Friction stir welding system

Abstract

This invention provides a friction stir welding system that prevents the joining trajectory from deviating from the taught trajectory, thereby ensuring high joining quality. [Solution] The friction stir welding system 1 comprises a robot 2 to which a friction stir welding tool 23 is attached, a control device 3 that controls the movement of the robot 2, a sensor 4 fixed to the robot 2, and a measurement target object 6a that extends parallel to the joining direction D of the friction stir welding and has a measurement target portion that is measured by the sensor 4. The sensor 4 measures data indicating the reference position of the measurement target portion in advance before the robot 2 starts the friction stir welding operation, and when the robot 2 starts the friction stir welding operation, it measures data to calculate the amount of deviation of the measurement target portion from the reference position in a direction substantially perpendicular to the central axis 26 of the tool 23 and the joining direction D. The control device 3 calculates the amount of deviation from the data measured by the sensor 4 and performs feedback control on the robot 2 so that the amount of deviation is eliminated.

Description

Technical Field

[0001] The present invention relates to a friction stir welding system that performs friction stir welding using a robot.

Background Art

[0002] Friction stir welding is a joining method in which the tip of a rotating tool is pressed into a workpiece, the workpiece is softened by frictional heat, and the surrounding of the joint is plastically flowed and kneaded by stirring with rotation to integrate a plurality of members. Friction stir welding is also called FSW (Friction Stir Welding), and there are a method using a dedicated friction stir device (see Patent Document 1) and a method using a general-purpose articulated robot. When using a general-purpose articulated robot, due to its high degree of freedom, it is possible to join complex shapes such as curved surfaces or continuously join from the top surface to the side surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When performing friction stir welding using an articulated robot, since the tip of the tool attached to the arm of the robot is pressed into a hard workpiece, the joints of the robot are deflected by the reaction force. This deflection may cause the actual joining trajectory to deviate from the taught trajectory, affecting the joining quality. This is a situation peculiar to a friction stir welding system using an articulated robot.

[0005] The present invention has been made in view of the above circumstances, and its object is to provide a friction stir welding system that can prevent the joining trajectory from deviating from the taught trajectory and ensure high joining quality.

Means for Solving the Problems

[0006] To achieve the aforementioned objectives, the present invention provides a friction stir welding system comprising: a robot to which a friction stir welding tool is attached; and a control device for controlling the operation of the robot, further comprising: a sensor fixed to the robot; and a measuring object extending parallel to the joining direction of the friction stir welding and having a measuring portion to be measured by the sensor, wherein the sensor measures data indicating a reference position of the measuring portion in advance before the robot starts the friction stir welding operation; when the robot starts the friction stir welding operation, it measures data for calculating the amount of deviation of the measuring portion from the reference position in a direction substantially perpendicular to the central axis of the tool and the joining direction; and the control device calculates the amount of deviation from the data measured by the sensor and performs feedback control on the robot so that the amount of deviation is eliminated.

[0007] The robot performs a pressing operation in which it presses the tip of the tool into a pair of workpieces to be joined by the tool, and a joining operation in which it moves the tool in the joining direction to join the pair of workpieces, and the control device may perform the feedback control so that the gain during the joining operation is smaller than the gain during the pressing operation.

[0008] Furthermore, the object to be measured may be the workpiece, a jig for fixing the workpiece, or an auxiliary member, and the sensor may be a profile sensor that measures data on the surface shape of the workpiece, the jig, or the auxiliary member in a cross section substantially perpendicular to the joining direction. [Effects of the Invention]

[0009] The present invention provides a friction stir welding system that prevents the joining trajectory from deviating from the taught trajectory and ensures high joining quality. [Brief explanation of the drawing]

[0010] [Figure 1] This figure shows the overall configuration of the friction stir welding system according to the first embodiment of the present invention. [Figure 2] Enlarged view of area II in Figure 1. [Figure 3] Figure 1 illustrates the process of calculating the amount of deviation by the control device. [Figure 4] Figure 1 illustrates the pushing and joining operations performed by the robot. [Figure 5] A flowchart showing an example of the processing flow realized by the control device in Figure 1. [Figure 6] A diagram illustrating the robotic pushing and joining operations in a second embodiment of the present invention. [Figure 7] A diagram illustrating the robotic pushing and joining operations in the third embodiment of the present invention. [Figure 8] A diagram illustrating the installation location of the sensor in the fourth embodiment of the present invention. [Figure 9] This figure illustrates the process for calculating the amount of deviation by the control device in the fourth embodiment of the present invention. [Figure 10] This figure shows the overall configuration of the friction stir welding system according to the fifth embodiment of the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the present invention will be described in detail below with reference to the drawings. Embodiments of the present invention relate to a friction stir welding system that performs friction stir welding using a robot. The friction stir welding system according to the embodiment of the present invention prevents the actual welding trajectory from deviating from the taught trajectory, and in particular prevents deviation in the direction perpendicular to the central axis of the tool mounted on the robot and the welding direction. Here, the welding direction means the direction in which the friction stir welding proceeds. More specifically, the welding direction means the direction in which the tip of the tool moves on a plane perpendicular to the central axis of the tool.

