DE102024108881A1 - Method for producing a high-pressure tank for a motor vehicle, high-pressure tank for a motor vehicle and motor vehicle - Google Patents

Abstract

The invention relates to a method for producing a high-pressure tank (10) for a motor vehicle, comprising the steps of: inserting a tubular insert element (18) into a cavity (20) enclosed by a tank shell (12), wherein an outer diameter of the insert element (18) is smaller at its respective ends (24) than in a central region (26) along the longitudinal direction of extent, and applying the insert element (18) to an inner wall (32) of the tank shell (12) delimiting the cavity (20) by internal high-pressure forming of the insert element (18), whereby the insert element (18) delimits a tank volume (34) in which a fuel for the motor vehicle can be accommodated, wherein the insert element (18) completely covers the inner wall (32) of the tank shell (12) towards the tank volume (34).

Description

The invention relates to a method for producing a high-pressure tank for a motor vehicle, a high-pressure tank for a motor vehicle and a motor vehicle.

The DE 10 2009 042 401 A1 discloses a high-pressure tank with closure pieces, a liner, and a reinforcement layer disposed on the liner, wherein the liner includes a gas barrier layer. This high-pressure tank is filled with hydrogen gas for a fuel cell.

Furthermore, the DE 10 2016 220 995 A1 A pressure vessel for storing fuel is known, which comprises a liner and a fiber-reinforced layer that at least partially surrounds the liner. Furthermore, the pressure vessel comprises an end piece, wherein the end piece is at least partially covered by the fiber-reinforced layer. Furthermore, the pressure vessel comprises at least one outlet for discharging fuel that has accumulated in a boundary layer between the liner and the fiber-reinforced layer and is to be drained. The outlet surrounds the end piece at least partially. The outlet is arranged and designed such that the fuel to be drained escapes from the boundary layer into the outlet.

The object of the present invention is to provide a solution by means of which a particularly stable and particularly lightweight high-pressure tank for a motor vehicle can be created.

This object is achieved according to the invention by the subject matter of the independent claims. Further possible embodiments of the invention are disclosed in the subclaims, the description, and the figures. Features, advantages, and possible embodiments presented in the description for one of the subject matter of the independent claims are to be regarded at least analogously as features, advantages, and possible embodiments of the respective subject matter of the other independent claims, as well as any possible combination of the subject matter of the independent claims, optionally in conjunction with one or more of the subclaims.

The invention relates to a method for producing a high-pressure tank for a motor vehicle, in particular a motor vehicle, in particular a passenger car. The high-pressure tank is particularly designed to store a fuel, in particular a gaseous fuel. The high-pressure tank can, in turn, provide this stored fuel to a drive device of the motor vehicle, whereby the motor vehicle can be driven by means of the fuel from the high-pressure tank. In particular, the high-pressure tank is designed to store the fuel at a pressure of at least 100 bar, in particular at a pressure of at least 200 bar, in particular at a pressure of at least 600 bar. Within the scope of the method for producing the high-pressure tank, a tubular insert element is inserted into a cavity enclosed by a tank shell. An outer diameter of the insert element is smaller at its respective ends than in a central region along the longitudinal direction. This means that the insert element can have the shape of a cigar and thus has a larger outer diameter in the central region than at its respective ends.

The method further provides for the insert element to be applied to an inner wall of the tank shell bounding the cavity by internal high-pressure forming of the insert element. The insert element inserted into the tank shell is thus internally high-pressure formed while arranged within the cavity, whereby the insert element enlarges at least in some areas and is thereby applied internally to the tank shell. Internal high-pressure forming is classified as hydroforming and involves the forming of metal tubes or hollow bodies in a closed mold using internal pressure. Internal high-pressure forming differs from other media-based processes for forming metal sheet in that the workpiece itself largely forms the sealing shell for the pressure. The pressure can then be introduced into the hollow body to be formed, for example, using a water-oil emulsion. The insert element is thus brought into contact with the tank shell by internal high-pressure forming. After internal high-pressure forming, the insert element defines a tank volume in which the fuel for the vehicle can be held. Internal high-pressure forming allows the insert element to be applied to the inside of the tank shell over a particularly large area, resulting in a particularly large tank volume, as the distance between the tank shell and the insert element is particularly small. This tank volume is thus enclosed to the outside by both the insert element and the tank shell. In particular, the insert element forms a permeation barrier for the fuel, preventing the fuel from diffusing through the tank shell from the tank volume to the outside. The tank shell serves to stabilize the high-pressure tank. Due to the two-layer design of the high-pressure tank, With the insert element and the tank shell, the permeation barrier provided by the insert element ensures particularly secure retention of the fuel within the tank volume. Furthermore, the tank shell can be designed to be particularly thin, as the tank shell serves solely to stabilize the insert element and should not be so thick that the tank shell alone prevents the fuel from permeating out of the tank volume. Thus, the insert element can be optimized for its function as a permeation barrier, and the tank shell can be optimized for its function as a stabilizing element for the insert element.

