Method for manufacturing a fuel tank and fuel tank

Abstract

The invention relates to a method for manufacturing a fuel tank on the basis of thermoplastic material, the method comprising the following method steps: producing semifinished products in sheet form from a fiber composite material with a matrix of thermoplastic material, laminating the semifinished products with a laminate that comprises at least one barrier layer for hydrocarbons, heat-treating the laminated semifinished products until the thermoplastic material plasticizes, thermoforming the plasticized semifinished products in a thermoforming mold to form shells and joining the shells to form an essentially closed tank.

Claims

1. A method for manufacturing a fuel tank, comprising: producing a laminate having a plurality of layers, at least one layer of the plurality of layers being a barrier layer for hydrocarbons, producing semifinished products in sheet form of fiber-reinforced material, each semifinished product of the semifinished products comprising woven or laid fibers embedded in a thermoplastic matrix, the fibers comprising at least one of glass fibers, carbon fibers and aramid fibers, after producing the laminate and the semifinished products, heat laminating the semifinished products with the laminate to provide laminated semifinished products, cooling the laminated semifinished products, after cooling the laminated semifinished products, heating the laminated semifinished products until the thermoplastic matrix plasticizes, thermoforming the plasticized laminated semifinished products to form shells, and joining the shells to form the fuel tank.

2. The method according to claim 1, wherein the laminated semifinished products are only laminated on one side and the laminated side forms an inner side of the fuel tank.

3. The method according to claim 1, wherein the shells are each formed with a peripherally encircling flange.

4. The method according to claim 1, wherein the step of joining the shells comprises a peripheral welding of the shells.

5. The method according to claim 4, wherein, during or after the welding, the flange of the shells is bent over to create an edge-formed seam.

6. The method according to claim 4, wherein the flange is provided with a peripheral profile, which reaches around the end faces of the shells.

7. The method according to claim 6, wherein the peripheral profile is adhesively bonded or welded to the shells.

8. The method according to claim 1, also comprising introducing inserts into the tank before the joining of the shells.

9. The method according to claim 8, wherein the inserts are premounted on an insert carrier and in that the insert carrier is inserted into at least one of the shells as a lost carrier.

10. The method according to claim 9, wherein the insert carrier is welded or clamped to at least one of the shells.

11. The method according to claim 1, wherein, before the joining, at least one shell is provided with at least one lead-through for at least one line connection, into which a connection element is inserted from the inside in a sealing manner.

12. The method according to claim 1, wherein the laminate has a maximum thickness of 1.25 mm.

13. The method according to claim 1, wherein the barrier layer has a thickness in a range of 50 to 250 micrometers.

14. The method according to claim 1, wherein a thickness ratio of the fiber-reinforced material to the laminate for at least one of the shells is in a range of 1.2 to 2.

15. The method according to claim 1, wherein the plurality of layers comprise at least five layers with EVOH as the barrier layer.

16. The method according to claim 15, wherein the barrier layer is sandwiched between two adhesion promoter layers, and the barrier layer and the two adhesion promoter layers are sandwiched between two covering layers.

17. The method according to claim 16, wherein each layer of the two adhesion promoter layers has a maximum thickness of 200 micrometers.

Description

(1) The invention is explained below on the basis of an exemplary embodiment that is represented in the drawings, in which:

(2) FIG. 1 shows a section through a tank wall of a fuel tank manufactured by the method according to the invention,

(3) FIG. 2 shows a view from the inside of an upper shell of the fuel tank according to the invention,

(4) FIG. 3 shows a section through the tank wall of the fuel tank according to the invention in the region of a lead-through,

(5) FIG. 4a shows a section through the tank wall in the region of the encircling flange before the bending over,

(6) FIG. 4b shows a section through the bent-over edge-formed seam of the tank,

(7) FIG. 5 shows a section through the tank wall in the region of the flange that is reached around by a peripheral profile and

(8) FIG. 6 shows a section through the tank wall in the region of the flange just before the welding of the shells.

(9) Reference is first made to FIG. 2 of the accompanying drawings.

(10) FIG. 2 shows a view into an upper shell 1 of a fuel tank according to the invention. The fuel tank is joined together from the upper shell 1 and a lower shell 2, complementing the upper shell, to form an essentially closed hollow body. A full view of the fuel tank is not shown in the drawings.

(11) Both the upper shell and the lower shell are provided with an encircling flange 8, at which the upper shell 1 and the lower shell 2 are joined to form the closed tank.

(12) As already mentioned at the beginning, both the upper shell 1 and the lower shell 2 consist of a carrier material in the form of an organometallic sheet 3 and a laminate 4 laminated-on on one side, which in the present case is formed as a multi-layer film. The organometallic sheet 3 consists, for example, of a base material/matrix material of HDPE (High-Density Polyethylene) with fibres embedded in it in the form of carbon fibres, glass fibres or aramid fibres. The fibres are embedded in the matrix material in the form of a laid or woven structure. The organometallic sheet may be additionally provided on the visible side/outer side with an HDPE covering layer, which ensures that the fibre reinforcement is completely covered.

