Bent tube for large unmanned aerial vehicle, its manufacturing method, and its control method for calculating value of cover factor

Abstract

To provide a bent tube for a large unmanned aerial vehicle, which satisfies a condition that a strength of a braided structure is not easily biased between an inside and outside of a bent shape.SOLUTION: A bent tube 1 used as a component of a large unmanned aerial vehicle is formed by combining a braided thread 71 and an axial thread 72, and has a braided structure with a circular cross section. In an inner circumference of a bent part 11 of the bent tube 1, a value of an inner cover factor cf3 (in), which indicates a ratio of a surface area of the braided structure occupied by the braided thread 71 and the axial thread 72, is 100% or less and 80% or more. In an outer circumference of the bent part 11 of the bent tube 1, a value of an outer cover factor cf3(out), which indicates a ratio of a surface area of the braided structure occupied by the braided thread 71 and the axial thread 72, is 100% or less and 80% or more. An axial thread ratio Rm satisfies a condition Rm≥0.50.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a braided bent pipe for a large unmanned aerial vehicle, a manufacturing method thereof, and a calculation and control method of the cover factor value. [Background technology]

[0002] Next-generation mobility such as large drones (large unmanned aerial vehicles) and flying cars is composed of components such as the main body frame, propellers, propeller guards, arms, and skids (legs) (for example, Patent Document 5). Carbon fiber reinforced plastics are often used for these components to reduce weight (for example, Patent Documents 1 to 4). In addition, curved pipes are used for many of the components.

[0003] Bends made of carbon fiber reinforced plastics are usually made using the sheet winding method or the filament winding method, but since it is difficult to make large bends, the hand layup method is the mainstream method for their manufacture.

[0004] However, since the hand layup method is a manual process, mass production is difficult. In this regard, the braiding method, which utilizes braiding technology, has no seams on the surface, making it possible to produce stable quality and making it easy to apply to the curved shapes of curved pipes. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-254361 A [Patent Document 2] Japanese Patent Application Publication No. 50-62271 [Patent Document 3] Japanese Patent Application Publication No. 6-344450 [Patent Document 4] Japanese Patent Application Publication No. 7-223271 [Patent Document 5] Patent No. 6738582 DISCLOSURE OF THEINVENTION [Problem to be solved by the invention]

[0006] When using such braiding techniques to form a curved pipe, it is necessary to braid the braided yarn into a curved shape. However, compared to when the yarn is braided in a straight line, the yarn shrinks on the inner side of the curved shape, while the yarn stretches on the outer side of the curved shape, resulting in unevenness in the braided structure of the curved pipe (difference in strength) and making it difficult to achieve uniformity. As various factors affect the structure, it was difficult to achieve optimal conditions.

[0007] Therefore, an object of the present invention is to provide a curved pipe or the like for a large unmanned aerial vehicle that satisfies the condition that the strength of the braided structure is unlikely to be uneven between the inside and outside of the curved shape. [Means for solving the problem]

[0008] The present invention relates to a bent pipe used as a component of a large unmanned aerial vehicle, The bent tube is formed by combining a braided yarn and an axial yarn, and has a braided structure with a circular cross section, The braided structure includes an axial thread that is integrated along a central axis direction of the curved tube, The width of the braid is b f [mm] The number of braided yarns is n [pieces] The inner diameter of the braided structure is D [mm] The orientation angle of the braid with respect to the central axis direction of the curved tube is θ [°] The width of one cell of the braided structure of the bent pipe is f [mm] The width of the axon is b m [mm] The number of axonemes is n m [Books] The fineness of the braided yarn is f b [dtex] The fineness of the axle is f m [dtex] The tensile modulus of the braided yarn is Eb [GPa] The tensile modulus of the axon is E m [GPa] the value of an inner cover factor cf3(in), which indicates the ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure corresponding to the inner circumference of the bent portion of the bent pipe, calculated by the following (Equation 1) is 100% or less and 80% or more, and the value of an outer cover factor cf3(out), which indicates the ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure corresponding to the outer circumference of the bent portion of the bent pipe, calculated by the following (Equation 1) is 100% or less and 80% or more, Furthermore, the axial yarn ratio R defined by the following formula (2) m But R m It is characterized by satisfying the condition of ≧0.50.

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[0009] In the bent pipe having a circular cross section formed by combining the braided yarn and the axial yarn as described above, the value of the inner cover factor cf3(in) of the inner circumference of the bent portion of the bent pipe and the value of the outer cover factor cf3(out) of the outer circumference of the bent portion of the bent pipe satisfy the above conditions, and further, the axial yarn ratio R m R m If the condition of ≧0.50 is satisfied, it is possible to achieve a configuration in which bias (difference in strength) in the strength of the braided structure is unlikely to occur between the inside and outside of the bent pipe. It also makes it possible to design a curved structure that is less prone to unevenness in the strength of the braided structure between the inside and outside of the curved tube, and it makes it possible to reduce the number of joints in the components of large unmanned aerial vehicles (for large drones, the main frame, propellers, propeller guards, arms, skids, etc.) and reduce the number of parts, making it possible to reduce weight. In addition, it will be possible to change the components of large unmanned aerial vehicles from the aluminum that is normally used to carbon fiber reinforced plastic, which will result in lighter weight, higher rigidity, and excellent vibration damping properties.

[0010] The present invention may also be characterized in that in the curved pipe for a large unmanned aerial vehicle having a braided structure formed by combining braided yarns, the braided yarn has a rectangular tape-shaped cross section. Also, in the curved pipe for a large unmanned aerial vehicle having a braided structure formed by combining braided yarns and axial yarns, the braided yarns and axial yarns have a rectangular tape-shaped cross section.

[0011] According to the above configuration, the value of the inner cover factor of the inner circumference of the bent portion of the curved pipe and the value of the outer cover factor of the outer circumference of the bent portion of the curved pipe can be increased, making it possible to make it less likely that a bias in strength (difference in strength) will occur in the braided structure between the inside and outside of the curved pipe.

[0012] The present invention also provides a method for manufacturing a curved tube that is formed by combining a braided yarn and an axial yarn and has a braided structure with a circular cross section and is used as a component of a large unmanned aerial vehicle, comprising: The bent pipe is The width of the braid is b f [mm] The number of braided yarns is n [pieces] The inner diameter of the braided structure is D [mm] The orientation angle of the braid with respect to the central axis direction of the curved tube is θ [°] The width of one cell of the braided structure of the bent pipe is f [mm] The width of the axon is b m [mm] The number of axonemes is n m [Books] The fineness of the braided yarn is f b [dtex] The fineness of the axle is f m [dtex] The tensile modulus of the braided yarn is E b [GPa] The tensile modulus of the axon is E m[GPa] the value of an inner cover factor cf3(in), which indicates the ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure corresponding to the inner circumference of the bent portion of the curved pipe, calculated by the following (Equation 3) is 100% or less and 80% or more, and the value of an outer cover factor cf3(out), which indicates the ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure corresponding to the outer circumference of the bent portion of the curved pipe, calculated by the following (Equation 3) is 100% or less and 80% or more, Furthermore, the axial yarn ratio R defined by the following formula (4) m But R m The curved tube is characterized in that the axial yarn is arranged along the central axial direction of the curved tube on the outer periphery of a mandrel so as to satisfy the condition of .gtoreq.0.50, and the braided yarn and the axial yarn are combined to form the curved tube.

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[0013] In a curved pipe having a circular cross section and formed by combining a braided yarn and an axial yarn, the value of the inner cover factor cf3(in) of the inner circumference of the curved portion of the curved pipe and the value of the outer cover factor cf3(out) of the outer circumference of the curved portion of the curved pipe satisfy the above conditions, and further, the axial yarn ratio R m R m If the condition of ≧0.50 is satisfied, it is possible to manufacture a curved pipe having a braided structure in which there is little bias (difference in strength) in the strength of the braided structure between the inside and outside of the curved pipe.

