Method and apparatus for inspecting friction stir welded parts

Abstract

To accurately inspect a friction stir joint part which is formed by joining an overlapped portion of two or more members using friction stirring and a fastening body.SOLUTION: A friction stir joint part is formed by forming a friction stir part 4 by press-fitting a tool 1 for friction stir point joint from the first member 31 side in a state where the second member 32 side is supported by a backing material 15 to an overlapped portion 30 including a first member 31 and a second member 32 arranged under the first member 31 and press-fitting a rivet 5 from the first member 31 side to the friction stir part 4. An inspection method of the friction stir joint part includes a step of detecting whether a lower end part 522 of the rivet 5 contacts the backing material 15. When a DC voltage is applied to a pin member 11 from a pin current carrying part 25, the method detects whether a penetration error in which the rivet 5 penetrates the overlapped portion 30 occurs depending on whether an electric current flows between the pin member 11 and the backing material 15.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for inspecting a friction stir welded portion formed by welding an overlapping portion of two or more members using friction stir welding and a fastener, and to a welding device for the overlapping portion. [Background technology]

[0002] Metallic members, resin members, thermoplastic resin members mixed with fiber reinforcement, etc. are used as components of structures such as aircraft, railroad cars, and automobiles. In 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.

[0003] Patent Document 1 discloses a joining method using a blind rivet. In this joining method, a blind rivet with a flange is driven into the overlapping portion of two components from the front side of the overlapping portion, penetrating the overlapping portion. After that, the penetrated portion of the blind rivet is bulged and deformed on the back side of the overlapping portion, forming a joint in which the overlapping portion is sandwiched between the bulge and the flange. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5250429 Summary of the Invention [Problem to be solved by the invention]

[0005] In the joints made by the method of Patent Document 1, the bulge and the flange are exposed to the outside. Therefore, it is relatively easy to check whether the joints are properly made by visual inspection or image processing. However, it is difficult to check whether the fasteners are properly pressed into the overlapping parts of joints made by driving the fasteners so that they do not penetrate the overlapping parts.

[0006] The present invention aims to provide an inspection method that can accurately inspect a friction stir welded joint formed by joining overlapping portions of two or more components using friction stir and a fastener, and a joining device that can perform the inspection method. [Means for solving the problem]

[0007] A method for inspecting a friction stir weld according to one aspect of the present invention is a method for inspecting a friction stir weld formed by pressing a friction stir tool into an overlapping portion including a first member and a second member disposed below the first member while the second member side is supported by a backing material to form a friction stir portion, and pressing a fastener into the friction stir portion from the first member side, and detecting whether a part of the fastener abuts against the backing material.

[0008] This inspection method can detect when the fastener penetrates the friction stir portion and the second member and contacts the backing material. In other words, it can detect defective welding in which the fastener penetrates the friction stir portion without causing the expected deformation of the fastener, such as forming an interlock portion with the base material of the second member. Therefore, it is possible to accurately inspect a friction stir weld in which the fastener is driven in such a way that it does not penetrate the overlap portion.

[0009] A joining apparatus according to another aspect of the present invention is a joining apparatus for joining an overlapping portion including a first member and a second member arranged below the first member, and includes a friction stir tool pressed into the overlapping portion from the first member side to form a friction stir portion in the overlapping portion, a press-in tool for pressing a fastener from the first member into the friction stir portion, a backing material supporting the overlapping portion from the second member side, and a detection means for detecting whether a portion of the fastener has contacted the backing material.

[0010] This welding device makes it possible to detect whether or not a part of the fastener has come into contact with the backing material during a series of steps in which the fastener is pressed into the friction stir portion to form the friction stir weld. In other words, it is possible to detect defective welding in which the fastener penetrates the friction stir portion without undergoing the expected deformation during the friction stir weld formation step. Therefore, it is possible to provide a welding device that forms a quality-guaranteed weld. Effect of the Invention

[0011] According to the present invention, it is possible to provide an inspection method that can accurately inspect a friction stir welded joint formed by joining overlapping portions of two or more components using friction stir and a fastener, and a joining device that can perform the inspection method. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a double-action friction stir spot welding apparatus capable of carrying out the method for inspecting a friction stir welded portion according to the present invention. [Diagram 2] FIG. 2(A) is a cross-sectional view showing the overlapping portion between a first member and a second member, FIG. 2(B) is a partially cutaway side view of a rivet (fastened body), and FIG. 2(C) is a cross-sectional view of a joint joined using a combination of friction stir welding and riveting. [Diagram 3] FIG. 3 is a block diagram showing the electrical configuration of the friction stir spot welding apparatus. [Figure 4] FIG. 4 is a cross-sectional view showing a preparation state for rivet-assisted friction stir welding. [Diagram 5] 5(A) to 5(D) are cross-sectional views sequentially showing the implementation of rivet-assisted friction stir welding. [Figure 6] FIG. 6 is a diagram showing a process chart of the method for inspecting a riveted friction stir welded portion according to this embodiment. [Figure 7] FIG. 7 is a schematic diagram showing an example of a process for inspecting rivet penetration errors. [Figure 8] FIG. 8 is a schematic diagram showing another example of the inspection process for rivet penetration errors. [Figure 9] FIG. 9 is a schematic diagram showing an example of a process for inspecting the floating of a rivet head. [Figure 10] FIG. 10A is a cross-sectional view showing a joint where no floating occurs in the head portion, and FIG. 10B is a cross-sectional view showing a joint where floating occurs in the head portion. [Figure 11] FIG. 11 is a schematic diagram showing an example of a process for inspecting the degree of expansion of the cylindrical portion of a rivet. [Figure 12] FIG. 12 is a schematic diagram showing another example of the inspection process for the degree of expansion of the cylindrical portion of the rivet. [Figure 13] FIG. 13 is a cross-sectional view showing the external heating of a rivet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. The friction stir welded portion to be inspected in the present invention is a welded portion formed by overlapping and spot-welding two or more structural members, such as plates, frames, exterior materials, or columnar materials, made of metal, thermoplastic resin, thermoplastic composite material, etc. A welded body having this friction stir welded portion becomes a component of a structure such as an aircraft, a railway vehicle, or an automobile.

[0014] [Configuration of friction stir spot welding device] 1 is a schematic diagram showing the configuration of a double-action friction stir spot welding apparatus M (joining apparatus) capable of carrying out the method for inspecting a friction stir welded portion according to the present invention. The friction stir spot welding apparatus M is attached to the arm tip of a multi-joint robot equipped with a robot arm having, for example, six movable joint axes. The friction stir spot welding apparatus M may also be attached to a mechanical device that only moves up and down along one axis. Furthermore, a single-action friction stir spot welding apparatus can also be used.

[0015] The friction stir spot welding device M includes a double-action friction stir spot welding tool 1, a tool driving unit 2 that rotates and raises and lowers the tool 1, and a tool fixing unit 17 that fixes the tool 1 to a workpiece. Note that although the directions "up" and "down" are indicated in FIG. 1, this is for the sake of convenience of explanation and is not intended to limit the actual direction of use of the tool 1. In this embodiment, the workpiece is an overlapping portion 30 in which a first member 31 and a second member 32 are overlapped in the vertical direction, and a joint 3 is finally formed by friction stir spot welding. The tool 1 in this embodiment is a tool that serves both as a tool for performing friction stirring and a tool for pressing a fastener (a rivet 5 described later) into a friction stir portion.

[0016] 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 member formed in a cylindrical shape, and is arranged so that its axis extends in the vertical direction. The pin member 11 is rotatable about the axis as a rotation axis R, and is movable forward and backward in the vertical direction as indicated by the arrow Z1 along the rotation axis R. When the tool 1 is in use, the tool 1 is fixed to the overlapping portion 30 so that the rotation axis R and the point joining position W in the overlapping portion 30 are aligned.

