阅读说明：本技术 构造物的约束构造 (Structure for restraining structure ) 是由 泽井统 于 2020-07-28 设计创作，主要内容包括：本发明的构造物的约束构造包括：被约束部,该被约束部是筒体或层叠体；一对保持部,设于所述被约束部；第一CFRP带,以架设于一对所述保持部之间的方式沿所述被约束部的轴向缠绕,并且具有沿着所述轴向的0°方向的碳纤维；以及第二CFRP带,与所述第一CFRP带的端部附近的最外层邻接地层叠,并且具有与所述轴向成45°至90°方向的碳纤维。所述保持部中的一方设于所述被约束部的一端。所述保持部中的另一方设于所述被约束部的另一端。(The constraint structure of a structure of the present invention includes: a constrained portion which is a cylindrical body or a laminated body; a pair of holding portions provided in the restrained portion; a first CFRP tape wound in an axial direction of the restrained portion so as to span between the pair of holding portions and having carbon fibers in a 0 ° direction along the axial direction; and a second CFRP tape laminated in abutment with an outermost layer in the vicinity of an end of the first CFRP tape and having carbon fibers oriented at 45 ° to 90 ° to the axial direction. One of the holding portions is provided at one end of the restrained portion. The other of the holding portions is provided at the other end of the restrained portion.)

1. A restraining structure for a structure, comprising:

a constrained portion which is a cylindrical body or a laminated body;

a pair of holding portions provided at the restrained portion, one of the holding portions being provided at one end of the restrained portion, and the other of the holding portions being provided at the other end of the restrained portion;

a first carbon fiber-reinforced resin tape wound in the axial direction of the restrained portion so as to be stretched between the pair of holding portions, the first carbon fiber-reinforced resin tape having carbon fibers in a 0 ° direction along the axial direction; and

a second carbon fiber reinforced resin tape laminated adjacent to an outermost layer in the vicinity of an end of the first carbon fiber reinforced resin tape and having carbon fibers oriented at 45 ° to 90 ° to the axial direction.

2. A restraining construction for a structure according to claim 1,

an end portion of the first carbon fiber reinforced resin tape is disposed in the vicinity of a connection portion between a bent portion of the first carbon fiber reinforced resin tape and a straight portion along the restrained portion.

3. A restraining construction for a structure according to claim 1 or 2, further comprising:

a third carbon fiber-reinforced resin tape having carbon fibers oriented at 45 DEG to 90 DEG to the axial direction,

wherein the third carbon fiber reinforced resin tape can be laminated between the wound layers of the first carbon fiber reinforced resin tape,

the constraint structure of the structure is formed as follows: the proportion of carbon fibers in the 45 DEG to 90 DEG direction to all the laminated tapes is 10% or more and 50% or less.

Technical Field

The present invention relates to a restraining structure for a structure including a cylindrical body or a laminated body.

Background

Japanese patent application laid-open No. 2018-119578 discloses a restraint structure of a high-pressure tank in which a sheet-like CFRP (Carbon Fiber Reinforced Plastics) tape is wound in an axial direction of a main body portion constituting the high-pressure tank. Such a restraining configuration can also be applied to a case where a battery including a plurality of unit cells (cells) is restrained.

However, in the above-described constraining structure, when the structure expands or the like and the tension applied to the CFRP tape increases, shear stress concentrates between layers at the winding end portion of the CFRP tape, and peeling may occur between the layers of the CFRP tape.

Disclosure of Invention

The invention provides a restraining structure of a structure, which can reduce the shearing stress at the winding end of a CFRP belt and can inhibit the interlayer peeling.

A first aspect of the present invention is a structure for restraining a structure. The restraining structure of the structure comprises: a constrained portion which is a cylindrical body or a laminated body; a pair of holding portions provided in the restrained portion; a first CFRP tape wound in an axial direction of the restrained portion so as to span between the pair of holding portions and having carbon fibers in a 0 ° direction along the axial direction; and a second CFRP tape laminated in abutment with an outermost layer in the vicinity of an end of the first CFRP tape and having carbon fibers oriented at 45 ° to 90 ° to the axial direction. One of the holding portions is provided at one end of the restrained portion, and the other of the holding portions is provided at the other end of the restrained portion.

