Patent Publication Number: US-2013236803-A1

Title: Fuel cell module

Description:
TECHNICAL FIELD  
     The present invention relates to a fuel cell module having a plurality of fuel cells. 
     BACKGROUND ART  
     A fuel cell is an apparatus which comprises a stacked structure comprising an electrolyte and a set of electrodes (anode and cathode) disposed in a manner to sandwich the electrolyte and which takes out the electrical energy generated in the stacked structure through a current collector (for example, separator) arranged outside the stacked structure. Among various fuel cells, solid polymer electrolyte fuel cell (hereinafter, referred to as “PEFC”.) used for domestic cogeneration system, automobiles, and so on can be operated in a low temperature region. Because of its high energy conversion efficiency, short start-up time, and small-sized and lightweight system, the PEFC has received attention as a power source of electric vehicles or cellular phones. 
     A unit cell of the PEFC comprises: an membrane electrode assembly (MEA); and cathode and anode both at least comprising a catalyst layer. Its theoretical electromotive force is 1.23 V. In the PEFC, a hydrogen-containing gas is supplied to an anode and an oxygen-containing gas is supplied to a cathode. The hydrogen supplied to the anode separates into proton and electron on a catalyst contained in a catalyst layer of the anode (hereinafter, referred to as “anode catalyst layer”.). The proton generated from the hydrogen reaches a catalyst layer of the cathode (hereinafter, referred to as “cathode catalyst layer”.) through the anode catalyst layer and the electrolyte membrane. On the other hand, the electron reaches the cathode catalyst layer through an external circuit; with this process, it is possible to take electrical energy out. Then, when the proton and electron respectively having reached the cathode catalyst layer react with the oxygen to be supplied to the cathode catalyst layer, water is produced. 
     As techniques related to such a fuel cell, for example, Patent document 1 discloses a fuel cell module, in which a plurality of fuel cells are stacked; gaskets are integrally formed at the peripheral edges of the stacked membrane electrode assemblies and porous bodies, to form a single module comprising a plurality of the fuel cells; and a plurality of stacked bodies are assembled. In the Patent document 1, the fuel cell is provided with a plurality of manifolds, separators are respectively disposed at both ends of the stacked body, and an endless first sealing member (i.e. O-ring) surrounding the manifold intervenes between separators of adjacent stacked bodies. In addition, Patent document 1 also discloses an embodiment where an endless groove is formed at a position around the manifold of opposing face of separators of the adjacent stacked bodies so that the position of the groove in one separator corresponds to that of the groove in the other separator, wherein in the form where adjacent stacked bodies are assembled, a part of or all of the first sealing member is received in an endless space defined by both of the grooves corresponding to each other. Patent document 2 discloses a fuel cell at least comprising a pair of a first and a second electrolyte membrane-electrode assemblies disposed at both ends of the electrolyte; the fuel cell is provided with a plurality of generating unit formed of: a first metal separator, the first electrolyte membrane-electrode assembly, a second metal separator, the second electrolyte membrane-electrode assembly, and a third metal separator, laminated in the mentioned order, wherein passage for cooling medium is formed between the generating unit. Patent document 3 discloses a fuel cell comprising: a first separator and a second separator, wherein the first separator has a smaller outer diameter than the second separator and wherein the outer periphery of the second separator has fluid communication holes, which at least includes: a fuel gas entrance communication hole, a fuel gas exit communication hole, an oxidizer gas entrance communication hole and an oxidizer gas exit communication hole, respectively penetrating in the stacking direction at the position protruding outwardly from an outer-shape end of the first separator. Patent document 4 discloses a separator for compact fuel cell, which comprises: a gas inlet manifold; gas passages penetrating in a strip-like manner over the electrode area in a battery side face; gas grooves for inletting gas formed in the face opposite to the battery side face so as to connect the manifold to the gas passage; and O-ring groove formed so as to encircle the gas passage and the gas groove. 
     CITATION LIST  
     Patent Literature  
     Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No. 2010-080222 
     Patent Document 2: JP-A No. 2009-043665 
     Patent Document 3: JP-A No. 2007-324108 
     Patent Document 4: JP-A No. 2002-056859 
     DISCLOSURE OF THE INVENTION  
     Problems to be Solved by the Invention  
     In the technique disclosed in Patent document 1, it is thought that when an inexpensive and easily exchangeable O-ring is used as the first sealing member, it is possible to improve, for example, working efficiency at a time of maintenance. In general, when the size and power of a fuel cell module is specified, the diameter of an O-ring for sealing fluid used in the fuel cell module is specified. Conventionally, in a case of using a separator of which thickness is larger than the depth of a recess portion for installing an O-ring having a required diameter, it is possible to adequately seal fluid by using an O-ring having an appropriate diameter and being installed in the groove formed in the separator. However, when using a thinner separator with the development of thin technology of unit cell, it is difficult to provide in a separator a groove which is capable of receiving an O-ring having an appropriate diameter. So, there is a potential difficulty to secure an adequate sealing function. Such a problem is difficult to be solved even by a combination of the technique disclosed in Patent document 1 and techniques of Patent documents 2 to 4. 
     Accordingly, an object of the present invention is to provide a fuel cell module which is capable of easily securing an adequate sealing function even when the unit cell is made thinner. 
