Abstract:
In a fuel cell stack constituting a fuel cell module, electrolyte/electrode assemblies and separators are alternately laminated. An electrolyte/electrode assembly is arranged on one end of the fuel cell stack in the lamination direction, while a separator is arranged on the other end of the fuel cell stack in the lamination direction. A terminal separator is arranged adjacent to the electrolyte/electrode assembly, while a load relaxation member is arranged adjacent to the separator. The terminal separator controls the supply of a fuel gas to a fuel gas channel, and the load relaxation member is configured of a laminate of a plurality of flat metal plates.

Description:
RELATED APPLICATIONS 
     This application is a 35 U.S.C. 371 national stage filing of International Application No. PCT/JP2010/056991, filed Apr. 20, 2010, which claims priority to Japanese Patent Application No. 2009-108042 filed on Apr. 27, 2009 in Japan. The contents of the aforementioned applications are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to a fuel cell module including a fuel cell stack formed by stacking electrolyte electrode assemblies and separators alternately. Each of the electrolyte electrode assemblies includes an anode, a cathode, and an electrolyte interposed between the anode and the cathode. 
     BACKGROUND ART 
     Typically, a solid electrolyte fuel cell (SOFC) employs an electrolyte of ion-conductive oxide such as stabilized zirconia. The electrolyte is interposed between an anode and a cathode to form an electrolyte electrode assembly (MEA). The electrolyte electrode assembly is interposed between separators (bipolar plates). In use, normally, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack. 
     In the fuel cell stack, since the electrolyte electrode assemblies and the separators are stacked alternately in the vertical direction, in particular, the entire weight of the fuel cell is directly applied to the fuel cell (electrolyte electrode assemblies and separators) provided at the lowermost position of the fuel cell stack. Therefore, the fuel cell at the lowermost position of the fuel cell stack tends to be damaged easily. 
     In this regard, for example, structure disclosed in Japanese Laid-Open Patent Publication No. 2002-280052 is known. As shown in  FIG. 13 , according to the disclosure of Japanese Laid-Open Patent Publication No. 2002-280052, a fuel cell  1  is formed by stacking power generation cells  2  and separators  3  alternately in a vertical direction. A single fuel end plate  4  is stacked at the end of the fuel cell  1  at the lowermost position, and a single air end plate  5  is stacked at the end of the fuel cell  1  at the uppermost position. 
     The fuel cell  1  is placed on a base plate  6 , and connection members  7  are inserted into four corners. Screw holes  8  are formed at four corners of the separator  3 , at four corners of the air end plate  5 , and at four corners of the fuel end plate  4 . Screws  9  are screwed into the screw holes  8 , and surface to surface contact is applied between tip ends of the screws  9  and the connection members  7 . 
     In the structure, it is possible to maintain the load applied to the power generation cells  2  at the lower positions of the fuel cell  1  to be substantially the same as the load applied to the other power generation cells  2 . According to the disclosure, the load is not applied to the power generation cells  2  excessively, and damages of the power generation cells  2  can be prevented. 
     SUMMARY OF INVENTION 
     Since the fuel cell  1  adopts structure where the screw holes  8  are formed at the four corners of the separator  3 , the air end plate  5 , and the fuel end plate  4 , and the screws  9  are screwed into the screw holes  8 , the overall structure of the fuel cell  1  is considerably complicated. 
     The present invention has been made to solve the problem of this type, and an object of the present invention is to provide a fuel cell module having simple and economical structure in which it is possible to reliably prevent damages or the like of MEAs due to the own weight of the MEAs positioned at ends, reduce the amount of wastefully discharged fuel gas as much as possible, and achieve improvement in the efficiency. 
     The present invention relates to a fuel cell module including a fuel cell stack formed by stacking electrolyte electrode assemblies and separators alternately in a stacking direction. Each of the electrolyte electrode assemblies includes an anode, a cathode, and an electrolyte interposed between the anode and the cathode. A fuel gas channel for supplying a fuel gas along an electrode surface of the anode is formed on one surface of the separator and an oxygen-containing gas channel for supplying an oxygen-containing gas along an electrode surface of the cathode is formed on the other surface of the separator. 
