WO2020031868A1

WO2020031868A1 - Pipe member crimp joining method

Info

Publication number: WO2020031868A1
Application number: PCT/JP2019/030367
Authority: WO
Inventors: 隆介日置; 智恵子今井; 今村　美速
Original assignee: 株式会社神戸製鋼所
Priority date: 2018-08-08
Filing date: 2019-08-01
Publication date: 2020-02-13
Also published as: JP2020025983A; JP6605775B1

Abstract

A hole portion (17a) of a forming jig (17) is arranged on the radially outer side of an overlapping portion formed by inserting a second pipe member (13) inside a first pipe member (11). A pipe end (21) on the overlapping portion side of the first pipe member is caused to protrude outward from the hole portion in the axial direction. A coil (19) including a conductor winding portion having a longer axial direction length than that of the overlapping portion is inserted inside the second pipe member, and the second pipe member is electromagnetically expanded to form a bulge portion (29) by simultaneously deforming the first pipe member and the second pipe member. In this way, the pipe end of the first pipe member is caused to expand diametrically along an inclined surface of the second pipe member, on the forming jig side of a maximum diameter portion of the bulge portion.

Description

Tube member caulking method

The present invention relates to a method of caulking pipe members for joining pipe members having different diameters by electromagnetic molding.

鋼 Steel members are often used in automobile structural parts from the viewpoint of cost and workability such as welding. However, in response to recent demands for improved fuel efficiency, some of the steel materials have been replaced with lightweight members. In addition to panel members, application of such lightweight members to frame members has been studied. ing.

管 In addition, a pipe member is also used as a lightening member, and a method of joining pipe members having different diameters to each other with high strength at a pipe end is desired. For example, Patent Literature 1 discloses a method in which a small-diameter pipe and a large-diameter pipe, which are made of steel, are coaxially overlapped with each other, and internal pressure is applied to the overlapped portion to integrally expand the diameter and caulk. . Patent Document 2 discloses a method of integrally expanding the diameter of an aluminum alloy or a steel material by electromagnetic forming.

Japanese Patent Application Laid-Open No. 11-201343 Japanese Patent Application Laid-Open No. 2018-83216

However, in the tube expansion technology of Patent Document 1, as shown in FIG. 11A, after the inner tube member 41 and the outer tube member 43 are both expanded by electromagnetic expansion of the inner tube member 41, as shown in FIG. 11B. Then, a springback difference is generated between the two

pipe members

41 and 43, and a gap region 45 that is not partially adhered is generated. This gap region 45 lowers the joint strength between the pipe members and causes looseness and crimping. Similarly, in the pipe expansion technique of Patent Document 2, a springback difference after expansion may occur. Furthermore, the joining strength of the pipe member in the circumferential direction is low, and the load resistance such as torsion may be reduced.

An object of the present invention is to provide a method for caulking a pipe member which can suppress a gap of a caulked portion caused by a springback difference after pipe expansion and improve torsional strength.

The present invention has the following configurations.
Preparing a first pipe member and a second pipe member smaller in diameter than the first pipe member;
A step of preparing a forming jig in which a hole having a larger diameter than the first pipe member is formed;
The second pipe member is inserted into the pipe of the first pipe member to form an overlapping portion between the first pipe member and the second pipe member, and is formed radially inward of the hole of the molding jig. A step of disposing the overlapping portion and projecting a pipe end of the first pipe member on the overlapping portion side outwardly in the axial direction from the hole;
Inserting a coil having a conductor winding portion having an axial length longer than the overlapping portion at an axial position of the overlapping portion in the pipe of the second pipe member;
The coil is energized to electromagnetically expand the second pipe member to form an expanded portion in which the first pipe member and the second pipe member are simultaneously expanded, and the expansion portion is larger than the maximum diameter portion of the expansion portion. A step of expanding the pipe end of the first pipe member along the slope of the second pipe member on the forming jig side.

According to the method for caulking pipe members of the present invention, it is possible to suppress the gap of the caulked portion caused by the springback difference after expanding the pipe, and improve the torsional strength.