     Means for Solving the Problems  
     So as to solve the above problem, the present invention takes the following means. In other words, the invention is a fuel cell module comprising a stacked body which comprises: a stacked structure including: an electrolyte layer, and a pair of electrodes provided to sandwich the electrolyte layer; and a pair of separators disposed to sandwich the stacked structure, the separators being arranged at least one end of the stacked body in the stacking direction, the separators which are arranged at the end of the stacked body having a groove which is capable of receiving a sealing member in a face which does not oppose to the stacked structure, and the at least one groove being a deep groove of which depth is larger than the thickness of the separator having the groove. 
     Here, in the invention, when a porous body (for example, a gas diffusion layer) for letting a fluid passing therethrough is arranged between an electrode and a separator, the porous body is also the constituent element of the stacked structure. Moreover, in the invention, the term “stacking direction (of the stacked body)” means a direction along which elements constituting the stacked body such as electrolyte layer, electrodes, and separators are stacked; it can be expressed by “thickness direction of the separator”. The term “the separators which are arranged at the end of the stacked body” means at least one separator out of the separators disposed at both ends of the stacked body when the separators are respectively arranged at both ends of the stacked body in the stacking direction. On the other hand, when a separator is arranged at one end of the stacked body in the stacking direction and a constituent element other than the separator is arranged at the other end in the stacking direction, the term “the separators which are arranged at the end of the stacked body” means a separator arranged at one end of the stacked body in the stacking direction. In the invention, the term “face which does not oppose to the stacked structure” means the lower face (or the upper face) of a separator when the upper face (or the lower face) of the separator opposes to the stacked body. In the invention, the term “thickness of the separator having the groove” means a thickness of a separator at a position thereof opposing to the stacked structure in the stacking direction of the stacked body. In addition, the fuel cell module of the invention has a single stacked body or laminated two or more stacked bodies. 
     In the above invention, the height of a protrusion formed in a face, which does not have the deep groove, of the separator having the deep groove may be larger than the thickness of the stacked structure contacting the separator. 
     Here, for example, when the deep groove is provided at the upper face (or the lower face) of the separator, the term “a face, which does not have the deep groove, of the separator having the deep groove” means the lower face (or the upper face) of the separator. The term “a protrusion formed in a face, which does not have the deep groove, of the separator having the deep groove” means a protrusion formed in the lower face (or the upper face) of the separator by providing the deep groove in the upper face (or the lower face) of the separator. 
     In addition, in the invention where the height of the protrusion is larger than the thickness of the stacked structure contacting the separator, at least one of the separators which does not have the deep groove may have a recess portion which is capable of absorbing at least a part of the height of the protrusion. 
     Here, the phrase “at least one of the separators which does not have the deep groove has a recess portion which is capable of absorbing at least a part of the height of the protrusion” means that at least one of the separators which does not have the deep groove has a recess portion where the total thickness of a separator which does not have a recess portion and a separator which has a protrusion is thicker than the total thickness of two separators. 
     Moreover, in the above invention, the area of a face, of which normal direction is the stacking direction, of at least one of the separators which do not have the deep groove may be smaller than the separator having the deep groove, the smaller-sized separator and the separator having the deep groove may be arranged so that the outer periphery of the separator having the deep groove locates in the periphery of the smaller-sized separator, and the deep groove may be provided in the outer periphery of the separator having the deep groove located in the periphery of the smaller-sized separator. 
     Further, in the above invention, preferably, the separator having the deep groove has a fluid inlet passage penetrating therein, and the groove provided at the position having the fluid inlet passage is shallower than at least one of the grooves provided at the position which does not have the fluid inlet passage. 
     Here, the term “the groove provided at the position having the fluid inlet passage” means a groove of the separator, where the groove is provided at the upper side or the lower side of the fluid inlet passage when seeing a cutting plane (which defines the thickness direction of the separator as the vertical direction) at a position (where the fluid inlet passage locates) of the separator having a groove; namely, it is a groove provided in a manner to stride across the fluid inlet passage. In the invention, the groove and the fluid inlet passage are not communicated to each other. 
     Still further, in the above invention, preferably, a face, which does not oppose to the stacked structure, of the separator arranged at an end of the stacked body in the stacking direction comprises a passage for making a cooling medium or an oxygen-containing gas pass through and a groove which is capable of receiving a sealing member for preventing outflow of a cooling medium or an oxygen-containing gas passing through the passage, and the groove is provided in the outer periphery of the separator so that the groove encircles the passage, the manifold for the air to be supplied to the stacked structure, and the manifold for the cooling medium. 
     Here, the term “air to be supplied to the stacked body” means a hydrogen-containing gas and an oxygen-containing gas. 
     Effects of the Invention  
     The fuel cell module of the present invention has separators having deep grooves. By a configuration with a separator having a deep groove, even when the unit cell is made thinner, it is possible to secure the deep groove formed with a depth necessary to receive a sealing member such as O-ring, gasket, and adhesive. By securing the deep groove with a depth necessary to receive the sealing member, it is possible to easily secure an adequate sealing function. Accordingly, with this invention, it is possible to provide a fuel cell module which is capable of easily securing an adequate sealing function even when the unit cell is made thinner. 
