Friction crimping tool and friction crimping method using the same

Abstract

To provide a friction crimping tool that can obtain sufficient joint strength more stably. [Solution] A friction crimping joining tool comprising a rotary tool 1 and a receiving member 2 positioned opposite the rotary tool, wherein the rotary tool 1 has a shoulder portion 11 that constitutes its base end and a probe portion 12 provided on the tip surface of the shoulder portion and having a tapered shape that becomes smaller in diameter towards the tip, the probe portion 12 having a curved shape on its side surface in cross-sectional view, and the receiving member 2 has a recess 20 having a bottom with a diameter larger than the tip diameter of the probe portion 12 of the rotary tool 1, for a friction crimping joining tool.

Description

Technical Field

[0001] The present invention relates to a tool for friction caulking joining and a friction caulking joining method using the same.

Background Art

[0002] When joining thick plates using conventional friction stir spot welding, in order to form a stirring region with sufficient plastic flow at the interface which is the joining part, not only a small-diameter probe but also the frictional heat generation and plastic flow due to the turning force of a large-diameter shoulder need to be efficiently transmitted to the interface.

[0003] However, in the case of thick plates, since the distance from the surface of the joined member to the interface is large, if the pressing of the shoulder is insufficient, sufficient heat generation and plastic flow cannot be transmitted to the interface, and a sufficient stirring region necessary for ensuring the joining strength cannot be obtained. Therefore, as shown in FIGS. 25(A) to (C), when joining thick plates (550 and 560) between a rotary tool 510 having a cylindrical probe portion P1 and a planar receiving member 520, it is necessary to increase the pressing force and the joining time to bring the pressing of the shoulder close to the vicinity of the interface. However, if this is done, the thickness of the joined member which becomes the upper plate 550 will naturally decrease, and the base material strength will decrease, and even if a sufficient stirring region is obtained, the joint strength will decrease (phenomenon K2 in FIG. 25(C)). FIGS. 25(A) to (C) are cross-sectional views of a joining apparatus showing the state during joining for explaining the mechanism by which sufficient joining strength cannot be obtained in an example of the prior art, and are schematic cross-sectional views sequentially showing the temporal change of the cross-section of the joined part in the joining method using the joining apparatus.

[0004] Therefore, it has been difficult to apply friction stir spot welding in the joining of thick plates.

[0005] Furthermore, in conventional friction stir point welding, as shown in Figures 26(A) to (C), when a first member 552 and a second member 562 are joined between a rotary tool 512 having a cylindrical probe portion P3 and a planar receiving member 522, with a gap between them, the following phenomena occur, and sufficient joint strength may not be obtained. Figures 26(A) to (C) are cross-sectional views of a welding device showing the state during welding to explain the mechanism by which sufficient joint strength cannot be obtained in another example of the prior art, and are schematic cross-sectional views sequentially showing the change over time of the joint cross section in a welding method using the said welding device.

[0006] In the initial stages of joining, the gap is compressed by the action of applied pressure, and joining is performed while maintaining contact between the interfaces (Figure 26(A)). As joining progresses, the deformation resistance of the first member decreases due to frictional heat generation, and the deformation is not sufficiently transmitted to the first member surrounding the elastically deformed joint. A force begins to act on the joint that tries to return it to its original state, releasing the elastic deformation (Figure 26(B)). If joining continues further in this state, the first member surrounding the joint becomes completely softened, and the first member rapidly returns to its original position along the side of the shoulder, sometimes resulting in insufficient joint strength (Figure 26(C)). Moreover, as the amount of sinking of the shoulder increases, the reduction in the thickness of the first member increases, and due to the decrease in the strength of the first member resulting from this reduction in thickness, sufficient joint strength cannot be obtained.

[0007] Furthermore, in recent years, various studies have been conducted on friction stir point welding for joining dissimilar metals, but many challenges remain due to differences in melting points, making it difficult to obtain stable joining quality at low cost.

[0008] For example, one challenge in joining dissimilar materials like steel and aluminum alloy is that the rotary tools used to generate frictional heat for plastic flow in the steel require high-temperature wear resistance. However, currently, no rotary tools exist that can withstand actual production use, necessitating frequent replacement of expensive tools. This increases the cost burden, hindering the widespread adoption of this technology.

[0009] Due to the above issues, when attempting to perform joining without the rotary tool contacting the steel material, the oxide film on the surface of the joined members became a problem, making it difficult to form a homogeneous solid-phase bonding layer at the interface.

[0010] Therefore, there is a need for joining technology that can provide stable, homogeneous, and sufficient joint strength not only when joining low-melting-point materials such as aluminum alloys, but also when joining dissimilar materials such as low-melting-point and high-melting-point materials. In particular, when joining low-melting-point materials, there is a need for joining technology that can provide stable, homogeneous, and sufficient joint strength not only when joining thin plates, but also when joining thick plates.

[0011] As such joining technologies, for example, the technologies described in Patent Documents 1 to 3 have been proposed. [Prior art documents] [Patent Documents]

[0012] [Patent Document 1] Patent No. 3864888 [Patent Document 2] Patent No. 4134837 [Patent Document 3] Patent No. 5854451 [Overview of the project] [Problems that the invention aims to solve]

[0013] The joining method described in Patent Document 1 is a technology previously proposed by the present inventors, but research has been conducted using punch and die-shaped tools used in mechanical clinching, as shown in Figures 27(A) to (D), with the aim of further amplifying the crimping effect. Specifically, as shown in Figures 27(A) to (D), research has been conducted on joining the first member 551 and the second member 561 between a rotary tool 511 having a cylindrical probe portion P2 and a receiving member 521 having a recess 5210. In crimping, in order to obtain stable crimping joint strength, it is important that the crimped shape is formed without the upper plate breaking, but this technology had the following problem: The joining conditions for softening the material and reducing deformation resistance (reducing the driving load required for crimping) are strong (high pressure and rotation speed), so the plastic flow within the material is strong, and instead of deforming the softened material, it breaks. As a result, the interface portion of the base material was only joined in a ring shape (phenomenon K4 in Figure 27(D)), resulting in the problem of insufficient joint strength. Furthermore, while a crimped section could be obtained by lowering the joining conditions and extending the processing time to allow the crimping of the materials to proceed slowly, this did not satisfy the production capacity that could be used in actual production sites. Figures 27(A) to (D) are cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joint strength cannot be obtained in yet another example of the conventional technology, and are schematic cross-sectional views sequentially showing the change over time of the cross section of the joint in a joining method using the said joining device.

[0014] The dissimilar material joining technology described in Patent Document 2 softens the materials with frictional heat generated by a rotating tool, causing plastic flow within the materials and at the interface (contact surface of the joining members) which is the joining surface. This plastic flow peels off and removes the oxide film of both materials, and by bringing the newly formed surfaces, which do not contain oxide film, into contact, a solid-state joining layer is formed. However, even with this technology, the area where the oxide film is removed is limited to a narrow area around the tip of the probe, making it difficult to secure a joining diameter sufficient to obtain sufficient joining strength. Furthermore, while increasing the probe diameter can be expected to expand the area where the oxide film is removed, increasing the probe diameter increases the distance traveled per rotation, resulting in a significant increase in peripheral speed and slippage in the screw grooves around the probe. As a result, the plastic flow is reduced, a sufficient area for oxide film removal cannot be obtained, the removal becomes uneven, and it is difficult to obtain a uniform solid-state joining layer.

[0015] The dissimilar material joining technology described in Patent Document 3 utilizes an anchoring effect that occurs when a rotating tool penetrates an aluminum member and comes into contact with a steel material, softening and deforming the steel material through frictional heat, and then causing the deformed portion to bite into the aluminum member. However, in this technology, since the rotating tool is in direct contact with the steel material, the issue of tool durability is not considered at all, making it difficult to use in actual production sites.

[0016] The present invention aims to provide a friction riveting tool and friction riveting method that enable stable, homogeneous, and sufficient bonding strength not only when joining low-melting-point materials such as aluminum alloys, but also when joining dissimilar materials such as low-melting-point and high-melting-point materials.

[0017] The present invention also aims to provide a friction riveting tool and friction riveting method that enable stable, homogeneous, and sufficient joint strength not only when joining thin plates but also when joining thick plates, particularly when joining low-melting-point materials. [Means for solving the problem]

[0018] The first embodiment of the present invention is A friction crimping tool comprising a rotary tool and a receiving member positioned opposite the rotary tool and supporting a first member and a second member to be joined from the second member side, The rotary tool has a shoulder portion that forms its base end, and a probe portion that is provided on the tip surface of the shoulder portion and has a tapered shape that becomes smaller in diameter towards the tip. The probe portion has a curved shape on its side surface when viewed in cross-section. The present invention relates to a friction crimping joining tool, wherein the receiving member has a recess having a bottom diameter larger than the tip diameter of the probe portion of the rotary tool.

[0019] The friction crimping joining tool according to the first embodiment of the present invention includes the following embodiments: The rotary tool has a side profile where the shoulder and probe are integrated, with a convex shape that is a continuous concave curved surface that gradually widens in diameter from the tip of the probe to the outermost part of the shoulder, and a screw groove is cut into this curved surface. The curved surface may have a single curvature or a continuously changing curvature. The term "concave" for the curved shape of the probe means that, in a cross-sectional view, it is recessed compared to the straight line connecting the tip of the probe and the outermost part of the shoulder, and can also be described as a shape that sinks toward the central axis of the rotary tool. A screw groove is a groove provided in a helical shape, as described later. There are no specific regulations regarding the cross-sectional shape of the screw groove, such as U-shape, V-shape, or square, but the direction of cutting of the screw groove is left-hand thread direction when joining with right-hand rotation, and right-hand thread direction when joining with left-hand rotation. The probe tip shape is designed to allow insertion into the joined member with low load, such as a spherical or conical shape, in order to stabilize the pivot point when the tool makes contact.

[0020] In the first embodiment, the receiving member is provided with a concave portion so as to oppose the convex portion shape of the rotary tool. The concave portion shape has a bottom portion larger than the tip diameter of the probe, and its side surface may have a curved surface shape having a single curvature, similar to the rotary tool, or may have a curved surface shape having a continuously changing curvature. The curved surface has a convex curved surface shape that follows the concave curved surface of the rotary tool, but it does not have to be the same shape such that the gap between the two completely matches, and as long as it does not have an inflection point that rapidly changes the plastic flow during joining (the distance between the curved surfaces of the upper and lower tools does not rapidly increase or decrease), different shaped curved surfaces may be used. The term "convex" with respect to the curved surface shape of the concave portion side surface of the receiving member means convex toward the central axis of the rotary tool in a cross-sectional view.

[0021] The second embodiment of the present invention relates to a friction caulking joining method in which friction caulking joining is performed using the friction caulking joining tool according to the above-described first embodiment.

[0022] In the friction caulking joining method according to the second embodiment of the present invention, specifically, the following steps (processing processes) are included: A step of gripping the joined member (particularly the first member and the second member) between the receiving member while the rotary tool is rotating; A step of generating frictional heat by maintaining rotation while applying a constant pressing force in that state to soften the joined member; A step of filling the softened joined member into the concave portion of the receiving member so as to bend the joined member along the curved surface shape provided on the rotary tool and the curved surface shape provided in the concave portion of the receiving member without breaking it; A step of causing plastic flow in the softened material by continuously applying a pressing force and a rotational speed to the filled material; A step of controlling the plastic flow direction along the curved surface shape of the rotary tool from the outermost peripheral portion of the shoulder portion to the central portion of the probe portion in a plan view and further from the surface of the joined member to the tip portion of the probe portion in a cross-sectional view by the action of the screw groove shape engraved on the curved surface shape portion of the rotary tool; The step in which the material in the plastic state is accumulated at the tip of the probe part due to its flow, causing the internal pressure at that part to rise and the stirring of the joined member to start; The step of increasing the stirring volume further by maintaining that state and growing the stirring region from the tip of the probe part to the upper part of the interface; The step of cooling and solidifying the joined member in the plastic state to form a joint by separating the rotating tool and the receiving member from the joined member in that state.