[0017] 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 along the rotation axis R in the up and down direction indicated by the arrow Z2. 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 rotating together around the axis of the rotation axis R. That is, the pin member 11 and the shoulder member 12 can not only simultaneously rise and fall along the rotation axis R, but also independently move such that one descends and the other ascends.

[0018] The clamp member 13 is a cylindrical member having 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 about its axis, but can move back and forth in the up and down directions indicated by arrow Z3 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 by the clamp member 13 prevents the friction stir material from scattering, and enables the friction stir spot welded portion to be finished smoothly.

[0019] The spring 14 is attached to the upper end portion 131 of the clamp member 13 so as to extend upward. The spring 14 biases the clamp member 13 in a direction toward the overlapping portion 30 (downward).

[0020] The tool fixing unit 17 includes a rotary tool fixing device 171 and a clamp fixing device 172. The rotary tool fixing device 171 is disposed above the shoulder member 12 into which the pin member 11 is inserted, and supports the pin member 11 and the shoulder member 12. The clamp fixing device 172 supports the clamp member 13 via a spring 14. In addition, the clamp fixing device 172 supports the rotary tool fixing device 171 via a rotation drive unit 23 described below.

[0021] A backing material 15 is disposed facing the lower end surface of the tool 1. The backing material 15 has a support plane 151 that abuts against the lower surface side of the work (overlapped portion 30) to be joined. The backing material 15 is a member that supports the overlapped portion 30 from the back surface when the pin member 11 or the shoulder member 12, and a rivet 5 described later are pressed into the overlapped portion 30. The backing material 15 is held by a tip portion 161 of a C-shaped frame 16. The clamp member 13 biased by the spring 14 presses the overlapped portion 30 against the backing material 15. As a result, the tool 1 is fixed to the overlapped portion 30. The C-shaped frame 16 is, for example, a frame attached to the tip of the robot arm.

[0022] The tool driving unit 2 includes a pin driving unit 21, a shoulder driving unit 22, and a rotation driving unit 23. The pin driving unit 21 is a mechanism for moving the pin member 11 back and forth (raising and lowering) along the rotation axis R. The pin driving unit 21 drives the lower end 11T of the pin member 11 to move down toward the overlapping portion 30, or to move up relative to the overlapping portion 30. For example, a linear actuator can be used as the pin driving unit 21. As the linear actuator, an actuator constituted by a servo motor and a rack / pinion, or an actuator constituted by a servo motor and a ball screw, can be used.

[0023] The shoulder drive unit 22 is a mechanism for moving the shoulder member 12 back and forth (raising and lowering) along the rotation axis R. The shoulder drive unit 22 drives the lower end 12T of the shoulder member 12 to press-fit into and retract from the overlapping portion 30. A linear actuator similar to that described above can be used as the shoulder drive unit 22. The shoulder drive unit 22 in this embodiment is a mechanism for raising and lowering the tool fixing portion 17 itself that supports the pin member 11, the shoulder member 12, and the clamp member 13. For this reason, the movements of the pin member 11, the shoulder member 12, and the clamp member 13 in the directions of the arrows Z1, Z2, and Z3 shown in FIG. 1 can all be realized by driving the shoulder drive unit 22.

[0024] However, the pin member 11 can be moved forward and backward independently of the shoulder member 12 and the clamp member 13 by being driven by the pin drive unit 21. For example, even in a situation where the shoulder member 12 is driven downward by the shoulder drive unit 22, the pin member 11 can be driven upward by the pin drive unit 21. In addition, when the clamp member 13 is lowered by the shoulder drive unit 22 and its lower end portion 13T abuts against the overlapping portion 30, the biasing force of the spring 14 also acts on the clamp member 13. Due to the biasing force, the clamp member 13 presses the overlapping portion 30 against the backing material 15, and fixes the tool 1 to the overlapping portion 30.

[0025] The rotation drive unit 23 includes a servo motor, a drive gear, etc., and is held by the clamp fixator 172. The rotation drive unit 23 rotationally drives the rotary tool fixator 171. Due to this rotational drive, the pin member 11 and the shoulder member 12 supported by the rotary tool fixator 171 rotate around the rotation axis R.

[0026] [Overview of friction stir welded parts] The inspection method according to the present invention inspects a friction stir welded portion obtained by welding overlapping portions of two or more members using friction stir welding and a fastener. The outline of this friction stir welded portion will be described below. Fig. 2(A) is a diagram showing an overlapping portion 30 of a first member 31 and a second member 32 before friction stir welding is performed. Fig. 2(B) is a partially cutaway side view of a rivet 5 (fastener) to be pressed into the friction stir portion 4, and Fig. 2(C) is a cross-sectional view of a joint 3 (friction stir welded portion) welded using a combination of friction stir welding and the rivet 5.

[0027] FIG. 2(A) shows an example in which the first member 31 and the second member 32 are composed of a stack of multiple thin sheets 33. As the thin sheet 33, a sheet (prepreg) in which a continuous fiber array is impregnated with a thermoplastic resin can be used. The first member 31 and the second member 32 may each be a member composed of a single fiber-reinforced thermoplastic resin molded body, or may be a metal or a thermoplastic resin member that does not contain a fiber reinforcement material. FIG. 2(A) shows an example in which the first member 31 and the second member 32 have the same thickness, but they may have different thicknesses as long as they have a thickness that allows friction stir welding.

[0028] 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. The overlapping portion 30 is not limited to such a two-layer structure. It may include the first member 31 and the second member 32 arranged in a lower layer of the first member 31, and one or more other layers may be interposed between them. The above-mentioned tool 1 is pressed into the overlapping portion 30 from the first member 31 side, and friction stirring is performed with the predetermined spot joining position W as the axis, and the friction stir portion 4 is formed. Furthermore, the rivet 5 is pressed into the friction stir portion 4 from the first member 31 side, and the construction of the joint 3 is completed.

[0029] Referring to FIG. 2(B), the rivet 5 is made of a conductive titanium alloy such as Ti-6Al-4V, and includes a cylindrical head portion 51 and a cylindrical body portion 52 connected to the lower side of the head portion 51. The head portion 51 has a larger diameter than the body portion 52, and the larger diameter portion is a flange portion 54. The head portion 51 is made of a solid body and has a top surface 51H that receives a press-in force from the tool 1. The body portion 52 includes an upper end portion 521 that is integrally connected to the head portion 51, and a lower end portion 522 that becomes a tip portion when driving into the overlapping portion 30. The body portion 52 has a cylindrical hollow region 523 therein in order to provide it with easy deformation. The lower end portion 522 is also an opening edge of the hollow region 523 and has an annular edge shape.

[0030] A self-piercing rivet, for example, can be used as the rivet 5. When the rivet 5 is driven into the overlapping portion 30, a portion of the rivet 5 deforms and generates an engaging force that integrates the first member 31 and the second member 32. Note that instead of a self-piercing rivet, various joining members, the portion of which is deformable, may be used as the fastener.

[0031] As shown in FIG. 2(C), the rivet 5 is pressed into the overlapping portion 30 in the friction stirring portion 4. The friction stirring portion 4 is formed to a depth extending from the first member 31 side to a part of the second member 32, and has a side peripheral surface 41 and a bottom surface 42. In this embodiment, the entire length of the cylindrical portion 52 is pressed into the friction stirring portion 4 (overlapping portion 30), and the lower end surface of the head portion 51 is expected to come into contact with the friction stirring portion 4. After being pressed into the friction stirring portion 4, the lower end portion 522 of the cylindrical portion 52 is expanded and deformed into a bell shape, and is also pressed into the base material portion around the friction stirring portion 4 in the second member 32. That is, the lower end portion 522 forms an interlock portion 53 by penetrating into the base material portion below the bottom surface 42 of the friction stirring portion 4 and radially outward from the side peripheral surface 41. The joining strength of the joined body 3 can be increased by the locking effect of the interlock portion 53 alone and the clamping effect of the interlock portion 53 and the flange portion 54.

