HYDROGEN GAS STORING DEVICE

TECHNICAL FIELD

The present invention relates to a hydrogen gas storing device.

BACKGROUND ART

As a hydrogen storage tank, there is known a technique in which powdered hydrogen absorbing metal (hereinafter, referred to as MH) is accommodated in a tank, and MH absorbs and stores hydrogen, and releases hydrogen to be utilized.

MH has a property of generating heat when storing hydrogen and a property of absorbing heat when releasing hydrogen. Each time MH stores and releases hydrogen, the MH generates or absorbs heat. Therefore, a hydrogen storage tank using MH may be provided with a function of a heat exchanger that heats and cools the MH.

As one example of a hydrogen storage tank that accommodates MH and has a function as an heat exchanger, a heat exchanger incorporating metal hydride has been proposed, in which an inner space between a sealed cylinder and a hydrogen pipe therein is divided into a plurality of small chambers with partitions, and each small chamber is filled with metal hydride powder (refer to Patent Document 1). In the heat exchanger incorporating metal hydride disclosed in Patent Document 1, the partitions defining the small chambers are formed by aluminum alloy plates and serve as heat-transfer plates. Since heat medium flows to contact the outer circumferential surface of the sealed cylinder, heat exchange takes place between the heat medium and the powdered metal hydride through the sealed cylinder and the partitions.

Patent Document 1: Japanese Laid-Open Patent Publication No. 8-178463

DISCLOSURE OF THE INVENTION

However, when the heat exchanger incorporating metal hydride disclosed in Patent Document 1 is installed on, for example, an electric vehicle having a fuel cell, a space having desired shape and size cannot be secured at a planned installation position (for example, between the axle of the rear wheels and the rear seats), and, in some cases, the heat exchanger cannot be installed. In this case, if the size of the heat exchanger is reduced, the single heat exchanger cannot provide performance required for an electric vehicle having a fuel cell. Therefore, the heat exchanger incorporating metal hydride disclosed in Patent Document 1 has a disadvantage in that it can be installed in only limited locations.

Thus, heat exchangers of a reduced size may be prepared in a number that satisfies required performance of the vehicle, and the heat exchangers may be arranged to form a desired shape. However, in this case, each of the heat exchangers needs to be fixed to the vehicle separately, which makes the installation of the heat exchangers troublesome.

Accordingly, it is an objective of the present invention to provide a hydrogen gas storing device that adds to the flexibility of installation and can be installed easily.

To achieve the foregoing objective and in accordance with a first aspect of the present invention, a hydrogen gas storing device including a plurality of tank modules, a housing, and a plurality of flow paths through which heat medium flows is provided. The tank modules each have a cylindrical member and a plurality of fins. The cylindrical member has a cylindrical wall, through which hydrogen can flow, and a plurality of straight grooves formed on the outer circumferential surface. The fins are attached to the grooves of the cylindrical member. One edge and another edge of each fin are attached to the grooves of the cylindrical member so that a plurality of accommodation chambers for accommodating hydrogen absorbing metal are defined. The housing accommodates the tank modules such that the tank modules are adjacent to each other and form a predetermined shape. Each flow path is arranged in the housing so as to be correspond to one or more of the accommodation chambers while contacting one or more of the fins.

The “predetermined shape” refers to a shape that allows the hydrogen gas storing device to be arranged in a space designed to receive the device.

According to this invention, a plurality of tank modules are adjacently arranged in the housing to form the predetermined shape. Thus, when forming the hydrogen gas storing device, the tank modules can be freely arranged to form a desired shape. Therefore, for example, even if a desired installation space cannot be secured, the shape of the housing can be changed to conform to the existing installation space. By adjacently arranging the tank modules in the housing, the outer shape of the hydrogen gas storing device can be adjusted to conform to the installation space. Thus, the device can be installed in a position in which a conventional device cannot be easily installed. This adds to the flexibility of installation.

A plurality of tank modules are accommodated in the housing. Thus, when installing the device in an electric vehicle having a fuel cell, the device can be installed simply by fixing the housing to the vehicle. Therefore, compared to the case where a plurality of tank modules are separately fixed, the hydrogen gas storing device is easily installed.

