Patent Publication Number: US-2005118484-A1

Title: Fuel cell separator and method of manufacturing the separator

Description:
TECHNICAL FIELD  
      This invention relates to a fuel cell separator having multiple passages provided in an outer peripheral part of the separator and used to guide reaction gases and a reaction product, and a manufacturing method thereof.  
     BACKGROUND ART  
       FIG. 6  shows a fuel cell of related art. This fuel cell  100  is made by disposing a negative electrode  102  and a positive electrode  103  respectively on the upper face side and the lower face side of an electrolyte membrane  101 , placing a separator  105  on the upper side of the negative electrode  102  and sandwiching an upper side gasket  106  with the peripheral vicinity of the electrolyte membrane  101  and the peripheral vicinity of the upper side separator  105 , and placing a separator  105  on the lower side of the positive electrode  103  and sandwiching a lower side gasket  106  with the peripheral vicinity of the electrolyte membrane  101  and the peripheral vicinity of the lower side separator  105 .  
      With this fuel cell  100 , hydrogen gas is supplied through multiple hydrogen gas passages  107  as shown by the arrow a. The hydrogen gas in the hydrogen gas passages  107  is guided toward a central part  105   a  of the upper side separator  105  as shown with an arrow. Oxygen gas is supplied through multiple oxygen gas passages  108  as shown by the arrow b. The oxygen gas in the oxygen gas passages  108  is guided toward the central part  105   a  of the lower side separator  105  as shown with an arrow.  
      As a result of hydrogen gas being introduced into the upper side central part  105   a , hydrogen molecules (H 2 ) come into contact with a catalyst included in the negative electrode  102 , and as a result of oxygen gas being introduced into the lower side central part  105   a , oxygen molecules (O 2 ) come into contact with a catalyst included in the positive electrode  103 , and electrons e −  flow as shown with an arrow and a current is produced.  
      At this time, product water (H 2 O) is produced from the hydrogen molecules (H 2 ) and the oxygen molecules (O 2 ), and this product water flows through multiple product water passages  109  as shown by the arrow c.  
      In this fuel cell  100 , to maintain resistance to corrosion of the gas passages  107 ,  108  and the product water passages  109 , it is necessary for the gas passages  107 ,  108  and the product water passages  109  to be sealed. To achieve this, in the manufacture of the fuel cell  100 , the upper side gasket  106  is sandwiched in the gap between the peripheral vicinity of the electrolyte membrane  101  and the peripheral vicinity of the upper side separator  105 , and the lower side gasket  106  is sandwiched in the gap between the peripheral vicinity of the electrolyte membrane  101  and the peripheral vicinity of the lower side separator  105 .  
      Here, it is desirable for the fuel cell  100  to be compact, and it is necessary for the upper and lower gaskets  106  to be made thin. Consequently, handling of the upper and lower gaskets  106  has been difficult, it has taken time for the upper and lower gaskets  106  to be disposed in the proper positions, and this has constituted a hindrance to raising fuel cell productivity.  
      As a method of resolving this problem, for example the “Manufacturing Method of a Silicone Resin—Metal Composite Body’ of JP-A-11-309746 has been proposed. According to this method, gaskets can be eliminated by injecting a silicone resin and forming a seal part on the peripheral part of the separator with the injected silicone resin.  
      An injection-molding mold for manufacturing a fuel cell separator of related art is shown in  FIG. 7 , and a separator manufacturing method of related art will now be described.  
      Referring to  FIG. 7 , by an injection-molding mold  110  being closed, a separator  113  is inserted in a gap between a fixed die  111  and a moving die  112  and a cavity  114  is formed by the fixed die  111  and the moving die  112 , and by the cavity  114  being filled with silicone resin as shown with an arrow, a seal  115  is formed on an outer peripheral part  113   a  of the separator  113 .  
      By the seal  115  being formed around the peripheral part  113   a  of the separator  113  like this, the upper and lower gaskets  106 ,  106  shown in  FIG. 6  can be made unnecessary. Therefore, in the manufacture of the fuel cell, it is possible to dispense with a step of incorporating the upper and lower gaskets  106 ,  106 .  
