WO2013174461A1

WO2013174461A1 - Tank made of thermoplastic material, in particular fuel tank or auxiliary fluid tank for a motor vehicle

Info

Publication number: WO2013174461A1
Application number: PCT/EP2013/000752
Authority: WO
Inventors: Timm Heidemeyer; Markus HÜTZEN; Stefan Lenz; Thomas Wagner
Original assignee: Kautex Textron Gmbh & Co. Kg
Priority date: 2012-05-22
Filing date: 2013-03-14
Publication date: 2013-11-28
Also published as: DE102012010447A1

Abstract

The invention relates to a tank (1) made of thermoplastic material, in particular a fuel tank or auxiliary fluid tank for a motor vehicle having at least one tensioning strap (2a, 2b) retaining the tank from below and/or encompassing the tank (1) in the installed position on the motor vehicle, said tensioning strap comprising means for fastening to the supporting structure of the motor vehicle, wherein the container (1) is characterized in that the tensioning strap (2a, 2b) comprises fibers having tensile strength and which are embedded in a plastics matrix and in that the tensioning strap (2a, 2b) is connected by a material connection at least in sections to the tank wall.

Description

Tank made of thermoplastic material, in particular fuel tank or auxiliary fluid tank for a motor vehicle

The invention relates to a tank made of thermoplastic material, in particular a fuel tank or auxiliary fluid tank, having at least one tensioning strap retaining the tank from below and/or encompassing the tank in the installed position on the motor vehicle, said tensioning strap comprising means for fastening to the supporting structure of the motor vehicle.

Such a tank is disclosed, for example, in DE 33 25 449 Al, wherein the fuel tank described therein has a plurality of ribs which may be fastened to the vehicle body by means of screws and which retain the fuel tank during normal operating conditions of the motor vehicle. Additionally, an auxiliary structure consisting of metal straps is provided for retention and support, said metal straps being positioned around the fuel tank in a cradle-shaped manner and being fastened by means of screws to the vehicle body. The metal straps are shaped and dimensioned such that in the mounted state they are tension-free and serve as back-up support for the fuel tank. This structure has the advantage that the metal straps have a relatively small thickness and, if required, i.e. in the event of a crash or fire, said metal straps increase the stability of the fuel tank.

However, the structure is also relatively costly. As the metal straps are only provided as an auxiliary structure and in the mounted state said metal straps are tension-free under normal operating conditions, when the fuel tank is full, the tank base is able to hang down to a certain extent.

This sagging of the tank base when the fuel tank is full is a problem, in particular in tanks of large volume and with tank wall regions which are relatively large but not additionally structurally reinforced/stiffened.

In principle, tensioning strap fastenings of fuel tanks are known in the prior art, said tensioning strap fastenings not being tension-free in the installed position of the tank, i.e. they receive the tank and secure the tank to the supporting structure of the body. Said tensioning straps have a certain inherent rigidity, so that due to their inherent rigidity they act in a reinforcing manner on the structure of the fuel tank. The mounting of such tensioning strap systems is relatively costly, in particular the mounting of the fuel tank on the motor vehicle is awkward. Finally, such an arrangement has a considerable weight.

For the purpose of reducing the weight of the fastening system, for safety reasons a functional separation between the fastening of the tank to the vehicle structure and the retention of the tank from below is proposed in DE 33 25 449 Al .

The object of the invention, therefore, is to configure a tank of the type mentioned in the introduction so that by relatively simple means it may be mounted on the supporting structure of the motor vehicle, wherein the mounting is intended both to stabilize the tank and to be relatively lightweight.

The object is achieved by a tank made of thermoplastic material, in particular a fuel tank or auxiliary fluid tank for a motor vehicle, having at least one tensioning strap retaining the tank from below and/or encompassing the tank in the installed position on the motor vehicle, said tensioning strap comprising means for fastening to the supporting structure of the motor vehicle, wherein the tank is characterized in that the tensioning strap comprises an arrangement of fibers having tensile strength and which are embedded in a plastics matrix and in that the tensioning strap is connected by a material connection at least in sections to the tank wall.

