHNICAL FIELD 
     The present invention relates to a fuel cell in which a cell stack that is a stack body of cells is fastened by a fastening band, and a method for disassembling such fuel cell. 
     BACKGROUND ART 
     A cell stack of a common fuel cell is configured by stacking a plurality of cells (unit cells) as disclosed in PTL 1, and a current collector, an insulating plate, and an end plate are disposed on each of both sides of the cell stack in a stack direction. Then, a stack body including the cell stack, the current collectors, the insulating plates, and the end plates is fastened by fastening rods (bolts and nuts) in the stack direction. Thus, electrical connections among the cells are maintained. 
     However, in such fastening structure using the fastening rods (bolts and nuts), heads and tip end portions of the bolts, and nuts project from the surface of the end plate, and the problem is that the size of the fuel cell increases. 
     Therefore, various technologies have been developed in recent years to reduce the size of the fuel cell by reducing the size of the fastening structure of the cell stack. For example, each of PTLs 2 and 3 discloses a technology in which the cell stack is fastened by using a thin fastening band. In addition, PTL 3 discloses a technology in which both end portions of the fastening band are connected to each other by using a small connecting portion, such as a turnbuckle or a latch. 
     Citation List 
     Patent Literature 
     PTL 1: Japanese Laid-Open Patent Application Publication No. 2007-59187 
     PTL 2: Published Japanese Translation of PCT Application No. 2001-504632 
     PTL 3: Japanese Laid-Open Patent Application Publication No. 2007-73509 
     SUMMARY OF INVENTION 
     Technical Problem 
     In the case of using the fastening band (PTLs 2 and 3) to fasten the cell stack, the end plates, and the like, the fastening band does not project so much from the surface of the end plate, and both end portions of the fastening band can be connected to each other by the small connecting portion (such as the turnbuckle or the latch). Therefore, the size of the fuel cell can be reduced. 
     However, in a case where the connection between both end portions of the fastening band is released or the fastening band is cut, the fastening band vigorously snaps by “an elastic force (elastic repulsive force) of the cell stack” or “an elastic force of the fastening band itself”. Therefore, a conventional problem is that the snapped fastening band breaks components positioned around the cell stack. 
     Solution to Problem 
     In order to solve the above problems, a fuel cell according to the present invention includes: a cell stack configured by stacking a plurality of cells; two end plates respectively disposed on both sides of the cell stack in a stack direction; a fastening band configured to fasten the cell stack and the end plates in the stack direction; a connecting portion configured to connect one end portion and the other end portion of the fastening band; and a displacement restricting portion provided on at least one of the end plates to restrict displacement of the fastening band in a direction away from a surface of the end plate. 
     In this configuration, in a case where the connecting portion loosens and the connection between both end portions of the fastening band is released or in a case where the fastening band is cut, a portion of the fastening band which portion is located on the surface of the end plate tends to displace in the direction away from the surface of the end plate by “the elastic force of the cell stack” or “the elastic force of the fastening band itself”. However, since the displacement of the fastening band in the direction away from the surface of the end plate is restricted by the displacement restricting portion, the fastening band does not vigorously snap in such direction. 
     A groove-shaped concave portion may be formed on a surface of at least one of the end plates, and the fastening band may be disposed to fit in the concave portion. 
     In this configuration, since the displacement of the fastening band in a width direction is restricted such that the side surface of the fastening band contacts the inner side surface of the concave portion, the positioning of the fastening band can be easily carried out on the surface of the end plate, and the positioning error of the fastening band in the width direction can be prevented. 
     The displacement restricting portion may be formed to cover at least a part of a surface of the fastening band. 
     In this configuration, if the fastening band tends to displace in the direction away from the surface of the end plate, at least a part of the surface of the fastening band contacts the displacement restricting portion, and this restricts the displacement of the fastening band. 
     The displacement restricting portion may be formed integrally with the end plate. 
     In this configuration, since the displacement restricting portion and the end plate are integrally formed, they can be manufactured easily at low cost by integral molding, such as injection molding. 
     The fastening band may be provided with a stopper portion configured to be stopped by the displacement restricting portion to restrict the displacement of the fastening band in a direction parallel to the surface of the end plate. 
     In this configuration, since the stopper portion of the fastening band is stopped by the displacement restricting portion, the displacement of the fastening band in the direction parallel to the surface of the end plate is restricted. 
     The connecting portion may be provided with a stopper portion configured to be stopped by the displacement restricting portion to restrict the displacement of the fastening band in a direction parallel to the surface of the end plate. 
     In this configuration, since the stopper portion of the connecting portion is stopped by the displacement restricting portion, the displacement of the fastening band in the direction parallel to the surface of the end plate is restricted. 
     A groove-shaped concave portion having a square cross section may be formed on a surface of at least one of the end plates, the fastening band may be a band-shaped member having a square cross section and disposed to fit in the concave portion, and the displacement restricting portion may include a facing portion having a planar facing surface facing at least a part of a surface of the fastening band and two coupling portions configured to couple the end plate and both end portions of the facing portion in a direction intersecting with the concave portion. 
     In this configuration, when the fastening band displaces, the lower surface of the fastening band contacts the bottom surface of the concave portion, the surface of the fastening band contacts the facing surface of the facing portion, and the side surface of the fastening band contacts the inner side surface of the concave portion. Therefore, it is possible to weaken the power of the displacement of the fastening band by the frictional forces generated by the surface contact. 
