Abstract:
A vehicle-mounted cell stack system includes a cell stack that comprises a plurality of laminated power generating cells, and power collecting plates that sandwich both outermost power generating cells, electric wires connected to the power collecting plates, and an electric load connected to the power collecting plates via the electric wires and configured to be activated by electric power that is supplied from the cell stack. The electric wires are connected to the power collecting plates in a direction other than a cell laminating direction.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Japanese Patent Application No. 2012-56138, filed with the Japan Patent Office on Mar. 13, 2012, the entire contents of which are incorporated into this specification by reference. 
       TECHNICAL FIELD 
       [0002]    This invention relates to a vehicle-mounted cell stack system. 
       BACKGROUND 
       [0003]    JP 2007-15615 A discloses that a fuel cell stack (cell stack) including laminated power generating cells (unit cells) is arranged under a floor. Further, JP 2007-15615 A discloses that a circuit case is arranged on a surface that is parallel to a lamination surface of the power generating cells. 
       SUMMARY 
       [0004]    By the way, the inventors of this invention have been developing a fuel cell stack structured to be arranged in a motor compartment (conventionally referred to as an engine compartment) in front of a cabin. The motor compartment (engine compartment) has a small free space. In a case where the fuel cell stack that is structured as disclosed in JP 2007-15615 A is arranged in such a limited space, there arises a problem in that a large number of the power generating cells cannot be laminated. 
         [0005]    The present invention has been made in view of such a problem inherent in the related art. It is an object of the present invention to provide a vehicle-mounted cell stack system that effectively utilizes a limited space so that a larger number of power generating cells can be laminated. 
         [0006]    According to one aspect of the present invention, there is provided a vehicle-mounted cell stack system, including: a cell stack that comprises a plurality of laminated power generating cells, and power collecting plates that sandwich both outermost power generating cells; electric wires connected to the power collecting plates; and an electric load connected to the power collecting plates via the electric wires and configured to be activated by electric power that is supplied from the cell stack. The electric wires are connected to the power collecting plates in a direction other than a cell laminating direction. 
         [0007]    Embodiments and advantages of the present invention will be described in detail below with reference to the attached figures. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1A  is an external perspective view illustrating a fuel cell stack. 
           [0009]      FIG. 1B  is an exploded view of a structure of a power generating cell of the fuel cell stack. 
           [0010]      FIG. 2  is an exterior view of a stack case for housing the fuel cell stack. 
           [0011]      FIG. 3  is a view of a state in which a CVM case is arranged on a stack case. 
           [0012]      FIG. 4  is a perspective view of an inside of the CVM case. 
           [0013]      FIG. 5  is a view of a state in which a PDM case is further arranged on the CVM case. 
           [0014]      FIG. 6  is a sectional view of insides of the CVM case and the PDM case. 
           [0015]      FIG. 7A  is a side view illustrating a state in which a vehicle-mounted cell stack system is mounted on a vehicle. 
           [0016]      FIG. 7B  is a plan view illustrating the state in which the vehicle-mounted cell stack system is mounted on the vehicle. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0017]      FIGS. 1A and 1B  are explanatory views of a fuel cell stack.  FIG. 1A  is an external perspective view.  FIG. 1B  is an exploded view of a structure of a power generating cell. 
         [0018]    As illustrated in  FIG. 1A , a fuel cell stack  100  includes a plurality of laminated power generating cells  10 , and power collecting plates  20 . The fuel cell stack  100  is formed into a rectangular parallelepiped shape. The fuel cell stack  100  of the type exemplified in this embodiment is housed in a stack case  200  as described later. 
         [0019]    The power generating cells  10  are each a unit cell of the fuel cell stack. The power generating cells  10  each generate an electromotive voltage of approximately one volt (V). Description of details of the structure of each of the power generating cells  10  is made later. 
         [0020]    The power collecting plates  20  are provided in a pair, and respectively arranged on outsides of the plurality of laminated power generating cells  10 . The power collecting plates  20  are each made of a gas-impermeable conductive member such as high density carbon and a metal material. 
         [0021]    One of the power collecting plates  20  (power collecting plate  20  that is a near side on the left in  FIG. 1A ) has an anode supply port  21   a , an anode discharge port  21   b , a cathode supply port  22   a , a cathode discharge port  22   b , a coolant supply port  23   a , and a coolant discharge port  23   b , which are provided along a short side of the power collecting plate  20 . In this embodiment, the anode supply port  21   a , the coolant supply port  23   a , and the cathode discharge port  22   b  are provided on the right side in  FIG. 1A . Further, the cathode supply port  22   a , the coolant discharge port  23   b , and the anode discharge port  21   b  are provided on the left side in  FIG. 1A . 
