Abstract:
The present invention is to provide a sealing member for a fuel cell which is able to keep surface pressure low, and to enhance sealing performance. The fuel cell includes an anode electrode and a cathode electrode which are sandwiched on both sides of a solid polymer electrolyte membrane, and an anode side separator and a cathode side separator which are then layered against both sides of this combination. Sealing members are installed into grooves on these separators. The cross section of each sealing member is formed with projecting portions extending in the widthwise direction of its groove on both sides of a semicircular shaped sealing member main body, and with a pair of cutaway portions in positions symmetrical about the center of a chord portion of the sealing member main body.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sealing member for a fuel cell, and more particularly relates to the sealing member which can enhance sealing performance. 
     2. Description of the Related Art 
     There is a per se known type of solid polymer electrolyte type fuel cell which has been developed, in which a plurality of fuel cell units are layered together, each fuel cell unit including a solid polymer electrolyte membrane with an anode electrode and a cathode electrode sandwiching it from its opposing sides, and with a pair of separators sandwiching this membrane electrode assembly having aforementioned structure from both its sides, the whole being secured together into a unit. These fuel cells are effective for various uses. 
     With these types of fuel cell, fuel gas—for example, hydrogen gas—is supplied to the anode electrode side, and is converted into hydrogen ions by an electrode catalyst, and then moves towards the cathode electrode via the solid polymer electrolyte membrane which is appropriately humidified. The electrons which are generated at the anode are emitted to an external circuit, and are used as DC electrical energy. An oxidizing gas, for example oxygen gas or air, is supplied to the cathode electrode, so that these hydrogen ions, this oxygen gas, and these electrons are reacted together at this cathode electrode to generate water. 
     Moreover, gas-tightness is ensured by the provision of sealing members between separators which are provided on both sides of the membrane electrode assembly, in order for this fuel gas and oxidizing gas which are supplied to the anode electrode and the cathode electrode not to leak to the outside, and it is arranged for the fuel gas and the oxidizing gas to be conducted to the reaction surfaces, which are the portions of these separators which are introduced by the sealing members. 
     Furthermore, in order to prevent rise of the temperature of the fuel cell due to the reaction between the fuel gas and the oxidizing gas, a coolant fluid is supplied to between neighboring ones of the separators when the fuel cell units are layered together, and sealing members are provided for preventing leaking out of the coolant fluid to the exterior around the peripheries of the cooling surfaces of the separators, as well. 
     In addition, when supplying the reaction gases such as fuel gas and oxidizing gas to the anode electrode and to the cathode electrode, and supplying coolant fluid to the cooling surfaces, if an internal manifold structure is used reaction gas supply holes (or openings)and coolant supply holes are formed to penetrate through each separator, it is furthermore necessary to seal the periphery of each supply hole with a sealing member. 
     An example of a prior art such sealing member which surrounds the reaction surfaces will now be explained with reference to FIG.  11 . In FIG. 11, reference numeral  1  denotes the solid polymer electrolyte membrane, and this solid polymer electrolyte membrane  1  is sandwiched between an anode electrode  2  and a cathode electrode  3 , to constitute a membrane electrode assembly  4 . This membrane electrode assembly  4  is further sandwiched between a pair of separators  5  and  6  on both its sides, and constituting the fuel cell. 
     The periphery of the solid polymer electrolyte membrane  1  extends further outwards than the peripheral edge portions of the electrodes  2  and  3 , and this projecting edge portion is sandwiched on both its sides by sealing members  8  which are fitted into grooves  7  formed upon the inwardly facing surfaces of the separators  5  and  6 . And reaction gas conduits  9  and  10  are formed in the surfaces of the separators  5  and  6  which face the electrodes  2  and  3 . 
     Accordingly, fuel gas and oxidizing gas are respectively supplied to the reaction gas conduits  9  and  10  defined between the electrodes  2  and  3  and the separators  5  and  6  which are surrounded by the above described sealing members  8 , and the sealing members  8  ensures that these reaction gases do not escape to the outside. This matter is disclosed in Japanese Patent Application, First Publication No. Hei 8-37012. 
