Extrusion-blow-molded fuel tank of thermoplastic material and method for the production thereof

Abstract

The invention relates to an extrusion-blow-molded fuel tank (1) of thermoplastic material comprising a tank wall of a composite of various layers obtained in various production operations, at least one first layer comprising at least one shell-shaped supporting shell (8) and a second layer of a thermoplastic material forming an adhesive bond with the supporting shell (8), and the supporting shell (8) having a greater strength than the second layer. The supporting shell (8) forms an inner layer of the tank and the second layer forms an outer skin of the tank, two supporting shells within the tank forming a supporting cage or a supporting housing.

Claims

1. A fuel tank comprising: a tank wall of a composite having a plurality of layers, the plurality of layers comprising at least a first layer and a second layer, the first layer having an outer surface, the second layer having an inner surface, the outer surface of the first layer and the inner surface of the second layer facing each other and at least one of welded and bonded to each other, the second layer formed of a thermoplastic material, the first layer provided by at least one shell-shaped supporting shell, the supporting shell having a greater strength than the second layer, and the supporting shell forms an inner layer of the tank and the second layer forms an outer skin of the tank, wherein: the first layer comprises a first polymer material; the second layer comprises a second polymer material; and the first polymer material and the second polymer material are different.

2. The fuel tank as claimed in claim 1, wherein the fuel tank comprises a supporting cage or a supporting housing made up of at least two supporting shells.

3. The fuel tank as claimed in claim 1, wherein at least one supporting shell is connected in a material-bonding and/or form-fitting manner to the outer skin of the tank.

4. The fuel tank as claimed in claim 1, wherein at least two supporting shells, forming a supporting housing or supporting cage, are connected to one another by at least one element absorbing at least tensile forces when the tank is subjected to internal pressure.

5. The fuel tank as claimed in claim 1, wherein at least one of the supporting shells is formed as a component carrier for functional components of the tank.

6. The fuel tank as claimed in claim 1, wherein at least one supporting shell is formed from a fiber composite material.

7. The fuel tank as claimed in claim 1, comprising two supporting shells, which are engaged from behind by a two-part tie bar.

8. The fuel tank as claimed in claim 1, wherein at least one supporting shell is welded and/or adhesively bonded to the outer skin.

9. The fuel tank as claimed in claim 1, wherein at least one supporting shell is adapted to the internal contour of the tank.

10. The fuel tank as claimed in claim 1, wherein the supporting shell comprises a sheet formed into a plurality of planar side wall sections of a three-dimensional shape.

11. The fuel tank as claimed in claim 1, wherein the supporting shell has a box-shaped contour with at least one slit provided in a corner region of the box-shaped contour.

12. A fuel tank comprising: a tank wall having a plurality of layers, the plurality of layers comprising at least a first layer and a second layer, the first layer disposed as an inner layer of the tank, and the second layer disposed as an outer layer of the tank, the first layer formed of a composite material comprising fibers in a matrix and having an outer surface, the second layer formed of thermoplastic and having an inner surface, the first layer provided by at least one box-shaped inner shell having an outer surface, the second layer provided by at least one box-shaped outer shell having an inner surface, the outer surface of the inner shell and the inner surface of the outer shell facing each other and bonded to each other, wherein: the matrix of the first layer comprises a first polymer material; the thermoplastic of the second layer comprises a second polymer material; and the first polymer material and the second polymer material are different.

13. The fuel tank as claimed in claim 12, wherein: the at least one box-shaped inner shell having an outer surface further comprises a first box-shaped inner shell having an outer surface, and a second box-shaped inner shell having an outer surface, the at least one box-shaped outer shell having an inner surface further comprises a first box-shaped outer shell having an inner surface, and a second box-shaped outer shell having an inner surface, the outer surface of the first inner shell and the inner surface of the first outer shell facing each other and bonded to each other, the outer surface of the second inner shell and the inner surface of the second outer shell facing each other and bonded to each other.

14. The fuel tank as claimed in claim 13, wherein: the inner surface of the first outer shell and the inner surface of the second outer shell facing each other and bonded to each other.

15. The fuel tank as claimed in claim 14, wherein: the inner surface of the first outer shell and the inner surface of the second outer shell are bonded to each other along a periphery of the fuel tank.

16. The fuel tank as claimed in claim 13, wherein: the first inner shell and the second inner shell form an interior cage or interior housing of the fuel tank.

