Method for manufacturing tubular body and tubular body

Abstract

To provide a method for manufacturing a tubular body having good molding accuracy by reducing the leakage or bonding failure of a secondary resin, and the tubular body.SOLUTION: The method for manufacturing the tubular body 1 includes a first mold forming step of forming the first divisional part 10, which is the semi-tubular portion on the outer side in the bending direction and has the straight tube portion 11a and the bent portion 11b provided continuously with the straight tube portion, by the first mold 4, and a second mold forming step of forming the second divisional part 20, which is the semi-tubular portion on the inner side in the bending direction of the bent portion, by the second mold 5. And a joining step of positioning the first divided part and the second divided part in a joined state, clamping the first mold and the second mold, and joining the first divided part and the second divided part with a secondary resin, wherein in the first mold molding step, a joint projection portion 13 including a flow path 40 that projects in a radial direction of the first divided part and is filled with a secondary resin 6, and a rib portion 15 provided in a convex shape along the radial direction on an outer surface of the joint projection portion are molded at a circumferential edge portion of the first divided part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a tubular body and a tubular body. [Background technology]

[0002] Conventionally, as a tubular body made of resin having a bent portion that is difficult to integrally mold by injection molding or the like, a body formed by joining half tubular portions divided in the radial direction with each other using a secondary resin has been known. For example, Patent Document 1 discloses a hollow product in which a joint is provided near a point where the bending moment generated by the pressure acting on the internal space of the hollow product becomes zero, and a reinforcing rib is formed by protruding from the joint to the end in the width direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-51221 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the manufacturing process of such tubular bodies, if molding shrinkage occurs in the primary molded product, when the molding dies are clamped together and joined with the secondary resin, a misalignment occurs at the joining points between the semi-tubular sections, which can cause leakage of the secondary resin or poor joining.

[0005] The present invention has been made in view of the above circumstances, and has as its object to provide a method for manufacturing a tubular body that reduces leakage of secondary resin and poor joining and has good molding accuracy, and a tubular body. [Means for solving the problem]

[0006] In order to achieve the above object, the method for manufacturing a tubular body according to the present invention is a method for manufacturing a tubular body constructed by joining two semi-tubular sections divided in the radial direction with a secondary resin, the method comprising: a first mold molding step of using a first mold to mold a first divided section which has a straight pipe section and a bent section connected to the straight pipe section and is the semi-tubular section on the outer side in the bending direction; a second mold molding step of using a second mold to mold a second divided section which is the semi-tubular section on the inner side in the bending direction of the bent section; and a joining step of positioning the first divided section and the second divided section in a joined state, clamping the first mold and the second mold, and joining the first divided section and the second divided section with the secondary resin, In the first mold molding step, a joining protrusion is molded on the circumferential edge of the first divided portion, the joining protrusion protruding radially from the first divided portion and having a flow path into which the secondary resin is filled, and a rib portion is provided on the outer surface of the joining protrusion in a convex strip along the radial direction.

[0007] In the above configuration, a portion of the rib portion facing the clamping direction of the first mold may be a flat surface. One end portion of the tubular body in the axial direction and the other end portion of the tubular body in the axial direction may be formed at different height positions.

[0008] The tubular body has a straight pipe section and a curved section and is constructed by joining two radially divided semi-tubular sections with a secondary resin. The first divided section has a straight pipe section and a semi-tubular section connected to the straight pipe section and located on the outside of the curved section in the bending direction, and the second divided section has a semi-tubular section located on the inside of the curved section in the bending direction. Both circumferential edges of the first divided section and the second divided section are each provided with a joining protrusion that protrudes radially from the semi-tubular section and has a flow path into which the secondary resin is filled, and the outer surface of the joining protrusion of the first divided section is provided with a plurality of convex rib sections spaced apart along the radial direction. [Effects of the Invention]

[0009] According to the tubular body manufacturing method and the tubular body of the present invention, leakage of secondary resin and poor joining can be reduced, and a tubular body with good molding accuracy can be obtained. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view schematically illustrating an example of a tubular body manufactured by a manufacturing method according to the present embodiment. [Figure 2] (a) and (b) are side views showing the same tubular body, where (a) is an exploded side view showing the first divided portion and the second divided portion separated (unjoined), and (b) is a side view showing the first divided portion and the second divided portion joined together. [Figure 3] (a) is a cross-sectional view for explaining the manufacturing process (joining step) of the same tubular body, and is a cross-sectional view of the part indicated by Z2 in Figure 2(b), and (b) is a side view for explaining the part that receives the mold clamping force in the joining step. [Figure 4] 2A is a longitudinal cross-sectional view taken along line XX in FIG. 1, and FIG. 2B is a cross-sectional view taken along line YY in FIG. [Figure 5] 1(a) is a plan view schematically showing another example of a tubular body manufactured by the same manufacturing method, and FIG. 1(b) is a side view schematically showing the same tubular body. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, each embodiment will be described with reference to the drawings. Note that in some drawings, some of the detailed reference numerals used in other drawings are omitted.

