1. A high-pressure tank, comprising:

a container body comprising a domed portion;

a reinforcement layer disposed on an outer surface of the container body and including a fiber-reinforced resin; and

a protective member disposed on an outer surface of the reinforcing layer, wherein

The protective member comprises a first layer disposed at the outer surface of the reinforcement layer covering at least a portion of the dome and a second layer disposed outside the first layer, and the first layer is more deformable than the second layer for the same load,

the first and second layers are both polyurethanes with no added expanded graphite and different static compression values.

2. The high pressure tank of claim 1, wherein the first layer has a static compression value that is less than a static compression value of the second layer.

3. The high-pressure tank according to claim 1, wherein the first layer and the second layer are resin layers.

4. The high-pressure tank according to claim 3, wherein the first layer and the second layer are resin layers comprising polyurethane.

5. The high-pressure tank according to any one of claims 1 to 4, wherein the second layer is provided to cover the entire outer surface of the first layer.

6. The high-pressure tank according to claim 2, wherein the static compression value of the first layer is 1/1.9 or less of the static compression value of the second layer.

7. The high-pressure tank according to any one of claims 1 to 4, wherein the protective member is provided at a position where the high-pressure tank, which is erected in a vertical direction, is in contact with a horizontal plane when the high-pressure tank is inclined at an angle of 45 degrees from the vertical direction.

Background

High-pressure tanks that store gas under high pressure, such as hydrogen, are required to have high pressure resistance; therefore, the high-pressure tank is generally provided with a reinforcing layer formed by winding a fiber reinforced resin such as CFRP (carbon fiber reinforced plastic) around the outer surface of the container body formed of the resin liner. If cracks are generated in the container body of the high-pressure tank due to, for example, accidental dropping during manufacture or transportation, gas leakage of such a high-pressure tank may occur during use. Therefore, the Safety standards for High-Pressure tanks are defined by the High Pressure Gas Safety Act (High Pressure Gas Safety Act) and the like. It has been conventionally proposed to provide a container body for high-pressure gas with a protection device to satisfy safety standards and to safely use a high-pressure tank (see japanese laid-open application publication No. 2014-74470).

Disclosure of Invention

By providing a protection means, the risk of cracks in the container body of the tank can be avoided or reduced even if the high-pressure tank falls and is subjected to an impact. Therefore, the protector is usually provided at a portion of the container body which is relatively weak in impact, such as a joint portion between the tub plate portion and the end plate portion (dome portion), so-called shoulder portion. Since the high-pressure tank is mounted in a vehicle, it is required to minimize the external shape thereof. Therefore, research into more desirable structures of the protection device is required.

The present invention can realize the following modes or application examples.

A first aspect of the invention relates to a high-pressure tank. The high-pressure tank includes: a container body having a domed portion; a reinforcement layer disposed on an outer surface of the container body and including a fiber-reinforced resin; and a protective member disposed on an outer surface of the reinforcing layer. Here, the protective member includes a first layer disposed at an outer surface of the reinforcement layer covering at least a portion of the dome and a second layer disposed outside the first layer. The first layer is more deformable than the second layer for the same load protection member. This configuration can promote improvement in the impact resistance of the high-pressure tank. Here, "high impact resistance" means that it is difficult to generate cracks or fissures in the container body when the high-pressure tank receives an impact due to dropping or the like. If two high-pressure tanks fall from the same height and one of the high-pressure tanks has cracks and fissures but the other high-pressure tank does not have cracks or fissures, it can be said that the other high-pressure tank has higher impact resistance. Regardless of such a drop test, in the case where a load in the same direction as the drop direction of the high-pressure tank is applied to the high-pressure tank, such a high-pressure tank that resists a higher load without cracking or cracking is considered to have higher impact resistance.

In the above-described high-pressure tank, the static compression value of the first layer may be smaller than the static compression value of the second layer. Here, the static compression value may be defined as the load per unit area necessary to achieve the target thickness reduction at the same rate, i.e., for example, target original thickness reduction 1/2. By setting the static compression value of the first layer to be smaller than the static compression value of the second layer, the first layer is more deformable than the second layer for the same load, thereby increasing the impact resistance of the high-pressure tank.

