JP7697407B2 - Tank manufacturing method - Google Patents

Description

The present invention relates to a method for manufacturing a tank, for example, a method for manufacturing a tank for storing hydrogen to be supplied to a fuel cell system.

A conventional manufacturing method for this type of high-pressure tank is to wind a fiber bundle that constitutes a fiber-reinforced resin layer around the outer periphery of the liner to form a fiber layer, and then place the liner with the fiber layer formed in a mold and inject resin into the mold to impregnate the fiber layer with the resin and form a fiber-reinforced resin layer (see, for example, Patent Document 1).

JP 2021-154637 A

However, in the manufacturing method of the high-pressure tank shown in Patent Document 1, when winding the fiber bundle, the fibers in the fiber layer sometimes do not reach a predetermined fiber volume density. As a result, it is not possible to stably increase the pressure resistance of the high-pressure tank.

The present invention was made in consideration of these problems, and aims to provide a method for manufacturing a tank that can stably increase the pressure resistance of the tank by increasing the fiber volume density of the wound fiber layer when winding a fiber bundle around the outer peripheral surface of the liner to form a fiber layer.

In view of the above problem, the method for manufacturing a tank according to the present invention is a method for manufacturing a tank having a liner filled with a fluid and a fiber-reinforced resin layer coated on the outer peripheral surface of the liner, and includes the steps of winding a fiber bundle constituting the fiber-reinforced resin layer around the outer peripheral surface of the liner to form a fiber layer, and placing the liner with the fiber layer formed thereon in a mold and injecting resin into the mold to impregnate the fiber layer with the resin and form the fiber-reinforced resin layer, the fiber bundle being formed by bonding continuous fibers together with a sizing agent, and the step of forming the fiber layer is characterized in that the fiber bundle is wound around the outer peripheral surface of the liner while being heated so that the sizing agent is softened.

In the manufacturing method of the tank of the present invention configured as described above, the fiber bundles constituting the fiber-reinforced resin layer are wound around the outer peripheral surface of the liner, and in the process of forming the fiber layer, the fiber bundles in which the continuous fibers are bonded together with a sizing agent are wound around the outer peripheral surface of the liner while being heated so that the sizing agent softens. As a result, the fiber bundles become soft and are easily compressed overall, so that the fiber bundles can be wound evenly, and the fiber volume density of the fiber layer can be increased while suppressing variation in the fiber bundles. As a result, the pressure resistance of the tank can be improved.

According to the present invention, the fiber bundle can be wound evenly around the outer peripheral surface of the liner, the fiber volume density of the fiber layer can be increased, and the pressure resistance of the tank can be improved.

1 is a front view showing a schematic appearance of a tank manufactured by a tank manufacturing method according to the present invention; 2A and 2B show a mode of winding a fiber bundle around the liner of the tank shown in FIG. 1, where FIG. 2A is a front view showing hoop winding, FIG. 2B is a front view showing helical winding, and FIG. 2C is a front view of a main part showing braider winding. 2 is a front view of a braider that winds a fiber bundle on the outer peripheral surface of the tank liner shown in FIG. 1, as viewed from the axial direction. FIG. 4 is a side view of the blader shown in FIG. 3 . 2A and 2B show a mold for impregnating the fiber layer of the tank liner shown in FIG. 1 with resin, FIG. 2A being an end view in an exploded state, and FIG. 2B being an end view in an assembled state. FIG. 11 is a graph showing the relationship between fiber volume density and liner surface temperature when a fiber bundle is wound around the outer peripheral surface of a liner while being heated and when the fiber bundle is wound without being heated in the tank manufacturing method of the present invention. FIG. 7 is a table showing the specifications of the graph shown in FIG. 6 .

One embodiment of the tank manufacturing method according to the present invention will be described in detail below with reference to the drawings. Figure 1 is a front view showing a schematic appearance of a tank manufactured by the tank manufacturing method according to this embodiment, and Figure 2 shows how a fiber bundle is wound around the tank shown in Figure 1, with (a) being a front view showing hoop winding, (b) being a front view showing helical winding, and (c) being a front view of the main part showing braider winding.

In Figures 1 and 2, a tank 10 manufactured by the tank manufacturing method of this embodiment stores hydrogen to be supplied to a fuel cell system, for example. Such a tank 10 includes a liner 11 filled with a fluid such as hydrogen, and a fiber layer 16 covering the outer periphery of the liner 11. The liner 11 constituting the tank 10 is made of resin, and a reinforcing fiber layer 16 is formed by wrapping, for example, multiple layers of fiber bundles 25 of carbon fiber around the outer periphery of the resin liner 11, and a fiber-reinforced resin layer is formed by impregnating the fiber layer with resin.

