Pressure tank for gas-powered vehicle

Abstract

Pressure tank (1) for storing gas as fuel in a gas-powered vehicle, having a rotationally symmetrical, elongated shape, with a cylindrical region (1a) in the middle along the longitudinal axis L and terminated at both ends with a domed pole cap (1c), which has a metallic connector, a so-called boss (4,4') at each of the pole caps (1c), and which has a wall enclosing a cavity (2) for storing the gas, wherein the wall comprises an inner liner (3) for sealing and a reinforcing layer (6) of fiber-reinforced plastic wound thereon in numerous layers, and wherein the reinforcing layer (6) in the cylindrical region (1a) has three regions in the radial direction R: an inner layer (D1), a middle layer (D2) and an outer layer (D3), each formed from several layers,wherein the inner layer (D1) and the outer layer (D3) each comprise at least 5 layers, and wherein the middle layer (D2) comprises more layers than both the inner layer (D1) and the outer layer (D3), wherein the middle layer (D2) is composed of at least 15 layers, preferably at least 20 layers, and comprises the following sequence with respect to the winding angle β, viewed from the inside out: After every 4 to 6 layers with a winding angle β in the range of 70° to 90°, a layer with a winding angle β of at most 25° follows, and wherein this sequence of 4 to 6 layers with a winding angle β in the range of 70° to 90° followed by a layer with a winding angle β of at most 25° is repeated at least three times in the middle layer (D2).

Description

[0001] The invention relates to a pressure tank for storing gas as fuel in a gas-powered vehicle, wherein the pressure tank has a rotationally symmetrical, elongated shape, cylindrical in its central region and terminated at both ends with domed end caps. At each of the two end caps, the pressure tank has a metallic connection piece, a so-called boss. The pressure tank has a wall that encloses a cavity for storing the gas, the wall comprising an inner liner for sealing and a reinforcing layer of fiber-reinforced plastic wound thereon in numerous layers, the reinforcing layer having three regions in the cylindrical region in the radial direction R: an inner layer (D1), a middle layer (D2), and an outer layer (D3), each formed from several layers.wherein the inner layer (D1) and the outer layer (D3) each comprise at least 5 layers, and wherein the middle layer (D2) comprises more layers than both the inner layer (D1) and the outer layer (D3).

[0002] Furthermore, the invention relates to a method for manufacturing such a pressure tank.

[0003] Gas-powered vehicles, for example, use a gas engine or a fuel cell with an electric motor as their drive system. To store sufficient fuel, the gas, which can include hydrogen, is stored under high pressure in the tank. Typical operating pressures for such pressure tanks exceed 200 bar. This means that the pressure tank must not only be gas-tight under this pressure, but also possess high mechanical stability. This requires a suitable layer structure and reliable, high-quality manufacturing of the reinforcing layer.

[0004] Pressure tanks for gas-powered vehicles are known in the prior art. These pressure tanks have a wall that includes an inner liner, for example made of thermoplastic such as polyamide, for sealing purposes, and a reinforcing layer made of fiber-reinforced plastic to provide mechanical stability. Such tanks are referred to as Type IV pressure tanks. The reinforcing layer is wound from numerous layers and is preferably made of CFRP (carbon fiber reinforced polymer). Winding is carried out on a winding machine by wrapping strands of carbon fibers impregnated with resin, for example epoxy resin, around the liner. The reinforcing layer is then cured by an oven curing process. CFRP stands for carbon fiber reinforced plastic.

[0005] The boss has a through-hole and an internal thread for connection. At least one of the two bosses is designed to accommodate a tank valve, allowing for filling the pressure tank or controlled gas withdrawal. The through-hole on the other boss may be sealed with a cap, or it may be equipped with an additional tank fitting or a safety valve.

[0006] Particular attention must be paid to the design of the reinforcement structure in such pressure tanks, as it must meet two conflicting requirements. On the one hand, it must ensure sufficient strength, which necessitates a high number of layers and thus a thick wall; on the other hand, it should be designed to be as material- and weight-efficient as possible. Furthermore, the required strength must be achieved with absolute reliability in every manufactured pressure tank throughout the production process. Significant variation is unacceptable.

