Abstract:
To enable a regulator for fuel cell systems having a first diaphragm on the back pressure chamber side and a second diaphragm on the pressure regulating chamber side, wherein the pressure in the pressure regulating chamber is regulated with the back pressure in the back pressure chamber, to regulate the pressure with a pressure differing from the pressure in the back pressure chamber, the pressure in the pressure regulating chamber is regulated by actuating the pressure regulating valve with the shifting of the two diaphragms depending on the relationship between the two pressures, wherein the effective area of the first diaphragm and the effective area of the second diaphragm are differentiated.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to a regulator for fuel cell systems, and more particularly to a regulator for regulating the pressure of fuel gas supplied to fuel cells in a fuel cell system comprising fuel cells which, supplied with fuel gas and oxidizer gas, generate electricity.  
         [0003]     2. Description of the Related Art  
         [0004]     Known regulators for use in fuel cell systems as mentioned above include one having a structure shown in  FIG. 3  (see for instance JP-A-2003-68334). This conventional regulator will be described below.  
         [0005]     In a body  101 , two pressure regulating diaphragms  102  and  103  are arranged opposite each other with a space  104  provided between them, a space above one pressure regulating diaphragm  102  is formed into a back pressure chamber  105 , and a space underneath the other pressure regulating diaphragm  103  is formed into a hydrogen gas passage  106  (pressure regulating chamber).  
         [0006]     The back pressure chamber  105  is provided with an air inlet  107 , and air pressurized by a compressor (not shown) is let into the back pressure chamber  105  through the air inlet  107 . The hydrogen gas passage  106  is provided in its intermediate part with a valve seat  108 , and a hydrogen gas passage  109  farther upstream than the valve seat  108  is supplied via a hydrogen gas inlet  110  with hydrogen gas discharged from a high pressure hydrogen tank (not shown). Further, a hydrogen gas passage  111  farther downstream from the valve seat  108  supplies hydrogen gas via a hydrogen gas outlet  112  to fuel cells (not shown).  
         [0007]     An effective area (pressure receiving area) in which the back pressure (air pressure) works on the diaphragm  102  and an effective area (pressure receiving area) in which hydrogen gas pressure works on the other diaphragm  103  are set to be equal. In other words, the two diaphragms  102  and  103  and formed to have equal diameters.  
         [0008]     Further, the two diaphragms  102  and  103  are linked by a stem  113  to be interlocked, and the tip of the stem  113  protruding into the hydrogen gas passage  109  is provided with a valve body  114  which alternately comes into or goes out of contact with the valve seat  108 . In the drawing, reference numeral  115  denotes a spring.  
         [0009]     In the structure described above, a first thrust attributable to the increased air pressure and the pressure of the spring work on the top face of the pressure regulating diaphragm  102 , while a second thrust attributable to the increased pressure of hydrogen gas works on the under face of the other pressure regulating diaphragm  103 , and the differential pressure of these two thrusts brings the valve body  114  into or out of contact with the valve seat  108 . Thus, when the pressure in the hydrogen gas passage  106  becomes lower than the air pressure supplied into the back pressure chamber  105 , the valve body  114  opens, and when the pressure in the hydrogen gas passage  106  becomes equal to the air pressure supplied into the back pressure chamber  105 , the valve body  114  closes, to control the pressure within the hydrogen gas passage  106  to a prescribed level.  
         [0010]     Then, as the effective areas of the two diaphragms  102  and  103  are set to be equal, the pressure of hydrogen gas in the hydrogen gas passage  106  is controlled equally to the pressure of air supplied to the back pressure chamber  105 . Thus, the regulated pressure of hydrogen gas becomes equal to the air pressure as indicated by characteristic B in  FIG. 4 .  
         [0011]     Incidentally, when high pressure hydrogen gas is to be supplied, after being regulated in pressure by a regulator such as the one described above, to fuel cells in a fuel cell system via piping, some item which could entail pressure loss, such as a shut-off valve, may be arranged on the piping between the regulator and the fuel cells. In such a case, to allow for that pressure loss, the pressure to which the hydrogen gas is to be regulated in the regulator part should be set higher than otherwise.  