FIG. 1 is a cross-sectional view illustrating the arrangement of a first tube member, a second tube member, an electromagnetic molding coil, and a molding jig before electromagnetic molding. FIG. 2 is an external perspective view of the forming jig of the first configuration example. FIG. 3 is a plan view showing a state where an overlapping portion of the first tube member and the second tube member shown in FIG. 1 is electromagnetically formed. FIG. 4 is a schematic perspective view showing a joined body of the first tube member and the second tube member from which the molding jig has been removed after the electromagnetic molding. FIG. 5A is a process explanatory view showing stepwise how the first tube member and the second tube member are deformed radially outward at the ends of the holes of the forming jig by electromagnetic forming. FIG. 5B is a process explanatory view showing stepwise how the first tube member and the second tube member are deformed radially outward at the end of the hole of the forming jig by electromagnetic forming. FIG. 5C is a process explanatory view showing stepwise how the first pipe member and the second pipe member are deformed radially outward at the ends of the holes of the forming jig by electromagnetic forming. FIG. 6 is a reference view showing a state of electromagnetic expansion of a conventional first pipe member in which the pipe end of the first pipe member does not protrude from a hole of a forming jig. FIG. 7 is a graph showing the relationship between the input energy to the coil and the strength of the joined structure obtained by electromagnetic forming for each plate thickness of the forming jig at the time of electromagnetic expansion. FIG. 8 is a schematic sectional view of a molding jig of the second configuration example. FIG. 9 is an explanatory diagram schematically showing the arrangement positions of the contact block, the first pipe member, and the second pipe member shown in FIG. FIG. 10 is a graph showing the change in the tensile peak load with respect to the input energy for each experimental example. FIG. 11A is an explanatory diagram showing a conventional pipe expanding technique. FIG. 11B is an explanatory diagram showing a conventional pipe expanding technique.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Here, a first pipe member and a second pipe member having different diameters and circular axial vertical cross sections are expanded by electromagnetic forming inside a forming jig, and the respective members are caulked and joined together. The method of caulking will be described.

<Arrangement of each member during electromagnetic molding>
FIG. 1 is a cross-sectional view illustrating the arrangement of a first tube member, a second tube member, an electromagnetic molding coil, and a molding jig before electromagnetic molding. In the figure, the Z direction is a vertical direction, the X and Y directions are horizontal directions, and the X direction is an axial direction of the first tube member 11 and the second tube member 13. The Y direction is a direction orthogonal to the X direction and the Z direction.

One tube end 14 of the second tube member 13 smaller in diameter than the first tube member 11 is inserted into the first tube member 11 from one tube end 21. Thereby, the overlapping portion 15 in which the first pipe member 11 and the second pipe member 13 overlap in the radial direction is formed.

成形 A molding jig 17 is arranged on the outer periphery of the overlapping portion 15. The forming jig 17 has a hole 17 a having a larger diameter than the first pipe member 11.

コイル A coil 19 for electromagnetic forming is arranged in the second tube member 13. The coil 19 shown in FIG. 1 represents a conductor winding portion which is a coil body around which a conductor is wound. The coil 19 is axially positioned in the second tube member 13 by, for example, attaching the coil body to a support rod (not shown) and inserting the coil body together with the support rod into the second tube member 13. The arrangement form of the coil 19 is not limited to this, and may be another form such as a configuration including a support mechanism (not shown) that is integrally positioned with the forming jig 17 in the axial direction.

The first tube member 11 and the second tube member 13 are supported concentrically by a support member (not shown) arranged at a predetermined axial distance from the overlapping portion 15.

<First pipe member>
The raw tube of the first tube member 11 before molding is not limited to a circular tube, but may be a square tube having a square or rectangular cross section, a hexagonal tube having a hexagonal cross section, or an octagonal tube having an octagonal cross section. And can be manufactured by welding plate materials. When the cross-sectional shape of the first pipe member 11 is circular, it is preferable that the second pipe member is formed in a similar shape, such as a circular cross section. Good.

材質 The material of the first pipe member 11 can be appropriately selected from steel (normal steel, high-tensile steel), aluminum alloy (JIS 6000 series, 7000 series, etc.), resin, and the like.

<Second pipe member>
The raw tube of the second tube member 13 before forming is the same as the first tube member 11 and is not limited to a circular tube, but has a square or rectangular cross section, a hexagonal hexagonal tube, and an octagonal cross section. May be manufactured by extrusion or welding of a plate material. In the case of an extruded material, a rib or the like protruding toward the inner diameter side may be provided. As a material of the second pipe member 13, a suitable material is an aluminum alloy (JIS6000-based, 7000-based, or the like) that is capable of electromagnetic expansion. The first pipe member and the second pipe member may be made of the same material or different materials.

