Patent Publication Number: US-2011076588-A1

Title: Fuel cell

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2009-223642 filed on Sep. 29, 2009 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a fuel cell. 
     2. Description of the Related Art 
     There is known a fuel cell having a gas manifold at a lateral surface portion of a fuel cell stack in a lamination direction thereof (e.g., Japanese Patent Application Publication No. 2008-251490 (JP-A-2008-251490)). 
     However, the fuel cell described in Japanese Patent Application Publication No. 2008-251490 (JP-A-2008-251490) is constructed such that the gas manifold is mounted to an upper portion of the fuel cell stack after the fuel cell stack has been formed. In disassembling this fuel cell stack, the gas manifold is removed, and then the fuel cell stack is disassembled. At the moment when the gas manifold is removed, the fuel cell stack is exposed with single cells connected in series to one another. When an external object comes into contact with the fuel cell stack to cause short-circuiting in this state, a current may flow through the fuel cell stack at a high voltage. This problem may be caused not only in fuel cells having external manifolds but also in fuel cells of other constructions when the fuel cells are disassembled. 
     SUMMARY OF THE INVENTION 
     The invention restrains a current from flowing through a fuel cell stack at a high voltage even when an object from the outside comes into contact with the fuel cell stack in disassembling a fuel cell. 
     A first aspect of the invention relates to a fuel cell that is equipped with a laminated body having a plurality of single cells and end plates clamping the single cells, and with an insulating body disposed at a lateral surface portion of the laminated body. The insulating body has a protrusion protruding to the laminated body side, and the laminated body is fastened with the protrusion clamped. According to this fuel cell, the insulating body cannot be removed unless the clamped protrusion is released. Therefore, in disassembling the fuel cell, an object from the outside can be restrained from coming into contact with the fuel cell stack. As a result, a current can be restrained from flowing through the fuel cell stack at a high voltage. 
     The protrusion may be clamped between a corresponding one of the single cells and a corresponding one of the end plates. In this manner, the insulating body can be easily supported by fastening the end plates together. 
     The insulating body may be formed using part of an external manifold for distributing gas to the single cells. In the fuel cell having the external manifold, the number of parts can be reduced by causing the external manifold to function as the insulating body. 
     The fuel cell may be equipped with a tension rod for fastening the single cells to the end plates, and the tension rod may penetrate the protrusion. In this manner, the insulating body cannot be removed unless the tension rod is drawn out. Then, when the tension rod is drawn out, the fuel cell is separated into the single cells. Accordingly, contact with the fuel cell stack composed of the laminated single cells can be suppressed. 
     The invention can be realized in various forms. For example, the invention can be realized in various forms such as a method of manufacturing a fuel cell as well as a fuel cell. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The features, advantages, and technical and industrial significance of this invention will be described in the following detailed description of an example embodiment of the invention with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is an explanatory view showing an exterior of a fuel cell equipped with an external manifold; 
         FIG. 2  is an explanatory view of the fuel cell as viewed in an x-direction shown in  FIG. 1 ; 
         FIG. 3  is an explanatory view showing part of a cross-section of the fuel cell taken along a cutting line shown in  FIG. 2 ; 
         FIGS. 4A and 4B  are explanatory views showing modification examples; 
         FIG. 5  is an explanatory view showing another modification example; 
         FIGS. 6A and 6B  are explanatory views showing modification examples of the shape of a protrusion; and 
         FIG. 7  is an explanatory view showing an example of a construction in which a tension rod penetrates the protrusion. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT 
       FIG. 1  is an explanatory view showing an exterior of a fuel cell equipped with an external manifold. A fuel cell  10  is equipped with a fuel cell stack  100 , end plates  200 , fixed plates  300 , and an external manifold  400 . The end plates  200  are disposed at both ends of the fuel cell stack  100  in a lamination direction (an x-direction in  FIG. 1 ) of single cells (not shown) respectively. The fixed plates  300  are disposed at both ends of the fuel cell stack  100  in a y-direction respectively. The external manifold  400  is disposed above the fuel cell stack  100  (a z-direction in  FIG. 1 ). That is, the fuel cell stack  100  is surrounded by the end plates  200  and the fixed plates  300  in a horizontal direction (the x-direction and the y-direction), and is covered above (the z-direction) with the external manifold  400 . It should be noted that bolts and the like for coupling these components are not shown in  FIG. 1 . 
