JP7573471B2 - Bonding method, bonded body, and bonding device - Google Patents

Description

The present invention relates to a joining method for joining overlapping portions of two or more members using friction stirring and a fastener, a joined body using this method, and a joining device used in the joining method.

Metal members, resin members, and thermoplastic resin members mixed with fiber reinforcement are used as components of structures such as aircraft, railway vehicles, and automobiles. When manufacturing such structures, it may be necessary to join two or more members by overlapping them. Known joining methods include joining using fasteners such as rivets and joining using friction stir welding.

Patent Document 1 discloses a method for joining fiber-reinforced thermoplastic resin members using a self-piercing rivet. In this joining method, a special lower die capable of heating and softening the resin member is used, and a self-piercing rivet is driven into the softened area. This driving is performed so that the head of the self-piercing rivet is flush with the surface of the joined body.

Patent No. 5333584

However, when joining overlapping parts of two or more components, the method of simply driving in a self-piercing rivet can sometimes result in delamination and make it difficult to obtain sufficient joint strength or joint quality. Furthermore, with joining methods that rely solely on friction stir welding, the joint strength tends to depend on the properties of the resin, so there are cases in which sufficient peel strength cannot be obtained.

The present invention aims to provide a joining method that can join overlapping portions of two or more members more firmly than ever before, a joined body using the same, and a joining device used in the joining method.

The joining method according to one aspect of the present invention is a joining method using a friction stir welding tool and a fastener to join an overlapping portion formed including a first member on the tool side and a second member placed below the first member, and is characterized in that the tool is pressed into the overlapping portion from the first member side to perform friction stirring, forming a friction stir portion in the overlapping portion, and using a fastener whose size as viewed from the pressing direction is smaller than the friction stir portion, and pressing one end of the fastener to press the other end of the fastener into the friction stir portion from the first member side, forming a head portion on one end of the fastener that is larger in size than the friction stir portion.

According to this joining method, a joint having excellent strength can be obtained by using both friction stir and the fastener. That is, a friction stir portion into which the fastener will be pressed is formed at the overlapping portion. In this friction stir portion, the constituent materials of the overlapping portion are kneaded by friction stirring and the constituent materials are softened. The fastener can be easily pressed into such a friction stir portion. Therefore, the fastener can easily exert its fastening effect. Furthermore, a head portion having a size larger than the friction stir portion is formed at one end of the fastener. That is, the head portion is finished to cover the boundary portion between the friction stir portion and the base material of the first member and the second member. The locking effect of the head portion can suppress breakage along the boundary portion.

A joint according to another aspect of the present invention is a joint of overlapping portions formed by including a first member and a second member, and includes an overlapping portion where the first member is disposed at one end side in the overlapping direction and the second member is disposed at the other end side in the overlapping direction, a friction stir portion provided in the overlapping portion, and a fastener pressed into the friction stir portion, and the fastener includes an interlock portion in which a part of the fastener is inserted into the second member, and a flange portion that abuts against the upper surface of the friction stir portion and the upper surface of the first member around the periphery of the friction stir portion.

With this joint, a joining force is applied to the overlapping portion by the friction stir portion formed in the overlapping portion and the fastener pressed into the friction stir portion. In other words, the first member and the second member can be firmly joined by the fastening effect of the fastener, without relying solely on friction stir welding. Furthermore, the friction stir portion is sandwiched between the interlock portion and the flange portion of the fastener. Therefore, fracture along the boundary between the friction stir portion and the base materials of the first member and the second member is suppressed, and a joint with excellent joining strength can be constructed.

The joining device according to yet another aspect of the present invention is a joining device that joins an overlapping portion formed including a first member and a second member using friction stirring and a fastener, and is equipped with a cylindrical pin member that can move back and forth in the axial direction, a cylindrical shoulder member that is positioned so as to cover the outer periphery of the pin member, rotates around the same axis as the pin member, and can move back and forth in the axial direction, a fastener that has one end side that is pressed by the pin member and the other end side that is pressed into the friction stirring portion formed in the overlapping portion by the pressing, and is loaded into a storage space created by the rise of the pin member, and a post-processing unit that forms a head portion having a size larger than the friction stirring portion on one end side of the fastener.

By using this joining device, the processes of friction stirring the overlapping portion, pressing in the fastener, and forming the head portion can be carried out smoothly on an assembly line.

According to the present invention, overlapping portions of two or more members can be firmly joined by using a combination of friction stirring and a fastener.

FIG. 1 is a schematic diagram showing the configuration of a double-action friction stir spot welding apparatus capable of carrying out the welding method according to the present invention. FIG. 2 is a diagram showing the configurations of a first member and a second member to be joined by the joining method. FIG. 3 is a diagram showing a process chart of the bonding method according to this embodiment. FIG. 4A is a cross-sectional view showing a state where a preparation step of the bonding method is being carried out, and FIG. 4B is a cross-sectional view showing a state where an overlapping portion forming step is being carried out. 5(A) to 5(D) are cross-sectional views sequentially showing the implementation of rivet-assisted friction stir welding. 6A is a cross-sectional view of the joined body after the step of forming the interlock portion, and FIG. 6B is a cross-sectional view of the joined body after the step of forming the head portion is completed. 7A and 7B are cross-sectional views showing a process for forming the head portion according to the first embodiment. FIG. 8(A) is a diagram showing a rivet and a head piece used in the head portion forming process according to the second embodiment, and FIG. 8(B) is a side view showing the rivet and the head piece joined together. 9A and 9B are cross-sectional views showing a process for forming the head portion according to the second embodiment. FIG. 10 is a cross-sectional view of a bonded body bonded by the bonding method according to the second embodiment. 11(A) and (B) are diagrams showing a hat-shaped head piece used in the process of forming the head portion according to the third embodiment, and FIG. 11(C) is a cross-sectional view showing the process of forming the head portion according to the third embodiment. FIG. 12 is a cross-sectional view of a bonded body bonded by the bonding method according to the third embodiment. FIG. 13 is a cross-sectional view showing a joining method according to a modified example of the third embodiment.