In the above-described high-pressure tank, the first layer and the second layer may be resin layers. By forming both the first resin layer and the second resin layer, the protective member can be easily formed.

In the above-described high-pressure tank, the first layer and the second layer may be resin layers including polyurethane. The static compression value of the polyurethane can be widely controlled based on the composition, and thus a desired protective member can be easily manufactured. For example, the hardness of the polyurethane may be adjusted by changing the combination of the polyol component and the polyisocyanate component used to form the polyurethane or by changing the kind and use ratio of polypropylene glycol (PPG) and polymer polyol (POP) in the polyol component. For example, in order to increase the hardness of polyurethane by using POP, the amount of vinyl monomer to be used may be increased to increase the content of polymer particles in POP. Thus, the polyurethane may be harder and less deformable under the same load.

In the above-described high-pressure tank, the second layer may be provided so as to cover the entire outer surface of the first layer. Of course, a portion of the outer surface of the first layer may be covered by the second layer. By covering the entire outer surface of the first layer, it is possible to prevent an external load from being directly applied to the first layer, and therefore, the function of the protective member formed in a double-layer structure can sufficiently function.

In the above-described high-pressure tank, the static compression value of the first layer may be 1/1.9 or less of the static compression value of the second layer. With this configuration, the impact resistance of the protective member can be sufficiently improved.

In the above-described high-pressure tank, the first protective member may be provided at a position where the high-pressure tank contacts a horizontal plane when the high-pressure tank erected in the vertical direction is inclined at an angle of 45 degrees from the vertical direction. This configuration allows the high-pressure tank to sufficiently exert the impact resistance when dropped in a 45-degree inclined state.

Drawings

The features, advantages and technical and industrial significance of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals refer to like elements, and wherein:

fig. 1 is a sectional view of a high-pressure tank as viewed in a sectional view taken along a central axis of the high-pressure tank;

fig. 2 is a sectional view showing an enlarged section of the protective member;

fig. 3 is an explanatory diagram showing an external shape of a test apparatus for simulating a drop test of a high-pressure tank to determine how much load the high-pressure tank can bear;

fig. 4 is a graph showing the impact resistance of the high-pressure tank of the embodiment;

fig. 5 is a graph showing the impact resistance of a high-pressure tank as a comparative example;

fig. 6 is an explanatory diagram showing the degree of load distribution when the static compression value of a first layer provided on a CFRP layer as a reinforcing layer is smaller than that of a second layer located outside the first layer;

fig. 7 is an explanatory diagram showing the degree of load distribution when the static compression value of a first layer provided on a CFRP layer as a reinforcing layer is larger than that of a second layer located outside the first layer;

fig. 8 is an enlarged sectional view showing still another configuration example of the first protective member and the second protective member; and

fig. 9 is an enlarged sectional view showing still another configuration example of the first protective member and the second protective member.

Detailed Description

Fig. 1 is a sectional view of the high-pressure tank 100 as viewed in a sectional view taken along a central axis O of the high-pressure tank 100. The high-pressure tank 100 of the present embodiment is mounted in an automobile, and the high-pressure tank 100 stores hydrogen gas. Here, the high-pressure tank refers to a high-pressure tank prescribed by the japanese high-pressure gas safety act. Needless to say, the high-pressure tank may be a high-pressure tank that conforms to the GHS standard. The high-pressure tank 100 includes: the resin liner 10, the reinforcing layer 20, the valve side mouth member 30, the end side mouth member 40, the valve 50, the first protective member 61, and the second protective member 62.

The resin liner 10 is a member for defining a space to be filled with hydrogen gas, and is produced by resin molding. The reinforcing layer 20 is a member for reinforcing the resin liner 10 and covers the outer periphery of the resin liner 10. The reinforcing layer 20 is made of a fiber reinforced resin, and the material thereof is CFRP (carbon fiber reinforced plastic). The reinforcing layer 20 is formed by an FW (filament winding) method. The resin liner 10 forms a container body of the high-pressure tank 100.

