FUEL PIPE, FUEL PIPE CONNECTION STRUCTURE, AND METHOD FOR MANUFACTURING FUEL PIPE

Abstract

A fuel pipeline includes an outer tube having a connecting head that extends outward in a radial direction on at least one end portion thereof, and an inner tube that is constructed on a portion of the outer tube and connects to both end portions of the connecting head in an axial direction.

Description

FUEL PIPE, FUEL PIPE CONNECTION STRUCTURE, AND METHOD FOR MANUFACTURING FUEL PIPE TECHNICAL FIELD This description relates to a fuel pipeline, a fuel pipeline connection structure, and a method for manufacturing a fuel pipeline. TECHNICAL BACKGROUND A fuel line for a direct-injection internal combustion engine (see Patent Literature 1) is known. In the end portion of this type of fuel line, a connecting head is provided that connects to a union component. The connecting head is a portion that projects radially, contacts the union component, and is further secured to the union component with a cap nut or the like, such that the connecting head is interposed between them and connects to the union component. APPOINTMENT LIST Patent Literature [Patent Literature 1] Unexamined Japanese Patent Application No. 2007-77807 SUMMARY OF THE INVENTION Technical Problem In fuel piping systems, if a certain tightening torque is exceeded when tightening the cap nut or similar fitting, the resulting axial force can cause the connecting head to deform, making it less likely that the predetermined axial force required to seal an internal pressure will be achieved. This is particularly problematic when the fuel piping is used as a high-pressure fuel line. One object of the present description is to solve the above problem, and one object of the present description is to provide a fuel pipe, a connection structure for the fuel pipe, and a method for manufacturing a fuel pipe, in which a predetermined axial force to seal an internal pressure can be easily obtained. SOLUTION The present description is a fuel pipe that includes: an outer pipe having a connecting head that extends outward in a radial direction, in at least one end portion thereof; and an inner pipe that is constructed (is installed within) a portion of the outer pipe, and connects to both end portions of the connecting head in an axial direction. on« / ηη / ζζηζ / Ε / γίΛΐ According to this fuel line design, the inner tube is constructed within a portion of the outer tube, and the inner tube connects to both end portions of the connecting head in the axial direction. As a result, even if the tightening torque applied to the clamping portion increases, the connecting head is less likely to deform, and it is easy to achieve a predetermined axial force to seal the internal pressure. The present description is of a fuel pipeline connection structure comprising: the aforementioned fuel pipeline; a connection portion having an internal flow path configured to receive and communicate with the fuel pipeline's connecting head; and a clamping portion configured to secure the connecting head to the connection portion. In this connection structure, even if the tightening torque applied by the clamping portion increases, the connecting head is less likely to be crushed, and a predetermined axial force is easily achieved to seal against internal pressure. This description is a method for manufacturing a fuel pipe, wherein a connecting head is formed by pressing an end portion of an outer tube with an inner tube constructed in at least one end portion in an axial direction, causing the outer tube to extend outward in a radial direction, and both end portions of the connecting head in the axial direction are connected to the inner tube. The fuel pipe can be readily manufactured using the outer tube, in which the inner tube is constructed and connected to both end portions of the connecting head. ADVANTAGEOUS EFFECTS OF THE INVENTION According to the present description, it is easy to obtain a predetermined axial force to seal the internal pressure. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is an enlarged cross-sectional view showing a portion of a fuel pipeline, according to one modality. Figure 2 is a cross-sectional view showing a connection structure for the fuel pipeline, according to one modality. Figure 3 is a cross-sectional view showing a connection structure for the fuel pipeline, according to another modality. Figure 4a-4c relates to a first method of manufacturing a fuel pipe, and each of Figure 4a, Figure 4b, and Figure 4c, is an explanatory view showing one step. Figure 5a-5c relates to the first method of manufacturing a fuel pipe, and each of Figure 5a, Figure 5b, and Figure 5c is an explanatory view showing one step. Figure 6a-6c relates to a second method of manufacturing a fuel pipe, and each of Figure 6a, Figure 6b, and Figure 6c is an explanatory view showing one step. Figure 7a-7c relates to the second method of manufacturing a