JP4855859B2 - Friction stir welding method - Google Patents

Description

  The present invention relates to a friction stir welding method in which friction stir welding is performed by pressing a workpiece while rotating the friction stir welding tool, and in particular, a gun frame including a friction stir welding tool, and the gun frame is moved. The present invention relates to a friction stir welding method for joining the workpieces using a moving means.

  In the friction stir welding, in order to improve the joining quality, there is a case where the friction stir welding tool is joined with a forward angle so that the tip of the friction stir welding tool precedes in the joining direction. Specifically, in the friction stir welding method described in Patent Document 1, a dedicated tilting mechanism is provided in a portion that holds the friction stir welding tool, and the friction stir welding tool is tilted under the action of the tilting mechanism.

  On the other hand, Patent Document 2 proposes providing an end effector for holding a friction stir welding tool at the tip of an industrial articulated robot and moving the friction stir welding tool under the action of the robot. . In the friction stir welding apparatus described in Patent Document 2, the friction stir welding tool is held by a C-shaped gun frame in order to complement the rigidity of the robot arm.

JP 2002-301580 A JP 2002-103061 A

  Although it is possible to provide a dedicated tilting mechanism as described in Patent Document 1 for the friction stir welding apparatus described in Patent Document 2, the structure is complicated, the cost increases, and the weight of the tip of the robot Becomes heavier and lowers stability. In addition, the number of axes is mechanically increased, which complicates the teaching procedure and calculation of the robot operation and increases teaching data.

  Furthermore, in friction stir welding, there is a case in which advancing in the axial direction and then moving in the lateral direction to join in a linear form (hereinafter referred to as line joining). In the case of wire joining, the friction stir welding tool moves in the axial direction and the joining direction. Therefore, when teaching the robot operation, when the tip of the friction stir welding tool is used as a reference, the friction stir welding tool is Teaching of the operation of tilting with respect to the workpiece is very complicated. That is, the teaching is complicated because setting is performed in a total of three axes, that is, one axis relating to the advance and retreat of the friction stir welding tool and three axes associated with the movement of the receiving member, and teaching by manual adjustment is difficult.

  Even when teaching is performed automatically, as shown in FIG. 10, when the workpiece is thick (or when the workpiece is placed on the table and held together with the gun arm), the gun arm 1 is frictionally stirred. In a simple operation of tilting around the tip of the welding tool 2, the receiving member 3 on the opposite side bites into the workpiece like a virtual line. In order to avoid such an inconvenience, it is necessary to calculate four motions related to the position and orientation of the receiving member, which complicates the structure and calculation. Here, the four operations required for teaching are the rotation operation of the friction stir welding tool 2, the retraction operation of the friction stir welding tool 2, the parallel operation of the gun arm 1, and the tilting operation of the gun arm 1. .

  Moreover, when tilting around the receiving member 3, the friction stir welding tool 2 bites into the workpiece and shifts from the original position.

  The present invention has been made in view of such problems, and facilitates teaching of the operation of the means for moving the gun frame, and the joint location of the friction stir welding tool shifts when the gun frame is tilted. An object of the present invention is to provide a friction stir welding method that does not occur.

The friction stir welding method according to the present invention includes a friction stir welding tool and a friction stir gun frame for holding a work by a receiving member, a moving means for moving the gun frame in the joining direction, and the friction stir welding tool. A pressure stir welding method for joining the workpieces using a limiter that limits the pressure command so as not to exceed a predetermined pressure force on the workpiece when pressurizing the workpiece by
By inserting the workpiece while rotating the friction stir welding tool, the first step that Soo clamping the joining starting position of the workpiece in the receiving member and the friction stir welding tool,
Wherein the tilting means及beauty before Symbol moving means, said receiving member to tilt the gun frame is moved toward the welding direction, the friction stir welding tool is retracted under the action of the limiter, the friction A second step in which the tip of the stir welding tool is maintained at the position inserted into the workpiece;
A third step of moving the gun frame toward the joining direction by the moving means after tilting the gun frame ;
It is characterized by having.

  In this way, the friction stir welding is performed by moving the receiving member in the joining direction and tilting the gun frame to retract the friction stir welding tool by limiting the pressure applied to the friction stir welding tool. The tip position of the tool for use and the amount of burial with respect to the workpiece are appropriately maintained, and teaching of the operation of the means for moving the gun frame is facilitated.

  According to the friction stir welding method according to the present invention, the receiving member is moved in the joining direction, the gun frame is tilted, and the friction stir welding tool is retracted by limiting the pressing force of the friction stir welding tool. Thus, the tip position of the friction stir welding tool and the amount of burying in the workpiece are appropriately maintained, and teaching of the operation of the means for moving the gun frame is facilitated.

