JP5967940B2 - Seam welding method and seam welding apparatus - Google Patents

Description

  The present invention relates to a seam welding method and a seam welding apparatus that perform welding continuously while applying pressure and energization with roller electrodes.

  Conventionally, when welding a workpiece such as a fuel tank that needs to be sealed, seam welding in which a nugget is continuously formed is used. In seam welding, resistance welding is continuously performed by sandwiching a welded part of a workpiece on which a base material is overlapped between a pair of roller electrodes, and applying pressure and energization to the welded part while rotating the roller electrode.

  However, when welding a portion where the welding locus has a certain degree of curvature, the length of the travel path differs between the center side and the opposite side of the curvature of the roller electrode. For this reason, the roller electrode is easily detached from the welding trajectory, which adversely affects the welding quality.

  Therefore, in Patent Document 1, when welding a portion where the welding locus has a certain degree of curvature, each roller electrode is inclined so that each axis of the pair of roller electrodes approaches the center side of the curvature. A seam welding method is described. According to this, since each roller electrode moves at a low speed on the center side of the curvature and at a high speed on the opposite side, slippage of the roller electrode and twisting of the work can be suppressed, and the welding quality can be improved.

JP 11-47943 A

  However, according to the seam welding method of Patent Document 1 described above, when welding a curved portion whose welding locus has a certain degree of curvature, the roller electrode is inclined toward the center of curvature with respect to the surface of the workpiece. For this reason, when welding is repeated such that the roller electrode is inclined to the same side, only one side of the roller electrode is worn.

  Each roller electrode is connected to a motor that rotates the roller electrode and an actuator that moves the roller electrodes closer to or away from each other. For this reason, in order to incline the roller electrode, a complicated mechanism is required, and the cost of the apparatus increases.

  Further, when welding a workpiece having a complicated welding locus, such as when manufacturing a gasoline tank for a two-wheeled vehicle, the curvature of the welding locus is reversed or greatly changed. In this case, it becomes difficult to control the inclination of the roller electrode.

  An object of the present invention is to improve the welding quality at the time of welding a curved portion in seam welding without cost, in view of such problems of the prior art.

The seam welding method according to the present invention includes a pressurizing step of pressurizing a workpiece with a pair of roller electrodes, a rotating step of rotating the roller electrode, a current supplying step of supplying a welding current to the roller electrode, and the pressurizing step. In parallel with the rotation and the supply, according to a predetermined welding locus, a moving process for moving the workpiece or the roller electrode at a welding speed, and correspondence data in which the angular speed and the rotational speed of the roller electrode are associated with each other are stored. A storage step, an angular velocity calculation step of calculating an angular velocity of the roller electrode based on the curvature of the curved portion of the welding locus and the welding velocity, and a rotational speed corresponding to the angular velocity calculated in the angular velocity calculation step. The rotational speed acquisition step acquired based on the data, and the rotational speed obtained in the rotational speed acquisition step, the roller electrode rotated in the rotation step And a rotational speed correction step of setting a rotational speed at the curved portion, the angular velocity and the rotational speed stored in the storage step, in the bending portion, the allowable deviation of the trajectory of the movement in the moving process for the welding path It is characterized by having a value that falls within the range .

  In the present invention, the amount of deviation from the welding trajectory of the roller electrode when welding a curved portion having a certain degree of curvature in the welding locus is related to the angular velocity determined by the curvature of the curved portion and the welding speed and the rotation speed of the roller electrode. To do. Therefore, in the storing step, correspondence data in which the angular speed and the rotational speed that can make the deviation amount fall within the allowable range can be stored prior to welding.

  In the rotation speed correction step, based on the correspondence data and the angular velocity calculated in the calculation step, the rotation speed corresponding to the angular velocity is acquired and set as the rotation speed of the roller electrode in the bending portion, thereby the bending portion. It is possible to keep the deviation amount of the roller electrode within the allowable range. Therefore, the welding quality at the time of welding the curved portion can be improved without cost.

