JP2020055009A - Seam-welding device and seam-welding method - Google Patents

Abstract

To provide a seam-welding device and a seam-welding welding method which can reduce time required for dealing with the cause of an abnormality (defect) of a detected result by a work-piece position detection sensor.SOLUTION: A seam-welding device 10 comprises: a first determination part 18c that determines whether or not there is an abnormality in a detected result by a work-piece position detection sensor 16 that detects positions of edge parts of two flanges 13 and 15; and a second determination part 18d that determines the cause of an abnormality on the basis of a state of variations of the detected result by the work-piece position detection sensor 16 when the first determination part 18c determines that there is the abnormality in the detected result by the work-piece position detection sensor 16.SELECTED DRAWING: Figure 4

Description

  The present invention provides a seam for seam welding a plurality of workpieces by sandwiching the plurality of workpieces between the pair of roller electrodes to which a voltage is applied and moving the plurality of workpieces while rotating the pair of roller electrodes. The present invention relates to a welding device and a seam welding method.

  Patent Literature 1 discloses that a plurality of workpieces are seam-welded by sandwiching the plurality of workpieces between a pair of roller electrodes to which a voltage is applied and moving the plurality of workpieces with respect to the plurality of workpieces while rotating the pair of roller electrodes. Seam welding equipment (seam welding equipment) is disclosed.

  In the seam welding equipment disclosed in Patent Document 1, the positions of the edges of a plurality of works are detected by a sensor, and the directions of the axes of a pair of roller electrodes are controlled based on the detection result.

Japanese Patent No. 6250555

  In the seam welding equipment described in Patent Literature 1, even if a sensor has erroneously detected, an abnormality cannot be detected because the position information indicates a normal range. Further, even if anomaly detection is enabled by adding some means, it takes time to identify the cause of the anomaly, and it takes a considerable amount of time to take measures.

  The present invention has been made in consideration of such problems, and can monitor the presence or absence of an abnormality in the detection result of the work position sensor, and can determine the cause of the abnormality when an abnormality occurs. It is an object to provide a simple seam welding apparatus and a seam welding method.

  According to a first aspect of the present invention, the plurality of stacked workpieces are sandwiched between a pair of roller electrodes to which a voltage is applied, and the pair of roller electrodes are moved with respect to the plurality of workpieces while rotating. A seam welding apparatus for seam welding a plurality of works, comprising: an electrode holding mechanism that holds the pair of roller electrodes so that the directions of the axes of the pair of roller electrodes can be changed; and a position of an edge of the plurality of works. A work position detection sensor to be detected, and a control unit that controls energization of the pair of roller electrodes and controls the electrode holding mechanism based on a detection result of the work position detection sensor, and the control unit includes: A first determination unit that determines whether there is an abnormality in the detection result of the work position detection sensor, and the first determination unit determines that there is an abnormality in the detection result of the work position detection sensor. If the, on the basis of the variation state of the workpiece position detecting sensor of the detection result, and a second determination unit determines abnormality cause a seam welding apparatus.

  According to a second aspect of the present invention, there is provided a method for starting seam welding in which a plurality of stacked workpieces are sandwiched between a pair of roller electrodes to which a voltage is applied and the pair of roller electrodes are moved while rotating the pair of roller electrodes. Step, a work position detection step of detecting the position of the edge of the plurality of works by a work position detection sensor, a first determination step of determining whether there is an abnormality in the detection result of the work position detection sensor, When the first determination step determines that the detection result of the work position detection sensor has an abnormality, a second determination step of determining an abnormality cause based on a variation state of the detection result of the work position detection sensor; And a seam welding method.

  According to the present invention, the control unit can monitor the presence or absence of an abnormality in the detection result of the work position detection sensor, determine the cause of the abnormality (fault) when an abnormality occurs, and respond to each case. You can take action. As a result, it is possible to reduce the time required to deal with the malfunction.

