Perforated tube

Abstract

To provide a perforated pipe made of FRP in which a fiber member is embedded inside a resin molded body and which can secure sufficient fastening strength when the perforated pipe is attached to another component, and to provide a method for manufacturing the same.SOLUTION: The perforated pipe 1 has a pipe body 2 in which a hole such as a hole 21A or a hole 21B is formed in a direction intersecting a central axis direction X, the braided sleeve has a braided structure in which braids (outer-layer braids 121 and the like) are combined, the hole such as the hole 21A or the hole 21B is formed in a braid of the braids, and a cover factor around the hole such as the hole 21A or the hole 21B in the braided structure is 100% or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a perforated pipe made of FRP in which a fibrous member is embedded inside a resin molding. [Background technology]

[0002] BACKGROUND ART Conventionally, aluminum structures have been used for structures such as golf shafts, tennis rackets, fishing rods, bicycle frames, automobile parts, power transmission shafts, and roofs because of their light weight and high rigidity. However, although aluminum is light among metals, when it is used in the above-mentioned structures, even lighter weight may be required.

[0003] In recent years, fiber-reinforced plastic (FRP) pipes (hollow tubular structures) with fiber components embedded inside a resin molded body have been widely used in components that require light weight and high rigidity, such as the structures mentioned above. Recently, they have also been used in structures such as the main body frame, propellers, propeller guards, arms, and skids (legs) of next-generation mobility such as large drones (large unmanned aerial vehicles) and flying cars.

[0004] When the above-mentioned FRP pipe (hollow tubular structure) is used in the above-mentioned structure, depending on the application and structure, holes may be formed in the FRP pipe so that it can be connected to other parts with bolts or the like (hereinafter, FRP pipes with holes drilled therein will be referred to as perforated pipes).

[0005] Here, Patent Document 1 discloses that an insert part having a screw hole is embedded in a fiber reinforced resin member and mechanically joined to another part with bolts, nuts, or the like. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-143609 DISCLOSURE OF THE INVENTION [Problem to be solved by the invention]

[0007] However, when drilling a hole in an FRP pipe (resin molded body), cutting the fiber material embedded inside can reduce the strength of the perforated pipe. To address this issue, it is possible to use a braided fiber material and form a hole by widening the braided threads before the resin molded body is cured.

[0008] However, when the braiding stitches are enlarged, the thickness of the fiber material increases around the hole. If the resin molded body is cured in this state, the pipe will be thicker around the hole than other parts, so the head of a bolt passed through the hole cannot be tightly attached to the pipe surface, and sufficient fastening strength to other parts cannot be ensured.

[0009] Therefore, the object of the present invention is to provide a perforated pipe made of FRP in which a fiber member is embedded inside a resin molded body, and a method for manufacturing the same, which can ensure sufficient fastening strength when the perforated pipe is attached to other parts. [Means for solving the problem]

[0010] The present invention is a perforated pipe made of FRP in which a fiber member is embedded inside a resin molded body, a pipe body having a pair of holes formed in a direction intersecting the central axis direction; The fiber member includes a sleeve having a braided structure made by combining braided yarns, Each of the pair of holes is formed in a braid of the braided yarn, The sleeve is characterized in that a cover factor, which is the ratio of the surface area of ​​the sleeve around each of the pair of holes that is occupied by the braided yarn, is 100% or less.

[0011] According to the above configuration, the cover factor around each of the pair of holes in the sleeve is 100% or less, which prevents a portion of the braiding yarn from floating on the surface of the perforated pipe around the holes and, as a result, prevents the thickness around the holes from being greater than other parts. This allows the bolt head to be in close contact with the surface of the perforated pipe when the perforated pipe is attached to another part, ensuring sufficient fastening strength.

[0012] Furthermore, the present invention may be characterized in that in the perforated pipe, the cover factor of the sleeve is 100% or less and 50% or more from one end to the other end of the perforated pipe.

[0013] According to the above configuration, it is possible to prevent the high rigidity, internal pressure resistance, and impact resistance of the perforated pipe from being reduced.

[0014] Further, the present invention provides a perforated pipe, further comprising an insert disposed in the pipe body from one of the pair of holes to the other, The insert may be characterized in that a through hole is formed in the insert, one end of which communicates with one of the pair of holes and the other end of which communicates with the other of the pair of holes.

[0015] According to the above configuration, when the perforated pipe is attached to another component with a bolt, the bolt is inserted into the through hole of the insert, which prevents the perforated pipe from being crushed and deformed by the insert when the bolt is tightened.

[0016] The present invention also provides a method for manufacturing a perforated pipe, which includes covering a mandrel with a sleeve, impregnating the sleeve with a resin, and curing the resin to form an intermediate body, and removing the mandrel from the intermediate body, thereby manufacturing a perforated pipe made of FRP and having a fiber member embedded inside a resin molded body, The sleeve has a braided structure made of a combination of braided yarns, the mandrel is formed of a material that is solid at room temperature and melts when heated; a covering step of covering the mandrel with the sleeve; a hole forming step in which a pair of holes is formed in the sleeve in a direction intersecting the central axis direction of the perforated tube during or after the covering step, and the pair of holes is formed in a braid of the braid while maintaining a cover factor, which is the ratio of the area of ​​the surface of the sleeve occupied by the braid around each of the pair of holes, to a surface area of ​​the sleeve that is equal to or less than 100%; an impregnation step of impregnating the sleeve with the resin after the hole forming step; and a removal step of removing the mandrel from the intermediate body after the resin has hardened.

[0017] In a perforated pipe manufactured by the above manufacturing method, the cover factor around the hole in the sleeve is 100% or less, which prevents part of the braiding yarn from floating on the surface of the perforated pipe around the hole and, as a result, prevents the thickness around the hole from being greater than other parts. This allows the head of the bolt to be in close contact with the surface of the perforated pipe when the perforated pipe is attached to another part, ensuring sufficient fastening strength.

[0018] In addition, in the method for manufacturing the perforated tube, the present invention may be characterized in that in the covering process, the sleeve is placed over the mandrel while maintaining the cover factor of the sleeve at 100% or less and 50% or more from one end of the perforated tube to the other end.

[0019] The perforated pipe manufactured by the above manufacturing method can prevent the high rigidity, internal pressure resistance, and impact resistance of the perforated pipe from decreasing.

[0020] Further, in the method for manufacturing a perforated pipe according to the present invention, an insert is embedded in the mandrel from one end to the other end in a direction intersecting a central axis direction of the perforated pipe, The insert has a through hole formed therein, In the hole forming step, the holes communicating with the through-hole may be formed in braids of the braided yarns corresponding to both ends of the through-hole.

[0021] When the perforated pipe manufactured by the above manufacturing method is attached to another component with a bolt, the bolt is inserted into the through-hole of the insert. Therefore, when the bolt is tightened, the insert can prevent the perforated pipe from being deformed in a crushing manner.

[0022] Further, in the above-mentioned method for manufacturing a perforated pipe, the mandrel is made of wax, The removing step may be characterized in that the mandrel is removed from the intermediate body by melting the mandrel.