     However, with the sealing member for a fuel cell according to the above describer prior art, when the sealing member  8  is affixed by being pushed into the groove  7  until the width of the groove  7  is filled, and the separators  5  and  6  are fitted to both sides of the membrane electrode assembly  4  and are fastened thereagainst by being clamped, since there is no space into which the deformed sealing member can be released, a great fastening force for the clamping mechanism is necessary, and the surface pressure upon the sealing member  8  becomes great. Accordingly, the problem arises that a clamping mechanism of relatively great size and weight is required for ensuring a sufficiently great clamping force, when a plurality of these fuel cell units are layered together into a fuel cell assembly. 
     By contrast, it would also be possible to make the width of the groove  7  relatively large with respect to the diameter of the sealing member  8  which is to be used, and to fit the sealing member  8  into the groove  7  with a degree of extra space being left available. However, if this is done, when the separators  5  and  6  are clamped against the membrane electrode assembly  4  from both its sides, positional deviation or slippage of the sealing members  8  in the grooves  7  of the separators can easily occur, as shown in FIG. 12, and thus the problem arises that it is not possible to ensure a reliable seal between the separators  5  and  6  and the solid polymer electrolyte membrane  1 , due to the shearing force which can deform the solid polymer electrolyte membrane  1 . 
     SUMMARY OF THE INVENTION 
     It is the objective of the present invention to provide a sealing member for a fuel cell, with which it is possible to keep the surface pressure which is applied to the sealing member low, thus making it possible to enhance the sealing performance. 
     In order to achieve the above described objective, the first aspect of the present invention proposes a sealing member (for example, in the disclosed embodiment, the sealing members S 1  and S 2 ) for a fuel cell which comprises a pair of electrodes (for example, in the disclosed embodiment, the anode electrode A and the cathode electrode C) which sandwich an electrolyte membrane (for example, in the disclosed embodiment, the solid polymer electrolyte membrane  15 ) on both its sides, and a pair of separators (for example, in the disclosed embodiment, the anode side separator  13  and the cathode side separator  14 ) which sandwich the electrolyte membrane on both its outer sides. The sealing member installed into a groove (for example, in the disclosed embodiment, the grooves  38  and  39 ) in each separators, and characterized by being formed, in cross section, with a pair of cutaway portions (for example, in the disclosed embodiment, the cutaway portions  43 ) in symmetrical positions with respect to the center of a chord portion (for example, in the disclosed embodiment, the chord portion  40   b ) of a generally semicircular shaped sealing member main body (for example, in the disclosed embodiment, the sealing member main body  40 ). 
     According to the sealing member having this structure, when pressure acts from the arcuate portion (for example, in the disclosed preferred embodiment, the arcuate portion  40   a ) which opposes the chord portion of the sealing member main body, the portion between said pair of cutaway portions becomes a sealing surface (for example, in the disclosed preferred embodiment, the bottom portion  40   c ), and it is possible to enhance the sealing performance. Furthermore, it is possible to ensure a relatively large amount of elastic deformation of the sealing member main body with a relatively small amount of pressure, since it is possible to release the portions which have been deformed by the pressure into the void portions (for example, in the disclosed preferred embodiment, the void portions  45 ) which are defined between the groove and the cutaway portions. Accordingly, if a plurality of these fuel cells are layered together into a single assembly, it is possible to reduce the overall force which is required for clamping them together as compared with the prior art, and thus it is possible to reduce the overall size and weight of the clamping structure. 
     The second aspect of the present invention proposes the sealing member as described above, further characterized in that projecting portions (for example, in the disclosed embodiment, the projecting portions  42 ) are provided on both sides of the chord portion extending in the widthwise direction of the groove, and the projecting portions extend to positions which adjoin or contact side walls (for example, in the disclosed embodiment, the side walls  38   a  and  39   a ) of the groove. 
     According to the sealing member having this structure, it is possible to position the central portion of the chord portion at the central portion of the groove in its widthwise direction, and it is possible to ensure that no slippage occurs in the widthwise direction of the groove, since the movement of the ends of these projecting portions which are provided as extending in the widthwise direction of the groove are prevented by the side walls of the groove. 
     And the third aspect of the present invention proposes the sealing member as described above, further characterized in that cutaway portions (for example, in the disclosed embodiment, the cutaway portions  44 ) are formed upon the projecting portions at predetermined intervals in the lengthwise direction of the groove. 
