Abstract:
An object of the present invention is to provide a high-pressure tank configured so as to suppress accumulation of gas in a space between a valve and a mouthpiece while achieving low cost. To this end, the high-pressure tank according to the present invention includes the mouthpiece and the valve installed on the mouthpiece, and is formed with: a communicating hole that communicatively connects spaces which are formed between the mouthpiece and the valve, and in the valve, respectively, and in which gas having permeated from the tank side may potentially accumulate; and a gas venting hole that connects either of the spaces to the outside of the tank. The communicating hole is preferably provided closer to a center of the tank than to a screw portion of the valve. In addition, preferably a gas venting hole is formed so as to extend from the space formed between the mouthpiece and the valve in a direction that intersects a contact surface between the mouthpiece and the valve.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to a high-pressure tank. More specifically, the present invention relates to an improvement of a structure around a valve in a high-pressure tank filled with hydrogen gas or the like. 
         [0002]    A high-pressure tank configured such that a valve assembly (a component including a built-in high pressure valve or the like) is mounted to a mouthpiece provided in an opening of a high-pressure tank main body is used as a high-pressure tank for storing gases such as hydrogen. In addition, for mounting the valve assembly to the mouthpiece, a simple screw structure is widely used in which a male screw portion of the valve assembly is screwed into a female screw portion of the mouthpiece. 
         [0003]    Conventionally, as such a high-pressure tank, for example, Patent Document 1 discloses a high-pressure container comprising a mouthpiece and an atmospheric pressure valve, the high-pressure container further including a ventilation hole having one end thereof opened on a surface of a flange portion facing a liner (a surface facing a liner constituting a tank casing among surfaces of the flange portion) of the mouthpiece. 
         [0004]    Patent Document 1: Japanese Patent Application Laid-Open No. 11-082887 
         [0005]    However, the high-pressure tank having the structure described above is incapable of discharging gas accumulated in gaps such as a gap between the mouthpiece and a seal plug (welch plug) to the outside. On the other hand, while a high-pressure tank configured such that gas accumulating in gaps in the tank can be discharged to the outside of the tank has been proposed, such a high-pressure tank may require considerable cost. 
       SUMMARY OF THE INVENTION 
       [0006]    In consideration thereof, it is an object of the present invention to provide a high-pressure tank configured so as to suppress accumulation of gas in a space between a valve and a mouthpiece or the like while achieving low cost. 
         [0007]    In order to solve the problems described above, the present inventor has performed various evaluations. Rubber seals are widely used at ends on a tank main body-side of a valve to prevent high-pressure gas inside a high-pressure tank from leaking to the outside. In addition, a vent hole of the gas (gas venting hole) is processed to prevent gas having permeated a rubber seal from accumulating inside a device. Furthermore, in this case, in order to avoid penetration (back penetration) of water from the outside of the gas venting hole into the tank, a seal or the like made of a waterproof and moisture-permeable material (for example, GORE-TEX®) having both waterproofing and aeration properties is provided at the gas venting hole. However, such an arrangement requires cost for processing the rubber seal, the gas venting hole, and the like. Furthermore, if pluralities of the gas venting holes and the GORE-TEX® seals are to be incorporated, processing cost and the trouble of assembly increase in proportion. Focusing on such points, through extensive evaluations on a structure capable of suppressing accumulation of gas while achieving low cost, the present inventor has made findings leading to a solution of the problems discussed above. 
         [0008]    The high-pressure tank according to the present invention is based on these findings and includes a mouthpiece and a valve installed on the mouthpiece, wherein the high-pressure tank is formed with: a communicating hole that communicatively connects spaces which are formed between the mouthpiece and the valve, and in the valve, respectively, and in which gas having permeated from the tank side may potentially accumulate; and a gas venting hole that connects either of the spaces to the outside of the tank. 
         [0009]    With a structure where spaces in which gas having permeated from the tank side may potentially accumulate (for example, a gas accumulation space formed between the mouthpiece and the valve or a gas accumulation space formed in a vicinity of a center of the valve) are mutually independent, members including a gas venting hole for venting gas from such a space and a GORE-TEX® seal provided at an outlet of the gas venting hole are required for each of the spaces. Conversely, with a high-pressure tank configured such that spaces are communicatively connected (bypassed) to each other, since gas accumulating in one space can be discharged from another space to the outside of the tank via the communicating hole, providing at least one gas venting hole and one GORE-TEX® seal becomes sufficient for the plurality of communicatively-connected spaces. Therefore, a part of the gas venting hole and GORE-TEX® seal which had conventionally been required for each of the spaces can now be omitted. 
