Abstract:
A fuel cell case that is configured to place a fuel cell therein, the fuel cell case includes: a first member including a bottom surface of the fuel cell case; and a second member fixed to an outer circumferential portion of the first member using a fastener, wherein a gasket seals between the first member and the second member, and the first member includes a rib, wherein the rib is positioned on an inner circumferential side of a portion where the first member comes into contact, with the gasket and is protruded upward from a surface where the first member comes into contact with the gasket.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to Japanese Patent Application No. 2014-232042 filed on Nov. 14, 2014, the contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Field 
         [0003]    The present invention relates to a fuel cell case. 
         [0004]    2. Related Art 
         [0005]    Conventionally, a fuel cell is accommodated in a fuel cell case to be protected from external force. The fuel cell case includes two members including an upper case and a lower case of a plate type. The upper case has an opening on one side and a flange around the opening. A gasket is disposed between the flange of the upper case and an outer circumferential portion of the lower case to prevent water and dirt from entering the fuel cell (for example, JP-A-2006-221854). 
         [0006]    The fuel cell case has been requested to be downsized to be more freely installed at various locations. Using a thinner lower case is one way of downsizing the fuel cell case. However, such a thin lower case might be deformed by reaction of the gasket due to the difference between a position of the belt fixing the upper case on the lower case and a position of the lower case in contact with the gasket. 
       SUMMARY 
       [0007]    The present invention is made to at least partially solve the problem described above, and can be implemented as the following aspects. 
         [0000]    (1) One aspect of the present invention provides a fuel cell case that is configured to place a fuel cell therein. The fuel cell case includes: a first member including a bottom surface of the fuel cell case; and a second member fixed to an outer circumferential portion of the first member using a fastener, wherein a gasket seals between the first member and the second member, and the first member includes a rib, wherein the rib is positioned on an inner circumferential side of a portion where the first member comes into contact with the gasket and is protruded upward from a surface where the first member comes into contact with the gasket. According to this aspect, the rib increases the rigidity of the fuel cell case so as not to be deformed by the reaction from the gasket.
 
(2) In the fuel cell case according to the above-described aspect, the second member may include a groove portion in which the gasket is disposed. According to this aspect, an increase in the size of the fuel cell case in the upper and lower direction can be prevented compared with a configuration where the groove portion is provided in the first member.
 
(3) In the fuel cell case according to the above-described aspect, the fuel cell may be formed by stacking a plurality of fuel cells, and the second member may cooperate with a third member that supports one surface of the fuel cell in a stacking direction to compress the fuel cell in the stacking direction. Since the second member compresses the fuel cell, it is difficult to reduce the rigidity of the second member. According to this aspect, the rib increases the rigidity of the first member of the fuel cell case so as not to be deformed by the reaction from the gasket. Thus, the thickness of the first member can be reduced, so that the whole fuel cell case can be downsized. with a smaller weight.
 
         [0008]    The present invention can be implemented in various aspects, examples of which include a method for manufacturing a fuel cell case, a computer program for implementing the manufacturing method, and a recording medium recording the computer program. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is an outer view of a fuel cell system  10  used in one embodiment of the present invention. 
           [0010]      FIG. 2  is an exploded perspective view of a fuel cell case  100 . 
           [0011]      FIG. 3  is a diagram illustrating a lower cover  115 . 
           [0012]      FIG. 4  is a diagram illustrating a conventional lower cover  215 . 
           [0013]      FIG. 5  is a diagram schematically illustrating force applied to the conventional lower cover  215 . 
           [0014]      FIG. 6  is a diagram illustrating a method of solving the problem described above. 
           [0015]      FIG. 7  is a cross-sectional view taken along the line A-A in  FIG. 1 . 
           [0016]      FIG. 8A  is a diagram schematically illustrating how external force is absorbed by a rib  117 . 
           [0017]      FIG. 8B  is a diagram schematically illustrating how the external force is absorbed by the rib  117 . 
           [0018]      FIG. 8C  is a diagram schematically illustrating how the external force is absorbed by the rib  117 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     A. Embodiment 
       [0019]      FIG. 1  is an outer view of a fuel cell system  10  used in one embodiment of the present invention. The fuel cell system  10  includes a fuel cell system case  140  and a frame  200 . The fuel cell system  10  is installed in a vehicle. In the present embodiment, the fuel cell system  10  is disposed below a vehicle interior. In  FIG. 1  and other figures, a positive X axis direction, a positive Y axis direction, a positive Z axis direction, respectively represent front, upper, and right sides of the vehicle. 