     According to the sealing member having this structure, when pressure acts upon the arcuate portion, it is possible to ensure a relatively great amount of elastic deformation, since it is possible to release the portions which are deformed into the void portions (for example, in the disclosed preferred embodiment, the void portions  45 ) which are defined between the side walls of the groove and the cutaway portions. Moreover, the ease of working when inserting the sealing member into the groove is enhanced, because the area of the projection portion which contacts the groove is reduced. 
    
    
     BRIEF EXPLANATION OF THE DRAWINGS 
     FIG. 1 is an exploded perspective view of a fuel cell which incorporates a sealing member according to a preferred embodiment of the present invention. 
     FIG. 2 is a sectional view of the fuel cell of FIG. 1 in its assembled state, taken in a sectional plane shown by the arrows X 1 —X 1 . 
     FIG. 3 is a view of the fuel cell of FIG. 1 as seen in the direction of the arrow X 2 . 
     FIG. 4 is a view of the fuel cell of FIG. 1 as seen in the direction of the arrow X 3 . 
     FIG. 5 is a view of the fuel cell of FIG. 1 as seen in the direction of the arrow X 4 . 
     FIG. 6 is an enlarged schematic view of essential portions of FIG.  2 . 
     FIG. 7 is a sectional view of a sealing member according to the preferred embodiment of the present invention shown in FIG. 8, taken in a sectional plane shown by the arrows X 5 —X 5 . 
     FIG. 8 is a plan view of the sealing member according to the preferred embodiment of the present invention. 
     FIG. 9 is a plan view corresponding to FIG. 8, showing another preferred embodiment of the present invention. 
     FIG. 10 is a sectional view of a sealing member according to another preferred embodiment of the present invention. 
     FIG. 11 is a sectional view of an example of the conventional fuel cell. 
     FIG. 12 is an explanatory partial sectional view of the fuel cell of FIG.  11 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Several preferred embodiments of the present invention will now be described with reference to the drawings. 
     FIG. 1 is an exploded perspective view showing a fuel cell which incorporates a sealing member according to a preferred embodiment of the present invention, and FIG. 2 is a sectional view of the fuel cell of FIG. 1 in its assembled state, taken in a sectional plane shown by the arrows X 1 —X 1 . In FIGS. 1 and 2, a fuel cell N comprises a fuel cell unit which is composed of a membrane electrode assembly  12 , and an anode side separator  13  and a cathode side separator  14  which are provided on both the sides of said assembly  12  so as to sandwich it, and a plurality of fuel cell units are layered and fixed together by a fixing structure consisting, for example, of bolts and nuts, so as to constitute a fuel cell stack for use in a vehicle. 
     This membrane electrode assembly  12  comprises a solid polymer electrolyte membrane  15 , and an anode side electrode catalytic layer  16  and a cathode side electrode catalytic layer  17  provided on both the sides of this solid polymer electrolyte membrane  15  so as to sandwich it. Furthermore, on the outsides of both the anode side electrode catalytic layer  16  and the cathode side electrode catalytic layer  17 , there are provided an anode side porous conductor  18  and a cathode side porous conductor  19 . 
     The above described anode side porous conductor  18  and cathode side porous conductor  19 , for example, may be made from porous carbon paper, porous carbon cloth, or porous carbon felt. Furthermore, a perfluorosulphonic acid polymer may be used for the solid polymer electrolyte membrane  15 . On the other hand, the anode side electrode catalytic layer  16  and the cathode side electrode catalytic layer  17  are mainly made from platinum. It should be understood that the above described anode side electrode catalytic layer  16  and anode side porous conductor  18  together constitute an anode electrode A, while the above described cathode side electrode catalytic layer  17  and cathode side porous conductor  19  together constitute a cathode electrode C. 
     To the solid polymer electrolyte membrane  15 , there is provided a projecting portion  15   a  which extends all around its outer peripheral edge and projects outwards from the outer peripheral edge portions of the anode electrode A and cathode electrode C which face it on either side so as to sandwich it. Furthermore, an anode side sealing member S 1  and a cathode side sealing member S 1  which will be described hereinafter are directly and tightly contacted against this projecting portion  15   a  from both sides. 
