Abstract:
The fuel cell vehicle, includes a fuel cell generating electricity by an electrochemical reaction of hydrogen and oxygen; an accessory for the fuel cell; and a fuel cell system box mounted on a vehicle body and housing the fuel cell and the accessory, wherein the fuel cell system box is formed in a vessel shape which has a bottom wall, a first side wall, and a second side wall, the first side wall supporting at least one pipe through which a fluid supplied to the fuel cell flows, and the first side wall is constituted of a material having a specific gravity that is greater than that of the bottom wall and the second wall.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a fuel cell vehicle, and particularly to a fuel cell vehicle provided with anti-vibration measures in a fuel cell system box that houses fuel cells and the like, and to a fuel cell vehicle able to rapidly measure the hydrogen concentration inside the casing that houses the fuel cells and the like.  
         [0003]     Priority is claimed on Japanese Patent Application No. 2004-343118, filed on Nov. 26, 2004, Japanese Patent Application No. 2004-343120, filed on Nov. 26, 2004, Japanese Patent Application No. 2004-343121, filed on Nov. 26, 2004, Japanese Patent Application No. 2005-308407, filed on Oct. 24, 2005, Japanese Patent Application No. 2005-308508, filed on Oct. 24, 2005, and Japanese Patent Application No. 2005-311435, filed on Oct. 26, 2005, the contents of which are incorporated herein by reference.  
         [0004]     2. Description of Related Art  
         [0005]     Fuel cell vehicles mounting fuel cells have previously been known. With regard to the mounting of fuel cells, a variety of countermeasures against vehicle vibration have been proposed. For example, there is a proposal that provides elastic mount member on the fuel cell, and that installs the fuel cell in the housing case via the mount member (see Japanese Unexamined Patent Application, First Publication Nos. 2002-367651 and 2003-297377).  
         [0006]     Moreover, when mounting the fuel cells, a variety of ventilation configurations are adopted for conducting ventilation of the interior of the casing that houses the fuel cells for reasons related to the use of hydrogen gas (see Japanese Unexamined Patent Application, First Publication No. 2004-161057).  
         [0007]     It is necessary to connect pipes to the fuel cells for supply of the reaction gas and the coolant, and the piping is configured so as to pass through the walls of the case that houses the fuel cells. Accordingly, when the feed pipes of the reaction gas and the coolant vibrate, this is transmitted to the fuel cells, which is undesirable and which tends to ruin quiet in the vehicle compartment.  
         [0008]     Conventional fuel cell vehicles have the merit of being able to elastically support the fuel cells relative to the housing case via the mount members, but there is the problem that it is not possible to fully secure support rigidity relative to the housing case of the fuel cells. Moreover, there is the problem that it is difficult to set the placement positions of the mount members.  
         [0009]     With conventional fuel cell vehicles, in the case where the interior of the casing that houses the fuel cells is ventilated, it is necessary to provide a hydrogen sensor inside the casing, and to conduct the ventilation based on the measurement results of the hydrogen sensor. In this regard, when the measurement accuracy of the hydrogen sensor is low, there is the problem that this engenders the trouble of having to conduct ventilation more than is necessary. When a plurality of hydrogen sensors are provided in order to raise measurement accuracy, there is the problem that it leads to higher cost.  
       SUMMARY OF THE INVENTION  
       [0010]     An object of the invention is to provide a fuel cell vehicle that is able to reliably prevent vibration from the various pipes, protect the fuel cells, and enhance quiet.  
         [0011]     Another object of the invention is to provide a fuel cell vehicle that is able to improve the measurement accuracy of the hydrogen sensor.  
         [0012]     The fuel cell vehicle of the invention includes: a fuel cell generating electricity by an electrochemical reaction of hydrogen and oxygen; an accessory for the fuel cell; and a fuel cell system box mounted on a vehicle body and housing the fuel cell and the accessory, wherein the fuel cell system box is formed in a vessel shape which has a bottom wall, a first side wall, and a second side wall, the first side wall supporting at least one pipe through which a fluid supplied to the fuel cell flows, and the first side wall is constituted of a material having a specific gravity that is greater than that of the bottom wall and the second wall.  
         [0013]     In the fuel cell vehicle of the invention, the pipe may pass through the first side wall.  
         [0014]     According to the fuel cell vehicle, it is possible to prevent the vibration transmitted from the pipes from being transmitted to other parts by increasing the support rigidity of the hydraulic pipes, with the result that the fuel cell can be protected from vibration and quiet can be enhanced.  
         [0015]     In the fuel cell vehicle of the invention, the first side wall may be constituted of an iron material, and the bottom wall and the second side wall may be constituted of an aluminum material.  
         [0016]     According to the fuel cell vehicle, it is possible to plan the entire fuel cell system box to be more lightweight, while ensuring the support rigidity of the pipes, with the result that one can plan a more lightweight vehicle, and contribute to improved fuel consumption.  
         [0017]     In the fuel cell vehicle of the invention, the first side wall having a coating thereon may be connected to the bottom wall and the second side wall by riveting.  