[0012] The manufacturing method of the tubular body according to this embodiment is a manufacturing method of a tubular body 1 configured by joining two radially divided semi-tubular portions with a secondary resin 6, and a tubular body 1 manufactured by the manufacturing method. The manufacturing method of the tubular body 1 includes at least a first mold-molding step, a second mold-molding step, and a joining step. In the first mold-molding step, a first divided portion 10, which has a straight pipe portion 11a and a bent portion 11b connected to the straight pipe portion 11a and is the semi-tubular portion on the outer side in the bending direction, is molded using a first mold 4. In the second mold-molding step, a second divided portion 20, which is the semi-tubular portion on the inner side in the bending direction of the bent portion 11b, is molded using a second mold 5. In the joining step, the first divided portion 10 and the second divided portion 20 are positioned in a joined state, the first mold 4 and the second mold 5 are clamped together, and the first divided portion 10 and the second divided portion 20 are joined with the secondary resin. The first molding step is characterized by molding, at the circumferential edge of the first divided section 10, a joint protrusion 13 that protrudes in the radial direction of the first divided section 10 and has a flow path 40 that is filled with the secondary resin 6, and a rib portion 15 that is provided in a convex shape along the radial direction on the outer surface of the joint protrusion 13. This will be described in detail below.

[0013] A method for manufacturing a tubular body 1 according to this embodiment will be described with reference to FIGS. 1 to 4. The tubular body 1 is a tubular body having a hollow section 30 (see FIG. 4(a)) formed by joining a semi-tubular first divided section 10 and a semi-tubular second divided section 20. The tubular body 1 shown in the figure includes a substantially cylindrical main pipe 2 and flange-like mounting sections 3, 3. The application location of the tubular body 1 is not particularly limited, and it may be disposed as a conduit for circulating a fluid such as a gas or liquid. Specifically, it may be applied as part of a pipe through which cooling water circulates to cool an automobile engine or electrical system. Furthermore, the tubular body 1 is not limited to automobiles and may be used as, for example, piping for gas or plumbing equipment. This method can be used to manufacture a hollow tubular body 1 that does not interfere with surrounding components.

[0014] As shown in FIGS. 2(a) and 2(b), one axial end 1a and the other axial end 1b of the tubular body 1 are located at different heights, with the one end 1a being higher than the other end 1b. Mounting portions 3, 3 are provided at both axial ends of the main pipe 2 for fixing the tubular body 1 to an attachment target. These mounting portions 3, 3 protrude radially outward from both axial ends of the main pipe 2. The mounting portions 3, 3 each include a flat plate-shaped mounting body 3a and bolt holes 3b, 3b through which bolts (not shown) are inserted to fix the mounting portion 3 to the attachment target. As shown in FIG. 2(a), the mounting portions 3, 3 are integrally formed with the second divided portion 20, and each mounting body 3a has one bolt hole 3b (see FIG. 1). The mounting portions 3, 3 are formed with mounting hollow portions (not shown) that communicate with the hollow portion 30, and the second divided portion 20 is provided with connecting portions 28, 28 that are formed so that fluids, etc. that pass through the hollow portion 30 communicate with the mounting hollow portion. Note that these bolt holes 3b, 3b may be formed by metallic cylindrical members (collars) that are embedded in the respective mounting bodies 3a, 3a.