[0023] According to the above configuration, the mandrel can be easily removed from the intermediate body while leaving the insert inside the intermediate body.

[0024] Further, the present invention provides the above-mentioned method for manufacturing a perforated pipe, a jig that is detachably attached to the through hole so as to close the through hole; Before the impregnation step, the jig is attached to the through hole of the insert; The jig may be removed from the through hole after the resin has hardened.

[0025] According to the above manufacturing method, by blocking the through-hole of the insert with the jig, it is possible to prevent the resin from flowing into the through-hole of the insert when the resin is impregnated into the sleeve.

[0026] Further, the present invention provides the above-mentioned method for manufacturing a perforated pipe, The jig has a shape that tapers in a direction of attachment to the through hole, The hole forming step may be characterized in that, after the covering step, the jig is attached to the through hole while the hole is formed in the sleeve with a tip of the jig.

[0027] According to the above manufacturing method, by passing the tip of the jig through the braided threads, a hole of a diameter equivalent to the diameter of the through hole in the insert can be formed (secured) in the braided threads. Therefore, when a bolt is passed through the through hole in the insert and tightened, the perforated pipe can be sandwiched in its thickness direction between the head of the bolt and the end face of the insert. As a result, when the bolt is tightened, the perforated pipe can be pressed against another component, allowing the bolt to firmly fasten the perforated pipe to the other component.

[0028] Further, the present invention provides the above-mentioned method for manufacturing a perforated pipe, the jig has a body portion shaped to fit into the through hole, and a tip portion having a diameter larger than the through hole and tapering in a direction of removal from the through hole, Before the coating step, the body portion of the jig is attached to the through hole of the insert; The covering step may be characterized in that the sleeve is placed over the mandrel while the hole is formed in the sleeve with the tip of the jig.

[0029] According to the above manufacturing method, by passing the tip of the jig through the braided threads, a hole corresponding to the outer diameter of the insert can be formed (secured) in the braided threads. Therefore, when a bolt is passed through the through hole of the insert and tightened, the head of the bolt can be brought into contact with the end face of the insert. This makes it possible to prevent the bolt from sliding sideways within the through hole (moving radially of the through hole) when tightening the bolt. [Effects of the Invention]

[0030] It is possible to provide a perforated pipe made of FRP in which a fiber member is embedded inside a resin molded body, which can ensure sufficient fastening strength when the perforated pipe is attached to other parts, and a method for manufacturing the same. [Brief explanation of the drawings]

[0031] [Figure 1]1A and 1B are a plan view and a cross-sectional view taken along line AA of a perforated pipe according to a first embodiment. [Figure 2] FIG. 2 is a rear view of the perforated pipe according to the first embodiment. [Figure 3] 1A is a cross-sectional view of the braided sleeve according to the first embodiment, and FIG. 1B is an explanatory view of the two-layer structure of the braided sleeve according to the first embodiment. [Figure 4] (A) An explanatory diagram of a braided structure (1 cell) formed only with inner layer braid yarns in an inner layer braided sleeve. (B) An explanatory diagram of a braided structure (1 cell) formed with inner layer braid yarns and an axial yarn in an inner layer braided sleeve. [Figure 5] FIG. 2 is an explanatory diagram of the braided structure (one cell) of the outer layer braided sleeve. [Figure 6] FIG. 3 is a detailed view of a hole formed in the pipe body of the perforated pipe according to the first embodiment. [Figure 7] 1 is an explanatory view of a perforated pipe insert according to a first embodiment. FIG. [Figure 8] 1A is a cross-sectional view showing a state in which a bolt has been inserted into a hole in a perforated pipe according to a modified example, and FIG. 1B is a cross-sectional view showing a state in which a bolt has been inserted into a hole in a perforated pipe according to the first embodiment. [Figure 9] 1A is an explanatory diagram of a sleeve braiding process, and FIG. 1B is an explanatory diagram of a spindle track in the sleeve braiding process. [Figure 10] 3 is an explanatory view of a step of embedding an insert into a perforated pipe forming mandrel according to the first embodiment. FIG. [Figure 11] FIG. 2 is an explanatory diagram of a manufacturing process of a preform according to the first embodiment. [Figure 12] FIG. 4 is an explanatory diagram of a hole forming step according to the first embodiment. [Figure 13] FIG. 2 is an explanatory view relating to a resin molding process for a preform according to the first embodiment. [Figure 14] 1 is a perspective view of a perforated pipe according to a first embodiment. FIG. [Figure 15] FIG. 10 is an explanatory view of a perforated pipe insert according to a second embodiment. [Figure 16] FIG. 10 is an explanatory view of a hole forming step according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] (First embodiment) A perforated pipe 1 according to a first embodiment of the present invention will be described below with reference to the drawings.

[0033] (Perforated pipe 1) As shown in Figures 1 and 2, the perforated pipe 1 is a rectangular tube (hollow molded body) made of FRP in which a braided structure made of a braided sleeve (a fiber member such as a carbon fiber material) is embedded inside a resin molded body. In detail, the perforated pipe 1 comprises a pipe body 2 in which four pairs of holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, holes 24A and 24B) are formed in a direction perpendicular to the central axis direction X of the perforated pipe 1, and four inserts arranged within the pipe body 2 from one pair of holes to the other (insert 31 arranged from hole 21A to hole 21B, insert 32 arranged from hole 22A to hole 22B, insert 33 arranged from hole 23A to hole 23B, and insert 34 arranged from hole 24A to hole 24B). Furthermore, the hollow molded body is a molded body having a hollow portion, and includes a molded body having a hollow portion with one end open and a molded body having a hollow portion with both ends open.

[0034] There are no particular limitations on how the perforated pipe 1 can be used, and the perforated pipe 1 can be used in structures such as golf shafts, tennis rackets, fishing rods, bicycle frames, automobile parts, power transmission shafts, roofs, and large drones (main body frames, propellers, propeller guards, arms, and skids).

[0035] (Braided structure of tube body 2) The pipe body 2 of the perforated pipe 1 has a square cylindrical shape, and one or more layers of braided sleeves having a cylindrical braided structure are embedded inside the resin molded body.

[0036] Here, a braided sleeve is a tubular braided structure made by combining three or more braided yarns. Its fiber structure is significantly different from that of fabrics, such as knitted fabrics (knitted fabrics) in which yarns are entangled in a loop and knitted together, or woven fabrics (woven fabrics) in which warp and weft yarns are woven perpendicular to each other. Unlike these fabrics, braided fabrics allow for easy adjustment of the width, spacing, and orientation angle of the braided yarns, allowing for greater flexibility in designing stretchability and yarn density, achieving higher stretchability and higher yarn density than fabrics. Furthermore, adjusting the spacing between the braided yarns allows for adjustment of the size of the braided yarns. Therefore, when forming holes in a perforated tube, arranging the holes at the braided yarns allows for holes to be drilled without breaking the braided yarns. In contrast, drilling holes in a perforated tube is difficult because it is difficult to drill holes in a fabric without breaking the yarns that make up the fabric, which reduces the strength of the perforated tube. In contrast, using a braided sleeve can prevent a decrease in the strength of the perforated tube.