     The fuel cell stack has the electrolyte electrode assembly at one end in the stacking direction, and has the separator at another end in the stacking direction. An end separator is provided at the one end in the stacking direction, adjacent to the electrolyte electrode assembly. The end separator is configured to limit supply of the fuel gas to the fuel gas channel, and allow supply of the oxygen-containing gas to the oxygen-containing gas channel. A load absorption member having a shape similar to the electrolyte electrode assembly is provided at the other end in the stacking direction, adjacent to the separator. 
     According to the present invention, at one end of the fuel cell stack in the stacking direction, the end separator limiting the supply of the fuel gas to the fuel gas channel is provided. Therefore, the fuel gas is not supplied wastefully. In the structure, consumption of the fuel gas is reduced, and the fuel gas can be supplied efficiently. 
     Further, since the load absorption member is provided at the other end of the fuel cell stack in the stacking direction, the load in the stacking direction is suitably absorbed, and damages of the electrolyte electrode assembly can be prevented. Further, since the load absorption member is provided instead of the electrolyte electrode assembly, damages of the electrolyte electrode assembly can be prevented without increasing the number of stacked components. Moreover, wasteful consumption of the fuel cell is reduced suitably. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross sectional view showing a fuel cell module according to a first embodiment of the present invention; 
         FIG. 2  is a perspective view schematically showing a fuel cell stack of the fuel cell module; 
         FIG. 3  is a cross sectional view showing the fuel cell stack, taken along a line III-III in  FIG. 2 ; 
         FIG. 4  is an exploded perspective view showing the fuel cell; 
         FIG. 5  is a partially exploded perspective view showing gas flows in the fuel cell; 
         FIG. 6  is a cross sectional view schematically showing operation of the fuel cell; 
         FIG. 7  is a partially exploded perspective view showing the fuel cell stack; 
         FIG. 8  is a view showing operation of assembling the fuel cell stack; 
         FIG. 9  is a cross sectional view showing a load absorption member of a fuel cell module according to a second embodiment of the present invention; 
         FIG. 10  is a cross sectional view showing a load absorption member of a fuel cell module according to a third embodiment of the present invention; 
         FIG. 11  is a cross sectional view showing a load absorption member of a fuel cell module according to a fourth embodiment of the present invention; 
         FIG. 12  is a cross sectional view showing a load absorption member of a fuel cell module according to a fifth embodiment of the present invention; and 
         FIG. 13  is a cross sectional view showing a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2002-280052. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     As shown in  FIGS. 1 to 3 , a fuel cell module  10  according to a first embodiment of the present invention is used in various applications, including stationary and mobile applications. For example, the fuel cell module  10  is mounted on a vehicle. 
     The fuel cell module  10  includes a fuel cell stack  12 , a heat exchanger  14  for heating the oxygen-containing gas before it is supplied to the fuel cell stack  12 , an evaporator  15  for evaporating water to produce a mixed fuel of the raw fuel and the water vapor, a reformer  16  for reforming the mixed fuel to produce a reformed gas, and a casing  17  containing the fuel cell stack  12 , the heat exchanger  14 , the evaporator  15 , the reformer  16 , and a load applying mechanism  19  as described later. 
     The reformer  16  reforms higher hydrocarbons (C 2+ ) such as ethane (C 2 H 6 ), propane (C 3 H 8 ), and butane (C 4 H 10 ) in the city gas (raw fuel) to produce the fuel gas chiefly containing methane (CH 4 ), hydrogen, and CO by steam reforming as a preliminary reformer, and the reformer  16  is operated at an operating temperature of several hundred degrees Celsius. 
     In the casing  17 , a fluid unit  18  including at least the heat exchanger  14 , the evaporator  15 , and the reformer  16  is disposed on one side of the fuel cell stack  12 , and the load applying mechanism  19  for applying a tightening load in the stacking direction indicated by an arrow A is disposed on the other side of the fuel cell stack  12 . The fluid unit  18  and the load applying mechanism  19  are provided symmetrically with respect to the axis of the fuel cell stack  12 . 
