JP2024002294A - High pressure tank and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology which enables an inner FRP layer and an outer FRP layer to be joined securely.

SOLUTION: A technology disclosed by the specification is realized by a high pressure tank having a shape in which both ends of a cylindrical part for storing high pressure fluid have dome parts. The high pressure tank includes: an inner FRP layer formed of a fiber reinforcement material; an outer FRP layer located at an outer side of the inner FRP layer and formed of a fiber reinforcement material; and an adhesion layer provided between the inner FRP layer and the outer FRP layer in at least the cylindrical part. The adhesion layer has: an inner adhesion layer which contacts with the inner FRP layer; an outer adhesion layer which contacts with the outer FRP layer; and a barrier layer located between the inner adhesion layer and the outer adhesion layer and having a barrier property higher than those of the inner FRP layer and the outer FRP layer.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

The technology disclosed herein relates to a high-pressure tank for storing high-pressure fluid and a method for manufacturing the same.

Patent Document 1 discloses a high-pressure tank having a cylindrical portion and dome portions at both ends. The high-pressure tank has an inner FRP layer (referred to as a reinforcing body in Patent Document 1) made of fiber-reinforced resin and an outer FRP layer made of fiber-reinforced resin located outside the inner FRP layer (Patent Document 1). 1, it comprises a further reinforcing layer).

JP 2021-119034 Publication

When a high-pressure tank is filled with high-pressure fluid or when high-pressure fluid is discharged from the high-pressure tank, the internal pressure of the high-pressure tank changes significantly. When the internal pressure of a high-pressure tank changes significantly, the high-pressure tank deforms. In particular, the cylindrical portion of the high-pressure tank that has a planar shape is more easily deformed when filling and discharging high-pressure fluid than the dome portion that is curved into a dome shape. In the high-pressure tank of Patent Document 1, the movement of the fibers in the outer FRP layer is restricted by the adhesive force of the resin in the inner FRP layer. In a high-pressure tank having such a configuration, when the high-pressure tank is deformed during filling and discharging of high-pressure fluid, there is a risk that the inner FRP layer and the outer FRP layer may become misaligned in the cylindrical portion. This specification discloses a technique that can firmly join an inner FRP layer and an outer FRP layer in a cylindrical portion.

The technology disclosed in this specification is realized by a high-pressure tank having a cylindrical part that stores high-pressure fluid and has dome parts at both ends. The high-pressure tank includes an inner FRP layer made of fiber-reinforced material, an outer FRP layer located outside the inner FRP layer and made of fiber-reinforced material, and at least the inner FRP layer in the cylindrical portion. and an adhesive layer provided between the outer FRP layer and the outer FRP layer. The adhesive layer is located between an inner adhesive layer in contact with the inner FRP layer, an outer adhesive layer in contact with the outer FRP layer, and the inner adhesive layer and the outer adhesive layer, and a barrier layer having higher barrier properties than the inner FRP layer and the outer FRP layer.

According to the high-pressure tank described above, the adhesive layer provided between the inner FRP layer and the outer FRP layer firmly joins the inner FRP layer and the outer FRP layer at least in the cylindrical portion. This can prevent the inner FRP layer and the outer FRP layer from shifting when the cylindrical portion is deformed due to a change in the internal pressure of the high-pressure tank. Furthermore, the adhesive layer is located between the inner adhesive layer that is in contact with the inner FRP layer, the outer adhesive layer that is in contact with the outer FRP layer, and both FRP layers, and the adhesive layer is located between the inner FRP layer and the outer FRP layer. It also has a barrier layer with barrier properties. Therefore, for example, there is no need to provide a barrier layer separate from the adhesive layer inside the inner FRP layer. The high-pressure tank disclosed herein can simplify its manufacturing process.

