Patent ID: 12222069

DESCRIPTION OF EMBODIMENTS

A preferred embodiment of an accumulator of the present disclosure will be described hereinafter in detail with reference to the drawings. Note that the embodiment described below is a preferred specific example of the present disclosure, and thus various technically preferable limitations are described. However, the scope of the present disclosure is not particularly limited to these embodiments unless otherwise specified in the following descriptions.

Configuration of Forklift100

FIG.1is a schematic configuration diagram illustrating a forklift100according to Embodiment of the present disclosure. The forklift100illustrated inFIG.1is a fuel-cell type transportation vehicle. The forklift100includes a loading device102at the front portion of a vehicle body101. The forklift100includes a driver's seat103at the central portion of the vehicle body101.

The forklift100includes a fuel cell104below the driver's seat103. The fuel cell104includes a power generation unit105and a high-pressure hydrogen tank1. The power generation unit105initiates a chemical reaction between oxygen in the air and hydrogen supplied from the high-pressure hydrogen tank1to generate electric power.

The forklift100includes a pair of front wheels106that are drive wheels at the front portion of the vehicle body101, and a pair of rear wheels107that are steering wheels at the rear portion of the vehicle body101. The pair of front wheels106is driven by an electric motor (not illustrated). The electric motor is supplied with electric power from the power generation unit105. The pair of rear wheels107is steered by a driver seated on the driver's seat103.

The forklift100includes a counterweight108at the rear portion of the vehicle body101. The counterweight108is designed to adjust the vehicle weight and keep the weight balance of the vehicle body101. The forklift100does not include a counterweight at the front portion of the vehicle body101. The high-pressure hydrogen tank1provided at the central portion of the vehicle body101of the forklift100has a weight appropriate to assist the counterweight108. That is, the high-pressure hydrogen tank1serves as a part of the counterweight of the forklift100. Due to this configuration, the fuel cell104is accommodated in a case (not illustrated) that is lightweight and easily machined. The case does not serve as a part of the counterweight.

Other Transportation Vehicles

As described above, the high-pressure hydrogen tank1is used in the forklift100. However, the high-pressure hydrogen tank1is not limited to being used in the forklift100. The high-pressure hydrogen tank1is also used in other transportation vehicles. Examples of the transportation vehicles may include a towing car that is used at an airport or other places.

Configuration of High-Pressure Hydrogen Tank1

FIG.2is an explanatory view of the high-pressure hydrogen tank1according to Embodiment of the present disclosure in cross-section taken along the extending direction of a metal circular cylinder2and an outer cylinder4of the high-pressure hydrogen tank1. The high-pressure hydrogen tank1illustrated inFIG.2stores high-pressure hydrogen therein. The high-pressure hydrogen tank1includes the metal circular cylinder2, a cap part3, and the outer cylinder4. The cap part3is fixed to the outer cylinder4by a bolt5that is a fastening part. The fixing is conducted by bolts5at plural locations on the same circumference at regular intervals. The outer cylinder4is an example of the outer cylinder. An outer circular cylinder with a circular-cylindrical shape is used as the outer cylinder4.

Metal Circular Cylinder2

The metal circular cylinder2is a circular-cylindrical part with its opposite end portions opened, and configured to store high-pressure hydrogen therein. The metal circular cylinder2is made up of a seamless circular-cylindrical part made of metal to prevent leakage of high-pressure hydrogen stored therein.

The metal circular cylinder2is made of, for example, low-alloy steel. That is, the metal circular cylinder2is made of a material including, for example, any one of chrome molybdenum steel, nickel-chrome molybdenum steel, manganese chrome steel, manganese steel, and boron steel.

On an inner peripheral surface of the metal circular cylinder2, a decarburized layer has been removed. On the inner peripheral surface of the metal circular cylinder2after removal of the decarburized layer, a residual compressive stress is applied to the inner surface by blasting shot balls with a relatively large mass.

Note that a carbon fiber-reinforced resin portion may be wound around the outer periphery of the metal circular cylinder2. The carbon fiber-reinforced resin portion is provided to ensure a mechanical strength, which is a resistance to pressure, required for the metal circular cylinder2. The carbon fiber-reinforced resin portion is a composite material in which carbon fiber is used as a reinforcement and is soaked with resin to improve the strength. For example, PAN-based carbon fiber or PITCH-based carbon fiber is used.