     In the invention, even in a case that the height of the protrusion formed in a face, which does not have the deep groove, of the separator having the deep groove is larger than the thickness of the stacked structure contacting the separator, by modifying a separator other than separator having the deep groove, even when the unit cell is made thinner, it is possible to provide a fuel cell module which is capable of securing an adequate sealing function easily. 
     Moreover, in the invention where the height of the protrusion is larger than the thickness of the stacked structure contacting the separator, when at least one of the separators which does not have the deep groove has a recess portion which is capable of absorbing at least a part of the height of the protrusion, it becomes easy to attain thinning of the unit cell while securing an adequate sealing function. 
     Further, in the invention, with a configuration where a deep groove is provided in the outer periphery of a separator having a deep groove located in the periphery of the smaller-sized separator, it becomes easy to attain thinning of the unit cell while securing an adequate sealing function. 
     Still further, in the invention, with a configuration where the groove provided at the position having the fluid inlet passage is shallower than at least one of the grooves provided at the position which does not have the fluid inlet passage, it is possible to effectively use the thickness of the separator; thereby it becomes easy to attain thinning of the unit cell while securing an adequate sealing function. 
     Still further, in the invention, with a configuration where a passage for making a cooling medium or an oxygen-containing gas pass through and a groove which is capable of receiving a sealing member for preventing outflow of a cooling medium or an oxygen-containing gas passing through the passage locate in a surface of the separator which does not oppose to the stacked structure and the groove is provided to encircle the passage, the manifold for the air to be supplied to the stacked structure, and the manifold for the cooling medium, in addition to the above effects, it is possible to reduce wasted space of the fuel cell module. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a cross-sectional view illustrating a fuel cell module  100 ; 
         FIG. 2  is a cross-sectional view illustrating the fuel cell module  100 ; 
         FIG. 3  is a cross-sectional view illustrating a stacked structure  5 ; 
         FIG. 4  is a top view of a separator  1 ; 
         FIG. 5  is a plan illustrating a mode of conventional sealing; 
         FIG. 6  is a cross-sectional view illustrating a stacked body  30 ; 
         FIG. 7  is a cross-sectional view illustrating the laminated stacked bodies  30 ,  30 ; 
         FIG. 8  is a top view of a separator  40 ; 
         FIG. 9  is a cross-sectional view of the separator  40 ; and 
         FIG. 10  is another cross-sectional view of the separator  40 . 
     
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION  
     Hereinafter, the present invention will be described with reference to the drawings. It should be noted that the embodiments shown below are examples of the present invention, so that the invention is not limited by the embodiments. In order to make the understanding of the present invention easier, a part of the reference numerals in the drawings may not be shown. 
       FIG. 1  is a cross-sectional view illustrating a fuel cell module  100 . In  FIG. 1 , a part of the cross section of the fuel cell module  100  is shown. In  FIG. 1 , a hydrogen gas inlet passage connecting a hydrogen manifold  7  to hydrogen gas flow paths  1   b,    3   a,  an air inlet passage connecting an air manifold (not shown) to air flow paths  2   a,    4   b,  and a cooling medium inlet passage connecting a cooling medium manifold (not shown) to cooling medium passages  1   a,    4   a,    11  are not shown. 
     As shown in  FIG. 1 , the fuel cell module  100  comprises a stacked body  10  comprising: stacked structures  5 ,  5 ; separators  1 ,  2 ,  3 ,  4  disposed to sandwich the stacked structures  5 ,  5 ; a hole  7  which functions as a hydrogen manifold; an air manifold (not shown); and a cooling medium manifold. At both ends of the stacked body  10  in the stacking direction (i.e. the vertical direction of  FIG. 1 .), a separator  1  and a separator  4  are respectively arranged. Adhesives  6 ,  6  are arranged in the outer periphery of the stacked structures  5 ,  5 ; with the adhesives  6 ,  6 , the outer periphery of the separators  1 ,  3 ,  4  and an end face of the separator  2  are fixed. The separator  1  has deep grooves  1   x,    1   y  which are capable of receiving O-rings  8 ,  9  as a sealing member in a face which does not oppose to the stacked structure  5 . Moreover, the separator  4  has deep grooves  4   x,    4   y  which are capable of receiving O-rings  8 ,  9  as a sealing member in a face which does not oppose to the stacked structure  5 . The fuel cell module  100  is used in a condition that the laminated a plurality of stacked bodies  10 ,  10 , . . . are incorporated in a case (not shown). 
       FIG. 2  is a cross-sectional view illustrating a condition that a plurality of the stacked bodies  10 ,  10  are laminated. In  FIG. 2 , a hydrogen gas inlet passage connecting the hydrogen manifold  7  to the hydrogen gas flow paths  1   b,    3   a,  an air inlet passage connecting the air manifold (not shown) to the air flow paths  2   a,    4   b,  and a cooling medium inlet passage connecting the cooling medium manifold (not shown) to the cooling medium passages  1   a,    4   a,    11 ,  12  are not shown. As shown in  FIG. 2 , when a plurality of the stacked bodies  10 ,  10  are laminated, the O-ring  8  is set in a space defined by the deep groove  1   x  and the deep groove  4   x  and the O-ring  9  is set in a space defined by the deep groove  1   y  and the deep groove  4   y.  So as to secure a predetermined sealing property, the total depth of the deep groove  1   x  and the deep groove  4   x  is smaller than the diameter of the O-ring  8 ; with the O-ring  8  thus set, leakage of hydrogen passing through the hydrogen manifold  7  can be prevented. In addition, so as to secure a predetermined sealing property, the total depth of the deep groove  1   y  and the deep groove  4   y  is smaller than the diameter of the O-ring  9 ; with the O-ring  9  thus set, leakage of cooling medium passing through the cooling medium passage  12  can be prevented. 
