Abstract:
The present invention relates to a fuel cell vehicle capable of efficiently cooling a fuel stack and supplying sufficient reactant gas to the fuel stack with only a single air supply means.

Description:
TECHNICAL FIELD OF THE INVENTION  
   The present invention relates to a fuel cell vehicle driven with a fuel cell as a drive energy source, and particularly to a fuel cell vehicle in which the structure of a piping system for taking in external air and supplying to the fuel cell as reactant gas and cooling gas is simplified. 
   BACKGROUND OF THE INVENTION 
   In the related art, a fuel cell type two-wheeled vehicle that is driven by supplying electrical power generated by a fuel cell to a motor and driving a rear wheel using this motor is known. With a fuel cell system, electricity is generated by an electrochemical reaction between hydrogen, as a fuel gas, and oxygen, as a reactant gas, but in this electrochemical reaction there is an appropriate reaction temperature, and at a low temperature or high temperature reaction efficiency is lowered and in particular, if the temperature is too high the lifespan of the fuel cell is shortened. Therefore, with an electrical generation system using fuel cells, it is necessary to have a cooling unit in order to remove heat generated during fuel cell electricity generation to the outside of the fuel cell, and keep the operating temperature of the fuel cell within a specified temperature range. 
   Generally, fuel cell systems have a laminated structure of a plurality of electrical cells, with a cooling plate interposed between each electrical cell. A cooling gas passage is formed in the cooling plates, and a stack is cooled by having cooling gas flow in this cooling passage. 
   Technology using external air as cooling gas and reactant gas is disclosed in Japanese patent laid open No. Hei. 2001-131468, and with this technology, an air blasting fan for cooling a fuel cell stack and a blower for supplying air to the fuel cell stack as reactant gas are provided as air cooling means. 
   With the above described technology of the related art, it is necessary to have first air cooling means (air blasting fan) for cooling the fuel cell stack and second air cooling means (blower) for supplying air to the fuel cell stack as reactant gas. For this reason, not only does this contribute towards an increase in the number of components, increase in vehicle weight and rise in cost, but since it is necessary to arrange two air cooling means in space that is limited in a two wheeled vehicle there is a technological problem that freedom of design is restricted. 
   The object of the present invention is to solve the above-described technical problems in the related art, and to provide a fuel cell vehicle capable of efficiently cooling a fuel cell stack and supplying sufficient reactant gas to the fuel cell stack. 
   SUMMARY OF THE INVENTION  
   In order to achieve the above described object, the present invention is directed to a fuel cell vehicle driven by electrical power obtained by causing a chemical reaction between reactant gas and fuel gas comprising a fuel cylinder for holding the fuel gas, a fuel cell stack structure including a fuel gas passage, a reactant gas passage and a cooling gas passage, a cooling gas supply passage for supplying cooling gas to the cooling gas passage, a reactant gas supply passage for supplying reactant gas to the reactant gas passage, a blowing passage branched at the cooling gas supply passage and the reactant gas supply passage, and air supply means for sucking in external air and pressure feeding to the blowing passage. Since external air is taken in by air cooling means and pressure fed to both the cooling gas supply passage and the reactant gas supply passage, it is possible to cool the fuel cell stack and supply reactant gas with only a single air cooling means. 
   The fuel cell vehicle may include a bypass valve for controlling the supply of reactant gas to the reactant gas supply passage. With only a single air cooling means it is possible to stop external air supply to the reactant gas supply passage while continuing with external air supply to the cooling gas supply passage. It is therefore possible to continue cooling of the fuel cell stack even after shutdown. 
   The fuel cell vehicle being a two-wheeled vehicle, provided with a head pipe for supporting a handle and a front fork of the two-wheeled vehicle in a steerable manner at the front of the vehicle, the air supply means may be attached to the front of the head pipe. Therefore, it is possible to smoothly introduce external air without being subject to the influence of mud or rainfall. 
