Abstract:
A fuel cell is provided with a separator that supports an electrolyte/electrode assembly sandwiched therebetween. The separator is provided with: first and second fuel gas supply parts in the center of which fuel gas supply holes are formed; first and second cross-link parts connected to the first and second fuel gas supply parts; and first and second surrounding support parts connected to the first and second cross-link parts. Each first surrounding support part is provided with a set of fuel gas exhaust passages that discharge fuel gas that has gone through a fuel gas passage and been used. The cross-sectional areas of the fuel gas exhaust passages are larger on the downstream sides than on the upstream sides, in terms of the direction of fuel gas flow.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a fuel cell formed by sandwiching electrolyte electrode assemblies between separators. Each of the electrolyte electrode assemblies includes an anode, a cathode, and an electrolyte interposed between the anode and the cathode. 
       BACKGROUND ART 
       [0002]    Typically, a solid oxide 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, predetermined numbers of the electrolyte electrode assemblies and the separators are stacked together to form a fuel cell stack. 
         [0003]    For example, in a flat plate type solid oxide fuel cell disclosed in Japanese Laid-Open Patent Publication No. 10-172594, a separator  1   a  as shown in  FIG. 17  is provided, and a plurality of unit cells (not shown) and separators  1   a  are stacked alternately. Gas supply holes  2   aa ,  3   aa , and gas discharge holes  2   ab ,  3   ab  extend through four corners of the separator  1   a  in the stacking direction, and a plurality of gas flow grooves  4   aa  and ridges  4   ab  in a plurality of rows are arranged alternately along the surface of the separator  1   a.    
         [0004]    The gas flow grooves  4   aa  are connected to the gas supply hole  2   aa  and the gas discharge hole  2   ab  through triangular recesses  5   aa ,  5   ab . A throttle section  6   a  and blocks  7   a  are provided in a gas inlet section of the triangular recess  5   aa , near the gas supply hole  2   aa , as means for limiting the flow rate of the gas. The throttle section  6   a  and the blocks  7   a  function to increase the pressure loss of the gas flowing from the gas supply hole  2   aa  to the gas inlet section for equal distribution of the gas. 
         [0005]    Further, at opposite ends of the gas flow grooves  4   aa , a shallow gas flow inlet section  8   aa  and a shallow gas flow outlet section  8   ab  are provided to cause a pressure loss in the gas flow. 
         [0006]    Further, in a solid oxide fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2005-085520, as shown in  FIG. 18 , the fuel cell is formed by stacking power generation cells  1   b , fuel electrode current collectors  2   b , air electrode current collectors  3   b , and separators  4   b . The power generation cell  1   b  includes a fuel electrode layer, and an air electrode layer, and a solid electrolyte layer interposed between the fuel electrode layer and the air electrode layer. The fuel electrode current collector  2   b  is provided outside the fuel electrode layer, and the air electrode current collector  3   b  is provided outside the air electrode layer. The separators  4   b  are provided outside the current collectors  2   b ,  3   b . Though not shown, a ring shaped metal cover covers the outer circumferential portion of a circular porous metal body making up the current collector  2   b , and a large number of gas outlets are provided over the entire circumferential side portion of the cover at predetermined intervals. 
         [0007]    In the structure, the fuel gas diffused in the porous metal body is prevented from being emitted from the entire outer circumferential portion of the porous metal body. According to the disclosure, the amount of the fuel gas which is not used in the power generation and discharged from the outer circumferential portion is suppressed, and the fuel gas is thus supplied to the power generation cell  1   b  efficiently. 
         [0008]    Further, in a flat stack fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2006-120589, as shown in  FIG. 19 , a separator  1   c  stacked on a power generation cell is provided. The separator  1   c  is formed by connecting left and right manifold parts  2   c  and a part  3   c  disposed at the center where the power generation cell is provided, by joint parts  4   c . The joint parts  4   c  have elasticity. 
         [0009]    The manifold parts  2   c  have gas holes  5   c ,  6   c . One gas hole  5   c  is connected to a fuel gas channel  7   c , and the other gas hole  6   c  is connected to an oxygen-containing gas channel  8   c . The fuel gas channel  7   c  and the oxygen-containing gas channel  8   c  extend in a spiral pattern into the part  3   c , and are opened to a fuel electrode current collector and an air electrode current collector (not shown), respectively, at positions near the center of the part  3   c.    
       SUMMARY OF INVENTION 
       [0010]    In Japanese Laid-Open Patent Publication No. 10-172594, since seals are provided, in comparison with seal-less structure, excessive loads tend to be applied to the MEAs. Therefore, for example, the MEAs may be cracked or damaged undesirably. Further, Japanese Laid-Open Patent Publication No. 10-172594 is not directed to a technique of suitably preventing the fuel gas, the oxygen-containing gas, or the exhaust gas from unnecessarily flowing around. 
         [0011]    Further, in Japanese Laid-Open Patent Publication No. 2005-085520, the ring-shaped metal cover has a large number of gas outlets formed at predetermined intervals over the entire circumferential side portion of the metal cover, and the metal cover and the separator are provided as separate components. Therefore, a larger number of components are required, the structure is complicated, and the cost is high. Further, a larger number of assembling steps are required, and thus, the operating efficiency is low. Further, the dimension in the thickness direction is large, and the length of the entire stack in the stacking direction is large. 
         [0012]    Further, in Japanese Laid-Open Patent Publication No. 2006-120589, the fuel gas, the oxygen-containing gas, or the exhaust gas tends to flow around to portions to which such a gas does not need to be supplied. As a result, the electrodes may be degraded undesirably, and power generation performance may be lowered undesirably. 
         [0013]    The present invention solves the above problems, and an object of the present invention is to provide a fuel cell having simple and economical structure, in which it is possible to prevent gases from unnecessarily flowing around to some portions, improve durability, and prevent excessive heat. 
         [0014]    The present invention relates to a fuel cell 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. 
         [0015]    Each of the separators includes a sandwiching section for sandwiching the electrolyte electrode assembly, a bridge connected to the sandwiching section, and a fuel gas supply section connected to the bridge. A fuel gas channel for supplying a fuel gas along an electrode surface of the anode of one electrolyte electrode assembly and an oxygen-containing gas channel for supplying an oxygen-containing gas along an electrode surface of the cathode of the other electrolyte electrode assembly are individually formed in the sandwiching section. A fuel gas supply channel for supplying the fuel gas to the fuel gas channel is formed in the bridge. A fuel gas supply passage extends through the fuel gas supply section in the stacking direction for supplying the fuel gas to the fuel gas supply channel. 