[0014] The present invention also provides a method for calculating and controlling a cover factor cf3 of a curved tube for a large unmanned aerial vehicle, the curved tube being formed by combining a braided yarn and an axial yarn arranged along the central axial direction of the curved tube and having a braided structure with a circular cross section, the curved tube being used as a component of the large unmanned aerial vehicle, the method indicating a ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure, (1A) The width b of the braid f [mm], the number of the braided yarns n [pieces], the inner diameter D [mm] of the braided structure, the orientation angle θ [°] of the braided yarns with respect to the central axis direction of the curved pipe, the width f [mm] per cell of the braided structure of the curved pipe, and the width b of the axial yarn m [mm], the number of said axon threads is n m storing the book in a storage device; (1B) The width b of the braid stored in step (1A) is calculated by the following formula (5): f [mm], the number of the braided yarns n [pieces], the inner diameter D [mm] of the braided structure, the orientation angle θ [°] of the braided yarns with respect to the central axis direction of the curved pipe, the width f [mm] per cell of the braided structure of the curved pipe, and the width b of the axial yarn m [mm], the number of said axle threads n m [this] to calculate the value of the cover factor cf3; (1C) outputting the value of the cover factor cf3 calculated in the step (1B); is executed by the control device.

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[0015] According to the above method, in a three-dimensional curved pipe formed by combining a braided yarn and an axial yarn and having a circular cross section, the value of the inner cover factor cf3(in) of the inner circumference of the curved portion of the curved pipe and the value of the outer cover factor cf3(out) of the outer circumference of the curved portion of the curved pipe, which are indicators for making it difficult for the braided structure to have a bias (difference in strength) in strength between the inside and outside of the curved pipe, are calculated by multiplying the width b of the braided yarn by the value of the inner cover factor cf3(in) of the inner circumference of the curved portion of the curved pipe and the outer cover factor cf3(out) of the outer circumference of the curved portion of the curved pipe. f[mm], number of braided yarns n [pieces], inner diameter D of the braided structure [mm], orientation angle θ of the braided yarn with respect to the central axis direction of the curved tube [°], width f per cell of the braided structure of the curved tube [mm], width b of the axial yarn m [mm] and the number of axon threads n m Based on two-dimensional data such as [book], it can be calculated as a value that is close to the calculated value based on three-dimensional data. Effect of the Invention

[0016] It is possible to provide a curved pipe for a large unmanned aerial vehicle that satisfies the condition that the strength of the braided structure is unlikely to be uneven between the inside and outside of the curved shape. [Brief description of the drawings]

[0017] [Figure 1] FIG. 4 is an explanatory diagram of a curved pipe according to the embodiment. [Diagram 2] 5A to 5C are explanatory diagrams of a manufacturing method of a curved pipe according to the present embodiment. [Diagram 3] FIG. 2 is an explanatory diagram of the braided structure (one cell) of the curved pipe according to the present embodiment. [Figure 4] FIG. 4 is an explanatory diagram of the orientation angle of a curved pipe according to the embodiment. [Diagram 5] FIG. [Figure 6] FIG. 4 is an explanatory diagram of a bent portion of a curved pipe. [Figure 7] FIG. 2 is a schematic diagram of the shape of the braid and the axial yarn. [Figure 8] 1 is an explanatory diagram for comparing the two-dimensional area of ​​a braided structure of a curved pipe with the area of ​​a three-dimensional torus shape. [Figure 9] 1 is an explanatory diagram for comparing the two-dimensional area of ​​a braided structure of a curved pipe with the area of ​​a three-dimensional torus shape. [Figure 10] FIG. 1 is an explanatory diagram of a large drone using a curved pipe according to this embodiment. [Figure 11] 13 is a graph showing the relationship between the orientation angle and the cover factor value according to Example A. [Figure 12]13 is a graph showing the relationship between the orientation angle and the cover factor value according to Example B. [Figure 13] 13 is a graph showing the relationship between the orientation angle and the cover factor value according to Example C. [Figure 14] FIG. 2 is an explanatory diagram of a mandrel used in manufacturing the curved pipe of the first embodiment. [Figure 15] 1A and 1B are explanatory diagrams of a method for manufacturing a curved pipe (straight portion) according to an embodiment and a comparative example, respectively; [Figure 16] FIG. 4 is an explanatory diagram of the inside and outside of the central part of the bent portion of the curved pipe according to the embodiment and the comparative example. [Figure 17] FIG. 1 is an explanatory diagram of a destructive test of curved pipes according to examples and comparative examples. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (Embodiment) Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The curved pipe 1 of this embodiment is used as a component of a large drone 100 (corresponding to a large unmanned aerial vehicle) that transports cargo unmanned, as shown in Fig. 10. For example, the curved pipe 1 is used in a main body frame 101 (forming a space for storing cargo to be transported), a propeller 102, a propeller guard 103, an arm 104, and a skid 105 (legs) that constitute the large drone 100. The main body frame 101, the propeller 102, the propeller guard 103, the arm 104, and the skid 105 that constitute the large drone 100 have curved parts in their shapes, and are required to be lightweight, highly rigid, and have excellent vibration damping properties.

[0019] In this embodiment, a large drone 100 is used as an example of a large unmanned aerial vehicle, and a large unmanned aerial vehicle is assumed to have an axis distance of the propellers 102 of 1000 mm or more.

[0020] (Bent Pipe 1) The curved pipe 1 is a pipe made of fiber reinforced plastic (FRP) that is configured by a braided structure of braided yarn (carbon fiber material, etc.) and resin molding. As shown in Fig. 1, the curved pipe 1 has a circular cross section and is bent at a certain bending angle. For example, when the curved pipe 1 of this embodiment is used for the propeller guard 103 or skid 105 (legs) of a large drone 100, it is bent at a certain bending angle as shown in Fig. 1.

[0021] The braided structure of the curved pipe 1 is formed by combining multiple braided yarns 71 and axial yarns 72 with each other, as shown in Fig. 3. The braided yarns 71 cross at a predetermined orientation angle θ [°] with respect to the central axial direction of the curved pipe 1, as shown in Fig. 3. The axial yarns 72 are incorporated into the multiple braided yarns 71 so as to be parallel to the central axial direction of the curved pipe 1, from the viewpoint of improving the strength of the curved pipe 1 in the central axial direction, etc.

[0022] The braided yarn 71 and the axial yarn 72 are made of a high-strength material, since they serve as reinforcing members for the curved pipe 1. Specific examples include carbon fiber, aramid fiber, glass fiber, basalt fiber, boron fiber, silicon carbide (SiC) fiber, and the like, and are not particularly limited as long as they are publicly known fibers with high strength. In order to maintain the shape of the braided curved pipe 1, nylon, polypropylene, polyethylene terephthalate, polylactic acid, and the like may be used as part of the fibers.

[0023] The resin material used for resin molding for the braided structure of the curved pipe 1 may be any known thermosetting resin, such as phenol resin, epoxy resin, or thermosetting polyimide resin.

[0024] (Braided structure of the bent portion of the bent pipe 1) When forming a curved pipe 1 with a braided structure, it is necessary to braid the braided yarns 71 and axial yarns 72 of the curved portion 11 in a curved shape as shown in Fig. 1, but compared to when the braided yarns 71 and axial yarns 72 are braided in a straight line, the braided yarns 71 and axial yarns 72 are subject to a shrinking action on the inner circumferential side 11A of the curved portion 11, while the braided yarns 71 and axial yarns 72 are subject to an expanding action on the outer circumferential side 11B of the curved portion 11, which may cause an unevenness (difference in strength) in the braided structure of the curved pipe 1. If an unevenness occurs in the braided structure of the curved pipe 1, the high rigidity, vibration damping performance, and impact resistance of the curved pipe 1 will decrease.

[0025] Therefore, the braided structure of the bent portion of the curved pipe 1 is formed using an index (value) called the cover factor cf (Equation 6, Equation 7, Equation 9), which indicates the proportion of the surface area of ​​the braided structure of the curved pipe 1 that is occupied by the braided yarn 71 (and the axial yarn 72), and serves as an index of strength of the curved pipe 1 having a braided structure with a circular cross section. Here, as shown in Figures 1 and 3, the width f [mm] per cell of the braided structure (one section surrounded by braided yarn 71: see Figure 3 (B)) is the same on the inner side 11A and outer side 11B of the curved portion 11 of the curved pipe 1, but the orientation angle θ [°] with respect to the central axis direction of the curved pipe 1 is different, so it is necessary to calculate the inner cover factor cf (in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the outer cover factor cf (out) of the outer side 11B of the curved portion 11 of the curved pipe 1. In addition, when calculating the cover factor cf, it is necessary to separately consider the case where the cells of the braided structure of the curved pipe 1 are composed only of the braided yarn 71 (cf1) and the case where the cells of the braided structure of the curved pipe 1 include the braided yarn 71 and the axial yarn 72 (cf2).