Furthermore, the present specification also discloses a method for manufacturing a high-pressure tank having a cylindrical portion and dome portions at both ends for storing high-pressure fluid. The high-pressure tank includes an inner FRP layer made of a fiber-reinforced material, an outer FRP layer located outside the inner FRP layer, and made of the fiber-reinforced material, and at least in the cylindrical portion, the inner FRP layer is located outside the inner FRP layer. and an adhesive layer provided between the outer FRP layer and the outer FRP layer. The adhesive layer is located between an inner adhesive layer in contact with the inner FRP layer, an outer adhesive layer in contact with the outer FRP layer, and the inner adhesive layer and the outer adhesive layer, and a barrier layer having higher barrier properties than the inner FRP layer and the outer FRP layer. The inner FRP layer includes a first inner FRP layer located in the cylindrical portion and a second inner FRP layer located in the dome portion. The fiber material of the fiber reinforced material is not continuous between the first inner FRP layer and the second inner FRP layer. The manufacturing method includes a first forming step of forming the first inner FRP layer with the fiber-reinforced material, a second forming step of forming the second inner FRP layer with the fiber-reinforced material, and a second forming step of forming the first inner FRP layer with the fiber-reinforced material. a bonding step of bonding the first inner FRP layer and the second inner FRP layer; a bonding layer forming step of providing the adhesive layer at least on the outside of the first inner FRP layer before or after the bonding step; and a third forming step of forming the outer FRP layer with the fiber reinforced material on the outside of the first inner FRP layer and the second inner FRP layer.

According to the manufacturing method described above, the adhesive layer is provided at least on the outside of the first inner FRP layer in the adhesive layer forming step performed before or after the bonding step. The adhesive layer has a barrier layer. For this reason, for example, compared to a structure in which the inner FRP layer is arranged on the outer peripheral surface of a barrier layer different from the adhesive layer and the adhesive layer is arranged outside the inner FRP layer, the barrier layer is the same as the inner and outer adhesive layers. Since it can be provided in the step of 1, the process can be simplified.

Details and further improvements of the technology disclosed in this specification will be explained in the following "Detailed Description of the Invention".

The perspective view of the high pressure tank 2 of an Example is shown. 2 shows a sectional view along line II-II in FIG. 1; FIG. The first formation step in the manufacturing method of the example is shown. The second forming step in the manufacturing method of the example is shown. The joining process in the manufacturing method of the example is shown. The adhesive layer forming step and the third forming step in the manufacturing method of the example are shown.

In one embodiment of the present technology, the inner FRP layer may include a first inner FRP layer located in the cylindrical portion and a second inner FRP layer located in the dome portion. In that case, the fiber material of the fiber reinforced material may not be continuous between the first inner FRP layer and the second inner FRP layer. According to such a configuration, each of the first inner FRP layer and the second inner FRP layer can be formed separately. Therefore, different amounts of fiber-reinforced material can be arranged for each FRP layer, for example, so that more fiber-reinforced material is arranged in the second inner FRP layer than in the first inner FRP layer. Thereby, an appropriate amount of fiber-reinforced material can be placed in each of the cylindrical part and the dome part. Furthermore, the first inner FRP layer and the second inner FRP layer of the inner FRP layer can be firmly connected by the outer FRP layer located outside the inner FRP layer.

In one embodiment of the present technology, a portion of the adhesive layer may extend to the dome portion and be located between the second inner FRP layer and the outer FRP layer. According to such a configuration, the adhesive layer can firmly connect the first inner FRP layer and the second inner FRP layer of the inner FRP layer.

In one embodiment of the present technology, a part of the adhesive layer extends to the dome part, and the first inner FRP layer and the second inner FRP layer overlap each other at the boundary between the cylindrical part and the dome part. It may be located between. According to such a configuration, the adhesive layer can firmly connect the first inner FRP layer and the second inner FRP layer of the inner FRP layer.

(Example)
FIG. 1 shows a perspective view of a high-pressure tank 2 according to an embodiment. The high-pressure tank 2 is mounted, for example, on a fuel cell vehicle (not shown). The high-pressure tank 2 stores high-pressure hydrogen gas used by the fuel cell vehicle to generate electricity. That is, the high pressure tank 2 is a tank that stores high pressure fluid. Note that the high-pressure fluid stored in the high-pressure tank 2 is not limited to hydrogen gas, and may be, for example, a high-pressure liquid.

The shape of the high-pressure tank 2 includes a cylindrical portion 21 having a cylindrical shape extending along the central axis CL, and dome portions 22 and 26 provided at both ends of the cylindrical portion 21. Hereinafter, a direction parallel to the central axis CL of the cylindrical portion 21 (that is, a positive direction and a negative direction of the Z axis in the coordinate axes in the figure) will be referred to as an axial direction.