It is preferable that at least one of the flow paths be located between two or more of the tank modules. In this case, a single flow path is configured to contact at least two fins, and it is possible to heat and cool hydrogen absorbing metal filling at least two accommodation chambers with heat medium flowing through a single flow path. Therefore, compared to the case where a flow path through which heat medium flows is provided for each accommodation chamber, the number of the flow paths can be reduced.

It is preferable that the flow paths extend in a direction parallel with the axial direction of the cylindrical members. In this case, for example, if the longitudinal direction of the fins is parallel with the axial direction of the cylindrical portions, the flow paths can be constructed to extend over the entire length of the fin. This allows the heat medium to perform heat exchange with the hydrogen absorbing metal over the entire length of the fins. Therefore, compared to the case where flow paths extend in a direction intersecting the axial direction of cylindrical members, the heat-transfer efficiency between heat medium and hydrogen absorbing metal is improved.

It is preferable that at least one of the flow paths be arranged to contact two or more of the fins.

In this case, it is possible to heat and cool hydrogen absorbing metal accommodated in at least two accommodation chambers with heat medium flowing through a single flow path. Therefore, compared to the case where a flow path through which heat medium flows is provided for each accommodation chamber, the number of the flow paths can be reduced.

It is preferable that a cross section of each tank module taken along a direction perpendicular to the center axis of the cylindrical member be shaped as a polygon, and that at least one of the flow paths be located at a position that corresponds to corners of two or more tank modules.

The “polygonal shape” includes not only a shape in which each corner is formed by two straight sides, but also a shape in which two straight sides are continuous with a curve in between, that is a shape having a curve at each corner.

In this case, compared to the case where a flow path through which heat medium flows is provided for each accommodation chamber, the number of the flow paths can be reduced.

It is preferable that the flow paths include a flow path through which heat medium flows in a direction from a first end toward a second end of the tank modules, and a flow path through which heat medium flows in a direction from the second end toward the first end of the tank modules.

Since the heat medium at the outlets of the flow paths has already performed heat exchange with the hydrogen absorbing metal, the temperature of the heat medium at the outlets of the flow paths is different from the temperature of the heat medium at the inlets of the flow paths. Therefore, since the temperature of the heat medium varies depending on the positions in the flow, the temperature of the hydrogen absorbing metal is uneven in some parts of the accommodation chamber if the heat medium flows in one direction.

However, in this preferred embodiment, a plurality of flow paths include flow paths in which heat medium flows from the first ends to the second ends of the tank modules and flow paths in which heat medium flows from the second ends to the first ends of the tank modules. This reduces the temperature difference between the hydrogen absorbing metal in the first ends of the tank modules and the hydrogen absorbing metal in the second ends of the tank modules.

It is preferable that each fin be bent to include a pair of partition portions that extend toward the corresponding cylindrical member and an outer wall portion that is continuous to the partition portions, one edge and another edge of the fin being attached to different grooves so as to one of the accommodation chambers, and that, in a state where the fins are attached to the cylindrical members, the outer wall portions function as outer walls of the tank modules.

In a case where an outer wall is provided about each tank module in addition to the fins, the fins and the outer walls need to be installed when assembling the tank modules. In this configuration, the fins are formed by bending, and each single fin is used to define one accommodation chamber. An outer wall portion, which is a part of each fin, is a used as the outer wall of a tank module. Therefore, no operation for attaching the fins to the outer walls is required. Compared to the case where outer walls separate from fins are provided, the assembly of the tank module is easy.

It is preferable that each fin have in its part a curved portion projecting into the corresponding accommodation chamber.