fuel pipe, and each of Figure 7a, Figure 7b, and Figure 7c is an explanatory view showing one step. an« / ηη / ζζηζ / Ε / γίΛΐ Figure 8a-8c relates to the second method of manufacturing a fuel pipe, and each of Figure 8a, Figure 8b, and Figure 8c is an explanatory view showing one step. DESCRIPTION OF THE MODALITIES A fuel pipeline according to one aspect of the present description includes an outer tube and an inner tube constructed (installed within) a portion of the outer tube. At least one end portion of the outer tube is provided with a connecting head extending outward in a radial direction. The inner tube connects to both end portions of the connecting head in an axial direction. In fuel piping, the inner tube is constructed within a portion of the outer tube, and the inner tube connects to both end portions of the fitting in the axial direction. As a result, even if the tightening torque due to the clamping portion increases, the fitting is less likely to deform, and it is easy to achieve a predetermined axial force to seal the internal pressure. Visually, the inner tube can be crimped onto both end portions of the connecting head in the axial direction. This crimping allows the inner tube and both end portions of the connecting head to be easily connected. In appearance, the inner tube can be brazed to both end portions of the connecting head in the axial direction. Due to the brazing, the inner tube and both end portions of the connecting head can be firmly connected to each other. In appearance, the outer tube includes a portion of the main body that has a constant outer diameter in the axial direction, and the connecting head extends outward radially from this portion of the main body. One end portion of the connecting head can be an open tip end, and the other end portion can be a portion on the opposite side of the tip end in the axial direction, where the outer diameter changes relative to the main body portion. When the connecting head is clamped using the clamping portion, stress concentration is likely to occur in a portion where the outer diameter changes relative to the main body portion. In the configuration described above, this portion is the other end portion of the connecting head.Since the inner tube connects to one end portion and the other end portion of the connecting head, the connecting head is less likely to be crushed, and it is easy to obtain a predetermined axial force to seal the internal pressure. A fuel pipeline connection structure according to one aspect of the present description includes: the aforementioned fuel pipeline; a connection portion having an internal flow path configured to receive and communicate with the fuel pipeline's connection head; and a clamping portion configured to secure the connection head to the connection portion. In this connection structure, even if the tightening torque due to the clamping portion increases, the connection head is less likely to be crushed, and a predetermined axial force is easily achieved to seal the internal pressure. on« / nn / zznz / E / YiAi In a method for manufacturing a fuel pipe according to one aspect of the present description, a connecting head is formed by pressing an end portion of an outer tube with an inner tube constructed in at least one end portion in an axial direction, causing the outer tube to extend outward in a radial direction, and both end portions of the connecting head, in the axial direction, are connected to the inner tube. The fuel pipe can be readily manufactured from the outer tube, in which the inner tube is constructed and connected to both end portions of the connecting head. In this process, brazing material can be placed on the outer circumference of the inner tube. After the connecting head is formed, heat treatment can be performed to relieve residual stress, thus brazing the inner tube and the connecting head of the outer tube together. A reliable connection between the inner tube and the connecting head of the outer tube can be achieved through brazing, while the heat treatment is being performed to relieve residual stress. A fuel line will be described here in a specific configuration. This fuel line, for example, connects a high-pressure pump to a gasoline direct injection engine and a supply line to the fuel line. In recent years, it has become necessary to increase the operating pressure of gasoline direct injection engines due to legal regulations and other factors. This fuel line configuration is particularly advantageous for high-pressure applications. For instance, fuel line 1 is used with one end connected to the supply line 2 (see Figure 2), and the other end connected to the high-pressure pump (not shown). As shown in Figure 1, the fuel pipe 1, according to the embodiment, includes an outer tube 4 and a cylindrical component 5 (an inner tube) constructed within the outer tube 4. For example, the outer tube 4 and the cylindrical component 5 