<Molding jig>
The molding jig 17 has a rigidity for receiving the pressing force from the first tube member 11 and the second tube member 13 when the Lorentz force is generated in the second tube member 13 by the excitation magnetic field from the coil 19 during the electromagnetic molding. Have. The forming jig 17 of this configuration is made of a plate material, and suitable materials include steel (for example, SS400 or the like), an extruded aluminum material, an aluminum casting, and a resin injection molded material.

<Coil>
The coil 19 is formed by winding a conductor wire around an insulating resin, and has a structure in which the conductor wire is further surrounded by the insulating resin. The coil 19 is fixed to a tip of a support (not shown). A conductor is wired inside the support, and the coil 19 is connected to an external power supply. The rod-shaped coil unit having the coil 19 and the support is inserted into the tube of the second tube member 13 manually or by a known linear moving mechanism or the like, and is positioned and fixed at a desired arrangement position.

<Dimensions of each part>
The outer diameter of the first pipe member 11 is φDout, the inner diameter is φdout, the outer diameter of the second pipe member 13 is φDin, the inner diameter is φdin, the inner diameter of the hole 17a of the forming jig 17 is φdp, and the outer diameter of the coil 19 is Is φDc. Each diameter has a relationship of φdp> φDout, φdout> φDin, φdin> φDc. Each member is arranged concentrically, and has a substantially constant radial gap along the circumferential direction.

ＬLet is the length of the coil 19 in the coil axis direction (X direction), Lk is the length of the overlapping portion 15 in the axial direction, and W is the width of the forming jig 17 in the axial direction (plate thickness). The pipe end 21 of the first pipe member 11 on the overlapping portion 15 side protrudes axially outward from the hole 17 a of the forming jig 17. Let S be the length of the pipe end 21 projecting axially outward from the end face (opening face 17b) of the forming jig 17. Each dimension has a relationship of Lc> Lk> W + S> W. The axial width W of the forming jig 17 depends on the diameters of the first tube member 11 and the second tube member 13, but is set to, for example, about 30 to 50 mm. The projecting length S of the tube end 21 is set to about 5 mm when the axial width W of the forming jig 17 is 40 mm.

The lower limit of the ratio Lc / W of the axial length Lc of the conductor winding portion of the coil 19 to the axial width W of the forming jig 17 is preferably 1.0, more preferably 1.2, and more preferably 1.2. Preferably it is 1.5. The upper limit of the ratio Lc / W is preferably 3, more preferably 2.8, and even more preferably 2.5. According to this, since the coil 19 (the conductor winding portion) is arranged within the range of not less than the axial width W of the forming jig 17, the forming jig 17 of the first tube member 11 and the second tube member 13 is formed. On both sides, the inflated portion (see 27 and 29 in FIG. 4) can be reliably formed.

The center position Oc of the winding portion of the coil 19 in the axial direction, the center position of the axial length Lk of the overlapping portion 15, and the center position of the axial width W of the forming jig 17 are at the same position in the X direction. Be placed.

[First configuration example]
When the forming jig 17 is a single plate material as in the forming jig 17 of the first configuration example, the first tube member 11 and the second tube member 13 are integrated after electromagnetic forming.

<Shape of molding jig>
FIG. 2 is an external perspective view of the molding jig 17 of the first configuration example.
The forming jig 17 of this configuration is a plate-like member having a hole 17a formed therein, and a pair of

concave portions

23a, 23b which are concave in an arc shape in a horizontal cross section are formed on the opening surfaces 17b, 17c of the hole 17a. Is preferred. The

recesses

23a and 23b are formed so as to include at least a part of the hole 17a, and are shown in FIG. 2 as arc grooves that are continuous in the Z direction. The center of curvature of the arc of each of the

recesses

23a and 23b may or may not coincide with the center axis of the hole 17a as shown in FIG. Further, each of the

recesses

23a and 23b may be formed so as to be shifted from each other in the Y direction.

