Fiber structure, pressure container, and method of producing fiber structure

A fiber structure that includes a liner, and a fiber reinforcement base material formed of a fabric. The fiber reinforcement base material externally covers a body portion and a dome-shaped portion of the liner, and includes first yarns and second yarns. The first yarns are arranged such 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. The second yarns are arranged such that a direction in which a yarn main axis of each of the second yarns in the body portion proceeds is an 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.

CROSS REFERENCE TO RELATED APPLICATION

This application is a National Stage of International Application No. PCT/JP2018/014631 filed Apr. 5, 2018, claiming priority based on Japanese Patent Applications No. 2017-083504 filed Apr. 20, 2017, the contents of all of which are incorporated herein by reference in their entirety.

The present invention relates to a fiber structure, a pressure container, and a method of producing the fiber structure.

BACKGROUND ART

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 Patent Document 1 below 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.

CITATION LIST

Patent Document

SUMMARY OF INVENTION

Technical Problem

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.

Solution to Problem

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 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.

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.

Advantageous Effects of Invention

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

DESCRIPTION OF EMBODIMENTS

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 inFIGS. 1 through 6C.

As shown inFIG. 1, a high-pressure tank10serving as a pressure container is formed of a fiber structure21impregnated with a matrix resin Ma. The fiber structure21includes an elongated hollow-shaped liner12, and a fiber reinforcement base material19that externally covers the liner12. The liner12of the high-pressure tank10is reinforced with a fiber-reinforced composite layer11formed of the fiber reinforcement base material19impregnated with the matrix resin Ma. This secures a pressure resistance (a mechanical strength) of the high-pressure tank10.

The liner12is made of resin, and has an elongated hollow shape. A direction in which a center axis L of the liner12extends is referred to as an axial direction. The liner12includes a cylindrical body portion13. A center axis of the body portion13coincides with the center axis L of the liner12. The liner12includes a dome-shaped portion14at each of both ends of the body portion13in an axial direction Y. An axial direction of each of the dome-shaped portions14coincides with the axial direction of the liner12. The liner12includes a mouthpiece15that outwardly protrudes from each of the dome-shaped portions14in the axial direction Y. The mouthpieces15are made of metal (e.g. stainless steel). Each of the mouthpieces15includes a hole portion16that communicates with a space in the liner12. A valve17is fitted into the hole portion16of one of the mouthpieces15at one end of the liner12in the axial direction Y, and a screw18is screwed into the hole portion16of the other of the mouthpieces15at the other end of the liner12in the axial direction Y.

The fiber reinforcement base material19uses 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 inFIG. 2 or 3, the fiber reinforcement base material19includes stacked layers of a fabric24that is woven with a plain weave out of a plurality of warp yarns22corresponding to first yarns and a plurality of weft yarns23corresponding to second yarns. Each of the warp yarns22and each of the weft yarns23are arranged orthogonal to each other. The plurality of warp yarns22are arranged in the body portion13and the dome-shaped portions14in a state where the warp yarns22are parallel to one another, along the axial direction Y of the liner12. A direction X1in which a yarn main axis of the warp yarns22proceeds ahead in the body portion13and the dome-shaped portions14is a circumferential direction Z of the liner12. The direction X1of the yarn main axis of the warp yarns22is orthogonal to a radial direction of the liner12.

The plurality of weft yarns23are arranged parallel to one another, along the circumferential direction Z of the liner12. A portion of each of the weft yarns23that proceeds ahead in the axial direction of the liner12along the outer peripheral surface of the body portion13is a body-portion weft yarn23a. A portion of each of the weft yarns23that proceeds in the axial direction of the liner12along each of the outer peripheral surfaces of each of the dome-shaped portions14is a dome-portion weft yarn23b. Each end of the body-portion weft yarn23ais continuous with each of the dome-portion weft yarns23bin the axial direction of the liner12. As to the weft yarns23, a direction X2in which a yarn main axis of each of the dome-portion weft yarns23bproceeds is the axial direction of the liner12, curving along the each of the curved surfaces of each of the dome-shaped portions14. Also as to the weft yarns23, the direction X2in which a yarn main axis of each of the body-portion weft yarns23aproceeds is the axial direction of the body portion13of the liner12.

Each of the warp yarns22and each of the weft yarns23are arranged orthogonal to each other. By making the direction X1in which the yarn main axis of the warp yarns22proceeds coincide with the circumferential direction Z of the liner12, the liner12is reinforced in the radial direction. By making the direction X2in which the yarn main axis of the weft yarns23proceeds coincide with the axial direction of the liner12, the liner12is reinforced in the axial direction.

As shown inFIG. 4A, the shape, the thickness, and the width of the weft yarns23of the body portion13are flat, thin, and wide. As shown inFIG. 4B, the thickness and the width of the weft yarns23of the dome-shaped portions14are thicker and narrower than those of the body-portion weft yarn23a, and become thicker and narrower even further as the diameter of the dome-shaped portion14decreases in a direction from the body portion13toward the mouthpiece15. On the other hand, the thickness and the width of the warp yarns22are the same in the body portion13and in the dome-shaped portions14. In the fiber structure21, the number of the weft yarns23in the circumferential direction Z of the liner12is the same in the body portion13and the dome-shaped portions14.