         [0012]     However, when the air pressure to be applied to the back pressure chamber  105  in the conventional structure described above can be supplied at only a limited low level under the constraint of the capacity of the compressor to generate this air pressure or for any other reason, the pressure of the hydrogen gas can be regulated only to an equal level to the air pressure. Therefore, it is impossible to supply the hydrogen gas regulated to a higher pressure than the air pressure to allow for the possible pressure loss and accordingly to secure the hydrogen gas pressure required by the fuel cells, involving the risk of inviting a performance deterioration of the fuel cells.  
         [0013]     Or, where the space  104  defined by the diaphragms  102  and  103  as described above is made a sealed space, the air in the space  104 , affected by an ambient condition such as the ambient temperature, repeats alternate thermal expansion and thermal contraction. This would affect the load transmitted between the back pressure chamber  105  and the hydrogen gas passage (pressure regulating chamber)  106 , making it impossible to secure stabilized pressure regulation.  
         [0014]     Furthermore, in the event that the diaphragms  102  and  103  are damaged, if the space  104  is in a sealed state, hydrogen and pressurized air may be combined in the regulator to invite a reaction of combustion.  
       BRIEF SUMMARY OF THE INVENTION  
       [0015]     The present invention is intended to solve the problems noted above, and to provide a regulator for fuel cell systems which can be smaller and less expensive than a regulator of any conventional structure.  
         [0016]     In order to solve the problems noted above, according to a first aspect of the invention, there is provided a regulator for fuel cell systems having a first diaphragm on which a pressure from a back pressure chamber side works and a second diaphragm on which a pressure from a pressure regulating chamber side works, wherein a pressure regulating valve is actuated by the shifting of the two diaphragms depending on the relationship between the two pressures, and the effective area of the first diaphragm and the effective area of the second diaphragm are differentiated.  
         [0017]     In the first aspect of the invention described above, the effective area of the second diaphragm can be set smaller than the effective area of the first diaphragm.  
         [0018]     In the first aspect of the invention, the effective area of the first diaphragm can as well be set smaller than the effective area of the second diaphragm.  
         [0019]     Further in the foregoing, pressurized air can be supplied to the back pressure chamber and pressurized hydrogen gas, to the pressure regulating chamber via the pressure regulating valve.  
         [0020]     Further in the foregoing, an atmosphere chamber can be disposed between the first diaphragm and second diaphragm, and the atmosphere chamber can be open to the atmosphere.  
         [0021]     Further in the foregoing, a hydrogen gas detector may be disposed on the flow path of atmosphere from the atmosphere chamber.  
         [0022]     According to a second aspect of the invention, there is provided a regulator for fuel cell systems having a back pressure chamber to which pressurized air is supplied, a first diaphragm which receives a pressure from the back pressure chamber, a passage for supplying pressurized hydrogen gas to a pressure regulating chamber, a pressure regulating valve disposed on the passage, a second diaphragm which receives a pressure from the pressure regulating chamber, an atmosphere chamber disposed between the second diaphragm and the first diaphragm, and a coupling shaft which couples the two diaphragms and connects them to the pressure regulating valve, wherein the effective area of the second diaphragm is set smaller than the effective area of the first diaphragm, and pressure regulation is accomplished by opening and closing the pressure regulating valve at a higher pressure than the air pressure of the back pressure chamber.  
         [0023]     In the second aspect of the invention described above, the configuration may as well be such that the pressure regulating valve, in which a valve part is formed on the upper side and a shaft part is formed on the lower side, is disposed to be liftable in a hollow housing having a bottom; a fixed seat having a passage is arranged above the valve part; a spring to press the pressure regulating valve toward the sheet and one O ring to provide sealing between the shaft part of the pressure regulating valve and the housing intervene in the housing; the housing is screwed into a housing accommodation chamber formed in the body of the regulator; and two O rings, positioned upward and downward, intervene between the housing and the body.  
         [0024]     According to a third aspect of the invention, there is provided a regulator for fuel cell systems wherein a back pressure chamber and a pressure regulating chamber are partitioned from each other by a diaphragm and a pressure regulating valve is actuated by the shifting of the diaphragm to regulate the pressure in the pressure regulating chamber,  
         [0025]     further comprising a valve mechanism,  
         [0026]     wherein the valve mechanism is provided with a housing accommodation chamber, whose lower end is open, formed in the body of the regulator; a hollow housing having a bottom screwed into the housing accommodation chamber; two O rings, positioned upward and downward, intervening between the housing and the body; a pressure regulating valve liftably accommodated in the housing and one O ring intervening between the pressure regulating valve and the housing; a spring pressing the pressure regulating valve upward; and a fixed seat having a passage arranged above the pressure regulating valve.  