can be made of SUS, and a copper coating is additionally applied to the cylindrical component 5. The cylindrical component 5 is not positioned along the entire length of the outer tube 4 in an axial direction X, but rather in a portion near one end (hereafter referred to as the “tip end”). The axial direction X of the outer tube 4 refers to a direction along an axis L of the outer tube 4. The outer tube 4 includes a portion of the main body 6, which has a constant outer diameter, and a connecting head 8 that extends outward in a radial direction r with respect to the portion of the main body 6.Here, the fact that the external diameter of the main body portion 6 is constant means that the change in the external diameter is within the error range, and that the external diameter is substantially constant. This error range is ±1 mm. Furthermore, the internal diameter of the cylindrical component 5 is, for example, 80% or less, preferably 70% or less, and more preferably 60% or less with respect to the internal diameter of the main body portion 6 of the outer tube 4. The connecting head 8 is provided as a portion that includes the tip end of the outer tube 4. Specifically, the connecting head 8 is provided to extend outward in the radial direction r along the outer diameter, and the inner diameter has both end portions of the outer tube 4 in the axial direction X, and both of the end portions are the starting points of the outward extension. One end portion is a tip end released from the outer tube 4. The other end portion is a portion on a side opposite the tip end in the axial direction X, which connects to the main body portion 6, and is a portion where the outer diameter changes with respect to the main body portion 6.In the following description, one end portion of the connection head 8 is referred to as a tip end portion 9, and the other end of the same is referred to as a neck portion 10. With respect to the neck portion 10, the portion where the outside diameter changes relative to the main body portion 6 includes both the case where the outside diameter becomes larger and the case where the outside diameter becomes smaller. Furthermore, the portion where the outside diameter changes relative to the main body portion 6 does not simply mean a location where the outside diameter begins to change relative to the main body portion 6 (a change start location), but rather a portion that includes a predetermined dimensional region in the axial X direction, with the change start location as a reference.Specifically, the portion where the outside diameter changes with respect to the main body portion 6 means a portion that includes a predetermined dimensional region on one side of the main body portion 6, and one side of the tip end portion 9 with the location of the start of the change as a reference, and it is possible to find the predetermined dimensional region as, for example, a dimensional region in the axial X direction that corresponds to 20% of the outside diameter of the main body portion 6. The cylindrical component 5 is placed inside the connecting head 8. The length of the cylindrical component 5 in the axial X direction is equal to or longer than the length of the connecting head 8 in the axial X direction. According to this embodiment, the cylindrical component 5 extends in the axial X direction from the end portion of the tip 9 of the connecting head 8, beyond a boundary between the connecting head 8 and the main body portion 6. Furthermore, the cylindrical component 5 connects to the end portion of the tip 9 and the neck portion 10 of the connecting head 8 by overlapping them. For example, the cylindrical component 5 is crimped onto the end portion of the tip 9 and the neck portion 10 of the connecting head 8.Furthermore, the copper coating is applied to the outer periphery of the cylindrical component 5, and thus the outer periphery of the cylindrical component 5 is brazed to the end portion of the tip 9 and the neck portion 10 of the connecting head 8, through the brazing of the copper coating. A brazing material such as brazing foil can be placed on the outer periphery of the cylindrical component 5, and the cylindrical component 5 and the connecting head 8 can be brazed to each other with the brazing material. Here, the connection between the neck portion 10 of the connecting head 8 and the cylindrical component 5 will be supplemented. As described above, since the neck portion 10 includes a predetermined dimensional region with the change start location as a reference, the connection between the neck portion 10 and the cylindrical component 5 means that the cylindrical component 5 connects to at least a portion of a region in the axial X direction where the neck portion 10 is formed. Furthermore, the same applies to crimping the cylindrical component 5 to the neck portion 10 or brazing the cylindrical component 5 to the neck portion 10, meaning that the cylindrical