[0023] That is, the friction caulking joining method according to the second embodiment of the present invention is characterized in that it is a joining method capable of forming a joint having the effects of both caulking joining methods such as mechanical clinch and friction stir spot joining at the same time.

[0024] When the friction caulking joining method according to the second embodiment of the present invention is used for joining different materials, for example, in the joining of an aluminum alloy material (first member) and a steel material (second member), in the above-described processing process, it is difficult to obtain the amount of heat generation required for deformation along the curved surface shape of the upper and lower tools by frictional heat generation, and there was a problem that the rotating tool might come into contact with the steel material. (Since joining is performed with the rotating tool in contact with the steel material, the problem regarding the durability of the rotating tool has not been solved). Therefore, as the third embodiment of the present invention, when the friction caulking joining method according to the second embodiment is used for joining different materials, in addition to the processing process of the second embodiment described above, a recess (pin) having a shape that fits into the recess of the receiving member is provided in advance at the joining part of the steel material, eliminating the need for the amount of heat generation for obtaining the deformation of the steel material. Since the basic processing process according to the third embodiment of the present invention is the same as the content of the second embodiment described above, only different parts will be briefly described below.

[0025] The friction caulking joining method according to the third embodiment of the present invention includes the following steps: The step of controlling the plastic flow direction along the curved surface shape of the rotating tool from the outermost peripheral part of the shoulder part to the central part of the probe part, and further from the surface of the joined member to the tip of the probe part, by the action of the screw groove shape engraved on the curved surface shape part of the rotating tool; The process involves the accumulation of a plastic material at the tip of the probe portion due to its flow, which increases the internal pressure at that point, causing the oxide film on the surface of the member located at the interface of the joined members to begin to peel off, and As the internal pressure increases, plastic flow is induced at the interface from the bottom upwards, and the peeling of the oxide film progresses further. The process involves the removal of the oxide film and its upward extrusion by plastic flow, causing the newly formed surfaces of both joined members to come into contact with each other. Maintaining this state further increases the contact area between newly formed surfaces, and the process involves growing the contact area between newly formed surfaces from the tip of the probe portion to the upper part of the interface. This process involves separating the rotating tool and the receiving member from the member to be joined in that state, thereby cooling and solidifying the plastically-stated member to be joined and forming a joint.

[0026] In other words, the dissimilar material joining method using the friction crimping joining method according to the third embodiment of the present invention is characterized by being a joining method that makes it possible to form a joint that simultaneously possesses the effects of both a crimping joining method such as mechanical clinching and a diffusion joining method. In the third embodiment, the shape of the recess (dowel) provided in advance when joining dissimilar materials is acceptable as long as it satisfies the same requirements as the requirements for the receiving member described above. However, the bottom of the recess (dowel) shape may be closed or open (through hole). The recess (dowel) shape provided in advance in the member to be joined (especially the second member) may be called a "recess-corresponding shape" in the sense that it follows the recess of the receiving member, as described later. [Effects of the Invention]

[0027] According to the present invention, it is possible to provide a friction riveting tool and friction riveting method that can stably and uniformly achieve sufficient joint strength not only when joining low-melting-point materials such as aluminum alloys, but also when joining dissimilar materials such as low-melting-point and high-melting-point materials. Furthermore, according to the present invention, it is possible to provide a friction riveting tool and friction riveting method that can provide stable, homogeneous, and sufficient joint strength not only when joining thin plates but also when joining thick plates, particularly when joining low-melting-point materials. [Brief explanation of the drawing]

[0028] [Figure 1] A schematic diagram showing the vicinity of the probe portion in an example of a rotary tool according to the first embodiment of the present invention is shown. [Figure 2] Figure 1 shows a schematic diagram illustrating the dimensions near the probe portion of the rotary tool. [Figure 3] In the first embodiment of the present invention, a schematic diagram showing the vicinity of a recess in an example of a receiving member used with a rotary tool is provided. [Figure 4] Figure 3 shows a schematic diagram illustrating the dimensions near the recess in the receiving member. [Figure 5] Figures (A) to (C) are cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joining strength is stably obtained in the second embodiment of the present invention, and are schematic cross-sectional views sequentially showing the change over time of the cross-section of the joint in a joining method using the said joining device. [Figure 6] This is a schematic cross-sectional view of a joining device showing the state during joining, for comprehensively explaining the details of the mechanism by which sufficient joining strength is stably obtained in a second embodiment of the present invention. [Figure 7] This is a schematic cross-sectional view of a joining device showing the state during joining, illustrating some of the details of the mechanism by which sufficient joining strength is stably obtained in a second embodiment of the present invention. [Figure 8] Figures (A) to (C) show schematic cross-sectional views of a joining device to illustrate a modified example 1-1 in the second embodiment. [Figure 9] Figures (A) to (C) show schematic cross-sectional views of a joining device to illustrate modified example 1-2 in the second embodiment. [Figure 10]A schematic cross-sectional view of a joining device is shown to illustrate modified examples 1-3 in the second embodiment. [Figure 11] A schematic cross-sectional view of a joining device is shown to illustrate modified examples 1-4 in the second embodiment. [Figure 12] Figures (A) to (C) are schematic cross-sectional views of a joining device for illustrating modified examples 1-5 in the second embodiment, and are schematic cross-sectional views sequentially showing the changes in the cross-section of the joint over time in a joining method using the said joining device. [Figure 13] Figures (A) to (C) show schematic cross-sectional views of a joining device to illustrate modified examples 1-6 in the second embodiment. [Figure 14] A schematic cross-sectional view is shown showing the vicinity of a concave joint in an example of a second member in the third embodiment of the present invention. [Figure 15] Figure 14 shows a schematic cross-sectional view illustrating the dimensions near the concave joint in the second member. [Figure 16] A schematic diagram showing the vicinity of a recess in an example of a receiving member that is preferably used in the third embodiment is shown. [Figure 17] Figure 16 shows a schematic diagram illustrating the dimensions near the recess in the receiving member. [Figure 18] Figures (A) to (C) are schematic cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joining strength is stably obtained in the third embodiment, and schematic cross-sectional views sequentially showing the change over time of the cross section of the joint in the joining method using the said joining device. [Figure 19] Figures (A) to (C) show schematic cross-sectional views of a joining device to illustrate a modified example 2-1 in the third embodiment. [Figure 20] Figures (A) to (C) show schematic cross-sectional views of a joining device to illustrate a modified example 2-2 in the third embodiment. [Figure 21] A schematic cross-sectional view of a joining device is shown to illustrate a modified example 2-3 of the third embodiment. [Figure 22]This graph shows the relationship between bonding strength and bonding time for the joint manufactured in the example of Experimental Example A (First Embodiment). [Figure 23] This graph shows the relationship between bonding strength and bonding time for the joint produced in the example of Experimental Example B (First Embodiment). [Figure 24] This graph shows the relationship between bonding strength and bonding time for the joint produced in the example of Experimental Example C (Third Embodiment). [Figure 25] Figures (A) to (C) are cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joint strength cannot be obtained in an example of the prior art, and are schematic cross-sectional views sequentially showing the change over time of the joint cross section in a joining method using the said joining device. [Figure 26] Figures (A) to (D) are cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joint strength cannot be obtained in another example of the prior art, and are schematic cross-sectional views sequentially showing the change over time of the joint cross section in a joining method using the said joining device. [Figure 27] (A) to (C) are cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joint strength cannot be obtained in yet another example of the prior art, and are schematic cross-sectional views sequentially showing the change over time of the joint cross section in a joining method using the said joining device. [Modes for carrying out the invention]

[0029] The friction crimping joining method using the friction crimping joining tool of the present invention is a joining method for joining two members (particularly metal members). Specifically, in the friction crimping joining method using the friction crimping joining tool of the present invention, a first member and a second member are overlapped, frictional heat is applied to the first member by the rotation of a rotary tool, and pressure is applied to the first member and the second member by pressing the rotary tool from the first member side, thereby joining the first member and the second member. Hereinafter, the deformation of the first member and the second member by such heating and pressurizing, so that they conform to the curved shape provided on the probe part of the rotary tool and the curved shape provided on the recess of the receiving member, will be referred to as "crimping". The first member is usually positioned higher and in direct contact with the rotary tool, and the second member is usually positioned lower and in direct contact with the receiving member.

[0030] As used herein, "section view" refers to the form obtained when viewed from a direction substantially perpendicular to the central axis C1 of the rotating tool or the central axis C2 of the receiving member, and includes cross-sectional views. In particular, "section view" refers to the form obtained when cut by a plane parallel to the central axis C1 of the rotating tool or the central axis C2 of the receiving member, and passing through the said central axis C1 or C2. "Side view" refers to the external form obtained when viewed from a direction substantially perpendicular to the central axis C1 of the rotating tool or the central axis C2 of the receiving member, and includes side views. "Plan view" refers to the form obtained when the object is viewed from above or below along the central axis C1 of the rotating tool or the central axis C2 of the receiving member, and includes plan views (top view and bottom view). In particular, "bottom view" refers to the form obtained when the object is viewed from below (below) along the central axis C1 of the rotating tool or the central axis C2 of the receiving member, and includes bottom views. The various elements shown in the drawings are for illustrative purposes only to facilitate understanding of the present invention, and it should be noted that dimensional ratios and appearances may differ from those of the actual objects. Furthermore, the term "vertical direction" used directly or indirectly in this specification corresponds to the vertical direction in the drawings. Unless otherwise specified, common symbols in these drawings indicate the same member, part, dimension, or area.

[0031] The present invention will be described in detail below with reference to a first embodiment relating to a friction crimping tool, a second embodiment relating to a friction crimping method using the friction crimping tool according to the first embodiment, and a third embodiment relating to a specific friction crimping method in the second embodiment.

[0032] <First Embodiment> [Friction crimping joining tool] The friction crimping joining tool of this embodiment will be described in detail with reference to the drawings. The tool of this embodiment is a joining kit that includes a specific rotary tool and a specific receiving member. The first member and the second member are joined between the rotary tool and the receiving member.

[0033] The rotary tool in this embodiment is a component that applies a pressing force to the first component and generates heat through friction with the first component due to its own rotation. The rotary tool moves from top to bottom while rotating around the central axis C1 with respect to a workpiece in which the first component is on top and the second component is on the bottom, driven by a drive source (not shown).

[0034] As shown in Figure 1, the rotary tool has a shoulder portion 11 that constitutes the base end of the rotary tool, and a probe portion 12 that is provided on the tip surface 110 of the shoulder portion 11 and has a tapered shape that becomes smaller in diameter towards the tip. Figure 1 is a schematic view showing the vicinity of the probe portion in an example of the rotary tool of this embodiment.