[0037] In addition, the braided sleeve has a seamless, tubular braided structure that is strong and has no joints. Because the braided sleeve has no seams, it is possible to prevent cracks from occurring in the perforated pipe 1 from the seams.

[0038] In this embodiment, as shown in FIG. 3(A), the braided structure of the pipe body 2 is a two-layer structure consisting of an outer layer braided sleeve 12 arranged on the outer periphery of the pipe body 2 and an inner layer braided sleeve 13 arranged on the inner periphery of the pipe body 2.

[0039] (Inner layer braided sleeve 13) The inner layer braided sleeve 13 is a cylindrical braided sleeve having a constant diameter in the longitudinal direction when not stretched, and is layered on the inner peripheral side of the outer layer braided sleeve 12 . As shown in Figures 3(B) and 4, the inner layer braided sleeve 13 is formed by crossing and combining an axial yarn 132 that is oriented in the central axis direction X (at an orientation angle of 0° relative to the central axis direction X) and is made of high-strength (high elastic modulus) fibers with an inner layer braided yarn 131 that is oriented at an orientation angle relative to the central axis direction X in the range of ±5 to 85° and is made of elastic yarn.

[0040] Furthermore, with regard to the elasticity (elasticity range) of the inner layer braided sleeve 13, from the viewpoint of preventing the inner layer braided sleeve 13 from becoming loose around the perforated pipe forming mandrel 51 in the manufacturing process (described later), it is preferable that the cross-sectional perimeter of the inner layer braided sleeve 13 (cross-sectional perimeter of a cross section perpendicular to the central axis direction of the inner layer braided sleeve 13) be elastic within a range from a value smaller than the cross-sectional perimeter of the perforated pipe forming mandrel 51 (cross-sectional perimeter of a cross section perpendicular to the central axis direction of the perforated pipe forming mandrel 51) used in the manufacturing process described later to a value larger than the cross-sectional perimeter of the perforated pipe forming mandrel 51. For example, if the cross-sectional circumference of the perforated pipe forming mandrel 51 is 60 mm, it is preferable that the cross-sectional circumference of the inner layer braid sleeve 13 expands or contracts within a range from a value smaller than 60 mm (e.g., 50 mm) to a value larger than 60 mm (e.g., 70 mm).

[0041] Examples of high-strength (high elastic modulus) fibers that can be used to form the axial thread 132 of the inner layer braided sleeve 13 include carbon fiber, glass fiber, aramid fiber, boron fiber, silicon carbide fiber, steel fiber, polyethylene fiber, nylon fiber, alumina fiber, Tyranno fiber, basalt fiber, and amorphous fiber.

[0042] Examples of elastic yarns that can be used to form the inner layer braided yarn 131 of the inner layer braided sleeve 13 include multifilament yarns made of thermoplastic resins such as nylon resin, polybutylene terephthalate resin, and polyester resin, and false twisted yarns (also called crimped yarns or woolly yarns) obtained by processing monofilament yarns, urethane fibers, etc.

[0043] (Outer layer braid sleeve 12) The outer layer braided sleeve 12 is a cylindrical braided sleeve having a constant diameter in the longitudinal direction when not stretched, and is layered on the outer peripheral side of the inner layer braided sleeve 13 . 3(B) and 5, the outer layer braided sleeve 12 is formed by combining outer layer braided yarns 121 made of high-strength (high elastic modulus) fibers so that they are oriented at an angle (θ) of ±5 to 85° with respect to the central axis direction X. Here, the outer layer braided sleeve 12 does not have an axial yarn that is oriented in the central axis direction X of the perforated pipe 1.

[0044] In addition, the stretchability of the outer layer braided sleeve 12 (more specifically, the stretchability range based on the cross-sectional circumference of the perforated pipe forming mandrel 51 including the inner layer braided sleeve 13 when the perforated pipe forming mandrel 51 is covered with the inner layer braided sleeve 13) is the same as that of the inner layer braided sleeve 13.

[0045] Examples of high-strength (high elastic modulus) fibers that can be used to form the outer layer braided yarn 121 of the outer layer braided sleeve 12 include carbon fiber, glass fiber, aramid fiber, boron fiber, silicon carbide fiber, steel fiber, polyethylene fiber, nylon fiber, alumina fiber, Tyranno fiber, basalt fiber, and amorphous fiber.

[0046] (Resin molding of pipe body 2) Resin materials used in resin molding for the braided structure (inner layer braided sleeve 13, outer layer braided sleeve 12) of the pipe body 2 of the perforated pipe 1 include thermosetting resins (matrix resins) such as epoxy resin, polyester resin, vinyl ester resin, phenolic resin, and polyurethane resin, as well as thermoplastic resins such as nylon resin, polyethylene resin, polypropylene resin, polyphenylene sulfide resin, polyether ether ketone resin, polycarbonate resin, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), polyacetal resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polystyrene resin, acrylonitrile-styrene resin, polyvinyl chloride resin, and acrylic resin. Resin molding methods include resin transfer molding (RTM: vacuum suction and pressure impregnation), VaRTM (vacuum impregnation method), and internal pressure molding.

[0047] (A pair of holes formed in the pipe body 2) As shown in FIG. 1, a pair of holes 21A and 21B are formed in the pipe body 2, with hole 21A formed on the rear left side of the plane of the pipe body 2 and hole 21B formed on the rear left side of the bottom surface of the pipe body 2, and holes 21A and 21B are formed so as to overlap in the vertical direction (thickness direction of the pipe body 2) when viewed in a plane. Here, the holes 21A are formed in a manner that does not cut the braided yarns in the braided structure of the braided sleeve of the tube main body 2. Specifically, as shown in Fig. 6, the holes 21A are formed so as to communicate between a portion of the outer layer braided sleeve 12 where the combined outer layer braided yarns 121 are not arranged (a portion where the braided yarns are widened) and a portion of the inner layer braided sleeve 13 where the combined inner layer braided yarns 131 and axial yarns 132 are not arranged (a portion where the braided yarns are widened). The same applies to the holes 21B.

[0048] Similarly, the pair of holes 22A and 22B are formed such that hole 22A is formed forward of hole 21A on the plane of the pipe body 2, and hole 22B is formed forward of hole 21B on the bottom surface of the pipe body 2, and holes 22A and 22B are formed so as to overlap vertically in a planar view. Similarly, a pair of holes 23A and 23B are formed such that hole 23A is formed on the rear right side of the plane of the pipe body 2, and hole 23B is formed on the rear right side of the bottom surface of the pipe body 2, and holes 23A and 23B are formed so as to overlap vertically when viewed in a plane. Similarly, the pair of holes 24A and 24B are formed such that hole 24A is formed forward of hole 23A on the plane of the pipe body 2, and hole 24B is formed forward of hole 23B on the bottom surface of the pipe body 2, and holes 24A and 24B are formed so as to overlap vertically in a planar view.