     The fuel cell stack  12  includes a plurality of solid oxide fuel cells  12   a  stacked in the direction indicated by the arrow A. As shown in  FIGS. 4 and 5 , the fuel cell  12   a  includes electrolyte electrode assemblies (MEAs)  26 . Each of the electrolyte electrode assemblies  26  includes a cathode  22 , an anode  24 , and an electrolyte (electrolyte plate)  20  interposed between the cathode  22  and the anode  24 . For example, the electrolyte  20  is made of ion-conductive oxide such as stabilized zirconia. 
     The electrolyte electrode assembly  26  has a circular disk shape. A barrier layer (not shown) is provided at least at the outer circumferential edge of the electrolyte electrode assembly  26  for preventing the entry or discharge of the oxygen-containing gas and the fuel gas. Four electrolyte electrode assemblies  26  are sandwiched between a pair of separators  28 . The four electrolyte electrode assemblies  26  are provided on a circle concentrically around a fuel gas supply passage  30  extending through the center of the separators  28 . 
     As shown in  FIG. 4 , each of the separators  28  includes, e.g., one metal plate of stainless alloy etc., or a carbon plate. A fuel gas supply section (reactant gas supply section)  32  is formed at the center of the separator  28 , and the fuel gas supply passage  30  extends through the fuel gas supply section  32 . Four first bridges  34  extend radially outwardly from the fuel gas supply section  32  at equal intervals, e.g., 90°. The fuel gas supply section  32  is integral with sandwiching sections  36  each having a relatively large diameter, through the first bridges  34 . The centers of sandwiching sections  36  are equally distanced from the center of the fuel gas supply section  32 . 
     Each of the sandwiching sections  36  has a circular disk shape, having substantially the same dimensions as the electrolyte electrode assembly  26 . The sandwiching sections  36  are separated from each other. A fuel gas inlet  38  for supplying the fuel gas is formed at the center of the sandwiching section  36 , or at an upstream position deviated from the center of the sandwiching section  36  in the flow direction of the oxygen-containing gas. 
     Each of the sandwiching sections  36  has a fuel gas channel  40  on a surface  36   a  which contacts the anode  24 , for supplying a fuel gas along an electrode surface of the anode  24 . Further, a fuel gas discharge channel  42  for discharging the fuel gas partially consumed in the fuel gas channel  40  and a circular arc wall  44  forming a detour path to prevent the fuel gas from flowing straight from the fuel gas inlet  38  to the fuel gas discharge channel  42  are provided on the surface  36   a.    
     The circular arc wall  44  has a substantially horseshoe shape. The fuel gas inlet  38  is provided inside the circular arc wall  44 , and the fuel gas discharge channel  42  is provided on a proximal end side of the sandwiching section  36 , near the first bridge  34 . On the surface  36   a , a circumferential protrusion  46  and a plurality of projections  48  are provided. The circumferential protrusion  46  protrudes toward the fuel gas channel  40 , and contacts the outer edge of the anode  24 , and the projections  48  contact the anode  24 . 
     The protrusion  46  has a substantially ring shape with partial cutaway at a position corresponding to the fuel gas discharge channel  42 . The projections  48  are made of solid portions formed by, e.g., etching, or hollow portions formed by press forming. 
     As shown in  FIGS. 6 and 7 , each of the sandwiching sections  36  has a substantially planar surface  36   b  which faces the cathode  22 . A plate  50  having a circular disk shape is fixed to the surface  36   b , e.g., by brazing, diffusion bonding, laser welding, or the like. A plurality of projections  52  are provided on the plate  50 , e.g., by press forming. By the projections  52 , an oxygen-containing gas channel  54  for supplying an oxygen-containing gas along an electrode surface of the cathode  22  is formed on the side of the surface  36   b  of the sandwiching section  36 . The projections  52  function as a current collector. 