[0035] The probe portion 12 has a curved shape on its side surface 120 in a cross-sectional view. The curved shape of the side surface is a specification relating to the surface shape of the probe portion side surface 120. More specifically, in a cross-sectional view, as shown in Figure 1, the curved shape of the side surface is a concave curved shape that sinks toward the central axis C1 of the rotary tool, and is a curved shape that is continuous with the shoulder portion 11. The probe portion 12 is positioned (or formed) over the entire surface of the tip surface 110 of the shoulder portion 11. Therefore, in a bottom view of the rotary tool 1, the tip surface (bottom surface) 110 of the shoulder portion 11 is completely covered by the probe portion 12. Thus, the curved shape that is continuous with the shoulder portion 11 means a curved shape that is continuously formed from the outer edge 111 of the shoulder portion 11 toward the tip of the probe portion 12 in a bottom view. In Figure 1, the rotary tool 1 has a tapered portion 13 with a tapered surface 130 on the outer circumference of the shoulder portion 11, but it may or may not have a tapered portion 13. When the rotary tool 1 has a tapered portion 13, the tapered surface 130 is usually formed continuously with the side surface (curved shape) 120 of the probe portion 12 in a cross-sectional view, and is, for example, flush with the side surface (curved shape) 120 of the probe portion 12. Flushness means that there is no step between the two surfaces. The two surfaces are the tapered surface 130 of the tapered portion 13 and the side surface (curved shape) 120 of the probe portion 12.

[0036] The curved shape of the side surface 120 of the probe portion 12 has a specific curvature. More specifically, this curved shape may have a constant (or single) curvature, or it may have a continuously changing curvature. Continuously changing curvature means that, in a cross-sectional view, the slope of the tangent to the curve that defines the curved shape of the side surface 120 of the probe portion changes gradually (or continuously). More specifically, when the position on the curve is plotted with the x-axis and the slope of the tangent to that position with the y-axis, the plot changes gradually (or continuously).

[0037] The probe portion 12 is integrated with the shoulder portion 11. This integration means that, in terms of appearance from the bottom and side views, the probe portion 12 is integrated with the shoulder portion 11. More specifically, in the bottom view, there is no boundary that would cause the probe portion 12 to be recognized as a separate component from the shoulder portion 11. As shown in Figure 1, for example, the rotary tool 1 has the probe portion 12 covering the entire surface of the tip surface 110 of the shoulder portion 11; therefore, in the bottom view, the boundary does not exist, and the probe portion 12 is integrated with the shoulder portion 11.

[0038] From the viewpoint of further improving the bonding strength and stability, the probe portion 12 is preferably threaded on its side surface 120, and as a result, it is preferable that the side surface 120 has a helical groove 121. The groove 121 of the probe portion 12 more sufficiently promotes heat conduction to the first member and the second member. The cross-sectional shape of the groove 121 is not particularly limited and may be U-shaped, V-shaped, square-shaped, etc.

[0039] The rotation direction of the rotary tool 1 equipped with a probe portion 12 having a groove portion 121 is not particularly limited, but from the viewpoint of further improving the joint strength and stability, it is preferable to use the rotary tool 1 by rotating it in the opposite direction to the screwing direction of the groove portion. The screwing direction is the helical direction, which is the rotation direction in which a screw is tightened. Therefore, assuming that the probe portion having the helical groove portion is a screw, it is preferable that the rotation direction of the rotary tool is the direction in which the screw is loosened. Specifically, for example, when the rotary tool is used in forward rotation (counterclockwise rotation when the rotary tool is viewed from the side of the member to be joined), it is preferable that the groove portion is cut in the reverse screw direction. Also, for example, when the rotary tool is used in reverse rotation (clockwise rotation when the rotary tool is viewed from the side of the member to be joined), it is preferable that the groove portion is cut in the forward screw direction. By having the relationship between the rotation direction of the rotary tool 1 and the helical direction of the groove portion as described above, it becomes possible to retain the material that has softened and become plastic due to frictional heat within the joint portion without discharging it to the outside, and plastic flow at the interface between the first member and the second member is more sufficiently promoted. In this specification, the first member and the second member may be collectively referred to as the "member to be joined."

[0040] The tip shape of the probe portion 12 tip portion 122 is not particularly limited, but it is preferable to have a shape that can be inserted into the first member with a low load, such as a spherical or conical shape, in order to stabilize the rotation axis when the rotary tool 1 comes into contact with the first member. The very tip of the tip portion 122 may be machined into a substantially flat shape and the corners may be chamfered.

[0041] The tip diameter R1 of the tip portion 122 of the probe portion 12 (see Figure 2) is not particularly limited, and the tip diameter R1 may be specifically 2 to 8 mm, and especially 3 to 5 mm. The radius R2 of the tip portion 122 may usually be 50% of the tip diameter R1. Figure 2 shows a schematic diagram to illustrate the dimensions near the probe portion in the rotary tool of Figure 1.

[0042] The radius of curvature R3 (see Figure 2) of the probe side surface 120 is not particularly limited, and the radius of curvature R3 may be specifically 2 to 8 mm, and more particularly 3 to 6 mm. If the curvature changes steplessly, the radius of curvature R3 may change within the above range.

[0043] The length (height) L1+R2 (see Figure 2) of the probe portion 12 is not particularly limited, and the length L1+R2 may be specifically 3 to 12 mm, and especially 4 to 8 mm.

[0044] The depth D1 of the groove 121 (see Figure 2) is not particularly limited and may be, for example, 0.1 to 3 mm, particularly 0.2 to 2 mm, but is preferably 0.3 to 1 mm from the viewpoint of further improving the joint strength and its stability.

[0045] The width W1 of the groove 121 (see Figure 2) is not particularly limited and may be, for example, 0.1 to 3 mm, particularly 0.2 to 2 mm, but is preferably 0.3 to 1 mm from the viewpoint of further improving the joint strength and its stability.

[0046] The pitch of the grooves 121 (not shown) is not particularly limited and may be, for example, 0.1 to 5 mm, particularly 0.2 to 4 mm, but is preferably 0.5 to 2 mm from the viewpoint of further improving the joint strength and its stability.

[0047] The diameter R4 of the shoulder portion 11 (see Figure 2) is not particularly limited and may be, for example, 10 to 30 mm, particularly 10 to 20 mm, but is preferably 12 to 16 mm from the viewpoint of further improving the joint strength and its stability.

[0048] The width T1 of the tapered portion 13 (see Figure 2) is not particularly limited, and the width T1 may be specifically 1 to 8 mm, and especially 1.5 to 5 mm.

[0049] The height H1 of the tapered surface of the tapered portion 13 (see Figure 2) is not particularly limited and may be, for example, 0.1 to 3 mm, and especially 0.5 to 2 mm.

[0050] The overall diameter R5 of the rotary tool 1 (see Figure 2) is not particularly limited, and the overall diameter R5 may be specifically 10 to 40 mm, and especially 10 to 30 mm.

[0051] The material constituting the rotary tool 1 (especially the probe portion 12) is not particularly limited as long as it is a material that can generate heat through friction with the first member, and is mainly determined according to the type of first member that the rotary tool 1 presses against. For example, if the first member is made of aluminum or an aluminum alloy, the rotary tool 1 is made of tool steel (e.g., SKD61). Also, for example, if the first member is made of steel, the rotary tool 1 is made of silicon nitride or PCBN (cubic boron nitride sintered body), etc.

[0052] The support member 2 is positioned opposite the rotary tool 1 and is usually located below the rotary tool 1. Specifically, the rotary tool 1 and the support member 2 are installed so that the central axis C1 of the rotary tool 1 and the central axis C2 of the support member 2 are aligned on the same straight line (for example, the same vertical line). The support member 2 supports the first and second members from the second member side and may optionally push them upward.

[0053] The receiving member 2 typically has a recess 20, as shown in Figure 3. The recess 20 may have a recessed shape. The recess 20 has a bottom (or bottom surface) 21 with a diameter R11 (see Figure 4) that is larger than the tip diameter of the tip portion 122 of the probe portion 12 of the rotary tool 1. Specifically, the bottom (or bottom surface) 21 of the recess 20 of the receiving member 2 is the lower part (particularly the bottom surface) of the recess 20, and the diameter R11 (see Figure 4) may be 3 to 14 mm, particularly 4 to 8 mm. Figure 3 is a schematic view showing the vicinity of the recess in an example of a receiving member that is preferably used with the rotary tool of the present invention. Figure 4 is a schematic view illustrating the dimensions of the vicinity of the recess in the receiving member of Figure 3.

[0054] In Figure 3, the bottom (or base surface) 21 of the recess 20 is composed of a flat surface, but it is not limited to this. For example, a recessed or uneven shape may be provided in the center of the base surface 21, or a cylindrical or conical shape may be provided. This results in a shape that is more similar to that of a spherical or conical rotating tool tip, leading to a more uniform pressure distribution, which stabilizes the plastic flow and increases the stirring volume. (If the bottom is flat, using a spherical or conical rotating tool tip will only result in a point-like pressure concentration point in the center.) Furthermore, when the internal pressure increases due to the material filled by plastic flow, it also has the effect of inducing plastic flow in the upward direction via the interface.

[0055] The connecting portion 26 (see Figure 3) between the bottom surface 21 and the side surface 210 of the recess 20 may be provided with a curved shape (R shape) or a tapered shape. This prevents the resulting joint from adhering to the connecting portion 26 and breaking, and allows the joint portion of the joint to easily separate from the recess of the receiving member.

[0056] The bottom (or bottom surface) 21 of the recess 20 is made up of a flat surface in Figure 3, but it may have a curved shape made up of a curved surface, as shown in Figure 16 which will be described later. In this embodiment, the receiving member 2 may be the receiving member 2' shown in Figure 16.

[0057] From the viewpoint of further improving the bonding strength and stability, it is preferable that the recess 20 has a curved surface shape on its side surface 210 in a cross-sectional view that corresponds to the curved surface shape of the side surface 120 of the probe portion 12. More specifically, it is preferable that the curved surface shape of the side surface 210 of the recess 20 corresponds to the curved surface shape of the side surface 120 of the probe portion 12, for example, it is preferable that it is a curved surface shape that is convex toward the central axis C2 of the recess 20. More specifically, the curved surface shape of the side surface 210 of the recess 20 may have a specific curvature that matches (or differs from) the specific curvature of the curved surface shape of the side surface 120 of the probe portion 12, or it may have a curvature that takes into account the specific curvature of the curved surface shape of the side surface 120 of the probe portion 12 and the thickness of the first member and the second member. The radius of curvature R12 (see Figure 4) of the curved surface shape of the side surface 210 of the recess 20 is usually about the same as, or smaller than, the radius of curvature R3 (see Figure 2) of the curved surface shape of the side surface 120 of the probe portion 12. Specifically, the radius of curvature R12 (see Figure 4) of the curved surface shape of the side surface 210 of the recess 20 may be 2 to 8 mm, and particularly 3 to 6 mm. The curved surface shape of the side surface 210 may have a constant (or single) curvature, or it may have a continuously changing curvature. If the curvature changes continuously, the radius of curvature R12 may change within the above range.

[0058] The depth D11 of the recess 20 (see Figure 4) is not particularly limited and may be, for example, about the same as the probe length L1 + R2. Specifically, the depth D11 may be 3 to 15 mm, and particularly 3 to 6 mm.

[0059] The opening diameter R13 of the recess 20 (see Figure 4) is not particularly limited and may be, for example, about the same as the diameter R4 of the shoulder portion 11. Specifically, the opening diameter R13 may be 10 to 30 mm, and particularly 10 to 20 mm.

[0060] The overall diameter R15 of the receiving member 2 (see Figure 4) is not particularly limited, and the overall diameter R15 may be specifically 10 to 40 mm, and more particularly 10 to 30 mm.

