Patent ID: 12241591

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of a high-pressure tank and a manufacturing method of the same according to the disclosure will be described below with reference to the drawings. In the following description, an example will be described in which the high-pressure tank1is installed in a fuel cell electric vehicle and is filled with high-pressure hydrogen gas therein, but the high-pressure tank1may be applied to other uses as well. Also, gasses with which the high-pressure tank1can be filled are not limited to high-pressure hydrogen gas, and other examples thereof include various types of compressed gases such as compressed natural gas (CNG), various liquefied gases such as liquefied natural gas (LNG) and liquefied petroleum gas (LPG), and other gases.

High-Pressure Tank

First, the high-pressure tank will be described with reference toFIGS.1and2.FIG.1is a sectional view of the high-pressure tank according to the embodiment, andFIG.2is an enlarged view illustrating a portion II inFIG.1. As illustrated inFIG.1, the high-pressure tank1according to the present embodiment is a high-pressure gas storage container that is substantially cylindrical in shape and is rounded dome-shaped on both ends, and includes a liner2that has gas barrier properties, a reinforcing layer3that covers an outer face of the liner2, and a neck4attached to one end portion of the high-pressure tank1.

The liner2is a hollow container having a storage space5for storing high-pressure hydrogen, and is formed of a resin material or the like having gas barrier properties with respect to hydrogen gas. The liner2has a body21that is cylindrical in shape, and a pair of dome portions22, each of the dome portions22being provided on a respective right-left side of the body21in an axial direction (i.e., a direction of an axis L of the high-pressure tank1). The body21extends over a predetermined length along the direction of the axis L of the high-pressure tank1. The dome portions22are formed continuing from both right and left sides of the body21, and each has a hemispherical shape of which the diameter decreases the farther away from the body21.

An opening is formed at a top portion of one dome portion22of the dome portions22(the dome portion22on the left side inFIG.1), and the aforementioned neck4is attached to the opening. No opening is formed in the other dome portion22.

The liner2is formed integrally by rotary blow molding using a resin material such as polyethylene, nylon, or the like, for example. Alternatively, the liner2may be formed by coupling a plurality of members obtained separately by injection or extrusion molding, instead of an integral molding manufacturing method such as rotary blow molding. Further, the liner2may be made of a metal material such as aluminum, instead of a resin material.

The neck4is made by machining a metal material, such as stainless steel, aluminum, or the like, into a predetermined shape. The neck4has a neck body41that is substantially cylindrical in shape, and a flange portion42that is fitted between the liner2and the reinforcing layer3. A valve (omitted from illustration) for filling and discharging hydrogen gas to and from the storage space5is attached to the neck4.

The reinforcing layer3is a layer that has a function of improving mechanical strength of the high-pressure tank1, such as rigidity and pressure resistance, by reinforcing the liner2. The reinforcing layer3includes a pair of resin rings31provided encircling respective end portions of an outer circumferential face of the body21, a hoop layer32that is disposed between the resin rings31and covers part of the body21, and a helical layer33covering the resin rings31, the hoop layer32, and the dome portions22.

The resin rings31correspond to “resin members” described in the claims, and are formed so as to cover part of the body21from boundary portions23between the body21and the dome portions22. More specifically, the resin rings31are disposed from the boundary portions23to portions corresponding to curvature ends of curved portions332(described later) of the helical layer33of the body21, in the direction of the axis L of the high-pressure tank1. The thicknesses of the resin rings31increase from the boundary portions23toward the middle of the body21.

The resin rings31are made of a resin material that has little difference in rigidity as compared to the liner2. In the present embodiment, the resin rings31are preferably made of nylon. Nylon has little difference in rigidity from the liner2, and accordingly gaps between the liner2, the hoop layer32, and the helical layer33can be filled when performing thermal curing after forming the helical layer33later. Also, nylon is relatively inexpensive, and accordingly manufacturing costs of the high-pressure tank1can be reduced. Moreover, nylon does not contain fibers. The resin rings31are made of a resin not reinforced by fibers. The term “rigidity” here refers to the coefficient of thermal expansion and the Young's modulus of the liner2.

The hoop layer32is formed so as to cover a portion of the outer circumferential face of the body21between the right and left resin rings31. The hoop layer32is formed of fiber-reinforced resin. The fiber-reinforced resin here is obtained by impregnating fibers with a resin, and for example, an article made by bundling monofilaments, several μm or so in diameter, is impregnated with uncured thermosetting resin or thermoplastic resin. Examples of monofilaments include fibers such as glass fiber, carbon fiber, aramid fiber, alumina fiber, boron fiber, steel fiber, polyparaphenylene benzobisoxazole (PBO) fiber, natural fiber, high-strength polyethylene fiber, and so forth, with carbon fiber being preferable for use from the viewpoints of reduced weight, mechanical strength, and so forth.