         [0020]    The fuel cell system case  140  includes a fuel cell case  100  and an auxiliary machine case  130 . A gasket is provided to seal among the components of the fuel cell system case  140  so that foreign matters such as water and dusts are prevented from entering the fuel cell system case  140 . 
         [0021]    A fuel cell causes an electrochemical reaction between hydrogen gas as anode gas and oxygen gas as cathode gas. The fuel cell case  100  accommodates the fuel cell that is formed by stacking a plurality of fuel cells in a left and right direction (Z axis direction) of the vehicle. 
         [0022]    The auxiliary machine case  130  accommodates a plurality of auxiliary machines (not illustrated) used for the fuel cell. The plurality of auxiliary machines include, for example, a hydrogen pump, an injector, an exhaust air and water discharge valve, a valve, a sensor, and the like. The auxiliary machine case  130  includes, in addition to the auxiliary machines, a cooling water pipe, wiring for supplying power to the auxiliary machines, and the like. 
         [0023]    Surfaces of the auxiliary machine case  130  are covered with noise vibration (NV) covers  141  and  142  (see  FIG. 1 ) to prevent vibration and noise produced by the auxiliary machines from being transmitted to the outside. In the present embodiment, each of the NV covers  141  and  142  has an outer layer formed of hard resin and an inner layer formed of urethane foam. 
         [0024]    In the present embodiment, the plurality of auxiliary machines are fixed to a manifold  120 . A side surface of the auxiliary machine case  130 , on the left side of the vehicle (a side of the negative Z axis direction), is covered by the manifold  120 . The manifold  120  forms a flow path for the hydrogen gas, the oxygen gas, and cooling water for cooling the fuel cell. The manifold  120  has a function of ensuring insulation from high voltage portions in the fuel cell case  100  and a function of compressing the cells in the fuel cell. The manifold  120  supports one surface of the fuel cell in the stacking direction. 
         [0025]    The frame  200  is disposed below the fuel cell system case  140 . The frame  200  supports the fuel cell system case  140  with bolts  112 A and  112 B inserted into bosses  111 A and  111 B formed on the fuel cell case  100  of the fuel cell system case  140 . An anti-vibration rubber piece is disposed between the fuel cell system case  140  and the frame  200  to reduce vibration. The frame  200  is fastened to a main body of a vehicle (not illustrated). 
         [0026]      FIG. 2  is an exploded perspective view of the fuel cell case  100 . The fuel cell case  100  includes a plurality a components. The fuel cell case  100  includes a stack case  105  and a lower cover  115 . The stack case  105  covers side surfaces, except for a side surface on the right side (a side on the positive Z axis direction) of the vehicle, and an upper surface of the fuel cell. The lower cover  115  covers a bottom surface of the fuel cell. The lower cover  115  includes a bottom surface of the fuel cell case  100 . The manifold  120  having a plate shape (see  FIG. 1 ) covers the side surface of the fuel cell on the right side (the side on the positive Z axis direction) of the vehicle. The lower cover  115  corresponds to a “first member”. The stack case  105  is fixed to an outer circumferential portion of the lower cover  115  with a fastener, and corresponds to a “second member”. The “outer circumferential portion” is a portion surrounding the fuel cell. In the present embodiment, a bolt  170  (described later) is used as the fastener. 
         [0027]    The fuel cell is formed by stacking the cells in the fuel cell, and thus needs to be compressed. In the fuel cell system  10 , the stack case  105  cooperates with the manifold  120  to compress the fuel cell in the stacking direction. The stack case  105 , the manifold  120 , and an unillustrated shaft hold the stacking load of the fuel cell. Thus, it is difficult to downsize the fuel cell case  100  with a lower rigidity of the stack case  105 . The manifold  120  corresponds to a “third member”. 
         [0028]    The gasket  107  seals between the stack case  105  and the lower cover  115 . The sealing is ensured by compressing the gasket  107  with predetermined force. The gasket  107  can prevent the foreign matters such as water and dust from entering the fuel cell case  100 . 
         [0029]      FIG. 3  is a diagram illustrating the lower cover  115 . As illustrated in  FIGS. 2 and 3 , the lower cover  115  includes a rib  117  protruding upward (in the positive Y axis direction). The rib  117  is positioned more on an inner circumference side than a portion where the lower cover  115  and the gasket come into contact with each other. Ribs  116  extending in the front and rear direction of the vehicle are provided. 
         [0030]      FIG. 4  is a diagram illustrating a conventional lower cover  215 . The conventional lower cover  215  is the same as the lower cover  115  according to the present embodiment except that the rib  117  is not provided. 