      To prevent the gas passages and product water passages of the separator  113  from being corroded by the gases and product water, it is necessary for the entire surfaces of the gas passages and the product water passages to be covered. Because of this, it is necessary not only for the upper face and the lower face of the peripheral part  113   a  of the separator  113  to be covered by the seal  115 , but also for the wall faces of the gas passages and product water passages in the peripheral part  113   a  to be covered by the seal  115 .  
      To cover the entire surfaces of the gas passages and product water passages of the peripheral part  113   a  with the seal  115  to raise their resistance to corrosion like this, it is necessary to raise the precision of equipment such as the injection-molding mold  110 , equipment costs consequently rise, and this constitutes a hindrance to keeping costs down.  
      Even if the precision of the equipment is raised, it is difficult to surely cover the entire surfaces of the gas passages and product water passages of the peripheral part  113   a  with the seal  115 , and yield in the manufacture of the separators is likely to fall, and this has constituted a hindrance to raising productivity.  
      Thus, a fuel cell separator has been awaited with which it is possible to secure corrosion resistance of the separator and also raise productivity as well as keeping costs down.  
     DISCLOSURE OF THE INVENTION  
      This invention provides, in a fuel cell separator having provided in an outer peripheral part a plurality of gas passages for guiding reaction gases and a plurality of reaction product passages for guiding a reaction product, reaction gases being guided from the gas passages to a central part and reaction product produced at the central part being guided to the reaction product passages, a fuel cell separator characterized in that the central part is made a metal member and the peripheral part is made a rubber member and a projecting part surrounding the central part is formed integrally with this rubber member.  
      In a separator according to the invention, the central part of the separator is made a metal member and the peripheral part of the separator is made a rubber member. By making the peripheral part of the separator a rubber member and forming gas passages and product water passages in this peripheral part like this, it is possible to secure resistance of the gas passages and product water passages to corrosion by the gases and product water.  
      Also, as a result of the peripheral part of the separator being made a rubber member and gas passages and reaction product passages being formed in this rubber member, because it is not necessary for the wall faces of the gas passages and the product water passages of the separator to be covered with a sealing material as in related art, the peripheral part can be molded with an injection-molding mold of ordinary precision. Consequently, because it is not necessary to use a high-precision injection-molding mold, costs of equipment such as injection-molding molds can be kept down, and cost increases can be suppressed.  
      Furthermore, with the separator of the invention, by the peripheral part of the separator being made a rubber member, the rubber member can be manufactured relatively simply. Therefore, the yield in manufacturing separators can be raised.  
      Also, with the separator of this invention, by a projecting part surrounding the central part being formed integrally with the peripheral part, because the peripheral part and the projecting part can be formed easily in a short time, separator productivity can be raised still further.  
      The rubber member forming the peripheral part of the separator in this invention is preferably made of silicone rubber. Although silicone rubber has a different thermal expansion coefficient from the metal member constituting the central part, it is relatively elastic and can absorb differential thermal expansion with respect to the central part. Consequently, the central part deforming and the peripheral part suffering fatigue failure because of differential thermal expansion between the peripheral part and the central part are prevented.  
      The invention also provides a method for manufacturing a fuel cell separator having provided in a silicone rubber peripheral part a plurality of gas passages for guiding reaction gases and a plurality of reaction product passages for guiding a reaction product, reaction gases being guided from the gas passages to a metal central part and reaction product produced at the central part being guided to the reaction product passages, characterized in that it includes: a step of disposing the metal central part in a cavity of an injection-molding mold; a step of keeping the inside of this cavity at a low temperature so that the silicone rubber does not reactively set and maintains a low viscosity; a step of injecting liquid silicone rubber into the cavity in this state and guiding it to an edge part of the central part; and a step of heating the inside of the cavity to reactively set the silicone rubber guided to the edge part of the central part.  