     A groove-shaped concave portion having a square cross section may be formed on a surface of at least one of the end plates, the fastening band may be a band-shaped member having a square cross section and disposed to fit in the concave portion, the displacement restricting portion may include a facing portion having a planar facing surface facing at least a part of a surface of the fastening band and a coupling portion configured to couple the end plate and one end portion of the facing portion in a direction intersecting with the concave portion, and an introducing port through which the fastening band is introduced into the concave portion may be formed between the other end portion of the facing portion and the surface of the end plate. 
     In this configuration, since the introducing port through which the fastening band is introduced into the concave portion is formed between the other end portion of the facing portion and the surface of the end plate, the fastening band provided on the surface of the end plate can be moved in the width direction to be introduced through the introducing port into the concave portion. Therefore, it is unnecessary to cause the end portion of the fastening band to pass through the lower space of the facing portion. Even in a case where the connecting portion is formed integrally at the end portion of the fastening band, the height of the connecting portion is not limited by the height of the lower space, and the “connecting portion” can be designed freely. 
     A pipe member through which a gas or a cooling medium is supplied to the plurality of cells may be connected to at least one of the end plates, and at least a part of the displacement restricting portion may be constituted by the pipe member. 
     In this configuration, at least a part of the displacement restricting portion can be easily configured by the pipe member at low cost. 
     The pipe member may be a pipe or a pipe joint having a facing portion facing at least a part of the surface of the fastening band. Moreover, the pipe member may be a pipe or a pipe joint, and a facing member facing at least a part of the surface of the fastening band may be attached to the pipe or the pipe joint. 
     In order to solve the above problems, a method for disassembling a fuel cell according to the present invention is a method for disassembling a fuel cell including a cell stack configured by stacking a plurality of cells, two end plates respectively disposed on both sides of the cell stack in a stack direction, a fastening band configured to fasten the cell stack and the end plates in the stack direction, and a connecting portion configured to connect one end portion and the other end portion of the fastening band, the method comprising the steps of: disposing on at least one of the end plates a displacement restricting portion configured to restrict displacement of the fastening band in a direction away from a surface of the end plate; and releasing the connection between said one end portion and the other end portion of the fastening band at the connecting portion while restricting the displacement of the fastening band by the displacement restricting portion. 
     In this configuration, since the displacement restricting portion can prevent the fastening band from vigorously snapping in the direction away from the surface of the end plate, the safety of the disassembling work can be improved. In addition, since the displacement restricting portion can be disposed on the end plate only when disassembling the fuel cell, it is unnecessary to dispose the displacement restricting portion on the end plate in advance, and this can reduce the manufacturing cost of the fuel cell. 
     The above object, other objects, features, and advantages of the present invention will be made clear by the following detailed explanation of preferred embodiments with reference to the attached drawings. 
     Advantageous Effects of Invention 
     The present invention is configured as above, and even if the connecting portion loosens and the connection between both end portions of the fastening band is released or even if the fastening band is cut, the displacement of the fastening band in the direction away from the surface of the end plate is restricted by the displacement restricting portion. Therefore, the fastening band does not vigorously snap in such direction. On this account, it is possible to prevent accidents, such as breakdown of components positioned around the cell stack by the snapped fastening band and also possible to provide a fuel cell which is small in size, light in weight, and high in safety. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view showing the configuration of a fuel cell according to Embodiment 1. 
         FIG. 2  is a front view showing the configuration of the fuel cell according to Embodiment 1. 
         FIG. 3  is a plan view showing the configuration of the fuel cell according to Embodiment 1. 
         FIG. 4  is a partial cross-sectional view taken along line IV-IV of  FIG. 3 . 
         FIG. 5  is a partially enlarged view of  FIG. 4 . 
         FIG. 6  is an exploded view showing a connecting portion in Embodiment 1. 
         FIG. 7  is a perspective view showing a stopper portion which stops by a displacement restricting portion. 
         FIG. 8  are diagrams showing the configurations of main portions of the fuel cell according to Embodiment 2.  FIG. 8(A)  is a perspective view, and  FIG. 8(B)  is a cross-sectional view. 
         FIG. 9  is an exploded view showing a modification example of the connecting portion. 
         FIG. 10  is an exploded view showing another modification example of the connecting portion. 
         FIG. 11  are diagrams showing the configurations of main portions of the fuel cell according to Embodiment 3.  FIG. 11(A)  is a perspective view, and  FIG. 11(B)  is a cross-sectional view. 
         FIG. 12  are diagrams showing the configurations of main portions of the fuel cell according to Embodiment 4.  FIG. 12(A)  is a perspective view, and  FIG. 12(B)  is a cross-sectional view. 
         FIG. 13  are diagrams showing the configurations of main portions of the fuel cell according to Embodiment 5.  FIG. 13(A)  is a perspective view, and  FIG. 13(B)  is a cross-sectional view. 
         FIG. 14  is a perspective view showing the configuration of the fuel cell according to Embodiment 6. 
         FIG. 15  is a perspective view showing the configuration of the fuel cell according to Embodiment 7. 
         FIG. 16  is an exploded perspective view showing the configuration of a part of the fuel cell according to Embodiment 7. 
         FIG. 17  is a cross-sectional view showing the displacement restricting portion in Embodiment 7. 
         FIG. 18  is a cross-sectional view showing a modification example of the displacement restricting portion in Embodiment 7. 
         FIG. 19  is a cross-sectional view showing another modification example of the displacement restricting portion in Embodiment 7. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, preferred embodiments of the present invention will be explained in reference to the drawings. In the following embodiments, the present invention is applied to a polymer electrolyte fuel cell (PEFC). However, the present invention is widely applicable to the other types of fuel cells, such as a solid oxide fuel cell (SOFC) and a phosphoric acid fuel cell (PAFC). 
