Pressure tank for a gas-operated vehicle

Abstract

Proposed is a pressure tank (1) for storing gas as fuel in a gas-operated vehicle, the pressure tank having: a rotationally symmetrical elongate shape which, along the longitudinal axis L, has a cylindrical region (1a) in the middle and is closed off at both ends by a domed pole cap (1c); a metal connection piece, a so-called boss (4, 4'), on each of the pole caps (1c); and a wall which encloses a cavity (2) for storing the gas, wherein the wall comprises an internal liner (3) for sealing purposes and a reinforcement layer (6) consisting of fiber-reinforced plastics material wound in numerous plies on said liner, and wherein, in the cylindrical region (1a), the reinforcement layer (6) has three regions in the radial direction R: an inner layer (D1), a middle layer (D2) and an outer layer (D3), which are each formed from a plurality of plies.

Description

[0001] Pressure tank for QAS-powered vehicle

[0002] 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 that is cylindrical in the central region and closed at both ends by curved pole caps. At each of the two pole caps, the pressure tank has a metallic connecting piece, a so-called boss. The pressure tank has a wall that encloses a cavity for storing the gas, wherein the wall comprises an internal liner for sealing and a reinforcing layer made of fiber-reinforced plastic wound thereon in numerous layers. wherein the reinforcing layer 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 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).

[0003] Furthermore, the invention relates to a method for producing such a pressure tank.

[0004] Gas-powered vehicles, for example, are powered by a gas engine or a fuel cell with an electric motor. To store sufficient fuel, the gas, which can be hydrogen, is stored in the tank under high pressure. Operating pressures of over 200 bar are typical for such pressure tanks. This means that the pressure tank must not only be gas-tight under this pressure but also require high mechanical stability. This requires a suitable layer structure and reliable, high-quality manufacturing of the reinforcement layer.

[0005] Pressure tanks for gas-powered vehicles are known in the prior art. These pressure tanks have a wall comprising an internal liner, for example made of a thermoplastic such as polyamide, for sealing, and a reinforcement layer of fiber-reinforced plastic to provide mechanical stability. Such tanks are referred to as Type IV pressure tanks. The reinforcement layer is wound from numerous layers and is preferably constructed as a CFRP layer. Winding takes place on a winding machine by wrapping carbon fiber strands impregnated with resin, for example, epoxy resin, around the liner. The reinforcement layer is then cured through an oven annealing process. CFRP stands for carbon fiber reinforced plastic.

[0006] 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 the pressure tank to be filled or gas to be withdrawn in a controlled manner. On the other boss, the through-hole can be sealed with a cap, or an additional tank fitting or safety valve can be installed.

[0007] Particular attention must be paid to the design of the reinforcement structure for such pressure tanks, as it must meet two contradictory requirements. Firstly, it must ensure sufficient strength, which requires a high number of layers and thus a high wall thickness. Secondly, it should be designed to minimize material and weight. Furthermore, the strength of each pressure tank manufactured must be achieved with absolute reliability during the manufacturing process. No significant variation is permitted.

[0008] Solving this problem is particularly challenging for larger hydrogen pressure tanks, such as those recently required for commercial vehicles powered by fuel cells or hydrogen combustion engines. To provide sufficient range for commercial vehicles, the pressure tanks must be much larger and capable of higher pressures than the pressure tanks currently used for 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.

[0009] US Pat. No. 11,204,131 A describes a hydrogen pressure tank that can be designed for passenger cars. During production, the bosses are inserted into the liner, and then the liner is wrapped with the reinforcement layer. Numerous layers are wound at different winding angles ß. In the cylindrical region, the reinforcement layer is formed from three layers: an inner layer, a middle layer, and an outer layer, as shown in Fig. 6.

[0010] There are so-called low-angle helical layers, which have a winding angle ß between 10° and 30°, so-called high-angle helical layers, which have a winding angle ß between 40° and 70°, and so-called hoop layers with a winding angle ß of 85°-90°, which are arranged in the circumferential direction. The low-angle helical layers are necessary to cover the pole caps and to stabilize the transition area between the pole caps and the cylindrical region. The hoop layers are circumferential layers and provide the strength of the cylindrical region.