The essential difference from the prior art may be seen to be that the tensioning straps used are relatively lightweight and flexible, and thus bear fully against the contour of the tank and are primarily connected by a material connection to the tank such that a relative movement in the pulling direction of the tensioning strap is not possible between the tank wall and the tensioning strap. As deformations of the tank wall directly introduce tensile forces into the tensioning strap, the tensioning strap reliably prevents the tank wall from sagging or hanging down, and at the same time the tensile forces are introduced into the structure of the motor vehicle so that the fastening system provided according to the invention combines all the previously mentioned advantages therein.

In particular, the tank according to the invention provided with one or more tensioning straps may be entirely prefabricated so that the mounting on the motor vehicle is substantially simplified.

The tensioning strap may have both a thermosetting matrix, for example based on epoxy resin and a thermoplastic matrix.

In a particularly preferred variant of the tank according to the invention, it is provided that the tensioning strap has a thermoplastic matrix which is welded to the external skin of the tank. The welding may, for example, take place by fusing and pressing a prefabricated strap (prepeg strap) onto the external skin of the tank, for example by means of a laser, infrared radiation or by means of hot air. The strap may be welded over its entire contact surface and/or length to the external skin of the tank but said strap may only be welded onto the external skin at predetermined anchoring points on the external skin of the tank, wherein the tensioning strap is arranged so that said tensioning strap, in particular in the case of deformation of the tank caused by internal pressure, absorbs tensile forces. For example, the tensioning strap is able to be clamped around the tank so that said tensioning strap extends between regions of the tank which are structurally and/or geometrically more rigid, wherein at least in the region of the more rigid regions of the tank the tensioning strap is welded thereto at predetermined anchoring points on the external skin of the tank.

Naturally, it is possible and expedient to weld the tensioning strap to the tank over its entire contact surface with the external skin of the tank.

For example, a matrix based on HDPE (high density polyethylene) may be provided as a thermoplastic matrix .

Expediently, the tank wall also comprises at least one HDPE external skin so that the tensioning strap and the tank are compatible in terms of their ability to be welded together.

It is possible, for example, for the tank to have been produced in one piece by the extrusion blow-molding of thermoplastic material. It is possible for said tank to have been produced, for example, as a multiply or multilayered tank with an internal barrier layer made of EVOH. Naturally, it is also possible for the tank to have been assembled from injection-molded or deep-drawn half-shells . Expediently, glass fibers or carbon fibers or aramid fibers or basalt fibers or the like are provided as fibers having tensile strength, said fibers preferably being aligned in the longitudinal extent of the tensioning strap. Preferably, the fibers are formed as endless fibers.

A variant of the tank according to the invention is characterized in that as fastening means at least one eye or at least one eyelet is inserted into the tensioning strap or said tensioning strap is provided at the end with at least one eye or at least one eyelet or a loop or the like.

In a particularly advantageous embodiment of the tank according to the invention, the tensioning strap is configured as a continuous strap loop which, for example, loops around correspondingly formed projections, retaining tabs or retaining brackets of the tank.

For example, at least one eye or at least one eyelet may be provided as a fastening means which passes through the tensioning strap and which is preferably arranged in a congruent manner with an eye or an eyelet in a fastening projection or retaining tab of the tank. In this sense, "congruent" means that the eye or the eyelet in the tensioning strap is arranged concentrically or aligned with an eye or an eyelet in a fastening projection or a retaining tab of the tank.

The tensioning strap may be welded to the tank, at least in the region of integrally formed retaining tabs or retaining brackets. In particular, when the tensioning strap extends over retaining brackets or retaining tabs of the tank which are integrally formed thereon, the tensioning strap not only fulfils the fastening function on the vehicle structure, but also forms a structural reinforcement of the relevant retaining tab or the relevant bracket. Retaining tabs or retaining brackets which are integrally formed on the tank, in particular due to the tendency of the plastics material to creep under continual load, have to be of a correspondingly stable design. In a particularly advantageous manner, the tensioning strap according to the invention increases the structural strength of such integrally formed retaining elements.