In this case, the curved portions reinforce the fins so that the fins have an increased strength against forces in a direction opposite to the direction of the recess. Therefore, even if the hydrogen absorbing metal filling the accommodation chambers is thermally expanded when absorbing hydrogen, and an outward force acts on the fins, the fins are prevented from being damaged.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional view illustrating a hydrogen gas storing device according to a preferred embodiment;

FIG. 2 is a perspective view illustrating an MH tank module;

FIG. 3 is a cross-sectional view taken along line 3-3, illustrating the hydrogen gas storing device shown in FIG. 1;

FIG. 4 is a cross-sectional view taken along line 4-4, illustrating the hydrogen gas storing device shown in FIG. 1;

FIG. 5 is a schematic cross-sectional view illustrating a hydrogen gas storing device according to another embodiment;

FIG. 6 is a perspective view illustrating an MH tank module according to another embodiment; and

FIG. 7 is a schematic view as viewed in an axial direction of porous members, illustrating a hydrogen gas storing device according to another embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

One embodiment of the present invention will now be described with reference to FIGS. 1 to 4.

As shown in FIG. 1, a hydrogen gas storing device 11 includes a substantially rectangular box-shaped housing 12 (which is, for example, made of aluminum). A plurality of (six in the present embodiment) of MH tank modules 13, serving as tank modules, are arranged in the housing 12. Specifically, the MH tank modules 13 are arranged adjacent to each other to form a substantially quadrangular prism shape. In the housing 12, the MH tank modules 13 are stacked to form multiple stages. The housing 12 has such a strength that it sufficiently withstands an inner pressure of a predetermined value (for example, 10 MPa) when the MH tank modules 13 are fully filled with hydrogen.

As shown in FIG. 2, each MH tank module 13 has a porous member 14, which serves as a cylindrical member formed of a porous material, at the center. The cross section of the MH tank module 13 taken along a direction perpendicular to the center axis of the porous member 14 is rectangular.

Each porous member 14 includes a cylindrical wall 14a, through which hydrogen flows (permeates), and a hydrogen flow path 15, which extends over the entire length of the MH tank module 13. Each porous member 14 has a plurality of (eight in the present embodiment) straight grooves 16, which are formed on the outer circumferential surface and extend along the center axis of the porous member 14.

The grooves 16 are arranged at equal intervals in the circumferential direction of the porous member 14. Each groove 16 has a width that is slightly greater than the thickness of two fins 17. Each groove 16 receives a first edge 18a of one of the fins 17 and a second edge 18b of an adjacent fin 17.

The fins 17 are formed by aluminum alloy plates, and are bent to be in the shape of a right triangle. Each fin 17 extends along the axial direction of the porous member 14 and is attached to the outer circumference of the porous member 14 by fitting one edge, or the first edge 18a, and the other edge, or the second edge 18b, into different grooves 16. When attached to the porous member 14, each fin 17 defines an accommodation chamber 19, which accommodates MH powder P. The fins 17 are attached to the porous member 14 with their longitudinal direction being parallel with the axial direction of the porous member 14, and a plurality of accommodation chambers 19 are formed in the MH tank module 13.

Spaces between the porous member 14 and each first edge 18a and each second edge 18b of the fins 17 are sealed, so that the MH powder P does not leak to the outside through the grooves 16. The MH powder P in each accommodation chamber 19 contacts the outer circumferential surface of the porous member 14. The MH tank module 13 shown in FIG. 2 has no MH powder P accommodated therein.

Each fin 17 is bent to include a pair of partition portions 23 extending toward the center of the MH tank module 13 and an outer wall portion 20 that is continuous to the pair of partition portions 23. The partition portions 23 extend from the sides of the outer wall portion 20 and prevent precipitation of the MH powder P.

With a plurality of the fins 17 attached to each porous member 14, the outer walls 20 also function as the outer walls of the MH tank module 13. In view of the space efficiency and thermal efficiency, adjacent fins 17 preferably contact each other.

Part of each outer wall portion 20 is bent so that a curved portion 21 is formed. The curved portion 21 projects into the accommodation chamber 19. The curved portions 21 are each formed such that its recess is slightly greater than half the outer circumference of heat medium pipes 22a, 22b. In portions that do not face the housing 12, two curved portions 21 face each other to form a piping space, into which one of the heat medium pipes 22a, 22b (see FIG. 1) is inserted.