The high-pressure tank 2 includes an inner FRP (Fiber Reinforced Plastics) layer 4, an outer FRP layer 6, and a cap 8. Each FRP layer 4, 6 is constructed by impregnating a long filament of carbon fiber with a thermosetting resin (eg, epoxy resin). That is, each FRP layer 4, 6 is made of fiber reinforced resin. The outer FRP layer 6 is located outside the inner FRP layer 4 and covers the outer surface of the inner FRP layer 4. In addition, in a modified example, the long carbon fiber filament may be impregnated with a thermoplastic resin instead of the thermosetting resin.

The cap 8 is a boss made of metal, and is provided at one end of the dome portion 22 in the axial direction (that is, the right end in FIG. 1). The cap 8 has a through hole that communicates the inside and outside of the high-pressure tank 2. Hydrogen gas in the high-pressure tank 2 is released to the outside through the through hole of the cap 8, and hydrogen gas is also supplied into the high-pressure tank 2 from the outside.

The detailed structure of the high pressure tank 2 will be described with reference to FIG. 2. FIG. 2 is a cross-sectional view along line II-II in FIG. The inner FRP layer 4 includes a first inner FRP layer 41 and a second inner FRP layer 42 . The first inner FRP layer 41 is located in the cylindrical portion 21 of the high-pressure tank 2 (see FIG. 1). The second inner FRP layer 42 is located in the dome portion 22 (see FIG. 1) of the high-pressure tank 2. Although details will be described later, each inner FRP layer 41, 42 is formed in separate filament winding processes. Therefore, the filaments (ie, fibrous material) of each inner FRP layer 41, 42 are not continuous.

The axial end of the first inner FRP layer 41 is located inside the second inner FRP layer 42 (that is, on the central axis CL side). That is, the first inner FRP layer 41 extends to the dome portion 22 in the axial direction. In other words, the inner FRP layers 41 and 42 overlap each other at the boundary B1 between the cylindrical portion 21 and the dome portion 22 of the high-pressure tank 2.

The adhesive layer 10 is provided between the inner FRP layer 4 and the outer FRP layer 6 in a part of the cylindrical part 21 and the dome part 22. The adhesive layer 10 adheres the inner FRP layer 4 and the outer FRP layer 6. The adhesive layer 10 is composed of a flat sheet.

As shown in the enlarged view of FIG. 2, the adhesive layer 10 includes an inner adhesive layer 14, an outer adhesive layer 16, and a first barrier layer 15. The layers 14, 15, and 16 are laminated to form one sheet-like adhesive layer 10. The inner adhesive layer 14 and the outer adhesive layer 16 of this embodiment are made of PP (polypropylene). The first barrier layer 15 of this embodiment is made of EVOH (ethylene-vinylalcohol copolymer). The first barrier layer 15 has higher gas barrier properties than each of the FRP layers 4 and 6. Therefore, the first barrier layer 15 prevents hydrogen gas in the high-pressure tank 2 from leaking to the outside.

In this way, in the high-pressure tank 2 of this embodiment, the inner FRP layer 4 and the outer FRP layer 6 are firmly adhered to each other in part of the cylindrical part 21 and dome part 22 by the adhesive layer 10. Thereby, when the cylindrical portion 21 is deformed due to a change in the internal pressure of the high-pressure tank 2, it is possible to prevent the inner FRP layer 4 and the outer FRP layer 6 from shifting from each other. Furthermore, as mentioned above, the adhesive layer 10 comprises a first barrier layer 15. Therefore, the high-pressure tank 2 does not need to have a separate barrier layer located inside the inner FRP layer 4, such as a conventional liner, for example. Therefore, the manufacturing process of the high-pressure tank 2 of this embodiment can be simplified compared to the conventional process of forming another barrier layer such as a liner and wrapping the inner FRP layer 4 around the outer periphery of the liner. .

Here, the cylindrical portion 21 and the dome portion 22 of the high-pressure tank 2 may have different required shape rigidities. For example, compared to the cylindrical portion 21, a large load is easily applied to the dome portion 22 located around the mouthpiece 8 in the axial direction when hydrogen gas is discharged and filled. Furthermore, since the cylindrical portion 21 is formed in a flat plane, it is easy to wind the filaments evenly around the entire outer peripheral surface of the cylindrical portion 21 without overlapping the filaments. On the other hand, since the dome portion 22 is formed with a curved surface, when the filaments are wound around the entire surface of the dome portion 22, the filaments tend to overlap each other.