     Extensions  56  extend from the outer circumferential positions of the respective sandwiching sections  36 . The extensions  56  are used for collecting and measuring generated electrical energy from the electrolyte electrode assemblies  26 , positioning the electrolyte electrode assemblies  26  to the separators  28 , and detecting the number of fuel cells (see  FIGS. 4 and 5 ). 
     As shown in  FIG. 4 , a channel member  60  is fixed to a surface of the separator  28  facing the cathode  22 , e.g., by brazing, diffusion bonding, or laser welding. The channel member  60  has a planar shape. The fuel gas supply passage  30  extends through a fuel gas supply section  62  at the center thereof in the channel member  60 . A predetermined number of reinforcement bosses  63  are formed in the fuel gas supply section  62 . 
     Four second bridges  64  extend radially from the fuel gas supply section  62 . Each of the second bridges  64  is fixed to the separator  28  from the first bridge  34  to the surface  36   b  of the sandwiching section  36  to cover the fuel gas inlet  38  (see  FIG. 6 ). 
     From the fuel gas supply section  62  to the second bridge  64 , a fuel gas supply channel  66  connecting the fuel gas supply passage  30  to the fuel gas inlet  38  is formed. For example, the fuel gas supply channel  66  is formed by, e.g., etching. 
     As shown in  FIG. 6 , the oxygen-containing gas channel  54  is connected to an oxygen-containing gas supply passage  68  for supplying the oxygen-containing gas from a space between an inner circumferential edge of the electrolyte electrode assembly  26  and an inner circumferential edge of the sandwiching section  36  in a direction indicated by an arrow B. The oxygen-containing gas supply passage  68  extends between the inside of the respective sandwiching sections  36  and the respective first bridges  34  in the stacking direction indicated by the arrow A. 
     An insulating seal  70  for sealing the fuel gas supply passage  30  is provided between the separators  28 . For example, crystal component material such as mica material and ceramic material, glass material, and composite material of clay and plastic may be used for the insulating seal  70 . The insulating seal  70  seals the fuel gas supply passage  30  from the electrolyte electrode assemblies  26 . For the fuel cell stack  12 , an exhaust gas channel  72  is provided outside (around) the sandwiching sections  36 . 
     As shown in  FIG. 4 , a flow rectifier member  74  is provided in each space between the adjacent sandwiching sections  36  for rectifying the flow of the oxygen-containing gas supplied from the oxygen-containing gas supply passage  68 , and flowing through the oxygen-containing gas channel  54  along the surface of each electrolyte electrode assembly  26  and rectifying the flow of the fuel gas flowing in the fuel gas channel  40  along the surface of each electrolyte electrode assembly  26 . The flow rectifier member  74  is a plate having a substantially fan shape. A predetermined number of the flow rectifier members  74  are stacked in the direction indicated by the arrow A. The number of the flow rectifier members  74  in a plan view is four, corresponding to positions between the sandwiching sections  36 . 
     The flow rectifier member  74  is formed by joining an electrically insulating member of, e.g., mica material, with silicone resin. The flow rectifier member  74  is provided along part of the outer edge of the sandwiching section  36  and part of the circumscribed circle of the separator  28 . One end of the flow rectifier member  74  along the part of the sandwiching section  36  is provided near the joint positions between the sandwiching sections  36  and the first bridges  34 , and an outer circumferential portion  78  as the other end of the flow rectifier member  74  form part of the circumscribed circle of the separator  28 . 
     The one end of the flow rectifier member  74  includes a cutout  80  which is cut in a direction away from the oxygen-containing gas supply passage  68  and the fuel gas supply passage  30 . Circular arc portions  82  respectively corresponding to the outer shapes of the sandwiching sections  36  are formed on both sides of the flow rectifier member  74 . 
     As shown in  FIGS. 7 and 8 , an end separator  84  is provided at one end of the fuel cell stack  12  in the direction in which the electrolyte electrode assemblies  26  and the separators  28  are stacked together (an upper end during assembling operation as shown in  FIG. 8 , and a lower end during the use in power generation as shown in  FIG. 7 ). The end separator  84  is provided adjacent to the electrolyte electrode assemblies  26 . The end separator  84  has structure substantially similar to that of the separator  28 , and the end separator  84  is produced by eliminating the step of forming the fuel gas inlet  38  during the production process of the separator  28 . 