[0061] The receiving member 2 typically has a corner portion 25 on its outer circumference and upper end. The corner portion 25 may be curved, as shown in Figure 3. The radius of curvature R14 of the corner portion 25 (see Figure 4) is not particularly limited and may be, for example, 1 mm, or it may be 100 to 300 mm by widening the overall diameter R15. Therefore, the radius of curvature R14 may be 1 to 300 mm, and in particular may be 3 to 100 mm. By curving the corner portion 25, the indentation that occurs at the contact point when the striking angle is misaligned during joining can be made shallower.

[0062] The material constituting the support member 2 may be the same as the material constituting the rotary tool 1. The material constituting the support member 2 is not particularly limited and may be set mainly according to the type of second member that the support member 2 directly supports. For example, if the second member is made of aluminum or an aluminum alloy, the support member 2 may be made of tool steel (e.g., SKD61). Also, for example, if the second member is made of steel, the support member 2 may be made of silicon nitride or PCBN (cubic boron nitride sintered body), etc.

[0063] The tool in this embodiment constitutes a joining device, which typically includes a drive control device. The drive control device may employ a pressure control method that controls the pressure applied by the rotary tool to the first member, the joining time, and the rotational speed.

[0064] Each of the first and second members has a generally flat shape as an overall form, as shown in the drawings described later, but is not limited to this. Each of the first and second members may have any shape as long as at least the portion that overlaps with each other has a generally flat shape. In each of the first and second members, the portion that overlaps with each other is usually composed of flat surfaces on both sides.

[0065] The materials constituting the first and second members are not particularly limited and may be any metal, for example. Among these, the following metals and alloys used in the automotive field are preferred: aluminum; Aluminum alloys such as 5000 series and 6000 series; Steel; Magnesium and its alloys; Titanium and its alloys.

[0066] In this embodiment, the metals constituting each of the first member and the second member are each independently preferably aluminum or an aluminum alloy, more preferably an aluminum alloy, from the viewpoint of further improving the joining strength and its stability.

[0067] The thickness T1 of the first member is usually 0.5 mm or more (particularly 0.5 to 10 mm), preferably 0.8 mm or more (particularly 0.8 to 5 mm), more preferably 1.0 to 3 mm, from the viewpoint of further improving the joining strength and its stability. The above thickness T1 of the first member may be the thickness (thickness before joining treatment) of the substantially flat plate-shaped portion that overlaps the second member in the first member.

[0068] The thickness T2 of the second member is usually not a problem as long as it is within substantially the same range of plate thickness as the thickness T1 of the first member, and there is no problem whether the plate thicknesses are the same or different. Also, regarding the stacking direction, it is possible to join without any problem even if T1 (upper plate) ≥ T2 (lower plate) or T1 (upper plate) < T2 (lower plate). The above thickness T2 of the second member may be the thickness T2 (thickness before joining treatment) of the substantially flat plate-shaped portion that overlaps the first member in the second member.

[0069] <Second Embodiment> [Friction caulking joining method] The friction caulking joining method of this embodiment joins the above-described first member and second member using the friction caulking joining tool according to the first embodiment. The joining method of this embodiment is characterized in that joining is performed by a joining mechanism in which so-called mechanical clinch joining and friction stir joining are fused.

[0070] The friction caulking joining method of this embodiment includes, for example, the following steps: The process involves a rotating tool gripping the members to be joined (particularly the first and second members) between itself and the receiving member while the rotating tool is in motion (hereinafter sometimes referred to as process (1)), The process involves maintaining rotation while applying a constant pressure in that state to generate frictional heat and soften the members to be joined (hereinafter sometimes referred to as process (2)), The process involves filling the recess of the receiving member with the softened member so that it conforms to the curved shape of the rotating tool and the curved shape of the recess of the receiving member, without breaking the member (hereinafter sometimes referred to as process (3)), A process (hereinafter sometimes referred to as process (4)) in which pressure and rotational speed are continuously applied to the filled material to induce plastic flow in the softened material, The process (hereinafter sometimes referred to as process (4.1A)) involves controlling the plastic flow direction along the curved surface of the rotating tool by the action of the screw groove shape engraved on the curved surface of the rotating tool, from the outermost part of the shoulder to the center of the probe in a plan view, and further from the surface of the member to be joined to the tip of the probe in a cross-sectional view, The process involves the accumulation of the plastic material at the tip of the probe due to its flow, which increases the internal pressure at that point and initiates stirring of the joined members (hereinafter sometimes referred to as process (4.2A)), Maintaining that state further increases the stirring volume, and the stirring region grows from the tip of the probe to the upper part of the interface (hereinafter sometimes referred to as step (4.3A)), In this state, the rotating tool and the receiving member are separated from the member to be joined, thereby cooling and solidifying the plastically deformed member to be joined and forming the joint (hereinafter sometimes referred to as step (5)).

[0071] Steps (1) and (2) are carried out sequentially, and after or during step (2), steps (3) and (4) are carried out sequentially, as shown in Figures 5(A) to (C). In this embodiment, the processing machine used is a conventional robot system for friction stir welding, and by using only the rotary tool 1 and receiving member 2 described above, it is possible to improve the joint strength and its stability. Specifically, by using the rotary tool 1 and receiving member 2 described above, as shown in Figures 5(A) to (C), the direction of the pressure applied during crimping is distributed not in the shear direction, but in the normal and tangential directions along the curvature of the curved shape of the side surface 120 of the probe portion 12 and the side surface 210 of the recess 20. In particular, as the rotary tool 1 sinks in, the direction and magnitude of the applied pressure change due to the change in curvature, thereby suppressing fracture of the interface and enabling the formation of a crimped portion accompanied by deformation behavior due to bending. Figures 5(A) to 5(C) are schematic cross-sectional views of a joining device showing the state during joining to explain the mechanism by which sufficient joining strength is stably obtained in this embodiment, and schematic cross-sectional views sequentially showing the change over time of the joint cross section in the joining method using the said joining device.

[0072] In step (4), significant flow occurs in the first member 5 and the second member 6, which is thought to contribute to improving the joint strength and its stability. Specifically, in step (4), steps (4.1A) to (4.3A) are usually performed. More specifically, due to the action of the groove 121 machined on the side surface of the probe, as shown in Figure 6, plastic flow F1 occurs on the surface of the member to be joined from the outermost part of the rotating tool 1 towards the center, and inside the member to be joined from the top to the bottom (probe tip side) (step (4.1A)). In this way, the material that has softened and become plastic due to frictional heat flows into the inside of the member, promoting heat conduction from the first member 5 to the second member 6. As a result, the deformation resistance of the second member 6 is reduced, and it is pushed into the recess of the receiving member 2, making it easier to form a more stable crimped shape. The crimped shape refers to a state in which the first member 5 and the second member are plastically deformed so as to be bent along the curved shapes provided on the side surfaces of the probe portion 12 and the recess 20, without causing fracture at the interface that forms the joint, which was a problem in conventional construction methods. By bending in the thickness direction, effective strength is exhibited against shear loads. Figure 6 is a cross-sectional view of the joining device showing the state during joining in order to comprehensively explain the details of the mechanism by which sufficient joining strength is stably obtained in the first embodiment.

[0073] Furthermore, maintaining the joint in this state increases the amount of plastic material pushed into the bottom of the recess 20. As a result, the plastic material accumulates at the tip of the probe due to its flow, increasing the internal pressure in that area and causing stirring of the joined members to begin (step (4.2A)). On the other hand, since the material is sandwiched between the curved shapes provided on the rotating tool 1 and the receiving member 2, the pushed-in material is pushed up along the outer circumference and interface of the material being pushed in, changing to an upward flow F2 (see Figure 6) (step (4.3A)). Meanwhile, as the softened material expands due to thermal expansion inside the recess 20, the pressure inside the recess 20 increases, increasing the force pressing the plastic material against the groove 121 on the side of the probe 12. This further promotes plastic flow F1, F2 (see Figure 6), and also causes rotational flow F3 (see Figure 6). In addition, as shown in Figure 7, horizontal flow F4 also occurs due to the rotation of the rotating tool 1. As a result, the flow volume in various directions increases, and the stirring volume increases. Therefore, a completely integrated joint is formed, at least in the area at the bottom of the recess 20. At this time, in the upper area, the interface between the first member 5 and the second member is tightly twisted and intersected by vibrations due to plastic flow, and a joint S is formed in which the first member 5 and the second member bite into each other. If the bonding time is extended, the integrated joint increases and grows up to the top of the crimped portion. Figure 7 is a cross-sectional view of a bonding apparatus showing the state during bonding to explain some of the details of the mechanism by which sufficient bonding strength is stably obtained in the first embodiment.

[0074] In this specification, fluid volume refers to the volume of the region in which a material that has become plastic (an intermediate state between solid and liquid phases) due to frictional heat generated by processing moves within the joined member due to the rotational force of the rotary tool and the action of the groove (a groove engraved on the curved side surface of the probe). The agitated volume refers to the volume within the plastic flow volume in which both the first and second members are in a plastic state, mixed together by the rotational force of the rotary tool and the action of the grooves (grooves engraved on the curved side surface of the probe), until the interface that forms the contact surface between the first and second members disappears and they become a single structure (especially a metallic structure). The joint in friction crimping is formed by the region where the interface is tightly twisted and intersected by vibrations due to plastic flow, biting into both members, and the region that becomes integrated by agitation. An integrated joint refers to a portion in the above-mentioned stirring region where the interface that forms the contact surface between the first member and the second member disappears, and the materials of both the first member and the second member are mixed together in a plastic state, resulting in a single structure (especially a metallic structure).

[0075] In conventional rotary tools, increasing the stirring volume and allowing growth to the upper region reduces the improvement in shear strength due to crimping, but the rotary tool can excessively bite into the first member, resulting in a reduction in plate thickness. However, in the rotary tool of this embodiment, the curved shape provided on the side of the probe portion prevents the rotary tool from excessively biting into the first member and causing a reduction in plate thickness, even if the joining time is extended. Therefore, problems such as a decrease in the strength of the first member and the formation of stress concentration points can be sufficiently suppressed. Thus, it becomes possible to stably obtain a joint with good joint strength.

[0076] Furthermore, the helical grooves machined on the side of the probe expand in diameter along the curvature as the rotating tool sinks in. As a result, even at a constant rotational speed, an increase in the contact diameter increases the peripheral speed (distance traveled per unit time), and the amount of heat generated increases closer to the outer circumference. Consequently, softening progresses closer to the outer circumference, further promoting material flow through the grooves.

[0077] As the rotary tool sinks further and the contact area increases, the load applied per unit area decreases even if the pressing force remains constant. This leads to a decrease in the pressing speed, which has the effect of suppressing the occurrence of defects such as holes. In this embodiment, the joining process can be accelerated by increasing the pressing force in multiple stages (for example, two stages) while suppressing the occurrence of defects such as holes.

[0078] This embodiment makes it possible to obtain a joint that combines the effect of improving joint strength in the shear direction by conventional mechanical clinching with the effect of improving workability with low heat input and low load in friction stir welding. In conventional mechanical clinching methods, loads of tens of kN are required to form the crimped part, but in this embodiment, joining is possible with a load of a few kN. Therefore, in this embodiment, the shear load that occurs during joining in the conventional technology is converted into a deformation behavior in which the curved shape provided on the side of the probe part of the rotary tool and the side of the recess of the receiving member bends. As a result, it is possible to enjoy the effects of both mechanical clinching and friction stir welding without causing interface fracture, which is a problem in the conventional technology.