It is a figure showing the whole seam welding device composition concerning this embodiment. FIG. 2A is a side view of a vehicle body including a welding target of the seam welding device. FIG. 2B is a partial cross-sectional view showing a state in which a welded portion (a pair of flanges) of a vehicle body is seam-welded by a seam welding apparatus. It is a figure for explaining the method of controlling the direction of the axis of a roller electrode pair (the method of correcting the welding track of seam welding). FIG. 3 is a block diagram showing a control configuration of the seam welding device. FIG. 8 is a diagram for explaining a method of determining whether or not there is an abnormality in a sensor output based on an average value of a control amount of a shaft direction of a roller electrode pair. FIG. 6A is a diagram illustrating the sensor output and the variance when the sensor output has an abnormality due to abnormality cause 1. FIG. 6B is a diagram illustrating the sensor output and the variance when the sensor output has an abnormality due to abnormality cause 2. FIG. 6C is a diagram illustrating the sensor output and the variance when the sensor output has an abnormality due to abnormality cause 3. FIG. 9 is a diagram illustrating a cause of abnormality according to a variance value of the sensor output when there is an abnormality in the sensor output. It is a flow chart for explaining operation of a seam welding device.

  Hereinafter, a seam welding apparatus and a seam welding method according to the present invention will be described in detail with reference to the accompanying drawings by way of preferred embodiments.

  FIG. 1 is a diagram illustrating an example of the configuration of the seam welding apparatus 10. The seam welding device 10 is a device for seam welding a plurality of stacked works. More specifically, the seam welding apparatus 10 sandwiches a plurality of stacked workpieces between a pair of roller electrodes 12A and 12B to which a voltage (pulse voltage) is applied while rotating the pair of roller electrodes 12A and 12B. This is a device for continuously spot welding the plurality of works by moving the works with respect to the work.

  FIG. 2A is a diagram illustrating a vehicle body B including a plurality of works to be welded by the seam welding apparatus 10. FIG. 2B is a view of the vicinity of the pair of roller electrodes 12A and 12B of the seam welding apparatus 10 as viewed from the welding direction of seam welding. The plurality of workpieces to be welded by the seam welding device 10 are, as an example, a flange 13 of an inner member and a flange 15 of an outer member in a center pillar 11 of a vehicle body B, as shown in FIGS. 2A and 2B. FIG. 2B shows a cross section taken along the line IIB-IIB of the center pillar 11 in FIG. 2A. Hereinafter, the flange 13 and the flange 15 are also collectively referred to as “flange pair FP”.

  As shown in FIG. 1, the seam welding apparatus 10 includes an electrode holding mechanism 14, a work position detection sensor 16, a control unit 18, a display unit 19, an operation unit, in addition to a pair of roller electrodes 12A and 12B. 21.

  The electrode holding mechanism 14 holds the pair of roller electrodes 12A, 12B so that the directions of the axes of the pair of roller electrodes 12A, 12B can be changed.

  The electrode holding mechanism 14 is, for example, a multi-joint robot (here, six joints (a first joint 14a, a second joint 14b, a third joint 14c, a fourth joint 14d, a fifth joint 14e, A six-axis robot having a sixth joint 14f). In the electrode holding mechanism 14, the first shaft portion 17 </ b> A (the shaft portion on the relatively distal side) and the second shaft portion 17 </ b> B (the shaft portion on the relatively proximal side) arranged coaxially with each other are connected to the first joint 17. The portions 14a are connected so as to be relatively rotatable around the axis.

  A support structure 9 that rotatably supports each of the pair of roller electrodes 12A and 12B is attached to the tip of the first shaft portion 17A. The support structure 9 supports the pair of roller electrodes 12A and 12B such that their axes are substantially parallel to each other and their outer peripheral surfaces face each other.

  More specifically, the support structure 9 includes a support member 9a which is arranged in the longitudinal direction (the direction connecting the distal end and the proximal end) and has three concave portions 9a1, 9a2, 9a3 each opening to the side surface. A motor 9b having a rotating shaft 9c to which the roller electrode 12A is coaxially fixed is fixed to the concave portion 9a1 on the distal end side of the support member 9a. A motor 9d is provided slidably in the longitudinal direction of the support member 9a in the recess 9a2 in the middle of the support member 9a (between the front end and the base end). A roller electrode 12B is coaxially fixed to a rotation shaft 9e of the motor 9d. The rotating shaft 9c and the rotating shaft 9e are substantially parallel to each other, and are substantially orthogonal to the axes of the first shaft portion 17A and the second shaft portion 17B.