[0012] <First Embodiment> FIG. 1 is a diagram showing the overall configuration of a friction stir welding system according to a first embodiment of the present invention. As shown in FIG. 1, the friction stir welding system 1 includes a robot 2 to which a tool 23 for friction stir welding is attached, and a control device 3 that controls the operation of the robot 2.

[0013] The robot 2 has an arm 21 and a base 22 that supports the arm 21. A rotatable tool 23 is attached to the tip of the arm 21. The arm 21 is composed of a link mechanism having a plurality of links and has joints that connect the links. Each joint is provided with a drive motor (not shown). As an example of the robot 2, a vertical multi-joint robot having six joints can be mentioned. However, the present invention is also applicable to other robots.

[0014] The tool 23 is connected to the arm 21 via a spindle 24. The spindle 24 is connected to a drive motor (not shown) and has a rotating part (not shown) that rotates at high speed inside. The tool 23 is held by a holder 25 that is connected to the rotating part of the spindle 24 and rotates together with the rotating part of the spindle 24. The central axis 26 of the tool 23 substantially coincides with the rotation axis of the rotating part of the spindle 24.

[0015] The CPU (Central Processing Unit) 31, memory 32, storage unit 33, and input / output I / F (interface) unit 34 of the control device 3 are connected via a bus 35. The CPU 31 reads a control program stored in the storage unit 33 or the like into the memory 32 and sequentially executes a plurality of instructions. The storage unit 33 is a hard disk drive, solid state drive, or the like, and stores data used in the processes described later. The input / output I / F unit 34 inputs signals from the robot 2 and the like or outputs signals to them. Note that all or part of the functions of the control device 3 may be configured by a logic circuit or an analog circuit, or the processing of various programs may be configured by an electronic circuit such as an FPGA (Field Programmable Gate Array).

[0016] The control device 3 may be built into the base 22 of the robot 2 or installed outside the robot 2. In the latter case, the robot 2 and the control device 3 are communicably connected via a communication cable. Alternatively, the robot 2 and the control device 3 may be wirelessly connected. The number of control devices 3 may be one or plural. In the case of plural control devices 3, the control devices 3 are communicably connected to each other. The control device 3 may be constituted by, for example, a numerical control device that controls the operation of the spindle 24 and a robot control device that controls the operation of the arm 21 of the robot 2. Hereinafter, the number of control devices 3 is assumed to be one, and one control device 3 will be described as controlling the operation of the robot 2.

[0017] FIG. 2 is an enlarged view of the region II in FIG. 1. A pair of workpieces 5a and 5b joined by the tool 23 are placed on the workbench 7. The workpieces 5a and 5b are fixed and positioned in a state where the joining portions are abutted against each other by a pair of jigs 6a and 6b fixed to the workbench 7.

[0018] The upper surface 71 of the workbench 7 on which the workpieces 5a and 5b are placed is a plane defined by an X-axis and a Y-axis orthogonal to each other. The direction perpendicular to the upper surface 71 of the workbench 7 is parallel to a Z-axis orthogonal to the X-axis and the Y-axis.

[0019] The workpieces 5a and 5b each have side surfaces 51a and 51b that abut against each other and upper surfaces 52a and 52b that are orthogonal to the side surfaces 51a and 51b and into which the tip 27 of the tool 23 is pushed. The pushing direction of the tip 27 of the tool 23 is substantially parallel to the central axis 26 of the tool 23. In the first embodiment, the workpieces 5a and 5b are rectangular parallelepipeds. The side surfaces 51a and 51b are substantially orthogonal to the upper surface 71 of the workbench 7. The upper surfaces 52a and 52b are substantially parallel to the upper surface 71 of the workbench 7.