       FIG. 3  is a cross-sectional view enlarging a part of the stacked structure  5 . As shown in  FIG. 3 , the stacked structure  5  comprises: a solid polymer electrolyte membrane  5   a  (hereinafter, referred to simply as “electrolyte membrane  5   a ”.); an MEA  5   x  having an anode electrode  5   b  and a cathode electrode  5   c  disposed in a manner to sandwich the electrolyte membrane  5   a;  and a gas diffusion layer  5   d  and a gas diffusion layer  5   e  disposed in a manner to sandwich the MEA  5   x.  In the stacked structure  5 , the gas diffusion layer  5   d  is disposed at the anode electrode  5   b  side; the gas diffusion layer  5   e  is disposed at the cathode electrode  5   c  side. The fuel cell module  100  will be described with reference to  FIGS. 1 to 3 . For example, a hydrogen gas which has been supplied to the stacked structure  5  through the hydrogen gas flow path  1   b  reaches the anode electrode  5   b  through the gas diffusion layer  5   d.  In the anode electrode  5   b,  a reaction expressed by the following formula (1); then protons and electrons are produced. 
       H 2 →2H + +2e −   (1)
 
     The protons produced in the anode electrode  5   b  reach the cathode electrode  5   c  through the electrolyte membrane  5   a;  while, since the electrolyte membrane  5   a  does not have electron conductivity, the electrons produced in the anode electrode  5   b  reach the cathode electrode  5   c  via the external circuit. 
     On the other hand, for example, the air which has been supplied to the stacked structure  5  through the air flow path  2   a  reaches the cathode electrode  5   c  through the gas diffusion layer  5   e.  Then, oxygen contained in the air which has been supplied to the cathode electrode  5   c  reacts with both protons and electrons transferred from the anode electrode  5   b  in the cathode electrode  5   c  to produce water. The reaction in the cathode electrode  5   c  to produce water is expressed by the following formula (2). 
       O 2 +4H + +4e − →2H 2 O   (2)
 
     As shown in  FIGS. 1 and 2 , the fuel cell module  100  comprises: the separator  1  having the deep grooves  1   x,    1   y;  and the separator  4  having the deep grooves  4   x,    4   y.  The deep grooves  1   x,    1   y  and the deep grooves  4   x,    4   y  can be formed by a known method such as press forming, drawing, and resin molding. In other words, with thinning of the unit cell, even when the thickness of the separator is made thinner, the deep groove in the fuel cell module of the invention can be easily formed. By securing the deep groove, even when the unit cell is made thinner, it is possible to secure an adequate sealing function (sealing property) by using not only gasket and adhesive but also inexpensive and easily exchangeable O-ring. Accordingly, with the present invention, even when the unit cell is made thinner, it is possible to provide the fuel cell module  100  which is capable of easily securing an adequate sealing function. 
       FIG. 4  is a top view of the separator  1 . As shown in  FIG. 4 , the separator  1  comprises: holes  7 ,  13  of the hydrogen manifold; holes  14 ,  15  of the air manifold; and holes  16 ,  18  of the cooling medium manifold. The holes  16  and  18  are connected to each other through a linear cooling medium passages  17  formed in the upper face of the separator  1 . In the separator  1 , a plurality of protrusions  17   a,    17   a,  . . . are provided between the hole  16  and the cooling medium passage  17 , and a plurality of protrusions  17   b,    17   b,  . . . are provided between the cooling medium passage  17  and the hole  18 . As shown in  FIG. 4 , the O-ring  8  is disposed around the hole  7 , the O-ring  19  is disposed around the hole  13 , the O-ring  20  is disposed around the hole  14 , and the O-ring  21  is disposed around the hole  15 . Then, the O-ring  9  is disposed at the outer periphery of the separator  1  in a manner to encircle these O-rings. With such a configuration, it is possible to prevent leakage of hydrogen gas by the O-rings  8 ,  19 ; it is possible to prevent leakage of the air by the O-rings  20 ,  21 ; and it is possible to prevent leakage of the cooling medium by the O-ring  9 . 
