Abstract
The invention relates to a method for producing a pressure accumulator (1), in particular for accumulating hydrogen in motor vehicles, wherein first of all an inner liner (3) of the pressure reservoir (1) is produced, preferably by means of a plastic blow molding process, wherein subsequently the inner liner (3) is provided, preferably braided, on the outside with a multi-ply reinforcing layer (9) including reinforcement fibers (8), and wherein the reinforcing layer (9) is then impregnated with a resin, preferably an epoxy resin, which, after curing, fixes the position of the reinforcement fibers (8) in the reinforcing layer (9). According to the invention the impregnation takes place from the contact region (K) of the outer surface of the inner liner (3) with the reinforcing layer (9) to the outer region of the reinforcing layer (9).
Claims
1.-12. (canceled)
13. A method for producing a pressure accumulator for storage of hydrogen in motor vehicles, comprising the steps of: producing an inliner of the pressure accumulator; providing an outside of the inliner with a multi-layered reinforcing layer having reinforcement fibers; impregnating the reinforcing layer with a resin which, after curing, fixes a position of the reinforcement fibers in the reinforcing layer; wherein the impregnation takes place beginning from a contact region of an outer surface of the inliner with the reinforcing layer towards an outer region of the reinforcing layer.
14. The method according to claim 13, wherein, in order to assist the flow process of the resin in the contact region, the outer surface of the inliner is provided with web-shaped recesses, which are uniformly distributed over a circumference of the inliner.
15. The method according to claim 14, wherein the recesses extend into pole regions of the inliner, which are curved in a side view.
16. The method according to claim 13, wherein the inliner is provided in at least one pole region with a pole cap attachment, in which at least one flow channel is introduced, through which the resin is directed to the contact region.
17. The method according to claim 13, wherein the inliner is produced from polyamide.
18. The method according to claim 13, wherein the pressure accumulator is introduced after application of the reinforcing layer for implementing the resin impregnation into a tool surrounding the reinforcing layer.
19. The method according to claim 18, wherein the tool is provided with a suction connection piece, through which, during the impregnation, a vacuum is maintained within the tool.
20. The method according to claim 18, wherein the inliner is subjected to an internal overpressure (p.sub.i) during the impregnation, so that the pressure accumulator abuts against an inner surface of the tool under pressing action.
21. The method according to claim 20, wherein the reinforcing layer is frozen by the curing of the resin in a state expanded by the internal overpressure (p.sub.i).
22. The method according to claim 18, wherein the reinforcing layer is surrounded by a coating before being introduced into the tool so as to compensate for tolerances to the inner surface of the tool.
23. The method according to claim 18, wherein, in at least one pole region of the inliner, at least one sealing ring arranged between the reinforcing layer and the tool is pressed against the inner surface of the tool so as to direct the resin towards the contact region during the impregnation.
24. A pressure accumulator produced according to a method according to claim 13.
Description
[0017] The invention is elucidated in detail below by means of a drawing representative of only one embodiment. Schematically
[0018] FIGS. 1a, b: show a pressure accumulator produced according to the present invention in the finished state;
[0019] FIGS. 2a, b: show the pressure accumulator shown in FIGS. 1a, b during the application of reinforcement fibers in a partial cross-sectional view or in a side view;
[0020] FIG. 3: shows the pressure accumulator shown in FIGS. 1a, b during the impregnation according to the present invention of the reinforcement fibers with a resin;
[0021] FIGS. 4a,b: show the inliner shown schematically in FIGS. 1-3 in a three-dimensional individual representation as well as in an individual side view;
[0022] FIGS. 5a,b: show two different embodiments of a boss already depicted in principle in FIGS. 1-3, which serves for the refueling or for the removal of hydrogen, and
[0023] FIG. 6: shows the boss depicted in FIG. 5b in a cross-sectional representation.
