Abstract:
Disclosed is an end plate for a fuel cell including an anti-bending plate, in which an anti-bending plate is assembled with an insert having a sandwich structure and the insert is injection molded, thereby easily preventing the insert from being bent due to an injection molding pressure. In the disclosed end plate, a sandwich insert including two or more stacked plates each having a specific shape is manufactured, and an anti-bending plate is coupled to the sandwich insert and then is injection molded, thereby easily preventing the sandwich insert from being bent due to a resin pressure in the injection molding process, contrary to a conventional integral metal insert.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims under 35 U.S.C. §119(a) the benefit of Korean Patent Application No. 10-2011-0090573 filed Sep. 7, 2011, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    (a) Technical Field 
         [0003]    The present invention relates to an end plate for a fuel cell including an anti-bending plate. More particularly, it relates to an end plate for a fuel cell including an anti-bending plate, in which an anti-bending plate is assembled with an insert having a sandwich-like structure and the insert is injection molded, thereby easily preventing the insert from being bent due to an injection molding pressure. 
         [0004]    (b) Background Art 
         [0005]    Referring to  FIG. 10 , in a unit cell of a fuel cell stack mounted on a fuel cell vehicle, a Membrane-Electrode Assembly (MEA) is located at the innermost side of the unit cell of the fuel cell stack. The MEA includes a solid polymer electrolyte membrane  10  through which protons pass and catalytic electrode layers, i.e., a cathode  12  and an anode  14 , coated on opposite surfaces of the solid polymer electrolyte membrane  10  such that hydrogen can react with oxygen. Gas Diffusion Layers (GDL)  16  and gaskets  18  are sequentially staked outside the cathode  12  and the anode  14 , and separation plates  20  including flow fields for supplying fuel and discharging water generated by the reaction are located outside the GDLs  16 . 
         [0006]    After several hundred unit cells are stacked, end plates  30  for supplying and fixing each of the unit cells are assembled at the outermost sides of the fuel cell stack. In this case, a current collector plate for collecting electricity generated in the fuel cell stack and sending the collected electricity to outside of the fuel cell stack is mounted inside the end plates  30 . 
         [0007]    An oxidation reaction of hydrogen occurs in the anode  14  of the fuel cell stack and protons and electrons are generated by the reaction. At this time, the generated protons and electrons flow to the cathode  12  respectively through the solid polymer electrolyte membrane  10  and the separation plate  20 , so that water is generated in the cathode  12  through an electrochemical reaction of the protons and electrons from the anode  14  with oxygen in the air and electrical energy, finally generated through flow of the electrons, is supplied to a load requiring electrical energy through the current collector plate of the end plates  30 . 
         [0008]    The end plates  30  of the fuel cell stack serve to fasten a plurality of stacked separation plates, MEAs, and GDLs and simultaneously serve to provide a uniform surface pressure to each unit cell from opposite sides of the fuel cell stack respectively. 
         [0009]    As can be seen in  FIG. 9 , the end plate  30  is formed with a metal insert  31 , a plastic injection molded body  32 , and a current collector plate  33 , which are integrally formed, for weight reduction and electrical insulation. That is, the metal insert  31  is disposed inside an injection mold and then a plastic injection molding material is filled in the injection mold, thereby embodying the end plate  30  including the metal insert  31  surrounded by the plastic injection molded body  32 . 
         [0010]    In the meantime, the current collector plate  33  is disposed inside the injection mold together with the metal insert  31  and is injection molded together with the plastic injection molded body  32  or separately assembled inside the plastic injection molded body  32  later. 
         [0011]    The metal insert of the end plate is required to have a high strength to resist an inner surface pressure. Accordingly, the metal insert is generally manufactured through machining of a metal material and also is manufactured in a complex shape to collect generated electricity from reactions within the fuel cell stack and fasten the fuel cell stack together securely. 
         [0012]    However, a conventional metal insert of the end plate is manufactured in an integral shape, so that it has the following disadvantages: 
         [0013]    First, in machining a material-reduction structure for weight reduction of the metal insert, it is difficult to perform injection molding for the metal insert. That is, a recess or an uneven portion should not be generated on a resin surface after the injection molding of the end plates, for assuring continuous contact with the gaskets to prevent a fuel leak. However, in applying the material-reduction structure to the metal insert, if a thickness of the resin material of the plastic injection molded body is not uniform, a recess or an uneven portion is disadvantageously generated on the surface of the resin due to the resin&#39;s contraction. In particular, if a pocket processing is performed to apply the material-reduction structure to the integral metal insert for reducing the weight, it is difficult to uniformly maintain the thickness of the injection molding material. 