[0007] Solving this problem is particularly challenging for larger hydrogen pressure tanks, such as those now required for commercial vehicles powered by fuel cells or hydrogen combustion engines. To provide sufficient range for these vehicles, the pressure tanks must be significantly larger and designed for higher pressures than the pressure tanks used in passenger cars. Such hydrogen pressure tanks for commercial vehicles can reach diameters of up to 600 mm and lengths of up to 2500 mm, and are designed for pressures of up to 700 bar, and in some cases even up to 850 bar.

[0008] US Patent 11,204,131A describes a hydrogen pressure tank suitable for passenger vehicles. For its manufacture, bosses are inserted into the liner, and then the liner is wrapped with a reinforcing layer. This involves winding numerous layers with varying winding angles β. In the cylindrical section, the reinforcing layer consists of three layers: an inner layer, a middle layer, and an outer layer, as described in the patent. Fig. 6 is shown.

[0009] There are so-called low-angle helical layers, which have a winding angle β between 10° and 30°; so-called high-angle helical layers, which have a winding angle β between 40° and 70°; and so-called hoop layers with a winding angle β of 85°–90°, which run circumferentially. The low-angle helical layers are necessary to cover the polar caps and to stabilize the transition zone between the polar caps and the cylindrical area. The hoop layers are circumferential layers and provide the strength of the cylindrical area.

[0010] As a solution to achieve the necessary strength while saving weight, it is proposed that the inner and outer layers each be wound only with so-called low-angle helical layers to cover the polar caps. High-angle helical layers offer no strength at the polar caps. The middle layer is constructed alternately from at least two so-called hoop layers followed by a high-angle helical layer, since low-angle helical layers offer no strength in the cylindrical area. This is considered an improvement over the previously known method, in which a high-angle helical layer (or a hoop layer) and a low-angle helical layer were wound alternately.

[0011] The state-of-the-art designs have the disadvantage that they do not reliably guarantee the necessary strength, or that they require too many layers, making the pressure tank too heavy.

[0012] The object of the invention is now to develop a manufacturing process and a pressure tank that has an improved layer structure of the reinforcement layer in order to ensure high reliability in manufacturing and thus achieve sufficient strength with the lowest possible weight.

[0013] The problem is solved, firstly, by a pressure tank according to claim 1. Further advantageous features are mentioned in the respective dependent claims.

[0014] According to the invention, the pressure tank according to claim 1 is characterized in that the middle layer (D2) is composed of at least 15 layers, preferably at least 20 layers, and comprises the following sequence with respect to the winding angle β, viewed from the inside out: After every 4 to 6 layers with a winding angle β in the range of 70° to 90°, a layer with a winding angle β of at most 25° follows, wherein this sequence of 4 to 6 layers with a winding angle β in the range of 70° to 90° followed by a layer with a winding angle β of at most 25° is repeated at least three times in the middle layer (D2).

[0015] The advantage of this sequence is that it ensures a uniform structure of the middle layer (D2) while simultaneously optimally utilizing the strength potential of the layers. This results in a very material-efficient and lightweight reinforcement layer.

[0016] Layers with a winding angle β between 70° and 90° contribute most to strength in cylindrical sections. However, extensive development tests have shown that the layer structure is often suboptimal when only layers with high winding angles are wound. Fiber strands from different layers wound with the same or very similar winding angles tend to slip into each other, potentially creating undesirable gaps. To stabilize the layer structure and more reliably ensure the desired strength properties, it is advantageous to wind a layer with a low winding angle β of no more than 25° after every four to six such layers. In this layer, the fiber strands are positioned almost perpendicular to the fiber strands in the previously wound layers. Initially, one might think this intermediate layer is superfluous, as it offers no circumferential strength.However, development and investigations have shown that these intermediate layers ensure that the circumferentially wound layers remain optimally positioned, thus preventing the formation of undesirable gaps. This is particularly advantageous when the fiber strands are wound with higher tensile stress, as the risk of slippage increases in such cases. Repeating this sequence at least three times provides enough layers to achieve the required pressure resistance of the pressure tank. The design according to the invention achieves an optimal combination of strength and low weight, or rather, low material consumption. This makes the pressure tanks more cost-effective and allows for more reliable production with consistent quality.