         [0018]     According to the fuel cell vehicle, it is possible to prevent the direct contact of the iron material and the aluminum material, with the result that one can prevent electrocorrosion.  
         [0019]     In the fuel cell vehicle of the invention, the fuel cell system box may have front and rear skeletal members provided at the front and rear of the bottom wall and extending in a widthwise direction of the vehicle, an anti-vibration material is disposed between the front and rear skeletal members, and the fuel cell is fixed to the front and rear skeletal members.  
         [0020]     According to the fuel cell vehicle, it is possible to reliably fix the fuel cell to the fuel cell system box by the front and rear skeletal members, and to prevent the vibration of the bottom face of the fuel cell system box from being transmitted to the fuel cell by anti-vibration material, with the result that one can stably support the fuel cell, protect the fuel cell, and enhance quiet.  
         [0021]     In the fuel cell vehicle of the invention, the anti-vibration material is covered by plates fixed to the front and rear skeletal members.  
         [0022]     According to the fuel cell vehicle, it is possible to suppress the surface vibration of the plates by attaching the plates to the front and rear skeletal members, with the result that one can enhance quiet.  
         [0023]     In the fuel cell vehicle of the invention, the vehicle may further include: a lid covering an upper part of the fuel cell system box and having an under surface formed with a varying height; and a hydrogen sensor placed at an elevated position inside the fuel cell system box and measuring a hydrogen concentration inside the fuel cell system box.  
         [0024]     According to the fuel cell vehicle, hydrogen gas with a lower specific gravity than air can be measured by a hydrogen sensor at an elevated position inside the fuel cell system box that is advantageous for purposes of measurement accuracy. The hydrogen sensor can be placed at a high position on the bottom face of the top wall. Accordingly, measurement accuracy can be increased. Moreover, the hydrogen sensor can be placed at a high position on the bottom face of the top wall, with the result that it is unnecessary to provide a plurality of hydrogen sensors, and it is possible to undertake cost reductions.  
         [0025]     In the fuel cell vehicle of the invention, the lid has spacers varying the height of the undersurface of the lid and guiding the hydrogen to the hydrogen sensor.  
         [0026]     According to the fuel cell vehicle, it is possible to adjust the bottom face of the lid—that is, the effective height of the fuel cell system box—by the height adjusting spacers, and to gradually guide the hydrogen gas to a high place where measurement can be conducted by the hydrogen sensor, with the result that a single hydrogen sensor can reliably and accurately conduct measurement.  
         [0027]     In the fuel cell vehicle of the invention, the vehicle may further include an air conveyance means conveying ventilation air into the fuel cell system box, wherein the hydrogen sensor is arranged downstream of the ventilation air inside the fuel cell system box.  
         [0028]     According to the fuel cell vehicle, the ventilation air inside the fuel cell system box from the air conveyance means can be quickly measured by the hydrogen sensor, with the result that measurement can be conducted within a short period of time.  
         [0029]     In the fuel cell vehicle of the invention, the accessory has hydrogen system accessory supplying hydrogen to the fuel cell or discharging hydrogen from the fuel cell.  
         [0030]     According to the fuel cell vehicle, a common hydrogen sensor can conduct measurement of the hydrogen concentration in the vicinity of the fuel cell stacks and the hydrogen system accessory where the hydrogen concentration would seem to be higher compared to other accessory equipment. Accordingly, measurement can be quickly conducted in a short period of time by the hydrogen sensor, and that the prescribed protective operations can be adopted.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0031]      FIG. 1  is a lateral perspective view of the fuel cell vehicle of an embodiment of the invention.  
         [0032]      FIG. 2  is a plan explanatory view of essential parts of the fuel cell vehicle of an embodiment of the invention.  
         [0033]      FIG. 3  is a sectional view along line A-A of  FIG. 2 .  
         [0034]      FIG. 4  is an exploded perspective view of the fuel cell system box of an embodiment of the invention.  
         [0035]      FIG. 5  is a plan view showing the state of connection of hydraulic pipes of the fuel cell system box of an embodiment of the invention.  
         [0036]      FIG. 6  is an exploded perspective view of the riveted parts of an embodiment of the invention.  
         [0037]      FIG. 7  is a plan view along line B-B of  FIG. 6 .  
         [0038]      FIG. 8  is an exploded perspective view of the fuel cell system box of a second embodiment.  
         [0039]      FIG. 9  is a plan view of the box body installing the fuel cells of the second embodiment.  
         [0040]      FIG. 10  is a plan view of the box body of the second embodiment.  
         [0041]      FIG. 11  is a plan view along line B-B of  FIG. 10 .  
         [0042]      FIG. 12  is a plan view along line C-C of  FIG. 10 .  
         [0043]      FIG. 13  is an exploded perspective view of the fuel cell system box of a third embodiment.  
         [0044]      FIG. 14  is a plan view showing the state of connection of hydraulic pipes of the fuel cell system box of the third embodiment.  