         [0010]    In such a high-pressure tank, preferably a gas venting hole is formed so as to extend from the space formed between the mouthpiece and the valve in a direction that intersects a contact surface between the mouthpiece and the valve. In this case, plane contact enables the sealed contact surface between the mouthpiece and the valve to remain unharmed and the gas accumulating in the space to be discharged by the gas venting hole. 
         [0011]    The communicating hole described above is formed, for example, for communicatively connecting the space formed in the valve in order to house wiring with the space formed between the mouthpiece and the valve. In this case, gas accumulating in a space at which a gas venting hole is not formed is discharged via the communicating hole from another space to the outside of the tank. 
         [0012]    In addition, preferably the communicating hole is provided closer to a center of the tank than to a screw portion of the valve. Providing the communicating hole while avoiding the screw portion makes processing of the communicating hole easier than a case where the communicating hole is provided at the screw portion. 
         [0013]    Furthermore, preferably the communicating hole communicatively connects at least two spaces among three or more spaces in which gas having permeated from the tank side may potentially accumulate. When there are three or more spaces, by communicatively connecting two spaces thereof or, more preferably all of the spaces by the communicating hole, a greater part of the gas venting hole and the GORE-TEX® seal which had previously been required for each of the spaces can now be omitted. 
         [0014]    Moreover, preferably the communicating hole linearly extends in a radial direction of the valve. In this case, a length of the communicating hole can be minimized. 
         [0015]    Furthermore, a waterproof and moisture-permeable material having both waterproofing and aeration properties is provided at an opening of the gas venting hole to the outside of the tank. 
         [0016]    According to the present invention, a structure capable of suppressing accumulation of gas in a space between a valve and a mouthpiece or the like while achieving low cost can be provided. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a cross-sectional view of a high-pressure tank according to an embodiment of the present invention; and 
           [0018]      FIG. 2  is a cross-sectional view showing features of the high-pressure tank. 
       
    
    
       [0000]    
       
           1  high-pressure tank 
           11  mouthpiece 
           50  valve assembly (valve) 
           51  communicating hole 
           52  gas venting hole 
           52   a  opening 
           53  screw portion 
           64  wiring 
           66  GORE-TEX® seal (waterproof and moisture-permeable material) 
           70  tubular space (a space in which gas having permeated from a tank side may potentially accumulate) 
           80  wiring space (a space in which gas having permeated from a tank side may potentially accumulate) 
       
     
       DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    Hereinafter, a configuration of the present invention will be described in detail with reference to examples of embodiments shown in the drawings. 
         [0031]      FIGS. 1 and 2  show embodiments of a high-pressure tank  1  according to the present invention. The high-pressure tank  1  is suitable as, for example, a tank for supplying fuel gas in a fuel-cell car. Hereinafter, a case will be described in which the high-pressure tank  1  according to the present invention is applied to a high-pressure hydrogen tank used as a fuel supply source in a fuel cell system (refer to  FIG. 1  and the like). 
         [0032]    Although particularly not shown, for example, three high-pressure tanks  1  are used mounted on a rear part of a fuel-cell vehicle. The high-pressure tank  1  constitutes a part of the fuel cell system and supplies fuel gas to a fuel cell through a fuel gas piping system. For example, while hydrogen gas is the fuel gas filled in the high-pressure tank  1 , the high-pressure tank  1  may alternatively be filled with a combustible high-pressure gas such as compressed natural gas. The high-pressure tank  1  according to the present embodiment is configured so that hydrogen gas can be filled at a pressure of, for example, 35 MPa. Although not particularly shown, when a main stop valve of the high-pressure tank  1  is opened, hydrogen gas flows into a supply channel. Subsequently, flow rate and pressure of the hydrogen gas are regulated by an injector. The pressure of the hydrogen gas is eventually reduced further downstream to around 200 kPa or the like by a pressure reducing valve such as a mechanical regulator, and then supplied to the fuel cell. 
         [0033]      FIG. 1  shows a schematic configuration of the high-pressure tank  1 . The high-pressure tank  1  comprises a cylindrical tank main body  10  whose both ends have, for example, an approximately hemispherical shape, and mouthpiece portions  11  and  18  respectively mounted to longitudinal ends of the tank main body  10 . For example, the tank main body  10  has a two-layer structure wall layer comprising a resin liner  20  that is an inner wall layer and a CFRP layer  21  that is a plastic fiber layer (reinforcement layer) constituting an outer wall layer outside of the resin liner  20 . The resin liner  20  that is formed in approximately the same shape as the tank main body  10  is formed of, for example, a hard resin such as polyethylene resin or polypropylene resin. In the present embodiment, the cylindrical resin liner  20  whose both ends have an approximately hemispherical shape is obtained by molding, in advance, two types of split resin liners having shapes created if the resin liner  20  is split approximately at a center of an axial direction of the tank, and subsequently welding the split parts. 