As shown in fig. 1, the can body includes: a tub plate 80, a first end plate 91, and a second end plate 92. The tub portion 80 includes a part of the resin liner 10 and a part of the reinforcing layer 20, and the tub portion 80 has a linear sectional shape. The direction of extension of the cross-sectional shape coincides with the direction of the central axis O shown in fig. 1. The first end plate portion 91 and the second end plate portion 92 include a part of the resin liner 10 and a part of the reinforcing layer 20 but do not include the tub portion 80. That is, each of these portions is a portion having a sectional shape that does not linearly extend in the longitudinal direction of the tank, and more specifically, the portion has a curved shape, typically a semicircular shape. Due to this shape, the first end plate portion 91 and the second end plate portion 92 are sometimes referred to as dome portions.

The valve-side mouth member 30 has a substantially cylindrical shape, and includes a flange protruding from an outer peripheral surface thereof. The valve-side mouth member 30 is fixed in a state in which the flange is held between the resin liner 10 and the reinforcing layer 20 in the first end plate portion 91. In fig. 1, for the purpose of simplifying the drawing, a hatching that represents a sectional view is not applied to the valve-side mouth member 30. The inner peripheral surface of the valve-side mouth member 30 serves as a port for hydrogen gas. The valve 50 is used to open and close the port of hydrogen gas in the valve-side mouth member 30. Valve 50 comprises a stoppable valve (not shown). The fusible plug valve is a kind of safety valve, and has a function of releasing the pressure of the stored gas to the outside when the temperature of the high-pressure tank 100 becomes a predetermined temperature or higher. The valve-side mouth member 30 is formed with an internal thread on its inner peripheral surface, and the valve 50 is formed with an external thread on its outer peripheral surface. The external thread and the internal thread are tightly combined together to seal the inside of the resin liner 10.

The end side mouth member 40 is provided to the second end plate portion 92 in such a manner as to be exposed to the inside and outside of the tank. This arrangement enables the heat inside the tank to be released to the outside. The end side mouth member 40 also serves to rotatably hold the resin liner 10 when the material CFRP as the reinforcing layer 20 is wound around the resin liner 10. In order to improve the efficiency of the heat radiation, metal, such as aluminum, is used as the material of the end mouth member 40 in the present embodiment. In fig. 1, for the purpose of simplifying the drawing, hatching indicating a sectional view is also not applied to the end side mouth member 40.

The first protective member 61 covers the thin-walled portion of the first end plate portion 91 and the vicinity thereof (hereinafter, both are also collectively referred to as "thin-walled portion and others") to protect the thin-walled portion from impact. The thin-walled portion of the first end plate portion 91 is a portion where the reinforcing layer 20 has the thinnest wall thickness in the first end plate portion 91, and corresponds to the intermediate portion of the first end plate portion 91. The intermediate portion is a portion spaced apart from the valve-side mouth member 30 and the barreled panel portion 80. The reason why such a thin-walled portion is generated is because the reinforcing layer 20 is formed by using the FW method. The thin-walled portion is weaker than other portions with respect to impact and high temperature. Needless to say, even if there is no thin wall portion, the first protective member 61 and the second protective member 62 may be provided.

In order to cover the thin-walled portion, the first protective member 61 is formed in a shape of a conical shape based on the top portion being removed, (hereinafter, this shape is referred to as a "flat marker cone shape"), and the first protective member 61 covers at least a part of the surface of the high-pressure tank 100. In order to improve the impact resistance of the first protective member 61, a structure including two resin layers described later is adopted in the first protective member 61. The first protective member 61 is fixed to the outer surface of the reinforcing layer 20 by an adhesive after injection molding. The positions at which the first protective member 61 and the second protective member 62 are arranged include positions at which the high-pressure tank 100 is in contact with a horizontal plane when the high-pressure tank 100 in a state of being erected in the vertical direction is inclined from the vertical direction at an angle of 45 degrees while the valve-side mouth member 30 is oriented in the downward or upward direction.