[0032] In this embodiment, an example is shown in which the entire length of the cylindrical portion 52 is pressed into the overlapping portion 30, but a predetermined length of the cylindrical portion 52 may be pressed into the overlapping portion 30. In this case, a gap of a predetermined length is formed between the upper surface 30U of the overlapping portion 30 and the lower end surface of the head portion 51. Also, a rivet 5 in which the head portion 51 and the cylindrical portion 52 have the same diameter, or a rivet 5 in which the head portion 51 has a smaller diameter than the cylindrical portion 52 may be used. Furthermore, after the rivet 5 is pressed into place, the head portion 51 may be rolled so that the diameter of the head portion 51 is larger than that of the friction stir portion 4.

[0033] [Control configuration of friction stir spot welding device] Fig. 3 is a block diagram showing a control configuration of the friction stir spot welding apparatus M. The friction stir spot welding apparatus M includes, as a control configuration, a controller 61 (control unit), an input unit 62, and an inspection unit 63. The friction stir spot welding apparatus M also includes, as a hardware configuration not shown in Fig. 1, an ammeter 26, a stroke sensor 27, and a temperature detection unit 28.

[0034] The controller 61 is composed of a microcomputer or the like, and executes a predetermined control program to comprehensively control the operation of each part of the tool driving unit 2 and the operation of the inspection unit 63. Specifically, the controller 61 controls the pin driving unit 21 to independently move the pin member 11 forward and backward. The controller 61 also controls the shoulder driving unit 22 to cause the pin member 11, the shoulder member 12, and the clamp member 13 to perform required forward and backward movements. These forward and backward movements perform the fixing of the tool 1 to the overlapping portion 30, the press-fitting of the pin member 11 or the shoulder member 12 into the overlapping portion 30, and the like. Furthermore, the controller 61 controls the rotation driving unit 23 to rotate the pin member 11 and the shoulder member 12 around the rotation axis R during an appropriate period of the forward and backward movements, and perform friction stir welding at the spot welding position W of the overlapping portion 30.

[0035] The above-mentioned double-action friction stir spot welding tool 1 can be used in a pin-first process or a shoulder-first process. When friction stir welding is performed in the pin-first process, the controller 61 presses the pin member 11 of the tool 1 into the overlapping portion 30 first to perform friction stir welding, while raising (retracting) the shoulder member 12. In the subsequent backfilling process, the pin member 11 is raised and retracted, while the shoulder member 12 is lowered.

[0036] On the other hand, when friction stir welding is performed in a shoulder-first process, the controller 61 first presses the shoulder member 12 of the tool 1 into the overlapping portion 30 to perform friction stir welding, while raising (retracting) the pin member 11. In the subsequent backfilling process, the shoulder member 12 is raised and retracted, while the pin member 11 is lowered. In an embodiment (FIG. 5) described later, an example in which friction stir welding is performed in a shoulder-first process will be described in detail.

[0037] The input unit 62 is composed of a keyboard, a touch panel, or the like, and receives required data input to the controller 61. The input data includes, for example, various parameters related to the control of friction stir welding, the thickness and material of the workpiece, the press-fit depth of the tool 1, and coordinate data of the spot welding position W.

[0038] The tool driving unit 2 includes an encoder 24 (measurement means) and a pin current supply unit 25 (detection means) in addition to the above-mentioned pin driving unit 21, shoulder driving unit 22, and rotation driving unit 23. In this embodiment, an electric motor is used as the driving source for each of the pin driving unit 21, shoulder driving unit 22, and rotation driving unit 23. The encoder 24 is attached to the electric motors of the pin driving unit 21 and shoulder driving unit 22, respectively, and outputs an electric signal that leads to identification of the height positions of the lower end 11T of the pin member 11 and the lower end 12T of the shoulder member 12.

[0039] The pin current supply unit 25 includes a DC voltage generation source and applies a DC voltage to the pin member 11 during a penetration error inspection of the rivet 5, which will be described later. An ammeter 26 (detection means) detects a current flowing between the pin member 11 (tool 1) and the backing material 15 during the penetration error inspection.

[0040] The stroke sensor 27 (measurement means) is a sensor that detects the relative positions of the shoulder member 12 and the clamp member 13. When the stroke sensor 27 detects that the shoulder member 12 and the clamp member 13 are in the same position while the clamp member 13 is clamping the overlapping portion 30, this means that the lower end portion 12T of the shoulder member 12 is in contact with the upper surface 30U of the overlapping portion 30.

[0041] The temperature detection unit 28 (shape estimation means) measures the temperature of the friction stir welded portion (overlap portion 30 / jointed body 3) during or after welding. As the temperature detection unit 28, various non-contact or contact type temperature measurement devices can be used. As the former, a thermograph and as the latter, a thermocouple can be exemplified as preferred temperature measurement devices.

[0042] The inspection unit 63 performs various inspection operations on the joint 3 using both the friction stir welding unit 4 and the rivet 5. The inspection unit 63 functionally comprises a contact current detection unit 64 (detection means), a motor current detection unit 65 (detection means), a tool position detection unit 66 (measurement means), a gap calculation unit 67 (measurement means), a shape estimation unit 68 (shape estimation means), and a determination unit 69 (shape estimation means). These functional units will be described in detail together with their operations when explaining the inspection process based on Figs. 6 to 13, so only an overview will be given here.

[0043] The contact current detection unit 64 determines whether or not the current flowing between the pin member 11 and the backing material 15 exceeds a predetermined threshold value based on the current value measured by the ammeter 26. Furthermore, when the current exceeds the predetermined threshold value, the contact current detection unit 64 determines that the lower end 522 of the rivet 5 is in contact with the backing material 15.

[0044] The motor current detection unit 65 detects the motor current of the electric motor that is the drive source of the pin drive unit 21, or the motor current of the electric motor that is the drive source of the shoulder drive unit 22. When the motor current exceeds a predetermined threshold value, the motor current detection unit 65 determines that the lower end 522 of the rivet 5 has come into contact with the backing material 15. Note that since the inspection functions of the contact current detection unit 64 and the motor current detection unit 65 are substantially the same, either one of them may be omitted.

[0045] The tool position detection unit 66 calculates the lowered positions of the pin member 11 and the shoulder member 12, i.e., the height positions of the lower ends 11T and 12T, based on the output value of the encoder 24. The height position of the lower end 12T of the shoulder member 12 may be calculated by the tool position detection unit 66 based on the output value of the stroke sensor 27.

[0046] The gap calculation unit 67 determines the distance between the lower end of the head portion 51 of the rivet 5 and the upper surface 30U of the overlapping portion 30 (the upper surface of the first member 31) based on the calculation result of the height position by the tool position detection unit 66. At this time, the gap calculation unit 67 refers to thickness information of the head portion 51 given in advance from the input unit 62.

[0047] The shape estimation unit 68 performs processing to estimate the degree of expansion (degree of deformation) of the tubular portion 52 of the rivet 5 based on temperature information of the friction stir welded portion detected by the temperature detection unit 28. The determination unit 69 compares the expanded shape of the tubular portion 52 estimated by the shape estimation unit 68 with a template stored in advance, and determines whether or not the expanded shape satisfies a required degree of expansion.

[0048] [Friction stir welding method using rivets] Next, a specific example of a method for forming a friction stir welded portion using a tool 1 for friction stir spot welding in combination with a rivet 5 in the overlapping portion 30 will be described with reference to Figs. 4 and 5. In this embodiment, an example is shown in which the tool 1 performs friction stirring of the overlapping portion 30 in a shoulder-first process. Also, an example is shown in which both the friction stir welding process and the process of pressing the rivet 5 into the friction stir portion 4 are performed by the tool 1. The process of pressing the rivet 5 may be performed by a press-fitting tool separate from the tool 1.