[0011] As a solution to achieve the necessary strength while saving weight, it is proposed to wind the inner and outer layers only with so-called low-angle helical layers to cover the pole caps. The high-angle helical layers do not provide any strength at the pole caps. And the middle layer is constructed from alternating at least two so-called hoop layers followed by a high-angle helical layer, since the low-angle helical layers do not provide any strength in the cylindrical area. This is considered an improvement over the previously known variant, in which a high-angle helical layer (or a hoop layer) and a low-angle helical layer are wound alternately. The state-of-the-art designs have the disadvantage that they do not reliably ensure the necessary strength, or that they require too many layers, thus making the pressure tank too heavy.

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

[0013] The object is achieved, on the one hand, 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 made up of at least 15 layers, preferably of at least 20 layers, and with regard to the winding angle ß, it comprises the following sequence, viewed from the inside to the outside: After every 4 to 6 layers with a winding angle ß in the range of 70° to 90°, there follows a layer with a winding angle ß of at most 25°, this sequence of 4 to 6 layers with a winding angle ß in the range of 70° to 90° followed by a layer with a winding angle ß of at most 25° being 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 utilizing the strength potential of the layers. Thus, the reinforcement layer is manufactured with minimal material consumption and the lowest possible weight.

[0016] Layers with a winding angle ß between 70° and 90° contribute most to the strength in the cylindrical area. However, extensive development tests have shown that the layer structure is often not good if only layers with a high winding angle are wound. The fiber strands of different layers wound on top of each other with the same or very similar winding angle slip into each other and undesirable gaps can arise. To stabilize the layer structure and more reliably ensure the desired strength properties, it is advantageous to wind a layer with a small winding angle ß of a maximum of 25° after 4 to 6 such layers. This means that the fiber strands in this layer lie almost transversely to the fiber strands in the previously wound layers. At first one might think that this intermediate layer is superfluous since it offers no strength in the circumferential direction.However, development and investigations have shown that these intermediate layers ensure that the layers wound in the circumferential direction remain optimally aligned, thus preventing unwanted gaps from forming. This is particularly advantageous when the fiber strands are wound with higher tensile stress, as this increases the risk of the wound fiber strands slipping. If this above-mentioned sequence is repeated at least three times, there are enough layers to achieve the pressure resistance of the pressure tank. The design according to the invention achieves an overall optimal combination of strength and low weight, as well as low material consumption. The pressure tanks are thus more cost-effective and can be manufactured more reliably with consistent quality.

[0017] In particular, if in the previously mentioned layer structure only exactly one layer with a winding angle ß of maximum 25° is arranged between two blocks of several layers with a winding angle ß between 70° and 90°, the layer structure can be used particularly well.

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

[0019] The invention can be used particularly advantageously when the reinforcement layer is wound from so-called towpreg tapes. These are fiber strands that are already pre-impregnated with resin and are drawn off a roll in this state and processed on the winding machine. The resin is relatively tough and cannot easily compensate for errors or gaps in the deposition of the fiber strands during the winding process. Therefore, the improvement achieved through the inventive layer sequence is particularly advantageous here.

[0020] In contrast to towpreg winding, in wet winding, dry fiber strands are drawn from a spool and soaked in a resin bath shortly before winding. The resin used for this is relatively thin, allowing the fiber strands to be completely impregnated in a short time. This allows for small gaps between the fiber strands deposited 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 is more uniform, thus achieving compressive strength more reliably and with less material.

[0021] The first and last layers, which are wound in the circumferential direction, i.e. with a winding angle ß in the range of 85° to 90°, serve to demarcate the various layers (inner (D1), middle (D2), outer (D3)) of the reinforcement layer. Viewed radially from the inside to the outside, the middle layer (D2) begins with the first layer, which is wound in the circumferential direction, i.e. has a winding angle ß in the range of 85° to 90°, and ends with the last layer, which is wound in the circumferential direction, i.e. has a winding angle ß in the range of 85° to 90°. The middle layer (D2) serves primarily to build up the circumferential strength in the cylindrical area of ​​the pressure tank; if necessary, it can also slightly reinforce the transition area to the pole caps.