         [0014]    Second, the integral metal insert is manufactured by cutting a metal plate or a non-metal plate through machining, so it takes a long time to manufacture a single integral metal insert, thereby making it difficult to mass produce and reduce costs accordingly. 
         [0015]    Third, the integral metal insert should be made of a single material. Therefore, applying different materials for weight reduction and strength improvement is also difficult. 
         [0016]    In this respect, contrary to a conventional integral metal insert, a sandwich insert in which two or more plates each having a specific shape are stacked has been manufactured to maintain strength and simultaneously promote weight reduction. However, since the sandwich insert employs the centrally disposed plate having material-reduction spaces among several plates of the sandwich insert, the central portion of the sandwich insert is often bent due to resin pressure in the injection molding process for surrounding the sandwich insert with the plastic injection molded body. 
       SUMMARY OF THE DISCLOSURE 
       [0017]    The present invention provides an end plate for a fuel cell including an anti-bending plate, in which a sandwich insert including two or more stacked plates each having a specific shape are combined, and an anti-bending plate is coupled to the sandwich insert and then is injection molded, thereby easily preventing the sandwich insert from being bent due to a resin pressure in the injection molding process, contrary to a conventional integral metal insert. 
         [0018]    In one aspect, the present invention provides an end plate for a fuel cell including an anti-bending plate, the end plate including: a sandwich insert in which a plurality of plates having manifold forming portions at opposite ends thereof are bonded by a bonding means, wherein an anti-bending plate that is in close contact with a surface of an injection mold are coupled to a surface of the sandwich insert opposite to where a resin pressure is directly applied in an injection molding and a plastic injection molded body is injection molded, so that the sandwich insert to which the resin pressure can be applied within the injection mold is supported by the anti-bending plate. 
         [0019]    In a first exemplary embodiment, the anti-bending plate has a first large diameter portion and a second smaller diameter portion which has a same thickness and is integrally formed therewith. A lower surface of the large diameter portion is in close contact with an outer surface of an outermost plate located at an outermost side of the sandwich insert to be injection molded, and a stepped portion between the large diameter portion and the small diameter portion is injection molded by the plastic injection molded body to be locked thereby. 
         [0020]    In a second exemplary embodiment, the anti-bending plate has a large diameter portion and a small diameter portion which are integrally formed, the large diameter portion being thicker than a small diameter portion, a lower end of the large diameter portion is inserted into a coupling recess formed on an outer surface of an outermost plate located at an outermost side of the sandwich insert, and a stepped portion between the large diameter portion and the small diameter portion is injection molded by the plastic injection molded body to be locked thereby. 
         [0021]    In a third exemplary embodiment, the anti-bending plate has a large diameter portion and a small diameter portion thicker than the large diameter portion which are integrally formed, the large diameter portion is inserted into a coupling recess formed at an outer surface of an outermost plate located at an outermost side of the sandwich insert, and a stepped portion between the large diameter portion and the small diameter portion is injection molded by the plastic injection molded body to be locked thereby. 
         [0022]    In a fourth exemplary embodiment, the anti-bending plate has a large diameter portion and a small diameter portion thicker than the large diameter portion which are integrally formed, a lower end of the large diameter portion is positioned within a positioning recess formed in a second plate located next to an outermost plate of the sandwich insert and the small diameter portion protrudes through a terminal insertion recess formed in the outermost plate at the same time, and a stepped portion between the large diameter portion and the small diameter portion is injection molded by the plastic injection molded body to be locked. 
