JP6164862B2 - Seam welding method and system - Google Patents

Description

  The present invention relates to a seam welding method and system.

  Conventionally, a plurality of workpieces (workpieces) are sandwiched between a pair of electrode rollers, and the electrode rollers are continuously moved by the robot while contacting the workpieces while rotating the electrode rollers while applying pressure. Seam welding for welding workpieces is known. There are cases where three or more workpieces having different thicknesses are seam welded.

  In Patent Document 1, when plate materials having different rigidity are overlapped and spot-welded, the pressure applied by the electrode tip located on the soft plate side is made smaller than the pressure applied by the electrode tip located on the hard plate side. The technology is described.

Japanese Patent No. 3894545

  However, when a work piece having a small thickness comes into contact with one electrode roller, the nugget does not grow sufficiently between the work piece and the work piece adjacent to the work piece, resulting in poor welding. May occur. This is presumably because the thickness is small and the specific resistance is small, so that sufficient heating resistance is not generated.

  In order to sufficiently grow the nugget, it is conceivable to increase the value of the current flowing between the electrode rollers. However, in this case, the work to be welded may be melted and scattered.

  In view of the above points, the present invention provides a seam welding method and system capable of growing necessary and sufficient nuggets between the workpieces when seam welding three or more workpieces having different thicknesses. The purpose is to do.

The seam welding method of the present invention continuously moves a contact point between the electrode roller and the workpiece to be welded in a state where three or more workpieces having different thicknesses are sandwiched between a pair of electrode rollers. However, in the seam welding method, seam welding is performed by energizing the electrode rollers, and the pair of electrode rollers in a state where three or more workpieces having different thicknesses are sandwiched between the pair of electrode rollers by elastic means. By moving an equalizing mechanism that elastically supports in the direction in which the electrode rollers are arranged, the welding force of the electrode roller located on the work piece having the thinnest thickness among the work pieces is restored by the restoring force of the elastic means. The pressing force on the object is made smaller than the pressing force of the other electrode roller on the workpiece.

According to the seam welding method of the present invention, the pressing force of the electrode roller located on the thinnest workpiece (hereinafter referred to as “thinnest workpiece”) to the workpiece is applied to the other electrode rollers. Make it smaller than the pressing force against the workpiece. As a result, the pressing force of the electrode roller against the thinnest workpiece is relatively small, and the contact resistance between the thinnest workpiece and the workpiece to be adjacent to the thinnest workpiece is increased. This increases the amount of heat generated at the contact portion between these workpieces, so that the nugget grows sufficiently.

On the other hand, the pressing force of the electrode roller with respect to the workpiece that is not the thinnest workpiece is relatively large, and the contact resistance between the workpiece and the workpiece adjacent to the workpiece is small. Since the amount of heat generated at the contact portion between these workpieces becomes relatively small due to the energization therebetween, there is no possibility that the workpieces melt and scatter. Therefore, it is possible to perform seam welding on the workpieces having different thicknesses.

The seam welding system of the present invention continuously moves a contact point between the electrode roller and the workpiece to be welded in a state where three or more workpieces having different thicknesses are sandwiched between a pair of electrode rollers. However, a seam welding system for performing seam welding by energizing between the electrode rollers, wherein one electrode roller of the pair of electrode rollers is moved toward the other electrode roller, and the pair of electrode rollers elastically supporting the elaborate viewed clamping three or more object to be welded and a pressure means for pressurizing the seam welding apparatus provided with the pair of electrodes rollers, in the direction of arrangement of said pair of electrodes rollers by an elastic means between the equalizing mechanism, a moving means for moving the equalizing mechanism, by moving the equalizing mechanism, by the restoring force of said resilient means, said thin most thickness of the object to be welded to be Control means for controlling the moving means so that the pressing force of the electrode roller located on the contact side to the workpiece is smaller than the pressing force of the other electrode roller to the workpiece. It is characterized by that.