         [0045]      FIG. 15  is a schematic plan view showing the arrangement of spacers in the third embodiment.  
         [0046]      FIG. 16  is a lateral view of  FIG. 15 .  
         [0047]      FIG. 17  is a perspective view of essential parts of the fuel cell system box of the third embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0048]     Next, the first embodiment of the invention is explained with reference to drawings.  
         [0049]     As shown in  FIG. 1 , the fuel cell vehicle  1  mounts fuel cells  3  that generate electricity by the electrochemical reaction of hydrogen and oxygen, and the motor is driven and movement occurs by the power produced from the generation of electricity. The fuel cell  3  is housed inside the fuel cell system box (casing)  5  that is installed on the bottom face of the front floor  4 . Power generation is conducted by the hydrogen gas supplied from the hydrogen tanks  19  and  20  arranged under the rear floor  6  in the rear part of the carbody and by the oxygen in the air supplied from the compressor  8  provided in the front part of the carbody.  
         [0050]     As shown in  FIG. 2  and  FIG. 3 , the main frames  9  with a hat-like sectional form are joined via the flanges  10  to both the left and right sides of the bottom face of the front floor  4 . The carbody skeleton  11  is formed in the longitudinal direction of the carbody with the main frames  9  and front floor  4 . Outriggers  12  of hat-like sectional form extending in the widthwise direction of the vehicle are joined in three places to the outer side wall of the main frames  9 , and the outer ends of the outriggers  12  are joined to the side sills  13 . As with the main frames  9 , the outriggers  12  are joined to the bottom face of the front floor  4 . The fuel cell system box  5  is fastened and fixed by the bolts  15  and nuts  16  to the bottom walls  14  of the main frames  9 . The front-back-left-right directional arrows in  FIG. 2  show the respective front-back-left-right directions of the carbody.  
         [0051]     The main frames  9  and side sills  13  are connected via the back ends of the side sills to the lateral rear frame  17  (see  FIG. 1 ) provided at the rear of the carbody in the longitudinal direction. As shown in  FIG. 1 , a sub-frame  18  provided with rear suspension (not illustrated) is attached from underneath to the rear frame  17 . The hydrogen tanks  19  and  20  are respectively fixed in a crosswise manner to the front side and rear side of the sub-frame  18 .  
         [0052]     As shown in  FIG. 4 , the fuel cell system box  5  that houses the fuel cells  3  and has the rectangular box-shaped box body  21  and the lid  22  that covers the box body  21  from above.  
         [0053]     The box body  21  includes the front wall (first side wall)  23  consisting of iron material, the rear wall (first side wall)  24  consisting of iron material, the two side walls (second side walls, other walls)  25  consisting of aluminum material, and the bottom wall (other wall)  26  consisting of aluminum material. The iron material has a specific gravity that is greater than that of the aluminum material. The attachment brackets  27  of the main frames  9  are attached to the front upper edges and rear upper edges of the side walls  25 . The side reinforcements  29  that form the skeletal part  28  are attached between the side walls  25  and the bottom wall  26 .  
         [0054]     The front stack frame  31  and rear stack frame  32  are joined to the bottom wall  26  of the box body  21  between each side reinforcement  29  in the widthwise direction of the vehicle. The front stack frame  31  is attached slightly to the rear of the forward end of the box body  21 , while the rear stack frame  32  is attached slightly to the front of the back end of the box body  21 . The attachment brackets  27 , front stack frame  31  and rear stack frame  32  are consisted of aluminum material.  
         [0055]     The front stack frame  31  and rear stack frame  32  have a hat-like sectional form. A skeletal part  35  of closed sectional structure is formed on the top face of the bottom wall  26  of the box body  21  by welding each peripheral flange  34  of the front stack frame  31  and rear stack frame  32  to the top face of the bottom wall  26  of the box body  21  and to the side reinforcements  29 .  
         [0056]     The fuel cells  3 , which are separated into right and left and electrically connected in a serial manner, are respectively fixed via the brackets  36  between the front stack frame  31  and rear stack frame  32 .  
         [0057]      FIG. 5  shows a typical view of accessories of the fuel cells  3  in a state where the fuel cells  3  are installed. Flow-through pipes for supply and discharge of the air, hydrogen gas and coolant of the fuel cells  3  are connected to the fuel cells  3  in the aforementioned manner. These flow-through pipes pass through the front wall  23  and rear wall  24 , and connect to the fuel cells  3  and to the accessories explained below.  
         [0058]     Specifically, the air supply pipe (hydraulic pipe)  50  that supplies air to the fuel cells  3  is provided so as to transit the part of the front wall  23  that is substantially at the center in the widthwise direction of the vehicle. The air supply pipe  50  is connected to the humidifier  51  arranged between the fuel cells  3 . The humidifier  51  serves to supply the reaction gas to the fuel cells  3  in a state where the reaction gas have been moistened by using the exhaust gas moisture, and to optimally maintain the ion exchange function of the solid polymer electrolyte membrane. The air discharge pipe  52  connected to the fuel cells  3  transits the part of the rear wall  24  of the fuel cells  3  that is substantially at the center in the widthwise direction of the vehicle via the dilution box  64  arranged at the rear of the fuel cells  3 , and connects to the exhaust pipe (hydraulic pipe)  53 .  