The seam welding apparatus according to the present invention includes a pair of roller electrodes for applying pressure and welding current to a workpiece, a roller motor for rotating the roller electrode, and the workpiece or roller electrode according to a predetermined welding locus. Moving means for moving the welding electrode at a welding speed, a storage unit for storing correspondence data in which the angular velocity and the rotation speed of the roller electrode are associated with each other, the roller electrode based on the curvature and the welding speed in the curved portion of the welding locus An angular velocity calculation unit that calculates an angular velocity of the angular velocity, a rotation speed acquisition unit that acquires a rotation speed corresponding to the angular velocity calculated by the angular velocity calculation unit based on the correspondence data, and a rotation speed obtained by the rotation speed acquisition unit and a rotational speed correction unit for setting a rotational speed at the curved portion of the roller electrode being rotated by the roller motor, before Angular and rotational speed storage unit stores, the curved portion in, and having a value to keep the deviation of the trajectory of movement of the moving means by the roller electrodes relative to the weld trajectory within the allowable range.

  According to the present invention, similarly to the seam welding method described above, the deviation amount of the roller electrode in the curved portion of the welding locus can be kept within an allowable range, so that the welding quality in the curved portion can be reduced without cost. Can be improved.

It is a block diagram which shows the structure of the seam welding apparatus which concerns on one Embodiment of this invention. It is a figure which shows the tendency of the shift | offset | difference with respect to the welding locus | trajectory of a roller electrode when welding a curved part. It is a figure which shows the speed difference in a roller electrode when welding a curved part. It is a figure which shows the result of having investigated the relationship between the angular velocity of a roller electrode when welding a curved part, and preferable rotational speed. It is a flowchart which shows the welding process by the controller of the apparatus of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, a seam welding apparatus 1 according to an embodiment includes a welding head 2 that supplies a welding current while applying pressure to a workpiece, a manipulator 3 that holds and moves the welding head 2, and a welding A welding power source 4 as a current supply source and a controller 5 for controlling each part of the apparatus are provided. The manipulator 3 corresponds to the moving means in the present invention.

  The welding head 2 includes a pair of roller electrodes 6a and 6b that rotate with a workpiece interposed therebetween, roller motors 7a and 7b that rotate the roller electrodes 6a and 6b, respectively, and a servo motor 8 that moves the roller electrode 6a together with the roller motor 7a. Is provided. As a base material which comprises a workpiece | work, the metal plate for comprising the fuel tank of a vehicle corresponds, for example.

  The roller electrode 6a and the roller motor 7a are guided and held by the welding head 2 so as to move integrally in a predetermined direction. This guide direction is a direction in which the roller electrode 6a approaches and separates from the roller electrode 6b. The servo motor 8 moves the roller electrode 6a and the roller motor 7a along this contact / separation direction.

  The controller 5 includes a CPU, a storage device, a program, and the like. The controller 5 includes a robot controller 9 that controls the operation of the manipulator 3, a servo motor controller 10 that controls the drive of the servo motor 8, and energization of the welding current supplied from the welding power source 4 to the roller electrodes 6a and 6b. An energization control unit 11 that controls on / off of the roller, and a roller motor control unit 12 that controls driving of the roller motors 7a and 7b.

  Control of the manipulator 3 by the robot controller 9 is performed such that the welding head 2 moves at a predetermined welding speed according to a predetermined welding locus on the workpiece. At this time, the workpiece may be fixed, or may be held by another manipulator while appropriately changing the posture and position.

  The energization controller 11 controls the welding power source 4 and repeats energization of the welding current from the welding power source 4 to the roller electrodes 6a and 6b at a predetermined cycle. This period includes an energization period in which the energization of the roller electrodes 6a and 6b is performed and a pause period in which the energization is suspended. The length of the energization period and the rest period and the magnitude of the welding current are determined according to the material of the workpiece and the welding speed.

  Control of the servo motor 8 by the servo motor control unit 10 is performed by position control or torque control. The position control is performed based on the output of the encoder of the servo motor 8. Torque control is performed based on the value of current flowing through the servo motor 8. The servo motor control unit 10 applies a pressing force to the workpiece via the roller electrodes 6a and 6b by the servo motor 8.

  Further, the controller 5 includes a storage unit 13 that stores necessary data, an angular velocity calculation unit 14 that calculates an angular velocity based on the data in the storage unit 13, and the angular velocity calculated by the data and the angular velocity calculation unit 14 in the storage unit 13. Rotation speed acquisition unit 15 that acquires the rotation speed based on the above, and rotation that sets the rotation speed acquired by rotation speed acquisition unit 15 as the rotation speed of roller electrodes 6a and 6b when welding the curved portion of the welding locus And a speed correction unit 16.

  The data stored in the storage unit 13 includes teaching point data 17 indicating a welding locus, and correspondence data 18 that associates a predetermined angular velocity with the rotational speed of the roller electrodes 6a and 6b. The teaching point data 17 is coordinate data indicating a plurality of points set in advance to indicate a welding trajectory for a target workpiece. At the time of welding, the welding head 2 is moved according to the welding locus indicated by the teaching point data 17, and welding is performed.

  The calculation of the angular velocity by the angular velocity calculator 14 is performed based on the teaching point data 17 and the welding speed. The acquisition of the rotation speed by the rotation speed acquisition unit 15 is performed by obtaining the rotation speed corresponding to the calculated angular speed using the correspondence data 18.

  FIG. 2 shows a tendency of deviation with respect to the welding locus of the roller electrodes 6a and 6b in the curved portion of the welding locus. FIG. 2 shows a state in which a part of the workpiece W is viewed from the roller electrode 6a side along the contact / separation direction of the roller electrodes 6a and 6b. The roller electrode 6b is not shown in the figure because it is located on the opposite side of the roller electrode 6a with the workpiece W interposed therebetween.

  2A and 2B show the case where the convex curved portion of the workpiece W is welded according to the welding locus L. FIG. 2C and 2D show a case where a concave curved portion of the workpiece W is welded according to the welding locus L. FIG.

  FIGS. 2A and 2C show a case where the rotational speeds of the roller electrodes 6a and 6b are considerably smaller than the rotational speed corresponding to the welding speed. In this case, as indicated by the movement trajectory M, the roller electrodes 6a and 6b are located on the inner side (on the side of the center of curvature C) with respect to the welding trajectory L in both cases of FIGS. ) And move.

  On the other hand, FIGS. 2B and 2D show a case where the rotational speeds of the roller electrodes 6a and 6b are considerably larger than the rotational speed corresponding to the welding speed. In this case, as indicated by the movement trajectory M, the roller electrodes 6a and 6b are opposite to the welding trajectory L (the opposite of the center of curvature C) in any of the cases of FIGS. 2B and 2D. To the side). Therefore, it is considered that the movement trajectory M can be matched with the welding trajectory L by adjusting the rotation speeds of the roller electrodes 6a and 6b.

  As described above, the movement trajectory M is deviated from the welding trajectory L when the roller electrodes 6a and 6b travel along the curved portion, because the roller electrodes 6a and 6b have a certain width. This is because the force of the roller electrodes 6a and 6b sending the workpiece W is larger than the force of the manipulator 3 moving the roller electrodes 6a and 6b along the welding locus L in addition to the speed difference. It is done.

  FIG. 3 shows a speed difference between the roller electrodes 6a and 6b when the curved portion is welded. As shown in FIG. 3, the speed difference Δv described above is such that the distance from the center of curvature C of the welding locus L to the inside of the roller electrodes 6a and 6b is R, the thickness of the roller electrodes 6a and 6b is T, and the center of curvature C If the angular velocity of the roller electrodes 6a and 6b around ω is ω, Δv = (R + T) ω−Rω = Tω, which is proportional to the angular velocity ω. Therefore, in order to make the movement locus M coincide with the welding locus L, it is necessary to adjust the rotation speeds of the roller electrodes 6a and 6b in accordance with the angular velocity ω.

  The angular velocity ω is ω = V / R, where V is the welding speed (speed at which the manipulator 3 moves the roller electrodes 6a and 6b). Therefore, for a plurality of welding speeds a, b, and c (a <b <c), the rotational speeds of the roller electrodes 6a and 6b that match the movement locus M with the welding locus L with respect to various angular velocities ω were examined. The result as shown in FIG. 4 is obtained.

  In FIG. 4, the horizontal axis is the angular velocity ω, and the vertical axis is the rotational speed. However, the rotation speed on the vertical axis is indicated by a ratio r of the rotation speed added to the rotation speed of the roller electrodes 6a and 6b corresponding to the welding speed V. When the addition ratio r is zero, the welding speed V and the rotation speed of the roller electrodes 6a and 6b correspond to each other one to one. That is, the welding speed V and the feed speed of the workpiece W by the roller electrodes 6a and 6b coincide.

  In FIG. 4, the results for each of the welding speeds a, b, and c are shown by graph curves A, B, and C, respectively. Therefore, based on the relationship between the angular velocity ω and the addition ratio r, an optimum rotational speed of the roller electrodes 6a and 6b according to the angular velocity ω can be obtained.

  Therefore, in the present embodiment, a storage process is performed in which data indicating a correspondence relationship between the angular velocity ω and the addition ratio r (rotational speed) is acquired in advance and stored in the storage unit 13 as the correspondence data 18 described above. In actual welding, the correspondence data 18 is used to correct the rotational speeds of the roller electrodes 6a and 6b. As the correspondence data 18, it is possible to use a table in which values of the corresponding addition ratios r are associated with various values of the angular velocity ω, or data indicating a function representing this correspondence.

  FIG. 5 is a flowchart showing the welding process by the controller 5. As shown in FIG. 5, when the welding process is started, first, the robot control unit 9 of the controller 5 controls the manipulator 3 to move the welding head 2, and the welding start position of the workpiece between the roller electrodes 6a and 6b. Are arranged (step S1).

  Next, the servo motor control unit 10 drives the servo motor 8 to move the roller electrode 6a to a predetermined position facing the roller electrode 6b, and the pressure applied to the workpiece by the roller electrodes 6a and 6b is a predetermined value. Then, a pressurizing process for controlling the torque of the servo motor 8 is started (step S2).

  At the same time, the robot controller 9 starts a moving process in which the manipulator 3 moves the welding head 2 at a predetermined welding speed V so that seam welding is performed according to a welding locus determined by the teaching point data 17 (step S3). ). Further, the roller motor control unit 12 starts a rotation process for driving the roller motors 7a and 7b so that the roller electrodes 6a and 6b rotate at a predetermined rotation speed Ma corresponding to the welding speed V (step S4).

  Next, the energization control unit 11 starts a current supply process for supplying a predetermined welding current to the roller electrodes 6a and 6b (step S5). Thereby, seam welding is started along the welding locus on the workpiece.

  Next, the controller 5 waits for the roller electrodes 6a and 6b to reach the curved portion on the welding locus (steps S6 and S7). During this time, welding proceeds according to the welding locus. Whether or not the bending portion has been reached can be determined based on the teaching point data 17. When the curved portion is reached, the rotational speed Ma of the roller electrodes 6a and 6b is corrected as follows.

  That is, first, the angular velocity calculation unit 14 obtains the angular velocity ω (= V / R) based on the curvature 1 / R (R is a radius of curvature) of the curved portion obtained from the teaching point data 17 and the welding speed V. (Step S8; angular velocity calculation step). Next, the rotational speed acquisition unit 15 acquires the addition ratio r (see FIG. 4) corresponding to the obtained angular speed ω based on the correspondence data 18 in the storage unit 13 (step S9; rotational speed acquisition step).

  Then, the rotation speed correction unit 16 instructs the roller motor control unit 12 to rotate the roller electrodes 6a and 6b at the rotation speed Mb (= Ma + Ma · r) indicated by the obtained addition ratio r (step S10; Rotational speed correction process). In response to this, the roller motor control unit 12 changes the rotation speed of the roller motors 7a and 7b so that the roller electrodes 6a and 6b rotate at the rotation speed Mb. Thereby, the correction of the rotational speed Ma is completed.

  Next, the controller 5 waits for the welding of the bending portion to end (steps S11 and S12). During this time, welding of the curved portion proceeds.

  When the welding of the curved portion is completed, the rotation speed correction unit 16 instructs the roller motor control unit 12 to return the rotation speed Mb of the roller electrodes 6a and 6b to the original rotation speed Ma. In response to this, the roller motor controller 12 changes the rotational speeds of the roller motors 7a and 7b so that the rotational speed Mb of the roller electrodes 6a and 6b becomes the original rotational speed Ma (step S13). Then, it returns to step S6 and waits to reach the next bending part (steps S6 and S7).

  During this time, if the controller 5 determines in step S7 or S12 that welding has been completed, the welding process ends.

  According to the present embodiment, the roller electrode 6a when welding the curved portion on the welding locus, based on the correspondence data 18 in which the angular velocity ω stored in advance and the preferable addition ratio r corresponding thereto are associated with each other, Since the rotational speed Ma of 6b is corrected, the deviation of the roller electrodes 6a and 6b from the welding trajectory can be within an allowable range.

  In addition, this invention is not limited to the above-mentioned embodiment. For example, as the correspondence data 18, instead of data indicating the correspondence between the angular velocity ω and the addition ratio r, data indicating the correspondence between the angular velocity ω and the rotation speeds of the roller electrodes 6a and 6b may be used.

  In the above-described embodiment, data indicating the correspondence between the angular velocity ω and the addition ratio r is used as the correspondence data 18, but in addition to these correspondences, data indicating the correspondence with the welding speed. May be used. According to this, even when the welding speed changes, it is possible to appropriately correct the rotational speed of the roller electrodes 6a and 6b.

  DESCRIPTION OF SYMBOLS 1 ... Seam welding apparatus, 3 ... Manipulator (moving means), 6a, 6b ... Roller electrode, 7a, 7b ... Roller motor, 8 ... Servo motor (actuator), 11 ... Current supply control part, 13 ... Memory | storage part, 14 ... Angle Calculation part, 15 ... rotational speed acquisition part, 16 ... rotational speed correction part, 18 ... correspondence data, W ... work.

Claims (3)

A pressurizing step of pressurizing the workpiece with a pair of roller electrodes;
A rotating step of rotating the roller electrode;
A current supply step for supplying a welding current to the roller electrode;
In parallel with the pressurization, rotation and supply, a moving step of moving the workpiece or the roller electrode at a welding speed according to a predetermined welding trajectory,
A storage step of storing correspondence data in which the angular velocity and the rotation speed of the roller electrode are associated with each other;
An angular velocity calculating step of calculating an angular velocity of the roller electrode based on the curvature at the curved portion of the welding locus and the welding velocity;
A rotational speed acquisition step of acquiring a rotational speed corresponding to the angular speed calculated in the angular speed calculation step based on the correspondence data;
A rotation speed correction step of setting the rotation speed obtained in the rotation speed acquisition step as a rotation speed in the curved portion of the roller electrode rotated in the rotation step ;
The seam welding method according to claim 1, wherein the angular velocity and the rotational speed stored in the storage step have values that allow a deviation of a movement locus in the movement step with respect to the welding locus to fall within an allowable range in the bending portion . In the moving step, the roller electrode is held by a manipulator,
  The angular velocity calculation in the angular velocity calculation step is obtained by ω = V / R, where ω is the angular velocity, V is the welding speed, and R is the radius of curvature of the curved portion. The described seam welding method. A pair of roller electrodes for applying pressure and welding current to the workpiece;
A roller motor for rotating the roller electrode;
Moving means for moving the workpiece or roller electrode at a welding speed according to a predetermined welding trajectory;
A storage unit for storing correspondence data in which the angular velocity and the rotation speed of the roller electrode are associated with each other;
An angular velocity calculating unit that calculates an angular velocity of the roller electrode based on a curvature in the curved portion of the welding locus and the welding speed;
A rotational speed acquisition unit that acquires a rotational speed corresponding to the angular speed calculated by the angular speed calculation unit based on the correspondence data;
A rotation speed correction unit that sets the rotation speed obtained by the rotation speed acquisition unit as a rotation speed of the curved portion of the roller electrode rotated by the roller motor ;
The angular velocity and the rotational speed stored in the storage unit have values that allow the deviation of the trajectory of the movement of the roller electrode by the moving unit with respect to the welding trajectory to fall within an allowable range in the bending portion. .

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