According to the seam welding system of the present invention, the pressing force of the electrode roller located on the thinnest workpiece side to the workpiece is made smaller than the pressing force of the other electrode rollers to the workpiece. As a result, the pressing force of the electrode roller against the thinnest workpiece is relatively small, and the contact resistance between the thinnest workpiece and the workpiece to be adjacent to the thinnest workpiece is increased. This increases the amount of heat generated at the contact portion between these workpieces, so that the nugget grows sufficiently.

On the other hand, the pressing force of the electrode roller with respect to the workpiece that is not the thinnest workpiece is relatively large, and the contact resistance between the workpiece and the workpiece adjacent to the workpiece is small. Since the amount of heat generated at the contact portion between these workpieces becomes relatively small due to the energization therebetween, there is no possibility that the workpieces melt and scatter. Therefore, it is possible to perform seam welding on the workpieces having different thicknesses.

  In addition, the above-described pressure difference is generated by the equalizing mechanism by moving the seam welding apparatus including the pair of electrode rollers in the direction in which the pair of electrode rollers are arranged by the moving means, so that the pressure difference is easily generated. Can be made.

Schematic which shows the whole structure of the seam welding system which concerns on the 1st Embodiment of this invention. The block diagram which shows the whole structure of a seam welding system. The flowchart explaining the seam welding method which concerns on the 1st Embodiment of this invention. It is a figure explaining the relationship between an electrode roller and a workpiece | work, (a) shows a feedback process, (b) shows the state in a playback process, respectively. It is a figure explaining the relationship between the electrode roller in another 1st Embodiment of this invention, and a workpiece | work, (a) shows a feedback process, (b) shows the state in a playback process, respectively. It is a figure explaining the relationship between the electrode roller and workpiece | work in the 2nd Embodiment of this invention, (a) shows the state in a feedback process, (b) shows in a playback process, respectively. It is a figure explaining the relationship between the electrode roller and workpiece | work in another 2nd Embodiment of this invention, (a) is a feedback process, (b) shows the state in a playback process, respectively.

  A seam welding system 100 according to a first embodiment of the present invention will be described with reference to the drawings. The seam welding system 100 is used when a plurality of workpieces (workpieces) W1 to W3 made of metal thin plates are joined by the seam welding apparatus 10 to manufacture a window frame, a fuel tank, or the like of an automobile.

  As shown in FIG. 1, the workpieces W <b> 1 to W <b> 3 are fixed at a predetermined position by a workpiece fixing base (not shown), and seam welding is performed by a seam welding apparatus 10 that is moved along a predetermined locus by a robot 20. Is done. Here, the workpieces W1, W2, and W3 are stacked adjacently in order from the top, and the workpiece W1 positioned at the top is the thinnest and the thinnest workpiece. The thicknesses of the other workpieces W2 and W3 may be the same or different as long as they are thicker than the workpiece W1.

  Referring to FIG. 2, the seam welding system 100 includes a control device 30 that controls the seam welding device 10 and the robot 20 and corresponds to the control means of the present invention.

  The robot 20 is an articulated robot such as a six-axis robot in which a plurality of arms are connected by joints, and is fixed to the base 21. Although not shown, the robot 20 includes a driving unit such as a servo motor and a detecting unit such as an encoder that detects the shaft angle of the servo motor, and is configured to be feedback-controlled by the control device 30. .

  The robot 20 is provided with an equalizing mechanism 22 at the distal end portion of an arm located at the distal end thereof, and corresponds to a moving means for moving the equalizing mechanism 22. The equalizing mechanism 22 has two identical elastic means 22a made of a spring or the like.

  The seam welding apparatus 10 includes a base 11 that is attached to the robot 20 via an equalizing mechanism 22. The base 11 is elastically supported at the tip of the arm of the robot 20 by being connected to two elastic means 22 a extending in the vertical direction of the equalizing mechanism 22.

  The equalizing mechanism 22 is provided with a displacement sensor 22b corresponding to a displacement amount detecting means for detecting an equalized displacement amount that is a displacement amount from the reference position of the base 11 in the vertical direction. The displacement sensor 22b is, for example, an encoder or a laser displacement sensor. When the equalizing displacement amount is increased, the pressure difference in the vertical direction from the equalizing mechanism 22 to the base 11 and consequently the seam welding apparatus 10 is increased by the restoring force of the elastic means 22a that has been expanded and contracted. This pressure difference can be detected indirectly via the displacement sensor 22b that detects the equalized displacement amount. In order to detect this pressure difference, a pressure sensor or the like may be provided instead of the displacement sensor 22b.