The liner 11 constitutes the core of the tank and has a cylindrical body 12 and approximately hemispherical dome sections 13, 13 arranged on the left and right ends of the body 12. The liner 11 is integrally formed by rotational blow molding using a resin member such as polyethylene or nylon. The liner 11 may also be formed from a light metal such as aluminum instead of a resin member. Furthermore, instead of a manufacturing method for integral molding such as rotational blow molding, the liner 11 may be formed by joining multiple divided members by injection or extrusion molding, etc.

An opening (not shown) is formed at the top of each of the dome sections 13, 13, and nozzle sections 14, 15 are attached to the opening. Specifically, as shown in FIG. 1, nozzle section 14 is inserted into the opening of the left dome section 13, and nozzle section 15 is inserted into the opening of the right dome section 13. The nozzle section 14 functions, for example, as a valve-side nozzle, and the nozzle section 15 functions, for example, as an end-side nozzle. These nozzle sections 14, 15 are formed into a cylindrical shape from a metal material, with one end inserted into the opening of one dome section 13 and the other end protruding outward from the other dome section 13 along the central axis L of the liner 11.

In the tank 10 thus constructed, a fiber layer 16 is formed that constitutes a fiber-reinforced resin layer coated on the outer peripheral surface of the liner 11. The fiber layer 16 can be wound in a variety of ways, including helical winding, hoop winding, and braider winding, by a filament winding device that winds fiber bundles 25 such as carbon fibers around the outer peripheral surface of the liner 11, or by a braider (braider) 20 described below. Helical winding is a method of winding the fiber bundles 25 in a spiral shape so that the angle (the so-called winding angle) between the central axis L of the liner 11 and the winding direction of the fiber bundles 25 is greater than 0° and less than 90°, as shown in FIG. 2(b). A helical layer is formed by this helical winding.

On the other hand, hoop winding is a method of winding the fiber bundles 25 in the circumferential direction of the liner 11 so that the winding angle between the central axis L of the liner 11 and the winding direction of the fiber bundles 25 is approximately perpendicular, as shown in Figure 2(a). Here, "approximately perpendicular" means both 90° and an angle of around 90° that can be created by shifting the winding positions of the fiber bundles 25 so that adjacent fiber bundles 25 do not overlap. Then, a hoop layer is formed by hoop winding.

Helical winding can be further divided into low-angle helical winding and high-angle helical winding depending on the winding angle. Low-angle helical winding is a type of helical winding where the winding angle is small (e.g., greater than 0° and less than 30°), and where the winding direction of the fiber bundle 25 in the dome portions 13, 13 is turned around before the fiber bundle 25 goes around the central axis L of the liner 11.

High-angle helical winding is a helical winding with a large winding angle (e.g., greater than 30° and less than 90°), in which the fiber bundle 25 in the body portion 12 goes around the central axis L of the liner 11 at least once before the winding direction of the fiber bundle 25 in the dome portions 13, 13 is turned back. Note that FIG. 2(b) shows low-angle helical winding. In this way, the helical winding and hoop winding in FIGS. 2(a) and (b) may be combined to form the fiber layer 16 described below, but for example, the fiber layer 16 may be formed by braider winding as shown in FIG. 2(c).

Furthermore, braider winding, as shown in FIG. 2(c), is a method of weaving wide fiber bundles 25 onto the outer peripheral surface of the liner 11 to form a fiber layer 16. This braider winding is performed by a braider (braiding machine) 20 (described later), in which bobbins with multiple fiber bundles 17 (25) wound around them are placed on the outer peripheral surface of the liner 11, and the multiple fiber bundles 25 pulled out from the multiple bobbins are weaved together to form a fiber layer 16 on the outer peripheral surface of the liner 11.

Next, the braider 20, which wraps multiple layers of fiber bundles around the outer circumference of the liner 11, will be described with reference to Figures 3 and 4. In Figures 3 and 4, the braider 20 comprises a disk 21 supported on a base (not shown) and a movement mechanism (not shown) that supports the liner 11 constituting the tank 10 and moves the liner 11 in the direction of axis C. The disk 21 has a through hole 22 in the center centered on axis C. The through hole 22 is set to a size that allows the liner 11 to pass through. Therefore, the liner 11 is configured to move within the through hole 22 by the movement mechanism.