     As shown in FIG. 1, the cathode side separator  14  comprises, on its outer circumferential edge portion at opposing upper side positions on both sides in the horizontal direction as seen in the figure, an inlet side fuel gas through hole  22   a  for passing a fuel gas such as a gas containing hydrogen or the like, and an inlet side oxidizing gas through hole  23   a  for passing an oxidizing gas which may be a gas containing oxygen or simply air. Moreover, in the cathode side separator  14  there are provided, on its outer circumferential edge portion at opposing middle side positions on both sides in the horizontal direction as seen in the figure, an inlet side cooling medium through hole  24   a  for passing in a cooling medium such as pure water or ethylene glycol or oil, and an outlet side cooling medium through hole  24   b  for passing out said cooling medium after it has been used. Furthermore, in the cathode side separator  14  there are provided, on its outer circumferential edge portion at opposing lower side positions on both sides in the horizontal direction as seen in the figure, an outlet side fuel gas through hole  22   b  for passing out said fuel gas after it has been used, and an outlet side oxidizing gas through hole  23   b  for passing out said oxidizing gas after it has been used, in positions diagonally opposing to the inlet side fuel gas through hole  22   a  and the inlet side oxidizing gas through hole  23   a , respectively. 
     In the surface  14   a  of the cathode side separator  14  which faces the cathode electrode C, there are provided a plurality of independent oxidizing gas flow grooves  25 —for example, six thereof—which communicate the inlet side oxidizing gas through hole  23   a , and which extend in the vertical direction while meandering in the horizontal direction. These oxidizing gas flow grooves  25  merge together into three oxidizing gas flow grooves  26 , and these three oxidizing gas flow grooves  26  terminate by closely approaching to the outlet side oxidizing gas through hole  23   b.    
     As shown in FIG. 3, on the cathode side separator  14  there are provided, penetrating through the cathode side separator  14 , oxidizing gas communication conduits  27  of which the one ends are connected to the inlet side oxidizing gas through hole  23   a  upon the surface  14   b  which is opposing to the surface  14   a  while their other ends are connected to the oxidizing gas flow grooves  25  upon said surface  14   a . Similarly, on the cathode side separator  14  there is provided, piercing through the cathode side separator  14 , oxidizing gas communication conduits  29  of which the one ends are connected to the outlet side oxidizing gas through hole  23   b  upon said surface  14   b  while their other ends are connected to the oxidizing gas flow grooves  26  upon said surface  14   a.    
     As shown in FIGS. 4 and 5, similar to the case of the cathode side separator  14 , there are formed, passing through the surface of the anode side separator  13  and positioned in its outer peripheral edge portion at both opposing ends in the horizontal direction, an inlet side fuel gas through hole  22   a , an inlet side oxidizing gas through hole  23   a , an inlet side cooling medium through hole  24   a , an outlet side cooling medium through hole  24   b , an outlet side fuel gas through hole  22   b , and an outlet side oxidizing gas through hole  23   b.    
     As shown in FIG. 4, in the surface  13   a  of the anode side separator  13  which faces the anode electrode A, there are formed a plurality of fuel gas flow grooves  30 —for example, six thereof—which closely approach the inlet side fuel gas through hole  22   a . These fuel gas flow grooves  30  extend in the vertical direction while meandering in the horizontal direction, and merge together into three fuel gas flow grooves  31 , with these three fuel gas flow grooves  31  terminating by closely approaching to the outlet side fuel gas through hole  22   b.    
     Moreover, in this anode side separator  13  there are provided, piercing through said anode side separator  13 , fuel gas communication conduits  32  which communicate the inlet side fuel gas through hole  22   a  from the side of the surface  13   b  to the fuel gas flow grooves  30 . Similarly, in this anode side separator  13  there are provided, piercing through said anode side separator  13 , fuel gas communication conduits  33  which communicate the outlet side fuel gas through hole  22   b  from the side of said surface  13   b  to the fuel gas flow grooves  31 . 
     As shown in FIG. 5, upon the surface  13   b  of the anode side separator  13  there are formed a plurality of main flow grooves  34   a  and  34   b  which approach close to the inlet side cooling medium through hole  24   a  and close to the outlet side cooling medium through hole  24   b , respectively. Between the main flow grooves  34   a  and  34   b  there are provided a plurality of branching flow grooves  35  which branch off therefrom and which extend in the horizontal direction as seen in the figure. 
