EP3074209A1

EP3074209A1 - Method for producing a pressure accumulator, and pressure accumulator

Info

Publication number: EP3074209A1
Application number: EP14796419.1A
Authority: EP
Inventors: Thomas Lanzl; Franz Hofmann; Markus FRIEDERICH; Marina FEIST; Andreas Gruhl
Original assignee: Rehau AG and Co
Current assignee: Rehau Automotive SE and Co KG
Priority date: 2013-11-29
Filing date: 2014-11-05
Publication date: 2016-10-05
Also published as: DE102013113208A1; US9956712B2; JP2017500223A; JP6526664B2; WO2015078555A1; CN105793019A; CN105793019B; US20170165894A1

Abstract

The invention relates to a method for producing a pressure accumulator (1), in particular for storing hydrogen in motor vehicles. First, a pressure accumulator (1) inliner (3) which has at least one pole cap (2, 2') is produced preferably by means of a plastic blow molding method, and the outside of the inliner (3) is then provided, preferably braided, with a multi-ply reinforcing layer (9), which has reinforcing fibers (8). According to the invention, a fiber supply cap (10, 10') is applied on the pole cap (2, 2') prior to applying the reinforcing fibers (8), the outer surface of the fiber supply cap being spaced from the pole region (21, 21') of the pole cap (2, 2'). The reinforcing fibers (8) are applied onto the body of the inliner (3) and in the pole region (21, 21') so as to correspond to the outer surface of the fiber supply cap (10, 10') while the reinforcing layer (9) is being applied such that the inner reinforcing layer (9) plies which are formed by the reinforcing fibers (8) are provided with a fiber supply (22) in the pole region (21, 21') on the basis of the distance between the outer surface of the fiber supply cap (10, 10') and the pole region (21, 21') of the pole cap (2, 2'). The invention also relates to a pressure accumulator (1) produced in a corresponding manner.

Description

Method for producing a pressure accumulator and pressure accumulator

The invention relates to a method for producing a pressure accumulator, in particular for storing hydrogen in motor vehicles,

- In which first, preferably by means of a plastic blow molding process, at least one pole cap having inliner of the pressure accumulator is prepared and

- Subsequently, the inliner is provided on the outside with a reinforcing fibers having multi-layer reinforcing layer, preferably braided. Such a method is known, for example, from WO 2010/145795 A2. Pressure accumulator for storing hydrogen in motor vehicles on the one hand must provide the largest possible storage volume in a given space and on the other hand have a low weight to ensure low fuel consumption. In addition, of course, there is the need to be able to produce such accumulators also at competitive costs.

Compared with hydrogen pressure accumulators, for example made of metal, pressure accumulators are characterized by a lower weight with a plastic liner. However, in order to withstand the high pressures required to store a sufficiently large amount of hydrogen, usually about 700 bar, such plastic inliners must be regularly provided with a reinforcing layer. This is applied to the inliner, for example, in a braiding or winding process. One goal in the production of the reinforcing layer is to load the individual reinforcing fibers of the reinforcing layer, which may be formed, for example, as carbon and / or glass fibers, as evenly as possible during operation. In this way it is ensured that the mechanical strength of the reinforcing fibers is utilized as well as possible. As a result, with a load on the reinforcing fibers which is as uniform as possible, a smaller total thickness of the reinforcing layer can be realized than with an uneven loading of the reinforcing fibers. tion of the fibers. On the one hand, this results in cost savings, which is particularly noticeable when comparatively expensive carbon fibers are used. On the other hand, a larger usable storage volume for the hydrogen can also be provided in the case of a thinner reinforcement layer given a predefined installation space.

If a plastic inliner is provided with a reinforcing layer consisting of reinforcing fibers, there is regularly the problem that at a common in-line pressure of the inliner of several hundred bars, the reinforcing fibers of the inner layers of the reinforcing layer are subjected to much higher mechanical stresses than the outer layers. This is particularly the case when the reinforcing layer is impregnated with a resin during the production of the pressure accumulator and forms a high-strength composite together with the resin after its curing. If there is a production-related uneven fiber tension during the curing phase, it remains permanently after curing of the resin and reduces the mechanical load capacity of the pressure accumulator or requires the design of a thicker reinforcing layer.