         [0027]     With the structure according to the first aspect of the invention, by setting the effective area ratio between the two diaphragms as desired, the pressure regulated by the pressure regulating valve can be readily set to a desired level differing from the pressure working on the back pressure chamber. And, by setting the effective area of the second diaphragm smaller than the effective area of the first diaphragm, pressure regulation can be accomplished at a higher level than the pressure on the back pressure chamber side. Or, by setting the effective area of the first diaphragm smaller than the effective area of the second diaphragm, pressure regulation can be accomplished at a lower level than the pressure on the back pressure chamber side.  
         [0028]     Therefore, in a fuel cell system, by setting the effective area of the second diaphragm smaller than the effective area of the first diaphragm, even if there is a constraint that, though hydrogen gas to be supplied to the fuel cells has to be regulated to a high pressure, the air available for this pressure regulation can be supplied only at a limited low pressure below the pressure to be regulated, the hydrogen gas can still be regulated to the high pressure with this available low pressure.  
         [0029]     Also in the foregoing, by supplying pressurized air to the back pressure chamber and pressurized hydrogen gas to the pressure regulating chamber via the pressure regulating valve, hydrogen gas can be regulated as described above.  
         [0030]     Further as described above, since setting one effective area smaller enables the pertinent diaphragm to be formed in a smaller diameter, this can contribute to reducing the size of the regulator and its cost.  
         [0031]     Also in the foregoing, where the pressure of hydrogen gas is regulated in a configuration in which the atmosphere chamber is disposed between the first and second diaphragms and the atmosphere chamber is open to the atmosphere, even if the diaphragms are broken and hydrogen gas leaks into the atmosphere chamber, that hydrogen gas is discharged into the atmosphere to ensure safety.  
         [0032]     Further in the foregoing, by disposing a hydrogen gas detector on the flow path from the atmosphere chamber to the atmosphere, that hydrogen gas leakage can be detected as mentioned above to ensure safety.  
         [0033]     The second aspect of the invention can provide the same advantages as those described above.  
         [0034]     In the second aspect, further, the pressure regulating valve, in which the valve part is formed on the upper side and the shaft part is formed on the lower side, is disposed to be liftable in the hollow housing having a bottom; the fixed seat having a passage is arranged above the valve part; the spring to press the pressure regulating valve toward the sheet and the single O ring to provide sealing between the shaft part of the pressure regulating valve and the housing intervene in the housing; the housing is screwed into the housing accommodation chamber formed in the body of the regulator; and the two O rings, positioned upward and downward, intervene between the housing and the body. This configuration can contribute to reducing the size and cost of the valve mechanism having the pressure regulating chamber for pressure regulation as stated above, and coupled with the aforementioned size reduction of the diaphragms, makes it possible to reduce the overall size of the regulator and its cost.  
         [0035]     Further according to the third aspect of the invention, even a regulator lacking the configuration described above is enabled to solve the problems of size and cost reduction, similarly to the above-described aspects of the invention, by serving to reduce the size and cost of the valve mechanism.  
         [0036]     Other objects, features and advantages of the present invention will become more apparent from the detailed description of the preferred embodiment thereof when taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]      FIG. 1  shows a vertical sectional view of a preferred embodiment according to the invention.  
         [0038]      FIG. 2  shows an enlarged vertical sectional view of the valve mechanism part in  FIG. 1 .  
         [0039]      FIG. 3  shows a schematic vertical sectional view of a conventional regulator.  
         [0040]      FIG. 4  is a characteristic diagram showing the relationship between the pressure applied to the back pressure chamber and the regulated pressure in the regulator according to the invention and the conventional regulator.  
         [0041]      FIG. 5  shows a partial sectional view of the valve mechanism in the conventional regulator. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0042]      FIG. 1  shows a vertical sectional view of a regulator for fuel cell systems, which is a preferred embodiment of the invention.  
         [0043]     Referring to  FIG. 1 , a regulator  1  has a lower body  2 , an upper body  3  and a cover  4 , and they are integrally linked with a bolt  5  and other elements.  