[0015] The main pipe 2 is formed by joining two radially separated semi-tubular sections with a secondary resin 6. The illustrated example includes a first divided section 10, which is one side of the semi-tubular section located on the outside of the arched curve in the bending direction (the corner of the curved section of the main pipe 2), and a second divided section 20, which is the other side of the semi-tubular section located on the inside of the arched curve in the bending direction (the corner of the curved section of the main pipe 2). The main pipe 2 has a straight pipe section formed at an angle and a bent section curved toward the mounting section 3 on one end 1a. Specifically, the first divided section 10 and the second divided section 20 each have a linear straight pipe section 11a, 21a and a bent section 11b, 21b that is bent in a roughly J-shape and connected to the straight pipe section 11a, 21a. 4(a) and 4(b), the first divided portion 10 and the second divided portion 20 are divided in half in the radial direction and have a substantially cylindrical shape when joined together. The first divided portion 10 and the second divided portion 20 each have a dome portion 11, 21 that is curved and bulges outward and has a substantially semicircular shape in cross section, and the inner wall surfaces 11c, 21c of the dome portions 11, 21 are each formed in a semicircular shape that is curved outward. Therefore, when the butting surfaces 17, 27 described below are butted together, a tubular body 1 having a substantially circular hollow portion 30 can be formed.

[0016] Joint protrusions 13 are provided on the circumferential edge of first divided section 10 so as to protrude radially. As shown in Fig. 1, joint protrusions 13 of first divided section 10 are provided around the entire circumference of first divided section 10 and are elliptical in plan view so as to surround dome section 11. Joint protrusions 23 of second divided section 20 are provided on the edge of second divided section 20 so as to protrude radially and are formed on both ends of dome section 21 along the axial direction.

[0017] As shown in FIGS. 4(a) and 4(b), recessed flow channel grooves 16, 26 are formed on the inner surfaces of the joining protrusions 13, 23 of the first divided section 10 and the second divided section 20, i.e., on the abutment surfaces 17, 27 where the joining protrusions 13, 23 abut against each other. The flow channel grooves 16, 26 face each other, and the abutment surfaces 17, 27 overlap to form the flow channel 40, which is generally rectangular in cross section. The flow channel grooves 16, 26 each include outer groove walls 16a, 26a, flow channel bottoms 16b, 26b, and inner groove walls 16c, 26c. Step-like steps 17a, 27a are provided on the abutment surfaces 17, 27 facing the hollow section 30. The overlapping of these steps 17a, 27a prevents the secondary resin 6 from leaking into the hollow section 30. In the illustrated example, the flow path 40 is shown as a rectangular groove when viewed in the longitudinal direction of the groove, but it may be a trapezoidal groove or a U-shaped groove. Also, in the illustrated example, the start end for filling the secondary resin is not shown, but it may be provided as an opening on the outer peripheral end face of the mounting portion 3, for example.

[0018] The outer surface of the joining protrusion 13 is provided with a convex rib portion 15 that protrudes upward along the radial direction (short direction) of the first divided portion 10. The upward direction here refers to the direction opposite to the mold clamping direction 100 during the joining step, and the opposite side of the mold clamping direction 100 refers to the direction opposite to the direction of the outline arrow shown in Figures 2(a) and 2(b). Multiple rib portions 15 are provided at intervals. A wall portion 12 that protrudes to the same height as the rib portion 15 is formed around the entire periphery of the outer surface of the joining protrusion 13, thereby providing multiple recesses 14 surrounded by the wall portion 12, rib portion 15, and dome portion 11. The end faces 12a of the wall portions 12 and the end faces 15a of the rib portions 15 are formed at the same height, making them a continuous surface. The shape of the rib portion 15 itself takes into consideration mold removal (a shape that can be removed in the mold release direction), and can take various forms depending on the position where it is formed, such as a trapezoidal or rectangular cross-sectional shape, or a shape with obliquely inclined surfaces. For example, the rib portion 15 shown in the enlarged view of Z1 in FIG. 2(b) is trapezoidal in cross-sectional view, and not only the end surface 15a of the rib portion 15 but also the upper side surface 15b and the lower side surface 15c are flat. Furthermore, the upper side surface 15b of the rib portion 15 shown in the enlarged view of Z2 in FIG. 3(a) is rounded in cross-sectional view. Regardless of the shape, the rib portion 15 functions as a mold shrinkage stopper for the first divided portion 10.

[0019] As described above, the rib portion 15 may have an upper side surface 15b that is rounded in cross section (see FIG. 3(a)). However, a portion 50 of the rib portion 15 that faces the clamping direction 100 of the first mold 4 (the portion indicated by the thick line in FIG. 3(b)) may be a flat surface. Therefore, in the rib portion 15 formed at this bent portion 11b, the end surface 15a of the rib portion 15 that faces the clamping direction 100 of the first mold 4 is a flat surface. The flat surface formed at the portion 50 that faces the clamping direction 100 may be approximately parallel to the butting surfaces 17, 27, which can also be called the parting surfaces between the first divided portion 10 and the second divided portion 20. This configuration allows the rib portion 15 to be easily subjected to the clamping force of the first mold 4, thereby further preventing the first mold 4 and the second mold 5 from being misaligned during the joining step. In particular, in the case of a tubular body 1 having a difference in height as shown in the figure, the clamping force acting on the inclined straight pipe portion 11a can be received by a flat surface, thereby improving the clamping force.