The disk 21 is formed with a concave spherical surface 23 centered on the axis C, and multiple carriers 24 are arranged on the concave spherical surface 23 so that they can move circumferentially and radially along the concave spherical surface by a moving mechanism (not shown). A bobbin 26 with a fiber bundle 25 wound around it is rotatably supported on the carrier 24. The rotation axis of the bobbin 26 is arranged so as to face the axis C of the disk 21. Therefore, the fiber bundle 25 wound around the bobbin 26 is extended from the bobbin 26 and wound around the outer circumferential surface of the liner 11 of the tank 10 as the carrier 24 moves and the liner 11 moves in the axial C direction. Depending on the movement mode, braider winding is performed, and a fiber layer 16 that reinforces the liner 11 of the tank 10 is formed. The fiber bundle 25 and the above-mentioned fiber bundle 25 are substantially equivalent.

The fiber bundle 25 is formed by bundling continuous fibers having a diameter of, for example, several μm together and bonding them with a sizing agent, and the surface of the carbon fibers constituting the fiber bundle 25 is coated with a commonly known sizing agent such as uncured thermosetting resin. Examples of the continuous fibers include glass fibers, carbon fibers, aramid fibers, alumina fibers, boron fibers, steel fibers, PBO fibers, natural fibers, and high-strength polyethylene fibers, and in this embodiment, carbon fibers are used. Examples of the sizing agent include modified epoxy resins such as epoxy resins and vinyl ester resins, phenolic resins, melamine resins, and thermosetting resins such as urea resins, unsaturated polyester resins, alkyd resins, polyurethane resins, and thermosetting polyimide resins. The sizing agent refers to a small amount of resin that exists to maintain the shape of the fiber bundle, and is added to the fiber bundle 25 at about 1.1% (volume %).

Therefore, when the fiber bundle 25 is heated to a predetermined temperature (below the curing start temperature), the thermosetting resin, which is the sizing agent, softens, and the flexibility of the fiber bundle 25 increases, making it easier to wind the fiber bundle 25 around the liner 11, allowing for high-speed winding, and improving the Vf (fiber volume density) of the liner 11 after winding, thereby reducing the variation in Vf. In this embodiment, a thermoplastic resin may be used as the sizing agent.

In the tank manufacturing method of this embodiment, as shown in FIG. 4, a series of steps from heating the liner 11 to winding the fiber bundle 25 around the outer periphery of the liner 11 can be carried out in the heating chamber 30. A hot air generator 31 is connected to the heating chamber 30, and the temperature inside the heating chamber 30 can be set to any desired temperature, for example, 50 to 100°C. The liner 11 placed in the heating chamber 30 is heated to a predetermined temperature. It is then moved to the right in FIG. 4, and the fiber bundle 25 supplied from the braider 20 is heated in the heating chamber 30 and heated, and wound around the outer periphery of the liner 11. The liner 11A shows a state in which the fiber bundle 25 has been wound partway and a fiber layer 16 has been formed.

Next, the fiber bundle 25 is wound from the braider 20, and the winding is completed around the entire outer peripheral surface of the liner 11B, forming the fiber layer 16. The fiber layer 16 is formed in a state where multiple layers are stacked. In this case, the multiple liners 11, 11 are connected in the axial direction and are moved back and forth multiple times. The process up to this point is carried out in the heating chamber 30. Finally, the connected liners 11, 11 are cut at the connection part.

The heating chamber 30 has a wide expansion chamber 30a formed in the area where the fiber bundle 25 is supplied, and the temperature rise of the fiber bundle can be stabilized by lengthening the time that the fiber bundle 25 stays in the heating chamber. As a result, the fiber volume density Vf of the fiber layer 16 can be increased. After this, although not shown, the liner 11B with the fiber layer 16 formed on the entire outer periphery is removed from the heating chamber 30, and after a quality inspection, a fiber-reinforced resin layer is formed by resin impregnation into the fiber layer 16.