When the

concave portions

23a and 23b are formed in the forming jig 17, the axial width W of the forming jig 17 on the inner peripheral surface of the hole 17a varies depending on the circumferential position of the hole 17a. That is, the axial width W2 at the inner peripheral surfaces at both ends in the Z direction of the hole 17a is smaller than the axial width W1 at the inner peripheral surfaces at both ends in the Y direction of the hole 17a (W1> W2). In this case, on the inner peripheral surface of the hole 17a, the axial width continuously changes between W1 and W2 along the circumferential direction.

<Electromagnetic molding method>
FIG. 3 is a plan view showing a state where the overlapping portion 15 of the first tube member 11 and the second tube member 13 shown in FIG. 1 is electromagnetically formed.

コイル The coil 19 is inserted into the pipe of the second pipe member 13, and the second pipe member 13 is electromagnetically expanded by energizing the coil 19. Energy of, for example, about 16 kJ is instantaneously applied to the coil 19 from a power supply unit (not shown), and an eddy current is excited in the second pipe member 13 facing the coil 19. Due to this eddy current, a Lorentz force is generated in the second pipe member 13 toward the outside in the radial direction, and the second pipe member 13 is expanded by the Lorentz force.

When the second pipe member 13 expands, the first pipe member 11 arranged on the outer periphery of the second pipe member 13 expands radially outward following the expansion deformation of the second pipe member 13. The outer peripheral surface of the first pipe member 11 abuts against the inner peripheral surface of the hole 17 a of the forming jig 17 to suppress the expansion, and the expansion proceeds further on both sides of the first pipe member 11. Accordingly, in the overlapping portion 15 of the first pipe member 11 and the second pipe member 13, in a region overlapping the axial length Lc of the coil 19 on both sides of the forming jig 17 with the hole 17 a interposed therebetween.

Expansion portions

27 and 29 bulging radially outward are formed.

The

expansion portions

27 and 29 are formed by deforming the first tube member 11 and the second tube member 13 at the same time by electromagnetic molding, and are caulked to the molding jig 17 in a state where their joint surfaces are in close contact with each other. Thereby, a joint structure in which the first pipe member 11, the second pipe member 13, and the forming jig 17 are integrated is obtained.

When the forming jig 17 is a split mold in which a plurality of dies can be disassembled by fastening members such as bolts, the forming jig 17 is formed from the first pipe member 11 and the second pipe member 13 after the electromagnetic jig. Can be removed. In this case, by disassembling the plurality of molds after the electromagnetic molding, a joint structure in which the first tube member 11 and the second tube member 13 are integrally joined can be obtained. Such a split mold may be any as long as a hole having a larger diameter than the first pipe member 11 is formed when a plurality of molds are combined. Further, a circumferential gap may be provided between the plurality of dies. In this case, it is sufficient that the portion of each mold facing the first pipe member 11 is circumscribed by a virtual circle having a larger diameter than the first pipe member 11.

FIG. 4 is a schematic perspective view showing a joined body of the first tube member 11 and the second tube member 13 from which the molding jig 17 has been removed after the electromagnetic molding.
As shown in the illustrated example,

expansion portions

27 and 29 are formed in the joined body of the first pipe member 11 and the second pipe member 13, and the first pipe member 11 and the second pipe member are formed inside the

expansion portions

27 and 29. The tube member 13 is caulked and fixed.

<Effects of electromagnetic molding>
Next, the effect of the electromagnetic forming of the first tube member 11 and the second tube member 13 will be described.
FIGS. 5A to 5C are step-by-step explanations showing steps in which the first pipe member 11 and the second pipe member 13 are deformed radially outward at the end of the hole 17a of the forming jig 17 by electromagnetic forming. FIG.

As shown in FIG. 5A, immediately after the start of the electromagnetic forming, the second pipe member 13 expands due to Lorentz force acting on the second pipe member 13 and collides with the inner peripheral surface of the first pipe member 11. By expanding the second pipe member 13, the outer peripheral surface of the first pipe member 11 is pressed against the inner peripheral surface of the hole 17 a of the forming jig 17.

5B, as shown in FIG. 5B, the portion of the second pipe member 13 that is not supported by the molding jig 17 (the right side of (B)) is expanded by Lorentz force. Along with this, the protruding portion 31 between the pipe end 21 of the first pipe member 11 and the forming jig 17 is pushed radially outward while being in close contact with the second pipe member 13 by expanding the second pipe member 13. Can be spread. At this time, the pipe end 21 of the first pipe member 11 is located in the middle of the slope 33 of the second pipe member 13 closer to the forming jig 17 than the maximum diameter portion of the inflatable portion 39, and deforms along the slope 33. .