In the first aspect, the restrained portion that is the cylindrical body or the laminated body is held from both sides by the pair of holding portions, and the first CFRP tape is wound in the axial direction of the restrained portion so as to be stretched between the pair of holding portions. The first CFRP belt has carbon fibers in a 0 ° direction along the axial direction of the restrained portion. Here, the axial direction is a direction along the central axis in the case of a cylindrical body, and is a direction along the stacking direction in the case of a stacked body. Further, the 0 ° direction along the axial direction includes an error in the direction of the carbon fiber when the first CFRP tape is manufactured and an error in the direction of the carbon fiber generated when the first CFRP tape is wound. And a second CFRP tape having carbon fibers oriented at 45 ° to 90 ° is laminated adjacent to the outermost layer in the vicinity of the end of the first CFRP tape. The numerical range denoted by "to" is defined as a numerical range including the numerical values described before and after "to" as the lower limit value and the upper limit value.

In the case where a cross section of the CFRP belt having the carbon fibers generates stress, the property of the carbon fibers greatly contributes to the force resisting the 0 ° direction, and the property of the resin greatly contributes to the force resisting the 90 ° direction. That is, according to the first aspect, the second CFRP belt in which the carbon fibers are arranged in the direction intersecting the tension can be provided with elasticity in the axial direction. Therefore, even if the shear stress is intensively applied to the winding end portion of the first CFRP tape, the shear stress is relaxed by the elasticity of the second CFRP tape, and therefore, the delamination between the layers can be suppressed.

In the first aspect, in the structure for restraining the structure, an end portion of the first CFRP belt may be disposed in the vicinity of a connection portion between a bent portion of the first CFRP belt and a straight portion along the restrained portion.

According to the above configuration, both bending stress and tensile stress act on the connection portion between the bent portion and the straight portion of the first CFRP belt, in other words, on the R-end (end portion of the curve). Here, the bending stress acting on the R end is an axially outer stress on the upper layer side and an axially inner stress on the lower layer side. Therefore, the resultant force of the bending stress and the tensile stress directed to the axially inner side is cancelled out on the upper layer side. According to the above configuration, the first CFRP tape is formed so that the tensile stress is relaxed as the upper layer becomes more gradual by ending the winding at the connection portion between the bent portion and the straight portion of the first CFRP tape. Therefore, the shear stress at the winding end portion of the first CFRP tape can be further reduced, so that the delamination between the layers can be further suppressed.

In the first aspect, the constraint structure may further include: a third CFRP band having carbon fibers oriented at 45 to 90 degrees to the axial direction. A third CFRP tape may be laminated between layers of the wound first CFRP tape, and the constraint configuration of the structure may be formed as: the proportion of carbon fibers in the 45 DEG to 90 DEG direction to all the laminated tapes is 10% or more and 50% or less.

In all the CFRP tapes laminated, there may be more than 10% to less than 50% of carbon fibers in the 45 ° to 90 ° direction. According to the above configuration, the second CFRP belt in which the carbon fibers are arranged in the direction intersecting the direction in which the tension acts can be provided with elasticity in the thickness direction. Therefore, it is possible to reduce the surface pressure in the thickness direction of the curved portion formed by bending the first CFRP tape having the carbon fibers in the 0 ° direction, and suppress the compression fracture of the first CFRP tape.

According to the first aspect of the present invention, the shear stress at the winding end of the CFRP tape can be reduced, and delamination between layers can be suppressed.

Drawings

Features, advantages and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, wherein like reference numerals denote like elements, and wherein:

fig. 1 is a perspective view of a tank module in which high-pressure tanks according to a first embodiment are combined.

Fig. 2 is a side sectional view of the high-pressure tank of the first embodiment.

Fig. 3 is a side sectional view (enlarged view of fig. 2) of the high-pressure tank in the vicinity of the joint according to the first embodiment.

Fig. 4 is a side view of the high-pressure tank in the vicinity of the joint according to the first embodiment, and is a schematic view of the resultant force acting on the R-end (end of the curve).

Fig. 5 is a partially enlarged side sectional view of the fastening band of the high-pressure tank according to the first embodiment.

Fig. 6 is a plan view of the fixing band of the high-pressure tank according to the first embodiment, and is a schematic view showing the direction of carbon fibers.

Fig. 7 is a perspective view of a battery module in which battery cells of the second embodiment are combined.