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

[0023] In particular, the outer layer (D3) consists of at least 8 layers, with the outer layer accounting for 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 pole caps on the outer surface. The upper limit is important because the layers with a small winding angle ß in the cylindrical region introduce a large amount of material over their length, which does not make a significant contribution to the compressive strength in the circumferential direction.

[0024] In a further advantageous embodiment, the inner layer (D1) comprises the following sequence:

[0025] Alternating there is a layer with a winding angle ß less than 45° and a layer with a winding angle ß greater than 45°, wherein, viewed from the inside to the outside, the winding angle ß 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 ß greater than 45° to the next layer with a winding angle ß greater than 45°, and wherein this aforementioned sequence makes up at least 50% of the number of layers of the inner layer (D1).

[0026] The inner layer (D1) of a pressure tank is subject to particularly high loads. Due to the proportion of layers with a winding angle ß greater than 45°, the inner layer (D1) can also contribute to the strength in the circumferential direction. Simulations have also shown that the alternating arrangement results in particularly good and uniform coverage and layer structure in the area of ​​the pole caps and in the transition zone, thus achieving a more even load distribution across the individual layers. Individual inner layers are not overloaded, as occurs in the prior art.

[0027] This can be particularly advantageous when the inner layer (D1) consists of at least 8 layers and accounts for 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.

[0028] A further improvement of the inventive design can be achieved if there is at least one layer and a maximum of four layers whose winding angle ß changes along the longitudinal axis L, in such a way that these layers have a winding angle ß in the range of 85° to 90° in the cylindrical region and a winding angle ß in the range of 45° to 75° in the so-called transition regions between the cylindrical region and the pole cap, whereby these layers are preferably located in the middle layer (D2). Such layers are referred to as bandages. They offer improved strength in the transition region due to the lower winding angle of less than 75°. And 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 ß in a layer in a controlled manner during winding.

[0029] In the current state of the art, strength in the transition region has been achieved with continuous layers with a winding angle ß 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 thus more layers and a greater wall thickness are required to achieve sufficient strength in the cylindrical region.

[0030] On the other hand, the object is also achieved by a method according to claim 8 for producing a pressure tank according to the invention as described above. Further advantageous features are mentioned in the associated dependent method claims.

[0031] 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 ß of 70°-90°, there follows a layer with a winding angle ß of at most 25°, wherein this sequence of 4 to 6 layers with a winding angle ß in the range of 70° to 90° followed by a layer with a winding angle ß of at most 25° is repeated at least three times in the middle layer (D2). In particular, in the aforementioned layer structure, between each two blocks of several layers with a winding angle ß of 70°-90°, only exactly one layer with a winding angle ß of at most 25° is wound. The improvement through the structure according to the invention is thus implemented particularly advantageously.

[0032] The advantages of the method according to the invention arise from the previously described advantages of the pressure tank according to the invention. Of particular note is the improved reliability and consistency of the winding process.

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

[0034] The method according to the invention can be used particularly advantageously when the reinforcement layer is wound from so-called towpreg tapes, where the towpreg tapes are fiber strands pre-impregnated with resin and drawn off from a roll in this state. Here, the sequence according to the invention has a particularly positive effect, since, on the one hand, towpregs fill gaps less effectively and, on the other hand, 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 illustrated combination, but also individually combined with one another. The figures show in detail: Fig. 1 Representation of a pressure tank according to the invention

[0036] Fig.2 Schematic representation of a winding machine for a method according to the invention

[0037] Fig.3 Schematic representation of the winding angle

[0038] Fig.4 Example of a length structure of the reinforcement layer on a pressure tank according to the invention

[0039] Fig.5 Schematic representation of the bandages

[0040] The figures are described in more detail below. Like reference numerals indicate like or similar parts or components.