[0079] In this embodiment, the pressing force, joining time, and rotation speed are appropriately determined according to various conditions such as the thickness and material type of the first and second members. For example, when using first and second members having a thickness of 0.5 mm to 3 mm and made of aluminum alloy or steel plate, the joining is performed under the following conditions: Pressing force: 2-8 kN, preferably 4-7 kN; Bonding time: 0.5 to 3 seconds, preferably 1.0 to 2.0 seconds; Rotational speed: 500-3000 rpm, preferably 1000-2500 rpm.

[0080] An example of machining operation control in this embodiment is shown below. First, operate the rotary tool to the set rotation speed at the start of machining.

[0081] Next, upon reaching the set rotational speed, the gun shaft pressurizing operation is started, bringing the rotating tool 1 and the receiving member 2 closer together and pressurizing the first and second members. At this time, if both the first and second members are thin plates (for example, both with a thickness of 1.5 mm or less), the deformation resistance is small and it is possible to easily form them into a crimped shape, so the pressurizing force and rotational speed may be single conditions. On the other hand, if at least one of the first and second members is a thick plate (for example, at least one with a thickness of more than 1.5 mm), the deformation resistance is large and it takes time to obtain a crimped shape, so multi-stage conditions may be used, and the initial pressurizing force and rotational speed settings may be changed to increase, thereby controlling the process to accelerate softening and forming by increasing the amount of heat generated and the pressing pressure.

[0082] As the rotating tool 1 sinks under pressure (Figure 5(A)), the first member 5 and the second member 6 deform (Figure 5(B)), and the joint between the first and second members is completely filled into the recess 20 of the receiving member 2 (Figure 5(C)), forming a crimped portion. When the members to be joined are filled into the recess 20 of the receiving member 2, the sinking speed of the rotating tool decreases rapidly, and the action of the grooves on the side surface 120 of the probe portion 12 promotes plastic flow, increasing the agitation volume. At this time, the plastic material filled in the recess 20 causes the members to be joined, which have been molded into the shape of the side surface 120 and bottom surface 21 in the recess 20, to expand due to heat. This expansion force acts as an even stronger force pressing the members to be joined into the grooves on the side surface of the probe portion 12, resulting in stronger plastic flow. On the other hand, since the volume in the recess 20 does not change, the flow changes to an upward direction, rapidly increasing the agitation volume. In this process, the pressing force against the groove is crucial for plastic flow. If the rotation speed is too high, the material will move before it can be pressed against the groove, causing it to slip and reducing the flow rate. In other words, in the case of thick plates, the rotation speed used at the start of joining will cause the material to slip, preventing an increase in the flow volume and thus preventing an increase in the agitation volume. Therefore, when joining thick plates, it may be advisable to reduce the rotation speed midway through the process to control the joining process so that sufficient pressing force is applied to the groove.

[0083] The joining process is completed after the set joining time has elapsed, and the rotary tool 1 and the receiving member 2 are separated from the members to be joined (the first and second members) and released. The release operation may be a one-stage release operation or a two-stage release operation. A one-stage release operation is the operation of releasing the rotary tool 1 and the receiving member 2 directly from the crimping position to a position where they are completely separated. A two-stage release operation is the operation of releasing the rotary tool 1 and the receiving member 2 while maintaining the crimping position, after bringing them into contact with the machined surface with virtually no load, to a position where they are completely separated. The two-stage release operation prevents friction of the crimped portion caused by deformation due to the deflection of the gun arm and the rotary tool pressure shaft, and also allows for a smoother surface finish by stopping at the position where the applied load has been removed and machining the surface of the crimped portion with the force based on the rotational movement of the pivot axis in a virtually no-load state. Therefore, it is preferable to set the pivot axis rotation speed at the time of release to a high-speed rotation condition in order to smooth the surface finish of the crimped portion. During the first stage release operation, it is preferable to use a rotation speed that does not cause scratches or burrs when the rotating tool is removed from the joined member.

[0084] In step (4), plastic flow is generated, and once completed, the rotating tool and receiving member are separated from the members to be joined in this state, thereby cooling and solidifying the members to be joined in a plastic state and forming a joint. The joint may also be called a "crimped section" where "crimping" has occurred.

[0085] [Quality assurance method for friction crimping joints] An example of a quality assurance method for friction crimping joints according to this embodiment is described below. In the friction crimping joint of this embodiment, a crimped joint is formed using the curved shape provided on the side surface 120 of the probe portion of the rotary tool 1 and the curved shape provided on the side surface 210 of the recess of the receiving member 2. Therefore, the outer diameter of the joint mark remaining on the surface of the first member changes depending on the quality of the crimping (crimping strength). Thus, the quality of the joint can be determined by measuring the diameter of the joint mark on the surface. However, quality assurance cannot be achieved solely by this joint mark diameter; in order to make this possible, the following conditions must be met. The reasons why each condition is necessary are explained below.

[0086] (The pressure is being applied correctly.) In the processing machine used, for example, a servo motor is used to control the drive unit that applies pressure. However, what is being controlled here is the current value applied to the motor, not the pressure itself. Therefore, if the sliding resistance of the drive unit changes, the generated pressure will change even if the controlled current value is properly controlled. Since the main cause of changes in sliding resistance is the deterioration of the drive unit over time, sudden changes rarely occur. Therefore, changes in the drive unit can be monitored by periodically checking the diameter of the joint mark after processing. (When the pressing force increases or decreases, the diameter of the joint mark also increases or decreases.) Sudden changes such as deformation of the workpiece or interference from foreign objects can be detected by the processing machine's general anomaly detection function. By monitoring for these anomalies, it is possible to monitor whether sudden changes are occurring (e.g., overload, deviation anomalies).

[0087] (The rotation speed is being applied correctly.) The rotational speed of the rotary tool is directly controlled using a servo motor and encoder, so it rarely deviates and can be easily monitored by the machine's abnormality detection function. However, abnormalities such as loosening or improper mounting (tightening) of the rotary tool's fixing part cannot be detected. First, since loosening occurs gradually rather than suddenly, the presence or absence of loosening (change in state) can be monitored by periodically checking the diameter of the joint mark after processing, similar to the applied pressure. (As the rotational speed decreases, the diameter of the joint mark shrinks.) Regarding malfunctions caused by improper installation, if the rotary tool comes off, no pressure can be obtained, so this can be detected as a gun shaft malfunction. If it comes off during joining, it can be detected by the malfunction detection functions of both the gun shaft and the swivel shaft.

[0088] (The tool shape of the rotation tool has not changed.) If the shape of the probe portion (convex shape) changes due to wear of the rotary tool used (the tool becomes shorter), the amount of pressure applied to the crimping portion decreases, resulting in a decrease in strength. In addition, if wear occurs in the groove on the side of the probe portion, plastic flow decreases, and sufficient stirring volume cannot be obtained, resulting in a decrease in strength. Wear on rotary tools can be easily detected using conventional wear measurement functions. Regarding groove wear, as the grooves become shallower, the amount of material flowing decreases (the tool slips and cannot increase the flow rate), and the operating resistance of the swivel axis decreases. This can be detected by monitoring the feedback current of the swivel axis. (Monitor the decrease in operating current)

[0089] As described above, by ensuring that no abnormalities occur in the gun axis and swivel axis of the machining center during joining, and that the tool shape does not change, it becomes possible to guarantee quality simply by evaluating the diameter of the joining mark.

[0090] Conventional semi-destructive testing involved driving a chisel into the gap between the plates (between the first and second members) to confirm that the joint did not break. However, driving the chisel could cause cracks in the joint, the first and second members, or delamination of the pressure-welded area around the stirring section, which is joined by torsion at the interface. This resulted in a decrease in strength. Therefore, it was necessary to obtain a joint strength that accounted for the strength reduction caused by semi-destructive testing, and it was difficult to secure a suitable range of conditions that would facilitate quality control. However, in the friction crimping joint of this embodiment, there is no need to drive a chisel between the plates, and the joint quality can be checked simply by checking the diameter of the joint marks on the surface. This simplifies inspection and significantly reduces the management burden on the production site.

[0091] The key points of quality assurance mentioned above are as follows: The rotary tool used in this embodiment has an enlarged diameter shape with a specific curvature (single curvature or multi-stage curvature (curvature that changes continuously)) extending from the tip of the probe portion toward the main body of the rotary tool. Therefore, as the rotary tool sinks in, the diameter of the joint mark remaining on the surface of the member to be joined increases.

[0092] The rotary tool used in this embodiment has the enlarged diameter shape described above, so that even when a gap (gap between plates) occurs between the plates, for example, the outermost part of the rotary tool does not sink into the first member, and the first member does not lift up, enabling joining. Therefore, the reduction in the thickness of the first member (stress concentration point at fracture) caused by the sinking of the outermost part does not occur in this embodiment.

[0093] (Extreme Variation 1-1) The receiving member (especially its recess) needs to be modified in terms of the width and depth of the recess and the curvature of its sides depending on the thickness of the members to be joined. For example, as the plate thickness increases, the amount of material filling the recess increases, and as the plate thickness decreases, the amount of material decreases. In this case, when joining thick plates, if a receiving member with insufficient recess volume is used, the recess will be filled with material in the initial stages of joining, resulting in insufficient crimping of the interface and an inability to obtain stable joint strength. On the other hand, when joining thin plates, if a receiving member with a large recess width and depth is used, the softened material cannot be adequately gripped between the curved surface of the probe on the rotary tool and the curved surface of the recess on the receiving member during joining. As a result, the softened material will break due to rotational vibration, and a good joint cannot be formed. Therefore, it is important to use a receiving member with a recess of the appropriate shape (especially dimensions) depending on the plate thickness and plate assembly of the members to be joined.

[0094] For example, Figure 8(A) shows a schematic cross-sectional view of a joining device used to join a first member 5 and a second member 6 of a specific thickness between a receiving member 2 having a specific recess and a rotary tool 1. Using the joining device shown in Figure 8(A) as a reference, for example, when joining a first member 5A and a second member 6A of greater thickness, a receiving member 2A having a larger recess 20A is used, as shown in Figure 8(B). Also, for example, when joining a first member 5B and a second member 6B of smaller thickness, a receiving member 2B having a smaller recess 20B is used, as shown in Figure 8(C). Figures 8(A) to 8(C) show schematic cross-sectional views of a joining device to illustrate a modified example 1-1 of the first embodiment.

[0095] (Variations 1-2) In actual parts manufacturing, it is necessary to produce not only joints of the same plate thickness and plate configuration, but also joints of different plate thicknesses and configurations. However, since only one receiving member can be attached to the processing machine, only one type of plate thickness and plate configuration can be joined. Joining other plate thicknesses and configurations required the use of a different processing machine equipped with a different receiving member. Therefore, the reduction in production efficiency due to switching between multiple processing machines and the increase in equipment costs are challenges in applying the joining device and joining method according to this embodiment.

[0096] Therefore, when using two or more types of support members, the support member for the plate thickness and plate assembly with the largest processing volume in a particular manufacturing process is attached to the processing machine, and for the joints of other plate thicknesses and plate assemblies, support members with shapes suitable for each plate thickness and plate assembly are placed below each joint in a manner that allows them to move up and down. By gripping each member to be joined with the support member attached to the processing machine and performing the joining, it becomes possible to join using the support member with the most suitable shape for that part.

