ROBUST HIGH-PRESSURE CONTAINER STRUCTURE WITH JOINTING AGENT

Description

[0001] The present invention relates to a method and a pressure vessel in which an adhesive is used between different layers of a pressure vessel structure to obtain a robust pressure vessel.

[0002] Pressure vessels are used to store gaseous or liquid substances. In automotive engineering, they are used as tanks for carrying gaseous hydrogen at pressures of several hundred bar. As a modification of the ideal sphere, a cylindrical central section with domed ends is commonly chosen. Such a pressure vessel consists of an inner container, the so-called liner, which is usually made of plastics such as HDPE (high-density polyethylene) or PA6.6 (nylon) and has an opening centrally located at least at one of the two domed ends. A usually metallic inlet body, called a boss, is inserted into this opening. A valve is screwed into the boss, allowing for the exchange of the stored gas. The outer container is constructed by wrapping the inner container and boss with a composite material, such as resin-impregnated carbon fibers.While the inner container primarily serves to ensure a tight seal with regard to the gas inside, the outer container is responsible for pressure stability and shock resistance to external influences.

[0003] German publication DE 603 ​​15 481 T2 describes a pressure vessel for storing cryogenic substances, but also pressurized hydrogen at ambient temperature, in which the outer container is spaced apart from the inner container and a vacuum is maintained in the space between them for thermal insulation. Additionally, the inner container is surrounded on its outer surface by an insulating layer.

[0004] The pressure vessel disclosed in German patent application DE 11 2004 000 261 B4 is designed for cryogenic liquids. Both the outer and inner containers are each composed of individual fiber-reinforced components, consisting of a cylindrical central section and curved end caps, which are joined by overlapping sections. At the joints, fiber-reinforced plastic ribs provide spacing between the outer and inner containers. Adhesive bonds may be present at the points where components overlap and ribs are wound.

[0005] Document EP 2 238 047 B1 describes a composite container in which parts of a flexible inner container are bonded to a rigid outer container. Both contact surfaces, or only one, may have recesses for the adhesive. The bonded surfaces are designed to withstand the pressure within the container and primarily serve to secure the desired arrangement of the inner container within the outer container during the manufacturing process, or to prevent unwanted separation of the inner container from the outer container during emptying.

[0006] Document US 5,429,845 A describes a boss, or component for receiving a valve of a pressure vessel, which has a filament-wound outer shell and a non-metallic inner lining. The boss has a tubular neck extending outward from the interior of the pressure vessel and an annular support flange extending radially from the inner end of the neck and supporting the circumference of a polar opening of the pressure vessel.

[0007] The different material choices and structures used for the outer and inner containers, including the boss, result in different coefficients of thermal expansion for the individual layers. These differences can lead to the formation of a gap between the layers of the pressure vessel during temperature changes. A gap can also occur during the manufacturing process. Whether and to what extent this gap appears can vary for each pressure vessel. Therefore, after the initial filling of any pressure vessel, or during its ongoing use, it may be advisable to check for the formation of a gap. Against this background, it is an object of the present invention to provide a method that ensures the prevention of gap formation between the layers of a pressure vessel. Furthermore, it is an object of the present invention to provide a suitable pressure vessel.

[0008] To solve the foregoing problem, a method for manufacturing a pressure vessel according to claim 1 is proposed, wherein the pressure vessel has several layers and comprises a cylindrical central part with two curved side parts, wherein at least one side part has a filling opening, characterized in that an joining agent is introduced between at least two layers of the pressure vessel in at least one planar area, which forms a further layer and compensates for forces occurring between the at least two layers of the pressure vessel within this further layer and prevents the formation of gaps in this at least one planar area.In the inventive method, an inlet body is inserted into the at least one side part with a filling opening. This inlet body forms an interface with at least two layers of the pressure vessel, and the bonding agent is applied as a further layer, at least partially, to the respective interfaces thus formed. Due to its adhesive properties, the bonding agent binds the inlet body to at least two layers of the at least one side part over a planar area. It is conceivable that the bonding agent is also applied outside the interface with the inlet body in a planar area between two layers of the side part. In this method, a layer thickness of the further layer is preferably between 0.3 mm and 3.5 mm between the respective interfaces, particularly in the area of ​​the inlet body.

[0009] The thickness of the layer can vary along the course of the interfaces, especially in the area of ​​the interfaces where the input body is no longer located, and can decrease to as low as 0 mm.

[0010] An adhesive property of the joining material prevents the layers between which it is inserted from tearing. Consequently, peaks in stress forces occurring between the adjacent layers, which can consist of shear and / or torsional forces, are compensated within the layer of the joining material. Thus, gap formation is not possible in the area covered by the inserted layer of the joining material, or it ceases at these points.

