Tubular pressure tank for storing fuel in a motor vehicle and manufacturing process

Abstract

The invention relates to a tubular pressure tank (100) for storing fuel in a motor vehicle, comprising a cylindrical hollow body (110) and two end pieces (120) with which the hollow body (110) is closed at both ends, wherein the end pieces (120) are arranged in the hollow body ends (115) and are fastened by radial deformation of the hollow body ends (115). According to the invention, the end pieces (120) have a conical, outwardly tapered section (122) and the hollow body ends (115) are pressed onto these conical sections (122) of the end pieces (120) in a form-fitting manner, wherein the conical sections (122) of the end pieces (120) are formed with longitudinal grooves (126) and the pressed-on hollow body ends (115) are also pressed into these longitudinal grooves (126). The invention further relates to a method for manufacturing such a tubular pressure tank (100).

Description

[0001] The invention relates to a tubular pressure tank for storing fuel in a motor vehicle according to the preamble of claim 1. The invention further relates to a method for producing a tubular pressure tank.

[0002] A tubular pressure tank in question is used in motor vehicles for storing fuel, in particular for storing hydrogen (H2) for a fuel cell drive or for storing natural gas (CNG) for a natural gas drive.

[0003] The closest DE 10 2019 203 544 A1 describes a tubular pressure tank (100) with a cylindrical hollow body (110) closed at both axial ends with end pieces (120). The end pieces (hereinafter referred to as end pieces) are arranged in the front ends of the cylindrical hollow body and are fixed to the cylindrical hollow body by direct, form-fitting pressing. The production of this pressure tank comprises the following steps: - Providing the cylindrical hollow body and the end pieces; - closing the (open) end faces of the cylindrical hollow body with the end pieces; and - Fixing the end pieces by positive pressing with the cylindrical hollow body.

[0004] Regarding the state of the art, reference is also made to EP 3 366 975 A1, which describes a pole cap with a pressed-in pressure connection element for a pressure tank, as well as to US 6 017 600 A.

[0005] The pressure tank according to the invention of claim 1 features optimized fastening of the end pieces. The independent claim also extends the invention to a method for manufacturing a pressure tank according to the invention. Preferred developments and refinements of the invention for the pressure tank and the manufacturing method are analogously apparent from the dependent claims, the following description of the invention, and the drawings.

[0006] The tubular or pipe-like pressure tank (pipe storage) according to the invention for storing fuel in a motor vehicle has a substantially cylindrical or pipe-like hollow body and two end pieces (end pieces, pipe end parts) with which the cylindrical hollow body is closed on both sides, i.e. on its two axial end faces. The end pieces are arranged in the (axial) hollow body ends of the cylindrical hollow body and are connected to the cylindrical hollow body by radial deformation of the hollow body ends and are thereby fastened or held in place. According to the invention, it is provided that the end pieces (each) have a conical or conical or frustoconical, extending (in the axial direction of the pressure tank) outwards, i.e.in an axial direction facing away from the tank interior, tapered section and that the hollow body ends of the cylindrical hollow body are pressed or pressed in a form-fitting manner onto these conical sections of the end pieces.

[0007] The end pieces, which have a conical section, are arranged in the hollow body ends, meaning the axial end sections or regions of the cylindrical hollow body, and are fastened to the hollow body ends by a direct or immediate form fit. The cylindrical hollow body or its hollow body wall (circumferential wall) is locally deformed or reshaped in the radial direction at its hollow body ends, in particular over the entire circumference, so that the hollow body ends of the cylindrical hollow body bear positively or contour-following at least against the conical sections of the end pieces. This creates a mechanical lock for the end pieces, so that they are securely held even at high internal tank pressures and cannot be forced out. Instead of a conical section, a paraboloid-shaped section or the like can also be provided on the end pieces with the same effect.

[0008] The conical sections of the end pieces are formed (on their circumferential surfaces) with longitudinal grooves or similar groove-like depressions which preferably extend substantially in the axial direction and which are arranged so as to be evenly distributed (i.e. at equal angular intervals) around the circumference. The hollow body ends which are pressed or pushed onto the conical sections of the end pieces are pressed into these longitudinal grooves. This means that the hollow body ends are deformed or reshaped radially inwards in such a way that they engage in the longitudinal grooves in a form-fitting manner or in a contour-following manner. The longitudinal grooves can be used to prevent the formation of folds in the hollow body wall which is a result of the conical diameter reduction, in that they function as a kind of circumferential length compensation. It is therefore preferably provided that the longitudinal grooves in the conical sections of the end pieces (in the axial direction) increase or decrease outwards.are designed with increasing groove depth, in particular such that the contour line has the same length in every cross-section of a conical section (virtually the same circumference with a reduced diameter). The longitudinal grooves and the positive engagement created by them with the hollow body wall or its hollow body ends also increase the mechanical stability of the pressure tank and also act as anti-twist protection for the end pieces.

[0009] The end pieces can furthermore (each) have an outer cylindrical section that adjoins the conical section (in the axial direction) outwards, wherein the hollow body ends of the cylindrical hollow body are also pressed or pressed onto these outer cylindrical sections of the end pieces in a form-fitting or contour-following manner. The longitudinal grooves in the conical sections described above can extend into these outer cylindrical sections to prevent wrinkling there as well.

[0010] In the (axial) area of ​​the outer cylindrical sections of the end pieces, additional reinforcements can be applied to the ends of the hollow cylindrical body. The reinforcements provide circumferential reinforcement. Such reinforcements can be, for example, rings or sleeves, preferably made of metal and in particular of steel, or wrappings, for example, wire wrappings, fiber tape wrappings, or the like. The reinforcements, e.g., the rings or sleeves, can also be adapted to the longitudinal grooves described above and can, for this purpose, have corresponding form-fitting elements on their inner circumferential surfaces.

[0011] The outer cylindrical sections of the end pieces can protrude (in the axial direction) from the hollow body ends or project in the axial direction (outwards), whereby the projecting or projecting sections can function as bearing or fastening flanges for the pressure tank.

[0012] The cylindrical hollow body can have a liner and a fiber sheath applied to the liner, as explained in more detail below. Preferably, the fiber sheath projects axially beyond the liner in the (axial) region of the hollow body ends, so that (in these projecting regions) only the fiber sheath is pressed or forced onto the end pieces, i.e., onto the conical sections and, if applicable, also onto the outer cylindrical sections. This means that the conical sections and, if applicable, also the outer cylindrical sections of the end pieces are only connected to the fiber sheath of the cylindrical hollow body. Thus, there is no risk of the integrity of the liner being compromised during manufacture of the pressure tank.

[0013] As already mentioned, the cylindrical hollow body can be formed from a liner (inner shell, inner tube) and a fiber sheath (outer shell, outer tube) applied to the liner. This structure can also be referred to as a composite pipe. The liner is made in particular from plastic (e.g., polyethylene or polyamide) or metal (e.g., aluminum). The fiber sheath is made in particular from a fiber-reinforced plastic, e.g., glass- or carbon-fiber-reinforced. The fiber sheath is applied to the liner in particular by means of a pultrusion process (as described in DE 10 2018 222 302 A1). The end pieces can be made of metal, e.g., steel or aluminum, and are in particular turned and / or milled parts. The metallic end pieces can be provided with an anti-corrosion coating. The end pieces can also be made of plastic (e.g.,Polyamide), possibly also made of fibre-reinforced plastic, in particular injection-moulded parts.

[0014] The method according to the invention for producing a tubular pressure tank according to the invention comprises at least the following steps: - Providing the (prefabricated) cylindrical hollow body, which is in particular a composite pipe, and the (prefabricated) end pieces; - closing the (open) end faces of the cylindrical hollow body with the end pieces, in particular by (axial) inserting the end pieces so that they are at least partially arranged in the hollow body ends or in the openings at the end faces of the cylindrical hollow body; - Connecting the cylindrical hollow body to the (inserted) end pieces, for which purpose the hollow body ends of the cylindrical hollow body or the hollow body wall are pressed or pushed radially (i.e. essentially in the radial inward direction) onto the conical sections of the end pieces, if necessary also onto the outer cylindrical sections of the end pieces (between the hollow body ends and the inserted end pieces there are axial overlaps within which the pressing or pushing takes place), in particular over the entire circumference, so that the hollow body ends fit positively or contour-following onto the conical sections of the end pieces, if necessary also onto the outer cylindrical sections of the end pieces, and are also pressed into the longitudinal grooves.

[0015] The connection between the end pieces and the cylindrical hollow body or the hollow body ends, and the resulting fastening of the end pieces, is preferably achieved solely by positive locking. However, it can also be provided that the end pieces are additionally glued to the cylindrical hollow body (the adhesive can also function as a seal) and / or fixed to the cylindrical hollow body by means of retaining rings or locking pins. As a further optional step, the attachment of reinforcements can be provided, particularly in the (axial) area of ​​the outer cylindrical sections, e.g., by pulling on rings or sleeves or by wrapping them with wire or fiber tape.

[0016] As already explained, the provided cylindrical hollow body or the composite pipe can have a liner and a fiber sheath applied to the liner, which is formed in particular from a fiber-reinforced plastic. For pressing onto the end pieces, it is preferably provided that the cylindrical hollow body is heated locally at its hollow body ends, then deformed or reshaped (radially inwardly) and cooled again, wherein it is particularly provided that the deformation force or the molding pressure is maintained during cooling in order to prevent reshaping. The fiber sheath can protrude beyond the liner in the axial direction in the region of the hollow body ends and form so-called projection areas in the form of hollow cylindrical extensions, which are then heated, deformed and cooled.

[0017] The fiber sheathing of the cylindrical hollow body or composite pipe is formed in particular from a fiber-reinforced plastic, e.g., glass- or carbon-fiber-reinforced plastic. The plastic can be a thermoplastic or a thermoplastic matrix. For pressing onto the end pieces, the hollow body ends are heated to at least the material-specific softening temperature. The plastic can also be a thermosetting plastic or a thermosetting plastic matrix. For pressing onto the end pieces, the hollow body ends are then heated to a temperature above the glass transition temperature (T g) and then formed (as described, for example, in DE 10 2005 050 925 A1). Preferably, the plastic or plastic matrix is ​​a resin (e.g., epoxy resin) or the like that is not fully cured or hardened, which only hardens or hardens as a result of the heating when pressed onto the end pieces. Heating can be achieved, for example, using hot air or infrared radiation.

[0018] The radial pressing or pressing of the hollow body ends of the cylindrical hollow body or its hollow body wall onto the end pieces can be carried out in one step, or optionally in several steps, using a pressure medium and / or a suitable pressing tool. Preferably, a pressing tool is used for the (radial) pressing of the hollow body ends. This pressing tool has several pressing jaws arranged like a chuck and performing a radial feed movement (during pressing). An electric, pneumatic, or hydraulic drive can be provided to generate force. The pressing jaws can be heated and thus also be used for heating. Optionally, the pressing or pressing can also be carried out in several steps (staggered deformation) using several such pressing tools.

[0019] The invention is explained in more detail below with reference to the drawing. Fig. 1 shows a schematic sectional view (longitudinal section) of a tubular pressure tank according to the invention. Fig. 2 shows a cross section through the end piece of the pressure tank from Fig. 1 according to the Fig. 1 indicated cutting line (AA). Fig. 3 illustrates in a schematic sectional view analogous to Fig. 2 a process step in the manufacture of the pressure tank from Fig. 1.

[0020] Fig. 1 shows the axial end region of a tubular pressure tank 100 for storing fuel in a motor vehicle. The other axial end region of the tubular pressure tank 100 is essentially identical or mirror-symmetrical. The pressure tank 100 has a cylindrical hollow body 110 which forms the pressure tank wall. The cylindrical hollow body 110 or its hollow body wall (circumferential wall) has a multi-layer construction (composite pipe) with a liner (inner shell, inner pipe) 112 made of plastic or metal, and a fiber sheath (outer shell, outer pipe) 114 applied to the liner 112, which is made of a fiber-reinforced plastic, in particular with a thermosetting plastic matrix. In the region of the front ends of the pressure tank 100 orIn the area of ​​the hollow body ends 115, the fiber sheath 114 projects beyond the liner 112 in the axial direction (with respect to the longitudinal axis L) and forms a so-called overhang area in the form of a tubular extension.

[0021] The cylindrical hollow body 110 is closed at both of its axial ends with end pieces 120. The end pieces 120 are formed with an axial bore 125 with a connecting thread so that a valve, a connecting line, or the like can be connected. Sealing is achieved by means of O-rings 129, which are arranged in circumferential grooves 128 and seal against the liner 112. Preferably, at least two O-rings are provided on each end piece 120 (double O-rings).

[0022] The end pieces 120 each have a first or (axially) inner, larger-diameter cylindrical section (axial section) 121. The outer diameter of the first or inner cylindrical sections 121 corresponds to the inner diameter of the (undeformed) cylindrical hollow body 110. The end pieces 120 further each have a conical or frustoconical section (axial section) 122 and a second or (axially) outer, smaller-diameter cylindrical section (axial section) 123, which adjoin the first or inner cylindrical section 121 (in the axial direction) outwards (i.e., facing away from the tank interior). The transitions between these axial sections are preferably rounded. The second or outer cylindrical sections 123 project or protrude in the axial direction from the hollow body ends 115, wherein the projecting or protruding sections 123a serve as storage or storage areas for the pressure tank 100.can serve as mounting flanges.

[0023] As in Fig. 1 with dashed lines, the conical sections 122 of the end pieces 120 are formed on their conical outer circumferential surfaces with longitudinal grooves 126 or the like, which are formed in the axial direction outwards (ie in the axial direction facing away from the tank interior) with increasing groove depth and extend into the second or outer cylindrical sections 123. As can be seen from Fig. As can be seen in Figure 2, the longitudinal grooves 126 are evenly distributed around the circumference and have a rounded groove profile. The longitudinal grooves 126 can be identical or different.

[0024] To fasten the end pieces 120, the cylindrical hollow body 110 is pressed or forced radially (i.e. in the radial direction perpendicular to the longitudinal axis L) onto the conical sections 122 and onto the second or outer cylindrical sections 123 of the end pieces 120 at the hollow body ends 115, namely in the projecting areas of the fiber sheath 114, so that the hollow body ends 115 bear positively or contour-following against the conical sections 122 and the outer, smaller-diameter cylindrical sections 123. The hollow body ends 115 are also pressed or contour-following into the longitudinal grooves 126, as can be seen from Fig. 2. Optionally, additional reinforcements 130, for example in the form of steel rings or sleeves, can be applied to the hollow body ends 115 in the area of ​​the second or outer cylindrical sections 123, as shown in Fig. 1 shown.

[0025] The end pieces 120 are supported (axially) outwardly on the conical tapers or constrictions of the hollow body ends 115, whereby the tapered or constricted hollow body ends 115 form quasi-mechanical locks for the end pieces 120, so that they cannot be reliably pushed out even at high internal tank pressures. The end pieces 120 are supported (axially) inwardly on the liner 112, for which purpose the first or inner cylindrical sections 121 of the end pieces 120 are each formed with an annular shoulder 127. The end pieces 120 are thus fixed in both axial directions.

[0026] To produce the pressure tank 100, the initially undeformed hollow body ends 115 of the cylindrical hollow body or the composite pipe 110 are heated and pressed or forced in the radial direction onto the conical sections 122 and onto the second or outer cylindrical sections 123 of the end pieces 120 inserted into the hollow body ends 115, and in the process also into the longitudinal grooves 126. The pressing and pressing can be carried out using a pressing tool 200, as in Fig. 3. The pressing tool 200 has a plurality of pressing jaws 210 formed with corresponding contours, which are arranged like a chuck and (during pressing) execute a radial feed movement, as illustrated by the double arrows.

Claims

[1] Tubular pressure tank (100) for storing fuel in a motor vehicle, comprising a cylindrical hollow body (110) and two end pieces (120) with which the hollow body (110) is closed on both sides, wherein the end pieces (120) are arranged in the hollow body ends (115) and are fastened by radial deformation of the hollow body ends (115), characterized by that the end pieces (120) have a conical, outwardly tapering section (122) and the hollow body ends (115) are pressed in a form-fitting manner onto these conical sections (122) of the end pieces (120), wherein the conical sections (122) of the end pieces (120) are formed with longitudinal grooves (126) and the pressed-on hollow body ends (115) are also pressed into these longitudinal grooves (126). [2] Tubular pressure tank (100) according to claim 1, characterized by that the longitudinal grooves (126) are formed outwards with increasing groove depth. [3] Tubular pressure tank (100) according to one of the preceding claims, characterized by that the end pieces (120) further have an outer cylindrical section (123) which adjoins the conical section (122) on the outside, wherein the hollow body ends (115) are also pressed in a form-fitting manner onto these outer cylindrical sections (123) of the end pieces (120). [4] Tubular pressure tank (100) according to claim 3, characterized by that in the region of the outer cylindrical sections (123) additional reinforcements (130) are applied to the hollow body ends (115). [5] Tubular pressure tank (100) according to claim 3 or 4, characterized by that the outer cylindrical sections (123) protrude from the hollow body ends (115), wherein the protruding sections (123a) function as bearing flanges for the pressure tank (100). [6] Tubular pressure tank (100) according to one of the preceding claims, characterized bythat the cylindrical hollow body (110) has a liner (112) and a fiber sheath (114) applied to the liner (112), wherein the fiber sheath (114) projects beyond the liner (112) in the axial direction in the region of the hollow body ends (115), so that only the fiber sheath (114) is pressed onto the end pieces (120). [7] A method of manufacturing a tubular pressure tank (100) according to any one of the preceding claims, comprising the steps of: - Providing the cylindrical hollow body (110) and the end pieces (120); - closing the end faces of the cylindrical hollow body (110) with the end pieces (120); - Connecting the cylindrical hollow body (110) to the end pieces (120), for which purpose the hollow body ends (115) are pressed radially onto the conical sections (122) of the end pieces (120) and are also pressed into the longitudinal grooves (126). [8] Method according to claim 7, characterized by in that the cylindrical hollow body (110) has a liner (112) and a fiber sheath (114) applied to the liner (112), which is formed from a fiber-reinforced plastic, wherein the hollow body ends (115) are heated for pressing onto the end pieces (120), then deformed and cooled again. [9] Method according to claim 7 or 8, characterized by that for pressing on the hollow body ends (115) a pressing tool (200) is used which has a plurality of pressing jaws (210) which are arranged like a chuck and carry out a radial feed movement.

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