The design of the insert element, with its larger outer diameter in the central region than at its respective ends and thus the cigar-shaped design, enables a port opening resulting at at least one of the ends of the high-pressure tank to be designed to be particularly small. As a result, a port area of the high-pressure tank can be designed to be particularly light and thin-walled. Furthermore, due to the small resulting port opening of approximately 30 millimeters in particular, a particularly small closure can be provided for the port opening, which is consequently particularly light and has particularly low material costs. Furthermore, due to the particularly small port opening, it is possible to select a closure thread size within approved standards and design tables. In particular, it is additionally provided that an inner diameter of the insert element is larger in the central region than in the region of the respective ends. This makes it possible to achieve a particularly large tank volume in the central region due to the particularly large inner diameter of the insert element, particularly after internal high-pressure forming while maintaining specified maximum physical extensibility. As a result, a particularly large amount of fuel can be stored in the tank volume, while, as already described, the port opening of the high-pressure tank is particularly small.

In a possible further development of the invention, a stainless steel insert is inserted into the tank shell as an insert element. Stainless steel represents a particularly efficient permeation barrier for gaseous fuel, in particular for hydrogen as a gaseous fuel. However, stainless steel has a maximum physical extensibility of 45 percent and can therefore increase its outer diameter to a maximum of 145 percent during internal high-pressure forming. Because the insert element has a larger outer diameter in its central region compared to its respective ends, despite the limited extensibility of the insert element due to the stainless steel used, it can be achieved that the insert element has a particularly large cross-section in the central region after internal high-pressure forming. As a result, the tank volume is particularly large, while the resulting port opening of the high-pressure tank can be kept particularly small. Large port openings are mechanically critical in 700 bar applications, as they require high wall thicknesses with high mass and high material costs. The smaller the port opening of the high-pressure tank can be designed, the lower the required wall thicknesses of the insert element or tank shell in the port area, as well as the closure required to close the port opening. Due to the smaller wall thicknesses, the closure, tank shell, or insert element in the port area have a particularly low mass and, consequently, particularly low material costs.

In a further possible embodiment of the invention, the insert element is inserted into the tank shell, which is made of steel, in particular high-strength steel. This means that a tank shell made of steel, in particular high-strength steel, is used to manufacture the high-pressure tank. Because the tank shell is made of steel, in particular high-strength steel, the high-pressure tank has particularly high stability.

In a further possible embodiment of the invention, it is provided that before internal high-pressure forming, the tank shell is formed at its respective ends as part of a hot spinning process, whereby the outer diameter of the tank shell is reduced at the ends. Hot spinning is a metalworking process in which the tank shell, particularly when a metal tube is to be formed as the tank shell, is rotated at high speed and formed into an axially symmetric part. By forming the respective ends of the tank shell, the tank shell is given the shape of a cigar. During hot spinning, the tank shell is rotated while it is heated to a high temperature. After heating, the tank shell is formed by a tool pressing against the heated surface of the tank shell, thereby forcing the tank shell to deform during rotation. Hot spinning allows the tank shell to be formed or constricted at its respective ends to a smaller diameter with little force, which can create a seamless shoulder.

In this context, it can be provided, in particular, that the ends of the tank shell are formed one after the other in a respective hot-spinning process, wherein the insert element is arranged in the cavity at least during the forming of the second formed end of the tank shell. In other words, for example, a first of the ends of the tank shell can be formed during the hot-spinning process, whereby the outer diameter of the tank shell at this end is reduced, then the insert element is inserted into the cavity of the tank shell, and subsequently the second end of the tank shell is formed during a further hot-spinning process. Due to the fact that, in addition to the outer diameter, the inner diameter at the respective ends of the tank shell is also reduced during the hot-spinning process, it can happen that the inner diameter of the tank shell at the respective ends is smaller than the largest outer diameter of the insert element. Subsequent insertion of the insert element into the cavity of the tank shell after the hot spinning process would therefore no longer be possible. The insert element is thus inserted into the cavity through the end of the tank shell that has not yet been formed during the hot spinning process, and only then is this end of the tank shell formed. This makes it particularly easy and reliable to position the insert element in the cavity of the tank shell, even if the largest outer diameter of the insert element is smaller than the respective inner diameters of the ends of the tank shell formed in the hot spinning process. To enable the insert element to be held rotationally fixed to the tank shell during this hot spinning process of the second end of the tank shell, and thus to rotate together with the tank shell, a connecting element can be used. This connecting element can be attached to both the tank shell and the insert element, whereby the insert element is held to the tank shell via the connecting element in a rotationally fixed manner, without any direct contact between the tank shell and the insert element. The connecting element can be designed as a clamping element. In particular, the connecting element is made of a temperature-resistant material, so that the connecting element is chemically resistant at least up to a temperature of 1200°C. In particular, the connecting element is made of a steel material and/or a ceramic material.