     Load absorption members  86  are provided at the other end of the fuel cell stack  12  in the stacking direction (a lower end during assembling operation as shown in  FIG. 8 , and an upper end during the use in power generation as shown in  FIG. 7 ). The load absorption members  86  are provided adjacent to the separators  28 . 
     The load absorption member  86  has a shape that is similar to that of the electrolyte electrode assembly  26 , i.e., has a circular disk shape. The load absorption member  86  is a metal stack body formed by integrally stacking a plurality of flat metal plates  86   a.    
     As shown in  FIGS. 2 and 3 , an end plate  88   a  having a substantially circular disk shape is provided at the other end of the fuel cell stack  12 . The end plate  88   a  is provided adjacent to the load absorption member  86 . Further, the fuel cell stack  12  includes a plurality of end plates  88   b  and a fixing ring  88   c  at the one end of the fuel cell stack  12 , next to a partition wall (terminal plate)  90  adjacent to the end separator  84 . Each of the end plates  88   b  has a small diameter, and a substantially circular shape, and the fixing ring  88   c  has a large diameter, and a substantially ring shape. The partition wall  90  prevents diffusion of the exhaust gas to the outside of the separator  28 . The number of end plates  88   b  is four, corresponding to the positions of stacking the electrolyte electrode assemblies  26 . 
     The end plate  88   a  and the fixing ring  88   c  include a plurality of holes  92 . Bolt insertion collar members  94  are integrally inserted into the flow rectifier member  74  in the stacking direction. Bolts  96  are inserted into the holes  92  and the bolt insertion collar members  94 , and screwed into nuts  98 . By the bolts  96  and the nuts  98 , the end plate  88   a  and the fixing ring  88   c  are fixedly tightened together. 
     One fuel gas supply pipe  100 , a casing  102 , and one oxygen-containing gas supply pipe  104  are provided at the end plate  88   a . The fuel gas supply pipe  100  is connected to the fuel gas supply passage  30 . The casing  102  has a cavity  102   a  connected to the respective oxygen-containing gas supply passages  68 . The oxygen-containing gas supply pipe  104  is connected to the casing  102 , and to the cavity  102   a.    
     A support plate member  110  is fixed to the end plate  88   a  through a plurality of bolts  96 , nuts  106   a ,  106   b , and plate collar members  108 . A first tightening load applying unit  112  for applying a first tightening load to the fuel gas supply sections  32 ,  62  (gas sealing position), and second tightening load applying units  114  for applying a second tightening load to each of the electrolyte electrode assemblies  26  are provided between the support plate member  110  and the end plate  88   a . The second tightening load is smaller than the first tightening load. The first tightening load applying unit  112  and the second tightening load applying units  114  form the load applying mechanism  19 . 
     The load applying mechanism  19  is provided on the end plate  88   b  side, and the first tightening load applying unit  112  and the second tightening load applying unit  114  support the load in the stacking direction through the end plate  88   a.    
     The first tightening load applying unit  112  includes a presser member  116  provided at the center of the fuel cell stack  12  (centers of the fuel gas supply sections  32 ,  62 ) for preventing leakage of the fuel gas from the fuel gas supply passage  30 . The presser member  116  is provided near the center of the four end plates  88   b  for pressing the fuel cell stack  12 . 
     A first spring  120  is provided at the presser member  116  through a first receiver member  118   a  and a second receiver member  118   b . A tip end of a first presser bolt  122  contacts the second receiver member  118   b . The first presser bolt  122  is screwed into a first screw hole  124  formed in the support plate member  110 . The position of the first presser bolt  122  is adjustable through a first nut  126 . 
