JP2014155950A - Seam weld method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seam weld method capable of maintaining preferable weld accuracy by grasping a distance between an electrode roller and a workpiece.SOLUTION: In an imaging process, an imaging sensor 40 captures images of electrode rollers 15, 16 and a workpiece W (STEP 1). In a detecting process, a distance between the electrode rollers 15, 16 and the workpiece W is determined on the basis of image data obtained by capturing images by the imaging sensor 40 (STEP 2). In a correcting process, the electrode roller 16 is moved so as to contact the workpiece W on the basis of the obtained distance (STEP 3). Then, in a weld process, seam weld is performed (STEP 5).

Description

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

  Conventionally, seam welding is known in which a workpiece (workpiece) is sandwiched between a pair of electrode rollers, and the workpiece is continuously welded by rotating the electrode roller while applying pressure.

  The outer peripheral surface of the electrode roller is pressed and abutted against the workpiece to be worn, and the outer diameter of the electrode roller becomes smaller as the number of seam welding is increased. Further, when the outer peripheral surface of the electrode roller is worn, irregularities (creeks) are generated and the welding current becomes unstable, which adversely affects the welding result of the workpiece. Therefore, it is necessary to periodically polish (dressing) the outer peripheral surface of the electrode roller, and this also reduces the outer diameter of the electrode roller.

  In order to maintain good welding accuracy in seam welding, it is necessary to apply an appropriate pressing force by the electrode roller that sandwiches the workpiece, and therefore it is necessary to grasp the outer diameter of the electrode roller.

  For example, Patent Document 1 describes a technique in which the outer diameter of a lower electrode is measured by a displacement sensor provided at the tip of a link that pivotally supports a central part of a lifting body that moves up and down the lower electrode.

Japanese Patent No. 3535700

  However, as described in Patent Document 1, the distance between the electrode roller and the work piece cannot be grasped only by obtaining the outer diameter of the electrode roller, and good welding accuracy may not be maintained. There is.

  For example, a large error occurs in grasping the distance between the electrode roller and the workpiece to be welded due to accumulation of errors inevitably inherent in the mechanism that moves the electrode roller or the robot that moves the seam welding apparatus including the electrode roller. There is. In this case, there is a possibility that the welding accuracy is deteriorated, for example, the pressing force applied to the workpiece is inappropriate.

  In view of the above points, an object of the present invention is to provide a seam welding method and apparatus capable of grasping the distance between an electrode roller and a workpiece and maintaining good welding accuracy.

  The seam welding method of the present invention performs seam welding by supplying a welding current for energizing the electrode rollers with a plurality of workpieces sandwiched between a pair of electrode rollers formed in a disk shape. A seam welding method to be performed, the imaging step of imaging at least a part of the pair of electrode rollers and the workpiece to be welded by an imaging sensor, and the pair of the images based on the image data obtained by imaging in the imaging step And detecting the distance between the electrode roller and the workpiece to be welded, and moving at least one of the pair of electrode rollers with respect to the workpiece based on the distance obtained in the detection step. And a correction step.

  According to the seam welding method of the present invention, a distance between a pair of electrode rollers and an object to be welded is obtained from image data obtained by imaging with an imaging sensor, and at least one of the pair of electrode rollers is determined based on this distance. The electrode roller is moved with respect to the workpiece and corrected. Thereby, even if the distance between the electrode roller and the workpiece is different from the preset distance, the difference can be eliminated by correction. Therefore, good welding accuracy can be maintained, for example, by appropriate pressing force applied to the workpiece.

  In the seam welding method of the present invention, when the first electrode roller of the pair of electrode rollers is configured to be movable with respect to the second electrode roller, the distance obtained in the detection step in the correction step Therefore, it is preferable to move the pair of electrode rollers so that the workpiece is in contact with the outer peripheral surface of the second electrode roller.

  In this case, it is possible to apply a preset appropriate pressing force to the workpiece by moving the first electrode roller by a preset distance.

