Joining method, joining system, and joining program

Abstract

To enhance the joining quality of workpieces while suppressing a wobble of the arm of an arm robot when friction stir joining workpieces having an inflection point.SOLUTION: In a joining method according to the present invention, an expected movement route is set for a workpiece 130 so that a height position changes when viewed in a side cross section, and a joining step is provided in which a rotary tool is inserted into the workpiece 130 and moved along a predetermined joining trajectory 170 to perform friction stir joining on the workpiece 130, and the joining trajectory 170 is provided with retreat sections 171, 172 in a direction intersecting with the expected movement route before, after an inflection point 133, or at the inflection point 133 on a surface of the workpiece 130 existing on the expected movement route, and in the joining step, an angle of the rotary tool relative to the workpiece 130 is changed to match an angle of the workpiece 130 while moving the rotary tool in the retreat sections 171, 172 in a direction intersecting with a joining direction of the workpiece 130.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a bonding method, a bonding system, and a bonding program. [Background technology]

[0002] A technique for machining a workpiece using a tool held by an arm robot is known. Typically, machining quality can be improved by maintaining a constant tool movement speed and angle relative to the workpiece.

[0003] When machining a workpiece using a tool held by an arm robot while maintaining a constant tool movement speed and tool angle, and when welding is performed by passing through a continuous welding trajectory in which straight sections change angle across a corner, the following problem occurs. That is, at the inflection point between the straight sections sandwiching the corner, the tool angle, which was kept constant in the straight sections, changes at the inflection point. This sudden change in the tool angular velocity at the inflection point causes the tool angular acceleration to become extremely large. More specifically, the sudden change in the tool angular velocity over a short time period when passing through the inflection point causes the angular acceleration to reach a maximum value. This causes the arm of the arm robot to shake at the inflection point, leading to a decrease in the machining quality of the workpiece.

[0004] In contrast, the technology of Patent Document 1 attempts to suppress sudden fluctuations in the angular velocity of the tool at the inflection point of the workpiece by slowing down the tool feed rate to approach zero at the inflection point (see particularly paragraph 0005 of the same document). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 7-152417 Summary of the Invention [Problem to be solved by the invention]

[0006] When friction stir welding workpieces using a rotating tool held by an arm robot, there is a problem that the arm of the arm robot may shake at the inflection point, leading to a decrease in the quality of the joint between the workpieces. In this case, if the feed speed of the rotating tool is reduced to almost zero at the inflection point, as in the technology disclosed in Patent Document 1, the effect (heat input) of the rotating tool on the workpieces at the inflection point increases, resulting in a problem of a decrease in the quality of the joint between the workpieces at the inflection point.

[0007] From this perspective, the present invention aims to provide a joining method, joining system, and joining program that can improve the joining quality of workpieces while suppressing arm vibration of an arm robot when friction stir welding workpieces that have inflection points. [Means for solving the problem]

[0008] (1) A joining method for performing friction stir welding of a workpiece along an assumed movement route using a rotating tool held by an arm robot, the assumed movement route being set so that the height position of the workpiece varies in a side cross-sectional view, the method comprising: a joining step of inserting the rotating tool into the workpiece and moving the rotating tool along a predetermined joining trajectory to perform the friction stir welding of the workpiece; the joining trajectory having a retraction section in a direction intersecting with the assumed movement route before, after, or at an inflection point on the surface of the workpiece that is present on the assumed movement route; the inflection point being a point at which angular acceleration of the rotating tool occurs as the rotating tool passes through the inflection point when welding is performed while maintaining a constant movement speed of the tip of the rotating tool, where the tip of the rotating tool contacts the workpiece, and maintaining an angle of the rotating tool relative to the workpiece; and the joining step comprising: moving the rotating tool in the retraction section in a direction intersecting with the joining direction of the workpiece, while changing the angle of the rotating tool relative to the workpiece in accordance with the angle of the workpiece.

[0009] (2) The joining method of (1), characterized in that, in a side cross-sectional view, the workpiece has a series of straight and curved sections along the expected movement route, with the inflection point sandwiched between them, and the joining trajectory has an evacuation section provided in a direction that intersects with the expected movement route of the workpiece in a plan view, passing through the straight and curved sections, before and after or at the inflection point between the straight and curved sections. (3) The joining method described in (1) is characterized in that, in a side cross-sectional view, the workpiece has a series of straight line sections along the expected movement route, with the angle changing around a corner that is the inflection point, and the joining trajectory has an evacuation section in a direction that intersects with the expected movement route in a planar view of the workpiece passing through the straight line section that sandwiches the corner, before and after or at the inflection point between the straight line section that sandwiches the corner and the corner. (4) The joining method described in (1) is characterized in that, in a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous along the expected movement route, with the inflection point in between, and the first curved section and the second curved section have different center points, and the joining trajectory has an evacuation section in a direction that intersects with the expected movement route of the workpiece in a planar view that passes through the first curved section and the second curved section before, after, or at the inflection point between the first curved section and the second curved section. (5) The joining method described in (1) is characterized in that, in a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous along the expected movement route, with the inflection point in between, and the first curved section and the second curved section have different curvatures, and the joining trajectory has an evacuation section provided in a direction that intersects with the expected movement route of the workpiece in a planar view that passes through the first curved section and the second curved section, before or after or at the inflection point between the first curved section and the second curved section. (6) The joining method described in (1) is characterized in that, in a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous along the expected movement route, with the inflection point in between, and the first curved section and the second curved section have different directions of concavity and convexity, and the joining trajectory has an evacuation section in a direction that intersects with the expected movement route of the workpiece in a planar view that passes through the first curved section and the second curved section, before or after or at the inflection point between the first curved section and the second curved section. (7) The joining method described in (1) is characterized in that, in a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous along the expected movement route, with the inflection point in between, and at one end of each of the continuous first and second curved sections, the angle between the tangent to the one end of the first curved section and the tangent to the one end of the second curved section is less than 180° or greater than 180°, and the joining trajectory has an evacuation section in a direction that intersects with the expected movement route of the workpiece in a plan view that passes through the first curved section and the second curved section before, after, or at the inflection point between the first curved section and the second curved section.

[0010] (8) The joining method according to (1), characterized in that in the joining process, the joining trajectory is a continuous curved section with a convex R and a curved section with a concave R on either side of the inflection point. (9) The welding method according to (1), wherein in the welding step, the time required for the rotary tool to pass through the retreat section is set to 1 second or more and 10 seconds or less. (10) The joining method according to (1), characterized in that in the joining step, the length of the evacuation section in a direction intersecting with the expected movement route is set to 1 mm or more and 100 mm or less. (11) The joining method according to (1), characterized in that in the joining step, the length of the retreat section in a direction parallel to the expected movement route is set to be greater than 0 and equal to or less than 10 mm. (12) The joining method according to (1), wherein in the joining step, the retreat section includes a curve in a plan view. (13) The joining method according to (1), characterized in that in the joining process, the plasticized region formed when the rotating tool moves through the retreat section is made to overlap on the expected movement route. (14) The joining method described in (1), characterized in that in the joining process, the length of the retreat section in a direction parallel to the expected movement route is set to be smaller than twice the radius of the rotating tool inserted into the workpiece at the position of the workpiece surface. (15) The welding method according to (1), wherein the moving speed of the rotary tool is constant in the welding step. (16) The joining method according to (1), characterized in that in the joining process, the angle of the axial direction of the rotary tool with respect to the surface of the workpiece is 80° or more and 100° or less. (17) The joining method according to (1), characterized in that the rotary tool has a base end pin and a tip end pin, the taper angle of the base end pin is larger than the taper angle of the tip end pin, and a stepped pin step portion is formed on the outer peripheral surface of the base end pin, and in the joining process, while maintaining a predetermined target angle of the rotary tool, friction stir welding is performed along the joining trajectory having the retraction section while pressing the plastic flow material at the step bottom surface of the pin step portion. (18) The welding method described in (1), characterized in that in the welding process, the ratio of the time required for the rotary tool to pass through the evacuation section to the time required for the rotary tool to pass through the section corresponding to the evacuation section of the expected movement route if the evacuation section is not provided is 3 or more.

[0011] (19) A joining system comprising an arm robot capable of controlling the movement of an arm and a rotary tool held by the arm, the system performing friction stir welding of a workpiece along an assumed movement route by the rotary tool driven by the arm robot, wherein the assumed movement route of the workpiece is set so that the height position of the workpiece changes in a side cross-sectional view, and the system comprises a joining section that inserts the rotary tool into the workpiece and moves the rotary tool along a predetermined joining trajectory to perform the friction stir welding of the workpiece, the joining trajectory occurring before, after or at an inflection point on the surface of the workpiece present on the assumed movement route. and an evacuation section is provided in a direction intersecting the expected movement route, and the inflection point is a point at which angular acceleration of the rotary tool occurs when the rotary tool passes through the inflection point when welding is performed while maintaining a constant movement speed of the tip of the rotary tool, where the tip of the rotary tool contacts the workpieces, and while maintaining the angle of the rotary tool relative to the workpieces, and in the welding process, the angle of the rotary tool relative to the workpieces is changed in accordance with the angle of the workpieces while moving the rotary tool in the evacuation section in a direction intersecting the welding direction of the workpieces.

[0012] (20) A joining program that causes a computer to execute the following steps: control a system including an arm robot capable of controlling arm movement and a rotary tool held by the arm, and perform friction stir welding of a workpiece along an assumed movement route by the rotary tool driven by the arm robot; the assumed movement route is set so that the height position of the workpiece changes in a side cross-sectional view; and the program causes a computer to execute a joining process in which the rotary tool is inserted into the workpiece and moved along a predetermined joining trajectory to perform the friction stir welding of the workpiece; and the joining trajectory is a trajectory that is determined by a surface of the workpiece present on the assumed movement route. a retreat section is provided before and after the inflection point or at the inflection point in a direction intersecting with the expected movement route, the inflection point being a point at which angular acceleration of the rotary tool occurs as the rotary tool passes through the inflection point when welding is performed while maintaining a constant movement speed of the tip of the rotary tool, whose tip contacts the workpieces, and while maintaining the angle of the rotary tool relative to the workpieces, and in the welding process, the angle of the rotary tool relative to the workpieces is changed in accordance with the angle of the workpieces while moving the rotary tool in the retreat section in a direction intersecting with the welding direction of the workpieces. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a joining method, joining system, and joining program that can improve the joining quality of workpieces while suppressing arm vibration of an arm robot when friction stir welding workpieces having an inflection point. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 2 is a front view of the rotary tool according to the embodiment. [Figure 2] FIG. 2 is an enlarged cross-sectional view of the rotary tool according to the embodiment. [Figure 3] 1 is a perspective view showing the appearance of an entire joining system according to an embodiment. [Figure 4]FIG. 1 is a perspective view showing a state in which friction stir welding is performed by a welding system according to an embodiment. [Figure 5] FIG. 2 is a block diagram showing electrical connections of the control device according to the embodiment. [Figure 6] 1A is a plan view illustrating a workpiece and an expected movement route according to each embodiment, and FIG. 1B is a plan view illustrating a workpiece and a joining trajectory according to each embodiment. [Figure 7] FIG. 2 is a side view illustrating a workpiece, an assumed movement route, and a welding trajectory when friction stir welding is performed by the welding method according to the first embodiment. [Figure 8] FIG. 10 is a side view illustrating a workpiece, an assumed movement route, and a welding trajectory when friction stir welding is performed by a welding method according to a second embodiment. [Figure 9] FIG. 10 is a side view illustrating the workpiece, the expected movement route, and the welding trajectory when friction stir welding is performed by the welding method according to the third embodiment. [Figure 10] FIG. 10 is a side view illustrating a workpiece, an assumed movement route, and a welding trajectory when friction stir welding is performed by a welding method according to a fourth embodiment. [Figure 11] FIG. 13 is a side view illustrating a workpiece, an assumed movement route, and a welding trajectory when friction stir welding is performed by a welding method according to a fifth embodiment. [Figure 12] FIG. 13 is a side view illustrating a workpiece, an expected movement route, and a welding trajectory when friction stir welding is performed by a welding method according to a sixth embodiment. [Figure 13A] FIG. 10 is a perspective view showing, from one side, workpieces, an assumed movement route, and a welding trajectory when friction stir welding is performed by a welding method according to a first modified example of the first embodiment. [Figure 13B] FIG. 10 is a perspective view showing the workpieces, the expected movement route, and the welding trajectory from the other side when friction stir welding is performed by the welding method according to the first modified example of the first embodiment. [Figure 14]1A is a side view illustrating a workpiece according to a second modified example of the first embodiment, FIG. 1B is a plan view illustrating a workpiece according to the second modified example of the first embodiment and an expected movement route, and FIG. 1C is a plan view illustrating a workpiece according to the second modified example of the first embodiment and a joining trajectory. [Figure 15] 1A is a side view illustrating the workpieces of an example and a comparative example, FIG. 1B is a plan view illustrating the workpieces of the comparative example and the joining trajectory, and FIG. 1C is a plan view illustrating the workpieces of the example and the joining trajectory. [Figure 16] 10 is a photograph, substituted for a drawing, showing a plan view of a workpiece for explaining a comparative example. [Figure 17] FIG. 10 is a diagram showing experimental data illustrating a comparative example. [Figure 18] 1 is a photograph, substituted for a drawing, showing a plan view of a workpiece for explaining the present embodiment. [Figure 19] FIG. 1 shows experimental data illustrating the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] The following describes embodiments of the present invention with reference to the accompanying drawings. The present invention is not limited to the following embodiments. Furthermore, some or all of the components in the embodiments and modifications can be combined as appropriate. The drawings are schematic illustrations and do not necessarily correspond to actual lengths, widths, thicknesses, dimensional ratios, etc. First, the rotary tool used in the joining system according to this embodiment will be described.

[0016] [1. Rotation Tool] The rotary tool is a tool used in friction stir welding. As shown in Fig. 1, the rotary tool F is made of, for example, tool steel, and is mainly composed of a base shaft portion F1, a base end pin F2, and a tip end pin F3. The base shaft portion F1 is cylindrical and is connected to the main shaft of the arm of the arm robot. The base pin F2 is continuous with the base shaft portion F1 and tapers toward the tip. The base pin F2 has a truncated cone shape. The taper angle A of the base pin F2 may be set appropriately, but is, for example, 80 to 160°. The taper angle A is larger than the taper angle B of the tip pin F3. The distal pin F3 is formed continuous with the proximal pin F2. The distal pin F3 has a truncated cone shape. The tip of the distal pin F3 forms a flat surface F4 perpendicular to the rotation axis. The taper angle B of the distal pin F3 may be set as appropriate, but is, for example, 40 to 120°. The taper angle B of the distal pin F3 is smaller than the taper angle A of the proximal pin F2.

[0017] As shown in Fig. 2, a stepped pin step F21 is formed on the outer peripheral surface of the base-end pin F2 over the entire height direction. The pin step F21 is formed in a clockwise or counterclockwise spiral shape. That is, the pin step F21 is spiral in plan view and stepped in side view. The pin step F21 is composed of a step bottom surface F21a and a step side surface F21b.

[0018] When performing friction stir welding using the rotary tool F, the entire tip pin F3 is inserted into the workpiece, and only a portion of the base pin F2 is inserted. In other words, the insertion depth of the rotary tool F is set so that the middle position in the height direction of the base pin F2 is located on the surface of the workpiece. Furthermore, when performing welding, friction stir welding is performed while maintaining a predetermined target angle of the rotary tool F and pressing the plastic flow material with the step bottom surface F21a of the pin step portion F21.

[0019] When the rotary tool F is rotated clockwise, the pin step portion F21 is set to rotate counterclockwise from the base end to the tip end. When the rotary tool F is rotated counterclockwise, it is preferable to set the pin step portion F21 to rotate clockwise from the base end to the tip end. This allows the pin step portion F21 to guide the plastic flow material to the tip end, thereby reducing the amount of metal that overflows outside the metal members to be joined (workpieces). The distance X1 (horizontal distance) between the vertices F21c, F21c of adjacent pin step portions F21 is set appropriately according to the step angle C and the height Y1 of the step side surface F21b, which will be described later.

[0020] The height Y1 of the step side surface F21b may be set appropriately, for example, between 0.1 mm and 0.4 mm. If the height Y1 is less than 0.1 mm, the joining surface roughness increases. On the other hand, if the height Y1 exceeds 0.4 mm, the joining surface roughness tends to increase and the number of effective step portions (the number of pin step portions F21 in contact with the workpiece) also decreases.

[0021] The step angle C formed by the step bottom surface F21a and the step side surface F21b may be set appropriately, but is set, for example, to 85° or more and 120° or less. In this embodiment, the step bottom surface F21a is parallel to the horizontal plane. The step bottom surface F21a may be inclined from the rotation center axis Z of the rotary tool F toward the outer periphery within a range of -5° or more and 15° or less with respect to the horizontal plane (negative means downward relative to the horizontal plane, positive means upward relative to the horizontal plane). The distance X1, the height Y1 of the step side surface F21b, the step angle C, and the angle of the step bottom surface F21a with respect to the horizontal plane are set appropriately so that, during friction stir welding, the plastic flow material can escape to the outside without remaining inside the pin step portion F21 and adhering, and the step bottom surface F21a can press the plastic flow material to reduce the joining surface roughness.

[0022] As shown in Figure 2, a spiral groove F31 is engraved on the outer peripheral surface of the tip-side pin F3. The spiral groove F31 may be either clockwise or counterclockwise, but when the rotary tool F is rotated clockwise, it is set counterclockwise from the base end to the tip. When the rotary tool F is rotated counterclockwise, it is preferable to set the spiral groove F31 clockwise from the base end to the tip. This allows the plastic flow material to be guided to the tip by the spiral groove F31, thereby reducing the amount of metal spilling outside the workpiece.

[0023] The spiral groove F31 is composed of a spiral bottom surface F31a and a spiral side surface F31b. The distance (horizontal distance) between the apexes F31c, F31c of adjacent spiral grooves F31 is defined as length X2. The height of the spiral side surface F31b is defined as height Y2. The spiral angle formed by the spiral bottom surface F31a and the spiral side surface F31b is, for example, 45° or more and 90° or less. The spiral groove F31 has the role of increasing frictional heat by contacting the workpiece and guiding plastic flow material toward the tip end.

[0024] [2. Overview of the joining system] Next, a description will be given of a joint system 1 according to one embodiment of the present invention, as shown in Fig. 3. In the following description, the surface opposite to the "rear surface" will be referred to as the "front surface."

[0025] 3 and 4, the joining system 1 includes a fixing device 3, a friction stir welding device 4, and a control device 5. In the example of FIGS. 3 and 4, the joining system 1 is a system that friction stir welds together end portions of a first metal member 101 and a second metal member 102 (workpiece).

[0026] 3, the first metal member 101 and the second metal member 102 are plate-like members made of a metal capable of friction stirring, such as aluminum, an aluminum alloy, titanium, a titanium alloy, magnesium, a magnesium alloy, copper, or a copper alloy. The thickness of the second metal member 102 is substantially the same as the thickness of the first metal member 101. In this embodiment, the first metal member 101 and the second metal member 102 are made of, for example, an aluminum alloy.

[0027] As shown in FIG. 3, an end face of a first metal member 101 and an end face of a second metal member 102 are butted together to form a butt joint J1. The joining system 1 can perform friction stir welding using the butt joint J1 as a joining part. The joining system 1 can also perform friction stir welding on any other joining part. The first metal member 101 and the second metal member 102 are merely examples of workpieces that are targets of this embodiment. Characteristic details of the workpieces that are targets of this embodiment will be described later.

[0028] [2-1.Fixing device] The fixing device 3 is a device that fixes the first metal member 101 and the second metal member 102 and serves as a base for friction stir welding. As shown in FIGS. 3 and 4, the fixing device 3 includes a base 21 and a clamp unit 24. The mount 21 is a base on the upper surface of which the first metal member 101 and the second metal member 102 are arranged, and has an outer shape of, for example, a rectangular parallelepiped. A reference position Y0 perpendicular to the longitudinal ridge 21a of the mount 21 is set at the center of the upper surface of the mount 21. The reference position Y0 is a reference position for positioning the first metal member 101 and the second metal member 102. The first metal member 101 and the second metal member 102 are arranged to form a butt joint J1 at the reference position Y0. Here, the X direction, Y direction, and Z direction in the following description are based on the arrows shown in FIGS. 3 and 4. As shown in FIGS. 3 and 4, the X direction, Y direction, and Z direction are mutually orthogonal. The X direction is parallel to the reference position Y0 on the upper plane of the mount 21. The Y direction is perpendicular to the reference position Y0 on the upper plane of the mount 21. The Z direction is perpendicular to the upper plane of the mount 21.

