Abstract:
A fuel cell system having an integral electrical conduction system is provided for the transmission of electrical energy created from a fuel cell stack. The electrical conduction system conducts electricity to a positive and a negative pole, each disposed at a common end of the fuel cell stack for reducing the amount of external wiring needed for connecting multiple fuel cell stacks together. The fuel cell stack and electrical system are both disposed in a housing.

Description:
FIELD OF THE INVENTION 
     The present invention relates to fuel cell systems, and more particularly, to integrated bus bars for use with a fuel cell stack. 
     BACKGROUND OF THE INVENTION 
     Fuel cell systems include a fuel cell stack that produces electrical energy based on a reaction between a hydrogen-based feed gas (e.g., pure hydrogen or a hydrogen reformate) and an oxidant feed gas (e.g., pure oxygen or oxygen-containing air). In proton exchange membrane (PEM) type fuel cells, the hydrogen-based feed gas is supplied to an anode of the fuel cell and an oxidant is supplied to a cathode of the fuel cell. PEM fuel cells include a membrane electrode assembly (MEA) comprising a thin, proton transmissive, non-electrically conductive, solid polymer membrane-electrolyte having the anode on one of its faces and the cathode on the opposite face. The MEA is sandwiched between a pair of electrically conductive elements which serve as current collectors for the anode and cathode and contain appropriate channels and/or openings therein for distribution of the fuel cell&#39;s gaseous reactants over the surfaces of the respective anode and cathode catalysts. A plurality of individual fuel cells are commonly stacked together to form a PEM fuel cell stack. 
     Generally multiple fuel cell stacks are arranged in series and are connected via high voltage external connection wires, as illustrated in  FIG. 3 . The use of external connection wires increases the volume, weight and complexity of the fuel cell stack system. In particular, fuel cell stacks typically have a positive pole  102  and a negative pole  104  that are disposed at opposite ends of the fuel cell stack  100 . Thus, in order to connect multiple fuel cell stacks  100 ,  100   a  in series, the external high voltage wires  106  are required to run from one end of a fuel cell stack  100  to another end of an adjacent fuel cell stack  100   a  as illustrated in  FIG. 3 . The external wires  106  are not protected by contactors, and contribute to increased electromagnetic interference (EMI) that requires shielding or other protection. The external wires  106  also contribute to additional sealing requirements. Thus, fully insulated and shielded wires require a large volume and increase the weight of the fuel cell system. Accordingly, a need exists for a system with reduced external wiring. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fuel cell system having an integral electrical conduction system. The electrical energy created by a fuel cell stack is transferred from the fuel cell stack by the electrical conduction system. Both the electrical conduction system and the fuel cell stack are retained in the same housing which reduces external wiring that is required for connecting multiple fuel cell stacks. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a fuel cell system including an integrated bus bar according to the present invention; 
         FIG. 2  is an exploded perspective view of a fuel cell system of  FIG. 1 ; and 
         FIG. 3  is a perspective view of a prior art fuel cell system including separate fuel cell stacks connected in series with high voltage external wires. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring now to  FIG. 1 , a fuel cell system  10  according to the principles of the present invention is shown. The fuel cell system  10  includes a fuel cell stack  12  (shown schematically) coupled to an electrical conduction system  14 . The fuel cell stack  12  and the electrical conduction system  14  are both disposed in a housing  16 , part of which is illustrated in phantom lines. 
     The fuel cell stack  12  produces electrical power which is conducted out of the fuel cell stack  12  via adjacent positive and negative poles  18 ,  20  connected to the electrical conduction system  14 . As illustrated in  FIG. 2 , the fuel cell stack  12  has a first end  22  and a second end  24  both of which are coupled to the electrical conduction system  14 . In particular, the electrical conduction system  14  includes a first current collector plate  26  in communication with the positive pole  18  and a second current collector plate  34  in communication with the negative pole  20  as will be described in detail herein. The first current collector plate  26  is in communication with the first end  22  of the fuel cell stack  12  while the second current collector plate  34  is in communication with the second end  24  of the fuel cell stack  12 . The second current collector plate  34  is coupled to the negative pole  20  via a conductive bus bar  30  which is connected to a third current collector plate  32 . 
     The first current collector plate  26  includes the positive pole  18 . The positive pole  18  is positively charged. The first current collector plate  26  is electrically conductive and can be manufactured from any electrically conductive material, such as, for example, copper. The first current collector plate  26  is in communication with the first end  22  of the fuel cell stack  12  such that the electrical energy generated by the fuel cell stack  12  passes therethrough. The first current collector plate  26  is separated from the third current collector plate  32  by a first insulating layer  36 . 