       FIG. 5  is a plan illustrating a mode of conventional sealing. In  FIG. 5 , to the elements having the same structure as those in the separator  1 , the same reference numerals as those used in  FIG. 4  are given and the explanation thereof is omitted. As shown in  FIG. 5 , in a conventional separator  91 , when sealing the cooling medium passing through the hole  16 , the cooling medium passage  17 , and the hole  18 , a sealing member  92  is disposed along the outer periphery of the hole  16 , the cooling medium passage  17 , and the hole  18 . By disposing the sealing member  92  in this way, it is possible to make the area surrounded by the sealing member  92  smaller. However, the sealing member  92  shown in  FIG. 5  has more complicated shape than the sealing member  9  shown in  FIG. 4 . So, when an O-ring is set in the groove having a complicated shape, the O-ring is twisted; thereby it is difficult to secure an adequate sealing function. Thus, it is difficult to use O-ring as the sealing member  92 . Even when the shape of grooves is complicated, sealing member such as gasket and adhesive can be used; so, conventionally, gasket and adhesive have been used as the sealing member  92 . However, when taking out one of the stacked bodies  10  which needs a replacement from a plurality of the stacked bodies  10 ,  10 , . . . which are laminated (shown in  FIG. 2 ), if an adhesive is used as the sealing member  92 , it is difficult to replace only the adhesive. Therefore, it is necessary to replace a plurality of the stacked bodies  10 ,  10 , . . . as a whole adhered by adhesive, which may raise the replacement cost. Other than this, it is difficult to inject and cure the adhesive after laminating a plurality of the stacked bodies  10 ,  10 , . . . . On the other hand, when using a gasket as the sealing member  92 , since the gasket can be replaceable, it is possible to replace, with a new gasket, a gasket broken at a time when taking out the stacked body  10 . However, gasket is more expensive than O-ring; so even when using gasket as the sealing member  92 , the replacement cost tends to be higher compared with the case of using O-ring. 
     On the other hand, as shown in  FIG. 4 , in the separator  1 , the O-ring  9  is arranged in the outer periphery of the separator  1  in a manner to encircle the O-ring  19 , the hole  16 , the O-ring  20 , the cooling medium passage  17 , the O-ring  8 , the hole  18 , and O-ring  21 . By arranging the O-ring  9  in such a position, the shape can be simplified than that of the sealing member  92  and it is possible to prevent twist of the O-ring  9 . Therefore, even when using the O-ring  9 , it is possible to secure an adequate sealing function. The O-ring  9  is more replaceable and inexpensive than gasket. So, compared with the case of using adhesive and gasket as the sealing member, it is possible to reduce the cost for replacing one of the stacked bodies  10  and reassembling the fuel cell module  100 . In addition, the O-ring  9  can be easily detached than gasket; so, it improves the efficiency of the replacement. Further, since O-ring does not have protrusions such as the ones which gasket has, it is possible to make the surface of the laminated stacked body smooth; thereby possible to improve the efficiency of the replacement. 
     In the above description, an embodiment in which the O-rings  8 ,  9 ,  19 ,  20 ,  21  are used as the sealing member is shown; the invention is not limited to this embodiment. In the fuel cell module of the invention, a sealing member other than O-ring (for example, adhesive and gasket) may be used. It should be noted that to have a configuration which is capable of easily securing an adequate sealing function with reduction of the cost of replacing the stacked body and improvement of the work efficiency, O-ring is preferably used as the sealing member. 
     Moreover, in the above description, as shown in  FIGS. 1 and 2 , embodiments comprise: a separator  1  having the deep grooves  1   x,    1   y  of which depth is larger than the thickness of the separator  1  opposing to the stacked structure  5  in the stacking direction of the stacked body  10 ; and a separator  4  having the deep grooves  4   x,    4   y  of which depth is larger than the thickness of the separator  4  at a position opposing to the stacked structure  5  in the stacking direction of the stacked body  10 . However, the invention is not limited to this embodiment. The fuel cell module of the invention may have a configuration where a separator having the deep grooves is provided at only one end of the stacked body in the stacking direction, while a separator without having the deep groove is provided at the other end of the stacked body. 
     In addition, in the above description, as shown in  FIGS. 1 and 2 , embodiments comprise the separator  1  where the height of protrusion formed in the face which does not have the deep grooves  1   x,    1   y  is larger than the thickness of the stacked structure  5 . However, the invention is not limited to this embodiment. The fuel cell module of the invention may be provided with a separator (which has the deep grooves and where the height of the protrusion is larger than the thickness of the stacked structure) each on both ends of the stacked body; it may also have a configuration where the separator (which has the deep grooves and where the height of the protrusion is larger than the thickness of the stacked structure) is not provided to the stacked body. 
     Further, in the above description, as shown in  FIGS. 1 and 2 , the embodiments has a configuration where the separator  1  and the separator  2  are arranged so that the outer periphery of the separator  1  locates in the periphery of the separator  2  of which area of a face whose normal direction is the stacking direction is smaller than the separator  1 ; and the deep grooves  1   x,    1   y  locate in the periphery of the separator  2 . However, the invention is not limited to this embodiment. When a separator where the height of the protrusion formed in the back-face side of the separator having the deep groove is larger than the thickness of the stacked structure is provided to the fuel cell module of the present invention, the height of the protrusion may be absorbed by modifying the shape in the thickness direction of the separator without having the deep groove, instead of being absorbed by reducing the size of the area of the separator  2  like the one in the fuel cell module  100 . An embodiment of the stacked body in which the height of the protrusion is absorbed by modifying the shape thereof in the thickness direction of the separator which does not have a deep groove is shown in  FIG. 6 . 