         [0044]     Between the upper body  3  and the cover  4  arranged over this upper body  3 , there is arranged a first diaphragm  6 , which is the back pressure chamber side diaphragm, and the circumferential edge of the first diaphragm  6  is held between the upper body  3  and the cover  4 .  
         [0045]     Between the upper body  3  and the lower body  2  arranged underneath this upper body  3 , there is arranged a second diaphragm  7 , which is the pressure regulating chamber side diaphragm, and the circumferential edge of the second diaphragm  7  is held between the upper body  3  and the lower body  2 . Therefore, the two diaphragms  6  and  7  constitute a double structure in which they face each other. Further, the diameter of the second diaphragm  7  is set smaller than that of the first diaphragm  6 .  
         [0046]     The central part of the first diaphragm  6  is held between a first plate  8  and a second plate  9 ; the central part of the second diaphragm  7  is held between the second plate  9  and a holder  10 ; and further the first plate  8  and the second plate  9  are held by a coupling shaft  11  formed integrally with the holder  10  and a nut  12 .  
         [0047]     A back pressure chamber  13  opening to the upper face of the first diaphragm  6  is disposed within the cover  4 , while a pressure regulating chamber  14  opening to the under face of the second diaphragm  7  is provided within the lower body  2 . Further the diameter of the back pressure chamber  13 , i.e. the opening diameter R 1  to the first diaphragm  6  and the diameter of the pressure regulating chamber  14 , i.e. the opening diameter R 2  to the second diaphragm  7  are set to be R 1 &gt;R 2 , and the diameter of the back pressure chamber  13  is set to be equal to or greater than the diameter of the pressure regulating chamber  14 .  
         [0048]     An atmosphere chamber  15  is disposed in the central part of the upper body  3 , penetrating it vertically. The atmosphere chamber  15  is formed by making the diameter of its upper compartment  15   a  opening to the first diaphragm  6  equal to the diameter of the back pressure chamber  13  and making the diameter of its lower compartment  15   b  opening to the second diaphragm  7  equal to the diameter of the pressure regulating chamber  14 .  
         [0049]     The setting of the diameter of the second diaphragm  7  to be smaller than the diameter of the first diaphragm  6  and the diameters of the pressure regulating chamber  14  and of the lower compartment  15   b  to be smaller than the diameters of the back pressure chamber  13  and of the upper compartment  15   a  makes the effective area (pressure receiving area) of the second diaphragm  7  smaller than the effective area (pressure receiving area) of the first diaphragm  6 .  
         [0050]     A spring chamber  16  is formed within the cover  4 , and the spring chamber  16  communicates with the back pressure chamber  13 . The spring chamber  16  is provided with a pressure regulating spring  17  to press the two diaphragms  6  and  7  downward, i.e. toward the pressure regulating chamber  14  with a prescribed load. The pressure of the pressure regulating spring  17  can be regulated with a regulating screw  18 .  
         [0051]     Further, a back pressure chamber inlet  19  for letting in pressurized air is disposed in the cover  4 . The pressurized air let in through the back pressure chamber inlet  19  is guided to the back pressure chamber  13  via the spring chamber  16  and works on the upper face of the first diaphragm  6 . The outer end side of the back pressure chamber inlet  19  is connected to piping from the generating source of the pressurized air, such as a compressor (not shown).  
         [0052]     The lower body  2  is provided with a pressure regulating chamber inlet  20 , and the outer end side of the pressure regulating chamber inlet  20  is connected to piping from a hydrogen tank (not shown). The pressure regulating chamber inlet  20  is equipped with a filter  21 , whose downstream side (inner side) communicates with the pressure regulating chamber  14  via a passage  20   a  and a valve mechanism  22 .  
         [0053]     The lower body  2  is also provided with a pressure regulating chamber outlet  23 , and the inner end side of the pressure regulating chamber outlet  23  communicates with the pressure regulating chamber  14  while its outer end side (not shown) is connected to piping on the anode side of the fuel cells.  
         [0054]     The upper body  3  is provided with an atmosphere port  24 , which communicates with the atmosphere chamber  15 . The outer end side of the atmosphere port  24  is open to the atmosphere. To the atmosphere port  24  is connected a hydrogen gas detector  25  for detecting any hydrogen gas via a tube or the like, so that any hydrogen gas having leaked into the atmosphere chamber  15  in the event that the second diaphragm  7  is damaged can be discharged into the atmosphere through the atmosphere port  24  and the hydrogen gas passing that atmosphere port  24  can be detected by the hydrogen gas detector  25 .  
         [0055]     Next will be described the valve mechanism  22  mentioned earlier.  
         [0056]     Underneath the pressure regulating chamber  14  in the lower body  2 , there is formed a cylindrical housing accommodation chamber  26  whose lower end is open, and a hollow housing  27  having a bottom is inserted into the housing accommodation chamber  26  from that lower end and fastened with a screw  28 . This constitution of the housing  27  having a bottom eliminates the need to block the lower end opening of the housing accommodation chamber  26  with another plug separate from the housing  27 . Between the outer circumferential face of the housing  27  inserted as described above and the lower body  2 , there intervenes a first O ring  29  consisting of an elastic material, positioned underneath the housing  27  in the axial direction, and also intervenes a second O ring  30  consisting of an elastic material, positioned substantially in the central part of the housing  27  in the axial direction.  
         [0057]     The housing  27  is formed hollow and open on the upper side, and this hollow part constitutes a valve accommodation chamber  31 , which is provided with a metallic pressure regulating valve  32  to be liftable. The pressure regulating valve  32  has a valve part  32   a  on the upper side and a shaft part  32   b  on the lower side. Between the lower portion of that shaft part  32   b  and the housing  27 , there intervenes a third O ring  33  consisting of an elastic material, and a plate  34  intervenes between the shaft part  32   b  in the upper portion of the third O ring  33  and the housing  27 . Further, between the under face of the third O ring  33  and the bottom face of the valve accommodation chamber  31 , a first ring  35  and a second ring  36  intervene in a lapped state between the shaft part  32   b  and the housing  27 .  
         [0058]     The plate  34  is engaged with a stepped part formed in the housing  27  and its downward motion is thereby obstructed. A spring  37  is compressed by and intervenes between the plate  34  and the valve part  32   a  of the pressure regulating valve  32 , and a prescribed pressing force (load) of the spring  37  presses the pressure regulating valve  32  upward.  
         [0059]     Above the pressure regulating valve  32  in the lower body  2 , there is fixed a metallic seat  38 , and the up and down motion of the pressure regulating valve  32  causes its valve part  32   a  to come into and out of contact with the lower face of the seat  38 . Incidentally, a sealing member  39  made of an elastic material protrudes from the upper face of the valve part  32   a , and contributes to sealing performance between the pressure regulating valve  32  and the seat  38  even if they are metallic and increased in strength. Additionally, a fourth O ring  40  intervenes between the seat  38  and the lower body  2 .  
         [0060]     The seat  38  is formed in an annular shape, and has a passage  41  in its central part. In a part of the lower body  2  corresponding to the passage  41  is formed a passage  42 , which establishes communication between the passage  41  and the pressure regulating chamber  14 .  
         [0061]     A rod  32   c  integrally protrudes from the upper face of the valve part  32   a  of the pressure regulating valve  32 . As the rod  32   c  penetrates both passages  41  and  42 , the rod  32   c  and the coupling shaft  11  are caused to move interlocked with each other by having its upper end come into contact or become coupled with the lower face of the coupling shaft  11 .  
         [0062]     Next will be described the operations which take place in the embodiment described above.  
         [0063]     When pressurized air from a compressor or the like (not shown) is let into the back pressure chamber  13  through the back pressure chamber inlet  19 , the downward pressing load working on the first diaphragm  6  is the product of the air pressure P 1  applied to the first diaphragm  6  and the effective area (pressure receiving area) W 1  of the first diaphragm  6 , i.e. P 1 ×W 1 .  
         [0064]     The upward pressing load working on the second diaphragm  7  in a state in which the valve part  32   a  is opened and hydrogen gas supplied from the hydrogen tank flows from the pressure regulating chamber inlet  20  in the passage  41  and is let into the pressure regulating chamber  14  is the product of the air pressure P 2  applied to the second diaphragm  7  and the effective area (pressure receiving area) W 2  of the second diaphragm  7 , i.e. P 2 ×W 2 .  