  The base 11 is provided with a guide rail 12 that extends in the vertical direction. The guide rail 12 is provided with a movable base 14 that can be moved in the vertical direction by an air cylinder 13 along the guide rail 12. ing. A movable base 14 is connected to the tip of the piston rod 13 a of the air cylinder 13. The driving means may be a hydraulic cylinder, a rotary motor equipped with a ball screw mechanism, a linear motor, or the like.

  An upper electrode 15 is pivotally supported on the movable base 14, and a lower electrode 16 is pivotally supported on the base 11. Thereby, the lower electrode 16 is provided at a predetermined height position, and the upper electrode 15 is arranged to be movable up and down with respect to the lower electrode 16. The upper electrode 15 and the lower electrode 16 are disk-like electrodes, and are also referred to as electrode rollers 15 and 16 together.

  The electrode rollers 15 and 16 are connected to rotation drive means 17 and 18 for rotating the electrode rollers 15 and 16 at a rotation speed set in a preset rotation direction, respectively. Here, the rotation driving means 17 and 18 are servo motors, but they may be ordinary motors including a pulse motor and a rotary encoder.

Further, the upper electrode 15 supplies current (welding current) required for welding, and is connected to the welding power supply 19 you corresponds to the welding current supply unit of the present invention. Here, the welding power source 19 supplies a DC pulse current, but it may supply an AC current.

  In this manner, the piston rod 13 a of the air cylinder 13 is extended to lower the upper electrode 15, and the welding current from the welding power source 19 to the upper electrode 15 is sandwiched between the electrodes 15 and 16. Supply. Thereby, a welding current flows from the upper electrode 15 to the lower electrode 16 (earth electrode) through the workpieces W1 to W3 sandwiched between the electrode rollers 15 and 16, and seam welding can be performed.

  As described above, the air cylinder 13 corresponds to a pressurizing unit that pressurizes the upper electrode 15 toward the lower electrode 16 and pressurizes the workpieces W1 to W3 sandwiched between the electrode rollers 15 and 16.

  As shown in FIG. 2, the control device 30 is an electronic circuit unit configured by a CPU or the like (not shown). The CPU executes the control program or the processing program held in the memory 31 to cause the air cylinder 13 to operate. A cylinder control unit 32 to control, a rotation drive control unit 33 to control the rotation drive means 17 and 18, a power supply control unit 34 to control the welding power source 19, a measurement signal input unit 35 to which a measurement signal is input from the displacement sensor 22b, and It functions as a robot control unit 36 that controls the robot 20 and controls the operations of the seam welding apparatus 10 and the robot 20.

  The memory 31 stores the teaching data of the robot 20 and supplies it from the amount of movement of the piston rod 13 a of the air cylinder 13, the rotational speed of the rotation driving means 17 and 18, and the welding power source 19 according to the welding conditions. Welding control data such as the value of the welding current is stored. The memory 31 also stores workpieces W1 to W3 having different thicknesses and teaching correction data of the robot 20 corresponding to the measurement signal input to the measurement signal input unit 35.

  When the CPU executes the control program, the control device 30 reads teaching correction data corresponding to the workpieces W1 to W3 having different thicknesses from the memory 31, and the entire seam welding device 10 including the electrode rollers 15 and 16 is transferred to the robot 20. It functions as a correction means for moving with. Further, when the CPU executes the control program, the control device 30 functions as a feedback control unit that feedback-controls the robot 20 in accordance with the measurement signal input to the measurement signal input unit 35.

  The control device 30 transmits control signals created by reading out the welding control data, teaching data, or teaching correction data stored in the memory 31 to the air cylinder 13, the rotation driving means 17, 18, the welding power source 19, and the robot 20. To do.

  Next, a seam welding method according to an embodiment of the present invention using the above-described seam welding system 100 will be described with reference to the drawings.