[0020] The jig 6a has a side surface 61a that is substantially parallel to the side surfaces 51a, 51b of the workpieces 5a, 5b, and an upper surface 62a that is substantially parallel to the upper surfaces 52a, 52b of the workpieces 5a, 5b. In the first embodiment, the jig 6a has an L-shaped cross-section in the XZ plane. The jig 6b has a similar shape to the jig 6a, but is not particularly limited.

[0021] The friction stir welding system 1 further comprises a sensor 4 fixed to a robot 2, and an object to be measured having a part to be measured by the sensor 4. In the first embodiment, the sensor 4 is a profile sensor that irradiates a linear laser beam to measure the surface shape and dimensions (=profile) of the object to be measured with high precision and without contact. Figure 2 virtually illustrates the irradiation range 41 of the laser beam by the sensor 4. The control device 3 and the sensor 4 are connected communicably via a communication cable or wirelessly. The sensor 4 transmits its own sensor values ​​to the control device 3.

[0022] In the first embodiment, the sensor 4 is installed on the outer surface 28 of the spindle 24. Even if the rotating part of the spindle 24 rotates, the outer surface 28 of the spindle 24 does not rotate, so the sensor 4 does not rotate at high speed.

[0023] In the first embodiment, the object to be measured by the sensor 4 is the jig 6a, and the measurement target area is the edge 63a of the jig 6a defined by the side surface 61a and the top surface 62a. As will be described later, the object to be measured is not limited to the jig 6a that fixes and positions the workpiece 5a, but may also be an auxiliary member attached to the jig 6a, etc. Furthermore, the measurement target area only needs to extend parallel to the joining direction of the friction stir welding.

[0024] Figure 3 is a diagram illustrating the calculation process of the displacement amount by the control device in Figure 1. Figure 3 shows three profile data 42a to 42c measured by the sensor 4. The profile data 42a to 42c are data that show the surface shape of the object to be measured, with the XZ plane as the cross-section at different Y coordinates. Line segments 43a to 43c show the top surface 62a of the jig 6a shown in Figure 2. Line segments 44a to 44c show the side surface 61a of the jig 6a shown in Figure 2. Line segments 45a to 45c show the top surface 52a of the workpiece 5a shown in Figure 2. Corners 46a to 46c show the edges 63a of the jig 6a shown in Figure 2.

[0025] Sensor 4 measures data indicating the reference position of the part to be measured in advance before the robot 2 starts the friction stir welding operation. The reference position is determined by the coordinates of the central axis 26 of the tool 23 and a direction approximately perpendicular to the welding direction. In the examples of Figures 1 and 2, the reference position is determined by the X coordinate. In the example of Figure 3, the profile data 42a is the data indicating the reference position of the part to be measured. Since the part to be measured is the edge 63a of the jig 6a, the reference position of the part to be measured is determined by the X coordinate of corner 46a in Figure 3.

[0026] Furthermore, when the robot 2 starts the friction stir welding operation, the sensor 4 measures data to calculate the amount of deviation of the part to be measured from the reference position in the direction substantially perpendicular to the central axis 26 of the tool 23 and the welding direction. In the example in Figure 3, profile data 42b is the data when the tip 27 of the tool 23 is shifted in the positive direction of the X-axis, and profile data 42c is the data when the tip 27 of the tool 23 is shifted in the negative direction of the X-axis.

[0027] The control device 3 then calculates the amount of deviation from the data measured by the sensor 4. Specifically, the control device 3 calculates the difference 47b and 47c between the X coordinate of angle 46a of the profile data 42a indicating the reference position and the X coordinates of angles 46b and 46c of the profile data 42a after the friction stir welding operation has started. These differences 47b and 47c represent the amount of deviation of the part to be measured from the reference position in a direction approximately perpendicular to the central axis 26 of the tool 23 and the joining direction.

[0028] Figure 4 illustrates the pushing and joining operations performed by the robot in Figure 1. Figure 4 shows the workpieces 5a and 5b, jigs 6a and 6b, and workbench 7 viewed from vertically above (=negative Z-axis direction).

[0029] At the starting point S, robot 2 performs a pushing motion, pushing the tip 27 of tool 23 into the pair of workpieces 5a and 5b in a direction approximately parallel to the central axis 26 of tool 23 (= Z-axis direction). Robot 2 terminates the pushing motion when it has pushed the tip 27 of tool 23 to the taught position. Next, robot 2 performs a joining motion, moving tool 23 along the joining direction D from the starting point S to the ending point E while rotating it at high speed, to join the pair of workpieces 5a and 5b. Robot 2 terminates the joining motion when it has moved the tip 27 of tool 23 to the ending point E. Finally, at the ending point E, robot 2 separates the tip 27 of tool 23 from the pair of workpieces 5a and 5b, ending the friction stir welding operation.