This makes it possible to ensure that the insert element with a particularly large outer diameter in the central area can be reliably inserted into the cavity and then applied to the inner wall of the tank shell by internal high-pressure forming.

In a further possible embodiment of the invention, it is provided that the insert element is produced by connecting at least two separately manufactured pipe shells to one another. These pipe shells each extend, in particular, over the entire longitudinal extent of the insert element. This results in a longitudinal connection of the pipe shells. These pipe shells are, in particular, each deep-drawn. In particular, at least two deep-drawn pipe shells are connected to one another to form the insert element, in particular welded to one another. A weld seam extends in the axial direction and thus along the longitudinal extension direction of the insert element. By producing the insert element by connecting the at least two pipe shells to one another, the insert element can be manufactured particularly easily with the smaller outer diameter arranged in the region of the respective ends compared to the outer diameter of the central region of the insert element.

In a further possible embodiment of the invention, it is provided that the insert element is produced from a tubular starting component with a constant outer diameter over its entire length running in the longitudinal direction. This is done by alternately expanding and solution annealing the starting component in several stages until the insert element has a predetermined starting shape for internal high-pressure forming. With this starting shape, the outer diameter of the insert element is smaller at its respective ends than in a central region along the longitudinal direction. The insert element can thus be produced by multi-stage expansion of the tubular starting component. In each expansion step, the insert element can be expanded taking into account a maximum physical extensibility that depends on the material of the insert element. After each expansion step, the insert element can again be solution annealed to achieve a relaxation of the microstructure. This can be followed by a further expansion step and then another solution annealing. In particular, expansion and solution annealing steps are repeated successively until the specified initial shape is achieved. Thus, the insert element with the specified initial shape can be manufactured from the tubular initial component while adhering to material-specific physical ductility limits.

The invention further relates to a high-pressure tank for a motor vehicle, comprising a tank shell enclosing a cavity and a tubular insert element. The tubular insert element is made of stainless steel, rests against an inner wall of the tank shell defining the cavity, and encloses a tank volume in which fuel for the motor vehicle can be accommodated. The insert element completely covers the inner wall of the tank shell towards the tank volume. An outer diameter of the insert element at its respective ends is smaller than in a central region along the longitudinal direction. In this case, it can be provided, in particular, that a port opening of the high-pressure tank is smaller than 70 millimeters in diameter, in particular smaller than 50 millimeters in diameter, in particular smaller than 40 millimeters in diameter. For example, the port opening of the high-pressure tank can have a diameter of approximately 30 millimeters. Both the entire high-pressure tank with its outer contour and the insert element have a smaller outer diameter at their respective ends than in their central region with respect to the longitudinal direction of extension and thus have at least substantially the shape of a cigar. The double-walled design of the high-pressure tank with the stainless steel insert element and the tank shell allows, on the one hand, a particularly secure permeation barrier to be created for the fuel contained in the tank volume due to the insert element and, on the other hand, particularly great stability of the high-pressure tank with a particularly low weight of the high-pressure tank due to the provision of the tank shell, in particular the tank shell made of steel, in particular the tank shell made of high-strength steel. In particular, the high-pressure tank was manufactured using a method as already described in connection with the method for manufacturing a high-pressure tank for a motor vehicle.

In a possible further development of the invention, it is provided that the insert element comprises at least two pipe shells that are integrally connected to one another. These pipe shells can be produced, in particular, by deep drawing and integrally connected to one another by welding. By designing the insert element from the two pipe shells that are integrally connected to one another, it can be achieved that, while maintaining maximum physical extensibility of the stainless steel used to manufacture the insert element, the insert element arranged in the cavity of the tank shell has a particularly large outer diameter and a particularly large inner diameter in its central region and, in comparison, a particularly small outer diameter and inner diameter at its respective ends. As a result, the high-pressure tank can be manufactured with a particularly small resulting port opening at at least one of the ends of the high-pressure tank, wherein the tank volume in the high-pressure tank simultaneously has a particularly large outer diameter in the central region, whereby a particularly large tank volume is delimited by the insert element. By designing the insert element from at least two pipe shells that are integrally connected to one another, it is possible to achieve a predetermined initial shape for the insert element for internal high-pressure forming with a particularly small number of forming steps, which the insert element has when inserted into the cavity of the tank shell. To apply the insert element arranged in the cavity to the inner wall of the tank shell, the insert element is internally high-pressure formed within the cavity of the tank shell.

