Abstract:
The present invention relates to an improvement of a fuel flow board structure for a fuel cell comprising a first substrate made of a material with good thermal conductivity and a second substrate made of a material with good adhesion connecting to the first substrate to become a one-piece structure.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a structure of flow layer in fuel cells, more particularly, to a fuel flow board applied to fuel cells adopting at least two materials.  
       BACKGROUND OF THE INVENTION  
       [0002]      FIG. 1  illustrates the structure of a conventional layer lamination integrated fuel cell system. The layer lamination integrated fuel cell system  10  includes a fuel flow layer  13 , a first power/signal transmission layer  15 , an anode current collection layer  113 , a membrane electrode assembly (MEA) layer  111 , a cathode current collection layer  115 , a second power/signal transmission layer  17 , and an electromechanical control layer  19 . The anode current collection layer  113 , the MEA layer  111  and the cathode current collection layer  115  constitute a core component  11  of the fuel cell. Taking a direct methanol fuel cell (DMFC) system as an example of the layer lamination integrated fuel cell system  10 , methanol solution passes to the core component  11  through the fuel flow layer  13 , and initiates an anodic electrochemical reaction at the anode of the MEA layer  111  as follow:
 CH 3 OH+H 2 O→6H + +6 e   − +CO 2   
 and a cathodic electrochemical reaction at the cathode of the MEA layer  111  as follow:
 1.5O 2 +6H + +6 e   − →3H 2 O 
 Accordingly, electricity generated during an electrochemical reaction transforming chemical energy to low voltage DC power is supplied for a loading  100 . 
 
         [0003]     The fuel flow layer  13  in  FIG. 1  is made of a printed circuit substrate or the like that has only one material. Such material, however, doesn&#39;t have a good heat-dissipating property intrinsically. As a result, each unit of the core component  11  has inconsistent temperature therein due to raised temperature induced by electrochemical reaction of anode fuel of the fuel flow layer  13 . Consequently, due to the anode fuel with inconsistent temperature in the fuel flow layer  13 , the core component  11  produces unstable DC voltages that affect the efficiency of transformation from chemical energy to electricity. Meanwhile, those units in the fuel cell have inconsistent durability and result in a shorter lifespan of the system  10  as a whole.  
         [0004]      FIG. 2  is a diagram that shows the correlation between the temperature of anode fuel and power generated by a DMFC system, wherein x-axis represents measuring time and y-axis represents power. As illustrated in  FIG. 2 , the DMFC system produces about 0.3 watts (W) at 40° C., about 0.4 W at 50° C. and about 0.45 W at 60° C. It can be understood that the temperature of anode fuel is highly related to the degree of the electrochemical reaction. Hence, it is of great importance to make the temperature of fuel uniform, so as to perform a consistent degree of electrochemical reaction in each unit and generate regular power.  
         [0005]     Therefore, a fuel flow board being able to maintain a uniform temperature distribution of the fuel in fuel cells is needed.  
       SUMMARY OF INVENTION  
       [0006]     It is a primary object of the invention to provide a fuel flow board structure for a fuel cell, which can prevent the fuel in fuel cells from inconsistent temperature distribution and eliminate negative effects on the efficiency of power generated thereof.  
         [0007]     It is a secondary object of the invention to provide a fuel flow board structure for a fuel cell, which combines at least two different materials. Taking advantages of these materials, fuels in the fuel cell may have a uniform temperature distribution, and the fuel flow board may be closely connected to the current collection layers of the cell.  