Against this background, the invention has for its object to provide a method with the features described above, which allows a minimum thickness of the reinforcing layer at a given internal operating pressure of the pressure accumulator.

According to the invention the object is achieved in that a fiber supply cap is applied to the pole cap before the application of the reinforcing fibers, whose outer surface is spaced from the pole region of the pole cap, wherein during the application of the reinforcing layer, the reinforcing fibers on the body of the liner and in the Polbe- rich be applied to the outer surface of the fiber supply cap, so that due to the distance between the outer surface of the fiber supply cap and the pole portion of the pole cap, the inner layers of the reinforcing layer formed by the reinforcing fibers of the reinforcing layer are provided in the pole region with a fiber supply. According to the invention, therefore, more fiber material is applied by means of the described method in the region of the inner layers of the reinforcing layer in the form of a fiber supply than would actually be required due to the geometry of the inliner, which usually has a cylindrical middle section. The size of this fiber supply is determined by the axial spacing of the outer surface of the fiber reservoir from the pole region of the polar cap, resulting in an extended braiding for the corresponding Armierungs- layers. This fiber stock is then according to the invention, as below is shown in detail, used to ultimately ensure the most uniform mechanical stress on the reinforcing fibers over the entire thickness of the reinforcing layer during operation of the pressure accumulator. Conveniently, the fiber supply cap and the polar cap together form a cavity during the application of the reinforcing layer. The axial length of this cavity significantly determines the size of the fiber supply, as it specifies the additional Flechtweg, which must be braided in addition to the application of the inner layers of the reinforcing layer in comparison to a direct braiding of the pole cap. During the application of the reinforcing layer, the fiber supply cap is expediently fixed by a fixing device which, during this working step, ensures the spacing of the fiber supply cap from the pole region. This ensures that during the braiding no premature, unwanted approach of the fiber supply cap takes place at the pole region, which would lead to a reduction of the fiber supply.

In order to obtain a very compact reinforcing layer, which allows a large usable storage volume for given external dimensions of the pressure accumulator, the following method is used: Preferably, after application of the reinforcing layer, the inliner is introduced into a tool enclosing the reinforcing layer and subjected to an internal overpressure, so that the pressure accumulator presses against the inner surface of the tool. The fixing device is expediently released after the application of the reinforcing layer and due to the internal overpressure in the inliner the fiber supply cap is pushed to the pole region and thereby released the fiber supply. This process is essentially based on two effects. Due to the internal overpressure, the reinforcing layer is radially expanded and contracts as compensation for this axially together. However, this effect is seen differently over the radius of the reinforcing layer. On the one hand, the inner layers of the reinforcing layer run on a smaller radius than the outer, so that in the inner layers less fiber material is available for expansion than the outside. At the same time, however, the inner layers have to be widened significantly more than the outer ones in the case of the desired radial compression of the reinforcing layer, since the radial extent of the outer layers is limited by the rigid inner surface of the tool. This has the overall result that for the inner layers, a significantly larger fiber stock is required than for the outer layers of the reinforcing layer. This situation is explained by a corresponding geometric design of the fiber taken care of. Appropriately, thereafter, the reinforcing layer is impregnated with a resin, preferably an epoxy resin, which freezes after its hardening the reinforcing layer in the expanded by the internal pressure in the inliner state. The resin can be introduced into the reinforcing layer by means of an infiltration (negative pressure method) or alternatively by means of an injection (overpressure method). After complete curing of the resin, the inliner is relieved and the pressure accumulator removed from the tool. The hardened resin ensures that the reinforcing layer remains in its radially compressed form, which it has assumed during pressurization of the inliner with the internal overpressure, ie is "frozen in." The reinforcing layer is thus permanently radially compressed and permits given external dimensions of the pressure accumulator the use of a large free container volume.

Advantageously, the reinforcing fibers are at least partially, preferably in the inner layers of the reinforcing layer, with an angle reduced from the neutral angle of about 54 °, e.g. 46 - 52 °, especially 48 - 50 °, braided around the inliner. The reinforcing layer thus endeavors to approach this neutral angle and, for this reason, contracts axially when the inner liner is pressurized internally, as a result of which the fiber supply caps are pressed against the polar caps.