  As shown in the flowchart of FIG. 3, first, a teaching process for teaching the robot 20 is performed (STEP 1). In this teaching step, as shown in FIG. 4A, the lowermost workpiece W3 with which the lower electrode 16 contacts is pushed in by a preset pushing amount, and the upper electrode 15 is the uppermost thinnest workpiece. Teaching is performed so that a certain gap is generated from W1. At this time, the pressing force from the lower electrode 16 to the workpiece W3 is already applied. The teaching data is stored in the memory in advance.

  Thereafter, a playback process is performed in which seam welding is performed by moving along the trajectory while energizing the workpieces W1 to W3 with both the electrode rollers 15 and 16 interposed therebetween (STEP 2). In this playback step, as shown in FIG. 4B, the amount of movement of the piston rod 13a of the air cylinder 13 is set to the amount of movement during the teaching step so that the upper electrode 15 contacts the thinnest workpiece W1 at the top. The robot 20 is operated so as to increase the movement amount set in advance. At this time, the lower electrode 16 moves along the same trajectory as the teaching step while the lowermost workpiece W3 in contact with the lower electrode 16 is pushed by a preset pushing amount (a pushing amount larger than the pushing amount in the teaching step). . The increase amount of the movement amount of the piston rod 13a is stored in the memory in advance.

  However, in the playback step, the pressing force P2 from the lower electrode 16 to the workpiece W3 is set to be larger than the pressing force P1 from the upper electrode 15 to the thinnest workpiece W1 by a predetermined pressure ΔP. This is feedback controlled by the measurement signal input from the displacement sensor 22b to the measurement signal input unit 35 during the playback process.

  Specifically, when ΔP indicated by the measurement signal input from the displacement sensor 22b is larger than a preset pressure difference ΔP0 (STEP 3: YES), the robot 20 performs seam welding so that ΔP becomes smaller. 10 is moved upward. On the other hand, when ΔP indicated by the measurement signal input from the displacement sensor 22b is smaller than the preset pressure difference ΔP0 (STEP 6: YES), the robot 20 lowers the seam welding apparatus 10 so that ΔP increases. Move in the direction.

  As described above, in the present embodiment, in the playback process, the pressing force P2 from the lower electrode 16 to the workpiece W3 becomes larger than the pressing force P1 from the upper electrode 15 to the thinnest workpiece W1 by a predetermined pressure ΔP.

If the pressing force P1 from the upper electrode 15 to the thinnest workpiece W1 is small, the contact resistance between the thinnest workpiece W1 and the workpiece W2 adjacent to the thinnest workpiece W1 increases. Since the amount of heat generated at the contact portion between W1 and W2 increases, the nugget grows sufficiently.

On the other hand, since the pressing force P2 from the lower electrode 16 to the workpiece W3 is large, the contact resistance between the workpiece W3 and the workpiece W2 adjacent to the workpiece W3 is small , and the energization between the electrode rollers 15 and 16 results in these workpieces W2, W3. Since the calorific value at the contact portion between them becomes relatively small , there is no possibility that the workpieces W2 and W3 are melted and scattered. Therefore, the workpieces W1 to W3 having different thicknesses can be seam welded satisfactorily.

  Further, the seam welding apparatus 10 is moved in the vertical direction by the robot 20, and the pressure difference ΔP is generated by the equalizing mechanism 22. Therefore, the pressure difference ΔP can be easily generated. Note that the pressure difference ΔP may be generated by the torque control of the robot 20, but in this case, the pressure difference ΔP is small with respect to the load capacity of the robot 20, and is caused by the friction of the speed reducer of each joint axis of the robot 20. It is difficult to generate an accurate pressure difference ΔP.

  Furthermore, since the pressure difference ΔP generated by the equalizing mechanism 22 is feedback-controlled using the displacement sensor 22b, the pressure difference ΔP can be reliably maintained constant. However, the displacement sensor 22b may be omitted and feedback control may not be performed.

  The pressure difference ΔP may be obtained experimentally depending on the thickness of the workpieces W1 to W3, the difference between them, and the like, but is, for example, several MPa or less.