[0017] The layer structure is particularly suitable when, in the aforementioned layer structure, only exactly one layer with a winding angle β of a maximum of 25° is arranged between each pair of blocks of several layers with a winding angle β between 70° and 90°.

[0018] Another advantage of the embodiment according to the invention is that, due to this layer structure, the transition areas have a relatively thin wall thickness overall, and thus a lower bending moment acts in the reinforcement layer.

[0019] The invention can be particularly advantageous when the reinforcing layer is wound from so-called towpreg tapes. These are fiber strands that are already pre-impregnated with resin and are unwound from a roll in this state and processed on the winding machine. The resin is relatively viscous and cannot easily compensate for errors or gaps in the placement of the fiber strands during the winding process. Therefore, the improvement provided by the inventive layer sequence is particularly beneficial in this case.

[0020] In contrast to towpreg winding, the so-called wet winding process involves unwinding dry fiber strands from a spool and impregnating them in a resin bath shortly before winding. The resin used is relatively low in viscosity to ensure that the fiber strands are completely impregnated within this short time. This allows any small gaps between the fiber strands laid down during winding to be filled with resin. However, the sequence according to the invention also offers significant advantages in wet winding, as the structure of the reinforcement layer becomes more uniform, resulting in more reliable compressive strength and the use of less material.

[0021] The first and last layers of the reinforcement layer, wound circumferentially with a winding angle β in the range of 85° to 90°, serve to delineate the different layers (inner (D1), middle (D2), outer (D3)). Thus, radially from the inside out, the middle layer (D2) begins with the first layer wound circumferentially, i.e., with a winding angle β in the range of 85° to 90°, and ends with the last layer wound circumferentially, i.e., with a winding angle β in the range of 85° to 90°. The middle layer (D2) primarily serves to build up circumferential strength in the cylindrical area of ​​the pressure tank; if necessary, it can also slightly reinforce the transition area to the polar caps.

[0022] Furthermore, it is preferred that the outer layer (D3) consists of at least 80% layers with a winding angle β of at most 30°. This results in a uniform outer surface of the pressure tank, particularly also at the transition areas between the pole cap and the cylindrical section. The arrangement according to the invention in the cylindrical section already provides sufficient pressure resistance in the circumferential direction.

[0023] In particular, the outer layer (D3) consists of at least 8 layers, comprising at least 20% but no more than 35% of the total number of layers in the reinforcement layer. The lower limit is necessary to ensure sufficient coverage of the polar caps on the outer surface. The upper limit is important because the layers with a small winding angle β in the cylindrical region introduce a significant amount of material along their length, which does not substantially contribute to the compressive strength in the circumferential direction.

[0024] In a further advantageous embodiment, the inner layer (D1) comprises the following sequence: There is an alternating layer with a winding angle β less than 45° and a layer with a winding angle β greater than 45°, wherein, viewed from the inside out, the winding angle β decreases from one layer with a winding angle less than 45° to the next layer with a winding angle less than 45° and increases from one layer with a winding angle β greater than 45° to the next layer with a winding angle β greater than 45°, and wherein this aforementioned sequence constitutes at least 50% of the number of layers of the inner layer (D1).

[0025] The inner layer (D1) of the pressure tank is subjected to particularly high stress. Due to the proportion of layers with a winding angle β greater than 45°, the inner layer (D1) can also contribute to the circumferential strength. Simulations have also shown that the alternating arrangement results in particularly good and uniform coverage and layer structure in the polar cap and transition areas, thus achieving a more even load distribution across the individual layers. Individual inner layers are not overloaded, as occurs in prior art.

[0026] This can be particularly advantageous when the inner layer (D1) consists of at least 8 layers and comprises at least 20% but no more than 35% of the total number of layers in the reinforcement layer. This achieves an optimal combination of reliable strength and coverage on the one hand, and weight optimization on the other.