Then, after the completion of the electromagnetic molding, as shown in FIG. 5C, the protrusions 31 of the first pipe member 11 and the springback amounts Δθ1 and Δθ2 of the second pipe member 13 become substantially equal, and There is no gap between the second pipe member 13 and the second pipe member 13. Specifically, the pipe end 21 is urged toward the second pipe member 13 (inward in the radial direction) by the elastic restoring force of the protruding portion 31 so that the pipe end 21 and the inclined surface 33 are always in close contact.

FIG. 6 is a reference view showing the state of electromagnetic expansion of a conventional first pipe member 11A in which the pipe end 21 of the first pipe member 11 does not protrude from the hole 17a of the forming jig 17.
In the case shown in FIG. 6, the springback amount Δθ of the second pipe member 13 after the electromagnetic forming is larger than the springback amount Δθ2 shown in FIG. 5C. This is because the bending rigidity of the second pipe member 13 is reduced and the deformation amount of the second pipe member 13 at the time of electromagnetic expansion is increased by the absence of the protruding portion 31 of the first pipe member 11A. This is because Δθ also increases.

In the case shown in FIG. 6, a gap is easily formed between the first pipe member 11A and the second pipe member 13 at the pipe end 21 of the first pipe member 11A after the springback, and this gap is The direction also varies. As a result, rattling and crimping failure may occur.

On the other hand, as shown in FIG. 5C, a gap due to a springback difference is hardly generated between the inner peripheral surface of the first pipe member 11 and the outer peripheral surface of the second pipe member 13, which are corners of the forming jig 17, The adhesion at the pipe end 21 is improved over the entire circumference, and a good caulking joint form is obtained.

As shown in FIGS. 2 and 3, when at least a part of the forming jig 17 along the circumferential direction of the hole 17 a is provided with a portion where the thickness of the forming jig 17 changes, the expansion jig 17 has The contact area between the first pipe member 11 and the hole 17a of the forming jig 17 is the contact area A shown by a dot pattern in FIG. The contact area A has different axial widths in the circumferential direction (see W1 and W2 (W1 <W2) shown in FIG. 2). Therefore, the widening portion and the narrow portion of the contact area A have different deformation patterns of the first pipe member 11 and the second pipe member 13 in diameter expansion, and the degree of diameter expansion along the circumferential direction changes. . That is, in the electromagnetic forming in this case, a deformation occurs in which the pipe is not expanded in a perfect circle, but is expanded largely locally in the circumferential direction such as an elliptical shape. In the case shown in FIG. 4, the pipe is expanded to have a larger diameter in the circumferential area including the axial width W1 than in the circumferential area including the axial width W2.

As described above, in the overlapping portion 15 of the first pipe member 11 and the second pipe member 13 after the expansion, if a portion where the expansion diameter is large and a portion where the diameter is small are mixed in the circumferential direction, the large diameter is The member having a small diameter serves as an anchor, and improves the load resistance in the circumferential direction between the first pipe member 11 and the second pipe member 13. Therefore, according to this electromagnetic molding, it is possible to improve the torsional strength while keeping the caulked joint form favorable.

FIG. 7 is a graph showing the relationship between the input energy to the coil and the strength of the joined structure obtained by electromagnetic molding for each axial width W of the molding jig at the time of electromagnetic expansion.

According to FIG. 7, when the axial width W of the forming jig is 40 mm, the maximum tensile strength is about 9 kN, but as the axial width W is reduced to 30 mm or 20 mm, the maximum tensile strength is improved. In particular, when the axial width W was changed from 40 mm to 30 mm, a remarkable improvement in strength was observed.

