Patent Description:
A pressure container, so-called a high-pressure tank, to contain compressed natural gas (CNG), liquefied natural gas (LNG), or the like is heavy in weight because the pressure container is generally made of metal such as steel and an aluminum alloy. In recent years, automobiles fueled by natural gas attract attention as green vehicles, and also automobiles powered by fuel cells attract attention as greener vehicles. Some of such vehicles store hydrogen gas in a fuel tank to fuel the fuel cells. However, the pressure container used as the fuel tank is heavy in weight, thereby resulting in poor fuel efficiency. To solve the problems described above, a pressure container that has a liner (an inner shell) impermeable to gas and covered with a pressure-resistant fiber-reinforced composite layer is proposed. (See <CIT> as an example.

In such a pressure container, a liner generally has curved-surfaced dome-shaped portions at the both ends of the liner in a direction in which the center axis of a cylindrical body portion of the liner extends (hereinafter referred to as an axial direction). Since the pressure container is filled with gas that may have a pressure as high as several tens of MPa, the liner of the pressure container is reinforced with a fiber-reinforced composite layer.

<CIT> discloses a pressure container manufacturing method for manufacturing a pressure container by forming an outer shell made of a fiber reinforced composite material on a periphery of a liner which has: preparing a first fiber bundle which has a large diameter fiber bundle unimpregnated with a resin, and a second fiber bundle (<NUM>) which has a small diameter resin bundle and a thermoplastic resin covering the small diameter resin bundle; forming a body on the periphery of the liner by braiding the first fiber bundle and the second fiber bundle with a braider; impregnating the first fiber bundle with the thermoplastic resin in the second fiber bundle which is heated and melted; and curing the thermoplastic resin to form the outer shell, wherein a tension applied to the first fiber bundle is larger than a tension applied to the second fiber bundle when forming the body and/or impregnating the thermoplastic resin.

<CIT> and <CIT> relate to a similar fiber structure.

In such a pressure container, an internal pressure stress generated under the gas pressure imposed on the liner is greater in the axial direction of the liner than in the radial direction of the liner. Reinforcement for the liner is therefore important in the axial direction.

An objective of the present invention is to provide a fiber structure reinforcing a liner in an axial direction, a pressure container, and a method of producing the fiber structure.

The above object is solved by a method as defined in claim <NUM>, a fiber structure as defined in claims <NUM> and <NUM>, and a pressure container as defined in claim <NUM>.

A fiber structure to solve the above problems is a fiber structure that includes a liner, and a fiber reinforcement base material formed of a woven fabric. The liner includes a body portion having a cylindrical shape, a dome-shaped portion being continuous with at least one end of the body portion in an axial direction, and a mouthpiece having a shape protruding from the dome-shaped portion in the axial direction of the body portion. The fiber reinforcement base material externally covers the body portion and the dome-shaped portion of the liner. The fiber reinforcement base material includes first yarns arranged in such a way that a direction in which a yarn main axis of each of the first yarns in the body portion and the dome-shaped portion proceeds is a circumferential direction of the liner, and second yarns forming the fabric with the first yarns and arranged in such a way that a direction in which a yarn main axis of each of the second yarns in the body portion proceeds is the axial direction of the body portion and that a direction in which a yarn main axis of a portion of each of the second yarns arranged in the dome-shaped portion proceeds is an axial direction of the dome-shaped portion. The first yarns and the second yarns are arranged orthogonal to each other.

According to the fiber structure described above, the direction in which the yarn main axis of each of the first yarns proceeds is the circumferential direction of the liner, which thereby reinforces the liner in a radial direction. The direction in which the yarn main axis of each of the second yarns proceeds is the axial direction of the body portion and the dome-shaped portion of the liner, which thereby reinforce the liner in the axial direction more strongly than in a case where the direction in which the yarn main axis of the second yarn proceeds is angled relative to the axial direction of the body portion and the axial direction of the dome-shaped portion.

In the fiber structure, the fabric may be a multi-layered fabric that includes a first yarn layer in which the first yarns are arranged, a second yarn layer in which the second yarns are arranged, and a binder yarn binding the first yarn layer and the second yarn layer.