  Further, in the seam welding method of the present invention, when the first electrode roller and the second electrode roller of the pair of electrode rollers are both configured to be movable with respect to the other electrode rollers, the correction step In the above, based on the distance obtained in the detection step, the pair of the pair of the first electrode roller and the second electrode roller so that a gap between the outer peripheral surface and the workpiece is the same. It is preferable to move each of the electrode rollers.

  In this case, it is possible to apply a preset appropriate pressing force to the workpiece by moving the first and second electrode rollers respectively by a preset distance.

  The seam welding apparatus according to the present invention is a seam welding apparatus that performs seam welding by energizing the electrode rollers with a plurality of workpieces sandwiched between a pair of electrode rollers formed in a disk shape. An image sensor for imaging at least a part of the pair of electrode rollers and the workpiece, and the pair of electrode rollers and the workpiece to be welded based on image data obtained by imaging with the imaging sensor. Detecting means for determining the distance to the workpiece, and correcting means for moving at least one of the pair of electrode rollers relative to the workpiece based on the distance obtained by the detecting means. And

  According to the seam welding apparatus of the present invention, the distance between the pair of electrode rollers and the workpiece is obtained from the image data obtained by imaging with the image sensor, and based on this distance, the correcting means is less of the pair of electrode rollers. Also, one electrode roller is moved relative to the work piece. Thereby, even if the distance between the electrode roller and the workpiece is different from the preset distance, the difference can be eliminated by correction. Therefore, good welding accuracy can be maintained, for example, by appropriate pressing force applied to the workpiece.

Schematic which shows the whole structure of the seam welding system provided with the seam welding apparatus which concerns on embodiment of this invention. The block diagram which shows the whole structure of a seam welding system. The figure explaining the image imaged with the imaging sensor. The flowchart explaining the seam welding method which concerns on embodiment of this invention. It is a figure explaining correction | amendment of the positional relationship of an electrode roller and a workpiece | work, (a) is a case where a lower electrode is contact | abutted to a workpiece | work, (b) is a case where each clearance gap between both electrode rollers and a workpiece | work is made the same. Respectively.

  A seam welding system 100 including a seam welding apparatus 10 according to an 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) W made of a thin metal plate are joined by the seam welding apparatus 10 to manufacture a window frame or a fuel tank of an automobile.

  As shown in FIG. 1, the workpiece W is seam welded by a seam welding apparatus 10 that is fixed at a predetermined position by a workpiece fixing base (not shown) and moved along a predetermined trajectory by a robot 20. . 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. .

  An equalizing mechanism 22 is provided at the tip of the arm located at the tip of the robot 20. The seam welding apparatus 10 is elastically supported at the tip of the arm of the robot 20 by an equalizing mechanism 22. Thereby, even if there is a minute change in the portion to be welded, the seam welding apparatus 10 can follow the change.

  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 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 the driving means 13 along the guide rail 12. ing. Here, the drive means 13 is the air cylinder 13, and the movable table 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 is supplied with a current (welding current) necessary for welding and is connected to a welding power source 19 corresponding to the welding current supply means of the present invention. Here, the welding power source 19 supplies a DC pulse current, but it may supply an AC current.

  In this way, the piston rod 13 a of the air cylinder 13 is extended to lower the upper electrode 15, and the welding current is supplied from the welding power source 19 to the upper electrode 15 with the workpiece W sandwiched between the electrodes 15 and 16. To do. As a result, a welding current flows from the upper electrode 15 to the lower electrode 16 (earth electrode) through the workpiece W sandwiched between the electrode rollers 15 and 16, and seam welding can be performed.

  As described above, the air cylinder 13 functions as a pressurizing unit that pressurizes the workpiece W sandwiched between the electrode rollers 15 and 16 by pressing the upper electrode 15 toward the lower electrode 16.

  An imaging sensor 40 such as a line sensor is fixed to the base 11 of the seam welding apparatus 10. The image sensor 40 is provided to detect the positional relationship between the electrode rollers 15 and 16 and the workpiece W in order to prevent the electrode rollers 15 and 16 from being detached from the workpiece W.

  Specifically, as shown in FIG. 3, it is based on image data obtained by imaging by the imaging sensor 40, particularly image data obtained by imaging a portion including the corners of the electrode rollers 15, 16 and the work W. The positional relationship between the electrode rollers 15 and 16 and the workpiece W is detected from the image, and the distance between the electrode rollers 15 and 16 and the workpiece W is obtained.

  If the calculated distance is different from the preset distance, the robot 20 is operated so as to eliminate this difference.

  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 for controlling, a rotation drive control unit 33 for controlling the rotation drive means 17, 18, a power supply control unit 34 for controlling the welding power source 19, and an image processing unit 35 for inputting image signals from the image sensor 40 and performing image processing. , And functions as a robot controller 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 correction data of the robot 20 according to the distance between the electrode rollers 15 and 16 and the workpiece W.

  When the CPU executes the image processing program, the control device 30 functions as detection means for obtaining the respective distances between the electrode rollers 15 and 16 and the workpiece W from the image data obtained by the imaging sensor 40. Further, when the CPU executes the control program, the control device 30 also functions as correction means for moving the entire seam welding device 10 including the electrode rollers 15 and 16 by the robot 20 based on the obtained distance.

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

  Here, the electrode rollers 15 and 16 are gradually consumed by performing seam welding, and further shaped by dressing. Therefore, the diameters of the electrode rollers 15 and 16 are reduced. In addition, an error inevitably occurs in the movement of the air cylinder 13 that moves the electrode roller 15 or the robot 20 that moves the seam welding apparatus 10. Due to the accumulation of this error and the like, the positional relationship between the electrode rollers 15 and 16 and the workpiece W differs from that set in advance. Therefore, the pressing force applied to the workpiece W becomes inappropriate, and the welding accuracy may be deteriorated.

  Therefore, the positional relationship between the electrode rollers 15 and 16 and the workpiece W is detected from the image data obtained by the imaging sensor 40, and the detection result is compared with a preset positional relationship. The robot 20 and the like are moved and controlled so as to eliminate the above.

  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. 4, first, an imaging process is performed in which the imaging sensor 40 images at least a portion including the respective ends of the electrode rollers 15 and 16 and the workpiece W (STEP 1).

  And the detection process which detects the positional relationship of the electrode rollers 15 and 16 and the workpiece | work W from the image data acquired by the imaging process is performed (STEP2). In this detection step, the distances between the electrode rollers 15 and 16 and the workpiece W are obtained based on the image data obtained in the imaging step.

  Next, based on the distance calculated | required at the detection process, the correction process which moves the whole seam welding apparatus 10 containing the electrode rollers 15 and 16 with respect to the workpiece | work W with the robot 20 is performed (STEP3).

  In this correction process, for example, when the detection process detects that a gap is generated between the lower electrode 16 and the workpiece W from the image data obtained by the imaging sensor 40 immediately before the start of seam welding, As shown in FIG. 5A, the movement control of the robot 20 is performed so that the lower electrode 16 contacts the workpiece W. Thus, in the next STEP 4, the piston rod 13a of the air cylinder 13 is extended by a preset stroke amount and the upper electrode 15 is lowered to apply a preset appropriate pressing force to the workpiece W. Is possible.

  Next, the piston rod 13a of the air cylinder 13 is extended by a preset stroke amount, the upper electrode 15 is lowered, and the work W is sandwiched between the electrode rollers 15 and 16 with an appropriate pressing force (STEP 4). ). Thereafter, a welding process for seam welding is performed on the workpiece W (STEP 5).

  As described above, in the present embodiment, the positional relationship between the electrode rollers 15 and 16 and the workpiece W is detected based on the image data obtained by imaging with the imaging sensor 40 (STEP 2), and the detected positional relationship is determined. Based on this, the positional relationship is corrected by moving the electrode rollers 15 and 16 with respect to the workpiece W (STEP 3).

  As a result, even if the positional relationship between the electrode rollers 15 and 16 and the workpiece W is different from that set in advance, it is possible to correct the difference so that the positional relationship is set in advance by eliminating the difference. It becomes. Therefore, it becomes possible to maintain good welding accuracy by making the pressing force applied to the workpiece W appropriate (STEP 4).