         [0016]    The sandwiching section includes a fuel gas inlet for supplying the fuel gas to the fuel gas channel, an outer circumferential protrusion protruding toward the fuel gas channel, and contacting an outer circumference of the anode, and at least one fuel gas outlet channel provided on a side opposite to a portion connecting the sandwiching section and the bridge for discharging the fuel gas partially consumed in the fuel gas channel (hereinafter referred to as the exhaust fuel gas). In the fuel gas outlet channel, the cross sectional area on the downstream side in the gas flow direction of the fuel gas is larger than the cross sectional area on the upstream side in the gas flow direction of the fuel gas. 
         [0017]    In the present invention, the separator includes the sandwiching sections for sandwiching the electrolyte electrode assemblies, the bridges connected to the sandwiching sections, and the fuel gas supply section connected to the bridges. In the structure, the tightening load in the stacking direction is not transmitted between the fuel gas supply section and the electrolyte electrode assembly through the bridge. Thus, with simple and compact structure, a relatively large load is applied to the portion requiring high sealing performance, and a relatively small load is applied to the electrolyte electrode assembly. Accordingly, damage of the electrolyte electrode assembly is prevented, and power generation and collection of electrical energy are performed efficiently. 
         [0018]    Further, the fuel gas supplied from the fuel gas inlet to the fuel gas channel is prevented from blowing to the outside by the outer circumferential protrusion protruding toward the fuel gas channel to contact the outer circumference of the anode. Therefore, the fuel gas can be utilized effectively by the power generation reaction, and the fuel utilization ratio is improved suitably. 
         [0019]    Further, gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas do not flow around to the anode from the outside of the electrolyte electrode assembly. Therefore, degradation in the power generation efficiency due to oxidation of the anode is prevented, and improvement in the durability of the separator and the electrolyte electrode assembly is achieved easily. 
         [0020]    Further, after the fuel gas supplied from the fuel gas inlet to the fuel gas channel is partially consumed in the reaction, the partially consumed fuel gas is discharged through at least one fuel gas outlet channel provided adjacent to the portion connecting the sandwiching section and the bridge. Therefore, since the exhaust fuel gas is discharged outside of the separator and the electrolyte electrode, it is possible to prevent excessive heat. 
         [0021]    Further, the fuel gas supplied from the fuel gas inlet to the fuel gas channel is discharged through the fuel gas outlet channel. The cross sectional area of the fuel gas outlet channel is large on the downstream side. In the structure, blowing of the fuel gas to the outside is prevented. Therefore, the fuel gas can be utilized effectively in the power generation reaction, and the fuel utilization ratio is improved suitably. 
         [0022]    Further, gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas do not flow around to the anode from the outside of the electrolyte electrode assembly. Therefore, degradation in the power generation efficiency due to oxidation of the anode is prevented, and improvement in the durability of the separator and the electrolyte electrode assembly is achieved easily. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0023]      FIG. 1  is a perspective view schematically showing a fuel cell stack formed by stacking a plurality of fuel cells according to a first embodiment of the present invention; 
           [0024]      FIG. 2  is a cross sectional view showing the fuel cell stack, taken along a line II-II shown in  FIG. 1 ; 
           [0025]      FIG. 3  is an exploded perspective view showing the fuel cell; 
           [0026]      FIG. 4  is a partially exploded perspective view showing gas flows in the fuel cell; 
           [0027]      FIG. 5  is a partial view showing a separator of the fuel cell; 
           [0028]      FIG. 6  is a cross sectional view schematically showing operation of the fuel cell; 
           [0029]      FIG. 7  is an exploded perspective view showing a fuel cell according to a second embodiment of the present invention; 
           [0030]      FIG. 8  is a partial view showing a separator of the fuel cell; 
           [0031]      FIG. 9  is an exploded perspective view showing a fuel cell according to a third embodiment of the present invention; 
           [0032]      FIG. 10  is a partial view showing a separator of the fuel cell; 
           [0033]      FIG. 11  is an exploded perspective view showing a fuel cell according to a fourth embodiment of the present invention; 
           [0034]      FIG. 12  is an exploded perspective view showing a fuel cell according to a fifth embodiment of the present invention; 
           [0035]      FIG. 13  is a partially exploded perspective view showing gas flows in the fuel cell: 
           [0036]      FIG. 14  is a partial view showing a separator of the fuel cell; 
           [0037]      FIG. 15  is a cross sectional view showing the separator, taken along a line XV-XV in  FIG. 14 ; 
           [0038]      FIG. 16  is an exploded perspective view showing a fuel cell according to a sixth embodiment of the present invention; 
           [0039]      FIG. 17  is a view showing a separator of a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 10-172594; 
           [0040]      FIG. 18  is a partially cross sectional view showing a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2005-085520; and 
           [0041]      FIG. 19  is a view showing a separator of a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2006-120589. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0042]    As shown in  FIGS. 1 and 2 , a fuel cell according to a first embodiment of the present invention is formed by stacking a plurality of fuel cells  10  in a direction indicated by an arrow A. The fuel cell  10  is a solid oxide fuel cell (SOFC) used in various applications, including stationary and mobile applications. For example, the fuel cell  10  is mounted on a vehicle. 
         [0043]    As shown in  FIGS. 3 and 4 , the fuel cell  10  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 entry or discharge of the oxygen-containing gas and the fuel gas. 
         [0044]    The fuel cell  10  is formed by sandwiching a plurality of (e.g., four) electrolyte electrode assemblies  26  between a pair of separators  28 . The four electrolyte electrode assemblies  26  are provided on a circle around a fuel gas supply passage  30  extending through the center of the separators  28 . 
         [0045]    As shown in  FIG. 3 , each of the separators  28  is formed by joining a first plate  28   a  and a second plate  28   b  made of, for example, a metal plate of stainless alloy, etc., or a carbon plate. A first fuel gas supply section  32  is formed in the first plate  28   a , and the fuel gas supply passage  30  cetnrally extends through the first fuel gas supply section  32 . Four first bridges  34  extend radially outwardly from the first fuel gas supply section  32  at equal angular intervals, e.g., 90°. The first fuel gas supply section  32  is integral with first sandwiching sections  36  each having a relatively large diameter through the first bridges  34 . The centers of the first sandwiching sections  36  are equally distanced from the center of the first fuel gas supply section  32 . 