[0029] As shown in FIGS. 3 and 4 , the clamp unit 24 is movably disposed around the pedestal 21 and is a device that fixes or releases the first metal member 101 and the second metal member 102 to or from the pedestal 21. The clamp unit 24 fixes or releases the first metal member 101 and the second metal member 102 based on a control signal transmitted from a clamp control unit 62 (see FIG. 5 ) of the control device 5. That is, after the first metal member 101 and the second metal member 102 are placed on the pedestal 21, the clamp unit 24 comes close to the first metal member 101 and the second metal member 102, and restrains the first metal member 101 and the second metal member 102 so that they cannot move relative to the pedestal 21. On the other hand, when the friction stir welding is completed, the clamp unit 24 releases the restraint and retreats to a position where it will not interfere when the metal members to be welded are removed. In addition, in Figure 4, the plate-shaped first metal member 101 and second metal member 102 are illustrated for the purpose of explaining the fixing device 3, and the shapes and sizes of the first metal member 101 and the second metal member 102 are not limited to those illustrated in Figure 4.

[0030] [2-2.Friction stirrer] 3 and 4, the friction stir welding apparatus 4 includes an arm robot 31, a rotation drive unit 32, a load application unit 33, a measurement unit 34, and a load measurement unit 35. The friction stir welding apparatus 4 is an apparatus that rotates and moves a rotary tool F to friction stir weld a first metal member 101 and a second metal member 102. The arm robot 31 is electrically connected to the control device 5. A welding control unit 61 (see FIG. 5) of the control device 5 controls the friction stir welding operation of the arm robot 31. The arm robot 31 includes a multi-joint arm 31a and an arm drive unit (not shown), and is capable of three-dimensional movement based on a control signal transmitted from the welding control unit 61.

[0031] The rotation drive unit 32 is configured to include a rotation drive means such as a motor that rotates the rotary tool F. The rotation drive unit 32, the load application unit 33, and the load measurement unit 35 are housed in a housing 39 (see FIG. 3). A chuck unit to which the rotary tool F can be attached and detached is provided at the tip of the rotation drive unit 32. A welding control unit 61 (see FIG. 5) controls the rotation drive unit 32 so that the rotary tool F rotates at a predetermined number of revolutions. The load applying unit 33 is configured to include a cylinder mechanism or the like that is movable in the axial direction of the rotary tool F, and is a part that adjusts the pressing force of the rotary tool F against the first metal member 101 and the second metal member 102 during friction stir welding. The welding control unit 61 feedback-controls the load applying unit 33 using the welding control unit 61 (see FIG. 5) so that the reaction load of the rotary tool F approaches a preset set load.

[0032] The load measuring unit 35 is interposed between the rotary tool F and a rotary driving means such as a motor, and is a device for measuring the axial reaction force load that the rotary tool F receives during friction stir welding. The measuring unit 34 is a measuring device attached to the outside of the rotation drive unit 32. In this embodiment, the measuring unit 34 uses a line sensor. The measuring unit 34 is capable of measuring unevenness (height of each part), gaps, shape, etc. of the workpieces around the butt joint J1 (joint) by the reflected light of the irradiated line laser. The results measured by the measuring unit 34 are sent to the joint control unit 61 of the control device 5.

[0033] [2-3. Control Device] As shown in FIG. 5 , the control device 5 is a control device that controls the overall operation of the fixing device 3 and the friction stir stirring device 4. The basic hardware configuration of the control device 5 is as follows. The control device 5 is equipped with a central processing unit 51 that performs various calculations and centrally controls each unit, and a main memory device 53 that is connected to the central processing unit 51 via a bus 52 and serves as a work area for the central processing unit 51. Connected to the bus 52 via a predetermined interface are an auxiliary memory device 54 such as an SSD (Solid State Drive) or HDD (Hard Disc Drive), an input device 55 such as a keyboard or a mouse, and a display device 56 such as a liquid crystal panel or an organic EL display. In addition, the fixing device 3 and the friction stir stirring device 4 are connected to the control device 5 via a predetermined interface.

[0034] A welding program 57 is set up in the auxiliary storage device 54. Based on the welding program 57, the central processing unit 51 executes various processes as described below. That is, based on the welding program 57, the central processing unit 51 executes the function (welding process, welding process) of a welding control unit 61 that controls the arm robot 31 to move the rotary tool F along a predetermined welding trajectory and perform friction stir welding on the workpieces. The central processing unit 51 also executes the function of a clamp control unit 62 that controls the clamp unit 24.

[0035] The joining program 57 may be set up in the auxiliary storage device 54 by reading it from a storage medium such as an optical disk, such as a CD-ROM (Compact Disc Read Only Memory) or a DVD-ROM (Digital Versatile Disc Read Only Memory), a USB (Universal Serial Bus) memory, or a flash memory, such as an SD memory, or by downloading it via a communication network, such as the Internet or an intranet.

[0036] [3.Joining method] Next, a joining method executed using the joining system 1 will be described. The joining method of the present invention is a joining method for performing friction stir welding along an assumed movement route of a workpiece using a rotary tool F held by an arm robot 31. The assumed movement route of the workpiece is set so that the height position of the workpiece changes in a side cross-sectional view. The joining method of the present invention includes a joining step in which the rotary tool F is inserted into the workpiece and moved along a predetermined joining trajectory to perform friction stir welding on the workpiece. In the joining method of the present invention, the joining trajectory has a retraction section in a direction intersecting with the assumed movement route before, after, or at an inflection point on the surface of the workpiece that exists on the assumed movement route. The inflection point is a point at which angular acceleration of the rotary tool F occurs as the rotary tool F passes through the inflection point when welding is performed while maintaining a constant movement speed of the tip of the rotary tool F, where the tip contacts the workpiece, and maintaining the angle of the rotary tool F relative to the workpiece. In the joining step, the rotary tool F is moved in a direction intersecting with the joining direction of the workpiece in the retraction section, and the angle of the rotary tool F relative to the workpiece is changed to match the angle of the workpiece.

[0037] The expected movement route is a desired route along which the workpieces are to be joined. For example, as described with reference to FIG. 4, when an end face of the first metal member 101 and an end face of the second metal member 102 are butted together to form a butt joint J1, the butt joint J1 can be set as the expected movement route. The expected movement route is not limited to this example, and any route along which joining is expected to be performed by moving the rotary tool F can be set.

[0038] The joining trajectory is the route along which the rotary tool F is moved during the joining process to perform welding. In other words, it represents the designated positions (teaching positions) for moving the rotary tool F. The joining trajectory specifies the path along which the rotary tool F passes by coordinate positions. For example, the joining trajectory can be specified by specifying the coordinate positions of the start and end points of the movement of the rotary tool, and by specifying the path along which the rotary tool moves along the line between the start and end points. The joining control unit 61 controls the rotary tool F to move along the trajectory specified by the joining trajectory by sending control signals to the friction stir apparatus 4 and the arm robot 31 based on the joining trajectory to operate them. When the rotary tool F is controlled to move along the expected movement route, the trajectory may deviate depending on the situation during joining, without the rotary tool F passing through the coordinate positions specified by the expected movement route. To reduce such displacement of the trajectory of the rotary tool F, the joining trajectory has evacuation sections provided in a direction that intersects with the expected movement route before, after, or at inflection points on the surface of the workpieces present on the expected movement route.

[0039] [3-1. First embodiment of joining method] A description will be given of a first embodiment of a joining method executed using the joining system 1. In the above description, a first metal member 101 and a second metal member 102 are exemplified as workpieces to be joined by the joining system 1, and a butt joint J1 is exemplified as a joining portion. In the following description, the shape of the entire workpieces is omitted, and the explanation will be centered on showing the expected movement route and joining trajectory that will be the joining portion of the workpieces to be joined.

[0040] [3-1-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 7 shows a side view of the surface shape of the workpiece 130a, the expected movement route 150a, and the joining trajectory 170a according to this embodiment. Fig. 6(a) shows the surface shape of the workpiece 130a and the expected movement route 150a according to this embodiment, shown in a plane along the surface of the workpiece 130a. Fig. 6(b) shows the joining trajectory 170a according to this embodiment, shown in a plane along the surface of the workpiece 130a.

[0041] As shown in FIG. 7 , in this embodiment, in a side cross-sectional view of the workpiece 130a, a first section 131a between points Aa and Ba and a second section 132a between points Ba and Ca are connected at point Ba. The first section 131a and the second section 132a are continuous across an inflection point 133a at point Ba. In the workpiece 130a, the first section 131a is a straight section, and the second section 132a is a curved section. The workpiece 130a is continuously formed with a planar workpiece portion having a planar portion including the first section 131a, which is a straight section, on its surface, and a curved workpiece portion having a curved portion including the second section 132a, which is a curved section, on its surface. More specifically, the curved workpiece including the second section 132a, which is a curved section, has an arc-like shape with a constant curvature in a cross-sectional view. The planar workpiece and the curved workpiece are continuous so that the surface of the planar workpiece and the tangent to one end of the arc-shaped surface of the curved workpiece overlap at one end of the arc-shaped surface. The assumed movement route 150a of this embodiment passes through the first section 131a, the inflection point 133a, and the second section 132a of the workpiece 130a in this order. Therefore, in a side cross-sectional view, the first section 131a, which is a straight section, and the second section 132a, which is a curved section, are continuous along the assumed movement route 150a, with the inflection point 133a sandwiched between them.

[0042] As shown in FIG. 7 , in a side cross-sectional view, the assumed movement route 150a of this embodiment includes a first section 151a passing through the first section 131a of the planar workpiece portion and a second section 152a passing through the second section 132a of the curved workpiece portion, connected across an inflection point 133a. As described above, the first section 131a of the workpiece 130a is a straight section, and the second section 132a of the workpiece 130a is a curved section. Therefore, the assumed movement route 150a connects the first section 151a, which is a straight section, and the second section 152a, which is a curved section. In this way, the assumed movement route 150a is set so that the height position of the workpiece 130a changes in a side cross-sectional view. Furthermore, in a side cross-sectional view, the assumed movement route 150a includes the first section 151a, which is a straight section, and the second section 152a, which is a curved section, connected across an inflection point 133a.

[0043] In the present specification, the phrase "the assumed movement route 150a is set so that the height position is displaced" means that, considering orthogonal X-, Y-, and Z-axes, the direction of the rotation axis of the rotary tool F is defined as the Z-axis, the direction of translation perpendicular to the direction of the rotation axis of the rotary tool F is defined as the X-axis, and the direction perpendicular to the direction of the rotation axis of the rotary tool F and the direction of travel of the rotary tool F is defined as the Y-axis, as the assumed movement route 150a travels in the X-axis direction, which is the travel direction, a change in the direction of the rotation axis toward the Z-axis also occurs. Therefore, for example, in the case of friction stir welding in which the rotation axis of the rotary tool F is held in a positional relationship perpendicular to the direction of gravity, a case in which the assumed movement route 150a changes to the horizontal direction, which is the direction of the rotation axis, as it travels in the travel direction is also included in the case of a displacement of the height position.

[0044] 7, in a side cross-sectional view, the joining trajectory 170a of this embodiment has a first section 171a passing through a first section 131a of the planar workpiece portion and a second section 172a passing through a second section 132a of the curved workpiece portion, connected across an inflection point 133a. As described above, the first section 131a of the workpiece 130a is a straight section, and the second section 132a of the workpiece 130a is a curved section. Therefore, the joining trajectory 170a has the first section 171a, which is a straight section, connected to the second section 172a, which is a curved section. Furthermore, in a side cross-sectional view, the joining trajectory 170a has the first section 171a, which is a straight section, and the second section 172a, which is a curved section, connected to each other across an inflection point 133a.

[0045] 6(a), when the workpiece 130a is represented in a plane along the surface of the workpiece 130a, a first section 131a between points Aa and Ba and a second section 132a between points Ba and Ca have a shape that is continuous in a straight line, with an inflection point 133a at the position of point Ba sandwiched between them. Note that in this specification and FIG. 6(a), unless there is a particular distinction to be made in the description in relation to the configurations described in each embodiment below, the workpiece 130a etc. will be denoted by the symbol "130", the point Aa etc. by the symbol "A", the point Ba etc. by the symbol "B", the point Ca etc. by the symbol "C", the first section 131a etc. of the workpiece 130a by the symbol "131", the second section 132a etc. of the workpiece 130a by the symbol "132", and the inflection point 133a etc. by the symbol "133".

[0046] As shown in Figure 6(a), when the assumed movement route 150a is represented in a plane along the surface of the workpiece 130a, a first section 151a passing through a first section 131a of the flat workpiece portion and a second section 152a passing through a second section 132a of the curved workpiece portion are connected in a straight line across an inflection point 133a. Note that in this specification and Figure 6(a), unless there is any particular distinction to be made in relation to the configurations described in each embodiment below, the assumed movement route 150a, etc. will be denoted by the symbol "150", the first section 151a, etc. of the assumed movement route 150a will be denoted by the symbol "151", and the second section 152a, etc. of the assumed movement route 150a will be denoted by the symbol "152".

[0047] 6(b), when the joining trajectory 170a is represented in a plane along the surface of the workpiece 130a, a first section 171a passing through the first section 131a of the planar workpiece portion and a portion of the first section 151a of the assumed movement route 150a, and a second section 172a passing through the second section 132a of the curved workpiece portion and a portion of the second section 152a of the assumed movement route 150a are connected across an inflection point 133a. Point Ba1 is set on the first section 131a of the workpiece 130a, and point Ba3 is set on the second section 132a of the workpiece 130a, at positions before and after the inflection point 133a on the surface of the workpiece 130a in the direction in which the assumed movement route 150a extends. Point Ba2 is set on the surface of the workpiece 130a at a position intersecting the inflection point 133a with respect to the assumed movement route 150a. Points Ba1 and Ba3 are set so that the length from point Ba1 to inflection point 133a is equal to the length from point Ba3 to inflection point 133a. Points Ba1, Ba2, and Ba3 are set so that the length from point Ba1 to point Ba2 is equal to the length from point Ba3 to point Ba2. The first section 171a of the joint trajectory 170a includes a first sub-section 171a1 between point Aa and point Ba1 and a first retreat section 171a2 between point Ba1 and point Ba2. The second section 172a of the joint trajectory 170a includes a second retreat section 172a1 between point Ba2 and point Ba3 and a second sub-section 172a2 between point Ba3 and point Ca. The joint trajectory 170a includes a first sub-section 171a1, a first evacuation section 171a2, a second evacuation section 172a1, and a second sub-section 172a2, which are arranged in this order. Among these, the first evacuation section 171a2 and the second evacuation section 172a1 (hereinafter also referred to as "evacuation sections 171a2, 172a1") deviate from the assumed movement route 150a, pass through point Ba2 located away from the assumed movement route 150a, and return to the assumed movement route 150a. When the joint trajectory 170a is plotted in a planar fashion along the surface of the workpiece 130a, the evacuation sections 171a2, 172a1 are provided in a direction intersecting with the assumed movement route 150a before and after an inflection point 133a between the first section 131a, which is a straight section of the workpiece 130a, and the second section 132a, which is a curved section.In this specification and in Figure 6(b), unless there is any particular distinction to be made in relation to the configurations described in each embodiment described later, the joint track 170a, etc. will be designated by the symbol "170", the first section 171a, etc. of the joint track 170a will be designated by the symbol "171", the second section 172a, etc. of the joint track 170a will be designated by the symbol "172", the point Ba1, etc. will be designated by the symbol "B1", the point Ba3, etc. will be designated by the symbol "B3", the point Ba2, etc. will be designated by the symbol "B2", the first sub-section 171a1, etc. will be designated by the symbol "1711", the first evacuation section 171a2, etc. will be designated by the symbol "1712", the second evacuation section 172a1, etc. will be designated by the symbol "1721", and the second sub-section 172a2, etc. will be designated by the symbol "1722".

[0048] [3-1-2. Joining method] The joining method according to the present embodiment performs friction stir welding on the above-described assumed movement route 150a of the workpiece 130a using the joining system 1. The joining method according to the present embodiment also includes a joining step of inserting a rotary tool F into the workpiece 130a and moving the rotary tool F along a joining trajectory 170a to perform friction stir welding on the workpiece 130a.

[0049] First, another robot arm (not shown) or the like places the workpiece 130a at a predetermined position on the pedestal 21 in a predetermined orientation. The workpiece 130a is placed so that the line of the reference position Y0 coincides with the assumed movement route 150a. Then, the clamp control unit 62 operates the clamp unit 24 of the fixing device 3 to fix the workpiece 130a on the pedestal 21.

[0050] The welding control unit 61 drives the arm robot 31 to insert the rotary tool F into the workpiece 130a fixed on the pedestal 21, thereby performing friction stir welding. The welding control unit 61 moves the rotary tool F along a predetermined welding trajectory 170a to perform the friction stir welding on the workpiece 130a (welding process, welding treatment). In this way, friction stir welding is performed on the assumed movement route 150a of the workpiece 130a.

[0051] In the joining process, the joining control unit 61 performs friction stir welding by keeping the moving speed of the rotary tool F relative to the workpiece 130a substantially constant. This can improve the joining quality of the workpiece 130a. The moving speed of the rotary tool F can be expressed by the TCP (Tool Center Point) speed, which is the speed of the tip of the rotary tool F held by the arm 31a. In this specification, the speed of the tip of the rotary tool F inserted into the workpiece 130a is defined as the moving speed of the rotary tool F.

[0052] In the welding process, the welding control unit 61 performs friction stir welding by maintaining a substantially constant angle of the rotary tool F relative to the surface of the workpiece 130a in the regions excluding the retreat sections 171a2 and 172a1, i.e., in the first sub-section 171a1 between Aa and point Ba1 and the second sub-section 172a2 between point Ba3 and point Ca. This improves the welding quality of the workpiece 130a. The rotary tool F is driven by the arm 31a (FIG. 3) to change its orientation in accordance with the surface shape of the workpiece 130a so that the rotation center axis Z is substantially perpendicular to the surface shape. Specifically, when viewed from the side, the angle of the axial direction of the rotary tool F relative to the surface of the workpiece 130a is preferably 80° or more and 100° or less. The angle is more preferably 85° or more and 95° or less, even more preferably 87° or more and 93° or less, and particularly preferably 89° or more and 91° or less. Unless otherwise specified in this specification, the angle of the rotary tool F with respect to the surface of the workpiece 130a refers to the angle formed between the surface of the workpiece 130a and the rotary tool F on a plane that is perpendicular to the surface of the workpiece 130a and parallel to the traveling direction of the rotary tool F. More specifically, the angle of the rotary tool F with respect to the surface of the workpiece 130a refers to the angle of the central axis of rotation of the rotary tool F with respect to the vertical axis of the surface of the workpiece 130a when the rotary tool F is viewed from the side with respect to the traveling direction.

[0053] In the joining process, the joining control unit 61 performs friction stir welding by keeping the insertion depth of the rotary tool F into the workpiece 130a approximately constant. This can improve the joining quality of the workpiece 130a. The insertion depth of the rotary tool F can be set appropriately depending on the size and shape of the rotary tool F, the material and shape of the workpiece 130a, and the movement speed and rotation speed of the rotary tool F when performing friction stir welding.

[0054] Here, consider a case where the rotary tool F is inserted into and brought into contact with the workpiece 130a so that the insertion depth of the rotary tool F into the workpiece 130a is approximately constant, and welding is performed while maintaining a constant movement speed of the tip of the rotary tool F where the tip is in contact and an approximately constant angle of the rotary tool F with respect to the workpiece 130a. In this case, while the rotary tool F passes through a first section 131a, which is a straight section between points Aa and Ba of the workpiece 130a, and welding is performed, the attitude (angle) of the rotary tool F does not change and the angular velocity of the rotary tool F also remains constant at 0, so no angular acceleration of the rotary tool F is generated. Furthermore, while the rotary tool F passes through a second section 132a, which is a curved section with a constant curvature between points Ba and Ca of the workpiece 130a, and welding is performed, the attitude (angle) of the rotary tool F changes in accordance with the surface shape of the curved portion. However, because the curvature of the curved portion is constant, the attitude of the rotary tool changes while the angular velocity is kept constant, so no angular acceleration of the rotary tool F is generated. In contrast, when the rotary tool F passes through point Ba where the first section 131a, which is a straight section of the workpiece 130a, connects with the second section 132a, which is a curved section, to perform welding, the attitude (angle) of the rotary tool F, which was maintained in the straight section between point Aa and point Ba, changes at point Ba to match the curved surface of the curved section between point Ba and point Ca. At this time, as the attitude (angle) of the rotary tool F changes from a stopped state, an angular velocity of the rotary tool F is generated, and in a short time span, a change occurs in the angular acceleration of the rotary tool F. When the angular velocity of the rotary tool F changes in this way, a force is applied to the rotary tool F, causing vibration (vibration) in the rotary tool F. When welding is performed while maintaining a constant moving speed of the tip of the rotary tool F, whose tip contacts the workpiece 130, and while maintaining the angle of the rotary tool F relative to the workpiece 130, as at point Ba described above, the point at which angular acceleration of the rotary tool F occurs as the rotary tool F passes is called an inflection point. In this specification, angular velocity may include either a clockwise (CW) or counterclockwise (CCW) direction. In this specification, angular acceleration includes both angular acceleration and angular deceleration.