  Further, since the imaging sensor 40 is fixed to the base 11, the positional relationship with the lower electrode 16 is constant. Therefore, the positional relationship between the electrode rollers 15 and 16 and the workpiece W can be stably detected based on the image data obtained by imaging with the imaging sensor 40.

  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.

  In the apparatus in which the lower electrode 16 can be moved up and down by the air cylinder as well as the upper electrode 15, the upper electrode 15 and the lower electrode are obtained from the image data obtained by the imaging sensor 40 immediately before the start of seam welding. When it is detected in the detection step that the gap between the electrode 16 and the workpiece W is different, the movement control of the robot 20 is performed so that the gap α is the same as shown in FIG. Just do it. Accordingly, it is possible to apply a preset appropriate pressing force to the workpiece W by lowering the upper electrode 15 and raising the lower electrode 16 by the same predetermined stroke amount.

  Further, for example, immediately before the start of seam welding, when the detection process detects that the upper electrode 15 or the lower electrode 16 and the workpiece W are not positioned in parallel from the image data obtained by the imaging sensor 40, The movement control of the robot 20 may be performed so that they are parallel. As a result, it is possible to apply a preset pressing force without an appropriate inclination to the workpiece W.

  Further, the case where the upper electrode 15 and the lower electrode 16 are arranged vertically has been described. However, the present invention is not limited to this, and the upper electrode 15 and the lower electrode 16 may be arranged horizontally or inclined.

  DESCRIPTION OF SYMBOLS 10 ... Seam welding apparatus, 11 ... Base, 12 ... Guide rail, 13 ... Drive means, air cylinder, 13a ... Piston rod, 14 ... Movable stand, 15 ... Upper electrode (1st electrode roller), 16 ... Lower electrode (Second electrode roller), 17, 18 ... rotational drive means, 19 ... welding power source, 20 ... robot, 21 ... base, 22 ... equalize mechanism, 30 ... control device (control means, detection means, correction means), 31 DESCRIPTION OF SYMBOLS ... Memory 32 ... Cylinder control part 33 ... Rotation drive control part 34 ... Power supply control part 35 ... Image processing part 36 ... Robot control part 40 ... Imaging sensor 100 ... Seam welding system W ... .

Claims (4)

A seam welding method for performing seam welding by supplying a welding current for energizing between the electrode rollers in a state where a plurality of workpieces are sandwiched between a pair of electrode rollers formed in a disk shape,
An imaging step of imaging at least a part of the pair of electrode rollers and the workpiece to be welded by an imaging sensor;
Based on the image data obtained by imaging in the imaging step, a detection step for obtaining a distance between the pair of electrode rollers and the workpiece,
A seam welding method comprising: a correction step of moving at least one electrode roller of the pair of electrode rollers with respect to the workpiece based on the distance obtained in the detection step. The first electrode roller of the pair of electrode rollers is configured to be movable with respect to the second electrode roller,
The pair of electrode rollers is moved in the correction step so that the workpiece is in contact with the outer peripheral surface of the second electrode roller based on the distance obtained in the detection step. Item 2. The seam welding method according to Item 1. Of the pair of electrode rollers, the first electrode roller and the second electrode roller are both configured to be movable with respect to the other electrode rollers,
In the correction step, based on the distance obtained in the detection step, the outer peripheral surface of the first electrode roller, the outer peripheral surface of the second electrode roller, and the gap to be welded are the same. The seam welding method according to claim 1, wherein each of the pair of electrode rollers is moved. A seam welding apparatus that performs seam welding by energizing between the electrode rollers in a state where a plurality of workpieces are sandwiched between a pair of electrode rollers formed in a disk shape,
An image sensor that images at least a part of the pair of electrode rollers and the workpiece;
Detection means for obtaining a distance between the pair of electrode rollers and the workpiece to be welded based on image data obtained by imaging with the imaging sensor;
A seam welding apparatus comprising: correction means for moving at least one of the pair of electrode rollers with respect to the workpiece based on the distance obtained by the detection means.

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