  The motor 9d is driven by a cylinder 9f provided over a concave portion 9a3 on the base end side of the support member 9a and a concave portion 9a2 in the middle. Note that an insertion hole through which the cylinder 9f is inserted is formed in a wall between the concave portion 9a3 on the base end side of the support member 9a and the intermediate concave portion 9a2. The moving direction (sliding direction) of the motor 9d, that is, the direction of expansion and contraction of the cylinder 9f is substantially parallel to the direction in which the pair of roller electrodes 12A and 12B are arranged (the longitudinal direction of the support member 9a). Due to the expansion and contraction operation of the cylinder 9f, the roller electrode 12B fixed to the rotating shaft 9e of the motor 9d has one axis including a direction approaching the roller electrode 12A fixed to the rotating shaft 9c of the motor 9b and a direction separating from the roller electrode 12A. It can be moved in any direction. Thus, the flange pair FP having an arbitrary thickness in a predetermined range can be sandwiched between the pair of roller electrodes 12A and 12B. Furthermore, it is possible to cope with a change in the thickness of the flange pair FP during seam welding. The control unit 18 controls the motor 9b and the motor 9d.

  A drive unit including a motor is built in the first joint unit 14a. The driving force of this motor causes the support member 9a and the pair of roller electrodes 12A and 12B to rotate integrally around the axes of the first shaft portion 17A and the second shaft portion 17B. That is, the directions of the shafts of the pair of roller electrodes 12A and 12B are changed synchronously by the driving force of the motor. As a result, the direction of the axis of the pair of roller electrodes 12A and 12B can be changed by operating the first joint 14a. Hereinafter, the pair of roller electrodes 12A and 12B will be collectively referred to as “roller electrode pair REP”.

  The configuration of the electrode holding mechanism 14 is not limited to the above-described configuration, but may be any other configuration as long as the pair of roller electrodes 12A, 12B can be held so that the directions of the axes of the pair of roller electrodes 12A, 12B can be changed. Is also good.

  As shown in FIG. 2B, the work position detection sensor 16 detects the positions of the edges of the two works, that is, the edges of the flange pair FP. More specifically, the work position detection sensor 16 detects the position of the end surface of the edge of the flange pair FP. Hereinafter, the end surface of the edge portion of the flange pair FP is also referred to as a “detected surface DS”. The work position detection sensor 16 is attached to a wall between the concave portion 9a1 on the distal end side of the support member 9a and the intermediate concave portion 9a2 so as to face the detection surface DS. That is, the work position detection sensor 16 is disposed between the rotation shaft 9c and the rotation shaft 9e. The detection surface DS is not limited to the end surface of the edge of the flange pair FP, and may be another surface of the edge of the flange pair FP.

  The work position detection sensor 16 includes a light irradiation unit 16a, a light receiving unit 16b, and a distance calculation unit 16c. The light irradiator 16a irradiates the detection surface DS and its surrounding area (for example, each roller electrode) with light. The light irradiation unit 16a includes a light emitting element such as a laser diode and an optical deflector for deflecting and scanning light from the light emitting element. That is, the light irradiation unit 16a scans the surface to be detected DS and its peripheral region with light. The light receiving section 16b has a light receiving element such as a photodiode, for example, and receives light emitted from the light irradiating section 16a and reflected by the detection surface DS and its surrounding area.

  The distance calculation unit 16c includes, for example, a CPU and the like. The distance calculation unit 16c calculates the time difference between the emission timing of the light irradiation unit 16a and the light reception timing of the light receiving unit 16b for each scanning position during the scanning of the detection surface DS and the surrounding area. The distance calculation unit 16c converts the minimum value of the calculation results of the time difference into a distance, and uses the converted value as a distance to the detection target surface DS (a detection result of the work position detection sensor 16). Output to Fig. 1). During the scanning of the detected surface DS and its surrounding area, the detected surface DS is located closest to the work position detection sensor 16.

  The light irradiation unit 16a, the light receiving unit 16b, and the distance calculation unit 16c are housed in a package 16e having a substantially U-shaped cross section in which a light transmission window 16d is provided at an opening end. More specifically, the light irradiation unit 16a, the light receiving unit 16b, and the distance calculation unit 16c are mounted on the same substrate disposed on the bottom surface of the package 16e. The light (emitted light) emitted from the light irradiation unit 16a is incident on the detection surface DS and its peripheral region via the light transmission window 16d. The light (reflected light) reflected on the detection surface DS and the surrounding area enters the light receiving unit 16b through the light transmission window 16d. In another aspect, the function of the distance calculation unit 16c may be performed by the control unit 18 without providing the distance calculation unit 16c.