As shown in FIGS. 2 to 4, an end wall 13a is welded to each of the ends (first end and second end) of each MH tank module 13 in the longitudinal direction, so that the openings of the accommodation chambers 19 in the longitudinal direction are closed. A pipe 24 is provided at one of the end walls 13a that forms a first end of each MH tank module 13. The pipe 24 communicates with the flow path 15 of the porous member 14 when attached to the MH tank module 13. At positions of each accommodation chamber 19 that corresponds to one of the end walls 13a, an injection hole and a plug for closing the injection hole (neither is shown) are provided. The MH powder P is introduced into each accommodation chamber 19 through the injection hole.

As shown in FIG. 1, the housing 12 includes a main body 25 having a rectangular cross section. The main body 25 has on the inner surface pipe recesses 25a for receiving half of each heat medium pipe 22a, 22b. With the MH tank modules 13 accommodated, the curved portions 21 of the fins 17 face the pipe recesses 25a, so that piping spaces for receiving the heat medium pipes 22b are formed. As shown in FIG. 3, a rectangular inlet header 27 with a bottom is attached to the main body 25 to face a first open end 26 of the main body 25. The inlet header 27 supplies heat medium (such as water, oil, and engine coolant) to the heat medium pipes 22a, 22b.

The inlet header 27 is installed by welding its open end to the first open end 26 of the main body 25. The interior of the inlet head 27 is connected to a heat medium tank (not shown) with a pipe and serves as a heat medium supply chamber 28. As shown in FIG. 4, pipe insertion holes 29 for receiving the pipes 24 are formed in the bottom of the inlet header 27. The number of the pipe insertion holes 29 is the same as the number of the MH tank modules 13. The gap between the open end of the inlet header 27 and the first open end 26 of the main body 25 is sealed to prevent heat medium from leaking.

On the opposite side of the main body 25 with respect to the inlet header 27, an outlet header 30 is provided. After performing heat exchange with the MH powder P, the heat medium is discharged to the outlet header 30. The outlet header 30 has a rectangular shape and a bottom. The outlet header 30 is fixed to a second open end 31 of the main body 25 by welding. With the outlet header 30 fixed to the second open end 31 of the main body 25, the interior of the outlet header 30 serves as a discharge chamber 32, which is connected to the heat medium tank with a pipe (neither is shown). After flowing through the heat medium pipes 22a, 22b, the heat medium flows into the discharge chamber 32.

All the heat medium pipes 22a, 22b extend parallel with axial direction of the porous members 14, and their inlet ends 33 extend into the supply chamber 28. Outlet ends 34 of the heat medium pipes 22a, 22b extend into the discharge chamber 32. As shown in FIG. 1, the heat medium pipes 22a, 22b are each arranged in a piping space and correspond to at least one of the accommodation chambers 19. Of the heat medium pipes 22a, 22b, each of the heat medium pipes 22a that are located between MH tank modules 13 contacts two fins 17 and corresponds to two accommodation chambers 19. Of the heat medium pipes 22a, 22b, each of the heat medium pipes 22a that are located between an MH tank modules 13 and the main body 25 contacts a fin 17 and corresponds to one accommodation chamber 19. The heat medium flows only in one direction. In the preset embodiment, the heat medium flows through the heat medium tank, the supply chamber 28, the heat medium pipes 22a, 22b, the discharge chamber 32, and the heat medium tank, in this order.

A method for assembling the hydrogen gas storing device 11 will now be described.

First, the main body 25 is prepared, and a plurality of the MH tank modules 13 are sequentially arranged from the lower row through the opening. At this time, the MH tank modules 13 are arranged such that the curved portions 21 of the fins 17 face the pipe recesses 25a of the main body 25. Accordingly, each pair of the curved portions 21 and each pair of a pipe recess 25a and the corresponding curved portion 21 defines a piping space. Next, the heat medium pipes 22a, 22b are inserted into the piping spaces in the main body 25. With the inlet ends 33 arranged outside from the first open end 26, the outlet ends 34 of the heat medium pipes 22a, 22b are arranged outside of the second open end 31. This procedure is repeated until all the piping spaces receive the heat medium pipes 22a, 22b. Then, the inlet header 27 and the outlet header 30 are fixed to the main body 25 through welding to assemble the housing 12. The inlet header 27 is fixed to the main body 25 with the pipes 24 inserted in the pipe insertion holes 29 and extending to the outside.

An operation of the hydrogen gas storing device 11 thus constructed will now be described.