[0055] In the joining process according to this embodiment, before and after an inflection point 133a between a first section 131a, which is a straight section of the workpiece 130a, and a second section 132a, which is a curved section, retreat sections 171a2 and 172a1 are provided in a direction intersecting with the assumed movement route 150a. The joining control unit 61 moves the rotary tool F in the retreat sections 171a2 and 172a1 in a direction intersecting with the joining direction of the workpiece 130a, and changes the angle of the rotary tool F with respect to the workpiece 130a in accordance with the angle of the workpiece 130a.

[0056] In the retreat sections 171a2 and 172a1, the angle of the rotary tool F with respect to the workpiece 130a in the first section 131a is changed from the angle of the rotary tool F with respect to the workpiece 130a in the first section 131a during the period from point Ba1 to point Ba3 to the angle of the rotary tool F with respect to the workpiece 130a in the second section 132a after the inflection point 133a. For example, this can be achieved by changing the angle of the rotary tool F with respect to the workpiece 130a when passing point Ba1 during the period from point Ba1 to point Ba3. Alternatively, the angle of the rotary tool F may be changed from the angle of the rotary tool F with respect to the workpiece 130a when passing point Ba1 during the period from point Ba1 to point Ba3.

[0057] More specifically, the angle of the rotary tool F is changed at point Ba2 so that it is an intermediate angle between the angle of the rotary tool F with respect to the workpiece 130a when passing through point Ba1 and the angle of the rotary tool F with respect to the workpiece 130a when passing through point Ba3 (hereinafter, this angle will be referred to as the "intermediate angle"). Between point Ba1 and point Ba2 before the inflection point 133a, the angle of the rotary tool F with respect to the workpiece 130a in the first section 131a is perpendicular when passing through point Ba1, and the angle of the rotary tool F is gradually changed so that it is at an intermediate angle when passing through point Ba2. Between point Ba2 and point Ba3 after the inflection point 133a, the angle of the rotary tool F is gradually changed so that it is at an intermediate angle when passing through point Ba2, and the angle of the rotary tool F with respect to the workpiece 130a in the second section 132a is perpendicular when passing through point Ba3. In this way, it is possible to control the change in angular velocity so as to suppress fluctuations in the angular velocity of the rotary tool F.

[0058] In the retraction sections 171a2, 172a1, it is preferable to make the angle change of the rotary tool F gentle from point Ba1 to point Ba3. That is, it is preferable to reduce the amount of angle change of the rotary tool F per unit time. It is also preferable to reduce fluctuations in angular velocity due to angle change of the rotary tool F to reduce angular acceleration. In particular, in order to suppress abrupt fluctuations in angular acceleration at point Ba1, which is the start point of the retraction sections 171a2, 172a1, it is preferable to reduce the amount of angle change of the rotary tool F near point Ba1 and gradually increase the amount of angle change from point Ba1 to point Ba2 (inflection point 133a), which is the midpoint of the retraction sections 171a2, 172a1, to maintain the angular acceleration. In addition, in order to suppress sudden fluctuations in angular acceleration at point Ba3, which is the end point of the retreat sections 171a2, 172a1, it is preferable to reduce the amount of angular change of the rotating tool F near point Ba3 and gradually decrease the amount of angular change from point Ba2 (inflection point 133a), which is the midpoint of the retreat sections 171a2, 172a1, to point Ba3, thereby maintaining the angular acceleration.

[0059] The time required for the rotary tool F to pass through the retraction sections 171a2 and 172a1 is preferably set to be 1 second or more and 10 seconds or less. This time is more preferably 3 seconds or more and 8 seconds or less, and particularly preferably 4 seconds or more and 7 seconds or less. By setting the time required to pass through the retraction sections 171a2 and 172a1 to be a predetermined time or more, the angular acceleration described above can be reduced, thereby suppressing vibrations generated in the arm 31a. To improve production efficiency, it is preferable that the time required for passing through the retraction sections 171a2 and 172a1 be short.

[0060] In the welding process, when the retraction sections 171a2, 172a1 are not provided between the points Ba1 and Ba3, the ratio of the time required for the rotary tool F to pass through the retraction sections 171a2, 172a1 to the time required for the rotary tool F to pass through the section of the assumed movement route 150a corresponding to the retraction sections 171a2, 172a1 is preferably 3 or greater. This value is more preferably 6 or greater, and particularly preferably 9 or greater. When this value is equal to or greater than the above-mentioned lower limit, the time required for the rotary tool F to pass through the retraction sections 171a2, 172a1 can be made longer and angular acceleration can be made smaller, compared to when the retraction sections 171a2, 172a1 are not provided, making it easier to suppress vibrations occurring in the arm 31a and the rotary tool F.

[0061] Furthermore, it is preferable to set the length L1 (see FIG. 13A) of the retraction sections 171a2, 172a1 in a direction intersecting with the assumed movement route 150a to 1 mm or more and 100 mm or less. This length L1 is more preferably 2 mm or more and 12 mm or less, and particularly preferably 5 mm or more and 15 mm or less. When the length L1 is equal to or greater than the above-mentioned lower limit, it becomes easier to lengthen the time required to pass through the retraction sections 171a2, 172a1 and to reduce angular acceleration, which makes it easier to suppress vibrations generated in the arm 31a and the rotary tool F. Furthermore, setting the length L1 makes it easier to shorten the length L2 of the retraction sections 171a2, 172a1, which will be described later.

[0062] It is preferable to set the length L2 (see FIG. 13A) of the retraction sections 171a2, 172a1 in a direction parallel to the assumed movement route 150a to be greater than 0 and not greater than 10 mm. This length L2 is more preferably 1 to 8 mm, and particularly preferably 2 to 5 mm. When the length L2 is equal to or greater than the above-mentioned lower limit, it becomes easier to ensure the time required to pass through the retraction sections 171a2, 172a1 and to reduce the angular acceleration, which makes it easier to suppress vibrations occurring in the arm 31a. Furthermore, by providing a certain width to the length L2 of the retraction sections 171a2 and 172a1 provided before and after the inflection point 133a in a direction parallel to the assumed movement route 150a, in the case where a tangent to one end Ba of the first section 131a between points Aa and Ba overlaps with a tangent to one end Ba of the second section 132a between points Ba and Ca as in this embodiment, it becomes possible to control the angular velocity of the rotary tool F to change while the rotary tool F moves between the retraction sections 171a2 and 172a1 before and after the inflection point 133a. By setting the length L2 to be equal to or less than the above upper limit, it becomes easier to make the plasticized region formed when the rotary tool F passes through the retraction sections 171a2 and 172a1 overlap on the assumed movement route 150a.

[0063] It is preferable that the welding region (plasticized region) formed when the rotary tool F moves through the retraction sections 171a2 and 172a1 overlap on the assumed movement route 150a. That is, when the rotary tool F leaves the assumed movement route 150a through the retraction sections 171a2 and 172a1 and returns, the overlapping of the plasticized region can prevent an unwelded portion from occurring on the assumed movement route 150a (the route linearly connecting points Ba1 and Ba3 in FIG. 6(b)). If an unwelded portion exists on the assumed movement route 150a, a section that is not welded at the butt joint J1 will be created, and this unwelded portion can be prevented.

[0064] In order to overlap the welding region (plasticized region) on the assumed movement route 150a, it is preferable to set the length L2 of the retreat sections 171a2, 172a1 in a direction parallel to the assumed movement route 150a to be smaller than twice the radius of the rotary tool F inserted into the workpiece 130 at the position on the surface of the workpiece 130. According to this, in the region between point Ba1 and point Ba3 where the rotary tool F leaves the assumed movement route 150a in the retreat sections 171a2, 172a1 and returns, the plasticized region formed when moving from point Ba1 to point Ba2 and the plasticized region formed when returning from point Ba2 to point Ba3 overlap, thereby preventing the occurrence of unwelded portions on the assumed movement route 150a.

[0065] Furthermore, in order to overlap the welding region (plasticized region) on the assumed movement route 150a, it is preferable to set the length L1 of the retreat sections 171a2, 172a1 in the direction intersecting with the assumed movement route 150a to be smaller than twice the radius of the rotating tool F inserted into the workpiece 130 at the position on the surface of the workpiece 130. According to this, in the region between point Ba1 and point Ba3 where the rotating tool F leaves the assumed movement route 150a in the retreat sections 171a2, 172a1 and returns, the plasticized region formed when moving from point Ba1 to point Ba2 and the plasticized region formed when returning from point Ba2 to point Ba3 overlap, thereby preventing the occurrence of unwelded portions on the assumed movement route 150a.

[0066] In this process, the welding control unit 61 controls the movement of the rotary tool F along a preset welding trajectory 170a through input processing by the input device 55. Of course, the welding control unit 61 may detect the shape of the periphery of the assumed movement route 150a of the workpiece 130a and control the movement of the rotary tool F based on the detected shape.

[0067] [3-1-3. Action and Effects] The workpiece 130a, which has a first section 131a that is a straight section and a second section 132a that is a curved section, appears to smoothly transition from the straight section to the curved section. When welding is performed while maintaining a constant moving speed of the tip of the rotary tool F, whose tip contacts the workpiece 130a, and while maintaining the angle of the rotary tool F relative to the workpiece 130a, as the rotary tool F passes through point Ba, which is located between the first section 131a and the second section 132a, the attitude (angle) of the rotary tool F, which was maintained in the straight section between points Aa and Ba, changes to match the curved surface of the curved section between points Ba and Ca, causing angular acceleration of the rotary tool F. That is, at point Ba, which is the inflection point 133a, angular acceleration of the rotary tool F occurs, causing vibration of the rotary tool F.

[0068] In the joining system 1 according to the present embodiment, the angle of the rotary tool F relative to the workpiece 130a is changed in accordance with the shape of a planar workpiece having a flat portion including the first section 131a, which is a straight section, and the shape of a curved workpiece having a curved portion including the second section 132a, which is a curved section, while moving the rotary tool F in a direction intersecting the joining direction of the workpiece 130a in the retraction sections 171a2, 172a1 before, after, or at the inflection point 133a between the first section 131a, which is a straight section, and the second section 132a, which is a curved section. In this case, if the retraction sections 171a2, 172a1 were not provided, joining would be performed while moving the rotary tool F linearly in a planar view from a position corresponding to point Ba1 to a position corresponding to point Ba3 on the assumed movement route 150a. However, by providing the retraction sections 171a2, 172a1, joining is performed while moving the rotary tool F from point Ba1 to point Ba3 via point Ba2 on the joining trajectory 170. This makes it possible to extend the welding time required to perform welding while moving the rotary tool F through the retraction sections 171a2 and 172a1 on the welding trajectory 170a, compared to the welding time required to perform welding while moving the rotary tool F through a section (from point Ba1 to point Ba3) on the assumed movement route 150a that corresponds to the retraction sections 171a2 and 172a1. As a result, the angular velocity of the rotary tool F changes slowly during the time duration associated with the movement of the rotary tool F through the retraction sections 171a2 and 172a1, thereby reducing the angular acceleration of the rotary tool F. In other words, compared to a case in which the retraction sections 171a2 and 172a1 are not provided and the rotary tool F is moved while changing the angle of the rotary tool F with respect to the workpiece 130a at the inflection point 133a, the angular velocity of the rotary tool F changes relatively slowly over a relatively long time duration, thereby reducing the angular acceleration of the rotary tool F. Therefore, when passing through the inflection point 133a, the angle of the rotary tool F can be changed to match the shape of the workpiece 130a while suppressing vibrations (shakes) occurring in the arm 31a of the arm robot 31 and the rotary tool F.Furthermore, the joining system 1 can prevent the amount of heat input near the inflection point 133a from becoming large by moving the rotary tool F in the retraction sections 171a2 and 172a1 (i.e., by stopping the movement of the rotary tool F and preventing the rotary tool F from continuing to rotate). Therefore, the joining system 1 can improve the joining quality of the workpiece 130a.

[0069] This embodiment is a joining method for performing friction stir welding on the assumed movement route 150a of the workpiece 130a using a rotary tool F held by an arm robot 31, and includes the above-described joining process. Typically, in friction stir welding, a large load is applied to the workpiece 130a while rotating the rotary tool F, generating a large frictional force between the rotary tool F and the workpiece 130a. Therefore, vibrations are likely to occur in the rotary tool F due to the interaction between the rotary tool F and the workpiece 130a. Furthermore, when vibrations occur in the rotary tool F during friction stir welding, a portion of the force applied to the rotary tool F in the normal direction of the workpiece 130a is directed in a direction horizontal to the workpiece 130a, increasing the vibrations of the rotary tool F. Therefore, if vibrations occur in the rotary tool F during friction stir welding, it becomes difficult for the arm 31a to suppress the vibrations, which can easily result in poor welding. This embodiment can solve the unique problems that arise when performing friction stir welding on a workpiece 130a whose assumed movement route 150a has an inflection point 133 using a rotary tool F held by an arm robot 31.

[0070] [3-1-4.Other] In the welding process according to this embodiment, the case where the retreat sections 171a2 and 172a1 are provided before and after the inflection point 133a in a direction intersecting the assumed movement route 150a has been described as an example. The retreat sections 171a2 and 172a1 may be provided at the inflection point 133a in a direction intersecting the assumed movement route 150a. That is, the retreat sections 171a2 and 172a1 may be configured so that the points Ba1 and Ba3 overlap, and the length L2 of the points Ba1 and Ba3 in a direction parallel to the assumed movement route 150a is zero. In this case, the welding control unit 61 moves the rotary tool F from point Ba1, which overlaps with the inflection point 133a, toward point Ba2, which is located away from the assumed movement route 150a, and then moves the rotary tool F back to point Ba3, which overlaps with the inflection point 133a. In this way, the welding control unit 61 changes the angle of the rotary tool F with respect to the workpiece 130a in accordance with the angle of the workpiece 130a while moving the rotary tool F in a direction intersecting or perpendicular to the welding direction of the workpiece 130a in the retraction sections 171a2, 172a1. In this way, by moving the rotary tool F while stopping the movement of the rotary tool F toward the assumed movement route 150a, it is possible to change the inclination of the rotary tool F at the inflection point 133a without stopping the movement of the rotary tool F.

[0071] In the first embodiment described above, the workpiece 130a, the assumed movement route 150a, and the joining trajectory 170a are configured such that the first straight sections 131a, 151a, and 171a are connected to the second curved sections 132a, 152a, and 172a, with the inflection point 133a in between, and the first straight section 131a and the second curved section 132a are joined in that order. The relationship between the straight section and the curved section may be reversed. That is, the joining method according to this embodiment can also be applied to the case where the second curved section 132a and the first straight section 131a are joined in that order to the workpiece 130a.

[0072] In the first embodiment described above, the workpiece 130a, the assumed movement route 150a, and the joining trajectory 170a are configured such that the first sections 131a, 151a, and 171a, which are straight sections, and the second sections 132a, 152a, and 172a, which are curved sections with a convex radius, are successively joined on either side of the inflection point 133a, and the first section 131a, which is a straight section, and the second section 132a, which is a curved section with a convex radius, are joined in that order. The curved section may be a curved section with a convex radius or a curved section with a concave radius. In other words, the joining method according to this embodiment can also be applied to the case of joining the first section 131a, which is a straight section, and the second section 132a, which is a curved section with a concave radius.

[0073] In the above-described first embodiment, a case has been described in which friction stir welding is performed with the movement speed of the rotary tool F kept substantially constant. The movement speed of the rotary tool F may be changed. In particular, by reducing the movement speed of the rotary tool F before and after the inflection point 133a, it becomes easier to lengthen the time required for the rotary tool F to pass through the inflection point 133a and to reduce the angular acceleration, which makes it easier to suppress vibrations occurring in the arm 31a.

[0074] In the above-described embodiment, an example was described in which the angle of the rotary tool F is gradually changed between points Ba1 and Ba2 and between points Ba2 and Ba3 such that the angle of the rotary tool F is perpendicular to the workpiece 130a when passing through point Ba1, is at an intermediate angle when passing through point Ba2 (inflection point 133a), and is perpendicular to the workpiece 130a when passing through point Ba3. The angle of the rotary tool F may be changed so as not to be at an intermediate angle when passing through point Ba2 (inflection point 133a). In other words, the intermediate angle may not be reached when passing through point Ba2, and may exceed the intermediate angle. Furthermore, when passing through point Ba2, the rotary tool F may reach an angle at point Ba3 at which it is perpendicular to the workpiece 130a. For example, the angle of the rotary tool F may be gradually changed between points Ba1 and Ba2 so as to be at an intermediate angle before passing through point Ba2. Furthermore, between point Ba2 and point Ba3, the angle of the rotary tool F may be gradually changed so that it becomes an intermediate angle after passing point Ba2. Furthermore, between point Ba1 and point Ba2, the angle of the rotary tool F may be gradually changed so that when passing point Ba1, the angle of the rotary tool F is perpendicular to the workpiece 130a, and by the time point Ba2 is reached, the angle of the rotary tool F becomes perpendicular to the workpiece 130a in the second section 132a. Furthermore, between point Ba2 and point Ba3, the angle of the rotary tool F may be gradually changed so that when passing point Ba2, the angle of the rotary tool F becomes perpendicular to the workpiece 130a in the first section 131a, and by the time point Ba3 is reached, the angle of the rotary tool F becomes perpendicular to the workpiece 130a.

[0075] In the first embodiment described above, points Ba1, Ba2, and Ba3 are set so that the length from point Ba1 to the inflection point 133a is equal to the length from point Ba3 to the inflection point 133a, and the length from point Ba1 to point Ba2 is equal to the length from point Ba3 to point Ba2, and the angle of the rotary tool F is changed so that the angle of the rotary tool F becomes an intermediate angle when passing through point Ba2. Points Ba1 and Ba3 may be set so that the length from point Ba1 to the inflection point 133a and the length from point Ba3 to the inflection point 133a are different in length, with one length being longer than the other. Points Ba1, Ba2, and Ba3 may also be set so that the length from point Ba1 to point Ba2 and the length from point Ba3 to point Ba2 are different in length, with one length being longer than the other. The angle of the rotary tool F may be changed proportionally according to the ratio between the length from point Ba1 to the inflection point 133a (point Ba2) and the length from point Ba3 to the inflection point 133a (point Ba2).

[0076] In the first embodiment described above, a case where friction stir welding is performed with the angle of the rotary tool F relative to the surface of the workpiece 130a being approximately constant in the regions excluding the retraction sections 171a2 and 172a1, i.e., the first sub-section 171a1 between points Aa and Ba1 and the second sub-section 172a2 between points Ba3 and Ca, has been described as an example. The angle of the rotary tool F relative to the surface of the workpiece 130a may also be changed in the regions excluding the retraction sections 171a2 and 172a1. That is, in the first sub-section 171a1 between points Aa and Ba1 or the second sub-section 172a2 between points Ba3 and Ca, the angle of the rotary tool F relative to the surface of the workpiece 130a may be changed while moving the rotary tool F on the assumed movement route 150a without moving the rotary tool F in a direction intersecting the welding direction of the workpiece 130a. In the embodiment described above, a case where the angle of the rotary tool F is gradually changed to an intermediate angle from point Ba1 to point Ba2 has been described. The angle of the rotary tool F may be gradually changed to an intermediate angle from point Aa to point Ba2. In the above-described embodiment, the angle of the rotary tool F is gradually changed from an intermediate angle from point Ba2 to point Ba3. The angle of the rotary tool F may be gradually changed from an intermediate angle from point Ba2 to point Ca.

[0077] In the above-described first embodiment, the case where friction stir welding is performed with the insertion depth of the rotary tool F into the workpiece 130a being approximately constant has been described as an example. The insertion depth of the rotary tool F into the workpiece 130a may be changed.