[0049] (Insert 31~34) 7, the insert 31 has a cylindrical shape with a through hole 311 formed in the central axis direction of the insert 31 (thickness direction of the pipe body 2). The insert 31 is fixed in the thickness direction of the pipe body 2 from hole 21A to hole 21B, with one end of the through hole 311 communicating with hole 21A and the other end of the through hole 311 communicating with hole 21B. A bolt is passed through the through hole 311 of the insert 31 to fasten the perforated pipe 1 to another component to be joined. In this embodiment, the insert 31 is made of iron, but may be made of aluminum, resin, or FRP, and is not particularly limited.

[0050] In addition, in this embodiment, as shown in Figure 7, the insert 31 is fixed within the pipe body 2 in such a manner that one end face 312A abuts against the inner surface of the pipe body 2 and the other end face 312B also abuts against the inner surface of the pipe body 2. Furthermore, the diameter of hole 21A, the diameter of through-hole 311 (the inner diameter of insert 31), and the diameter of hole 21B are the same. Therefore, the inner peripheral surfaces of hole 21A, insert 31, and hole 21B are flush with each other. With this configuration, when a bolt is passed through the through-hole 311 of the insert 31 and tightened, the pipe body 2 of the perforated pipe 1 can be sandwiched in its thickness direction between the head of the bolt and the end face 312A of the insert 31. As a result, when the bolt is tightened, the pipe body 2 can be pressed against another component to be joined, allowing the perforated pipe 1 to be firmly fastened to the other component with the bolt.

[0051] The other inserts 32 to 34 have the same configuration as the insert 31.

[0052] According to the above configuration, when the perforated pipe 1 is attached to another component to be joined with bolts, the bolts are inserted into the through holes 311, 321, 331, and 341 of the inserts 31 to 34. Therefore, when the bolts are tightened, the inserts 31 to 34 can prevent the perforated pipe 1 from being deformed so as to be crushed. The holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B) formed in the pipe body 2 are formed in the braided yarns (outer layer braided yarns 121) of the outer layer braided sleeve 12 and the braided yarns (inner layer braided yarns 131 and axial yarns 132) of the inner layer braided sleeve 13. In other words, when the holes are formed in the pipe body 2, the braided yarns (outer layer braided yarns 121, inner layer braided yarns 131, and axial yarns 132) are not cut. Therefore, compared to when holes are formed by cutting the braiding yarns (outer layer braiding yarns 121, inner layer braiding yarns 131, and axial yarns 132), it is possible to suppress a decrease in strength of the perforated pipe 1 caused by drilling holes in the pipe body 2.

[0053] (Cover factor of braided sleeve of pipe body 2) When manufacturing the perforated pipe 1, the braided structures of the inner layer braided sleeve 13 and the outer layer braided sleeve 12 are formed using an index (value) called the cover factor cf (Equations 1 to 3), which indicates the proportion of the surface area of ​​the braided inner layer braided sleeve 13 and the outer layer braided sleeve 12 that is occupied by braided yarns (outer layer braided yarns 121, inner layer braided yarns 131, and axial yarns 132), so that the perforated pipe 1 maintains the desired strength.

[0054] The calculation of the cover factor cf must take into consideration the following cases: a case where the cells of the braided structure are composed only of the outer layer braid yarn 121 (cf1), as in the outer layer braided sleeve 12 shown in Figure 5; and a case where the cells (see Figure 4(A)) include a braided structure (cf1) composed only of the inner layer braid yarn 131, as in the inner layer braided sleeve 13 shown in Figure 4, and a case where the cells (see Figure 4(B)) include a braided structure (cf2) having the inner layer braid yarn 131 and an axial yarn 132 (cf3).

[0055] (Cover factor of outer layer braid sleeve 12) When the braided cell is made up of only the outer layer braid yarn 121, as in the outer layer braided sleeve 12 shown in FIG. 5, the width b fThe cover factor cf1 of the outer layer braid sleeve 12 is calculated from values ​​based on two-dimensional data such as the length (mm) of the outer layer braided sleeve 12, the number n of outer layer braided yarns 121, the inner diameter D of the outer layer braided sleeve 12, and the orientation angle θ of the outer layer braided yarns 121 relative to the central axis direction X of the perforated tube 1, using the following formula (1).

[0056]

number

[0057] (Cover factor of inner layer braid sleeve 13) When the cover factor cf3 is calculated for a braided structure having a cell (see FIG. 4(A)) composed only of an inner layer braid 131, as in the case of the inner layer braided sleeve 13 shown in FIG. 4, and a cell (see FIG. 4(B)) composed of a braided structure having an inner layer braid 131 and an axial yarn 132, the cover factor cf3 is calculated taking into account the cover factor cf1 (calculated in the same manner as for the outer layer braided sleeve 12: see Equation 1) for the cell shown in FIG. 4(A) whose braided structure is composed only of the inner layer braid 131, and the cover factor cf2 for the cell shown in FIG. 4(B) whose braided structure is composed of the inner layer braid 131 and an axial yarn 132.

[0058] Here, as shown in FIG. 4(B), when the braided cell includes an inner layer braid 131 and an axial thread 132, the width b f [mm], the number n [pieces] of the inner layer braided yarns 131, the inner diameter D [mm] of the inner layer braided sleeve 13, and the orientation angle θ [°] of the inner layer braided yarns 131 with respect to the central axis direction X, in addition to the width f [mm] per cell of the braided structure (one section surrounded by the inner layer braided yarns 131: see FIG. 4(B)), the width b m [mm] and the number n of the axle threads 132 m The cover factor cf2 of the inner layer braid sleeve 13 is calculated from values ​​based on two-dimensional data such as [number of pieces] by the following (Equation 2).

[0059]

number

[0060] As shown in Figures 4(A) and 4(B), in (Equation 2), A is the area of ​​one cell of the braided structure of the inner layer braided sleeve 13, and A S is the area of ​​the voids in one cell of the braided structure of the inner layer braided sleeve 13 excluding the inner layer braid 131 portion, and A a is the area of ​​the axial yarn 132 (excluding the portion overlapping with the inner layer braid yarn 131) in one cell of the braided structure of the inner layer braided sleeve 13.

[0061] When the cover factor cf3 is calculated for a braided structure in which the cell (see FIG. 4(A)) is composed only of the inner layer yarn 131, and the cell (see FIG. 4(B)) is composed of the inner layer yarn 131 and the axial yarn 132, as in the case of the inner layer braided sleeve 13, the cover factor cf3 of the inner layer braided sleeve 13 is calculated using the following formula (3), which takes into account the cover factor cf1 for the cell whose braided structure is composed only of the inner layer yarn 131 as shown in FIG. 4(A) and the cover factor cf2 for the cell whose braided structure is composed of the inner layer yarn 131 and the axial yarn 132 as shown in FIG. 4(B).

[0062] In the case of the above-mentioned braided sleeve for the inner layer 13, elastic yarn is used for the braided yarn for the inner layer 131, and therefore the braided sleeve for the inner layer 13 itself can be made flexible, and the axial yarn 132 can be arranged seamlessly and uniformly along the central axis direction X from one end to the other end of the perforated pipe 1.