Examples of the thermosetting resin used for the fiber-reinforced resin include phenol resin, melamine resin, urea resin, epoxy resin, and so forth, with epoxy resin being preferably used from the viewpoint of mechanical strength and so forth. Generally, epoxy resins are resins obtained by mixing a prepolymer that is a copolymer of bisphenol A and epichlorohydrin, or the like, with a curing agent such as polyamine or the like, and thermally curing the resin. Epoxy resins have fluidity in an uncured state and form sturdy cross-linked structures after being thermally cured. On the other hand, examples of thermoplastic resin used for the fiber-reinforced resin include polyether ether ketone, polyphenylene sulfide, polyacrylate ester, polyimide, polyamide, and so forth.

The hoop layer32may be formed by, for example, directly performing hoop winding of fibers impregnated with resin on the outer circumferential face of the body21. Hoop winding is a form in which the fibers are wound in the circumferential direction of the liner2so that an angle between an axis of the liner2(i.e., the axis L of the high-pressure tank1) and the winding direction of the fibers (so-called winding angle) is substantially perpendicular. The term “substantially perpendicular” as used here includes both 90° and angles around 90° that may be formed by winding the fibers while shifting the winding position so that fibers do not overlap each other.

Further, the hoop layer32may be formed by, for example, fabricating a hoop layer wound body by winding fibers impregnated with resin around an outer circumferential face of a cylindrical mold using hoop winding, hardening the fabricated hoop layer wound body, and thereafter inserting the liner into the hoop layer wound body.

Note that the thickness of the hoop layer32is preferably the same as the greatest thickness of the resin rings31. Thus, when the helical layer33is formed on the outside of the resin rings31and the hoop layer32, gaps due to the difference in thickness can be suppressed from being formed.

The helical layer33is formed of a fiber-reinforced resin so as to cover the resin rings31, the hoop layer32, and the dome portions22. The fiber-reinforced resin used for the helical layer33may be the same as or different from the fiber-reinforced resin used for the hoop layer32, but is preferably the same from the viewpoint of cost reduction.

The helical layer33is formed by, for example, performing helical winding of fibers impregnated with resin so as to cover the resin rings31, the hoop layer32, and the dome portions22. Note that helical winding is a form in which the fibers are spirally wound so that the angle between the axis of the liner2and the winding direction of the fiber (winding angle) is greater than 0° and smaller than 90°. This helical winding is further divided into low-angle helical winding and high-angle helical winding, in accordance with the winding angle.

Low-angle helical winding is a helical winding form when the winding angle is small (e.g., greater than 0° and no greater than 30°), and the winding direction of the fibers at the dome portions22is reversed before the fibers make a full circle around the axis of the liner2. High-angle helical winding is a helical winding form when the winding angle is great (for example, greater than 30° and smaller than 90°), and the fibers are wound at least one full circle on the body21around the axis of the liner2, until the winding direction of the fibers at the dome portions22is reversed.

The helical layer33has a right and left pair of curved portions332formed following the forms of the dome portions22of the liner2, and a straight cylinder portion331connecting the right and left curved portions332.

In the high-pressure tank1according to the present embodiment, the structure of the resin rings31and the helical layer33is used in the vicinity of the boundary portions23between the body21and the dome portions22, instead of the conventional structure of the hoop layer and the helical layer. This does away with the interface made up of fibers having different orientation directions in the vicinity of the boundary portion as in conventional arrangements, and thus delamination of the hoop layer32and the helical layer33in the vicinity of the boundary portions23can be suppressed. As a result, strain that the fibers of the helical layer33are subjected to can be reduced as compared with conventional structures, and fiber wear can be suppressed.

Note that in the present embodiment, the term “vicinity of the boundary portions” does not mean from the boundary portions23between the body21and the dome portions22toward the dome portion22sides, but rather partial regions of the body21from the boundary portions23toward the middle of the body21.

Also, the resin rings31are disposed from the boundary portions23to portions corresponding to the curvature ends of the curved portions332of the helical layer33of the body21, in the direction of the axis L of the high-pressure tank1. In the conventional structure of the hoop layer and the helical layer, regions from the boundary portions to portions corresponding to the curvature ends of the curved portions of the body are regions in which the thickness of the hoop layer changes. By disposing the resin rings31in the regions where the thickness changes, the effect of suppressing delamination can be sufficiently ensured, and effects on the strength of the reinforcing layer3due to disposing the resin rings31can be suppressed.

That is to say, when the positions of disposing the resin rings31are positions closer to the boundary portion23sides than the curvature ends of the curved portions332, portions are formed in which the thickness of the hoop layers32changes, and accordingly there is a possibility that the delamination suppression effects will be insufficient. On the other hand, when the positions of disposing the resin rings31exceed the curvature ends of the curved portions (i.e., when these positions are closer to the middle of the body21), disposing of the resin rings31may affect the strength of the reinforcing layer3. The resin rings31are preferably disposed in the regions from the boundary portions23to the portions corresponding to the curvature ends of the curved portions332of the helical layer33in the body21, taking the above into consideration.