[0078] In the first embodiment described above, the retraction sections 171a2 and 172a1 of the joining trajectory 170a are linear in plan view. The retraction sections 171a2 and 172a1 may include a curve in plan view. For example, the retraction sections 171a2 and 172a1 may include a curve near point Ba1. This allows the rotary tool F to move smoothly while changing its movement direction from the direction of the assumed movement route 150a to a direction intersecting the assumed movement route 150a from the first sub-section 171a1 to the first retraction section 171a2. The retraction sections 171a2 and 172a1 may also include a curve near point Ba2. This allows the rotary tool F to move smoothly while changing its movement direction from the first retraction section 171a2 to the second retraction section 172a1. The retraction sections 171a2 and 172a1 may also include a curve near point Ba3. This allows the rotating tool F to move smoothly from the second evacuation section 172a1 to near point Ba2 while changing its movement direction from a direction intersecting the expected movement route 150a toward the direction of the expected movement route 150a.

[0079] In the above-described first embodiment, an example has been described in which the rotary tool F moves in one direction along the expected movement route 150a in the retreat sections 171a2, 172a1 of the welding trajectory 170a. The retreat sections 171a2, 172a1 may be provided so that the rotary tool F moves in the opposite direction to the expected movement route 150a. For example, the retreat sections 171a2, 172a1 may be provided so that the rotary tool F moves away from the expected movement route 150a, makes a loop, and then returns to the expected movement route 150a.

[0080] [3-2. Second embodiment of joining method] Next, a second embodiment of the joining method will be described with reference to Fig. 8, Fig. 6(a), and Fig. 6(b). As shown in Fig. 8, in the second embodiment, the shape of the workpiece 130b, and the shapes of the assumed movement route 150b and the joining trajectory 170b when viewed from the side are different from those in the first embodiment. In the second embodiment, the parts that are different from the first embodiment will be mainly described, and a description of the parts that are common to the first embodiment will be omitted.

[0081] [3-2-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 8 shows a side view of the surface shape of the workpiece 130b according to this embodiment, as well as the assumed movement route 150b and the joining trajectory 170b. Fig. 6(a) shows the surface shape of the workpiece 130b according to this embodiment and the assumed movement route 150b shown in a plane along the surface of the workpiece 130b. Fig. 6(b) shows the joining trajectory 170b according to this embodiment shown in a plane along the surface of the workpiece 130b.

[0082] As shown in FIG. 8, in this embodiment, in a side cross-sectional view, the workpiece 130b has a first section 131b between points Ab and Bb and a second section 132b between points Bb and Cb, which are connected at point Bb. The first section 131b and the second section 132b are continuous across an inflection point 133b at point Bb. In the workpiece 130b, the first section 131b is a straight section, and the second section 132b is a straight section. The workpiece 130b has a first planar workpiece portion having a flat surface including the first section 131b, which is a straight section, and a second planar workpiece portion having a flat surface including the second section 132b, which is a straight section, which are continuously formed on the surface. More specifically, the first planar workpiece and the second planar workpiece are connected so that the first section 131b, which is a straight section, and the second section 132b, which is also a straight section, are not linear; in other words, the first section 131b and the second section 132b form an angle at point Bb that is greater than 0° and less than or greater than 180°. Here, the assumed movement route 150b of this embodiment passes through the first section 131b, the inflection point 133b, and the second section 132b of the workpiece 130b in this order. Therefore, in a side cross-sectional view, the first section 131b, which is a straight section, and the second section 132b, which is another straight section, are continuous along the assumed movement route 150b, with the angle varying across the inflection point 133b, which is a corner.

[0083] As shown in FIG. 8 , in a side cross-sectional view, the assumed movement route 150b of this embodiment includes a first section 151b passing through a first section 131b of the first planar workpiece part and a second section 152b passing through a second section 132b of the second planar workpiece part, connected across an inflection point 133b. As described above, the first section 131b of the workpiece 130b is a straight section, and the second section 132b of the workpiece 130b is a straight section. Therefore, the assumed movement route 150b includes the first section 151b, which is a straight section, and the second section 152b, which is also a straight section. In this manner, the assumed movement route 150b is set so that the height position of the workpiece 130b changes in a side cross-sectional view. Furthermore, in a side cross-sectional view, the assumed movement route 150b includes the first section 151b, which is a straight section, and the second section 152b, which is another straight section, connected at an angle across the inflection point 133b.

[0084] 8, in a side cross-sectional view, the joining trajectory 170b of this embodiment includes a first section 171b passing through a first section 131b of the first planar workpiece part and a second section 172b passing through a second section 132b of the second planar workpiece part, the first section 171b being connected to a second section 172b passing through a second section 132b of the second planar workpiece part, with an inflection point 133b in between. As described above, the first section 131b of the workpiece 130b is a straight section, and the second section 132b of the workpiece 130b is a straight section. Therefore, the joining trajectory 170b includes a connection between the first section 171b, which is a straight section, and the second section 172b, which is another straight section. In addition, in a side cross-sectional view, the joining trajectory 170b includes a first section 171b, which is a straight section, and a second section 172b, which is another straight section, that are connected to each other with a changing angle across the inflection point 133b, which is a corner.

[0085] As shown in Figure 6(a), when the workpiece 130b is represented in a plane along its surface, a first section 131b between points Ab and Bb and a second section 132b between points Bb and Cb have a shape that is continuous in a straight line, sandwiched between an inflection point 133b at the position of point Bb.

[0086] As shown in Figure 6(a), when the expected movement route 150b is represented in a plane along the surface of the workpiece 130b, a first section 151b passing through a first section 131b of the first planar workpiece and a second section 152b passing through a second section 132b of the second planar workpiece are connected in a straight line across an inflection point 133b.

[0087] As shown in FIG. 6(b), when the joint trajectory 170b is represented in a plane along the surface of the workpiece 130b, a first section 171b passing through the first section 131b of the first planar workpiece part and a portion of the first section 151b of the assumed movement route 150a, and a second section 172b passing through the second section 132b of the second planar workpiece part and a portion of the second section 152b of the assumed movement route 150b are connected across an inflection point 133b. Point Bb1 is set on the first section 131b of the workpiece 130b at positions before and after the inflection point 133b on the surface of the workpiece 130b in the direction in which the assumed movement route 150b extends, and point Bb3 is set on the second section 132b of the workpiece 130b. Point Bb2 is set on the surface of the workpiece 130b at a position intersecting the inflection point 133b with respect to the assumed movement route 150b. The first section 171b of the joint trajectory 170b has a first sub-section 171b1 between points Ab and Bb1 and a first evacuation section 171b2 between points Bb1 and Bb2. The second section 172b of the joint trajectory 170b has a second evacuation section 172b1 between points Bb2 and Bb3 and a second sub-section 172b2 between points Bb3 and Cb. The joint trajectory 170b has the first sub-section 171b1, the first evacuation section 171b2, the second evacuation section 172b1, and the second sub-section 172b2, which are arranged in this order. Of these, the first evacuation section 171b2 and the second evacuation section 172b1 (hereinafter also referred to as "evacuation sections 171b2, 172b1") describe a trajectory that deviates from the assumed movement route 150b, passes through point Bb2 located away from the assumed movement route 150b, and returns to the assumed movement route 150b. When expressed in a planar form along the surface of the workpiece 130b in this way, the joining trajectory 170b has the evacuation sections 171b2, 172b1 provided in a direction that intersects with the assumed movement route 150b before and after the inflection point 133b between the first section 131b, which is a straight section of the workpiece 130b, and the second section 132b, which is also a straight section.

[0088] [3-2-2. Joining method] The joining method according to the present embodiment performs friction stir welding on the above-described assumed movement route 150b of the workpiece 130b using the joining system 1. The joining method according to the present embodiment also includes a joining step of inserting the rotary tool F into the workpiece 130b and moving the rotary tool F along the joining trajectory 170b to perform friction stir welding on the workpiece 130b.

[0089] In the joining process according to this embodiment, before and after an inflection point 133b between a first section 131b, which is a straight section of the workpiece 130b, and a second section 132b, which is also a straight section, there are provided retreat sections 171b2 and 172b1 in a direction intersecting with the assumed movement route 150b. The joining control unit 61 then moves the rotary tool in the retreat sections 171b2 and 172b1 in a direction intersecting with the joining direction of the workpiece 130b, and changes the angle of the rotary tool F with respect to the workpiece 130b in accordance with the angle of the workpiece 130b in the retreat sections 171b2 and 172b1. The change in the angle of the rotary tool F in the retreat sections 171b2 and 172b1 can be performed in the same manner as described in the first embodiment.

[0090] [3-2-3. Action and Effects] The workpiece 130b has a first section 131b, which is a straight section, and a second section 132b, which is also a straight section, and these sections are continuous with varying angles across an inflection point 133b, which is a corner. When joining is performed while maintaining a constant moving speed of the tip of the rotary tool F, whose tip contacts the workpiece 130b, and while maintaining the angle of the rotary tool F relative to the workpiece 130b, when the rotary tool F passes through point Bb, which is located between the first section 131b and the second section 132b, the attitude (angle) of the rotary tool F is maintained in the straight section between points Ab and Bb. The attitude of the rotary tool F changes from a state in which this attitude is maintained in the straight section between points Bb and Cb in accordance with the change in the angle between the first section 131b and the second section 132b, and angular acceleration of the rotary tool F occurs. That is, the angular acceleration of the rotary tool F occurs at point Bb, which is the inflection point 133b, and vibration occurs in the rotary tool F.

[0091] The joining system 1 moves the rotary tool F in a direction intersecting the joining direction of the workpiece 130b before and after an inflection point 133b between the first section 131b, which is a straight section, and the second section 132b, which is also a straight section, or in the retreat sections 171b2, 172b1 at the inflection point 133b, and changes the angle of the rotary tool F with respect to the workpiece 130b in accordance with the shape of the first planar workpiece part having a planar portion including the first section 131b, which is a straight section, and the shape of the second planar workpiece part having a planar portion including the second section 132b, which is a straight section. As a result, by the same action as in the first embodiment, it is possible to change the angle of the rotary tool F in accordance with the shape of the workpiece 130b while suppressing vibrations (shaking) generated in the arm 31a of the arm robot 31 and the rotary tool F when passing through the inflection point 133b, thereby improving joining quality.

[0092] [3-2-4.Other] In the welding process according to this embodiment, the case where the retreat sections 171b2 and 172b1 are provided before and after the inflection point 133b in a direction intersecting with the assumed movement route 150b has been described as an example. At the inflection point 133b, the retreat sections 171b2 and 172b1 may be provided in a direction intersecting with or perpendicular to the assumed movement route 150b. That is, the retreat sections 171b2 and 172b1 may be configured such that the points Bb1 and Bb3 overlap, and the length L2 of the points Bb1 and Bb3 in a direction parallel to the assumed movement route 150b is zero. In this case, the welding control unit 61 moves the rotary tool F from the point Bb1, which overlaps with the inflection point 133b, toward the point Bb2, which is located away from the assumed movement route 150b, and then moves the rotary tool F back to the point Bb3, which overlaps with the inflection point 133b. In this way, when passing through the retraction sections 171b2 and 172b1 at the inflection point 133b, the welding control section 61 moves the rotary tool F in a direction intersecting the welding direction of the workpiece 130b, and changes the angle of the rotary tool F with respect to the workpiece 130b to match the angle of the workpiece 130b. More specifically, in the retraction section 171b2, the angle of the rotary tool F is gradually changed so that the angle of the rotary tool F with respect to the workpiece 130b in the first section 131b is perpendicular when passing through point Bb1, and becomes an intermediate angle when passing through point Bb2. In the retraction section 172b1, the angle of the rotary tool F is gradually changed so that the angle of the rotary tool F with respect to the workpiece 130b in the second section 132b is an intermediate angle when passing through point Bb2, and becomes perpendicular when passing through point Bb3. In this case, by moving the rotary tool F while stopping the movement of the rotary tool F in the direction of the assumed movement route 150b, it is possible to change the inclination of the rotary tool F at the inflection point 133b without stopping the movement of the rotary tool F in the direction of the assumed movement route 150b. This type of control is effective when the tangent to one end B of the first section 131 between points A and B and the tangent to one end B of the second section 132 between points B and C do not overlap (match), as in the second, fifth, and sixth embodiments.

[0093] [3-3. Third embodiment of joining method] Next, a third embodiment of the joining method will be described with reference to Fig. 9, Fig. 6(a), and Fig. 6(b). As shown in Fig. 9, in the third embodiment, the shape of the workpiece 130c, and the shapes of the assumed movement route 150c and the joining trajectory 170c when viewed from the side are different from those in the first embodiment. In the third embodiment, the parts that are different from the first embodiment will be mainly described, and a description of the parts that are common to the first embodiment will be omitted.

[0094] [3-3-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 9 shows a side view of the surface shape of the workpiece 130c according to this embodiment, as well as the expected movement route 150c and the joining trajectory 170c. Fig. 6(a) shows the surface shape of the workpiece 130c according to this embodiment and the expected movement route 150c shown in a plane along the surface of the workpiece 130c. Fig. 6(b) shows the joining trajectory 170c according to this embodiment shown in a plane along the surface of the workpiece 130c.

[0095] As shown in FIG. 9 , in this embodiment, in a side cross-sectional view of the workpiece 130c, a first section 131c between points Ac and Bc and a second section 132c between points Bc and Cc are connected at point Bc. The first section 131c and the second section 132c are continuous across an inflection point 133c at point Bc. In the workpiece 130c, the first section 131c is a curved section, and the second section 132c is a curved section. The workpiece 130c is continuously formed with a first curved workpiece having a curved surface portion including the first section 131c, which is a curved section, and a second curved workpiece having a curved surface portion including the second section 132c, which is a curved section. More specifically, the first curved workpiece having a curved surface portion including the first section 131c, which is a curved section, and the second curved workpiece having the second section 132c, which is a curved section, each have an arc-like shape with a constant curvature in a cross-sectional view, but the curvatures are different. The curvature of the first section 131c is smaller than the curvature of the second section 132c. The first curved-surface workpiece and the second curved-surface workpiece are continuous such that a tangent to one end of the arc-shaped surface of the first curved-surface workpiece overlaps a tangent to one end of the arc-shaped surface of the second curved-surface workpiece. In other words, the first section 131c and the second section 132c are continuous such that, at one end of the first section 131c and the second section 132c, the angle between a tangent drawn from point Bc, which is one end of the first section 131c, in the direction extending to point Ac, which is the other end, and a tangent drawn from point Bc, which is one end of the second section 132c, in the direction extending to point Cc, which is the other end, is 180°. The first section 131c, which is a curved section with a convex radius, and the second section 132c, which is a curved section with a convex radius, are continuous across an inflection point 133c. That is, the first section 131c and the second section 132c are curved in the same direction in a side cross-sectional view. Here, the assumed movement route 150c of the present embodiment passes through the first section 131c, the inflection point 133c, and the second section 132c of the workpiece 130c in this order. Therefore, in a side cross-sectional view, the workpiece 130c has the first section 131c and the second section 132c, which are curved sections, continuing along the assumed movement route 150c with the inflection point 133c in between, and the first section 131c and the second section 132c have different curvatures.In addition, the first section 131c, which is a curved section, and the second section 132c, which is a curved section, have different positions of the center points of the circular arc-shaped curves. In this specification, "a curved section having a convex R" means that the workpiece is formed so as to have a convex R on the side of the workpiece where the rotary tool F is inserted. In addition, "a curved section having a concave R" means that the workpiece is formed so as to have a concave R on the side of the workpiece where the rotary tool F is inserted.

[0096] As shown in FIG. 9 , in a side cross-sectional view, the assumed movement route 150c of this embodiment includes a first section 151c passing through a first section 131c of the first curved-surface workpiece part and a second section 152c passing through a second section 132c of the second curved-surface workpiece part, connected across an inflection point 133c. As described above, the first section 131c of the workpiece 130c is a curved section, and the second section 132c of the workpiece 130c is also a curved section. Therefore, the assumed movement route 150c includes a connection between the first section 151c, which is a curved section, and the second section 152c, which is also a curved section. In this way, the assumed movement route 150c is set so that the height position of the workpiece 130c changes in a side cross-sectional view. Furthermore, in a side cross-sectional view, the assumed movement route 150c includes a first section 151c and a second section 152c, which are curved sections with different curvatures, connected across an inflection point 133c.

[0097] 9, in a side cross-sectional view, the joint trajectory 170c of this embodiment has a first section 171c passing through a first section 131c of the first curved surface workpiece part and a second section 172c passing through a second section 132c of the second curved surface workpiece part, which are connected across an inflection point 133c. As described above, the first section 131c of the workpiece 130c is a curved section, and the second section 132c of the workpiece 130c is also a curved section, so the joint trajectory 170c has a connection between the first section 171c, which is a curved section, and the second section 172c, which is also a curved section. Furthermore, in a side cross-sectional view, the joint trajectory 170c has a first section 171c and a second section 172c, which are curved sections with different curvatures, which are connected across an inflection point 133c.

[0098] As shown in Figure 6(a), when the workpiece 130c is represented in a plane along its surface, a first section 131c between points Ac and Bc and a second section 132c between points Bc and Cc have a shape that is continuous in a straight line, sandwiched between an inflection point 133c at the position of point Bc.

[0099] As shown in Figure 6(a), when the expected movement route 150c is represented in a plane along the surface of the workpiece 130c, a first section 151c passing through a first section 131c of the first curved surface workpiece part and a second section 152c passing through a second section 132c of the second curved surface workpiece part are connected in a straight line with an inflection point 133c in between.

[0100] 6(b), when the joining trajectory 170c is represented in a plane along the surface of the workpiece 130c, a first section 171c passing through a first section 131c of the first curved surface workpiece part and a portion of the first section 151c of the assumed movement route 150c, and a second section 172c passing through a second section 132c of the second curved surface workpiece part and a portion of the second section 152c of the assumed movement route 150c are connected across an inflection point 133c. Point Bc1 is set on the first section 131c of the workpiece 130c, and point Bc3 is set on the second section 132c of the workpiece 130c, at positions before and after the inflection point 133c on the surface of the workpiece 130c in the direction in which the assumed movement route 150c extends. Point Bc2 is set on the surface of the workpiece 130c at a position intersecting the inflection point 133c with respect to the assumed movement route 150c. The first section 171c of the joint trajectory 170c includes a first sub-section 171c1 between points Ac and Bc1 and a first evacuation section 171c2 between points Bc1 and Bc2. The second section 172c of the joint trajectory 170c includes a second evacuation section 172c1 between points Bc2 and Bc3 and a second sub-section 172c2 between points Bc3 and Cc. The joint trajectory 170c includes the first sub-section 171c1, the first evacuation section 171c2, the second evacuation section 172c1, and the second sub-section 172c2, which are arranged in this order. Of these, the first evacuation section 171c2 and the second evacuation section 172c1 (hereinafter also referred to as "evacuation sections 171c2, 172c1") describe a trajectory that deviates from the assumed movement route 150c, passes through point Bc2 located away from the assumed movement route 150c, and returns to the assumed movement route 150c. When expressed in a planar form along the surface of the workpiece 130c in this way, the joining trajectory 170c has evacuation sections 171c2, 172c1 provided in a direction that intersects with the assumed movement route 150c before and after an inflection point 133c between the first section 131c, which is a curved section of the workpiece 130c, and the second section 132c, which is also a curved section.

[0101] [3-3-2. Joining method] The joining method according to the present embodiment performs friction stir welding on the above-described assumed movement route 150c of the workpiece 130c using the joining system 1. The joining method according to the present embodiment also includes a joining step of inserting a rotary tool F into the workpiece 130c and moving the rotary tool F along a joining trajectory 170c to perform friction stir welding on the workpiece 130c.

[0102] In the joining process according to this embodiment, before and after an inflection point 133c between a first curved section 131c and a second curved section 132c of the workpiece 130c, retreat sections 171c2 and 172c1 are provided in a direction intersecting with the assumed movement route 150c. The joining control unit 61 moves the rotary tool in the retreat sections 171c2 and 172c1 in a direction intersecting with the joining direction of the workpiece 130c, and changes the angle of the rotary tool F with respect to the workpiece 130c in accordance with the angle of the workpiece 130c in the retreat sections 171c2 and 172c1. The angle of the rotary tool F in the retreat sections 171c2 and 172c1 can be changed in the same manner as described in the first embodiment.