         [0059]     The coolant supply pipe (hydraulic pipe)  54  that is connected to the radiator (not illustrated) arranged at the front of the carbody is configured so as to pass through the part of the front wall  23  that is on the right side in the widthwise direction of the vehicle. The coolant supply pipe  54  is connected to a wax pellet type thermostat  55  arranged to the front of the fuel cells  3  on the right. The coolant cools both the fuel cells  3  and the high voltage electrical parts such as the power supply system of the fuel cells  3 , and heat discharge is conducted by the radiator.  
         [0060]     As the thermostat  55  gives priority to activating the fuel cells  3  when warm-up operation is conducted, the coolant supply pipe  54  with respect to the radiator is closed, and the communicating pipe  56  with respect to the below-mentioned water pump  57  is opened. The coolant supply pipe  54  disposed front of the thermostat  55  along the coolant flow is routed toward the back along the inner side of the side wall  25  on the right side of the fuel cell system box  5 , and connects to the back end of each fuel cell  3 . The coolant return pipe  58 , which connects to the back end of each fuel cell  3  via the cooling channels inside the fuel cells  3 , is routed this time toward the front along the inner side of the side wall  25  on the left side of the fuel cell system box  5 . Furthermore, the coolant return pipe  58  connects to the water pump  57  for coolant supply arranged to the front of the fuel cells  3  on the left, where it becomes the coolant discharge pipe (hydraulic pipe)  59 , and passes through the front wall  23 , and is routed toward the radiator (not shown).  
         [0061]     The hydrogen supply pipe (hydraulic pipe)  60  for hydrogen gas connected to the hydrogen tanks  19  and  20  is configured so as to pass through the part of the rear wall  24  on the left side in the widthwise direction of the vehicle. The hydrogen supply pipe  60  is connected to the hydrogen circulation system  61  arranged at the back of the fuel cells  3  on the left. The hydrogen circulation system  61  supplies hydrogen gas to the fuel cells  3  from the supply pipe  62 , and returns unreacted hydrogen gas discharged from the fuel cells via the circulation pipe  63 , where it is recirculated. The hydrogen discharge pipe (not shown) of the hydrogen gas provided for power generation inside the fuel cells  3  is connected to the dilution box  64 .  
         [0062]     The air supply pipe  50 , exhaust pipe  53 , coolant supply pipe  54 , coolant discharge pipe  59 , and hydrogen supply pipe  60  pass through the front wall  23  and rear wall  24  of the fuel cell system box  5  in the aforementioned manner, and these are supported in the front wall  23  and rear wall  24  of the fuel cell system box  5  via brackets  66  fixed in place by bolts  65 . The front wall  23  and rear wall  24  are both consisted of iron material which has greater weight per unit volume and better support rigidity compared to the aluminum material that forms both side walls  25  and  25  and the bottom wall  26  or the members other than these.  
         [0063]     Moreover, the front wall  23  and rear wall  24  are provided with a cationic electrodeposition coating, and are joined and fixed in the state by rivets  67  to both side walls  25 , the bottom wall  26  or other members.  
         [0064]     When the front wall  23  is shown as a specific example in  FIG. 6 , the front wall  23  is provided with the upper edge flange  23   a , the side edge flange  23   b  and lower flange  23   c , which respectively extend toward the interior. The lower edge flange  23   c  is overlaid from above by the bottom wall, the side edge flange  23   b  is overlaid from the outside by the side wall  25 , and the corner of the outer side of the upper edge flange  23   a  in the widthwise direction of the vehicle is overlaid from above by the attachment bracket  27 . As shown in  FIG. 7 , the side wall  25 , bottom wall  26  and attachment bracket  27  are joined and fixed by the rivets  67  that are inserted through the attachment holes  68 . In  FIG. 7, 67   a  is the head of the rivet  67 , and  67   b  is the caulking part of the rivet  67 . As the rear wall  24  is joined to the side walls  25  and bottom wall  26  in the same configuration as the front wall  23 , an explanation thereof is omitted.  
         [0065]     In the aforementioned first embodiment, the front wall  23  and rear wall  24  of the fuel cell system box  5  are constituted of iron material with better support rigidity than the side walls  25  and bottom wall  26  constituted of aluminum material, with the result that it is possible to increase the support rigidity of the air supply pipe  50 , exhaust pipe  53 , coolant supply pipe  54 , coolant discharge pipe  59  and hydrogen supply pipe  60 , which are supported via the bracket  66  as they pass through the front wall  23  and rear wall  24 . Accordingly, it is possible to prevent the vibration transmitted from the air supply pipe  50 , exhaust pipe  53 , coolant supply pipe  54 , coolant discharge pipe  59  and hydrogen supply pipe  60  from being transmitted to the entirety of the fuel cell system box  5 . Consequently, it is possible to protect the fuel cell  3  from vibration, and to enhance quiet.  
