Pressurized fluid tank, in particular compressed gas tank for a motor vehicle

Translation of description of equivalent WO 03085314 A2

Title of invention

Tank for pressurized fluid, in particular compressed gas tank for a motor vehicle

Field of the Invention

A tank for fluid under high pressure, that is to say a higher pressure than 1 MPa.

A particular area, but not exclusive, application of the invention is that of CNG tanks (Natural Gas Vehicle) for containing a compressed gas to about 20 MPa for motor vehicles.

Background of the invention

The development of automobile powered by gaseous or liquefied fuels under pressure led to a search of fuel storage solutions under the best security conditions:

- Obtaining a performance index in volume, or load factor (ratio between volume and embedded space allowed) the highest possible - obtaining a constructive index (ratio between mass and volume onboard the vessel) the highest possible, and

- The use of lower cost technologies.

In the case of the engine by LPG (Liquefied Petroleum Gas), operating pressures are relatively low (about 1 MPa), so that the constructive index is less discriminating than other factors.

Against by, in the case of the actuator by CNG, the pressure is much higher, of the order of 20 MPa. In this area, existing tanks consist of one or more individual containers or modules generally cylindrical shape and is made of metallic material or composite material.

A reservoir for storing a fluid under high pressure while consenting a good load factor has been proposed in patent application WO 98/26209. This known container is formed of a plurality of tubular individual containers and has a polymorphic architecture with the following particular advantages:

- Ease of adaptation to the space available,

- Modularity - splitting volume storage with eventual isolation possibility of individual containers to meet the security objectives, and

- A relatively low mass, since the wall thickness requirement for each individual container is less severe than a unibody reservoir having the same total useful volume.

When the modules are made of metallic material, they have a relatively low constructive index. In the case of modules made of composite material, the constructive index is substantially higher, but the pressure resistance of stress induces a high wall thickness, which affects the load factor. In addition, the realization of monolithic tanks type funds + shell composite material causes significant manufacturing constraints, including the achievement of the winding and / or the draping of the fiber reinforcement of the composite material, and the necessary tools, especially chucks or forms which must permit removal of the coiled or draped structure.

It has been proposed in the patent application DE 3026116 to provide a reservoir for pressurized fluid comprising a plurality of tank portions in mutual contact via flat surfaces. The tank portions are held together by peripheral straps. Lids seal the tank portions at their longitudinal ends. Each of the longitudinal straps taking support on adjacent edges of the covers contribute to the maintenance thereof.

In that each cover is held by a single longitudinal strap which bears on an edge portion of the cover does not ensure a resistance to high pressures.

In addition, the fact that each longitudinal strap is common to two parts tanks limits the flexibility in the construction of the reservoir, in particular does not allow joining parts of different lengths tanks. Improving the holding tanks to pressure by strapping is also written in JP 10-274391 shows that the use of peripheral straps as fiber reinforced tapes.

OBJECT AND SUMMARY OF THE INVENTION

The invention aims to provide tanks for pressurized fluid which are formed of one or a plurality of individual containers, but with a simplification of the completion of elementary or containers, and therefore a significant reduction in the cost of manufacture, while allowing to obtain compact and efficient reservoirs.

The invention also aims to provide reservoirs having excellent resistance under high pressures, typically pressures of the order of those encountered in the CNG tanks, that is to say, about 20 MPa.

The invention also aims to provide a modular construction with flexibility including construction of various shapes of tanks adaptable to locations available for housing the tanks.

This object is achieved in that the or each container comprises a cylindrical body of composite material, two sealing flanges the cylindrical body at its axial ends, and at least two straps that surround the substantially longitudinal direction of the container by bearing on parts of external faces of the flanges, and which are arranged one on either side of a median longitudinal plane of the cylindrical body.