      As the rubber for the peripheral part, a silicone rubber having the characteristic that above a certain temperature hardening is steeply accelerated and along with that its viscosity rises is used. Therefore, the silicone rubber can be guided to the edge of the central part at a temperature (a low-viscosity state) before that at which rapid setting occurs and then the temperature quickly raised to reactively harden the silicone rubber. By this means, because as a result of the silicone rubber being molded at a low viscosity the injection pressure can be kept to a low pressure, the occurrence of burrs can be prevented. As a result of the injection pressure being kept down, the incidence of local stresses on the metal central part (of the separator) can be moderated and deformation of the central part can be prevented.  
      The invention also provides a method for manufacturing a fuel cell separator having provided in a silicone rubber peripheral part a plurality of gas passages for guiding reaction gases and a plurality of reaction product passages for guiding a reaction product, reaction gases being guided from the gas passages to a metal central part and reaction product produced at the central part being guided to the reaction product passages, characterized in that it includes: a step of disposing the metal central part in a cavity of an injection-molding mold; a step of keeping the inside of this cavity at a low temperature so that the silicone rubber does not reactively set and maintains a low viscosity; a step of injecting liquid silicone rubber into the cavity in this state and guiding it to an edge part of the central part; and a step of heating the central part to reactively set the silicone rubber guided to the edge part of the central part.  
      With this manufacturing method, by only the central part being heated quickly to harden the liquid silicone rubber, a heating mechanism for heating the injection-molding mold can be rendered unnecessary. Also, because it is not necessary for the injection-molding mold to be heated, the electrical power needed to heat the silicone rubber can be kept down and distortion arising in the injection-molding mold due to high temperatures can be moderated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an exploded perspective view of a fuel cell having a fuel cell separator according to the invention;  
       FIG. 2  is a sectional view on the line  2 - 2  in  FIG. 1 ;  
       FIG. 3  is a sectional view on the line  3 - 3  in  FIG. 2 ;  
       FIG. 4A  to  FIG. 4E  are views showing a method for manufacturing a fuel cell separator according to the invention,  FIG. 4A  being a view showing a primer treatment having been carried out on the edge of a central part of a separator,  FIG. 4B  a view showing the central part set on a fixed die of an injection-molding mold,  FIG. 4C  a view showing a moving die having been lowered to close the mold and molten silicone having been injected into a cavity,  FIG. 4D  a view showing a part  4 D of  FIG. 4C  enlarged, and  FIG. 4E  a view showing silicone rubber having reactively set and the moving die having been raised for the separator to be taken out;  
       FIG. 5  is a graph showing a characteristic of silicone rubber molded to the peripheral part of a fuel cell separator according to the invention;  
       FIG. 6  is an exploded perspective view showing a fuel cell of related art; and  
       FIG. 7  is a sectional view showing the manufacture of a fuel cell separator of related art. 
    
    
     BEST MODE FOR CARRYING OU THE INVENTION  
      A fuel cell  10  shown in  FIG. 1  has a structure wherein a negative electrode  15  and a positive electrode  16  are respectively disposed on the upper face  11   a  side and the lower face  1   b  (see  FIG. 2 ) side of an electrolyte membrane  11  and an upper side separator  20  (fuel cell separator) is superposed on the negative electrode  15  and a lower side separator  20  is superposed on the positive electrode  16 .  
      Here, generally the fuel cell  10  made by stacking the electrolyte membrane  11 , the negative electrode  15 , the positive electrode  16  and the upper and lower separators  20 ,  20  is referred to as a cell, and multiple cells arrayed in a stack are referred to as a fuel cell; however, in this specification, to facilitate understanding, the cell will be called a fuel cell.  
      In an outer peripheral part thereof, the electrolyte membrane  11  has multiple hydrogen gas passages (gas passages)  12  for guiding hydrogen gas (a reaction gas), multiple oxygen gas passages (gas passages)  13  for guiding oxygen gas (a reaction gas), and multiple product water passages (reaction product passages)  14  for guiding product water (a reaction product).  
      The negative electrode  15  and the positive electrode  16  are each formed somewhat smaller than the electrolyte membrane  11 . The peripheries of the negative electrode  15  and the positive electrode  16  are positioned inward of the hydrogen gas passages  12 , the oxygen gas passages  13  and the product water passages  14 .  
