Method for manufacturing a pressure vessel and pressure vessels manufactured using such a method

Abstract

[Method for manufacturing a pressure vessel which is designed to store a storage medium under high pressure in a pressure vessel interior, wherein the following steps are carried out to manufacture this pressure vessel: - Providing a pressure vessel core body, wherein the pressure vessel core body corresponds at least substantially to the shape of the pressure vessel interior and consists substantially or entirely of a temporarily bonded core material, - direct or indirect application of a pressure vessel wall to this pressure vessel core body, wherein the pressure vessel wall consists at least substantially of a fiber composite material, - at least partial hardening of the applied fiber composite material and thus formation of the pressure vessel wall, - Breaking the temporary bond of the core material and thus removing the pressure vessel core body from the pressure vessel interior.]

Description

[0001] The invention relates to a method for manufacturing a pressure vessel and to a pressure vessel manufactured by such a method. From DE 10 2021 124 236 A1, a pressure vessel, a pressure vessel system, a motor vehicle, and a method for forming ribs on a vessel wall of such a pressure vessel are known.

[0002] The invention is described below using a hydrogen tank for a passenger car as an example; this is not to be understood as limiting the invention to such an application. In a passenger car with a hydrogen drive, regardless of whether the drive is powered by a fuel cell or in another form, the required hydrogen is carried in a high-pressure tank. This high-pressure tank can contain one or more pressure vessels for storing hydrogen. The following section describes a pressure vessel whose wall is made of a fiber-reinforced composite material such as CFRP or the like. When manufacturing such a pressure vessel, an inner liner is used, which typically contains or consists of polyamide. The inner liner forms the internal volume of the pressure vessel, and the fiber-reinforced composite material is applied to it from the outside.Besides providing shape, this liner also serves to make the pressure vessel gas-tight. A disadvantage of such an internal liner is that its wall thickness is not insufficient to ensure adequate dimensional stability for the application of the fiber-reinforced composite material and sufficient gas tightness. The volume occupied by the wall of the internal liner is lost to hydrogen storage in the pressure vessel.

[0003] Against this background, it is an objective to specify a manufacturing method for a pressure vessel by which an improved pressure vessel compared to the prior art can be produced, as well as a pressure vessel produced by this method. This objective is achieved by a method for manufacturing a pressure vessel according to claim 1, and by a pressure vessel according to claim 12; preferred embodiments of the invention are the subject of the dependent claims.

[0004] In light of the prior art described above, one aspect of the invention is particularly advantageous in eliminating the need for an internal and dimensionally stable liner. This can preferably be achieved by using a "lost" core as a manufacturing aid. It is preferably proposed that this lost core comprises, or consists of, an organic or inorganic granular mixture, wherein, for the purposes of the invention, a granular mixture is understood to mean, in particular, granules. This granular mixture can preferably be formed in a mold, using binder material, pressure, and temperature, into the desired geometry, which in particular corresponds at least substantially to the internal volume of the pressure vessel to be manufactured.This granular mixture is hereinafter also referred to as core material or, if it is formed into a predetermined geometry, as temporarily bound core material. A fundamental aspect of the invention is to shape the core material into the interior of the pressure vessel and to temporarily bind it in this shape, thus creating a core for the interior of the pressure vessel, a so-called pressure vessel core body. The wall surrounding the interior of the pressure vessel is then fabricated onto this pressure vessel core body, and subsequently, the pressure vessel core body is removed from the interior of the pressure vessel by partially or completely dissolving the temporary bond. Preferably, one or more salts, preferably liquid-soluble, can also be provided to form such a "lost" core.

[0005] For the purposes of the invention, a method for manufacturing a pressure vessel is understood to be a method by which a pressure vessel can be manufactured, which is designed, in particular, for storing a storage medium under high pressure, preferably hydrogen, preferably in a gaseous or liquid state, or a gaseous and liquid state. For storage purposes, the pressure vessel has an interior space which is surrounded by a pressure vessel wall, apart from planned recesses, in particular for connections in this pressure vessel. The proposed manufacturing method thus relates in particular to the manufacture of the wall surrounding this interior space and therefore to an essential component of a pressure tank, in particular a hydrogen tank, and not to the manufacture of such a tank with all its attachments as such.