         [0031]      FIG. 5  is a drawing illustrating farce applied to the conventional lower cover  215 . A bolt is inserted in each hole  220 . A line  230  represents a portion to be in contact with the gasket  107  when the lower cover  215  is fixed to the stack case  105 . In  FIG. 5 , a region where larger force is applied to the lower cover  215  is illustrated to be darker than a region where smaller force is applied to the lower cover  215 . 
         [0032]    The lower cover  215  receives force F 1  in an upward direction of the vehicle (positive Y axis direction) from the bolts, and receives force F 2  in a downward direction of the vehicle (negative Y axis direction) from the gasket  107 . A position of the lower cover  215  where the force F 1  is received is different from a position where the lower cover  215  receives the force F 2 , and thus the lower cover  215  with a small thickness can deform. As a result, the force compressing the gasket  107  applied from the lower cover  215  is small at a region T 1  between the holes  220 , and thus the sealing performance of the gasket  107  is degraded. As a result of the deformation of the lower cover  215  in the downward direction of the vehicle (the negative Y axis direction) in the region T 1 , the lower cover  215  comes into close contact with the stack case  105  in a region T 2 . Thus, as illustrated in  FIG. 5 , the lower cover  215  receives force at the region T 2 . 
         [0033]      FIG. 6  is a diagram illustrating a method of solving the problem. As one method of preventing the lower cover  215  from deforming, the thickness of the lower cover  215  at a region T 3  may be increased. However, to increase the thickness at the region T 3 , the thickness of the lower cover  215  as a whole needs to be increased, and this requires a higher cost and leads to a larger volume. 
         [0034]    As another method of preventing the lower cover  215  from deforming, the number of bolts may be increased to achieve shorter distances among the bolts. However, this method requires an extra process of tightening the bolts, and thus leads to low productivity. 
         [0035]    Thus, in the present embodiment, the problem is solved by providing the rib  117  (se  FIG. 3 ) on the lower cover  115 . 
         [0036]      FIG. 7  is a cross-sectional view taken along the line A-A in  FIG. 1 . The gasket  107  seals between the lower cover  115  and the stack case  105 . The stack case  105  is fixed to the outer circumferential portion of the lower cover  115  with the bolts  170 . The rib  117  extending in the upper direction (positive Y axis direction) is arranged at a portion of the lower cover  115  more on the inner side than a portion to be in contact with the gasket  107 . 
         [0037]    The rib  117  is positioned more on the inner side than the portion of the lower cover  115  in contact with the gasket  107 , and is provided over the entire circumference. Thus, the fuel cell case  100  has increased rigidity so as not to be deformed by the reaction from the gasket  107 . 
         [0038]    The rib  117  protrudes upward (in the positive Y axis direction) beyond a surface where the lower cover  115  and the gasket  107  come into contact with each other. Thus, an increase in the site of the fuel cell case  100  in the upper and lower direction can be prevented compared with a configuration where the rib  117  extends in the lower direction (negative Y axis direction). 
         [0039]    When a groove portion in which the gasket  107  is disposed is provided on the lower cover  115 , the size of the fuel cell case  100  increases in the upper and lower direction because the groove portion protrudes downward (in the negative Y axis direction). In the present embodiment, the stack case  105  includes the groove portion  106  in which the gasket  107  is disposed. Thus, an increase in the size of the fuel cell case  100  in the upper and lower direction can be prevented. 
         [0040]      FIGS. 8A to 8C  are diagram schematically illustrating how external. force is absorbed by the rib  117 .  FIG. 8A  is a diagram illustrating a state where no external force in the horizontal direction is applied to the rib  117 .  FIG. 8B  is a diagram illustrating a state where external force in an expanding direction in the horizontal direction is applied to the rib  117 . Here, the external force in the expanding direction can be absorbed by the rib  117  expanding in the horizontal direction.  FIG. 8C  is a diagram illustrating a state where external force in a compressing direction in the horizontal direction is applied to the rib  117 . Here, the external force in the compressing direction can be absorbed by the rib  117  compressed in the horizontal direction. 
       B. Modification 
     B1. Modification 1 
       [0041]    In the present embodiment, the lower cover  115  includes a groove portion in which the gasket  107  is disposed. However, the present invention is not limited to this, and the lower cover  115  may not include the groove portion in which the gasket  107  is disposed. 
         [0042]    The present invention is not limited to the above-described embodiment and modifications, and can be implemented in various modes without departing from the spirit of the present invention. For example, the technical features of the embodiment and modifications corresponding to the technical features of each aspect described in the summary can be replaced or combined as appropriate so as to solve a part or the whole of the problem described above or achieve a part or the whole of the effects described above. Furthermore, technical features that are not described as being essential in the specification can be deleted as appropriate.