     Piercing through the anode side separator  13 , there are formed cooling medium communication conduits  36  which connect the inlet side cooling medium through hole  24   a  and the main flow grooves  34   a , and cooling medium communication conduits  37  which connect the outlet side cooling medium through hole  24   b  and the main flow grooves  34   b.    
     As shown in FIG. 4, upon the surface  13   a  of the anode side separator  13  there is provided a groove  38  which is just outside the peripheral portion of the anode electrode A and which faces the solid polymer electrolyte membrane  15  in a position which opposes the projecting portion  15   a  thereof, and a sealing member S 1  is fitted in this groove  38 . Furthermore, grooves  39  are formed upon this face  13   a  of this anode side separator  13 , one of which surrounds each of the inlet side fuel gas through hole  22   a , the inlet side oxidizing gas through hole  23   a , the inlet side cooling medium through hole  24   a , the outlet side cooling medium through hole  24   b , the outlet side fuel gas through hole  22   b , and the outlet side oxidizing gas through hole  23   b ; and sealing members S 2  are fitted in these grooves  39 . These sealing members S 2  will be described hereinafter. 
     As shown in FIG. 4, the grooves  39  upon the surface  13   a  of the anode side separator  13  which surround the inlet side cooling medium through hole  24   a  and the outlet side cooling medium through hole  24   b  are also respectively formed so as to surround the cooling medium communication conduits  36  and the cooling medium communication conduits  37 . Furthermore, as shown in FIG. 1, in positions facing the grooves  38  and  39  of the surface  13   a  of the anode side separator  13 , further grooves  38  and  39  are formed upon the surface  14   a , which opposes the outer peripheral portion of the cathode electrode C, of the cathode side separator  14  which, together with the anode side separator  13 , sandwiches the membrane electrode assembly  12 ; and respective sealing members S 1  and S 2  are fitted into these grooves  38  and  39 . 
     Accordingly, as shown in FIGS. 2 and 6, the sealing members S 1 , which are fitted into the grooves  38  formed upon the anode side separator  13  and the cathode side separator  14  which together sandwich the membrane electrode assembly  12  on both its sides, seal the periphery of the membrane electrode assembly  12  by directly contacting tightly against the projecting portion  15  of the solid polymer electrolyte membrane  15  and sandwiching it from both its sides. Furthermore, around the peripheries of the various through holes  22   a,    22   b,    23   a,    23   b,    24   a,  and  24   b,  each of the respective sealing members S 2  is tightly fitted so as to form a peripheral seal therearound. 
     In addition, as shown in FIGS. 5 and 6, in the surface  13   b  of the anode side separator  13 , there is provided a groove  38  in a position which surrounds the periphery of the branching flow grooves  35 , which is a position which opposes the surface  14   b  of the mutually neighboring cathode side separator  14  when a plurality of these fuel cells N are layered together; and a sealing member S 1  is fitted into this groove  38 . Furthermore, grooves  39  are formed upon this face  13   b  of this anode side separator  13 , one of which surrounds each of the inlet side fuel gas through hole  22   a,  the inlet side oxidizing gas through hole  23   a , the inlet side cooling medium through hole  24   a , the outlet side cooling medium through hole  24   b , the outlet side fuel gas through hole  22   b , and the outlet side oxidizing gas through hole  23   b ; and sealing members S 2  are fitted in these grooves  39 . It should be noted that, in FIG. 3, the positions where the sealing members S 1  and S 2  contact the surface  14   b  of the cathode side separator  14  are shown by double dotted lines. 
     Moreover, referring to FIG. 5, the grooves  39  which surround the inlet side fuel gas through hole  22   a  and the outlet side fuel gas through hole  22   b  are formed so as respectively to surround the fuel gas communication conduits  32  and the fuel gas communication conduits  33 . Furthermore, as shown in FIG. 3, the grooves  39  which surround the inlet side oxidizing gas through hole  23   a  and the outlet side oxidizing gas through hole  23   b  are formed so as respectively to surround the oxidizing gas communication conduits  27  and the oxidizing gas communication conduits  29  of said cathode side separator  14 . 