[0041] Fig. 1 shows the pressure tank 1 (Type IV pressure tank) manufactured according to the method and designed according to the invention, with a boss 4, 4' on each of the two pole caps. A tank fitting 5 for filling and controlled gas removal 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 internal liner 3 and a reinforcement layer 6. The liner 3 is preferably made of thermoplastic material such as polyamide. The reinforcement 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.

[0042] The pressure tank 1 is rotationally symmetrical about the longitudinal axis L and has the cylindrical region 1a in the center. At both ends, the pressure tank 1 comprises a pole cap 1c. The transition region 1b is located between the pole cap 1c and the cylindrical region 1a. The radial direction is designated R. With such pressure tanks 1, particular attention must be paid to the compressive strength on the one hand and the weight on the other. Especially with large pressure tanks, such as those required in commercial vehicles to enable a sufficient range, the optimization of these conflicting requirements is a particular challenge. Particular attention must be paid to the reliability of the winding process for the reinforcement layer 6, since this is the only way to achieve the smallest possible wall thickness d of the reinforcement layer 6 and thus the lowest possible weight.

[0043] Section A of pressure tank 1 shows an enlarged view of the wall structure, allowing the inventive design to be seen. First, the inner layer D1 is 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 ß. Together, they form the reinforcement layer 6.

[0044] It can be seen that the thickness of the middle layer D2 is greater than both the thickness of the inner layer D1 and 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: viewed radially from the inside to the outside, after 4 to 6 layers with a winding angle ß of 70°-90°, there follows a layer with a winding angle ß of at most 25°. 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 arise 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.

[0045] Fig. 2 shows a schematic view of the structure of the winding machine 20 with which the method according to the invention can be carried out. The liner 3 serves as the winding core; it is driven and rotates about the longitudinal axis L. The fiber strands 10 for building up the reinforcement layer 6 are preferably so-called Towpreg tapes, which are drawn off from the roving spools 23. They are guided via feed rollers 22 to the thread eye 21, where they are combined to form a wider tape. The thread eye 21 is pivoted about the rotation axis 24 so that the winding angle ß can be adjusted, 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 gradually deposited one on top of the 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 pole caps 1c. The middle layer D2 is primarily responsible for the circumferential strength in the cylindrical region 1a and additionally for the reinforcement of the transition regions 1b.

[0046] After the winding process, the wound pressure tank is treated in the tempering oven to cure the reinforcement layer, i.e. the resin inside.

[0047] Fig. 3 shows an example of how the fiber strands 10 are deposited onto the already wound layers 11 at different winding angles ß. The fiber strand with the winding angle ß2 represents a layer with ß<45° or ß<25°. The fiber strand with the winding angle ß1 represents a layer with ß greater than 45°. The maximum value for the winding angle is ß = 90°, at which a layer is created exactly in the circumferential direction.

[0048] In this description, the winding angle ß is always given as a positive value, i.e. as an absolute value, regardless of the direction in which the winding angle deviates from the longitudinal axis L.

[0049] Fig. 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 to the outside. The middle layer D2 begins with the first layer, which is wound in the circumferential direction with a winding angle β between 85° and 90° (layer 13 in the example shown), and ends with the last layer, which is wound in the circumferential direction 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 has four consecutive layers of 4 to 6 layers with a winding angle β between 70° and 90°, followed by a layer with a winding angle β of no more than 25°.Between two blocks of layers with a winding angle ß between 70° and 90° there is exactly one layer with a winding angle ß of at most 25°. The transverse layers with a winding angle ß of at most 25° ensure that the fiber strands in the layers with a winding angle ß between 70° and 90° do not slip, and thus guarantee 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 - and thus no unnecessary weight and no unnecessary material expenditure is created.

[0050] In this example, the outer layer D3 consists of 8 layers, all wound at a maximum winding angle ß of 30°. This is advantageous for achieving good coverage of the pole caps 1c on the surface of the pressure tank while requiring minimal material.

[0051] 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 ß less than 45° and with a winding angle ß greater than 45°, whereby the winding angle ß 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 ß greater than 45° to the next layer with a winding angle ß greater than 45°. For layers 8 and 9, as well as 10 and 11, double layers are wound, each with approximately the same winding angle. Alternatively, two layers can always be wound with approximately the same winding angle before changing from less than 45° to greater than 45°.