[0026] Specifically, as shown in FIG. 3(A), when the braided structure of the curved pipe 1 is composed of only the braid 71, the width b fFrom values ​​based on two-dimensional data such as the length of the braided yarn 71 (mm), the number n [pieces] of the braided yarns 71, the inner diameter D [mm] of the curved pipe 1 (braided structure), and the orientation angle θ [°] of the braided yarns 71 relative to the central axis direction of the curved pipe 1, the value of the inner cover factor cf1(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf1(out) of the outer side 11B of the curved portion 11 of the curved pipe 1, calculated using the following (Equation 6), are calculated.

[0027]

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[0028] On the other hand, as shown in FIG. 3B, when the cell of the braided structure of the curved pipe 1 includes a braid 71 and an axial thread 72, the width b f In addition to the inner diameter D [mm] of the curved pipe 1 (braided structure), and the orientation angle θ [°] of the braid 71 with respect to the central axis direction of the curved pipe 1, the width f [mm] of one cell (one section surrounded by the braid 71: see FIG. 3(B)) of the braided structure of the curved pipe 1, the width b m [mm] and the number n of axial threads 72 m From values ​​based on two-dimensional data such as [pieces], the value of the inner cover factor cf2(in) of the inner side 11A of the curved portion 11 of the curved pipe 1, and the value of the outer cover factor cf2(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 are calculated using the following (Equation 7).

[0029]

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[0030] Here, it is believed that a configuration in which there is less likelihood of bias (difference in strength) in the braided structure between the inside and outside of the curved pipe can be achieved when the cells of the braided structure of the curved pipe 1 include not only the braided yarn 71 but also the axial yarn 72. When the cells of the braided structure of the curved pipe 1 include not only the braided yarns 71 but also the axial yarns 72, the number of braided yarns 71 is n [pieces], the number of axial yarns 72 is n m [Number of pieces], fineness of braided yarn 71 f b [dtex], fineness of axial yarn 72 m [dtex], tensile modulus E of braided yarn 71 b [GPa], tensile modulus of elasticity of axon 72 E m From the values ​​based on two-dimensional data such as [GPa], the axial ratio R defined by the following (Equation 8) is m But R m It is preferable to satisfy the condition ≧0.50.

[0031]

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[0032] In consideration of the above, when the braided structure of the curved pipe 1 includes the braided yarn 71 and the axial yarn 72 (see the braided structure of the curved pipe 1 in FIG. 3), the calculation of the value of the cover factor cf3 takes into consideration the cover factor cf1 in the cell in which the braided structure of the curved pipe 1 is composed only of the braided yarn 71 as shown in FIG. 3(A) and the cover factor cf2 in the cell in which the braided structure of the curved pipe 1 is composed of the braided yarn 71 and the axial yarn 72 as shown in FIG. 3(B). The inner cover factor cf3(in) calculated by the following (Equation 9) is in the range of 100% to 80%, and the outer cover factor cf3(out) calculated by the following (Equation 9) is in the range of 100% to 80%, and the axial yarn ratio R defined by the above (Equation 8) is also in the range of 100% to 80%, and the cover factor cf3(out) is in the range of 100% to 80%, and the cover factor cf3(in) calculated by the following (Equation 9) is in the range of 100% to 80%, and the axial yarn ratio R m But R mBy satisfying the condition of ≧0.50, a braided structure is formed in the curved portion 11 of the curved pipe 1 such that there is no bias (difference in strength) in the strength of the braided structure between the inner side 11A and the outer side 11B of the curved portion 11 of the curved pipe 1 (see [Verification based on Examples 1 to 5 and Comparative Examples 1 to 5] in the examples described below).

[0033]

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[0034] As described above, the value of the inner cover factor cf(in) is set to be in the range of 100% or less and 80% or more, and the value of the outer cover factor cf(out) is set to be in the range of 100% or less and 80% or more. This is because, if the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) exceeds 100%, it will be greater than the surface area of ​​the curved pipe 1 formed by the braided structure of the braided yarns 71 (braided yarns 71 and axial yarns 72), and part of the braided yarns 71 (braided yarns 71 and axial yarns 72) will float from the surface of the curved pipe 1, and a load will be applied to the floated part or its surroundings, which may reduce the high rigidity, vibration damping performance, and impact resistance of the curved pipe 1. Also, if the value of the inner cover factor cf(in) is less than 80% or the value of the outer cover factor cf(out) is less than 80, a bias (difference in strength) will occur in the strength of the braided structure between the inner peripheral side 11A and the outer peripheral side 11B of the bent portion 11 of the curved pipe 1, which may reduce the high rigidity, vibration damping performance, and impact resistance of the curved pipe 1.

[0035] (Shapes of braided yarn 71 and axial yarn 72) Furthermore, when carbon fiber materials (6k, 12k) are used for the braid 71 and the axial thread 72, since the fibers are a bundle of thin threads, it is unlikely that the cross section will be a perfect circle (see FIG. 7) when the braided structure of the curved pipe 1 is formed. Therefore, it is preferable that the shape of the fibers of the braid 71 and the axial thread 72 has a rectangular tape shape (see FIG. 7). This makes it possible to increase the value of the inner cover factor cf(in) of the inner circumference of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf(out) of the outer circumference of the curved portion 11 of the curved pipe 1, and to achieve a configuration in which bias (difference in strength) in the strength of the braided structure is less likely to occur between the inside and outside of the curved pipe.

[0036] (Method for calculating and controlling the cover factor of a curved tube made only of braided yarn) Prior to producing the braided structure of the curved pipe 1, we will explain the calculation process (calculation control method) for the value of the inner cover factor cf1(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf1(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 when the braided structure of the curved pipe 1 is composed only of braided yarn 71 (when the braided structure of the curved pipe 1 does not include an axial yarn 72).

[0037] First, the user inputs the width b of the braid 71 that the user expects through an input unit of an information processing device (a control device such as a personal computer). f The values ​​of various parameters, such as the length [mm], the number n [pieces] of braided yarns 71, the inner diameter D [mm] of the curved pipe 1, and the orientation angle θ [°] of the braided yarns 71 relative to the central axis direction of the curved pipe 1 (the orientation angle θ [°] of the inner side 11A of the curved portion 11 of the curved pipe 1, and the orientation angle θ [°] of the outer side 11B of the curved portion 11 of the curved pipe 1), are input and stored in a memory unit provided in the information processing device (step (1A)).

[0038] Next, the user inputs the width b of the braid 71 stored in the storage unit in the step (1A) into the above formula (6) stored as a program in the storage unit of the information processing device. fThe values ​​of various parameters, such as the length of the braided yarn 71 [mm], the number n [pieces] of the braided yarns 71, the inner diameter D [mm] of the curved pipe 1, and the orientation angle θ [°] of the braided yarn 71 relative to the central axis direction of the curved pipe 1 (the orientation angle θ [°] of the inner side 11A of the curved portion 11 of the curved pipe 1, and the orientation angle θ [°] of the outer side 11B of the curved portion 11 of the curved pipe 1), are substituted to calculate the inner cover factor cf1(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the outer cover factor cf1(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 (step (1B)).

[0039] Then, the value of the inner cover factor cf1(in) and the value of the outer cover factor cf1(out) calculated in the above step (1B) are displayed on a display connected to the information processing device (step (1C)).

[0040] In this way, when the value of the inner cover factor cf1(in) shown on the display satisfies the condition of 100% or less and 80% or more, and the value of the outer cover factor cf1(out) satisfies the condition of 100% or less and 80% or more, the various parameters assumed by the user are presumed to be values ​​that do not result in any bias in terms of strength (difference in strength) of the braided structure between the inner side 11A and outer side 11B of the bent portion 11 of the curved pipe 1, and these are taken as the design values ​​(specifications) of the braided structure of the curved pipe 1. On the other hand, if the value of the inner cover factor cf1(in) does not satisfy the condition of 100% or less and 80% or more, or the value of the outer cover factor cf1(out) does not satisfy the condition of 100% or less and 80% or more, it is presumed that the various parameters assumed by the user are values ​​that will cause a bias in strength (difference in strength) of the braided structure between the inner side 11A and the outer side 11B of the bent portion 11 of the curved pipe 1, the values ​​of the various parameters are changed, and the processing of the above steps (1A) to (1C) is performed again.