     Both the second and third current collector plates  34 ,  32  are electrically conductive and can be manufactured from any electrically conductive material, such as, for example, copper. The first insulating layer  36  may be made from any substantially non-conductive material. The third current collector plate  32  is located adjacent to an upper cap  64  of the housing  16  and includes the negative pole  20  which is negatively charged. The third current collector plate  32  further includes an opening  40  for non-contact receipt of the positive pole  18  from the first current collector plate  26  therethrough. A mating flange  42  on the third current collector plate  32  couples the conductive bus bar  30  to the third current collector plate  32 . Specifically, the mating flange  42  includes a plurality of openings  44  for receipt of a plurality of standard fasteners  46  therethrough. The conductive bus bar  30  is shown coupled to the mating flange  42  via the fasteners  46 , however any other suitable fastening mechanism may also be used, such as, for example, welding, adhesives, crimping or rivets. The conductive bus bar  30  is further coupled to the second current collector plate  34 . 
     The conductive bus bar  30  is joined to the second current collector plate  34  via a mating flange  48 . The mating flange  48  includes a plurality of openings  50  for receipt of a plurality of fasteners  52  therethrough. The conductive bus bar  30  is shown coupled to the mating flange  48  via the fasteners  52 , however any other suitable fastening mechanism may also be used, such as, for example, welding, adhesives, crimping or rivets. The second current collector plate  34  is in communication with the second end  24  of the fuel cell stack  12  and is negatively charged. The second current collector plate  34  further includes a plurality of openings  54  which serve as passages for reactant gases as described below. The second current collector plate  34  is located adjacent to a second insulating layer  38 . 
     The second insulating layer  38  is located between the second current collector plate  34  and a lower cap  66  of the housing  16 . The second insulating layer  38  has a tab  56  for securing the second insulating layer  38  to the housing  16  and a plurality of openings  58  which provide passages for reactant gases as described below. The first insulating layer  36  is located between the third current collector plate  32  and the first current collector plate  26 . The first insulating layer  36  serves to insulate the first current collector plate  26  and positive pole  18  from the negatively charged third current collector plate  32  and has an opening  59  through which the positive pole  18  passes. The first insulating layer  36  also includes a tab  60  for securing the first insulating layer  36  to the housing  16 . 
     The conductive bus bar  30  couples the third current collector plate  32  and the second current collector plate  34  together such that an electric charge can flow therethrough. The conductive bus bar  30  includes a plurality of openings  62  for the receipt of the fasteners  46  from the third current collector plate  32  and the fasteners  52  from the second current collector plate  34  therein. The conductive bus bar  30  can be made from any conductive material, such as, for example, copper. 
     The housing  16  has an upper cap  64 , a lower cap  66 , and a main body as shown in phantom lines in  FIG. 1 . The upper cap  64  encloses the first end  22  of the fuel cell stack  12  including the first current collector plate  26 , the third current collector plate  32  and first insulating layer  36 . The lower cap  66  encloses the second end  24  of the fuel cell stack  12  including second current collector plate  34  and second insulating layer  38 . The upper cap  64  includes a pair of openings  70  for receipt of the positive pole  18  from the first current collector plate  26  and the negative pole  20  from the third current collector plate  32 . The lower cap  66  of the housing  16  includes an anode inlet  72   a  for receipt of the hydrogen-based feed gas, a cathode inlet  72   b  for the receipt of the oxidant feed gas, and a coolant inlet  72   c  through which coolant fluid passes. In addition, the lower cap  66  includes an anode exhaust  74   a,  a cathode exhaust  74   b  and a coolant exhaust  74   c  for removing the exhaust gases and coolant from the fuel cell stack  12 . Thus, the plurality of openings  54 ,  58  of the second current collector plate  34 , and second insulating layer  38 , respectively, serve as passages for the inlet and exhaust gases for the anode, cathode and coolant when positioned within the lower cap  66 . 
     The fuel cell system  10  enables the connection of multiple fuel cell stacks  12  via the closely located positive and negative poles  18 ,  20  instead of through a complex bulky wiring system, reducing the amount of assembly space and overall size of the fuel cell system  10 . In addition, by integrating the conductive bus bar  30  within the housing  16 , the conductive bus bar  30  is protected from being touched or mishandled during assembly. The conductive bus bar  30  can also be utilized for different sizes of fuel cell stacks  12 . Furthermore, both the positive pole  18  of the third current collector plate  32  and the negative pole  20  of the third current collector plate  32  can be placed at any location along the first current collection plate  26  and the third current collector plate  32 , respectively, as needed. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.