component 5 is crimped or brazed to at least a portion of the region in the axial X direction where the neck portion 10 is formed. on« / ηη / ζζηζ / Ε / γίΛΐ The connecting head 8 extends outwards, such that not only the outer diameter but also the inner diameter expands in the radial direction r, and there is a gap Ag between the connecting head 8 and the cylindrical component 5. However, a form without the gap Ag is also possible. In this case, the cylindrical component 5 is connected to the connecting head 8 along the entire region of the connecting head 8 in the axial X direction, in addition to the tip end portion 9 and the neck portion 10 (both end portions) of the connecting head 8. The technical significance of the cylindrical component 5 being connected to the connecting head 8 relates to an aspect in which the cylindrical component 5 is fixed to the connecting head 8 to such a degree that the movement of the cylindrical component 5 in the axial X direction is restricted.In the present embodiment, the space Ag is between the connecting head 8 and the cylindrical component 5, and the cylindrical component 5 extends beyond the space Ag and connects to the connecting head 8. That is, when the space Ag is taken into consideration as a reference, it is also possible to find a portion where the connecting head 8 comes into contact with the cylindrical component 5 and closes the space Ag on one side of the tip end of the space Ag as the tip end portion 9 of the connecting head 8, and it is also possible to find a portion where the connecting head 8 comes into contact with the cylindrical component 5 and closes the space Ag on an opposite side of the tip end side in the axial direction, as the neck portion 10 of the connecting head 8. The following describes a connection structure J of fuel pipe 1. As shown in Figure 2, the connection structure J includes fuel pipe 1, a pipe joint 22, and a clamping portion 3 for securing the connection head 8 to the pipe joint 22. An internal flow path R, which receives the connection head 8 from fuel pipe 1 and communicates with fuel pipe 1, is formed at the pipe joint 22. In the present embodiment, the pipe joint 22 is attached to a receiving port 21 of supply pipe 2 and is an example of a connection portion. In a case where fuel pipe 1 is directly connected to a receiving port 21 or similar port of supply pipe 2, the receiving port 21 is an example of a connection portion. A fixed tube portion 22a, which is installed in and joined to the receiving port 21, is provided on one side of a tube joint end portion 22, with the internal flow path R as a reference. A threaded tube portion 22b, threaded into the clamping portion 3, is provided on one side of the other tube joint end portion 22. A flange portion 22c, which contacts the receiving port 21, is provided between the fixed tube portion 22a and the threaded tube portion 22b. A receiving surface 22d, which comes into contact with the connection head 8 of the fuel pipe 1, is formed on the end portion (the tip end) of the threaded pipe portion 22b. On the receiving surface 22d, the internal flow path R expands into a narrowed shape. A sloped surface 8a of the connection head 8 on one side of the tip end portion 9 comes into contact with the receiving surface 22d, and a sloped surface 8b of the connection head 8 on one side of the neck portion 10 comes into contact with the clamping portion 3. The clamping portion 3 includes a tubular body portion 31, in which a female screw is formed to be screwed into the threaded tube portion 22b, and a pressing portion 32 that contacts and is pressed against the connecting head 8. An end portion of the body portion 31 is open, and the pressing portion 32 is provided on an end portion of the body portion 31 on the opposite side. The pressing portion 32 is provided in an annular shape (a donut shape) to reduce the diameter of the body portion 31, and a central hole H, through which the main body portion 6 of the fuel pipe 1 is inserted, is formed in the center of the pressing portion 32.A narrowed pressing surface 33 that comes into contact with the tilting surface of the connecting head 8 on one side of the neck portion 10, is formed within the pressing portion 32. The following describes a method for forming the connection structure J of the fuel pipe 1. The pipe joint 22 is fixed to the receiving port 21 of the supply pipe 2. The main body portion 6 of the fuel pipe 1 passes through the central hole H of the clamping portion 3, and in this state, the connection head 8 of the fuel pipe 1 comes into contact with the receiving surface 22d of the pipe joint 22. The body portion 31 of the clamping portion 3 is threaded into the threaded pipe portion 22b of the pipe joint 22. The connection head 8 is then interposed between the receiving surface 22d of the pipe joint 22 and the pressing surface 33 of the clamping portion 3.In order to ensure sufficient sealing