[0097] For example, Figure 9(A) shows a schematic cross-sectional view of a joining device used to join a first member 5 and a second member 6 of a specific thickness between a receiving member 2 having a specific recess and a rotary tool 1. Using the joining device shown in Figure 9(A) as a reference, for example, when using a receiving member 2A with a larger recess to join a first member 5A and a second member 6A of a larger thickness, the receiving member 2A is lifted using the originally used receiving member 2. Then, as shown in Figure 9(B), the members to be joined are gripped by each receiving member 2A and joined. Similarly, when using a receiving member 2B with a smaller recess to join a first member 5B and a second member 6B of a smaller thickness, the receiving member 2B is lifted using the originally used receiving member 2, and the members to be joined are gripped by each receiving member 2B and joined, as shown in Figure 9(C). In other words, by positioning a receiving member with an optimal shape for each part in a jig that can move up and down, in all parts where joining cannot be performed with a receiving member attached to the processing machine, it becomes possible to achieve good joining even at joints of different plate thicknesses and plate assemblies. Figures 9(A) to (C) show schematic cross-sectional views of a joining device to explain a modified example 1-2 of the first embodiment.

[0098] (Variations 1-3) The parts to be joined may have complex three-dimensional shapes. In such cases, since the processing direction differs for each joining area, when using the jig-mounted receiving member described above, the crimped shapes formed at the bottom of the joining parts may be formed in a direction that causes them to gnaw at each other. As a result, there is a risk that the parts may not be able to be removed from the jig (especially the receiving member) after joining. In such cases, as shown in Figure 10, by providing the above-mentioned vertically movable eco-rise mechanism or lifting mechanism 8 on one of the joining parts formed in the gnawing direction, it becomes possible to separate the receiving member 2B from the crimped shape of the joined part after joining, thereby preventing gnawing. Figure 10 shows a schematic cross-sectional view of a joining device to explain modified examples 1-3 of the first embodiment.

[0099] Springs, air cylinders, magnetic forces, and electric motors can be used as the drive source for the equalization mechanism or lifting mechanism, but other drive sources can also be used as long as they do not affect the positioning jig, the processing machine, or the processing state. The drive source for the equalization mechanism or lifting mechanism may be used alone or in combination with multiple drive sources.

[0100] (Variations 1-4) As shown in Modification 1-3, by using an eco-rise mechanism or a lifting mechanism, it becomes possible to join boards of different thicknesses and board assemblies using multiple receiving members with appropriate shapes (especially dimensions). However, if the number of board thicknesses and board assemblies that can be joined with the same receiving member shape increases, it becomes possible to reduce the number of types of receiving members used, and joining can be performed without using the above-mentioned mechanisms. As a result, very significant effects can be obtained, such as a reduction in equipment investment costs and management costs.

[0101] This section describes methods for increasing the compatible plate thickness and plate assembly of the receiving member. The plate assembly that can be accommodated is one in which the plate thickness is increased compared to the optimal plate thickness of the receiving member shape in use. For example, in a plate assembly with increased plate thickness, as shown in Figure 11, by providing a through hole 8 in the first member 5, the amount of material to be filled into the recess 20 of the receiving member 2 can be reduced, and good joining can be achieved even when using receiving members 2 of the same shape (especially dimensions). The diameter R8 of the through hole is set to about 1 / 2 to 3 / 2 of the tip diameter R1 of the tip portion 122 of the probe portion 12. However, in plate assemblies with extremely different plate thicknesses, it may not be possible to accommodate them without further increasing the diameter R8 of the through hole. However, if the diameter R8 of the through hole is made too large, the crimping effect will be drastically reduced, resulting in a significant decrease in joining strength. Therefore, it is preferable to keep the ratio of the tip diameter of the rotary tool to the diameter of the through hole within the above range and to apply it to plate assemblies in which the increase in plate thickness is 1.0 mm or less. Figure 11 shows a schematic cross-sectional view of the joining device to explain modified examples 1-4 of the first embodiment.

[0102] By pre-creating through holes in the first component, the rotary tool reaches the joining interface earlier during the initial stages of joining, allowing for faster mixing of the interface and thus reducing the joining time. As the joining process progresses, any misalignment between the through holes and the rotary tool is filled by the filling material, mixed by plastic flow, and integrates with the second component, resulting in a structure that is not affected by deviations of approximately ±1.0 mm.

[0103] (Variations 1-5) In conventional friction stir welding methods, as shown in Figures 26(A) to (C), when attempting to join a first member and a second member with a gap between them, sufficient joint strength could not be obtained. This phenomenon is particularly pronounced when joining thick plates, where the shoulder needs to be recessed close to the interface, and has been a factor in the difficulty of joining thick plates using friction stir welding.

[0104] In this embodiment, as shown in Figures 12(A) to (C), the probe side surface 120 has a curved shape with a specific curvature. Therefore, even if the rotating tool 1 sinks in as the joining progresses, the outermost part of the sinking position of the curved shape always remains in contact with the surface of the first member 5C. For this reason, unlike conventional friction stir welding, the entire shoulder portion does not sink into the member to be joined. Thus, the load applied by the applied pressure always acts in a direction that pushes the surface of the first member, and the phenomenon of the first member lifting up due to the decrease in deformation resistance accompanying the softening of the member to be joined does not occur. Figures 12(A) to (C) are schematic cross-sectional views of a joining device for explaining modified examples 1-5 of the first embodiment, and are schematic cross-sectional views sequentially showing the changes in the cross-section of the joint over time in a joining method using the joining device.

[0105] (Extreme Variations 1-6) In Figure 13(A), the rotary tool 1 has a helical groove 121 on the entire surface of the side surface 120 of the probe portion 12. However, the position and shape of the groove are not particularly limited, as long as the helical groove is formed in the screwing direction, at least near the tip of the side surface of the probe portion. Figures 13(A) to (C) show schematic cross-sectional views of the joining device to illustrate modified examples 1-6 of the first embodiment. In each of Figures 13(A) to (C), the upper view is a schematic cross-sectional view of the rotary tool (especially near the probe portion), and the lower view is a schematic bottom view of the rotary tool (especially near the probe portion).

[0106] For example, as shown in Figure 13(B), the rotary tool 1A may have a linear groove 121A on the tapered surface 130 of the tapered portion. The shape (particularly the direction of formation) of the groove 121A is in the same direction as the helical direction of the groove on the side surface. More specifically, the direction of formation of the groove 121A is inclined in the same direction as the helical direction of the groove on the side surface when viewed from the bottom, with respect to the central axis C1 of the rotary tool. More specifically, the direction of formation of the groove 121A is the direction in which plastic flow occurs, pushing in the softened material when the rotary tool 1A is rotated.

[0107] For example, as shown in Figure 13(C), the rotary tool 1B may have a helical groove 121C in the proximal region 125 from the tip on the side surface of the probe, and a linear groove 121D in the distal region 126 from the tip on the side surface of the probe. The shape (especially the direction of formation) of the groove 121D is in the same direction as the helical direction of the groove 121C. More specifically, the direction of formation of the groove 121D is inclined in the same direction as the helical direction of the groove 121C when viewed from the bottom, with respect to the central axis C1 of the rotary tool.

[0108] <Third Embodiment> [Friction crimping joining method] The friction crimping joining method of this embodiment is the same as the friction crimping joining method of the second embodiment, except that a specific second member is used, and consequently, in step (4), steps (4.1B) to (4.5B) shown below are usually performed: The process involves controlling the plastic flow direction along the curved surface of the rotating tool by the action of the screw groove shape engraved on the curved surface of the rotating tool, from the outermost part of the shoulder to the center of the probe, and further from the surface of the member to be joined to the tip of the probe (hereinafter sometimes referred to as process (4.1B)), The process involves the accumulation of the plastic material at the tip of the probe due to its flow, which increases the internal pressure at that point, causing the oxide film on the surface of the member located at the interface of the joined members to begin to peel off (hereinafter sometimes referred to as process (4.2B)), As the internal pressure increases, plastic flow is induced at the interface from the bottom upward, and the peeling of the oxide film progresses (hereinafter sometimes referred to as process (4.3B)), The process involves the removal of the oxide film and its upward extrusion by plastic flow, causing the newly formed surfaces of both joined members to come into contact (hereinafter sometimes referred to as process (4.4B)), Maintaining this state further increases the contact area between the newly formed surfaces, and the process of growing the contact area between the newly formed surfaces from the tip of the probe part to the upper part of the interface (hereinafter sometimes referred to as process (4.5B)). The rotating tool and receiving member used in the third embodiment may be the same as those in the first embodiment.

[0109] This embodiment is particularly effective when the second member has a higher melting point than the first member. In such cases, the joint strength and its stability become more significant problems in the conventional art, but such problems do not occur in this embodiment.

[0110] In this embodiment, if the second member has a melting point higher than the first member, the first and second members cannot simultaneously achieve a plastic state in the same temperature range. Therefore, in this embodiment, joining is performed by a joining mechanism that combines mechanical clinch joining and diffusion joining.

[0111] In this embodiment, the joint portion of the second member is pre-formed with a recess-corresponding shape 61 that follows the recess of the receiving member, as shown in Figure 14. The joint portion of the second member is the part of the second member that is joined (or connected) to the first member (or the part that is planned to be joined (or connected) to the first member), and is a part that is predetermined during friction crimping. The recess-corresponding shape that follows the recess of the receiving member is a shape in which the joint portion of the second member (or the area including the joint portion) is deformed along the inner surface of the recess of the receiving member. Conventionally, the second member has an overall plate-like shape, but in this embodiment, the joint portion of the second member is pre-formed with a recess-corresponding shape that follows the recess of the receiving member. As a result, immediately before the start of friction crimping, the joint portion of the second member may be in a fitted state with the recess of the receiving member. When the joint portion of the second member and the recess of the receiving member are in a fitted state, it means that the lower surface of the joint portion of the second member and the inner surface of the recess of the receiving member are in good contact with each other immediately before the start of friction crimping. In this embodiment, the fitting state does not require a strictly gap-free fit; for example, a gap of 1 mm or less may be permitted. The dimension of the gap may be the dimension in the normal direction from the inner surface of the receiving member. The normal direction is the direction parallel to the direction perpendicular to the tangential direction of the inner surface of the receiving member. The portion of the joint of the second member that has a shape corresponding to the recess along the recess of the receiving member may hereinafter be referred to as the "concave joint." Figure 14 shows a schematic cross-sectional view of the vicinity of the concave joint in an example of the second member in the third embodiment.

[0112] As shown in Figure 14, the concave joint portion 61 of the second member 60 is composed of a side portion 611 and a bottom portion 612. The second member 60 is joined by being gripped by a rotary tool and a lower support so that the concave joint portion 61 is fitted into the recess of a receiving member attached to the processing machine.

[0113] From the viewpoint of further improving the joint strength and stability, it is preferable that the upper surface 6110 of the side portion 611 has a curved shape in cross-sectional view that corresponds to the curved shape of the side portion 120 of the probe portion 12. More specifically, it is preferable that the curved shape of the side portion 611 (particularly its upper surface 6110) corresponds to the curved shape of the side portion 120 of the probe portion 12, for example, it is preferable that it is a convex curved shape toward the central axis C3 of the concave joint portion 61 of the second member 60. More specifically, the curved shape of the side portion 611 (particularly its upper surface 6110) may have a specific curvature that matches (or differs from) the specific curvature of the curved shape of the side portion 120 of the probe portion 12, or it may have a curvature that takes into account the specific curvature of the curved shape of the side portion 120 of the probe portion 12 and the thickness of the first member. The radius of curvature R62 (see Figure 15) of the curved shape of the side portion 611 (especially its upper surface 6110) is usually about the same as, or smaller than, the radius of curvature R3 (see Figure 2) of the curved shape of the side portion 120 of the probe portion 12. Specifically, the radius of curvature R62 (see Figure 15) of the curved shape of the side portion 611 (especially its upper surface 6110) may be 2 to 8 mm, particularly 4 to 6 mm. The curved shape of the upper surface 6110 may have a constant (or single) curvature, or it may have a continuously changing curvature. If the curvature of the upper surface 6110 changes continuously, the radius of curvature R62 may change within the above range. Figure 15 shows a schematic cross-sectional view to illustrate the dimensions near the joint in the second member of Figure 14.