By means of the tensioning strap, alternative retaining brackets or retaining tabs may be fixed to the tank. For example, the tensioning strap may overlap parts of at least one retaining bracket or retaining tab such that the retaining tab or the retaining bracket is wrapped around on the tank. The tensioning strap may be wound in multiple layers as a whole or just in the regions in which the fastening means are intended to be fastened to the tank.

The tensioning strap may be deposited on the tank, for example in the region of the retaining tabs or retaining brackets, such that said tensioning strap loops around the retaining tabs or retaining brackets at least once, preferably repeatedly.

In an advantageous embodiment of the tank according to the invention, it may be provided that at least one guide groove is provided for at least one tensioning strap at least in partial regions of the tank. As a result, on the one hand, it is ensured that the tensioning strap extends as straight as possible between the corners and edges of the tank, so that it is ensured that in the event of deformation of the tank caused by internal pressure said tensioning strap always absorbs tensile forces, and at the same time the tensioning strap may thus be relatively easily incorporated into the tank contour. In a preferred variant of the tank according to the invention, it is provided that a continuous tensioning strap loops around at least two integrally formed retaining tabs of the tank, wherein the retaining tabs are provided in each case with a guide track or a guide groove into which the tensioning strap is inserted.

The tensioning strap may be configured, for example, as a figure of eight or in the shape of a pretzel, preferably as a continuously looped tensioning strap, which in each case at the end loops around a retaining tab and in the region of the strap intersection retains the large surface area of the underside of the tank from below. The invention is described hereinafter with reference to an exemplary embodiment shown in the drawings, in which : figure 1: shows a schematic view of a tank according to the invention in the installed position, figure 2: shows a perspective view of a tank according to a second exemplary embodiment of the invention in the installed position, figure 3: shows a side view of a part of the tank shown in figure 2.

The tank 1 according to the invention is configured, for example, as a fuel tank made of thermoplastic material. It is possible for the tank to have been produced, for example, by extrusion blow-molding and in the simplest case the tank has an approximately cuboidal shape. Said tank is fastened, for example, to the underbody of the motor vehicle in the rear of the vehicle by means of a plurality of tensioning straps 2. According to the size and shape of the tank, said tank is able to be fastened to the structure of the motor vehicle by means of just one tensioning strap 2. In the variant shown in figures 2 and 3, the tank 1 is fastened by a plurality of tensioning straps 2.

Figure 1 illustrates the simplest variant of a tank 1 which is fastened in the installed position to a motor vehicle by a tensioning strap 2. The tensioning strap 2 is configured as longitudinal fiber strap and comprises glass fibers and/or aramid fibers and/or carbon fibers having tensile strength and which are aligned in the longitudinal direction of the tensioning strap 2 and embedded in a thermoplastic matrix. These so-called prepeg straps may be prefabricated in the form of rolled goods, and preferably immediately after molding the tank, for example by extrusion blow-molding, deposited by the roller onto the tank 1, for example welded to the external skin of the tank 1. Such welding may, for example, take place by means of laser radiation, infrared radiation or hot air fans, wherein the tensioning strap 2 is deposited flat on the external skin of the tank 1, locally heated and fused by means of infrared radiation or laser radiation or hot air in the contact region on the external skin of the tank 1 during the deposition and pressed in the softened region against the external skin of the tank by means of a contact pressure unit, not shown, for example a contact pressure roller, so that due to the pressure applied in the region of the contact line, the tensioning strap 2 is welded to the external skin of the tank 1.

Alternatively, the tensioning strap 2 may comprise fibers having tensile strength and which are embedded in an epoxy resin matrix, wherein the tensioning strap 2 is then deposited on the tank in the still plastic state . In the variant shown in figure 1 of the tensioning strap 2, said tensioning strap comprises at the end fastening eyelets 3 by means of which the tensioning strap 2 may be fastened to the structure of a motor vehicle, for example an underbody of the motor vehicle, and namely by means of screw bolts which pass through the fastening eyelets 3. In the variant shown in figure 1 of the tank 1, the tensioning strap 2 is welded over its entire bearing surface to the external skin of the tank 1, so that a relative movement is not possible between the tensioning strap 2 and the tank 1 in the pulling direction of the tensioning strap.