   Further, the fuel cell vehicle may have an external air introduction port of the air supply means oriented in a sideways direction of the vehicle. This makes it possible to safely introduce a fixed amount of external air according to the performance of the air cooling means without affecting dynamic pressure such as traveling speed. 
   The cooling gas supply passage and the reactant gas supply passage of the fuel cell vehicle may be divided to one side and another side with respect to the width direction of the vehicle. Since it becomes easy to bombard the cooling gas supply passage and the reactant gas supply passage with traveling wind, it is possible to keep the temperature of the cooling gas and the reactant gas low. 
   A fuel cell box housing the fuel cell stack, may be provided with a scavenge gas supply passage for supplying scavenge gas to the inside of the fuel cell box, with the scavenge supply passage branching from the blowing passage. With only a single air cooling means it is possible not only to supply cooling gas and reactant gas, but also to supply scavenge gas. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a partially broken side elevation showing the structure of main parts of a fuel cell motorcycle of the present invention. 
       FIG. 2  is a partially broken perspective view showing the structure of main parts of a fuel cell motorcycle of the present invention. 
       FIG. 3  is a drawing schematically showing the skeleton of a vehicle frame. 
       FIG. 4  is a front view showing the appearance of a fuel cylinder supported by upper frames. 
       FIG. 5  is a drawing of a blower module looking diagonally from the front right of the vehicle. 
       FIG. 6  is a drawing of the blower module looking diagonally from the front left of the vehicle 
       FIG. 7  is a drawing showing the structure of an air cleaner. 
       FIG. 8  is a side elevation showing the structure of a piping system for connecting to a subsequent stage to the blower module. 
       FIG. 9  is a front elevation showing the structure of a piping system for connecting to a subsequent stage to the blower module. 
       FIG. 10  is a cross section along line A-A of the fuel cell box shown in  FIG. 8 . 
       FIG. 11  is a cross section along line B-B of the fuel cell box shown in  FIG. 8 . 
       FIG. 12  is a perspective view of a fuel cell stack. 
       FIG. 13  is a plan view of a battery cell. 
       FIG. 14  is a cross sectional drawing along line A-A in  FIG. 13 . 
   

   DETAILED DESCRIPTION OF THE INVENTION  
   A detailed description will now be given of the present invention with reference to the drawings. 
     FIG. 1  is a partially broken side elevation showing the structure of main parts of a fuel cell motorcycle of the present invention.  FIG. 2  is a perspective drawing of the fuel cell vehicle.  FIG. 3  is a drawing schematically showing the skeleton of a vehicle frame. 
   The vehicle frame  10  is made up of a head pipe  11 , a pair of left and right upper down frames  13  (L, R) extending diagonally downwards with the head pipe  11  as a start point, a pair of left and right lower down frames  12  (L, R) further down that the upper down frames  13  extending downwards with the head pipe  11  as a start point, a pair of left and right upper frames  14  (L, R) extending diagonally upwards from substantially the center of the lower down frames  12  and connecting to the other end of the upper down frames  13  midway, and a pair of left and right lower frames  15  (L, R) further down than the upper frames  14  and extending to the rear from a lower end of the lower down frames  12 . 
   The vehicle frame  10  is also a substantially square annular structure, provided with an annular frame  16  supporting a rear end of the upper frame  14  and the lower frame  15  at the four corners of the square annular structure, a rear plate  17  extending diagonally upwards from the rear end of the lower frame  15 , and an upper connecting frame  18  and a lower connecting frame  19  connected at a position where the lower frame  14  and the lower frame  15  connect. 
   A front fork  32  axially supporting a front wheel FW and steering handle  30  connected to the front fork  32  are supported on the head pipe  11  a manner capable of being steered. A pair of left and right swing frames  20  are swingably supported at a lower part of the rear plate  17  with a shaft  21  as a fulcrum, and a rear wheel WR as a drive wheel is supported at a rear end of the swing frames  20 . 