Here, for example, a comparative example is assumed in which the first inner FRP layer 41 and the second inner FRP layer 42 are integrally formed by filament winding. In this comparative example, when the required amount of filament is wrapped around the entire surface of the second inner FRP layer 42 forming the dome part 22 while overlapping the filaments, the first inner FRP layer 41 forming the cylindrical part 21 is wrapped. The filaments that are wound also overlap. As a result, in this comparative example, the amount of filaments arranged in the first inner FRP layer 41 may increase more than necessary. In the high-pressure tank 2 of this embodiment, as described above, the inner FRP layers 41 and 42 are formed in separate filament winding processes. Therefore, the amount of carbon fiber filaments in each inner FRP layer 41, 42 can be set separately. Unlike the comparative example, since the filament is wound around the entire surface of the second inner FRP layer 42 forming the dome portion 22, the amount of filament in the first inner FRP layer 41 forming the cylindrical portion 21 does not increase. An appropriate amount of filament can be wound around each inner FRP layer 41, 42.

Further, in the outer FRP layer 6, carbon fiber filaments are wound around the cylindrical portion 21 and the dome portion 22. Therefore, in the high-pressure tank 2, the outer FRP layer 6 can firmly connect the first inner FRP layer 41 and the second inner FRP layer 42, which are separately configured.

A second barrier layer 44 is provided inside the second inner FRP layer 42 . Like the first barrier layer 15, the second barrier layer 44 is also made of an EVOH sheet. In addition, in a modified example, the second barrier layer 44 may be formed by applying polyethylene to the inside of the second inner FRP layer 42, for example.

The axial end of the adhesive layer 10 is located on the outer surface of the second inner FRP layer 42 beyond the boundary B1. That is, a portion of the adhesive layer 10 extends to the dome portion 22 of the high-pressure tank 2. As a result, the adhesive layer 10 bonds the first inner FRP layer 41 and the second inner FRP layer 42. Thereby, the separate first inner FRP layer 41 and second inner FRP layer 42 can be firmly connected.

Next, a method for manufacturing the high pressure tank 2 will be described with reference to FIGS. 3 to 6. First, the first formation step will be described with reference to FIG. In the first forming step, the filament F1 is wound around the outer peripheral surface of the cylindrical first mandrel M1 by a so-called hoop winding method of filament winding. As shown in the left diagram of FIG. 3, in the first forming step, the first mandrel M1 is rotated in the rotational direction R1 about the central axis CL, and the nozzle N1 is rotated in the direction G1 parallel to the axial direction. move back and forth along the Thereby, the filament F1 is wound around the outer peripheral surface of the first mandrel M1. By repeatedly reciprocating the nozzle N1 in the direction G1, the filament F1 is laminated in multiple layers on the outer peripheral surface of the first mandrel M1.

After being wound around the outer peripheral surface of the first mandrel M1, the filament F1 is heated. By the heating, the thermosetting resin impregnated into the filament F1 is cured. The first mandrel M1 is then removed from the cured filament F1. As a result, the first inner FRP layer 41 is formed as shown in the right diagram of FIG.

The second forming step will be explained with reference to FIG. 4. In the second forming step, the filament F2 is wound around the outer peripheral surface of the second mandrel M2 by so-called helical winding of the filament winding method. The second mandrel M2 has an oval shape in side view. Both ends of the second mandrel M2 in the axial direction are curved into a dome shape. A cap 8 is fixed to one end of the second mandrel M2 in the axial direction.

As shown in the left diagram of FIG. 4, in the second forming step, the second mandrel M2 is rotated in the rotation direction R2 about the central axis CL, and the nozzle N1 is rotated at an angle with respect to the central axis CL. It moves in the direction G2 inclining by θ2. Thereby, the filament F2 is wound around the outer circumferential surface of the second mandrel M2 which curves into a dome shape. Here, the angle θ2 is set depending on the shape of the curved surface of the second mandrel M2, the diameter of the filament F2, etc. By repeatedly reciprocating the nozzle N2 in the direction G2, the filament F2 is laminated in multiple layers on the outer peripheral surface of the second mandrel M2.