The invention further relates to a motor vehicle with a high-pressure tank, as already described in connection with the high-pressure tank according to the invention. The high-pressure tank is particularly designed to store hydrogen. The high-pressure tank can provide this stored hydrogen to a drive device of the motor vehicle, whereby the motor vehicle can be powered by the hydrogen. For example, the hydrogen can be used in an internal combustion engine designed for hydrogen combustion or by a fuel cell device to power the motor vehicle.

Further features of the invention may emerge from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as the features and combinations of features shown below in the description of the figures and/or in the figures alone, can be used not only in the respective combinations specified, but also in other combinations or on their own, without departing from the scope of the invention.

The drawing shows in the only figure ( 1 ) a process diagram for a method for producing a high-pressure tank for a motor vehicle.

In 1 A process flow for a method for producing a high-pressure tank 10 for a motor vehicle is shown. The produced high-pressure tank 10 is designed to store a fuel, in particular hydrogen as fuel for the motor vehicle. For the production A tubular tank shell 12 is used to form the high-pressure tank 10 (S1). This tubular tank shell 12 is then formed at a first end 14 using a tool 16 as part of a hot spinning process, whereby the outer diameter of the tank shell 12 at this first end 14 is reduced (S2). An insert element 18 is then inserted into a cavity 20 enclosed by the tank shell 12. The insert element 18 is made of stainless steel in the present case. To produce the insert element 18, two separately produced pipe shells were joined together. To produce the respective pipe shells, the pipe shells were each deep-drawn. The pipe shells can in particular be welded together using a laser welding process. In the present case, the pipe shells were welded together to produce the insert element 18, creating a weld seam 22. This weld seam 22 runs in the longitudinal direction of the insert element 18, wherein the longitudinal direction of the insert element 18 runs parallel to a central axis of the insert element 18. An outer diameter and an inner diameter of the insert element 18 are smaller at their respective ends 24 than in a central region 26 along the longitudinal direction. After the insert element 18 has been pushed into the cavity 20 of the tank shell 12 over the not yet formed second end 28 of the tank shell 12 (S3), this second end 28 of the tank shell 12 is also formed in a hot spinning process, whereby the outer diameter of the tank shell 12 is reduced at the second end 28 (S4). The insert element 18 is thus arranged in the cavity 20 delimited by the tank shell 12 during the forming of the second end 28 of the tank shell 12.

After both ends 14, 28 of the tank shell 12 have been formed, the insert element 18 is internally high-pressure formed in the cavity 20 by introducing a forming medium 30 (S5). As a result of the internal high-pressure forming, the insert element 18 lies flat against an inner wall 32 of the tank shell 12 that defines the cavity 20. This forms the high-pressure tank 10. The insert element 18 defines a tank volume 34 of the high-pressure tank 10, in which the fuel for the motor vehicle can be accommodated. The insert element 18 completely covers the inner wall 32 of the tank shell 12 toward the tank volume 34, as shown in 1 can be recognized particularly well.

Within the scope of the method, the high-pressure tank 10 has thus been produced, with the tank shell 12 enclosing the cavity 20 and the tubular insert element 18. The insert element 18 is made of stainless steel in the present case, rests against the inner wall 32 of the tank shell 12 delimiting the cavity 20 and encloses the tank volume 34. The outer diameter of the insert element 18 is smaller at its respective ends 24 than in the central region 26 along the longitudinal direction, both before and after the internal high-pressure forming.

Alternatively or in addition to producing the insert element 18 from the two separately manufactured pipe shells, the insert element 18 can be produced from a tubular starting component with a constant outer diameter and inner diameter over its entire length in the direction of extension. In this case, the starting component can be alternately expanded and solution-annealed in several stages until the insert element 18 has a predetermined starting shape for internal high-pressure forming. In this starting shape for internal high-pressure forming, the outer diameter and the inner diameter of the insert element 18 are smaller at its respective ends 24 than in the central region 26 along the longitudinal direction of extension.

By forming the tank shell 12 during the hot spinning process, a high-strength steel cylinder is produced from the tank shell 12, into which the insert element 18 is inserted as a welded pipe insert. In particular, after the internal high-pressure forming, the insert element 18 can have an inner diameter of 80 millimeters in the central region 26 and an inner diameter of 30 millimeters in the region of the respective ends 24.