17. The fuel tank as claimed in claim 13, wherein: the first inner shell and the second inner shell are connected to each other by at least one element arranged to absorb at least tensile forces when the tank is subjected to internal pressure.

18. The fuel tank as claimed in claim 17, wherein: the at least one element comprises a tie-bar.

19. The fuel tank as claimed in claim 13, wherein: at least one of the first inner shell and the second inner shell is a component carrier for at least one component within the tank.

20. The fuel tank as claimed in claim 12, wherein: the outer surface of the inner shell and the inner surface of the outer shell facing each other are at least one of welded and adhesively bonded to each other.

21. The fuel tank as claimed in claim 12, wherein: the composite material of the first layer further comprises a fiber mat encapsulated in a thermoplastic matrix or a thermosetting matrix.

22. The fuel tank as claimed in claim 12, wherein: the first outer shell and the second outer shell form a hollow body.

23. The fuel tank as claimed in claim 21, wherein: the fiber mat is encapsulated in the thermoplastic matrix; and the thermoplastic matrix does not form the second layer.

24. The fuel tank as claimed in claim 21, wherein: the fiber mat is encapsulated in the thermosetting matrix; and the thermosetting matrix does not form the second layer.

25. The fuel tank as claimed in claim 12, wherein: the thermoplastic of the second layer is an extrudate.

26. The fuel tank as claimed in claim 1, wherein: the thermoplastic material of the second layer is an extrudate.

27. The fuel tank as claimed in claim 1, wherein: the thermoplastic material of the second layer does not form the first layer.

Description

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

(2) FIG. 1 shows a schematic sectional view through a blow-molding tool in the production of the extrusion-blow-molded fuel tank according to the invention, the representation showing the introduction of the preforms into the blow-molding tool,

(3) FIG. 2 shows a view corresponding to FIG. 1, which illustrates the molding of the preforms in the mold,

(4) FIG. 3 shows a view corresponding to FIG. 2, which shows the introduction of the supporting shells into the mold impression,

(5) FIGS. 4 and 5 show schematic representations of the supporting shells,

(6) FIG. 6 shows a method step of the method according to the invention in the fixing of the supporting shells on the shells forming the outer skin of the tank,

(7) FIG. 7 shows a view corresponding to FIG. 6 after complete attachment of the supporting shells,

(8) FIG. 8 shows a view corresponding to FIG. 7, without the manipulator represented in FIG. 6 for the purpose of attaching the supporting shells,

(9) FIGS. 8 and 9 show the operation of joining the tank shells to form a closed tank and

(10) FIG. 10 shows the finished tank demolded from the tool.

(11) FIGS. 1 to 3 first illustrate the method according to the invention for producing the fuel tank 1 according to the invention. Therefore, the method is discussed first hereinafter.

(12) The method described below comprises the extrusion of two preforms 2 in web or strip form of thermoplastic material. The plastic has previously been plasticated in an extruder and fed to an extrusion head, which for the sake of simplicity is only represented in an indicated manner. The extrusion head comprises two slot dies, from which the extrudate in melt form emerges in the form of sheet-like preforms 2 in web form. In the case of the exemplary embodiment described, the preforms 2 are extruded directly between the opened halves 3a, 3b of a blow-molding tool 3. The halves 3a, 3b of the blow-molding tool 3 respectively form a part-cavity and define a mold impression for the molding of the preforms 2 into shell-shaped semifinished products, which in a further method step are joined to form a closed tank. As soon as the preforms 2 have been extruded to their full length, the halves 3a, 3b of the blow-molding tool 3 are displaced against a tool divider 4, as is represented in an indicated manner in FIG. 2. The tool divider 4 may be formed as a plate or surrounding sealing frame, which respectively seals off the part-cavity of the halves of the blow-molding tool 3 in such a way that the preforms can be molded into shells 5 by using differential pressure in the part-cavities, as is represented in FIG. 2. This may be accomplished either by evacuation of the part-cavities or else by subjecting them to blowing pressure by means of a blowing pin that is not shown or outlets that are not shown in the tool divider 4.

(13) For the purposes of this application, in the case of the method step described in FIGS. 1 and 2 reference is only made to a partial molding of the preforms 2 into shells, since the shells 5 are only molded to the extent that is required for them to be brought to bear against the contour of the tool.