         [0066]     In the aforementioned first embodiment, the side walls  25 , bottom wall  26  and other members apart from the front wall  23  and rear wall  24  are constituted of aluminum material, with the result that it is possible to plan the entirety of the fuel cell system box to be more lightweight, and, thus, to plan a more lightweight carbody and contribute to improved fuel consumption.  
         [0067]     In the aforementioned first embodiment, the front wall  23  and rear wall  24  constituted of iron material are joined, in a state where they have received a cationic electrodeposition coating, to the side walls  25 , bottom wall  26  or other members such as the attachment brackets  27  constituted of aluminum material by the rivets  67 , with the result that it is possible to prevent direct mutual contact of the iron material and aluminum material. Consequently, it is possible to prevent local current corrosion—that is, electrocorrosion—due to formation of a local battery from the electric potential difference produced when two different types of metal come into contact  
         [0068]     In the first embodiment, an explanation was made for the case where hydraulic pipes pass through, for example, the front wall  23  and rear wall  24 , but it is also acceptable to make the side walls  25  and  25  from iron material, and have the hydraulic pipes pass through there.  
         [0069]     Next, a second embodiment of the invention is explained based on drawings. Explanation is made with regard to the fuel cell system box  5  in particular, and the remaining configuration is identical to that of the first embodiment.  
         [0070]     As shown in FIGS.  8  to  10 , the fuel cell system box  5  that houses the fuel cells  3  is configured from the rectangular box-shaped box body  221  and the lid  222  covering the box body  221  from above.  
         [0071]     The box body  221  includes the front wall  223  (first side wall), the rear wall  224  (first side wall), the two side walls  225 , and the bottom wall (bottom face)  226 . The attachment brackets  227  for the main frames  9  are attached to the front upper edges and rear upper edges of the side walls  225 . The side reinforcements  229  that form the skeletal part  228  are attached between the side walls  225  and the bottom wall  226 .  
         [0072]     The front stack frame (skeletal member)  231  and rear stack frame (skeletal member)  232  are joined to the bottom wall  226  of the box body  221  between each side reinforcement  229  in the widthwise direction of the vehicle. The front stack frame  231  is attached slightly to the rear of the forward end of the box body  221 , while the rear stack frame  232  is attached slightly to the front of the back end of the box body  221 .  
         [0073]     The front stack frame  231  and rear stack frame  232  have a hat-like sectional form. A skeletal part  235  of closed sectional structure is formed on the top face of the bottom wall  226  of the box body  221  by welding each peripheral flange  234  of the front stack frame  231  and rear stack frame  232  to the top face of the bottom wall  226  of the box body  221  and to the side reinforcements  229 . The fuel cells  3  and  3 , which are divided in two and electrically connected in a serial manner are respectively fixed via the brackets  236  between the front stack frame  231  and rear stack frame  232 . These brackets  236  have an L-shaped sectional form, and the bottom wall  237  of the bracket  236  is fixed to the top face of the front stack frame  231  or rear stack frame  232  by the bolts  238 , while the vertical wall  239  of the bracket  236  is fixed in place by the bolts  238  to the front end vertical wall or back end vertical wall of the fuel cells  3 .  
         [0074]     As shown in FIGS.  6  to  8 , between the front stack frame  231  and rear stack frame  232 , crosswise pairs of sandwich panels (plates)  241  are attached to the underside of the placement areas of the front and rear stack frames  231  and  232 , that is, to areas that respectively correspond to the bottom face of each fuel cell  3 . These sandwich panels  241  form the space  240  with the top face of the bottom wall  226  of the box body  221 . With regard to these sandwich panels  241 , the front flange  242  is joined to the rear edge of the peripheral flange  234  of the front stack frame  231 , and the rear flange  243  is joined to the front edge of the rear stack frame  232 . The space  240  formed between the sandwich panel  241  and the bottom wall of the box body  221  is filled with anti-vibration material  244  consisting of, for example, foam rubber.  
         [0075]     The central part of the sandwich panel  241  in the widthwise direction of the vehicle is fixed to the bottom wall  226  of the box body  221 , with the result that two spaces  240  are formed in one sandwich panel, with anti-vibration material  244  inserted in each space  240 .  
         [0076]     The front cover member  246  that forms the space  245  with the bottom wall  226  of the box body  221  is attached to the front stack frame  231 , while the rear cover member  248  that forms the space  247  with the bottom wall  226  of the box body  221  is attached to the rear stack frame  232 . Vibration-proof material  249  consisting of foam resin or the like is also packed into each space  245  and  247 . The front cover member  246  and rear cover member  248  are lower in height than the top face of the sandwich panels  241 , and the accessories of the fuel cells  3  are arranged on the top of the front cover member  246  and rear cover member  248 .  