  The configuration and arrangement of the work position detection sensor 16 are not limited to those described above, and can be changed as appropriate. The work position detection sensor 16 may be, for example, an image sensor including an image sensor and an image processing unit. In this case, the position of the edge of the flange pair FP can be detected by performing edge detection processing on the output image (distance image) of the image sensor by the image processing unit. The work position detection sensor 16 may be, for example, a stereo image sensor including two image sensors. In this case, the distance to the edge of the flange pair FP can be detected from the parallax values obtained from the outputs of the two image sensors. The light irradiation unit 16a and the light receiving unit 16b may be housed in different packages. The light irradiating section 16a may not have a light deflector. In this case, a light-emitting element array in which a plurality of light-emitting elements are arranged may be used to irradiate light on the detection surface DS and its peripheral region. The light irradiation unit 16a may include a lens that suppresses diffusion of light from the light emitting element. In this case, the lens may be provided in the package 16e such that the lens is exposed without providing the light transmission window 16d. The light receiving unit 16b may include a lens that collects light incident on the light receiving element. In this case, the lens may be provided in the package 16e such that the lens is exposed without providing the light transmission window 16d.

  The control unit 18 shown in FIG. 1 controls energization of the pair of roller electrodes 12A and 12B, and controls the electrode holding mechanism 14 based on the detection result of the work position detection sensor 16 (hereinafter also referred to as “sensor output”). Control. The control unit 18 includes, for example, a CPU and the like.

  By the way, in seam welding, a roller electrode pair to which a voltage (pulse voltage) is applied is moved relative to a plurality of workpieces while rotating along a desired welding trajectory in a plurality of stacked workpieces (for example, a pair of flanges). This is done by letting However, at the time of actual seam welding, the distance between the seam welding device and a plurality of superimposed works fluctuates slightly over time, so if the roller electrode pair is moved as it is (in a state where the direction of the shaft is constant), The roller electrode pair deviates from a target range centered on a desired welding trajectory.

  Therefore, the control unit 18 controls the electrode holding mechanism 14 based on the sensor output of the work position detection sensor 16. Specifically, as shown in FIG. 3, the control unit 18 controls the roller electrode pair REP based on the sensor output so that the roller electrode pair REP does not deviate from the target range TR centering on the desired welding trajectory DWT. The direction (angle) of the axis of the pair REP, that is, the steering angle of the roller electrode pair REP is controlled.

  FIG. 4 is a block diagram showing a configuration of control by the control unit 18. As shown in FIG. As shown in FIG. 4, the control unit 18 includes an energization control unit 18a, a mechanism control unit 18b, a first determination unit 18c, and a second determination unit 18d.

  The mechanism control unit 18b controls the electrode holding mechanism 14 based on the sensor output of the work position detection sensor 16. More specifically, the mechanism control unit 18b calculates the control amount CA of the electrode holding mechanism 14 based on the sensor output, sends the calculation result to the first determination unit 18c, and if necessary, the electrode holding mechanism 14 Output to The electrode holding mechanism 14 controls the direction (steering angle) of the axis of the roller electrode pair REP using the input control amount CA. The control amount CA is a difference between a target value of the angle (direction) of the roller electrode pair REP based on the sensor output and the angle of the roller electrode pair REP at that time (during control). The control amount CA is positive or negative depending on the control direction of the axis of the roller electrode pair REP.

  The first determination unit 18c determines whether the detection result (sensor output) of the work position detection sensor 16 is abnormal. The first determination unit 18c determines whether there is an abnormality in the sensor output based on the control amount CA from the mechanism control unit 18b.

  Here, the control amount CA of the electrode holding mechanism 14 (the control amount of the direction of the axis of the roller electrode pair REP) based on the sensor output by the control unit 18 has a normal distribution ND as shown in FIG. When there is no abnormality in the sensor output, the average value Ave of the normal distribution ND is smaller than a predetermined threshold Th. Therefore, when the average value Ave of the normal distribution ND is equal to or larger than the threshold Th, it can be determined that there is an abnormality in the sensor output. Here, the threshold value Th is, for example, an average value Ave + 4σ. Here, σ is the standard deviation of the normal distribution ND.

  Therefore, the first determination unit 18c illustrated in FIG. 4 determines that there is an abnormality in the sensor output when the average value of the control amount CA is equal to or greater than the threshold Th. The average value Ave of the control amount CA is equal to or larger than the threshold Th, for example, when a foreign matter is attached to the light transmission window 16d of the work position detection sensor 16 shown in FIG. 2B. Further, in the mechanism control unit 18b, teaching corresponding to the shape of the work is performed so that the roller electrode pair REP processes the target range TR, but the teaching of the work is shifted due to a change of the work or the like. There are also cases.