         [0046]    Each of the first sandwiching sections  36  has a circular disk shape, having substantially the same dimensions as the electrolyte electrode assembly  26 . The first 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 first sandwiching section  36 , or at a position deviated upstream from the center of the first sandwiching section  36  in the flow direction of the oxygen-containing gas. 
         [0047]    Each of the first 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 pair of fuel gas outlet channels  42   a , a pair of fuel gas outlet channels  42   b , and a pair of fuel gas outlet channels  42   c  for discharging the fuel gas partially consumed in the fuel gas channel  40  and a circular arc wall (detour channel forming wall)  44  contacting the anode  24  and forming a detour path to prevent the fuel gas from flowing straight from the fuel gas inlet  38  to the fuel gas outlet channels  42   a ,  42   b ,  42   c  are provided on the surface  36   a  of the first sandwiching section  36 . 
         [0048]    As shown in  FIG. 5 , the fuel gas outlet channels  42   a ,  42   b ,  42   c  are provided on a side opposite to a portion connecting the first sandwiching section  36  and the first bridge  34 , on both sides of an extended line L of the first bridge  34  at equal intervals. In the fuel gas outlet channels  42   a ,  42   b ,  42   c , the cross sectional area on the downstream side in the gas flow direction of the fuel gas along the fuel gas channel  40  is larger than the cross sectional area on the upstream side in the gas flow direction of the fuel gas. 
         [0049]    Specifically, an outer circumferential protrusion  46  and a plurality of projections  48  are provided on the surface  36   a  of each first sandwiching section  36 . The outer circumferential protrusion  46  protrudes toward the fuel gas channel  40  to contact the outer circumferential portion of the anode  24 , and the projections  48  contact the anode  24 . The fuel gas outlet channels  42   a ,  42   b ,  42   c  are formed at the outer circumferential protrusion  46  by directly cutting out portions of the outer circumferential protrusion  46 . 
         [0050]    In the fuel gas outlet channels  42   a ,  42   b ,  42   c , the width H 2  on the outer side of the outer circumferential protrusion  46  is larger than the width H 1  on the inner side of the outer circumferential protrusion  46  (H 1 &lt;H 2 ). The depth of the fuel gas outlet channels  42   a ,  42   b ,  42   c  is the same over the entire surfaces of the fuel gas outlet channels  42   a ,  42   b ,  42   c . Thus, the cross sectional area on the downstream side in the gas flow direction is larger than the cross sectional area on the upstream side in the gas flow direction. 
         [0051]    As shown in  FIG. 3 , the circular arc wall  44  has a substantially horseshoe shape (circular arc shape with partial cutout). The fuel gas inlet  38  is provided inside the circular arc wall  44 . The projections  48  are made of, e.g., solid portions formed by etching or hollow portions formed by press forming. 
         [0052]    The first sandwiching section  36  has a pair of extensions  50  for collecting electricity generated in the power generation of the electrolyte electrode assembly  26 , and for measuring the state of the electrolyte electrode assembly  26 . The extensions  50  protrude from the outer circumferential portion of the first sandwiching section  36  or from between the fuel gas outlet channels  42   a ,  42   b.    
         [0053]    As shown in  FIGS. 3 and 6 , each of the first sandwiching sections  36  has a substantially planar surface  36   b  which contacts the cathode  22 . A second plate  28   b  is fixed to the surface  36   b , e.g., by brazing, diffusion bonding, laser welding, or the like. 
         [0054]    As shown in  FIG. 3 , a second fuel gas supply section  52  is formed in the second plate  28   b , and the fuel gas supply passage  30  extends through the center of the second fuel gas supply section  52 . A predetermined number of reinforcement bosses  53  are formed on the second fuel gas supply section  52 . Four second bridges  54  extend radially from the second fuel gas supply section  52 . Each of the second bridges  54  has a fuel gas supply channel  56  connecting the fuel gas supply passage  30  of the second fuel gas supply section  52  to the fuel gas inlet  38 . The fuel gas supply channel  56  is formed, for example, by etching or by press forming. 
         [0055]    Each of the second bridges  54  is integral with a second sandwiching section  58  having a relatively large diameter. A plurality of projections  60  are provided on the second sandwiching section  58 , e.g., by etching or press forming. The projections  60  form an oxygen-containing gas channel  62  for supplying an oxygen-containing gas along an electrode surface of the cathode  22  on the surface  36   b  of the first sandwiching section  36 . The projections  60  function as a current collector (see  FIGS. 3 and 6 ). 
         [0056]    As shown in  FIG. 6 , an oxygen-containing gas supply passage  68  is connected to the oxygen-containing gas channel  62  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 first and second sandwiching sections  36 ,  58  in a direction indicated by an arrow B. The oxygen-containing gas supply passage  68  extends inside the first and second sandwiching sections  36 ,  58  in the stacking direction indicated by the arrow A, between the respective first and second bridges  34 ,  54  to form an oxygen-containing gas supply section. 
         [0057]    An insulating seal  70  for sealing the fuel gas supply passage  30  is provided between the separators  28 . For example, mica material, ceramic material or the like, i.e., crustal component material, glass material, or 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 . 
         [0058]    In the fuel cell  10 , exhaust gas discharge passages  72  are provided around the first and second sandwiching sections  36 ,  58 . The exhaust gas discharge passages  72  form an exhaust gas discharge section for discharging the fuel gas and the exhaust gas partially consumed in the electrolyte electrode assemblies  26  as an exhaust gas in the stacking direction. As necessary, an air regulating plate  73  is provided in each space between the first and second sandwiching sections  36 ,  58  (see  FIG. 3 ). 
         [0059]    As shown in  FIGS. 1 and 2 , a fuel cell stack  12  includes a first end plate  74   a  having a substantially circular disk shape at one end in the stacking direction of the fuel cells  10 . Further, the fuel cell stack  12  includes a plurality of second end plates  74   b  and a fixing ring  74   c  at the other end in the stacking direction of the fuel cells  10 , through a partition wall  75 . Each of the second end plates  74   b  has a small diameter and a substantially circular shape, and the fixing ring  74   c  has a large diameter and a substantially ring shape. The partition wall  75  prevents diffusion of the exhaust gas to the outside of the fuel cells  10 . The number of the second end plates  74   b  is four, corresponding to the positions of the stacked electrolyte electrode assemblies  26 . 