(13) The laminate 4 that is provided on the inside of the organometallic sheet 3 comprises two HDPE covering layers 5, two layers of adhesion promoter 6 and an EVOH layer 7 as a barrier layer.

(14) A method for manufacturing the fuel tank according to the invention envisages the provision of a completely made-up and laminated semifinished product in the form illustrated in FIG. 1. The semifinished product is first subjected to a heat treatment and then shaped into shells in a thermoforming mould.

(15) At the same time, the shells are formed with a preferably encircling flange 8.

(16) In the region of this flange, the shells, i.e. the upper shell 1 and the lower shell 2, are preferably joined, i.e. connected to one another with a material bond, preferably welded to one another.

(17) The different variants of the peripheral connection of the upper shell 1 and the lower shell 2 are illustrated in FIGS. 4 to 6.

(18) FIGS. 4a and 4b show two successive method steps of the peripheral joining of the upper shell 1 and the lower shell 2, the procedure that is shown in FIGS. 4a and 4b being favourable if the flange 8 of the upper shell 1 and the lower shell 2 are respectively of different lengths.

(19) In a first step, the just-formed upper shell 1 and lower shell 2 are placed one on top of the other, as represented in FIG. 4a. In this state, the upper shell 1 and the lower shell 2 may be still warm and plastic, so that subsequent welding can be performed by using the basic heat of the material.

(20) In principle, however, the upper shell 1 and the lower shell 2 may also have been placed one on top of the other in the cold state. Then, for example, the flange 8 of both shells 1, 2 is heated by means of infrared radiation and softened until they plasticize.

(21) In a next step, for example, the flange 8 of the lower shell 2 is folded over around the flange 8 of the upper shell 1 with a suitable tool (see FIG. 4b), so that the fuel tank is given a peripheral edge-formed seam 9, which in particular also forms a sealing labyrinth because of the multiple folding of the individual layers.

(22) This type of connecting technique makes allowance in particular for the fact that the layer thickness of the laminate 4 is at most 1.25 nm, essentially only the covering layers 5 of the laminate 4 contributing to the welding.

(23) An alternative embodiment of the joining operation is represented in FIG. 5.

(24) The upper shell 1 and the lower shell 2 have a flange of the same dimensions; the flanges 8 are placed flush one on top of the other for the purpose of connecting the shells. Then, a U-shaped peripheral profile 10 of thermoplastic material, preferably of HDPE, is placed onto the tank seam, reaching around the flanges 8. The peripheral profile 10 is welded to the outer side of the organometallic sheets 3 while applying pressing pressure under heat.

(25) Alternatively, adhesive bonding of the peripheral profile 10 may be provided, for example, with an adhesion promoter on the basis of LDPE.

(26) The method according to the invention comprises the introduction of inserts 11 into the fuel tank before the joining of the upper shell 1 and the lower shell 2. For this purpose, the inserts, for example in the form of valves, nipples, filling-level sensors, surge tanks or the like, are premounted in a predetermined layout of the tank shell concerned on an insert carrier 12 in the form of a lattice support of thermoplastic material. The insert carrier 12 is then placed in the position shown in FIG. 2 in the upper shell 1 of the fuel tank.

(27) The insert carrier 12 is formed, for example, as an injection-moulded plastic carrier, which is adapted to the contour of the upper shell 1 and has, for example, been placed into the upper shell 1. Alternatively, clamping or else welding is possible. The inserts 11, in the present case valves, are connected to one another by way of a relatively stiff venting line 13. One of the inserts 11 is provided with a connection nipple 14, which passes through a lead-through 15 of the upper shell 1.

(28) The lead-through 15 is produced, for example, after completion of the upper shell 1 and before joining of the upper shell 1 to the lower shell 2, by cutting out a circle. Then, the insert carrier 12 is brought into the upper shell 1 in such a way that the connection nipple 14 passes through the lead-through 15. The connection nipple 14 lies, for example, with an encircling collar 16 against the laminate 4. The collar is provided with an annular groove 17, placed in which is an O-ring seal, which seals off the connection nipple 14 from the lead-through 15.

(29) The connection nipple 14 is also provided with a thread 19, which passes through the lead-through 15. On the outer side of the upper shell 1, the nipple is secured by a nut 20, which engages in the thread 19.

(30) Alternatively, the connection nipple 15 may be latched by a fastening element provided on the outer side of the upper shell 1.

LIST OF REFERENCE SIGNS

(31) 1 Upper shell

(32) 2 Lower shell

(33) 3 Organometallic sheet

(34) 4 Laminate

(35) 5 HDPE covering layer

(36) 6 Layer of adhesion promoter

(37) 7 EVOH layer

(38) 8 Flange

(39) 9 Sealing labyrinth

(40) 10 Peripheral profile

(41) 11 Inserts

(42) 12 Insert carrier

(43) 13 Venting line

(44) 14 Connection nipple

(45) 15 Lead-through

(46) 16 Collar

(47) 17 Annular groove

(48) 18 O-ring seal

(49) 19 Thread

(50) 20 Nut