After the filament F2 is wound around the outer peripheral surface of the second mandrel M2, the filament F2 is heated, and the thermosetting resin impregnated in the filament F2 is cured. Then, the cured filament F2 is cut along the cut line C1. The cut filament F2 is removed from the second mandrel M2. At this time, the cap 8 is also removed from the second mandrel M2 together with the filament F2. As a result, as shown in the right diagram of FIG. 4, second inner FRP layers 42 and 46 curved into a dome shape are formed. Thereafter, sheet-shaped second barrier layers 44 and 48 are attached to the inner circumferential surfaces of the formed second inner FRP layers 42 and 46, respectively.

The bonding process will be described with reference to FIG. 5. In the joining process, the second inner FRP layers 42 and 46 are attached to both ends of the first inner FRP layer 41 in the direction J1. At this time, as shown in the upper enlarged view of FIG. 5, the second inner FRP layer 42 is arranged to cover the outer peripheral surface of the first inner FRP layer 41. In other words, in the bonding process, the first inner FRP layer 41 is inserted into the second inner FRP layer 42. As a result, the first inner FRP layer 41 overlaps with the second inner FRP layer 42 at the end of the first inner FRP layer 41 .

With reference to FIG. 6, the adhesive layer forming step and the third forming step will be described. In the adhesive layer forming step, the sheet-like adhesive layer 10 is wrapped around the outer peripheral surfaces of the first inner FRP layer 41 and second inner FRP layers 42 and 46 assembled in the bonding step. As described with reference to FIG. 2, the adhesive layer 10 includes an inner adhesive layer 14, an outer adhesive layer 16, and a first barrier layer 15.

Next, in the third forming step, the outer peripheries of the first inner FRP layer 41, the second inner FRP layers 42, 46, and the adhesive layer 10 (hereinafter referred to as a bonded body) are formed by hoop winding and helical winding using the filament winding method. A filament F3 is wound around the surface. In the helical winding of the third forming step, the nozzle N3 moves in a direction G3 inclined by a predetermined angle θ3 with respect to the central axis CL while the joined body is rotated in the rotation direction R3 about the central axis CL. do. Here, the angle θ3 is set depending on the shape of the joined body, the diameter of the filament F3, etc. In addition, in a modification, the filament F3 may be wound around the outer peripheral surface of the joined body only by helical winding in the third forming step.

After being wound around the outer peripheral surface of the bonded body in the third forming step, the filament F3 is heated. By the heating, the thermosetting resin impregnated into the filament F3 is cured. As a result, the high pressure tank 2 (see FIG. 1) is manufactured.

In addition, since the adhesive layer 10 is provided between the inner FRP layer 4 and the outer FRP layer 6 in a part of the cylindrical part 21 and the dome parts 22 and 26, especially in the cylindrical part 21, each FRP layer 4 and 6 is Firmly fixed. Although the adhesive layer 10 is only partially provided on the dome parts 22 and 26, the dome parts 22 and 26 have a curved shape and have higher rigidity than the cylindrical part 21. Therefore, even if the internal pressure of the high-pressure tank 2 changes, the dome parts 22 and 26 are less likely to deform than the cylindrical part 21. Therefore, the area of the adhesive layer 10 can be made smaller in the dome parts 22 and 26 than in the cylindrical part 21. Thereby, the size of the adhesive layer 10 can be reduced.

Although specific examples of the technology disclosed in this specification have been described above in detail, these are merely examples and do not limit the scope of the claims. The techniques described in the claims include various modifications and changes to the specific examples illustrated above. Modifications of the above embodiment are listed below.

(Modification 1) The adhesive layer forming step may be performed before the bonding step. In that case, a part of the adhesive layer 10 may be located between the first inner FRP layer 41 and the second inner FRP layer 42 which overlap each other at the boundary B1 between the cylindrical part 21 and the dome part 22. According to such a configuration, the second barrier layer 44 is fixed to the outer adhesive layer 16, so that the first inner FRP layer 41 and the second inner FRP layer 42 can be firmly connected.

(Modification 2) The inner adhesive layer 14 and the outer adhesive layer 16 may be made of epoxy resin instead of PP. In a further variant, the inner adhesive layer 14 and the outer adhesive layer 16 may be composed of polyimide or of thermoplastic polyester.