         [0060]    The first end plate  74   a  and the fixing ring  74   c  include a plurality of holes  76 . Bolts  78  are inserted into the holes  76  and bolt insertion collar members  77 , and screwed into nuts  80 . By the bolts  78  and the nuts  80  through which the bolts  78  are screwed, the first end plate  74   a  and the fixing ring  74   c  are fixedly tightened together. 
         [0061]    One fuel gas supply pipe  82 , a casing  83 , and one oxygen-containing gas supply pipe  84  are provided at the first end plate  74   a . The fuel gas supply pipe  82  is connected to the fuel gas supply passage  30 . The casing  83  has a cavity  83   a  connected to the respective oxygen-containing gas supply passages  68 . The oxygen-containing gas supply pipe  84  is connected to the casing  83 , and to the cavity  83   a.    
         [0062]    A support plate  92  is fixed to the first end plate  74   a  through a plurality of bolts  78 , nuts  88   a ,  88   b , and plate collar members  90 . A first load applying unit  94  for applying a tightening load to the first and second fuel gas supply sections  32 ,  52  and second load applying units  98  for applying a tightening load to each of the electrolyte electrode assemblies  26  are provided between the support plate  92  and the first end plate  74   a . The first load applying unit  94  and the second load applying units  98  form a load applying mechanism. 
         [0063]    The first load applying unit  94  includes a presser member  100  provided at the center of the fuel cells  10  (centers of the first and second fuel gas supply sections  32 ,  52 ) for preventing leakage of the fuel gas from the fuel gas supply passage  30 . The presser member  100  is provided near the center of the four second end plates  74   b  for pressing the fuel cells  10  through the partition wall  75 . A first spring  104  is provided at the presser member  100  through a first receiver member  102   a  and a second receiver member  102   b . A front end of a first presser bolt  106  contacts the second receiver member  102   b . The first presser bolt  106  is screwed into a first screw hole  108  formed in the support plate  92 . The position of the first presser bolt  106  is adjustable through a first nut  110 . 
         [0064]    Each of the second load applying units  98  includes a third receiver member  112   a  at the second end plate  74   b , corresponding to each of the electrolyte electrode assemblies  26 . The third receiver member  112   a  is positioned on the second end plate  74   b  through a pin  114 . One end of a second spring  116  contacts the third receiver member  112   a  and the other end of the second spring  116  contacts a fourth receiver member  112   b . A front end of a second presser bolt  118  contacts the fourth receiver member  112   b . The second presser bolt  118  is screwed into a second screw hole  120  formed in the support plate  92 . The position of the second presser bolt  118  is adjustable through a second nut  122 . 
         [0065]    Operation of the fuel cell stack  12  will be described below. 
         [0066]    As shown in  FIG. 1 , the fuel gas is supplied through the fuel gas supply pipe  82  connected to the first end plate  74   a . Then, the fuel gas flows into the fuel gas supply passage  30 . The air as the oxygen-containing gas is supplied from the oxygen-containing gas supply pipe  84  to each of the oxygen-containing gas supply passages  68  through the cavity  83   a.    
         [0067]    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  56  of each fuel cell  10  along the surface of the separator  28 . 
         [0068]    The fuel gas flows from the fuel gas supply channel  56  into the fuel gas channel  40  through the fuel gas inlet  38  formed in the first 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 center of the anode  24 , and flows along the fuel gas channel  40  from substantially the central region to the outer circumferential region of the anode  24 . 
         [0069]    The air (oxygen-containing gas), which has been supplied to the oxygen-containing gas supply passages  68 , flows from the space between the inner circumferential edge of the electrolyte electrode assembly  26  and the inner circumferential edges of the first and second sandwiching sections  36 ,  58  into the oxygen-containing gas channel  62  in the direction indicated by the arrow B. In the oxygen-containing gas channel  62 , the air flows from the inner circumferential edge (center of the separator  28 ) of the cathode  22  to the outer circumferential edge (outer circumferential edge of the separator  28 ) of the cathode  22 , i.e., from one end to the other end of the cathode  22  of the electrolyte electrode assembly  26 . 
         [0070]    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 air flows in one direction indicated by the arrow B on the electrode surface of the cathode  22 . At this time, oxide ions flow through the electrolyte  20  toward the anode  24  for generating electricity by electrochemical reactions. 
         [0071]    The exhaust gas chiefly containing the air after partial consumption in the power generation reaction is discharged from the outer circumferential region of each of the electrolyte electrode assemblies  26 , and flows through the exhaust gas discharge passage  72  as the off gas, and the off gas is discharged from the fuel cell stack  12  (see  FIG. 1 ). 
         [0072]    In the first embodiment, the separator  28  includes the first and second sandwiching sections  36 ,  58  for sandwiching the electrolyte electrode assemblies  26 , the first and second bridges  34 ,  54  connected to the first and second sandwiching sections  36 ,  58 , and the first and second fuel gas supply sections  32 ,  52  connected to the first and second bridges  34 ,  54 . 
         [0073]    Thus, the tightening load in the stacking direction is not transmitted between the first and second fuel gas supply sections  32 ,  52  and the electrolyte electrode assemblies  26 . With simple and compact structure, a relatively large load is applied to the portion requiring high sealing performance, and a relatively small load is applied to the electrolyte electrode assemblies  26 . Thus, damages of the electrolyte electrode assemblies  26  are prevented, and power generation and collection of electrical energy are performed efficiently. 
         [0074]    The outer circumferential protrusion  46  which contacts the outer circumferential portion of the anode  24  is provided on the surface  36   a  of the first sandwiching section  36 . Therefore, after the fuel gas is supplied from the fuel gas inlet  38  to the fuel gas channel  40 , blowing of the fuel gas to the outside is prevented. Therefore, the fuel gas can be utilized effectively by the power generation reaction, and the fuel utilization ratio is improved suitably. 
         [0075]    Further, gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas do not flow around to the anode  24  from the outside of the electrolyte electrode assembly  26 . Therefore, degradation in the power generation efficiency due to oxidation of the anode  24  is prevented, and improvement in the durability of the separator  28  and the electrolyte electrode assembly  26  is achieved easily. 