In the fiber structure described above, the fiber structure formed of the multi-layered fabric includes the fiber reinforcement base material. During production of a pressure container, a matrix resin is impregnated along the binder yarn into the fiber reinforcement base material through the stacking direction of the fiber reinforcement base material. Impregnation of the matrix resin in the stacking direction of the fiber structure is thereby facilitated, which accordingly reinforces the strength of the layers formed of the fiber reinforcement base material.

A pressure container to solve the above problem is a pressure container that includes a fiber structure impregnated with a matrix resin. The fiber structure includes a fiber reinforcement base material that is formed of a fabric and externally covers a liner.

According to the pressure container described above, a direction in which a yarn main axis of each of first yarns proceeds is a circumferential direction of the liner, which reinforces the pressure container in a radial direction. A direction in which yarn main axis of each of second yarns proceeds is an axial direction of a body portion and a dome-shaped portion of the liner. The pressure container is thereby reinforced in the axial direction more strongly in comparison with a case where the direction in which the yarn main axis of the second yarn proceeds is angled relative to the axial direction of the body portion and the axial direction of the dome-shaped portion.

A method of producing a fiber structure to solve the above problems is the method of producing the fiber structure that includes a liner, and a fiber reinforcement base material formed of a fabric. The liner includes a body portion having a cylindrical shape, a dome-shaped portion being continuous with at least one end of the body portion in an axial direction thereof, and a mouthpiece having a shape protruding from the dome-shaped portion in the axial direction of the body portion. The fiber reinforcement base material externally covers the body portion and the dome-shaped portion of the liner. The fiber structure further includes warp yarns arranged in the body portion and the dome-shaped portion, and weft yarns forming the fabric with the warp yarns. The warp yarns are arranged in such a way that a direction in which a yarn main axis of each of the warp yarns proceeds is a circumferential direction of the liner. The method of producing the fiber structure includes arranging the warp yarns along the axial direction of the body portion and the dome-shaped portion of the liner, inserting each of the weft yarns into a shed formed between the warp yarns adjacent to each other in the axial direction of the liner, pressing the inserted weft yarn towards the liner by beating with a reed to weave the fabric out of the warp yarns and the weft yarn, and winding the woven fabric around the liner by rotating the liner around a center axis of the liner.

According to the method described above, the fabric is woven in a state where the direction in which the yarn main axis of each of the warp yarns proceeds is the circumferential direction of the liner and the direction in which the yarn main axis of each of the weft yarns proceeds is the axial direction of the body portion and the dome-shaped of the liner. The fabric is wound around the liner while being woven. Productivity in producing the fiber structure according to the method described above is enhanced in comparison with, for example, a case where a fabric is woven into a tubular shape by braiding, cut open, and then wound around a liner. Productivity in producing the fiber structure according to the method described above is enhanced also in comparison with a case where yarns are wound around a liner individually one by one to produce a fiber structure, as seen in filament winding.

The liner is reinforced in the axial direction according to the present invention.

A fiber structure, a pressure container, and a method of producing the fiber structure will now be described with reference to an embodiment that embodies the fiber structure used in a high-pressure tank, the high-pressure tank, and a method of producing the fiber structure, shown in <FIG>.

As shown in <FIG>, a high-pressure tank <NUM> serving as a pressure container is formed of a fiber structure <NUM> impregnated with a matrix resin Ma. The fiber structure <NUM> includes an elongated hollow-shaped liner <NUM>, and a fiber reinforcement base material <NUM> that externally covers the liner <NUM>. The liner <NUM> of the high-pressure tank <NUM> is reinforced with a fiber-reinforced composite layer <NUM> formed of the fiber reinforcement base material <NUM> impregnated with the matrix resin Ma. This secures a pressure resistance (a mechanical strength) of the high-pressure tank <NUM>.