[0049] Fig. 4 is a cross-sectional view showing a preparation step for friction stir welding in which a rivet is also used. In the preparation step, an overlapping portion 30 is formed in which a first member 31 and a second member 32 overlap with at least a portion of the first member 31 and the second member 32 in contact with each other. Fig. 4 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 backing material 15 side (lower side). A lower surface 30B of the overlapping portion 30 is supported by the backing material 15, and a lower end surface of the tool 1 abuts against an upper surface 30U.

[0050] In the preparation step, the rivet 5 to be driven is also loaded in the tool 1 in advance. Specifically, the controller 61 (FIG. 3) operates the pin drive unit 21 to raise the pin member 11, creating a storage space for the rivet 5 in the hollow portion of the shoulder member 12. That is, the lower end 11T of the pin member 11 is relatively raised by more than the height of the rivet 5 with respect to the lower end 12T of the shoulder member 12, and a storage space is provided near the lower end opening of the shoulder member 12. Then, the rivet 5 is loaded into the storage space. Next, the tool 1 is clamped to the overlapping portion 30. At this time, the rotation axis R (FIG. 1) of the tool 1 is aligned with the point joining position W in the overlapping portion 30. In this state, the clamping member 13 presses the overlapping portion 30 against the backing material 15 with the lower end 13T accompanied by the biasing force of the spring 14. The lower end 12T of the shoulder member 12 is also in contact with the upper surface 30U.

[0051] 5(A) to 5(D) are cross-sectional views sequentially showing the implementation state of riveting-assisted friction stir welding. FIG. 5(A) shows 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. The controller 61 controls the shoulder drive unit 22 and the rotation drive unit 23 to lower the shoulder member 12 while rotating it at high speed around its axis, and starts pressing the shoulder member 12 into the overlapping portion 30. Meanwhile, the controller 61 controls the pin drive unit 21 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 spot joining position W as the center. Since the pin member 11 is moved upward to accommodate the rivet 5, the retraction operation of the pin member 11 may be omitted.

[0052] 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 pressed-in area of ​​the shoulder member 12. The material that overflows from the overlapping portion 30 due to the pressing of the shoulder member 12 is released into the hollow portion within the shoulder member 12. The frictional stirring softens the material of the pressed-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 of a laminate of prepreg thin layer sheets 33, the continuous fibers of the thin layer sheets 33 are cut and crushed in the frictional stirring portion 4. This makes it easier to drive and deform the rivet 5 in the following process.

[0053] FIG. 5(B) is a diagram showing a backfilling process of the material that overflowed from the overlapping portion 30 in the previous friction stir process. In the backfilling process, the shoulder drive unit 22 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 region that was occupied by the vicinity of the lower end portion 12T of the shoulder member 12 in the friction stir section 4. Therefore, the material that overflowed from the overlapping portion 30 is also backfilled in the press-in region. By performing the above steps, the friction stir section 4 is formed in the overlapping portion 30, which has a cylindrical side peripheral surface 41 with a depth d and a disk-shaped bottom surface 42.

[0054] FIG. 5(C) is a diagram showing the implementation status of the rivet 5 installation process. In the installation process, the rivet 5 is pressed into the friction stir part 4 from the first member 31 side. Specifically, the pin driving part 21 lowers the pin member 11 to apply a pressing force to the head part 51, and the rivet 5 is pressed into the overlapping part 30. The rivet 5 is loaded in advance into the accommodation 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. In this embodiment, the tool 1 for friction stir spot welding is used as a tool for pressing the rivet 5, so there is no need to separately prepare a press-in tool for installing the rivet 5.

[0055] 5(D) is a diagram showing a process of deforming a part of the driven rivet 5 to form an interlock portion 53. In this process, after the rivet 5 reaches the second member 32, the rivet 5 is deformed so that a part of the rivet 5 enters the base material portion around the friction stir portion 4 in the second member 32, thereby forming the interlock portion 53. In this embodiment, the cylindrical tube portion 52 is deformed into a bell shape with an expanded lower end portion 522, and the expanded lower end portion 522 is pressed into the base material portion, thereby forming the interlock portion 53.

[0056] 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 portion 30 is supported by the backing material 15 at a position directly below the bottom surface 42. For this reason, if the pin member 11 continues to press the rivet 5 further after it reaches the bottom surface 42, the cylindrical portion 52 is deformed into a bell shape, as shown in Fig. 5(D).

[0057] 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 passes over the side circumferential surface 41 and is pressed into the base material portion on the side of the friction stir portion 4. Of these, the portion pressed into the base material portion beyond the side circumferential surface 41 becomes an 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 tubular portion 52 of the rivet 5 may occur before it reaches the second member 32. For example, the deformation may be such that the expanding deformation of the tubular portion 52 gradually starts in the region of the first member 31 after it is pressed into the friction stir portion 4, and further expanding deformation occurs after it reaches the bottom surface 42.

[0058] Thereafter, the tool 1 is removed from the overlapping portion 30, and construction at one welding point is completed. The state after construction is completed is as shown in the joined body 3 in FIG. 2(C). If necessary, a process of crushing the head portion 51 of the rivet 5 is additionally performed. For example, in the crushing process, the head portion 51 is pressed so that the diameter of the head portion 51 becomes larger than the diameter of the friction stir portion 4. According to the welding method described above, the overlapping portion 30 can be joined with excellent joining strength by using the friction stir portion 4 and the rivet 5 together with the tool 1.

[0059] [Inspection flow for riveted friction stir welds] To guarantee the quality of the friction stir welded portion in which the rivet 5 is used, it is necessary to inspect whether the rivet 5 is normally driven into the friction stir portion 4. The rivet 5 in this embodiment is driven in a manner that does not penetrate the overlapping portion 30, so it is difficult to judge the quality of the rivet 5 by visual inspection or by appearance inspection using image processing. Therefore, in this embodiment, the friction stir welded portion in which the rivet is used is inspected by a method that does not rely on appearance inspection.

[0060] 6 is a diagram showing a process chart of the inspection method for a rivet-assisted friction stir weld according to this embodiment. The first inspection process is a penetration error inspection of the rivet 5 (step S1). A penetration error refers to a state in which the cylindrical portion 52 of the rivet 5 driven into the friction stir weld 4 penetrates the overlapping portion 30. The occurrence of penetration means that the expected expansion deformation of the cylindrical portion 52 does not occur, and as a result, the interlock portion 53 is not formed. In this case, the rivet 5 does not exert an engaging effect on the overlapping portion 30.

[0061] Since the overlapping portion 30 is supported by the backing material 15, if a penetration error occurs, the lower end portion 522 (part of the fastener) of the tubular portion 52 will abut against the backing material 15. In this embodiment, this abutment is inspected based on the state of electrical current between the pin member 11 that presses the rivet 5 and the backing material 15 (FIG. 7), or based on fluctuations in the motor current of the electric motor that is the driving source of the pin driving portion 21 or the rotation driving portion 23 (FIG. 8). If the abutment of the rivet 5 against the backing material 15 is detected as a result of these inspections (NO in step S2), the joint is determined to be defective (step S8). On the other hand, if the rivet 5 is not abutting against the backing material 15 (YES in step S2), the inspection in step S3 is subsequently performed.

[0062] In step S3, a floating inspection of the head portion 51 of the rivet 5 is performed. The floating of the head portion 51 refers to a state in which the lower end portion 522 of the head portion 51 does not abut against the upper surface 30U of the overlapping portion 30 (the upper surface of the friction stir portion 4) and a gap is generated between them. If the head portion 51 floats, it means that the cylindrical portion 52 is not pressed into the friction stir portion 4 to the predetermined press-in depth d. In this case, it is expected that the rivet 5 will not fully exert its locking effect due to insufficient press-in.