[0052] 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 allows for thinner wall thicknesses and thus less weight for a pressure tank of a given size and specification.

[0053] Fig. 5 shows the further improved design with so-called bandages. In the middle layer D2, one or more layers (two layers are shown here) are wound in such a way that the winding angle ß in this layer changes across the longitudinal axis L, namely such that the winding angle ß in the cylindrical region 1 a lies between 85° and 90° (fiber strands not shown here) and the winding angle ß ' in the transition region 1 b lies between 45° and 75°. This allows the transition region 1 b to be reinforced without winding material over the entire length, which does not optimally contribute to strength in the circumferential direction. This offers enormous weight savings, especially for long pressure tanks.

[0054]

[0055] 1 Pressure tank 1 a cylindrical area 1 b transition area 1 c polar cap

[0056] 2 cavity

[0057] 3 liners

[0058] 4, 4' Boss

[0059] 5 Tank fitting

[0060] 6 Reinforcement layer

[0061] 10 fiber strands

[0062] 11 wrapped layers

[0063] 20 winding machine

[0064] 21 Thread eye

[0065] 22 feed rollers

[0066] 23 roving spools

[0067] 24 Axis of rotation of the thread eye d Wall thickness of the reinforcement layer

[0068] D1 Inner layer

[0069] D2 Middle Layer

[0070] D3 Outer layer

[0071] Hoop Hoop position

[0072] HA High Angle Helical Position

[0073] LA Low Angle Helical Position

[0074] L Longitudinal axis of the pressure tank

[0075] R Radial direction of the pressure tank ß Winding angle n Number of layers

Claims

Patent claims 1. A pressure tank (1) for storing gas as fuel in a gas-powered vehicle, having a rotationally symmetrical, elongated shape, which has a cylindrical region (1a) in the center 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'), 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 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 in that the middle layer (D2) is constructed from at least 15 layers, preferably from at least 20 layers, and with regard to the winding angle ß, comprises the following sequence, viewed from the inside outwards: After every 4 to 6 layers with a winding angle ß in the range of 70° to 90°, there follows a layer with a winding angle ß of at most 25°, wherein this sequence of 4 to 6 layers with a winding angle ß in the range of 70° to 90° followed by a layer with a winding angle ß of at most 25° is repeated at least three times in the middle layer (D2).

2. Pressure tank (1) according to claim 1, characterized in 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 in that the outer layer (D3) consists of at least 80% of layers with a winding angle ß of at most 30°.

4. Pressure tank (1) according to one of the preceding claims, characterized in that the outer layer (D3) 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).

5. Pressure tank (1) according to one of the preceding claims, characterized in that the inner layer (D1) comprises the following sequence: Alternating there is a layer with a winding angle ß less than 45° and a layer with a winding angle ß greater than 45°, wherein, viewed from the inside to the outside, the winding angle ß 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 ß greater than 45° to the next layer with a winding angle ß 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 in 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 in that there is at least one layer and a maximum of four layers, the winding angle ß of which changes along the longitudinal axis L, such that these layers have a winding angle ß in the range of 85° to 90° in the cylindrical region (1a) and in the so-called transition regions (1b), between the cylindrical region (1 a) and the pole cap (1 c), have a winding angle ß in the range of 45° to 75°, these layers preferably being 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 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 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 outwards,has: After 4 to 6 layers with a winding angle ß of 70°-90°, there follows a layer with a winding angle ß of at most 25°, whereby this sequence of 4 to 6 layers with a winding angle ß in the range of 70° to 90° followed by a layer with a winding angle ß of at most 25° is repeated at least three times in the middle layer (D2).

9. Method according to claim 8, characterized in that at least one layer and a maximum of four layers are wound, the winding angle ß of which changes along the longitudinal axis L, such that these layers have a winding angle ß in the range from 85° to 90° in the cylindrical region (1a) and a winding angle ß 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 in 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 drawn off from a roll in this state.

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