The liner <NUM> is made of resin, and has an elongated hollow shape. A direction in which a center axis L of the liner <NUM> extends is referred to as an axial direction. The liner <NUM> includes a cylindrical body portion <NUM>. A center axis of the body portion <NUM> coincides with the center axis L of the liner <NUM>. The liner <NUM> includes a dome-shaped portion <NUM> at each of both ends of the body portion <NUM> in an axial direction Y. An axial direction of each of the dome-shaped portions <NUM> coincides with the axial direction of the liner <NUM>. The liner <NUM> includes a mouthpiece <NUM> that outwardly protrudes from each of the dome-shaped portions <NUM> in the axial direction Y. The mouthpieces <NUM> are made of metal (e.g. stainless steel). Each of the mouthpieces <NUM> includes a hole portion <NUM> that communicates with a space in the liner <NUM>. A valve <NUM> is fitted into the hole portion <NUM> of one of the mouthpieces <NUM> at one end of the liner <NUM> in the axial direction Y, and a screw <NUM> is screwed into the hole portion <NUM> of the other of the mouthpieces <NUM> at the other end of the liner <NUM> in the axial direction Y.

The fiber reinforcement base material <NUM> uses a carbon fiber as a reinforcement fiber according to the present embodiment. The reinforcement fiber is not limited to the carbon fiber, but other reinforcement fibers that are generally said to have high elasticity and high strength may be used, such as glass fibers, silicon-carbide base ceramic fibers, aramid fibers, and ultra-high molecular weight polyethylene fibers.

As shown in <FIG> or <FIG>, the fiber reinforcement base material <NUM> includes stacked layers of a fabric <NUM> that is woven with a plain weave out of a plurality of warp yarns <NUM> corresponding to first yarns and a plurality of weft yarns <NUM> corresponding to second yarns. Each of the warp yarns <NUM> and each of the weft yarns <NUM> are arranged orthogonal to each other. The plurality of warp yarns <NUM> are arranged in the body portion <NUM> and the dome-shaped portions <NUM> in a state where the warp yarns <NUM> are parallel to one another, along the axial direction Y of the liner <NUM>. A direction X1 in which a yarn main axis of the warp yarns <NUM> proceeds ahead in the body portion <NUM> and the dome-shaped portions <NUM> is a circumferential direction Z of the liner <NUM>. The direction X1 of the yarn main axis of the warp yarns <NUM> is orthogonal to a radial direction of the liner <NUM>.

The plurality of weft yarns <NUM> are arranged parallel to one another, along the circumferential direction Z of the liner <NUM>. A portion of each of the weft yarns <NUM> that proceeds ahead in the axial direction of the liner <NUM> along the outer peripheral surface of the body portion <NUM> is a body-portion weft yarn 23a. A portion of each of the weft yarns <NUM> that proceeds in the axial direction of the liner <NUM> along each of the outer peripheral surfaces of each of the dome-shaped portions <NUM> is a dome-portion weft yarn 23b. Each end of the body-portion weft yarn 23a is continuous with each of the dome-portion weft yarns 23b in the axial direction of the liner <NUM>. As to the weft yarns <NUM>, a direction X2 in which a yarn main axis of each of the dome-portion weft yarns 23b proceeds is the axial direction of the liner <NUM>, curving along the each of the curved surfaces of each of the dome-shaped portions <NUM>. Also as to the weft yarns <NUM>, the direction X2 in which a yarn main axis of each of the body-portion weft yarns 23a proceeds is the axial direction of the body portion <NUM> of the liner <NUM>.

Each of the warp yarns <NUM> and each of the weft yarns <NUM> are arranged orthogonal to each other. By making the direction X1 in which the yarn main axis of the warp yarns <NUM> proceeds coincide with the circumferential direction Z of the liner <NUM>, the liner <NUM> is reinforced in the radial direction. By making the direction X2 in which the yarn main axis of the weft yarns <NUM> proceeds coincide with the axial direction of the liner <NUM>, the liner <NUM> is reinforced in the axial direction.

As shown in <FIG>, the shape, the thickness, and the width of the weft yarns <NUM> of the body portion <NUM> are flat, thin, and wide. As shown in <FIG>, the thickness and the width of the weft yarns <NUM> of the dome-shaped portions <NUM> are thicker and narrower than those of the body-portion weft yarn 23a, and become thicker and narrower even further as the diameter of the dome-shaped portion <NUM> decreases in a direction from the body portion <NUM> toward the mouthpiece <NUM>. On the other hand, the thickness and the width of the warp yarns <NUM> are the same in the body portion <NUM> and in the dome-shaped portions <NUM>. In the fiber structure <NUM>, the number of the weft yarns <NUM> in the circumferential direction Z of the liner <NUM> is the same in the body portion <NUM> and the dome-shaped portions <NUM>.