     According to this structure, when a plurality of these fuel cells N are layered together so that the surface  14   b  of each cathode side separator  14  is pressed against the surface  13   b  of the adjacent anode side separator  13 , respective sealing members S 1  and S 2  on the side of the anode side separator  13  around the peripheries of the inlet side fuel gas through hole  22   a , the outlet side fuel gas through hole  22   b , the inlet side cooling medium through hole  24   a , the outlet side cooling medium through hole  24   b , the inlet side oxidizing gas through hole  23   a , and the outlet side oxidizing gas through hole  23   b , and around the periphery of the branching flow grooves  35 , are pressed against the surface  14   b  of the cathode side separator  14 . As a result, the liquid-tight sealing together of the anode side separator  13  and the cathode side separator  14  is reliably assured. 
     Next, the sealing members S 1  and S 2  will be explained with reference to FIGS. 7 and 8. Here, since this sealing member S 1  and sealing member S 2  have the same cross sectional shape and are made from the same material although their sizes are different, the sealing member S 1 , which surrounds the oxidizing gas flow grooves  25 , the fuel gas flow grooves  30 , the branching flow grooves  35 , and the like, will be explained as a representative example. It should be understood that FIG. 8 is a plan view of a portion of the sealing member S 1 , while FIG. 7 is a sectional view taken in a sectional plane shown by the arrows X 5 —X 5  in FIG.  8 . 
     The sealing member S 1  is made from siliconized rubber, fluorinated rubber, ethylene propylene rubber, butyl rubber or the like, and comprises a sealing member main body  40  whose sectional shape is roughly semi-circular. Upon the upper surface of this sealing member main body  40  there is formed an arcuate portion  40   a , while upon its lower surface there is formed a flat chord portion  40   b.    
     As shown by the broken lines, a core portion  41  of circular cross sectional shape which generates sealing pressure is ensured upon the central portion of the sealing member main body  40 . It should be noted that it would also be acceptable for this core portion  41  to be of elliptical cross sectional shape. 
     Projecting portions  42  are provided upon both the sides of the sealing member main body  40  which extend outwards in the widthwise direction of the groove  38 . The ends of these projecting portions  42  are formed in arcuate shapes which match the shapes of the outer walls  38   a  of the groove  38 , and these projecting portions  42  project as far as positions which contact (or neighbor) these groove side walls  38   a.    
     Furthermore, a pair of cutaway portions  43  are formed in symmetrical positions about the center of the chord portion  40   b.  Since these cutaway portions  43  are cut away in semicircular cross sectional shapes towards the arcuate portion  40   a  of the sealing member main body  40 , the cutaway depth of these cutaway portions  43  is formed in the depth dimension so as to be received within the depth dimension of the groove  38 . Accordingly, void portions are defined between the cutaway portions  43  and the bottom surface of the groove  38 . Furthermore, a flat bottom portion (sealing surface)  40   c  comes to be defined on the chord portion  40   b  between the two above described cutaway portions  43 . It should be understood that the cross sectional shape of these cutaway portions  43  is not restricted to being semicircular; it only needs to be a smooth curved shape. 
     As shown in FIG. 8, along the direction of said projecting portions  42  which lies along the length direction of the groove  38 , there are formed cutaway portions  44  (of widthwise dimensions D 2 ) at predetermined intervals, and between these cutaway portions  44  there remain outstanding projecting portions  42  of widthwise dimensions D 1 . By this structure, void portions  46  are defined between the cutaway portions  44  and the side walls  38   a  of the groove  38 . Moreover, as shown in FIG. 9, by forming the cutaway portions  44  in an arcuate shape, it is possible for the profiles as seen in plan view of the projecting portions  42  to be deformed smoothly into a wave shape. 
     FIG. 10 shows a variation of the above described structure, in which a flat portion  40   d  is provided upon the arcuate portion  40   a  of the sealing member main body  40 . This flat portion  40   d  is formed of the same widthwise dimension as that of the bottom portion  40   c,  so that applied pressure can reliably be transmitted to the bottom portion  40   c.  It should be understood that in FIGS. 9 and 10, to portions which correspond to portions of the structure shown in FIGS. 7 and 8, the same reference symbols are affixed, and the description thereof is curtailed in the interests of brevity. 