(14) In a further method step, the halves 3a, 3b of the blow-molding tool 3 are opened again. The tool divider 4 is removed from the intermediate space between the halves 3a, 3b of the blow-molding tool 3, after which (FIG. 3) a mounting carrier 6 is brought between the halves 3a, 3b of the blow-molding tool. The mounting carrier 6 may take the form of a frame or a platen with pneumatic and/or hydraulic devices or a core with the same such devices. In the present case, pneumatic adjusting devices 7, which respectively receive a supporting shell 8 on both sides of the mounting carrier 6, are provided on the mounting carrier 6. The supporting shells 8 respectively consist of a so-called organometallic sheet, for example an aramid-fiber mat embedded in a thermoplastic matrix. The supporting shells 8 are self-supportingly stiff and dimensionally stable. They have been produced in a separate method step. The contour thereof is in the present case box-shaped and corresponds approximately to the given internal contour of the finished fuel tank 1. The supporting shells have been previously fitted out with functional components 81 and also with in each case a column-shaped support 9.

(15) For the purposes of the present application, functional components 81 are understood as meaning the internals required for the operation of a fuel tank for a motor vehicle, such as venting valves, rollover valves, surge tanks, pumps and sensors. The functional components 81 may be connected to one another by lines. The complete fabrication of the supporting shells with functional components arranged on them and connected to one another by lines may have been performed outside the molding and joining operation that is represented in the figures. The functional components 81 have been attached to the supporting shells 8 in an ideal layout for the fuel tank 1 concerned.

(16) The supporting shells 8 lying opposite the supports 9 respectively comprise plug-in elements 9a, 9b, which have been formed so as to complement one another and fit in one another, are for example of a cylindrical form and may be respectively equipped with locking means that are not represented. In addition, the supports 9 may be respectively provided with a base, which engages behind the supporting shell 8 concerned, in the region of a depression 11. The plug-in elements 9a, 9b of the supports 9 pass through corresponding openings 15 in the bottom of the supporting shells 8.

(17) On their side facing the shells 5, the supporting shells 8 may be provided with reinforcing ribs, channels or a profiling.

(18) The pneumatic adjusting devices are formed as pneumatic cylinders, which are respectively provided with receptacles 12 for the supporting shells 8.

(19) With the aid of the pneumatic adjusting devices, which can for example be retracted and extended in and counter to the possible adjusting movement of the halves 3a, 3b of the blow-molding tool 3, the supporting shells 8 are brought into the cavities of the blow-molding tool 3 and press there against the still molten shells 5. This may be performed if appropriate with an adhesion promoter that is not shown interposed. If the supporting shells 8 have a thermoplastic matrix, they are previously heated by means of a heating device that is not represented and then pressed against the shells 5.

(20) As is represented in FIG. 6, the pneumatic adjusting devices 7 are provided with pneumatic cylinders, which allow an extending movement of the receptacles 12 transversely in relation to the opening and closing direction of the halves 3a, 3b of the blow-molding tool 3, so that the surrounding skirt 13 of the supporting shell 8 can be pressed together with the opposing inner wall of the shells 5.

(21) Since the supporting shells 8 are a self-supportingly stiff construction, a corresponding compliance of the skirt 13 is ensured by slits 14 provided in the corner regions of the box-shaped contour. Once the supporting shells 8 have been connected to the preforms 2 molded into shells 5, the mounting carrier 6 is moved away between the halves 3a, 3b of the blow-molding tool 3.

(22) In a further method step, the halves 3a, 3b of the blow-molding tool are moved together, the halves concerned of the fuel tank being respectively joined together as a composite of the thermoplastic shells 5 and the supporting shells 8, to be precise essentially by welding of the surrounding periphery 16 of the shells 5. The pin-shaped plug-in end 9a of one supporting shell 8 thereby penetrates into the socket-shaped plug-in element 9b on the other supporting shell. The plug-in elements 9a and 9b lock together, so that in the finished fuel tank 1 they form a tie bar connecting the walls thereof.

LIST OF DESIGNATIONS

(23) 1 Fuel tank 2 Preforms 3 Blow-molding tool 3a, 3b Halves of the blow-molding tool 4 Tool divider 5 Shells 6 Mounting carrier 7 Pneumatic adjusting device 8 Supporting shell 81 Functional components 9 Support 9a, 9b Plug-in elements 10 Base 11 Depression 12 Receptacles 13 Skirt 14 Slits 15 Openings 16 Periphery of the shells