[0063] The head portion 51 is pressed by the lower end portion 11T of the pin member 11. Therefore, if the thickness of the head portion 51 is known, the distance between the lower end portion 522 of the head portion 51 and the upper surface 30U can be obtained by calculating the difference between the lowered position of the lower end portion 11T and the position of the upper surface 30U of the overlapping portion 30. The position of the upper surface 30U can be obtained from the height position of the lower end portion 12T of the shoulder member 12 that is in contact with the upper surface 30U. In this embodiment, the height positions of the lower ends 11T and 12T are calculated based on the output value of the encoder 24 attached to the electric motor that is the driving source of the pin driving portion 21 and the shoulder driving portion 22 (FIG. 9). If there is a gap corresponding to the floating of the head portion 51 (NO in step S4), the joint is determined to be defective (step S8). On the other hand, if there is no gap (YES in step S4), the inspection in step S5 is subsequently performed.

[0064] In step S5, an inspection is performed on the degree of expansion of the tubular portion 52 of the rivet 5. The degree of expansion of the tubular portion 52 is an index showing the degree to which the diameter of the lower end portion 522 has increased compared to the original diameter due to the deformation of the cylindrical tubular portion 52 into a bell shape. Even if the rivet 5 does not penetrate the overlapping portion 30 and no floating is detected in the head portion 51, it is assumed that the tubular portion 52 has not been expanded and deformed as expected. If the tubular portion 52 is not expanded enough or has a distorted expanded shape, it is assumed that the interlock portion 53 that exerts a sufficient locking effect will not be formed.

[0065] In general, the first member 31 and the second member 32 forming the overlapping portion 30 and the rivet 5 are often made of different materials. In the above example, the former is a fiber-reinforced thermoplastic resin, and the latter is a titanium alloy, and the two have different thermal conductivities. Therefore, if the temperature of the friction stir welded portion where the rivet 5 is driven is measured, it is possible to estimate the expansion shape of the tubular portion 52 based on the temperature difference between the rivet 5 and its surroundings. In this embodiment, the temperature measurement is performed using a thermograph 281 (FIG. 11) and a thermocouple 282 embedded in the backing material 15 (FIG. 12) as examples. If the expansion degree of the tubular portion 52 is abnormal (NO in step S6), the joint is determined to be defective (step S8). On the other hand, if the expansion degree of the tubular portion 52 is normal (YES in step S6), the joint is determined to be acceptable (step S7).

[0066] [Details of each inspection] Hereinafter, specific examples of the penetration error inspection in step S1, the floating inspection of head portion 51 in step S3, and the expansion degree inspection of tubular portion 52 in step S5 will be described in detail with reference to FIGS.

[0067] <Through-through error inspection> FIG. 7 is a schematic diagram showing an example of an inspection process for a penetration error of a rivet 5. FIG. 7 shows a state (penetration error) in which the rivet 5 does not expand and deform, penetrates the overlapping portion 30, and the lower end portion 522 abuts against the backing material 15. In this inspection example, whether or not the lower end portion 522 abuts against the backing material 15, that is, whether or not a penetration error has occurred, is detected based on whether or not a conductive path is formed between the pin member 11 and the backing material 15. Therefore, in this inspection example, it is assumed that conductive materials are used as the pin member 11, the rivet 5, and the backing material 15, and non-conductive materials are used as the first member 31 and the second member 32 forming the overlapping portion 30.

[0068] The pin member 11 is electrically connected to the pin current-carrying portion 25, and a DC voltage can be applied from a DC power source provided in the pin current-carrying portion 25. Meanwhile, an ammeter 26 is incorporated in the ground path of the backing material 15. The current value measured by the ammeter 26 is transmitted to a contact current detection unit 64 of the inspection unit 63 (FIG. 3).

[0069] 7, when a penetration error occurs in the rivet 5, the top surface 51H of the rivet 5 abuts against the lower end 11T of the pin member 11, and the lower end 522 abuts against the backing material 15. As a result, the pin member 11 and the backing material 15 are electrically short-circuited by the rivet 5. In this state, if a DC voltage is applied to the pin member 11, a current flows in the ground path of the backing material 15 at the same time as the occurrence of a penetration error. Therefore, when the rivet 5 is driven with the pin member 11 to which a DC voltage is applied, the ammeter 26 will detect a large current if a penetration error occurs.

[0070] When the current value measured by the ammeter 26 exceeds a predetermined threshold, the contact current detection unit 64 determines that the lower end 522 of the rivet 5 has contacted the backing material 15. In other words, it determines that a penetration error has occurred. When a penetration error has not occurred, the current value measured by the ammeter 26 is equal to zero. Therefore, the predetermined threshold may be a value that allows the ON / OFF state of the current to be distinguished. According to this inspection example, a penetration error can be easily detected electrically by installing a simple electrical device.

[0071] Fig. 8 is a schematic diagram showing another example of the inspection process for a penetration error of the rivet 5. Fig. 8 also shows a state in which a penetration error of the rivet 5 has occurred. In this inspection example, it is detected whether or not the lower end 522 of the rivet 5 has come into contact with the backing material 15 based on the motor current of the electric motor that is the drive source of the pin drive unit 21 or the rotation drive unit 23. The motor current is monitored by a motor current detection unit 65.

[0072] The rivet 5 is driven into the friction stir section 4 by the downward movement of the pin member 11. A motor current corresponding to the downward load of the pin member 11 flows through the electric motor of the pin drive section 21. When a penetration error occurs and the lower end 522 abuts against the backing material 15, the downward load increases rapidly. As a result, the motor current also increases rapidly. A motor current threshold value that serves as a criterion for determining a penetration error is given to the motor current detection section 65 in advance. When the motor current detection section 65 detects a motor current that exceeds the threshold value, it determines that the lower end 522 of the rivet 5 has abutted against the backing material 15.

[0073] The rivet 5 may be driven while being rotated around its axis. In this case, engaging portions for engaging the pin member 11 with the rivet 5 are provided on the lower end portion 11T and the top surface 51H, respectively. When the rivet 5 is pressed into place, the rotation drive unit 23 rotates the pin member 11. At this time, a motor current corresponding to the rotation load of the pin member 11 flows through the electric motor of the rotation drive unit 23.

[0074] When such a rivet 5 is rotary driven, if a penetration error occurs, the rotating lower end 522 will hit the backing material 15. This hit causes a sudden increase in the rotational friction resistance of the lower end 522, and the motor current also increases suddenly. The motor current detection unit 65 determines that the lower end 522 of the rivet 5 has hit the backing material 15 when the motor current of the rotation drive unit 23 exceeds the threshold value.

[0075] The motor current of the pin drive unit 21 or the rotation drive unit 23 is often monitored during friction stir spot welding for the purpose of controlling the press-in amount of the tool 1 into the overlapping portion 30, etc. In other words, the friction stir spot welding apparatus M often inherently has a functional unit equivalent to the motor current detection unit 65. According to the inspection example of Fig. 8, a penetration error can be detected by utilizing the functional unit required for the original control of the friction stir spot welding apparatus M.

[0076] <Inspection of head floating> FIG. 9 is a schematic diagram showing an example of a floating inspection process for the head portion 51 of the rivet 5. FIG. 9 shows an example in which the press-fit of the tubular portion 52 of the rivet 5 is insufficient, and the lower end surface 51B of the head portion 51 floats up from the upper surface 30U of the overlapping portion 30. In contrast, FIG. 10(A) shows a normal overlapping portion 30 in which the head portion 51 does not float. The lower end surface 51B is in contact with the upper surface 30U, and the entire length of the tubular portion 52 is pressed into the friction stir portion 4. On the other hand, FIG. 10(B) shows a state in which the tool 1 has been removed from the overlapping portion 30 in FIG. 9 in which a floating defect has occurred. A gap h2 is generated between the lower end surface 51B and the upper surface 30U.

[0077] In this inspection example, floating of the head portion 51 is detected by performing a process to obtain the distance h2 between the lower end surface 51B and the upper surface 30U. Specifically, the distance h2 is calculated from the lowered position of the pin member 11, which is a press-fitting tool that presses the rivet 5, and the thickness h1 of the head portion 51. As described above, the output value of the encoder 24 is used in the calculation.