     The operation of the fuel cell with this structure will now be explained. 
     Along with hydrogen gas which serves as fuel gas being supplied to the fuel cell N shown in FIG. 1, air which serves as an oxidizer is also supplied. Moreover, a supply of the cooling medium is also provided, in order to cool the reaction surfaces of both the electrodes. 
     As shown in FIGS. 4 and 5, the hydrogen gas which has been supplied to the inlet side fuel gas through hole  22   a  of the fuel cell passes from the side of the surface  13   b  via the fuel gas communication conduits  32  to the surface  13   a , and is supplied into the fuel gas flow grooves  30  which are formed upon this surface  13   a.    
     The fuel gas which is being supplied to the fuel gas flow grooves  30  works its way in the vertical direction while meandering in the horizontal direction along the surface  13   a  of the anode side separator  13 . At this time, the gas which contains hydrogen in the fuel gas is supplied as shown in FIG. 1 via the anode side porous conductor  18  to the anode side electrode catalytic layer  16 . And the unused fuel gas, while on the one hand being supplied to the anode side electrode catalytic layer  16  while working its way along the fuel gas flow grooves  30 , is also directed into the fuel gas communication conduits  33  via the fuel gas flow grooves  31 , and, after arriving at the surface  13   b , is expelled through the outlet side fuel gas through hole  22   b.    
     Furthermore, the air which is supplied to the inlet side oxidizing gas through hole  23   a  of the fuel cell, as shown in FIG. 3, is fed to the oxidizing gas flow grooves  25  via the oxidizing gas communication conduits  27  which are connected to the inlet side oxidizing gas through hole  23   a  of the cathode side separator  14 . This air which is being supplied to the oxidizing gas flow grooves  25  works its way in the vertical direction while meandering in the horizontal direction. At this time, the gas which contains oxygen in this air is supplied as shown in FIG. 1 from the cathode side porous conductor  19  to the cathode side electrode catalytic layer  17 . And the unused oxidizing gas, while on the one hand being supplied to the cathode side electrode catalytic layer  17  while working its way along the oxidizing gas flow grooves  25 , is also directed into the oxidizing gas communication conduits  29  via the oxidizing gas flow grooves  26 , and, after arriving at the surface  14   b , is expelled through the outlet side oxidizing gas through hole  23   b . Due to the above described fuel and oxidizer flows, the fuel cell N generates electricity, which may for example be supplied to an electric motor not shown in the figures for powering it. 
     Furthermore, the cooling medium which is supplied to the fuel cell, after entering through the inlet side cooling medium through hole  24   a , is supplied to the main flow groove  34   a  on the side of the surface  13   b  of the anode side separator  13  via the cooling medium communication conduits  36 , as shown in FIG.  5 . This cooling medium flow branches out from this main flow groove  34   a  into the plurality of branching flow grooves  35 , and, after cooling the reacting surfaces of the fuel cell, comes together again in the main flow groove  34   b . And after use the cooling medium is expelled via the cooling medium communication conduit  37  out from the outlet side cooling medium through hole  24   b.    
     During this process, the projecting portion  15   a  of the solid polymer electrolyte membrane  15  is securely sealed against the sides of the anode side separator  13  and the cathode side separator  14 , with no possibility of slippage, by the sealing members S 1  and S 2  which are closely contacted to this projecting portion  15   a  of the solid polymer electrolyte membrane  15 . Furthermore, in the same manner, the peripheries of the branching flow grooves  35  on the surface  13   b  of the anode side separator  13  are also reliably sealed by the sealing member S 1 . Moreover, the peripheries of the various through holes  22   a,    22   b,    23   a,    23   b,    24   a,  and  24   b  are also securely sealed by the sealing members S 2 . 
     In other words, since the ends of the projecting portions  42  which are provided upon the sealing members S 1  and S 2  are prevented from movement by the side walls  38   a  and  39   a  of the grooves  38  and  39 , the positions of the sealing members S 1  and S 2  are accurately fixed by the central portions in the widthwise direction of the grooves  38  and  39 . As a result, for example, when the solid polymer electrolyte membrane  15  is pinched by the sealing members S 1 , it is possible for these sealing members S 1  to seal against said solid polymer electrolyte membrane  15  with no possibility of slippage. 