[0030] Generally, the workpieces 5a and 5b subjected to friction stir welding are hard materials. During the pushing motion of robot 2, the reaction force when the tip 27 of tool 23 contacts the hard workpieces 5a and 5b causes deflection in the joints of robot 2, resulting in a displacement of the tip 27 of tool 23. Immediately after robot 2 starts the joining motion, the actual joining trajectory deviates from the taught trajectory due to the deflection of robot 2's joints and friction with workpieces 5a and 5b caused by the high-speed rotation of tool 23. During the joining motion of robot 2, friction with workpieces 5a and 5b due to the high-speed rotation of tool 23 continues, causing the actual joining trajectory to deviate from the taught trajectory. Immediately after robot 2 finishes the joining motion, the deflection of robot 2's joints is released as the tip 27 of tool 23 separates from the pair of workpieces 5a and 5b, causing a displacement as it tries to return to its original position.

[0031] To eliminate these discrepancies, the control device 3 calculates the amount of misalignment of the tip 27 of the tool 23 from the data measured by the sensor 4, and performs feedback control on the robot 2 to eliminate this misalignment. Based on the amount of misalignment, the control device 3 controls the rotation angle of the drive motors related to the joints of the robot 2, moving the tip 27 of the tool 23 to eliminate the aforementioned misalignment.

[0032] Figure 4 virtually illustrates the tip 27 of the tool 23 and the laser beam irradiation range 41 from the sensor 4. During the joining operation of the robot 2, the control device 3 controls the posture of the robot 2 so that the laser beam irradiation range 41 is perpendicular to the joining direction D. In the first embodiment, the control device 3 maintains a posture in which the outer surface 28 of the spindle 24 does not rotate around the central axis 26 of the tool 23 while moving the tip 27 of the tool 23 from the starting point S to the ending point E.

[0033] Thus, during the joining operation of robot 2, the irradiation range 41 of the laser light is perpendicular to the joining direction D. Also, as described above using Figure 2, the edge 63a of the jig 6a, which is the part to be measured, extends parallel to the joining direction D. Based on these conditions, the control device 3 performs the displacement calculation process described above in Figure 3, thereby enabling accurate measurement of the displacement of the tool 23 in a direction approximately perpendicular to the central axis 26 and the joining direction D during the joining operation of robot 2.

[0034] Furthermore, even if the position of the tip 27 of the tool 23 shifts from the taught position in the joining direction D, it will not significantly affect the joining quality. Therefore, the friction stir welding system 1 can ensure high joining quality by accurately measuring the shift of the tool 23 in a direction approximately perpendicular to the central axis 26 and the joining direction D, and eliminating this shift.

[0035] Figure 5 is a flowchart showing an example of the processing flow realized by the control device in Figure 1. As shown in Figure 5, the control device 3 acquires data indicating the reference position of the part to be measured (step S1). The sensor 4 measures data indicating the reference position of the part to be measured in advance before the robot 2 starts the friction stir welding operation and transmits it to the control device 3. The control device 3 receives the data indicating the reference position of the part to be measured from the sensor 4 and stores it in the memory 32 or storage unit 33.

[0036] Next, the control device 3 moves the tip 27 of the tool 23 in the pushing direction at the starting point S (step S2). The pushing direction is approximately parallel to the central axis 26 of the tool 23, and in the first embodiment, it is the negative direction of the Z-axis.

[0037] Next, the control device 3 acquires data from the sensor 4 to calculate the amount of deviation from the reference position and calculates the amount of deviation (step S3). During the pushing operation of the robot 2, the sensor 4 measures data to calculate the amount of deviation of the part to be measured from the reference position in a direction substantially perpendicular to the central axis 26 of the tool 23 and the joining direction D, and transmits it to the control device 3. The control device 3 calculates the amount of deviation based on the data indicating the reference position stored in the memory 32 or storage unit 33 in step S1 and the data received from the sensor 4 during the pushing operation of the robot 2.

[0038] Next, the control device 3 performs first feedback control based on the amount of deviation calculated in step S3 (step S4). The gain of the first feedback control may be a proportional gain, a differential gain, an integral gain, or a combination of these.