      The upper and lower separators  20  each have a stainless steel (metal) central part  22  and a silicone rubber (rubber) peripheral part  30  around that. A projecting part (projecting central seal part)  41  surrounding the central part  22  is formed integrally with the peripheral part  30 .  
      The peripheral part  30  has multiple hydrogen gas passages (gas passages)  31  for guiding hydrogen gas, multiple oxygen gas passages (gas passages)  32  for guiding oxygen gas, and multiple product water passages (reaction product passages)  33  for guiding product water.  
      By the peripheral part  30  of each of the separators  20  being made a silicone rubber member and this silicone rubber peripheral part  30  being provided with hydrogen gas passages  31 , oxygen gas passages  32  and product water passages  33 , corrosion resistance of the hydrogen gas passages  31 , the oxygen gas passages  32  and the product water passages  33  with respect to the gases and product water is ensured.  
      The hydrogen gas passages  31  and oxygen gas passages  32  formed in the peripheral part  30  of each separator  20  are formed in locations such that they are aligned with the respective hydrogen gas passages  12  and oxygen gas passages  13  formed in the peripheral parts of the electrolyte membrane  11  when the fuel cell  10  is assembled.  
      Also, the multiple product water passages  33  formed in each separator  20  are formed in locations such that they are aligned with the multiple product water passages  14  formed in the electrolyte membrane  11  when the fuel cell  10  is assembled.  
      With this fuel cell  10 , hydrogen gas is supplied to the hydrogen gas passages  31 ,  12  so as to pass through the hydrogen gas passages  31 ,  12  as shown by the arrow A and guided to the central part  22  between the negative electrode  15  and the upper side separator  20  as shown by the arrow B. Oxygen gas is supplied to the oxygen gas passages  32 ,  13  so as to pass through the oxygen gas passages  32 ,  13  as shown by the arrow C and guided to the central part  22  between the positive electrode  16  and the lower side separator  20  as shown by the arrow D.  
      As a result of hydrogen gas being guided to the central part  22 , hydrogen molecules (H 2 ) are brought into contact with a catalyst included in the negative electrode  15 , and as a result of oxygen gas being guided to the central part  22 , oxygen molecules (O 2 ) are brought into contact with a catalyst included in the positive electrode  16 , and electrons e −  flow as shown with an arrow and a current is produced.  
      At this time, product water (H 2 O) is produced from the hydrogen molecules (H 2 ) and the oxygen molecules (O 2 ). This product water is guided to the product water passages  14 ,  33  as shown by the arrow E from the central part  22 , and flows as shown by the arrow F.  
       FIG. 2  shows the fuel cell separators  20  each made up of a stainless steel central part  22  and a silicone rubber peripheral part  30 .  
      The central part  22  is a stainless steel plate having multiple flow passages  23  for guiding hydrogen gas and multiple flow passages  24  for guiding oxygen gas formed in its upper face  22   a  and its lower face  22   b , and multiple passages for guiding product water (not shown), and having had an anti-corrosion plating treatment carried out on its upper face  22   a  and lower face  22   b.    
      This central part  22  has primer-treated parts  25   a ,  25   b , on which a primer treatment has been carried out, on its upper and lower faces along its edge part  22   c , and has multiple openings  26  provided at a predetermined spacing in the primer-treated parts  25   a ,  25   b.    
      The shape of the multiple openings  26  may be round holes, slots or rectangular, and there is no restriction on this. The reasons for providing the primer-treated parts  25   a ,  25   b  and the openings  26  will be discussed later.  
      The peripheral part  30  is a frame made of silicone rubber which covers the primer-treated parts  25   a ,  25   b  of the central part  22  with silicone rubber and fills the openings  26  with silicone rubber and has the hydrogen gas passages  31 , the oxygen gas passages  32  and the product water passages  33  (the flow passages  32 ,  33  are shown in  FIG. 1 ) formed in it.  
      On the upper face  30   a  of the peripheral part  30 , projecting passage seal parts  34  are formed along the respective edges of the hydrogen gas passages  31 , the oxygen gas passages  32  and the product water passages  33  so as to individually surround the hydrogen gas passages  31 , oxygen gas passages  32  and product water passages  33 . A projecting central seal part  41  surrounding the central part  22  is formed along the edge  22   c  of the central part  22 .  
      On the lower face  30   b  of the peripheral part, passage recesses  35  are formed along the respective edges of the hydrogen gas passages  31 , the oxygen gas passages  32  and the product water passages  33  so as to individually surround the hydrogen gas passages  31 , oxygen gas passages  32  and product water passages  33 .  
      The multiple projecting passage seal parts  34  are formed so that when the fuel cell  10  is assembled, they are pressed against the passage recesses  35  of the separator  20  disposed above on the other side of the passages  12 ,  13  and  14  (see  FIG. 1  for passages  13 ,  14 ) formed in the electrolyte membrane  11 .  
      Because, in the peripheral part  30 , the projecting passage seal parts  34  are provided so as to surround each of the hydrogen gas passages  31 , each of the oxygen gas passages  32  and each of the product water passages  33 , and the projecting central seal part  41  is provided surrounding the central part  22 , when the separator  20  is assembled to the fuel cell  10 , there is no need to include a gasket for surrounding the central part of the separator or gaskets for surrounding the hydrogen gas passages, the oxygen gas passages and the product water passages as in related art. As a result, the time and labor of incorporating gaskets when assembling the fuel cell  10  can be saved.  
      Also, because the projecting central seal part  41  is provided on the peripheral part  30 , when the fuel cell  10  is assembled, the projecting central seal part  41  can be pressed against the electrolyte membrane  11  to surely seal the central part  22 .  
      By this means it is possible to guide hydrogen gas and oxygen gas introduced to the central part  22  surely to the proper positions and to guide product water produced at the central part  22  surely to the proper positions.  
      In addition, because the projecting passage seal parts  34  are provided so as to surround the hydrogen gas passages  31 , the oxygen gas passages  32  and the product water passages  33  individually, on assembly of the fuel cell  10 , the projecting passage seal parts  34  can be pressed against the passage recesses  35  to surely seal the hydrogen gas passages  31 , oxygen gas passages  32  and product water passages  33 .  
      Because the projecting passage seal parts  34  and the central seal part  41  are formed with silicone rubber integrally with the peripheral part  30 , when the peripheral part  30  is molded, the passage seal parts  34  and the central seal part  41  can be molded at the same time. Consequently, the peripheral part  30 , the passage seal parts  34  and the central seal part  41  can be formed easily in a short time.  
      Here, by silicone rubber filling the multiple openings  26  when the upper and lower primer-treated parts  25   a ,  25   b  of the central part  22  are covered with silicone rubber, the peripheral part  30  can be provided with anchors  42  in the multiple openings  26  as shown in  FIG. 3 . By this means it is possible to prevent the peripheral part  30  from detaching from the central part  22  and join the peripheral part  30  strongly to the central part  22 .  
      Here, because the thermal expansion coefficients of the silicone rubber of the peripheral part  30  and the stainless steel of the central part  22  are different, when the peripheral part  30  is joined to the central part  22  directly, there is a possibility of the central part  22  deforming due to differential thermal expansion between the peripheral part  30  and the central part  22  and the peripheral part  30  suffering fatigue failure.  
      However, by the peripheral part  30  being molded with silicone rubber it becomes possible for the peripheral part  30  to be deformed elastically to some extent, and differential thermal expansion between the peripheral part  30  and the central part  22  can be absorbed by elastic deformation. As a result, the central part  22  deforms under differential thermal expansion between the peripheral part  30  and the central part  22 , and the peripheral part  30  is prevented from suffering fatigue failure.  
      Next, a method for manufacturing the fuel cell separator  20  will be described, on the basis of  FIG. 4A  to  FIG. 4E .  