A method of producing a high-pressure tank10will now be described.

In producing the high-pressure tank10, the woven fabric24is wound around the liner12while the warp yarns22and the weft yarns23are woven with the plain weave.

As shown inFIG. 5, the fabric24is woven with, for example, a plain-weave loom that includes two heddle frames31aand31bused to create a shed between warp yarns22aand warp yarns22bof the warp yarns22separated upper and lower. The plain-weave loom includes a warp beam32that supplies the warp yarns22a, one of the warp yarns22aand22b, and a warp beam33that supplies the warp yarns22b, the other of the warp yarns22aand22b. The plain-weave loom has a structure in which one of the warp beams32and33is arranged at an upper position and the other of the warp beams32and33is arranged at a lower position. The warp yarns22asent out from the warp beam32, one of the warp beams32and33, is raised and lowered with the heddle frame314one of the heddle frames31aand31b. The warp yarns22bsent out from the warp beam33, the other of the warp beams32and33, is raised and lowered with the heddle frame31b, the other of the heddle frames31aand31b. Eyes of the heddle frames31aand31bare indicated with black-filled circles inFIG. 5. A reed34is interposed between the two heddle frames of31aand31band a cloth fell35. Each of the weft yarns23is to be inserted in the shed between the warp yarns22aand22busing a weft inserting device (not shown). At a position ahead of the cloth fell35in the sent-out direction of the warp yarns22aand22b, the liner12is rotatably supported. The liner12rotates around the center axis L.

In weaving the fiber reinforcement base material19with the plain-weave loom described above, the ends of a plurality of warp yarns22aand a plurality of warp yarns22bthat are drawn out of the warp beams32and33respectively are fixed to the outer peripheral surface of the liner12using a fixing member36made of, for example, an adhesive tape, as shown inFIG. 6A. The warp yarns22aand22bare arranged along the axial direction Y of the liner12in the body portion13and the dome-shaped portions14.

By alternately shifting to raise and lower the heddle frames31aand31bwithout rotating the liner12, the heddle frame31a, the one of the heddle frames, and the heddle frame31b, the other of the heddle frames, are shifted in the directions opposite to each other. Then, each of the weft yarns23is inserted into a warp shed37formed between the warp yarns22aand22bevery time the warp yarns22aand22badjacent to each other are alternately raised and lowered. The weft yarns23have a flat shape after inserted.

Each of the weft yarns23is inserted and beaten with the reed34. Then, the heddle frames31aand31bare 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 fabric24is woven with the plain weave out of the warp yarns22and the weft yarns23and the part of the fabric24is integrated with the liner12into a single piece.

As shown inFIG. 6B, the weft yarns23is sent into the fixing member36by being beaten with the reed34. The reed34is a member linearly extends in the axial direction of the liner12. Since the diameter of the dome-shaped portions14is smaller than the diameter of the body portion13, the weft yarns23arranged in the dome-shaped portions14are pressed further than the portion of the weft yarns23arranged in the body portion13when beaten with the reed34, which causes the weft yarns23in the dome-shaped portions14to be deformed thicker. The resultant deformation in the weft yarns23in the dome-shaped portions14allows the weft yarns23to be arranged parallel to one another, along the circumferential direction Z of the liner12, even in the state where the body portion13has a different diameter from that of the dome-shaped portions14.

Subsequently, as shown inFIG. 6C, the liner12is rotated around the center axis L so that the fabric24is wound around the liner12while the fabric24continues to be woven in a like manner as described above. As a result, the fabric24is wound around the liner12entirely covering the dome-shaped portions14and the body portion13. By winding the predetermined number of the layers of the fabric24around the liner12, the fiber structure21that includes the fiber reinforcement base material19on the outer peripheral surface of the liner12is produced.

In the fiber structure21configured as described above, the fiber-reinforced composite layer11is formed of the fiber reinforcement base material19with the matrix resin Ma impregnated thereinto and hardened, and then, the high-pressure tank10is produced with the liner12externally covered with the fiber-reinforced composite layer11. For impregnating and hardening the matrix resin Ma, the resin transfer molding (RTM) method, for example, is used.

The operation of a high-pressure tank10will now be described.

The high-pressure tank10is used, for example, as a hydrogen-supply source for fuel cells of a fuel cell vehicle. The high-pressure tank10is used in a state where a pipe (not shown) is connected to the valve17. Hydrogen gas is filled into the high-pressure tank10through the pipe for filling the hydrogen gas. In the high-pressure tank10, 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 tank10, the pressure in the high-pressure tank10increases so that the liner12is pressed from the inside. Great forces are exerted on the liner12in the axial direction Y and the radial direction, by which an internal pressure stress is generated. According to the present embodiment, the liner12is reinforced in the axial direction by the weft yarns23and is reinforced in the radial direction by the warp yarns22, which suppresses deformation in the high-pressure tank10.

The above-described embodiment has the following advantages.

(1) In the fiber structure21that forms the high-pressure tank10, the direction X2in which the yarn main axis of the weft yarns23proceeds coincides with the axial direction Y of the body portion13and the dome-shaped portions14. The weft yarns23thereby reinforce the liner12in the axial direction.

(2) The direction X2in which the yarn main axis of the weft yarns23proceeds curves along the curved surfaces of the dome-shaped portions14of the liner12toward the axial direction Y in the dome-shaped portion14. In this state, the weft yarns23are not angled relative to the axial direction Y. Even the dome-shaped portion14is thereby reinforced in the axial direction Y.

(3) The weft yarn23that is just inserted is beaten with the reed34to be sent to the weft yarn23that has been previously inserted, which allows the weft yarns23to be arranged closely one another along the circumferential direction Z of the liner12. In the dome-shaped portions14that have smaller diameters than the body portion13has, the weft yarns23are beaten and pressed by the reed34, which allows the weft yarns23to be arranged parallel to one another even in the dome-shaped portions14and which also prevents from generating wrinkles. The density of the weft yarns23is thereby the same in the body portion13and the dome-shaped portions14, and wrinkles are prevented from being generated in the fiber structure21even on the curved surfaces of the dome-shaped portions14.

(4) An example of a conventional method of producing the fiber structure21that includes the fiber reinforcement base material19externally covering the liner12may be filament winding. In this method, productivity is low because yarns are wound around the liner12individually one by one. On the other hand, the productivity in producing the fiber structure21according to the present embodiment is enhanced as compared to the filament winding, because the fabric24is wound around the liner12while the fabric24is woven out of the warp yarns22and the weft yarns23.

Another example of a conventional method of producing the fiber structure21that includes the fiber reinforcement base material19on the outer peripheral surface of the liner12may be braiding, in which a fabric is woven into a tubular shape to fit to the shape of the liner12by braiding, cut open into a flat shape, and then wound around the liner12, In contrast to this conventional method, the fiber reinforcement base material19according to the present embodiment is wound around the liner12while the fiber reinforcement base material19is woven out of the warp yarns22and the weft yarns23, 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 liner12according to the present embodiment is reinforced in the axial direction because the direction X2in which the yarn main axis of the weft yarns23proceeds is the axial direction of the liner12.

The following modifications may be made to the embodiment described above. As shown inFIG. 7, a fiber reinforcement base material40may be a multi-layered fabric woven with multilayer weaving. The fiber reinforcement base material40includes warp layers41and42corresponding to first yarn layers in which warp yarns22are arranged parallel to one another, a weft layer43corresponding to a second yarn layer in which weft yarns23are arranged parallel to one another, and a binder yarn45that binds the warp layers41and42and the weft layer43in the stacking direction. The binder yarn45proceeds around the outer surface of one of the warp yarns22that form the warp layer41, proceeds through the warp layer41in the stacking direction, and then proceeds around the outer surface of another of the warp yarns22that form the warp layer42.

In a fiber structure46including the fiber reinforcement base material40described above, a matrix resin (not shown) is impregnated along the binder yarn45into the fiber reinforcement base material40through the stacking direction of the fiber reinforcement base material40. The fiber structure46is 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 material19includes the stacked layers of the fabric24that 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 material19may 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 yarns22corresponding to the first yarns and a plurality of the weft yarns23corresponding to the second yarns.

In the embodiment described above, the warp yarn22is referred to as the first yarn, and the weft yarn23is referred to as the second yarn. However, the weft yarn23may be referred to as the first yarn and the warp yarn22may be referred to as the second yarn.

The liner12may have a shape in which one end of the body portion13in the axial direction Y is continuous with the dome-shaped portion14and the other end of the body portion13in the axial direction Y is continuous with a flat bottom surface. In this case, the mouthpiece15is provided only to the one end of the line12in the axial direction Y where the dome-shaped portion14is disposed.

The liner12may be entirely made of aluminum or aluminum alloy. The mouthpiece15may be made of metal other than stainless steel.

The body portion13and the dome-shaped portions14of the liner12may be welded into a single piece, instead of being separated.

The high-pressure tank10in 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 tank10may be used as a hydrogen-supply source to power a hydrogen engine or may be used for a heat pump. Alternatively, the high-pressure tank10may be used as a hydrogen-supply source for fuel cells for household use.

The high-pressure tank10in the embodiment described above is used to store hydrogen as the pressure container. The scope of the present invention is not limited to the embodiment. For example, the pressure container may be used to store other types of gases such as nitrogen and compressed natural gas.

REFERENCE SIGNS LIST

L center axisY axial directionZ circumferential directionMa matrix resinX1, X2direction of yarn main axis10high-pressure tank as pressure container12liner13body portion14dome-shaped portion15mouthpiece19,40fiber reinforcement base material21,46fiber structure22warp yarn as first yarn23weft yarn as second yarn24fabric41,42warp layer as first yarn layer43weft layer as second yarn layer45binder yarn