[0039] Next, the control device 3 checks whether the pushing operation is complete or not (step S5). The pushing operation is complete when the tip 27 of the tool 23 is pushed to the taught position. If the pushing operation is not complete (No in step S5), the control device 3 repeats from step S2. If the pushing operation is complete (Yes in step S5), the control device 3 proceeds to step S6.

[0040] In step S6, the control device 3 moves the tip 27 of the tool 23 along the joining direction D. In the first embodiment, the joining direction D is the positive direction of the Y axis. Next, the control device 3 obtains data from the sensor 4 to calculate the amount of deviation from the reference position, as in step S3, and calculates the amount of deviation (step S7).

[0041] Next, the control device 3 performs a second feedback control based on the amount of deviation calculated in step S7 (step S8). The gain of the second feedback control may be a proportional gain, a differential gain, an integral gain, or a combination thereof, similar to the gain of the first feedback control.

[0042] Here, it is known that the displacement due to the deflection of the joints of the robot 2 during the pushing operation is greater than the displacement due to friction with the workpieces 5a and 5b during the joining operation. Therefore, the control device 3 performs feedback control so that the gain during the joining operation is smaller than the gain during the pushing operation. That is, the gain of the second feedback control in step S8 is set to a smaller value than the gain of the first feedback control in step S4. In this way, the control device 3 can perform feedback control with high accuracy using appropriate gains for both the pushing operation and the joining operation.

[0043] Next, the control device 3 checks whether the tip 27 of the tool 23 has reached the endpoint E (step S9). If the endpoint E has not been reached (No in step S9), the control device 3 repeats from step S6. If the endpoint E has been reached (Yes in step S5), the control device 3 separates the tip 27 of the tool 23 from the pair of workpieces 5a and 5b (step S10) and terminates the process.

[0044] As described above, the friction stir welding system 1 comprises a sensor 4 fixed to the robot 2 and a measurement target object that extends parallel to the joining direction D of the friction stir welding and has a measurement target portion measured by the sensor 4. The sensor 4 measures data indicating the reference position of the measurement target portion in advance before the robot 2 starts the friction stir welding operation, and when the robot 2 starts the friction stir welding operation, it measures data to calculate the amount of deviation of the measurement target portion from the reference position in a direction substantially perpendicular to the central axis 26 of the tool 23 and the joining direction D. The control device 3 calculates the amount of deviation from the data measured by the sensor 4 and performs feedback control on the robot 2 to eliminate the amount of deviation. Therefore, the friction stir welding system 1 can prevent the joining trajectory from deviating from the taught trajectory and ensure high joining quality.

[0045] <Second Embodiment> In the first embodiment, only a single face of a pair of workpieces was joined, but in the second embodiment, an example of joining multiple faces of a pair of workpieces is described. In the first embodiment, the joining direction was determined by a single straight line, but in the second embodiment, the joining direction is determined by multiple straight lines.

[0046] Figure 6 illustrates the robotic pushing and joining operations in a second embodiment of the present invention. Workpieces 5a and 5b each have sides 51a and 51b that abut each other, top surfaces 52a and 52b perpendicular to the sides 51a and 51b, and front surfaces 53a and 53b perpendicular to the sides 51a and 51b and the top surfaces 52a and 52b. Workpieces 5a and 5b also have corners 54a and 54b which are common vertices of the sides 51a and 51b, the top surfaces 52a and 52b, and the front surfaces 53a and 53b. In the example shown in Figure 6, workpieces 5a and 5b are rectangular parallelepipeds.

[0047] The jig 6c has a side surface 61c that is substantially parallel to the side surfaces 51a, 51b of the workpieces 5a, 5b, a top surface 62c that is substantially parallel to the top surfaces 52a, 52b of the workpieces 5a, 5b, and a front surface 64c that is substantially parallel to the front surfaces 53a, 53b of the workpieces 5a, 5b. The jig 6c also has a border 63c defined by the side surface 61c and the top surface 62c, and a border 65c defined by the top surface 62c and the front surface 64c. The jig 6c has an inverted U-shaped cross-section in the YZ plane. The jig 6d has a similar shape to the jig 6c, but is not particularly limited.