         [0034]    A valve assembly  50  controls supply and discharge of fuel gas between an outside gas supply line (supply channel  22 ) and the inside of the high-pressure tank  1 . Seal members  60  and  61  are interposed between an outer circumferential surface of the valve assembly  50  and an inner circumferential surface of the mouthpiece portion  11 . 
         [0035]    A folded portion  30  bent inward is formed on a distal end side of the resin liner  20  where the mouthpiece  11  is provided (refer to  FIG. 2 ). The folded portion  30  is folded toward the inside of the high-pressure tank main body  10  so as to separate from the outer CFRP layer  21 . For example, the folded portion  30  comprises a diameter-reduced portion  30   a  whose diameter gradually decreases the closer to a distal end of the fold, and a cylindrical portion  30   b  which is connected to a distal end of the diameter-reduced portion  30   a  and whose diameter is constant. The cylindrical portion  30   b  forms an opening of the resin liner  20 . 
         [0036]    The mouthpiece  11  has an approximately cylindrical shape and is fitted into the opening of the resin liner  20 . For example, the mouthpiece  11  is made of aluminum or an aluminum alloy and manufactured into a predetermined shape by die casting or the like, and is mounted to the resin liner  20  by insert molding. A female screw portion  42  for screwing and connecting the valve assembly  50  is formed on an inner circumferential surface of the mouthpiece  11 . 
         [0037]    The valve assembly  50  controls supply and discharge of fuel gas between an outside gas supply line (the supply channel  22 ) and the inside of the high-pressure tank  1 . A screw portion  53  that screws into the female screw portion  42  of the mouthpiece  11  is formed on an axial part of the valve assembly  50 . In order to illustrate a tubular space  70  to be described later in an easily understood manner,  FIG. 2  shows the screw portion  53  not meshed with the female screw portion  42 , which is a state that differs from an actual state. In addition, the seal members  60  and  61  are interposed between the outer circumferential surface of the valve assembly  50  and the inner circumferential surface of the mouthpiece portion  11 . 
         [0038]    Furthermore, for example, a flange portion  11   a  is formed on a distal end-side (outside in an axial direction of the high-pressure tank  1 ) of the mouthpiece  11 , and a depressed portion  11   b  is formed on a rearward side (inside in the axial direction of the high-pressure tank  1 ) of the flange portion  11   a  (refer to  FIG. 2 ). A vicinity of a distal end of the CFRP layer  21  is in contact with the depressed portion  11   b  in an airtight manner. In addition, a solid lubrication coating such as fluorinated resin is applied to a surface of the depressed portion  11   b  that is in contact with the CFRP layer  21 . Accordingly, a coefficient of friction between the CFRP layer  21  and the depressed portion  11   b  is reduced. 
         [0039]    For example, a further rearward side of the depressed portion  11   b  of the mouthpiece  11  is formed so as to conform to the shape of the folded portion  30  of the resin liner  20 , a large-diameter protruding portion  11   c  is formed continuously from the depressed portion  11   b , and a mouthpiece cylindrical portion  11   d  having a constant diameter is formed to the rear of the protruding portion  11   c . The diameter-reduced portion  30   a  of the folded portion  30  of the resin liner  20  is in close contact with a surface of the protruding portion  11   c , and the cylindrical portion  30   b  is in close contact with a surface of the mouthpiece cylindrical portion  11   d . Although not particularly shown, a seal member such as an O ring is interposed between the cylindrical portion  30   b  and the mouthpiece cylindrical portion  11   d.    
         [0040]    In addition, a metallic seal  90  is formed at a contact portion of an outside end surface of the mouthpiece  11  and a rear surface of a head part of the valve assembly  50  so that the outside end surface of the mouthpiece  11  and the rear surface of the head part of the valve assembly  50  come into contact with each other in an airtight manner (refer to  FIG. 2 ). Therefore, in a state where the valve assembly  50  is fastened to the mouthpiece  11 , the contact surface therebetween is sealed so that gas does not permeate between the mouthpiece  11  and the valve assembly  50 . For example, in the case of the high-pressure tank  1  according to the present embodiment, the metallic seal  90  is formed at least an radially-outward portion than the tubular space  70 , thereby creating a state where a gap between the tubular space  70  and the outside of the tank is sealed. 