performance to withstand the internal pressure generated within the fuel pipe 1, it is necessary to apply additional torque to the clamping portion 3 for threading. If the connection head 8 deforms under the axial force generated by this threading, ensuring sufficient sealing performance becomes difficult. However, in the fuel pipe 1 according to the present embodiment, the cylindrical component 5 is constructed on the connection head 8, and the cylindrical component 5 is connected to both end portions of the connection head 8 in the axial X direction, that is, the tip end portion 9 and the neck portion 10. Thus, the fuel pipe 1 has a structure capable of withstanding deformation of the connection head 8. A fuel pipeline 1A, according to another embodiment, will now be described with reference to Figure 3. This fuel pipeline 1A includes the same members and elements as fuel pipeline 1 and the connection structure J of fuel pipeline 1 according to the previous embodiment. Therefore, similar members and elements are designated using the same reference symbols, and their detailed descriptions are omitted. In fuel line 1A, a perforated tube 5A is used instead of the cylindrical component 5 mentioned above. The perforated tube 5A is, for example, a tube made of SUS, and can be cut and manufactured accordingly. The length of the perforated tube 5A in the axial X direction is equal to or longer than the length of the connecting head 8 in the axial X direction. The perforated tube 5A is positioned to overlap the end portion of the tip 9 and the neck portion 10 of the connecting head 8. Furthermore, the perforated tube 5A is crimped onto the end portion of the tip 9 and the neck portion 10 of the connecting head 8. Additionally, copper plating is applied to the outer periphery of the perforated tube 5A, and thus, the outer periphery of the perforated tube 5A is brazed to the end portion of the tip 9 and the neck portion 10 of the connecting head 8 by brazing the copper plating.Also, in the fuel pipe 1A, the perforated tube 5A and the connecting head 8 can be brazed together with brazing material such as a brazing sheet. The perforated tube 5A has a smaller internal diameter than the cylindrical component 5. Specifically, the thickness of the aforementioned cylindrical component 5 is smaller than the internal diameter of the cylindrical component 5, but the thickness of the perforated tube 5A is greater than the internal diameter of the perforated tube 5A. Furthermore, the internal diameter of the perforated tube 5A is, for example, 30% or less, preferably 22% or less, and more preferably 20% or less with respect to the external diameter of the perforated tube 5A. Additionally, the internal diameter of the perforated tube 5A is, for example, 60% or less, preferably 40% or less, and more preferably 30% or less with respect to the internal diameter of the main body portion 6 of the outer tube 4. The operation and effect of fuel line 1 or 1A and the J-connection structure of fuel line 1 or 1A, as described above, will now be discussed. As the pressure of the gasoline direct injection engine increases, the stress generated by the internal pressure also increases, making it necessary to ensure the sealing performance can withstand this internal pressure. Therefore, it is necessary to increase the tightening torque on the clamping portion. However, in a fuel line that does not have an internal tube like the cylindrical component (a comparative shape), the axial force generated by the added tightening torque on the clamping portion can cause the connecting head to deform, making it difficult to ensure a predetermined axial force to seal the internal pressure. Furthermore, in fuel pipe 1 or 1A and fuel pipe connection structure J, the cylindrical component 5 or the perforated tube 5A is constructed on the connection head 8, and the cylindrical component 5 or the perforated tube 5A is connected to the tip end portion 9 and the neck portion 10 of the connection head 8. That is, in fuel pipe 1 or 1A and fuel pipe connection structure J, the cylindrical component 5 or the perforated tube 5A has a structure designed to withstand deformation of the connection head 8. As a result, even if the tightening torque on the clamping portion 3 is increased to ensure sealing performance, the connection head 8 withstands the axial force generated by the increased tightening torque, thus easily achieving a predetermined axial force to seal the internal pressure. Furthermore, the cylindrical component 5 or the perforated tube 5A, depending on the configuration, is connected to at least the end portion of the tip 9 and the neck portion 10. As a result, even if a force is applied to deform the connecting head 8, due to the added tightening torque, this force acts as a force that causes the end portion of the tip 9 or the neck portion 10 to decrease in diameter. Therefore, the adhesion of the connecting head 8 to the