Detailed Description

[ first embodiment ]

The high-pressure tank 10 according to the first embodiment to which the structure constraint structure is applied will be described below with reference to fig. 1 to 6.

As shown in fig. 1, a high-pressure tank 10 as a structure constitutes a part of a tank module 12. That is, the plurality of high-pressure tanks 10 are arranged and connected to constitute the tank module 12. As an example, the tank module 12 is housed on the vehicle lower side of a floor panel of a fuel cell vehicle. As an example, the high-pressure tank 10 of the present embodiment contains hydrogen as a fluid.

The high-pressure tank 10 is formed in a cylindrical shape with the vehicle front-rear direction as the axial direction (longitudinal direction). The high-pressure tank 10 is configured to include: a cylindrical main body portion 20; joints 30 provided at both ends of the body 20 in the axial direction; and a fixing band 40 wound in the axial direction of the main body 20 so as to be stretched between the pair of joints 30. The body portion 20 is an example of a restrained portion as a cylindrical body, and the joint 30 is an example of a holding portion. Hereinafter, unless otherwise specified, only the axial direction of the body 20 is referred to as the axial direction, and only the radial direction of the body 20 is referred to as the radial direction.

As shown in fig. 2 and 3, the main body 20 includes, as an example: a cylindrical inner liner 24 formed of an aluminum alloy; and a reinforcing layer 26 made of CFRP (carbon fiber reinforced plastic) provided on the outer peripheral surface of the liner 24. The reinforcing layer 26 is formed by: a sheet-like CFRP impregnated with resin in advance is wound around the outer circumferential surface of the liner 24, or carbon fibers are wound around the outer circumferential surface of the liner 24 and then impregnated with resin. On the inner circumferential surface side of the reinforcing layer 26, carbon fibers, not shown, in the fiber-reinforced resin are arranged along the liner 24 and further along the circumferential direction of the main body portion 20.

The joint 30 is formed in a substantially semi-cylindrical shape with an axially outer portion projecting toward the axially outer side. The joint 30 has an insertion portion 32 and a communication flow path 34. The insertion portion 32 is a portion inserted into the opening 22 of the high-pressure tank 10, and is formed in a substantially cylindrical shape protruding inward in the axial direction. The outer peripheral surface of the insertion portion 32 abuts against the inner peripheral surface of the body portion 20. Further, a packing (packing) accommodating portion 36 formed by cutting out an outer edge portion is provided at a distal end portion of the insertion portion 32, and an O-ring 38 is accommodated inside the packing accommodating portion 36. The O-ring 38 is elastically deformed in the radial direction. The axial end portion of the body 20 on one side and the axial end portion on the other side are closed by the insertion portion 32.

The communication flow path 34 is formed inside the joint 30. The communication flow path 34 is configured to include: a first communication passage 34A that opens axially inward of the insertion portion 32; and a second communication flow path 34B extending in the width direction and connected to the first communication flow path 34A (see fig. 4). The second communication passages 34B are connected to each other in the adjacent high-pressure tanks 10, and thereby the interiors of the main bodies 20 of the plurality of high-pressure tanks 10 communicate with each other. The plurality of main bodies 20 may be connected to a joint having the plurality of insertion portions 32.

The communication flow path 34 in the joint 30 is provided with a valve, not shown, as a valve member, so that the amount of fluid flowing through the communication flow path 34 can be controlled. The communication flow path 34 is connected to a fuel cell stack, a supply pipe, and the like, not shown.

The fixing band 40 is provided radially outside the main body 20 and outside the pair of joints 30. Specifically, the fixing band 40 is wound around the outer surfaces of the pair of joints 30 so as to span in the axial direction. The fixing band 40 has: a wrap-around band 42 that axially wraps around the main body portion 20; and an interlayer tape 44 included between the layers surrounding the tape 42. As shown in fig. 5, the fastening tape 40 is laminated with twenty layers on the a-a line, the interlayer tape 44 exists in the second and eighteenth layers from the radially inner side, and the encircling tape 42 exists in the other layers.