Cap Part3

The cap part3is attached to each of the opposite end portions of the metal circular cylinder2to cover each of the opposite end portions of the metal circular cylinder2to close the metal circular cylinder2. A pair of cap parts3is a disc-like part. At least one of the cap parts3is provided with a valve (not illustrated) connecting to a hydrogen passage hole (not illustrated). The valve is used to fill or discharge high-pressure hydrogen. The pair of cap parts3is made of metal similarly to the metal circular cylinder2.

The pair of cap parts3is formed with a plurality of insertion holes3athrough which the bolts5are inserted. Each of the insertion holes3ain the cap parts3is formed with a recessed portion3bin which a head portion5aof the bolt5is accommodated. Note that the recessed portion3bmay not be formed. In a case where there is not the recessed portion3b, the head portion5aof the bolt5protrudes outward from the cap part3.

Outer Cylinder4

The outer cylinder4is a circular-cylindrical part opened at its opposite end portions, and surrounding the outer periphery of the circular-cylindrical portion of the metal circular cylinder2. The outer cylinder4may be a seamed circular-cylindrical part made of metal, such as a welded pipe, such that the production costs are reduced. The outer cylinder4is made of metal that is lower-cost steel material than the material of the metal circular cylinder2. It is preferable that the outer cylinder4be made of material with a density equal to or greater than the density of the material of the metal circular cylinder2.

The outer cylinder4is formed with a screw hole4ainto which the bolt5is screwed. The bolt5is inserted from the cap part3into the outer cylinder4and screwed into the screw hole4a. The bolt5is screwed by inserting a tool such as a spanner between the recessed portion3bof the cap part3and the head portion5aof the bolt5. The bolt5may have an insertion hole on the head portion5a, into which a tool such as a hexagonal wrench is fitted to screw the bolt5.

Gap6with Circular-Cylindrical Shape

Between the outer periphery of the metal circular cylinder2and the inner periphery of the outer cylinder4, a gap6with a circular-cylindrical shape is provided so as to allow the metal circular cylinder2and the outer cylinder4to be spaced apart from each other. The gap6has a width of, for example, preferably 1 mm or greater, and more preferably 2 mm or greater in the radial direction. The metal circular cylinder2is in direct contact with high-pressure hydrogen stored therein, and thus the hydrogen permeates through the metal circular cylinder2. However, the hydrogen escaping from the metal circular cylinder2accumulates in the gap6, and does not permeate into the outer cylinder4separated from the metal circular cylinder2by the gap6. Thus, the high-pressure hydrogen tank1prevents the occurrence of hydrogen degradation of the outer cylinder4and the bolts5. The gap6is present between the outer periphery of the metal circular cylinder2and the inner periphery of the outer cylinder4, so that even when the metal circular cylinder2becomes deformed in the circumferential direction by high-pressure hydrogen stored therein, the gap6prevents the deforming stress from being transmitted to the outer cylinder4and the bolts5.

Details on Part of High-Pressure Hydrogen Tank1

FIG.3is an enlarged view of a part of the high-pressure hydrogen tank1according to Embodiment of the present disclosure, illustrated by enlarging an A portion inFIG.2. As illustrated inFIG.3, it is desirable that the outer cylinder4is formed with a flow path7passing from the gap6to the outside on the outer peripheral side. The hydrogen having accumulated in the gap6flows through the flow path7to the outside, so that high-concentration hydrogen does not accumulate in the gap6and this can ensure the safety of the high-pressure hydrogen tank1. Note that the flow path7may not be provided. One flow path7or a plurality of flow paths7may be provided.

The metal circular cylinder2and the cap part3are fitted to each other by a first fitting structure8. The first fitting structure8is a structure to fit a projecting portion8ainto a recessed portion8b. The projecting portion8ais formed on the outer peripheral portion at each of the opposite end portions of the metal circular cylinder2. The recessed portion8bis formed on the inner surface of the cap part3. The projecting portion8aand the recessed portion8bhave an annular shape. There may be a plurality of projecting portions8alocated separately from each other on the same circumference, and correspondingly a plurality of recessed portions8blocated separately from each other on the same circumference. Note that the first fitting structure8may employ another form to fit the metal circular cylinder2and the cap part3to each other.