cylindrical component 5 or the perforated tube 5A is increased, which is advantageous in terms of improving sealing performance. Furthermore, in a case where the fuel pipe 1 or 1A is manufactured according to each embodiment, even if a terminal processing method such as a manufacturing method described later is employed—for example, a method for forming the connection head 8 by pressing the end portion of the tip 9 of the outer tube 4—it is possible to prevent a depression from forming in the neck portion 10 of the connection head 8. Specifically, it is possible to prevent the tube wall of the outer tube 4 from retracting toward the center of the tube and from forming a depression that extends in a circumferential direction. That is, in each embodiment, the cylindrical component 5 or the perforated tube 5A is constructed in the outer tube 4, and the cylindrical component 5 or the perforated tube 5A extends from the end portion of the tip 9 of the connection head 8 to the neck portion 10 of the connection head 8.As a result, the cylindrical component 5 or the perforated tube 5A supports the force to reduce the diameter of the neck portion 10 of the connecting head 8 during terminal processing, and it is possible to prevent a depression from being generated in the neck portion 10. Furthermore, in the case of fuel pipe 1A, from which the orifice tube 5A is constructed, the orifice tube 5A can be manufactured by cutting or similar means, and the internal diameter dimension of the orifice tube 5A can be appropriately designed (adjusted). Here, for example, in a fuel pipe that does not have the orifice tube 5A or similar (a comparative form), it is difficult to create an orifice that locally narrows the flow path when testing to form the connection head through end processing. On the other hand, in the fuel pipe 1A described above, the orifice can be easily created by constructing the orifice tube 5A within the outer tube 4.Furthermore, by removing the perforated tube 5A from the outer tube 4 as needed, it is possible to improve the leakage of the liquid when cleaning the inside of the outer tube 4, it becomes easier to meet the internal foreign matter requirement and the defect due to residual contamination can also be reduced. Furthermore, the cylindrical component 5 or the perforated tube 5A, according to each modality, is crimped into the end portion of the tip 9 and the neck portion 10 of the connection head 8. Due to this crimping, in the present modality, the cylindrical component 5 and the end portion of the tip 9 and the neck portion 10 of the connection head 8 can be easily connected to each other. Furthermore, the cylindrical component 5 or the perforated tube 5A, according to each modality, is bronze welded to the tip end portion 9 and the neck portion 10 of the connecting head 8. Due to this bronze welding, in the present modality, the cylindrical component 5 and the tip end portion 9 and the neck portion 10 of the connecting head 8 can be firmly connected to each other. Furthermore, in the fuel pipe 1 or 1A, depending on the configuration, the neck portion 10 of the connecting head 8 is a portion whose external diameter differs from the main body portion 6. When the connecting head 8 is secured with the clamping portion 3, a stress concentration is likely to occur in a portion where the external diameter differs from the main body portion 6, and this portion is the neck portion 10 of the connecting head 8. Since the cylindrical component 5 or the orifice pipe 5A connects to the tip end portion 9 and the neck portion 10 of the connecting head 8, the connecting head 8 is less likely to be crushed, and it is easy to obtain a predetermined axial force to seal the internal pressure. A method for manufacturing fuel pipe 1 will be described below. Hereafter, fuel pipe 1 according to one modality will be described as an example, but fuel pipe 1A according to another modality is substantially the same.The method for manufacturing the fuel pipe 1 includes a step of constructing the cylindrical component 5 (the inner tube) on the tip end portion 9 of the outer tube 4 (a construction step), a step of forming the connecting head 8 by pressing the tip end portion 9 of the outer tube 4 with the cylindrical component 5 constructed on the tip end portion 9 in the axial direction X and causing the outer tube 4 to extend outward in the radial direction r (a terminal processing step), and a step of connecting the tip end portion 9 and the neck portion 10 of the connecting head 8 to the cylindrical component 5 (a connection step). Furthermore, the connection step according to the present embodiment includes a crimping step and a brazing step.The setting step is performed simultaneously with the final processing step, and the brazing step is performed after the setting step. A first manufacturing method and a second manufacturing method will be described later. First, the first manufacturing