A method of producing a high-pressure tank <NUM> will now be described.

In producing the high-pressure tank <NUM>, the woven fabric <NUM> is wound around the liner <NUM> while the warp yarns <NUM> and the weft yarns <NUM> are woven with the plain weave.

As shown in <FIG>, the fabric <NUM> is woven with, for example, a plain-weave loom that includes two heddle frames 31a and 31b used to create a shed between warp yarns 22a and warp yarns 22b of the warp yarns <NUM> separated upper and lower. The plain-weave loom includes a warp beam <NUM> that supplies the warp yarns 22a, one of the warp yarns 22a and 22b, and a warp beam <NUM> that supplies the warp yarns 22b, the other of the warp yarns 22a and 22b. The plain-weave loom has a structure in which one of the warp beams <NUM> and <NUM> is arranged at an upper position and the other of the warp beams <NUM> and <NUM> is arranged at a lower position. The warp yarns 22a sent out from the warp beam <NUM>, one of the warp beams <NUM> and <NUM>, is raised and lowered with the heddle frame 31a, one of the heddle frames 31a and 31b. The warp yarns 22b sent out from the warp beam <NUM>, the other of the warp beams <NUM> and <NUM>, is raised and lowered with the heddle frame 31b, the other of the heddle frames 31a and 31b. Eyes of the heddle frames 31a and 31b are indicated with black-filled circles in <FIG>. A reed <NUM> is interposed between the two heddle frames of 31a and 31b and a cloth fell <NUM>. Each of the weft yarns <NUM> is to be inserted in the shed between the warp yarns 22a and 22b using a weft inserting device (not shown). At a position ahead of the cloth fell <NUM> in the sent-out direction of the warp yarns 22a and 22b, the liner <NUM> is rotatably supported. The liner <NUM> rotates around the center axis L.

In weaving the fiber reinforcement base material <NUM> with the plain-weave loom described above, the ends of a plurality of warp yarns 22a and a plurality of warp yarns 22b that are drawn out of the warp beams <NUM> and <NUM> respectively are fixed to the outer peripheral surface of the liner <NUM> using a fixing member <NUM> made of, for example, an adhesive tape, as shown in <FIG>. The warp yarns 22a and 22b are arranged along the axial direction Y of the liner <NUM> in the body portion <NUM> and the dome-shaped portions <NUM>.

By alternately shifting to raise and lower the heddle frames 31a and 31b without rotating the liner <NUM>, the heddle frame 31a, the one of the heddle frames, and the heddle frame 31b, the other of the heddle frames, are shifted in the directions opposite to each other. Then, each of the weft yarns <NUM> is inserted into a warp shed <NUM> formed between the warp yarns 22a and 22b every time the warp yarns 22a and 22b adjacent to each other are alternately raised and lowered. The weft yarns <NUM> have a flat shape after inserted.

Each of the weft yarns <NUM> is inserted and beaten with the reed <NUM>. Then, the heddle frames 31a and 31b are shifted in the directions opposite to each other so that the shedding state is changed. Subsequently, the next weft insertion is performed. These series of actions described above are repeated so that part of the fabric <NUM> is woven with the plain weave out of the warp yarns <NUM> and the weft yarns <NUM> and the part of the fabric <NUM> is integrated with the liner <NUM> into a single piece.

As shown in <FIG>, the weft yarns <NUM> is sent into the fixing member <NUM> by being beaten with the reed <NUM>. The reed <NUM> is a member linearly extends in the axial direction of the liner <NUM>. Since the diameter of the dome-shaped portions <NUM> is smaller than the diameter of the body portion <NUM>, the weft yarns <NUM> arranged in the dome-shaped portions <NUM> are pressed further than the portion of the weft yarns <NUM> arranged in the body portion <NUM> when beaten with the reed <NUM>, which causes the weft yarns <NUM> in the dome-shaped portions <NUM> to be deformed thicker. The resultant deformation in the weft yarns <NUM> in the dome-shaped portions <NUM> allows the weft yarns <NUM> to be arranged parallel to one another, along the circumferential direction Z of the liner <NUM>, even in the state where the body portion <NUM> has a different diameter from that of the dome-shaped portions <NUM>.