[0011] In a further embodiment of the method according to the invention, a centering body is inserted into the side part without a filling opening. This centering body forms an interface with at least two layers of the pressure vessel, and the bonding agent is applied as a further layer, at least partially, to the interfaces thus formed. The centering body can have centrally located bores into which an inner layer engages, or into which the pressure vessel can be aligned on its cylindrical axis of rotation. Due to its adhesive properties, the bonding agent binds the centering body to at least two layers of the side part over a planar area. It is conceivable that the bonding agent is also applied outside the interface with the centering body in a planar area between two layers of the side part.

[0012] In one embodiment of the method according to the invention, the at least one planar area in which the joining agent forms a layer is explicitly designed in such a way as to prevent at least one possible defect such as corrosion, material cracks, or stress peaks leading to material cracks (see Figure 5 ).

[0013] In one embodiment of the method according to the invention, the joining agent is introduced between at least two layers of a pressure vessel, wherein the outermost layer of the pressure vessel is formed from a synthetic resin, in particular an epoxy resin, together with a carbon fiber, a so-called CFRP, i.e., a carbon fiber reinforced plastic, and at least one inner layer is formed from a plastic, in particular PA6.6. Accordingly, such a joining agent must be selected which possesses adhesive properties with respect to the materials used for layer formation in the at least two layers of the pressure vessel between which it is introduced.

[0014] In a further embodiment of the method according to the invention, the respective inlet body or centering body inserted into the respective side part is formed from a metal, in particular aluminum. This metal can be coated at least partially using a coating process, in particular a cathodic dip coating process referred to as KTL for short.

[0015] In a further embodiment of the method according to the invention, the bonding agent is selected from a list of the following materials: Sikaflex® < 222i UV, Henkel Loctite® < , Henkel Teroson® < RB 3225. These bonding agents are advantageously suited for bonding the aforementioned materials CFRP and aluminum with e-coating. In particular, they protect against delamination of the e-coat layer from the aluminum, improve corrosion protection, and provide insulation. In the area where the at least two layers meet the inlet or centering body, they help to avoid a so-called hard transition (CFRP - PA6.6 - metal), i.e., stress concentrations are reduced. Bonding agents other than those mentioned are also conceivable, provided they possess the required adhesive properties for the materials used in the layer structure of the pressure vessel.

[0016] A pressure vessel according to claim 5 is claimed, comprising several layers and a cylindrical central part with two curved side parts, wherein at least one side part has a filling opening, and in which an joining agent is introduced between at least two layers in at least one planar area, which forms a further layer and is designed to compensate for forces occurring between the at least two layers of the pressure vessel within this further layer and to prevent the formation of gaps.

[0017] The claim includes a pressure vessel comprising at least one side part with a filling opening, and in which an inlet body is inserted into the side part, thereby forming an interface to at least two layers of the pressure vessel, wherein the joining agent is applied as a further layer at least partially to the respective interfaces thus formed.

[0018] Finally, in a further embodiment, a pressure vessel is claimed in which a centering body is inserted into the side part without a filling opening, whereby an interface to at least two layers of the pressure vessel is formed, wherein the joining agent is applied as a further layer at least partially to the respective interfaces thus formed.

[0019] The inlet body of the claimed pressure vessel has the following layer thickness when covering the inlet body as a further layer, in order to ensure good thermal insulation of the inlet body and to avoid or reduce relative movements between the inlet body and the outer and inner layers, wherein, with reference to the layer thicknesses listed below, the outer diameter of the inlet body is a maximum of 85 mm, in particular 30 to 85 mm: Layer thickness of the next layer (in mm) in the area of ​​the entrance body Preferred material for the next layer Property (thermal insulation; prevention / reduction of relative movement) / Test results less than 0.3 Elastomer or thermosets Less pronounced or not pronounced / rather negative greater than 3.5 Elastomer or thermosets Less pronounced or not pronounced / rather negative 0.3 to 3.5 Elastomer or thermosets Particularly positive characteristic & positive effect / particularly positive result

[0020] An input body is also known as a boss. The maximum thickness of the next layer is approximately 15 mm. The minimum thickness of the next layer is 0 mm.

[0021] In the claimed pressure vessel, the inlet body is covered with a layer thickness of 0.3 to 3.5 mm, the layer itself preferably being an elastomer or thermoset. Thermosets are also known as thermosetting plastics. The additional layer is thus arranged between the respective interfaces formed according to the invention. In an edge region where no inlet body is present and where the interfaces are still present, the thickness of the additional layer can be reduced to as little as 0.3 mm or even 0 mm.

[0022] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawing.

[0023] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or on their own, without leaving the scope of the present invention.