Between the metal circular cylinder2and the cap part3on the inner-diameter side relative to the first fitting structure8, a first O-ring9aand a second O-ring9bare provided to serve as a sealing part. The first O-ring9ais located on the inner peripheral side relative to the second O-ring9b. The first O-ring9aseals the gap between the metal circular cylinder2and the cap part3. The second O-ring9bis a sealing part in case of degradation of the first O-ring9aand thus a leakage of hydrogen from the first O-ring9a.

Between the first O-ring9aand the second O-ring9b, a leaked-hydrogen discharge hole10is formed through the cap part3. The leaked-hydrogen discharge hole10passes through the cap part3to the outside on the outer side thereof. A hydrogen sensor11is provided at the exit of the leaked-hydrogen discharge hole10. The hydrogen sensor11monitors leakage of hydrogen.

The outer cylinder4and the cap part3are fitted to each other by a second fitting structure12. The second fitting structure12is a structure to fit a projecting portion12ainto a recessed portion12b. The projecting portion12ais formed on the central portion at each of the opposite end portions of the outer cylinder4. The recessed portion12bis formed on the inner surface of the cap part3. The projecting portion12aand the recessed portion12bhave an annular shape. There may be a plurality of projecting portions12alocated separately from each other on the same circumference, and correspondingly a plurality of recessed portions12blocated separately from each other on the same circumference. Note that the second fitting structure12may employ another form to fit the outer cylinder4and the cap part3to each other.

The second fitting structure12is provided at the fastening portion of the bolt5. The outer cylinder4and the cap part3are fastened by the bolt5at a portion where the outer cylinder4is assembled with the cap part3by precise positioning due to the second fitting structure12.

Modification 1

FIG.4is an explanatory view of the high-pressure hydrogen tank1according to Modification 1 of Embodiment of the present disclosure in cross-section taken along the extending direction of the metal circular cylinder2and the outer cylinder4of the high-pressure hydrogen tank1.FIG.5is a side view of the high-pressure hydrogen tank1according to Modification 1 of Embodiment of the present disclosure when viewed from the direction of an arrow B inFIG.4. Descriptions of similar components as those according to Embodiment described above are omitted, and only the characteristic portions are hereinafter described.

As illustrated inFIGS.4and5, the insertion hole3aof the cap part3is not formed with a recessed portion in which the head portion5aof the bolt5is accommodated. The head portion5aof the bolt5protrudes outward from the cap part3. The bolt5has an insertion hole5a1on the head portion5a, into which a tool such as a hexagonal wrench is fitted to screw the bolt5.

Modification 2

FIG.6is a side view of the high-pressure hydrogen tank1according to Modification 2 of Embodiment of the present disclosure when viewed from the direction of the arrow B inFIG.4.FIG.7is an explanatory view of the metal circular cylinder2and the outer cylinder4of the high-pressure hydrogen tank1according to Modification 2 of Embodiment of the present disclosure in cross-section viewed from the direction of the arrow B inFIG.4. Descriptions of similar components as those according to Embodiment described above are omitted, and only the characteristic portions are hereinafter described.

As illustrated inFIG.6, the cap part3includes a flat lower surface. The cap part3is a plate-like part. The outer cylinder4also includes a flat lower surface similarly to the cap part3illustrated inFIG.6. As illustrated inFIG.7, the outer cylinder4is an outer square cylinder with a square-cylindrical shape and having four sides of an identical shape according to the outer peripheral shape of the cap part3. The outer cylinder4is formed by combining four plate-like parts4b. Fixing parts such as bolts4care used to fix the four plate-like parts4bto each other.

Note that the outer cylinder4may have a shape with a flat lower surface differently from the shape of the outer square cylinder. For example, the outer cylinder4may be a cylindrical part with a U-shape, a truncated conical shape, or a polygonal shape such as a truncated square pyramid shape. In this case, it suffices that the cap part3is a plate-like part with a shape according to the outer peripheral shape of the outer cylinder4.