The realization of each container, a cylindrical body provided with two end flanges held by two longitudinal straps provides a number of advantages:

- The cylindrical body may be sized to hold only the radial forces generated by the internal pressure, which enables a reduced wall thickness,

- Separation of functions radial recovery efforts and recovery of the longitudinal forces broadens the possibility of choice materials used for the cylindrical body, or straps and the flanges, and the dimensioning of these parts,

- The cylindrical body being of constant cross section, different continuous modes of manufacture or semi-continuous may be used, that is to say not only the technical winding or draping, but other structures obtaining process tubular composite material, such as pultrusion process,

- The use of two longitudinal straps allows efficient maintenance of the flanges on the cylindrical body, including at elevated pressures,

- The space between the straps, at at least one of the flanges, can be utilized to form a recess for housing measuring equipment, safety or connection, without penalizing the clutter. The straps can be made of metallic material or composite material. In the latter case, they comprise a fibrous reinforcement formed of continuous fibers.

The flanges may be of metal material or structural composite material. Advantageously, each strap passes in a groove formed in the outer face of each flange.

Advantageously, each end plate has a plug-shaped with a portion sealingly engaged at one end of the cylindrical body. A rotary locking member may be further provided between the cylindrical body and at least one of the flanges to oppose a rotation of the flange relative to the cylindrical body about the axis thereof.

The cylindrical body and the flange of each container may be provided with an internal coating of a sealing material to the fluid, depending on the nature of the constituent materials of the container and the contained fluid.

In the case of a plurality of containers, the latter is advantageously part of parallelepipedal or prismatic volumes defined by the flanges, which allows an assembly of modular containers arranging them side by side. The mechanical connection between two adjacent containers can then be obtained by a mechanical connection member connecting the example at the level of plates arranged side by side of the two containers.

Alternatively, containers can be assembled in bundle being held together at least partially by a device encircling the beam. The containers can be of different lengths.

The internal volumes of two adjacent containers can be placed in communication with each other through at least one fluid connection connecting the plates situated side by side of the two containers.

Alternatively or additionally, at least some of the containers may be connected to a fluid manifold by at least one outlet formed through a flange.

Brief Description of Drawings

Other features and advantages of the tank of the invention appear on reading the description given below by way of non-limiting with reference to the accompanying drawings, wherein:

- Figure 1 is a highly diagrammatic partial perspective view of one embodiment of a reservoir according to the invention;

- Figure 2 is a partial perspective view on an enlarged scale of an elementary container of the Figure 1 container;

- Figure 3 is a partial longitudinal sectional view of the container of Figure 2; - Figure 4 is a partial perspective view on an enlarged scale exploded view showing one embodiment of a connection between adjacent containers in the container of Figure 1;

- Figure 5 is a partial sectional view of the connection between two adjacent containers according to the embodiment of Figure 4; - Figure 6 shows very diagrammatically a variant of the assembly of container forming a reservoir;

- Figure 7 shows very diagrammatically a variant embodiment of the connection of the internal volumes of the container forming a reservoir; - Figure 8 is a schematic sectional view showing a connection between a container from a reservoir and a collection tube;

- Figures 9 to 11 are sectional views showing alternative embodiments of a flange of a container for the equipment housing (s).

Detailed description of embodiments of the invention

Figure 1 shows a reservoir 10 formed of an assembly of individual containers or modules 20 arranged side by side (not all shown). Each container 20 includes a cylindrical body 22 closed at its axial ends by flanges 30. The containers 20 are arranged parallel to each other, each inscribed within a parallelepiped volume 21 defined by the shape of the flanges 30 . all the container is in a volume defined by the space allowed for the tank. In cross section, this set is part of a regular polygon or not regular, some containers may also have different lengths from those of other containers, so that the tank may have recesses or projections (not shown on Figure 1). Figures 2 and 3 illustrate in more detail an elementary container

20. The cylindrical body 22, for example with circular section, is made of structural composite material formed of fiber reinforcement densified by a matrix. The reinforcing fibers may be for example carbon fibers, glass, aramid, polyethylene or the like. The matrix may for example be a thermoplastic or thermosetting resin. The cylindrical body 22 could also be made of thermostructural composite material with reinforcing fibers and carbon matrix or ceramic.