[0027] A further improvement of the embodiment according to the invention can be achieved if there is at least one layer and a maximum of four layers whose winding angle β changes along the longitudinal axis L, such that these layers have a winding angle β in the range of 85° to 90° in the cylindrical region and a winding angle β in the range of 45° to 75° in the so-called transition regions between the cylindrical region and the pole cap, with these layers preferably being located in the middle layer (D2). Such layers are referred to as a bandage. They offer improved strength in the transition region due to the lower winding angle of less than 75°. At the same time, with the higher winding angle of at least 85°, they fully contribute to the circumferential strength in the cylindrical region. Modern winding machines make it possible to adjust the winding angle β in a layer in a controlled manner during winding.

[0028] In the prior art, the strength in the transition region is achieved using continuous layers with a winding angle β in the range of 45° to 75°. However, this leads to an increase in weight in the cylindrical region, as these layers contribute less to the circumferential strength, and therefore more layers and a greater wall thickness are required to achieve sufficient strength in the cylindrical region.

[0029] On the other hand, the problem is also solved by a method according to claim 8 for manufacturing a pressure tank according to the invention as described above. Further advantageous features are mentioned in the corresponding dependent method claims.

[0030] The method according to the invention is characterized in that the middle layer (D2) is wound from at least 15 layers, preferably from at least 20 layers, and has the following layer structure, viewed from the inside out: After 4 to 6 layers with a winding angle β of 70°-90°, a layer with a winding angle β of at most 25° follows, wherein this sequence of 4 to 6 layers with a winding angle β in the range of 70° to 90° followed by a layer with a winding angle β of at most 25° is repeated at least three times in the middle layer (D2).

[0031] In particular, in the aforementioned layer structure, only exactly one layer with a winding angle β of at most 25° is wound between each pair of blocks of several layers with a winding angle β of 70°–90°. This is a particularly advantageous way in which the improvement achieved by the structure according to the invention is implemented.

[0032] The advantages of the method according to the invention result from the advantages already described for the pressure tank according to the invention. Particularly noteworthy is the improved reliability and consistency of the winding process.

[0033] Furthermore, it is advantageous to wrap one or more so-called bandages. For this purpose, at least one layer and a maximum of four layers are wrapped, the winding angle β of which changes along the longitudinal axis L, such that these layers have a winding angle β in the range of 85° to 90° in the cylindrical area and a winding angle β in the range of 45° to 75° in the so-called transition areas between the cylindrical area and the pole cap, with these layers preferably being located in the middle layer (D2).

[0034] The inventive method can be applied particularly advantageously when the reinforcing layer is wound from so-called towpreg tapes, wherein the towpreg tapes are already resin-impregnated fiber strands that are unwound from a roll in this state. Here, the sequence according to the invention has a particularly positive effect, since, firstly, towpregs do not fill gaps as well and, secondly, towpregs are often wound with higher tensile stress.

[0035] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. These features can be advantageously implemented not only in the combination shown, but also individually combined with one another. The figures show in detail: Fig. 1 Illustration of a pressure tank according to the invention Fig. 2 Schematic representation of a winding machine for a method according to the invention Fig. 3 Schematic representation of the winding angles Fig. 4 Example of a linear structure of the reinforcement layer on a pressure tank according to the invention Fig. 5 Schematic representation of the bandages

[0036] The figures are described in more detail below. Identical reference numbers denote identical or analogous parts or components.

[0037] The Fig. Figure 1 shows the pressure tank 1 (Type IV pressure tank) produced and designed according to the inventive method and design, with a boss 4, 4' at each of the two end caps. A tank fitting 5 for filling and controlled gas withdrawal is screwed into the boss 4. The boss 4' is sealed with a closure. Alternatively, it can accommodate a safety valve or another tank fitting. The wall of the pressure tank 1 encloses the cavity 2 and is formed by an inner liner 3 and a reinforcing layer 6. The liner 3 is preferably made of thermoplastic material such as polyamide. The reinforcing layer 6 is produced by a winding process with fiber strands made of fiber-reinforced plastic, preferably CFRP. In particular, the fiber strands are so-called towpreg tapes, in which the fiber strands are already pre-impregnated with resin and are thus unwound from a roll.After winding, the reinforcement layer 6 is cured in a tempering process.