[0006] Furthermore, the proposed method for manufacturing a pressure vessel includes at least the following steps: - Providing a pressure vessel core body, wherein the pressure vessel core body corresponds at least substantially to the shape of the pressure vessel interior and consists substantially or entirely of a temporarily bonded core material, - direct or indirect application of a pressure vessel wall to this pressure vessel core body, wherein the pressure vessel wall consists at least substantially of a fiber composite material, - at least partial hardening of the applied fiber composite material and thus formation of the pressure vessel wall, - Breaking the temporary bond of the core material and thus removing the pressure vessel core body from the pressure vessel interior.

[0007] For the purposes of the invention, the direct application of the pressure vessel wall to this pressure vessel core body, i.e., the direct application of a fiber-reinforced composite material to such a pressure vessel core body, is understood to mean that this occurs directly and, in particular, without an intermediate layer, i.e., without an intermediate layer. Furthermore, for the purposes of the invention, the indirect application of the pressure vessel wall to this pressure vessel core body, i.e., the indirect application of a fiber-reinforced composite material to such a pressure vessel core body, is understood to mean that the material is applied indirectly to this pressure vessel core body; preferably, a film or coating is applied to the pressure vessel core body, which is geometrically arranged between this pressure vessel core body and the fiber-reinforced composite material of the pressure vessel wall.This film or coating is not located within the pressure vessel wall itself, but rather forms a true intermediate layer between the pressure vessel core and the pressure vessel wall. In particular, directly applying the pressure vessel wall to the pressure vessel core allows for a particularly efficient manufacturing process. In particular, indirectly applying the pressure vessel wall to this pressure vessel core can improve the pressure vessel's tightness and media resistance.

[0008] In the context of the invention, the at least partial curing of the applied fiber composite material of the pressure vessel wall is understood to mean that it is cured for a considerable period of time, or that thermal energy or radiant energy, particularly in the form of UV radiation, is supplied for curing, thereby increasing the dimensional stability of the pressure vessel wall. Furthermore, the pressure vessel wall is cured at least to a degree sufficient to achieve sufficient dimensional stability for further processing or transport.

[0009] In the context of the invention, "breaking the temporary bond of the core material" means that the geometric shape into which the core material was formed and in which it is held by the temporary bond is broken, at least to the extent that it can be removed from the interior of the pressure vessel without damaging the pressure vessel wall. Preferably, the temporary bond of the core material is completely broken, so that it is again in its original geometric shape. Particularly with regard to a water-soluble salt as the core material, breaking the temporary bond results in the material being at least partially transformed from a solid to a liquid state.

[0010] In particular, the proposed method makes it possible to dispense with a dimensionally stable liner for applying the pressure vessel wall to it and to use the volume that would be occupied by it for storing the medium to be stored in the pressure vessel, and thus the proposed method represents an improved method compared to known manufacturing methods.

[0011] In a preferred embodiment of the invention, a granular core material is temporarily bonded to form the pressure vessel core body. This granular core material is preferably pressed into a mold. Preferably, this granular core material is subjected to temperature to initiate or at least promote a bonding reaction. The application of pressure and temperature to create a core with temporary bonding is a particularly efficient production method for a pressure vessel core body.

[0012] In a preferred embodiment of the invention, a core material binder is added to the granular core material for temporary bonding in order to provide the pressure vessel core body. Preferably, this binder is introduced only into the outer region of the pressure vessel core body, or core material mixed with the core material binder is used only in the outer region of the pressure vessel core body. In particular, by only partially and not completely mixing the granular core material with the core material binder, a pressure vessel core body is achieved that can be removed from the interior of the pressure vessel particularly efficiently. In particular, by completely mixing the granular core material, a particularly dimensionally stable pressure vessel core body is made possible, which enables efficient manufacturing under high winding pressure of the fiber composite material.

[0013] In a preferred embodiment of the invention, the pressure vessel core is subjected to vibration to break the temporary bond of the core material. Preferably, this vibration is transmitted to the pressure vessel core without contact, preferably by means of sound waves, preferably ultrasonic waves. Preferably, the vibration is transmitted to the pressure vessel core by means of physical contact. Preferably, a vibration sensor is embedded in the pressure vessel core during its manufacture, preferably a vibration sensor that is at least partially metallic.In particular, a contactless transmission of the vibration stress enables a particularly simple lifting of the temporary bond of the pressure vessel core body, and in particular a contact-based transmission of the vibration stress enables the transmission of a particularly high intensive vibration stress and thus a rapid lifting of the temporary bond of the pressure vessel core body.

[0014] In a preferred embodiment of the invention, the core material for forming the pressure vessel core body comprises, at least as a component, a liquid-soluble material; preferably, this core material consists of such a material. Preferably, such a liquid-soluble material is understood to be, in particular, a salt or a compound. Furthermore, it is proposed to introduce a core material flushing fluid into the pressure vessel interior to break the temporary bond of such a core material and thus to remove the pressure vessel core body from the interior. In particular, the core material flushing fluid is selected such that it breaks the temporary bond of the core material, or rather, converts it from a solid to a liquid state, and in particular, thereby flushes the pressure vessel core body out of the interior of the pressure vessel.Preferably, to improve the flushing of the pressure vessel core body from the interior of the pressure vessel, at least one pressure vessel core body flushing channel is provided in the pressure vessel core body, by means of which core material flushing fluid can be introduced into the pressure vessel core body and thus a particularly efficient dissolution of the pressure vessel core body is enabled.

[0015] In a preferred embodiment of the invention, a pressure vessel barrier layer is preferably applied completely or preferably partially to the pressure vessel core before the pressure vessel wall, or the fiber composite material used to form the pressure vessel wall, is applied. Preferably, the pressure vessel barrier layer is applied to the pressure vessel core at least where it will subsequently be covered by the pressure vessel wall. In particular, where a pressure vessel barrier layer is arranged between the pressure vessel wall and the pressure vessel core, the pressure vessel wall is indirectly positioned on the pressure vessel core. This pressure vessel barrier layer can preferably be applied to the pressure vessel core as a coating, and more preferably, it is applied in the form of a thin-walled film or film layer.In particular, the application of a coating enables a particularly free shaping of the pressure vessel core body; in particular, a film layer can have controlled material properties and thus provide a high level of tightness.

[0016] In a particularly preferred embodiment, the pressure vessel barrier layer has a metal coating or metal foil or is designed as such.

[0017] In a preferred embodiment, the pressure vessel wall is manufactured on the pressure vessel core body using a thermosetting wet winding process. Furthermore, a thermosetting resin system is preferably used in such a wet winding process to bond reinforcing fibers in this fiber-reinforced composite material.

[0018] In a preferred embodiment, the pressure vessel wall is produced on the pressure vessel core body by a braiding process, wherein the textile braided structure is subsequently injected with a thermoset matrix system using a resin transfer molding (RTM) process. In particular, in such a braiding process, when applying the pressure vessel wall to the pressure vessel core body, this textile braided structure is first created, and after it has been at least partially or preferably completely created, i.e., after its production, a preferably thermoset matrix system is preferably applied or injected into the textile braided structure using the RTM process.

[0019] In a preferred embodiment of the invention, the pressure vessel wall is produced on the pressure vessel core body by winding a filament material with a polymer matrix. More preferably, such a filament material with a polymer matrix can be considered a so-called fiber-reinforced composite material. In a preferred embodiment, a filament material with a polymerizing thermoplastic is used as the polymer matrix.

[0020] In a preferred embodiment of the invention, the fiber composite material of the pressure vessel wall comprises the fiber material as a component; preferably, these fibers are embedded in a polymer matrix within the pressure vessel wall. More preferably, the fiber material comprises one or more types of fibers. Preferably, "type" refers to the geometric shape of these fibers and more preferably to their composition or material. Preferably, the fiber material comprises fibers of at least one, or more preferably several, of the following types: - Carbon fibers, - Fiber optics, - Aramid fibers, - renewable fibers, - Metal fibers.