   As a fuel cell system, the motorcycle of the present invention includes a fuel cell box  42  storing a fuel cell stack ( 48 ), a fuel cylinder  41  storing fuel gas (hydrogen) for supply to the fuel cell stack inside the fuel cell box  42 , and a piping system  43  for supplying scavenge gas taken in from the atmosphere and reactant gas and cooling gas to the inside of the fuel cell box  42 , and also has a plurality of secondary batteries  81 ,  83  and fuel cells  82  fitted as an auxiliary power source. 
   The fuel cylinder  41  is supported by and between the left and right upper frames  14 , and is mounted further forward than a seat  31  along the upper frames  14 , at an inclined attitude such that the shut-off valve  44  side faces to the rear and one end of the shut-off valve side is higher than the other end. 
     FIG. 4  is a front view showing the appearance of the fuel cylinder  41  supported by the upper frames  14 , and since the left and right upper frames  14  (L, R) have a narrower gap between the two going from bottom to top, it is possible to support the fuel cylinder  41  in a recumbent attitude. An impact absorbing member is fitted to a surface of the upper frames  14  contacting the fuel cylinder  41 . As will be described in detail later, the fuel cylinder  41  is rigidly restrained in the upper frames  14  by a suitable restraint, such as binding bands  24 ,  25 . 
   The fuel cell box  42  is positioned below the fuel cylinder  41  between the pair of left and right lower frames  15 , and is fixed by being suspended from brackets  38 ,  39  provided at two places (a total of four places) on the left and right upper frames  14  (L, R), so as to overlap and run along a line connecting a rotational axis of the front wheel FW and the rotational axis of the rear wheel RW. 
   In this manner, with this embodiment the fuel cylinder  41  and the fuel cell box  42  are arranged so that the fuel cylinder  41  is positioned almost directly above the fuel cell stack, and the seat is positioned behind them, which means that drivability is improved by centralizing the mass. Also, since the fuel cylinder  41  and the fuel cell box  42  are arranged further forward than the seat position, load shared by the rear wheel which was excessive previously, is reduced, while load shared by the front wheel, which was slight previously, is increased, which means that load sharing between the front and ear wheels is made suitable. Also, since the fuel cylinder  41  and the fuel cell stack are arranged close to each other it is possible to shorten the length of a fuel gas supply passage. 
   Secondary batteries  81 ,  83 , as an auxiliary power source, and the fuel cell  82  are arranged in a dispersed manner at the front of the vehicle, below the seat  31  and at the rear of the vehicle, respectively. Also, a down converter  84  for converting the output voltage of the fuel cell system to a voltage for auxiliary devices (for example, 12V), and peripheral circuits for the down converter, are mounted to the rear of the vehicle. A blower module  60 , for taking in external air at the front of the vehicle and strongly supplying the air to the fuel cell box  42  as scavenge gas, reactant gas or cooling gas, is mounted on the front frame  22  extending forwards from the head pipe  11 . 
     FIG. 5  is a drawing of the blower module  60  looking diagonally from the front right of the vehicle, while  FIG. 6  is a drawing of the blower module  60  looking diagonally from the front left of the vehicle, and reference numbers that are the same in the two drawings represent the same parts. 
   The blower module  60  is mainly comprised of a blower body  61  housing a blower motor and a blower fan (neither of which are shown in the drawing), an air cleaner  63 , and an intake pipe  62  connecting the air cleaner  63  and the blower body  61 . As shown in  FIG. 7 , the air cleaner  63  has an air filter  63   c  housed inside a case made up of a right case  63   a  and a left case  63   b . An intake port  64  for taking in external air is formed in a lower end side of the right case  63   a,  while an exhaust port  65  is formed in a main surface of the left case  63   b . The intake pipe  62  is connected to the exhaust port  65 . 
   As shown in  FIG. 5 , the air cleaner  63  is attached to the vehicle body at an attitude with the intake port  64  oriented diagonally downwards to the left of the vehicle body. A cut-out  63   d  is formed in the side surface of the air cleaner  63 , and a blower motor section  61   a  of the blower body  61  is stored in the cut-out  63   d.    