(Modification 3) Each of the barrier layers 15, 44, and 48 may be composed of a nylon sheet instead of an EVOH sheet. In a further variant, each barrier layer 15, 44, 48 may be constituted by a sheet of PET (PolyEthylene Terephthalate). Further, a sheet similar to that of the adhesive layer 10 may be used for the second barrier layer 44. That is, the second barrier layers 44, 48 may include the inner adhesive layer 14 and the outer adhesive layer 16. According to such a configuration, the first inner FRP layer 41 and the second inner FRP layer 42 can be more firmly connected by the adhesive layers 14 and 16 of the second barrier layers 44 and 48.

The technical elements described in this specification or the drawings exhibit technical utility alone or in various combinations, and are not limited to the combinations described in the claims as filed. Furthermore, the techniques illustrated in this specification or the drawings can achieve multiple objectives simultaneously, and achieving one of the objectives has technical utility in itself.

2 : High pressure tank 4 : Inner FRP layer 6 : Outer FRP layer 8 : Base 10 : Adhesive layer 14 : Inner adhesive layer 15 : First barrier layer 16 : Outer adhesive layer 21 : Cylindrical part 22, 26 : Dome part 41 : No. 1 inner FRP layer 42 : 2nd inner FRP layer 44, 48 : 2nd barrier layer B1 : Boundary C1 : Cut line CL : Central axis F1 to F3 : Filament M1 : First mandrel M2 : Second mandrel N1 to N3 : Nozzle

Claims (5)

A high-pressure tank having a cylindrical part and dome parts at both ends for storing high-pressure fluid,
an inner FRP layer made of fiber-reinforced material;
an outer FRP layer located outside the inner FRP layer and made of the fiber reinforced material;
an adhesive layer provided between the inner FRP layer and the outer FRP layer at least in the cylindrical portion;
Equipped with
The adhesive layer is
an inner adhesive layer in contact with the inner FRP layer;
an outer adhesive layer in contact with the outer FRP layer;
a barrier layer located between the inner adhesive layer and the outer adhesive layer and having higher barrier properties than the inner FRP layer and the outer FRP layer;
high pressure tank. The inner FRP layer has a first inner FRP layer located in the cylindrical part and a second inner FRP layer located in the dome part,
The high-pressure tank according to claim 1, wherein the fiber material of the fiber reinforced material is not continuous between the first inner FRP layer and the second inner FRP layer. The high-pressure tank according to claim 2, wherein a portion of the adhesive layer extends to the dome portion and is located between the second inner FRP layer and the outer FRP layer. A part of the adhesive layer extends to the dome part and is located between the first inner FRP layer and the second inner FRP layer that overlap each other at the boundary between the cylindrical part and the dome part. The high pressure tank according to item 2. A method for manufacturing a high-pressure tank having a cylindrical portion and dome portions at both ends for storing high-pressure fluid, the method comprising:
The high pressure tank is
an inner FRP layer made of fiber-reinforced material;
an outer FRP layer located outside the inner FRP layer and made of the fiber reinforced material;
an adhesive layer provided between the inner FRP layer and the outer FRP layer at least in the cylindrical portion;
Equipped with
The adhesive layer is
an inner adhesive layer in contact with the inner FRP layer;
an outer adhesive layer in contact with the outer FRP layer;
a barrier layer located between the inner adhesive layer and the outer adhesive layer and having higher barrier properties than the inner FRP layer and the outer FRP layer;
The inner FRP layer has a first inner FRP layer located in the cylindrical part and a second inner FRP layer located in the dome part,
Between the first inner FRP layer and the second inner FRP layer, the fiber material of the fiber reinforced material is not continuous,
The manufacturing method includes:
a first forming step of forming the first inner FRP layer with the fiber reinforced material;
a second forming step of forming the second inner FRP layer with the fiber reinforced material;
a joining step of joining the formed first inner FRP layer and the second inner FRP layer;
Before or after the bonding step, an adhesive layer forming step of providing the adhesive layer on at least the outside of the first inner FRP layer;
a third forming step of forming the outer FRP layer using the fiber reinforced material on the outer side of the joined first inner FRP layer and the second inner FRP layer;
Equipped with
Production method.

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