In a case where the hydrogen gas storing device 11 is installed, for example, in an electric vehicle with a fuel cell, and hydrogen is directly used as fuel, consumption of hydrogen at the fuel electrodes causes each MH tank module 13 to release hydrogen, which is in turn supplied to the fuel electrodes through the pipes 24. When hydrogen is released from each MH tank module 13, reaction that occurs in the MH powder P is shifted to hydrogen release reaction between hydrogen storage and release reactions, which causes the MH powder P to release hydrogen. Since the release of hydrogen is an endothermic reaction, if heat required for releasing hydrogen is not supplied by the heating medium, the MH powder P releases hydrogen by using sensible heat, which causes the temperature of the MH powder P to drop. However, since heat medium of a predetermined temperature is supplied to the supply chamber 28 of the inlet header 27, and flows through the heat medium pipes 22a, 22b, the heat medium heats the MH powder P to a predetermined temperature through the fins 17. Accordingly, the reaction of hydrogen release smoothly progresses.

Then, the MH powder P in the accommodation chambers 19 releases hydrogen into the MH tank modules 13 along the entire length of the MH tank modules 13. Since the MH powder P in the accommodation chambers 19 contacts the outer circumferential surface of the porous members 14 along the entire length of the porous members 14, the released hydrogen reaches the hydrogen flow paths 15 through minute holes of the cylindrical walls 14a. The hydrogen is then released to the outside of the hydrogen gas storing device 11 through the pipes 24 of the MH tank modules 13 and is supplied to the fuel electrodes. The temperature of the MH powder P is maintained to a temperature that allows the release reaction of hydrogen to smoothly progress by adjusting the temperature or the flow rate of the heating medium, and the release of hydrogen is efficiently executed so that the amount of hydrogen corresponding to the amount required by the fuel cell is released.

When filling the hydrogen gas storing device 11 with hydrogen after hydrogen has been released therefrom, that is, when causing the MH powder P to absorb hydrogen, hydrogen is caused to flow into the hydrogen flow paths 15 of the porous members 14 from the pipes 24. The hydrogen that has flowed into the hydrogen flow paths 15 is diffused while flowing along the entire length of the MH tank modules 13. Then, the hydrogen reacts with the MH powder P, which is present over the entire length of the MH tank modules 13 in the accommodation chambers 19, to become hydride and be stored in the MH powder P. The supply of hydrogen to the MH powder P is continued until the interior of each MH tank module 13 reaches a predetermined pressure (for example, 10 MPa). Even if repetitive storing and release of hydrogen pulverizes the MH powder P, the pulverized MH powder P is prevented from leaking to the outside of the MH tank modules 13 because the porous members 14 have a function as filters to the MH powder P.

Since the storage reaction of hydrogen is an exothermic reaction, the storage reaction of the hydrogen is hampered unless the heat generated by the reaction is removed. However, when charging hydrogen, low temperature heating medium is supplied to the supply chamber 28 of the inlet header 27 and flows into the heat medium pipes 22a, 22b, the heat generated in the MH powder P is absorbed by the heating medium through the fins 17 and carried out of the hydrogen gas storing device 11. Therefore, the temperature of the MH powder P is maintained to a temperature that permits a smooth storing reaction of hydrogen, so that the hydrogen is efficiently stored.

Also, in the electric vehicle having a fuel cell, the hydrogen gas storing device 11 is installed between the axle of the rear wheels and the rear seat. The hydrogen gas storing device 11 of the present invention is configured by arranging three MH tank modules 13 adjacent to each other, and stacking another set of three MH tank modules 13 over the first three MH tank modules 13, so that the device 11 has a quadrangular prism shape. Therefore, while maintaining the performance of the conventional product, the hydrogen gas storing device 11 has a less height than the conventional product while having a greater width. The device 11 thus can be arranged between the rear wheel axle and the rear seat.

When installing the hydrogen gas storing device 11 between the rear wheel axle and the rear seat, the housing 12 is fixed using brackets (not shown), so that the multiple MH tank modules 13 can be simultaneously fixed. Therefore, for example, compared to a case where the MH tank modules 13 are separately fixed using a bracket, the installation is facilitated.