[0024] FIGS. 1a, b show a pressure accumulator 1 for the storage of hydrogen in a motor vehicle. The pressure accumulator 1 possesses an inliner 3 having two pole caps 2, 2′, produced from plastic with a cylindrical center section 4. The two pole caps 2, 2′ are integrally formed on the end side of this center section 4. The pole cap 2 of the pressure accumulator 1 additionally comprises a connecting piece 5 also referred to as boss 5 with an opening 6 for the filling or for the dispensing of hydrogen. The pole cape 2′ provided on the opposite end of the pressure accumulator 1 additionally comprises in the embodiment a so-called blind boss 7, therefore a boss without an opening, which only serves for mounting the pressure accumulator 1 in the vehicle. On the inliner 3 a braided, multi-layered reinforcing layer 9 having a reinforcement fiber 8 is applied on the outside. The reinforcement fibers 8 are designed in the embodiment as carbon fibers and in FIGS. 1a, b are only indicated individually for the purpose if improving the clarity. Likewise, to improve the understanding, the multi-layered reinforcing layer 9 having, for example, more than 30 reinforcement fiber layers is only schematically depicted in FIG. 1a. It can be seen from FIGS. 1a, b, that between the pole caps 2, 2′ and the reinforcing layer 9 in each case its so-called fiber supply cap 10, 10′ is provided, which during the application of the reinforcement fibers 8 on the inliner ensures a fiber supply 22 (see FIG. 2a) for the inner layers of the reinforcing layer 9. It can be seen from FIG. 2a, that during the application of the reinforcing layer 9 supply cap 10 and the pole cap 2 jointly form a cavity 11 and the fiber supply cap 10 is fixed by a fixation device 12 in a corresponding position. Analogously the fiber supply cap 10′ and the pole cap 2′ are also positioned relative to each other (see FIG. 2b). The fiber supply caps 10, 10′ are in each case designed thin-walled with an average wall thickness <5 mm and produced from plastic. FIGS. 1a and b show, that—in contrast to FIGS. 2a, b—in the finished state of the pressure accumulator 1 the design of the fiber supply caps 10, 10′ is adapted to the outer contour of the pole caps 2, 2′. For this purpose, the fiber supply caps 10, 10′ have an elastic deformability in the outer area 13 (FIG. 2a), which makes possible the adaptation to the outer contour of the pole caps 2, 2′.
[0025] The method according to the present invention for producing the pressure accumulator 1 is now elucidated by means of FIGS. 2a, 2b and 3. Initially, the inliner 3 (see FIGS. 4a, 4b) of the pressure accumulator 1 constructed from a cylindrical center section 4 with end-side pole caps 2, 2′ is produced by means of a plastic blow-molding process. In each case a pole cap attachment in the form of a boss 5 or a blind boss 7, preferably in each case produced from metal, is mounted on the pole caps 2, 2′, which were mounted after the blow-molding process (see FIGS. 1a, 1b). Subsequently, the inliner 3 is braided on the outside with multi-layered reinforcing layer 9 having reinforcement fibers 8. On the two pole caps 2, 2′ before the application of the reinforcement fibers 8 further pole cap attachments in the form in each case of a fiber supply cap 10, 10′ are mounted, the outer surface of which is spaced apart from the pole region 21, 21′ of the corresponding pole cap 2, 2′ (see FIG. 2b). During the application of the reinforcing layers 9 the reinforcement fibers 8 are applied to the body of the inliner 3 and in the pole regions 21, 21′ correspondingly to the outer surface of the fiber supply caps 10, 10′. Due to the distance between the outer surface of the fiber supply caps 10, 10′ and the pole region 21, 21′ of the pole caps 2, 2′ the inner layers of the reinforcing layer 9 formed from the reinforcement fibers 8 in the pole regions 21, 21′ are provided with a fiber supply 22 (FIG. 2a). The fiber supply cap 10 and the pole cap 2 with the boss 5 jointly form a hollow space 11 during the application of the reinforcing layer 9. The fiber supply cap 10 is fixed when the reinforcing layer 9 is applied by a fixation device 12, which ensures the spacing of the fiber supply cap 10 from the pole region 21 during this step.
[0026] After applying the complete reinforcing layer 9, the pressure accumulator 1 located in the production process is introduced into a tool 30 depicted in FIG. 3, completely surrounding the reinforcing layer 9, adapted to the outer contour of the reinforcing layer 9, having two tool halves 31, 32, which tool serves for the impregnation of the reinforcing layer with a resin H in the vacuum-assisted RTM process. The fixation device 12 is released and the inliner is subjected to an internal overpressure p.sub.i. In this connection, the reinforcing layer 9 is applied under pressing action to the inner surface of the two tool halves 31, 32 of the tool 30. Due to the tension of the applied reinforcement fibers 8 the fiber supply cap 10 is displaced to the pole region 21 in the direction of the arrow X (FIG. 2a) and in this connection the fiber supply 22 is released. When the fiber supply 22 is released the fiber supply caps 10, 10′ are adapted to the—in each case partially formed from the boss 5 or blind boss 7—outer contour of the pole caps 2, 2′ (see also FIGS. 1a, b). For this purpose, the outer region 13 of the fiber supply caps 10, 10′ is formed elastically. In the embodiment the transition from the rigid inner region 16 to the elastic outer region of the fiber supply cap 10 corresponds in respect to the outer surface of the pole cap substantially to the transition from the boss to the blow-molded part of the inliner. I.e., the rigid inner region 16 of the fiber supply cap is applied to the surface of the boss 5, whereas the outer region 13 under an elastic deformation of a circumferential material weakening 14 of the fiber supply caps 10, 10′ adapts to the adjacent surface contour of the blow-molded part of the inliner 3. The circumferential material weakening 14 serves during the adaptation of the fiber supply cap 10, 10′ to the outer contour of the pole cap 2 or 2′ as a rotary joint for the outer region 13 of the fiber supply cap 10, 10′. The material weakening 14 is formed in the embodiment from several circumferential slots 15. The circumferential slots 15 are distributed uniformly over the circumference. They penetrate completely through the material of the fiber supply cap 10. The circumferential slots 15 can be provided with spacers facing towards the inliner 3 (not shown in detail), which prevent a planar application of the fiber supply cap 10, 10′ to the boss 5 and thus facilitate the melt flow of the resin H under the fiber supply cap 10, 10′. The spacers can be designed as lugs integrally formed on the boundary of the circumferential slots 15.