     Embodiment 1 
       FIG. 1  is a perspective view showing the configuration of a fuel cell  10  according to Embodiment 1 of the present invention.  FIG. 2  is a front view showing the configuration of the fuel cell  10 .  FIG. 3  is a plan view showing the configuration of the fuel cell  10 .  FIG. 4  is a partial cross-sectional view taken along line Iv-Iv of  FIG. 3 .  FIG. 5  is a partially enlarged view of  FIG. 4 . 
     The fuel cell  10  ( FIGS. 1 to 3 ) is a polymer electrolyte fuel cell (PEFC) used in domestic cogeneration systems, motorcycles, electric cars, hybrid electric cars, and the like. As shown in  FIGS. 1 and 2 , the fuel cell  10  includes: a cell stack  12 ; current collectors  14 , insulating plates  16 , and end plates  18 , which are disposed on both sides of the cell stack  12  in a stack direction; compression springs  20  disposed between the insulating plate  16  the end plate  18  on one end side of the cell stack  12  in the stack direction; a plurality of (four in the present embodiment) fastening bands  22  configured to fasten these components; a connecting portion  24  ( FIGS. 1 and 3 ) configured to connect one end portion  22   e  and the other end portion  22   f  of the fastening band  22 ; and a displacement restricting portion  26  ( FIGS. 1 and 3 ) configured to restrict the displacement of the fastening band  22 . 
     The cell stack  12  ( FIGS. 1 and 2 ) is a layer-built cell configured by stacking a plurality of cells (unit cells)  28  which generate an electromotive force and connecting these cells  28  with one another in series. Each of the cells  28  is a square plate shaped component formed such that an MEA (Membrane-Electrode Assembly) including an anode (fuel electrode), a cathode (air electrode), and a solid polymer membrane (ion-exchange membrane) sandwiched between the anode and the cathode is sandwiched between two electrically conductive separators (bipolar plates). The separators of the adjacent cells  28  contact each other, so that all the cells  28  are connected to one another in series. 
     Here, in order to stabilize the electromotive force of the cell  28 , it is desirable that the anode (fuel electrode), the cathode (air electrode), and the solid polymer membrane (ion-exchange membrane) constituting the MEA (Membrane-Electrode Assembly) contact one another at an even surface pressure. Moreover, in order to maintain electrical connections among the cells  28 , it is desirable that the cells  28  contact one another at a predetermined surface pressure. Therefore, in the fuel cell  10 , a fastening mechanism including the end plates  18 , the fastening bands  22 , and the connecting portions  24  is designed such that these demands are satisfied. 
     As shown in  FIG. 2 , each of two current collectors  14  includes a square plate shaped power collecting portion  14   a  made of a gas impermeable and electrically conductive material, such as dense carbon or copper. An output terminal  14   b  is integrally formed at one side end edge of the power collecting portion  14   a.    
     Each of two insulating plates  16  insulates a surface of the current collector  14  which surface faces the end plate  18 . The insulating plate  16  is formed in a square plate shape by an insulating material, such as rubber or plastic. 
     Each of two end plates  18  applies the fastening power of the fastening band  22  to the cell stack  12  and the current collectors  14  at the even surface pressure. The end plate  18  is formed in a square plate shape by a high stiffness material, such as rigid plastic or copper, to prevent deformation by the fastening power. As shown in  FIGS. 1 and 2 , the size of the end plate  18  is designed to be slightly larger than each of the size of the cell stack  12  and the size of the current collector  14 . Therefore, the fastening band  22  hanged between a pair of end plates  18  is provided to be separated from the side surface of the cell stack  12  and the side surface of the current collector  14 . On this account short-circuit of the cell stack  12  and the current collector  14  by the fastening band  22  does not occur. 
     In Embodiment 1, each of the cells  28 , the current collectors  14 , the insulating plates  16 , and the end plates  18  is formed in the square plate shape. However, the shape is not especially limited and may be an oval plate shape, a hexagonal plate shape, or the like. 
     Then, as shown in  FIGS. 1 to 4 , four groove-shaped concave portions  30  which accommodate the fastening bands  22  are formed in parallel with one another at regular intervals on two parallel side surfaces  18   a  and  18   b  and a surface  18   c  ( FIG. 1 ) of the end plate  18 . 
     The concave portion  30  positions the fastening band  22  and prevents a positioning error of the fastening band  22  in a width direction. As shown in  FIG. 5 , a cross-sectional shape of the concave portion  30  is designed to have a square shape including a bottom surface  30   a  facing (contacting) a lower surface  22   a  of the fastening band  22  and inner side surfaces  30   b  and  30   c  which respectively face side surfaces  22   b  and  22   c  of the fastening band  22 . Moreover, the width of the concave portion  30  is designed to be slightly larger than the width of the fastening band  22 , and the depth of the concave portion  30  is designed to be slightly larger than the thickness of the fastening band  22 . 
     The compression spring  20  applies a pressing force in the stack direction to the stack body including the cell stack  12 , the current collectors  14 , and the like. As shown in  FIGS. 1 and 2 , four compression springs  20  are disposed at positions corresponding to four corner portions of the cell stack  12 . 
     The fastening band  22  is a band-shaped or linear member having a square cross section and configured to fasten the cell stack  12 , the current collectors  14 , the insulating plates  16 , the end plates  18 , and the compression springs  20  in the stack direction. The fastening band  22  is formed by a material, such as stainless steel (SUS304 or the like) or chromium molybdenum steel, which excels in tensile strength and rust prevention. Then, as shown in  FIG. 6 , through holes  32  constituting a part of the connecting portion  24  are respectively formed at the end portions  22   e  and  22   f  of the fastening band  22 . 