         [0008]     In accordance with the aforesaid objects of the invention, an improved fuel flow board structure for a fuel cell is provided. The structure comprises a first substrate made of a material with good thermal conductivity and a second substrate made of a material with good adhesion connecting to the first substrate to make a one-piece structure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     The foregoing aspects, as well as many of the attendant advantages and features of this invention will become more apparent by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:  
         [0010]      FIG. 1  illustrates the structure of a conventional layer lamination integrated fuel cell system;  
         [0011]      FIG. 2  is a diagram showing the correlation between temperature of anode fuel and power generated by a DMFC system;  
         [0012]      FIG. 3  illustrates the structure of a fuel flow board according to one embodiment of the present invention; and  
         [0013]      FIG. 4  illustrates the structure of a fuel flow board according to another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0014]      FIG. 3  illustrates the structure of a fuel flow board according to one embodiment of the invention. A fuel flow board  20  includes a first substrate  21  and a second substrate  23 , which are described hereinafter respectively. The first substrate  21  is made of a material with good thermal conductivity, such as aluminum, copper, aluminum alloy, copper alloy, or other metals and alloys. The first substrate  21  has at least one concave portion  211  thereon, which is disposed corresponding to each unit of the fuel cell. Fuel flowing into the concave portion  211 , e.g. methanol solution, hydrogen gas, anode fuel, and cathode fuel, thus has a uniform temperature distribution due to good heat conduction of the first substrate  21 . The second substrate  23  is made of a material with good adhesion, for example, plastic. Also, the second substrate  23  is connected to the first substrate  21 . From its appearance, the fuel flow board  20  represents a one-piece structure. Additionally, the fuel flow board  20  is closely connected to current collection layers by the second substrate  23  through its good adhesion.  
         [0015]     The second substrate  23  includes an inlet  231 , a flow channel  233  and an outlet  235 , which are individually described as follow. The inlet  231  is used to inject fuel like methanol solution, hydrogen gas, anode fuel, cathode fuel, and so on, and is disposed at the side of the second substrate  23 . The flow channel  233  serves to circulate fuels in the fuel flow board  20  through each fuel cell unit (not shown). The flow channel  233  is disposed on the surface of the second substrate  23  and connected to the inlet  231  and the outlet  235 . In one embodiment, the flow channel  233  is in a form with plural trenches and set on the surface of the second substrate  23 .  
         [0016]     As shown in  FIG. 3 , the flow channel  233  may be in the form of a first channel  233 A and a second channel  233 B. Accordingly, fuel of the inlet  231  diverge from the first channel  233 A to fuel cell units through each concave portion  211  and each fuel cell unit then generates electricity by electrochemical reaction. Fuel in the concave portion  211  and products of electrochemical reaction are drifted in the second channel  233 B and drained out of the outlet  235 .  
         [0017]     Because the first substrate  21  of the fuel flow board  20  is made of a material having good heat-dissipating and heat-conducing properties and its thermal conductivity is better than conventional PCB or similar materials, the fuel flow board  20  does not influence temperature of fuel when heat is generated during an electrochemical reaction. In practical, fuel in the fuel flow board  20  remains in a consistent degree of temperature. Moreover, the surface of the first substrate  21  is treated to be acid-proof, so as to prevent it from the damages by fuels or products of electrochemical reaction. The treatment is performed by, for instance, coating Teflon on whole surfaces of the first substrate  21  such that the fuel flow board  20  is resistant to acids.  
         [0018]     Furthermore, the fuel flow board  20  includes a third substrate  25  as illustrated in  FIG. 4 . The third substrate  25  adopts a printed circuit substrate, and is connected at least to the second substrate  23 . From its appearance, the fuel flow board  20  of  FIG. 4  represents an one-piece structure. The third substrate  25  has at least one electrical device  251  soldered thereon, and hence the fuel flow board  20  can provide electrical circuits.  
         [0019]     The aforementioned fuel flow board  20  can be applied to a methanol fuel cell system or other fuel cell systems using gas or liquid fuel.  
         [0020]     To sum up, the fuel flow board of the present invention possesses the advantages as follows: 
    1. The fuel flow board provides anode fuel or cathode fuel a uniform temperature distribution by means of materials with good thermal conductivity. Consequently, the efficiency of power generation in the system is increased, and the lifespan of fuel cell units are prolonged;     2. The fuel flow board has a better utility since it is closely connected to current collection layers through materials with good adhesion; and     3. It is feasible to form an intelligent fuel flow board by combining a printed circuit substrate having electrical circuits.    
 
         [0024]     While the invention has been particularly shown and described with reference to the preferred embodiments thereof, these are, of course, merely examples to help clarify the invention and are not intended to limit the invention. It will be understood by those skilled in the art that various changes, modifications, and alterations in form and details may be made therein without departing from the spirit and scope of the invention, as set forth in the following claims.