     Accordingly, no leakage of fuel gas or of oxidizing gas can occur from between the sealing member S 1  and the solid polymer electrolyte membrane  15  to the exterior, and therefore it is possible to enhance the sealing performance of the fuel cell N. 
     Furthermore, at the portions which are tightly contacted by each of the various ones of the sealing members S 2  as well, since the positions of these sealing members S 2  are accurately fixed by the central portions in the widthwise direction of the grooves  39 . Thereby it is possible to prevent the oxidizing gas, the fuel gas, and the cooling medium from leaking from between the anode side separator  13  and the cathode side separator  14  to the exterior from the inlet side or the outlet side fuel gas through hole  22   a  or  22   b , from the inlet side or the outlet side oxidizing gas through hole  23   a  or  23   b , or from the inlet side or the outlet side cooling medium through hole  24   a  or  24   b . Thus, it is possible to enhance the sealing performance. 
     Moreover, since the pair of cutaway portions  43  are formed at positions upon the chord portion  40   b  which are symmetrical about its center, thereby, if pressure acts from the arcuate portion  40   a , the portions the portions which are pressed out by elastic deformation due to this pressure can be released to the void portions  45  which are defined between the grooves  38 ,  39  and the cutaway portions  43 . Accordingly, along with making it possible to ensure a relatively great amount of elastic deformation of the sealing members S 1  and S 2  with a relatively small applied pressure, it is also possible to moderate the surface pressure which is required to ensure this amount of elastic deformation. 
     Accordingly, when a plurality of these fuel cells N are layered together into a superimposed assembly, it is possible to reduce the overall pressing force which is required as compared with the prior art, and it is possible to make the fastening mechanism smaller and lighter. Furthermore, since the height dimension of the sealing members S 1  and S 2  is largely set by these cutaway portions  43  and it is possible to ensure a sufficient amount of elastic deformation, thereby it will be appropriate for the depth dimension of the grooves  38  and  39  to be made to be extremely small, and for the diameter of the core portions  41  of the sealing members S 1  and S 2  to be made to be less than or equal to 1 mm. 
     In addition, by providing the cutaway portions  44  in the sealing members S 1  and S 2 , the portions of the sealing members S 1  and S 2  which are deformed by the above described pressure can be released by the void portions  46  which are defined between these cutaway portions  44  and the side walls  38   a ,  39   a  of the grooves  38 ,  39 . Therefore, it is possible to ensure a relatively great amount of elastic deformation, and it is possible to moderate the surface pressure which is required to ensure this amount of elastic deformation to a further extent. Accordingly, it is possible to set the height dimension of the sealing members S 1  and S 2  to be relatively great, and to ensure a sufficient amount of elastic deformation, while making the depth dimension of the grooves  38  and  39  extremely small. It should be noted that, since the greater that the widthwise dimension D 2  is set with respect to the widthwise dimension D 1 , the smaller does the area of the projecting portions  42  which contact the side walls  38   a  and  39   a  of the grooves  38  and  39  become. Therefore, along with making it possible to enhance the ease of working when fitting the sealing members S 1  and S 2  into the grooves  38  and  39 , it also becomes possible to reduce the amount of deformation in the widthwise direction of the grooves  38  and  39 . 
     Furthermore, when the provision of a flat portion  40   d  upon the arcuate portion  40   a  of the sealing member main body  40  of the type shown in FIG. 10, it is possible to act the pressure more securely upon the bottom portion  40   c  on the under sides of the sealing members S 1 , S 2  due to the provision of this flat portion  40   d , in cooperation with the sealing members S 2  and S 2  being supported more stably in position due to this flat bottom portion  40   c.    
     It should be understood that the present invention is not to be considered as being limited to its preferred embodiment as disclosed above; for example, it would be also possible to apply the present invention to a sealing member for use with separators made of a metallic material. Furthermore, it is also possible for the cutaway portions to be formed in various shapes; for example, it is possible to form the shapes of the projecting portions  42  which contact the grooves  38  and  39  by the cutaway portions  44  to be of triangular shape as seen in plan view. In this case, it is possible to reduce the initial surface pressure upon the side walls  38   a  and  39   a  of the grooves  38  and  39 .