     As described above, the thickness of the fastening band  22  is designed to be smaller than the depth of the concave portion  30  ( FIG. 5 ). Therefore, when the fastening band  22  is accommodated in the concave portion  30 , the fastening band  22  does not project from the surface  18   c  of the end plate  18 , and the size of the fuel cell  10  does not increase by the thickness of the fastening band  22 . The fastening band  22  does not have to be constituted by a single member extending over the entire length, and may be constituted by connecting a plurality of band-shaped or linear members with one another in a length direction. 
     The connecting portion  24  connects the end portion  22   e  and end portion  22   f  of the fastening band  22  on the surface  18   c  of the end plate  18 . As shown in  FIG. 6 , the connecting portion  24  is constituted by the through holes  32  respectively formed at the end portions  22   e  and  22   f  of the fastening band  22 , a bolt  34  inserted through the through holes  32 , and a nut  36  threadedly engaging with the bolt  34 . Therefore, a gap between the end portions  22   e  and  22   f  of the fastening band  22  can be adjusted by adjusting the length of thread engagement of the bolt  34  with respect to the nut  36 . Thus, the fastening power of the fastening band  22  can be adjusted. The connecting portion  24  does not have to be provided on the surface  18   c  of the end plate  18 . For example, the connecting portion  24  may be provided at a position facing a side surface spreading in a direction perpendicular to the stack direction of the cells  28  of the cell stack  12 . 
     A displacement restricting portion  26  is formed integrally with the end plate  18  on which the connecting portion  24  is located. The displacement restricting portion  26  restricts the displacement of the fastening band  22  in a direction away from the surface  18   c  of the end plate  18 . As shown in  FIGS. 3 and 5 , the displacement restricting portion  26  has a flat facing surface  38   c  which faces at least a part of a surface  22   d  of the fastening band  22  (to be specific, which covers at least a part of the surface  22   d  of the fastening band  22 ). In addition, the displacement restricting portion  26  includes: a plate shaped facing portion  38  disposed to intersect with (herein, to be perpendicular to) the concave portion  30 ; and two coupling portions  40   a  and  40   b  configured to couple the end plate  18  and both end portions  38   a  and  38   b  of the facing portion  38  in a direction intersecting with the concave portion  30 . 
     Then, two displacement restricting portions  26  are respectively provided on both sides of the connecting portion  24  to cover the fastening band  22 . These two displacement restricting portions  26  restrict the displacement of the end portions  22   e  and  22   f  of the fastening band  22 . The number of displacement restricting portions  26  for one fastening band  22  is not especially limited and may be one or three or more. In addition, the displacement restricting portion  26  does not have to be provided on the end plate  18  on which the connecting portion  24  is located. The displacement restricting portion  26  may be provided on the end plate  18  opposite to the end plate  18  on which the connecting portion  24  is located or may be provided on each of both end plates  18 . 
     When assembling the fuel cell  10  ( FIGS. 1 to 3 ), first, the current collector  14 , the insulating plate  16 , and the end plate  18  are disposed on each of both sides of the cell stack  12  in the stack direction, and the compression springs  20  are provided between the insulating plate  16  and the end plate  18  which are located on one side. Then, while these components are being fastened by the fastening bands  22  in the stack direction, the end portion  22   e  and end portion  22   f  of each fastening band  22  are connected to each other by the connecting portion  24 . 
     In order to apply the even surface pressure to the cell stack  12  and the current collectors  14 , it is necessary to equalize the fastening powers of four fastening bands  22 . Therefore, regarding the fastening band  22  which lacks the fastening power, the fastening power is increased by increasing the length of thread engagement of the bolt  34  with respect to the nut  36  ( FIG. 6 ). In contrast, regarding the fastening band  22  which has the excessive fastening power, the fastening power is reduced by reducing the length of thread engagement of the bolt  34  with respect to the nut  36 . 
     In a case where the connecting portion  24  loosens and the connection between the end portions  22   e  and  22   f  of the fastening band  22  is released or the fastening band  22  is cut on the surface  18   c  of the end plate  18  while the fuel cell  10  ( FIGS. 1 to 3 ) is being used or after the fuel cell  10  is discarded, “the elastic force of the cell stack  12 ”, “the elastic force of the compression spring  20 ”, and “the elastic force of the fastening band  22  itself” act on the fastening band  22 , and a portion of the fastening band  22  which portion is located on the surface  18   c  of the end plate  18  intends to displace in the direction away from the surface  18   c  of the end plate  18  while displacing in such a direction that the gap between the end portions  22   e  and  22   f  widens. 
     However, since the displacement of the fastening band  22  in the direction away from the surface  18   c  of the end plate  18  is restricted by the displacement restricting portion  26 , the fastening band  22  does not vigorously snap in such direction. Moreover, as can be imagined from  FIG. 5 , when the fastening band  22  displaces, the lower surface  22   a  of the fastening band  22  contacts the bottom surface  30   a  of the concave portion  30 , the surface  22   d  of the fastening band  22  contacts the facing surface  38   c  of the facing portion  38 , and the side surface  22   b  or  22   c  of the fastening band  22  contacts the inner side surface  30   b  or  30   c  of the concave portion  30 . Therefore, the power of the displacement of the fastening band  22  weakens by the frictional forces generated by the surface contact. On this account, accidents caused by the snapped fastening band  22  can be surely prevented. 