By the described release of the fiber supply are in the unloaded state of the pressure accumulator, the reinforcing fibers in the inner layers of the reinforcing layer under a lower bias than without application of the method., The mechanical stress of these layers is reduced during operation and it can be a thinner overall design Armierungsschicht done, which allows an increase in the usable container volume and at the same time the saving of expensive - reinforcing material. As already explained, after the fixing device has been released, the fiber supply cap, due to the tensile stress in the reinforcing fibers, presses against the polar cap. In the context of the invention, it is in this case in particular that the fiber supply cap adapts at least regionally to the outer contour of the pole cap. This ensures that during operation of the pressure accumulator the fiber supply cap can not move relative to the pole cap. Conveniently, the fiber supply cap is elastically deformed in their adaptation to the outer contour of the pole cap and thus remains permanently in the pressure accumulator in this elastically deformed state. Expediently, the individual layers of the reinforcing layer are applied in such a way that the reversal points arising on the fiber supply cap are shifted axially in the direction of the inliner with increasing layer thickness at the transition between the individual layers. This is particularly due to the previously described, decreasing outwardly demand for fiber stock. Overall, this results in an optimal design of the entire braiding, which ensures the most uniform possible loading of all reinforcing fibers. Expediently, the reinforcing layer composed of a multiplicity of fibers is impregnated with a resin after or, if appropriate, prior to the release of the filtrate, for example by injection or infiltration of the resin, and hardened after release of the fiber supply, to be between the fibers Free space to fill and strengthen the strength of the reinforcing layer thereby further. Preferably, the reinforcing layer is pressed during the infiltration from the outside or by the application of an internal overpressure on the inliner from the inside to reduce the volume of the free spaces during this process step and thus to obtain the smallest possible thickness of the reinforcing layer after curing of the resin. For example, during the resin infiltration or injection, the inliner can be subjected to an internal overpressure of 2 to 100 bar, preferably 2 to 50 bar. In this state of the pressure accumulator, the reinforcing layer, which is radially compressed by the internal overpressure, is then impregnated with the resin, which cures while the internal overpressure remains upright. In this way, the reinforcing layer is "frozen" in this radially compressed state so that the high fiber density in the reinforcing layer is retained even after the inliner has been relieved of stress.

The invention further provides a pressure accumulator according to claim 8. Preferred embodiments of this accumulator are described in the subclaims 9 to 16. In the following the invention will be explained with reference to a drawing showing only one embodiment. They show schematically:

1a, b: an accumulator according to the invention during the manufacturing process in a side view and a three-dimensional view, respectively; 2 a, b: the pressure accumulator shown in Fig. 1 a, b in the finished state,

3 shows a fragmentary cross-sectional view of the pressure accumulator shown in FIGS. 1a-2b during the production process, and FIG

4a to d: the fiber supply cap illustrated in FIG. 3 in various individual views.

FIGS. 1a, b and 2a, b show a pressure accumulator 1 for storing hydrogen in a motor vehicle. The pressure accumulator 1 has a two pole caps 2, 2 'having, made of plastic inliner 3 with a cylindrical central portion 4. At this central portion 4, the two pole caps 2, 2' are integrally formed. The polar cap 2 of the pressure accumulator 1 additionally comprises a nozzle 5, also referred to as a boss, with an opening 6 for filling or dispensing hydrogen. The polar cap 2 'provided at the opposite end of the pressure accumulator 1 additionally comprises a so-called blind boss 7, which merely used for mounting the pressure accumulator 1 in the vehicle. On the inliner 3, a reinforcing fibers 8 having, braided, multi-layer reinforcing layer 9 is applied on the outside. The reinforcing fibers 8 are formed in the embodiment as carbon fibers and in the figures 1a - 2b for the purpose of clarity, only indicated individually. Similarly, for better understanding of the drawings, the reinforcing layer 9 is shown schematically only in Figures 1a and 2a. It can be seen from FIGS. 1a and 2a that between the pole caps 2, 2 'and the reinforcing layer 9 a respective fiber supply cap 10, 10' is provided, which during the application of the reinforcing fibers 8 to the inliner 3 has a fiber supply 22 (see FIG. Fig. 3) ensures the inner layers of the reinforcing layer 9. 3 it can be seen that during the application of the reinforcing layer 9, the fiber supply cap 10 and the polar cap 2 together form a cavity 11 and the fiber supply cap 10 is fixed by a fixing device 12 in a corresponding position. Analogously, the fiber supply cap 10 'and the polar cap 2' are positioned relative to one another. The fiber reservoir caps 0, 10 'are each formed thin-walled with a mean wall thickness <5 mm and made of plastic. In particular, Figs. 2a and b show that in the finished state of the pressure accumulator 1, the shape of the fiber storage caps 10, 10 'is adapted to the outer contour of the pole caps 2, 2'. For this purpose, the fiber reservoir caps 10, 10 'in the outer region 13 on an elastic deformability, the the adaptation to the outer contour of the pole caps 2, 2 'allows. This can be seen in particular from a comparative examination of FIGS. 1a and 2a.