The cylindrical body 22 gives the container 20 held in the radial component of the fluid pressure in it. Various known methods may be used to make the cylindrical body 22, such as for example by filament winding prepreg on a mandrel wire or the winding tape or preimpregnated fiber plies on a mandrel or the mold transfer layers with resin (or RTM). The cylindrical shape also allows to use the pultrusion process which allows continuous production of long tubes in which the cylindrical body 22 are cut to desired lengths.

The cylindrical body 22 is provided if necessary on its inner side with a coating 24 (or liner) fluid-tight with a substantially constant thickness. The coating 24 may be formed by a metal foil, for example aluminum alloy, or a plastic material, eg polyethylene or polytetrafluoroethylene (PTFE), or an elastomer. The coating 24 is present at least on the entire inner surface in contact with the fluid. The coating 24 may be bonded to the inner face of the cylindrical body 22 after completion thereof. Alternatively, integration of the coating 24 may be carried out at the stage of manufacture of the cylindrical body 22, for example by performing a winding or draping directly on the cover sheet or by producing pultrusion with simultaneous supply of coating material.

The flanges 30, closing the cylindrical body 22 at its ends has a plug-shaped with a head 32 which presses on the end of the cylindrical body and a skirt 34 which penetrates inside thereof.

The flanges can be made in one piece structural composite material. As well as the cylindrical body 22, the flanges can then be provided if necessary of a fluid tight coating on their internal surfaces, coating made continuous with that 24 of the cylindrical body 22.

Preferably, the flanges 30 are made in one piece of metal material, for example aluminum alloy.

The head 32 has a polygonal cross-section which is in the section of box volume 21 defining the footprint of the container 20.

The skirt 34 has at least one groove in which is housed a sealing gasket 35 which rests on the inner face of the coating 24.

To oppose a rotation between each flange 30 and the cylindrical body 22 about the axis thereof, a rotational locking is achieved by means for example of one or several pins 16, each mounted through a slot 28 formed in the wall of the cylindrical body 22 and into a blind hole formed in the skirt 34, the side outside of the seal 35 relative to the internal volume of the container. The lumen 28 extends in the longitudinal direction to allow a relative axial movement between the cylindrical body and the flange when the container is pressurized. The holding flanges 30 at the axial pressure exerted by the fluid contained in the primary tank 20 is ensured by at least two straps 40a, 40b. These surround the container 20 longitudinally relying on the external faces of the flanges 30. Preferably, the straps 40a, 40b extend through grooves 36a, 36b formed in the outer faces of the heads 32 of the flanges, so that the straps are effectively held in position.

The depth of the grooves 36a, 36b is selected so that the straps 40a, 40b there lodge in their entire thickness and do not create any protuberances on the external faces of the heads 32. The grooves 36a, 36b thus provide a protection function straps to the ends of the container in addition to the guiding function. An interposing layer, for example of elastomer, may be disposed at the bottom of the grooves 36a, 36b, the straps pressing this interposition layer.

Straps 40a, 40b may be constituted by metal strips fixed around the container. Preferably, the straps are made of a structural composite material with a fibrous reinforcement and resin matrix, for example. The reinforcement fibers are continuous fibers for holding the longitudinal forces. The fibers may be carbon, glass, aramid, polyethylene or other, while the matrix is ​​for example a phenolic or epoxy resin. Straps 40a, 40b can then be put in place by filament winding or fiber texture tape prepregs by the matrix resin.

The two straps 40a, 40b extend along parallel planes located on either side of a median plane of the container. In this way, the straps 40a, 40b as well as the relief grooves 36a, 36b are within the parallelepipedal volume 21 and do not increase the space requirement.

Although the use of two straps is preferred, it is also possible to provide more than two straps, for example with one or more additional straps arranged in a plane non-parallel with those of Straps 40a, 40b and crossing them as they pass over the heads 32 of the flanges.

In the embodiment of Figures 1 to 3, each individual container is in internal communication with each or at least one of its neighbors at one end.