     In Embodiment 1, the displacement of the fastening band  22  “in the direction away from the surface  18   c  of the end plate  18 ” is restricted by the displacement restricting portion  26 , and the displacement of the fastening band  22  “in a direction parallel to the surface  18   c  of the end plate  18 ” and “in a direction perpendicular to the groove-shaped concave portion  30  (in the width direction of the fastening band  22 ))” is restricted by the inner side surfaces  30   b  and  30   c  of the concave portion  30 . Further, by providing a stopper portion  42  shown in  FIG. 7  on the fastening band  22 , the displacement of the fastening band  22  “in the direction parallel to the surface  18   c  of the end plate  18 ” and “in a direction parallel to the groove-shaped concave portion  30  (in the length direction of the fastening band  22 )) may also be restricted. 
     The stopper portion  42  ( FIG. 7 ) is constituted by two linear slits  44  and a stopper rod  50 . These two linear slits  44  extend in a longitudinal direction of the fastening band  22  on the fastening band  22  in parallel with each other. The stopper rod  50  is inserted through these two slits  44  while lifting up a center portion  46  of the fastening band  22  and is provided on surfaces of both end portions  48   a  and  48   b  sandwiching the center portion  46 . Therefore, in the fuel cell  10  including the stopper portion  42 , the stopper rod  50  or the center portion  46  of the fastening band  22  lifted up by the stopper rod  50  stops by the facing portion  38  of the displacement restricting portion  26  or by the coupling portions  40   a  and  40   b  of the displacement restricting portion  26 , so that the displacement of the fastening band  22  “in the direction parallel to the surface  18   c  of the end plate  18 ” and “in the direction parallel to the groove-shaped concave portion  30  (in the length direction of the fastening band  22 )” is restricted. 
     Embodiment 2 
       FIGS. 8(A) and 8(B)  are respectively a perspective view and a cross-sectional view showing main portions of a fuel cell  60  according to Embodiment 2 of the present invention. The fuel cell  60  is the same in configuration as the fuel cell  10  ( FIG. 1 ) according to Embodiment 1 except that the displacement restricting portion  26  of the fuel cell  10  is replaced with a displacement restricting portion  62 . 
     The displacement restricting portion  62  is formed integrally with the end plate  18  on which the connecting portion  24  is located. The displacement restricting portion  62  restricts the displacement of the fastening band  22  in the direction away from the surface  18   c  of the end plate  18 . The displacement restricting portion  62  includes: a planar facing surface  64   c  facing at least a part of the surface  22   d  of the fastening band  22 ; a plate shaped facing portion  64  disposed to intersect with (herein, be perpendicular to) the concave portion  30 ; and a coupling portion  66  configured to couple the end plate  18  and one end portion  64   a  of the facing portion  64  in a direction intersecting with the concave portion  30 . Then, an introducing port  68  through which the fastening band  22  is introduced into the concave portion  30  is formed between the other end portion  64   b  of the facing portion  64  and the surface  18   c  of the end plate  18 . 
     In accordance with Embodiment 2, the fastening band  22  disposed on the surface  18   c  of the end plate  18  can be moved in the width direction to be introduced through the introducing port  68  into the concave portion  30 . Therefore, it is unnecessary to cause the end portion  22   e  or  22   f  of the fastening band  22  to pass through a lower space A of the facing portion  64 . On this account, the fastening band  22  can be easily attached. 
     Modification Example of Connecting Portion 
     In Embodiment 2 ( FIG. 8 ), since the height of the connecting portion  24  is not limited by a height H0 ( FIG. 8(B) ) of the lower space A, the degree of freedom of the design of “the connecting portion” can be improved. For example, a connecting portion  70  shown in  FIG. 9  or a connecting portion  80  shown in  FIG. 10  can be used. 
     As shown in  FIG. 9 , the connecting portion  70  is constituted by two internal screw members  72  respectively formed at the end portions  22   e  and  22   f  of the fastening band  22  and one external screw member  74  connecting these two internal screw members  72  each other. 
     One of the internal screw members  72  has an internal screw  72   a  extending in the longitudinal direction of the fastening band  22 , and the other internal screw member  72  has an internal screw  72   b  extending in the longitudinal direction of the fastening band  22 . The internal screw  72   a  and the internal screw  72   b  are formed to be opposite to each other. Moreover, the external screw member  74  includes two external screws  74   a  and  74   b  formed on the same straight line and a tool stopper portion  74   c  formed between these two external screws  74   a  and  74   b  and having a polygonal cross section (square shape in the present embodiment). The external screw  74   a  and the external screw  74   b  are formed to be opposite to each other. Then, the external screw  74   a  and the internal screw  72   a  threadedly engage with each other, and the external screw  74   b  and the internal screw  72   b  threadedly engage with each other. Therefore, by applying a tool (not shown) to the tool stopper portion  74   c  to rotate the external screw member  74 , the length of thread engagement of the external screw  74   a,    74   b  with respect to the internal screw  72   a,    72   b  can be adjusted. Thus, the gap between the end portions  22   e  and  22   f  of the fastening band  22  can be adjusted. 
     As shown in  FIG. 10 , the connecting portion  80  includes two external screw members  82  respectively formed at the end portions  22   e  and  22   f  of the fastening band  22  and one internal screw member  84  connecting these two external screw members  82  each other. 
     One of the external screw members  82  has an external screw  82   a  extending in the longitudinal direction of the fastening band  22 , and the other external screw member  82  has an external screw  82   b  extending in the longitudinal direction of the fastening band  22 . The external screw  82   a  and the external screw  82   b  are formed to be opposite to each other. Moreover, the internal screw member  84  has two internal screws  84   a  and  84   b  formed on the same straight line and a tool stopper portion  84   c  formed on outer peripheral portions of these two internal screws  84   a  and  84   b  and having a polygonal cross section (hexagonal shape in the present embodiment). The internal screw  84   a  and the internal screw  84   b  are formed to be opposite to each other. Then, the internal screw  84   a  and the external screw  82   a  threadedly engage with each other, and the internal screw  84   b  and the external screw  82   b  threadedly engage with each other. Therefore, by applying a tool (not shown) to the tool stopper portion  84   c  to rotate the internal screw member  84 , the length of thread engagement of the external screw  82   a,    82   b  with respect to the internal screw  84   a,    84   b  can be adjusted. Thus, the gap between the end portions  22   e  and  22   f  of the fastening band  22  can be adjusted. 