[0103] [3-3-3. Action and Effects] In the workpiece 130c having the first section 131c and the second section 132c which are curved sections, the positions of the center points of the curves of the first section 131c and the second section 132c are different. In addition, in the workpiece 130c having the first section 131c and the second section 132c which are curved sections, the curvatures of the first section 131c and the second section 132c are different. In the workpiece 130c having the first section 131c and the second section 132c which are curved sections, the curved section appears to be smoothly continuous from one curved section to the other. When joining is performed while maintaining a constant movement speed of the tip of the rotary tool F, whose tip contacts the workpiece 130c, and while maintaining the angle of the rotary tool F relative to the workpiece 130c, when the rotary tool F passes through point Bc located between the first section 131c and the second section 132c, the attitude (angle) of the rotary tool F changes in the curved section of constant curvature between point Ac and point Bc, i.e., from a state in which the angular velocity was maintained, to match the curved surface of the curved section between point Bc and point Cc in accordance with the change in curvature between the first section 131c and the second section 132c, angular acceleration of the rotary tool F is generated. In other words, angular acceleration of the rotary tool F occurs at point Bc, which is the inflection point 133c, and vibration occurs in the rotary tool F.

[0104] The joining system 1 moves the rotary tool F in a direction intersecting the joining direction of the workpiece 130c before and after an inflection point 133c between the first section 131c, which is a curved section, and the second section 132c, which is a curved section, or in the retreat sections 171c2, 172c1 at the inflection point 133c, and changes the angle of the rotary tool F with respect to the workpiece 130c in accordance with the shape of the first curved workpiece part having a curved surface portion including the first section 131c, which is a curved section, and the shape of the second curved workpiece part having a curved surface portion including the second section 132c, which is a curved section. As a result, by the same action as in the first embodiment, it is possible to change the angle of the rotary tool F in accordance with the shape of the workpiece 130c while suppressing vibrations (shaking) generated in the arm 31a of the arm robot 31 and the rotary tool F when passing through the inflection point 133c, and thereby improve joining quality.

[0105] [3-3-4.Other] In the above-described third embodiment, a case has been described in which the workpiece 130c, the assumed movement route 150c, and the joining trajectory 170c are configured such that the first section 131c, 151c, 171c, which is a curved section with a convex R, and the second section 132c, 152c, 172c, which is a curved section with a convex R, are continuous with each other, on either side of the inflection point 133c. The joining method according to this embodiment can also be applied to a case in which the workpiece 130c, the assumed movement route 150c, and the joining trajectory 170c are configured such that the first section 131c, 151c, 171c, which is a curved section with a concave R, and the second section 132c, 152c, 172c, which is a curved section with a concave R, are continuous with each other, on either side of the inflection point 133c.

[0106] In the third embodiment described above, a case has been described in which the angle between the tangents of the curved first section 131c and the curved second section 132c at their respective ends Bc, Bc where the curved first section 131c and the curved second section 132c are continuous is 180°. The joining method according to this embodiment can also be applied to cases in which the angle between the tangents of the curved first section 131c and the curved second section 132c at their respective ends Bc, Bc where the curved first section 131c and the curved second section 132c are continuous is greater than or less than 180°.

[0107] [3-4. Fourth embodiment of joining method] Next, a fourth embodiment of the joining method will be described with reference to Fig. 10, Fig. 6(a), and Fig. 6(b). As shown in Fig. 10, in the fourth embodiment, the shape of the workpiece 130d, and the shapes of the assumed movement route 150d and the joining trajectory 170d when viewed from the side are different from those of the first embodiment. In the fourth embodiment, the differences from the first embodiment will be mainly described, and a description of the parts common to the first embodiment will be omitted.

[0108] [3-4-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 10 shows a side view of the surface shape of the workpiece 130d according to this embodiment, as well as the expected movement route 150d and the joining trajectory 170d. Fig. 6(a) shows the surface shape of the workpiece 130d according to this embodiment and the expected movement route 150d shown in a plane along the surface of the workpiece 130d. Fig. 6(b) shows the joining trajectory 170d according to this embodiment shown in a plane along the surface of the workpiece 130d.

[0109] As shown in FIG. 10 , in this embodiment, in a side cross-sectional view of the workpiece 130d, a first section 131d between points Ad and Bd and a second section 132d between points Bd and Cd are connected at point Bd. The first section 131d and the second section 132d have a continuous shape with an inflection point 133d at the position of point Bd sandwiched between them. In the workpiece 130d, the first section 131d is a curved section, and the second section 132d is a curved section. The workpiece 130d is continuously formed with a first curved-surface workpiece having a curved surface portion including the first section 131d, which is a curved section, on its surface, and a second curved-surface workpiece having a curved surface portion including the second section 132d, which is a curved section, on its surface. More specifically, the first curved-surface workpiece having a curved surface portion including the first section 131d, which is a curved section, and the second curved-surface workpiece having a curved surface portion including the second section 132d, which is a curved section, each have an arc-like shape with approximately the same curvature in a cross-sectional view. The first curved-surface workpiece and the second curved-surface workpiece are continuous so that a tangent to one end of the arc-shaped surface of the first curved-surface workpiece overlaps a tangent to one end of the arc-shaped surface of the second curved-surface workpiece. In other words, the first section 131d and the second section 132d are continuous so that, at one end of each section where the first section 131d and the second section 132d are continuous, the angle between a tangent drawn from point Bd, which is one end of the first section 131d, in the direction extending to point Ad, which is the other end, and a tangent drawn from point Bd, which is one end of the second section 132d, in the direction extending to point Cd, which is the other end, is 180°. Furthermore, the first section 131d, which is a curved section with a concave R, and the second section 132d, which is a curved section with a convex R, are continuous across an inflection point 133d. That is, the first section 131d and the second section 132d have different concave and convex directions. In other words, the first section 131d and the second section 132d are curved in different directions in a side cross-sectional view. Here, the assumed movement route 150d of the present embodiment passes through the first section 131d, the inflection point 133d, and the second section 132d of the workpiece 130d in this order. Therefore, in a side cross-sectional view, the workpiece 130d has the first section 131d and the second section 132d, which are curved sections, continuing along the assumed movement route 150d with the inflection point 133d in between, and the first section 131d and the second section 132d have different concave and convex directions.In addition, the first section 131d, which is a curved section, and the second section 132d, which is a curved section, have different positions of the center points of the circular arc curves.

[0110] 10, in a side cross-sectional view, the assumed movement route 150d of this embodiment is such that a first section 151d passing through a first section 131d of the first curved surface workpiece part and a second section 152d passing through a second section 132d of the second curved surface workpiece part are connected across an inflection point 133d. As described above, the first section 131d of the workpiece 130d is a curved section, and the second section 132d of the workpiece 130d is also a curved section, so the assumed movement route 150d connects the first section 151d, which is a curved section, and the second section 152d, which is also a curved section. In this way, the assumed movement route 150d is set so that the height position of the workpiece 130d changes in a side cross-sectional view. In addition, in a cross-sectional side view, the assumed movement route 150d is configured such that a first section 151d and a second section 152d, which are curved sections, are continuous with each other across an inflection point 133d, and the directions of the projections and depressions in the first section 151d and the second section 152d are different.

[0111] 10, in a side cross-sectional view, the joint trajectory 170d of this embodiment includes a first section 171d passing through the first section 131d of the first curved surface workpiece part and a second section 172d passing through the second section 132d of the second curved surface workpiece part, which are connected across an inflection point 133d. As described above, the first section 131d of the workpiece 130d is a curved section, and the second section 132d of the workpiece 130d is also a curved section, so the joint trajectory 170d includes a connection between the curved first section 171d and the curved second section 172d. Furthermore, in a side cross-sectional view, the curved first section 171d and the curved second section 172d of the joint trajectory 170d are continuous across the inflection point 133d, and the first section 171d and the second section 172d have different concave and convex directions.

[0112] As shown in Figure 6(a), when the workpiece 130d is represented in a plane along its surface, a first section 131d between points Ad and Bd and a second section 132d between points Bd and Cd have a shape that is continuous in a straight line, sandwiched between an inflection point 133d at the position of point Bd.

[0113] As shown in Figure 6(a), when the expected movement route 150d is represented in a plane along the surface of the workpiece 130d, a first section 151d passing through a first section 131d of the curved workpiece part and a second section 152d passing through a second section 132d of the second curved workpiece part are connected in a straight line with an inflection point 133d in between.

[0114] 6(b), when the joint trajectory 170d is represented in a plane along the surface of the workpiece 130d, a first section 171d passing through the first section 131d of the first curved surface workpiece part and a portion of the first section 151d of the assumed movement route 150d, and a second section 172d passing through the second section 132d of the second curved surface workpiece part and a portion of the second section 152d of the assumed movement route 150d are connected across the inflection point 133d. Point Bd1 is set on the first section 131d of the workpiece 130d at positions before and after the inflection point 133d on the surface of the workpiece 130d in the direction in which the assumed movement route 150d extends, and point Bd3 is set on the second section 132d of the workpiece 130d. Point Bd2 is set on the surface of the workpiece 130d at a position in a direction intersecting the inflection point 133d with the assumed movement route 150d. The first section 171d of the joint trajectory 170d includes a first sub-section 171d1 between points Ad and Bd1 and a first evacuation section 171d2 between points Bd1 and Bd2. The second section 172d of the joint trajectory 170d includes a second evacuation section 172d1 between points Bd2 and Bd3 and a second sub-section 172d2 between points Bd3 and Cd. The joint trajectory 170d includes the first sub-section 171d1, the first evacuation section 171d2, the second evacuation section 172d1, and the second sub-section 172d2, which are arranged in this order. Of these, the first evacuation section 171d2 and the second evacuation section 172d1 (hereinafter also referred to as "evacuation sections 171d2, 172d1") describe a trajectory that deviates from the assumed movement route 150d, passes through point Bd2 located away from the assumed movement route 150d, and returns to the assumed movement route 150d. When expressed in a planar form along the surface of the workpiece 130d in this way, the joining trajectory 170d has the evacuation sections 171d2, 172d1 provided in a direction that intersects with the assumed movement route 150d before and after the inflection point 133d between the first section 131d, which is a curved section of the workpiece 130d, and the second section 132d, which is also a curved section.

[0115] [3-4-2. Joining method] The joining method according to the present embodiment performs friction stir welding on the above-described assumed movement route 150d of the workpiece 130d using the joining system 1. The joining method according to the present embodiment also includes a joining step of inserting a rotary tool F into the workpiece 130d and moving the rotary tool F along a joining trajectory 170d to perform friction stir welding on the workpiece 130d.

[0116] In the joining process according to this embodiment, before and after an inflection point 133d between a first curved section 131d and a second curved section 132d of the workpiece 130d, retreat sections 171d2 and 172d1 are provided in a direction intersecting with the assumed movement route 150d. The joining control unit 61 moves the rotary tool in the retreat sections 171d2 and 172d1 in a direction intersecting with the joining direction of the workpiece 130d, and changes the angle of the rotary tool F with respect to the workpiece 130d in accordance with the angle of the workpiece 130d in the retreat sections 171d2 and 172d1. The change in the angle of the rotary tool F in the retreat sections 171d2 and 172d1 can be performed in the same manner as described in the first embodiment.

[0117] [3-4-3. Action and Effects] In the workpiece 130d having the first section 131d and the second section 132d, which are curved sections, the positions of the center points of the curves in the first section 131d and the second section 132d are different. In addition, in the workpiece 130d having the first section 131d and the second section 132d, which are curved sections, the directions of the concaves and convexes in the first section 131d and the second section 132d are different. In the workpiece 130d having the first section 131d and the second section 132d, which are curved sections, the curved section appears to be smoothly continuous from one curved section to the other. When joining is performed while maintaining a constant movement speed of the tip of the rotary tool F, whose tip contacts the workpiece 130d, and while maintaining the angle of the rotary tool F relative to the workpiece 130d, when the rotary tool F passes through point Bd located between the first section 131d and the second section 132d, the attitude (angle) of the rotary tool F changes in the curved section with a constant curvature between point Ad and point Bd, i.e., from a state in which the angular velocity was maintained, in accordance with the change in the direction of the concaves and convexes between the first section 131d and the second section 132d, the attitude of the rotary tool F changes to match the curved surface of the curved section between point Bd and point Cd, generating angular acceleration of the rotary tool F. In other words, at point Bd, which is the inflection point 133d, angular acceleration of the rotary tool F occurs, causing vibrations in the rotary tool F.

[0118] The joining system 1 moves the rotary tool F in a direction intersecting the joining direction of the workpiece 130d before and after an inflection point 133d between the first section 131d, which is a curved section, and the second section 132d, which is a curved section, or in the retreat sections 171d2, 172d1 at the inflection point 133d, and changes the angle of the rotary tool F with respect to the workpiece 130d in accordance with the shape of the first curved workpiece part having a curved surface portion including the first section 131d, which is a curved section, and the shape of the second curved workpiece part having a curved surface portion including the second section 132d, which is a curved section. As a result, by the same action as in the first embodiment, it is possible to change the angle of the rotary tool F in accordance with the shape of the workpiece 130d while suppressing vibrations (shaking) generated in the arm 31a of the arm robot 31 and the rotary tool F when passing through the inflection point 133d, and thereby improve joining quality. In the present embodiment, when the first section 131d, which is a curved section, and the second section 132d, which is also a curved section, are continuous with each other across the inflection point 133d and the directions of the concave and convex portions of the first section 131d and the second section 132d are different, the tilt direction of the rotary tool F is reversed when passing through the inflection point 133d, which tends to increase the angular acceleration. According to the present embodiment, the angular acceleration can be reduced even in such a case.

[0119] [3-4-4.Other] In the fourth embodiment described above, a case has been described in which the workpiece 130d, the assumed movement route 150d, and the joint trajectory 170d are configured such that the first section 131d, 151d, 171d, which is a curved section having a concave R, and the second section 132d, 152d, 172d, which is a curved section having a convex R, are continuous with each other, with the inflection point 133d in between, and the first section 171d, which is a curved section having a concave R, and the second section 172d, which is a curved section having a convex R, are joined in sequence. The joining method according to this embodiment can also be applied to a case in which the workpiece 130d, the assumed movement route 150d, and the joint trajectory 170d are configured such that the first section 131d, 151d, 171d, which is a curved section having a convex R, and the second section 132d, 152d, 172d, which is a curved section having a concave R, are continuous with each other, with the inflection point 133d in between, and the first section 171d, which is a curved section having a convex R, and the second section 172d, which is a curved section having a concave R, are joined in sequence.

[0120] In the fourth embodiment described above, the case where the first section 131d and the second section 132d, which are curved sections, have approximately the same curvature, has been described as an example. The joining method according to this embodiment can also be applied to cases where the first section 131d and the second section 132d have different curvatures.

[0121] In the fourth embodiment described above, a case has been described in which the angle formed between the tangents of the curved first section 131d and the curved second section 132d at their respective ends Bd, Bd is 180°. The joining method according to this embodiment can also be applied to cases in which the angle formed between the tangents of the curved first section 131d and the curved second section 132d at their respective ends Bd, Bd is greater than or less than 180°.

[0122] [3-5. Fifth embodiment of joining method] Next, a fifth embodiment of the joining method will be described with reference to Fig. 11, Fig. 6(a), and Fig. 6(b). As shown in Fig. 11, in the fifth embodiment, the shape of the workpiece 130e and the shapes of the assumed movement route 150e and the joining trajectory 170e when viewed from the side are different from those in the first embodiment. In the fifth embodiment, the differences from the first embodiment will be mainly described, and a description of the parts common to the first embodiment will be omitted.

[0123] [3-5-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 11 shows a side view of the surface shape of the workpiece 130e according to this embodiment, as well as the expected movement route 150e and the joining trajectory 170e. Fig. 6(a) shows the surface shape of the workpiece 130e according to this embodiment and the expected movement route 150e shown in a plane along the surface of the workpiece 130e. Fig. 6(b) shows the joining trajectory 170e according to this embodiment shown in a plane along the surface of the workpiece 130e.

[0124] As shown in FIG. 11 , in this embodiment, in a side cross-sectional view of the workpiece 130e, a first section 131e between points Ae and Be and a second section 132e between points Be and Ce are connected at point Be. The first section 131e and the second section 132e have a continuous shape with an inflection point 133e at point Be sandwiched between them. In the workpiece 130e, the first section 131e is a curved section, and the second section 132e is a curved section. The workpiece 130e is continuously formed with a first curved workpiece having a curved surface portion including the first section 131e, which is a curved section, on its surface, and a second curved workpiece having a curved surface portion including the second section 132e, which is a curved section, on its surface. More specifically, the first curved workpiece having a curved surface portion including the first section 131e, which is a curved section, and the second curved workpiece having the second section 132e, which is a curved section, each have an arc-like shape with approximately the same curvature in cross-sectional view. The first curved-surface workpiece and the second curved-surface workpiece are continuous such that a tangent to one end of the arc-shaped surface of the first curved-surface workpiece intersects a tangent to one end of the arc-shaped surface of the second curved-surface workpiece. In other words, the first section 131e and the second section 132e are continuous such that, at their respective ends Be, Be, where the first section 131e and the second section 132e are continuous, the angle formed by a tangent drawn from point Be, which is one end of the first section 131e, in the direction extending to point Ae, which is the other end, and a tangent drawn from point Be, which is one end of the second section 132e, in the direction extending to point Ce, which is the other end, is less than 180°. Furthermore, the first section 131e, which is a curved section with a convex R, and the second section 132e, which is a curved section with a convex R, are continuous across an inflection point 133e. In other words, the first section 131e and the second section 132d have the same concave-convex direction. Here, the assumed movement route 150e of this embodiment passes through the first section 131e, the inflection point 133e, and the second section 132e of the workpiece 130e in this order.Therefore, in a side cross-sectional view, the workpiece 130e has a first section 131e and a second section 132e that are continuous along the assumed movement route 150e with an inflection point 133e in between, and at points Be, Be that are one end of the first section 131e and the second section 132e where the first section 131e and the second section 132e are continuous, the angle formed by the tangent to one end Be of the first section 131e and the tangent to one end Be of the second section 132e is less than 180°. In addition, the first section 131e, which is a curved section, and the second section 132e, which is also a curved section, have different positions of the center points of the circular arc-shaped curves.

[0125] 11, in a side cross-sectional view, the assumed movement route 150e of this embodiment is such that a first section 151e passing through a first section 131e of the first curved-surface workpiece part and a second section 152e passing through a second section 132e of the second curved-surface workpiece part are connected across an inflection point 133e. As described above, the first section 131e of the workpiece 130e is a curved section, and the second section 132e of the workpiece 130e is also a curved section, so the assumed movement route 150e is connected between the first section 151e, which is a curved section, and the second section 152e, which is also a curved section. In this way, the assumed movement route 150e is set so that the height position of the workpiece 130e changes in a side cross-sectional view. Furthermore, in a side cross-sectional view, the assumed movement route 150e has a first section 151e and a second section 152e that are continuous across an inflection point 133e, and at one end Be, Be of the first section 151e and the second section 152e where they are continuous, the angle between the tangent to one end Be of the first section 151e and the tangent to one end Be of the second section 152e is less than 180°.

[0126] 11, in a side cross-sectional view, the joint trajectory 170e of this embodiment has a first section 171e passing through a first section 131e of the first curved surface workpiece part and a second section 172e passing through a second section 132e of the second curved surface workpiece part, which are connected across an inflection point 133e. As described above, the first section 131e of the workpiece 130e is a curved section, and the second section 132e of the workpiece 130e is a curved section, so the joint trajectory 170e has the first section 171e, which is a curved section, connected to the second section 172e, which is also a curved section. In addition, in a side cross-sectional view, the joint track 170e has a first section 171e and a second section 172e that are continuous across an inflection point 133e, and at one end Be2 where the first section 171e and the second section 172e are continuous, the angle between the tangent to one end Be2 of the first section 171e and the tangent to one end Be2 of the second section 172e is less than 180°.

[0127] As shown in Figure 6(a), when the workpiece 130e is represented in a plane along its surface, a first section 131e between points Ae and Be and a second section 132e between points Be and Ce have a shape that is continuous in a straight line, sandwiched between an inflection point 133e at the position of point Be.

[0128] As shown in Figure 6(a), when the expected movement route 150e is represented in a plane along the surface of the workpiece 130e, a first section 151e passing through a first section 131e of the first curved surface workpiece part and a second section 152e passing through a second section 132e of the second curved surface workpiece part are connected in a straight line with an inflection point 133e in between.