[0041] According to the above method, in the curved pipe 1 formed by combining the braided yarns 71 and having a circular cross section, the value of the inner cover factor cf1(in) of the inner circumferential side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf1(out) of the outer circumferential side 11B of the curved portion 11 of the curved pipe 1 are indexes for making it difficult for the braided structure to have a bias (difference in strength) in strength between the inside and outside of the curved pipe 1, and are calculated by multiplying the value of the inner cover factor cf1(in) of the inner circumferential side 11A of the curved portion 11 of the curved pipe 1 by the width b of the braided yarns 71. f Based on two-dimensional data such as the number of strands of thread 71 (n [pieces]), the inner diameter D [mm] of the braided structure, and the orientation angle θ [°] of the braided thread 71 relative to the central axis direction of the curved pipe 1, it can be calculated as a value that is close to the calculated value calculated based on three-dimensional data.

[0042] (Method for calculating and controlling the cover factor of a curved pipe including braided yarn and axial yarn) Next, we will explain the calculation process (calculation control method) for the value of the inner cover factor cf3(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf3(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 when the braided structure of the curved pipe 1 includes a braided yarn 71 and an axial yarn 72 (see the braided structure of the curved pipe 1 in Figure 3).

[0043] First, the user inputs the width b of the braid 71 that the user expects through an input unit of an information processing device (a control device such as a personal computer). f [mm], number n [pieces] of braided yarns 71, inner diameter D [mm] of curved pipe 1, orientation angle θ [°] of braided yarn 71 with respect to the central axis direction of curved pipe 1 (orientation angle θ [°] of inner circumferential side 11A of curved portion 11 of curved pipe 1, and orientation angle θ [°] of outer circumferential side 11B of curved portion 11 of curved pipe 1), width f [mm] per cell of braided structure of curved pipe 1, width b of axial yarn 72 m [mm] and the number n of axial threads 72 m The values ​​of various parameters of [this] are input and stored in a storage unit of the information processing device (step (2A)).

[0044] Next, the user inputs the width b of the braid 71 stored in the storage unit in the step (2A) into the above formula (9) stored as a program in the storage unit of the information processing device. f [mm], number n [pieces] of braided yarns 71, inner diameter D [mm] of curved pipe 1, orientation angle θ [°] of braided yarn 71 with respect to the central axis direction of curved pipe 1 (orientation angle θ [°] of inner circumferential side 11A of curved portion 11 of curved pipe 1, and orientation angle θ [°] of outer circumferential side 11B of curved portion 11 of curved pipe 1), width f [mm] per cell of braided structure of curved pipe 1, width b of axial yarn 72 m [mm] and the number n of axial threads 72 m The values ​​of the various parameters in [this] are substituted to calculate the inner cover factor cf3(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the outer cover factor cf3(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 (step (2B)).

[0045] Then, the value of the inner cover factor cf3(in) and the value of the outer cover factor cf3(out) calculated in the above step (2B) are displayed on a display connected to the information processing device (step (2C)).

[0046] In this way, when the value of the inner cover factor cf3(in) shown on the display satisfies the condition of 100% or less and 80% or more, and the value of the outer cover factor cf3(out) satisfies the condition of 100% or less and 80% or more, the various parameters assumed by the user are presumed to be values ​​that do not result in any bias in strength (difference in strength) of the braided structure between the inner side 11A and outer side 11B of the bent portion 11 of the curved pipe 1, and these are set as the design values ​​(specifications) of the braided structure of the curved pipe 1. On the other hand, if the value of the inner cover factor cf3(in) does not satisfy the condition of 100% or less and 80% or more, or the value of the outer cover factor cf3(out) does not satisfy the condition of 100% or less and 80% or more, it is presumed that the various parameters assumed by the user are values ​​that will cause a bias in strength (difference in strength) of the braided structure between the inner side 11A and the outer side 11B of the bent portion 11 of the curved pipe 1, the values ​​of the various parameters are changed, and the processing of the above steps (2A) to (2C) is performed again.

[0047] According to the above method, in a three-dimensional curved pipe 1 formed by combining the braided yarn 71 and the axial yarn 72 and having a circular cross section, the value of the inner cover factor cf3(in) of the inner circumferential side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf3(out) of the outer circumferential side 11B of the curved portion 11 of the curved pipe 1 are indexes for making it difficult for the braided structure to have a bias (difference in strength) in strength between the inside and outside of the curved pipe 1, and are calculated by multiplying the value of the inner cover factor cf3(in) of the inner circumferential side 11A of the curved portion 11 of the curved pipe 1 by the width b of the braided yarn 71. f [mm], the number of braided yarns 71 n [pieces], the inner diameter D of the braided structure [mm], the orientation angle θ [°] of the braided yarns 71 with respect to the central axis direction of the curved tube 1, the width f [mm] per cell of the braided structure of the curved tube 1, and the width b of the axial yarn 72. m [mm] and the number n of axial threads 72 m Based on two-dimensional data such as [book], it can be calculated as a value that is close to the calculated value based on three-dimensional data.

[0048] (Manufacturing method of curved pipe 1: Braiding process) Next, a method for manufacturing the curved pipe 1 will be described. As shown in Fig. 2(A), the braided structure of the curved pipe 1 is produced using a circular braider 20. The axial yarn 72 is fed from the bottom of the circular braider 20 through a fixed tube 22, and the braided yarn 71 is wound around a spindle 21. In addition, as shown in FIG. 5 , a cylindrical mandrel 30 is installed at the center of the circular braider 20, and has a curved portion 31 that forms the curved portion 11 of the curved pipe 1 to be manufactured, and straight portions 32 and 33 at both ends of the curved portion 31. The braided yarn 71 and the axial yarn 72 are combined on the outer periphery of the upper part of the mandrel 30 to form the braided structure of the curved pipe 1. Specifically, as shown in Figure 2 (B), while the mandrel 30 is controlled to be pulled out by a robot arm (not shown) so that the inner surface of the curved pipe 1 to be braided on the surface of the mandrel 30 and the circular braider 20 are kept parallel, the spindle 21 moves along the track 23, combining the braided yarn 71 and the axial yarn 72, and a braided structure of the curved pipe 1 is formed on the surface of the mandrel 30. The diameter of the cylindrical mandrel 30 is the same as the inner diameter D of the curved pipe 1 to be braided.

[0049] Here, when the braided structure of the curved pipe 1 is composed only of the braid 71 (when the braided structure of the curved pipe 1 does not include the axial thread 72), the width b of the braid 71 is f The values ​​of various parameters, namely, the length [mm], the number n [pieces] of the braided yarns 71, the inner diameter D [mm] of the curved pipe 1 (braided structure), and the orientation angle θ [°] of the braided yarns 71 with respect to the central axis direction of the curved pipe 1, must satisfy the conditions that there is no bias (difference in strength) in the strength of the braided structure between the inner side 11A and outer side 11B of the curved portion 11 of the curved pipe 1, within the range of the inner cover factor cf1(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 (calculated by the above formula 6) (80% or more and 100% or less), and within the range of the outer cover factor cf1(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 (80% or more and 100% or less), calculated by the above formula 6. In other words, the various parameters mentioned above must satisfy the condition that the value of the inner cover factor cf1(in) calculated by the above-mentioned "method for controlling calculation of the cover factor of a curved tube including braided yarn" is 80% or more and 100% or less, and that the value of the outer cover factor cf1(out) is 80% or more and 100% or less.

[0050] In this way, in a curved pipe 1 formed by combining braided yarns 71 and having a braided structure with a circular cross section, if the value of the inner cover factor cf1(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf1(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 satisfy the above conditions, it is possible to manufacture a curved pipe 1 with a braided structure in which there is little bias (difference in strength) in the strength of the braided structure between the inside and outside of the curved pipe 1.

[0051] In addition, when the braided structure of the curved pipe 1 includes the braided yarn 71 and the axial yarn 72 (see the braided structure of the curved pipe 1 in FIG. 3), the width b f In addition to the inner diameter D [mm] of the curved pipe 1 (braided structure), and the orientation angle θ [°] of the braid 71 with respect to the central axis direction of the curved pipe 1, the width f [mm] of one cell (one section surrounded by the braid 71: see FIG. 3(B)) of the braided structure of the curved pipe 1, the width b m [mm] and the number n of axial threads 72 m [This] must satisfy the conditions that there is no bias (difference in strength) in the strength of the braided structure between the inner side 11A and outer side 11B of the curved portion 11 of the curved pipe 1, that the inner cover factor cf3(in) of the inner side 11A of the curved portion 11 of the curved pipe 1, calculated by the above (Equation 9), is within the range (80% or more and 100% or less), and that the outer cover factor cf3(out) of the outer side 11B of the curved portion 11 of the curved pipe 1, calculated by the above (Equation 9), is within the range (80% or more and 100% or less). In other words, the above various parameters must satisfy the condition that the value of the inner cover factor cf3(in) calculated by the above-mentioned "Cover factor calculation and control method for a curved tube including braided yarn and axial yarn" is 80% or more and 100% or less, and the value of the outer cover factor cf3(out) is 80% or more and 100% or less.