method will be described with reference to Figures 4a-4c and 5a-5c. In the construction step of the first manufacturing method, the cylindrical component 5 is pre-inserted into the outer tube 4 before the formation of the connecting head 8 to form a precursor tube 100. For example, a fuel pipe manufacturing apparatus 1 includes a clamp 51. The clamp 51 has a groove 61 that follows the shape of the sloped surface of the connecting head 8 on one side of the neck portion 10 and the shape of the main body portion 6. The precursor tube 100 is placed in the groove 61 of the clamp 51 in an open state (see Figure 4a). The manufacturing apparatus includes a stop 53 that pushes the cylindrical component 5 into a predetermined position on the outer tube 4. The stop 53 moves to a predetermined position that intersects the axis L of the outer tube 4 (see Figure 4b). The precursor tube 100 is then pressed against the stop 53 for positioning, and the clamp 51 closes (see Figure 4c). The stop 53 then separates from the precursor tube 100 and returns to its original position (see Figure 5a). Next, the terminal processing step is performed. In this step, a punch 54 positioned on the L-axis of the outer tube 4 is brought close to the precursor tube 100 (see Figure 5b). In this state, the movement of the precursor tube 100 is restricted in the axial X direction. The punch 54 has a notch 62 that follows the shape of the tilting surface of the connecting head 8 on one side of the tip end portion 9. When the punch 54 presses the tip end portion 9 of the precursor tube 100, the outer tube 4 of the precursor tube 100 protrudes outward in the radial r direction, while being flattened in the axial X direction. A protruding portion of the outer tube 4 is shaped to follow the shapes of the notches 61 and 62 of the clamp 51 and the punch 54, and the connecting head 8 is turned.When the cylindrical component 5, constructed on the outer tube 4, is pressed by the punch 54, the cylindrical component 5 slides in the axial X direction instead of being crushed. The tip end portion 9 and the neck portion 10 of the connecting head 8, formed by the bulge in the outer tube 4, are slightly reduced in diameter and substantially crimped onto the cylindrical component 5 to connect to it (the crimping step in the connecting step). When the connecting head 8 is formed, the precursor tube 100 becomes the fuel pipe 1, the punch 54 retracts away from the connecting head 8, and the clamp 51 opens. on« / ηη / ζζηζ / Ε / γίΛΐ Next, the fuel pipe 1 removed from clamp 51 is placed in a heating furnace and subjected to heat treatment to relieve residual stress. In the fuel pipe 1 according to the present embodiment, copper coating is applied to the outer periphery of the cylindrical component 5 as a brazing material, and the copper coating melts through the aforementioned heat treatment, resulting in brazing between the cylindrical component 5 and the outer tube 4 (the brazing passage). The second manufacturing method will now be described with reference to Figures 6a-6c, 7a-7c, and 8a-8c. In the construction step of the second manufacturing method, the cylindrical component 5 is constructed on the end portion of the tip 9 of the outer tube 4. For example, the fuel pipe manufacturing apparatus 1 includes a mounting portion 55 for constructing the cylindrical component 5 on the outer tube 4. The mounting portion 55 includes a fitting portion 55a for holding the cylindrical component 5, and the cylindrical component 5 is mounted on the fitting portion 55a (see Figure 6a). First, stop 53 moves to a predetermined position that intersects the L-axis of the outer tube 4 (see Figure 6b). Next, the outer tube 4 is pressed against stop 53 for positioning, and clamp 51 closes (see Figure 6c). Then, stop 53 separates from the outer tube 4 and returns to its original position (see Figure 7a). Next, mounting portion 55 moves into the outer tube 4, and fitting portion 55a is pressed into the outer tube 4 along with the cylindrical component 5 (see Figure 7b). Fitting portion 55a separates from the outer tube 4 while leaving the cylindrical component 5 in the outer tube 4, and precursor tube 100 is formed (see Figure 7c). Next, the terminal processing step is performed. In the terminal processing step, punch 54 is moved to a position on axis L of the outer tube 4, instead of the mounting portion 55 (see Figure 8a). Then, punch 54 is brought close to the precursor tube 100 (see Figure 8b). In this state, the movement of the precursor tube 100 is restricted in the axial X direction. The punch 54 has a groove 62 that follows the shape of the tilting surface of the connecting head 8 on one side of the tip end portion 9. When the punch 54 presses the tip end portion 9 of the precursor tube 100, the outer tube 4 of the precursor tube 100 protrudes to extend outward in the radial r direction, while it is flattened in the axial X direction. A protruding