  The energization control unit 18a illustrated in FIG. 4 controls energization to the roller electrode pair REP. Specifically, the power supply control unit 18a controls the power supply to the roller electrode pair REP based on the determination result of the first determination unit 18c.

  Here, if seam welding is continued when there is an abnormality in the sensor output, the roller electrode pair REP may greatly deviate from the desired welding trajectory DWT. Therefore, when the first determination unit 18c determines that there is an abnormality in the sensor output, the power supply control unit 18a stops the power supply to the roller electrode pair REP and stops the seam welding.

  When the first determination unit 18c determines that there is an abnormality in the sensor output, the second determination unit 18d determines the cause of the abnormality based on the variance value DV (fluctuation) of the sensor output. The second determination unit 18d receives the detection result of the work position detection sensor 16 and calculates a variance value DV of the sensor output. The variance value DV of the sensor output indicates the degree of fluctuation of the sensor output value. The variance value DV of the sensor output is the average of the square of the difference between each sensor output value and the average of the sensor output values. Note that the second determination unit 18d is not limited to the variance value DV indicating the fluctuation state of the sensor output, but may be another value indicating the fluctuation state of the sensor output such as a standard deviation (positive square root of the variance value DV) of the sensor output. May be used to determine the cause of the abnormality.

  Specifically, when the variance value DV is not within the predetermined range PR (see FIG. 7), the second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16. The second determination unit 18d outputs the determination result to the display unit 19. The display unit 19 displays the input determination result on a screen (for example, “displays a foreign substance adhering to the work position detection sensor 16”). Note that an audio output unit including a speaker may be provided instead of or in addition to the display unit 19, and the determination result of the second determination unit 18d may be output by audio via the audio output unit.

  6A to 6C are diagrams for explaining the different causes 1 to 3 of the sensor output. In each of FIGS. 6A to 6C, Ta indicates a target distance (a distance at which the roller electrode pair REP can be positioned on a desired welding trajectory DWT) between the work position detection sensor 16 and the detected surface DS.

  In the example shown in FIG. 6A, for example, minute foreign matter adheres to the light transmitting window 16d of the work position detection sensor 16 over a wide area at a high density (for example, the foreign matter is contaminated with dust, oil, or the like) (abnormal cause 1). . In this case, the light emitted from the light irradiation unit 16a is scattered by the light transmission window 16d, and the light reflected on the detection surface DS and the surrounding area is scattered by the light transmission window 16d. Therefore, the variance value DV of the sensor output becomes large (specifically, it becomes larger than the upper limit PRu of the predetermined range PR (see FIG. 7)). At this time, if the direction of the axis of the roller electrode pair REP is controlled based on the sensor output, the roller electrode pair REP may deviate from the target range TR.

  Therefore, when the variance value DV is larger than the upper limit PRu of the predetermined range PR, the second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16 over a wide range, and outputs the determination result to the display unit 19. . The display unit 19 displays the input determination result on a screen (for example, displays "dirt on the work position detection sensor").

  In the example shown in FIG. 6B, for example, a foreign substance (granular solid or liquid) is locally attached to the light transmitting window 16d of the work position detection sensor 16 (abnormal cause 2). In this case, the light from the light irradiation unit 16a may be reflected by the foreign matter and received by the light receiving unit 16b. That is, the work position detection sensor 16 may detect the position of the foreign matter, not the position of the detection surface DS. In this case, since the direction of the axis of the roller electrode pair REP is controlled based on the distance to the foreign matter, the roller electrode pair REP may deviate from the target range TR. In the case of FIG. 6B, since the work position detection sensor 16 detects the position of the foreign matter adhered to the light transmitting window 16d at a fixed distance from the light irradiation unit 16a, the sensor output hardly fluctuates (substantially constant value). Is shown). Therefore, the variance value DV of the sensor output becomes very small (specifically, becomes smaller than the lower limit PRl of the predetermined range PR (see FIG. 7)).

  Therefore, when the variance value DV is smaller than the lower limit PRl of the predetermined range PR, the second determination unit 18d determines that the foreign matter is locally attached to the work position detection sensor 16, and outputs the determination result to the display unit 19. I do. The display unit 19 displays the input determination result on a screen (for example, “dust adheres to the work position detection sensor”).

  When the variance value DV is larger than the upper limit PRu of the predetermined range PR (see FIG. 7), the second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16 over a wide range, and outputs the variance value DV. Is smaller than the lower limit PRl of the predetermined range PR, it is determined that the foreign matter has locally adhered to the work position detection sensor 16, but the present invention is not limited thereto. For example, the second determination unit 18d determines only whether or not the dispersion value DV is within the predetermined range PR (whether or not foreign matter has adhered to the work position detection sensor 16), and notifies the determination result (for example, the display unit). 19). For example, the second determination unit 18d determines whether the variance value DV is greater than the upper limit PRu of the predetermined range PR (whether or not foreign matter has adhered to the work position detection sensor 16 over a wide range) and whether the variance value DV is within the predetermined range PR. It is also possible to determine only one of whether or not it is smaller than the lower limit PRl (whether or not foreign matter has locally adhered to the work position detection sensor 16) and notify the determination result (for example, display it on the display unit 19).

  In the example shown in FIG. 6C, a deviation of the teaching input to the mechanism control unit 18b (a state in which appropriate teaching corresponding to the work shape is not performed) has occurred in the electrode holding mechanism 14 (abnormal cause 3). In this case, as shown in FIG. 6C, the sensor output moves away from the target distance Ta (the target distance between the work position detection sensor 16 and the detection surface DS) over time (decreases monotonously). In this case, if the direction of the axis of the roller electrode pair REP is controlled based on the sensor output, the roller electrode pair REP may deviate from the target range TR (see FIG. 3).

  Therefore, when the dispersion value DV is within the predetermined range PR, the second determination unit 18d determines that the teaching deviation set in the electrode holding mechanism 14 has occurred such that the roller electrode pair REP follows the desired welding trajectory DWT. .

  Even if there is no problem in the teaching itself, it is conceivable that the electrode holding mechanism 14 has poor followability to the teaching and causes an abnormality in the sensor output. Therefore, when the variance value DV of the sensor output is within the predetermined range PR, the second determination unit 18d determines that "the electrode holding mechanism 14 has poor followability to teaching or there is a problem with the teaching itself". Then, the determination result may be notified (for example, displayed on the display unit 19).

  Next, the operation of the seam welding apparatus 10 configured as described above will be described with reference to the flowchart of FIG.

  In the first step S1, the operator causes the seam welding device 10 to start seam welding. More specifically, the operator controls the electrode holding mechanism 14 to hold the flange pair FP with the roller electrode pair REP, and then transmits a welding start trigger signal to the control unit 18 via the operation unit 21. More specifically, the operator appropriately moves (slides) the motor 9d that rotationally drives the roller electrode 12B via the operation unit 21, and also operates the first joint unit 14a, the second joint unit 14b, and the third joint unit. By appropriately operating 14c, the fourth joint 14d, the fifth joint 14e, and the sixth joint 14f, the pair of roller electrodes 12A and 12B clamp the flange pair FP.

  The control unit 18 having received the welding start trigger signal applies a voltage to the roller electrode pair REP, controls the electrode holding mechanism 14, and moves the roller electrode pair REP along the desired welding trajectory DWT of the flange pair FP. To start. Specifically, the control unit 18 operates the motor 9b and the motor 9d to rotationally drive the pair of roller electrodes 12A and 12B in directions opposite to each other, and also controls the first joint 14a, the second joint 14b, and the third joint 14b. By appropriately operating the joint 14c, the fourth joint 14d, the fifth joint 14e, and the sixth joint 14f, the movement of the roller electrode pair REP along the desired welding trajectory DWT of the flange pair FP is started. .

  In the next step S2, the work position detection sensor 16 detects the position of the detected surface DS, and outputs the detection result (sensor output) to the mechanism control unit 18b.

  In the next step S3, the mechanism control unit 18b calculates the control amount CA of the direction of the axis of the roller electrode pair REP based on the sensor output, and sends the calculation result to the first determination unit 18c.

  In the next step S4, the first determination unit 18c determines whether or not the control amount CA is equal to or greater than the threshold Th, that is, whether or not the sensor output is abnormal. If the determination here is negative, the process proceeds to step S5, and if affirmative, the process proceeds to step S8.

  In step S5, the first determination unit 18c determines that the sensor output is normal (there is no abnormality in the sensor output).

  In the next step S6, the control unit 18 controls the direction of the axis of the roller electrode pair REP with the calculated control amount CA. Specifically, the mechanism control unit 18b outputs the control amount CA calculated in step S3 to the driving unit of the first joint 14a of the electrode holding mechanism 14. Thereby, the direction of the axis of the roller electrode pair REP is controlled (changed) by the control amount CA.

  In the next step S7, control unit 18 determines whether or not seam welding has been completed. Specifically, when the control unit 18 determines that the roller electrode pair REP has reached the end of the desired welding trajectory DWT based on the control amount of each joint of the electrode holding mechanism 14, the seam welding is completed. Judge that you have done. If the determination here is affirmed, the flow ends, and if denied, the process returns to step S2.

  In step S8, the first determination unit 18c determines that the sensor output is abnormal (the sensor output is abnormal).

  In the next step S9, the control unit 18 stops the seam welding. Specifically, the power supply controller 18a stops supplying power to the roller electrode pair REP.

  In the next step S10, the second determination unit 18d calculates a variance value DV of the sensor output.

  In the next step S11, the second determination unit 18d determines whether or not the variance value DV is larger than the upper limit PRu of the predetermined range PR. If the determination here is affirmed, the process proceeds to step S12, and if denied, the process proceeds to step S13.

  In step S12, the second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16 (for example, the light transmission window 16d) over a wide range, and notifies the determination result (displays the display unit 19). After confirming the determination result displayed on the display unit 19, the operator can promptly take measures such as cleaning and replacing the work position detection sensor 16. When step S12 is executed, the flow ends.

  In step S13, the second determination unit 18d determines whether the variance value DV is smaller than the lower limit PRl of the predetermined range PR. If the determination here is affirmed, the process proceeds to step S14, and if denied, the process proceeds to step S15.

  In step S14, the second determination unit 18d determines that a foreign matter has locally adhered to the work position detection sensor 16 (for example, the light transmission window 16d), and notifies the determination result (displays the result on the display unit 19). After confirming the determination result displayed on the display unit 19, the operator can promptly take measures such as cleaning and replacing the work position detection sensor 16. When step S14 is performed, the flow ends.

  In step S15, the second determination unit 18d determines that a deviation in teaching for teaching the target range TR has occurred in the electrode holding mechanism 14, and notifies the determination result (displays the result on the display unit 19). After confirming the determination result displayed on the display unit 19, the operator can promptly take measures to suppress the deviation of teaching. When step S15 is executed, the flow ends.

  Next, effects of the seam welding apparatus 10 configured as described above will be described.

  The seam welding apparatus 10 of the present embodiment rotates a pair of roller electrodes 12A and 12B by sandwiching the two overlapped flanges 13 and 15 (a plurality of works) between a pair of roller electrodes 12A and 12B to which a voltage is applied. This is a seam welding apparatus for seam welding the two flanges 13 and 15 by moving the two flanges 13 and 15 with respect to the other. The seam welding apparatus 10 includes an electrode holding mechanism 14 that holds the pair of roller electrodes 12A and 12B so that the directions of the axes of the pair of roller electrodes 12A and 12B can be changed, and positions of the edges of the two flanges 13 and 15 ( In addition to controlling the energization of the work position detection sensor 16 that detects the position of the detected surface DS) and the pair of roller electrodes 12A and 12B, the electrode holding mechanism 14 is controlled based on the detection result of the work position detection sensor 16. A control unit 18. The control unit 18 determines whether the detection result of the work position detection sensor 16 is abnormal or not, and the first determination unit 18c determines that the detection result of the work position detection sensor 16 is abnormal. And a second determination unit 18d that determines the cause of the abnormality based on the variance value DV of the detection result of the work position detection sensor 16 in the case where it has been performed.

  Thereby, the control unit 18 can determine the cause of the abnormality (fault) in the detection result of the work position detection sensor 16, and can take measures corresponding to each case. As a result, it is possible to reduce the time required to deal with the malfunction.

  The second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16 when the dispersion value DV is not in the predetermined range PR. Thus, the cause (fault) of the abnormality in the detection result of the work position detection sensor 16 can be recognized separately for the case where the foreign matter adheres to the work position detection sensor 16 and the other cases.

  When the dispersion value DV is larger than the upper limit PRu of the predetermined range PR, the second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16 over a wide range. As a result, when the dispersion value DV is larger than the upper limit PRu of the predetermined range PR, foreign matter adheres to the work position detection sensor 16 over a wide range, and the work position detection sensor 16 detects the edges of the two flanges 13 and 15. Is not detected, it is possible to make such an appropriate determination.