The second protective member 62 covers the thin-walled portion and other portions of the second end plate portion 92 to protect the thin-walled portion from impact and high temperature. The external shape and structure of the second protective member 62 are almost the same as those of the first protective member 61. The second sheathing member 62 is fixed to the reinforcing layer 20 by an adhesive. The second protective member 62 has a double-layered internal structure similar to that of the first protective member 61. The second protective member 62 is produced by injection molding. The first protective member 61 and the second protective member 62 are also referred to as "protective devices" in some cases.

A double-layer structure included in each of the first protective member 61 and the second protective member 62 will be described with reference to fig. 2. Fig. 2 is a sectional view showing an enlarged section of the first protective member 61 and the second protective member 62. As shown in fig. 2, each of the first protective member 61 and the second protective member 62 is formed of an inner first layer 71 and an outer second layer 72. In the present embodiment, the second layer 72 covers the entire area of the first layer 71. In this embodiment, the material of the first layer 71 andthe materials of the second layer 72 are both polyurethane, but the first layer 71 and the second layer 72 are different in deformability. The first layer 71 is more deformable than the second layer 72 for external loads. In this embodiment, the first layer 71 has the following characteristics: the density was 0.25g/cm³(ii) a And a static compression value of about 570kPa, and the second layer 72 has the following characteristics: the density was 0.67g/cm³(ii) a And a static compression value of 1100kPa or higher. The physical property values of the polyurethane can be easily controlled based on the additives and the degree of foaming. Expanded graphite may be considered as an additive, but in terms of the static compression value, the above values can be achieved without adding expanded graphite. In this embodiment, the static compression value is defined as the load at the time when the target is compressed by 50% in the thickness direction. Thus, in this embodiment, the ratio of the static compression value of the second layer/the static compression value of the first layer is about 1100/570 ≈ 1.9.

The impact strength of the high-pressure tank 100 including the first protective member 61 and the second protective member 62 configured as described above will be described. Fig. 3 is an explanatory diagram showing an external shape of a test apparatus for simulating a drop test of a high-pressure tank to determine how much load the high-pressure tank 100 can bear. As for the drop test, a drop test at an angle of 45 degrees (japanese society for automotive research, "Technical Standards for Compressed Hydrogen gas containers for automotive Fuel systems" ("JARIS 001(2004)) as the most severe conditions for the high-pressure tank 100 was simulated. In fig. 3, the high-pressure tank 100 as a test target is fixed to a jig GG at an angle of 45 degrees by a band BT or the like, and a static load is applied to the first protective member 61 from above by using a pressure plate 200 of a load test apparatus 210. The pressure plate 200 is moved downward by the load testing apparatus 210. The load applied by moving onto the first protective member 61 of the high-pressure tank 100 is measured using a load cell or the like.

Fig. 4 shows the results of the drop test. In fig. 4, the horizontal axis indicated as "pressure plate displacement" represents the amount of movement of the pressure plate 200 from the position where the pressure plate 200 contacts the first protective member 61. As shown in the graph, in the high-pressure tank 100 including the first protective member 61 of the present embodiment, the load that has monotonically increased varies in the vicinity of the pressure plate displacement XS1, indicating that any crack or flaw is generated in the CFRP layer of the high-pressure tank 100. The load at this point is approximately 200kN (kilonewtons). In fact, when the high-pressure tank 100 is inspected after the test, it is found that the CFRP layer has cracks in the vicinity of the first protective member 61.

Meanwhile, fig. 5 shows a graph of the result of the drop test as a comparative example, and a case where the material of the first layer and the material of the second layer are interchanged with each other in the first protective member 61. In other words, the curve of fig. 5 shows the drop test results for the following cases: in this case, in the first protective member 61, a material having a static compression value of 1100 is used for the inner first layer and a material having a static compression value of about 570 is used for the outer second layer. As shown in the graph, in the high-pressure tank 100 including the first protective member 61 in which the arrangement of the physical properties of the first layer and the second layer is reversed in the first protective member 61 of the present embodiment, the load that has monotonically increased varies in the vicinity of the pressure plate displacement XS2, indicating that any cracking or splitting occurs in the resin liner 10 of the high-pressure tank 100. The displacement XS2 of the pressure plate 200 at this time is about 20 to 30% smaller than that of the high-pressure tank 100 of this embodiment at XS1, and the load at the time of rupture is close to 100kN (kilonewton).