The following describes in detail an embodiment of the present invention with reference to the drawings. The joining method according to the present invention can be applied to the manufacture of various joined bodies formed by overlapping and spot-joining two or more structural members, such as plates, frames, exterior materials, or columnar materials, made of metal, thermoplastic resin, thermoplastic composite material, etc. The thermoplastic composite material is, for example, a composite material containing fiber reinforcement such as carbon fiber. The joint body thus manufactured becomes, for example, a component part of a structure such as an aircraft, a railway vehicle, or an automobile.

[Configuration of double-action friction stir spot welding apparatus]
First, a configuration example of a double-action friction stir spot welding apparatus M capable of executing a welding method according to an embodiment of the present invention will be described with reference to Fig. 1. The friction stir spot welding apparatus M includes a double-action friction stir spot welding tool 1, a tool drive unit 2 that drives the tool 1 to rotate and elevate, a controller C that controls the operation of the tool drive unit 2, and a heating device 61 (post-processing unit) that can execute a required heating operation. Note that although Fig. 1 has directional indications of "up" and "down", this is for convenience of explanation and is not intended to limit the actual direction of use of the tool 1.

The tool 1 is supported by a tool support member (not shown). The tool support member can be, for example, a support frame such as a C-frame attached to the tip of an articulated robot. A backing material 15 is arranged facing the lower end surface of the tool 1. At least two members to be joined are arranged between the tool 1 and the backing material 15. FIG. 1 shows an example in which an overlapping portion 30 in which a part of a first member 31 made of a flat plate and a part of a second member 32 also made of a flat plate overlap in the vertical direction is arranged between the tool 1 and the backing material 15. Such an overlapping portion 30 is joined by a joining method that uses both friction stirring and a rivet 5 (fastening body), thereby forming a joint 3 of the first member 31 and the second member 32. The overlapping portion 30 may be one in which one or more members are further interposed between the first member 31 and the second member 32.

The tool 1 includes a pin member 11, a shoulder member 12, a clamp member 13, and a spring 14. The pin member 11 is a cylindrical member, and is arranged so that its axis extends in the vertical direction. The pin member 11 can rotate about the axis R, and can move up and down (advance and retreat) along the rotation axis R. When the tool 1 is in use, the rotation axis R is aligned with the point joining position W at the overlapping portion 30.

The shoulder member 12 is positioned so as to cover the outer periphery of the pin member 11. The shoulder member 12 is a cylindrical member having a hollow portion into which the pin member 11 is inserted. The axis of the shoulder member 12 is coaxial with the axis line (rotation axis R) of the pin member 11. The shoulder member 12 can rotate around the same rotation axis R as the pin member 11, and can move up and down (advance and retreat) along the rotation axis R. The shoulder member 12 and the pin member 11 inserted in the hollow portion can move relatively in the direction of the rotation axis R while both rotating around the axis of the rotation axis R. In other words, the pin member 11 and the shoulder member 12 can not only simultaneously move up and down along the rotation axis R, but can also move independently, with one descending and the other ascending.

The clamp member 13 is a cylindrical member with a hollow portion into which the shoulder member 12 is inserted. The axis of the clamp member 13 is also coaxial with the rotation axis R. The clamp member 13 does not rotate around its axis, but can move up and down (advance and retreat) along the rotation axis R. The clamp member 13 serves to surround the outer periphery of the pin member 11 or the shoulder member 12 when they perform friction stirring. The enclosure of the clamp member 13 prevents the friction stirring material from scattering, and allows the friction stir spot welded portion to be finished smoothly.

The spring 14 is attached to the upper end side of the clamp member 13 and biases the clamp member 13 in a direction (downward) toward the overlapping portion 30. The clamp member 13 is attached to the tool support portion via the spring 14. The backing material 15 has a flat surface that abuts against the underside of the object to be joined (overlapping portion 30). The backing material 15 is a backing material that supports the overlapping portion 30 when the pin member 11 or shoulder member 12 is pressed into the overlapping portion 30. The clamp member 13 biased by the spring 14 presses the overlapping portion 30 against the backing material 15.

The tool drive unit 2 includes a rotation drive unit 21, a pin drive unit 22, a shoulder drive unit 23, and a clamp drive unit 24. The rotation drive unit 21 includes a motor, a drive gear, etc., and drives the pin member 11 and the shoulder member 12 to rotate around the rotation axis R. The pin drive unit 22 is a mechanism for moving the pin member 11 forward and backward (raising and lowering) along the rotation axis R. The pin drive unit 22 drives the pin member 11 so as to press the pin member 11 into the overlapping portion 30 and to retract it from the overlapping portion 30. The shoulder drive unit 23 is a mechanism for moving the shoulder member 12 forward and backward along the rotation axis R, and presses the shoulder member 12 into the overlapping portion 30 and retracts it. The clamp drive unit 24 is a mechanism for moving the clamp member 13 forward and backward along the rotation axis R. The clamp driver 24 moves the clamp member 13 toward the overlapping portion 30, pressing the overlapping portion 30 against the backing material 15. At this time, the biasing force of the spring 14 acts.

The heating device 61 is a device used when externally heating the rivet 5. Specifically, when the head portion 51 (see FIG. 6) of the rivet 5 is rolled, the heating device 61 heats the head portion 51 to facilitate the rolling process. The heating device 61 may be a radiant heating device, a resistance heating device, an induction heating device, a laser heating device, a heating burner, or the like. The heating device 61 may be supported on the tool support portion together with the tool 1, for example, or may be supported on a separate support member. The heating control unit 62 controls the amount of heat input to the rivet 5 by controlling the operation of the heating device 61.