         [0022]    As examples of a method of supplying hydrogen as an anode gas to the anode supply port  21   a , there are given a method of supplying a hydrogen gas directly from a hydrogen storage device, and a method of supplying a hydrogen-containing gas that is obtained through reformation of fuel containing hydrogen. It should be noted that examples of the hydrogen storage device include a high-pressure gas tank, a liquefied hydrogen tank, and a hydrogen absorbing alloy tank. Examples of the fuel containing hydrogen include a natural gas, methanol, and gasoline. Further, air is generally used as a cathode gas to be supplied to the cathode supply port  22   a.    
         [0023]    As illustrated in  FIG. 1B , each of the power generating cells  10  has such a structure that an anode separator (anode bipolar plate)  12   a  and a cathode separator (cathode bipolar plate)  12   b  are arranged on both surfaces of a membrane electrode assembly (MEA)  11 . 
         [0024]    In the MEA  11 , electrode catalyst layers  112  are formed on both surfaces of an electrolyte membrane  111  formed of an ion exchange membrane. Gas diffusion layers (GDL)  113  are formed on the electrode catalyst layers  112 . 
         [0025]    The electrode catalyst layers  112  are each formed, for example, of carbon black particles that carry platinum. 
         [0026]    The GDLs  113  are each formed of a member having sufficient gas diffusion property and conductivity, such as carbon fiber. 
         [0027]    The anode gas supplied through the anode supply port  21   a  flows along the GDL  113   a , reacts with the anode electrode catalyst layer  112  ( 112   a ), and is discharged through the anode discharge port  21   b.    
         [0028]    The cathode gas supplied through the cathode supply port  22   a  flows along the GDL  113   b , reacts with the cathode electrode catalyst layer  112  ( 112   b ), and is discharged through the cathode discharge port  22   b.    
         [0029]    The anode separator  12   a  is laminated on one surface (back surface in  FIG. 1B ) of the MEA  11  through intermediation of the GDL  113   a  and a seal  14   a . The cathode separator  12   b  is laminated on another surface (front surface in  FIG. 1B ) of the MEA  11  through intermediation of the GDL  113   b  and a seal  14   b . Examples of the seals  14  ( 14   a  and  14   b ) include rubber elastic materials such as silicone rubber, ethylene propylene rubber (ethylene propylene diene monomer; EPDM), and fluororubber. The anode separator  12   a  and the cathode separator  12   b  are each obtained through press forming of a separator preform made of a metal such as stainless steel so that reactant gas flow paths are formed on one surface thereof, and that coolant flow paths are formed on an opposite surface thereof in arrays alternately to the reactant gas flow paths. The anode separator  12   a  and the cathode separator  12   b  are laminated as illustrated in  FIG. 1B . With this, the coolant flow paths are formed. 
         [0030]    Holes  21   a ,  21   b ,  22   a ,  22   b ,  23   a , and  23   b  are formed in the MEA  11 , the anode separator  12   a , and the cathode separator  12   b , respectively. Those holes are aligned with each other so as to form the anode supply port (anode supply manifold)  21   a , the anode discharge port (anode discharge manifold)  21   b , the cathode supply port (cathode supply manifold)  22   a , the cathode discharge port (cathode discharge manifold)  22   b , the coolant supply port (coolant supply manifold)  23   a , and the coolant discharge port (coolant discharge manifold)  23   b.    
         [0031]    It should be noted that, although not shown, harnesses  30  for taking out electric power generated by the power generating cells  10  are connected to the power collecting plates  20 . 
         [0032]      FIG. 2  is an exterior view of the stack case for housing the fuel cell stack. 
         [0033]    The stack case  200  is formed into a rectangular parallelepiped shape. The stack case  200  is formed of six surfaces, that is, a front wall  210 , side walls  220  and  230 , a rear wall  240 , an upper wall  250 , and a bottom wall  260 . The front wall  210  and the rear wall  240  are parallel to surfaces (lamination surfaces) of the power generating cells  10 . The side walls  220  and  230  are perpendicular to the surfaces (lamination surfaces) of the power generating cells  10 , and parallel to short sides of the power generating cells  10 . In other words, the side walls  220  and  230  are perpendicular to longitudinal sides of the power generating cells  10 . The upper wall  250  and the bottom wall  260  are perpendicular to the surfaces (lamination surfaces) of the power generating cells  10 , and parallel to the longitudinal sides of the power generating cells  10 . In other words, the upper wall  250  and the bottom wall  260  are perpendicular to the short sides of the power generating cells  10 . 