[0020] The outer surface of the joining protrusion 23 is provided with a convex rib portion 25 that protrudes downward along the radial direction (short-side direction) of the second divided portion 20. The downward direction here refers to the same direction as the mold clamping direction 100 during the joining step, and the same direction as the outline arrows shown in Figures 2(a) and 2(b). A plurality of rib portions 25 are provided at intervals, and the rib portions 25 themselves have various shapes, such as trapezoidal or rectangular in cross section, or those with obliquely inclined surfaces. A wall portion 22 that protrudes to the same height as the rib portion 25 is formed along the axial direction on the peripheral portion of the outer surface of the joining protrusion 23, thereby providing a plurality of recesses 24 surrounded by the wall portion 22, the rib portion 25, and the dome portion 21.

[0021] Next, a method for manufacturing the tubular body 1 will be described. The manufacturing method described below is suitable for a method of manufacturing the tubular body 1 by so-called DSI (die slide injection) molding, in which the first divided section 10 and the second divided section 20 are molded as primary molded articles, and then a mold is slid over one of them relative to the other, filling the flow path 40 with the secondary resin 6. Note that the manufacturing method according to this embodiment is not limited to DSI molding and can also be applied to cases where primary molded articles molded in separate molds are joined with the secondary resin. The synthetic resin constituting the first divided section 10, the second divided section 20, and the secondary resin 6 may be, for example, a thermoplastic resin such as polyethylene, polypropylene, ABS, acrylic, polycarbonate, polyamide, polyacetal, polyphenylene sulfide, or polyether ether ketone, or a thermosetting resin such as a phenolic resin, epoxy resin, or polyurethane resin. Furthermore, the synthetic resin may contain various additives or may be a fiber-reinforced resin containing reinforcing fibers such as carbon fiber or glass fiber. Furthermore, the tubular body 1 may be made mainly of synthetic resin, and may be configured to include a metal member in part by insert molding or the like as described above.

[0022] First, in the first mold forming step, a first mold 4 is used to form a first divided portion 10, which is a semi-tubular portion on the outer side in the bending direction and has a straight pipe portion 11a and a bent portion 11b connected to the straight pipe portion 11a. In addition to the above, this first mold forming step forms, at the circumferential edge of the first divided portion 10, a joining protrusion 13 that protrudes radially from the semi-tubular portion and is equipped with a flow path 40 to be filled with the secondary resin 6, and a convex rib portion 15 that protrudes radially from the outer surface of the joining protrusion 13 in the opposite direction from the mold clamping direction 100 during the joining step.

[0023] In the second mold molding step, a second mold 5 is used to mold the second divided portion 20, which is a semi-tubular portion on the inner side of the bending direction of the bending portion 21b. In addition to the above, this second mold molding step molds, at the circumferential edge of the second divided portion 20, a joining protrusion 23 that protrudes radially from the semi-tubular portion and has a flow path 40 to be filled with the secondary resin 6, and a convex rib portion 25 that protrudes radially from the outer surface of the joining protrusion 23 in the same direction as the mold clamping direction 100 during the joining step.

[0024] Next, in the joining step, the first divided portion 10 and the second divided portion 20 are positioned in a joined state with the first divided portion 10 held in the first mold 4 and the second divided portion 20 held in the second mold 5. The first mold 4 and the second mold 5 are then joined and clamped, and the first divided portion 10 and the second divided portion 20 are joined with the secondary resin 6. When the resin injected into the cavity in the closed mold state cools during the die sliding from this first mold molding step and second mold molding step to the joining step, molding shrinkage occurs in the first divided portion 10 in the first mold 4 and in the second divided portion 20 in the second mold 5, but the ribs 15, 25 have a molding shrinkage prevention effect. That is, even if the first divided section 10 and the second divided section 20 attempt to shrink in either direction within the first mold 4 or the second mold 5 (see shrinkage direction 200 in FIG. 3( a)), the ribs 15, 25 function as stoppers to prevent misalignment of the joints (butt surfaces 17, 27) between the first divided section 10 and the second divided section 20. In other words, without the ribs 15, 25, the first divided section 10 and the second divided section 20 would be misaligned in the shrinkage direction 200, resulting in poor formation of the hollow section 30 or injection leakage of the secondary resin 6. This necessitates adjustment of the joint in the joining step by adjusting the positioning of the first mold 4 or the second mold 5 or by adjusting molding conditions such as the molding temperature and cooling timing. However, according to the manufacturing method of this embodiment, the ribs 15, 25 can suppress molding shrinkage, making such adjustments unnecessary.