[0038] The pressure tank 1 is rotationally symmetric about the longitudinal axis L and has a cylindrical region 1a in its center. At both ends, the pressure tank 1 comprises a pole cap 1c. Between the pole cap 1c and the cylindrical region 1a is a transition region 1b. The radial direction is denoted by R.

[0039] With such pressure tanks 1, particular attention must be paid to both pressure resistance and weight. Optimizing these conflicting requirements is a particular challenge, especially for large pressure tanks like those needed in commercial vehicles to ensure sufficient range. Particular attention must be paid to the reliability of the winding process for the reinforcement layer 6, as this is the only way to achieve the smallest possible wall thickness d of the reinforcement layer 6 and thus the lowest possible weight.

[0040] Section A of the pressure tank 1 shows an enlarged view of the wall structure, so that the embodiment according to the invention becomes apparent. The inner layer D1 is first wound onto the liner 3, followed by the middle layer D2, and then the outer layer D3. The three layers D1, D2, and D3 each consist of several layers of wound fiber strands wound at different winding angles β. Together they form the reinforcing layer 6.

[0041] It can be seen that the thickness of the middle layer D2 is greater than both the thickness of the inner layer D1 and that of the outer layer D3. According to the invention, the middle layer D2 has a layer structure in which the following sequence of layers is repeated at least three times: radially from the inside out, after 4 to 6 layers with a winding angle β of 70°–90°, a layer with a winding angle β of at most 25° follows. This layer structure significantly improves the uniformity and thus the quality of the reinforcement layer compared to the prior art. Because the fiber strands cannot slip as much between the fiber strands of the previously wound layers, fewer defects occur during winding, and thus the wall thickness d of the reinforcement layer 6 can be reduced without the risk of the desired compressive strength not being reliably achieved.

[0042] Fig. Figure 2 schematically shows the setup of the winding machine 20 with which the method according to the invention can be carried out. The liner 3, which is driven and rotates about the longitudinal axis L, serves as the winding core. The fiber strands 10 for building up the reinforcement layer 6 are preferably so-called towpreg tapes, which are unwound from the roving spools 23. They are guided to the yarn eye 21 via feed rollers 22 and there joined together to form a wider tape. The yarn eye 21 is pivoted about the axis of rotation 24 so that the winding angle β can be set, at which the fiber strands 10 are wound onto the winding core, in this case onto the liner 3. In this way, several wound layers 11 are successively laid on top of each other on the liner 3, thus building up the reinforcement layer 6. First, the inner layer D1 is wound, then the middle layer D2, and finally the outer layer D3.The inner layer D1 and the outer layer D3 are wound in such a way that they also cover the polar caps 1c. The middle layer D2 is primarily responsible for the circumferential strength in the cylindrical area 1a and additionally for reinforcing the transition areas 1b.

[0043] After the winding process, the wound pressure tank is treated in a tempering oven to harden the reinforcement layer, i.e., the resin inside.

[0044] In Fig. Figure 3 illustrates how the fiber strands 10 are laid onto the already wound layers 11 at different winding angles β. The fiber strand with winding angle β2 represents a layer with β < 45° or β < 25°. The fiber strand with winding angle β1 represents a layer with β greater than 45°. The maximum winding angle is β = 90°, at which a layer is created exactly in the circumferential direction.

[0045] In this description, the winding angle β is always given as a positive value, that is, as a magnitude, regardless of the direction in which the winding angle deviates from the longitudinal axis L.

[0046] Fig. Figure 4 shows the winding diagram for a possible layer structure of the reinforcement layer 6 for a pressure tank according to the invention. The winding angle β is plotted against the number of layers n, with the number of layers being counted radially from the inside out.