Subsequently, as shown in <FIG>, the liner <NUM> is rotated around the center axis L so that the fabric <NUM> is wound around the liner <NUM> while the fabric <NUM> continues to be woven in a like manner as described above. As a result, the fabric <NUM> is wound around the liner <NUM> entirely covering the dome-shaped portions <NUM> and the body portion <NUM>. By winding the predetermined number of the layers of the fabric <NUM> around the liner <NUM>, the fiber structure <NUM> that includes the fiber reinforcement base material <NUM> on the outer peripheral surface of the liner <NUM> is produced.

In the fiber structure <NUM> configured as described above, the fiber-reinforced composite layer <NUM> is formed of the fiber reinforcement base material <NUM> with the matrix resin Ma impregnated thereinto and hardened, and then, the high-pressure tank <NUM> is produced with the liner <NUM> externally covered with the fiber-reinforced composite layer <NUM>. For impregnating and hardening the matrix resin Ma, the resin transfer molding (RTM) method, for example, is used.

The operation of a high-pressure tank <NUM> will now be described.

The high-pressure tank <NUM> is used, for example, as a hydrogen-supply source for fuel cells of a fuel cell vehicle. The high-pressure tank <NUM> is used in a state where a pipe (not shown) is connected to the valve <NUM>. Hydrogen gas is filled into the high-pressure tank <NUM> through the pipe for filling the hydrogen gas. In the high-pressure tank <NUM>, the hydrogen gas that may have a pressure as high as several tens of MPa, for example, is filled.

When the hydrogen gas is filled into the high-pressure tank <NUM>, the pressure in the high-pressure tank <NUM> increases so that the liner <NUM> is pressed from the inside. Great forces are exerted on the liner <NUM> in the axial direction Y and the radial direction, by which an internal pressure stress is generated. According to the present embodiment, the liner <NUM> is reinforced in the axial direction by the weft yarns <NUM> and is reinforced in the radial direction by the warp yarns <NUM>, which suppresses deformation in the high-pressure tank <NUM>.

The above-described embodiment has the following advantages.

Another example of a conventional method of producing the fiber structure <NUM> that includes the fiber reinforcement base material <NUM> on the outer peripheral surface of the liner <NUM> may be braiding, in which a fabric is woven into a tubular shape to fit to the shape of the liner <NUM> by braiding, cut open into a flat shape, and then wound around the liner <NUM>. In contrast to this conventional method, the fiber reinforcement base material <NUM> according to the present embodiment is wound around the liner <NUM> while the fiber reinforcement base material <NUM> is woven out of the warp yarns <NUM> and the weft yarns <NUM>, which does not require an individual process to weave the fabric, a process to cut open the fabric, and a process to paste the fabric to the liner. Productivity is thereby enhanced as compared to the braiding. The liner <NUM> according to the present embodiment is reinforced in the axial direction because the direction X2 in which the yarn main axis of the weft yarns <NUM> proceeds is the axial direction of the liner <NUM>.

The following modifications may be made to the embodiment described above.

As shown in <FIG>, a fiber reinforcement base material <NUM> may be a multi-layered fabric woven with multilayer weaving. The fiber reinforcement base material <NUM> includes warp layers <NUM> and <NUM> corresponding to first yarn layers in which warp yarns <NUM> are arranged parallel to one another, a weft layer <NUM> corresponding to a second yarn layer in which weft yarns <NUM> are arranged parallel to one another, and a binder yarn <NUM> that binds the warp layers <NUM> and <NUM> and the weft layer <NUM> in the stacking direction. The binder yarn <NUM> proceeds around the outer surface of one of the warp yarns <NUM> that form the warp layer <NUM>, proceeds through the warp layer <NUM> in the stacking direction, and then proceeds around the outer surface of another of the warp yarns <NUM> that form the warp layer <NUM>.

In a fiber structure <NUM> including the fiber reinforcement base material <NUM> described above, a matrix resin (not shown) is impregnated along the binder yarn <NUM> into the fiber reinforcement base material <NUM> through the stacking direction of the fiber reinforcement base material <NUM>. The fiber structure <NUM> is thereby reinforced also in the stacking direction. The number of the warp layers and the weft layers may be appropriately changed.