When producing the insert element 18 from the tubular starting component by means of multi-stage alternating expansion and solution annealing, a seamless tube with an inner diameter of 30 millimeters can be used as the starting component. In a first expansion step, the inner diameter can be expanded to 140 percent and thus to 42 millimeters. This results in a wall thickness of 1.2 millimeters. This can be followed by a first solution annealing step. This can then be followed by a second expansion step, in which the inner diameter of the starting component is again expanded to 140 percent and thus to 59 millimeters, resulting in a wall thickness of 0.7 millimeters. This can then be followed by a second solution annealing step. Subsequently, in a third expansion step, the starting component can be expanded to an inner diameter of 136 percent and consequently to 80 millimeters, resulting in a wall thickness of 0.5 millimeters. A third solution annealing step can then be performed.

By using the insert element 18 with the particularly small inner diameters at the respective ends 24 of, for example, 30 millimeters, a resulting port opening of the high-pressure tank 10 of approximately 30 millimeters can be achieved. This allows a port area of the tank shell 12 to be designed with particularly light and thin walls. As a result, a closure intended for the port opening can be manufactured particularly small, particularly light, and with particularly low material costs. Furthermore, this allows a closure thread size to be within the approved standards and design tables.

Overall, the invention shows how internal high-pressure forming of a permeation barrier layer can be implemented in a hydrogen steel tank with a reduced port opening.

List of reference symbols

10

high-pressure tank

12

Tank cover

14

first end

16

Tool

18

Insert element

20

cavity

22

Weld seam

24

End

26

central area

28

second end

30

Forming medium

32

interior wall

34

Tank volume

S1 to S5

respective procedural steps

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10 2009 042 401 A1 [0002]
• DE 10 2016 220 995 A1 [0003]

Claims (10)

A method for producing a high-pressure tank (10) for a motor vehicle, comprising the steps of: - inserting a tubular insert element (18) into a cavity (20) enclosed by a tank shell (12), wherein an outer diameter of the insert element (18) is smaller at its respective ends (24) than in a central region (26) along the longitudinal direction of extension, - applying the insert element (18) to an inner wall (32) of the tank shell (12) delimiting the cavity (20) by internal high-pressure forming of the insert element (18), whereby the insert element (18) delimits a tank volume (34) in which a fuel for the motor vehicle can be accommodated, wherein the insert element (18) completely covers the inner wall (32) of the tank shell (12) towards the tank volume (34). Procedure according to Claim 1 , characterized in that an insert element (18) made of stainless steel is inserted into the tank shell (12) as the insert element (18). Procedure according to Claim 1 or 2 , characterized in that the insert element (18) is inserted into the tank shell (12), which is made of steel, in particular high-strength steel. Method according to one of the preceding claims, characterized in that before the internal high-pressure forming, the tank shell (12) is formed at its respective ends (14, 28) in a hot spinning process, whereby the outer diameter of the tank shell (12) is reduced at the ends (14, 28). Procedure according to Claim 4 , characterized in that the ends (14, 28) of the tank shell (12) are successively formed in a respective hot spinning process, wherein at least during the forming of the second formed end (28) of the tank shell (12) the insert element (18) is arranged in the cavity (20). Method according to one of the preceding claims, characterized in that the insert element (18) is produced by connecting at least two separately produced pipe shells to one another. Method according to one of the preceding claims, characterized in that the insert element (18) is produced from a tubular starting component with a constant outer diameter over its entire length running in the longitudinal direction, in that the starting component is alternately expanded and solution-annealed in several stages until the insert element (18) has a predetermined starting shape for internal high-pressure forming, in which the outer diameter of the insert element (18) is smaller at its respective ends (24) than in a central region (26) along the longitudinal direction. High-pressure tank (10) for a motor vehicle, with a tank shell (12) enclosing a cavity (20) and a tubular insert element (18) which is made of stainless steel, rests against an inner wall (32) of the tank shell (12) delimiting the cavity (20) and encloses a tank volume (34) in which a fuel for the motor vehicle can be accommodated, wherein the insert element (18) completely covers the inner wall (32) of the tank shell (12) towards the tank volume (34) and wherein an outer diameter of the insert element (18) is smaller at its respective ends (24) than in a central region (26) along the longitudinal direction. High pressure tank (10) to Claim 8 , characterized in that the insert element (18) comprises at least two pipe shells which are connected to one another in a materially bonded manner. Motor vehicle with a high-pressure tank (10) according to Claim 8 or 9 , wherein the high-pressure tank (10) is particularly designed to store hydrogen.