[0047] The middle layer D2 begins with the first layer, which is wound circumferentially with a winding angle β between 85° and 90° (layer 13 in the example shown), and ends with the last layer, which is also wound circumferentially with a winding angle β between 85° and 90° (layer 37 in the example shown). This means that in this example, the middle layer D2 consists of 25 layers. It contains four consecutive sequences of 4 to 6 layers with a winding angle β between 70° and 90°, followed by a layer with a winding angle β of at most 25°. Between each set of layers with a winding angle β between 70° and 90°, there is only one layer with a winding angle β of at most 25°.The transverse layers with a winding angle β of at most 25° ensure that the fiber strands in the layers with a winding angle β between 70° and 90° do not slip, thus guaranteeing a stable, uniform structure of the reinforcement layer 6. The design according to the invention achieves a particularly reliable result in the winding process, so that the wall thickness d can be reduced to a minimum – depending on the desired compressive strength and size of the pressure tank – thereby avoiding unnecessary weight and material expenditure.

[0048] In this example, the outer layer D3 consists of 8 layers, all wound with a winding angle β of no more than 30°. This is advantageous for achieving good coverage of the polar caps 1c on the surface of the pressure tank while requiring minimal material.

[0049] In the example shown, the inner layer D1 consists of 12 wound layers. From the second to the eighth layer, these are wound alternately with a winding angle β less than 45° and with a winding angle β greater than 45°, whereby the winding angle β decreases from one layer with a winding angle less than 45° to the next layer with a winding angle β greater than 45°, and increases from one layer with a winding angle β greater than 45° to the next layer with a winding angle β greater than 45°. Layers 8 and 9, as well as 10 and 11, are double layers wound, each with approximately the same winding angle.

[0050] Alternatively, two layers can always be wound with approximately the same winding angle before switching from less than 45° to greater than 45°.

[0051] The alternating structure of the inner layer D1 allows for a more even load distribution across the different layers, significantly reducing the risk of overloading individual layers. This also enables a thinner wall thickness and therefore less weight for a pressure tank of a given size and specification.

[0052] Fig.Figure 5 shows a further improved version with so-called bandages. In this design, one or more layers (two layers are shown here) are wound in the middle layer D2 such that the winding angle β changes along the longitudinal axis L in this layer. Specifically, the winding angle β in the cylindrical region 1a lies between 85° and 90° (fiber strands not shown here), and the winding angle β' in the transition region 1b lies between 45° and 75°. This allows the transition region 1b to be reinforced without wrapping the entire length with material that does not optimally contribute to circumferential strength. This offers enormous weight savings, especially for long pressure tanks. Reference symbol list 1 pressure tank 1a cylindrical area 1b Transition area 1c Polarizing cap 2 cavities 3 Liner 4, 4' Boss 5 Tank fitting 6 Reinforcing layer 10 fiber strands 11 wound layers 20 winding machine 21 Thread eye 22 feed rollers 23 roving spools 24 Axis of rotation of the thread eye d wall thickness of the reinforcing layer D1 Inner layer D2 Middle layer D3 Outer layer Hoop Hoop position HA High Angle Helical Position LA Low Angle Helical Position L Longitudinal axis of the pressure tank R Radial direction of the pressure tank β winding angle n layer number QUOTES CONTAINED 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] US 11,204,131 A

[0008]