         [0077]     In the aforementioned second embodiment, the fuel cells  3  are supported by the front stack frame  231  and rear stack frame  232  provided in the widthwise direction of the vehicle on the bottom wall  226  of the box body  221  such that the fuel cells  3  are straddled by the side reinforcements  229 . Accordingly, the fuel cells  3  are supported by the skeletal part  228  formed by the side reinforcements  229  in the longitudinal direction of the vehicle and by the skeletal part  235  formed by the front stack frame  231  and rear stack frame  232 . Consequently, it is possible to reliably and stably fix the fuel cells  3  to the fuel cell system box  5 .  
         [0078]     With the aforementioned second embodiment, the sandwich panels  241  are connected so as to be straddled by the front stack frame  231  and rear stack frame  232  underneath the fuel cells  3 , the spaces  240  are formed between the sandwich panels  241  and the bottom wall  226  of the box body  221 , and these spaces  240  are filled with the anti-vibration material  244 . Consequently, even if the bottom wall  226  of the box body  221  positioned under the fuel cells  3  vibrates, this vibration is absorbed by the anti-vibration material  244 , with the result that transmission of this vibration to the fuel cells  3  can be prevented. Consequently, it is possible to protect the fuel cells  3  from vibration, and to enhance quiet in the vehicle compartment.  
         [0079]     With the aforementioned second embodiment, the anti-vibration material  244  is covered by the sandwich panel  241  fixed to the front stack frame  231  and rear stack frame  232 , with the result that the support rigidity of the sandwich panel  241  is increased, surface vibration of the sandwich panel  241  can also be suppressed, and quiet can be enhanced with this point as well.  
         [0080]     With the aforementioned second embodiment, anti-vibration material  249  is packed into the space  245  formed between the front cover member  246  and the bottom wall  226  of the box body  221  at the front of the front stack frame  231 , and anti-vibration material  249  is packed into the space  247  formed between the rear cover member  248  and the bottom wall  226  of the box body  221  at the back of the rear stack frame  232 . Consequently, it is also possible to reliably suppress surface vibration of the bottom wall  226  of the box body  221  in these parts as well, with the result that quiet in the vehicle compartment can be further enhanced. As the transmission of vibration to the accessories arranged above the front cover member  246  and rear cover member  248  is prevented, these can be protected from vibration.  
         [0081]     Next, a third embodiment of the invention is explained based on drawings. Explanation is made with regard to the fuel cell system box  5  in particular; the remaining configuration is identical to that of the first embodiment.  
         [0082]     As shown in  FIG. 13 , the fuel cell system box  5  that houses the fuel cells  3  is configured from the rectangular box-shaped box body  321  and the lid  322  covering the box body  321  from above.  
         [0083]     The box body  321  is formed in a box shape (vessel shape) and includes the front wall  323  (first side wall), the rear wall  324  (first side wall), the two side walls  325  and  325 , and the bottom wall (bottom face)  226 . The attachment brackets  327  for the main frames  9  are attached to the front upper edges and rear upper edges of the side walls  325 . The side reinforcements  329  that form the skeletal part  328  are attached between the side walls  325  and the bottom wall  326 . The front stack frame  331  and rear stack frame  332  are joined to the bottom wall  326  between each side reinforcement  329  in the widthwise direction of the vehicle. The front stack frame  331  is attached slightly to the rear of the forward end of the box body  321 , while the rear stack frame  332  is attached slightly to the front of the back end of the box body  321 .  
         [0084]     The front stack frame  331  and rear stack frame  332  have a hat-like sectional form. A skeletal part  335  of closed sectional structure is formed on the top face of the bottom wall  326  of the box body  321  by welding each peripheral flange  334  of the front stack frame  331  and rear stack frame  332  to the top face of the bottom wall  326  of the box body  321  and to the side reinforcements  329 .  
         [0085]     The fuel cells  3  and  3 , which are divided in two and electrically connected in a serial manner are respectively fixed via the brackets  336  between the front stack frame  331  and rear stack frame  332 .  
         [0086]      FIG. 14  shows a typical view of accessories of the fuel cells  3  in a state where the fuel cells  3  are installed.  
         [0087]     Flow-through pipes for supply and discharge of the air, hydrogen gas and coolant of the fuel cells  3  are connected to the fuel cells  3  in the aforementioned manner. These flow-through pipes pass through the front wall  323  and rear wall  324 , and connect to the fuel cells  3  and to the accessories explained below.  
         [0088]     Specifically, the air supply pipe  350  that supplies air to the fuel cells  3  is provided so as to transit the part of the front wall  323  that is substantially at the center in the widthwise direction of the vehicle. The air supply pipe  350  is connected to the humidifier  351  arranged between the fuel cells  3 . The humidifier  351  serves to supply the reaction gas to the fuel cells in a state where the reaction gas have been moistened by using the exhaust gas moisture, and to optimally maintain the ion exchange function of the solid polymer electrolyte membrane. The air discharge pipe  352  connected to the fuel cells  3  transits the part of the rear wall  324  of the fuel cells  3  that is substantially at the center in the widthwise direction of the vehicle via the dilution box  364  arranged at the rear of the fuel cells  3 , and connects to the exhaust pipe  353 .  