[0129] 6(b), when the joining trajectory 170e is represented in a plane along the surface of the workpiece 130e, a first section 171e passing through a first section 131e of the first curved-surface workpiece part and a portion of the first section 151e of the assumed movement route 150e, and a second section 172e passing through a second section 132e of the second curved-surface workpiece part and a portion of the second section 152e of the assumed movement route 150e are connected across an inflection point 133e. Point Be1 is set on the first section 131e of the workpiece 130e, and point Be3 is set on the second section 132e of the workpiece 130e, at positions before and after the inflection point 133e on the surface of the workpiece 130e in the direction in which the assumed movement route 150e extends. Point Be2 is set on the surface of the workpiece 130e at a position intersecting the inflection point 133e with respect to the assumed movement route 150e. The first section 171e of the joint trajectory 170e includes a first sub-section 171e1 between points Ae and Be1 and a first evacuation section 171e2 between points Be1 and Be2. The second section 172e of the joint trajectory 170e includes a second evacuation section 172e1 between points Be2 and Be3 and a second sub-section 172e2 between points Be3 and Ce. The joint trajectory 170e includes the first sub-section 171e1, the first evacuation section 171e2, the second evacuation section 172e1, and the second sub-section 172e2, which are arranged consecutively in this order. Of these, the first evacuation section 171e2 and the second evacuation section 172e1 (hereinafter also referred to as "evacuation sections 171e2, 172e1") describe a trajectory that deviates from the assumed movement route 150e, passes through point Be2 located away from the assumed movement route 150e, and returns to the assumed movement route 150e. When expressed in a planar form along the surface of the workpiece 130e in this way, the joining trajectory 170e has evacuation sections 171e2, 172e1 provided in a direction that intersects with the assumed movement route 150e before and after an inflection point 133e between the first section 131e, which is a curved section of the workpiece 130e, and the second section 132e, which is also a curved section.

[0130] [3-5-2. Joining method] The joining method according to the present embodiment performs friction stir welding on the above-described assumed movement route 150e of the workpiece 130e using the joining system 1. The joining method according to the present embodiment also includes a joining step of inserting a rotary tool F into the workpiece 130e and moving the rotary tool F along a joining trajectory 170e to perform friction stir welding on the workpiece 130e.

[0131] In the joining process according to this embodiment, before and after an inflection point 133e between a first curved section 131e and a second curved section 132e of the workpiece 130e, retreat sections 171e2 and 172e1 are provided in a direction intersecting with the assumed movement route 150e. The joining control unit 61 then moves the rotary tool in the retreat sections 171e2 and 172e1 in a direction intersecting with the joining direction of the workpiece 130e, while changing the angle of the rotary tool F with respect to the workpiece 130e in accordance with the angle of the workpiece 130e in the retreat sections 171e2 and 172e1. The angle of the rotary tool F in the retreat sections 171e2 and 172e1 can be changed in the same manner as described in the first embodiment.

[0132] [3-5-3. Action and Effects] In the workpiece 130e having the first section 131e and the second section 132e, which are curved sections, the positions of the center points of the curves of the first section 131e and the second section 132e are different. In the workpiece 130e having the first section 131e and the second section 132e, which are curved sections, the first section 131e and the second section 132e are continuous such that the angle formed by the tangents of the respective one end portions Be, Be at which the first section 131e and the second section 132e are continuous is less than 180°. When joining is performed while maintaining a constant movement speed of the tip of the rotary tool F, whose tip contacts the workpiece 130e, and while maintaining the angle of the rotary tool F relative to the workpiece 130e, when the rotary tool F passes through point Be located between the first section 131e and the second section 132e, the attitude (angle) of the rotary tool F changes in the curved section with a constant curvature between point Ae and point Be, i.e., from a state in which the angular velocity was maintained, and in response to a change in the direction of the tangent to the first section 131e and the second section 132e, the attitude of the rotary tool F changes to match the curved surface of the curved section between point Be and point Ce, generating angular acceleration of the rotary tool F. In other words, at point Be, which is the inflection point 133e, angular acceleration of the rotary tool F occurs, causing vibration in the rotary tool F.

[0133] The joining system 1 moves the rotary tool F in a direction intersecting the joining direction of the workpiece 130e before and after an inflection point 133e between the first section 131e, which is a curved section, and the second section 132e, which is also a curved section, or in the retreat sections 171e2, 172e1 at the inflection point 133e, and changes the angle of the rotary tool F with respect to the workpiece 130e in accordance with the shape of the first curved workpiece part having a curved surface portion including the first section 131e, which is a curved section, and the shape of the second curved workpiece part having a curved surface portion including the second section 132e, which is a curved section. As a result, by the same action as in the first embodiment, it is possible to change the angle of the rotary tool F in accordance with the shape of the workpiece 130e while suppressing vibrations (shaking) generated in the arm 31a of the arm robot 31 and the rotary tool F when passing through the inflection point 133e, and thereby improve joining quality.

[0134] [3-5-4.Other] In the above-described fifth embodiment, a case has been described in which the workpiece 130e, the assumed movement route 150e, and the joint trajectory 170e are configured such that the first section 131e, 151e, 171e, which is a curved section having a convex R, and the second section 132e, 152e, 172e, which is a curved section having a convex R, are continuous on either side of the inflection point 133e, and the first section 171e, which has a convex R, and the second section 172e, which has a convex R, are joined in that order. The workpiece 130e, the assumed movement route 150e, and the joint trajectory 170e may be configured such that both the first section 131e, 151e, 171e, which is a curved section, and the second section 132e, 152e, 172e, which is a curved section, have a concave R, or one of them may be a curved section having a convex R and the other a curved section having a concave R.

[0135] In the fifth embodiment described above, the curvatures of the first section 131e and the second section 132e, which are curved sections, are approximately equal to each other. The joining method according to this embodiment can also be applied to cases where the curvatures of the first section 131e and the second section 132e are different from each other.

[0136] [3-6. Sixth embodiment of joining method] Next, a sixth embodiment of the joining method will be described with reference to Fig. 12, Fig. 6(a), and Fig. 6(b). As shown in Fig. 12, in the sixth embodiment, the shape of the workpiece 130f, and the shapes of the assumed movement route 150f and the joining trajectory 170f when viewed from the side are different from those in the first embodiment. In the sixth embodiment, the differences from the first embodiment will be mainly described, and a description of the parts common to the first embodiment will be omitted.

[0137] [3-6-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 12 shows a side view of the surface shape of the workpiece 130f according to this embodiment, as well as the expected movement route 150f and the joining trajectory 170f. Fig. 6(a) shows the surface shape of the workpiece 130f according to this embodiment and the expected movement route 150f shown in a plane along the surface of the workpiece 130f. Fig. 6(b) shows the joining trajectory 170f according to this embodiment shown in a plane along the surface of the workpiece 130f.

[0138] As shown in FIG. 12 , in this embodiment, in a side cross-sectional view of the workpiece 130f, a first section 131f between points Af and Bf and a second section 132f between points Bf and Cf are connected at point Bf. The first section 131f and the second section 132f have a continuous shape with an inflection point 133f at the position of point Bf sandwiched between them. In the workpiece 130f, the first section 131f is a curved section, and the second section 132f is a curved section. The workpiece 130f is continuously formed with a first curved-surface workpiece having a curved surface portion including the first section 131f, which is a curved section, on its surface, and a second curved-surface workpiece having a curved surface portion including the second section 132f, which is a curved section, on its surface. More specifically, the first curved-surface workpiece having a curved surface portion including the first section 131f, which is a curved section, and the second curved-surface workpiece having a curved surface portion including the second section 132f, which is a curved section, each have an arc-like shape with approximately the same curvature in a cross-sectional view. The first curved-surface workpiece and the second curved-surface workpiece are continuous so that a tangent to one end of the arc-shaped surface of the first curved-surface workpiece intersects with a tangent to one end of the arc-shaped surface of the second curved-surface workpiece. In other words, at one end Bf, Bf where the first section 131f and the second section 132f are continuous, the first section 131f and the second section 132f are continuous so that the angle between a tangent drawn from point Bf, which is one end of the first section 131f, in the direction extending to point Af, which is the other end, and a tangent drawn from point Bf, which is one end of the second section 132f, in the direction extending to point Cf, which is the other end, exceeds 180°. Furthermore, the first section 131f, which is a curved section having a convex R, and the second section 132f, which is a curved section having a convex R, are continuous across an inflection point 133f. That is, the first section 131f and the second section 132f have the same direction of the concave and convex portions. Here, the assumed movement route 150f of the present embodiment passes through the first section 131f, the inflection point 133f, and the second section 132f of the workpiece 130f in this order.Therefore, in a side cross-sectional view, the workpiece 130f has a first section 131f and a second section 132f that are continuous along the assumed movement route 150f with an inflection point 133f in between, and at points Bf, Bf that are one end of the first section 131f and the second section 132f where the first section 131f and the second section 132f are continuous, the angle formed by the tangent to one end Bf of the first section 131f and the tangent to one end Bf of the second section 132f exceeds 180°. In addition, the first section 131f, which is a curved section, and the second section 132f, which is a curved section, have different positions of the center points of the circular arc-shaped curves.

[0139] 12, in a side cross-sectional view, the assumed movement route 150f of this embodiment is such that a first section 151f passing through a first section 131f of the first curved surface workpiece part and a second section 152f passing through a second section 132f of the second curved surface workpiece part are connected with an inflection point 133f in between. As described above, the first section 131f of the workpiece 130f is a curved section, and the second section 132f of the workpiece 130f is also a curved section, so the assumed movement route 150f connects the first section 151f, which is a curved section, and the second section 152f, which is also a curved section. In this way, the assumed movement route 150f is set so that the height position of the workpiece 130f changes in a side cross-sectional view. In addition, in a side cross-sectional view, the assumed movement route 150f has a first section 151f and a second section 152f that are continuous with each other across an inflection point 133f, and at one end Bf, Bf where the first section 151f and the second section 152f are continuous, the angle between the tangent to one end Bf of the first section 151f and the tangent to one end Bf of the second section 152f exceeds 180°.

[0140] 12, in a side cross-sectional view, the joining trajectory 170f of this embodiment is such that a first section 171f passing through a first section 131f of the first curved surface workpiece part and a second section 172f passing through a second section 132f of the second curved surface workpiece part are connected across an inflection point 133f. As described above, the first section 131f of the workpiece 130f is a curved section, and the second section 132f of the workpiece 130f is also a curved section, so the joining trajectory 170f is such that the first section 171f, which is a curved section, is connected to the second section 172f, which is also a curved section. In addition, in a side cross-sectional view, the joint track 170f has a first section 171f and a second section 172f that are continuous with each other across an inflection point 133f, and at one end Bf2, Bf2 where the first section 171f and the second section 172f are continuous, the angle formed by the tangent to one end Bf2 of the first section 171f and the tangent to one end Bf2 of the second section 172f exceeds 180°.

[0141] As shown in Figure 6(a), when the workpiece 130f is represented in a plane along its surface, a first section 131f between points Af and Bf and a second section 132f between points Bf and Cf have a shape that is continuous in a straight line, sandwiched between an inflection point 133f at the position of point Bf.

[0142] As shown in Figure 6(a), when the expected movement route 150f is represented in a plane along the surface of the workpiece 130f, a first section 151f passing through a first section 131f of the first curved surface workpiece part and a second section 152f passing through a second section 132f of the second curved surface workpiece part are connected in a straight line with an inflection point 133f in between.

[0143] 6(b), when the joining trajectory 170f is represented in a plane along the surface of the workpiece 130f, a first section 171f passing through the first section 131f of the first curved surface workpiece part and a portion of the first section 151f of the assumed movement route 150f, and a second section 172f passing through the second section 132f of the second curved surface workpiece part and a portion of the second section 152f of the assumed movement route 150f are connected across an inflection point 133f. Point Bf1 is set on the first section 131f of the workpiece 130f, and point Bf3 is set on the second section 132f of the workpiece 130f, at positions before and after the inflection point 133f on the surface of the workpiece 130f in the direction in which the assumed movement route 150f extends. Point Bf2 is set on the surface of the workpiece 130f at a position intersecting the inflection point 133f with respect to the assumed movement route 150f. The first section 171f of the joint trajectory 170f includes a first sub-section 171f1 between points Af and Bf1 and a first evacuation section 171f2 between points Bf1 and Bf2. The second section 172f of the joint trajectory 170f includes a second evacuation section 172f1 between points Bf2 and Bf3 and a second sub-section 172f2 between points Bf3 and Cf. The joint trajectory 170f includes the first sub-section 171f1, the first evacuation section 171f2, the second evacuation section 172f1, and the second sub-section 172f2, which are arranged in this order. Of these, the first evacuation section 171f2 and the second evacuation section 172f1 (hereinafter also referred to as "evacuation sections 171f2, 172f1") describe a trajectory that deviates from the assumed movement route 150f, passes through point Bf2 located away from the assumed movement route 150f, and returns to the assumed movement route 150f. When expressed in a plane along the surface of the workpiece 130f in this way, the joining trajectory 170f has evacuation sections 171f2, 172f1 provided in a direction that intersects with the assumed movement route 150f before and after an inflection point 133f between the first section 131f, which is a curved section of the workpiece 130f, and the second section 132f, which is also a curved section.

[0144] [3-6-2. Joining method] The joining method according to the present embodiment performs friction stir welding on the above-described assumed movement route 150f of the workpiece 130f using the joining system 1. The joining method according to the present embodiment also includes a joining step of inserting the rotary tool F into the workpiece 130f and moving the rotary tool F along the joining trajectory 170f to perform friction stir welding on the workpiece 130f.

[0145] In the joining process according to this embodiment, before and after an inflection point 133f between a first curved section 131f and a second curved section 132f of the workpiece 130f, retreat sections 171f2 and 172f1 are provided in a direction intersecting with the assumed movement route 150f. The joining control unit 61 moves the rotary tool F in the retreat sections 171f2 and 172f1 in a direction intersecting with the joining direction of the workpiece 130f, and changes the angle of the rotary tool F with respect to the workpiece 130f to match the angle of the workpiece 130f in the retreat sections 171f2 and 172f1. The change in the angle of the rotary tool F in the retreat sections 171f2 and 172f1 can be performed in the same manner as described in the first embodiment.

[0146] [3-6-3. Action and Effects] In the workpiece 130f having the first section 131f and the second section 132f, which are curved sections, the positions of the center points of the curves of the first section 131f and the second section 132f are different. In the workpiece 130f having the first section 131f and the second section 132f, which are curved sections, the first section 131f and the second section 132f are continuous such that the angle formed by the tangents of the respective one end portions Bf, Bf exceeds 180°. When joining is performed while maintaining a constant movement speed of the tip of the rotary tool F, whose tip contacts the workpiece 130f, and while maintaining the angle of the rotary tool F relative to the workpiece 130f, when the rotary tool F passes through point Bf located between the first section 131f and the second section 132f, the attitude (angle) of the rotary tool F changes in the curved section with a constant curvature between point Af and point Bf, i.e., from a state in which the angular velocity was maintained, in accordance with a change in the direction of the tangent to the first section 131f and the second section 132f, and the attitude of the rotary tool F changes to match the curved surface of the curved section between point Bf and point Cf, generating angular acceleration of the rotary tool F. In other words, angular acceleration of the rotary tool F occurs at point Bf, which is the inflection point 133f, and vibration occurs in the rotary tool F.

[0147] The joining system 1 moves the rotary tool F in a direction intersecting the joining direction of the workpiece 130f before and after an inflection point 133f between the first section 131f, which is a curved section, and the second section 132f, which is a curved section, or in the retreat sections 171f2, 172f1 at the inflection point 133f, and changes the angle of the rotary tool F with respect to the workpiece 130f in accordance with the shape of the first curved workpiece part having a curved surface portion including the first section 131f, which is a curved section, and the shape of the second curved workpiece part having a curved surface portion including the second section 132f, which is a curved section. As a result, by the same action as in the first embodiment, it is possible to change the angle of the rotary tool F in accordance with the shape of the workpiece 130f while suppressing vibrations (shaking) generated in the arm 31a of the arm robot 31 and the rotary tool F when passing through the inflection point 133f, thereby improving joining quality.

[0148] [3-6-4.Other] In the sixth embodiment described above, a case has been described in which the workpiece 130f, the assumed movement route 150f, and the joint trajectory 170f include a first section 131f, 151f, 171f that is a curved section having a convex R and a second section 132f, 152f, 172f that is a curved section having a convex R, which are continuous on either side of the inflection point 133f, and the first section 171f with a convex R and the second section 172f with a convex R are joined in that order. The workpiece 130f, the assumed movement route 150f, and the joint trajectory 170f may include a first section 131f, 151f, 171f that is a curved section and a second section 132f, 152f, 172f that is a curved section both having a concave R, or one of the first sections 131f, 151f, 171f that is a curved section and the other section having a concave R.

[0149] In the sixth embodiment described above, the case where the first section 131f and the second section 132f, which are curved sections, have approximately the same curvature has been described as an example. The joining method according to this embodiment can also be applied to cases where the first section 131f and the second section 132f have different curvatures.

[0150] [3-7. First Modification of First Embodiment of Joining Method] A first modified example of the first embodiment of the joining method performed using the joining system 1 will be described. As shown in Figures 13A and 13B, in this modified example, the shape of a workpiece 130g, an expected movement route 150g, and a joining trajectory 170g are different from those in the first embodiment. In this modified example, the parts that are different from the first embodiment will be mainly described, and a description of the parts that are common to the first embodiment will be omitted.

[0151] [3-7-1. Workpiece shape, expected movement route, and joining trajectory] Fig. 13A shows a perspective view of a workpiece 130g according to this modified example, as well as an assumed movement route 150g and a joining trajectory 170g, as viewed from one side. Fig. 13B shows a perspective view of a workpiece 130g according to this modified example, as well as an assumed movement route 150g and a joining trajectory 170g, as viewed from the other side.

[0152] 13A and 13B, in this modification, a side end surface of a first workpiece 130gA and a side end surface of a second workpiece 130gB are butted together along the longitudinal direction to form an butt joint Jg. The joining system 1 performs friction stir welding using the butt joint Jg as a joining part.

[0153] As shown in FIGS. 13A and 13B, in this modified example, a workpiece 130g has a first section 131g between points Ag and Bg and a second section 132g between points Bg and Cg, which are connected at point Bg. The first section 131g and the second section 132g are continuous across an inflection point 134g at point Bg. The workpiece 130g also has a second section 132g between points Bg and Cg and a third section 133g between points Cg and Dg, which are connected at point Bg. The second section 132g and the third section 133g are continuous across an inflection point 135g at point Cg. In the workpiece 130g, the first section 131g is a straight section, the second section 132g is a curved section, and the third section 133g is a straight section. The first workpiece 130gA is formed successively with a planar workpiece 130gA1 having a planar portion including a first section 131g which is a straight section on its surface, a curved workpiece 130gA2 having a curved portion including a second section 132g which is a curved section on its surface, and a planar workpiece 130gA3 having a planar portion including a third section 133g which is a straight section on its surface. The second workpiece 130gB is formed successively with a planar workpiece 130gB1 having a planar portion including the first section 131g which is a straight section on its surface, a curved workpiece 130gB2 having a curved portion including a second section 132g which is a curved section on its surface, and a planar workpiece 130gB3 having a planar portion including a third section 133g which is a straight section on its surface. The workpiece 130g has a first section 131g formed by butting together a flat workpiece portion 130gA1 and a flat workpiece portion 130gB1, a second section 132g formed by butting together a curved workpiece portion 130gA2 and a curved workpiece portion 130gB2, and a third section 133g formed by butting together a flat workpiece portion 130gA3 and a flat workpiece portion 130gB3.

[0154] The workpiece 130g, expected movement route 150g, and joining trajectory 170g of this modified example are similar to those of the first embodiment for the workpiece 130a, in which the first section 131g, 151g, 171g and the second section 132g, 152g, 172g have the first section 131a, 151a, 171a which is a straight section and the second section 132a, 152a, 172a which is a curved section. The workpiece 130g, assumed movement route 150g, and joining trajectory 170g of this modified example have a relationship similar to that of the first embodiment, in which the second section 132g, 152g, 172g and the third section 133g, 153g, 173g are joined in the order of second section 132a to first section 131a in relation to the workpiece 130a having a first section 131a which is a straight section and a second section 132a which is a straight section. In this way, this modification is a combination of modifications of the first embodiment.

[0155] That is, the workpiece 130g, assumed movement route 150g, and joint trajectory 170g of this modified example have first sections 131g, 151g, 171g which are straight sections and second sections 132g, 152g, 172g which are curved sections, similar to the workpiece 130a, assumed movement route 150a, and joint trajectory 170a of the first embodiment, which have first sections 131a, 151a, 171a which are straight sections and second sections 132a, 152a, 172a which are curved sections, and further have third sections 133g, 153g, 173g which are straight sections on the side of the second sections 132g, 152g, 172g. In other words, in this modified example, the workpiece 130g, the assumed movement route 150g, and the first section 131g, 151g, 171g, the second section 132g, 152g, 172g, and the third section 133g, 153g, 173g of the joining trajectory 170g are a combination of a section in which the first section 131a, 151a, 171a, which is a straight section in the first embodiment, is joined to the second section 132a, 152a, 172a, which is a curved section, in that order, and a section in which the second section 132a, 152a, 172a, which is a curved section in the first embodiment, is joined to the first section 131a, 151a, 171a, which is a straight section, in that order.