In the embodiment described above, the fiber reinforcement base material <NUM> includes the stacked layers of the fabric <NUM> that is woven with the plain weave. The scope of the present invention is not limited to the embodiment described above. For example, the fiber reinforcement base material <NUM> may include the stacked layers of a fabric that is woven with a satin weave or a twill weave out of a plurality of the warp yarns <NUM> corresponding to the first yarns and a plurality of the weft yarns <NUM> corresponding to the second yarns.

In the embodiment described above, the warp yarn <NUM> is referred to as the first yarn, and the weft yarn <NUM> is referred to as the second yarn. However, the weft yarn <NUM> may be referred to as the first yarn and the warp yarn <NUM> may be referred to as the second yarn.

The liner <NUM> may have a shape in which one end of the body portion <NUM> in the axial direction Y is continuous with the dome-shaped portion <NUM> and the other end of the body portion <NUM> in the axial direction Y is continuous with a flat bottom surface. In this case, the mouthpiece <NUM> is provided only to the one end of the line <NUM> in the axial direction Y where the dome-shaped portion <NUM> is disposed.

The liner <NUM> may be entirely made of aluminum or aluminum alloy. The mouthpiece <NUM> may be made of metal other than stainless steel.

The body portion <NUM> and the dome-shaped portions <NUM> of the liner <NUM> may be welded into a single piece, instead of being separated.

The high-pressure tank <NUM> in the embodiment described above is used as a hydrogen-supply source for fuel cells to be mounted on a fuel cell vehicle. The scope of the present invention is not limited to the embodiment. For example, the high-pressure tank <NUM> may be used as a hydrogen-supply source to power a hydrogen engine or may be used for a heat pump. Alternatively, the high-pressure tank <NUM> may be used as a hydrogen-supply source for fuel cells for household use.

Claim 1:
A method of producing a fiber structure (<NUM>, <NUM>), the fiber structure (<NUM>, <NUM>) comprising:
a liner (<NUM>) including:
a body portion (<NUM>) having a cylindrical shape;
a dome-shaped portion (<NUM>) being continuous with at least one end of the body portion (<NUM>) in an axial direction (Y) thereof; and
a mouthpiece (<NUM>) having a shape protruding from the dome-shaped portion (<NUM>) in the axial direction (Y) of the body portion (<NUM>); and
a fiber reinforcement base material (<NUM>, <NUM>) formed of a fabric (<NUM>), the fiber reinforcement base material (<NUM>, <NUM>) externally covering the body portion (<NUM>) and the dome-shaped portion (<NUM>) of the liner (<NUM>);
warp yarns (<NUM>, 22a, 22b) arranged in such a way that a direction (X1) in which a yarn main axis of each of the warp yarns (<NUM>, 22a, 22b) in the body portion (<NUM>) and the dome-shaped portion (<NUM>) proceeds is a circumferential direction (Z) of the liner (<NUM>); and
weft yarns (<NUM>, 23a, 23b) forming the fabric (<NUM>) with the warp yarns (<NUM>, 22a, 22b),
characterized in that the method of producing the fiber structure (<NUM>, <NUM>) comprises:
arranging the warp yarns (<NUM>, 22a, 22b) along the axial direction (Y) of the body portion (<NUM>) and the dome-shaped portion (<NUM>) of the liner (<NUM>), such that the warp yarns (<NUM>, 22a, 22b) and the weft yarns (<NUM>, 23a, 23b) are orthogonal to each other;
inserting each of the weft yarns (<NUM>, 23a, 23b) into a shed (<NUM>) formed between the warp yarns (<NUM>, 22a, 22b) adjacent to each other in the axial direction (Y) of the liner (<NUM>);
pressing the inserted weft yarn (<NUM>, 23a, 23b) toward the liner (<NUM>) by beating with a reed (<NUM>) to weave the fabric (<NUM>) out of the warp yarns (<NUM>, 22a, 22b) and the weft yarns (<NUM>, 23a, 23b); and
winding the woven fabric (<NUM>) around the liner (<NUM>) by rotating the liner (<NUM>) around a center axis (L) of the liner (<NUM>).