         [0041]    The valve assembly (in the present specification, also simply referred to as a valve)  50  controls supply and discharge of fuel gas between an outside gas supply line and the inside of the high-pressure tank  1 . An O ring  60  as a seal member is interposed between the outer circumferential surface of the valve assembly  50  and the inner circumferential surface of the mouthpiece  11  (refer to  FIG. 2 ). 
         [0042]    In addition, a solenoid valve  62  and a feedthrough  63  are provided at an end of the valve assembly  50  near the tank main body (refer to  FIG. 2 ). The solenoid valve  62  opens and closes in accordance with electrical signals and is controlled so as to supply a predetermined amount of fuel gas to the fuel cell system at a predetermined time. The feedthrough  63  is a device for feeding wiring  64  that is connected to the solenoid valve  62  into a high-pressure interior of the tank from the outside of the tank. The feedthrough  63  according to the present embodiment is installed in a depressed portion formed at an end of the valve assembly  50  in a state where a part of the wiring  64  is airtightly sealed. An O ring  61  as a seal member is interposed between the depressed portion and the feedthrough  63  (refer to  FIG. 2 ). 
         [0043]    The wiring  64  is routed using a wiring space  80  formed inside the valve assembly  50 . The wiring space  80  is an elongated space formed along the axial direction of the tank so as to penetrate the inside of the valve assembly  50 , and an end of the wiring space  80  is linked to the outside of the tank (refer to  FIG. 2 ). At this end of the wiring space  80 , a grommet  65  for protecting the wiring  64  is provided between an inner circumferential surface of the wiring space  80  and the wiring  64 . The wiring space  80  having both ends sealed by the grommet  65  and the O ring  61  is a space in which any hydrogen gas having permeated the seal (specifically, the O ring  61 ) may accumulate. 
         [0044]    In addition, the tubular space  70  constituted by an approximately tubular gap is formed between the mouthpiece  11  and the valve assembly  50  described above (refer to  FIG. 2 ). Since one end of the tubular space  70  is sealed by the metallic seal  90  described above and another end of the tubular space  70  is sealed by the O ring  60 , the tubular space  70  is a space in which any hydrogen gas permeating the seal (specifically, the O ring  60 ) may accumulate. 
         [0045]    In the present embodiment, a communicating hole  51  that communicatively connects the wiring space  80  with the tubular space  70  described above is provided in the valve assembly  50  (refer to  FIG. 2 ). Specifically, the communicating hole  51  is constituted by a narrow hole formed so as to link the outer circumferential surface of the valve assembly  50  to the wiring space  80 . While a diameter of the communicating hole  51  is not particularly limited as long as the communicating hole  51  is capable of discharging gas accumulating in the spaces  70  and  80 , since an excessively narrow communicating hole  51  may adversely affect processing, the diameter of the communicating hole  51  should be set as appropriate in consideration of various circumstances. 
         [0046]    Furthermore, in the present embodiment, a gas venting hole  52  for discharging gas having permeated from inside the high-pressure tank  1  to the outside of the tank is provided only for the tubular space  70  (refer to  FIG. 2 ). A GORE-TEX® seal  66  having both waterproofing and aeration properties is provided at an opening  52   a  of the gas venting hole  52  in order to avoid penetration (back penetration) of water or the like from the outside of the gas venting hole  52  (refer to  FIG. 2 ). 
         [0047]    As described above, with the high-pressure tank  1  configured such that spaces in which gas having permeated from the tank side may potentially accumulate (in the case of the present embodiment, the tubular space  70  formed between the mouthpiece  11  and the valve assembly  50  and the wiring space  80  formed in a vicinity of the center of the valve assembly  50 ) are bypassed to each other, for example, gas accumulating in the wiring space  80  can be discharged via the communicating hole  51  from another space (the tubular space  70 ) to the outside of the tank through the gas venting hole  52 . Therefore, with the high-pressure tank  1  according to the present embodiment, a part of gas venting holes and GORE-TEX® seals which were conventionally required can be omitted. Specifically, a gas venting hole  152  and a GORE-TEX® seal  166  which were conventionally provided in correspondence with the wiring space  80  are omitted in the high-pressure tank  1  according to the present embodiment (refer to dashed-two dotted lines in  FIG. 2 ). 