The controller C is composed of a microcomputer or the like, and controls the operation of each part of the tool driving unit 2 by executing a predetermined control program. Specifically, the controller C controls the rotation driving unit 21 to cause the pin member 11 and shoulder member 12 to perform the required rotational operation. The controller C also controls the pin driving unit 22, shoulder driving unit 23, and clamp driving unit 24 to cause the pin member 11, shoulder member 12, and clamp member 13 to perform the required forward and backward movement operation. The controller C also gives a heating instruction to the heating control unit 62 to cause the heating device 61 to operate as intended.

The above-mentioned double-action friction stir spot welding tool 1 can be used in a pin-first process and a shoulder-first process. In the friction stir process of the pin-first process, the pin member 11 of the tool 1 is pressed into the overlapping portion 30 in advance to perform friction stirring, while the shoulder member 12 is raised (retracted). In the subsequent backfilling process, the pin member 11 is raised and retracted, while the shoulder member 12 is lowered. On the other hand, in the friction stir process of the shoulder-first process, the shoulder member 12 of the tool 1 is pressed into the overlapping portion 30 in advance to perform friction stirring, while the pin member 11 is raised (retracted). In the subsequent backfilling process, the shoulder member 12 is raised and retracted, while the pin member 11 is lowered.

[Parts to be joined]
2 is a diagram showing the configuration of an overlapping portion 30 to be joined by the joining method of this embodiment. A first member 31 and a second member 32 are overlapped in the vertical direction to form the overlapping portion 30. The first member 31 has a thickness t1 in the overlapping direction. The second member 32 has a thickness t2 (t1=t2) that is the same as the thickness t1. t1 and t2 may be different thicknesses as long as they are thicknesses that allow friction stir welding.

As mentioned above, there is no particular restriction on the members to be joined in the present invention, and members made of metal, thermoplastic resin, thermoplastic composite material, etc. can be selected. Of these, it is desirable that both the first member 31 and the second member 32 are molded bodies made of fiber-reinforced thermoplastic resin. Examples of molded bodies made of fiber-reinforced thermoplastic resin include molded bodies in which short fibers or long fibers as fiber reinforcement are mixed with thermoplastic resin, fiber alignment bodies in which continuous fibers are aligned in a predetermined direction, and molded bodies in which a woven fabric of continuous fibers is impregnated with thermoplastic resin.

Examples of thermoplastic resins that can be used as constituent materials for the first member 31 and the second member 32 include polypropylene (PP), polyethylene (PE), polyamide (PA), polystyrene (PS), polyaryletherketone (PEAK), polyacetal (POM), polycarbonate (PC), polyethylene terephthalate (PET), polyetheretherketone (PEEK), polyphenylene sulfide (PPS), ABS resin, thermoplastic epoxy resin, etc. Examples of fiber reinforcing materials that can be used include carbon fiber, glass fiber, ceramic fiber, metal fiber, and organic fiber.

The first member 31 and the second member 32 may each be composed of a single fiber-reinforced thermoplastic resin molded body, but it is preferable that they are composed of a stack of multiple thin sheets. Figure 2 shows an example in which a molded body made by laminating multiple layers of a sheet (prepreg) in which a continuous fiber array is impregnated with a thermoplastic resin is used as the first member 31 and the second member 32.

Figure 2 shows a part of the sheet stack 33 constituting the first member 31. The sheet stack 33 includes a first sheet layer 33A, a second sheet layer 33B, and a third sheet layer 33C, each of which is made of a sheet impregnated with a thermoplastic resin in an array of continuous fibers. The first sheet layer 33A is a sheet having a thickness of about 0.1 mm to 0.5 mm, in which a large number of continuous fibers 34 are arranged in a predetermined arrangement direction and the array is impregnated with a thermoplastic resin to integrate them. The second sheet layer 33B and the third sheet layer 33C are also sheets similar to those described above, but the arrangement directions of the continuous fibers 34 are mutually different. In this way, for example, by stacking three types of sheets in which the arrangement directions of the continuous fibers 34 are different from each other in three axial directions in multiple layers, the first member 31 has pseudo-isotropy. The second member 32 is also a plate made of a multi-layer laminate of sheets similar to the first member 31.

The continuous fibers 34 may be, for example, carbon fibers, glass fibers, ceramic fibers, metal fibers, or organic fibers. In FIG. 2, a sheet in which the continuous fibers 34 are arranged in one direction is shown as an example, but a fabric-type sheet may also be used in which a woven fabric is formed using continuous fibers as warp and weft and then impregnated with a thermoplastic resin. Also, instead of the continuous fibers 34, a sheet or plate in which long fibers or short fibers with a length of about 2 mm to 20 mm are mixed with a thermoplastic resin may be used.

The first member 31 and the second member 32 may be made of the same material as in the above example, but may be made of different materials. For example, one of the first member 31 and the second member 32 may be a molded body of thermoplastic resin, and the other may be a molded body of fiber-reinforced thermoplastic resin. In this case, it is desirable to use a molded body of fiber-reinforced thermoplastic resin, or a molded body in which continuous fibers are impregnated with thermoplastic resin, as the second member 32 located on the side where the pin member 11 or shoulder member 12 of the tool 1 is finally pressed in. Alternatively, one of the first member 31 and the second member 32 may be a molded body of a specific thermoplastic resin or metal, and the other may be a molded body of a thermoplastic resin or metal of a different nature.

As an example of the fastener, a self-piercing rivet can be used as the rivet 5 shown in FIG. 1. When the rivet 5 is driven into the overlapping portion 30, a portion of the rivet deforms, generating an engagement force that integrates the first member 31 and the second member 32. As will be described in detail later, in this embodiment, the rivet 5 is driven into the area of the overlapping portion 30 that has been friction-stirred by the tool 1, and a portion of the rivet penetrates into the portion of the base material that has not been friction-stirred, generating the engagement force. There are no particular restrictions on the material of the rivet 5, and a rivet made of a metal such as titanium, a thermoplastic resin, or a thermoplastic composite material can be used. Instead of a self-piercing rivet, various joining members that are partially deformable, such as a simple cylindrical rivet, can be used as the fastener.