This embodiment provides the following advantages.

(1) The multiple MH tank modules 13 are arranged adjacent to each other to form a predetermined shape when being arranged in the housing 12. Therefore, when designing the hydrogen gas storing device 11, the shape can be made to correspond to the installation space between the rear wheel axle and the rear seat. Thus, the device 11 can be installed in a place where a conventional product cannot be placed. This adds to the flexibility of design.

(2) The hydrogen gas storing device 11 is configured such that the multiple MH tank modules 13 are adjacent to each other. Therefore, for example, when the device 11 is installed in an electric vehicle with a fuel cell, the MH tank modules 13 are easily fixed in the vehicle compared to a case where multiple MH tank modules 13 are separately fixed. The hydrogen gas storing device 11 is therefore easily installed.

(3) The first edge 18a and the second edge 18b of each fin 17 are fitted in the grooves 16 on the outer circumferential surface of the porous member 14, so that the fins 17 are attached to the porous member 14. The fins 17 define the accommodation chambers 19 for accommodating the MH powder P. Therefore, unlike a case where each MH tank module 13 only has a single accommodation chamber 19, each MH tank module 13 has segmented accommodation chambers 19. This increases the area at which the MH powder P and the fins 17 contact each other. Thus, heat exchange between the MH powder P and the heating medium through the fins 17 is efficiently performed.

(4) Each porous member 14 has a cylindrical wall 14a and a hydrogen flow path 15 extending along the entire length of the MH tank module 13. The first edge 18a and the second edge 18b of each fin 17 are fitted in grooves 16 in the outer circumferential surface of the porous member 14, so that the accommodation chambers 19 are defined by the fins 17. The hydrogen flow path 15 allows hydrogen to flow along the entire length of the MH tank module 13 and to react with the MH powder P in the accommodation chambers 19 through the cylindrical wall 14a. Therefore, in the MH tank module 13, hydrogen is allowed to smoothly react with the MH powder P along the entire length.

(5) The heat medium pipes 22a, 22b pass through the housing 12, so that the housing 12 does not intervene when heat exchange takes place between heat medium and the MH powder P. Thus, compared to a case where the heat medium pipes 22a, 22b are located outside of the housing 12, and heat exchange with the MH powder P takes place with the housing 12 in between, the heat exchange between the heat medium and the MH powder P is efficiently performed.

(6) Among the heat medium pipes 22a, 22b, which function as flow paths, each of the heat medium pipes 22a located between MH tank modules 13 contacts two fins 17, and heats and cools the MH powder P in two accommodation chambers 19 using heat medium flowing through the single heat medium pipe 22a. Therefore, compared to a case where heat pipes are separated from the accommodation chambers 19, the number of the heat medium pipes can be reduced.

(7) The heat medium pipes 22a, 22b extend parallel with the axial direction of the porous members 14, and the fins 17 are attached with the longitudinal direction being parallel with the axial direction of the porous members 14. This enlarges the area of the surfaces of the heat medium pipes 22a, 22b that contact the fins 17. Therefore, for example, if the heat medium pipes 22a, 22b are configured to extend along the entire length of the fins 17, heat medium is allowed to perform heat exchange with the MH powder P along the entire length with the fins 17 in between. Thus compared to a case where heat medium pipes extend to intersect the axial direction of the porous members 14, the heat-transfer efficiency between the heat medium and the MH powder P is improved.

(8) Each fin 17 is bent to have a pair of partition portions 23 extending toward the center of the MH tank module 13 and an outer wall portion 20 that is continuous to the partition portions 23. The first edge 18a and the second edge 18b of each fin 17 are attached to different grooves 16 and define an accommodation chamber 19, and multiple outer wall portions 20 function as the outer walls of the MH tank module 13. In other words, each fin 17 defines a single accommodation chamber 19 and the outer wall portion 20 functions as an outer wall of the MH tank module 13. Unlike the case of an MH tank module in which an outer wall is provided separately from fins, a process for attaching fin to the outer wall is not required in the above embodiment. Therefore, compared to the assembly of the MH tank module having an outer wall provided separately from fins, the assembly of the MH tank module 13, which includes the fins 17 and the outer walls, is easy.