[0063]

number

[0064] As described above, the cover factors cf (cover factor cf3 of the inner layer braid sleeve 13, cover factor cf1 of the outer layer braid sleeve 12) of the braid sleeves (inner layer braid sleeve 13, outer layer braid sleeve 12) are calculated.

[0065] Here, from the viewpoint of high rigidity for the entire perforated pipe 1, the cover factor cf of the braided sleeve is set to satisfy the condition of being in the range of 100% or less and 50% or more from one end to the other end of the perforated pipe 1. This is because if the cover factor cf value exceeds 100%, the surface area will be greater than or equal to the surface area of ​​the inner layer braided sleeve 13 and the outer layer braided sleeve 12, which are formed by the braided structure of the outer layer braid 121 and the braided structure of the inner layer braid 131 and the axial yarn 132, and therefore the outer layer braid 121, the inner layer braid 131, and the axial yarn 132 will partly float on the surface of the perforated pipe 1, and loads will be applied to the floated parts or their surroundings, which may reduce the high rigidity and impact resistance of the perforated pipe 1. Also, if the cover factor cf value is less than 50%, the spacing between the outer layer braid 121, the inner layer braid 131, and the axial yarn 132 in the inner layer braided sleeve 13 and the outer layer braided sleeve 12 in the perforated pipe 1 will increase, reducing the yarn density and potentially reducing the high rigidity and impact resistance of the perforated pipe 1.

[0066] In addition, in order to further enhance the high rigidity and impact resistance of the perforated pipe 1, it is more preferable that the cover factor cf of the inner layer braided sleeve 13 and the outer layer braided sleeve 12 that constitute the perforated pipe 1 satisfy the condition of being in the range of 100% or less and 60% or more, and it is most preferable that the cover factor cf satisfy the condition of being in the range of 100% or less and 70% or more.

[0067] (Cover factor around the hole in the braided sleeve) As described above, when holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B) are formed in the braided yarns, the braided yarns become dense around the holes. Therefore, the cover factor cf around the holes of the inner layer braid sleeve 13 and the outer layer braid sleeve 12 of the pipe body 2 tends to be large, but in this embodiment, the cover factor cf is set to 100% or less.

[0068] The term "around the hole" refers to at least one of the following areas: an overlapping area that overlaps with the head of the bolt inserted into the hole (through hole of the insert) when viewed from the thickness direction of the pipe body 2 (the direction of the central axis of the insert); and an area where the braid becomes denser by forming a hole in the braid compared to before the hole was formed.

[0069] Here, consider a case (hereinafter referred to as a comparative example) in which the cover factor cf around the holes in the braided sleeves (the inner layer braided sleeve 13 and the outer layer braided sleeve 12) of the pipe body 2 exceeds 100%. A perforated pipe 501 according to the comparative example shown in Fig. 8(a) has the same configuration as the perforated pipe 1 according to this embodiment, except that the cover factor cf around the holes in the braided sleeves of the pipe body 2 exceeds 100%.

[0070] 8(a), if the cover factor cf around the hole in the braided sleeve of the pipe body 2 exceeds 100%, it will be equal to or greater than the surface area of ​​the braided sleeves (the inner layer braided sleeve 13 and the outer layer braided sleeve 12), causing part of the braiding threads to float on the surface of the perforated pipe 1, making the thickness around the hole thicker than other parts. As a result, when the perforated pipe 501 is attached to another part, the head of the bolt cannot be brought into close contact with the surface of the perforated pipe 501, reducing the fastening strength.

[0071] In contrast, in the perforated pipe 1 of this embodiment shown in FIG. 8(b), the cover factor cf around the holes in the braided sleeves (the inner layer braided sleeve 13 and the outer layer braided sleeve 12) of the pipe body 2 is 100% or less. This prevents some of the braided yarns from floating on the surface of the perforated pipe 1 around the holes, and as a result, prevents the thickness around the holes from being thicker than other parts. That is, for example, the thickness around the holes can be made the same as the thickness of other parts. This allows the head of the bolt to be in close contact with the surface of the perforated pipe 1 when the perforated pipe 1 is attached to another part, ensuring sufficient fastening strength.

[0072] (Manufacturing method of perforated pipe 1) Next, a method for manufacturing the perforated pipe 1 will be described.

[0073] (1) Sleeve braiding process First, as shown in FIG. 9(a), the outer layer braided sleeve 12 and the inner layer braided sleeve 13 are manufactured using a braiding machine.

[0074] For example, in the case of the outer layer braided sleeve 12, braided yarns (outer layer braided yarns 121) wound around a spindle are combined on the outer periphery of a cylindrical sleeve-forming mandrel to form the outer layer braided sleeve 12. As shown in Fig. 9(b), the spindle moves along the track, so that the braided yarns (outer layer braided yarns 121) are combined, and a seamless outer layer braided sleeve 12 is formed on the sleeve-forming mandrel and then wound up by a winding device.

[0075] In the case of the inner layer braided sleeve 13, the braided yarn (inner layer braided yarn 131) wound around the spindle and the axial yarn 132 supplied from the bottom of the braiding machine (supplied from a fixed cylinder) are combined on the outer periphery of a cylindrical sleeve-forming mandrel to form the inner layer braided sleeve 13. As shown in Fig. 9(b), the spindle moves along the track, so that the braided yarn (inner layer braided yarn 131) and the axial yarn 132 are combined, and a seamless inner layer braided sleeve 13 is formed on the upper part of the sleeve-forming mandrel, and is then wound up by a winding device.

[0076] (2) Embedding the insert into the mandrel for forming the perforated tube Next, as shown in FIG. 10, a perforated pipe forming mandrel 51 made of wax and having a prismatic shape corresponding to the inner peripheral shape of the pipe body 2 of the perforated pipe 1 is prepared.

[0077] The inserts 31 to 34 are then embedded in this perforated pipe forming mandrel 51 at positions corresponding to the holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B) to be formed in the pipe body 2 of the perforated pipe 1 to be manufactured. As a result, the inserts 31 to 34 are embedded in the perforated pipe forming mandrel 51 from the flat surface 51A (one end) to the bottom surface 51B (other end) of the perforated pipe forming mandrel 51, which is a direction intersecting the central axis direction X of the perforated pipe 1 to be manufactured (see FIG. 10 ).

[0078] In this embodiment, wax is used for the perforated tube forming mandrel 51, but any material that is solid at room temperature and melts when heated can be used, such as thermoplastic resin, polystyrene foam, or low-melting-point alloy.

[0079] (3) Preform manufacturing (coating process) Next, as shown in FIG. 11, the inner layer braided sleeve 13 and the outer layer braided sleeve 12 are sequentially placed over the perforated pipe forming mandrel 51 with the inserts 31 to 34 embedded therein to produce a preform having two layers of cylindrical braided sleeves stacked on top of each other (hereinafter referred to as a preform).

[0080] In this covering process, the sleeves (the inner layer braided sleeve 13 and the outer layer braided sleeve 12) are placed over the perforated pipe forming mandrel 51 while maintaining a cover factor of 100% or less and 50% or more from one end of the perforated pipe 1 to the other end.