[0078] A first encoder 241 is attached to the electric motor of the pin driving unit 21. A second encoder 242 is attached to the electric motor of the shoulder driving unit 22. The output values ​​of the first and second encoders 241 and 242 are transmitted to the tool position detection unit 66. In the state shown in FIG. 9, the lower end 11T of the pin member 11 abuts against the top surface 51H of the head unit 51. Therefore, the output value of the first encoder 241 is information corresponding to the lowered position of the lower end 11T, that is, the height position of the top surface 51H. In addition, the lower end 12T of the shoulder member 12 is in contact with the upper surface 30U of the overlapping portion 30. Therefore, the output value of the second encoder 242 is information corresponding to the height position of the upper surface 30U. The tool position detection unit 66 identifies the height positions of the lower end 11T and the upper surface 30U based on these pieces of information, and transmits the position data to the gap calculation unit 67.

[0079] The gap calculation unit 67 is provided with data on the thickness h1 of the head portion 51, which is thickness information of the head portion 51. The gap calculation unit 67 calculates the interval h2, which is the distance between the lower end surface 51B of the head portion 51 and the upper surface 30U, from the height positions of the lower end portion 11T and the upper surface 30U and the head portion thickness h1. The gap calculation unit 67 determines whether or not a floating defect of the head portion 51 has occurred based on the calculated interval h2. When it is planned that the entire length of the cylindrical portion 52 is pressed into the friction stirring portion 4, the allowable value of the interval h2 is zero or close to zero. When it is not planned to press-fit the entire length of the cylindrical portion 52 and a certain degree of floating of the head portion 51 is allowed, the allowable value of the interval h2 is set accordingly.

[0080] The height position of the upper surface 30U may be obtained from the output value of the stroke sensor 27. During joining, the clamp member 13 clamps the overlapping portion 30. Therefore, the lower end portion 13T of the clamp member 13 is securely in contact with the upper surface 30U. Meanwhile, the stroke sensor 27 detects the relative position between the shoulder member 12 and the clamp member 13. Therefore, when the origin alignment between the pin member 11 and the shoulder member 12 is performed, the height difference between the upper surface 30U and the lower end portion 11T can be obtained from the output value of the first encoder 241 and the output value of the stroke sensor 27.

[0081] Note that a rivet 5 may be used in which the head portion 51 has a smaller diameter than the cylindrical portion 52. In this case, the distance h2 is the distance between the boundary line (the lower end of the head portion) between the head portion 51 and the cylindrical portion 52, and the upper surface 30U. Furthermore, when a press-fitting tool separate from the tool 1 (pin member 11) is used to press in the rivet 5, the height position of the top surface 51H of the head portion 51 can be known based on the lowered position of the press-fitting tool.

[0082] In this inspection example, the output values ​​of the first and second encoders 241, 242 are used. Generally, the electric motors of the pin drive unit 21 and the shoulder drive unit 22 are equipped with encoders as standard for the purpose of controlling the position of the pin member 11, etc. Therefore, according to this inspection example, it is possible to inspect the floating of the head unit 51 without adding a new measuring device.

[0083] <Inspection of the degree of expansion of the cylinder part> In this embodiment, a shape estimation means is provided that estimates the degree of expansion of the tubular portion 52 by measuring the temperature of the friction stir welded portion where the rivet 5 is driven, and the pass / fail judgment of the degree of expansion is performed. In other words, it is judged whether the tubular portion 52 is expanded so that the interlock portion 53 (part of the tubular portion) enters the second member 32 around the friction stir welded portion 4.

[0084] Fig. 11 is a schematic diagram showing an example of an inspection process for the degree of expansion of the tubular portion 52 of the rivet 5. Fig. 11 shows an example in which a thermograph 281, the above-mentioned shape estimation unit 68, and the determination unit 69 are used as the shape estimation means. The thermograph 281 is a non-contact temperature measuring instrument capable of detecting the heat distribution of an object by sensing infrared rays emitted from the object. Fig. 11 shows an example in which the thermograph 281 is placed below the overlapping portion 30 where the rivet 5 is driven. In this example, the two-dimensional temperature distribution on the underside of the overlapping portion 30 is measured by the thermograph 281.

[0085] The thermograph 281 can be mounted on the C-frame 16 in parallel with the backing material 15. In this case, after the clamping of the overlapping portion 30 by the clamping member 13 is released, the robot arm is moved, for example, to make the thermograph 281 face the driving position of the rivet 5. Of course, the thermograph 281 may be held by a separate holding member. Also, if the backing material 15 is made of an infrared-transparent material, the thermograph 281 may be disposed below the backing material 15. Furthermore, if temperature measurement is performed in a separate process after joining, the thermograph 281 may be disposed either above or below the overlapping portion 30.

[0086] The rivet 5 heats up when it is pressed into the overlapping portion 30. Specifically, the causes of the high temperature are heat transfer from the friction stir portion 4 that is heated by friction stirring, friction heat caused by contact with the pin member 11 rotating at high speed, and friction heat caused by the press-in itself. In the case of heat transfer from the friction stir portion 4, the thermal conductivity of the rivet 5 is different from that of the second member 32, so a clear temperature difference occurs between the area where the rivet 5 (cylindrical portion 52) is present and the other areas. In the case of friction heat, the rivet 5 itself generates heat, so a temperature difference also occurs with the second member 32. Therefore, if the temperature is measured by the thermograph 281 at the stage when the friction stir welded portion is formed or immediately after the formation, and the rivet 5 is retaining a higher temperature than the second member 32, the temperature distribution based on the temperature difference can be clearly detected.

[0087] The upper graph in Fig. 11 is a graph in which the temperature gradient TP is displayed to match the temperature distribution detected by the thermograph 281 to the cross-sectional shape of the overlapping portion 30 shown in the figure. The temperature gradient TP has a curve that rises sharply at positions L1 and L2. Here, an example is shown in which positions L1 and L2 correspond to the most open portion of the cylindrical portion 52, i.e., the interlock portion 53. In the temperature distribution from the underside of the overlapping portion 30, the interlock portion 53 appears as a thermal boundary between the rivet 5 and the second member 32.

[0088] When the cylindrical portion 52 is expanded normally, the interlock portion 53 extends radially outward beyond the side circumferential surface 41 of the friction stirring portion 4. Therefore, positions L1 and L2 of the temperature gradient TP appear radially outward beyond the planned outer edge (side circumferential surface 41) of the friction stirring portion 4. On the other hand, when the cylindrical portion 52 is not expanding properly, positions L1 and L2 appear at approximately the same position as the side circumferential surface 41 or radially inward beyond the side circumferential surface 41.

[0089] 11 assumes a case where positions L1 and L2 correspond to interlock portion 53. In reality, positions L1 and L2 may deviate from the position of interlock portion 53 depending on the thermal conductivity of the materials constituting second member 32 and rivet 5, the thickness of second member 32, the degree of press-fit of rivet 5, and the like. In this case, positions L1 and L2 can be associated with interlock portion 53 by determining the amount of deviation in advance through an experiment or the like and setting a correction value.

[0090] The shape estimation unit 68 estimates the expanded shape of the tubular portion 52 based on the temperature distribution of the overlapping portion 30 after the rivet 5 is pressed in, as measured by the thermograph 281. For example, the shape estimation unit 68 identifies the above-mentioned positions L1 and L2 by detecting a point at which the rate of change of the temperature gradient TP exceeds a predetermined threshold value. As described above, the determination unit 69 compares the expanded shape estimated by the shape estimation unit 68 with a reference template or the like to determine whether the degree of expansion of the tubular portion 52 is normal or not. According to this inspection example, the difference in thermal conductivity between the rivet 5 and the second member 32 is utilized to non-destructively inspect the degree of expansion of the tubular portion 52.