(9) A curved portion 21, which projects into the accommodation chamber 19, is formed in the outer wall portion 20 of each fin 17. The curved portion 21, which is formed to projects into the accommodation chambers 19, increases the strength of the fin 17 against force acting in a direction away from the accommodation chamber 19 (outward direction).

Therefore, even if the MH powder P accommodated in the accommodation chambers 19 is expanded when absorbing hydrogen, and an outward force acts on the fins 17, the fins 17 are prevented from being damaged.

(10) The flow paths through which heat medium flows are formed by the heat medium pipes 22a, 22b. Therefore, even if the fins 17 are configured to contact the flow paths through which heat medium flows, no sealing needs to be provided between the fins 17 and the paths. Therefore, the flow paths through which heat medium flows are easily formed in the housing 12.

The present invention is not limited to the embodiment described above, but may be embodied as follows, for example.

As long as the heat medium pipes 22a, 22b serving as flow paths are provided to correspond to the accommodation chambers 19, all the heat medium pipes 22a, 22b may be formed continuously. For example, a heat medium pipe that is repeatedly folded back at the first end and the second end of the MH tank modules 13 so as to meander may be provided. In this case, one continuous heat medium pipe form a plurality of flow paths corresponding to each of the accommodation chambers 19 in the housing.

The positions of the heat medium pipes 22a, 22b serving as flow paths may be changed. For example, as shown in FIG. 5, heat medium pipes 39a, 39b, 39c may be provided at the corners of the MH tank modules 13. In this case, each heat medium pipe 39a, which is located at one of the four corners of the main body 25 and corresponds to a corner of an MH tank module 13, contacts two of the fins 17. Heat medium flowing through each heat medium pipe 39a thus heats and cools the MH powder P in two accommodation chambers 19. Also, each heat medium pipe 39b, which is located between two MH tank modules 13 and the main body 25 and correspond to corners of the two MH tank modules 13, contacts four fins 17. Heat medium flowing through each heat medium pipe 39b thus heats and cools the MH powder P in four accommodation chambers 19.

Also, each heat medium pipe 39c, which is located between four MH tank modules 13 and correspond to corners of the four MH tank modules 13, contacts eight fins 17. Heat medium flowing through each heat medium pipe 39c thus heats and cools the MH powder P in eight accommodation chambers 19. Therefore, compared to a case where one heat medium pipe is provided for each accommodation chamber 19, the configuration of the heat medium pipes 39a, 39b, 39c needs less number of heat medium pipes to correspond to all the accommodation chambers 19. That is, the number of the heat medium pipes can be reduced without lowering the heating and cooling performance of the MH powder P.

If the cross-sectional shape of each MH tank module 13 taken along a direction perpendicular to the axis of the porous member 14 is polygonal, the corners of the polygon are not limited to be defined by two straight sides. For example, each MH tank module 13 may have such a cross-sectional shape taken along a direction perpendicular to the axis of the porous member 14, that two straight sides are connected to each other via a curve. That is, each corner may be rounded.

The cross-sectional shape of each MH tank module 13 taken along a direction perpendicular to the axis of the porous member 14 may be changed. The cross-sectional shape of each MH tank module 13 taken along a direction perpendicular to the axis of the porous member 14 may be changed to a polygon, such as a triangle and a hexagon. The cross-sectional shape of the porous member 14 of each MH tank module 13 does not need to be polygonal, but may be circular like an MH tank module 40 shown in FIG. 6. In this case, the MH tank module 40 has a plurality of fins 41. The outer wall plate 42 of each fin 41 has an arcuate cross-sectional shape, which forms a part of the circular cross section when the fins 41 are attached to the porous member 14.

In place of the heat medium pipes 22a, 22b, which extend parallel with the axial direction of the porous members 14, heat medium pipes that intersect the axial direction of the porous members 14 may be used. For example, a plurality of heat medium pipes that extend in a direction perpendicular to the axial direction of the porous members 14 may be arranged along the axial direction of the porous members 14 at equal intervals. In this case, each heat medium pipe extends through the main body 25 and passes the housing 12, such that the inlet end and outlet end of each pipe extend to the outside of the housing 12. The inlet header 27 is attached to the outer circumferential surface of the main body 25, and the outlet header 30 is attached to the main body 25 on the side opposite to the inlet header 27. This structure allows heat medium to flow through the heat medium tank, the supply chamber, the heat medium pipes, the discharge chamber, and the heat medium tank in sequence, so that the heat medium heats and cools the MH powder P.