[0114] The concave joint 61 has a bottom 612 with a diameter R61 that is larger than the tip diameter of the tip portion 122 of the probe portion 12 of the rotary tool 1. Specifically, the diameter R61 of the bottom (or bottom surface) 612 of the concave joint 61 (see Figure 15) may be R1+1 to R1+6 mm, and especially R1+2 to R1+4 mm, when the tip diameter of the probe is R1 (mm).

[0115] The depth D61+D62 (see Figure 15) of the concave joint 61 is not particularly limited, and the depth D61+D62 may be specifically 2 to 10 mm, and especially 4 to 6 mm.

[0116] In Figure 14, the bottom 612 of the concave joint 61 has a curved surface shape that is convex downwards in accordance with the concave shape of the receiving member 2', which will be described later. However, it is not limited to this, and for example, it may have a concave or convex shape in the center, or it may be cylindrical, conical, or frustoconical in shape. Furthermore, the bottom 612 may be closed or open (through hole). It may also have a planar shape in accordance with the concave shape of the receiving member.

[0117] In this embodiment, the receiving member may be the same as the receiving member in the first embodiment, or a receiving member 2' having a curved shape with a bottom (or bottom surface) 21' that is convex downwards may be used, as shown in Figures 16 and 17. Note that the receiving member 2' in Figure 16 is the same as the receiving member 2 in Figure 3, except that the bottom (or bottom surface) 21' has a curved shape with a convex downwards. Figure 16 shows a schematic view showing the vicinity of a recess in an example of a receiving member that is preferably used in the third embodiment. Figure 17 shows a schematic view to explain the dimensions of the vicinity of the recess in the receiving member of Figure 16. By using such a receiving member 2', the same effects as in the first embodiment can be obtained, and it is possible to promote the removal of the oxide film at the interface.

[0118] The friction crimping joining method of the third embodiment is the same as the joining method of the second embodiment, except that the second member 60 described above is used and other details are noted below. Furthermore, the "quality assurance method" and "modifications 1-1 to 1-6" of the first embodiment are also valid in the third embodiment and can be applied to the third embodiment.

[0119] The joining method of this embodiment is, in detail, similar to steps (1) to (5) of the second embodiment, but in step (4), steps (4.1B) to (4.5B) are performed. More specifically, in steps (1) to (4), as shown in Figures 18(A) to (C), the first member 5 and the second member 60 are overlapped between the rotating tool 1 and the receiving member 2', pressure is applied to the second member by pressing from the first member 5 side by the rotating tool 1, and frictional heat is applied to the first member 5 and the second member 60 by the rotation of the rotating tool 1. Figures 18(A) to (C) are schematic cross-sectional views of the joining device showing the state during joining to explain the mechanism by which sufficient joining strength is stably obtained in this embodiment, and schematic cross-sectional views sequentially showing the change over time of the cross section of the joint in the joining method using the joining device.

[0120] In this embodiment, more specifically, in step (1), the second member 60 is gripped together with the first member 5 by the rotating tool and the receiving member 2' so that the concave joint portion 61 of the second member 60 fits into the recess of the receiving member 2' attached to the processing machine.

[0121] Next, in steps (2) and (3), the rotary tool 1 is rotated while pressure is applied to the first member 5, generating frictional heat and deforming the softened first member 5 to conform to the concave joint portion 61 of the second member 60 (Figures 18(A) and (B)). At this time, the first member 5 is deformed so that it can be bent without breaking the material due to the curved shape provided on the side surface 120 of the probe portion 12 of the rotary tool 1, and is pressed into the concave joint portion 61 of the second member 60.

[0122] In step (4), significant flow occurs in the first member 5 and the second member 60, which is thought to contribute to improving the joint strength and its stability. Specifically, in step (4), steps (4.1B) to (4.5B) are usually performed. More specifically, as the joining process progresses, the amount of heat generated by the rotation of the rotary tool 1 increases further, the softening state of the first member 5 progresses, and it transitions to a plastic state (Figure 18(C)). At this time, the material that has transitioned to a plastic state undergoes plastic flow on the surface of the first member from the outermost part in contact with the probe part 12 toward the center, and further from the top toward the bottom of the tip of the probe part, due to the action of the spiral groove engraved on the side surface of the probe part (step (4.1B)). The material in the plastic state accumulates at the tip of the probe part due to its flow, increasing the internal pressure at that point, and the oxide film on the surface of the member located at the interface of the joined members begins to peel off (step (4.2B)). Furthermore, the pressure and thermal expansion force of the material of the first member 5 that is filled into the concave joint 61 of the second member 60 are sufficiently maintained between the side surface 611 of the concave joint 61 of the second member 60 and the side surface 120 of the probe part of the rotary tool 1. As a result, the internal pressure increases, and the force pressing the plastic material against the helical groove engraved on the side surface of the probe part increases, promoting plastic flow. As the internal pressure increases, plastic flow is induced at the interface from the bottom upward, and the peeling of the oxide film progresses further (step (4.3B)). As the oxide film is peeled off and pushed upward by the plastic flow, the newly formed surfaces of both joined members come into contact (hereinafter, step (4.4B)). By maintaining this state, the contact area between the newly formed surfaces increases further, and the contact area between the newly formed surfaces grows from the tip of the probe part to the upper part of the interface (hereinafter, this may be called step (4.5B)).

[0123] In this embodiment as well, the pressing force, joining time, and rotation speed are appropriately determined according to various conditions such as the thickness and material type of the first and second members, and may be selected from the same range as the pressing force, joining time, and rotation speed in the second embodiment.

[0124] An example of machining operation control in this embodiment is shown below. First, operate the rotary tool to the set rotation speed at the start of machining.

[0125] Next, upon reaching the set rotational speed, the gun shaft pressurizing operation is started, bringing the rotating tool 1 and the receiving member 2' closer together and pressurizing the first and second members. At this time, if the first member is a thin plate (for example, with a thickness of 1.5 mm or less), the deformation resistance is small and it is possible to easily form it into a crimped shape, so the pressurizing force and rotational speed may be single conditions. On the other hand, if the first member is a thick plate (for example, with a thickness of more than 1.5 mm), the deformation resistance is large and it takes time to obtain the crimped shape (filling the concave joint portion 61 of the second member 60), so multi-stage conditions may be used, and the initial pressurizing force and rotational speed settings may be changed to increase, and the softening and forming may be accelerated by increasing the amount of heat generated and the pressing pressure.

[0126] As the rotating tool 1 sinks under pressure, the first member 5 deforms (Figure 18(A)), and the joint of the first member is completely filled into the concave joint 61 of the second member 60, forming a crimped portion (Figure 18(B)). When the member to be joined is filled into the concave joint 61 of the second member 60, the sinking speed of the rotating tool decreases rapidly, and plastic flow is promoted by the action of the groove on the side surface 120 of the probe portion 12, increasing the agitation volume. At this time, the plastic material filled into the concave joint 61 expands due to the frictional heat of the probe portion, and this expansion force acts as an even stronger force pressing the member to be joined into the groove on the side surface of the probe portion 12. As a result, the flow pressure in the concave joint 61 of the second member 60 increases, the flow changes to an upward direction from the bottom, and the agitation volume increases rapidly (Figure 18(C)). This stirring and upward plastic flow causes the oxide film present at the interface between the first member 5 and the second member 60 to peel off and be discharged, resulting in homogeneous contact between the newly formed surfaces of both members. Here, the pressing force against the groove is important for plastic flow; if the rotation speed is too high, the material will move before it can be pressed against the groove, causing the material to slip and reducing the flow. In other words, in the case of thick plates, if the rotation speed used at the start of joining is used, the material will slip and the flow volume will not increase, nor will the stirring volume increase. Therefore, when joining thick plates, the rotation speed may be changed to decrease midway through the process to control the joining under conditions where sufficient pressing force is applied to the groove.

[0127] The joining process is completed after the set joining time has elapsed, and the rotary tool 1 and the receiving member 20 are separated from the members to be joined (the first and second members) and released. The release operation may be a one-stage release operation or a two-stage release operation. A one-stage release operation is the operation of releasing the rotary tool 1 and the receiving member 2 directly from the crimping position to a position where they are completely separated. A two-stage release operation is the operation of releasing the rotary tool 1 and the receiving member 2 while maintaining the crimping position, after bringing them into contact with the machined surface with virtually no load, to a position where they are completely separated. The two-stage release operation prevents friction of the crimped portion caused by deformation due to the deflection of the gun arm and the rotary tool pressure shaft, and also allows for a smoother surface finish by stopping at the position where the applied load has been removed and machining the surface of the crimped portion with the force based on the rotational movement of the pivot axis in a virtually no-load state. Therefore, it is preferable to set the pivot axis rotation speed at the time of release to the high-speed rotation side in order to smooth the surface finish of the crimped portion. During the first stage release operation, it is preferable to use a rotation speed that does not cause scratches or burrs when the rotating tool is removed from the joined member.

[0128] (Variation 2-1) The second member 60 (especially its concave joint portion 61) requires adjustment of the width and depth of the concave joint portion 61 and the curvature of its side surface depending on the thickness of the members to be joined. For example, as the plate thickness increases, the amount of material filled into the concave joint portion 61 increases, and as the plate thickness decreases, the amount of material decreases. In this case, when joining thick plates, if a second member 60 with insufficient volume for the concave joint portion 61 is used, the concave joint portion 61 will be filled with material in the initial stages of joining, the tip position of the probe portion entering the concave joint portion 61 will be shallow, sufficient peeling and discharge of the oxide film will not occur, and stable joint strength cannot be obtained. On the other hand, when joining thin plates, if a second member 60 with a large width and depth for the concave joint portion 61 is used, the softened material cannot be gripped between the curved shape of the probe portion's side surface and the curved shape of the second member 60's side surface 611 during joining, the softened material will break due to rotational vibration, and a good joint cannot be formed. Therefore, it is important to use a second member 60 having a concave joint portion 61 of an appropriate shape (especially dimensions) depending on the plate thickness and plate assembly of the members to be joined.

[0129] For example, Figure 19(A) shows a schematic cross-sectional view of a joining device used to join a first member 5 and a second member 60 of a specific thickness between a receiving member 2' having a specific recess 20' and a rotary tool 1. Using the joining device shown in Figure 19(A) as a reference, for example, when joining a first member 5A and a second member 60A of greater thickness, a second member 60A having a larger concave joint 61A and a receiving member 2A' having a larger recess 20A' are used, as shown in Figure 19(B). Also, for example, when joining a first member 5B and a second member 60B of smaller thickness, a second member 60B having a smaller concave joint 61B and a receiving member 2B' having a smaller recess 20B' are used, as shown in Figure 19(C). Figures 19(A) to (C) show schematic cross-sectional views of a joining device to illustrate a modified example 2-1 in the third embodiment.