[0091] In the above example, a thermograph 281, which is a non-contact type temperature measuring device, is used. Next, an example using a contact type temperature measuring device is shown. FIG. 12 is a schematic diagram showing another example of the inspection process for the degree of expansion of the cylindrical portion 52. A thermocouple 282 is incorporated in the backing material 15 as a contact type temperature measuring device. The backing material 15 is abutted against the bottom surface of the overlapping portion 30 during joining. That is, the heat of the overlapping portion 30 is directly transferred to the backing material 15. Therefore, by embedding the thermocouple 282 in the backing material 15, the temperature state of the bottom surface of the overlapping portion 30 can be detected.

[0092] The temperature-sensing portion of the thermocouple 282 is disposed near the surface of the backing material 15 at a position that faces up and down with respect to the assumed position of the interlock portion 53 when the cylindrical portion 52 is normally expanded. When the cylindrical portion 52 is normally expanded, the thermocouple 282 detects a high temperature. This is because the thermocouple 282 faces the interlock portion 53 directly and detects the heat emitted from the interlock portion 53. On the other hand, when the cylindrical portion 52 is not properly expanded, the thermocouple 282 detects a relatively low temperature. This is because the thermocouple 282 does not face the interlock portion 53 directly and detects the temperature of the second member 32. In this way, it is possible to know whether the interlock portion 53 is present at a predetermined position in the overlapping portion 30 based on the temperature detected by the thermocouple 282.

[0093] A large number of thermocouples 282 may be incorporated in the backing material 15 to detect the temperature distribution on the underside of the overlapping portion 30. In this case, it is desirable to arrange a large number of thermocouples 282 on the backing material 15 so as to draw a concentric circular pattern. Also, the thermocouple 282 may be incorporated in a temperature measuring member separate from the backing material 15, and brought into contact with the underside of the overlapping portion 30 immediately after the formation of the friction stir welded portion. Furthermore, a contact type temperature measuring element other than the thermocouple 282 may be used.

[0094] During or immediately after the formation of the friction stir weld, the inspection example of Fig. 11 or 12 can be carried out based on the temperature difference between the rivet 5 and the second member 32. However, once the rivet 5 has returned to normal temperature over time since the formation of the weld, the above-mentioned inspection example cannot be applied. For example, if the process of forming the friction stir weld and the inspection process are carried out in separate processes with a time interval between them, the temperature difference disappears and no temperature distribution appears in the overlapping portion 30. In such a case, heat is applied to the rivet 5 from the outside before the inspection.

[0095] FIG. 13 is a cross-sectional view showing the external heating of the rivet 5. FIG. 13 shows a state in which heat H is applied from a heating source 283 to the head 51 of the rivet 5. As the heating source 283, for example, a contact type heating source using a heating rod or a non-contact type heating source emitting hot air can be used. In addition, the head 51 may be held by a pair of electrodes to heat the rivet itself by resistance heating, or an IH heating source may be used when the rivet 5 is a magnetic material. Furthermore, heat H may be applied indirectly to the rivet 5 from the underside of the overlapping portion 30 via the second member 32. By applying heat H to the rivet 5 from the heating source 283 and then measuring the temperature with the thermograph 281 or the thermocouple 282, the temperature distribution of the underside of the overlapping portion 30 described above can be reliably detected.

[0096] [Variations] 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.

[0097] (1) In the above embodiment, an example is shown in which three types of inspections are performed: a penetration error inspection of the rivet 5 (step S1 in FIG. 6), a floating inspection of the head portion 51 (step S3), and an expansion degree inspection of the tubular portion 52 (step S5). Alternatively, one or both of the floating inspection and the expansion degree inspection may be omitted. Furthermore, the order in which the three types of inspections are performed is arbitrary, and the floating inspection or the expansion degree inspection may be performed first.

[0098] (2) In the above embodiment, an example was shown in which a penetration error inspection of the rivet 5 was performed by detecting electrical current flow between the pin member 11 and the backing material 15 (FIG. 7) or by detecting a motor current (FIG. 8). The penetration error can also be detected by a sound wave sensor that detects the impact sound when the lower end 522 of the rivet 5 impacts the backing material 15, or a vibration sensor or load cell that detects vibration or pressure fluctuation of the backing material 15 at the time of impact.

[0099] (3) In the above embodiment, an example (FIG. 9) has been shown in which the floating of the head portion 51 is detected based on the encoder value of the electric motor that is the driving source of the pin driving portion 21 and the shoulder driving portion 22. Alternatively, the floating of the head portion 51 may be detected by image processing. For example, after the rivet 5 is driven into the overlapping portion 30, an oblique image of the head portion 51 is captured by a camera arranged on the upper surface 30U side. Since a difference in image density occurs between the top surface 51H and the side peripheral surface of the head portion 51, the two can be distinguished from each other. If the head portion 51 is floating, the area of ​​the side peripheral surface increases in the captured oblique image. Therefore, the floating of the head portion 51 can be detected by calculating the area ratio between the top surface 51H and the side peripheral surface on the image.

[0100] (4) In the above embodiment, an example has been shown in which the double-action friction stir spot welding tool 1 is used as the tool for forming the friction stir portion 4. Instead of this, a friction stir line welding tool, a single-action friction stir spot welding tool, or other friction stir welding tools may be used as the tool. Furthermore, when using the double-action friction stir spot welding tool 1, friction stirring may be performed by the pin-first process.

[0101] As described above, the method for inspecting a friction stir weld according to the present invention includes a step of detecting whether the lower end 522 of the rivet 5 has come into contact with the backing material 15. Therefore, it is possible to detect whether the rivet 5 has penetrated the friction stir portion 4 and the second member 32 and come into contact with the backing material 15. In other words, it is possible to detect defective construction in which the rivet 5 has penetrated the friction stir portion 4 without undergoing the expected deformation, that is, deformation that would form the interlock portion 53 with the second member 32 around the friction stir portion 4. Therefore, it is possible to accurately inspect a friction stir weld in which the rivet 5 is driven in a manner that does not penetrate the overlap portion 30.

[0102] [Inventions included in the above embodiments] The above-described embodiment further includes the following inventions.

[0103] In one embodiment, a method for inspecting a friction stir welded portion includes the steps of: forming a friction stir portion by pressing a friction stir tool into an overlapping portion including a first member and a second member disposed below the first member while supporting the second member with a backing material from the first member side; and, in the friction stir welded portion formed by pressing a fastener into the friction stir portion from the first member side, A method for inspecting a friction stir welded portion, in which a fastener is used that includes a head portion and a cylindrical portion connected to the head portion, and a predetermined length of the cylindrical portion is press-fitted into the overlapping portion, The distance between the bottom end of the head portion and the top surface of the first member is determined.

[0104] A joining device according to one embodiment is a joining device that joins an overlapping portion including a first member and a second member disposed below the first member, a friction stir tool that is press-fitted into the overlapping portion from the first member side to form a friction stir portion in the overlapping portion; a press-in tool that includes a head portion and a cylindrical portion connected to the head portion, and presses a fastener in which a predetermined length of the cylindrical portion is pressed into the overlapping portion from the first member side into the friction stir portion; A backing material that supports the overlapping portion from the second member side; and a measuring means for determining the distance between the lower end of the head portion and the upper surface of the first member.

[0105] According to the above-mentioned inspection method or joining device, it is possible to inspect whether the distance between the lower end of the head part of the fastener and the upper surface of the first member is appropriate based on the measurement result of the measuring means. In other words, by measuring the distance, it is possible to inspect whether the tubular part of the fastener is pressed into the friction stir joint by a specified press-in depth. For example, if the press-in depth is insufficient due to buckling of the tubular part, a distance of a predetermined specified value or more will be opened between the lower end of the head part and the upper surface of the first member. More specifically, if the lower end of the head part and the upper surface of the first member are expected to be in close contact when the fastener is pressed in normally, a gap will be detected between them when insufficient press-in occurs. Therefore, it is possible to accurately inspect the friction stir joint where the fastener is cast in a manner that does not penetrate the overlapping part.