       FIG. 6  is a cross-sectional view illustrating a stacked body  30 .  FIG. 6  shows a cross-section of a part of the stacked body  30 . In  FIG. 6 , a hydrogen gas inlet passage connecting the hydrogen manifold  7  to hydrogen gas flow paths  31   b,    33   a,  an air inlet passage connecting the air manifold (not shown) to the air flow paths  32   a,    34   b,  and a cooling medium inlet passage connecting the cooling medium manifold (not shown) to cooling medium passages  31   a,    34   a,    11 , are not shown. In  FIG. 6 , to the elements having the same structure as those in the fuel cell module  100 , the same reference numerals as those used in  FIG. 1  are given and the explanation thereof is omitted. As shown in  FIG. 6 , the stacked body  30  comprises: stacked structures  5 ,  5 ; separators  31 ,  32 ,  33 ,  34  arranged to sandwich the stacked structures  5 ,  5 ; a hole  7  which functions as a hydrogen manifold; an air manifold (not shown); and a cooling medium manifold. The stacked body  30  is provided with the separator  31  on one end and the separator  34  on the other end in the stacking direction (i.e. vertical direction of  FIG. 6 .). Adhesives  6 ,  6 ,  6  are arranged in the outer periphery of the stacked structures  5 ,  5 ; by using the adhesives  6 ,  6 ,  6 , the outer periphery of the separators  31 ,  32 ,  33 ,  34  are fixed. The separator  31  has deep grooves  31   x,    31   y,  which are capable of receiving O-rings  8 ,  9 , as a sealing member in a face which does not oppose to the stacked structure  5 ; while, the separator  34  has deep grooves  34   x,    34   y  which are capable of receiving O-rings  8 ,  9 , as a sealing member in a face which does not oppose to the stacked structure  5 . The deep grooves  31   x,    31   y  and the deep grooves  34   x,    34   y  can be formed by a known method such as press forming, drawing, and resin molding. 
       FIG. 7  is a cross-sectional view illustrating a state where a plurality of the stacked bodies  30 ,  30  are laminated. In  FIG. 7 , a hydrogen gas inlet passage connecting the hydrogen manifold  7  to the hydrogen gas flow paths  31   b,    33   a,  an air inlet passage connecting the air manifold (not shown) to the air flow paths  32   a,    34   b,  and a cooling medium inlet passage connecting the cooling medium manifold (not shown) to the cooling medium passages  31   a,    34   a,    11 ,  12 , are not shown. In  FIG. 7 , to the elements having the same structure as those in the fuel cell module  100 , the same reference numerals as those used in  FIG. 2  are given and the explanation thereof is omitted. As shown in  FIG. 7 , when a plurality of the stacked bodies  30 ,  30  are laminated, the O-ring  8  is set in a space defined by the deep groove  31   x  and the deep groove  34   x  and the O-ring  9  is set in a space defined by the deep groove  31   y  and the deep groove  34   y.  To secure a predetermined sealing property, the total depth of the deep groove  31   x  and the deep groove  34   x  is smaller than the diameter of the O-ring  8 ; with the O-ring  8  thus arranged, it is possible to prevent leakage of hydrogen passing through the hydrogen manifold  7 . To secure a predetermined sealing property, the total depth of the deep groove  31   y  and the deep groove  34   y  is smaller than the diameter of the O-ring  9 ; with the O-ring  9  thus arranged, it is possible to prevent leakage of the cooling medium passing through the cooling medium passage  12 . 
     As shown in  FIG. 6 , the separator  32  which does not have the deep groove absorbs a part of the height of the protrusion formed in the back-face side of the deep grooves  31   x,    31   y  (i.e. the lower side of  FIG. 6 .) by modifying the shape of the separator  32  in the thickness direction (i.e. the vertical direction of  FIG. 6 .) and forming the recess portion  32   x  in the top-face side of the separator  32  (i.e. the upper side of  FIG. 6 .). The separator  33  which does not have the deep groove absorbs a part of the height of the protrusion formed in the back-face side of the deep grooves  34   x,    34   y  (i.e. the upper side of  FIG. 6 .) by modifying the shape of the separator  33  in the thickness direction (i.e. the vertical direction of  FIG. 6 .) and forming the recess portion  33   x  in the underside of the separator  33  (i.e. the lower side of  FIG. 6 .). Even by the stacked body  30  with this configuration, it is possible to secure the deep grooves  31   x,    31   y  and the deep grooves  34   x,    34   y.  Therefore, in the same manner as the stacked body  10 , even when the thickness of the separator is made thinner, it is possible to secure the sealing function (sealing property) by not only using gasket and adhesive but also using inexpensive and easily replaceable O-rings  8 ,  9 . Accordingly, by the present invention with the stacked body  30 , it is possible to provide a fuel cell module which is capable of easily securing an adequate sealing function even when the unit cell is made thinner. 
     As shown in  FIGS. 1 ,  2 ,  5 , and  7 , the above description regarding the invention shows embodiments in which depth of respective separators is all the same. However, the fuel cell module of the present invention is not limited to these embodiments. The fuel cell module of the invention may have an embodiment which comprises a separator having a plurality of grooves of which depth is respectively different. So, the embodiment which comprises a separator having a plurality of grooves of which depth is respectively different will be described as follows. 