Effects of Embodiment

According to Embodiment, the high-pressure hydrogen tank1includes the metal circular cylinder2configured to store high-pressure hydrogen therein. The high-pressure hydrogen tank1includes the cap part3configured to cover each of the opposite end portions of the metal circular cylinder2. The high-pressure hydrogen tank1includes the outer cylinder4surrounding the outer periphery of the circular-cylindrical portion of the metal circular cylinder2. The high-pressure hydrogen tank1includes the fastening part configured to fix the cap part3to the outer cylinder4.

With this configuration, the high-pressure hydrogen tank1can be produced by fixing the cap part3configured to cover each of the opposite end portions of the metal circular cylinder2to the outer cylinder4surrounding the outer periphery of the circular-cylindrical portion of the metal circular cylinder2by using the bolts5that are the fastening parts. Therefore, the high-pressure hydrogen tank1having a simple configuration without requiring much time and effort to produce, while being safe and able to reduce production costs, can be provided.

According to Embodiment, the bolt5is used as the fastening part.

With this configuration, the high-pressure hydrogen tank1can be produced by fixing the cap part3configured to cover each of the opposite end portions of the metal circular cylinder2to the outer cylinder4surrounding the outer periphery of the circular-cylindrical portion of the metal circular cylinder2by using the bolts5.

According to Embodiment, the bolt5is inserted from the cap part3into the outer cylinder4. The cap part3is formed with the recessed portion3bin which the head portion5aof the bolt5is accommodated.

With this configuration, the bolts5do not protrude from the opposite end portions of the high-pressure hydrogen tank1, and the circular-cylindrical portion of the high-pressure hydrogen tank1provided between the cap parts3can be maximized in size within a limited installation space, so that the amount of high-pressure hydrogen stored in the high-pressure hydrogen tank1can be increased. Particularly, it is effective for the high-pressure hydrogen tank1mounted in a transportation vehicle in that the size of the high-pressure hydrogen tank1can be maximized within the limited installation space of the vehicle.

According to Embodiment, between the outer periphery of the metal circular cylinder2and the inner periphery of the outer cylinder4, the gap6with a circular-cylindrical shape is formed by which the metal circular cylinder2and the outer cylinder4are spaced apart from each other.

With this configuration, the metal circular cylinder2is in direct contact with high-pressure hydrogen stored therein, and thus the hydrogen permeates through the metal circular cylinder2. However, the hydrogen escaping from the metal circular cylinder2accumulates in the gap6, and does not permeate into the outer cylinder4separated from the metal circular cylinder2by the gap6. Thus, the high-pressure hydrogen tank1is safe since the high-pressure hydrogen tank1prevents the occurrence of hydrogen degradation of the outer cylinder4and the bolts5that are the fastening parts. The gap6is present between the outer periphery of the metal circular cylinder2and the inner periphery of the outer cylinder4, so that even when the metal circular cylinder2becomes deformed in the circumferential direction by high-pressure hydrogen stored therein, the gap6prevents the deforming stress from being transmitted to the outer cylinder4and the bolts5that are the fastening parts.

According to Embodiment, the outer cylinder4is formed with the flow path7passing from the gap6to the outside on the outer peripheral side of the outer cylinder4.

With this configuration, hydrogen escaping from the metal circular cylinder2accumulates in the gap6. The hydrogen having accumulated in the gap6flows through the flow path7to the outside, so that high-concentration hydrogen does not accumulate in the gap6and this can ensure the safety of the high-pressure hydrogen tank1. This configuration also prevents the occurrence of hydrogen degradation of the outer cylinder4and the bolts5that are the fastening parts.

According to Embodiment, the high-pressure hydrogen tank1has the first fitting structure8to fit the metal circular cylinder2and the cap part3to each other.

With this configuration, the metal circular cylinder2that is not fixed to the cap part3with a fastening part or other parts is assembled with the cap part3by precise positioning due to the first fitting structure8. This eliminates the need for fixing the metal circular cylinder2to the cap part3by using a fastening part or other parts. For this reason, the production man-hours can be reduced, and accordingly the production costs can be reduced. In addition, hydrogen degradation of the fastening part in a case where the metal circular cylinder2is fixed to the cap part3by using the fastening part or other parts can be eliminated. Further, since the metal circular cylinder2and the cap part3are fixed in position by the first fitting structure8, the metal circular cylinder2does not contact the outer cylinder4, and thus the gap6with a circular-cylindrical shape is not closed.

According to Embodiment, the first O-ring9aand the second O-ring9bthat are sealing parts are provided between the metal circular cylinder2and the cap part3on the inner-diameter side relative to the first fitting structure8.

With this configuration, the sealing performance in the section of the first fitting structure8is insufficient since the gap between the metal circular cylinder2and the cap part3changes in shape in a complicated manner. The first O-ring9aand the second O-ring9bthat are sealing parts are provided between the metal circular cylinder2and the cap part3on the inner-diameter side relative to the first fitting structure8, so that the first O-ring9aand the second O-ring9bthat are sealing parts seal the metal circular cylinder2and the cap part3on the inner-diameter side relative to the section with insufficient sealing performance. This can prevent high-pressure hydrogen stored in the metal circular cylinder2from leaking from the outer peripheral side relative to the first O-ring9aand the second O-ring9bthat are sealing parts.

According to Embodiment, the high-pressure hydrogen tank1has the second fitting structure12to fit the outer cylinder4and the cap part3to each other.

With this configuration, the outer cylinder4to be fixed to the cap part3with the bolts5that are the fastening parts is assembled with the cap part3by precise positioning due to the second fitting structure12. Thus, the outer cylinder4can be easily fixed to the cap part3by using the bolts5that are the fastening parts. This makes it easy to perform the production step of fastening with the bolts5that are the fastening parts, and accordingly can reduce the production costs.

According to Embodiment, the second fitting structure12is provided at the fastening portion of the bolt5that is the fastening part.

With this configuration, the outer cylinder4can be fastened by using the bolts5that are the fastening parts at a portion where the outer cylinder4is assembled with the cap part3by precise positioning due to the second fitting structure12. This makes it easier to perform the production step of fastening with the bolts5that are the fastening parts, and accordingly can further reduce the production costs.

According to Embodiment, the outer cylinder4includes a flat lower surface.

With this configuration, the outer cylinder4can be installed on the installation surface below with its flat lower surface. This stabilizes the installation of the outer cylinder4with a flat lower surface on the installation surface.

According to Embodiment, the outer cylinder4is an outer square cylinder with a square-cylindrical shape.

With this configuration, the outer cylinder4has upper and lower surfaces parallel to each other, and opposite lateral surfaces parallel to each other, and is formed with the upper and lower surfaces perpendicular to the opposite lateral surfaces. With this configuration, the outer cylinder4formed into an outer square cylinder does not have any excess projecting portions on its outer peripheral surface, and therefore in an upward-downward direction and in a rightward-leftward direction relative to a single high-pressure hydrogen tank1, another high-pressure hydrogen tank1with an outer square cylinder can be located adjacent to the single high-pressure hydrogen tank1, so that a plurality of high-pressure hydrogen tanks1can be stacked on one another without wasting the space.

According to Embodiment, the outer cylinder4is an outer circular cylinder with a circular-cylindrical shape.

With this configuration, the outer cylinder4formed into an outer circular cylinder has a uniform resistance to pressure over the entire circumferential direction. This improves the rigidity of the outer cylinder4formed into an outer circular cylinder.

According to Embodiment, the high-pressure hydrogen tank1serves as a part of the counterweight of a transportation vehicle.

With this configuration, the weight of the high-pressure hydrogen tank1is increased by a double circular-cylindrical part made up of the metal circular cylinder2and the outer cylinder4. Thus, the total volume of the counterweight mounted on a transportation vehicle can be reduced, and accordingly the number of components of the transportation vehicle can be reduced. This can reduce the production costs of the transportation vehicle.

REFERENCE SIGNS LIST

1high-pressure hydrogen tank2metal circular cylinder3cap part3ainsertion hole3brecessed portion4outer cylinder4ascrew hole4bplate-like part4cbolt5bolt5ahead portion5a1insertion hole6gap7flow path8first fitting structure8aprojecting portion8brecessed portion9afirst O-ring9bsecond O-ring10leaked-hydrogen discharge hole11hydrogen sensor12second fitting structure12aprojecting portion12brecessed portion100forklift101vehicle body102loading device103driver's seat104fuel cell105power generation unit106front wheel107rear wheel108counterweight