Instead of heat medium pipes, piping spaces defined by the curved portions 21 or by the pipe recesses 25a and the curved portions 21 may be used as flow paths through which heat medium flows. In this case, to ensure the sealing of the flow paths, joint lines between contacting curved portions 21 and joint lines between a curved portion 21 and a pipe recess 25a need to be sealed.

Heat medium that flows through the heat medium pipes 22a, 22b does not need to flow only in one direction. For example, the heat medium pipes 22a, 22b at the same height may include alternately arranged first heat medium pipes and second heat medium pipes. Through each first heat medium pipe, heat medium flows from the first end of the MH tank module 13 (the end wall 13a at which the pipes 24 are provided) to the second end of the MH tank module 13 (the end wall 13a at which no pipes 24 are provided), and through each second heat medium pipe, heat medium flows from the second end of the MH tank module 13 to the first end of the MH tank module 13. In this case, the housing is formed only by the main body 25. In addition to the housing, a first supply portion incorporating the inlet ends of the first heat medium pipes and a first discharge portion incorporating the outlet ends of the second heat medium pipes are provided. On the opposite side of the housing to the first supply portion and the first discharge portion, a second discharge portion incorporating the outlet ends of the first heat medium pipes and a second supply portion incorporating the inlet ends of the second heat medium are provided. This configuration includes flow paths through which heat medium flows from the first ends of the MH tank modules 13 to the second ends, and flow path through which heat medium flows from the second ends of the MH tank modules to the first ends. This reduces the temperature difference between the MH powder P in parts of the MH tank modules 13 closer to the first ends and the MH powder in parts of the MH tank modules 13 closer to the second ends.

The outer shape of the hydrogen gas storing device 11 may be changed by changing the shape of the housing 12. For example, in accordance with the shape of a space in an electric vehicle, the housing 12 may be formed to have a staircase like shape as shown in FIG. 7 before accommodating the MH tank modules 13 in the housing 12. Therefore, even if the shape of a remaining space has a staircase like shape, the hydrogen gas storing device 11 can be installed in the electric vehicle.

The material of the housing 12 is not particularly limited as long as the housing 12 has a sufficient strength that withstands a predetermined pressure in the MH tank modules 13 (for example, 10 MPa) when the MH tank modules 13 is filled with hydrogen. For example, instead of aluminum, the housing 12 may be formed of iron or fiber reinforced plastic.

When the width of each groove 16 is wider than the combined width of the first edge 18a and the second edge 18b of the fin 17, and the first edge 18a and the second edge 18b of the fin 17 cannot be firmly fitted into the groove 16, the first edge 18a and the second edge 18b of the fin 17 may be attached to the groove 16 using adhesive after inserting the first edge 18a and the second edge 18b into the groove 16.

The grooves 16 do not need to be formed to extend in a straight line as long as each groove 16 is capable of receiving the first edge 18a and the second edge 18b of fins 17. For example, if porous members having wavy shapes are used, grooves on the outer surface of the porous members extend along a wavy line, but not in a straight line.

The fins 17 with the curved portions 21 can be made by a method other than bending of parts of the outer wall portion 20. For example, it is possible to form fins 17 with a curved portion 21 in the outer wall portions 20 by extrusion molding.

The hydrogen gas storing device 11 is not restricted to use in an electric vehicle with a fuel cell, but may be employed in a hydrogen supply source of a hydrogen engine or a heat pump.

The heat medium pipes 22a, 22b do not need to extend in a straight line. For example, if the diameters of the heat medium pipes 22a, 22b remain the same, the pipes 22a, 22b have a greater area contacting the fins 17 when they have wavy shapes than when they are formed to extend in straight lines.

HYDROGEN GAS STORING DEVICE

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PCT Information