     In the case of using the connecting portion  70  ( FIG. 9 ) or  80  ( FIG. 10 ), by designing the internal screw member  72  and the external screw member  82  such that each of a height H1 ( FIG. 9 ) of the internal screw member  72  and a height H2 ( FIG. 10 ) of the external screw member  82  is higher than the height H0 ( FIG. 8(B) ) of the lower space A of the facing portion  64 , each of the internal screw member  72  and the external screw member  82  can be stopped by the displacement restricting portion  62  ( FIG. 8 ). Therefore, the displacement of the fastening band  22  “in the direction parallel to the surface  18   c  of the end plate  18 ” and “in the direction parallel to the groove-shaped concave portion  30  (in the length direction of the fastening band  22 )” can be restricted. To be specific, in this case, each of the internal screw member  72  ( FIG. 9 ) and the external screw member  82  ( FIG. 10 ) can serve as the “stopper portion” instead of the stopper portion  42  ( FIG. 7 ). 
     Needless to say, the stopper portion  42  ( FIG. 7 ) can be used even in the case of using the connecting portion  70  ( FIG. 9 ) or  80  ( FIG. 10 ). 
     Embodiment 3 
       FIGS. 11(A) and 11(B)  are respectively a perspective view and a cross-sectional view showing main portions of a fuel cell  90  according to Embodiment 3 of the present invention. The fuel cell  90  is the same in configuration as the fuel cell  10  ( FIG. 1 ) according to Embodiment 1 except that the displacement restricting portion  26  of the fuel cell  10  is replaced with a displacement restricting portion  92 . 
     The displacement restricting portion  92  includes screw holes  94 , a plate shaped facing member  96 , and two bolts  98 . The screw holes  94  are respectively formed on both sides of the concave portion  30  on the surface  18   c  of the end plate  18 . The plate shaped facing member  96  has two through holes  96   a  corresponding to the screw holes  94  and faces at least a part of the surface  22   d  of the fastening band  22 . Each of the bolts  98  is inserted into the through hole  96   a  and threadedly engages with the screw hole  94 . 
     In accordance with Embodiment 3, after the fastening band  22  is accommodated in the concave portion  30 , the facing member  96  can be attached so as to cover the fastening band  22 . Therefore, the facing member  96  does not become an obstacle when attaching the fastening band  22 . Thus, the workability of attachment of the fastening band  22  can be improved. 
     Embodiment 4 
       FIGS. 12(A) and 12(B)  are respectively a perspective view and a cross-sectional view showing main portions of the fuel cell  100  according to Embodiment 4 of the present invention. The fuel cell  100  is the same in configuration as the fuel cell  10  ( FIG. 1 ) according to Embodiment 1 except that the displacement restricting portion  26  of the fuel cell  10  is replaced with a displacement restricting portion  102 . 
     The displacement restricting portion  102  includes a screw hole  104 , a stopper projecting portion  106 , a facing member  108 , and a bolt  110 . The screw hole  104  is formed on the surface of the end plate  18  on one side of the concave portion  30  in the width direction. The stopper projecting portion  106  is formed integrally with the end plate  18  on the other side of the concave portion  30  in the width direction. The facing member  108  has a through hole  108   a  corresponding to the screw hole  104  and faces at least a part of the surface  22   d  of the fastening band  22 . The bolt  110  is inserted through the through hole  108   a  and threadedly engages with the screw hole  104 . Then, a stopper groove  106   a  is formed on a side surface of the stopper projecting portion  106  which surface faces the concave portion  30 . Since one end portion  108   b  of the facing member  108  is stopped by the stopper groove  106   a,  the rotation of the facing member  108  about the bolt  110  is restricted. 
     In accordance with Embodiment 4, the facing member  108  can be easily attached to the end plate  18  only by one bolt  110 . 
     Embodiment 5 
       FIGS. 13(A) and 13(B)  are respectively a perspective view and a cross-sectional view showing main portions of a fuel cell  120  according to Embodiment 5 of the present invention. The fuel cell  120  is the same in configuration as the fuel cell  10  ( FIG. 1 ) according to Embodiment 1 except that the displacement restricting portion  26  of the fuel cell  10  is replaced with a displacement restricting portion  122 . 
     The displacement restricting portion  122  includes a screw hole  124 , an elongate hole  126 , and a bolt  128 . The screw hole  124  is formed on the bottom surface  30   a  of the groove-shaped concave portion  30 . The elongate hole  126  is formed on a center portion of the fastening band  22  in the width direction to extend in the longitudinal direction and corresponds to the screw hole  124 . The bolt  128  is inserted through the elongate hole  126  and threadedly engages with the screw hole  124 . A largest outer diameter of a head portion  128   a  of the bolt  128  is designed to be larger than a largest width of the elongate hole  126  such that the head portion  128   a  can cover at least a part of the surface  22   d  of the fastening band  22 . 
     In accordance with Embodiment 5, the displacement of the fastening band  22  in any direction can be restricted by an extremely simple configuration using one bolt  128 . Moreover, since the displacement of the fastening band  22  in the longitudinal direction is allowed to some extent in the elongate hole  126 , it is possible to prevent the bolt  128  from becoming an obstacle when adjusting the gap between the end portions  22   e  and  22   f  of the fastening band  22 . 