[0081] (4) Hole forming process Next, holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, holes 24A and 24B) communicating with the through holes 311, 321, 331, and 341 of the inserts 31 to 34 are formed in the braids of the outer layer braid sleeve 12 (outer layer braid 121) (locations where the combined outer layer braid 121 is not arranged) and in the braids of the inner layer braid sleeve 13 (inner layer braid 131 and axial yarn 132) (locations where the combined inner layer braid 131 and axial yarn 132 are not arranged) corresponding to both ends of the through holes 311, 321, 331, and 341 of the inserts 31 to 34.

[0082] At this time, the braided yarns are widened to form holes while maintaining the cover factor cf around the holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B) in the braided sleeves (braided sleeve 12 for the outer layer, braided sleeve 13 for the inner layer) of the pipe body 2 at 100% or less.

[0083] In this embodiment, a jig 71 that can be attached to and detached from the through hole 311 is used. Specifically, as shown in Fig. 12(A), the jig 71 has a head 711 that is larger in diameter than the through hole 311 of the insert 31, a cylindrical body 712 that is formed below the head 711 and has a diameter equivalent to the diameter of the through hole 311, and a conical tip 713 that is formed below the body 712 and is tapered further than the body 712, and has a nail-like shape overall (i.e., the jig 71 has a shape that tapers in the direction in which the jig 71 is attached to the through hole 311 of the insert 31). With this jig 71, the body 712 can be inserted into the through hole 311 of the insert 31 to close the through hole 311. The jig 71 can be made of any material that can be processed into the shape of the through-hole 311, such as silicone resin, metal materials such as steel, or plastic materials.

[0084] Specifically, as shown in Figures 12(A) and (B), the tip portions 713 of the jig 71 are inserted into the braids of the outer layer braided sleeve 12 (the outer layer braided yarns 121) (locations where the combined outer layer braided yarns 121 are not arranged) and the braids of the inner layer braided sleeve 13 (the inner layer braided yarns 131 and the axial yarns 132) (locations where the combined inner layer braided yarns 131 and the axial yarns 132 are not arranged) that correspond to both ends of the through hole 311 of the insert 31, and the braids of the outer layer braided sleeve 12 and the inner layer braided sleeve 13 are widened to form holes 21A and 21B that communicate with the through hole 311. Furthermore, while forming holes 21A and 21B in the joints of the outer layer braid sleeve 12 and the joints of the inner layer braid sleeve 13 with the tip end 713 of the jig 71, the jig 71 is inserted into the through hole 311 of the insert 31 and attached to the through hole 311. As a result, as shown in Fig. 12(B) , the holes 21A and 21B formed in the outer layer braid sleeve 12 and the inner layer braid sleeve 13 and the through hole 311 of the insert 31 can be blocked by the jig 71.

[0085] Similarly, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B are formed in the joints of the outer layer braid sleeve 12 and the joints of the inner layer braid sleeve 13.

[0086] (5) Installation in the mold Next, as shown in Figure 13, the perforated tube forming mandrel 51, with the jig 71 inserted into the through holes 311, 321, 331, and 341 of the inserts 31 to 34 via the holes formed in the preform (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B), is fitted into the cavity of the mold and the lid is closed.

[0087] (6) Resin molding process (impregnation process) Next, as shown in Fig. 13, thermosetting resin (matrix resin) is injected under pressure into the cavity of the mold by resin transfer molding (RTM), the preform is impregnated with the thermosetting resin, and the excess thermosetting resin is vacuum-sucked out. Then, the thermosetting resin impregnated in the preform hardens, thereby obtaining an intermediate body in which a resin molded body is formed around the outer periphery of the perforated pipe forming mandrel 51 in which the inserts 31 to 34 are embedded, with the inner layer braid sleeve 13 and the outer layer braid sleeve 12 embedded inside. At this time, since jig 71 blocks the holes formed in the preform (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, holes 24A and 24B) and the through holes 311, 321, 331, and 341 of inserts 31 to 34, when the preform is impregnated with thermosetting resin, it is possible to prevent resin from flowing into the holes formed in the preform (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, holes 24A and 24B) and the through holes 311, 321, 331, and 341 of inserts 31 to 34.

[0088] The resin molding method may be Vacuum Reverse Transfer Molding (VaRTM) or internal pressure molding.

[0089] (7) Removal of the mandrel and removal of the jig (removal process) Next, the obtained intermediate body is heated to melt the wax perforated pipe forming mandrel 51, and the perforated pipe forming mandrel 51 is removed from the intermediate body while the inserts 31 to 34 remain inside the intermediate body. Thereafter, the jig 71 is removed from the through holes 311, 321, 331, and 341 of the inserts 31 to 34 of the intermediate body. After the thermosetting resin impregnated in the preform has hardened, the jig 71 may be first removed from the through holes 311, 321, 331, 341 of the inserts 31 to 34 of the intermediate body, and then the intermediate body may be heated to melt and remove the perforated tube forming mandrel 51.

[0090] (8) Finishing Finally, the perforated pipe 1 is obtained by removing burrs, cutting, and painting (see FIG. 14).

[0091] In the perforated pipe 1 manufactured by the above manufacturing method, the cover factor cf around the holes in the braided sleeves (the outer layer braided sleeve 12 and the inner layer braided sleeve 13) is 100% or less. This prevents some of the braided yarns from floating on the surface of the perforated pipe 1 around the holes, and as a result, prevents the thickness around the holes from being greater than other parts. This allows the head of the bolt to be in close contact with the surface of the perforated pipe 1 when the perforated pipe 1 is attached to another component, ensuring sufficient fastening strength. Furthermore, when the perforated pipe 1 is attached to another component to be joined with bolts, the bolts are inserted into the through holes 311, 321, 331, and 341 of the inserts 31 to 34. Therefore, when the bolts are tightened, the inserts 31 to 34 can prevent the perforated pipe 1 from being deformed so as to be crushed. The holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B) formed in the pipe body 2 are formed at the braided yarns of the outer layer braided sleeve 12 (outer layer braided yarns 121) and the braided yarns of the inner layer braided sleeve 13 (inner layer braided yarns 131 and axial yarns 132). In other words, the braided yarns are not cut when the holes are formed in the pipe body 2. Therefore, compared to when holes are formed by cutting the braiding yarns (outer layer braiding yarns 121, inner layer braiding yarns 131, and axial yarns 132), it is possible to suppress a decrease in strength of the perforated pipe 1 caused by drilling holes in the pipe body 2.

[0092] Furthermore, in the above manufacturing method, since the perforated pipe forming mandrel 51 is made of wax, in the removal process, the perforated pipe forming mandrel 51 can be melted by heating, thereby easily removing the perforated pipe forming mandrel 51 from the intermediate body while leaving the inserts 31 to 34 inside the intermediate body.

[0093] Furthermore, according to the above manufacturing method, by passing the tip 713 of the jig 71 through the braided joints of the outer layer braid sleeve 12 and the braided joints of the inner layer braid sleeve 13, holes (holes 21A and 21B, holes 22A and 22B, holes 23A and 23B, and holes 24A and 24B) having diameters equivalent to the through holes 311, 321, 331, and 341 of the inserts 31 to 34 can be formed (secured) in the outer layer braid sleeve 12 and the inner layer braid sleeve 13 without cutting the braiding yarns. Therefore, in the manufactured perforated pipe 1, for example, when a bolt is passed through the through hole 311 of the insert 31 and tightened, the pipe body 2 of the perforated pipe 1 can be sandwiched in the thickness direction between the head of the bolt and the end face 312A of the insert 31. This allows the pipe body 2 to be pressed against another part to be joined when the bolt is tightened, so that the perforated pipe 1 can be firmly fastened to the other part with the bolt.

[0094] (Second embodiment) A perforated pipe 1001 of the second embodiment will be described. Explanation of the same configuration as the first embodiment will be omitted.

[0095] In the first embodiment described above, with regard to the insert, as shown in FIG. 7, the insert 31 is fixed within the pipe body 2 in such a manner that one end face 312A abuts against the inner circumferential surface of the pipe body 2 and the other end face 312B also abuts against the inner circumferential surface of the pipe body 2. However, this is not limited to this, and in the perforated pipe 1001 of the second embodiment, as shown in Figure 15, the insert 1031 is fixed within the pipe body 1002 in such a manner that the outer surface of one end 313A abuts the inner surface of the hole 1021A, and the outer surface of the other end 313B also abuts the inner surface of the hole 1021B. The diameter of hole 1021A, the outer diameter of insert 1031, and the diameter of hole 1021B are the same, and both end faces of insert 1031 are flush with the outer peripheral surface of pipe body 1002.

[0096] (Manufacturing method of perforated pipe 1001) Next, a method for manufacturing the perforated tube 1001 according to the second embodiment will be described. (1) The sleeve braiding step and (2) the step of embedding the insert into the perforated tube forming mandrel are the same as those in the first embodiment.

[0097] (Jig installation process) In the second embodiment, after (2) the process of embedding the insert into the perforated tube forming mandrel, a removable jig 81 is inserted into the through hole 1311 (both ends) of the insert 1031, and the jig 81 is attached to the through hole 1311, as shown in Figure 16(A). 16(A), the jig 81 has a cylindrical body 811 (body 811 is shaped to fit into the through hole 1311) having a diameter equivalent to the diameter of the through hole 1311 of the insert 1031, and a tapered conical tip 812 (tip 812 is shaped to taper in the direction of removal from the through hole 1311) having a diameter equivalent to the outer diameter of the insert 1031 (larger than the diameter of the through hole 1311), and has an umbrella shape overall. With this jig 81, the body 811 can be inserted into the through hole 1311 of the insert 1031 to close the through hole 1311. Similarly, the jig 81 is attached to the through holes 1321, 1331, and 1341 of the inserts 1032-1034.

[0098] (Preform manufacturing (covering process and hole forming process)) After the jig 81 is attached to the through holes 1311, 1321, 1331, and 1341 of the inserts 1031-1034, the inner layer braided sleeve 13 and the outer layer braided sleeve 12 are sequentially placed over the perforated pipe forming mandrel 51 with the inserts 1031-1034 embedded therein to produce a preform having two layers of cylindrical braided sleeves (hereinafter referred to as a preform). At this time, the sleeves are placed over the perforated pipe forming mandrel 51 from one end to the other of the perforated pipe 1001 while maintaining the cover factor of the sleeves (the inner layer braided sleeve 13 and the outer layer braided sleeve 12) at 50% or more and 100% or less.

[0099] At this time, the braided sleeves (braided sleeve 13 for the inner layer and braided sleeve 12 for the outer layer) are covered onto the perforated pipe forming mandrel 51 while forming holes (holes 1021A and 1021B, holes 1022A and 1022B, holes 1023A and 1023B, and holes 1024A and 1024B) in the braided sleeves (braided sleeve 13 for the inner layer and braided sleeve 12 for the outer layer) using the tip 812 of the jig 81.

[0100] Specifically, as shown in FIGS. 16(A) and 16(B), the braids of the outer layer braid sleeve 12 (the outer layer braid 121) corresponding to both ends of the through holes 1311, 1321, 1331, and 1341 of the inserts 1031 to 1034 (places where the combined outer layer braid 121 is not arranged) and the braids of the inner layer braid sleeve 13 (the inner layer braid 131 and the axial yarn 132) (places where the combined inner layer braid 121 is not arranged) are separated. The tip 812 of the jig 81 is inserted into the through holes 1311, 1321, 1331, 1341 (areas where the braided sleeves 12 and 132 are not arranged) and the braided sleeves 12 and 132 for the outer layer and the braided sleeves 13 for the inner layer are widened to form holes (holes 1021A and 1021B, holes 1022A and 1022B, holes 1023A and 1023B, holes 1024A and 1024B) that communicate with the through holes 1311, 1321, 1331, 1341. At this time, the holes are formed while maintaining the cover factor cf around the holes of the braided sleeves (the braided sleeves 13 and 12 for the inner layer) at 100% or less. As a result, as shown in Figure 16(B), the holes (holes 1021A and 1021B, holes 1022A and 1022B, holes 1023A and 1023B, and holes 1024A and 1024B) formed in the outer layer braid sleeve 12 and the inner layer braid sleeve 13, and the through holes 1311, 1321, 1331, and 1341 of the inserts 1031 to 1034 can be blocked by the jig 81.

[0101] Thereafter, as in the first embodiment, the perforated tube 1001 of the second embodiment is obtained through the following steps: (5) placement in a mold, (6) resin molding process (impregnation process), (7) removal of the mandrel and removal of the jig (removal process), and (8) finishing process (see Figure 15).

[0102] According to the above manufacturing method, by passing the tip portion 812 of the jig 81 through the braided portions of the outer layer braid sleeve 12 and the braided portions of the inner layer braid sleeve 13, holes (holes 1021A and 1021B, holes 1022A and 1022B, holes 1023A and 1023B, and holes 1024A and 1024B) corresponding to the outer diameters of the inserts 1031 to 1034 can be formed (secured) in the outer layer braid sleeve 12 and the inner layer braid sleeve 13 without cutting the braiding yarns. Therefore, in the manufactured perforated pipe 1001, for example, when a bolt is passed through the through hole 1311 of the insert 1031 and tightened, the head of the bolt can be brought into contact with the end face 1312A of the insert 1031. This makes it possible to prevent the bolt from sliding sideways within the through hole 1311 (moving radially of the through hole 1311) when tightening the bolt.

[0103] (Other embodiments) The pipe body 2 of the perforated pipe 1 of the first embodiment has a square tube shape, but is not limited to this and may have a cylindrical shape, or a shape in which a cylindrical shape and a square tube shape are connected, or the pipe body 2 itself may have a curved shape as a whole, and the shape is not particularly limited.