       FIG. 2  is an explanatory view of the fuel cell as viewed in the x-direction shown in  FIG. 1 . In the x-direction, one of the end plates  200  and the external manifold  400  are visible, and the fuel cell stack  100  and the fixed plates  300  are invisible.  FIG. 2  shows tension rods  220  and mounting bolts  420 , which are not shown in  FIG. 1 . The tension rods  220  are used to fasten the single cells (not shown) of the fuel cell stack  100  ( FIG. 1 ) to the end plates  200 . The mounting bolts  420  are used in joining the external manifold  400  to the fixed plates  300 . 
       FIG. 3  is an explanatory view showing part of a cross-section of the fuel cell taken along a cutting line III-III shown in  FIG. 2 . The fuel cell stack  100  is composed of a plurality of single cells  110  laminated on one another. Collector plates  120  are disposed outside the single cells  110  in the lamination direction thereof (the x-direction) respectively. The end plates  200  are disposed outside the collector plates  120  respectively. The tension rods  220  penetrate the end plates  200 , the collector plates  120 , and the single cells  110  to fasten the end plates  200 , the collector plates  120 , and the single cells  110  together. 
     The external manifold  400  is formed of, for example, resin, and assumes the shape of a hollow and generally rectangular parallelepiped. The external manifold  400  is open on the fuel cell stack  100  side. Therefore, a space  450  is formed between the external manifold  400  and the fuel cell stack  100 . The space  450  is supplied with air. It should be noted that an air introduction portion for the space  450  is not described. This air introduction portion may be connected to a peak portion of the external manifold  400 . The single cells  110  have open holes (not shown) on the space  450  side, and air (O 2 ) is supplied from the space  450  to the respective single cells  110  through these holes. 
     Protrusions  410  protruding to the fuel cell stack  100  side are formed at outer edge portions at both ends of the external manifold  400  in the x-direction respectively. It should be noted that the external manifold  400  is formed of resin as described above, and that the protrusions  410  can be easily formed during injection molding of the external manifold  400 . Each of the protrusions  410  is clamped between a corresponding one of the single cells  110  and a corresponding one of the collector plates  120 . The tension rods  220  fasten the end plates  200 , the collector plates  120 , and the single cells  110  (the fuel cell stack  100 ) together with the protrusions  410  clamped. It should be noted herein that the external manifold  400  is designed to be irremovable unless the tension rods  220  are loosened to unfasten the fuel cell stack  100 . However, in this embodiment of the invention, the tension rods  220  are inserted through those regions where the protrusions  410  do not exist, instead of penetrating the protrusions  410  respectively. 
     In the fuel cell, a multitude of the single cells  110  with a small electromotive force are connected in series to one another to generate a high voltage. That is, the tension rods  220  apply a tension to the end plates  200  at both the ends, between which the plurality of the single cells  100  are clamped. When the fuel cell stack  100  is formed by connecting in series these single cells  110  to one another, a high voltage can be generated by this fuel cell stack  100 . On the other hand, when the tension serving to clamp the plurality of the single cells  110  by the end plates  200  is stopped from being applied due to the unfastening of the fuel cell stack  100  by the tension rods  220 , the respective single cells  110  are separated from one another and no longer connected in series to one another, thereby stopping the generation of a high voltage. 