   If the blower body  61  is activated, the intake pipe  62  is put at negative pressure, and external air is sucked from the intake port  64  of the air cleaner  63 . This external air is filtered by the air filter  63   c  inside the air cleaner  63 , then taken in to the inside of the intake pipe  62  from the exhaust port  65  and finally supplied to a blowing passage  71  by means of the blower body  61 . 
   In this way, with this embodiment, since external air is compressed and supplied to the fuel cell box  42  using the blower module  60 , it is possible to improve the power generation efficiency of the fuel cells. Also, with this embodiment, because the air cleaner  63  is arranged further upstream than the blower body  61 , it is possible to reduce intake noise generated by the blower body  61  at the air cleaner  63 . Further, since with this embodiment the intake port  64  of the air cleaner  63  is oriented to the bottom of the vehicle body, it is possible to prevent rain water penetrating to the intake port  64 . 
     FIG. 8  and  FIG. 9  are a side elevation ( FIG. 8 ) and a front elevation ( FIG. 9 ) showing the structure of a piping system  43  connected to a subsequent stage to the blower module  60 , and reference numerals that are the same in these two drawing represent the same parts. 
   Two bypass valves  73 ,  74  are provided in the blowing passage  71 , and a scavenge gas supply passage  72  for introducing external air into the inside of the fuel cell box  42  as scavenge gas is branched from the upstream bypass valve  73 . The upstream bypass valve  73  is an electromagnetic valve, and external air is only supplied to the scavenge gas supply passage  72  when this valve is open. The downstream bypass valve  74  contains an electromagnetic three-way valve, and the blowing passage  71  branches into a reactant gas supply passage  75  and a cooling gas supply passage  79  at the downstream bypass valve  74 . Each of the upstream and downstream bypass valves  73 ,  74  are subjected to opening and closing control by the same ECU that controls the vehicle. 
   The reactant gas supply passage  75  supplies external air that is supplied from the blowing passage  71  to the fuel cell stack  48  as reactant gas (oxygen). The cooling gas supply passage  79  supplies external air supplied from the blowing passage  71  to the fuel cell stack  48  as cooling gas. The reactant gas supply passage  75  and the cooling gas supply passage  79  are divided to the left side (cooling gas supply passage  79 ) and the right side (reactant gas supply passage  75 ) of the vehicle body, so that internal gas (air) is cooled by being blown by traveling wind. 
   With this embodiment, if an ignition switched is turned on, the blower module  60  is energized to commence suction of external air, and pumping of the sucked in air, which means that the external air passes from the upstream bypass valve  73  of the blowing passage  71  through the scavenge gas supply passage  72 , and is guided to the inside of the fuel cell box  42  as scavenge air. At the same time, since the downstream bypass valve  74  is open with this embodiment, the external air is supplied through the reactant gas supply passage  75  to the fuel cell stack  48 , and also supplied through the cooling gas supply passage  79  to the fuel cell stack  48 . 
   On the other hand, with this embodiment, the temperature Tbatt of the fuel cell stack  48  is routinely measured by a temperature sensor, not shown, and if the ignition switch is turned off, the stack temperature Tbatt is compared with a specified reference temperature Tref 1 . Control is carried out so that if Tbatt&lt;Tref  1 , the downstream bypass valve  74  does not supply external air that has been supplied from the blowing passage  71  to either the reactant gas supply passage  75  side or to the cooling gas supply passage  79 , while if Tbatt≧Tref  2 , supply to the reactant gas supply passage  75  side is stopped and supply only continues to the cooling gas supply passage  79 . 
   A scavenge air outlet passage  76  for discharging the scavenge gas, and a hydrogen outlet passage  77  for discharging purged fuel gas (hydrogen) are also connected to the fuel cell box  42 , and the other end of each passage is connected to a silencer  70 . The scavenge gas and purged hydrogen gas are mixed in the silencer  70  and discharged to the outside. In this way, with this embodiment scavenge gas and purged hydrogen gas are discharged through the silencer  70 , which means that it is possible to reduce exhaust noise. 