  Hereinafter, embodiments of the friction stir welding apparatus and the friction stir welding method according to the present invention will be described with reference to FIGS. 1 to 9.

  As shown in FIG. 1, a friction stir welding apparatus 10 according to the present embodiment includes an industrial articulated (for example, 6-axis) robot 12 and an end effector (provided at the tip of the robot 12). A gun frame) 14 and a control unit 16 that controls the entire system. The end effector 14 can be moved to an arbitrary position and orientation under the action of the robot 12, and is set to have an appropriate posture with respect to the workpiece W. Further, when performing line joining, the end effector 14 moves in the joining direction under the action of the robot 12. That is, the robot 12 acts as a moving unit and a tilting unit for the end effector 14.

  The workpiece W is, for example, two aluminum plates that are laminated or end surfaces are attached to each other, and is fixed by a fixing base 18. In FIG. 1, the end effector 14 is schematically shown in a large size.

  The end effector 14 includes a C-shaped arm 20 extending so as to clamp the workpiece W from the side, a tool drive mechanism 22 provided at one end of the arm 20, and a low columnar shape provided at the other end. Receiving member 24, and connection portion 26 that connects tool drive mechanism 22 and robot 12.

  The tool drive mechanism unit 22 includes a friction stir welding tool 30 that performs friction stir of the workpiece W, a first motor 32 that rotates the friction stir welding tool 30 about the axis, and the friction stir welding tool 30 in the axial direction. A second motor 34 that moves forward and backward, a ball screw mechanism 36 that converts the rotation of the second motor 34 into a linear motion and transmits it to the friction stir welding tool 30, and a controller that detects the rotational speed of the second motor 34. 16 and a detection unit 38 that supplies the data to the sensor 16. As the first motor 32 and the second motor 34, for example, a servo motor may be used.

  The friction stir welding tool 30 has a thin cylindrical shape provided coaxially with respect to the receiving member 24, and includes a small cylindrical probe 40 (see FIG. 3) slightly protruding at the center of the tip. The periphery of the probe 40 is a shoulder 42 having a cylindrical end face shape.

  As shown in FIG. 2, the control unit 16 amplifies a signal from the robot control unit 50 that controls the operation of the robot 12, a rotation command unit 53 that gives a rotation command to the first motor 32, and the rotation command unit 53. And a position control loop 56 for controlling the tip position of the friction stir welding tool 30.

The position control loop 56 includes an advance amount command unit 60 that gives a command c of the tip position of the friction stir welding tool 30 and a current tip position z of the friction stir welding tool 30 based on a signal obtained from the detection unit 38. An input processing unit 62 for obtaining the difference, an amplifier 64 for amplifying a deviation ε between the command c and the tip position z, a limiter 66 for limiting the current signal I obtained by the amplifier 64, and a saturation value of the limiter 66 are set. And a saturation value setting unit 68. The signal supplied to the second motor 34 at the output of the limiter 66 and the current signal I _L.

  The input processing unit 62 multiplies the signal supplied from the detection unit 38 by a predetermined ratio based on the ball screw mechanism 36 and takes the thickness of the workpiece W into account, and uses the surface of the workpiece W as a reference. The advance amount z of the friction stir welding tool 30 is calculated. The advance amount z is positive in the direction of entering the workpiece W and negative in the direction of upward separation. The robot control unit 50, the rotation command unit 53, and the advance amount command unit 60 operate in cooperation with each other.

By the way, since the 2nd motor 34 generate | occur | produces the torque according to an electric current similarly to a general motor and the load is a pressurizing force which mainly presses the workpiece | work W, the electric current signal I is regarded with a pressurization command. can do. Further, in the case of wire joining, when moving laterally at a constant speed, there is a correlation between the amount of insertion of the friction stir welding tool 30 with respect to the workpiece W and the pressing force of the friction stir welding tool 30 with respect to the workpiece W. The required pressure increases as the amount of insertion increases. Therefore, the amount of insertion of the friction stir welding tool 30 into the workpiece W can be adjusted by the magnitude of the current signal I. Further, by limiting the current signal I to I _L is provided a limiter 66, so that it is possible to limit the amount of insertion of the friction stir welding tool 30 to a predetermined amount.