         [0089]     The coolant supply pipe  354  that is connected to the radiator (not illustrated) arranged at the front of the carbody is configured so as to transit the part of the front wall  323  that is on the right side in the widthwise direction of the vehicle. The coolant supply pipe  354  is connected to a wax pellet type thermostat  355  arranged to the front of the fuel cells  3  on the right. The coolant cools both the fuel cells  3  and the high voltage electrical parts such as the power supply system of the fuel cells  3 , and heat discharge is conducted by the radiator.  
         [0090]     As the thermostat  355  gives priority to activating the fuel cells  3  when warm-up operation is conducted, the coolant supply pipe  354  with respect to the radiator is closed, and the communicating pipe  356  with respect to the below-mentioned water pump  357  is opened. The coolant supply pipe  354  disposed front of the thermostat  355  is routed toward the back along the inner side of the side wall  325  on the right side of the fuel cell system box  5 , and connects to the back end of each fuel cell  3 . The contact box  349  that houses the contacts which constitute the electromagnetic make-and-break switch is arranged to the side of the thermostat  355 .  
         [0091]     The coolant return pipe  358 , which connects to the back end of each fuel cell  3  via the cooling channels inside the fuel cells  3 , is routed this time toward the front along the inner side of the side wall  325  on the left side of the fuel cell system box  5 . Furthermore, the coolant return pipe  358  connects to the water pump  357  for coolant supply arranged to the front of the fuel cells  3  on the left, where it becomes the coolant discharge pipe  359 , and passes through the front wall  323 , and is routed toward the radiator.  
         [0092]     The hydrogen supply pipe  360  for hydrogen gas connected to the hydrogen tanks  19  and  20  is configured so as to pass through the part of the rear wall  324  on the left side in the widthwise direction of the vehicle. The hydrogen supply pipe  360  is connected to the hydrogen circulation system (hydrogen system accessories)  361  arranged at the back of the fuel cells  3  on the left. The hydrogen circulation system  361  supplies hydrogen gas to the fuel cells  3  from the supply pipe  362 , and returns unreacted hydrogen gas discharged from the fuel cells via the circulation pipe  363  by the hydrogen pump and ejector (not shown), where it is recirculated. The hydrogen discharge pipe (not shown) of the hydrogen gas provided for power generation inside the fuel cells  3  is connected to the dilution box  364 .  
         [0093]     The air supply pipe  350 , exhaust pipe  353 , coolant supply pipe  354 , coolant discharge pipe  359 , and hydrogen supply pipe  360  passes through the front wall  323  and rear wall  324  of the fuel cell system box  5  in the aforementioned manner, and these are supported in the front wall  323  and rear wall  324  of the fuel cell system box  5  via brackets  366  fixed in place by bolts  365 .  
         [0094]     As shown in a typical representation by  FIG. 15  and  FIG. 16 , the first to the third height adjusting spacers S 1 -S 3  are provided in the lid  322  that constitutes the top wall of the fuel cell system box  5 . These first to third spacers S 1 -S 3  are attached to the rear face of the lid  322 , and form height variations on the bottom face of the lid  322 . That is, the height of the ceiling of the fuel cell system box  5  varies according to the thickness of the first to third spacers S 1 -S 3  attached to the bottom face of the lid  322 . The lid  322  has a chevron sectional form in the widthwise direction where the central part in the widthwise direction is elevated more than the side parts.  
         [0095]     To explain with specificity, the resin first spacer S 1  with thickness D 1  (the height of its bottom face from the bottom wall  326  is H 1 ) is attached to the rear face of the lid  322  extending in the widthwise direction of the fuel cell system box  5  above the thermostat  355 , contact box  349  and water pump  357  which are the accessories farther toward the front than the fuel cells  3 . The second spacer S 2  with thickness D 2  (the height of its bottom face from the bottom wall  326  is H 2  (H 2 &gt;H 1 )) is attached to the bottom face of the lid  322  extending in the widthwise direction of the fuel cell system box  5  above the fuel cells  3  and the humidifier  351 . The thickness D 1  is set larger than thickness D 2 , and the bottom face height of the lid  322  is set to H (H&gt;H 2 ).  
         [0096]     The third spacer S 3  made of resin or the like with thickness D 2  (the height of its bottom face from the bottom wall  326  is H 2 ) is attached to the rear face of the lid  322  extending in the widthwise direction of the fuel cell system box  5  above the dilution box  364  and hydrogen circulation system  361  which are the accessories farther toward the back than the fuel cells  3 .  
         [0097]     The third spacer S 3  is provided with the notch C where the vicinity of the rear end of the fuel cells  3  and humidifier  351  is excised in a substantially trapezoidal shape when viewed in a planar manner. At the notch C, the bottom face of the lid  322  that is exposed downward is positioned at its highest point inside the fuel cell system box  5 .  