         [0034]    The upper wall  250  has holes  201  formed therein. The harnesses  30 , which are connected to the power collecting plates  20  so as to take out the electric power generated by the power generating cells  10 , are inserted through the holes  201 . The fuel cell stack as a whole generates high electric current, and hence the harnesses  30  are each formed to have a large diameter and a high rigidity. 
         [0035]    Further, the upper wall  250  has an angular hole  202  formed therein. As described later, terminals of a cell voltage monitor are inserted to the angular hole  202 . 
         [0036]      FIG. 3  is a view of a state in which a CVM case is arranged on the stack case. 
         [0037]    A CVM case  300  is superimposed on the stack case  200 . The CVM case  300  houses the cell voltage monitor (CVM) for monitoring a voltage of each of the power generating cells  10 . The terminals of the cell voltage monitor are inserted to the angular hole  202  formed through the upper wall  250  of the stack case  200 , and are connected respectively to the power generating cells  10 . The CVM case  300  is provided with spaces  310  through which the harnesses  30  are inserted. As illustrated in  FIG. 4 , the harness insertion space  310  is surrounded by a partition wall  311 , and is isolated from the cell voltage monitor. It should be noted that the harness insertion space  310 , which is formed into an oblong shape in this embodiment, is merely an example, and hence may be formed into another shape. 
         [0038]      FIG. 5  is a view of a state in which a PDM case is further arranged on the CVM case. 
         [0039]    A PDM case  400  is superimposed on the CVM case  300 . The PDM case  400  houses a power delivery module (PDM) for managing electric power that is generated in the system. Further, as illustrated in  FIG. 6 , the PDM case  400  houses a relay circuit  500 . A hole is formed in a bottom wall of the PDM case  400 , and the harnesses  30  are inserted through the hole. The harnesses  30  are connected to a drive motor or an air supply compressor through intermediation of the relay circuit  500 . In a situation in which electric current needs to be shut off, the relay circuit  500  is opened. The PDM case  400  is fixed to the CVM case  300 . Specifically, the PDM case  400  is fixed to the CVM case  300  with, for example, bolts. The PDM case  400  may be held in direct contact with the CVM case  300 , or a gasket may be interposed therebetween. With this structure, higher fitting property is obtained, and hence entry of foreign matters such as moisture is prevented. 
         [0040]      FIGS. 7A and 7B  are each a view illustrating a state in which a vehicle-mounted cell stack system is mounted on a vehicle.  FIG. 7A  is a side view, and  FIG. 7B  is a plan view. 
         [0041]    The fuel cell stack  100  is mounted in a space (engine compartment) located in front of a cabin. It should be noted that a fuel cell vehicle does not have an internal combustion engine mounted thereto, but the front space in which an internal combustion engine for an engine vehicle is to be mounted is conventionally referred to as an engine compartment. The power generating cells  10  of the fuel cell stack  100  are arrayed in a width direction of a vehicle  900 . In other words, the lamination surfaces of the power generating cells  10  are parallel to a fore-and-aft direction and a vertical direction of the vehicle  900 . Further, as described above, the harnesses  30  for taking out the electric power generated by the power generating cells  10  are perpendicular to the surfaces (lamination surfaces) of the power generating cells  10 , and are inserted through the holes  201  in the upper wall  250  that is parallel to the longitudinal sides of the power generating cells  10 . In addition, the harnesses  30  are inserted through the harness insertion spaces  310  of the CVM case  300 , and are connected to the relay circuit  500  housed in the PDM case  400 . With this structure, the relay circuit  500  is not arranged side by side with the power generating cells  10 . Thus, even in a case where the fuel cell stack  100  is arranged in a limited space such as the engine compartment, a larger number of the power generating cells  10  can be reliably arrayed. 
         [0042]    According to this embodiment, among the outer walls of the stack case for housing the power generating cells, the holes  201  are formed through the upper wall  250  that is perpendicular to the lamination surfaces of the power generating cells, and the harnesses  30  are inserted through the holes  201 . As described above, the harnesses  30  each have a large diameter and a high rigidity. The relay circuit  500  is arranged in an extension direction of the harnesses  30  having such a high rigidity. With this structure, the relay circuit  500  is not arranged side by side with the power generating cells  10 . In a case where the harnesses each have a low rigidity, the relay circuit  500  can be arranged irrespective of positions of holes to be formed through the outer wall of the stack case. However, actually, the harnesses  30  each have a high rigidity, and hence it is impractical to arrange the relay circuit  500  irrespective of the positions of the holes to be formed through the outer wall of the stack case. In this embodiment, with the structure described above, the relay circuit  500  is not arranged side by side with the power generating cells  10 . As a result, even in a case where the fuel cell stack  100  is arranged in the limited space such as the engine compartment, higher mountability can be achieved, and hence a larger number of the power generating cells  10  can be reliably arrayed. Thus, output from the fuel cell stack can be increased. 