[Second configuration example]
FIG. 8 is a schematic sectional view of a molding jig 17A of the second configuration example.
The forming jig 17A of the second configuration example includes a plurality of (four in this configuration) pressing portions 51 disposed radially outside the first pipe member 11 and the plurality of pressing portions 51. 11 is a jig having a split type structure comprising: a block support 53 movably supported in a radial direction of No. 11;

The block support 53 includes a base 55 fixed to a base (not shown), a lower support 57 formed integrally with the base 55, and fastening of a bolt or the like (not shown) to the lower support 57. And an upper supporting portion 59 fixed by a member. When the upper support portion 59 is fixed to the lower support portion 57, a hole 53 a is formed in the block support 53 by the concave portion 57 a of the lower support portion 57 and the concave portion 59 a of the upper support portion 59. The first tube member 11 and the second tube member 13 are arranged radially inside the hole 53a, and their radial positions are adjusted by a tube member support mechanism (not shown) so that they are concentric with each other.

The pressing portion 51 includes a support shaft 61 and a contact block 63. The support shaft 61 is movably supported by the lower support portion 57 and the upper support portion 59 along the radial direction of the hole 53a. A radially inner side of the contact block 63 has a contact surface 63 a facing the outer peripheral surface of the first pipe member 11. The contact surface 63a preferably has a vertical cross section in the axial direction (axial direction of the first pipe member 11) formed in an arc shape along the outer peripheral surface of the first pipe member 11, but has a flat surface or another curvature. It may be a curved surface.

一対 A pair of pin holes 65 and 67 are formed on both sides of the contact block 63 of the lower support portion 57 and the upper support portion 59, respectively. A pin 69 is inserted into each of the pin holes 65 and 67. The pin 69 guides the radial movement of the contact block 63.

The support shaft 61 is connected to a pushing mechanism (not shown), and the pushing mechanism is driven to move in the radial direction. As the pushing mechanism, an appropriate mechanism such as a hydraulic cylinder, a mechanical pressurizing mechanism using a screw or the like can be used. The pushing mechanism drives the contact block 63 in the radial direction to dispose the contact block 63 such that the contact surface 63 a of the contact block 63 is concentric with the outer peripheral surface of the first pipe member 11.

In FIG. 8, the pressing portions 51 are arranged at 90 ° intervals in the circumferential direction around the central axis O of the first pipe member 11, but the configuration is not limited thereto. For example, another configuration such as a configuration in which the pressing portions 51 are arranged at 120 ° intervals in the circumferential direction, a configuration in which the pressing portions 51 are arranged at 180 ° intervals, or the like may be used.

<Electromagnetic molding method>
When performing electromagnetic forming using the forming jig 17A having the above configuration, the coil 19 (see FIG. 1) is inserted into the tube of the second tube member 13 and the coil 19 is energized in the same manner as in the first configuration example described above. Thereby, the second pipe member 13 is electromagnetically expanded. When the second pipe member 13 is expanded, the first pipe member 11 is expanded radially outward following the expansion deformation of the second pipe member 13. As a result, an expansion portion is formed in which both the first pipe member 11 and the second pipe member 13 bulge radially outward.

In the case of the forming jig 17A, a gap is formed in the circumferential direction between the contact blocks 63, so that the first pipe member 11 and the second pipe member 13 project into the gap in the radial direction. Is formed. Thereby, the torsional strength between the pipe members can be improved.

The result of electromagnetically forming the first pipe member and the second pipe member using the forming jig 17A of the second configuration example will be described below.

FIG. 9 is an explanatory diagram schematically showing the arrangement positions of the contact block 63, the first tube member 11, and the second tube member 13 shown in FIG.
Here, the radial distance between the contact surface 63a of the contact block 63 and the outer peripheral surface of the first pipe member 11 is L1, and the inner peripheral surface of the first pipe member 11 and the outer peripheral surface of the second pipe member 13 Is defined as L2.

Table 1 shows the molding conditions of Experimental Examples 1 to 6 in which the radial distances L1 and L2 and the input energy for electromagnetic expansion were changed.

The specifications of the used first and second pipe members are as follows.
・ First pipe member Material: A6063-T5
Shape: circular pipe Thickness: 2.0 [mm]
・ Second pipe member Material: A6063-T5
Shape: circular pipe Thickness: 2.0 [mm]

As shown in Table 1, in Experimental Example 1, the radial distance L1 before electromagnetic forming was 1.0 [mm], the radial distance L2 was 1.5 [mm], and the input energy was 12.8 [kJ]. , 14.5 [kJ] and 16.2 [kJ], respectively, were subjected to electromagnetic molding. As a result, a joined body in which the first tube member and the second tube member had the expanded portion was obtained. The axial width W of the contact surface of the contact block that comes into contact with the first pipe member was 30 [mm]. Similarly, electromagnetic molding was performed under the conditions of Experimental Examples 2 to 6 to obtain a joined body having an expanded portion.