[0025] After the joining step, once the first divided portion 10, the second divided portion 20 and the secondary resin 6 have cooled, the first mold 4 and the second mold 5 can be opened and demolded to obtain the tubular body 1 shown in Figure 1.

[0026] According to the above manufacturing method, in the first mold molding step, a convex rib portion 15 is molded on the outer surface of the joint projection 13, projecting in the direction opposite to the mold clamping direction. Therefore, even if molding shrinkage occurs in the first segment 10 in the joining step, the rib portion 15 of the first segment 19 is engaged with the first mold 4, preventing the first segment 10 from shifting in position in the shrinkage direction. This allows the first mold 4 and the second mold 5 to be properly positioned, reducing leakage of the secondary resin 6 and poor joining between the first segment 10 and the second segment 20, resulting in the manufacture of a tubular body 1 with high molding accuracy. While it is particularly difficult to accurately mold a tubular body 1 with a long straight tube portion 11a in the axial direction, the manufacturing method of this embodiment allows for high molding accuracy. Furthermore, the ribs 15, 25 formed on the joint projections 13, 23 of the finished tubular body 1 reinforce the rigidity of the tubular body 1, making it less susceptible to deformation.

[0027] As shown in FIG. 3( a), the rib portion 15 of the first divided portion 10 protrudes in the direction opposite to the mold clamping direction 100. However, the rib portion 15 itself is shaped to allow smooth release from the mold when the mold is opened and to easily withstand the force acting in the mold clamping direction 100 (mold clamping force). The end face 15a of the rib portion 15 formed at the bent portion 11b is formed substantially parallel to the mold clamping direction 100, thereby making it easier to withstand the mold clamping force. The straight pipe portion 11a of the first divided portion 10 is inclined because the tubular body 1 has a height difference. However, by forming the end face 15a of the rib portion 15 in a larger area than the rib portion 15 formed at the bent portion 11b, it can be made easier to withstand the mold clamping force. That is, if the height positions of both ends 1a, 1b of the axial direction of the tubular body 1 are different and there is a height difference, misalignment in the contraction direction is more likely to occur during the joining step. However, with the above configuration, the rib portion 15 can suppress misalignment, thereby enabling the molding of a tubular body with high molding precision. Furthermore, by making it easier to receive the mold clamping force in this way, the occurrence of flash in the molded product can be suppressed. Furthermore, since the second divided section 20 also has rib sections 25 formed therein, molding shrinkage of the second divided section 20 can also be suppressed. Furthermore, the rib sections 15 of the first divided section 10 and the rib sections 25 of the second divided section 20 protrude in different directions and are formed alternately (not formed back to back in the same position) as shown in Figure 2(b), so the first divided section 10 and the second divided section 20 can be accurately overlapped, effectively suppressing misalignment of the abutting surfaces 17, 27.

[0028] Next, another embodiment of the tubular body according to this embodiment will be described with reference to Figures 5(a) and 5(b). Differences from the above embodiment will be mainly described, and the same components will be denoted by the same reference numerals and their description will be omitted or simplified.

[0029] In the above embodiment, a tubular body 1 having one axial end 1a and the other axial end 1b at different height positions and a manufacturing method thereof were described. In this embodiment, a tubular body 1A will be described in which one axial end 1a and the other axial end 1b are at the same height, and which has a different shape including a straight pipe portion 11a and a bent portion 11b on both axial sides of the straight pipe portion 11a. The tubular body 1A according to this embodiment differs in that the second divided portion 20 does not have a rib portion 25 and a connecting portion 28, and in that the positions of the bolt holes 3b, 3b of the mounting portion 3 and the height of the rib portion 25 provided in the first divided portion 10 are higher than the height of the wall portion 12 provided in the joint protrusion 13. The tubular body 1A is also different in that the rib portions 15 formed on the outer surface of the joining protrusion 13 of the first divided portion 10 are arranged at intervals along the radial direction (width direction), and rib portions 15 are also provided at both axial ends (one end 1a side and the other end 1b side).However, a manufacturing method similar to that of the above embodiment can also be applied to such a tubular body 1A.