The test results in which the high-pressure tank 100 is placed upside down and the load is applied by the load testing apparatus 210 from the state in which the pressure plate 200 is in contact with the second protective member 62 are the same as described above. Further, the high-pressure tank 100 including the first protective member 61 and the second protective member 62 of the present embodiment exhibits high impact resistance, as compared with a high-pressure tank including the first protective member 61 having a single layer. In particular, when the ratio of the static compression value of the first layer to the static compression value of the second layer, i.e., the static compression value of the first layer/the static compression value of the second layer, is 1/1.9 or less, a significant improvement in impact resistance is exhibited.

According to the above embodiment, each of the first protective member 61 and the second protective member 62 provided near the shoulder portion of the high-pressure tank 100 is configured as the double-layer structure, and the static compression value of the inner first layer 71 is set smaller than the static compression value of the outer second layer 72. As a result, it was found that the load causing the resin liner 10 to crack or craze was increased, and therefore, higher impact resistance against an impact such as falling can be achieved as compared with the case of employing a single-layer structure or the case where the static compression value of the inner first layer is larger than that of the outer second layer. When the same impact resistance is achieved, the thickness of the protective member may be thinner than that of the conventional protective member, thereby reducing the overall thickness.

It is considered that the reason why higher impact resistance can be achieved in each of the first protective member 61 and the second protective member 62 in which the static compression value of the inner first layer 71 is smaller than that of the outer second layer 72 is as follows. Fig. 6 shows a case where the static compression value of the first layer disposed on the CFRP layer as the enhancement layer 20 is smaller than that of the layer above the first layer, i.e., the outer second layer. A layer having a lower static compression value is referred to herein as a "low compressive strength layer," and a layer having a higher static compression value as compared to the lower static compression value is referred to as a "high compressive strength layer. As illustrated in fig. 6, when the load F is applied from the outside, i.e., from the high compression strength layer as the second layer, the high compression strength layer is deformed, but the deformation range is small. On the other hand, since the low compressive strength layer has a compressive strength smaller than that of the outer second layer, deformation of the low compressive strength layer propagates in a wide range when the load F is transferred to the low compressive strength layer. As a result, the load F transferred from the inner first layer to the CFRP layer as the reinforcing layer 20 is distributed in a wide range, and thus the load per unit area can be reduced to a smaller load.

On the other hand, as shown in fig. 7, if the arrangement relationship of the first layer and the second layer is reversed, the outer second layer is a low compression strength layer, so that the layer is easily deformed by a load F from the outside. However, since the inner first layer is a high compressive strength layer, the load F transferred to the inner first layer is transferred to the CFRP layer as the reinforcing layer 20 without being widely spread. As a result, the load per unit area increases; therefore, cracking or crazing of the resin liner 10 may be caused.

The hardness relationship between the first layer 71 and the second layer 72 in each of the first protective member 61 and the second protective member 62 is not particularly limited as long as the inner first layer is more deformable than the outer second layer. If both the first layer 71 and the second layer 72 are resin layers, the deformability can be defined in terms of the degree of the static compression value. The outer second layer 72 is not limited to resin, and may be formed of metal, a wooden material, carbon fiber, or the like. In this case, it does not make sense to limit the load so as to reduce the thickness by 50%, and so on, and therefore the static compression value may instead be defined according to the degree of deformation when a constant load is applied in the direction in which the thickness is compressed. The deformability can also be defined using other values of the physical property, such as young's modulus.

The combination of the first layer and the second layer may be such a combination comprising a first soft resin layer and a second hard resin layer. The combination may be a combination including a first soft resin layer and a second metal layer. The combination may be a combination including a first soft resin layer and a second carbon resin layer. Alternatively, the combination may be a combination including a first foamed resin layer and a second hard resin layer.