         [0076]    Further, in the surface  36   a  of the first sandwiching section  36 , the fuel gas outlet channels  42   a ,  42   b ,  42   c  are provided on the side opposite to the portion connecting the first sandwiching section  36  and the first bridge  34 , on both sides of the extended line L of the first bridge  34 . Therefore, the fuel gas is supplied from the fuel gas inlet  38  to the fuel gas channel  40 , and the fuel gas is partially consumed in the reaction. Then, the fuel gas is distributed into the fuel gas outlet channels  42   a ,  42   b ,  42   c , and discharged separately. 
         [0077]    Therefore, in the cathode surface of the separator  28 , the water vapor and the unconsumed fuel gas are not concentrated in a certain region (outwardly and a side opposite to the portion connecting the first sandwiching section and the first bridge), and thus, an ununiform temperature distribution due to overheating is prevented suitably. Accordingly, it becomes possible to achieve a uniform temperature distribution in the fuel cell  10 , and the durability of the fuel cell  10  is improved advantageously. 
         [0078]    Further, the exhaust fuel gas is discharged outside of the separator  28  and the electrolyte electrode assembly  26 . Thus, the generation of excessive heat can be prevented. 
         [0079]    Further, in the fuel gas outlet channels  42   a ,  42   b ,  42   c , the width H 2  on the outer side of the outer circumferential protrusion  46  is larger than the width H 1  on the inner side of the outer circumferential protrusion  46  (H 1 &lt;H 2 ). Thus, in the fuel gas outlet channels  42   a ,  42   b ,  42   c , the cross sectional area on the downstream side in the gas flow direction is larger than the cross sectional area on the upstream side in the gas flow direction. In the structure, blowing of the fuel gas to the outside is prevented. Thus, the fuel gas is utilized effectively in the power generation reaction, and improvement in the fuel utilization ratio is achieved advantageously. 
         [0080]    Further, gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas do not flow around to the anode  24  from the outside of the electrolyte electrode assembly  26 . Therefore, degradation in the power generation efficiency due to oxidation of the anode  24  is prevented, and improvement in the durability of the separator  28  and the electrolyte electrode assembly  26  is achieved easily. 
         [0081]    Further, in the first embodiment, as shown in  FIG. 3 , the circular arc wall  44  is provided in the path connecting the fuel gas inlet  38  and the fuel gas outlet channels  42   a  to  42   c  on the surface  36   a  of the first sandwiching section  36  of the separator  28 . The circular arc wall  44  contacts the anode  24  of the electrolyte electrode assembly  26 , and thus, improvement in the electricity collecting efficiency is obtained. 
         [0082]    In the structure, the fuel gas supplied from the fuel gas inlet  38  to the fuel gas channel  40  is blocked by the circular arc wall  44 . Thus, the fuel gas does not flow straight from the fuel gas inlet  38  to the fuel gas outlet channels  42   a  to  42   c . The fuel gas flows around in the fuel gas channel  40 , and the fuel gas flows along the anode  24  over a longer distance. That is, the fuel gas flows along the anode  24  over a longer period of time, and the fuel gas can be consumed effectively in the power generation reaction. Accordingly, the fuel gas utilization ratio is improved effectively. 
         [0083]    Further, the fuel gas outlet channels  42   a  to  42   c  are formed by slits or the like formed in the outer circumferential protrusion  46 . Therefore, the structure is simplified comparatively. Further, reduction in the production cost and reduction in the number of components are achieved. 
         [0084]    Further, the first and second fuel gas supply sections  32 ,  52  are provided at the central part of the separator  28 , and the plurality of, e.g., four electrolyte electrode assemblies  26  are arranged on a circle around the first and second fuel gas supply sections  32 ,  52 . In the structure, even if the fuel gas supplied to the fuel cells  10  (fuel cell stack  12 ) is overheated by heat produced in power generation, it is possible to enhance the prevention of excessive heat in the fuel cells  10  (fuel cell stack  12 ). 
         [0085]    Further, the fuel gas can be distributed uniformly to each of the electrolyte electrode assemblies  26  from the first and second fuel gas supply sections  32 ,  52 . Thus, improvement and stability in the power generation performance are achieved in each of the electrolyte electrode assemblies  26 . 
         [0086]    Further, the first and second sandwiching sections  36 ,  58  have a shape corresponding to the electrolyte electrode assemblies  26 , and the first and second sandwiching sections  36 ,  58  are separated from each other. Since the first and second sandwiching sections  36 ,  58  have a shape, e.g., circular disk shape corresponding to the electrolyte electrode assemblies  26 , it becomes possible to efficiently collect electrical energy generated in the electrolyte electrode assemblies  26 . 
         [0087]    Further, since the first and second sandwiching sections  36 ,  58  are separated from each other, it becomes possible to absorb variation of the load applied to the respective electrolyte electrode assemblies  26  due to dimensional differences in the electrolyte electrode assemblies  26  and the separators  28 . Thus, the undesired distortion does not occur in the entire separators  28 . It is possible to apply the load equally to each of the electrolyte electrode assemblies  26 . 
         [0088]    Further, thermal distortion or the like of the electrolyte electrode assemblies  26  is not transmitted to the adjacent, other electrolyte electrode assemblies  26 , and no dedicated dimensional variation absorbing mechanisms are required between the electrolyte electrode assemblies  26 . Thus, the electrolyte electrode assemblies  26  can be provided close to each other, and the overall size of the fuel cell  10  can be reduced easily. 
         [0089]    Further, the first and second bridges  34 ,  54  extend radially outwardly from the first and second fuel gas supply sections  32 ,  52  such that the first and second bridges  34 ,  54  are spaced at equal angular intervals. In the structure, the fuel gas can be supplied from the first and second fuel gas supply sections  32 ,  52  equally to the respective electrolyte electrode assemblies  26  through the first and second bridges  34 ,  54 . Thus, improvement and stability in the power generation performance can be achieved in each of the electrolyte electrode assemblies  26 . 
         [0090]    Further, in the separator  28 , the number of the first and second sandwiching sections  36 ,  58  and the number of the first and second bridges  34 ,  54  correspond to the number of the electrolyte electrode assemblies  26 . Therefore, the fuel gas is uniformly supplied from the first and second fuel gas supply sections  32 ,  52  to each of the electrolyte electrode assemblies  26  through the first and second bridges  34 ,  54  and the first and second sandwiching sections  36 ,  58 . Thus, improvement and stability in the power generation performance can be achieved in each of the electrolyte electrode assemblies  26 . 