Claims

[1] Pressure tank (1) for storing gas as fuel in a gas-powered vehicle, which has a rotationally symmetrical, elongated shape, which has a cylindrical region (1a) in the middle along the longitudinal axis L and is closed at both ends by a curved pole cap (1c), which has a metallic connecting piece, a so-called boss (4, 4'), on each of the pole caps (1c), and which has a wall enclosing a cavity (2) for storing the gas, wherein the wall comprises an internal liner (3) for sealing and a reinforcing layer (6) made of fiber-reinforced plastic wound thereon in numerous layers, and wherein the reinforcing layer (6) in the cylindrical region (1a) has three regions in the radial direction R: an inner layer (D1), a middle layer (D2) and an outer layer (D3), each formed from several layers,wherein the inner layer (D1) and the outer layer (D3) each comprise at least 5 layers, and wherein the middle layer (D2) comprises more layers than both the inner layer (D1) and the outer layer (D3), , characterized by that the middle layer (D2) is made up of at least 15 layers, preferably of at least 20 layers, and with regard to the winding angle β, comprises the following sequence, viewed from the inside outwards: after every 4 to 6 layers with a winding angle β in the range from 70° to 90°, there follows a layer with a winding angle β of at most 25°, this sequence of 4 to 6 layers with a winding angle β in the range from 70° to 90° followed by a layer with a winding angle β of at most 25° being repeated at least three times in the middle layer (D2). [2] Pressure tank (1) according to claim 1 characterized by that the reinforcement layer (6) is wound from so-called Towpreg tapes, which are fiber strands already pre-impregnated with resin. [3] Pressure tank (1) according to one of claims 1 or 2 characterized by that the outer layer (D3) consists of at least 80% layers with a winding angle β of not more than 30°. [4] Pressure tank (1) according to one of the preceding claims characterized by that the outer layer (D3) consists of at least 8 layers and represents at least 20% but a maximum of 35% of the number of all layers of the reinforcement layer (6). [5] Pressure tank (1) according to one of the preceding claims characterized by that the inner layer (D1) comprises the following sequence: Alternating there is a layer with a winding angle β less than 45° and a layer with a winding angle β greater than 45°, wherein, viewed from the inside to the outside, the winding angle β decreases on the one hand from a layer with a winding angle less than 45° to the next layer with a winding angle less than 45° and on the other hand increases from a layer with a winding angle β greater than 45° to the next layer with a winding angle β greater than 45°, and wherein this aforementioned sequence makes up at least 50% of the number of layers of the inner layer (D1). [6] Pressure tank (1) according to one of the preceding claims characterized by that the inner layer (D1) consists of at least 8 layers and accounts for at least 20% but a maximum of 35% of the number of all layers of the reinforcement layer (6). [7] Pressure tank (1) according to one of the preceding claims characterized bythat there is at least one layer and a maximum of four layers whose winding angle β changes along the longitudinal axis L, such that these layers have a winding angle β in the range from 85° to 90° in the cylindrical region (1a) and a winding angle β in the range from 45° to 75° in the so-called transition regions (1b), between the cylindrical region (1a) and the pole cap (1c), wherein these layers are preferably located in the middle layer (D2). [8] A method for producing a pressure tank (1) according to one of the preceding claims, wherein the wall comprises an inner liner (3) for sealing and a reinforcing layer (6) made of fiber-reinforced plastic wound thereon in numerous layers, and wherein the reinforcing layer (6) has three regions in the cylindrical region in the radial direction R: an inner layer (D1), a middle layer (D2) and an outer layer (D3), each formed from a plurality of layers, wherein the inner layer (D1) and the outer layer (D3) each comprise at least 5 layers, and wherein the middle layer (D2) comprises more layers than both the inner layer (D1) and the outer layer (D3), characterized bythat the middle layer (D2) is wound from at least 15 layers, preferably from at least 20 layers, and has the following layer structure, viewed from the inside to the outside: after 4 to 6 layers with a winding angle β of 70°-90°, there follows a layer with a winding angle β of at most 25°, this sequence of 4 to 6 layers with a winding angle β in the range from 70° to 90° followed by a layer with a winding angle β of at most 25° being repeated at least three times in the middle layer (D2). [9] Method according to claim 8 characterized bythat at least one layer and a maximum of four layers are wound, the winding angle β of which changes along the longitudinal axis L, such that these layers have a winding angle β in the range from 85° to 90° in the cylindrical region (1a) and a winding angle β in the range from 45° to 75° in the so-called transition regions (1b), between the cylindrical region (1a) and the pole cap (1c), wherein these layers are preferably located in the middle layer (D2). [10] Method according to one of claims 8 or 9, characterized by that the reinforcement layer (6) is wound from so-called Towpreg tapes, wherein the Towpreg tapes are fiber strands already pre-impregnated with resin, which are pulled off a roll in this state.

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