     Each of the second tightening load applying units  114  includes a third receiver member  128   a  at the end plate  88   b , corresponding to each of the electrolyte electrode assemblies  26 . The third receiver member  128   a  is positioned on the end plate  88   b  through a pin  130 . One end of a second spring  132  contacts the third receiver member  128   a  and the other end of the second spring  132  contacts a fourth receiver member  128   b . A tip end of a second presser bolt  134  contacts the fourth receiver member  128   b . The second presser bolt  134  is screwed into a second screw hole  136  formed in the support plate member  110 . The position of the second presser bolt  134  is adjustable through a second nut  138 . 
       FIG. 1  shows an orientation of the fuel cell module during the use in power generation. The casing  17  includes a first case unit  160   a  containing the load applying mechanism  19 , and a second case unit  160   b  containing the fuel cell stack  12  at upper and lower positions. The joint portion between the first case unit  160   a  and the second case unit  160   b  is tightened by screws  162  and nuts  164  through the partition wall  90 . The partition wall  90  functions as a gas barrier for preventing entry of the hot exhaust gas or the hot air from the fluid unit  18  into the load applying mechanism  19 . An end of a ring shaped wall plate  166  is joined to the second case unit  160   b , and a head plate  168  is fixed to the other end of the wall plate  166 . 
     A fuel gas supply pipe  170  is connected to the evaporator  15 . The fuel gas supply pipe  170  is connected to a raw fuel supply unit (not shown) for supplying a raw fuel (methane, ethane, propane, or the like). The outlet of the evaporator  15  is connected to the inlet of the reformer  16 . An exhaust gas pipe  172  is provided adjacent to the fuel gas supply pipe  170 . 
     An oxygen-containing gas supply pipe  174  is connected to the head plate  168 , and the oxygen-containing gas supply pipe  174  extends through a channel  176  in the casing  17 , and connects the heat exchanger  14  to the oxygen-containing gas supply passage  68 . 
     Operation of the fuel cell module  10  will be described below. 
     As shown in  FIG. 1 , the air ejected from an air pump (not shown) as an oxygen-containing gas is supplied from the oxygen-containing gas supply pipe  174  to the channel  176  in the casing  17 . The air is heated by the heat exchanger  14 , and then, the air is supplied through the oxygen-containing gas supply pipe  104  to each of the oxygen-containing gas supply passages  68  through the cavity  102   a.    
     A raw fuel (methane, ethane, propane or the like) is supplied from the fuel gas supply pipe  170  to the reformer  16 , and water is supplied from the fuel gas supply pipe  170  to the reformer  16 . The raw fuel flows through the reformer  16 , and the raw fuel is reformed to produce a fuel gas (hydrogen-containing gas). The fuel gas is supplied from the fuel gas supply pipe  100  connected to the end plate  88   a  to the fuel gas supply passage  30 . 
     As shown in  FIG. 6 , the fuel gas flows along the fuel gas supply passage  30  of the fuel cell stack  12  in the stacking direction indicated by the arrow A. The fuel gas moves through the fuel gas supply channel  66  along the surface of the separator  28 . 
     The fuel gas flows from the fuel gas supply channel  66  into the fuel gas channel  40  through the fuel gas inlet  38  formed in the sandwiching section  36 . The fuel gas inlet  38  is provided at substantially the central position of the anode  24  of each electrolyte electrode assembly  26 . Thus, the fuel gas is supplied from the fuel gas inlet  38  to substantially the central region of the anode  24 , and flows along the fuel gas channel  40  to the outer circumferential region of the anode  24 . 
     Under the rectifying operation of the flow rectifier member  74 , the oxygen-containing gas is supplied to the oxygen-containing gas supply passage  68 , and flows into the space between the inner circumferential edge of the electrolyte electrode assembly  26  and the inner circumferential edge of the sandwiching section  36 , and flows in the direction indicated by the arrow B toward the oxygen-containing gas channel  54 . In the oxygen-containing gas channel  54 , the oxygen-containing gas flows from the inner circumferential edge (center of the separator  28 ) to the outer circumferential edge (outer circumferential edge of the separator  28 ) of the electrolyte electrode assembly  26 . 