         [0091]    Further, the projections  48  provided on the first sandwiching section  36  protrude toward the fuel gas channel  40 , and contact the anode  24 . In the structure, electrical energy is collected suitably through the projections  48 . 
         [0092]    Further, the projections  60  provided on the second sandwiching section  58  protrude toward the oxygen-containing gas channel  62 , and contact the cathode  22 . In the structure, electrical energy is collected suitably through the projections  60 . 
         [0093]    Further, the first sandwiching section  36  has the extensions  50 . In the structure, for example, electrical energy generated in the power generation of the electrolyte electrode assembly  26  can be collected, and a state such as the temperature of the electrolyte electrode assembly  26  can be measured easily, through the extensions  50 . 
         [0094]    Further, the extensions  50  are provided at the outer circumference of the first sandwiching section  36 , between the fuel gas outlet channels  42   a ,  42   b . In the structure, the extensions  50  are displaced from positions directly exposed to the exhaust fuel gas. Thus, overheating by the hot exhaust fuel gas is suppressed. The temperature measurement or the like of the separator  28  or the electrolyte electrode assembly  26  is performed highly accurately. 
         [0095]    Further, since the fuel cell  10  has the exhaust gas discharge section where the exhaust gas discharge passage  72  extends in the stacking direction and the oxygen-containing gas supply section having the oxygen-containing gas supply passage  68  for supplying the oxygen-containing gas before supplied to the electrolyte electrode assembly  26 , the overall size of the fuel cell  10  is reduced easily. 
         [0096]    Moreover, the first and second fuel gas supply sections  32 ,  52  are provided at the center of the separator  28 , and the plurality of, e.g., four oxygen-containing gas supply passages  68  are arranged on a circle around the first and second fuel gas supply sections  32 ,  52 . Further, the oxygen-containing gas supply passages  68  are arranged between the plurality of, e.g., four first and second bridges  34 ,  54 . In the structure, even if the fuel gas and the oxygen-containing gas supplied to the fuel cells  10  (fuel cell stack  12 ) are overheated by heat produced in power generation, it is possible to enhance the prevention of excessive heat in the fuel cell  10  (and the fuel cell stack  12 ). 
         [0097]    The fuel gas supplied to and partially consumed in the electrolyte electrode assembly  26  is discharged through the fuel gas outlet channels  42   a ,  42   b ,  42   c  to the exhaust gas discharge passages  72 . In the structure, even if the exhaust gas is overheated by reaction with unconsumed fuel gas and unconsumed oxygen-containing gas remaining in the exhaust fuel gas, it is possible to enhance the prevention of excessive heat. 
         [0098]    Further, the oxygen-containing gas supplied to and partially consumed in the electrolyte electrode assemblies  26  is discharged as an exhaust oxygen-containing gas through the oxygen-containing gas channel  62  to the exhaust gas discharge passages  72 . Thus, even if exhaust gas is overheated by reaction with unconsumed fuel gas and unconsumed oxygen-containing gas remaining in the exhaust gas, it is possible to prevent generation of excessive heat. 
         [0099]    Further, the fuel cell  10  is a solid oxide fuel cell. With simple structure, the oxygen-containing gas and the exhaust gas can be prevented from flowing around to the anode  24 . Further, the exhaust gas is distributed to achieve a uniform temperature distribution. Thus, it is possible to improve durability of the fuel cell  10  (fuel cell stack  12 ) and prevent excessive heat. 
         [0100]    In the first embodiment, the three fuel gas outlet channels  42   a ,  42   b ,  42   c  are provided on each of both sides of the first bridge  34 , on a side opposite to the portion connecting the first sandwiching section  36  and the first bridge  34 . However, the present invention is not limited in this respect. For example, two or more fuel gas outlet channels may be provided on each of both sides of the first bridge  34 . Preferably, the area where the fuel gas outlet channels are formed is within a range of 180° of each of the first sandwiching sections  36  on the inner circumferential side of the separator (see  FIG. 5 ). In this respect, preferably, the range of the fuel gas outlet channels is limited by the air regulating plate  73 . 
         [0101]    Further, the separator  28  is made of the first plate  28   a  and the second plate  28   b . For example, the second plate  28   b  may be formed of two pieces, i.e., a circular plate and a cross-shaped plate. 
         [0102]      FIG. 7  is an exploded perspective view showing a fuel cell  140  according to a second embodiment of the present invention. The constituent elements that are identical to those of the fuel cell  10  according to the first embodiment are labeled with the same reference numerals, and descriptions thereof will be omitted. Also in third and other embodiments as described later, the constituent elements that are identical to those of the fuel cell  10  according to the first embodiment are labeled with the same reference numerals, and descriptions thereof will be omitted. 
         [0103]    In the fuel cell  140 , oxygen-containing gas supply passages  68  are positioned outside around the first and second sandwiching sections  36 ,  58 . A plurality of exhaust gas discharge passages  72  are arranged on a circle around the first and second fuel gas supply sections  32 ,  52 . Each of the exhaust gas discharge passages  72  is provided between the first and second bridges  34 ,  54 . That is, the oxygen-containing gas is supplied in directions indicated by arrows D (in directions opposite to the directions indicated by the arrows B) from the outside of the first and second sandwiching sections  36 ,  58 , and the oxygen-containing gas is discharged to the exhaust gas discharge passages  72  on the center side of the separator, inside the first and second sandwiching sections  36 ,  58 . 
         [0104]    The fuel cell  140  includes separators  142 , and the separator  142  is formed by joining a first plate  142   a  and a second plate  142   b  together. A pair of fuel gas outlet channels  144   a , a pair of fuel gas outlet channels  144   b , and a pair of fuel gas outlet channels  144   c  are provided on a surface  36   a  of each of first sandwiching sections  36  of the first plate  142   a . A fuel gas partially consumed in the fuel gas channel  40  is discharged through the fuel gas outlet channels  144   a ,  144   b ,  144   c.    
         [0105]    The fuel gas outlet channels  144   a ,  144   b ,  144   c  are provided on a side opposite to a portion connecting the first sandwiching section  36  and the first bridge  34 , on both sides of an extended line L of the first bridge  34  at equal intervals. In the fuel gas outlet channels  144   a ,  144   b ,  144   c , the cross sectional area on the downstream side in the gas flow direction of the fuel gas along the fuel gas channel  40  is larger than the cross sectional area on the upstream side in the gas flow direction of the fuel gas. 