[Joining method using friction stir welding and riveting in combination]
3 is a diagram showing a process chart of the bonding method according to the present embodiment. The bonding method according to the present embodiment is a method for bonding an overlapping portion 30 including a first member 31 and a second member 32, and includes the following steps S1 to S6.
Step S1: A preparation step in which the rivet 5 to be driven is loaded into the tool 1 in advance.
Step S2: An overlapping portion forming step of forming the overlapping portion 30 including the first member 31 and the second member 32.
Step S3: A friction stir process in which the shoulder member 12 of the tool 1 is pressed into the overlapping portion 30 to perform friction stirring.
Step S4: A riveting step in which the pin member 11 of the tool 1 presses the rivet 5 into the friction stir portion from the first member 31 side.
Step S5: A step of deforming a part of the driven rivet 5 to form an interlock portion.
Step S6: forming the head portion 51 of the rivet 5.

Each of the above steps S1 to S6 will be described in detail below. FIG. 4(A) is a cross-sectional view showing the preparation step of the above step S1. FIG. 4(A) shows a longitudinal section of the rivet 5. The rivet 5 is made of a titanium alloy such as Ti-6Al-4V, and includes a head portion 51 (one end side) and a tubular portion 52 (the other end side) connected to the lower side of the head portion 51. The head portion 51 is made of a cylindrical body and has a top surface 51H that receives a pressure force from the tool 1. The tubular portion 52 is made of a cylinder with a slightly smaller diameter than the head portion 51. The tubular portion 52 has an upper end portion 521 that is integrally connected to the head portion 51, a lower end portion 522 that becomes the tip portion when driving into the overlapping portion 30, and an internal hollow region 523. By providing the hollow region 523, the tubular portion 52 has easy deformation properties. The lower end 522 is also the opening edge of the hollow area 523 and has a ring-shaped edge shape.

On the tool 1 side, an operation for loading the rivet 5 is performed. Specifically, the controller C (FIG. 1) operates the pin drive unit 22 to raise the pin member 11, creating a storage space H for the rivet 5 in the hollow portion of the shoulder member 12. In other words, the lower end 11T of the pin member 11 is raised relatively to the lower end 12T of the shoulder member 12 by more than the height of the rivet 5, creating a storage space H near the lower end opening of the shoulder member 12. The rivet 5 is then loaded into the storage space H. Note that the above preparation process is premised on the application of the shoulder-first process to perform friction stir welding.

Because pre-loading into the storage space H is required, a rivet 5 having an outer diameter smaller than the inner diameter of the hollow portion of the shoulder member 12 is selected. For this reason, the size of the head portion 51 before machining, as viewed from the direction in which the rivet 5 is pressed in, must be smaller than the friction stir portion 4 (see FIG. 6(A)) formed by the tool 1. For this reason, in this embodiment, in step S6 described below, machining is performed so that the head portion 51 has a larger diameter than the friction stir portion 4.

Figure 4 (B) is a cross-sectional view showing the implementation status of the overlapping portion 30 formation process of step S2. In step S2, the overlapping portion 30 is formed by overlapping the first member 31 and the second member 32 with at least a portion of them abutting each other. Figure 4 (B) shows an example in which the first member 31 is disposed on the tool side (upper side), and the second member 32 is disposed on the lower layer side of the first member 31 and on the backing material 15 side (lower side). The tool 1 is pressed into the first member 31 first, and the tool 1 is pressed into the second member 32 last. The lower surface 30B of the overlapping portion 30 is supported by the backing material 15, and the lower end surface of the tool 1 abuts against the upper surface 30U. The overlapping portion 30 may be formed by interposing one or more other members between the first member 31 and the second member 32.

Referring also to FIG. 2, the overlapping portion 30 has a mating surface BD where the joining surface 31A (lower surface) of the first member 31 and the joining surface 32A (upper surface) of the second member 32 are in direct contact with each other. In such a two-layer overlapping portion 30, friction stirring is performed by the tool 1 with the required spot joining position W as the axis, and the rivet 5 is pressed in. The clamping member 13 clamps the tool 1 to the overlapping portion 30 so that the lower end surface of the tool 1 abuts against the upper surface of the first member 31 with the rotation axis R (FIG. 1) of the tool 1 aligned with the spot joining position W. FIG. 4(B) shows a state in which the lower end 12T of the shoulder member 12 and the lower end 13T of the clamping member 13 are in contact with the upper surface 30U of the overlapping portion 30. The clamping member 13 presses the overlapping portion 30 against the backing material 15 with the biasing force of the spring 14.

5(A) to (D) are cross-sectional views sequentially showing the implementation status of riveting-assisted friction stir welding. FIG. 5(A) shows the friction stir welding process of step S3, in which the shoulder member 12 of the tool 1 is pressed into the overlapping portion 30 from the first member 31 side to perform friction stirring. The controller C controls the rotation drive unit 21 and the shoulder drive unit 23 to lower the shoulder member 12 while rotating it at high speed around the axis, and starts pressing the shoulder member 12 into the overlapping portion 30. Meanwhile, the controller C controls the pin drive unit 22 to retract the pin member 11 upward so as to allow the resin material overflowing from the press-in to escape. The clamp member 13 is immobile. As a result, friction stirring is performed with the point joining position W as the center. Note that since the pin member 11 is moved upward to accommodate the rivet 5, the retraction operation of the pin member 11 may be omitted.

When the shoulder member 12, rotating at high speed, is pressed into the overlapping portion 30, the material of the overlapping portion 30 is frictionally stirred in the press-in area of the shoulder member 12. The material that overflows from the overlapping portion 30 due to the press-in of the shoulder member 12 is released into the hollow portion within the shoulder member 12. The frictional stirring softens the material in the press-in area, and a frictional stirring portion 4 is formed in the overlapping portion 30. For example, when the first member 31 and the second member 32 are formed in a prepreg sheet stack 33, the continuous fibers 34 of each sheet layer 33A, 33B, and 33C are cut and crushed in the frictional stirring portion 4. This makes it easier to drive and deform the rivet 5 that follows.