[0052] In this way, in a curved pipe 1 having a braided structure with a circular cross section formed by combining a braided yarn 71 and an axial yarn 72, if the value of the inner cover factor cf3(in) of the inner side 11A of the curved portion 11 of the curved pipe 1 and the value of the outer cover factor cf3(out) of the outer side 11B of the curved portion 11 of the curved pipe 1 satisfy the above conditions, it is possible to manufacture a curved pipe 1 having a braided structure in which there is little bias (difference in strength) in the strength of the braided structure between the inside and outside of the curved pipe 1.

[0053] In addition, the orientation angle θ [°] is calculated as two-dimensional data using the following equation (10), assuming that the revolution angular velocity of the spindle 21 is ω [rad / s], the diameter D [mm] of the mandrel 30, and the take-up speed of the mandrel 30 is v [mm / s], as shown in Figure 4.

[0054]

number

[0055] Furthermore, as shown in Figure 6, if the radius of the curved pipe 1 is R, the radius of the inner circumference of the curved portion 11 of the curved pipe 1 is R1, the radius of the outer circumference of the curved portion 11 of the curved pipe 1 is R2, the length of the inner arc of the curved portion 11 of the curved pipe 1 is L1, the length of the outer arc of the curved portion 11 of the curved pipe 1 is L2, and the outer diameter of the curved pipe 1 is 2a, the relationship between the radius and the circumference gives the following relationship (Equation 11).

[0056]

number

[0057]

number

[0058]

number

[0059] (Manufacturing method of curved pipe 1: resin molding process) Furthermore, after the braided structure of the curved pipe 1 is formed on the surface of the mandrel 30, a resin molding process is performed to fill gaps in the braided structure and to increase rigidity, vibration damping performance, and impact resistance. Examples of resin molding processes for the braided structure of the curved pipe 1 include a method in which the braided structure of the curved pipe 1 is impregnated with a resin component such as phenolic resin, epoxy resin, or thermosetting polyimide resin by heat treatment and then hardened, and a method in which the braided structure of the curved pipe 1 is formed using braided yarns 71 (and axial yarns 72) made of fibers (prepregs) previously impregnated with a resin component such as phenolic resin, epoxy resin, or thermosetting polyimide resin, and then hardened by heat treatment. The resin molding process is not particularly limited, and any known method can be used, such as RTM (resin transfer molding: resin injection) molding, VaRTM (vacuum-assisted resin transfer molding: vacuum-assisted resin injection) molding, autoclave molding, press molding, internal pressure molding, shrink tape (heat-shrinkable film) molding, etc. Through the above steps, a curved pipe 1 made of fiber reinforced plastic (FRP) having a braided structure and resin molding is manufactured.

[0060] (Regarding the validity of the cover factor value) In the present invention, the braided structure of the bent portion 11 of the curved pipe 1 is formed using a value called the cover factor cf (see Equation 6, Equation 7, and Equation 9), which is an indicator of the strength of the curved pipe 1 having a braided structure with a circular cross section. In the above embodiment, the braided structure of the curved portion 11 of the curved pipe 1 is formed based on the two-dimensional cell area and cover factor cf. However, in reality, the curved pipe 1 is braided into a three-dimensional torus shape, so it is necessary to consider the cell area and cover factor cf in three dimensions. In order to prove that the value of the cover factor cf calculated by the above (Equation 6), (Equation 7), and (Equation 9) is valid, the rectangle inscribed by each vertex of the cell shown in Fig. 8 (the area e × f in Fig. 8) was defined as an expanded cell, and the two-dimensional expanded cell area S' when the number of braided yarns is n was compared with the expanded area S on the three-dimensional torus surface to investigate the degree of error that would occur.

[0061] As shown in Figure 8, if the width of one cell (one section surrounded by braided yarn 71) of the braided structure on the outer circumferential side 11B of the bent portion 11 of the curved pipe 1 is f, the vertical width is e, and the number of braided yarns is n, the width f is calculated using the following formula (14) and the vertical width e is calculated using the following formula (15), and therefore the two-dimensional expansion area S' is calculated using the following formula (16).

number

number

number

[0062] On the other hand, the expansion area S (micro area) on the three-dimensional torus surface of the curved pipe 1 can be calculated from the circumference in the torus direction (rotation direction around the z-axis) and the circumference of the torus cross section (φ direction) shown in Figure 9. That is, the infinitesimal area dS (infinite section) is Rotation direction around the z axis: 2π(R+a cosφ)dz Length of the circumference (φ direction) of the torus cross section: adφ (see Figure 9) Therefore, it is calculated using the following (Equation 17).

number

[0063] And the integral interval (see FIG. 9) is as follows: Rotation direction around the z-axis: (-β / 2) → (β / 2) φ direction: (-2π / n)→(2π / n) Here, β in (Equation 18) indicates the ratio of the vertical width of the expanded cell to the entire circumference of the torus. As a result, the expanded area S on the three-dimensional torus surface is calculated by the following (Equation 19).

number

number

[0064] The relationship (ratio) between the two-dimensional expanded cell area S' calculated from the above (Equation 16) and the expanded area S on the three-dimensional torus surface calculated from the above (Equation 19) is S' / S = 1.002, with an error within 1%, when the conditions of the curved pipe 1 are, for example, the orientation angle θ2 with respect to the central axis direction of the curved pipe 1 = 51.4°, the radius R of the curved pipe 1 = 100 mm, the radius a of the curved pipe 1 = 16 mm, and the number of braided yarns n = 24. Therefore, the cover factor of a three-dimensional torus shape can be considered to be the same as that of a linear braid at the moment of braiding, and there is no problem in approximating it to two dimensions.

[0065] As described above, it is possible to design a curved structure that is less likely to cause unevenness in the strength of the braided structure between the inside and outside of the curved tube 1, and it is possible to reduce the number of joints in the components of the large unmanned aerial vehicle (in the case of a large drone 100, the main body frame 101, propeller 102, propeller guard 103, arm 104, skid 105, etc.) and thereby reduce the number of parts, making it possible to reduce weight. In addition, it will be possible to change the components of the large drone 100 from the aluminum that is normally used to carbon fiber reinforced plastic, resulting in lighter weight, higher rigidity, and superior vibration damping properties.

[0066] (Other embodiments) In the above embodiment, a curved pipe 1 is used in the main body frame 101, propeller 102, propeller guard 103, arm 104, and skid 105 that make up a large drone 100, which is a large unmanned aerial vehicle. However, the curved pipe 1 may also be used in a manned aircraft (for example, a large drone-type flying taxi).

[0067] The process of calculating the cover factor executed in the above embodiment may be installed as software (program, data) in an information processing device such as a mobile information device such as a smartphone, a portable computer, a laptop computer, a notebook computer, a tablet PC, a handheld PC, a PDA (Personal Data Assistant), etc., and executed. In this case, the software may be downloaded from a server or the like by a communication means and stored in a storage device (such as a flash memory) in the mobile information device. The communication means may be a transmission path capable of two-way communication such as the Internet or cable television, or may be a broadcast that transmits information in only one direction.

[0068] In addition, the software that executes the process of calculating the cover factor may be stored in a storage medium such as a CD-ROM, DVD-ROM, MO (magneto-optical disk), hard disk, flash memory, etc., and may be read from the storage medium as needed and installed in the memory unit of the information processing device.

[0069] In addition, the contents described in the above embodiments may be implemented as a service executed between an information terminal such as a smartphone or a PC (input of various parameters) and an information processing device (calculation of the cover factor) via the Internet (communication line).

[0070] The processes executed in the above-described embodiment may be programs installed on a smartphone or a PC. The programs may be stored in a storage medium.

[0071] Furthermore, the processes executed in the above-described embodiment may be realized as a calculation control device that calculates a cover factor using an information processing device.

[0072] Although the embodiments of the present invention have been described above, they are merely illustrative examples and do not limit the present invention, and the specific configurations of each means etc. can be appropriately modified in design. Furthermore, the effects described in the embodiments of the present invention are merely a list of the most preferable effects resulting from the present invention, and the effects of the present invention are not limited to those described in the embodiments of the present invention. EXAMPLES

[0073] (Example of calculation of cover factor for bent pipe) Examples of calculation of the cover factor of a curved pipe are shown as Examples A to C.