         [0106]    The gas flow directions indicated by arrows C at the fuel gas outlet channels  144   a ,  144   b ,  144   c  intersect straight lines connecting the first fuel gas supply section  32  and the fuel gas outlet channels  144   a ,  144   b ,  144   c  (see  FIG. 8 ). 
         [0107]    In the second embodiment, the oxygen-containing gas flows along the cathode  22  from the outside of the first and second sandwiching sections  36 ,  58  toward the first and second fuel gas supply sections  32 ,  52 . In the structure, it is possible to prevent the other gases such as the oxygen-containing gas and the exhaust gas from flowing around to the anode  24  from the outside of the electrolyte electrode assembly  26 . Thus, degradation of the power generation efficiency due to oxidation of the anode  24  is prevented, and improvement in the durability of the separator  142  and the electrolyte electrode assembly  26  is achieved. 
         [0108]    In the second embodiment, the oxygen-containing gas flows in directions indicated by the arrows D, and the gas flow directions at the fuel gas outlet channels  144   a ,  144   b ,  144   c  are the directions indicated by the arrows C. The directions indicated by the arrows D and the directions indicated by the arrows C intersect each other. In the structure, it is possible to prevent gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas from flowing around to the anode  24  from the outside of the electrolyte electrode assembly  26 . Therefore, degradation in the power generation efficiency due to oxidation of the anode  24  is prevented, and improvement in the durability of the separator  142  and the electrolyte electrode assembly  26  is achieved. 
         [0109]    Therefore, thanks to the negative pressure effect by the flow of the oxygen-containing gas, the exhaust fuel gas is discharged smoothly from the fuel gas outlet channels  144   a ,  144   b ,  144   c . In the structure, efficient operation can be performed. 
         [0110]    Further, in the second embodiment, the exhaust gas discharge passages  72  are arranged on a circle around the first and second fuel gas supply sections  32 ,  52 . Further, each of the exhaust gas discharge passages  72  is arranged between the first and second bridges  34 ,  54 . In the structure, even if the fuel gas supplied to the fuel cell  140  (and the fuel cell stack) is overheated by the heat generated by the power generation and the exhaust gas, the prevention of excessive heat can be enhanced. 
         [0111]    Further, the fuel gas supplied to and partially consumed in the electrolyte electrode assembly  26  is discharged to the oxygen-containing gas supply passage  68  through the fuel gas outlet channels  144   a ,  144   b ,  144   c . In the structure, even if the oxygen-containing gas before consumption is overheated by reaction with the unconsumed fuel gas remaining in the exhaust fuel gas, the prevention of excessive heat can be enhanced. 
         [0112]    Further, in the oxygen-containing gas channel  62 , the oxygen-containing gas supplied to and partially consumed in the electrolyte electrode assembly  26  is discharged to the exhaust gas discharge passage  72 . In the structure, even if the exhaust gas is overheated by reaction of the unconsumed fuel gas and the unconsumed oxygen-containing gas remaining in the exhaust gas, the excessive heat can be prevented. 
         [0113]      FIG. 9  is an exploded perspective view showing a fuel cell  150  according to a third embodiment of the present invention. 
         [0114]    The fuel cell  150  includes separators  152 , and each of the separators  152  is formed by joining a first plate  152   a  and a second plate  152   b  together. A pair of fuel gas outlet channels  154   a , a pair of fuel gas outlet channels  154   b , and a pair of fuel gas outlet channels  154   c  are provided on a surface  36   a  of each of first sandwiching sections  36  of the first plate  152   a . A fuel gas partially consumed in the fuel gas channel  40  is discharged through the fuel gas outlet channels  154   a ,  154   b ,  154   c.    
         [0115]    The fuel gas outlet channels  154   a ,  154   b ,  154   c  are provided on a side opposite to a portion connecting the first sandwiching section  36  and the first bridge  34 , on both sides of an extended line L of the first bridge  34  at equal intervals. In the fuel gas outlet channels  154   a ,  154   b ,  154   c , the cross sectional area on the downstream side in the gas flow direction of the fuel gas along the fuel gas channel  40  is larger than the cross sectional area on the upstream side in the gas flow direction. 
         [0116]    The gas flow directions (indicated by arrows E) at the fuel gas outlet channels  154   a ,  154   b ,  154   c  are the same directions as straight lines connecting the first fuel gas supply section  32  and the fuel gas outlet channels  154   a ,  154   b ,  154   c  (see  FIG. 10 ). 
         [0117]    In the third embodiment, the oxygen-containing gas flows in the directions indicated by the arrows B, and the gas flow directions at the fuel gas outlet channels  154   a ,  154   b ,  154   c  are the directions indicated by the arrows E. In the structure, the directions indicated by the arrows B and the directions indicated by the arrows E are the same. Thus, the same advantages as in the cases of the first and second embodiments are obtained. For example, it is possible to prevent the other gases such as the oxygen-containing gas and the exhaust gas from flowing around to the anode  24  from the outside of the electrolyte electrode assembly  26 . Also, thanks to the negative pressure effect by the flow of the oxygen-containing gas, the exhaust fuel gas is discharged smoothly through the fuel gas outlet channels  154   a ,  154   b ,  154   c.    
         [0118]      FIG. 11  is an exploded perspective view showing a fuel cell  160  according to a fourth embodiment of the present invention. 
         [0119]    The fuel cell  160  includes a separator  162 , and the separator  162  is formed by joining a first plate  162   a  and a second plate  162   b  together. Each of first sandwiching sections  36  of the first plate  162   a  has a spiral wall  164  on the surface  36   a . A fuel gas inlet  38  is formed adjacent to the center of the spiral wall  164 . 
         [0120]    One fuel gas outlet channel  42  is formed on the surface  36   a  on a side opposite to a portion connecting the first sandwiching section  36  and the first bridge  34 . In the fuel gas outlet channel  42 , the cross sectional area on the downstream side of the gas flow direction of the fuel gas along the fuel gas channel  40  is larger than the cross sectional area on the upstream side in the gas flow direction. 
         [0121]    In the fourth embodiment, the fuel gas supplied into the fuel gas channel  40  through the fuel gas inlet  38  is supplied to substantially the entire area in the surface  36   a  by the guidance of the spiral wall  164 . Then, the fuel gas is discharged through the single fuel gas outlet channel  42 . Thus, in the fourth embodiment, the same advantages as in the cases of the first to third embodiments are obtained. 