         [0023]    Accordingly, the present invention provides the following effects: 
         [0024]    According to the present invention, the sandwich insert including several stacked plates is employed as the insert of the end plate and the anti-bending plate is coupled to the sandwich insert, so that the anti-bending plate serves to support the sandwich insert within the injection mold, thereby preventing the sandwich insert from being bent due to a resin pressure applied to the sandwich insert in the injection molding process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The above and other features of the present invention will now be described in detail with reference to certain exemplary embodiments thereof illustrated in the accompanying drawings which are given herein below by way of illustration only, and thus are not limitative of the present invention, and wherein: 
           [0026]      FIG. 1  is an exploded perspective view illustrating a metal insert of an end plate for a fuel cell and an anti-bending plate coupled to the metal insert according to a first exemplary embodiment of the present invention; 
           [0027]      FIG. 2  is a sectional view illustrating a state in which a metal insert of an end plate for a fuel cell is assembled with an anti-bending plate and is injection molded according to the first exemplary embodiment of the present invention; 
           [0028]      FIG. 3  is an exploded perspective view illustrating a metal insert of an end plate for a fuel cell and an anti-bending plate coupled to the metal insert according to a second exemplary embodiment of the present invention; 
           [0029]      FIG. 4  is a sectional view illustrating a state in which a metal insert of an end plate for a fuel cell is assembled with an anti-bending plate and is injection molded according to the second exemplary embodiment of the present invention; 
           [0030]      FIG. 5  is an exploded perspective view illustrating a metal insert of an end plate for a fuel cell and an anti-bending plate coupled to the metal insert according to a third exemplary embodiment of the present invention; 
           [0031]      FIG. 6  is a sectional view illustrating a state in which a metal insert of an end plate for a fuel cell is assembled with an anti-bending plate and is injection molded according to the third exemplary embodiment of the present invention; 
           [0032]      FIG. 7  is an exploded perspective view illustrating a metal insert of an end plate for a fuel cell and an anti-bending plate coupled to the metal insert according to a fourth exemplary embodiment of the present invention; 
           [0033]      FIG. 8  is a sectional view illustrating a state in which a metal insert of an end plate for a fuel cell is assembled with an anti-bending plate and is injection molded according to the fourth exemplary embodiment of the present invention; 
           [0034]      FIG. 9  is a perspective view illustrating a conventional end plate; and 
           [0035]      FIG. 10  is a view schematically illustrating a fuel cell stack. 
       
    
    
     DETAILED DESCRIPTION 
       [0036]    Hereinafter reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings and described below. 
         [0037]    It is understood that the term fuel cell “vehicle” or “vehicular” or other similar term as used herein is inclusive of all types of fuel cell motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid fuel cell vehicles, electric motor powered fuel cell vehicles, auxiliary plug-in fuel cell hybrid electric vehicles, hydrogen-powered fuel cell vehicles and other alternative fuel cell vehicles (e.g., fuels derived from resources other than petroleum). 
         [0038]    The present invention provides an end plate for a fuel cell including an insert  100  having a sandwich structure where manifold forming portions for flowing hydrogen, air, and cooling water are formed at opposite ends thereof and a plastic injection molded body  300  is injection molded after surrounding the sandwich insert  100  with a plastic injection molding material. The end plate for the fuel cell of the present invention has a feature in that an anti-bending plate  200  is assembled with the sandwich insert  100  to prevent the sandwich insert  100  from being bent by an injection molding resin pressure in the injection molding process in which the sandwich insert  100  is surrounded with the plastic injection molded body  300 . 
         [0039]    As illustrated in  FIGS. 1 ,  3 ,  5 , and  7 , in the sandwich insert  100 , an outermost plate  100  is a first plate having manifold forming portions  102  at opposite ends thereof, and a second plate  120 , a third plate  130 , and a fourth plate  140  are sequentially stacked and bonded by a bonding means. The second plate  120  has first material-reducing spaces  122  for weight reduction. 
         [0040]    The sandwich insert  100  having the above structure is disposed inside an injection mold  400  while being maintained in a floated state and then a plastic resin is injected into a space between an inner surface of the injection mold  400  and an outer surface of the sandwich insert  100 , so that the outer surface of the sandwich insert  100  is surrounded by the plastic injection molded body  300  to be injection molded. 
         [0041]    In this case, pins (not-shown) are inserted into pin apertures formed at four corners of the sandwich insert  100  disposed inside the injection mold  400  and opposite ends of the pins are in close contact with and supported by an upper surface and a bottom surface of the injection mold at the same time, so that the sandwich insert  100  is maintained in a floated state at a central portion of the injection mold  400 . However, since a resin pressure is applied to a central portion of the sandwich when the plastic resin is injected into the injection mold  400  from a lower portion of the injection mold  400 , the central portion of the sandwich insert  100  is often finely bent. 
         [0042]    Accordingly, the present invention provides an anti-bending plate  200  which is coupled to the sandwich insert  100  to prevent the sandwich insert  100  from being bent. Hereinafter, exemplary embodiments of the anti-bending plate coupled to the sandwich insert of the end plate for the fuel cell according to the present invention will be described. 
       First Embodiment 
       [0043]    As illustrated in  FIG. 1 , the anti-bending plate  200  according to the first embodiment of the present invention includes a relatively large diameter portion  202  in comparison to a smaller diameter portion  204  which both have the same thickness and are integrally formed therewith. The relatively large diameter portion  202  at a lower side of the anti-bending plate  200  and the small diameter portion  204  at an upper side of the anti-bending plate  200  form a hat-like shape. 
         [0044]    The anti-bending plate  200  is disposed inside the injection mold while being in close contact with the sandwich insert  100  together with the sandwich insert  100 . More specifically, as can be seen in  FIG. 2 , when the sandwich insert  100  is disposed inside the injection mold  400  in a floated state, a bottom surface of the relatively large diameter portion  202  of the anti-bending plate  200  is in close contact with the outermost plate  110  located at the outermost side of the sandwich insert  100  and an upper surface of the smaller diameter portion  204  is in close contact with an upper surface of the injection mold  400  at the same time. 
         [0045]    Subsequently, by injecting a plastic resin into a space between the inner surface of the injection mold  400  and the outer surface of the sandwich insert  100 , the outer surface of the sandwich insert  100  is surrounded by the plastic injection molded body  300  so that the sandwich insert is injection molded thereby. 
         [0046]    At this time, although a resin pressure is directly applied to the bottom surface of the sandwich insert  100  in the injection molding, the outermost plate  100  of the sandwich insert  100 , which corresponds to an opposite surface of the sandwich insert  100 , is held and supported by the anti-bending plate  200 . Thus, it is possible to easily prevent the sandwich insert  100  from being bent due to the resin pressure. 
         [0047]    When the injection mold  400  is removed from the completely injection molded end plate, the upper surface of the smaller diameter portion  204  of the anti-bending plate  200  is exposed to the outside while forming the same plane as the plastic injection molded body  300 . 
         [0048]    In particular, since the sandwich insert  100  is injection molded while a stepped portion  206  between the relatively large diameter portion  202  and the smaller diameter portion  204  of the anti-bending plate  200  is surrounded by the plastic injection molded body  300 , the anti-bending plate  200  is not removed from the sandwich insert  100  and is maintained in a fixed state even after the completion of the injection molding process. 
         [0049]    Additionally, a current collector plate  500  for collecting electricity generated in the fuel cell stack is attached to the inner surface of the end plate, e.g., an opposite side of the anti-bending plate  200 . 
       Second Embodiment 
       [0050]    As illustrated in  FIG. 3 , the anti-bending plate  200  according to the second embodiment of the present invention includes a relatively large diameter portion  202  in comparison to a smaller diameter portion  204  which is integrally formed therewith. The relatively large diameter portion  202  is thicker than the smaller diameter portion  204 . The relatively large diameter portion  202  is formed at a lower side of the anti-bending plate  200  and the smaller diameter portion  204  is formed at an upper side of the anti-bending plate  200  to form a hat-like shape. 
         [0051]    The anti-bending plate  200  is disposed inside the injection mold while being in close contact with the sandwich insert  100 , together with the sandwich insert  100 . More particularly, as can be seen in  FIG. 4 , when the sandwich insert  100  is disposed inside the injection mold  400  in a floated state, a lower end of the large diameter portion  202  of the anti-bending plate  200  is inserted into a coupling recess  105  formed on the outer surface of the outermost plate  110  located at the outermost side of the sandwich insert  100  and an upper surface of the small diameter portion  204  is in close contact with the upper surface of the injection mold  400 . 
         [0052]    Subsequently, by injecting a plastic resin into a space between the inner surface of the injection mold  400  and the outer surface of the sandwich insert  100 , the sandwich insert  100  is surrounded by the plastic injection molded body  300  so that the sandwich insert  100  is injection molded thereby. 