[0074] Example A In Example A, as shown in the graph of FIG. 11, the width b f The inner diameter of the curved pipe (outer diameter of the mandrel) D [mm] was 2 mm, the inner diameter of the curved pipe (outer diameter of the mandrel) D [mm] was 26 mm, the number of braided yarns n [pieces] was 32, and the number of axial yarns was 0. The radius R of the curved pipe was changed to 60 mm, 90 mm, or 120 mm, and the orientation angle θ1 [°] on the inner side of the bent part of the curved pipe was plotted on the horizontal axis, and the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) was plotted on the vertical axis. The orientation angle θ2 [°] on the outer circumferential side of the bent portion of the curved pipe can be calculated using the above formulas (11) to (13), and is therefore omitted in FIG.

[0075] In Example A, the number of braided yarns n is 32, which is fewer than the number of braided yarns in Example B (48) and Example C (64), as described below. Therefore, even if the orientation angle θ1 and the orientation angle θ2 are relatively large, the condition that the value of the inner cover factor cf(in) is 100% or less and 80% or more, and the condition that the value of the outer cover factor cf(out) is 100% or less and 80% or more can be satisfied.

[0076] Furthermore, in Example A, when the radius R of the curved pipe is changed to 60 mm, 90 mm, or 120 mm, the larger the radius R of the curved pipe, the smaller the difference between the value of the inner cover factor cf(in) and the value of the outer cover factor cf(out) becomes. Therefore, it is possible to set (design) a wide range of the orientation angle θ1 and the range of the orientation angle θ2 such that the value of the inner cover factor cf(in) satisfies the condition of being 100% or less and 80% or more, and the value of the outer cover factor cf(out) satisfies the condition of being 100% or less and 80% or more.

[0077] Example B In Example B, as shown in the graph of FIG. 12, the width b f The inner diameter of the curved pipe (outer diameter of the mandrel) D [mm] was 2 mm, the inner diameter of the curved pipe (outer diameter of the mandrel) D [mm] was 26 mm, the number of braided yarns n [pieces] was 48, and the number of axial yarns was 0. The radius R of the curved pipe was changed to 60 mm, 90 mm, or 120 mm, and the orientation angle θ1 [°] on the inner side of the bent part of the curved pipe was plotted on the horizontal axis, and the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) was plotted on the vertical axis. The orientation angle θ2 [°] on the outer circumferential side of the bent portion of the curved pipe can be calculated using the above formulas (11) to (13), and is therefore omitted from FIG.

[0078] In Example B, the number of braided yarns n is 48, which is less than that of Example C (64), described later. Therefore, even if the orientation angle θ1 and the orientation angle θ2 are made larger than those of Example C, it is possible to satisfy the condition that the value of the inner cover factor cf(in) is 100% or less and 80% or more, and the value of the outer cover factor cf(out) is 100% or less and 80% or more.

[0079] Also, in Example B, when the radius R of the curved pipe is changed to 60 mm, 90 mm or 120 mm, the larger the radius R of the curved pipe is, the smaller the difference between the value of the inner cover factor cf(in) and the value of the outer cover factor cf(out) becomes. Therefore, it is possible to set (design) a wide range of the orientation angle θ1 and the range of the orientation angle θ2 such that the value of the inner cover factor cf(in) satisfies the condition of being 100% or less and 80% or more, and the value of the outer cover factor cf(out) satisfies the condition of being 100% or less and 80% or more.

[0080] Example C In Example C, as shown in the graph of FIG. 13, the width b f The inner diameter of the curved pipe (outer diameter of the mandrel) D [mm] was 2 mm, the inner diameter of the curved pipe (outer diameter of the mandrel) D [mm] was 26 mm, the number of braided yarns n [pieces] was 64, and the number of axial yarns was 0. The radius R of the curved pipe was changed to 60 mm, 90 mm, or 120 mm, and the orientation angle θ1 [°] on the inner side of the bent part of the curved pipe was plotted on the horizontal axis, and the value of the inner cover factor cf(in) or the value of the outer cover factor cf(out) was plotted on the vertical axis. The orientation angle θ2 [°] on the outer circumferential side of the bent portion of the curved pipe can be calculated using the above formulas (11) to (13), and is therefore omitted in FIG.

[0081] In Example C, the number of braided yarns n is 64, which is more than the aforementioned Example A (32) and Example B (48). Therefore, it can be seen that unless the orientation angle θ1 and the orientation angle θ2 are smaller than those of Example A or Example B, the condition that the value of the inner cover factor cf(in) is 100% or less and 80% or more and the condition that the value of the outer cover factor cf(out) is 100% or less and 80% or more cannot be met.

[0082] Also, in Example C, when the radius R of the curved pipe is changed to 60 mm, 90 mm or 120 mm, the larger the radius R of the curved pipe is, the smaller the difference between the value of the inner cover factor cf(in) and the value of the outer cover factor cf(out) becomes. Therefore, it is possible to set (design) a wide range of the orientation angle θ1 and the range of the orientation angle θ2 such that the value of the inner cover factor cf(in) satisfies the condition of being 100% or less and 80% or more, and the value of the outer cover factor cf(out) satisfies the condition of being 100% or less and 80% or more.

[0083] [Verification based on Examples 1 to 5 and Comparative Examples 1 to 5] In the present invention, in a curved pipe formed by combining a braided yarn and an axial yarn and having a circular cross section, the value of the inner cover factor cf3(in) of the inner circumference of the curved portion of the curved pipe is 80% or more and 100% or less, and the value of the outer cover factor cf3(out) of the outer circumference of the curved portion of the curved pipe is 80% or more and 100% or less, and the axial yarn ratio R m But R m By satisfying the condition of ≧0.50, a configuration is created in which the strength of the braided structure is less likely to be biased (difference in strength) between the inside and outside of the bent pipe.

[0084] In this embodiment, bent pipes according to Examples 1 to 5 and Comparative Examples 1 to 5 were produced, and the V f The following tests were carried out for comparative verification: (1) Measurement of fiber volume content, (2) Measurement of tensile modulus of curved pipe, and (3) Destructive testing of curved pipe. The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0085] (Structure of bent pipes made of fiber reinforced plastic (FRP)) <Braiding yarns and axial yarns used in the braided structure of curved pipes> Table 1 shows carbon fibers 1 to 3 constituting the braiding yarn and axial yarn used in the braided structure of the curved pipe. [Table 1] <Resin composition used for bent pipe> Thermosetting resin: Vinyl ester resin (brand CBZ500LM-AS, viscosity 200-350 mPa·s, made by Japan U-Pica) Accelerator: PR-CBZ01 (made by Japan U-Pica) Hardener: 328E (made by Nouryon Chemical)

[0086] (Manufacturing method of curved pipes) The manufacturing method for the curved pipes of Examples 1 to 5 and Comparative Examples 1 to 5 was to form braided structures described in Examples 1 to 5 and Comparative Examples 1 to 5 so as to have the axial yarn ratio (Rm) and cover factor (cf3) shown in Table 2, and then resin molding was performed on these to produce curved pipes made of fiber reinforced plastic (FRP).

[0087] [Table 2]

[0088] The manufacturing method of the curved pipe will be described below. 1) A mandrel was created using a 3D printer (Creator3, FLASHFORGE) and polylactic acid filament for 3D printers (PLA-F35, FLASHFORGE). Mandrels were produced by setting the diameter D and radius of curvature R as shown in Examples 1 to 5 and Comparative Examples 1 to 5 in Table 2, bending the wire at a 60° angle, and fixing the lengths of the straight portions (chuck portions) at both ends to 100 mm. The mandrel of Example 1 is shown in FIG.

[0089] 2) The necessary number of bobbins were prepared for braiding and for the axis thread. The carbon fibers used as the braiding yarn and the axial yarn were wound around a bobbin for a braiding machine using a single-spindle semi-automatic bobbin winder (KUW-100, manufactured by Kokubun Limited).

[0090] 3) The above bobbins were attached to the braiding yarn carrier (spindle) and the axial yarn carrier (spindle) of a braiding machine (40Z032C, manufactured by Kokubun Limited).

[0091] 4) The mandrel was attached to a NACHI robot arm (MZ10LF, Fujikoshi).

[0092] 5) The braid and axial yarn were pulled out from the bobbin attached to the carrier and fixed to the starting point of lamination on the mandrel.