      In  FIG. 4A , a primer treatment is carried out on the upper and lower faces  22   a ,  22   b  along the edge  22   c  of a metal central part  22 . That is, silicone rubber is baked onto the upper and lower faces  22   a ,  22   b  at a temperature of 150° C. to form primer-treated parts  25   a ,  25   b.    
      In  FIG. 4B , the central part  22  having the primer-treated parts  25   a ,  25   b  is placed on a fixed die  51  of an injection-molding mold  50 . Then, a moving die  52  is lowered as shown by the arrow [1] and the injection-molding mold  50  is thereby closed.  
      In  FIG. 4C , by a plunger  56  of an injecting device  55  being actuated, molten silicone rubber  57  is injected into a cavity  58  as shown by the arrow [2]. At this time, the inside of the cavity  58  (that is, the injection-molding mold  50 ) is kept at a low temperature while liquid silicone rubber  57  is injected into the cavity  58 , so that the injected silicone rubber  57  does not undergo reactive setting and maintains a low viscosity.  
       FIG. 4D  shows molten silicone rubber  57  having been injected into the cavity. With multiple projections  51   a  formed on the fixed die  51  in the cavity  58  made to project as far as the moving die  52 , and multiple shoulder parts  51   b  protruding inside the cavity  58 , the cavity  58  is filled with the molten silicone rubber  57 .  
      As a result of the molten silicone rubber  57  being injected into the cavity  58  it is guided to the edge  22   c  of the central part  22  and the upper and lower primer-treated parts  25   a ,  26   b  of the central part  22  are covered with the molten silicone rubber  57 .  
      Here, although the metal central part  22  is a metal member, because the upper and lower primer-treated parts  25   a ,  25   b  have been provided around the periphery of the central part  22 , the peripheral part  30  can be fixed to the edge  22   c  of the central part  22  well.  
      The silicone rubber  57  in this liquid state is reactively set at the edge of the central part  22  by rapid heating of the inside of the cavity  58  (that is, of the injection-molding mold  50 ).  
      By this means, in the molding of the peripheral part  30 , it is possible to form multiple hydrogen gas passages  31 , multiple oxygen gas passages  32  and multiple product water passages  33  (the flow passages  32 ,  33  are shown in  FIG. 1 ) and to mold passage recesses  35  (see  FIG. 2 ) around the edges of these flow passage  31 ,  32  and  33 .  
      Also, by passage sealing grooves  52   a  and a central sealing groove  52   b  being provided in the molding face of the moving die  52 , when the peripheral part  30  is molded, the passage seal parts  34  and the central seal part  41  can be molded at the same time.  
      Additionally, when the peripheral part  30  is molded, by the multiple openings  26  being filled with the silicone rubber  57 , anchors  42  can be simultaneously provided in the openings  26 .  
      Because multiple passage seal parts  34 , a central seal part  41  and anchors  42  can be molded simultaneously like this when the peripheral part  30  is molded, a fuel cell separator  20  can be manufactured relatively easily.  
      After the silicone rubber  57  injected into the cavity  58  has set reactively the moving die  52  is raised as shown by the arrow [3] and the injection-molding mold  50  is thereby opened.  
      In  FIG. 4E , after the injection-molding mold  50  is opened, the fuel cell separator  20  is removed from the fixed die  51  as shown by the arrow [4] and the process of manufacturing the fuel cell separator  20  ends.  
      As described above with reference to  FIG. 4A  through  FIG. 4E , by the peripheral part of the separator being made a rubber member, the rubber member can be manufactured relatively easily. Consequently, because the manufacturing yield of separators can be raised, the productivity of separators can be increased.  
      As a result of the projecting passage seal parts  34  formed integrally with the peripheral part  30  so as to individually surround the hydrogen gas passages  31 , the oxygen gas passages  32  and the product water passages  33  and the projecting central seal part  41  surrounding the central part  22  being formed integrally with the peripheral part  30 , the fuel cell separator  20  can be formed easily in a short time and productivity can be increased still more.  
      Next, a specific example of the fuel cell separator manufacturing method explained with reference to  FIG. 4A  through  FIG. 4E  will be described, on the basis of the graph of  FIG. 5  showing a characteristic of silicone rubber. The vertical axis shows setting time of the silicone rubber and the horizontal axis shows temperature of the silicone rubber.  
      This graph shows a typical characteristic of silicone rubber. As shown in the graph, at low temperatures of 100 to 120° C., the setting time of silicone rubber can be made long, at 50 to 330 seconds.  
      At high temperatures of 120 to 200° C., the setting time of silicone rubber can be made short, at less than 50 seconds.  
      Therefore, by keeping the inside of the cavity  58  (that is, the injection-molding mold  50 ) in a low temperature region of for example 100 to 120° C. as shown in  FIG. 4C , it is possible to fill the inside of the cavity  58  with liquid silicone rubber  57  in such a way that the silicone rubber  57  does not reactively set and also is kept at a low viscosity.  
      After the molten silicone rubber  57  is guided to the edge  22   c  of the central part  22 , by the inside of the cavity  58  being rapidly heated to a high temperature of for example 120 to 200° C., the liquid silicone rubber  57  introduced can be made to set reactively at the edge  22   c  of the central part  22 .  
      By molding the silicone rubber  57  in a state of low viscosity like this, it is possible to suppress falls in injection pressure. Consequently, the incidence of local stresses on the metal central part  22  can be moderated and the occurrence of deformation and burring of the central part  22  can be prevented.  
      Accordingly, a step of removing burrs after the central part  22  is molded can be made unnecessary, and also a step of correcting deformation of the central part  22  can be made unnecessary, and consequently it is possible to simplify the separator production process and raise productivity.  
      In the fuel cell separator manufacturing method of the foregoing embodiment, an example was described wherein the injection-molding mold  50  is rapidly heated to set the liquid silicone rubber  57 ; however, in the invention, it is also possible to adopt another embodiment wherein the injection-molding mold  50  is not heated and only the central part  22  is heated rapidly to set the liquid silicone rubber  57 .  
      Whereas in the foregoing embodiment a heating mechanism for heating the injection-molding mold  50  is needed, because in the other embodiment it is not necessary to heat the injection-molding mold  50 , the heating device for heating the injection-molding mold  50  can be rendered unnecessary. Therefore, plant costs can be kept down and also electrical power used for steady-state heating can be eliminated.  
      Also, because it is not necessary to heat the injection-molding mold  50 , distorting affects on the injection-molding mold  50  caused by high temperatures can be moderated. By moderating the distorting affects of high temperatures on the injection-molding mold  50  like this, it is possible to lengthen the maintenance intervals of the injection-molding mold  50  and to raise the availability of the injection-molding mold  50  and so raise productivity.  
      Although in the embodiment described above an example was described wherein the peripheral part  30 , the multiple passage seal parts  34  and the central seal part  41  were molded integrally from silicone rubber, the invention is not limited to this, and alternatively some other rubber material or resin material can be used.  
      Also, the peripheral part  30 , the multiple passage seal parts  34  and the central seal part  41  can alternatively each be formed individually, and furthermore these members  30 ,  34  and  41  can each be formed using a different material.  
      Also, although in the embodiment described above stainless steel was used as an example of a metal member for forming the central part  22  of the fuel cell separator  20 , the metal member used to form the central part  22  is not limited to this.  
      Although in the above embodiment an example was described wherein projecting passage seal parts  34  surrounding each of the gas passages  31 ,  32  and the product water passages  33  were provided on the peripheral part  30  of the separator  20 , alternatively the passage seal parts  34  may be dispensed with.  
      Although in the embodiment described above hydrogen gas and oxygen gas were used as examples of reaction gases and product water was used as an example of a reaction product, the invention is not limited to this and can also be applied to other reaction gases and reaction products.  
     INDUSTRIAL APPLICABILITY  
      As described above, as a result of the peripheral part of a separator being made a silicone rubber member and gas passages and product water passages being formed in this peripheral part, corrosion resistance of the gas passages and product water passages with respect to gases and product water is ensured and the invention is useful in the manufacture of fuel cells.