Figure 5 (B) is a diagram showing the backfilling process of the overflowing material in the friction stir process of step S3. In the backfilling process, the shoulder drive unit 23 raises the shoulder member 12. If the pin member 11 has been raised, it is lowered. This action causes the softened material to flow into the area occupied by the lower end 12T of the shoulder member 12 in the friction stir section 4. Therefore, the material overflowing from the overlapping section 30 is also backfilled in the press-in area. By performing the above steps, the friction stir section 4 is formed in the overlapping section 30, which has a cylindrical side surface 41 with a depth d and a disk-shaped bottom surface 42. Meanwhile, in the base material portion around the friction stir section 4, the original hardness of the first member 31 and the second member 32 is maintained, and the reinforcement structure by the continuous fibers 34 is also maintained.

Figure 5 (C) is a diagram showing the implementation status of the rivet driving process of step S4. In the driving process, the rivet 5 is pressed into the friction stir part 4 from the first member 31 side. Specifically, the pin drive part 22 lowers the pin member 11 to apply a pressing force to the head part 51 (one end side of the fastening body), and the rivet 5 is pushed into the overlap part 30. The rivet 5 is loaded in advance into the storage space so that the top surface 51H of the head part 51 faces the lower end part 11T of the pin member 11. Therefore, when the pin member 11 descends, the rivet 5 also descends and enters the inside of the friction stir part 4 from the side of the lower end part 522 (the other end side of the fastening body). In this embodiment, the friction stir spot welding tool 1 is used as a tool for pressing the rivet 5, so there is no need to separately prepare a pressing tool for driving the rivet 5.

Figure 5 (D) is a cross-sectional view showing the implementation status of the step of forming the interlock portion 53 in step S5. In this step, after the rivet 5 reaches the second member 32, the rivet 5 is deformed so that a part of the rivet 5 penetrates into the base material portion around the friction stir portion 4 in the second member 32, forming the interlock portion 53. In this embodiment, the cylindrical tube portion 52 is deformed into a bell shape with an expanded lower end 522, and the expanded lower end 522 is pressed into the base material portion to form the interlock portion 53.

As the pin member 11 continues to press the rivet 5 from the state shown in FIG. 5(C), the lower end 522 of the rivet 5 eventually reaches the bottom surface 42 of the friction stir section 4. The area below the bottom surface 42 is the base material and has not been softened. In addition, the overlapping section 30 is supported by the backing material 15 at a position directly below the bottom surface 42. Therefore, if the pin member 11 continues to press the rivet 5 further after it reaches the bottom surface 42, the cylindrical section 52 is deformed into a bell shape as shown in FIG. 5(D).

That is, the lower end 522 is not only pressed into the base material portion below the friction stir portion 4 beyond the bottom surface 42, but also expands in the radial direction and presses into the base material portion on the side of the friction stir portion 4 beyond the side surface 41. Of these, the portion pressed into the base material portion beyond the side surface 41 becomes the interlock portion 53 that exerts an anchor effect in the peeling direction (up and down direction) between the first member 31 and the second member 32. The deformation of the cylindrical portion 52 of the rivet 5 may occur before reaching the second member 32. For example, the cylindrical portion 52 may gradually start to expand and deform in the area of the first member 31 after being pressed into the friction stir portion 4, and further expand and deform after reaching the bottom surface 42.

Figure 6 (A) is a cross-sectional view showing the joint 3 after step S5. During steps S1 to S5, the head 51 is housed in the hollow part of the shoulder member 12, and its outer circumferential surface is in a restrained state. Therefore, the head 51 does not expand or deform, and maintains its shape before casting. On the other hand, the friction stir part 4 is formed by pressing into the overlapping part 30 of the shoulder member 12. Therefore, the diameter of the head 51 is smaller than that of the friction stir part 4. The head 51 has a flange part 54 that engages with the upper surface of the friction stir part 4, but does not engage with the upper surface 30U of the overlapping part 30. With such a joint 3, there is a concern that the side surface 41 of the friction stir part 4 may break. For this reason, the head 51 formation process of step S6 is performed next.

In step S6, a head portion 5 having a size larger than that of the friction stir portion 4 is formed on the upper end side of the rivet 5. In other words, a head portion 51 including a portion that contacts the surface (upper surface 30U) of the friction stir portion 4 and the first member 31 is formed on the upper end side of the rivet 5. The above-mentioned "contacting the surface" includes not only a state in which the head portion 51 actually contacts the surface, but also a case in which a small gap is interposed between the two but the two are treated as being substantially in contact. Figure 6 (B) is a cross-sectional view showing the joint 3 after step S6 is completed. The head portion 51 shown here is processed to have a larger diameter than that shown in Figure 6 (A). The flange portion 54A of the head portion 51 has a size that contacts the upper surface of the friction stir portion 4 and also contacts the upper surface of the first member 31 on the periphery of the friction stir portion 4. With such a joint 3 having a flange 54A, the friction stir part 4 is sandwiched between the interlock part 53 that is inserted into the base material part of the second member 32 and the flange 54A that engages with the upper surface of the base material part of the first member 31. This improves the fixation of the friction stir part 4 to the overlapping part 30, resulting in a joint 3 with excellent stability. A specific example of the process for forming the head part 51 is described below.

[Step of forming head portion according to the first embodiment]
7A and 7B are cross-sectional views showing the process (step S6) of forming the head portion 51 according to the first embodiment. In the first embodiment, after the above-mentioned step S5 is completed, an example is shown in which the head portion 51 (one end side of the fastener) is deformed so as to reach the surface (upper surface 30U) of the first member 31 from the friction stirring portion 4. Specifically, the head portion 51 is heated and pressurized using a heating device 61 and a tool 1 as a post-treatment portion.