Next, the mold 40 for impregnating the fiber bundle 25 in a state where it is wound in multiple layers, i.e., the fiber layer 16, with resin will be described with reference to FIG. 5. The mold 40 includes an upper mold 41 and a lower mold 42 that is connected to the upper mold 41. When the upper mold 41 and the lower mold 42 are assembled, an internal space 45 that conforms to the shape of the liner 11 is formed inside the mold 40. By separating the upper mold 41 and the lower mold 42, the liner 11 can be placed and contained in the internal space 45 of the mold 40, and the contained liner 11 can be removed. The mold 40 is an injection molding mold for impregnating the liner 11 contained in the internal space 45 with resin, and the upper mold 41 and the lower mold 42 are metal molds in this example.

The upper mold 41 has a flow path 43 that connects the outside to the internal space, and the internal space can be reduced in pressure through the flow path 43. In addition, an uncured thermosetting resin similar to that exemplified as the sizing agent described above is injected into the mold 40 as a resin composition through the flow path 43. This allows the resin to be impregnated into the fiber layer 16 formed of the fiber bundles 25 wound around the liner 11. By impregnating the fiber layer 16 with resin, a fiber-reinforced resin layer is formed, and the liner 11 can be reinforced. The mold 40 is preferably equipped with a heating means and a temperature control means (not shown).

The operation of the manufacturing method of the tank of this embodiment configured as described above will be described below. In the manufacturing method of the tank 10 configured as described above, the liner 11, into which the fluid is filled, is wound with fiber bundles around the outer peripheral surface of the liner 11 to form a fiber layer. The fiber bundles 25, which are continuous fibers bonded together with a sizing agent, are wound around the outer peripheral surface of the liner 11 while being heated so that the sizing agent softens.

In other words, in FIG. 4, the liner 11 is placed in the heating chamber 30, and the hot air generator 31 is operated to raise the temperature in the heating chamber 30 and heat the liner 11 itself. At this time, it is preferable to measure the surface temperature of the liner 11 with a thermocouple thermometer or the like to confirm that it is within a predetermined temperature range. After this, the liner 11 is moved to the winding position of the braider 20, and the fiber bundle 25 wound around the bobbin 26 is stretched and wound around the outer circumferential surface of the liner 11. The carrier 24 is moved along the concave spherical surface 23, and the liner 11 is moved in the direction of the axis C to wind the fiber bundle 25 around the outer circumferential surface of the liner. When forming multiple fiber layers 16, the liner 11 is moved back and forth between the position of the liner 11A and the position of the liner 11B.

In the manufacturing method of this embodiment, when the fiber bundle 25 is wound around the outer peripheral surface of the liner 11, it is heated so that the sizing agent that binds the fiber bundle 25 is softened. As a result, the sizing agent softens, the bonds between the continuous fibers become soft, and the shape of the fiber bundle 25 easily follows the shape of the part to be wound. As a result, the fiber layer 16 wound around the outer peripheral surface of the liner 11 is easily compressed, and the fiber bundle 25 is evenly wound around the outer peripheral surface of the liner 11, resulting in good adhesion. After this, the liner 11 on which the fiber layer 16 is formed with the fiber bundle 25 wound around it is placed in a mold 40, and resin is injected into the mold 40 to impregnate the fiber layer 16 with the resin, forming a fiber-reinforced resin layer. In this way, the liner 11 on which the fiber layer 16 is formed can have an increased fiber volume density Vf. And, by increasing the fiber volume density Vf, the pressure resistance of the tank 10 is improved.

Below, we will explain the change in fiber volume density Vf in the fully wound fiber layer when the winding method of the fiber bundle 25 wound around the liner 11 is changed and when multiple layers are wound at room temperature and when multiple layers are wound in a heated state, with reference to Figures 6 and 7. In the table showing the specifications in Figure 7, "full braid" is a mode in which the body portion 12 and the dome portions 13, 13 of the liner 11 are all braid-wound (= woven). Also, "switching" is a mode in which the portion that forms the dome-shaped dome portion 13 from the end of the liner is braid-wound (= woven), and the straight body portion 12 is helically wound (not woven).

In Figures 6 and 7, the circles, triangles, squares, crosses, and ●s indicate the heating state and winding specifications, respectively. Specifically, the circles and triangles indicate that, at room temperature and without heating, all fiber layers 1 to 16 are "fully braided," and the body 12 and dome sections 13, 13 of the liner 11 are all braided (woven).

The square marks indicate that, at room temperature and without heating, the fiber layers 1 to 15 are "switched", with the dome-shaped dome sections 13, 13 extending from the end of the liner being braided (= woven), and the straight body section 12 being helically wound (not woven), while the 16th layer is "fully braided", with the body section 12 and dome sections 13, 13 of the liner 11 all being braided (= woven).