       FIG. 8  is a top view of a separator  40  provided to the fuel cell module of the invention. As shown in  FIG. 8 , a separator  41  is provided in one end of the stacked body  40  in the stacking direction. The separator  41  comprises: holes  46 ,  47  of the hydrogen manifold; holes  48 ,  49  of the air manifold; and holes  50 ,  51  of cooling medium manifold. The holes  50  and  51  are connected to each other through a linear cooling medium passage  41   a  formed in the surface of the separator  41 . In the separator  41 , a plurality of protrusions  41   c,    41   c,  . . . are provided between the hole  50  and the cooling medium passage  41   a,  and a plurality of protrusions  41   d,    41   d,  . . . are provided between the cooling medium passage  41   a  and the hole  51 . As shown in  FIG. 8 , an O-ring  52  is disposed around the hole  46 , an O-ring  53  is disposed around the hole  47 , an O-ring  54  is disposed around the hole  48 , and an O-ring  55  is disposed around the hole  49 . Then, an O-ring  56  of which diameter is larger than the O-rings  52 ,  53 ,  54 ,  55  is disposed in the outer periphery of the separator  41  in a manner to encircle these O-rings. With such a configuration, it is possible to prevent leakage of hydrogen gas by the O-rings  52 ,  53 ; it is possible to prevent leakage of air by the O-rings  54 ,  55 ; and it is possible to prevent leakage of the cooling medium by the O-ring  56 . 
       FIG. 9  is a view enlarging the cross section taken along the line IX-IX of  FIG. 8 . To make seeing of the groove  41   x  easier,  FIG. 9  does not show the O-ring  55  provided to the groove  41   x.    FIG. 10  is a view enlarging the cross section taken along the line X-X of  FIG. 8 . To make seeing of the groove  41   z  easier,  FIG. 10  does not show the O-ring  53  provided to the groove  41   z.  As shown in  FIGS. 9 and 10 , the stacked body  40  comprises: the stacked structures  5 ,  5 ; the separators  41 ,  42 ,  43 ,  44  provided to sandwich the stacked structures  5 ,  5 ; the hole  47  which functions as a hydrogen manifold; and the hole  49  which functions as an air manifold. In the stacked body  40 , the separator  41  is provided in one end and the separator  44  is provided in the other end thereof in the stacking direction (i.e. the vertical direction of  FIGS. 9 and 10 .). Adhesives  45 ,  45 ,  45  are arranged in the outer periphery of the stacked structures  5 ,  5 ; by using the adhesives  45 ,  45 ,  45 , the outer periphery of the separators  41 ,  42 ,  43 ,  44  are fixed. The separator  41  has: the deep groove  41   y  to which the O-ring  56  is set, the groove  41   x  to which the O-ring  55  is set, and the groove  41   z  to which the O-ring  53  is set, respectively in a face which does not oppose to the stacked structure  5 , while the separator  44  has: the cooling medium passage  44   a,  the deep groove  44   y  which is capable of receiving the O-ring  56 , the groove  44   x  which is capable of receiving the O-ring  55 , and the groove  44   z  which is capable of receiving the O-ring  53 , respectively in a face which does not oppose to the stacked structure  5 . The grooves  41   x,    41   z,    44   x,    44   z  and the deep grooves  41   y,    44   y  can be formed by a known method such as press forming, drawing, and resin molding. 
     As shown in  FIG. 10 , the separator  41  is provided with a fluid inlet passage  41   p  (hereinafter, referred to as “hydrogen inlet passage  41   p ”.) which connects the hole  47  to the hydrogen gas flow path  41   b;  while the separator  43  is provided with a fluid inlet passage  43   x  which connects the hole  47  to the hydrogen gas flow path  43   a.  In addition, as shown in  FIG. 9 , the separator  42  is provided with a fluid inlet passage  42   x  which connects the hole  49  to the air flow path  42   a;  while the separator  44  is provided with a fluid inlet passage  44   p  (hereinafter, referred to as “air inlet passage  44   p ”.) which connects the hole  49  to the air flow path  44   b.  As shown in  FIGS. 9 and 10 , the depth of the groove  41   z  provided in a manner to stride across the hydrogen inlet passage  41   p  is smaller than the depth of the groove  41   x  which does not stride across the fluid inlet passage; the depth of the groove  44   x  provided in a manner to stride across the air inlet passage  44   p  is smaller than the depth of the groove  44   z  which does not stride across the fluid inlet passage. By setting the depth of the grooves  41   x,    41   z,    44   x,    44   z  in this way, thinning of the unit cell tends to be easily attained while securing an adequate sealing function. It should be noted that since the stacked body  40  has the deep grooves  41   y,    44   y,  with the fuel cell module of the invention having the stacked body  40 , it is possible to easily secure an adequate sealing function even when the unit cell is made thinner. 