Therefore, the saturation value setting unit 68 limits the current signal I so as not to exceed the pressure L corresponding to the proper insertion amount z _A (see FIG. 3) of the workpiece W and outputs the current signal I _L. 66 is set. The proper insertion amount z _A is set based on the thickness at which the work W can obtain the proper joint strength. For example, as shown in FIG. 3, the depth h based on the surface of the work W at the end face of the shoulder 42 is About 0.05 mm to 0.5 mm is preferable, and it is preferable to set the position to be 0.2 mm. In other words, when the height of the probe 40 is hp, the appropriate insertion amount z _A is preferably z _A = (hp + 0.05) mm to (hp + 0.5) mm, and more preferably z _A = The position may be set to (hp + 0.2) mm.

The saturation value setting unit 68 monitors the insertion amount z of the friction stir welding tool 30 and compares the insertion amount z with a predetermined threshold value z _T (not shown), and z> z _T Then, the limiter 66 is set to saturate at the proper insertion amount z _A. When z ≦ z _T , a sufficiently large value is set so that the limiter 66 is not saturated. In other words, the limiter 66 does not act when z ≦ z _T , and switching is performed so that the limiter 66 acts when the insertion amount exceeds the threshold value z _T. Threshold z _T is set as a value slightly smaller than the proper insertion amount z _A.

Further, the command c of the tip position z of the friction stir welding tool 30 supplied by the advance amount command unit 60 is within the range of the thickness D of the workpiece W, and the depth corresponding to the applied pressure L limited by the limiter 66. A value equal to the deep position z _L1 is set.

In the friction stir welding, when the workpiece W is heated by frictional heat, the material becomes soft and tends to be buried deeper even with the same pressure. Thus, even when the workpiece W becomes hot or when the tip of the friction stir welding tool 30 enters deeper than the proper insertion amount z _A of the workpiece W due to some unexpected situation, the position control loop Since the two-stage limit is set by 56, the friction stir welding tool 30 is not excessively buried in the workpiece W, and the yield is improved. Further, the command c may be set so as to be equal to the lower limit value of the range in which the workpiece W can obtain the appropriate joint strength. That is, when h = 0.05 to 0.5 mm is suitable, c = z _L1 = (hp + 0.5) mm may be set. Thereby, even if the limiter 66 is not limited based on the applied pressure, the workpiece W can obtain an appropriate bonding strength.

  Further, since the friction stir welding tool 30 needs to be moved in the pre-stage and the post-stage of the joining process, the position control loop 56 is normally provided, and the position control loop 56 is used as the limiter 66. It can be easily used as a second stage depth limiting means. In addition, the cross hatching part in FIG. 3 has shown the location by which friction stirring was carried out. In addition, the measurement reference may be any position, and is not limited to the tip of the probe 40 as shown in FIG. 3. For example, the end of the shoulder 42 may be used as a reference.

  Next, a friction stir welding method performed using the friction stir welding apparatus 10 configured as described above will be described with reference to FIGS. The friction stir welding method according to the present embodiment is divided into a first stage in which the operation of the robot 12 is taught and a second stage in which the workpiece W is joined based on the teaching data.

  When teaching is performed, a teaching tool 80 shown in FIG. 4 is used instead of the friction stir welding tool 30. The teaching tool 80 has a body part 80a and a flange part 80b provided at the tip of the body part 80a. The body 80a has the same diameter as the body 30a (see FIG. 3) in the friction stir welding tool 30. The flange portion 80b has a thin disk shape, and the tip surface is orthogonal to the axis. In a state where the teaching tool 80 is mounted on the tool drive mechanism portion 22, the position of the end portion of the flange portion 80b is above the end face of the shoulder 42 of the corresponding friction stir welding tool 30 by a distance h (see FIG. 3). It is aligned with the position (that is, the surface of the workpiece W). For teaching, a friction stir welding tool 30 without the probe 40 may be used for convenience.

  In addition, the workpiece | work W demonstrates the example currently mounted through the support | pillar 102 on the table 100, as shown in FIG. In this case, the table 100 can also be regarded as a part of the workpiece W, which is equivalent to the thick workpiece W.

  Next, the first stage of the friction stir welding method, that is, the teaching method will be described.

  In step S <b> 1 of FIG. 5, the teaching tool 80 is attached to the tool driving mechanism unit 22.

  In step S2, the end effector 14 is moved under the action of the robot 12, and as shown in FIG. 4, the teaching tool 80 is pressed against the joining start point S in the joining line, and the receiving member 24 is applied from the back surface. The workpiece W is clamped. At this time, since the flange 80 b is provided at the tip of the teaching tool 80, the axis of the teaching tool 80 comes into contact with the workpiece W in a plane. In this case, it suffices if the axis is perpendicular to the workpiece W. For example, the friction stir welding tool 30 without the probe 40 as described above may be used.