[0106] In another embodiment, a method for inspecting a friction stir welded portion includes the steps of: forming a friction stir portion by pressing a friction stir tool into an overlapping portion including a first member and a second member disposed below the first member, while supporting the second member with a backing material, from the first member side; and pressing a fastener into the friction stir portion from the first member side. In the friction stir welded portion thus formed, A method for inspecting a friction stir welded portion using a fastener including a cylindrical portion that deforms so that at least a part of the cylindrical portion enters the second member around the friction stir weld, The degree of deformation of the cylindrical portion is detected by measuring the temperature of the friction stir welded portion.

[0107] A joining device according to one embodiment is a joining device that joins an overlapping portion including a first member and a second member disposed below the first member, a friction stir tool that is press-fitted into the overlapping portion from the first member side to form a friction stir portion in the overlapping portion; a press-in tool for press-in a fastener including a cylindrical portion that deforms so that at least a part of the fastener enters the second member around the friction stir portion from the first member side to the friction stir portion; A backing material that supports the overlapping portion from the second member side; and a shape estimation means for estimating the degree of deformation of the cylindrical portion by measuring the temperature of the friction stir welded portion.

[0108] According to the above inspection method or welding device, the shape of the inside of the overlapping part of the fastener (tubular part) can be estimated based on the temperature difference between the first and second members and the fastener by measuring the temperature of the friction stir welded part. Then, based on the estimated degree of deformation of the tubular part, it is possible to inspect whether the deformation state of the tubular part is appropriate. In other words, it is possible to inspect whether the tubular part is normally deformed and whether a part of the tubular part is inserted into the second member around the friction stir part. If the deformation of the tubular part is insufficient, the part of the tubular part cannot be inserted into the second member existing around the friction stir part, and a sufficient interlock effect cannot be achieved. Therefore, it is possible to accurately inspect the friction stir welded part in which the fastener is cast in a manner that does not penetrate the overlapping part. [Explanation of symbols]

[0109] 1 Tools 11 Pin material (press-in tool) 12 Shoulder member 15 Backing material 21 Pin drive unit (electric motor) 22 Shoulder drive unit (electric motor) 23 Rotation drive unit (electric motor) 24 Encoder (Measuring means) 25 pin current carrying part (detection means) 26 Ammeter (detection means) 27 Stroke sensor (measurement means) 28 Temperature detection unit (shape estimation means) 281 Thermography 282 Thermocouple (thermocouple built into backing material) 283 Heating source 3 Joined body (friction stir welded part) 30 Overlap 30U Top surface (top surface of first component) 31 First member 32 Second member 4 Friction stirring section 5 Rivet (fastener) 51 Head 52 Shaft 522 Lower end (lower end) 53 Interlocking part (part of fastening body) 61 Controller (control unit) 63 Inspection Department 64 Contact current detection unit (detection means) 65 Motor current detection unit (detection means) 66 Tool position detection unit (measurement means) 67 Gap calculation unit (measurement means) 68 Shape estimation unit (shape estimation means) 69 Judgment unit (shape estimation means) M Friction stir spot welding equipment

Claims

1. A method for inspecting a friction stir weld formed by pressing a friction stir tool into an overlapping portion including a first member and a second member disposed below the first member while the second member is supported by a backing material, from the first member side to form a friction stir portion, and pressing a fastener into the friction stir portion from the first member side, comprising: Detecting whether or not a part of the fastening body abuts against the backing material. A method for inspecting friction stir welds.

2. The method for inspecting a friction stir welded portion according to claim 1, a conductive material is used as the friction stir tool, the fastener, and the backing material, and a non-conductive material is used as the first member and the second member; A method for inspecting a friction stir weld, comprising determining that a portion of the fastener has come into contact with the backing material when a current flowing between the friction stir tool and the backing material exceeds a predetermined threshold value.

3. The method for inspecting a friction stir welded portion according to claim 1, An electric motor is used as a driving source for the friction stir tool, A method for inspecting a friction stir weld, comprising determining that a portion of the fastener has come into contact with the backing material when a motor current driving the electric motor exceeds a predetermined threshold value.

4. The method for inspecting a friction stir welded portion according to claim 1, The fastener includes a head portion and a cylindrical portion connected to the head portion, and a predetermined length of the cylindrical portion is press-fitted into the overlapping portion, A method for inspecting a friction stir welded portion, the method comprising determining a distance between a lower end of the head portion and an upper surface of the first member.

5. The method for inspecting a friction stir welded portion according to claim 4, The fastening body is pressed into the overlapping portion by lowering a press-in tool to push the fastening body into the overlapping portion; A method for inspecting a friction stir welded portion, comprising determining a distance between a lower end of the head portion and an upper surface of the first member from a lowered position of the press-in tool and a thickness of the head portion.

6. The method for inspecting a friction stir welded portion according to claim 5, The friction stir tool is used as the press-in tool, A method for inspecting a friction stir welded portion, comprising calculating a lowering position of the friction stir tool based on an output value of an encoder attached to an electric motor that drives the friction stir tool.

7. The method for inspecting a friction stir welded portion according to claim 1, the fastening body includes a cylindrical portion that deforms so that at least a portion of the cylindrical portion enters the second member around the friction stir portion, A method for inspecting a friction stir welded portion, comprising: detecting a degree of deformation of the cylindrical portion by measuring a temperature of the friction stir welded portion.

8. The method for inspecting a friction stir welded portion according to claim 7, A method for inspecting a friction stir welded portion, comprising measuring a temperature distribution in the friction stir welded portion after the fastener is pressed in, and detecting a degree of deformation of the cylindrical portion by estimating a deformed shape of the cylindrical portion based on the temperature distribution.

9. The method for inspecting a friction stir welded portion according to claim 7, A method for inspecting a friction stir welded portion, comprising: measuring the temperature of the friction stir welded portion with a thermometer incorporated in the backing material.

10. The method for inspecting a friction stir welded portion according to any one of claims 7 to 9, A method for inspecting a friction stir welded portion, comprising applying heat to the fastener after formation of the friction stir welded portion, and measuring a temperature of the friction stir welded portion.

11. The method for inspecting a friction stir welded portion according to any one of claims 7 to 9, A method for inspecting a friction stir welded portion, comprising measuring the temperature of the friction stir welded portion during or immediately after the formation of the friction stir welded portion, at a stage where the fastener maintains a higher temperature than the second member.

12. A joining device that joins an overlapping portion including a first member and a second member disposed below the first member, a friction stir tool that is press-fitted into the overlapping portion from the first member to form a friction stir portion in the overlapping portion; a press-in tool for press-injecting a fastener into the friction stir section from the first member side; A backing material that supports the overlapping portion from the second member side; A detection means for detecting whether or not a part of the fastener is in contact with the backing material; A joining device comprising:

13. The joining device according to claim 12, As a tool serving as both the friction stir tool and the press-in tool, A cylindrical pin member that rotates about an axis and is movable back and forth in the axial direction; A double-action friction stir spot welding tool including a cylindrical shoulder member that is positioned so as to cover an 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; a control unit of the tool, The control unit is When forming the friction stir portion, the pin member or the shoulder member is pressed into the overlapping portion to perform a friction stir operation; When the fastener is pressed in, the pin member or the shoulder member is lowered so as to press the fastener into the overlapping portion.

14. The joining device according to claim 12 or 13, The fastener includes a head portion and a cylindrical portion connected to the head portion, and a predetermined length of the cylindrical portion is press-fitted into the overlapping portion. The joining apparatus further comprises a measuring means for determining a distance between a lower end of the head portion and an upper surface of the first member.

15. The joining device according to claim 12 or 13, the fastening body includes a cylindrical portion that deforms so that a portion of the cylindrical portion enters the second member around the friction stir portion, The joining apparatus further comprises a shape estimation means for estimating a degree of deformation of the cylindrical portion by measuring a temperature of the friction stir portion.

Images