   The fuel cylinder  41  and the fuel cell box  42  are connected by a fuel gas supply passage  78 , and fuel gas (hydrogen) to the fuel cell stack  48  inside the fuel cell box  42  is supplied from the fuel cylinder  41  through this fuel gas supply passage  78 . With this embodiment, the voltage of each cell constituting the fuel cell stack is monitored, and if even one of them drops below a reference voltage hydrogen purging is carried out. 
     FIG. 10  and  FIG. 11  are a cross section along line A-A and line B-B of the fuel cell box  42  ( FIG. 8 ), and the same reference numerals in each drawing represent the same parts. 
   Inside the fuel cell box  42 , the substantially cube-shaped fuel cell stack  48  is supported so that a scavenge air space is ensured between the  6  surfaces of the fuel cell stack  48  and the box cases  42   a ,  42   b . External air introduced from the scavenge gas supply passage  72  to the inside of the fuel cell box  42  as scavenge gas turns gas retained in the space between the box cases  42   a  and  42   b  and the fuel cell stack  48  into scavenge gas and discharges it from the scavenge air outlet passage  76 . 
     FIG. 12  is a perspective view of the fuel cell stack  48 , and a laminated body  90 , which is a main part of the fuel cell stack  48  is constructed of a plurality of cells  50  laminated in the direction of arrow A, and with power collection electrodes  58  arranged on either side.  FIG. 13  is a plan view of a cell, and  FIG. 14  is a cross section along line A-A in FIG. 
   As shown in  FIG. 14 , a cell  50  is constructed by overlapping a negative electrode side separator  51 , a negative electrode  52 , a fuel cell ion exchange membrane  53 , a positive electrode  54  and a positive electrode side separator  55 , and as shown in  FIG. 13 , has a cooling gas manifold  56  and a reactant gas manifold  57  formed for passing these components through. The negative electrode  52  and the positive electrode  54  are formed from a catalyst bed and a porous layer, and have a gas diffusion function. 
   A cooling gas flow groove  51   a  is formed in the negative electrode side separator  51 , in an outer main surface, and a hydrogen flow groove  51   b  is formed in a surface of the negative electrode side separator  51  that is opposite the fuel cell ion exchange membrane  53 , at an inner main surface. An air flow passage  55   b  is formed in a surface of the negative electrode  52  that is opposite to the fuel cell ion exchange membrane  53 . The cooling gas flow groove  51   a  links to the cooling gas manifold  56 , and the air flow passage  55   b  links to the reactant gas manifold  57 . Although omitted from the drawings, fuel gas supplied from the connecting wall section  41  through the fuel gas supply passage  78  is supplied to the hydrogen flow groove  51   b  formed in the negative electrode side separator  51 . 
   Returning to  FIG. 12 , the laminated body  90  is covered by endplates  93  arranged on both sides in a laminate direction, side plates  94  arranged on the sides, a top plate  95  arranged at the top, and a bottom plate arranged at the bottom, and pressure increase is maintained so that a constant elastic force acts in the laminate direction. 
   A reactant gas introduction port  91  and a cooling gas introduction port  92  are provided in endplate  93  side end sections. The reactant gas introduction port  91  links to the reactant gas manifold  57 , and external air from the reactant gas supply passage  75  is introduced as reactant gas for power generation. This reactant gas is supplied to the air flow passage  55   b  through the reactant gas manifold  57 . The cooling gas introduction port  92  is linked to the cooling gas manifold  56 , and cooling gas is introduced from an end section of the blowing passage  71 . This cooling gas is supplied through the cooling gas manifold  56  to the cooling gas flow groove  51   a.    
   With the above described embodiment, description has been given where the present invention is applied to a two-wheeled vehicle, but the present invention is not thus limited, and can also be similarly applied to a three wheeled vehicle or a four wheeled vehicle.