As shown in fig. 3, the fixing band 40 has: a pair of linear portions 40A along the axial direction of the body portion 20; a pair of outer peripheral portions 40B along outer surfaces on axially outer sides of the joint 30; and a curved portion 40C connecting the linear portion 40A and the outer peripheral portion 40B. The outer peripheral portion 40B and the curved portion 40C are an example of a curved portion. Here, the following are formed: when the radius of the curved portion 40C is R and the height of the high-pressure tank 10 is H, R > H/3 is obtained. Further, the following is formed: when the radius of the outer peripheral portion 40B is defined as r, r > H/2.

As shown in fig. 6, the encircling band 42 as the first CFRP band is a CFRP band, and is a UD (Uni Direction: unidirectional) band having carbon fibers CF in the 0 ° Direction along the axial Direction. The 0 ° direction along the axial direction includes an error in the direction of the carbon fibers CF when the wrap around tape 42 is manufactured and an error in the direction of the carbon fibers CF when the wrap around tape 42 is wound. The wrap tape 42 is a so-called prepreg (prepreg) in which carbon fibers CF are impregnated with resin in advance, and the wrap tape 42 is cured after being wound. The wrap-around band 42 is adhesively fixed to the outer surface of the joint 30 at the radially inner end E1 (see fig. 3), and after the wrap-around layer CL is formed around seventeen turns of the main body portion 20, the radially outer end E2 is adhesively fixed to the interlayer band 44 in the vicinity of the connection between the linear portion 40A and the curved portion 40C (see fig. 5).

As shown in fig. 6, the interlayer tape 44 is a CFRP tape, and is a UD tape having carbon fibers CF extending in a direction of 90 ° along the width direction of the main body 20. The 90 ° direction along the axial direction includes an error in the direction of the carbon fibers CF when the interlayer tape 44 is manufactured and an error in the direction of the carbon fibers CF when the interlayer tape 44 is wound. The interlayer tape 44 is a so-called prepreg in which carbon fibers CF are impregnated with resin in advance, and the interlayer tape 44 is cured after being wound. Here, in the present embodiment, the following are formed: the carbon fibers CF of the interlayer tape 44 account for 10% of the entire fixing tape 40.

As shown in fig. 5, an interlayer tape 44 as a second CFRP tape is adjacently laminated with the surrounding tape 42 of the uppermost TL as the outermost layer. Specifically, the interlayer tape 44 is wound once between the encircling tape 42 of the uppermost layer TL of the fixing tape 40 and the encircling tape 42 one turn before the uppermost layer TL.

An interlayer belt 44 as a third CFRP belt is laminated adjacently to the encircling belt 42 of the lowermost layer BL. Specifically, the interlayer tape 44 is wound around the lowermost layer BL of the fixing tape 40 by one turn between the encircling tape 42 and the encircling tape 42 after one turn of the lowermost layer BL.

(production method)

The high-pressure tank 10 is manufactured as follows. First, the operator prepares the joint 30 in which the O-ring 38 is accommodated in the seal accommodating portion 36 in advance. Next, the operator inserts the insertion portions 32 of the fittings 30 into the openings 22 of the main body portion 20, and attaches the fittings 30 to both ends of the main body portion 20 in the axial direction.

Next, the operator brings the end E1 of the wrap band 42 into contact with the outer peripheral surface of the joint 30, and wraps the wrap band 42 around in the axial direction of the body 20 by about one turn. After the resin cures, the end E1 of the encircling band 42 is bonded to the joint 30. Here, the operator winds the interlayer tape 44 around the first layer of the encircling tape 42 for one turn and cuts the interlayer tape 44. It is desirable that the starting point (end portion) and the end point (end portion) of the interlayer tape 44 as the second layer are kept away from the curved portion 40C.

Then, the operator winds the wrap tape 42 around the interlayer tape 44 for about sixteen turns, that is, until the eighteenth layer is formed. Here, the operator winds the interlayer tape 44 around the winding tape 42 of the seventeenth layer by one turn and cuts the interlayer tape 44. It is preferable that the start point (end portion) and the end point (end portion) of the interlayer tape 44 as the eighteenth to nineteenth layers are provided in the linear portion 40A, respectively.

Further, the operator winds the wrap tape 42 around the interlayer tape 44 by about one turn, that is, until the twentieth layer is formed. Then, the wraparound tape 42 of the twentieth layer is wrapped from the outer peripheral portion 40B to the linear portion 40A via the curved portion 40C. Then, the operator cuts the remaining encircling band 42 so that the end E2 of the encircling band 42 is located near the connection of the linear portion 40A and the curved portion 40C.