[0024] The following figures illustrate the method according to the invention by way of example using a pressure vessel with two layers, the outer layer of which defines an outer vessel and the inner layer of which defines an inner vessel. However, the method according to the invention is not limited to this embodiment, but can also be applied in the same way to pressure vessels with more than two layers.

[0025] The figures are described in a coherent and comprehensive manner; identical components are assigned the same reference symbols. Figure 1Figure 1 shows a schematic representation of an external view of an embodiment of a pressure vessel as it is produced using an embodiment of the method according to the invention. Figure 2 The upper half of the figure shows a schematic representation of a section through a further embodiment of a pressure vessel according to the invention, as produced using a further embodiment of the method according to the invention. Figure 3 Figure 1 shows a schematic representation of an enlarged sectional drawing in the area of ​​an input body in which a layer of an joining agent according to another embodiment of the inventive method is introduced. Figure 4 Figure 1 shows a schematic representation of an enlarged sectional drawing in the area of ​​a centering body in which a layer of an joining agent according to another embodiment of the method according to the invention is introduced. Figure 5The figure shows in schematic representation several cross-sectional images in the area of ​​a gap formation, in which, in addition to a gap formation, several possible areas for the introduction of a layer of an joining agent according to a further embodiment of the inventive method are illustrated.

[0026] In Figure 1 Figure 1 shows a schematic external view of a pressure vessel 100 as manufactured according to one embodiment of the inventive method. A cylindrical central section in a region 102 is closed off on both sides by a convex side section in respective regions 104 and 106. An inlet body, a so-called boss, with an access opening 108, through which gas exchange with the pressure vessel takes place, is located on the front side section visible here. An joining element may be located at the edge 110 of the access opening 108 (see reference numeral 226 in [reference number]). Figure 2). An inlet body for gas exchange may also be located in the rear side panel in area 106, which is not fully visible here.

[0027] However, it is also a construction method with a centering body (see reference numeral 222 in Figure 2 ) or a closed surface is possible.

[0028] In Figure 2 The upper part shows a schematic cross-section through the upper half of a pressure vessel according to the invention. The lower part shows an external view of the pressure vessel 100. Figure 1 The cylindrical central section in area 102 and the two side sections in areas 104 and 106 have two layers: an outer layer 216 and an inner layer 218. The outer layer 216 can be made of carbon fiber reinforced plastic. The inner layer 218 can be made of PA6.6 plastic. In the front side section, in the Figure 2On the left side in area 104, there is an inlet body 220, which can be made of a metal, e.g., aluminum. It has an access opening 108 through which gas exchange with the interior 212 of the pressure vessel takes place. In the rear side panel, in the Figure 2On the right side in area 106, a centering body 222 is located. According to the inventive method, a layer 224 formed by an adhesive is located in area 104 between the outer layer 216, the inner layer 218, and the input body 220. The layer 224 of the adhesive protrudes at point 226 on the edge 110 of the input body and extends between the outer layer 216 and the inner layer 218 to a point 228 in the area of ​​the left extension of the cylindrical central part, which constitutes area 102. The thickness of the adhesive layer can vary. Advantageously, the layer thickness of the joining material from point 226 at the edge 110 of the inlet body 220 is approximately 3 mm or more, which tapers down to 0 mm at point 228, thereby completely filling any potential gap.Similarly, in area 106, between the outer layer 216, the inner layer 218, and the centering body 222, there is a layer 230 formed by an adhesive. The layer 230 of the adhesive protrudes at point 232 on the edge of the centering body 222 and extends between the outer layer 216 and the inner layer 218 to a point 234 in the region of the right-hand extension of the cylindrical central part, which constitutes area 102. Advantageously, the thickness of the adhesive layer from point 232 onward at the edge of the centering body 222 is approximately 3 mm or more, tapering to 0 mm at point 234, thus completely filling any gap. Particularly preferably, the layers 224, 230 have a layer thickness between 0.3 mm and 3.5 mm over their course when the maximum outer diameter of the input body is 85 mm, in particular 30 to 85 mm.

[0029] In Figure 3A schematic representation shows an enlarged sectional drawing 300 in the area of ​​the inlet body 220, in which a layer of an adhesive is introduced according to the inventive method. More precisely, it is defined here that the layer 224 of the adhesive projects from the edge of the inlet body 220 to a point 226 with a dimension 344 of approximately 5 mm or more. The inlet body 220, which can be made of aluminum, for example, has a coating on its "outer" surface 340 by means of cathodic dip coating (e-coating), while its "inner" surface 338 has no coating. The layer 224 of the adhesive can extend between the inner layer 218 and the inlet body 220 to a point 342.

[0030] In Figure 4A schematic representation shows an enlarged sectional drawing 400 in the area of ​​the centering body 222, in which a layer of an adhesive is introduced according to the inventive method. More precisely, it is defined here that the layer 230 of the adhesive projects from the edge of the centering body 222 to a point 232 with a dimension 446 of approximately 5 mm or more. The centering body 222, which can be made of aluminum, for example, has a coating on its "outer" surface 449 applied by means of cathodic dip coating (e-coating). The layer 230 of the adhesive can extend between the inner layer 218 and the inlet body 220.

[0031] In Figure 5Several cross-sectional views of a gap formation are shown schematically, illustrating not only the gap formation itself but also several possible areas for the introduction of a layer of an adhesive according to the inventive method. This is demonstrated by way of example in the area of ​​a side part that has an input body 220. Figure 550 shows a formed gap 552 extending from a point 554 to a point 556, which has formed between the outer layer 216 and the inner layer 218, or between the input body 220 and the inner layer 218. Figure 560 shows a maximum area in which a layer 224 of an adhesive has been introduced between the outer layer 216, the inner layer 218, and the input body 220.Figure 570 shows a minimal area 572 necessary to prevent corrosion and form a layer of an adhesive, which is essentially intended to prevent material exchange with the environment. A gap 552 remains between the outer layer 216 and the inner layer 218. Finally, Figure 580 shows a minimal area 582 necessary to prevent a stress concentration, which is essentially intended to prevent movement at the point of contact between the outer layer 216 made of CFRP, the inner layer 218 made of PA6.6, and the aluminum inlet body 220 with or without e-coating. Except for this area with the adhesive, a gap 552 remains between the outer layer 216 and the inner layer 218.

Claims

1. Method for producing a pressure container (100) having multiple layers and comprising a cylindrical central part with two curved side parts, wherein at least one side part has a filling opening (108), characterized in that a joining means is introduced between at least two layers (216, 218) of the pressure container (100) in at least one flat region, which forms a further layer (224, 230) and compensates for forces occurring between the at least two layers (216, 218) of the pressure container (100) within this further layer (224, 230) and prevents the formation of a gap (552) in this at least one flat region, wherein for forming the at least one side part with filling opening an inlet body (220) is inserted into the side part and thereby forms in each case an interface with at least two layers (216, 218) of the pressure container (100), wherein the joining means is applied at least in regions to the thus formed interfaces as a further layer (224), characterized in that the further layer (224) of the joining means for covering the inlet body (220) has a layer thickness of 0.3 mm to 3.5 mm, in particular in the region of the inlet body (220), and wherein the inlet body (220) has an outer diameter of at most 85 mm, in particular 30 to 85 mm.

2. Method according to claim 1, in which for forming a side part without a filling opening a centering body (222) is inserted into the side part and thereby forms in each case an interface with at least two layers (216, 218) of the pressure container (100), wherein the joining means is applied at least in regions to the thus formed interfaces as a further layer (230).

3. Method according to claim 1 or 2, in which the joining means is introduced between at least two layers (216, 218) of a pressure container (100), in which the outermost layer (216) is formed from a synthetic resin, in particular an epoxy resin, together with a carbon fiber, and at least one inner layer (218) is formed from plastic, in particular PA6.6.

4. Method according to any one of the preceding claims, in which the inlet body (220) or centering body (222) inserted into the respective side part is formed from a metal, in particular aluminum, which has been coated at least partially with a painting method, in particular a cathodic dip painting method.

5. Pressure container (100) having multiple layers (216, 218) and comprising a cylindrical central part with two curved side parts, wherein at least one side part has a filling opening (108), and in which a joining means is introduced between at least two layers (216, 218) in at least one flat region, which forms a further layer (224, 230) and is designed to compensate for forces occurring between the at least two layers (216, 218) of the pressure container (100) within this further layer (224, 230) and to prevent the formation of a gap (552), wherein the pressure container (100) comprises at least one side part with filling opening, in which an inlet body (220) is inserted into the side part, whereby forming in each case an interface with at least two layers (216, 218) of the pressure container (100), wherein the joining means is applied at least in regions to the thus formed interfaces as a further layer (224), characterized in that the further layer (224) of the joining means for covering the inlet body (220) has a layer thickness of 0.3 mm to 3.5 mm, in particular in the region of the inlet body (220), and wherein the inlet body (220) has an outer diameter of at most 85 mm, in particular 30 to 85 mm.

6. Pressure container according to claim 5, in which a centering body (222) is inserted into a side part without a filling opening, whereby forming in each case an interface with at least two layers (216, 218) of the pressure container (100), wherein the joining means is applied at least in regions to the thus formed interfaces as a further layer (230).