[0093] 6) The straight part of the mandrel was braided by taking up the mandrel at a take-up speed γ1 calculated by the following (Equation 20). At this time, the braiding was performed while holding the braiding machine and the mandrel (straight part) so that the axis of the drawing direction was perpendicular (Figure 15(A)).

[0094]

number

[0095] 7) The bent portion of the mandrel was braided by taking up the mandrel at a take-up speed γ1 calculated by the above (Equation 20). At this time, the angle was adjusted with the robot arm so that the axis of the drawing direction of the braiding machine and the mandrel (bent portion) was perpendicular to each other, forming a braided structure of a curved tube (Figure 15 (B)). The angle of the robot arm was controlled by the angular velocity ω calculated by the following (Equation 21). r was used.

[0096]

number

[0097] 8) A mandrel with a braided structure formed on its surface was placed in a mold adjusted to a vacuum (-0.1 MPa). The resin component (vinyl ester resin composition) was pressurized and injected using the RTM method, and then the material was left at room temperature for 3 hours and in an 80°C atmosphere for 2 hours to harden, forming a curved FRP pipe. After being released from the mold, the FRP bent pipe was heated to 200°C to melt and remove the mandrel, resulting in a hollow bent pipe. As an example, the bent pipe obtained in Example 1 of Table 2 is shown in Figure 16.

[0098] (Test Method) <Bend pipe V f (Measurement of fiber volume content) The mass of the test piece was measured by the combustion method according to the method of JIS K7075 (1991), and the density of the test piece was measured. The obtained value was then applied to the following (Equation 22) to obtain the fiber volume content V f was calculated.

number

[0099] <Measurement of tensile modulus of elasticity of curved pipe> Test pieces measuring L50mm x W5mm x 1.5tmm were taken from the center of the bent part of the curved pipe prepared by the above method using the water jet method, one on the inside and one on the outside (see Figure 16). Then, for test pieces taken from the inside and outside of the central part of the bent part of the curved pipe, tensile tests were performed at a speed of 1 mm / min in an environment of a temperature of 23±2°C and a humidity of 50±10% according to a method in accordance with JIS K7164 (2005), and the tensile modulus E was calculated from the obtained stress-strain curve using the following formula (23).

[0100]

number

[0101] In this test, the area where the slope is linear is set as the strain reading range. σ1: Tensile stress measured at strain ε1 = 0.0025 (MPa) σ2: Tensile stress measured at strain ε2 = 0.0050 (MPa) The tensile modulus E is calculated by the above formula (23). The tensile modulus of the test piece taken from the inside of the central part of the bent portion of the curved pipe was defined as E(in) (see Figure 16), and the tensile modulus of the test piece taken from the outside of the central part of the bent portion of the curved pipe was defined as E(out) (see Figure 16).

[0102] <Bent pipe destructive test> For the curved pipes produced by the above method, the tensile test method was performed in accordance with the above-mentioned "Measurement of the tensile modulus of elasticity of curved pipes", by gripping the chuck part shown in FIG. 17 with a chuck and measuring the tensile stress (test force: F) until the test piece broke at a test speed of 6 mm / min. The breaking strength was calculated by the following formula (24) (each test was performed three times). Destructive test method for bent pipes ·Equipment Autograph: Amsler Strain gauge: KFGS-2-120-C1-11LIM3R Kyowa Electric Industries Strain gauge adhesive: CC-33A Kyowa Electric Industries Conditioning Temperature 23±2℃, humidity 50±10%, 16 hours or more Test conditions Test environment: Temperature 23±2℃, humidity 50±10% Load cell capacity: 100kN Test speed: 6mm / min Number of tests: 3 Chuck: A core bar is inserted to prevent crushing by the chuck

[0103]

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[0104] (Regarding test results) <Determining the pass / fail criteria for bent pipes> Since FRP bent pipes are often used as replacements for metal parts (e.g. aluminum alloys), from the viewpoint of replacing aluminum alloys, if they maintain the strength characteristics (elastic modulus) equivalent to aluminum alloys, they are deemed to pass. The tensile elastic modulus of the center part of the bent part of the bent pipe, calculated in the above tensile test, was used as the index value for strength characteristics.

[0105] It is also preferable that the strength characteristics of each portion of a curved pipe be uniform. However, in the bent portion of the bent pipe, the strength characteristics tend to differ between the inside and outside due to the condition of the fiber material. Therefore, it is preferable to form the braided structure so that the difference in strength properties between the inside and outside of the bent portion of the bent pipe is as small as possible. If there is a large difference in strength properties between the inside and outside of the bent part of a curved pipe, the side with the higher elastic modulus may break when a load is applied to the curved pipe and stress is concentrated at the bent part of the curved pipe. Therefore, the more uniform the strength properties are between the inside and outside of the bent part of a curved pipe, the less likely it is to break even if stress is concentrated at the bent part of the curved pipe. From the above perspective, the pass / fail judgment of the strength characteristics of a curved pipe was based on measuring the tensile modulus E(in) of a test piece taken from the inside of the center of the bent portion of the curved pipe, and the tensile modulus E(out) of a test piece taken from the outside of the center of the bent portion of the curved pipe, and the judgment criterion was whether their ratio E(in) / E(out) was close to 1 (i.e., the strength properties were equal between the inside and outside of the bent portion of the curved pipe). A mode in which E(in) / E(out) was close to 1 was considered to be the preferred mode, and the allowable range of E(in) / E(out) was set based on the results of destructive testing of the curved pipe. Specifically, among Examples 1 to 5 and Comparative Examples 1 to 5 listed in Table 2, destructive tests were conducted on the curved pipes of Example 2 [E(in) / E(out)=1.05], Example 3 [E(in) / E(out)=0.90], Example 5 [E(in) / E(out)=1.00], Comparative Example 1 [E(in) / E(out)=0.82], and Comparative Example 5 [E(in) / E(out)=1.73], which had different measurement results for E(in) / E(out), and the results are shown in Table 3. In Comparative Example 1, where E(out) was larger than E(in), the outside of the bent portion of the curved pipe broke at 341 MPa due to stress concentration. In Comparative Example 5, where E(in) was larger than E(out), the inside of the bent portion of the curved pipe broke at 720 MPa due to stress concentration. In contrast, in Examples 2, 3, and 5, in which E(in) and E(out) were equivalent, the bent portion of the curved pipe did not break even when the pressure exceeded 1,000 MPa, and the pipe ultimately broke near the chuck portion, which is not the bent portion. From the above results, curved pipes with a breaking strength of 1,000 MPa or more were judged to be at an acceptable level, maintaining strength characteristics (elastic modulus) equivalent to that of an aluminum alloy, and based on the E(in) / E(out) ratios of Examples 2, 3, and 5 in which such breaking strengths were obtained, the allowable range of E(in) / E(out) was set to 0.85 to 1.05. Based on this criterion, for Examples 1 to 5 and Comparative Examples 1 to 5 shown in Table 2, bent pipes for which E(in) / E(out) was in the range of 0.85 to 1.05 were rated as Rank A (pass), and bent pipes outside this range were rated as Rank B (fail).

[0106] [Table 3]

[0107] <Bent pipe test results> [Comparative Example 1: Example where none of cf3(in)=80-100%, cf3(out)=80-100%, and Rm≧0.50 is satisfied] Comparative Example 1 is an example using a braided structure with cf3(in) of 78.7%, cf3(out) of 77.9%, and an axial yarn ratio Rm of 0 (no axial yarn used), but the E(in) / E(out) of the curved pipe was 0.82, meaning that the strength was not uniform between the inside and outside of the curved pipe, and it was ranked B (failed).

[0108] [Comparative Example 2: An example in which Rm≧0.50 is satisfied, but cf3(in)=80-100% and cf3(out)=80-100% are not satisfied] Comparative Example 2 is an example using a braided structure with cf3(in) of 73.4%, cf3(out) of 62.0%, and an axial yarn ratio Rm of 0.50. However, the E(in) / E(out) of the bent pipe was 0.83, meaning that the strength was not uniform between the inside and outside of the bent pipe, and the pipe was ranked B (failed).

[0109] [Comparative Example 3: An example in which cf3(in)=80-100% and cf3(out)=80-100% are satisfied, but Rm≧0.50 is not satisfied] Comparative Example 3 is an example using a braided structure with cf3(in) of 95.8%, cf3(out) of 87.9%, and an axial yarn ratio Rm of 0.40. However, the E(in) / E(out) of the bent pipe was 0.80, and the strength was not uniform between the inside and outside of the bent pipe, resulting in a B rank (failure).