The x marks indicate that the fabric is in an unheated room temperature state, and that the 1st, 2nd, 4th, 5th, 7th, 8th, 10th, 11th, 13th, and 14th fiber layers are "switched", with the dome-shaped dome sections 13, 13 extending from the end of the liner being braided (= woven), and the straight body section 12 being helically wound (not woven). The 3rd, 6th, 9th, 12th, 15th, and 16th fiber layers are "all braided", with the body section 12 of the liner 11 and the dome sections 13, 13 all being braided (= woven).

● marks indicate that in the heated state, the 3rd, 4th, 6th, 7th, 9th, 10th, 12th, 13th, and 15th fiber layers are "switched", with the dome-shaped dome sections 13, 13 extending from the end of the liner being braid-wound (= woven), and the straight body section 12 being helically wound (not woven). The 1st, 2nd, 5th, 8th, 11th, 14th, and 16th fiber bundle layers are "fully braided", with the body section 12 of the liner 11 and the dome sections 13, 13 all being braid-wound (= woven).

As shown in Figure 6, when the fiber layer is wound without heating at room temperature with a liner surface temperature of 2 to 21°C, the fiber volume density Vf of the fiber layer varies widely as shown in ranges A1 and A2, as indicated by the circles, ▲ marks, cross marks, and square marks, and is a small value of 47 to 57%. In contrast, when the fiber layer is wound in a heated state with a liner surface temperature of 52 to 54°C, the fiber volume density Vf of the fiber layer varies less as shown in ranges B1 and B2, as indicated by the circles, as indicated by the square marks, and is a large value of 61 to 64%.

In this way, when the fiber bundle 25 is wound around the outer peripheral surface of the liner 11 to form the fiber layer 16, if the fiber bundle 25 is heated while being wound around the outer peripheral surface of the liner 11 so that the sizing agent that bonds the continuous fibers of the fiber bundle is softened, the variation in the fiber volume density Vf of the fiber layer 16 can be reduced and the numerical value of Vf can be improved. As a result, the strength of the fiber-reinforced resin layer coated on the outer peripheral surface of the liner 11 can be increased, and the pressure resistance of the tank 10 can be improved.

In the above embodiment, as shown in FIG. 4, an example is shown in which three liners are stored in the heating chamber 30 and the process of winding the fiber bundle 25 around the outer peripheral surface of the liner 11 while heating it is performed continuously, but the number of liners is not limited to three, and the process may be performed while transporting more liners continuously.

Although one embodiment of the present invention has been described in detail above, the present invention is not limited to the above embodiment, and various design modifications can be made without departing from the spirit of the present invention described in the claims. The present invention allows the configuration of one embodiment to be added to the configuration of another embodiment, the configuration of one embodiment to be replaced with another embodiment, or part of the configuration of one embodiment to be deleted.

As an example of winding the fiber bundles that make up the fiber reinforced resin layer around the outer periphery of the liner, an example of winding the fiber bundles 25 around the liner 11 by the braider 20 has been shown, but helical winding or hoop winding may also be used. As a means of heating to soften the sizing agent that bonds the continuous fibers of the fiber bundles, an example of blowing hot air from a hot air generator 31 into the heating chamber 30 has been shown, but heating by an electric heater or other suitable changes may also be used.

10: Tank, 11: Liner, 20: Braider (braiding machine), 16: Fiber layer, 25: Fiber bundle, 30: Heating chamber, 31: Hot air generator, 40: Mold, Vf: Fiber volume density

Claims (1)

A method for manufacturing a tank including a liner filled with a fluid and a fiber-reinforced resin layer coated on an outer peripheral surface of the liner, comprising:
A step of winding a fiber bundle constituting the fiber reinforced resin layer around an outer peripheral surface of the liner to form a fiber layer;
The liner on which the fiber layer is formed is placed in a mold, and a resin is injected into the mold to impregnate the fiber layer with the resin, thereby forming the fiber reinforced resin layer.
The fiber bundle is formed by bonding continuous fibers together with a sizing agent,
A method for manufacturing a tank, characterized in that in the process of forming the fiber layer, the liner is placed in a heating chamber, and hot air from a hot air generator is blown into the heating chamber to heat the liner together with the fiber bundle in the heating chamber so as to soften the sizing agent, while the fiber bundle is wound around the outer peripheral surface of the liner.

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