The present application claims priority 35 U.S.C. § 119 to European Patent Publication No. EP 20178480.8 (filed on Jun. 5, 2020), which is hereby incorporated by reference in its entirety.
One or more embodiments relate to a high-pressure container, in particular, a high-pressure container for storing a fuel for a motor vehicle.
It is known that high-pressure containers, e.g. those for storing hydrogen as fuel for motor vehicles, can be constructed from an inner layer, referred to as the “liner,” and a winding of fiber material around the liner.
The use of the technologies of blow moulding and thermoforming for the production of a container is known. Production is then based on the forming of semi-finished products in tube or sheet form. These are given their final shape via a vacuum and/or excess pressure. It is possible, for example, to produce two half-shells, which are joined together to form a container.
In the case where gas-tight liners are used for type IV containers, which are used for the pressurized storage of gases, there are two common production methods. On the one hand, the blow moulding of entire liners and, on the other hand, the method of producing segments of the container by injection moulding and extrusion, and subsequent connection of these components via a joining method.
The materials used in this process are mostly based on HDPE (high density polyethylene) or polyamides.
An important distinguishing feature for liner materials are the mechanical low-temperature properties as well as the emission properties. Monolayer materials such as polyamide have a good barrier property for gases, but do not have optimum low-temperature properties. HDPE, on the other hand, does not have a suitable barrier effect, but has very good low-temperature properties.
For this reason, it is principally polyamide that is currently being used for applications in the hydrogen sector. However, this sets limits with regard to component size, especially for blow moulding technology. Moreover, the available suitable grades are expensive and problematic when used at low temperatures because of their extensive use of additives.
High-pressure containers for gases are subject to large temperature fluctuations in the course of their operation (filling, storage and emptying). This puts high demands on the materials and, in particular, on the liner.
In connection with lightweight construction and the use of composite materials, the challenge arises in this context of connecting the different materials to one another in a gas-tight manner at the joint.
One or more embodiments are to enhance a high-pressure container in this respect and, in particular, to specify a high-pressure container which, even in a region of transition to a boss member, meets the requirements for sealing and permeation for a high-pressure container and, at the same time, can be produced in a simple and low-cost manner.
In accordance with one or more embodiments, a high-pressure container comprises a cylinder, composed of a plastic, to serve as a central member; at least one half-shell, composed of a plastic, at one axial end of the cylinder, the half-shell comprising a substantially rotationally symmetrical insert as a boss member, the insert having a foot member at the end thereof facing the container interior and which is embedded in the plastic of the half-shell to substantially form a hollow cone or hollow cylinder; a sleeve arranged within the inner circumference of the foot member such that the plastic of the half-shell is arranged between the sleeve and the inner circumference of the foot member; a valve arranged in the boss member, the valve having a stem portion arranged in the sleeve; and a seal member to form a seal between the stem portion of the valve and the sleeve.
In accordance with the one or more embodiments, a plastic, in particular, a plastic multilayer composite, is used as the material for the liner, both in the central member formed by the cylinder and in at least one, or in both axial end regions of the container. Plastics, in particular, multilayer plastics which also comprise a barrier layer, can be formed into a half-shell in a simple manner via blow moulding, or deep drawing, or vacuum moulding. It is likewise possible, for example, for the cylinder in the central member to be blow-moulded or extruded.
In accordance with the one or more embodiments, use is made of a boss member which has a foot member that substantially forms a hollow cone or hollow cylinder. The foot member of the insert is embedded in the plastic of the half-shell. The plastic thus surrounds the boss member at least on two sides. The foot member has a greater diameter than an adjacent central member of the boss member. The foot member thus forms an undercut with respect to a plastic of the liner introduced from the side of the foot member or the center of the container. The plastic is preferably arranged axially on both sides of the foot member, that is to say on both sides of the undercut, i.e., on a surface of the boss member facing the center of the container and on a surface of the boss member facing away from the center of the container.
The production of the half-shell with embedded boss member and of the entire high-pressure container is nevertheless possible in an inexpensive manner, since, as will be described in more detail later, the introduction of the plastic is possible via blow moulding or vacuum deep drawing despite undercutting on the foot member of the boss member.