         [0122]      FIG. 12  is an exploded perspective view showing a fuel cell  170  according to a fifth embodiment of the present invention. 
         [0123]    The fuel cell  170  includes a separator  172 , and the separator  172  is formed by joining a first plate  172   a  and a second plate  172   b  together. Each of first sandwiching sections  36  of the first plate  172   a  has fuel gas outlet channels  174   a ,  174   b  on a side opposite to a portion connecting the first sandwiching section  36  and the first bridge  34 , on both sides of an extended line L of the first bridge  34 , for discharging the fuel gas partially consumed in the fuel gas channel  40  ( FIGS. 12 and 13 ). 
         [0124]    A continuous outer circumferential protrusion  46  is formed in a surface  36   a  of each of the first sandwiching sections  36 , and the fuel gas outlet channels  174   a ,  174   b  include outlet holes  176   a ,  176   b  extending through the first sandwiching section  36  at positions inside the outer circumferential protrusion  46  (see  FIGS. 14 and 15 ). 
         [0125]    Cover members  178   a ,  178   b  are fixed to a surface  36   b  opposite to the surface  36   a  of the first sandwiching section  36 . Each of the cover members  178   a ,  178   b  has a substantially trapezoidal shape in a plan view, and flanges  180   a ,  180   b  are provided on three sides excluding an opened front end. The outlet holes  176   a ,  176   b  are formed on the surface  36   b  of the first sandwiching section  36 , and the flanges  180   a ,  180   b  are fixed to the surface  36   b  of the first sandwiching section  36  such that the outlet holes  176   a ,  176   b  are positioned inside of the flanges  180   a ,  180   b.    
         [0126]    Channels  182   a ,  182   b  are formed between the cover members  178   a ,  178   b  and the surface  36   b . Each of the channels  182   a ,  182   b  has one end connected to the outlet hole  176   a  or the outlet hole  176   b , and the other end opened to the outside. In the channels  182   a ,  182   b , the cross sectional area is increased from the outlet holes  176   a ,  176   b  toward the outside. The width H 3  of the channels  182   a ,  182   b  at positions adjacent to the outlet holes  176   a ,  176   b  side is smaller than the width H 4  of the channels  182   a ,  182   b  adjacent to the ends opened to the outside (see  FIG. 14 ). 
         [0127]    As shown in  FIG. 12 , the second sandwiching section  58  of the second plate  172   b  has cutouts  184   a ,  184   b  for inserting the cover members  178   a ,  178   b  on both sides of the second bridge  54 . 
         [0128]    In the fifth embodiment, after the fuel gas supplied from the fuel gas inlet  38  to the fuel gas channel  40  is partially consumed in the reaction, the partially consumed fuel gas moves toward the surface  36   b  through the outlet holes  176   a ,  176   b  of the fuel gas outlet channels  174   a ,  174   b , and flows into the channels  182   a ,  182   b  formed in the cover members  178   a ,  178   b . Further, the exhaust fuel gas flows through the channels  182   a ,  182   b , and then, the exhaust fuel gas is discharged from each opened end toward the exhaust gas discharge passage  72 . 
         [0129]    As described above, in the fifth embodiment, the fuel gas outlet channels  174   a ,  174   b  include the outlet holes  176   a ,  176   b  extending through the first sandwiching sections  36  at positions inside the outer circumferential protrusion  46 . In the structure, blowing of the fuel gas to the outside from the fuel gas channel  40  is prevented. Thus, the fuel gas is utilized effectively in the power generation reaction, and improvement in the fuel utilization ratio is achieved advantageously. 
         [0130]    Further, gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas do not flow around to the anode  24  from the outside of the electrolyte electrode assembly  26 . Therefore, degradation in the power generation efficiency due to oxidation of the anode  24  is prevented, and improvement in the durability of the separator  172  and the electrolyte electrode assembly  26  is achieved easily. 
         [0131]    Further, the fuel gas outlet channels  174   a ,  174   b  include the channels  182   a ,  182   b  each having one end connected to the outlet hole  176   a  or the outlet hole  176   b , and the other end opened to the outside. In the channels  182   a ,  182   b , the cross sectional area is increased from the outlet holes  176   a ,  176   b  toward the outside. 
         [0132]    In the structure, gases other than the fuel gas, such as the oxygen-containing gas and the exhaust gas do not flow around to the anode  24  through the channels  182   a ,  182   b  from the outside of the electrolyte electrode assembly  26 . Therefore, degradation in the power generation efficiency due to oxidation of the anode  24  is prevented, and improvement in the durability of the separator  172  and the electrolyte electrode assembly  26  is achieved easily. 
         [0133]    In the channels  182   a ,  182   b , the width H 4  at the end on the outer side is larger than the width H 3  on the inner side. Further, as necessary, as shown in  FIG. 15 , the dimension in the stacking direction on the outer side may be larger than the dimension in the stacking direction on the inner side. Further, one of the width and the dimension in the stacking direction on the outer side may be larger than that on the inner side. 
         [0134]      FIG. 16  is an exploded perspective view showing a fuel cell  190  according to a sixth embodiment of the present invention. 
         [0135]    The constituent elements that are identical to those of the fuel cell  170  according to the fifth embodiment are labeled with the same reference numerals, and description thereof will be omitted. 
         [0136]    The fuel cell  190  includes a separator  192 , and the separator  192  is formed by joining a first plate  192   a  and a second plate  192   b  together. No circular arc wall is provided on the surface  36   a  of each first sandwiching section  36  of the first plate  192   a . A fuel gas inlet  38  is provided at a position deviated toward the inside (in a direction toward the center of the separator  192 ). In the second plate  192   b , the fuel gas supply channel  56  extends inside compared to the center of the second sandwiching section  58  up to a position corresponding to the fuel gas inlet  38 . 
         [0137]    In the sixth embodiment, the fuel gas inlet  38  is provided deviated inwardly from the center of each first sandwiching section  36 . In the structure, without requiring the circular arc wall, the fuel gas flowing from the fuel gas inlet  38  to the fuel gas channel  40  is supplied to the entire surface of the fuel gas channel  40 , and discharged to the fuel gas outlet channels  174   a ,  174   b . Thus, in the sixth embodiment, the same advantages as in the case of the fifth embodiment are obtained.