Here, the soft resin refers to a resin having a low static compression value, such as polyurethane, EVA resin, and low density polyethylene (LDPE or PE-LD). Examples of the hard resin may include epoxy resin, urea resin, phenol resin, melamine resin, unsaturated polyester resin; and such typical resins are resins having a relatively high static compression value compared to that of soft resins, such as polycarbonate, polyacetal, ABS resin and high-density polyethylene.

The above metals also include alloys. Relatively soft metals such as aluminum, copper, and soft iron may be used. Metals, ceramics, resins and other composite materials may be used. Furthermore, a material formed of metal fiber clusters, a material formed of woven metal fibers, or a honeycomb structure may also be employed.

In the present embodiment, the first and second protective members 61 and 62 provided to the first and second end plate portions 91 and 92 of the high-pressure tank 100, respectively, are denoted by different reference numerals, but both may be formed of the same member. Alternatively, the two may be different members. The meaning of "both are different" may include the case where the material forming the first layer and the material of the second layer are at least partially different from each other or the case where the materials are the same but both are at least partially different in thickness or width. Further, only either one of the first protective member 61 and the second protective member 62 may be provided. Alternatively, a third protective member may be provided in addition to the first protective member 61 and the second protective member 62 at a position where the third protective member does not overlap with the first protective member 61 and the second protective member 62.

In the above embodiment, the first protective member 61 and the second protective member 62 are fixed to the reinforcing layer 20 by the adhesive, but the first protective member 61 and the second protective member 62 may be fixed using a double-sided tape, or may be fixed by another fixing member such as a tape. In the configuration shown in fig. 2, the outer second layer 72 completely covers the first layer 71, and the outer second layer 72 is in direct contact with the reinforcing layer 20 on the outer periphery of the first layer 71. In the contact portion, the first layer 71 may or may not be bonded to the reinforcing layer 20. Alternatively, as illustrated in fig. 8, it may be configured that the second layer 72a is not spread from the first layer 71 in the circumferential direction of the first layer 71 so as not to contact the reinforcing layer 20.

Further, any one of the first layer 71 and the second layer 72 is not always a single member, and may be divided into a plurality of members. For example, as shown in fig. 9, the first protective member 61A and the second protective member 62A may each be configured to further provide a third layer 73 outside the second layer 72 in order to divide the second layer 72 into two. In this case, if the respective static compression values of the first layer to the third layer are defined as SP1 to SP3, any one of SP1< SP2 and SP2< SP3 may be satisfied, and the other two layers may be constructed regardless of the degree of the static compression values. Of course, the static compression values of the first layer to the third layer may have the same static compression value.

The first layer 71 may not be divided in the stacking direction but in a direction different from the stacking direction. The first protective member 61, the second protective member 62, and the like are each formed in a flat mark taper shape, but the shape is not limited to this shape; also, for example, in the case of the second panel portion 92 side, the shape may be a bowl shape covering the end side mouth member 40. Alternatively, the shape is not always required to be a circular shape (circular ring shape) as seen from the direction of the center axis O, but may be formed by arranging a plurality of small protection members. In this case, the plurality of protective members may be arranged on a circumference equidistant from the central axis O, or may be arranged irrespective of the circumference equidistant from the central axis O. For example, the protective members may be arranged arbitrarily, or may be arranged according to some rule, such as a staggered arrangement.

The fluid stored in the high-pressure tank may be a fluid other than hydrogen gas, such as methane gas and propane gas. The high-pressure tank is not limited to a tank in a vehicle, but may be a tank installed in a house, a research facility, or a medical facility.

The present invention is not limited to the above-described embodiments, examples, and modifications, but may be embodied in various other forms without departing from the spirit of the invention. For example, in order to partially or fully solve the problems described above or to partially or fully achieve the effects described above, technical features of embodiments, examples, and modifications corresponding to technical features of the modes described in the summary of the invention may be appropriately replaced or combined. The technical features are to be eliminated as appropriate unless the present invention proposes that the technical features be mandatory.