After executing step S5 shown in FIG. 5(D), the controller C temporarily separates the tool 1 including the clamp member 13 from the upper surface 30U of the overlapping portion 30 as shown in FIG. 7(A). Furthermore, the controller C operates the pin drive unit 22, the shoulder drive unit 23, and the clamp drive unit 24 so that the lower ends 11T, 12T, and 13T of the pin member 11, the shoulder member 12, and the clamp member 13 are flush with each other. This operation exposes the head portion 51 on the upper surface 30U. The heating device 61 is placed in a position where it can radiate heat HE to the target head portion 51. If the heating device 61 is an induction heating device, an IH coil is placed in a position where a magnetic circuit is formed between the heating device 61 and the head portion 51.

Next, the controller C provides the heating control unit 62 with heating setting information including the heating temperature and heating time of the target head portion 51. The heating control unit 62 operates the heating device 61 based on the setting information. The heating device 61 applies heat HE from the outside to the head portion 51 to soften it. At the same time, the controller C lowers the entire tool 1 and applies pressure P to the top surface 51H of the head portion 51. Although not shown in the figure, the back surface of the joint body 3 is supported by a backing material 15.

Figure 7 (B) shows the state in which the heated and softened head portion 51 is pressed by the tool 1 and the head portion 51 is rolled. The flush lower ends 11T, 12T, and 13T of the pin member 11, shoulder member 12, and clamp member 13 press the top surface 51H of the head portion 51. This pressing causes the head portion 51 to be rolled to a diameter larger than the friction stir portion 4. The flange portion 54A after rolling extends radially outward beyond the side peripheral surface 41 of the friction stir portion 4 and covers the upper surface of the first member 31 that is not friction stirred.

The clamp member 13 does not necessarily have to be lowered. However, the range that can be pressed by the lower ends 11T, 12T of the pin member 11 and shoulder member 12 is limited to the range corresponding to the upper surface of the friction stir portion 4. If the clamp member 13 is also lowered, the pressing range can be expanded. That is, the lower end 13T of the clamp member 13 presses the flange portion 54A against the upper surface of the first member 31, bringing them into close contact with each other. The effect of clamping the friction stir portion 4 by the interlock portion 53 and the flange portion 54A can be further enhanced.

In the above embodiment, an example was shown in which the tool 1 only applied pressure, but the tool 1 may also heat the head portion 51. In this case, the tool 1 is rotated at high speed around the rotation axis R with the flush lower ends 11T, 12T, and 13T of the pin member 11, shoulder member 12, and clamp member 13 in contact with the top surface 51H of the head portion 51. This heats and softens the head portion 51 with frictional heat. At the same time, the tool 1 is lowered to roll the head portion 51.

According to the first embodiment described above, the head portion 51 itself, which cannot be made larger in diameter than the friction stir portion 4 because it is driven with the pin member 11 of the double-action friction stir spot welding tool 1, is deformed so as to reach from the friction stir portion 4 to the surface of the first member 31. This makes it possible to increase the joining strength of the rivet 5 without using additional locking members or the like. In addition, since the head portion 51 is heated and pressurized, it can be easily deformed. Furthermore, at least the head portion 51 is pressurized using the tool 1 that forms the friction stir portion 4, so there is no need to prepare a separate tool for pressurizing the head portion 51.

[Step of forming head portion according to the second embodiment]
In the second embodiment, after the above-mentioned step S5 is completed, a head piece 55 (head member) which is a member separate from the rivet 5 and is used to form a head having a larger diameter than the friction stirring part 4 is joined to the head part 51 (one end side of the fastened body). Fig. 8(A) is a diagram showing a rivet 5A and a head piece 55 used in the head part forming step according to the second embodiment. Fig. 8(B) is a side view showing the state in which the rivet 5A and the head piece 55 are joined.

The rivet 5A has a head portion 51A and a cylindrical portion 52, similar to the rivet 5 of the first embodiment, but the head portion 51A is relatively thin. The head piece 55 is a disk-shaped member made of the same metal as the rivet 5A or a different metal that can be joined to the rivet 5A. The outer diameter of the head piece 55 is larger than that of the head portion 51A and is larger than the diameter of the friction stirring portion 4. The upper surface of the head piece 55 is provided with a pair of engagement holes 551 for transmitting rotational torque. Instead of the engagement holes 551, a protrusion may be provided on the upper surface of the head piece 55. The head piece 55 is joined and integrated as shown in FIG. 8(B) by friction welding in which the head piece 55 is pressed against the head portion 51A while rotating it relative to the rivet 5A.

Figures 9 (A) and (B) are cross-sectional views showing the process of forming the head portion according to the second embodiment. Figure 9 (A) shows the state where the driving of the rivet 5A into the friction stir portion 4 is completed, that is, the state where the process of forming the interlock portion 53 in step S5 described above is completed. The interlock portion 53 has entered the second member 32 beyond the side surface 41 of the friction stir portion 4. Meanwhile, the head portion 51A has a smaller diameter than the friction stir portion 4.

Figure 9 (B) shows the state of friction welding of the head piece 55. In this embodiment, a friction welding tool 63 for the friction welding is used as a post-treatment unit, and the heating device 61 illustrated in Figure 1 is not used. The friction welding tool 63 is a cylindrical tool that can be rotated around the rotation axis R by a rotation drive mechanism (not shown), and can be raised and lowered along the rotation axis R by a lift drive mechanism (not shown). The lower end surface of the friction welding tool 63 is provided with a protrusion that fits into the engagement hole 551 of the head piece 55.