     Embodiment 6 
       FIG. 14  is a perspective view showing a fuel cell  130  according to Embodiment 6 of the present invention. The fuel cell  130  is the same in configuration as the fuel cell  10  ( FIG. 1 ) according to Embodiment 1 except that the displacement restricting portion  26  of the fuel cell  10  is replaced with a displacement restricting portion  132 . 
     The displacement restricting portion  132  includes a pair of attaching portions  134 , a bolt  136 , and a nut  138 . The attaching portions  134  respectively project on both end portions of the end plate  18  and respectively include through holes  134   a  facing each other. The bolt  136  is disposed to intersect with all the concave portions  30  and inserted through the through holes  134   a  of the pair of attaching portions  134 . The nut  138  threadedly engages with the bolt  136 . 
     In accordance with Embodiment 6, the displacement of all the fastening bands  22  can be easily restricted only by attaching the bolt  136  between the pair of attaching portions  134  after the fastening bands  22  are attached. 
     Needless to say, in Embodiment 3 to 6, the stopper portion  42  ( FIG. 7 ), the connecting portion  70  ( FIG. 9 ) or  80  ( FIG. 10 ) can be used. 
     Embodiment 7 
       FIG. 15  is a perspective view showing a fuel cell  140  according to Embodiment 7 of the present invention.  FIG. 16  is an exploded perspective view showing a part of the configuration of the fuel cell  140 . In the fuel cell  140 , a fastening band  142  is constituted by two band-shaped divided pieces  142   a  and  142   b.  Both end portions of the divided piece  142   a  in the length direction and both end portions of the divided piece  142   b  in the length direction are connected to each other by connecting portions  144  at positions other than the surface  18   c  of the end plate  18  (in Embodiment 7, positions facing the side surfaces of the cell stack  12  which surfaces are perpendicular to the stack direction of the cells  28 ). Moreover, three pipe members  146  each configured to supply a gas or a cooling medium to a plurality of cells  28  are connected to one of the end plates  18 , and these pipe members  146  serve as “the displacement restricting portions” which restrict the displacement of the fastening band  142  in the direction away from the surface  18   c  of the end plate  18 . 
     The width of each of the divided pieces  142   a  and  142   b  constituting the fastening band  142  is designed to be substantially the same as the width of the cell  28  such that the even surface pressure is applied to the cells  28  over the entire surfaces of the cells  28 . The divided piece  142   a  has three holes  148  through which three pipe members  146  are respectively inserted and each of which is formed to have an oval shape extending in the length direction of the fastening band  142 . Moreover, a plurality of tubular portions  150   a  extending in the width direction of the divided piece  142   a  are formed at both end portions of the divided piece  142   a  in the length direction so as to be spaced apart from one another in the width direction, and a plurality of tubular portions  150   b  extending in the width direction of the divided piece  142   b  are formed at both end portions of the divided piece  142   b  in the length direction so as to be spaced apart from one another in the width direction. Then, as shown in  FIG. 15 , the plurality of tubular portions  150   b  of the divided piece  142   b  are continuously provided among the plurality of tubular portions  150   a  of the divided piece  142   a,  and a coupling rod  152  ( FIG. 16 ) is inserted through insides of the tubular portions  150   a  and  150   b.  With this, the divided piece  142   a  and the divided piece  142   b  are connected to each other. 
     To be specific, in Embodiment 7, the connecting portion  144  is constituted by the plurality of tubular portions  150   a  of the divided piece  142   a,  the plurality of tubular portions  150   b  of the divided piece  142   b,  and the coupling rod  152 , and the fastening band  142  is constituted by connecting the divided piece  142   a  and the divided piece  142   b  using the connecting portion  144 . Then, one end portion and the other end portion of the fastening band  142  in the length direction are connected to each other by the other connecting portion  144 . In Embodiment 7, the fastening band  142  is constituted by two band-shaped divided pieces  142   a  and  142   b.  However, the fastening band  142  may be constituted by one band-shaped member or three or more band-shaped divided pieces. 
     As shown in  FIG. 17 , each of three pipe members  146  includes a pipe  160  through which a gas or a cooling medium flows and a joint  164  configured to cause the pipe  160  to be communicated with a passage (a gas passage or a cooling medium passage)  162  in the cell stack  12 . The joint  164  includes an end plate connecting portion  166 , a pipe connecting portion  168 , and a coupling member  170 . The end plate connecting portion  166  is fixed to a through hole  18   d  of the end plate  18  by an adhesive or the like. The pipe connecting portion  168  is fixed to an end portion of the pipe  160  by an adhesive or the like. The coupling member  170  causes the end plate connecting portion  166  and the pipe connecting portion  168  to be detachably coupled to each other. The coupling member  170  is configured to have an annular shape by detachably connecting two divided pieces  170   a  and  170   b  divided in a diametrical direction. A stopper portion  172   a  configured to be stopped by a flange  166   a  of the end plate connecting portion  166  is formed at one axial end portion of each of the divided pieces  170   a  and  170   b,  and a stopper portion  172   b  configured to be stopped by a flange  168   a  of the pipe connecting portion  168  is formed at the other axial end portion of each of the divided pieces  170   a  and  170   b.    