  Hereinafter, another first embodiment of the present invention will be described. In this embodiment, as shown in FIG. 5A, in the teaching process, the lower electrode 16 comes into contact with the workpiece W3, and the upper electrode 15 has a certain gap with the thinnest workpiece W1 at the top. To teach.

  Thereafter, in this playback step, as shown in FIG. 5B, the amount of movement of the piston rod 13a of the air cylinder 13 is set so that the upper electrode 15 contacts the thinnest workpiece W1 at the top. The robot 20 is operated so as to increase the movement amount by a preset movement amount (a movement amount larger than the movement amount described above). At this time, the lower electrode 16 moves along the same trajectory as the teaching step while the lowermost workpiece W3 that is in contact with the lower electrode 16 being pushed by a preset pushing amount.

  As in the above-described embodiment, in the playback step, the pressing force P2 from the lower electrode 16 to the workpiece W3 is set to be larger than the pressing force P1 from the upper electrode 15 to the thinnest workpiece W1 by a predetermined pressure ΔP. . This may be feedback controlled by the measurement signal input from the displacement sensor 22b to the measurement signal input unit 35 during the playback process. Also in the present embodiment, similarly to the above-described embodiment, the workpieces W1 to W3 having different thicknesses can be seam welded satisfactorily.

  Hereinafter, a second embodiment of the present invention will be described. In this embodiment, as shown in FIGS. 6 (a) and 6 (b), the three workpieces W4 to W6 are stacked adjacent to each other in the order of the workpieces W4, W5, and W6 from the top. The workpiece W6 located at is the thinnest and the thinnest workpiece. The other workpieces W4 and W5 may be the same or different as long as they are thicker than the workpiece W6. The seam welding system 100 is the same as that in the first embodiment described above.

  In the second embodiment, as shown in FIG. 6A, in the teaching process, the lower electrode 16 has a certain gap with the thinnest workpiece W6 at the lowermost portion, and the upper electrode 15 is at the uppermost workpiece W4. Teaching to create a certain gap.

  Thereafter, in the playback process, as shown in FIG. 6B, the movement amount of the piston rod 13a of the air cylinder 13 is determined from the movement amount in the teaching process so that the upper electrode 15 pushes in the uppermost work W4. The robot 20 is operated so as to increase by a preset movement amount (a movement amount larger than the movement amount in the first embodiment described above). At this time, the lower electrode 16 is pushed along the same trajectory as the teaching process while the lowermost thinnest workpiece W6 that is in contact is pushed by a preset pushing amount (a pushing amount smaller than the pushing amount of the upper electrode 15). Moving.

  In the playback step, the pressing force P3 from the upper electrode 15 to the workpiece W4 is set to be larger than the pressing force P4 from the lower electrode 16 to the thinnest workpiece W6 by a predetermined pressure ΔP. This may be feedback controlled by the measurement signal input from the displacement sensor 22b to the measurement signal input unit 35 during the playback process. Also in the second embodiment, similarly to the first embodiment described above, the workpieces W4 to W6 having different thicknesses can be seam welded satisfactorily.

  Hereinafter, another second embodiment of the present invention will be described. In this embodiment, as shown in FIG. 7A, in the teaching process, the lower electrode 16 is in contact with the thinnest workpiece W6 and the upper electrode 15 has a certain gap from the uppermost workpiece W4. Teaching to occur.

  Thereafter, in the playback process, as shown in FIG. 7B, the movement amount of the piston rod 13a of the air cylinder 13 is determined from the movement amount in the teaching process so that the upper electrode 15 pushes the uppermost work W4. The robot 20 is operated so as to increase the movement amount set in advance. At this time, the lower electrode 16 is pushed along the same trajectory as the teaching process while the lowermost thinnest workpiece W6 that is in contact is pushed by a preset pushing amount (a pushing amount smaller than the pushing amount of the upper electrode 15). Moving.