[0130] (Variation 2-2) As shown in Modification 2-1, the need to use different shapes (especially dimensions) for the concave joint portion 61 of the second member 60 and the recess 20' of the receiving member 2' depending on the plate thickness and plate assembly necessitates switching between the second member 60 and the receiving member 2' (especially the receiving member 2'). However, since only one receiving member can be attached to the processing machine, only one type of plate thickness and plate assembly can be joined, and joining other plate thicknesses and plate assemblies requires the use of a different processing machine equipped with a different receiving member. Therefore, the reduction in production efficiency due to switching between multiple processing machines and the increase in equipment costs are challenges in applying the joining device and joining method according to this embodiment.

[0131] Therefore, when using two or more types of support members, the support member for the plate thickness and plate assembly with the largest processing volume in a particular manufacturing process is attached to the processing machine, and for the joints of other plate thicknesses and plate assemblies, support members with shapes suitable for each plate thickness and plate assembly are placed below each joint in a manner that allows them to move up and down. By gripping each member to be joined with the support member attached to the processing machine and performing the joining, it becomes possible to join using the support member with the most suitable shape for that part.

[0132] For example, Figure 20(A) shows a schematic cross-sectional view of a joining device used to join a first member 5 and a second member 60 of a specific thickness between a receiving member 2' having a specific recess and a rotary tool 1. Using the joining device shown in Figure 20(A) as a reference, for example, when using a receiving member 2A' with a larger recess to join a first member 5A and a second member 60A of a larger thickness, the receiving member 2A' is lifted using the originally used receiving member 2'. Then, as shown in Figure 20(B), the receiving member 2A' grips the members to be joined and the joining is performed. Similarly, when using a receiving member 2B' with a smaller recess to join a first member 5B and a second member 60B of a smaller thickness, the receiving member 2B' is lifted using the originally used receiving member 2', and as shown in Figure 20(C), the receiving member 2B' grips the members to be joined and the joining is performed. In other words, by positioning a receiving member with an optimal shape for each part in the jig so that it can move up and down, it becomes possible to achieve good joining even at joints of different plate thicknesses and plate assemblies. Figures 20(A) to (C) show schematic cross-sectional views of the joining device to illustrate modified example 2-2 of the third embodiment.

[0133] (Variations 2-3) In this embodiment as well, an eco-releasing mechanism or a lifting mechanism 8 may be provided, similar to the modification 1-3 of the first embodiment. Specifically, as shown in Figure 21, by providing an eco-releasing mechanism or a lifting mechanism 8 on either one of the joint portions formed in the galling direction, it becomes possible to separate the receiving member 2B' from the joined member after joining, thereby preventing galling from occurring. Figure 21 shows a schematic cross-sectional view of a joining device for explaining modification 2-3 in the third embodiment.

[0134] The present invention encompasses the following preferred embodiments. <1> A friction crimping tool comprising a rotary tool and a receiving member positioned opposite the rotary tool, The rotary tool has a shoulder portion that forms its base end, and a probe portion that is provided on the tip surface of the shoulder portion and has a tapered shape that becomes smaller in diameter towards the tip. The probe portion has a curved shape on its side surface when viewed in cross-section. The receiving member is a friction crimping tool having a recess with a bottom diameter larger than the tip diameter of the probe portion of the rotary tool. <2> The curved shape on the side of the probe portion is, in cross-sectional view, a concave curved shape that sinks toward the central axis of the rotating tool. <1> The friction crimping joining tool described above. <3> The aforementioned curved surface shape has a specific curvature, which is either a constant curvature or a continuously changing curvature. <1> or <2> The friction crimping joining tool described above. <4> The probe portion is integrated with the shoulder portion. <1> ~ <3> A friction crimping tool described in any of the following. <5> The probe portion has a helical groove on its side surface. <1> ~ <4> A friction crimping tool described in any of the following. <6> The rotary tool is used by rotating it in the opposite direction to the screwing direction of the groove. <5> The friction crimping joining tool described above. <7> The tip shape of the probe portion is spherical or conical. <1> ~ <6> A friction crimping tool described in any of the following. <8> The recess of the receiving member has, in cross-sectional view, a curved shape on its side corresponding to the curved shape of the side of the probe portion. <1> ~ <7> A friction crimping tool described in any of the following. <9> The curved surface shape of the recess of the receiving member on its side is, in cross-sectional view, a curved surface shape that is convex toward the central axis of the recess. <8> The friction crimping joining tool described above. <10> <1> ~ <9> A friction crimping joining method, which involves performing friction crimping using a friction crimping joining tool described in any of the above. <11> The aforementioned friction crimping joining method is a method for joining a first member positioned higher and a second member positioned lower. As the second member, a member is used that has a melting point higher than that of the first member, and has a shape corresponding to the recess along the recess of the receiving member that is pre-formed at the joint. <10> The friction crimping joining method described above. <12> The receiving member is separated from the second member by an eco-rise mechanism and / or a lifting mechanism. <10> or <11> The friction crimping joining method described above. [Examples]

[0135] <Experimental Example A (First and Second Embodiments)> (Example A1) [First member and second member] As the first and second components, flat plate-shaped members made of 6000 series aluminum alloy (100 mm long x 30 mm wide x 1.0 mm thick) were used.

[0136] [Rotate Tool] The rotary tool 1 (made of tool steel) shown in Figure 2 was used. Its dimensions and shape are as follows. Probe tip diameter R1 = 4.0 mm; Probe tip shape = Machined to a roughly flat shape (corners chamfered); Probe side curvature R3 = 5.0 mm (single curvature);

[0137] [Support member] The receiving member 2' (made of tool steel) shown in Figures 16 and 17 was used. Its dimensions and shape are as follows. Bottom diameter R11 in recess 20 = 6.0 mm; Bottom shape of recess 20 = gently concave spherical shape; The lateral curvature R12 in the recess 20 is 3.0 mm (single curvature);

[0138] [Manufacturing of bonded parts] (Pressure control method) First, the first and second components were placed on top of each other. Next, as shown in Figure 5(A), the rotary tool 1 was pressed onto the first member 5 and the second member 6 with a pressing force of 4.90 kN, a rotational speed of 1500 rpm, and a joining time of 0.6 to 1.5 seconds, resulting in a joined body obtained by sequentially going through the states shown in Figures 5(B) and 5(C). The joint strength between the first and second members in the resulting joint was measured using the AGX-100kNVD autograph manufactured by Shimadzu Corporation.

[0139] (evaluation) In all of the joints, no fracture of the first member (or fracture at the interface between the first and second members) occurred, demonstrating that joints with sufficient joint strength can be stably obtained using the rotating tool and receiving member of the present invention. These results are shown in Figure 22. Figure 22 is a graph showing the relationship between the joint strength and bonding time of the joints produced in the example of Experimental Example A. In particular, it was found that uniform strength characteristics without variation can be obtained by setting the bonding time to 1.0 to 1.5 seconds.

[0140] <Experimental Example B (First and Second Embodiments)> [First component] As the first component, a flat plate-shaped member made of 6000 series aluminum alloy (100 mm long x 30 mm wide x 2.0 mm thick) was used.

[0141] (Example B1) A jointed body was obtained in the same manner as in Example A1, except that the first member described above was used, the pressing force was set to 5.88 kN, the joining time was set to 1.5 to 2.0 seconds, and the rotation speed was initially set to 2500 rpm and then changed to 1000 rpm. The joint strength between the first and second members in the resulting joint was measured using the Shimadzu Autograph "AGX-100kNVD" as in Example A1.

[0142] (evaluation) In all of the joints, no fracture of the first member (or fracture at the interface between the first and second members) occurred, demonstrating that joints with sufficient joint strength can be stably obtained using the rotating tool and receiving member of the present invention. These results are shown in Figure 23. Figure 23 is a graph showing the relationship between the joint strength and the bonding time of the joints produced in the example of Experimental Example B. In particular, it was found that uniform strength characteristics without variation can be obtained by setting the bonding time to 1.5 to 2.0 seconds.

[0143] <Experimental Example C (Third Embodiment)> [First component] As the first component, a flat plate-shaped member made of 6000 series aluminum alloy (100 mm long x 30 mm wide x 2.0 mm thick) was used. [Second component] A 1.0 mm thick alloyed hot-dip galvanized steel sheet was given a recessed shape that matched the groove shape of the receiving member, and this was used as the second member (Figure 15).

[0144] (Example C1) A jointed body was obtained in the same manner as in Example A1, except that the first and second members described above were used, the recessed shape of the second member was fitted into the groove of the receiving member when the first and second members were overlapped, the pressing force was set to 4.90 kN, the joining time was set to 1.4 to 2.0 seconds, and the rotation speed was initially set to 2500 rpm and then changed to 1000 rpm. The joint strength between the first and second members in the resulting joint was measured using the Shimadzu Autograph "AGX-100kNVD" as in Example A1.

[0145] (evaluation) In all of the joints, no fracture of the first member (or fracture at the interface between the first and second members) occurred, demonstrating that joints with sufficient joint strength can be stably obtained using the rotating tool and receiving member of the present invention. These results are shown in Figure 24. Figure 24 is a graph showing the joint strength of the joints produced in the example of Experimental Example C. The following matters have become clear. Compared to the joints obtained in Examples A and B, the joint obtained in Example C shows slightly greater variation in joint strength, but still achieves sufficient joint strength. • By further extending the bonding time, the variability is expected to converge. [Industrial applicability]

[0146] The rotary tool, joining device, and joining method according to the present invention are useful for joining (especially joining metal members) in fields such as automobiles, railway vehicles, aircraft, and home appliances.

Claims

1. A friction crimping tool comprising a rotating tool and a receiving member positioned opposite the rotating tool, The rotary tool has a shoulder portion that forms its base end, and a probe portion that is provided on the tip surface of the shoulder portion and has a tapered shape that becomes smaller in diameter towards the tip. The probe portion has a curved shape on its side surface when viewed in cross-section. The receiving member is a friction crimping tool having a recess with a bottom diameter larger than the tip diameter of the probe portion of the rotary tool.

2. The friction crimping tool according to claim 1, wherein the curved surface shape on the side of the probe portion is a concave curved surface shape that sinks toward the central axis of the rotating tool in a cross-sectional view.

3. The friction crimping joining tool according to claim 1, wherein the curved surface shape has a specific curvature, and the specific curvature is either a constant curvature or a continuously changing curvature.

4. The friction crimping tool according to claim 1, wherein the probe portion is integrated with the shoulder portion.

5. The friction crimping tool according to claim 1, wherein the probe portion has a helical groove on its side surface.

6. The friction crimping joining tool according to claim 5, wherein the rotating tool is used by rotating it in the opposite direction to the screwing direction of the groove.

7. The friction crimping tool according to claim 1, wherein the tip shape of the probe portion is spherical or conical.

8. The friction crimping joining tool according to claim 1, wherein the recess of the receiving member has, in cross-sectional view, a curved shape on its side corresponding to the curved shape of the side of the probe portion.

9. The friction crimping joining tool according to claim 8, wherein the curved surface shape of the recess of the receiving member on its side surface is a convex curved surface shape toward the central axis of the recess in a cross-sectional view.

10. A method for friction crimping, comprising performing friction crimping using a friction crimping tool described in any one of claims 1 to 9.

11. The aforementioned friction crimping joining method is a method for joining a first member positioned higher and a second member positioned lower. The friction crimping joining method according to claim 10, wherein the second member has a melting point higher than the melting point of the first member, and the joint portion is pre-formed with a shape corresponding to the recess along the recess of the receiving member.

12. The friction crimping joining method according to claim 10, wherein the receiving member is separated from the second member by an eco-rise mechanism and / or a lifting mechanism.

Images