[0104] In the above embodiment of the perforated pipe 1, an example of a braided structure in which two layers of braided sleeves (braided sleeve 12 for the outer layer and braided sleeve 13 for the inner layer) having a tubular braided structure are embedded in a stacked state has been described, but the braided sleeves may be one layer or three layers, or may further be a structure in which four or more layers are stacked. For example, when the braided sleeve is a single layer, only one layer of either the braided sleeve for inner layer 13 or the braided sleeve for outer layer 12 described in the above embodiment may be embedded in the resin molded body. The arrangement and type of the braided yarns and axial yarns that make up the braided structure can be selected as appropriate depending on the required characteristics of the perforated tube 1. The braided structure includes at least braided yarns, but the axial yarns may be either included or not included.

[0105] Regarding the braided sleeve of the perforated pipe 1 of the above embodiment, the type of thread must be a high-strength fiber with high reinforcing properties (carbon fiber, aramid fiber, glass fiber, etc.), and may also include elastic thread. When multiple braided sleeves are layered, the type of thread to be applied to which thread (braiding thread, axial thread) in which layer of the braided sleeve can be selected appropriately depending on the required characteristics.

[0106] Although the perforated pipe 1 in the above embodiment is provided with the inserts 31 to 34, the inserts are not essential.

[0107] Although the embodiments of the present invention have been described above, they are merely illustrative examples and do not particularly 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. [Example]

[0108] The perforated pipe according to the present invention can ensure sufficient fastening strength when attached to other components. Therefore, in order to confirm the effects of the present invention, perforated pipes according to examples and comparative examples were produced and the fastening strength of each was evaluated. The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0109] (Perforated pipe configuration) The perforated pipes of the examples and comparative examples used for evaluation have the same configuration except for the difference in the cover factor values ​​around the holes in the braided sleeve of the pipe body, as described below.

[0110] <High-strength fiber used in braided structures for perforated pipes> Table 1 lists the high-strength fibers (carbon fibers) used in the braided structure of the perforated pipe. [Table 1]

[0111] <Elastic thread used in braided structure of perforated pipe> Table 2 lists the elastic threads (polyamide fibers) used in the braided structure of the perforated tube. [Table 2]

[0112] (Manufacturing method of perforated pipe) Perforated pipes of the example and comparative example were each produced using the "perforated pipe manufacturing method" described in the above embodiment. Here, in the example, the holes were formed in the hole-forming step by widening the braided yarns of the braided sleeves (the outer layer braided sleeve 12 and the inner layer braided sleeve 13) while maintaining a cover factor of 100% or less around the holes to be formed. On the other hand, in the comparative example, the holes were formed in the hole-forming step by widening the braided yarns of the braided sleeves (the outer layer braided sleeve 12 and the inner layer braided sleeve 13) while maintaining a cover factor of more than 100% around the holes to be formed.

[0113] (Evaluation of fastening strength) A bolt was passed through the hole in the perforated pipe produced by the above manufacturing method, and the perforated pipe was fastened to another component. In this case, the bolt head of the perforated pipe of the example was in close contact with the surface of the perforated pipe, so sufficient fastening strength was obtained. On the other hand, the bolt head of the perforated pipe of the comparative example was not in close contact with the surface of the perforated pipe, so sufficient fastening strength was not obtained. From these results, it was confirmed that by manufacturing a perforated pipe while maintaining a cover factor around the formed hole of 100% or less, sufficient fastening strength can be obtained when the pipe is attached to another component with a bolt. [Explanation of symbols]

[0114] 1 Perforated pipe 2. Tube body 21A~24A holes 31~34 insert 311, 321, 331, 341 through holes 12 Braided sleeve for outer layer 13 Braided sleeve for inner layer

Claims

1. A perforated pipe made of FRP in which a fiber member is embedded inside a resin molded body, a pipe body having a pair of holes formed in a direction intersecting the central axis direction; The fiber member includes a sleeve having a braided structure made by combining braided yarns, Each of the pair of holes is formed in a braid of the braided yarn, A perforated tube characterized in that a cover factor, which is the ratio of the surface area of ​​the sleeve around each of a pair of holes that is occupied by the braided yarn, is 100% or less.

2. 2. The perforated pipe according to claim 1, wherein the cover factor of the sleeve is 100% or less and 50% or more from one end of the perforated pipe to the other end.

3. The pipe further includes an insert disposed in the pipe body from one end to the other end of the pair of holes, A perforated pipe as described in claim 1 or 2, characterized in that the insert has a through hole formed therein, one end of which communicates with one of the pair of holes and the other end of which communicates with the other of the pair of holes.

4. A method for manufacturing a perforated pipe, comprising: covering a mandrel with a sleeve, impregnating the sleeve with a resin, and curing the resin to form an intermediate body; and removing the mandrel from the intermediate body, thereby manufacturing a perforated pipe made of FRP and having a fiber member embedded inside a resin molded body, The sleeve has a braided structure made of a combination of braided yarns, the mandrel is formed of a material that is solid at room temperature and melts when heated; a covering step of covering the mandrel with the sleeve; a hole forming step in which a pair of holes is formed in the sleeve in a direction intersecting the central axis direction of the perforated tube during or after the covering step, and the pair of holes is formed in a braid of the braid while maintaining a cover factor, which is the ratio of the area of ​​the surface area of ​​the sleeve occupied by the braid around each of the pair of holes, of 100% or less; an impregnation step of impregnating the sleeve with the resin after the hole forming step; a removal step of removing the mandrel from the intermediate body after the resin has hardened.

5. A method for manufacturing a perforated tube as described in claim 4, characterized in that in the covering process, the sleeve is placed over the mandrel while maintaining the cover factor of the sleeve from one end of the perforated tube to the other end at a level not exceeding 100% and not exceeding 50%.

6. an insert is embedded in the mandrel from one end to the other end in a direction intersecting the central axis direction of the perforated tube; The insert has a through hole formed therein, 5. The method for manufacturing a perforated tube according to claim 4, wherein in the hole forming step, the holes communicating with the through holes are formed in the braids of the braid corresponding to both ends of the through holes.

7. the mandrel is made of wax; 7. The method for manufacturing a perforated tube according to claim 6, wherein the mandrel is removed from the intermediate body by melting the mandrel in the removing step.

8. a jig that is detachably attached to the through hole so as to close the through hole; Before the impregnation step, the jig is attached to the through hole of the insert; The method for manufacturing a perforated pipe according to claim 6, wherein the jig is removed from the through hole after the resin has hardened.

9. the jig has a shape tapered in a direction of attachment to the through hole, A method for manufacturing a perforated pipe as described in claim 8, characterized in that in the hole forming process, after the covering process, the jig is attached to the through hole while forming the hole in the sleeve with the tip of the jig.

10. the jig has a body portion shaped to fit into the through hole, and a tip portion having a diameter larger than the through hole and tapering in a direction of removal from the through hole, Before the coating step, the body portion of the jig is attached to the through hole of the insert; 9. The method for manufacturing a perforated pipe according to claim 8, wherein in the covering step, the sleeve is placed over the mandrel while the hole is formed in the sleeve with the tip of the jig.

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