  In step S3, when the output torque of the second motor 34 increases, the position z of the fixed point (center point) O is obtained by referring to the protruding amount z of the teaching tool 80 at that time. The determined fixed point O is stored as the joining start location S. That is, when the output torque of the second motor 34 increases, the teaching tool 80 comes into contact with the surface of the workpiece W, and therefore, the joining start location S at one end of the joining line is specified.

  The fixed point O in this case is preferably a point on the axis of the teaching tool 80 as shown in FIG. Further, as shown in FIG. 6, when the corresponding friction stir welding tool 30 is assumed, the probe 40 is located on the axis of the friction stir welding tool 30 from the position O1 intersecting the surface of the workpiece W. You may set to any one point of the position O2 of a front-end | tip.

  In step S4, the distance L1 between the fixed point O and the receiving member is stored.

  In step S5, once the teaching tool 80 is retracted and separated from and retracted from the workpiece W, the end effector 14 is moved under the action of the robot 12 in the same manner as in step S2, and the joining end point E in the joining line is obtained. The teaching tool 80 is pressed against the workpiece W, and the workpiece W is clamped by applying the receiving member 24 from the back surface.

  In step S6, as in step S3, a fixed point O is obtained, and the fixed point O is stored as a joining end point E. Thereafter, the teaching tool 80 is retracted to be separated from and retracted from the workpiece W.

  In step S7, as shown in FIG. 7, a vector V connecting the stored joining start point S and joining end point E is obtained. This vector V indicates the joining line of the workpiece W. When the joining line is a broken line or a curve, the above process may be repeated at both ends of the straight section or at both ends of the section that can be close to the straight line. Further, the vector V may be defined based on predetermined setting condition data.

  In step S8, based on a preset advance angle θ (see FIG. 4), the amount of movement L2 of the receiving member 24 is determined as L2 ← L1 · tan θ. The obtained movement amount L2 is stored in the storage unit. The advance angle θ is provided such that the probe 40 of the friction stir welding tool 30 is advanced in the joining direction in order to improve the joining quality, and is set to 3 ° to 10 °, for example. The movement amount L2 indicates the distance that the receiving member 24 moves when the end effector 14 is tilted by the advance angle θ about the fixed point O.

  In step S8, a posture in which the receiving member 24 is moved by the movement amount L2 in the joining direction (V direction) and is inclined by the advance angle θ is defined. Based on this position and posture, the robot 12 Ask for posture. The posture of the robot 12 is obtained by a known inverse operation using a determinant based on the position and posture of the receiving member 24.

  That is, teaching is performed in which the receiving member 24 is moved in the joining direction (V) and the end effector 14 is tilted.

  Further, the operations required for teaching in step S8 are two complex operations. That is, this is a combined operation of a parallel operation for moving the end effector 14 by the movement amount L2 in the joining direction (V) and a tilting operation for inclining the advance angle θ. As described above, the teaching in step S8 can be easily performed without requiring a complicated calculation because a combination of two operations is sufficient. For example, the teaching can be performed by manual adjustment.

  The manual adjustment here refers to teaching performed while visually confirming the operation while actually moving the robot 12 and the end effector 14 using an adjustment pendant or the like.

  Next, a second stage in which the workpieces W are joined based on the first stage teaching data will be described with reference to FIG.

  In step S <b> 101, the friction stir welding tool 30 is attached to the tool driving mechanism unit 22.

In step S102, the end effector 14 is moved under the action of the robot 12 while referring to the data of the joining start location S stored in the storage unit, and the friction stir welding tool 30 is pressed against the joining start location S. The workpiece W is clamped by applying the receiving member 24 from the back surface. Further, the friction stir welding tool 30 is rotated by the first motor 32. As a result, the workpiece W is heated and softened by frictional heat, and a part of the probe 40 and the shoulder 42 enters the workpiece W, and friction stirring is started. At this time, the advancement amount of the friction stir welding tool 30 is controlled by the position control loop 56 so as to become the position z _L1, and is limited by the proper insertion amount z _A by the pressure limiting action of the limiter 66. That is, when the friction stir welding tool 30 is replaced with the teaching tool 80, the position is equivalent to that shown in FIG.

  In step S103, the robot 12 is operated so as to have the posture obtained in step S8. That is, as shown in FIG. 9, the receiving member 24 is moved by the movement amount L2 in the traveling direction. The advancing angle θ indicates an angle inclined in the direction opposite to the joining direction with respect to the vertical line in a plane perpendicular to the surface of the workpiece W including the joining line.