The resin impregnated in the encircling band 42 and the interlayer band 44 is cured, thereby producing the high-pressure tank 10. The above-described steps are assumed to be performed by an operator, but are not limited thereto, and may be mechanized by a manufacturing apparatus.

(Effect)

Next, the operation and effect of the present embodiment will be described.

In the high-pressure tank 10 of the present embodiment, when the pressure inside the high-pressure tank 10 rises due to the fluid contained therein, the joint 30 is pushed outward in the axial direction, and tension is generated in the fixing band 40. On the other hand, the fixing tape 40 receives a force of compression in the thickness direction, that is, a surface pressure at the contact portion with the joint 30.

On the other hand, in the high-pressure tank 10, the length in the axial direction is shortened as r is increased in the outer peripheral portion 40B, that is, as the outer peripheral radius of the joint 30 is increased, but the angle at which the straight portion 40A and the outer peripheral portion 40B are connected is closer to a right angle. Further, the smaller the radius R of the curved portion 40C which is a connecting portion between the linear portion 40A and the outer peripheral portion 40B, the greater the surface pressure acts on the fixing band 40. When the surface pressure acting on the fastening tape 40 is denoted by P and the tension acting on the fastening tape 40 is denoted by F, P ^ F/R is obtained. That is, the larger the tension F, the smaller the radius R, and the larger the surface pressure acts.

The high-pressure tank 10 of the present embodiment is formed such that the curved portion 40C satisfies R > H/3 in the fixing band 40. This reduces the surface pressure in the thickness direction of the fastening tape 40 and suppresses compression fracture. The radius R of the curved portion 40C does not need to be constant, and the strength of the fixing band 40 against compression can be further increased by gradually increasing the radius R toward the R end (the end of the curve, the connecting portion between the linear portion 40A and the curved portion 40C) having a curvature and a large tensile stress.

In addition, in the present embodiment, the following is formed: the carbon fibers CF in the 90 ° direction account for 10% of the entire fixing tape 40. The wrap-around tape 42 having the carbon fibers CF oriented at 0 ° to the axial direction has difficulty in securing the strength in the thickness direction in the case where the tension acts in the 0 ° direction. Here, the performance of the resin constituting the UD tape of the fixing tape 40 contributes more to the resistance to the force in the 90 ° direction than the carbon fiber CF. Therefore, the interlayer tape 44 having the carbon fibers CF oriented at 90 ° to the axial direction is less likely to be affected by the tension in the 0 ° direction, and can secure the elasticity in the thickness direction. Therefore, in the present embodiment, compared to the case where all the fastening tapes 40 are constituted by the wrap-around tapes 42, elasticity can be imparted in the thickness direction by including the interlayer tape 44 having the carbon fibers CF in the 90 ° direction at a certain ratio in the fastening tape 40. Therefore, according to the present embodiment, in the curved portion 40C where the surface pressure becomes high, the strength of the fastening tape 40 in the tensile direction can be secured, and the compression fracture can be suppressed.

In order to reduce the influence of the compressive force (surface pressure) applied to the fixing tape 40 from the joint 30 at the curved portion 40C, it is desirable to provide the interlayer tape 44 as much as possible in the lower layer, specifically, in the second layer.

In addition, in the fastening tape 40 of the present embodiment, the interlayer tape 44 is stacked adjacent to the uppermost layer TL near the end E2 where the winding of the encircling tape 42 is completed. Here, the stress is equally applied to both axial sides of the lower wrap around band 42 without the end portion E2, whereas the stress is concentrated between the layers on the side where the wrap around band 42 is broken at the end portion E2. Therefore, when the wrap tape 42 is simply wound without the interlayer tape 44, the shear stress is concentrated on the end portion E2, and hence there is a fear that delamination may occur.