[0110] [Comparative Example 4: An example in which cf3(in)=80-100% is satisfied, but cf3(out)=80-100%, Rm≧0.50 are not satisfied] Comparative Example 4 is an example using a braided structure with cf3(in) of 99.8%, cf3(out) of 77.5%, and an axial yarn ratio Rm of 0. However, the E(in) / E(out) of the bent pipe was 0.24, and the strength was not uniform between the inside and outside of the bent pipe, resulting in a B rank (failure).

[0111] [Comparative Example 5: An example in which cf3(in)=80-100% and Rm≧0.50 are satisfied, but cf3(out)=80-100% is not satisfied] Comparative Example 5 is an example using a braided structure with cf3(in) of 99.5%, cf3(out) of 48.0%, and an axial yarn ratio Rm of 0.50. However, the E(in) / E(out) of the bent pipe was 1.73, meaning that the strength was not uniform between the inside and outside of the bent pipe, and the pipe was ranked B (failed).

[0112] [Example 1] Example 1 is an example using a braided structure with cf3(in) of 82.2%, cf3(out) of 81.5%, and an axial yarn ratio Rm of 0.50. The E(in) / E(out) of the bent pipe was 0.99, and the strength was uniform on the inside and outside of the bent pipe, earning an A rank (pass).

[0113] [Example 2] Example 2 is an example using a braided structure with cf3(in) of 90.1%, cf3(out) of 89.4%, and an axial yarn ratio Rm of 0.50. The E(in) / E(out) of the bent pipe was 1.04, and the strength was uniform on the inside and outside of the bent pipe, earning an A rank (pass).

[0114] [Example 3] Example 3 is an example using a braided structure with cf3(in) of 99.9%, cf3(out) of 99.6%, and an axial yarn ratio Rm of 0.50. The E(in) / E(out) of the bent pipe was 0.86, and the strength was uniform on the inside and outside of the bent pipe, earning an A rank (pass).

[0115] [Example 4] Example 4 is an example using a braided structure with cf3(in) of 100%, cf3(out) of 95.0%, and an axial yarn ratio Rm of 0.67. The E(in) / E(out) of the bent pipe was 0.91, and the strength was uniform on the inside and outside of the bent pipe, earning an A rank (pass).

[0116] [Example 5] Example 5 is an example using a braided structure with cf3(in) of 100%, cf3(out) of 99.1%, and an axial yarn ratio Rm of 0.67. The E(in) / E(out) of the bent pipe was 1.00, and the strength was uniform on the inside and outside of the bent pipe, earning an A rank (pass).

[0117] Regarding the upper limit of cf3, cases where cf3(in) exceeds 100%, where cf3(out) exceeds 100%, and where both cf3(in) and cf3(out) are 100% have not been verified, since these are practically impossible to manufacture.

[0118] From the above results, it was confirmed that in bent pipes using a braided structure that satisfies all of the following conditions: cf3(in) = 80~100%, cf3(out) = 80~100%, and Rm ≧ 0.50, the strength properties on the inside and outside of the bent section are uniform (E(in) / E(out) is in the range of 0.85~1.05), and the strength characteristics (elastic modulus) are equivalent to those of an aluminum alloy. [Explanation of symbols]

[0119] 1 Bend Pipe 11 Bent part 11A Inner circumference of bent part 11B Outer circumference of bent part 20 Circular braider 21 Spindle 22 tubes 30 Mandrel 71 Braided Thread 72 Axon 100 Large Drones 101 Main frame 102 Propeller 103 Propeller Guard 104 Arm 105 Skid

Claims

1. A bent pipe used as a component of a large unmanned aerial vehicle, The bent pipe is made of FRP, which is formed by a braided structure formed by combining braided yarns and axial yarns and by resin molding, and has a circular cross section. The braided structure has the axial thread incorporated along the central axis direction of the curved tube, The width of the braid is b f [mm] The number of the braided yarns is n [pieces] The inner diameter of the braided structure is D [mm] The orientation angle of the braided yarn with respect to the central axis direction of the curved tube is θ [°] The width per cell of the braided structure of the bent pipe is f [mm] The width of the axon is b m [mm] The number of the axons is n m [Books] The fineness of the braided yarn is f b [dtex] The fineness of the axial yarn is f m [dtex] The tensile modulus of the braided yarn is E b [GPa] The tensile modulus of the axial yarn is E m [GPa] An inner cover factor cf, which indicates the ratio of the braided yarns and the axial yarn to the surface area of ​​the braided structure, which corresponds to the inner circumference of the bent portion of the bent pipe, is calculated by the following (Equation 1) when 3 The value of (in) is 100% or less and 80% or more, and the outer cover factor cf indicates the ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure corresponding to the outer periphery of the bent portion of the bent tube, which is calculated by the following (Equation 1): 3 The value of (out) is 100% or less and 80% or more, Furthermore, the axial yarn ratio R defined by the following (Equation 2) m But, R m A bent pipe for a large unmanned aerial vehicle, characterized in that it satisfies the condition of ≧0.

50. [Equation 1] ...(Formula 1) [Equation 2] ...(Formula 2)

2. 2. The curved pipe for a large unmanned aerial vehicle according to claim 1, wherein the braided yarn has a tape shape with a rectangular cross section.

3. 2. The curved pipe for a large unmanned aerial vehicle according to claim 1, wherein the braided yarn and the axial yarn are in the shape of a tape with a rectangular cross section.

4. A method for manufacturing a curved pipe used as a component of a large unmanned aerial vehicle, which is made of FRP and has a circular cross section, and is constructed by combining a braided structure formed by combining a braided yarn and an axial yarn and resin molding, The bent pipe is The width of the braid is b f [mm] The number of the braided yarns is n [pieces] The inner diameter of the braided structure is D [mm] The orientation angle of the braided yarn with respect to the central axis direction of the curved tube is θ [°] The width per cell of the braided structure of the bent pipe is f [mm] The width of the axon is b m [mm] The number of the axons is n m [Books] The fineness of the braided yarn is f b [dtex] The fineness of the axial yarn is f m [dtex] The tensile modulus of the braided yarn is E b [GPa] The tensile modulus of the axial yarn is E m [GPa] An inner cover factor cf, which indicates the ratio of the braided yarns and the axial yarns to the surface area of ​​the braided structure, which corresponds to the inner circumference of the bent portion of the bent pipe, is calculated by the following (Equation 3) when 3 The value of (in) is 100% or less and 80% or more, and the outer cover factor cf indicates the ratio of the braided yarn and the axial yarn to the surface area of ​​the braided structure corresponding to the outer periphery of the bent portion of the bent tube, which is calculated by the following (Equation 3): 3 The value of (out) is 100% or less and 80% or more, Furthermore, the axial yarn ratio R defined by the following (Equation 4) m But, R m A method for manufacturing a curved tube for a large unmanned aerial vehicle, characterized in that the axial thread is arranged along the central axis direction of the curved tube on the outer periphery of a mandrel so as to satisfy the condition of .gtoreq.0.50, and the curved tube is formed by combining the braided thread and the axial thread. [Equation 3] ...(Formula 3) [Equation 4] ...(Formula 4)

5. The cover factor cf of a curved pipe for a large unmanned aerial vehicle indicates the proportion of the surface area of ​​the braided structure that is occupied by the braided yarn and the axial yarn arranged along the central axis of the curved pipe, in the curved pipe that is used as a component of a large unmanned aerial vehicle and that is made of FRP and constructed by resin molding, and that has a circular cross section. 3 A calculation control method for (1A) The width b of the braid f [mm], the number of the braided yarns n [pieces], the inner diameter D [mm] of the braided structure, the orientation angle θ [°] of the braided yarns with respect to the central axis direction of the curved pipe, the width f [mm] per cell of the braided structure of the curved pipe, and the width b of the axial yarn m [mm], the number of the axon threads is n m storing the book in a storage device; (1B) The width b of the braid stored in step (1A) is added to the following (Equation 5). f [mm], the number of the braided yarns n [pieces], the inner diameter D [mm] of the braided structure, the orientation angle θ [°] of the braided yarns with respect to the central axis direction of the curved pipe, the width f [mm] per cell of the braided structure of the curved pipe, and the width b of the axial yarn m [mm], the number of said axial yarns n m [Book] is substituted, and the cover factor cf 3 calculating the value of (1C) The cover factor cf calculated in step (1B) 3 a step of outputting the value of The cover factor cf of the bent pipe for the large unmanned aerial vehicle is calculated by the control device. 3 Calculation control method. [Equation 5] ...(Formula 5)

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