[0027] Furthermore, it can be seen by means of FIG. 2a, that before the release of the fiber supply 22 the individual layers of the reinforcing layer 9 were applied in such a manner that the reversal points 23 arising on the fiber supply cap 10 are displaced axially in the direction of the inliner 3 with increasing layer thickness at the transition between the individual layers. The fiber supply cap 10 itself ensures a predetermined distance Δ X to the pole cap 2, which significantly determines the size of the fiber supply 22. By means of the fiber supply caps 10, 10′ the fiber lengths can be provided and positioned precisely in all layers. After the fiber supply caps 10, 10′ have been applied to the pole caps 2, 2′, the reinforcing layer 9 is impregnated in the tool 30 with the resin H, in order to fill up the free spaces located between the individual reinforcement fibers 8 and thus to further strengthen the strength of the reinforcing layer 9. According to the present invention, the impregnation now begins in the form of an injection beginning from the contact region K of the outer surface of the inliner 3 with a reinforcing layer 9 towards the outer region of the reinforcing layer 9. This is depicted in FIG. 3 by the arrows depicting the flow of the resin H. The arrows show, that the resin H flows during the impregnation of the reinforcing layer 9 initially along the contact region K and migrates outwards from there with a radial flow component. For this purpose, the resin H is initially introduced through flow channels 40 provided both in the boss 5 as well as in the blind boss 87, in each case distributed uniformly over the circumference, through which flow channels the resin H is directed to the contact region K. In the pole regions 21, 21′, in this connection the flow front of the resin H as a rule reaches the outer region of the reinforcing layer 9 earlier than this is the case in the region of the cylindrical center section 4 of the inliner 3. The impregnation of the reinforcing layer 9 in the contact region K is furthermore assisted in that the outer surface of the inliner 3 during the blow-molding process was provided with web-shaped recesses 50 (FIGS. 4a,b), which are arranged distributed uniformly over the circumference of the inliner 3. In the cylindrical region of the inliner 3 the recesses 50 run parallel to the axis of rotation x of the pressure accumulator 1. It can be seen by means of FIGS. 4a, b, that the recesses 50 extend into the pole regions 21, 21′ of the inliner, which are curved in a side view. The inliner 3 is produced from polyamide and therefore is deformed elastically only slightly due to the internal overpressure p.sub.i. The tool 30 is provided with a suction connection piece 33, by means of which during the infiltration within the tool a vacuum is maintained. Due to the internal overpressure p.sub.i in the inliner 3 the pressure accumulator 1 abuts against the inner surface of the tool 30 under pressing action. When the resin H is cured the reinforcing layer 9 is frozen in the state slightly expanded by the internal overpressure p.sub.i. Before being introduced into the tool 30 the reinforcing layer 9 was surrounded with a fleece 70, which compensates for tolerances to the inner surface of the two tool halves 31, 32 of the tool 30 and thus prevents a direct overshoot of resin H in this region. By means of FIG. 3 it can furthermore be seen, that when the two tool halves 31, 32 are joined together in two pole regions 21, 21′ of the inliner 3 in each case a sealing ring 60 is pressed against the inner surface of the tool 30, which during the subsequent impregnation of the resin H direct the resin towards the contact region K.
[0028] The above-described method according to the present invention makes possible a very uniform impregnation of the reinforcing layer 9 with the resin H, so that in particular also the intermediate spaces between the individual reinforcement fibers 8 in the contact region K can be filled with resin. Thus, the individual reinforcement fibers 8 are fixed very well relative to each other within the entire reinforcing layer 9, whereby a high performance of the reinforcing layer 9 is ensured.