Figures 2 and 3 show alternative embodiments of the tank according to the invention, wherein the tank 1 comprises two tensioning straps 2a, 2b, wherein the tensioning strap 2a shown in figure 2 on the left-hand side is laid in a strap track 4 of the tank 1 which has a groove-shaped cross-sectional profile. The second tensioning strap 2b is configured as a continuous strap and looped in a figure of eight and/or in the shape of a pretzel, wherein the regions of the tensioning strap 2b positioned to form loops encompass integrally-formed retaining tabs 5 of the tank 1, as shown in the detailed view of figure 3. The strap intersection 6 formed by the tensioning strap 2b comes to bear against the large surface area of the underside 7 of the tank 1 such that the tank 1 is retained from below at numerous points so that the stability of the underside 7 of the tank 1 is markedly increased. Such an arrangement and configuration of the tensioning strap 2b has proved particularly advantageous, in particular to prevent the underside 7 of the tank 1 from hanging down. As may be derived from figure 3, the tensioning strap 2b shown to the right in figure 2 in the region in which it is arranged on the retaining tabs 5, is provided with a fastening eyelet 3, which is arranged coaxially to a fastening bore 8 in the retaining tab 5, so that the fastening bore 8 and the fastening eyelet 3 arranged coaxially thereto may be penetrated by a threaded bolt. The tensioning strap 2b is preferably welded over its entire length to the external skin of the tank 1.

As already mentioned above, it is also possible for the tensioning straps 2, 2a, 2b to be welded only in sections to the external skin of the tank 1.

List of reference numerals

1 Tank

2, 2a, 2b Tensioning straps 3 Fastening eyelets

4 Strap track

5 Retaining tabs

6 Strap intersection

7 Underside of the tank 8 Fastening bore

Claims

1. A tank made of thermoplastic material, in particular a fuel tank or auxiliary fluid tank for a motor vehicle, having at least one tensioning strap (2, 2a, 2b) retaining the tank from below and/or encompassing the tank (1) in the installed position on the motor vehicle, said tensioning strap comprising means for fastening to the supporting structure of the motor vehicle, characterized in that the tensioning strap (2, 2a, 2b) comprises an arrangement of fibers having tensile strength and which are embedded in a plastics matrix and in that the tensioning strap (2, 2a, 2b) is connected by a material connection at least in sections to the tank wall.

2. The tank as claimed in claim 1, characterized in that the tensioning strap (2, 2a, 2b) has a thermoplastic matrix which is welded to the external skin of the tank (1).

3. The tank as claimed in one of claims 1 or 2, characterized in that glass fibers and/or carbon fibers and/or aramid fibers or the like are provided as fibers having tensile strength, said fibers being preferably aligned in the longitudinal extent of the tensioning strap (2, 2a, 2b) .

4. The tank as claimed in one of claims 1 to 3, characterized in that as fastening means at least one eye or at least one eyelet is inserted into the tensioning strap (2, 2a, 2b) or said tensioning strap is provided at the end with at least one eye or at least one eyelet.

5. The tank as claimed in one of claims 1 to 4, characterized in that the tensioning strap (2, 2a, 2b) is configured as a continuous strap loop.

6. The tank as claimed in one of claims 1 to 5, characterized in that at least one eye or at least one eyelet is provided as a fastening means which passes through the tensioning strap (2, 2a, 2b) and which is arranged in a congruent manner with an eye or an eyelet in a fastening projection or retaining tab of the tank (1) -

7. The tank as claimed in one of claims 1 to 6, characterized in that the tensioning strap (2, 2a, 2b) is welded to the tank (1), at least in the region of integrally formed retaining tabs (5) or retaining brackets .

8. The tank as claimed in one of claims 1 to 7, characterized in that at least one guide groove or strap track (4) is provided for at least one tensioning strap (2, 2a, 2b) at least in partial regions of the tank (1) .

9. The tank as claimed in one of claims 1 to 8, characterized in that a continuous tensioning strap (2b) loops around at least two integrally formed retaining tabs (5) of the tank (1), wherein the retaining tabs (5) are provided in each case with a strap track (4) or a guide groove into which the tensioning strap (2b) is inserted.