In contrast, in the present embodiment, the end E2 of the wrap around tape 42 is bonded to the interlayer tape 44. Here, for the UD tape constituting the fixing tape 40, the performance of the carbon fiber CF greatly contributes to the force resisting the 0 ° direction, and the performance of the resin greatly contributes to the force resisting the 90 ° direction. That is, the CFRP having the carbon fibers CF arranged in the 0 ° direction can secure the tensile strength in the 0 ° direction, and the CFRP having the carbon fibers CF arranged in the 90 ° direction can impart elasticity in the 0 ° direction. Further, as in the present embodiment, the interlayer tape 44 in which the carbon fibers CF are arranged in the direction orthogonal to the tension can be provided with elasticity in the axial direction. According to the present embodiment, even if the shear stress is intensively applied to the end portion E2 of the wrap around tape 42, the shear stress is relaxed by the elasticity of the interlayer tape 44, and therefore, delamination between layers can be suppressed.

In the present embodiment, the end E2 of the looped belt 42 is disposed in the vicinity of the connection between the linear portion 40A and the curved portion 40C. As shown in fig. 4, at the end R switched from the curved portion 40C to the linear portion 40A, both bending stress and tensile stress act on the fixing tape 40. The bending stress acting on the R-end is axially outward stress on the upper layer side and axially inward stress on the lower layer side of the encircling band 42. Therefore, the resultant force of the bending stress and the tensile stress is cancelled on the upper layer side. That is, the tension stress is relaxed as the upper layer of the looped belt 42 is moved toward the R end, which is the connection portion between the linear portion 40A and the curved portion 40C. Therefore, the end E2 of the wrap tape 42 is provided near the end R, thereby further suppressing interlayer peeling.

[ second embodiment ]

The second embodiment is an example in which the constraint structure of the structure is applied to the battery unit 50. The same components as those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

As shown in fig. 7, a battery cell 50 as a structure constitutes a part of a battery module 52. That is, the plurality of battery cells 50 are arranged and coupled to constitute the battery module 52. As an example, the battery module 52 is housed on the vehicle lower side of a floor panel of an electric vehicle. The battery cell 50 of the present embodiment is an example of an all-solid battery.

The battery unit 50 is formed in a prismatic shape with the vehicle front-rear direction as the stacking direction. Here, in the present embodiment, the stacking direction of the cells 60 and the longitudinal direction of the case 70 are axial directions, and the direction orthogonal to the stacking direction of the cells 60 is a radial direction. The battery unit 50 includes: a plurality of unit cells 60 arranged in the axial direction; a cylindrical case 70 covering the unit cell 60; fixing portions 80 provided at both ends of the housing 70 in the axial direction; and a fixing band 40 wound in the axial direction of the housing 70 so as to be bridged between the pair of fixing portions 80. The cell 60 is an example of a constrained portion as a laminated body, and the fixing portion 80 is an example of a holding portion.

The unit cells 60 are stacked in the axial direction, and the adjacent unit cells 60 are connected in series. The unit cell 60 is axially held by the fixing portion 80. The case 70 is a square tubular member that covers the radial outer sides of the stacked unit cells 60.

In the present embodiment, the stacked unit cells 60 are axially restrained by the fixing band 40. Therefore, if the unit cell 60 swells during a charge/discharge cycle, an axial tensile force F is generated in the fixing band 40. Therefore, the present embodiment also provides the same operational advantages as the first embodiment.

[ remarks ]

In each embodiment, the angle of the carbon fibers CF of the interlaminar tape 44 does not necessarily have to be 90 ° or more and 90 ° or less from the axial direction. In addition, the angles of the carbon fibers CF in the interlayer belt 44 may be different between the interlayer belt 44 on the lower layer side and the interlayer belt 44 on the upper layer side.

In addition, in each embodiment, the following is formed: the proportion of the carbon fibers CF in the 90 ° direction to the entire fixing tape 40 is 10%, but the fixing tape 40 may have 10% to 50% of the carbon fibers CF in the 45 ° to 90 ° direction.

In each embodiment, the end E1 of the wrap tape 42 is bonded to the outer peripheral surface of the tab 30, but the present invention is not limited thereto, and the end E1 of the wrap tape 42 may be bonded to the main body portion 20 or the fastening tape 40. When the tape is adhered to the fastening tape 40, the end E1 of the wrapping tape 42 is preferably adhered and fixed to the adjacently disposed interlayer tape 44, similarly to the end E2. Thus, even if shear stress is intensively applied to the end portion E1, the shear stress is relaxed by the elasticity of the interlayer tape 44, and therefore, delamination between layers can be suppressed.

While the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and it goes without saying that various modifications other than the above embodiments may be made without departing from the scope of the invention.