Here, in Experimental Examples 1 to 4, a gap is provided between the contact block and the first pipe member before the electromagnetic forming. In Experimental Example 5, the first pipe member was deformed radially inward by the contact block before the electromagnetic molding, and the first pipe member and the second pipe member were deformed at the contact position between the contact block and the first pipe member. The gap between them has been eliminated. In Experimental Example 6, both the first tube member and the second tube member were deformed radially inward by the contact block before the electromagnetic forming.

(4) Next, a tensile test was performed in which the joined body in which the expanded portions were formed in the first pipe member and the second pipe member was pulled in the axial direction, and the tensile peak load was obtained from the obtained stress-strain diagram. The results are shown in FIG.

The tensile peak loads of Experimental Examples 1 to 4 were 24.780 [kJ] at the maximum in Experimental Example 3, but in Experimental Examples 5 and 6, the tensile peak loads exceeding 27 [kJ] were obtained in all cases. . In particular, when the radial distance L2 between the first pipe member and the second pipe member was reduced, a remarkable increase in the tensile peak load was observed.

As described above, the present invention is not limited to the above-described embodiment, and a person skilled in the art can modify and apply the configuration based on the combination of the components of the embodiment with each other, the description in the specification, and the well-known technology. The present invention is also intended to be included in the scope for which protection is sought.

As described above, the following items are disclosed in this specification.
(1) preparing a first pipe member and a second pipe member smaller in diameter than the first pipe member;
Preparing a forming jig having a hole having a diameter larger than that of the first pipe member;
The second pipe member is inserted into the pipe of the first pipe member to form an overlapping portion between the first pipe member and the second pipe member, and is formed radially inward of the hole of the molding jig. Disposing the overlapping portion, and projecting a tube end of the first pipe member on the overlapping portion side from the hole portion in an axially outward direction;
Inserting a coil having a conductor winding portion whose axial length is longer than the overlapping portion at an axial position of the overlapping portion in the pipe of the second pipe member;
The coil is energized to electromagnetically expand the second pipe member to form an expanded portion in which the first pipe member and the second pipe member are simultaneously expanded, and the expansion portion is larger than the maximum diameter portion of the expansion portion. A step of expanding the pipe end of the first pipe member along the slope of the second pipe member on the forming jig side.
According to this tube member caulking method, when the second tube member is electromagnetically expanded by electromagnetic forming and the first tube member is expanded in diameter, the tube end of the first tube member is inflated by the expanded portion of the second tube member. Is formed along the slope. As a result, there is no gap between the first pipe member and the second pipe member, and it is possible to prevent rattling and poor crimping, thereby improving the bonding strength between the pipe members.

(2) The method of caulking a pipe member according to (1), wherein at least a part of the hole along the circumferential direction is provided with a portion on the inner peripheral surface of the hole where the axial width changes.
According to the crimping method of the pipe member, the expanded portion expanded by electromagnetic expansion includes a portion having a large diameter and a portion having a small diameter in the circumferential direction. It is possible to increase the load resistance in the circumferential direction between them. Thereby, the torsional strength between the pipe members is improved.

(3) The forming jig includes a plurality of pressing portions circumscribing a virtual circle having a diameter larger than that of the first pipe member, and the plurality of pressing portions are formed along a circumferential direction of the virtual circle. The method of caulking a pipe member according to (1), wherein the pipe members are spaced apart from each other.
According to the method of caulking the pipe members, the first pipe member is pressed against the divided block having a circumferential gap when the second pipe member is electromagnetically expanded. Then, at the position where the first pipe member comes into contact with the divided block, expansion of the pipe after the contact is suppressed, and at the position where it does not come into contact with the divided block of the first member, the pipe is directed radially outward from the inner peripheral surface of the divided block. It is expanded. Therefore, in the first pipe member and the second pipe member, portions having a small expansion amount (division block arrangement positions) and portions having a large expansion amount (division block non-position positions) are alternately formed along the circumferential direction. You. Thereby, the load resistance in the circumferential direction between the first pipe member and the second pipe member is enhanced. Thereby, the torsional strength between the pipe members is improved.