     The shape and outer diameter of a portion of the end plate connecting portion  166  which portion projects from the surface  18   c  of the end plate  18  are designed such that this portion can be inserted through the hole  148  of the fastening band  142 . The shape and outer diameter of the coupling member  170  are designed such that a part of the coupling member  170  can face at least a part of a surface of the fastening band  142 . Therefore, in a state where the end plate connecting portion  166  is inserted through the hole  148  of the fastening band  142 , and the end plate connecting portion  166  and the pipe connecting portion  168  are connected to each other by the coupling member  170 , the fastening band  142  can be provided along the surface  18   c  of the end plate  18 , and the displacement of the fastening band  142  in the direction away from the surface  18   c  of the end plate  18  can be restricted by a part (that is, the facing portion) of the coupling member  170 . 
     In Embodiment 7, the end plate connecting portion  166  is fixed to the through hole  18   d  by an adhesive or the like. However, the end plate connecting portion  166  may be detachably connected to the through hole  18   d  by a screw structure or the like. In this case, after the fastening band  142  is provided along the surface  18   c  of the end plate  18 , the end plate connecting portion  166  can be attached to the through hole  18   d . Therefore, a part of the end plate connecting portion  166  can be designed so as to be able to face at least a part of the surface of the fastening band  142 , and the displacement of the fastening band  142  in the direction away from the surface  18   c  of the end plate  18  can be restricted by a part (that is, the facing portion) of the end plate connecting portion  166 . 
     Moreover, the type of the “joint” configured to cause the pipe  160  to be communicated with the passage  162  in the cell stack  12  is not especially limited. Instead of the joint  164  ( FIG. 17 ), a known “joint” may be suitably selected and used. 
     Further, the number of pipe members  146  is not especially limited and may be one, two, or four or more. 
     Modification Example of Pipe Member 
     For example, the pipe member  180  shown in  FIG. 18  or the pipe member  190  shown in  FIG. 19  may be used as “the pipe member” constituting at least a part of “the displacement restricting portion”. 
     As shown in  FIG. 18 , the pipe member  180  is a “pipe” which is bend in a substantially L shape, an end portion of the pipe member  180  is connected to the through hole  18   d  of the end plate  18 , and a part of the pipe member  180  is provided along the surface  18   c  of the end plate  18 . Therefore, in this modification example, a part of the pipe member  180  is provided to face at least a part of the surface of the fastening band  142 , and the displacement of the fastening band  142  in the direction away from the surface  18   c  of the end plate  18  can be restricted by a part (that is, the facing portion) of the pipe member (pipe)  180 . To be specific, the pipe member (pipe)  180  has the function of “the displacement restricting portion”. 
     As shown in  FIG. 19 , the pipe member  190  is a substantially straight “pipe”, and an end portion of the pipe member  190  is connected to the through hole  18   d  of the end plate  18 . Then, an annular (or projecting) facing member  192  is attached to an outer peripheral surface of the pipe member  190 . The shape and outer diameter of the facing member  192  are designed such that the facing member  192  can face at least a part of the surface of the fastening band  142 . Therefore, in this modification example, the displacement of the fastening band  142  in the direction away from the surface  18   c  of the end plate  18  can be restricted by the facing member  192 . To be specific, the pipe member (pipe)  190  and the facing member  192  have the function of “the displacement restricting portion”. 
     Method for Disassembling Fuel Cell 
     In the fuel cells  90  ( FIG. 11 ),  100  ( FIG. 12 ),  120  ( FIGS. 13 ), and  130  ( FIG. 14 ) according to Embodiments 3 to 6 and the mode ( FIG. 19 ) using the facing member  192  of the fuel cell  140  ( FIG. 15 ) according to Embodiment 7, after one end portion and the other end portion of the fastening band  22 ,  142  are connected to each other by the connecting portion  24 ,  70 ,  80 ,  144 , the displacement restricting portion  92 ,  102 ,  122 ,  132  or the facing member  192  as “the displacement restricting portion” can be configured. Therefore, the displacement restricting portion can be configured when manufacturing the fuel cell and when disassembling the fuel cell. 
     To be specific, when disassembling the fuel cells  90 ,  100 ,  120 ,  130 , and  140  according to Embodiments 3 to 7, it is possible to adopt “a fuel cell disassembling method” including the steps of (a) disposing on at least one of two end plates  18  the displacement restricting portion  92 ,  102 ,  122 ,  132  or the facing member  192  configured to restrict the displacement of the fastening band  22 ,  142  in the direction away from the surface  18   c  of the end plate  18 ; and (b) releasing the connection between one end portion and the other end portion of the fastening band  22 ,  142  at the connecting portion  24 ,  70 ,  80 ,  144  while restricting the displacement of the fastening band  22 ,  142  by the displacement restricting portion  92 ,  102 ,  122 ,  132  or the facing member  192 . 
     In accordance with this “fuel cell disassembling method”, the displacement restricting portion can be disposed on the end plate  18  only when disassembling the fuel cell. Therefore, it is unnecessary to dispose the displacement restricting portion on the end plate  18  in advance, and the manufacturing cost of the fuel cell can be reduced. 
     REFERENCE SIGNS LIST 
     A: lower space 
       10 ,  60 ,  90 ,  100 ,  120 ,  130 ,  140 : fuel cell 
       12 : cell stack 
       14 : current collector 
       16 : insulating plate 
       18 : end plate 
       20 : compression spring 
       22 : fastening band 
       24 ,  70 ,  80 : connecting portion 
       26 ,  62 ,  92 ,  102 ,  122 ,  132 : displacement restricting portion 
       146 ,  180 ,  190 : pipe member (displacement restricting portion) 
       28 : cell 
       30 : concave portion 
       38 ,  64 : facing portion 
       96 ,  108 ,  192 : facing member 
       40   a,    40   b,    66 : coupling portion 
       42 : stopper portion