  At this time, the friction stir welding tool 30 is passively retracted by the pressure limiting action of the limiter 66, and the tip position of the friction stir welding tool 30 and the amount of burial with respect to the workpiece W are appropriately maintained. This operation moves and tilts the end effector 14 with the receiving member 24 as a reference, but apparently tilts around a fixed point O at the tip of the friction stir welding tool 30. .

  Specifically, although the friction stir welding tool 30 tends to be buried excessively in the workpiece W, the torque increases accordingly, and eventually the torque exceeding the predetermined value is caused by the saturation action of the limiter 66. Cannot occur. Therefore, the friction stir welding tool 30 is retracted passively and automatically along the axial direction while maintaining a predetermined torque. As described above, when the limiter 66 is used, it is not necessary to calculate and store the reverse amount, and it is not particularly necessary to output a reverse command or the like, and the operation control suitable for the actual work becomes easy.

  The burial amount of the friction stir welding tool 30 with respect to the workpiece W does not change before and after the tilting, and can be appropriately maintained, and the joining quality can be maintained.

  In step S104, under the action of the robot 12, the end effector 14 is moved at a predetermined speed in the joining direction (that is, the direction of the vector V) while maintaining the posture tilted by the advance angle θ. By this movement, line joining of the workpiece W is performed.

  In step S105, after the friction stir welding tool 30 reaches the joining end point E, the friction stir welding tool 30 is retracted and separated from the workpiece W, and the friction stir welding is finished.

  As described above, according to the friction stir welding apparatus 10, the friction stir welding method, and the teaching method according to the present embodiment, the receiving member 24 is moved in the joining direction, and the end effector 14 is tilted to obtain the friction stir welding. By retracting the friction stir welding tool 30 by limiting the pressure applied to the tool 30 for working, the tip position of the friction stir welding tool 30 and the amount of burying in the workpiece W are appropriately maintained, and the end effector 14 is moved. Teaching of the operation of the means to be performed becomes easy.

  Such an effect is particularly noticeable when the workpiece W is thick. However, the case where the workpiece W is thick is not limited to the case where the workpiece W is placed on the table 100 as described above. In some cases.

  Of course, the friction stir welding method according to the present invention is not limited to the above-described embodiment, and various configurations and processes can be adopted without departing from the gist of the present invention.

It is a schematic block diagram of a friction stir welding apparatus. It is a block block diagram of a control part. It is sectional drawing of the workpiece | work which shows the state which is performing friction stirring when the instruction | command of a position is set in the range of the thickness of a workpiece | work. It is a schematic side view of the workpiece | work at the time of teaching, the tool for friction stir welding, and a receiving member. It is a flowchart which shows the procedure of teaching of operation | movement of a robot. It is a schematic side view of the front-end | tip part of a workpiece | work and an end effector. It is a schematic perspective view of the workpiece | work at the time of teaching, and the tool for friction stir welding. It is a flowchart which shows the procedure of the friction stir welding method which concerns on this Embodiment. It is a schematic side view of the workpiece | work at the time of performing friction stir welding, the tool for friction stir welding, and a receiving member. It is explanatory drawing which shows the procedure of teaching based on a prior art.

Explanation of symbols

10: Friction stir welding apparatus 12 ... Robot (moving means, tilting means)
14 ... End effector 24 ... Receiving member 30 ... Friction stir welding tool 32, 34 ... Motor 40 ... Probe 42 ... Shoulder 56 ... Position control loop 66 ... Limiter 80 ... Teaching tool E ... Joining end point O ... Fixed point S ... Joining Starting point V ... Vector W ... Workpiece

Claims (1)

A friction stir gun frame for holding a workpiece by a friction stir welding tool and a receiving member;
Moving means for moving the gun frame in the joining direction;
Tilting means for tilting the gun frame;
A limiter for limiting the pressure command so as not to exceed a predetermined pressure on the workpiece when the workpiece is pressurized by the friction stir welding tool;
A friction stir welding method for joining the workpieces using
By inserting the workpiece while rotating the friction stir welding tool, the first step that Soo clamping the joining starting position of the workpiece in the receiving member and the friction stir welding tool,
Wherein the tilting means及beauty before Symbol moving means, said receiving member to tilt the gun frame is moved toward the welding direction, the friction stir welding tool is retracted under the action of the limiter, the friction A second step in which the tip of the stir welding tool is maintained at the position inserted into the workpiece;
A third step of moving the gun frame toward the joining direction by the moving means after tilting the gun frame;
A friction stir welding method characterized by comprising:

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