FIGS. 4a to d show the fiber supply cap 10 illustrated in FIG. 3 as a single part in different views. In Fig. 4a is a plan view from above, in Fig. 4b of the section AA in Fig. 4a and in Fig. 4c, d is a three-dimensional view obliquely from above or obliquely below. The fiber supply cap 10 has a peripheral material weakening 14, which serves as a hinge for the outer region 13 of the fiber supply cap 10 during the adaptation of this cap 0 to the outer contour of the polar cap 2. The material weakening 14 is formed in the embodiment of several circumferential slots 5. The circumferential slots 15 are evenly distributed over the circumference. They completely penetrate the material of the fiber supply cap 10. As already described above, the outer region 13 is elastic, so that it can assume the corresponding contour of the polar cap 2 in this region. On the other hand, in its inner area 16 near the axis, the fiber storage cap 10 is rigidly formed so that it can form a rigid connection with the fixing device 12. The geometry of the rigid inner region 16 of the fiber supply cap 10 is adapted to the near-axis contour of the pole cap 2 - which is formed in the embodiment by the contour of the boss 5 - adapted. The fiber supply cap 10 also has in its outer region 13 to the outer edge extending towards material weaknesses 17, which serve in this area 13 to facilitate the adaptation to the outer contour of the polar cap 2. These material weakenings 17 are each formed in the embodiment as a longitudinal slot. The longitudinal slots 17 are distributed uniformly over the circumference. When the fiber supply cap 10 is adapted to the geometry of the polar cap 2, the longitudinal slots 17 are widened (see FIGS. 2a, b). The longitudinal slots 17 also completely penetrate the material of the fiber supply cap 10. In its near-axis inner region 16, the fiber supply cap 10 further comprises a plurality of fixing openings 19, which together form a connecting device 20 for connecting the fiber supply cap 10 with the fixing device 12. The inventive method for producing the pressure accumulator 1 will be explained with reference to FIG. 3. First of all, the inliner 3 of the pressure accumulator 1 constructed from a cylindrical middle section 4 with end pole caps 2, 2 'is produced by means of a plastic blow molding process. The pole caps 2, 2 'additionally comprise a boss 5, which is preferably made of metal, or a blind boss 7, which are mounted after the blow molding process. Subsequently, the inliner 3 is provided on the outside with the reinforcing fibers 8 having, multi-layer reinforcing layer 9 braided (for the sake of simplicity of illustration, Fig. 3 shows only the innermost layers of the reinforcing layer 9). On the two pole caps 2, 2 ', a fiber supply cap 10, 10' is applied before the application of the reinforcing fibers 8, whose outer surface is spaced from the pole region 21, 21 'of the corresponding polar cap 2, 2'. During the application of the reinforcing layer 9, the reinforcing fibers 8 are applied to the body of the inliner 3 and in the pole areas 21, 21 'respectively on the outer surface of the fiber storage caps 2, 2'. Due to the distance between the outer surface of the fiber storage caps 10, 10 'and the pole region 21, 21' of the pole caps 2, 2 ', the inner layers of the reinforcing layer 9 formed by the reinforcing fibers 8 are provided with a fiber supply 22 in the pole regions 21, 21' ,

3 shows that the fiber supply cap 10 and the polar cap 2 together with the boss 5 during the application of the reinforcing layer 9 together form a cavity 1 1. The fiber supply cap 10 is fixed during the application of the reinforcing layer 9 by a fixing device 12, which ensures the spacing of the fiber supply cap 10 from the pole region 21 during this working step.