[0048] The joining direction D is parallel to the front surfaces 53a, 53b from the starting point S to the corners 54a, 54b (hereinafter referred to as the "first joining direction"), and parallel to the top surfaces 52a, 52b from the corners 54a, 54b to the ending point E (hereinafter referred to as the "second joining direction"). Figure 6 virtually illustrates the tip 27a of the tool 23 and the irradiation range 41a of the laser light from the sensor 4 in the first joining direction. Similarly, Figure 6 virtually illustrates the tip 27b of the tool 23 and the irradiation range 41b of the laser light from the sensor 4 in the second joining direction.

[0049] At the starting point S, robot 2 performs a pushing motion in which the tip 27a of tool 23 is pushed into the pair of workpieces 5a and 5b from a direction perpendicular to the front surfaces 53a and 53b of workpieces 5a and 5b (= Y-axis direction). At this time, the central axis 26 of tool 23 is perpendicular to the front surfaces 53a and 53b of workpieces 5a and 5b.

[0050] Next, robot 2 performs a joining operation to join a pair of workpieces 5a and 5b by moving tool 23 along the joining direction D from the starting point S to the ending point E while rotating tool 23 at high speed. From the starting point S to the corners 54a and 54b, robot 2 moves the tip 27a of tool 23 along the first joining direction. When the tip 27a of tool 23 reaches the corners 54a and 54b, robot 2 changes the orientation of tool 23 so that its central axis 26 is perpendicular to the upper surfaces 52a and 52b of workpieces 5a and 5b. Then, robot 2 moves the tip 27b of tool 23 along the second joining direction from the corners 54a and 54b to the ending point E.

[0051] While the tip 27a of tool 23 is moving along the first joining direction, the laser beam irradiation range 41a is perpendicular to the edge 65c of jig 6c. Also, while the tip 27b of tool 23 is moving along the second joining direction, the laser beam irradiation range 41b is perpendicular to the edge 63c of jig 6c.

[0052] Therefore, in the second embodiment, the object to be measured by the sensor 4 is the jig 6c. Furthermore, the measurement target area is the edge 65c of the jig 6a while the tip 27a of the tool 23 is moving along the first joining direction, and the edge 63c of the jig 6a while the tip 27b of the tool 23 is moving along the second joining direction.

[0053] Similar to the first embodiment, sensor 4 is a profile sensor that measures data indicating the reference position of the part to be measured in advance before the robot 2 starts the friction stir welding operation. When the robot 2 starts the friction stir welding operation, sensor 4 measures data to calculate the amount of deviation from the reference position of the part to be measured in a direction substantially perpendicular to the central axis 26 of the tool 23 and the joining direction D. Similar to the first embodiment, the control device 3 executes the flowchart shown in Figure 5, calculates the amount of deviation from the data measured by sensor 4, and performs feedback control on the robot 2 to eliminate the amount of deviation.

[0054] <Third Embodiment> In the first and second embodiments, the surfaces where the workpieces abutted were flat, but in the second embodiment, an example is described where the surfaces where the workpieces abutted were curved. In the first and second embodiments, the joining direction was determined by a straight line, but in the third embodiment, the joining direction is determined by a curve.

[0055] Figure 7 illustrates the robotic pushing and joining operations in a third embodiment of the present invention. The workpieces 5c and 5d each have side surfaces 51c and 51d that abut against each other, and upper surfaces 52c and 52d that are perpendicular to the side surfaces 51c and 51d. The side surfaces 51c and 51d are curved surfaces of the same shape.

[0056] The jigs 6c and 6d are the same as in the second embodiment. An auxiliary member 8a is attached to the upper surface 62c of the jig 6c. The auxiliary member 8a has a side surface 81a that is substantially parallel to the side surfaces 51c and 51d of the workpieces 5c and 5d, and an upper surface 82a that is substantially parallel to the upper surfaces 52c and 52d of the workpieces 5c and 5d. The auxiliary member 8a also has a border 83a defined by the side surface 81a and the upper surface 82a. The border 83a is substantially parallel to the side surfaces 51c and 51d of the workpieces 5c and 5d when viewed from the Z direction.

[0057] Figure 7 virtually illustrates the tip 27c of the tool 23 and the irradiation range 41c of the laser light from the sensor 4. In the third embodiment, the object to be measured by the sensor 4 is the auxiliary member 8a. The measurement target area is the edge 83a of the auxiliary member 8a. At the starting point S, the robot 2 performs a pushing operation in which it pushes the tip 27c of the tool 23 into the pair of workpieces 5c and 5d from a direction perpendicular to the upper surfaces 52c and 52d of the workpieces 5c and 5d (= Z-axis direction). At this time, the central axis 26 of the tool 23 is perpendicular to the upper surfaces 52c and 52d of the workpieces 5c and 5d.