     Thus, in each of the electrolyte electrode assemblies  26 , the fuel gas flows from the center to the outer circumferential side on the electrode surface of the anode  24 , and the oxygen-containing gas flows in one direction indicated by the arrow B on the electrode surface of the cathode  22 . At this time, oxide ions move through the electrolyte  20  toward the anode  24  for generating electricity by chemical reactions. 
     The exhaust gas chiefly containing the air after partial consumption in the power generation reaction is discharged to the outer circumferential region of each of the electrolyte electrode assemblies  26 , and flows through the exhaust gas channels  72  as the off gas, and the off gas is discharged from the fuel cell stack  12  (see  FIG. 1 ). 
     In the first embodiment, as shown in  FIG. 8 , the end plate  88   a  is provided at the lowermost position during the assembling operation of the fuel cell stack  12 , and the fluid unit  18  is provided at the end plate  88   a . Firstly, the four load absorption members  86  are disposed on the end plate  88   a.    
     Then, the separator  28  is placed on the load absorption members  86  such that each oxygen-containing gas channel  54  is oriented toward the load absorption members  86 . Then, the four electrolyte electrode assemblies  26  are provided on the separator  28  at positions corresponding to the load absorption members  86 . Then, the separators  28  and the electrolyte electrode assemblies  26  are provided alternately in the vertical direction upwardly. 
     Then, during the assembling operation, after the electrolyte electrode assemblies  26  at the uppermost position in the vertical direction are placed, the end separator  84  is placed on the electrolyte electrode assemblies  26 . The end plate  88   b  is stacked on the end separator  84 , and the load applying mechanism  19  is stacked on the end plate  88   b.    
     As described above, the end separator  84  is provided at one end of the fuel cell stack  12  in the stacking direction (upper end during the assembling operation), and the end separator  84  limits the supply of the fuel gas to the fuel gas channel  40 . In the structure, the fuel gas is not wastefully supplied from the fuel gas channel  40  to the end plate  88   b . Consumption of the fuel gas is reduced, and the fuel gas can be supplied efficiently. 
     Further, the load absorption members  86  are provided at the other end of the fuel cell stack  12  in the stacking direction (lower end during the assembling operation). In the structure, by the load absorption members  86  provided at the lowermost position during the assembling operation of the fuel cell stack  12 , the load in the stacking direction (weights of the separators  28  and the electrolyte electrode assemblies  26 ) are absorbed suitably, and the damages or the like of the electrolyte electrode assemblies  26  can be prevented. 
     Further, in effect, the load absorption members  86  disposed at the lowermost position during the assembling operation are used instead of the electrolyte electrode assemblies  26 . In the structure, the damages of the electrolyte electrode assembles  26  can be prevented without increasing the number of the stacked fuel cells of the fuel cell stack  12 , and the wasteful consumption of the fuel gas can be reduced suitably. 
     Further, the fuel gas inlet  38  for supplying the fuel gas to the fuel gas channel  40  is formed in the separator  28 , the fuel gas inlet  38  is not formed in the end separator  84 . In this respect, the end separator  84  is different from the separator  28 . In the structure, the end separator  84  can be produced in the same manner as the separator  28 , simply by eliminating the process of forming the fuel gas inlet  38 . Thus, the production cost can be reduced suitably. 
     Further, the fuel gas is not unnecessarily discharged from the end separator  84  that is not used for power generation. Therefore, wasteful consumption of the fuel gas can be prevented effectively. 
     Further, in the end separator  84 , the fuel gas channel  40  is positioned at the extreme end of the fuel cell stack  12  in the stacking direction, i.e., the fuel gas channel  40  is oriented toward the end plate  88   b . In the structure, no electrolyte electrode assemblies  26  are provided outside the end separator  84  in the stacking direction. For example, by providing the end separator  84  on the lower side during assembling or during operating, buckling and damages of the electrolyte electrode assemblies  26  can be prevented. Moreover, since the fuel gas is not wastefully supplied to the extreme end of the fuel cell stack  12 , consumption of the fuel gas is reduced, and power generation operation can be performed efficiently. 