(4) Before the coil is energized, the pressing portion supported by the forming jig is pushed inward in the radial direction to deform the first tube member inward in the radial direction. Caulking method.
According to the tube member caulking method, the distance between the first tube member and the second tube member is reduced by deforming the first tube member radially inward before electromagnetic forming, and the second tube member is formed. The deformation allowance of the first pipe member due to the electromagnetic expansion described above increases, and the joining strength between the two further improves.

(5) The method according to (4), wherein the pressing portion is further pushed in before the coil is energized until the second tube member is deformed radially inward.
According to this caulking method of the pipe members, since the expanding force of the second pipe member due to the electromagnetic expansion is directly transmitted to the first pipe member, the swelling amount of the first pipe member and the second pipe member increases, The joining strength of both is further improved.

(6) The tube according to (1), wherein a ratio Lc / W of an axial length Lc of the conductor winding portion of the coil to an axial width W on an inner peripheral surface of the hole is 1 to 3. The method of caulking members.
According to the method of caulking and joining the pipe members, the coil is arranged in a range not less than the axial width of the forming jig. An inflatable portion can be formed at the bottom.

Further, in the method of caulking a pipe member according to any one of the above (1) to (6), at least one of the first pipe member and the second pipe member is made of a T1 tempered aluminum alloy. There is a feature.
According to the method of caulking a pipe member, the strength can be improved by natural aging after cooling from high-temperature processing of the pipe member.

Further, in the method of caulking a pipe member according to any one of the above (1) to (6), the first pipe member and the second pipe member are heat-treated aluminum alloys, and the electromagnetic expansion pipe It is characterized in that T5 refining is performed later.
According to the tube member caulking method, a natural member is aged after the solution treatment, thereby reducing residual stress and obtaining a tube member having improved joint strength.

This application is based on a Japanese patent application filed on August 8, 2018 (Japanese Patent Application No. 2018-149497) and a Japanese patent application filed on March 29, 2019 (Japanese Patent Application No. 2019-655562). The contents of which are incorporated by reference into this application.

11 first pipe member 13 second pipe member 15 overlapping

portion

17, 17A forming jig 17a hole 17b, 17c opening surface 19 coil 21

tube end

23a, 23b recess 27 expansion portion 29 expansion portion 31 protrusion portion 33 slope 51 pressing Part 53 block support 53a hole

Claims

Preparing a first pipe member and a second pipe member smaller in diameter than the first pipe member;
A step of preparing a forming jig in which a hole having a larger diameter than the first pipe member is formed;
The second pipe member is inserted into the pipe of the first pipe member to form an overlapping portion between the first pipe member and the second pipe member, and is formed radially inward of the hole of the molding jig. A step of disposing the overlapping portion and projecting a pipe end of the first pipe member on the overlapping portion side outwardly in the axial direction from the hole;
Inserting a coil having a conductor winding portion having an axial length longer than the overlapping portion at an axial position of the overlapping portion in the pipe of the second pipe member;
The coil is energized to electromagnetically expand the second pipe member to form an expanded portion in which the first pipe member and the second pipe member are simultaneously expanded, and the expansion portion is larger than the maximum diameter portion of the expansion portion. A step of expanding the pipe end of the first pipe member along the slope of the second pipe member on the forming jig side.
The swaging method according to claim 1, wherein at least a portion of the inner peripheral surface of the hole portion where the width in the axial direction changes is provided in at least a part of the hole along the circumferential direction.
The molding jig has a plurality of pressing portions circumscribing a virtual circle having a diameter larger than that of the first pipe member, and separates the plurality of pressing portions along a circumferential direction of the virtual circle. The method for caulking a pipe member according to claim 1, wherein
4. The method according to claim 3, wherein the pressing portion supported by the forming jig is pressed inward in the radial direction before the coil is energized to deform the first pipe member inward in the radial direction. .
5. The method of claim 4, wherein the pressing portion is further pushed in before the coil is energized until the second tube member is deformed radially inward.
The caulking of the pipe member according to claim 1, wherein a ratio Lc / W of an axial length Lc of the conductor winding portion of the coil to an axial width W of the inner peripheral surface of the hole portion is 1 to 3. Joining method.