[0058] Next, the robot 2 rotates the tool 23 at high speed and moves it along the joining direction D from the starting point S to the ending point E to join the pair of workpieces 5c and 5d, performing a joining operation. Since the joining direction D in the third embodiment is a curve, the robot 2 moves the tip 27c of the tool 23 along the joining direction D while changing the orientation of the tool 23 so that the irradiation range 41c of the laser beam is perpendicular to the edge 83a of the auxiliary member 8a.

[0059] Sensor 4, as in the first and second embodiments, is a profile sensor and measures data indicating the reference position of the part to be measured in advance before the robot 2 starts the friction stir welding operation. When the robot 2 starts the friction stir welding operation, sensor 4 measures data to calculate the amount of deviation from the reference position of the part to be measured in a direction substantially perpendicular to the central axis 26 of the tool 23 and the joining direction D. The control device 3 executes the flowchart shown in Figure 5, as in the first and second embodiments, calculates the amount of deviation from the data measured by sensor 4, and performs feedback control on the robot 2 to eliminate the amount of deviation.

[0060] <Fourth Embodiment> In the first to third embodiments, the object measured by the sensor was a jig or auxiliary member, but in the fourth embodiment, an example will be described where the object measured by the sensor is a workpiece.

[0061] Figure 8 illustrates the installation location of the sensor in the fourth embodiment of the present invention. The workpieces 5a and 5b and jigs 6c and 6d are the same as in the second embodiment. The joining direction D is the opposite direction to that of the first embodiment and is the negative direction of the Y axis.

[0062] Sensor 4 is a profile sensor, as in the first to third embodiments. As shown in Figure 8, sensor 4 is fixed to the spindle 24 of robot 2 so as to face the front surfaces 53a, 53b of a pair of workpieces 5a, 5b while robot 2 is performing friction stir welding. Sensor 4 may be attached to the spindle 24 via a mounting member (not shown). Figure 8 virtually illustrates the tip 27d of tool 23 and the irradiation range 41d of the laser beam from sensor 4.

[0063] In the fourth embodiment, the objects to be measured by the sensor 4 are workpieces 5a and 5b. The measurement target area is the groove 54 between the sides 51a and 51b of the workpieces 5a and 5b. For example, if the workpieces 5a and 5b are chamfered, the shape of the groove 54 can be measured accurately by the profile sensor.

[0064] Figure 9 illustrates the calculation process of the displacement amount by the control device in the fourth embodiment of the present invention. Figure 9 shows three profile data 42d to 42f measured by the sensor 4. The profile data 42d to 42f are data indicating the surface shape of the object to be measured with the XZ plane as the cross-section. The recesses 48d to 48f indicate the grooves 54 shown in Figure 8.

[0065] Sensor 4 measures data indicating the reference position of the part to be measured in advance before the robot 2 starts the friction stir welding operation. The reference position is determined by the coordinates (=X coordinate) in a direction approximately perpendicular to the central axis 26 of the tool 23 and the joining direction D. In the example in Figure 9, the profile data 42d is the data indicating the reference position of the part to be measured. Since the part to be measured is the groove 54, the reference position of the part to be measured is determined by the X coordinate of the recess 48d in Figure 9.

[0066] Furthermore, when the robot 2 starts the friction stir welding operation, the sensor 4 measures data to calculate the amount of displacement of the part to be measured from the reference position in a direction approximately perpendicular to the central axis 26 of the tool 23 and the joining direction D (=X direction). In the example in Figure 9, profile data 42e is the data when the tip 27d of the tool 23 is shifted in the positive direction of the X axis, and profile data 42f is the data when the tip 27d of the tool 23 is shifted in the negative direction of the X axis.

[0067] The control device 3 then calculates the amount of displacement from the data measured by the sensor 4. Specifically, the control device 3 calculates the difference 49e and 49f between the X coordinate of the recess 48d in the profile data 42d indicating the reference position and the X coordinate of the recesses 48e and 48f in the profile data 42e and 42f after the friction stir welding operation has started. This difference 49e and 49f is the amount of displacement of the part to be measured from the reference position in a direction approximately perpendicular to the central axis 26 of the tool 23 and the joining direction D. The control device 3 executes the flowchart shown in Figure 5, similar to the first to third embodiments, calculates the amount of displacement from the data measured by the sensor 4, and performs feedback control on the robot 2 so that the amount of displacement is eliminated.