         [0043]    Further, the CVM case  300  is superimposed on the stack case, and the PDM case  400  is superimposed on the CVM case  300 . In addition, the CVM case  300  is provided with the harness insertion spaces  310  each surrounded by the partition wall and isolated from the cell voltage monitor, and the harnesses  30  are inserted through the spaces  310 . The cell voltage monitor is configured to monitor the voltage of each of the power generating cells. The voltage of each of the power generating cells is as small as approximately one volt, and hence the voltage may not be accurately detected when any noise is present. Meanwhile, according to this embodiment, the harnesses  30  are inserted through the spaces  310  that are surrounded by the partition walls and isolated from the cell voltage monitor. Thus, adverse effects on the cell voltage monitor can be prevented. 
         [0044]    Still further, the harnesses  30  are inserted through the spaces  310  of the CVM case  300 , and hence additional structures for protecting the harnesses  30  need not be provided. As a result, the structure can be simplified. 
         [0045]    Yet further, the power delivery module is heavy, and hence the PDM case  400  housing the power delivery module becomes heavier in accordance therewith. Meanwhile, the partition walls are provided to the CVM case  300 , and hence a strength of the CVM case  300  can also be increased. 
         [0046]    Yet further, the PDM case  400  is fixed to the CVM case  300  (with, for example, bolts). In a case where a gasket is interposed therebetween, higher fitting property is obtained, and hence entry of foreign matters such as moisture is prevented. 
         [0047]    Yet further, the relay circuit  500  is housed in the PDM case  400 . Thus, an additional case for housing the relay circuit  500  is unnecessary. In addition, the power delivery module, through which high electric current is caused to flow, is housed in the PDM case  400 . Such a power delivery module is less liable to be influenced by noise, and hence the electric power that is generated in the system can be accurately managed even when the relay circuit  500  is provided. In addition, the PDM case  400  is large in size, and hence a sufficient space for housing the relay circuit  500  can be secured. 
         [0048]    Yet further, the holes  201  are formed through the upper wall  250 . Even in a case where the holes  201  are formed through the bottom wall  260 , and the stack case  200  is underlaid with the CVM case  300  and the PDM case  400 , a larger number of the power generating cells  10  can be reliably arrayed. However, moisture that is generated in the fuel cell stack may enter the CVM case  300 . As a countermeasure, in this embodiment, the holes  201  are formed through the upper wall  250 , and the CVM case  300  and the PDM case  400  are superimposed on the stack case  200 . With this, even when the moisture is generated in the fuel cell stack, the moisture can be prevented from entering the CVM case  300 . 
         [0049]    In order to secure the reactant flow paths, it is desired that the longitudinal sides of the power generating cells  10  be as large as possible. Further, in order to suppress variation of flow among the cells, it is desired that the short sides thereof be as small as possible. In view of this, in this embodiment, the holes  201  are formed through the wall that is perpendicular to the short sides of the power generating cells  10 , in other words, through the wall that is parallel to the longitudinal sides of the power generating cells  10 , and the harnesses  30  are inserted therethrough. The CVM case  300  and the PDM case  400  are superimposed along the longitudinal sides of the stack case  200 . With this, the desired structure as described above can be obtained. 
         [0050]    An embodiment of the present invention was described above, but the above embodiment merely illustrates a part of examples of applications of the present invention, and the technical scope of the present invention is not limited to the specific configurations described in the embodiment. 
         [0051]    For example, the fuel cell stack (cell stack)  100  of the type exemplified in the above description is housed in the stack case  200 . However, this invention is not limited thereto. This invention is applicable also to a type in which the fuel cell stack (cell stack)  100  is not housed in the stack case  200 . 
         [0052]    Further, as in the above description, the harnesses  30  are connected to the power collecting plates  20 . The harnesses  30  may be provided separately from the power collecting plates  20 , or extended parts may be provided to the power collecting plates  20  so as to be used instead of the harnesses  30 . In other words, the harnesses  30  may be provided integrally with the power collecting plates  20 . With this, the structure can be simplified to reduce a thickness, and hence a larger number of the power generating cells can be laminated.