The head piece 55 is set on the head portion 51A of the rivet 5A with the engagement hole 551 fitted to the protrusion of the friction welding tool 63. The friction welding tool 63 is then rotated at high speed by the rotation drive mechanism and lowered by the elevation drive mechanism. This action causes the lower surface 55A of the head piece 55 to come into contact with the top surface 51H of the head portion 51A, and the head piece 55 rotates at high speed. Frictional heat caused by the high speed rotation of the head piece 55 and a pressure force caused by the lowering of the head piece 55 are applied to the head portion 51. The frictional heat and pressure force cause the head portion 51A and head piece 55 to be frictionally welded together.

Figure 10 is a cross-sectional view of a joint 3 joined by the joining method according to the second embodiment. As is clear from comparison with Figure 9 (A), the diameter of the head portion 51A is increased by joining the head piece 55. The lower surface 55A of the head piece 55 abuts the upper surface of the friction stir portion 4 and also abuts the upper surface of the first member 31 on the periphery of the friction stir portion 4. With a joint 3 having such a lower surface 55A, the friction stir portion 4 is sandwiched between the interlock portion 53 and the head piece 55 that engages with the upper surface of the first member 31. This improves the fixation of the friction stir portion 4 to the overlapping portion 30, resulting in a joint 3 with excellent stability.

According to the second embodiment described above, by selecting the size, thickness, and material of the head piece 55, a variety of head parts can be retrofitted to the rivet 5A. In addition, since there is no need to heat the rivet 5A, the construction equipment can be simplified. Note that the pin member 11 of the friction stir spot welding tool 1 may be used instead of the friction welding tool 63.

[Step of forming head portion according to the third embodiment]
In the third embodiment, after the above-mentioned process S5 is completed, an example is shown in which a hat-shaped head piece 56 (head portion member), which is a separate member from the rivet 5 and is used to form a head portion having a larger diameter than the friction stir portion 4, is resistance welded to the head portion 51A.

Figure 11 (A) is a plan view of the hat-shaped head piece 56 as viewed from below, and Figure 11 (B) is a side view of the hat-shaped head piece 56. The hat-shaped head piece 56 is a member made of the same metal as the rivet 5A or a dissimilar metal that can be welded to the rivet 5A. The hat-shaped head piece 56 has a main body 561, a cavity 562, and a side opening 563. The main body 561 is a substantially rectangular member with arc-shaped short sides and straight long sides when viewed from above. The short sides are shorter than the diameter of the head portion 51A of the rivet 5A, and the long sides are longer than the diameter of the friction stirring portion 4.

The cavity 562 is a space formed by recessing the underside of the main body 561, and has a volume large enough to accommodate the head 51A. The side opening 563 is an opening provided on the side of the long side of the main body 561. As shown by the dotted line in FIG. 11(A), when the head 51A is accommodated in the cavity 562, a part of the side periphery of the head 51A protrudes from the side opening 563.

11C is a cross-sectional view showing the head forming process according to the third embodiment. In this process, the hat-shaped head piece 56 is fitted into the head part 51A. In this embodiment, a resistance welding device 64 that integrates the head part 51A and the hat-shaped head piece 56 by resistance welding is used as a post-treatment device. The resistance welding device 64 includes a first electrode 641, a second electrode 642, a pressure piece 643, a transformer 644, and a power source 645. The first electrode 641 is a disk electrode having a diameter approximately the same as that of the head part 51A, and is in contact with the upper surface of the hat-shaped head piece 56. The second electrode 642 is in contact with the side peripheral surface of the head part 51A exposed from the side opening 563. The pressure piece 643 generates a pressing force that presses the hat-shaped head piece 56 against the head part 51A. The transformer 644 and the power source 645 supply the voltage required for the resistance welding to the first electrode 641 and the second electrode 642.

Figure 12 is a cross-sectional view of a joint 3 joined by the joining method according to the third embodiment. The rivet 5A and the hat-shaped head piece 56 are integrated by the welded portion 56A in a manner that the head portion 51A is accommodated in the cavity 562. The diameter of the head portion 51A is increased by welding the hat-shaped head piece 56. The hat-shaped head piece 56 abuts against the upper surface of the friction stir portion 4 and the upper surface of the first member 31 on the periphery of the friction stir portion 4. Therefore, a joint 3 can be formed in a manner in which the friction stir portion 4 is sandwiched between the interlock portion 53 and the hat-shaped head piece 56 that engages with the upper surface of the first member 31.

In the third embodiment, if there is a conductive layer inside the second member 32 that can ensure a conductive path to the rivet 5A, the conductive layer may be used to pass current for resistance welding. FIG. 13 is a cross-sectional view showing a joining method according to a modified example of the third embodiment. A conductive layer 32B is provided near the lower end of the second member 32. The conductive layer 32B is in contact with the interlock portion 53 of the rivet 5A. A hat-shaped head piece 56 is fitted into the head portion 51A. In this modified example, the hat-shaped head piece 56 can be a member that does not have a side opening 563 and is circular in top view.

The first electrode 641 is in contact with the hat-shaped head piece 56, and pressure is applied by the pressure piece 643. The conductive layer 32B is used as the second electrode 642 in the above example. The resistance welding device 64 supplies the voltage required for resistance welding to the first electrode 641 and the conductive layer 32B from the power source 645 via the transformer 644. As a result, the rivet 5A and the hat-shaped head piece 56 are integrated by the welded portion 56A.

[Other Modifications]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. For example, the following modified embodiments are possible.

(1) In the above embodiment, an example was shown in which a double-action friction stir spot welding tool 1 was used as the tool for forming the friction stir portion 4. Alternatively, a single-action friction stir spot welding tool or other friction stir welding tool may be used as the tool. In this case, the single-action friction stir spot welding tool itself or a separate press-in tool can be used as the tool for pressing the rivet 5 into the friction stir portion 4.

(2) In the above embodiment, an example is shown in which the double-action friction stir spot welding tool 1 is used in a shoulder-first process to form the friction stir portion 4. Alternatively, the tool 1 may be used in a pin-first process to form the friction stir portion 4.