  In the playback step, the pressing force P3 from the upper electrode 15 to the workpiece W4 is set to be larger than the pressing force P4 from the lower electrode 16 to the thinnest workpiece W6 by a predetermined pressure ΔP. This may be feedback controlled by the measurement signal input from the displacement sensor 22b to the measurement signal input unit 35 during the playback process. Also in this embodiment, similarly to the second embodiment described above, the workpieces W4 to W6 having different thicknesses can be seam welded satisfactorily.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to this. For example, the case where the upper electrode 15 can be moved up and down and the lower electrode 16 is fixed has been described. However, the present invention is not limited to this, and even if the upper electrode 15 is fixed and the lower electrode 16 can move up and down, both the upper electrode 15 and the lower electrode 16 may move up and down.

  Moreover, the case where the workpiece | work W1-W3 and W4-W6 are 3 sheets was demonstrated. However, four or more workpieces may be overlapped and seam welded. When seam welding is performed with two workpieces overlapped, there is no need to generate a pressure difference ΔP, so monitoring may be performed with a detection signal from the displacement sensor 22b so that the pressure difference ΔP does not occur. .

  DESCRIPTION OF SYMBOLS 10 ... Seam welding apparatus, 11 ... Base, 12 ... Guide rail, 13 ... Air cylinder (pressurizing means), 13a ... Piston rod, 14 ... Movable stand, 15 ... Upper electrode, electrode roller), 16 ... Lower electrode, Electrode rollers), 17, 18 ... Rotation drive means, 19 ... Welding power supply, 20 ... Robot (moving means), 21 ... Base, 22 ... Equalizing mechanism, 22a ... Elastic means, 22b ... Displacement sensor (displacement amount detecting means), DESCRIPTION OF SYMBOLS 30 ... Control apparatus (control means, correction | amendment means) 31 ... Memory, 32 ... Cylinder control part, 33 ... Rotation drive control part, 34 ... Power supply control part, 35 ... Measurement signal input part, 36 ... Robot control part, 100 ... Seam welding system, W1, W6 ... thinnest workpiece, W2, W3, W4, W5 ... workpiece.

Claims (6)

While three or more workpieces having different thicknesses are sandwiched between a pair of electrode rollers, the contact points between the electrode rollers and the workpiece are continuously moved while energizing between the electrode rollers. A seam welding method for performing seam welding by
Restoring the elastic means by moving an equalizing mechanism that elastically supports the pair of electrode rollers in a state in which the three or more workpieces having different thicknesses are sandwiched between the pair of electrode rollers by elastic means. Due to the force, the pressing force of the electrode roller located on the side of the workpiece to be welded with the smallest thickness among the workpieces is smaller than the pressing force of the other electrode roller on the workpiece. A seam welding method characterized by:   The seam welding method according to claim 1, wherein a displacement amount of the equalizing mechanism from a reference position in a direction in which the pair of electrode rollers are arranged is detected. The seam welding method according to claim 2, wherein the pressure difference of the pressing force is feedback-controlled by detecting the displacement amount. While three or more workpieces having different thicknesses are sandwiched between a pair of electrode rollers, the contact points between the electrode rollers and the workpiece are continuously moved while energizing between the electrode rollers. A seam welding system for performing seam welding by
One electrode roller of the pair of electrode roller is moved toward the other electrode roller, and a pressurizing means for pressurizing the three or more of the weldment elaborate seen sandwiched between the pair of electrodes rollers ,
An equalizing mechanism for elastically supporting the seam welding apparatus including the pair of electrode rollers in an arrangement direction of the pair of electrode rollers by an elastic means ;
Moving means for moving the equalizing mechanism;
The equalizing mechanism is moved, and by the restoring force of the elastic means, the pressing force of the electrode roller, which is positioned on the work piece having the thinnest thickness among the work pieces, is applied to the work piece. A seam welding system comprising: control means for controlling the moving means so as to be smaller than a pressing force of the electrode roller against the workpiece.   The seam welding system according to claim 4, further comprising a displacement amount detection unit that detects a displacement amount of the equalization mechanism from a reference position in a direction in which the pair of electrode rollers are arranged. Wherein the control means, in response to the displacement amount of the displacement amount detected by the detecting means, by further moving the equalizing mechanism in the moving means, characterized by feedback control of the pressure difference between the pressing force Item 6. The seam welding system according to item 5.