The foot member is hollow in the interior, in the region of its longitudinal central axis, and therefore, substantially forms a hollow cone or a hollow cylinder.
In accordance with the one or more embodiments, a sleeve, composed of metal, is introduced into the inner circumference of the foot member. In this case, the plastic of the half-shell is arranged in some section or sections in intermediate spaces between the sleeve and the inner circumference of the foot member.
In accordance with the one or more embodiments, the high-pressure container also comprises a valve for withdrawing the medium in the high-pressure container. The valve is accommodated in the boss member in a manner such that a cylindrical stem portion of the valve is accommodated in the sleeve. One section of the stem portion of the valve is thus inserted directly in the boss member and one section in the sleeve, within the boss member.
In accordance with the one or more embodiments, a seal member, in particular, a ring seal, is arranged between the stem portion of the valve and the sleeve in such a high-pressure container in order to form a seal between the valve and the sleeve. The seal member extends around the entire stem portion of the valve, and can have a round, or a rectangular, or a conical cross section. The seal member comprises an independent, separate component. In an alternative embodiment, the seal member can also be formed integrated on the stem portion of the valve. A seal is thus used in a deep region of the valve, namely only in the stem portion of the valve and in the foot region of the boss member. The sleeve extends at least as far as the axial end of the boss member which faces the center of the container, the sleeve particularly extending beyond this end of the boss member. The seal is configured to seal the valve against the sleeve. Radially outside the sleeve, in the intermediate space towards the boss member, plastic is arranged, which can be very thin in one or more regions, and particularly, in regions in which the sleeve is press-fit into the boss member. By virtue of the arrangement of the seal member and of the sealing of said seal member with respect to the sleeve, it is possible to achieve a reliable sealing effect.
There is also preferably a sufficiently high degree of sealing in the region of the plastic radially outside the sleeve, in particular by virtue of thin formation of the plastic in one or more regions between the sleeve and the boss member. It is thus possible to dispense with an additional seal at a higher level, above the sleeve. The sleeve is preferably press-fit into the inner circumference of the foot member in a manner such that a thin plastic layer is compressed between the sleeve and the inner circumference of the foot member in the region of press fitting. The plastic of the half-shell preferably fills the entire space between the sleeve and the inner circumference of the foot member.
The plastic of the liner, i.e., the plastic of the central member and of the half-shell, preferably both half-shells, comprises a multilayer composite plastic which comprises a barrier layer.
A first groove or depression filled with the plastic of the half-shell extends around the inner circumference of the foot member, at the level of the sleeve, at least in some section or sections, that is to say, for example, in individual sectors or around the entire inner circumference of the hollow cylinder or hollow cone. The first groove or depression is filled with the plastic of the half-shell. A “depression” can be designed in a manner similar to a groove and in any case has at least one edge which acts as an undercut for the plastic lying behind it, with the result that the plastic is held positively behind the edge in the region of the inner circumference. The plastic of the half-shell is preferably pressed against the inner circumference of the foot member and into the first groove by the sleeve. The plastic thus remains reliably in the first groove and the sealing effect is further enhanced.
The foot member also has at least one second groove which is filled with the plastic of the half-shell. The second groove extends around at least in some section or sections proximate to the inner circumference of the foot member on the bottom of the foot member that faces the container interior. The second groove likewise serves primarily to increase sealing between the liner and the boss member.
The foot member additionally has at least one third groove which is filled with the plastic of the half-shell. The third groove extends around at least in some section or sections on the top surface of the foot member that faces the outside of the container. In addition to increasing sealing, the third groove also prevents detachment of the plastic from the boss member on the top surface of the foot member.
The foot member further has at least one fourth groove which is filled with the plastic of the half-shell. The fourth groove extends around at least in some section or sections proximate to the outer circumference of the foot member on the bottom of the foot member that faces the container interior. The fourth groove also prevents detachment of the plastic from the boss member.