         [0065]     Therefore, the load at which the two diaphragms  6  and  7  become balanced is P 1 ×W 1 =P 2 ×W 2 .  
         [0066]     In this embodiment of the invention, as the effective area (pressure receiving area) W 1  of the second diaphragm  7  is set smaller than the effective area (pressure receiving area) W 2  of the first diaphragm  6 , when the two diaphragms  6  and  7  become balanced, the hydrogen gas pressure in the pressure regulating chamber  14  is greater than the air pressure in the back pressure chamber  13 .  
         [0067]     Thus, where the ratio between the effective area of the second diaphragm  7  on the pressure regulating chamber  14  side and the effective area of the first diaphragm  6  on the back pressure chamber side is 1:n, the regulating pressure that is obtained is n times the pressure applied to the back pressure chamber as indicated by characteristic A in  FIG. 4 .  
         [0068]     If, for instance, the effective area (pressure receiving area) of the first diaphragm  6  is set to 4 mm 2 , the effective area (pressure receiving area) of the second diaphragm  7  is set to 1 mm 2 , and an air pressure of 50 kPa is let into the back pressure chamber  13 , an equilibrium will be attained when the hydrogen gas pressure in the pressure regulating chamber  14  is 200 kPa.  
         [0069]     Therefore, when the hydrogen gas pressure in the pressure regulating chamber  14  drops below 200 kPa, the two diaphragms  6  and  7  come down to cause the coupling shaft  11  to move the valve part  32   a  away from the seat  38 , and high pressure hydrogen gas to be supplied to the pressure regulating chamber  14  through the pressure regulating chamber inlet  20  to raise the hydrogen gas pressure in the pressure regulating chamber  14 . Further, when the hydrogen gas pressure in the pressure regulating chamber  14  rises in this way, the two diaphragms  6  and  7  move upward and, along with that, the valve part  32   a  also moves upward. When the hydrogen gas pressure in the pressure regulating chamber  14  reaches 200 kPa, the valve part  32   a  comes into contact with the seat  38  and is closed. This pressure regulating operation serves to keep the hydrogen gas pressure in the pressure regulating chamber  14  at 200 kPa, and the secondary pressure of hydrogen gas supplied from the pressure regulating chamber outlet  23  to the fuel cells is maintained at 200 kPa.  
         [0070]     Incidentally, the aforementioned values of the effective areas of the two diaphragms  6  and  7 , air pressures and hydrogen gas pressures are mere examples for the convenience of explanation, but their values are not limited to these and can be set as desired. Therefore, the effective area ratio between the first diaphragm  6  and the second diaphragm  7  can be set as desired, and the hydrogen pressures can be set as desired correspondingly to this effective area ratio.  
         [0071]     The operations so far described make it possible in a fuel cell system, even if air pressure supplied into the back pressure chamber  13  is rather low, limited by the performance of the compressor generating this air pressure or any other factor, to regulate the pressure of hydrogen gas in the pressure regulating chamber  14  with that low air pressure in a higher pressure range than the air pressure and to supply that hydrogen gas of the higher pressure to the fuel cells. For instance, where any item that would entail a pressure loss is to be arranged on the hydrogen gas piping to the fuel cells as mentioned earlier, hydrogen gas of a higher pressure with an allowance for this pressure loss can be supplied.  
         [0072]     The opening of the atmosphere chamber  15  between the two diaphragms  6  and  7  to the atmosphere through the atmosphere port  24  as in the above-described embodiment of the invention can prevent the destabilization of pressure regulation, which would result from thermal expansion and thermal contraction in a sealed air chamber as in the conventional structure described above. Thus, it is made possible to stabilize the loads mutually transmitted between the back pressure chamber  13  and the pressure regulating chamber  14 .  
         [0073]     Or, even if the two diaphragms  6  and  7  are broken and hydrogen and pressurized air leak into the atmosphere chamber  15 , that hydrogen is discharged through the atmosphere port  24 , and it is therefore made possible to prevent the hydrogen and pressurized air from combining with each other in the atmosphere chamber  15  and thereby inviting combustion reaction.  
         [0074]     Also, by providing the hydrogen gas detector  25  to detect hydrogen flowing out of the atmosphere port  24 , it is made possible to detect any hydrogen leak as in the aforementioned case, to establish a fail-safe function and, where the regulator is applied to a wheeled vehicle, to ensure its safety.  