[0156] [3-7-2. Joining method] The welding method according to this modified example performs friction stir welding on the assumed movement route 150g of the workpiece 130g described above using the welding system 1. The welding method according to this embodiment also includes a welding step of inserting a rotary tool F into the workpiece 130g and moving the rotary tool F along a welding trajectory 170g to perform friction stir welding on the workpiece 130g.

[0157] In the joining process according to this modification, as in the first embodiment, the first section 171g of the joining trajectory 170g includes a first sub-section 171g1 between points Ag and Bg1 and a first retraction section 171g2 between points Bg1 and Bg2. The second section 172g of the joining trajectory 170g includes a second retraction section 172g1 between points Bg2 and Bg3, a second sub-section 172g2 between points Bg3 and Cg1, and a third retraction section 172g3 between points Cg1 and Cg2. The third section 173g of the joining trajectory 170g includes a fourth retraction section 173g1 between points Cg2 and Cg3 and a third sub-section 173g2 between points Cg3 and Dg. The first evacuation section 171g2 and the second evacuation section 172g1 will also be referred to as "evacuation sections 171g2, 172g1" hereinafter. The third evacuation section 172g3 and the fourth evacuation section 173g1 will also be referred to as "evacuation sections 172g3, 173g1" hereinafter.

[0158] In the joining process according to this modified example, before and after an inflection point 134g between a first section 131g, which is a straight section, and a second section 132g, which is a curved section, of the workpiece 130g, retreat sections 171g2 and 172g1 are provided in a direction intersecting with the assumed movement route 150g. The joining control unit 61 moves the rotary tool F in the retreat sections 171g2 and 172g1 in a direction intersecting with the joining direction of the workpiece 130g, and changes the angle of the rotary tool F with respect to the workpiece 130g in accordance with the angle of the workpiece 130g in the retreat sections 171g2 and 172g1.

[0159] Furthermore, in the joining process according to this modified example, before and after an inflection point 135g between the second section 132g, which is a curved section of the workpiece 130g, and the third section 133g, which is a straight section, retreat sections 172g3 and 173g1 are provided in a direction intersecting with the assumed movement route 150g. The joining control unit 61 moves the rotary tool F in the retreat sections 172g3 and 173g1 in a direction intersecting with the joining direction of the workpiece 130g, and changes the angle of the rotary tool F with respect to the workpiece 130g in accordance with the angle of the workpiece 130g in the retreat sections 172g3 and 173g1.

[0160] [3-7-3. Action and Effects] In this modified example, as in the first embodiment, when passing through the inflection points 134g and 135g, the angle of the rotary tool F can be changed to match the shape of the workpiece 130g while suppressing vibrations (shakes) that occur in the arm 31a of the arm robot 31 and the rotary tool F, thereby improving the joining quality.

[0161] Furthermore, as in this modified example, two or more of the first to sixth embodiments described above can be combined. That is, the present invention can be applied to a combination of the workpieces 130a-f, the assumed movement routes 150a-f, and the joining trajectories 170a-f according to the first to sixth embodiments. Of the first to sixth embodiments, the same type of embodiments may be combined, or different types of embodiments may be combined. Furthermore, the first to sixth embodiments described above may be modified and combined.

[0162] [3-7-4.Other] In the joining process according to this modified example, the workpiece 130g has two inflection points 134g and 135g, and for both the retraction sections 171g2 and 172g1 provided before and after the inflection point 134g and the retraction sections 172g3 and 173g1 provided before and after the inflection point 135g, the retraction sections are provided so that the rotary tool moves in a direction that intersects with the assumed movement route 150g toward the right side of the joining direction of the workpiece 130g. When the workpiece has multiple inflection points and retraction sections are provided for each of the multiple inflection points, the multiple retraction sections may be provided in directions that intersect with the assumed movement route toward the same side, or the multiple retraction sections may be provided in directions that intersect with the assumed movement route toward different sides.

[0163] [3-8. Second Modification of First Embodiment of Joining Method] A second modification of the first embodiment of the joining method performed using the joining system 1 will be described. In this modification, the shape of the workpiece 130h, the assumed movement route 150h, and the joining trajectory 170h are different from those of the first embodiment. In this modification, the parts different from the first embodiment will be mainly described, and the parts common to the first and fourth embodiments will not be described.

[0164] [3-8-1. Workpiece shape, expected movement route, and joining trajectory] FIG. 14(a) shows a side view of the shape of a workpiece 130h according to this modified example, as well as an assumed movement route 150h and a joining trajectory 170h.

[0165] 14(a), in this modification, the workpiece 130h has, in a side cross-sectional view, a first section 131h between points Ah and Bh, a second section 132h between points Bh and Ch, a third section 133h between points Ch and Dh, a fourth section 134h between points Dh and Eh, a fifth section 135h between points Eh and Fh, and a sixth section 136h between points Fh and Gh. In the workpiece 130h, the first section 131h and the sixth section 136h are straight sections, while the second section 132h and the fifth section 135h are curved sections with a concave radius. The third section 133h and the fourth section 134h are curved sections with a convex radius. The third section 133h and the fourth section 134h have the same curvature, and the angle between a tangent drawn from point Dh, which is one end of the third section 133h, in the direction extending to point Ch, which is the other end, and a tangent drawn from point Dh, which is one end of the fourth section 134h, in the direction extending to point Eh, which is the other end, is 180°, so that the third section 133h and the fourth section 134h are a continuous, integrated arc.

[0166] The first section 131h and the second section 132h of this modified example are similar to those in the first embodiment relating to the workpiece 130a having the first section 131a which is a straight section and the second section 132a which is a curved section, in which the second section 132a has a concave R. The second section 132h and the third section 133h of this modified example are configured in the same manner as in the fourth embodiment with respect to the workpiece 130d having the first section 131d and the second section 132d that are curved sections with different concave and convex directions. The fourth section 134h and the fifth section 135h of this modified example are similar to those of the fourth embodiment relating to the workpiece 130d having a first section 131d and a second section 132d which are curved sections with different concave and convex directions, in which the second section 132d has a convex R and the second section 132d has a concave R. The fifth section 135h and the sixth section 136h of this modified example have a relationship similar to that in the first embodiment of the workpiece 130a having a first section 131a which is a straight section and a second section 132a which is a curved section, in which the second section 132a has a concave R and the sections are joined in the order from the second section 132a to the first section 131a. In this way, this modification is a combination of modifications of the first embodiment and the fourth embodiment.

[0167] More specifically, in a cross-sectional side view, the workpiece 130h is arranged such that, along the assumed movement route 150h, a first section 131h, which is a straight section, and a second section 132h, which is a curved section with a concave R, are continuous with each other, separated by a point Bh, which is an inflection point 137h. In a cross-sectional side view, the workpiece 130h is arranged along an assumed movement route 150h, with a second section 132h, which is a curved section with a concave R, and a third section 133h, which has a convex R, continuing on either side of an inflection point 138h, point Ch, and the directions of the concave and convex curves of the second section 132h and the third section 133h are different. In a cross-sectional side view, the workpiece 130h is arranged along the assumed movement route 150h, with a fourth section 134h, which is a curved section with a convex R, and a fifth section 135h, which has a concave R, continuing on either side of an inflection point 139h, point Eh, and the directions of the convex and concave curves of the fourth section 134h and the fifth section 135h are different. In a cross-sectional side view, the workpiece 130h has a fifth section 135h, which is a curved section with a concave R, and a sixth section 136h, which is a straight section, that are connected along the expected movement route 150h, with point Fh, which is an inflection point 140h, in between.

[0168] 14(a), the assumed movement route 150h of this modified example, in a side cross-sectional view, includes a first section 151h passing through the first section 131h of the planar workpiece, a second section 152h passing through the second section 132h of the curved workpiece, a third section 153h passing through the third section 133h of the curved workpiece, a fourth section 154h passing through the fourth section 134h of the curved workpiece, a fifth section 155h passing through the fifth section 135h of the curved workpiece, and a sixth section 156h passing through the sixth section 136h of the planar workpiece, connected in this order. As described above, the first section 131h and the sixth section 136h of the workpiece 130h are straight sections, the second section 132h and the fifth section 135h are curved sections with concave R, and the third section 133h and the fourth section 134h are curved sections with convex R. Therefore, the assumed movement route 150h is formed by connecting, in order, a first section 151h which is a straight section, a second section 152h which is a curved section with a concave R, a third section 153h which is a curved section with a convex R, a fourth section 154h which is a curved section with a convex R, a fifth section 155h which is a curved section with a concave R, and a sixth section 156h which is a straight section. In this way, the assumed movement route 150h is set so that the height position of the workpiece 130h changes in a side cross-sectional view.

[0169] 14(a), in a side cross-sectional view, the joining track 170h of this modified example includes a first section 171h passing through the first section 131h of the planar workpiece, a second section 172h passing through the second section 132h of the curved workpiece, a third section 173h passing through the third section 133h of the curved workpiece, a fourth section 174h passing through the fourth section 134h of the curved workpiece, a fifth section 175h passing through the fifth section 135h of the curved workpiece, and a sixth section 176h passing through the sixth section 136h of the planar workpiece, connected in this order. As described above, the first section 131h and the sixth section 136h of the workpiece 130h are straight sections, the second section 132h and the fifth section 135h are curved sections with a concave R, and the third section 133h and the fourth section 134h are curved sections with a convex R. Therefore, the joint track 170h is made up of a first section 171h which is a straight section, a second section 172h which is a curved section with a concave R, a third section 173h which is a curved section with a convex R, a fourth section 174h which is a curved section with a convex R, a fifth section 175h which is a curved section with a concave R, and a sixth section 176h which is a straight section, which are connected in this order.

[0170] 14(b), when the workpiece 130h is represented in a plane along the surface of the workpiece 130h, a first section 131h between points Ah and Bh and a second section 132h between points Bh and Ch are linearly connected with an inflection point 137h at point Bh. The second section 132h between points Bh and Ch, a third section 133h between points Ch and Eh, and a fourth section 134h therebetween are linearly connected with an inflection point 138h at point Ch. The third section 133h and fourth section 134h between points Ch and Eh, and a fifth section 135h between points Eh and Fh are linearly connected with an inflection point 139h at point Eh. A fifth section 135h between points Eh and Fh and a sixth section 136h between points Fh and Gh have a shape that is continuous in a straight line with an inflection point 140h at the position of point Fh in between.

[0171] 14(b), when the assumed movement route 150h is represented in a plane along the surface of the workpiece 130h, a first section 151h passing through the first section 131h of the flat workpiece portion and a second section 152h passing through the second section 132h of the curved workpiece portion are connected in a straight line across an inflection point 137h. Furthermore, the second section 152h passing through the second section 132h of the curved workpiece portion are connected in a straight line across an inflection point 138h. Furthermore, the third section 153h and fourth section 154h passing through the third section 133h and fourth section 134h of the curved workpiece portion are connected in a straight line across an inflection point 139h. Furthermore, a fifth section 155h passing through the fifth section 135h of the curved workpiece part and a sixth section 156h passing through the sixth section 136h of the flat workpiece part are connected in a straight line across an inflection point 140h.

[0172] As shown in FIG. 14(c), the joining trajectory 170h is as follows when expressed in a plane along the surface of the workpiece 130h.

[0173] First, the joint trajectory 170h between point Bh and point Dh will be described. A second section 172h, which passes through the second section 132h of the curved workpiece part and a portion of the second section 152h of the assumed movement route 150h, and a third section 173h, which passes through the third section 133h of the curved workpiece part and a portion of the third section 153h of the assumed movement route 150h, are connected across an inflection point 138h. Point Ch1 is set on the second section 132h of the workpiece 130h at positions before and after the inflection point 138h on the surface of the workpiece 130h in the direction in which the assumed movement route 150h extends, and point Ch3 is set on the third section 133h of the workpiece 130h. Furthermore, point Ch2 is set on the surface of the workpiece 130h at a position in a direction that intersects with the inflection point 138h of the assumed movement route 150h. Points Ch1 and Ch3 are set so that the length from point Ch1 to inflection point 138h is equal to the length from point Ch3 to inflection point 138h. Points Ch1, Ch2, and Ch3 are set so that the length from point Ch1 to point Ch2 is equal to the length from point Ch3 to point Ch2. The second section 172h of the joint trajectory 170h includes a first sub-section 172h1 between point Bh and point Ch1 and a first evacuation section 172h2 between point Ch1 and point Ch2. The third section 173h of the joint trajectory 170h includes a second evacuation section 173h1 between point Ch2 and point Ch3 and a second sub-section 173h2 between point Ch3 and point Dh. In the joint trajectory 170h, a first sub-section 172h1, a first evacuation section 172h2, a second evacuation section 173h1, and a second sub-section 173h2 are successively arranged in this order. Of these, the first evacuation section 172h2 and the second evacuation section 173h1 (hereinafter also referred to as "evacuation sections 172h2, 173h1") deviate from the assumed movement route 150h, pass through point Ch2 located away from the assumed movement route 150h, and trace a trajectory that returns to the assumed movement route 150h.

[0174] Next, the joint trajectory 170h between point Dh and point Fh will be described. A fourth section 174h, which passes through the fourth section 134h of the curved workpiece part and a portion of the fourth section 154h of the assumed movement route 150h, and a fifth section 175h, which passes through the fifth section 135h of the curved workpiece part and a portion of the fifth section 155h of the assumed movement route 150h, are connected across an inflection point 139h. Point Eh1 is set on the fourth section 134h of the workpiece 130h at positions before and after the inflection point 139h on the surface of the workpiece 130h in the direction in which the assumed movement route 150h extends, and point Eh3 is set on the fifth section 135h of the workpiece 130h. Point Eh2 is set on the surface of the workpiece 130h at a position in the direction that intersects with the inflection point 139h of the assumed movement route 150h. Points Eh1 and Eh3 are set so that the length from point Eh1 to inflection point 139h is equal to the length from point Eh3 to inflection point 139h. Points Eh1, Eh2, and Eh3 are set so that the length from point Eh1 to point Eh2 is equal to the length from point Eh3 to point Eh2. The fourth section 174h of the joint trajectory 170h includes a third sub-section 174h1 between point Dh and point Eh1 and a third evacuation section 174h2 between point Eh1 and point Eh2. The fifth section 175h of the joint trajectory 170h includes a fourth evacuation section 175h1 between point Eh2 and point Eh3 and a fourth sub-section 175h2 between point Eh3 and point Fh. In the joint trajectory 170h, a third sub-section 174h1, a third evacuation section 174h2, a fourth evacuation section 175h1, and a fourth sub-section 175h2 are successively arranged in this order. Of these, the third evacuation section 174h2 and the fourth evacuation section 175h1 (hereinafter also referred to as "evacuation sections 174h2, 175h1") deviate from the assumed movement route 150h, pass through point Eh2 located away from the assumed movement route 150h, and trace a trajectory that returns to the assumed movement route 150h.

[0175] Next, the remaining joining trajectory 170h will be described. The first section 171h passing through the first section 131h of the planar workpiece and the first sub-section 172h1 of the second section 172h passing through the second section 132h of the curved workpiece are connected in a straight line across the inflection point 137h. The second sub-section 173h2 of the third section 173h passing through the third section 133h of the curved workpiece and the third sub-section 174h1 of the fourth section 174h passing through the fourth section 134h of the curved workpiece are connected in a straight line across the point Dh. The fourth sub-section 175h2 of the fifth section 175h passing through the fifth section 135h of the curved workpiece and the sixth section 176h passing through the sixth section 136h of the planar workpiece are connected in a straight line across the inflection point 140h.

[0176] In this way, when expressed in a plane along the surface of the workpiece 130h, the joint trajectory 170h has retreat sections 172h2 and 173h1 provided in a direction intersecting with the assumed movement route 150h before and after an inflection point 138h between the second section 132h, which is a curved section with a concave R, and the third section 132h, which is a curved section with a convex R. Also, the joint trajectory 170h has retreat sections 174h2 and 175h1 provided in a direction intersecting with the assumed movement route 150h before and after an inflection point 139h between the fourth section 134h, which is a curved section with a convex R, and the fifth section 135h, which is a curved section with a concave R.

[0177] [3-8-2. Joining method] The joining method according to this modified example performs friction stir welding on the assumed movement route 150h of the workpiece 130h described above using the joining system 1. The joining method according to this embodiment also includes a joining step of inserting a rotary tool F into the workpiece 130h and moving the rotary tool F along a joining trajectory 170h to perform friction stir welding on the workpiece 130h.

[0178] In the joining process according to this modified example, similarly to the fourth embodiment, before and after an inflection point 138h between a second section 132h, which is a curved section of the workpiece 130h, and a third section 133h, which is also a curved section, there are provided retreat sections 172h2 and 173h1 in a direction intersecting with the assumed movement route 150h. Then, the joining control unit 61 moves the rotary tool F in the retreat sections 172h2 and 173h1 in a direction intersecting with the joining direction of the workpiece 130h, and changes the angle of the rotary tool F with respect to the workpiece 130h in accordance with the angle of the workpiece 130h in the retreat sections 172h2 and 173h1.

[0179] Furthermore, in the joining process according to this modified example, similarly to the fourth embodiment, retreat sections 174h2 and 175h1 are provided in a direction intersecting with the assumed movement route 150h before and after an inflection point 139h between a fourth section 134h, which is a curved section of the workpiece 130h, and a fifth section 135h, which is also a curved section. Then, the joining control unit 61 changes the angle of the rotary tool F with respect to the workpiece 130h in accordance with the angle of the workpiece 130h in the retreat sections 174h2 and 175h1 while moving the rotary tool in a direction intersecting with the joining direction of the workpiece 130h.

[0180] [3-8-3. Action and Effects] In this modified example, as in the fourth embodiment, when passing through the inflection points 138h and 139h, the angle of the rotating tool F can be changed to match the shape of the workpiece 130h while suppressing vibrations (shakes) that occur in the arm 31a of the arm robot 31, thereby improving the joining quality.

[0181] Furthermore, as in this modified example, two or more of the first to sixth embodiments described above can be combined. That is, the present invention can be applied to a combination of the workpieces 130a-f, the assumed movement routes 150a-f, and the joining trajectories 170a-f according to the first to sixth embodiments. Of the first to sixth embodiments, embodiments of the same type may be combined, or different types of embodiments may be combined. Furthermore, the first to sixth embodiments described above may be combined with modifications.

[0182] [3-8-4.Other] In this modified example, a case has been described in which no evacuation zones are provided around inflection points 137h and 140h or around them, but evacuation zones are provided around inflection points 138h and 139h. Evacuation zones may also be provided around inflection points 137h and 140h or around them. In other words, if the workpiece 130h has multiple inflection points 137h, 138h, 139h, and 140h, evacuation zones may be provided at some of the inflection points, or at all of the inflection points.

[0183] Here, at inflection points 137h and 140h, the change in posture of the rotary tool F tends to be greater when the rotary tool F moves between the first section 131h, which is a straight section, and the second section 132h, which is a curved section, or between the fifth section 135h, which is a curved section, and the sixth section 136h, which is a straight section.At inflection points 138h and 139h, the change in posture of the rotary tool F tends to be greater when the rotary tool F moves between the second section 132h and the third section 133h, which are curved sections with different unevenness directions, or between the fourth section 134h and the fifth section 135h, which are curved sections with different unevenness directions. For this reason, the angular acceleration of the rotary tool F caused by a change in attitude of the rotary tool F when the rotary tool F passes through inflection points 138h and 139h is greater than the angular acceleration of the rotary tool F caused by a change in attitude of the rotary tool F when the rotary tool F passes through inflection points 137h and 140h, and the vibration of the rotary tool F also tends to be greater. Therefore, a retraction section may be provided at inflection points 138h and 139h where the change in attitude of the rotary tool is relatively large, and no retraction section may be provided at inflection points 137h and 140h where the change in attitude of the rotary tool is relatively small. Alternatively, a long (large) retraction section may be provided at inflection points 138h and 139h where the change in attitude of the rotary tool is relatively large, and a short (small) retraction section may be provided at inflection points 137h and 140h where the change in attitude of the rotary tool is relatively small. As a result, vibrations are suppressed by the retraction section at inflection points 138h and 139h, where the change in the attitude of the rotary tool is relatively large, and the welding time is not extended or can be suppressed from being extended at inflection points 137h and 140h, where the change in the attitude of the rotary tool is relatively small. Therefore, the welding quality can be improved while suppressing a decrease in production efficiency due to an extension of the welding time caused by providing the retraction section.