After application of the entire reinforcing layer 9, the pressure accumulator 1 is introduced into an unillustrated, the reinforcing layer 9 completely enclosing, adapted to the outer contour of the reinforcing layer 9 Infiltrations- or injection tool, the fixing device 12 is released and the inliner 3 applied with an internal pressure. Here, the reinforcing layer 9 applies under pressing action on the inner surface of the tool. Due to the tensile stress of the applied reinforcing fibers 8, the fiber supply cap 10 shifts to the pole region 21 in the direction of the arrow x and in this case the fiber supply 22 is released.

When the fiber supply 22 is released, the fiber supply caps 10, 10 'adapt to the outer contour of the pole caps 2, 2', which is formed in each case by boss 5 or blind boss 7 (see also FIGS. 2 a, b). For this purpose, as already described previously in connection with FIGS. 4a-e, the outer region 13 of the fiber supply caps 10, 10 'has an elastic design. In the exemplary embodiment, the transition from the rigid inner region 16 to the elastic outer region 13 of the fiber reservoir cap 10 with respect to the outer surface of the polar cap 2 essentially corresponds to the transition from Boss 5 to the blow molded part of the inliner 3. That is, the rigid inner region 16 of the fiber reservoir caps the surface of the boss 5, whereas the outer region 13 adapts to the adjacent surface contour of the blow molded part of the inliner 3 under elastic deformation on the peripheral material weakening 14. Furthermore, it can be seen with reference to FIG. 3 that prior to the release of the fiber supply 22, the individual layers of the reinforcing layer 9 were applied in such a way that the reversal points 23 formed on the fiber supply cap 10 at the transition between the individual layers axially with increasing layer thickness in the direction of inliner 3 are moved. The fiber supply cap 10 itself ensures a predetermined distance .DELTA.X to the polar cap 2, which determines the size of the fiber supply 22 significantly. Through the fiber supply caps 10, 10 ', the fiber lengths can be exactly pre-held and positioned in all layers.

After the fiber supply caps 10, 10 'have been applied to the pole caps 2, 2', the reinforcing layer 9 in the infiltration or injection tool is impregnated with a resin (likewise not shown) in order to fill up the free spaces located between the individual reinforcing fibers 8 and further strengthen the strength of the reinforcing layer 9 thereby. Due to the internal overpressure in the inliner 3, the reinforcing layer 9 is radially compressed and thus has a reduced wall thickness. At the same time reduced by this radial compression, the total volume of the free spaces between the fibers 8, which must be filled up by the resin. As a result of the curing of the resin at an internal overpressure in the inliner 3, the shape of the compressed reinforcing layer 9 in the finished, unloaded pressure accumulator 1 is largely retained; On the one hand, this leads to a reduction in weight and material, since less resin material is required, and on the other hand simultaneously ensures a larger usable storage volume for given outer dimensions of the pressure accumulator 1.

claims

Claims

claims

1. A method for producing a pressure accumulator (1), in particular for storing hydrogen in motor vehicles,

- In which first, preferably by means of a plastic blow molding, at least one pole cap (2, 2 ') having Inliner (3) of the pressure accumulator (1) is prepared and

- In which then the inliner (3) on the outside with a reinforcing fibers (8) having multi-layer reinforcing layer (9) is preferably braided, characterized in that on the polar cap (2, 2 ') before the application of the reinforcing fibers (8) Fiber supply cap (10, 10 ') is applied, the outer surface of the pole region (21, 21') of the pole cap (2, 2 ') spaced apart, wherein during the application of the reinforcing layer (9), the reinforcing fibers (8) on the body of the Inliners (3) and in the pole region (21, 21 ') are respectively applied to the outer surface of the fiber supply cap (10, 10'), so that due to the distance between the outer surface of the fiber supply cap (10, 10 ') and the pole region (21 , 21 ') of the polar cap (2, 2') that of the reinforcing fibers

(8) formed inner layers of the reinforcing layer (9) in the pole region (21, 21 ') are provided with a fiber supply (22).