         [0075]     Further, the smaller diameter of the second diaphragm  7  on the pressure regulating chamber side than the diameter of the first diaphragm  6  on the back pressure chamber side as in this embodiment of the invention can contribute to reducing the size of this second diaphragm  7  and the space occupied by the pressure regulating chamber  14 , making it possible to reduce the overall size of the regulator  1  and its cost.  
         [0076]     Also, when hydrogen is to be supplied from the hydrogen tank to the fuel cells in a fuel cell system, the extremely high pressure of hydrogen in the hydrogen tank can be reduced at multiple stages including primary reduction and secondary reduction, and yet the hydrogen can be supplied at a prescribed high pressure to the fuel cells.  
         [0077]     In this way, where the above-described regulator  1  according to the invention is used on piping for high pressure hydrogen gas reduced in pressure to a prescribed level, the pressure of the hydrogen supplied through the pressure regulating chamber inlet  20  is appropriately high, though made lower than the extremely high pressure of hydrogen in the hydrogen tank. Therefore, the air-tightness requirement of the valve mechanism  22  can be less strict than that of the regulator for primary pressure reduction arranged immediately downstream of the hydrogen tank.  
         [0078]     In this connection, the embodiment of the invention is intended to reduce the number of components required and the size of the valve mechanism compared with the valve mechanism shown in  FIG. 5 , generally used for regulating very high gas pressures, and to reduce the overall size of the regulator and its cost besides taking advantage of the reduced size of the diaphragm  7  and the pressure regulating chamber  14  mentioned above.  
         [0079]     Thus, the conventional configuration shown in  FIG. 5  comprises a seat  202  disposed on a body  201 , a housing  203  snapped onto the body  201 , two O rings  204  and  205  and two O rings  206  and  207  intervening between the body  201  and the housing  203 , a valve part  208  which is disposed in the housing  203  and comes into and out of contact with the seat  202 , two O rings  210  and  211  and four rings  212  through  215  intervening between the shaft part  209  of the valve part  208  and the housing  203 , a plate  216 , a spring  217  pressing the valve part  208 , two plugs  218  and  219  disposed in the lower part of the housing  203 , an O ring  220  disposed on the seat  202 , and an O ring  221  disposed on the plug  219 .  
         [0080]     As the valve mechanism  22  in the embodiment of the present invention is configured as earlier described unlike this conventional one, the four  0  rings  206 ,  207 ,  212  and  215  and the two O rings  211  and  221  in the conventional configuration shown in  FIG. 5  are eliminated, and the housing  203  and the two plugs  218  and  219  are integrated to dispense with the two other plugs  218  and  219 .  
         [0081]     In this way, the embodiment of the invention is intended to be smaller in size and lower in cost than the conventional structure.  
         [0082]     To add, this embodiment is a case in which the effective area of the second diaphragm  7  on the pressure regulating chamber  14  side is set smaller than the effective area of the first diaphragm  6  on the back pressure chamber  13  side and, even if the pressure from the back pressure source is rather low, the hydrogen gas pressure is regulated to an amplified level, higher than that back pressure. It is also possible, where the pressure from the back pressure source is high and the required regulated level of hydrogen gas is lower than that pressure from the back pressure source, to meet that requirement by setting the effective area (pressure receiving area) of the first diaphragm  6  on the back pressure chamber side than the effective area (pressure receiving area) of the second diaphragm  7  on the pressure regulating chamber side.  
         [0083]     Thus, for instance, where the air pressure of the back pressure source is 200 kPa and the required regulated level of hydrogen gas is 50 kPa, the effective area of the first diaphragm  6  on the back pressure chamber can be set to 1 mm 2  and the effective area of the second diaphragm  7  on the pressure regulating chamber side to 4 mm 2 .  
         [0084]     Also, though the gas whose pressure is to be regulated is supposed to be hydrogen gas in the above-described embodiment, where the regulator is to be applied to fuel cells using some other fuel gas than hydrogen gas, that other fuel gas can be supplied to the pressure regulating chamber and regulated in pressure.  
         [0085]     Furthermore, the regulator according to the invention can be applied as effectively as to an automotive fuel cell system for mounting on a motor vehicle as to a non-automotive fuel cell system.