(3) In the above embodiment, an example was shown in which the interlock portion 53 is formed on the cylindrical portion 52 of the rivet 5. The joined body 3 may be configured in such a manner that the interlock portion 53 is not actively formed. Also, an example was shown in which the interlock portion 53 has a larger diameter than the friction stir portion 4. That is, an example was shown in which the lower end portion 522 of the cylindrical portion 52 is expanded radially outward from the side peripheral surface 41 of the friction stir portion 4. The interlock portion 53 only needs to exert an anchor effect on the base material portion of the second member 32, and may be configured to penetrate into the base material portion below the bottom surface 42.

According to the joining method of the present invention described above, a joint 3 having excellent strength can be obtained by using friction stir and rivet 5 in combination. A friction stir portion 4 into which the rivet 5 will be pressed is formed in the overlapping portion 30. In this friction stir portion 4, the first member 31 and the second member 32 constituting the overlapping portion 30 are kneaded by friction stirring, and are softened. With such a friction stir portion 4, the rivet 5 can be easily pressed in. Therefore, the fastening effect of the rivet 5 is easily exerted. Furthermore, a head portion 51 having a size larger than the friction stir portion 4, that is, the head portion 51 including a portion in contact with the surface of the friction stir portion 4 and the first member 31, is formed on the upper end side of the rivet 5. In other words, the head portion 51 is finished to cover the side peripheral surface 41, which is the boundary portion between the friction stir portion 4 and the base material of the first member 31 and the second member 32. The locking effect of the head portion 51 can suppress breakage along the side peripheral surface 41.

In addition, according to the joint 3 of the present invention, a joining force is applied to the overlapping portion 30 by the friction stir portion 4 formed in the overlapping portion 30 and the rivet 5 pressed into the friction stir portion 4. In other words, the first member 31 and the second member 32 can be firmly joined by the fastening effect of the rivet 5 without relying solely on friction stir welding. Furthermore, the friction stir portion 4 is clamped between the interlock portion 53 of the rivet 5 and the flange portion 54 of the head portion 51. Therefore, breakage along the side peripheral surface 41 is further suppressed, and a joint 3 with excellent joining strength can be constructed.

REFERENCE SIGNS LIST 1 Tool 11 Pin member 12 Shoulder member 3 Joint 30 Overlapped portion 31 First member 32 Second member 4 Friction stir portion 5, 5A Rivet (fastened body)
51, 51A Head portion (one end side)
52 Cylindrical body part (other end side)
53 Interlocking part (part of fastening body)
54, 54A Flange portion
55 Head piece (head part member)
61 Heating device (post-treatment section)
63 Friction welding tool (post-processing section)
64 Resistance welding device (post-treatment section)
M Friction stir spot welding device H Storage space

Claims (12)

A joining method for joining an overlapping portion formed by using a friction stir welding tool and a fastener, the overlapping portion including a first member on the tool side and a second member disposed below the first member, the method comprising the steps of:
The tool is pressed into the overlapping portion from the first member side to perform friction stirring, thereby forming a friction stir portion in the overlapping portion;
A fastener having a size smaller than the friction stir portion as viewed from the press-in direction is used, and one end of the fastener is pressed to press the other end of the fastener into the friction stir portion from the first member side;
A head portion having a size larger than that of the friction stir portion is formed on one end side of the fastening body.
Joining method. The bonding method according to claim 1 ,
After the fastener is pressed in, the other end of the fastener is inserted into the second member to form an interlock portion. The bonding method according to claim 1 or 2,
A joining method, comprising: deforming one end side of the fastener from the friction stir portion to the surface of the first member, thereby forming the head portion. The joining method according to claim 3,
A joining method in which one end of the fastener is deformed by applying heat and pressure. The joining method according to claim 4,
At least the application of heat and pressure is performed by pressing one end side of the fastener with the tool. The bonding method according to claim 1 or 2,
A joining method in which a head portion member that is a separate member from the fastener and corresponds to the head portion is joined to one end side of the fastener. The joining method according to claim 6,
The fastener and the head member are joined together by pressing them together while rotating them relatively. The bonding method according to any one of claims 1 to 7,
The tools include:
A cylindrical pin member that rotates about an axis and is movable back and forth in the axial direction;
a cylindrical shoulder member that is positioned so as to cover the outer periphery of the pin member, rotates around the same axis as the pin member, and is movable back and forth in the axial direction;
The joining method includes pressing the fastener into the friction stir portion by lowering the pin member or the shoulder member. The bonding method according to claim 8,
The pin member is raised to create an accommodation space in the shoulder member, and the fastener is pre-loaded into the accommodation space;
The shoulder member is pressed into the overlapping portion to perform the friction stirring.
The fastener is pressed into place by lowering the pin member. A joint body of an overlapping portion formed including a first member and a second member,
an overlapping portion where the first member is disposed on one end side in an overlapping direction and the second member is disposed on the other end side in the overlapping direction;
A friction stir portion provided in the overlapping portion;
A fastening body press-fitted into the friction stir portion,
The fastening body is
an interlock portion in which a part of the fastening body is inserted into the second member;
A joint comprising an upper surface of the friction stir portion and a flange portion abutting against the upper surface of the first member at a periphery of the friction stir portion. The joint body according to claim 10,
The second member, or both the first member and the second member, are made of a fiber-reinforced thermoplastic resin. A joining device that joins an overlapping portion formed including a first member and a second member using friction stirring and a fastener,
A cylindrical pin member that is movable back and forth in an axial direction;
a cylindrical shoulder member that is positioned so as to cover an outer periphery of the pin member, that rotates about the same axis as the pin member, and that is movable back and forth in the axial direction;
a fastening body having one end side pressed by the pin member and the other end side pressed into a friction stir portion formed in the overlapping portion by the pressing, and loaded into an accommodation space created by the rise of the pin member;
a post-processing section that forms a head section having a size larger than that of the friction stir section on one end side of the fastener;
A joining device comprising: