Fuel tank for a motor vehicle and method for producing

Abstract

Fuel tank (1) for a motor vehicle, in the interior of which a net-like fabric (4) is introduced, wherein two support elements (3) are arranged on two mutually opposite inner walls of the fuel tank (1), between which the net-like fabric (4) is stretched, characterized in that the support elements (3) are connected via their extension to the inner walls of the fuel tank (1) and the net-like fabric (4) in order to achieve a uniform distribution of occurring tensile stresses, wherein the connection between the inner walls and the support elements (3) is produced during the manufacture of the fuel tank (1) by pressing the support elements (3) into the still heated inner walls.

Description

[0001] According to the preamble of claim 1, the invention relates to a fuel tank for a motor vehicle in the interior of which a net-like fabric is introduced, as well as to a method for producing such a fuel tank.

[0002] Fuel tanks are commonly made from thermoplastic, for example, by extrusion blow molding or by welding injection-molded half-shells made from thermoplastic. However, if the fuel is left idle for extended periods, it will begin to outgas. In vehicles powered solely by a combustion engine, these volatile components are vented into an activated carbon filter via vent valves located in the fuel tank. This prevents the outgassing from building up excessive pressure in the tank. In the activated carbon filter, the hydrocarbons contained in the outgassing are bound or trapped by the activated carbon. However, the activated carbon only has a limited absorption capacity and becomes saturated once it has absorbed a certain amount of hydrocarbon.For this reason, it is necessary to flush the activated carbon filter at regular intervals. To do this, a vacuum is created by the combustion engine via a regeneration line. Fresh air is drawn in through the atmospheric opening of the activated carbon filter and passed through the activated carbon. This process causes the hydrocarbons to detach from the activated carbon. The dissolved hydrocarbons are then transported to the engine via the regeneration line, where they are burned.

[0003] With hybrid vehicles, however, it is possible that the vehicle is driven purely electrically for an extended period. During electric operation, however, the fuel continues to emit gases, which can build up pressure in the fuel tank if the activated carbon filter is saturated. However, the activated carbon filter only regenerates when the vehicle is running with the combustion engine. If the vehicle is used in electric operation for an extended period, the fuel tank can swell due to the gases. This swelling of the fuel tank must be avoided, as it could otherwise damage the tank bladder and / or adjacent components. Functional components located in the tank bladder can also be damaged by swelling.

[0004] Reinforcement measures are known that strengthen the fuel tank from the outside, for example by inserting a tubular space frame (see Fig. 1). However, these solutions are complex and increase the weight of the fuel tank.

[0005] Reinforcement measures provided inside the fuel tank are also known. DE 102 37 187 A1 discloses a fuel tank that is completely enclosed by a mesh during the molding process, so that the mesh is integrated into the outer surface of the tank in a force-fitting and / or form-fitting manner.

[0006] DE 10 2012 019 334 A1 describes a fuel tank with a support arranged inside the tank. The support is designed to absorb a supporting load on the tank walls caused by negative pressure in the fuel tank and to withstand a tensile force caused by excess pressure. A band is provided to absorb tensile forces, which acts as a tensioning element between two bases of the support.

[0007] However, the use of solid supports is disadvantageous with regard to their insertion into the fuel tank. Furthermore, volume loss occurs and the fuel tank is insufficiently flexible, which is particularly disadvantageous in the event of a crash.

[0008] The closest KR 10 2006 0 010 496 A describes a fuel tank with a net arranged inside. The net is designed to reduce fuel sloshing in the fuel tank. The net has a surrounding frame that is attached to the inner wall of the fuel tank by means of two L-shaped brackets or guides. The brackets are welded to the inner wall and have grooves into which the frame is inserted.

[0009] Regarding the state of the art, reference is also made to KR 10 2009 0 124 128 A, which describes a urea tank with a built-in net that divides the interior space. The net is installed using hooks attached to the interior walls of the urea tank.

[0010] The object of the present invention is to provide a fuel tank which does not swell despite pressure increases occurring inside the fuel tank and which also provides a high degree of volume and flexibility.

[0011] This object is achieved by a fuel tank according to patent claim 1, in the interior of which a net-like fabric is inserted and two support elements are arranged on two opposite inner walls of the fuel tank, between which the net-like fabric is stretched. The net-like fabric is suitable for absorbing tensile stresses caused by the outgassing of the fuel and thus preventing the fuel tank from swelling. Because the net-like fabric is stretched inside the fuel tank, in addition to absorbing tensile stresses, the net-like fabric also functions as a baffle. A baffle reduces sloshing noises of the fuel during driving. The net structure of the fabric can also reduce sloshing noises. This effect can be influenced by selecting the mesh size.Furthermore, the movable mesh fabric allows the tank to react flexibly to external forces in the event of a crash. In contrast to rigid components inserted between the inner surfaces of the fuel tank, the risk of damage to the fuel tank in the event of a crash is significantly reduced. The mesh fabric is formed, for example, from a plastic braid. Alternative materials include metals, natural fibers, glass, or carbon fibers. Furthermore, the mesh fabric is firmly connected to the support element. The support element is preferably injection-molded onto the mesh fabric in a prior step.

[0012] According to the invention, the support elements are connected to the inside of the fuel tank and the mesh fabric essentially through their extension. The connection of the mesh fabric to the support elements, which in turn are connected to the inside of the fuel tank, ensures a secure connection of the mesh fabric to the fuel tank. Because the support elements are connected essentially through their extension to the inner wall, or more precisely to the opposing inner walls (see above), of the fuel tank and the mesh fabric, an even distribution of the tensile stresses across the fuel tank is achieved.

[0013] It is also advantageous that the support elements have an arcuate shape, at least in sections. This arcuate shape allows the arrangement of the support elements and thus also the shape of the mesh-like fabric to be optimally adapted to the geometry of the fuel tank.

[0014] In a particularly practical variant, the two support elements are arranged essentially parallel to each other. This arrangement ensures optimal tensioning of the mesh-like fabric inside the fuel tank and allows it to absorb any tensile stresses that may occur. However, it is also possible to arrange the support elements at an angle to each other if, for example, the geometry of the fuel tank makes this necessary.

[0015] In a further advantageous embodiment, the mesh fabric is arranged essentially perpendicular to the support element. Arranging the mesh fabric perpendicular to the support elements optimizes the absorption of tensile forces and also fulfills the baffle function particularly well. It is also possible to increase the surface area of ​​the mesh fabric, for example, by arranging the support elements offset and parallel.

[0016] It is also advantageous if the support elements are connected to one another by means of a spacer element. It is conceivable that the support elements are connected by the spacer element by clipping the spacer element into the support elements or connecting them in some other way. One or more spacer elements can be provided for the connection. This also includes the possibility of the support elements being designed as a single piece, i.e. as a single-piece frame, wherein the spacer element in this case refers to the leg of the frame that runs through the interior of the fuel tank in the direction of extension of the mesh-like fabric. One leg is sufficient to fulfill the function.

[0017] In another advantageous variant, a shrinkage compensation element is provided in at least one support element. The shrinkage compensation element is designed in the form of a bulge in at least one support element toward the fuel tank interior. In the area of ​​the shrinkage compensation element, the support element is not connected to the inner wall of the fuel tank and can therefore react flexibly to shrinkages that occur, particularly during the manufacturing process.

[0018] According to the invention, during the production of the fuel tank, the support elements are pressed into the still-heated and flexible fuel tank inner wall to create a connection between the inner wall and the support elements. As the fuel tank cools, the plastic material shrinks. This shrinkage can cause stresses to build up, which can be compensated for by the aforementioned shrinkage compensation in the support elements. This prevents the support element from detaching from the fuel tank interior. However, even during normal operation, expansion and shrinkage due to temperature fluctuations occur.

[0019] Preferably, at least one functional component can be attached to at least one support element. Functional components, such as vent valves or bubble cups, increasingly need to be arranged inside the fuel tank. Attaching these functional components to the support element is particularly advantageous because the functional components can be mounted on the support element before being inserted into the fuel tank and then inserted into the fuel tank together with the support element during the manufacturing process.

[0020] It is further preferred that the mesh-like fabric be substantially tensile-resistant. A tensile-resistant fabric particularly effectively prevents the fuel tank from expanding due to outgassing fuel.

[0021] The invention further relates to a method for producing a fuel tank. First, a preform is extruded, then the preform is positioned between two open mold halves. In a further step, two support elements are introduced into the preform in such a way that the support elements are completely surrounded by the preform and the support elements are connected to one another by a mesh-like fabric. The mold is then closed and a blow molding process for the preform begins, in which the preform is pressed against the mold wall to shape the fuel tank geometry. In a subsequent step, a connection is created between the inside of the fuel tank and the support elements, and the mesh-like fabric is stretched inside the fuel tank by pressing the support elements into the still-heated wall of the fuel tank.In this way, the support elements form a bond with the inside of the fuel tank, so that the support elements are connected to the inner wall of the fuel tank and the mesh fabric via their expansion. Finally, the fuel tank is cooled and removed from the mold. Due to its flexible design, the mesh fabric can be easily inserted into the preform during the manufacturing process, as a compact arrangement of mesh fabric and support elements can be achieved for insertion into the preform.

[0022] In an advantageous embodiment, at least one carrier element has elevations on its side facing the inside of the fuel tank. These elevations are preferably made of the same material as the carrier element. The elevations increase the adhesion of the carrier element to the inside of the fuel tank because the elevations enlarge the surface of the carrier element that can bond to the inside of the fuel tank. During the manufacturing process, the elevations can at least partially melt and thus bond to the material of the fuel tank. The elevations can preferably be arranged in groups at particularly stressed areas of the carrier element in order to increase adhesion at these locations.

[0023] In a preferred embodiment of the invention, the support elements are introduced into the preform in a compact state with the mesh-like fabric arranged between the support elements. In this compact state, the mesh-like fabric is preferably folded, and the support elements are spaced apart or abut one another. This compact arrangement simplifies the introduction of the support elements into the preform, since the through-opening in the preform is significantly smaller than the subsequent size of the fuel tank.

[0024] It is further preferred that the support elements with mesh-like fabric be introduced into the preform by means of a movable device. The support elements with mesh-like fabric are introduced into the movable device in a compact state. The support elements with mesh-like fabric are then inserted into the extruded preform. The compressed state prevents the support elements from coming into contact with the preform. Premature contact can lead to damage to the preform.

[0025] In a further preferred variant, after completion of the blow molding process for forming the fuel tank geometry, the movable device increases the distance between the support elements such that the support elements are pressed against the inside of the fuel tank and the mesh-like fabric is stretched inside the fuel tank. Thus, the support elements can be inserted into the preform and the mesh-like fabric can be stretched inside the fuel tank with just one device.

[0026] Alternatively, it is possible for the movable device to increase the distance between the support elements during the blow molding process in such a way that the support elements are pressed against the inside of the fuel tank and the mesh-like fabric is stretched in the interior of the fuel tank.

[0027] The invention is explained in more detail with reference to the following schematic figures.

[0028] Showing: Fig. 1: a fuel tank with reinforcements according to the state of the art; Fig. 2: Support elements with stretched net-like fabric; Fig. 3: a fuel tank with support elements and mesh fabric placed therein; Fig. 4: Support elements with stretched net-like fabric and functional components attached to the support elements; Fig. 5: a shrinkage compensation in the support element; Fig. 6: the manufacturing process of a fuel tank according to the invention; Fig. 7: the rod in the retracted position; Fig. 8: the rod in assembled state.

[0029] Fig. Figure 1 shows a fuel tank (1) with a tubular frame (2) serving as a reinforcement element. This solution for hybrid vehicles is known from the prior art. The tubular frame (2) is attached to the fuel tank (1) from the outside and is intended to prevent expansion due to resulting outgassing. However, the disadvantages of this known solution are the high additional weight, the additional effort required to attach the tubular frame (2), and the volume loss within the fuel tank (1).

[0030] Fig. Figure 2 shows the net-like fabric (4) arranged between the support elements (3). The net-like fabric (4) is provided with meshes (6). The tensile strength of the net-like fabric (4) as well as the surge function are influenced by the size of the meshes (6). The support elements (3) have several elevations (5) arranged in groups at various locations on the support element (3). The elevations (5) serve to improve the connection between the support element (3) and the inside of the fuel tank (not shown in this figure). The support elements (3) are arranged parallel to one another and, at least in sections, have an arcuate shape to enable optimal adaptation to the geometry of the fuel tank (1). The net-like fabric (4) is arranged essentially vertically between the support elements (3).

[0031] Fig. Figure 3 shows an example of a fuel tank (1) with support elements (3) arranged therein and the mesh fabric (4) stretched in the interior. The support elements (3) are arranged on two opposing inner sides of the fuel tank (1), with the mesh fabric (4) stretched between them. The elevations (5) are also shown in this illustration, but the elevations (5) form a bond with the inner side of the fuel tank (1) during the manufacturing process and thereby melt at least partially. Fig. 3 also shows that the partially curved shape allows for good adaptation to the component geometry of the fuel tank (1). An opening is provided in the fuel tank through which functional parts, such as the fuel pump, can be inserted into the tank after the manufacturing process has been completed, or through which the interior of the fuel tank (1) can be accessed, for example for maintenance purposes. The curved shape of the support elements (3) also allows for the absorption of tensile forces caused by pressure development in the tank and also achieves a good surge effect, without having to change the existing layout of the fuel tank (1) with regard to the opening (7).

[0032] Fig. Figure 4 shows the mesh-like fabric (4) arranged between the support elements (3) and also the functional components (8) attached to the support element (3). The functional components (8) are connected to the support element (3) via a connection point (9), which is preferably formed integrally with the support element (3). A fuel tank (1) contains several functional components (8), such as valves or bubble containers. Because a connection directly to the support element (3) is possible, the functional components (8) can be easily attached to the support element (3) before being inserted into the fuel tank (1), and then inserted into the preform during the manufacturing process together with the support elements (3) and the mesh-like fabric (4). The connection point (9) is preferably formed in a tool directly together with the support element (3) and is matched to the functional component (8) to be attached to it.Fastening can be achieved, for example, by clipping the functional component (8) onto the connection point.

[0033] In Fig. 5, a shrinkage compensation element (10) is provided in the support elements (3). The shrinkage compensation element (10) is provided as a bulge that projects into the interior in the plane of the net-like fabric. In the area of ​​the shrinkage compensation element (10), the support element (3) is not connected to the inside of the fuel tank (1), so that the support element (3) can flexibly respond to stresses caused by shrinkage, which can occur in particular during the cooling of the fuel tank (1) in the manufacturing process, but also during operation of the fuel tank (1). The provision of a shrinkage compensation element (10) prevents the support element (3) from becoming detached from the inside of the fuel tank (1) because the stress differences between the two components become too great.Even in the event of a crash, a shrinkage compensation (10) in addition to the flexible mesh-like fabric can better absorb the forces that occur and thus prevent damage to the fuel tank (1).

[0034] Fig. Figure 6 shows a simplified representation of the manufacturing process of a fuel tank (1) according to the invention. In step a), a preform (11) is first extruded from plastic. The preform (11) is then guided between two open tool halves (12). In a preceding step, the movable device is equipped with the support elements (3) and the mesh-like fabric (4). The movable device comprises a rod assembly (13) that can be moved vertically in the drawing direction and thus in the longitudinal alignment of the fuel tank (1), as well as two arms (14) that can be moved perpendicular to the rod assembly (13). In step a), the mesh-like fabric (4) is inserted into the preform (11) in a compact state compared to its later position in the fuel tank (1). The support elements (3) are arranged close to one another on the rod assembly (13) or lie against one another.It is possible to pre-blow the preform (11) during this step, i.e., to inject air into the preform for stabilization and pre-expansion. This prevents the rod assembly (13) with the support elements (3) and mesh fabric (4) arranged thereon from hitting the inner walls of the preform (11).

[0035] In step b) of the process shown, the mold halves (12) are closed, thus forming a cavity. The preform (11) is then formed into a fuel tank (1) by being pressurized with air and thus pressed against the mold wall. After the blow molding process is completed, the arms (14) of the movable device with the support strips (3) located thereon are extended, thereby stretching the mesh-like fabric (4) inside the fuel tank (1). The wall of the fuel tank (1) is still warm and therefore soft. The arms (14) press the support elements (3) into the wall of the fuel tank (1), thus achieving a permanent and resilient connection between the support element (3) and the fuel tank (1). It is also possible for the arms (14) to be extended during the blow molding process.However, the pressing of the support elements (3) against the inside of the fuel tank can only take place when the preform is in contact with the tool wall.

[0036] In step c), the arms (14) are retracted. They are completely accommodated in the rod (13) to minimize the opening created when the fuel exits the fuel tank (1). The mesh-like fabric (4) is stretched inside the fuel tank (1), and the support elements (3) are connected to the inside of the fuel tank (1).

[0037] In step d), the rod (13) is removed from the finished molded fuel tank (1). The remaining hole in the fuel tank (1) is closed and pinched using slides provided in the mold, so that the fuel tank (1) is completely sealed. The finished fuel tank (1) continues to cool in the mold and is then removed from the mold.

[0038] The Fig. 7 and Fig. 8 show detailed views of the movable device in the retracted and assembled state. In Fig. 7, the rod assembly (13) is shown with the arms (14) folded in. However, the arms (14) are not fully retracted into the rod assembly (13), but protrude perpendicularly to the rod assembly (13) just enough to allow the support elements (3) to be attached to the arms (14) for assembly. For this purpose, a support point (15) can be provided on the support elements (3), which is preferably formed integrally with the support elements (3). The mesh-like fabric (4) is folded for insertion into the preform (11), and the support elements (3) are thus arranged at a short distance from one another. This compact arrangement is necessary because the inlet opening in the preform has a smaller diameter than the subsequent fuel tank (1). Furthermore, this minimizes the risk of contact between the support elements (3) on the inside of the fuel tank (1) before the start of the blow molding process. Fig.Figure 8 shows the movable device in its assembled state. After or during the blow molding process, the arms (14) move toward the rods (13) such that the mesh-like fabric (4) is stretched inside the fuel tank (1) and the support elements (3) are pressed into the interior of the fuel tank (1) to form a permanent connection there. List of reference symbols 1 fuel tank 2 tubular frames 3 support element 4 net-like tissue 5 surveys 6 stitches 7 Opening 8 Functional component 9 Connection point for functional component 10 Shrinkage compensation 11 Preform 12 tool halves 13 rods 14 arms 15 support point

Claims

[1] Fuel tank (1) for a motor vehicle, in the interior of which a net-like fabric (4) is introduced, wherein two support elements (3) are arranged on two opposite inner walls of the fuel tank (1), between which the net-like fabric (4) is stretched, characterized by that the support elements (3) are connected via their extension to the inner walls of the fuel tank (1) and the net-like fabric (4) in order to achieve a uniform distribution of occurring tensile stresses, wherein the connection between the inner walls and the support elements (3) is established during the manufacture of the fuel tank (1) by pressing the support elements (3) into the still heated inner walls. [2] Fuel tank (1) according to claim 1, characterized by that the support elements (3) have an arcuate shape at least in sections. [3] Fuel tank (1) according to one of the preceding claims, characterized bythat the two support elements (3) are arranged parallel to each other. [4] Fuel tank (1) according to one of the preceding claims, characterized by that the net-like fabric (4) is arranged perpendicular to the support element (3). [5] Fuel tank (1) according to one of the preceding claims, characterized by that the support elements (3) are connected to one another by means of a spacer element. [6] Fuel tank (1) according to one of the preceding claims, characterized by that a shrinkage compensation (10) is provided in at least one support element (3). [7] Fuel tank (1) according to one of the preceding claims, characterized by that at least one functional component (8) can be attached to at least one carrier element (3). [8] Fuel tank (1) according to one of the preceding claims, characterized by that the net-like fabric (4) is essentially tensile-resistant. [9] Method for producing a fuel tank (1) comprising the following steps: a. extruding a preform (11); b. Positioning the preform (11) between two open tool halves (12); c. introducing two support elements (3) into the preform (11) such that the support elements (3) are completely surrounded by the preform (11) and the support elements (3) are connected to one another by a net-like fabric (4); d. closing the tool and starting a blow molding process of the preform (11) by pressing it against the tool wall to form the fuel tank geometry; e. Creating a connection between the inside of the fuel tank (1) and the support elements (3) and stretching the mesh-like fabric (4) in the interior of the fuel tank (1) so that the support elements (3) are connected to the inner wall of the fuel tank (1) and the mesh-like fabric (4) via their expansion, wherein the support elements (3) are pressed into the still heated wall of the fuel tank (1) and thus form a connection with it; f. Cool the fuel tank (1) and remove it from the tool. [10] Method according to claim 9, characterized by that at least one support element (3) has elevations (5) on its side facing the inside of the fuel tank (1). [11] Method according to one of claims 9 or 10, characterized bythat the support elements (3) with the net-like fabric (4) arranged between the support elements (3) are introduced into the preform in a compact state. [12] Method according to claim 11, characterized by that the carrier elements (3) with net-like fabric (4) are introduced into the preform (11) by means of a movable device (13, 14). [13] Method according to claim 12, characterized by that the movable device (13, 14) increases the distance between the support elements (3) after the end of the blow molding process for forming the fuel tank geometry in such a way that the support elements (3) are pressed against the inside of the fuel tank (1) and the net-like fabric (4) is stretched in the interior of the fuel tank (1). [14] Method according to claim 12, characterized bythat the movable device (13, 14) already increases the distance between the support elements (3) during the blow molding process in such a way that the support elements (3) are pressed against the inside of the fuel tank (1) and the net-like fabric (4) is stretched in the interior of the fuel tank (1).

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