A method according to claim, characterized in that the fiber supply cap (10, 10 ') and the polar cap (2, 2') during the application of the reinforcing layer

(9) together form a cavity (1 1).

A method according to claim 1 or 2, characterized in that the fiber supply cap (10, 10 ') during the application of the reinforcing layer (9) by a fixing device (12) is fixed, during this operation, the spacing of the fiber supply cap (10, 10') from the pole region (21, 21 '). Method according to one of claims 1 to 3, characterized in that after application of the reinforcing layer (9) of the inliner (3) is introduced into a reinforcing layer (9) enclosing tool and subjected to an internal pressure, so that the pressure accumulator (1) presses against the inner surface of the tool, and that the fixing device (12) is released after application of the reinforcing layer (9) and due to the internal overpressure in the inliner (3), the fiber supply cap (10, 10 ') to the pole region (21, 21 ') pushed and in this case the fiber supply (22) is released.

A method according to claim 4, characterized in that hiemach the reinforcing layer (9) is impregnated with a resin, preferably an epoxy resin, which freezes after its hardening the reinforcing layer (9) in the expanded state by the internal overpressure.

A method according to claim 5, characterized in that the fiber supply cap (10, 10 ') in this case at least partially adapts to the outer contour of the pole cap (2, 2').

Method according to one of claims 1 to 6, characterized in that the individual layers of the reinforcing layer (9) are applied such that on the fiber supply cap (10, 10 ') resulting inversion points (23) at the transition between the individual layers with increasing layer thickness axially displaced in the direction of inliner (3).

Pressure accumulator (1), in particular for the storage of hydrogen in motor vehicles, with

- an inliner (3) having at least one polar cap (2, 2 '), preferably made of plastic

- a reinforcing fibers (8) having, preferably braided, multi-layer reinforcing layer (9) which is externally applied to the inliner (3), characterized in that between the polar cap (2, 2 ') and reinforcing layer (9) a fiber supply cap (10, 10 ') is provided during the application the reinforcing fibers (8) on the inliner (3) ensures a fiber supply (22) for the inner layers of the reinforcing layer (9).

9. Pressure accumulator (1) according to claim 8, characterized in that the fiber supply cap (10, 10 ') thin-walled, e.g. with a mean wall thickness <10 mm, formed and preferably made of plastic.

10. Pressure accumulator (1) according to claim 8 or 9, characterized in that in the finished state of the pressure accumulator (1), the shape of the fiber supply cap (10, 10 ') to the outer contour of the pole cap (2, 2') is adjusted.

1 1. pressure accumulator (1) according to claim 10, characterized in that the fiber supply cap (10, 10 ') at least partially, in particular in the outer region (13), one, preferably elastic, deformability, the adaptation to the outer contour of the polar cap ( 2, 2 ') allows.

12. Pressure accumulator (1) according to claim 10 or 11, characterized in that the fiber supply cap (10, 10 ') has a circumferential material weakening (14), which during the adaptation of the fiber supply cap (10, 10') to the outer contour of the polar cap ( 2, 2 ') serves as a hinge for the outer region (13) of the fiber supply cap (10, 10').

13. Pressure accumulator (1) according to any one of claims 8 to 12, characterized in that the fiber supply cap (10, 10 ') in its axially proximal inner region (16) is rigid.

14. Pressure accumulator (1) according to one of claims 10 to 13, characterized in that the fiber supply cap (10, 10 ') in its outer region (13) to the outer edge extending material weakenings (17), in this region (13) for Facilitate the adaptation to the outer contour of the polar cap (2, 2 ') serve.

15. Pressure accumulator (1) according to one of claims 8 to 14, characterized in that the fiber supply cap (10, 10 ') in the near-axis inner region (16) at least one connecting means (20) for connecting the fiber supply cap (10, 10') with a Fixing device (12), which serves for fixing the fiber supply cap (10, 10 ') during the application of the reinforcing layer (9).

16. Pressure accumulator (1) according to one of claims 8 to 15, characterized in that the reinforcing layer (9) is impregnated with a resin, preferably an epoxy resin.