[0068] <Fifth Embodiment> In the first to fourth embodiments, the sensor was a profile sensor, but in the fifth embodiment, we will describe an example where the sensor is a distance sensor.

[0069] Figure 10 shows the overall configuration of a friction stir welding system according to the fifth embodiment of the present invention. The workpieces 5a and 5b and jigs 6a and 6b are the same as in the first embodiment. An auxiliary member 8b is attached to the upper surface 62a of jig 6a. The auxiliary member 8b has a side surface 81b that is substantially parallel to the side surfaces 51c and 51d of the workpieces 5c and 5d. Sensor 9 is a distance sensor that measures the distance to an object by irradiating it with laser light or the like.

[0070] In the fifth embodiment, the object measured by the sensor 9 is the auxiliary member 8b. The measurement target is the side surface 81b of the auxiliary member 8b. The sensor 9 measures data indicating the reference position of the measurement target before the robot 2 starts the friction stir welding operation. When the robot 2 starts the friction stir welding operation, the sensor 9 measures data to calculate the amount of deviation of the measurement target from the reference position in a direction approximately perpendicular to the central axis 26 of the tool 23 and the joining direction D (= X-axis direction). The control device 3 executes the flowchart shown in Figure 5, similar to the first to fourth embodiments, calculates the amount of deviation from the data measured by the sensor 4, and performs feedback control on the robot 2 to eliminate the amount of deviation.

[0071] As described above, in the second to fifth embodiments, similar to the first embodiment, the friction stir welding system 1 includes a sensor 4 fixed to the robot 2 and a measurement target object that extends parallel to the joining direction D of the friction stir welding and has a measurement target portion measured by the sensor 4. The sensor 4 measures data indicating the reference position of the measurement target portion in advance before the robot 2 starts the friction stir welding operation, and when the robot 2 starts the friction stir welding operation, it measures data to calculate the amount of deviation of the measurement target portion from the reference position in a direction substantially perpendicular to the central axis 26 of the tool 23 and the joining direction D. The control device 3 calculates the amount of deviation from the data measured by the sensor 4 and performs feedback control on the robot 2 so that the amount of deviation is eliminated. Therefore, the friction stir welding system 1 can prevent the joining trajectory from deviating from the taught trajectory and ensure high joining quality.

[0072] Preferred embodiments of the friction stir welding system and the like according to the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. It will be clear to those skilled in the art that various modifications and alterations can be conceived within the scope of the technical idea disclosed herein, and these will naturally also fall within the technical scope of the present invention. [Explanation of Symbols]

[0073] 1…Friction stir welding system 2…Robot 3…Control device 4. Sensor (profile sensor) 5a...Workpiece (object to be measured) 5b...Workpiece (object to be measured) 5c...work 5d...work 6a... Jig (object to be measured) 6b... Jig 6c... Jig (object to be measured) 6d... Jig 8a, 8b... Auxiliary members (objects to be measured) 9. Sensor (distance sensor) 23... Tools 26……Center axis D……Joining direction

Claims

1. A friction stir welding system comprising a robot to which a friction stir welding tool is attached, and a control device for controlling the movement of the robot, A sensor fixed to the robot, An object to be measured having a portion to be measured that extends parallel to the bonding direction of the friction stir welding and is measured by the sensor, Furthermore, The sensor measures data indicating the reference position of the part to be measured in advance before the robot starts the friction stir welding operation, and when the robot starts the friction stir welding operation, it measures data for calculating the amount of deviation of the part to be measured from the reference position in a direction substantially perpendicular to the central axis of the tool and the welding direction. The control device calculates the amount of deviation from the data measured by the sensor and performs feedback control on the robot to eliminate the amount of deviation. A friction stir welding system characterized by the following features.

2. The robot performs a pressing operation in which it presses the tip of the tool into a pair of workpieces to be joined by the tool, and a joining operation in which it moves the tool in the joining direction to join the pair of workpieces. The control device performs the feedback control such that the gain during the joining operation is smaller than the gain during the pushing operation. The friction stir welding system according to feature 1.

3. The object to be measured is one of the workpiece, a jig for fixing the workpiece, or an auxiliary member. The sensor is a profile sensor that measures data on the surface shape of the workpiece, the jig, or the auxiliary member in a cross-section substantially perpendicular to the joining direction. The friction stir welding system according to feature 2.

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