         [0098]     The hydrogen sensor  348  for measuring the hydrogen concentration inside the fuel cell system box is arranged on the bottom face of the lid  322  that is exposed by the notch C, at the part of the fuel cell system box  5  that is at the center in the widthwise direction. Accordingly, the hydrogen gas inside the fuel cell system box  5  is gradually guided upward by the first spacer S 1 , second spacer S 2  and third spacer S 3 , and directed to the hydrogen sensor  348 .  
         [0099]     Incidentally, the hydrogen circulation system  361  disposed behind the fuel cells  3  is a hydrogen supply accessory for supplying hydrogen gas to the fuel cell  3 , while the dilution box  364  is hydrogen discharge accessory for discharging the hydrogen gas that has already reacted from the fuel cells  3 . Accordingly, it would seem that the rear area of the fuel cells  3  which is the placement area of these hydrogen system accessories would have a higher hydrogen measurement frequency than other areas. It would be particularly conspicuous at the hydrogen circulation system  361 . For this reason, the front fourth spacer S 4  and rear fifth spacer S 5  are arranged in this area in order to function as front and rear vertical walls, to guide the hydrogen gas upward as is without dispersion, and to have it measured by the hydrogen sensor  348 . In other words, while the first spacer S 1  to third spacer S 3  guide the hydrogen gas horizontally, the fourth spacer S 4  and fifth spacer S 5  guide the hydrogen gas upward. The fourth spacer S 4  and fifth spacer S 5  are omitted from the drawings of FIGS.  13  to  15 .  
         [0100]     As specifically shown in  FIG. 17 , the induction tube (air conveyance means)  338  that passes through the front wall  323  of the fuel cell system box  5  is attached to the contact box  349 . The induction tube  338  guides the ventilation air supplied from the fan (not shown) at the front of the fuel cell system box  5  to the interior of the fuel cell system box  5 . The induction tube  338  that passes through the front wall  323  is connected to the left side wall  339   a  of the upper connection port  339  of the contact box  349 . The supply tube (air conveyance means)  340  that supplies the ventilation air that passes through the interior of the contact box  349  from the front right side toward the rear inside the fuel cell system box  5  is connected to the right side wall  339   b  of the connection port  339 . The open end (air conveyance means)  341  of the supply tube  340  is open toward the front end of the fuel cell  3  on the right side. The hydrogen sensor  348  is disposed front of the open end  341  of the supply tube  340  along the hydrogen flow.  
         [0101]     In the case where the hydrogen concentration inside the fuel cell system box  5  increases, and where hydrogen is measured by the hydrogen sensor  348 , the prescribed protective operations are conducted such as interrupting the supply of hydrogen to the fuel cells  3 , suspending power generation by the contacts of the fuel cells  3 , and increasing the quantity of air provided from the supply tube  340  using the air conveyance means.  
         [0102]     With the third embodiment, hydrogen gas with lower specific gravity than air is measured by the hydrogen sensor  348  at the highest position inside the fuel cell system box  5  that is advantageous for measurement accuracy, with the result that measurement accuracy can be increased. In particular, as the hydrogen sensor  348  is positioned at the highest area in the bottom face of the lid  322 , it is acceptable to use only one hydrogen sensor  348 , and it is possible to bring about cost reductions compared to the case where a plurality of hydrogen sensors  348  are used.  
         [0103]     In short, the effective height of the bottom face of the lid  322 —that is, of the fuel cell system box  5 —is adjusted by the first spacer S 1 , second spacer S 2  and third spacer S 3 , with the result that hydrogen gas is gradually guided to the higher elevations of height H 1 , height H 2  and height H regardless of the area where hydrogen gas exists, and that the hydrogen concentration is reliably and accurately measured there by the hydrogen sensor  348 . In the area of the hydrogen circulation system  361  and dilution box  364  where measurement is most necessary, the hydrogen sensor  348  measures the hydrogen gas that is reliably led upward by the fourth spacer S 4  and fifth spacer S 5  that prevent horizontal dispersion of hydrogen gas. In particular, with the third embodiment, as the central part of the lid  322  in the widthwise direction has a substantially trapezoidal shape, it is advantageous in that it is able to more effectively guide the hydrogen gas from the side parts to the higher central part in the widthwise direction.  
         [0104]     The ventilation air supplied from the fan at the front of the fuel cell system box  5  is introduced into the contact box  349  after transiting the induction tube  338 , cools the contact box  349 , and is subsequently discharged toward the rear from the open end  341  of the supply tube  340 . This enables quick measurement of the ventilation air in a short period by the hydrogen sensor  348  positioned downstream from the open end  341  of the supply tube  340 , and adoption of the prescribed protective operations.  
         [0105]     In the third embodiment, the form and the like of the lid  322 , for example, is but one example, and the form of the lid  322  is not limited by the aforementioned embodiment if it is able to bring about variations in the effective height of the ceiling of the fuel cell system box  5 . Moreover, the spacers were shown as separated in a typical depiction, but a variety of modes may be adopted such as providing the respective spacers on the rear side of the lid  322  in an integral form.  
         [0106]     While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention, and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as being limited by the foregoing description, and is only limited by the scope of the appended claims.