         [0048]    Furthermore, in the present embodiment, the gas venting hole  52  described above is formed so as to extend from the tubular space  70  in a direction that intersects a contact surface between the mouthpiece  11  and the valve assembly  50  (refer to  FIG. 2 ). In other words, the gas venting hole  52  is formed approximately perpendicular to the contact surface between the mouthpiece  11  and the valve assembly  50  on which the metallic seal  90  is formed (refer to  FIG. 2 ). In such a case, plane contact between metals enables the sealed contact surface between the mouthpiece  11  and the valve assembly  50  to remain unharmed and gas accumulating in the spaces  70  and  80  to be discharged through the gas venting hole  52 . 
         [0049]    In addition, in the present embodiment, the communicating hole  51  described above is provided closer to the center of the tank than to the screw portion  53  of the valve assembly  50  (refer to  FIG. 2 ). In the case of the present embodiment where the communicating hole  51  is provided so as to avoid the screw portion  53  as described above, the communicating hole  51  can be processed more easily than in a case where the communicating hole  51  is provided at the screw portion  53 . Furthermore, in the present embodiment, the communicating hole  51  is arranged so as to extend linearly in a radial direction of the valve assembly  50  (refer to  FIG. 2 ). In such a case, a length of the communicating hole  51  can be minimized (refer to  FIG. 2 ). 
         [0050]    As described above, in the present embodiment, in the high-pressure tank  1  having a configuration where internal gas is sealed using the O rings (seal members)  60  and  61  and which requires a plurality of gas venting holes  52  to discharge gas having permeated the O rings  60  and  61  to the outside of the tank and also requires GORE-TEX® seals  66  to avoid penetration of liquids such as water, a part of the gas venting holes ( 152 ) and GORE-TEX® seals  66  can be omitted by using the communicating hole  51 . Generally, a space (the space  70 ) exists between the mouthpiece  11  and the valve assembly  50 , and other spaces such as the wiring space  80  may also exist. Accordingly, as the numbers of gas venting holes  52  and GORE-TEX® seals  66  increase, costs of processing, assembly, and materials increase proportionally. In the present embodiment, by adopting a structure that enables a part of the gas venting holes  52  and GORE-TEX® seals  66  to be omitted, a reduction of such costs is achieved. 
         [0051]    Moreover, while embodiments described above are examples of a preferable embodiment of the present invention, the present invention is not limited thereto and various modifications can be made without departing from the spirit of the present invention. For example, while a case where the gas venting hole  152  linked to the wiring space  80  and the GORE-TEX® seal  166  are omitted has been described for the respective embodiments above (refer to  FIG. 2 ), it is obvious that, conversely, the gas venting hole  52  linked to the tubular space  70  and the GORE-TEX® seal  66  can be omitted. However, when the gas venting hole  152  becomes longer than the gas venting hole  52  as in the case of the high-pressure tank  1  illustrated in  FIG. 2 , it is more advantageous to omit the longer gas venting hole  152  from the perspective of performing ventilation more readily. 
         [0052]    In addition, while the GORE-TEX® seal  66  is provided at the opening  52   a  of the gas venting hole  52  in the embodiments described above, this is merely a preferable example of a waterproof and moisture-permeable material having both waterproofing and aeration properties. Other members may alternatively be used as long as such members are capable of avoiding penetration of water into the tank from the outside of the gas venting hole  52 . 
         [0053]    Furthermore, while two spaces, namely, the tubular space  70  and the wiring space  80  have been illustrated as spaces in which gas having permeated from the tank side may potentially accumulate in the embodiments described above, the present invention is obviously also applicable to cases where three or more such spaces exist. In such a case, while two spaces among the three or more existing spaces may be communicatively connected by the communicating hole  51 , communicatively connecting all of the spaces is more preferable from the perspective of omitting the gas venting holes  52  and the GORE-TEX® seals  66 . An example of a case where there are three or more spaces is when other components such as a sensor are provided in addition to the aforementioned solenoid valve  62  and the number of spaces for wiring increases. 
         [0054]    Moreover, while a case where the high-pressure tank  1  is a hydrogen high-pressure tank as a fuel supply source in a fuel cell system has been described in the above embodiments, this is also merely an example of a preferable embodiment of the present invention. To summarize, the present invention is applicable to a high-pressure tank having a valve structure in which high-pressure gas is sealed by an O ring or the like, the high-pressure tank comprising a gas venting hole that discharges gas having permeated the seal to the outside and prevents a liquid from penetrating from the outside, and two or more spaces in which gas may potentially accumulate. 
         [0055]    The present invention can be suitably applied to various types of high-pressure tanks configured such that a valve is fastened to a mouthpiece, including a high-pressure tank filled with hydrogen gas or the like.