[0184] [4. Other] In the above-described embodiment, a rotary tool F having a base end pin F2 and a tip end pin F3, with a stepped pin step F21 formed on the outer peripheral surface of the base end pin F2, is used to perform friction stir welding while holding down the plastic flow material with the pin step. The shape and contact manner of the rotary tool F are not limited to this. For example, a rotary tool having a shoulder and a stirring pin hanging down from the shoulder may be used, with the stirring pin inserted into the workpiece and friction stir welding performed with the shoulder in contact with the surface of the workpiece. Furthermore, for example, a rotary tool F having a stirring pin tapered toward the tip may be used, with only the stirring pin inserted into the workpiece to perform friction stir welding. [Example]

[0185] Next, examples of the present invention will be described in comparison with comparative examples. In the examples and comparative examples, the rotary tool F was attached to the joining system 1 configured as described above. The rotary tool F had a tip pin F3 with a taper angle B of 90° and a base pin F2 with a taper angle A of 120°. The rotary tool F had a base pin F2 with a height of 2.17 mm and a tip pin F3 with a height of 1 mm. The rotary tool F had a base shaft portion F1 with a thickness of 12 mm, a flat surface F4 with a diameter of 2.5 mm, and a base diameter of the tip pin F3 with a diameter of 4.5 mm. The workpieces used in the examples and comparative examples were similar in shape to the workpiece 130h of the second modified example of the first embodiment described with reference to Fig. 14(a). The workpiece h was an aluminum alloy made of A6063-T5. The assumed movement route of the example and comparative example is similar to the assumed movement route 150h of the second modified example of the first embodiment described with reference to FIG. 14(b).

[0186] FIG. 15(a) shows the dimensions of each part of the workpiece 130h (see FIGS. 14(a) to 14(c)) used in this example and the comparative example. This workpiece 130h has a thickness of 1.5 mm, a distance 124 between points Ah and Bh of 3 mm, a distance 123 between points Bh and Ch of 5 mm, a distance 127 between points Ch and Dh of 5 mm, a distance 128 between points Dh and Eh of 5 mm, a distance 125 between points Eh and Fh of 5 mm, and a distance 126 between points Fh and Gh of 3 mm. Note that these distances refer to the horizontal distances in the workpiece 130h. The ascending angle of the distance (curved section) 123 is 20°, the ascending angle (descending angle) of the distance (curved section) 124 is 20°, and the height difference between the lowest and highest points of the bottom surface (the bottom position of point Dh) is 2 mm. The radius of curvature of the curve Bh-Ch and the curve Eh-Fh is R=9.78, and the radius of curvature of the curve Ch-Dh is R=14.28. The joining conditions were: the moving speed of the rotary tool F was 3.5 mm / s (TCP speed), the rotation speed of the rotary tool F was 4000 rpm, the pressure applied by the rotary tool F to the workpiece 130h was 750 N, and the insertion depth of the rotary tool F was approximately 1.5 mm.

[0187] [Comparative Example] In the comparative example, friction stir welding was performed on a workpiece 130h by moving a rotary tool F along a welding trajectory 180h shown in FIG. 15(b). The welding trajectory 180h is the same as the assumed movement route 150h described with reference to FIG. 14(b) in the second modified example of the first embodiment. That is, the welding trajectory 180h is a linear trajectory in a plan view from point Ah to point Gh. The welding conditions in the comparative example are shown in FIG. 17.

[0188] FIG. 17 shows the data for the comparative example. That is, the data includes the inclination of the workpiece (130h), the sign (+, -, 0) of the angle at which the tool (rotating tool F) is tilted, the angle of the tool (rotating tool F) within the section, the amount of change in the angle of the tool (workpiece 130h) within the section, the length (mm) of the joining trajectory (180h) within the section, the time (s) required to move along the joining trajectory (180h) within the section, the time required to change the angle of the tool (rotating tool F) by 1° within the section, the angular velocity (° / s) within the section, the length of the section equivalent to the evacuation section (evacuation section 172h2, 173h1, evacuation section 174h2, 175h1) in the direction of the expected movement route (150h), the time (s) required to move through the section equivalent to the evacuation section (evacuation section 172h2, 173h1, evacuation section 174h2, 175h1) in the direction of the expected movement route (150h), and the vibration evaluation results.

[0189] "Inclination of workpiece" indicates the degree to which the tangent to the surface of the workpiece 130h at each point is inclined relative to the direction of travel (horizontal direction in Figure 15(a)). The horizontal direction (x direction) is set to 0°, and a negative value is used when the tangent to the surface of the workpiece 130h is inclined counterclockwise, and a positive value is used when the tangent is inclined clockwise.

[0190] The "sign of the tool tilt angle" is - when the rotation tool F is tilted counterclockwise around the tip of the rotation tool F, + when the tilt is changed clockwise, and 0 when the tilt is not changed.

[0191] The "tool angle" is defined as 0° when the rotary tool F is inserted perpendicularly to a horizontal point on the workpiece 130h. In other words, the normal direction to a workpiece tilt of 0° is defined as 0°. When the rotary tool F is tilted counterclockwise around the tip of the rotary tool F, the value is a negative value, and when the rotary tool F is tilted clockwise, the value is a positive value.

[0192] The length of the section corresponding to the evacuation section in the direction of the assumed movement route at point Ch represents the length between points Ch1 and Ch3 on the assumed movement route 150h for evacuation sections 172h2 and 173h1 of the joint trajectory 170h. Also, the length of the section corresponding to the evacuation section in the direction of the assumed movement route at point Eh represents the length between points Eh1 and Eh3 on the assumed movement route 150h for evacuation sections 174h2 and 175h1 of the joint trajectory 170h.

[0193] The drawing-substitute photograph in Figure 16 shows the top surface of the workpiece 130h after friction stir welding in the comparative example. In the comparative example, many vibration marks were observed between Bh and Gh in the plasticized region W, indicating poor appearance quality. The vibration marks were particularly large between points Bh and Dh, and especially between points Ch and Dh, indicating that large vibrations occurred in the rotary tool F.

[0194] [Example] In the example, friction stir welding was performed on a workpiece 130h by moving a rotary tool F along a welding trajectory 170h shown in FIG. 15(c). The welding trajectory 170h is the same as the welding trajectory 170h described with reference to FIG. 14(c) in the second modified example of the first embodiment. In the example, the lengths of the retraction sections 172h2, 173h1 and the retraction sections 174h2, 175h1 in the direction perpendicular to the assumed movement route 150h (y direction) were 10 mm. That is, the lengths from the line segment connecting points Ch1 and Ch3 to point Ch2 and from the line segment connecting points Eh1 and Eh3 to point Eh2 were 10 mm. The distances between points Ch1 and Ch3 and between points Eh1 and Eh3 were 2.13 mm. The welding conditions in the example are shown in FIG. 19.

[0195] Figure 19 shows the following data: the inclination of the workpiece (130h), the sign (+, -, 0) of the angle at which the tool (rotary tool F) is tilted, the tool (rotary tool F) angle (°), the amount of change in the tool (rotary tool F) angle within the section, the length of the joining trajectory within the section, the time (s) required to move the joining trajectory (170h) within the section, the time (s) required to change the tool (rotary tool F) angle by 1° within the section, the angular velocity within the section (° / s), the time (s) required to move through the evacuation sections (evacuation sections 172h2, 173h1, evacuation sections 174h2, 175h1), and the vibration evaluation results.

[0196] 18 shows the top surface of the workpiece 130h after friction stir welding in the example. It can be seen that the plasticized region W in the example has less waviness and the appearance quality is better than that of the comparative example.

[0197] [Consider] In the comparative example, the rotary tool F was moved through a first section 131h, which is a straight section, and a second section 132h, which is a curved section with a concave radius, and then passed through point Ch, which is an inflection point 138h, and moved through a third section 133h, which is a curved section with a convex radius. As shown in FIG. 17 , from point Ah before inflection point 138h to point Ch, the rotary tool F was tilted in the negative direction so that the tool angle changed from 0° at point Ah to -20° at point Ch as the inclination of the workpiece 10h changed from 0° at point Ah to -20° at point Ch. From point Ch after inflection point 138h to point Dh, the rotary tool F was tilted in the positive direction so that the tool angle changed from -20° at point Ch to 0° at point Dh as the inclination of the workpiece 10h changed from -20° at point Ch to 0° at point Dh. Here, the angular velocity of the rotary tool F in the second section 132h is calculated to be 10.87° / sec from the change in angle from point Bh to point Ch and the time required to move along the welding trajectory from point Bh to point Ch. Furthermore, the angular velocity of the rotary tool F in the third section 133h is calculated to be 13.59° / sec from the change in angle from point Ch to point Dh and the time required to move along the welding trajectory from point Ch to point Dh. That is, while the rotary tool F was tilted in the negative direction at an angular velocity of 10.87° / sec in the second section 132h, the rotary tool F was tilted in the positive direction at an angular velocity of 13.59° / sec in the third section 133h. Thus, at the inflection point 138h between the second section 132h and the third section 133h, the tilt direction of the rotary tool F is reversed, and a large change in angular velocity occurs. For this reason, it is thought that a large angular acceleration occurred at point Ch, which is the inflection point 138h, and the vibration at and after inflection point Ch became large (a shake occurred).

[0198] In the example, the rotary tool F moved through the first section 131h, which is a straight section, and the first sub-section 172h1 and the first retraction section 172h2 of the second section 132h, which is a curved section with a concave R, and then passed through point Ch, which is the inflection point 138h, and moved through the second retraction section 173h1 and the second sub-section 173h2 of the third section 133h, which is a curved section with a convex R. As shown in Fig. 19 , similar to the comparative example, from point Ah before the inflection point 138h to point Ch2, the rotary tool F was tilted in the negative direction so that the tool angle changed from 0° at point Ah to -20° at point Ch in accordance with the change in the inclination of the workpiece 10h from 0° at point Ah to -20° at point Ch. From point Ch2 after the inflection point 138h to point Dh, the rotary tool F was tilted in the positive direction so that the tool angle changed from -20° at point Ch to 0° at point Dh as the inclination of the workpiece 10h changed from -20° at point Ch to 0° at point Dh. In the example, the rotary tool was moved in a direction intersecting the welding direction of the workpiece 130h in the first retraction section 172h2 from point Ch1 to point Ch2 and the second retraction section 173h1 from point Ch2 to point Ch3. As a result, in the comparative example, the time required to move through the sections corresponding to the first retraction section 172h2 and the second retraction section 173h1 from point Ch1 to point Ch3 was 0.61 seconds, whereas in the example, the time required to move along the welding trajectory 170h from point Ch1 to point Ch3 via point Ch2 was 5.75 seconds. Furthermore, in the example, the angular velocity of the rotary tool F in the first retraction section 172h2 from point Ch1 to point Ch2 is calculated to be 0.87° / sec. The angular velocity of the rotary tool F in the second retraction section 173h1 from point Ch2 to point Ch3 is calculated to be 1.04° / sec. That is, in the example, the rotary tool F is tilted in the negative direction at an angular velocity of 0.87° / sec in the first retraction section 172h2, whereas the rotary tool F is tilted in the positive direction at an angular velocity of 1.04° / sec in the second retraction section 173h1. Thus, in the example, by providing the retraction sections, the tool angle is changed around the inflection point 138h over a period of approximately nine times longer than in the comparative example.Furthermore, in the embodiment, in the first retraction section 172h2 and the second retraction section 173h1 before and after the inflection point 138h, the tool angle is changed at an angular velocity that is less than one-tenth of that in the comparative example, and the range of change in angular velocity is also small.Therefore, in the embodiment, the change in angular velocity (angular acceleration) when changing the angle of the rotating tool F before and after point Ch (point Ch2), which is the inflection point 138h, is small, and it is thought that vibration is suppressed.

[0199] Comparing the above comparative example with the working example, it was found that when friction stir welding a workpiece having an inflection point 138h, the working example can suppress vibration of the arm 31a of the arm robot 31. It was also found that the working example can improve the welding quality (appearance quality) of the workpiece. [Explanation of symbols]

[0200] 1. Joint System 31 Arm Robot 31a Arm 57 Bonding Program 61 Joining control section 130, 130a, 130b, 130c, 130d, 130e, 130f Work 131 First Section of Work 132 Second Section of Work 131a, 131b First section of work (straight section) 131c, 131d, 131e, 131f First section of work (first curved section) 132a Second section of work (curved section) 132b Second section of work (another straight section) 132c, 132d, 132e, 132f Second section of work (second curved section) 133,133a,133b,133c,133d,133e,133 Inflection point 150, 150a, 150b, 150c, 150d, 150e, 150f Expected movement route 170,170a,170b,170c,170d,170e,170f Joint orbit 1712,171a2,171b2,171c2,171d2,171e2,171f2,1721,172a1,172b1,172c1,172d1,172e1,172f1 Evacuation section F Rotate Tool F2 base end pin F3 Tip side pin L1 length L2 length W plasticization region

Claims

1. A joining method for performing friction stir welding along an expected movement route of a workpiece using a rotary tool held by an arm robot, comprising: the assumed movement route is set so that the height position of the workpiece is displaced in a side cross-sectional view, a joining step of inserting the rotary tool into the workpiece and moving the rotary tool along a predetermined joining trajectory to perform the friction stir welding on the workpiece, The joining trajectory has an evacuation section provided in a direction intersecting with the assumed movement route before and after an inflection point on the surface of the workpiece present on the assumed movement route or at the inflection point, the inflection point is a point at which angular acceleration of the rotary tool occurs when the rotary tool passes through the inflection point when welding is performed while keeping the moving speed of the tip of the rotary tool, whose tip contacts the workpiece, constant and maintaining the angle of the rotary tool with respect to the workpiece, In the joining step, the angle of the rotary tool with respect to the workpiece is changed in accordance with the angle of the workpiece while moving the rotary tool in a direction intersecting a joining direction of the workpiece in the retreat section. A joining method characterized by:

2. In a side cross-sectional view, the workpiece has a straight section and a curved section that are continuous with the inflection point along the assumed movement route, 2. The joining method according to claim 1, wherein the joining trajectory has a retreat section provided before or after or at the inflection point between the straight section and the curved section, in a direction intersecting the expected movement route of the workpiece in a planar view passing through the straight section and the curved section.

3. In a side cross-sectional view, the workpiece is arranged such that a straight line section and another straight line section are continuous along the assumed movement route with angles changing across a corner portion that is the inflection point, 2. The joining method according to claim 1, wherein the joining trajectory has a retreat section provided in a direction intersecting the expected movement route in a planar view of the workpiece passing through the straight section sandwiching the corner portion before and after or at the inflection point between the straight section sandwiching the corner portion and the corner portion.

4. In a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous with each other across the inflection point along the assumed movement route, and the first curved section and the second curved section have center points that are different in position; 2. The joining method according to claim 1, wherein the joining trajectory has an evacuation section provided in a direction intersecting the expected movement route of the workpiece in a planar view passing through the first curved section and the second curved section before, after, or at the inflection point between the first curved section and the second curved section.

5. In a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous with each other across the inflection point along the assumed movement route, and the first curved section and the second curved section have different curvatures; 2. The joining method according to claim 1, wherein the joining trajectory has an evacuation section provided in a direction intersecting the expected movement route of the workpiece in a planar view passing through the first curved section and the second curved section before, after, or at the inflection point between the first curved section and the second curved section.

6. In a side cross-sectional view, the workpiece has a first curved section and a second curved section that are continuous with each other across the inflection point along the assumed movement route, and the first curved section and the second curved section have different concave and convex directions; 2. The joining method according to claim 1, wherein the joining trajectory has an evacuation section provided in a direction intersecting the expected movement route of the workpiece in a planar view passing through the first curved section and the second curved section before, after, or at the inflection point between the first curved section and the second curved section.

7. In a side cross-sectional view of the workpiece, a first curved section and a second curved section are continuous along the assumed movement route with the inflection point in between, and at one end of the first curved section and one end of the second curved section where the first curved section and the second curved section are continuous, the angle formed by a tangent to the one end of the first curved section and a tangent to the one end of the second curved section is less than 180° or greater than 180°, 2. The joining method according to claim 1, wherein the joining trajectory has an evacuation section provided in a direction intersecting the expected movement route of the workpiece in a planar view passing through the first curved section and the second curved section before, after, or at the inflection point between the first curved section and the second curved section.

8. 2. The joining method according to claim 1, wherein in the joining step, the joining trajectory has a curved section with a convex R and a curved section with a concave R, the curved section being continuous with the inflection point in between.

9. 2. The welding method according to claim 1, wherein in the welding step, a time required for the rotary tool to pass through the retraction section is set to 1 second or more and 10 seconds or less.

10. 2. The joining method according to claim 1, wherein in the joining step, a length of the retreat section in a direction intersecting with the assumed movement route is set to 1 mm or more and 100 mm or less.

11. 2. The joining method according to claim 1, wherein in the joining step, a length of the retreat section in a direction parallel to the assumed movement route is set to be greater than 0 mm and equal to or less than 10 mm.

12. The joining method according to claim 1 , wherein in the joining step, the retraction section includes a curve in a plan view.

13. The welding method according to claim 1 , wherein in the welding step, a plasticized region formed when the rotary tool moves through the retraction section is made to overlap on the assumed movement route.

14. The welding method according to claim 1, characterized in that in the welding process, the length of the evacuation section in a direction parallel to the expected movement route is set to be smaller than twice the radius of the rotary tool inserted into the workpiece at the position of the workpiece surface.

15. 2. The welding method according to claim 1, wherein the moving speed of the rotary tool is constant in the welding step.

16. 2. The welding method according to claim 1, wherein in the welding step, an angle of the axial direction of the rotary tool with respect to the surface of the workpiece is equal to or greater than 80 degrees and equal to or less than 100 degrees.

17. the rotation tool has a proximal pin and a distal pin, a taper angle of the base end pin is larger than a taper angle of the tip end pin, and a stepped pin step portion is formed on an outer circumferential surface of the base end pin; 2. The joining method according to claim 1, wherein in the joining process, friction stir welding is performed along the joining trajectory having the retraction section while maintaining a predetermined target angle of the rotary tool and pressing the plastic flow material at the step bottom surface of the pin step portion.

18. 2. The welding method according to claim 1, wherein in the welding process, a ratio of a time required for the rotary tool to pass through the retraction section to a time required for the rotary tool to pass through a section of the assumed movement route corresponding to the retraction section when the retraction section is not provided is 3 or more.

19. An arm robot that can control arm movement, a rotary tool held by the arm, A welding system that performs friction stir welding along an expected movement route of a workpiece by the rotary tool driven by the arm robot, the assumed movement route is set so that the height position of the workpiece is displaced in a side cross-sectional view, a welding unit that inserts the rotary tool into the workpiece and moves the rotary tool along a predetermined welding trajectory to perform the friction stir welding on the workpiece, The joining trajectory has an evacuation section provided in a direction intersecting with the assumed movement route before and after an inflection point on the surface of the workpiece present on the assumed movement route or at the inflection point, the inflection point is a point at which angular acceleration of the rotary tool occurs when the rotary tool passes through the inflection point when welding is performed while keeping the moving speed of the tip of the rotary tool, whose tip contacts the workpiece, constant and maintaining the angle of the rotary tool with respect to the workpiece, In the joining section, the angle of the rotary tool with respect to the workpiece is changed in accordance with the angle of the workpiece while moving the rotary tool in a direction intersecting a joining direction of the workpiece in the retreat section. A joining system characterized by:

20. An arm robot that can control arm movement, a rotary tool held by the arm, A joining program that causes a computer to execute friction stir welding along an expected movement route of a workpiece by the rotary tool driven by the arm robot, the assumed movement route is set so that the height position of the workpiece is displaced in a side cross-sectional view, causing a computer to execute a joining process in which the rotary tool is inserted into the workpiece, and the rotary tool is moved along a predetermined joining trajectory to perform the friction stir welding on the workpiece; The joining trajectory has an evacuation section provided in a direction intersecting with the assumed movement route before and after an inflection point on the surface of the workpiece present on the assumed movement route or at the inflection point, the inflection point is a point at which angular acceleration of the rotary tool occurs when the rotary tool passes through the inflection point when welding is performed while keeping the moving speed of the tip of the rotary tool, whose tip contacts the workpiece, constant and maintaining the angle of the rotary tool with respect to the workpiece, In the joining process, the angle of the rotary tool with respect to the workpiece is changed in accordance with the angle of the workpiece while moving the rotary tool in a direction intersecting a joining direction of the workpiece in the retreat section. A bonding program characterized by:

Images