Manufacturing Method of High-Pressure Tank

Next, the manufacturing method of the high-pressure tank1according to the present embodiment will be described with reference toFIGS.3to4D.FIG.3is a flowchart showing the manufacturing method of the high-pressure tank according to the embodiment, andFIGS.4A to4Dare schematic views illustrating the manufacturing method of the high-pressure tank according to the embodiment. The manufacturing method of the high-pressure tank1includes a liner manufacturing step S1, a hoop layer wound body manufacturing step S2, a resin ring manufacturing step S3, a hoop layer forming step S4, a resin ring disposing step S5, and a helical layer forming step S6. Note that the liner manufacturing step S1, the hoop layer wound body manufacturing step S2, and the resin ring manufacturing step S3are steps that are independent from each other, and accordingly may be performed in parallel, and any of these steps may be performed first.

In the liner manufacturing step S1, the liner2having the body21that is cylindrical in shape, and the dome portions22provided at both ends of the body21in the axial direction, is manufactured. Specifically, first, the liner2is integrally formed by rotary blow molding, using a resin member such as polyethylene, nylon, or the like. Next, the neck4is attached to one end portion of the formed liner2(seeFIG.4A).

In the hoop layer wound body manufacturing step S2, first, a sheet made of fiber-reinforced resin is wound around the outer circumferential face of a drum-shaped mandrel, so that the fibers are oriented in the circumferential direction of the mandrel, thereby forming a hoop layer wound body30that is cylindrical in shape and that is an intermediate form of the hoop layer32. Next, the hoop layer wound body30that has been formed is removed from the mandrel and hardened (seeFIG.4A).

The method for hardening the hoop layer wound body30(in other words, hardening the resin with which the fibers are impregnated) is not limited in particular, but when the resin used for impregnating is a thermosetting resin, the resin may be pre-cured. Pre-curing conditions (temperature and time) vary depending on the type of resin used for impregnating, but viscosity of the resin is set to be higher than viscosity when wound on a predetermined mold (viscosity before pre-curing). Here, pre-curing is performed until the resin used for impregnating loses its fluidity. On the other hand, when the resin used for impregnating is a thermoplastic resin, the resin may be hardened by cooling the fibers in a state in which the resin has fluidity.

Further, in this hoop layer wound body manufacturing step S2, the hoop layer wound body30may be formed by a centrifugal winding (CW) method, in which a fiber sheet impregnated with resin is attached to an inner face of a rotating cylindrical mold. The fiber sheet used at that time has fibers oriented in the circumferential direction of the cylindrical mold, for example.

In the resin ring manufacturing step S3, the resin rings31are manufactured by injection molding using nylon, such that the thickness thereof gradually increases from the boundary portions23between the body21and the dome portions22toward the middle of the body21, in a state in which the manufactured resin rings31are provided encircling the outer circumferential face of the body21of the liner2later (seeFIG.4A).

In the hoop layer forming step S4, the liner2manufactured in the liner manufacturing step S1is inserted into the hoop layer wound body30manufactured and hardened in the hoop layer wound body manufacturing step S2, thereby forming the hoop layer32(seeFIG.4B).

In the resin ring disposing step S5, the resin rings31manufactured in the resin ring manufacturing step S3are disposed at both end portions of the hoop layer32formed in the hoop layer forming step S4. At this time, the resin rings31are fitted onto the outer circumferential face of the body21, so that the thickest end portions of the resin rings31abut the end portions of the hoop layer32(seeFIGS.4B and4C). Further, the end portions of the resin rings31and the end portions of the hoop layer32are preferably fixed with an adhesive, in order to suppress deviation of the positions of the resin rings31.

In the helical layer forming step S6, a helical layer is formed that covers the hoop layer32, the resin rings31disposed at both ends of the hoop layer32, and the dome portions22of the liner2. Specifically, first, fibers impregnated with resin are wound by helical winding so as to cover the entire hoop layer32, the resin rings31, and the dome portions22thereby forming a wound body for the helical layer. Next, the liner2on which the wound body for the helical layer, the hoop layer32, and the resin rings31are formed is transported into a thermosetting furnace, and the fiber impregnated with the resin is thermally cured by heating in the thermosetting furnace at 160° C. for 10 minutes, for example. Thus, the high-pressure tank1is manufactured.

In the high-pressure tank1manufactured by the above manufacturing method, there is no interface made up of fibers having different orientation directions in the vicinity of the boundary portions as in conventional arrangements, and accordingly delamination between the hoop layer32and the helical layer33in the vicinity of the boundary portions23between the body21and the dome portions22can be suppressed.

Although the embodiment of the disclosure has been described in detail above, the disclosure is not limited to the embodiment described above, and various design changes can be made without departing from the spirit of the disclosure described in the claims.

For example, in the above embodiment, the resin members have been described as being resin rings, but in addition to resin rings, C-shaped resin members or a combination of a plurality of arc-shaped resin members may be used, for example.