         [0053]    At this time, although the resin pressure is directly applied to the bottom surface of the sandwich insert  100  in the injection molding process, the outermost plate  100  of the sandwich insert  100 , which corresponds to an opposite surface of the sandwich insert  100 , is held and supported by the anti-bending plate  200 , so that it is possible to easily prevent the sandwich insert  100  from being bent due to the resin pressure. 
         [0054]    When the injection mold  400  is removed from the completely injection molded end plate, the upper surface of the smaller diameter portion  204  of the anti-bending plate  200  is exposed to the outside while forming the same plane as the plastic injection molded body  300 . In particular, since the sandwich insert  100  is injection molded while the stepped portion  206  between the relatively large diameter portion  202  and the smaller diameter portion  204  of the anti-bending plate  200  is surrounded by the plastic injection molded body  300 , the anti-bending plate  200  is not removed from the sandwich insert  100  and is maintained in a fixed state even after the completion of the injection molding process. 
         [0055]    Similarly, the current collector plate  500  for collecting electricity generated in the fuel cell stack is attached to the inner surface of the end plate, e.g., an opposite surface of the anti-bending plate  200 . 
       Third Embodiment 
       [0056]    As illustrated in  FIG. 5 , the anti-bending plate  200  according to the third embodiment of the present invention includes a relatively large diameter portion  202  in comparison to a smaller diameter portion  204  which is integrally formed therewith. The smaller diameter portion  204  is thicker than the large diameter portion  202 . The relatively large diameter portion  202  at a lower side of the anti-bending plate  200  and the smaller diameter portion  204  at an upper side of the anti-bending plate  200  forms a hat-like shape. 
         [0057]    As can be seen in  FIG. 6 , when the sandwich insert  100  is disposed inside the injection mold  400  in a floated state, the entire large diameter portion  202  of the anti-bending plate  200  is inserted into the coupling recess  105  formed on the outer surface of the outermost plate  110  located at the outermost side of the sandwich insert  100  and the upper surface of the smaller diameter portion  204  is in close contact with the upper surface of the injection mold  400 . 
         [0058]    The remaining processes are the same as those of the second embodiment, so that a detailed description thereof will be omitted. 
       Fourth Embodiment 
       [0059]    As illustrated in  FIG. 7 , the anti-bending plate  200  according to the fourth embodiment of the present invention includes a relatively large diameter portion  202  and a smaller diameter portion  204  which is integrally formed therewith. The smaller diameter portion  204  is thicker than the large diameter portion  202 . The integral shape of the large diameter portion  202  at a lower side of the anti-bending plate  200  and the small diameter portion  204  at an upper side of the anti-bending plate  200  form a hat like shape. 
         [0060]    As can be seen in  FIG. 8 , when the sandwich insert  100  is disposed inside the injection mold  400  in a floated state, a lower end of the large diameter portion  202  is positioned in a positioning recess  107  formed in the second plate  120  located next to the outermost plate  110  of the sandwich insert  100  and the small diameter portion  204  protrudes through a terminal insertion recess  108  formed at the outermost plate  110  at the same time. 
         [0061]    At this time, the stepped portion  206  between the relatively large diameter portion  202  and the smaller diameter portion  204  of the anti-bending plate  200  is fixed by the lower surface of the outermost plate  110 , to be in a fixed state. 
         [0062]    Accordingly, although the resin pressure is directly applied to the bottom surface of the sandwich insert  100  in the injection molding, the outermost plate  100  of the sandwich insert  100 , which corresponds to an opposite surface of the sandwich insert  100 , is held and supported by the anti-bending plate  200 . Thus, it is possible to easily prevent the sandwich insert  100  from being bent due to the resin pressure. 
         [0063]    When the injection mold  400  is removed from the completely injection molded end plate, the upper surface of the smaller diameter portion  204  of the anti-bending plate  200  is exposed to the outside while forming the same plane as the plastic injection molded body  300 . 
         [0064]    In particular, since a stepped portion  206  between the relatively large diameter portion  202  and the smaller diameter portion  204  of the anti-bending plate  200  is secured and locked by the lower surface of the outermost plate  110 , the anti-bending plate  200  is not removed from the sandwich insert  100  and is maintained in a secured state even after the completion of the injection molding process. 
         [0065]    Similarly, the current collector plate  500  for collecting electricity generated in the fuel cell stack is attached to the inner surface of the end plate, e.g., an opposite surface of the anti-bending plate  200 .