[0021] In a preferred embodiment of the invention, at least one metallic pressure vessel functional body is applied to the pressure vessel core before the pressure vessel wall is applied. For the purposes of the invention, a pressure vessel functional body is understood to be a metallic body. Preferably, the pressure vessel functional body is configured to form or provide at least one functional surface or functional area, preferably a sealing surface and more preferably a thread. Furthermore, preferably, the pressure vessel wall is applied at least partially or completely to the pressure vessel functional body. Due to the ductility of metal, such a pressure vessel functional body is particularly suitable for providing a connection for attaching a pressure line to this pressure vessel or for integrating a sensor into this pressure vessel.In figurative terms, this pressure vessel functional body can be understood in particular as a kind of metallic insert used in the manufacture of the pressure vessel wall.

[0022] Furthermore, a pressure vessel is proposed which is manufactured using a method of the type described above and wherein the pressure vessel is configured as a hydrogen pressure vessel. Preferably, the pressure vessel is manufactured as a hydrogen pressure vessel for a passenger car.

[0023] In a preferred embodiment of the invention, this pressure vessel comprises a pressure vessel functional body, wherein at least one such pressure vessel functional body has an internal thread. Preferably, this internal thread is configured for screwing in an inlet and / or outlet to this pressure vessel. More preferably, the pressure vessel functional body is materially bonded to the pressure vessel wall. Furthermore, the pressure vessel functional body is configured to allow an inlet or outlet of medium stored in the pressure vessel; preferably, an inlet and / or outlet line can be connected to the pressure vessel functional body.

[0024] The following section explains individual features and embodiments of the invention in more detail with reference to the figures, noting that combinations of features other than those shown in the figures are also possible, as shown by: Fig. 1: A sectional view of a pressure vessel during the proposed manufacturing process, Fig. 2: A sectional view of a pressure vessel during the proposed manufacturing process, Fig. 3: two different variants of the pressure vessel according to the proposed manufacturing process, Fig. 4: a highly schematic process plan for the proposed manufacturing process.

[0025] In Fig. Figure 1 depicts a pressure vessel at a stage during its manufacture using the proposed manufacturing process. The pressure vessel 1 is intended for the storage of hydrogen. At the depicted manufacturing stage, the pressure vessel core 3, shown as a dotted line, is located within the interior of the pressure vessel 2. This core fills the interior of the pressure vessel 2. The core consists of temporarily bonded sand and is completely removed from the interior of the pressure vessel 2 in a subsequent manufacturing step by breaking the temporary bond of the core material.

[0026] The pressure vessel wall 4 is directly applied to the pressure vessel core body 3. This wall consists of a fiber-reinforced composite material, in this case a carbon fiber reinforced plastic, so-called CFRP material, which was applied using a wet winding process.

[0027] Furthermore, connection pieces designed as pressure vessel functional bodies 5 are mounted on the pressure vessel core body 3. These connection pieces are covered by the pressure vessel wall 4 after the wall is placed on the pressure vessel core body 3. Both pressure vessel functional bodies 5 have an internal thread, thus enabling easy connection of such a pressure vessel to a piping system, in particular for supplying hydrogen to a motor vehicle engine.

[0028] In Fig. 2 is a further embodiment of the in Fig. The pressure vessel shown in Figure 1 is a key difference. Fig. However, the difference between the pressure vessel shown in Figure 2 and the pressure vessel shown is that it does not have any pressure vessel functional bodies; it is therefore to be understood as a pressure vessel 6 without functional parts, but it can also be manufactured using the proposed manufacturing method.

[0029] The pressure vessel wall 9 of this function-free pressure vessel 6 therefore does not cover any pressure vessel functions, but is applied to a function-free pressure vessel core body 8, which occupies the pressure vessel interior 7 of this function-free pressure vessel 6.

[0030] In Fig. 3 are partial sections of the in the Fig. 1 and Fig. 2 pressure vessels 1, 6 shown at a later stage of production, wherein the in Fig. 3 a) the pressure vessel 6 shown is the pressure vessel 6 without a functional component. Fig. 2 corresponds, however, in the Fig. 3 a) In the stage shown, the pressure vessel core body 8 has already been removed from it, so that the pressure vessel interior 7 of this function-free pressure vessel 6 is released.

[0031] After the pressure vessel wall 9 has been applied to the pressure vessel core body 8, which is in Fig. Once part 3 has been removed, the fiber composite material of the pressure vessel wall 9 is cured to achieve sufficient structural stability for further processing. The same applies to the pressure vessel wall 4, which receives additional stabilization from the pressure vessel functional body 5. The metal pressure vessel functional body 5 has an internal thread 10, thus enabling easy connection of an inlet / outlet line to the pressure vessel 1.

[0032] In Fig.Figure 4 shows a highly schematic flowchart for the proposed manufacturing process. In the proposed process for manufacturing a pressure vessel for storing hydrogen under high pressure, the first step involves providing the pressure vessel core, which has the shape of the pressure vessel interior and consists of temporarily bonded core material. In the subsequent second step 102, the pressure vessel wall is applied directly or indirectly to this pressure vessel core. This wall consists of fiber-reinforced composite material and is applied by a suitable winding or braiding process or the like. In the third step 103, the previously applied pressure vessel wall is cured or solidified at least to the point where the applied fiber-reinforced composite material exhibits sufficient structural stability for further processing.In the fourth step 104, the pressure vessel core body is removed from the pressure vessel interior; for this purpose, its temporary bond is released and it is removed from the cavity (pressure vessel interior) in the same way as a lost core in a casting process.

[0033] In other words, one aspect of the invention is to provide a "stable" core, the so-called pressure vessel core body, for the manufacture of a pressure vessel, wherein this core, with regard to its shape, corresponds, at least substantially, to the later internal volume of the pressure vessel. Furthermore, this core is only temporarily bonded and is destroyed after the wall, i.e., the so-called pressure vessel wall, of the pressure vessel has been applied to it directly or indirectly during manufacturing.In the proposed manufacturing process, this temporary bond of the core is specifically broken, and by breaking the temporary bond, the core disintegrates into "small" individual pieces or is liquefied, so that it can be removed from the pressure vessel through an opening planned for the pressure vessel, which can serve as an inlet or outlet to the interior of the pressure vessel during normal operation, thus releasing the internal volume of the pressure vessel, after the pressure vessel wall has achieved sufficient strength.

[0034] In a preferred embodiment of the invention, a so-called barrier layer is applied to the core, which can be applied as a film or as a coating. Such a barrier layer has the particularly positive effect of preventing plastic matrix components from penetrating the pores of the core, especially when the plastic matrix is ​​injected into the fibers applied to the core in a subsequent injection process. Furthermore, it results in a smooth, and in particular refined, surface on the inside of the pressure vessel, which limits the internal volume. Among other things, a composite film made of co-extruded polyamide and polyethylene, so-called EVOH film (ethyl vinyl alcohol film), or a surface sealant applied by coating the core using a spray process, has been proposed for such a barrier layer.

[0035] In a further preferred embodiment of the invention, a metallic component for providing a functional area or surface is integrated into at least one port area of ​​the pressure vessel. This metallic component is designed to contribute to stabilizing the geometry of the pressure vessel and to enable the cutting or provision of an internal thread for connecting components such as valves, pipes, and the like to the pressure vessel.

[0036] A cover layer is applied to the temporarily bonded core using a winding process known from the prior art. One possible winding process for applying the cover layer is thermosetting wet winding, but winding with a mixture of carbon fibers and thermoplastic threads is also possible. Furthermore, it is proposed to use a textile manufacturing process such as braiding for the application. Suitable fibers for applying the cover layer are windable or braidable fibers with sufficient strength; in particular, glass fibers, aramid fibers, renewable fibers, and the like are possible.

[0037] In a process step that takes place after sufficient curing of the applied top layer on the temporarily bonded core, this core is removed from the pressure vessel. To break the temporary bond of the core, a vibration process ("shaking") or a rinsing process ("flushing") or similar methods are particularly suitable.

[0038] In particular, after the removal of the temporarily bound core from the pressure vessel, the proposed manufacturing process results in a pressure tank consisting exclusively of a load-bearing layer (wall of the pressure vessel) and containing no "liner" as is known from the prior art, thus enabling a higher internal volume for such a manufactured pressure vessel and, in an application as a pressure vessel for storing hydrogen for traction propulsion in a motor vehicle, enabling a long range for hydrogen propulsion. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2021 124 236 A1

[0001]

Claims

[1] Method for manufacturing a pressure vessel (1, 6) which is designed to store a storage medium under high pressure in a pressure vessel interior (2, 7), wherein the following steps are carried out to manufacture this pressure vessel (1, 6): - Providing a pressure vessel core body (3, 8) wherein the pressure vessel core body (3, 8) corresponds at least substantially to the shape of the pressure vessel interior (2, 7) and consists substantially or entirely of a temporarily bonded core material, - direct or indirect application of a pressure vessel wall (4, 9) to this pressure vessel core body (3, 8), wherein the pressure vessel wall (4, 9) consists at least substantially of a fiber composite material, - at least partial hardening of the applied fiber composite material and thus formation of the pressure vessel wall (4, 9), - Breaking the temporary bond of the core material and thus removing the pressure vessel core body (3, 8) from the pressure vessel interior (2, 6). [2] Method according to claim 1, characterized by , that to provide the pressure vessel core body (3, 8) a granular core material is temporarily bound and thus the pressure vessel core body is formed and that the temporary bonding of this core material occurs through the application of pressure or temperature, or through the application of pressure and temperature to the granular core material. [3] Method according to any one of the preceding claims, characterized by , that to provide the pressure vessel core body (3, 8) a granular core material is temporarily bound and thus the pressure vessel core body (3, 8) is formed and that to achieve the temporary binding of this core material a core material binder is added to it. [4] Method according to any one of the preceding claims, characterized by, that to break the temporary bond of the core material of the pressure vessel core body (3, 8) a vibration stress is applied to it and thus the core material and therefore the pressure vessel core body (3, 8) is removed from the pressure vessel interior (2, 7). [5] Method according to any one of claims 1 to 3, characterized by , that the core material has a liquid-soluble material as a component or consists of it, and that in order to break the temporary bond of the core material and thus to remove the pressure vessel core body (3, 8) from the pressure vessel interior (2, 7), a core material flushing fluid is supplied to the pressure vessel interior (2, 7) and thus the pressure vessel core body (3, 8) is flushed out of the pressure vessel interior (2, 7). [6] Method according to any one of claims 1 to 5, characterized by, that before the pressure vessel wall (4, 9) is applied to the pressure vessel core body (3, 8), a pressure vessel barrier layer is applied to the latter completely or partially, so that the pressure vessel wall (4, 9), where this pressure vessel barrier layer is applied to the pressure vessel core body (3, 8), is applied directly to this and thus indirectly to the pressure vessel core body (3, 8). [7] Method according to claim 6, characterized by that the pressure vessel barrier layer is designed as or comprises a metal coating or metal foil. [8] Method according to any one of claims 1 to 7, characterized by , that the pressure vessel wall (4, 9) is manufactured on the pressure vessel core body (3, 8) by a thermosetting wet winding process. [9] Method according to any one of claims 1 to 7, characterized by, that the pressure vessel wall (4, 9) is produced on the pressure vessel core body (3, 8) by winding a winding material made of fiber material with a plastic matrix. [10] Method according to any one of claims 1 to 7, characterized by , that the pressure vessel wall (4, 9) is produced on the pressure vessel core body (3, 8) by a braiding process. [11] Method according to any one of the preceding claims, characterized by , that the material of the pressure vessel wall (4, 9) is to be understood as a fiber composite material which has as a component a fiber material with one or more types of different fibers and that these fibers are selected from at least one of the following types of fibers: - Carbon fibers, - Fiber optics, - Aramid fibers, - renewable fibers, - Metal fibers. [12] Method according to any one of the preceding claims, characterized by, that at least one metallic pressure vessel functional body (5) is applied to the pressure vessel core body (3) before the pressure vessel wall (4) is applied and that at least one pressure vessel functional body (5) is applied to the pressure vessel wall (4) at least section by section. [13] Pressure vessel manufactured by a method according to any one of claims 1 to 12, wherein the pressure vessel is configured as a hydrogen pressure vessel. [14] Pressure vessel according to claim 13, characterized by that it has at least one such pressure vessel functional body (5) with an internal thread (10).

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