     According to this embodiment of the invention, when the fuel cell stack  100  is formed by the tension rods  220 , the external manifold  400  covers the fuel cell stack  100 . Therefore, no external object comes into contact with the fuel cell stack  100 , and there is no possibility of short-circuiting. On the other hand, when the fuel cell stack  100  is unfastened by the tension rods  220 , the external manifold  400  is removed. Therefore, an external object may come into contact with the single cells  110  (the fuel cell stack  100 ). However, even when the external object comes into contact with the single cells  110  (the fuel cell stack  100 ) to cause short-circuiting, a low voltage is generated due to a small electromotive force. Therefore, according to this embodiment of the invention, a current can be restrained from flowing through the fuel cell stack  100  at a high voltage even when an external object comes into contact with the fuel cell stack  100 . 
       FIGS. 4A and 4B  are explanatory views showing modification examples. In this embodiment of the invention shown in  FIG. 3 , each of the protrusions  410  is clamped between a corresponding one of the single cells  110  and a corresponding one of the collector plates  120 . However, as shown in  FIG. 4A , each of the protrusions  410  may be clamped between a corresponding one of the collector plates  120  and a corresponding one of the end plates  200 . Further, as shown in  FIG. 4B , each of the protrusions  410  may be located outside a corresponding one of the end plates  200 . In this case, the tension rods  220  penetrate the protrusions  410 . 
       FIG. 5  is an explanatory view showing another modification example. In this embodiment of the invention shown in  FIG. 3 , the protrusions  410  are formed on the external manifold  400 . However, it is also appropriate to adopt a construction in which an insulating plate  600  separate from the external manifold  400  is disposed on an upper surface of the fuel cell stack  100  and protrusions  610  are provided on the insulating plate  600 . It should be noted that the protrusions  610  may be formed at various positions as shown in  FIGS. 4A and 4B  even when the insulating plate  600  is provided. It should be noted that the provision of the protrusions  410  on the external manifold  400  is preferred from the standpoint of reducing the number of parts. It should be noted that the modification example shown in  FIG. 5  is also applicable to an inner manifold-type fuel cell unequipped with an external manifold. 
     It should be noted that although the external manifold  400  or the insulating plate  600  is provided with the two protrusions  410  or  610  in the foregoing embodiment of the invention or each of the modification examples, there may be provided a single protrusion 410 or 610 or more than two protrusions  410  or  610 . The support strength can be enhanced by providing a plurality of protrusions. 
       FIGS. 6A and 6B  are explanatory views showing modification examples of the shape of the protrusions. As shown in  FIG. 6A , the protrusions  410  may assume a tapered shape. Further, as shown in  FIG. 6B , the protrusions  410  may assume a curved shape. In the modification examples, when the external manifold  400  is pulled upward in  FIG. 6A  or  6 B, tapered portions or curved portions press the collector plates  120  toward the end plates  200  respectively. As a result, the single cells  110  are easily separated from the end plates  200  respectively. In this manner, the protrusions  410  may assume various shapes except a rectangular shape. 
     In the fuel cell according to the invention, it is possible to adopt either a construction in which the tension rods  220  penetrate the protrusions  410  or a construction in which the tension rods  220  do not penetrate the protrusions  410 .  FIG. 7  shows an example of the construction in which the tension rods  220  penetrate the protrusions  410 . As shown in  FIG. 7 , in the case where the tension rods  220  penetrate the protrusions  410 , the external manifold  400  or the insulating plate  600  cannot be removed unless the tension rods  220  are drawn out. When the tension rods  220  are drawn out, the fuel cell stack  100  is separated into the single cells  110 . Accordingly, in disassembling the fuel cell, an object from the outside can be restrained from coming into contact with the fuel cell stack  100  composed of the laminated single cells  110 . As a result, a current can be restrained from flowing through the fuel cell stack  100  at a high voltage. 
     The embodiment of the invention has been described above on the basis of the examples thereof. However, the foregoing embodiment of the invention is intended to facilitate the understanding of the invention and does not limit the invention. It is obvious that the invention can be modified or improved without departing from the gist thereof or the claims and includes equivalents thereof.