     The above description regarding the present invention shows an embodiment where, for example, the cooling medium passages  1   a,    4   a  and the deep grooves  1   y,    4   y  to which the O-ring  9  is to be set for preventing outflow of the cooling medium passing in the cooling medium passages  1   a,    4   a  are provided in a face (which does not oppose to the stacked structures  5 ,  5 ) of the separators  1 ,  4  provided at the ends of the stacked body  10  in the stacking direction. However, the invention is not limited to the embodiment. The fuel cell module of the invention may have an embodiment in which a passage for making the air pass through and a groove which is to be provided with a sealing member for preventing outflow of air passing through the passage are provided, in a face (which does not oppose to the stacked structure) of the separator provided at the ends of the stacked body in the stacking direction. Other than this, the fuel cell module of the invention may have an embodiment in which a passage for making fluid pass through and a groove which is to be provided with a sealing member corresponding to the passage for making fluid pass through are not provided, in a face (which does not oppose to the stacked structure) of the separator provided to the ends of the stacked body in the stacking direction. It should be noted that in view of obtaining a configuration which is capable of thinning and attaining higher performance by reduction of wasted space of the fuel cell module, the fuel cell module preferably has a configuration comprising a passage for making the cooling medium or air pass through and grooves for setting a sealing member for preventing outflow of the cooling medium or air passing through the passage, in a face (which does not oppose to the stacked structure) of the separator provided at the end of the stacked body in the stacking direction. Moreover, so as to provide an inexpensive fuel cell module in which the sealing member can be easily replaced, the groove for the sealing member provided in a face which does not oppose to the stacked structure is preferably provided in the outer periphery of the separator disposed at the end of the stacked body in the stacking direction. To the groove, an O-ring is preferably provided. 
     Further, the above description shows an embodiment in which sealing member for preventing outflow of the cooling medium or air passing through the passage is provided in a face which does not oppose to the stacked structure when providing a passage for cooling medium or air in a face (which does not oppose to the stacked structure) of the separator disposed at the end of the stacked body in the stacking direction. However, the invention is not limited to the embodiment. The fuel cell module of the invention may also have a configuration where the sealing member for preventing outflow of the cooling medium or air passing through the passage is not provided in a face which does not oppose to the stacked structure even when providing the passage for cooling medium or air in a face (which does not oppose to the stacked structure) of the separator provided at the end of the stacked body in the stacking direction. In such a case, it maybe thought that the cooling medium or air flows out from the stacked body; however, as described above, since the fuel cell module of the invention is used in a state where the stacked body is housed in a case, it is assumed that there is no influence to the external environment as long as the cooling medium or air does not flow out from the case. Because of this, when the sealing member for preventing outflow of the cooling medium or air passing in the face (which does not oppose to the stacked structure) of the separator disposed at the end of the stacked body in the stacking direction is not disposed in a face which does not oppose to the stacked structure, sealing function for preventing outflow of the cooling medium or air may be given to the case receiving the stacked body. For example, let us study a case that a laminated plurality of the stacked bodies are received in a case by making a laminated plurality of the stacked bodies received in a rectangular first case, whose one of the faces is opened and covering the opening with a sheet member. In this case, for example, when providing liquid packing, O-ring, and so on, in a face which opposes to the stacked body of a sheet member, by covering with the sheet member the opening of the first case which receives the plurality of the stacked body, it is possible to give the sealing function for preventing outflow of the cooling medium or air to the case for receiving the stacked body. By handing over the sealing function to the case which receives the stacked body, there is no need for providing a sealing member for preventing outflow of the cooling medium or air passing through the passage provided in the face (which does not oppose to the stacked structure) of the separator provided at the end of the stacked body in the stacking direction to the face which does not oppose to the stacked structure; so, it is possible to provide a fuel cell module which is capable of simplifying the production process. 
     DESCRIPTION OF THE REFERENCE NUMERALS  
       1 ,  2 ,  3 ,  4  separator 
       1   a,    4   a,    11 ,  12 ,  17  cooling medium passage 
       1   b,    3   a  hydrogen gas flow path 
       1   x,    1   y,    4   x,    4   y  deep groove 
       2   a,    4   b  air flow path 
       5  stacked structure 
       6  adhesive 
       7 ,  13  hole (hydrogen manifold) 
       8 ,  9 ,  19 ,  20 ,  21  O-ring (sealing member) 
       10  stacked body 
       14 ,  15  hole (air manifold) 
       16 ,  18  hole (cooling medium manifold) 
       30  stacked body 
       31 ,  32 ,  33 ,  34  separator 
       31   a,    34   a  cooling medium passage 
       31   b,    33   a  hydrogen gas flow path 
       31   x,    31   y,    34   x,    34   y  deep groove 
       32   a,    34   b  air flow path 
       32   x,    33   x  recess portion 
       40  stacked body 
       41 ,  42 ,  43 ,  44  separator 
       41   a  cooling medium passage 
       41   b,    43   a  hydrogen gas flow path 
       41   p  hydrogen inlet passage (fluid inlet passage) 
       41   x,    41   z  groove 
       41   y  deep groove 
       42   a,    44   b  air flow path 
       42   x,    43   x  fluid inlet passage 
       44   a  cooling medium passage 
       44   p  air inlet passage (fluid inlet passage) 
       44   x,    44   z  groove 
       44   y  deep groove 
       45  adhesive 
       46 ,  47  hole (hydrogen manifold) 
       48 ,  49  hole (air manifold) 
       50 ,  51  hole (cooling medium manifold) 
       52 ,  53 ,  54 ,  55 ,  56  O-ring (sealing member) 
       100  fuel cell module