     Further, the load absorption member  86  is the metal stack body formed by integrally stacking the plurality of flat metal plates  86   a . In the structure, in the fuel cell stack  12 , the electrical energy produced in the power generation can be transmitted efficiently, and the load in the stacking direction is absorbed. Further, buckling or damages of the electrolyte electrode assemblies  26  can be prevented. 
     Further, at the time of stacking components of the fuel cell stack  12 , the load absorption members  86  are provided on the lower side (see  FIG. 8 ), and during power generation of the fuel cell stack  12 , as shown in  FIG. 1 , the end separator  84  is provided on the lower side. In this manner, at both ends of the fuel cell stack  12 , deformation, buckling or the like of the electrolyte electrode assemblies  26  and the separators  28  can be prevented, and the durability of the fuel cell stack  12  is improved suitably. 
     Further, in the fuel cell stack  12 , the load applying mechanism  19  for applying the load to the fuel cell stack  12  in the stacking direction is provided adjacent to the end separator  84 . Further, the fluid unit  18  having the reformer  16  for producing the fuel gas supplied to the fuel cell stack  12  and the heat exchanger  14  is provided adjacent to the load absorption members  86 . In the structure, the overall size of the fuel cell module  10  is reduced easily, and the load in the stacking direction can be transmitted efficiently. Further, heat distortion can be suppressed suitably. 
     Moreover, the load applying mechanism  19  and the fluid unit  18  are provided symmetrically with respect to the axis of the fuel cell stack  12 . In the structure, occurrence of the heat distortion can be suppressed as much as possible. 
       FIG. 9  is a cross sectional view showing a load absorption member  180  of a fuel cell module according to a second embodiment of the present invention. 
     The constituent elements that are identical to those of the load absorption member  86  according to the first embodiment are labeled with the same reference numerals, and descriptions thereof will be omitted. Also in third to fifth embodiments as described later, the constituent elements that are identical to those of the load absorption member  86  according to the first embodiment are labeled with the same reference numerals, and descriptions thereof will be omitted. 
     The load absorption member  180  is a metal stack body formed by integrally stacking a pair of flat metal plates  182   a ,  182   b , and a corrugated metal plate  184  sandwiched between the metal plates  182   a ,  182   b  together. 
     Thus, in the second embodiment, electrical energy generated in the power generation can be transmitted efficiently. In particular, since the corrugated metal plate  184  itself functions as a spring, the load in the stacking direction can be absorbed to a greater extent. Thus, the same advantages as in the case of the first embodiment are obtained. For example, buckling and damages of the electrolyte electrode assemblies  26  can be prevented. 
       FIG. 10  is a cross sectional view showing a load absorption member  190  of a fuel cell module according to a third embodiment of the present invention. The load absorption member  190  is made of foamed metal. 
       FIG. 11  is a cross sectional view showing a load absorption member  200  of a fuel cell module according to a fourth embodiment of the present invention. The load absorption member  200  is made of mesh-like metal. 
     Therefore, in the cases of using the load absorption members  190 ,  200 , electrical energy produced in the power generation can be transmitted efficiently. Further, the same advantages as in the cases of the first and second embodiments are obtained. For example, the load in the stacking direction is absorbed, and buckling and damages of the electrolyte electrode assemblies  26  can be prevented. 
       FIG. 12  is a cross sectional view showing a load absorption member  210  of a fuel cell module according to a fifth embodiment of the present invention. 
     The load absorption member  210  is a stack body formed by stacking a ceramic felt  212  and an electrically conductive metal plate  214  together. The metal plate  214  is folded at an end of the felt  212  to protrude along both surfaces of the felt  212 . 
     In the case of using the load absorption member  210 , the same advantages as in the cases of the first to fourth embodiments are obtained. Further, improvement in the heat insulating performance is achieved easily by the ceramic felt  212 . 
     In the first to fifth embodiments, the function to absorb the load in the stacking direction is provided to prevent buckling or the like of the electrolyte electrode assemblies  26 . However, in order to maintain the rigidity, the load should not be absorbed excessively to a state where the load in the stacking direction is not sufficiently applied to the fuel cell stack  12 .