The first groove, and/or the second groove, and/or the third groove, and/or the fourth groove can have a trapezoidal shape which grows larger towards the bottom of the groove, thus enhancing the positive engagement of the plastic in the groove. In each of the grooves, particularly the first groove and/or the second groove, an additional seal member can be arranged at the bottom of the groove.
The plastic of the cylinder preferably merges into the plastic of the half-shell. A barrier layer extends as continuously as possible in the plastic at the transition between the cylinder and the half-shell.
The plastic comprises a multilayer composite plastic. The multilayer composite plastic of the half-shell, and preferably also the multilayer composite plastic of the cylinder, comprise at least one layer of HDPE and a barrier layer comprising EVOH, a regranulate such as a regrind layer, and/or a second HDPE layer, and/or at least one adhesion-promoting layer.
The high-pressure container comprises two half-shells at the axial ends of the cylinder, both half-shells being preferably designed as described hereinabove for the first half-shell. The cylinder and the two half-shells are wrapped with a fiber material, such as a composite material comprising carbon fibers, and/or glass fibers, and/or epoxy resin.
In accordance with one or more embodiments, a method of producing a high-pressure container can preferably be conducted with a die having a first die half which forms a female die, the method comprising: placing a preheated first plastic sheet on the first die half; sucking via a vacuum or pressing via a pressure force, the first plastic sheet against the first die half in a manner such that the plastic of the first plastic sheet is arranged laterally at a distance from an insert/boss member behind an undercut of the insert/boss member, in one or more regions; and sucking or pressing via a slide, or a vacuum, or a pressure force, the plastic of the first plastic sheet from a position laterally at a distance from the insert to a position against the insert behind the undercut, thus ensuring that a space behind the undercut of the insert is filled with the plastic.
Alternatively, the first plastic sheet is sucked or pressed against the first die half in a manner such that the insert/boss member is positioned in such a way that the plastic of the first plastic sheet is arranged laterally at a distance from the insert behind an undercut of the insert in one or more regions.
In accordance with the method, the boss member is inserted into the die as an insert and enclosed with the plastic sheet such as an impermeable multilayer composite, in a blowing or deep-drawing process. The method ensures that the plastic also gets into regions behind an undercut. For this purpose, a plastic sheet is first of all sucked or pressed against the first die half via a vacuum or a pressure force. In this case, the insert can already be positioned in such a way that, as a result of the plastic being sucked or pressed against the first die half, the plastic of the first plastic sheet is arranged behind an undercut of the insert, laterally at a distance from the insert, in one or more regions.
Alternatively, it is possible for the insert to be positioned in such a way that the plastic of the first plastic sheet is arranged laterally at a distance from the insert behind the undercut only after the plastic has been sucked or pressed against the first die half, e.g., with the insert being displaced or the insert only now being introduced into the first die half.
After this, the plastic of the first plastic sheet is pressed or sucked against the insert from the side of the insert via a slide or a vacuum or a pressure force, thus ensuring that a space behind the undercut of the insert is filled with the plastic that was previously situated at the side, and positive engagement arises.
As a result, despite simple production via blow moulding or vacuum moulding, the plastic also gets into regions behind the insert, and an enhanced sealing effect of the plastic, in particular of the multilayer composite, results with respect to the insert, in particular with respect to the metallic boss member. To achieve the enclosure in the plastic, slides and/or a vacuum or compressed air are/is used.
“Laterally at a distance” in this case means essentially at a distance from a longitudinal central axis of the insert, which can also coincide with the longitudinal central axis of the pressure container. The plastic can initially be substantially parallel to the longitudinal central axis of the insert and preferably also to the surrounding container wall. The plastic is then sucked, blown, or pushed substantially normal to the longitudinal central axis of the insert, in particular, radially inwards on all sides, towards the insert.
The fact that the sucking or pressing of the plastic against the insert takes place at a later time than the positioning of the insert, with the result that the plastic is arranged laterally at a distance from the insert in one or more regions, can also be accomplished in a continuous process such that the insert is moved further and positioned in each case and that, during this process, new plastic continues to be sucked in or pressed on in each case. As a result, the positioning of the insert and the sucking in or pressing of the plastic behind the undercut takes place virtually simultaneously.
The sleeve is press-fit into the inner circumference of the foot member of the insert, wherein a thin plastic layer is preferably formed between the sleeve and the inner circumference of the foot member in the region of press fitting.
The resulting half-shell can be connected in an additional process block to a second half-shell or to an extruded or blow-moulded multilayer cylinder. This forms the core, and thus, the basis for a further winding process, in which the container can obtain its mechanical strength from a composite material of carbon and/or glass and epoxy resin.
In accordance with one or more embodiments, the die comprises a second die half which forms a punch. The second die half can be driven onto the first die half in order to form the inner contour of the half-shell. For this purpose, the second die half can form the shape of the first plastic sheet in the interior of the half-shell. It is also possible instead for a second plastic sheet, which forms the inner contour of the half-shell, to be mounted on the second die half.
After the first plastic sheet has been sucked or pressed against the first die half, the insert/boss member is raised in relation to the first die half in order to position the insert in such a way that plastic of the first plastic sheet is arranged behind the undercut, laterally at a distance from the insert. Lifting can be performed with the aid of a movable mount for the insert. In this case, the insert can be arranged on the outside of the container on the first plastic sheet and the lifting can thus take place along the longitudinal central axis of the insert and also along the longitudinal central axis of the high-pressure container, in particular, in the direction of the subsequent center of the container.
After the space behind the undercut of the insert has been filled with the plastic, the insert is lowered again in relation to the first die half. As a particular preference, the lowering takes place simultaneously with the movement of the second die half onto the first die half.
In accordance with one or more embodiments, it is only after the first plastic sheet has been sucked or pressed against the first die half that the insert is placed on the first plastic sheet in order to position the insert in such a way that plastic of the first plastic sheet is arranged behind the undercut, laterally at a distance from the insert. The insert can thus be arranged against the first plastic sheet on the inside of the container. A second plastic sheet can in turn be arranged on the inside of the container with respect to the insert.
The plastic of the first plastic sheet can be cut off axially behind the space filled with plastic, behind the undercut, ensuring that plastic is no longer present behind the undercut, in particular, on the outside of the container with respect to the undercut.
A preheated second plastic sheet is placed on the second die half, after which the second plastic sheet is sucked or pressed against the second die half via a vacuum or a pressure force, and the second die half is driven together with the second plastic sheet onto the first die half in order to form the inner contour of the half-shell.
The first plastic sheet comprises a multilayer composite that itself comprises a layer of HDPE (high density polyethylene) and a barrier layer such as EVOH (ethylene-vinyl alcohol copolymer). As a particular preference, the multilayer composite also comprises a regrind material or regranulate and/or one or more adhesion-promoting layers. HDPE forms the outermost layer of the multilayer composite and can additionally also form the innermost layer.
In accordance with one or more embodiments, a method for producing a high-pressure container comprises producing a first half-shell by a method as described hereinabove, and connecting the first half-shell to a second half-shell which can likewise comprise an insert, and which can be produced in the same manner described hereinabove; and connecting the connected first half-shell and second half-shell to at least one cylinder that is extruded or blow-moulded, and one or more end caps in order to form a closed container. The closed container may be wrapped with a fiber material such as a composite material comprising carbon fibers, and/or glass fibers, and/or epoxy resin.
One or more embodiments will be illustrated by way of example in the drawings and explained in the description hereinbelow.
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From being laterally at a distance from the insert 1, the plastic of the first plastic sheet 3 is then pressed or sucked against the insert 1 behind the undercut via a slide 4, or a vacuum, or a pressure force, thus ensuring that a space behind the undercut of the insert 1 is filled with the plastic.
Finally, the second die half 5 is driven onto the first die half 2 in order to form the inner contour of the half-shell.
In detail, the single-sheet method illustrated in
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The plastic sheet 3 is sucked with the aid of a vacuum into the first die half 2, which reproduces the outer component geometry.
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The undercut is formed by a foot member 14 at the end of the insert 1 facing the container interior, which foot member has a greater diameter than a central member of the insert 1. The multilayer composite plastic 11 is arranged axially on both sides of the foot member 14. The foot member 14 has a plurality of grooves 15 which are filled with the multilayer composite plastic 11 of the half-shell 13. The insert 1 substantially has the shape of a hollow cylinder. The foot member 14 substantially has the shape of a hollow cone. The grooves 15 filled with the multilayer composite plastic 11 of the half-shell 13 extends around an inner circumference of the foot member 14.
The multilayer composite plastic 11 of the cylinder 10 merges into the multilayer composite plastic 11 of the half-shell 13. The multilayer composite plastic 11 of the half-shell 13 and also that of the cylinder 10 comprises a layer of HDPE as the outermost layer and a barrier layer 12 of EVOH. The HDPE can be in the form of HDPE-S (black), which can be followed by a regranulate layer, an adhesion promoter, the EVOH layer, optionally again by an adhesion promoter and optionally also, once again, by an HDPE layer as the innermost layer.
The high-pressure container comprises two half-shells 13 at the axial ends of the cylinder 10, both half-shells 13 being designed as described hereinabove, i.e., having an insert as a boss member 1 which is embedded in the multilayer composite plastic 11. The cylinder 10 and the two half-shells 13 are preferably wrapped with a fiber material 16, preferably with a composite material comprising carbon fibers and/or glass fibers and/or epoxy resin.
Overall, a high-pressure container is thus specified which can be used for the storage of gases under high pressure. This is of lightweight construction and has a multi-part multilayer plastic liner, comprising two dome caps 13 and a cylinder 10, which ensures gas tightness and contains a permeation barrier 12. Inserts 1, namely boss members, more precisely a “headstock” and a “tailstock” are integrated into both dome caps 13. Both in the dome caps 13 and in the cylinder tube 10, the permeation properties are provided by a sealing layer or barrier layer 12 contained in the layered structure of the liner. The high-pressure container acquires its mechanical strength from a fiber-reinforced composite 16, which is applied to the plastic liner in a winding process and subsequently cured.
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A first groove 15 filled with the multilayer composite plastic 11 of the half-shell 13 extends around the inner circumference of the foot member 14. The multilayer composite plastic 11 of the half-shell 13 is arranged axially on both sides of the foot member 14.
The foot member 14 has a second groove 17 which is filled with the multilayer composite plastic 11 of the half-shell 13, the second groove 17 extending around proximate to the inner circumference of the foot member 14 on the bottom of the foot member 14, the bottom facing the container interior.
The foot member 14 also has a third groove 18 which is filled with the multilayer composite plastic 11 of the half-shell 13, the third groove 18 extending around on the top surface of the foot member 14, the top surface facing the outside of the container.
The foot member 14 additionally has a fourth groove 19 which is filled with the multilayer composite plastic 11 of the half-shell 13, the fourth groove 19 extending around proximate to the outer circumference of the foot member 14 on the bottom of the foot member 14, the bottom facing the interior of the container.
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The terms “coupled,” “attached,” or “connected” may be used herein to refer to any type of relationship, direct or indirect, between the components in question, and may apply to electrical, mechanical, fluid, optical, electromagnetic, electromechanical or other connections. In addition, the terms “first,” “second,” etc. are used herein only to facilitate discussion, and carry no particular temporal or chronological significance unless otherwise indicated.
Those skilled in the art will appreciate from the foregoing description that the broad techniques of the embodiments can be implemented in a variety of forms. Therefore, while the embodiments have been described in connection with particular examples thereof, the true scope of the embodiments should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, specification, and following claims.
1 insert, boss member
2 first die half
3 first plastic sheet
4 slide
5 second die half
6 second plastic sheet
7 mount
10 cylinder
11 multilayer composite plastic
12 barrier layer
13 half-shell
14 foot member
15 first groove
16 fiber material
17 second groove
18 third groove
19 fourth groove
20 sleeve
21 valve
22 seal member
Number | Date | Country | Kind |
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20178480.8 | Jun 2020 | EP | regional |