[0030] In the tubular body 1A according to this embodiment, a convex rib portion 15 is formed on the outer surface of the joining protrusion 13 in the first mold molding step, protruding radially in the direction opposite to the mold clamping direction 100 during the joining step. Therefore, even if molding shrinkage occurs in the first divided section 10 during the joining step, the rib portion 15 of the first divided section 10 is engaged with the first mold 4, thereby preventing the first divided section 10 from shifting in position in the shrinkage direction. This allows the first mold 4 and the second mold 5 to be properly positioned, reducing leakage of the secondary resin 6 and poor joining between the first divided section 10 and the second divided section 20, and enabling the production of a tubular body 1A with high molding accuracy. In this embodiment, the portion 50 of the rib portion 15 facing the mold clamping direction of the first mold (see FIG. 5(b)) corresponds to the end face 15a of the rib portion 15. 5(b), the end surface 15a of the rib portion 15 can be made flat so that it can easily receive the clamping force of the first mold 4, and since the rib portion 15 is formed not only in the radial direction but also in the axial direction, it is possible to further suppress misalignment of the butting surfaces during the joining step. Furthermore, since the tubular body 1A formed by the above manufacturing method is provided with a plurality of rib portions 15, it can be made to have the rigidity required of a tubular body.

[0031] As mentioned above, the configuration and shape of the tubular bodies 1, 1A are not limited to those shown in the figures. For example, they may have a serpentine shape with multiple bent portions 11b, and the bend angle of the bent portions 11b is not particularly limited. The length and number of straight pipe portions 11a and the axial flow of the tubular bodies 1, 1A are also not limited to those shown in the figures. The configuration of the mounting portion 3 is also not limited to those shown in the figures, and may have a different shape and thickness, and the presence or absence of bolt holes 3b and the number of bolt holes 3b are not limited. Furthermore, the configuration of the butting surfaces 17, 27 of the first divided portion 10 and the second divided portion 20 is also not limited to those shown in the figures. [Explanation of symbols]

[0032] 1. Tubular body 1a One end 1b Other end 2 Main pipe section 3 Mounting part 4 Type 1 5 Type 2 6 Secondary Resin 10 1st division 20 Second division 13,23 Joint protrusion 15,25 Rib section 15a, 25a end face 40 flow path

Claims

1. A method for manufacturing a tubular body formed by joining two radially divided semi-tubular portions with a secondary resin, comprising: a first mold molding step of molding, with a first mold, a first divided portion which is a semi-tubular portion on the outer side in the bending direction and which has a straight pipe portion and a bent portion connected to the straight pipe portion; a second mold molding step of molding a second divided portion, which is a semi-tubular portion on the inner side of the bending direction of the bending portion, using a second mold; a joining step of positioning the first divided portion and the second divided portion in a joined state, clamping the first mold and the second mold, and joining the first divided portion and the second divided portion with the secondary resin, In the first molding step, A method for manufacturing a tubular body, characterized in that a joining protrusion protruding radially from the semi-tubular portion and having a flow path into which the secondary resin is filled is molded on the circumferential edge of the first divided portion, and a rib portion provided convexly along the radial direction on the outer surface of the joining protrusion.

2. In claim 1, A method for manufacturing a tubular body, characterized in that a portion of the rib portion facing the clamping direction of the first mold is made into a flat surface.

3. In claim 1 or claim 2, A method for manufacturing a tubular body, characterized in that one end portion in the axial direction of the tubular body and the other end portion in the axial direction are at different height positions.

4. A tubular body having a straight pipe portion and a bent portion, and configured by joining two semi-tubular portions divided in the radial direction with a secondary resin, a first divided portion having a straight pipe portion and a semi-tubular portion connected to the straight pipe portion and located on an outer side in a bending direction of the bending portion; a second divided portion having a semi-tubular portion on the inner side of the bending portion in the bending direction; a joining protrusion protruding in a radial direction of the semi-tubular portion and having a flow path into which the secondary resin is filled is provided on each of circumferential edge portions of the first divided portion and the second divided portion, A tubular body characterized in that a plurality of convex rib portions are provided at intervals along the radial direction on the outer surface of the joint protrusion of the first divided portion.

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