For this purpose, as shown in Figures 4 and 5, tubular connectors 42 provided with an internal passage 42a is provided to be inserted into bores 38 formed in at least one of the lateral faces 32ι, 32₂, 32₃, 32₄ heads 32 of the flanges 30. The seals 46 are also mounted on the fittings 42 to be interposed between portions of the connectors extending into the bores 38 and the inner walls thereof. The holding in position of the tubular connector 42 between the two adjacent plates is obtained for example by the presence of a flange 44 being received in counterbores 38 formed in the adjacent side faces of the flanges 30.

Communication between the internal volumes of two adjacent containers is then provided by the tubular fittings 42 and the bores 38 which open into the internal volume of the cylindrical body through the skirt 34 of the flanges (see Figure 3). Each container is in direct physical contact with natural one or more adjacent containers between support flanges 30 at the faces 32i, 32₂, 32₃, 32₄ . The assembly may be performed using local fasteners such as clamps 50 fixed for example by screws 51 engaged in holes 39 of the heads 32 of the flanges 30 (see Figures 1 and 4).

Flanged connections are made at both ends of the containers.

Alternatively, or in addition, the assembly of the tank can be achieved by at least one belt 17 which encircles the reservoir 10 at the flanges, perpendicular to the axes of the elementary containers as shown by Figure 6. The reservoir can be formed of different lengths of containers.

When the containers 20 are directly interconnected, the fluid connection between the reservoir and a collection tube 14 (Figure 1) can be performed at a single container 20, at the reservoir level that best suits in its configuration of use.

Alternatively, if necessary, in particular when the containers are not interconnected or not all interconnected, multiple fluid connections between one or more collecting pipes and individual containers can be realized. 7 shows very schematically containers each connected at one end to a collector tube 14. The collector tubes 14 which are connected in common to a collector conduit 15, can then have a mechanical assembly according to the containers 20.

The lengths and / or arrangements of containers may be selected to give the container a desired general shape (see Figures 6 and 7) corresponding to the space available for the reservoir housing. A tank 10 as particularly described above suitable for the storage of gas under pressure in a motor vehicle running on CNG. It is then advantageously provided with a protective metallic shield or composite material (not shown), as known per se (reference may be made to WO 98/26209 cited above), at least to protect exposed portions of composite material vis-à-vis external aggressions.

8 illustrates an embodiment of the connection of the inner volume of a container 20 with a collecting tube 14. A conduit 48 is connected to a bore 37 formed in the head 32 of the flange 30 at one end of the elementary tank. The conduit 48 is connected to a collector tube 14.

A similar arrangement may be provided at the other end of elementary tank, in which case it is not connected to just one, but two collection tubes. Advantageously, the space between the straps at the flanges may be used to incorporate at least a measuring equipment, security or connection, such as pressure gauge, system isolation, thermal fuse, flow restrictor, connector with a collection tube. This arrangement allows to integrate this equipment into the tank volume and, moreover, helps to protect. In the example illustrated by Figure 9, a device 52, for example a manometer, is screwed into a central opening formed in the end plate 30 with the interposition of a seal 54.

In the embodiment of Figure 10, equipment 52 is also introduced into a central opening of the flange 30 with gasket 54, but a mechanical connection is realized by screw 56 passing through a flange 58 integral with the equipment 52 .

As for the embodiment of Figure 11, it differs from that of Figure 9 in that the equipment 52 is traversed by a conduit 60 for connecting the internal volume of the container to a collecting tube 14. In the illustrated embodiment of Figure 11, the mechanical connection of the equipment 52 on the flange could be achieved by screws, as shown in Figure 10.

Of course, other variants can be envisaged without departing from the scope of the invention.

Thus, the volume wherein each unit container fits may be of prismatic shape other than parallelepipedic, the shape of the heads of the flanges. It could for example give the flanges heads form a hexagonal cross section. In addition, a container may be made of various sub-assemblies each comprising an assembly of containers and interconnected by pipes. An embodiment of the tank in such subsets can tap different spaces available in a vehicle. Furthermore, the tank can have only one container made in a similar manner to that described above for the individual containers.

Finally, although an application to a gas tank for a motor vehicle with CNG engine was contemplated by the invention is applicable to any fluid reservoir under high pressure.