portion of the outer tube 4 is formed to follow the shapes of the grooves 61 and 62 of the clamp 51 and the punch 54 and becomes the connecting head 8.When the cylindrical component 5, constructed on the outer tube 4, is pressed by the punch 54, the cylindrical component 5 slides in the axial X direction instead of being crushed. The tip end portion 9 and the neck portion 10 of the connecting head 8, formed by the bulge in the outer tube 4, are slightly reduced in diameter and substantially crimped into the cylindrical component 5 to connect to it (the crimping step in the connecting step). When the connecting head 8 is formed, the precursor tube 100 becomes the fuel pipe 1, the punch 54 retracts away from the connecting head 8, and the clamp 51 opens (see Figure 8c). Next, the fuel pipe 1 removed from clamp 51 is placed in a heating furnace and subjected to heat treatment to relieve residual stress. In the fuel pipe 1 according to the present method, copper coating is applied to the outer periphery of the cylindrical component 5 as a brazing material, and the copper coating melts through the aforementioned heat treatment, and as a result, brazing is performed between the cylindrical component 5 and the outer tube 4 (the brazing passage). According to the above method for manufacturing fuel pipe 1, it is possible to easily manufacture fuel pipe 1 provided with the outer tube 4, in which the cylindrical component 5 is built connected to the end portion of the tip 9 and the neck portion 10 of the connecting head 8. Although the present description has been written using each modality as an example, it is not limited to the previous modality. For example, the connection between the connection head and the inner tube may be solely crimped without brazing, or it may be solely brazed without crimping. Crimping is intended to include a concept of fit, and the connection between the connection head and the inner tube includes screwing and other mating aspects. Furthermore, the outer tube is not limited to a shape having two ends, one at one end and the other at the other, and may be, for example, a shape that branches in the middle and has three or more ends. The outer tube includes an aspect in which the connecting head is formed at at least one end of a plurality of ends. List of Reference Signs, 1A Fuel Pipe External tube Fastening portion Cylindrical component (inner tube) 5A Tube with holes (inner tube) Portion of the main body Connection head Tip end portion (a connection head end portion) Neck portion (the other end portion of the connection head) Pipe joint (connecting portion) J Connection structure R Internal flow path r Radial direction X Axial direction

Claims

1. A fuel pipeline, comprising: an outer tube having a connecting head extending outwards in a radial direction in at least one end portion thereof; and an inner tube constructed in a portion of the outer tube and connected to both end portions of the connecting head in an axial direction.

2. The fuel pipe according to claim 1, wherein the inner tube is crimped into both of the end portions of the connecting head in the axial direction.

3. The fuel pipe according to claim 1 or 2, wherein the inner tube is bronze welded to both of the end portions of the connecting head in the axial direction.

4. The fuel pipe according to any of claims 1 to 3, wherein the outer tube includes a portion of the main body having a constant outer diameter in the axial direction, and the connecting head extends outward in the radial direction, with respect to the portion of the main body, and wherein one end portion of both of the end portions of the connecting head is an open tip end, and the other end portion is a portion on a side opposite the tip end in the axial direction, wherein the outer diameter changes with respect to the portion of the main body.

5. A fuel pipe connection structure comprising: the fuel pipe according to any of claims 1 to 4; a connection portion having an internal flow path configured to receive the fuel pipe connection head and to communicate with the fuel pipe; and a clamping portion configured to secure the connection head to the connection portion.

6. A method for manufacturing a fuel pipe, wherein a connecting head is formed by pressing an end portion of an outer tube with an inner tube constructed in at least one end portion in an axial direction and causing the outer tube to extend outward in a radial direction, and both of the end portions of the connecting head in the axial direction are connected to the inner tube.

7. The method for manufacturing a fuel pipe according to claim 6, wherein a brazing material is placed on an outer circumference of the inner tube, and wherein, after the connection head is formed, heat treatment is performed to relieve residual stress in order to braze the inner tube and the connection head of the outer tube together.

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