  When the variance value DV is smaller than the lower limit PRl of the predetermined range PR, the second determination unit 18d determines that the foreign matter has locally adhered to the work position detection sensor 16. Accordingly, when the variance value DV is smaller than the lower limit PRl of the predetermined range PR, the work position detection sensor 16 is locally attached to the work position detection sensor 16 instead of the edges of the two flanges 13 and 15 to be detected. Since it is considered that a foreign object is detected, such a proper determination can be made.

  When the variance value DV is larger than the upper limit PRu of the predetermined range PR, the second determination unit 18d determines that the foreign matter has adhered to the work position detection sensor 16 over a wide range, and the variance value DV is smaller than the lower limit PRl of the predetermined range PR. In this case, it is determined that the foreign matter has locally adhered to the work position detection sensor 16. When the variance value DV is larger than the upper limit PRu of the predetermined range PR and when the variance value DV is smaller than the lower limit PRl of the predetermined range PR, it is possible to make an appropriate determination according to each.

  When the dispersion value DV is within the predetermined range PR, the second determination unit 18d determines that the teaching of the electrode holding mechanism 14 for teaching the target range TR has occurred. Thereby, it is possible to prompt to cope with the deviation of the teaching.

  The first determination unit 18c determines whether there is an abnormality in the detection result of the work position detection sensor 16 based on the control amount CA of the electrode holding mechanism 14 based on the detection result of the work position detection sensor 16. Thus, for example, it is possible to determine whether or not the detection result of the work position detection sensor 16 is abnormal by a simple method of comparing the average value Ave of the control amount CA with the threshold value Th.

  The control unit 18 stops the seam welding when the first determination unit 18c determines that the detection result of the work position detection sensor 16 is abnormal. Accordingly, it is possible to prevent the seam welding from being continued in a state where the pair of roller electrodes 12A and 12B is largely displaced from the desired welding trajectory DWT (a state where the pair of roller electrodes 12A and 12B deviate from the target range TR).

  In the seam welding method of the present embodiment, the two flanges 13 and 15 (a plurality of works) overlapped are sandwiched between the pair of roller electrodes 12A and 12B to which a voltage is applied, and the pair of roller electrodes 12A and 12B are rotated. A seam welding start step for starting seam welding performed by moving the workpiece, a work position detection step for detecting the positions of the edges of the two flanges 13 and 15 with the work position detection sensor 16, and a detection result of the work position detection sensor 16 A first determination step of determining whether there is an abnormality in the work position detection sensor, and a variance value of the detection result of the work position detection sensor 16 when the first determination step determines that the detection result of the work position detection sensor 16 is abnormal. A second determining step of determining the cause of the abnormality based on the DV.

  Thus, in the second determination step, it is possible to determine the cause of the abnormality (fault) in the detection result of the work position detection sensor 16 and to take measures corresponding to each case. As a result, it is possible to reduce the time required to deal with the malfunction.

  In the second determination step, when the variance value DV is not in the predetermined range PR, it is determined that the foreign matter has adhered to the work position detection sensor 16. Thus, the cause of the abnormality (fault) in the detection result of the work position detection sensor 16 can be notified separately when the foreign matter adheres to the work position detection sensor 16 and in other cases.

  In the second determination step, when the variance value DV is larger than the upper limit PRu of the predetermined range PR, it is determined that foreign matter has adhered to the work position detection sensor 16 over a wide range. As a result, when the dispersion value DV is larger than the upper limit PRu of the predetermined range PR, foreign matter adheres to the work position detection sensor 16 over a wide range, and the work position detection sensor 16 detects the edges of the two flanges 13 and 15. Is not detected, it is possible to make such an appropriate determination.

  In the second determination step, when the variance value DV is smaller than the lower limit PRl of the predetermined range PR, it is determined that the foreign matter has locally adhered to the work position detection sensor 16. Accordingly, when the variance value DV is smaller than the lower limit PRl of the predetermined range PR, the work position detection sensor 16 is locally attached to the work position detection sensor 16 instead of the edges of the two flanges 13 and 15 to be detected. Since it is considered that a foreign object is detected, such a proper determination can be made.

  In the second determination step, when the variance value DV is larger than the upper limit PRu of the predetermined range PR, it is determined that foreign matter has adhered to the work position detection sensor 16 over a wide range, and when the variance value DV is smaller than the lower limit PRl of the predetermined range PR. Then, it is determined that foreign matter has locally adhered to the work position detection sensor 16. Accordingly, when the variance value DV is larger than the upper limit PRu of the predetermined range PR and when the variance value DV is smaller than the lower limit PRl of the predetermined range PR, it is possible to make an appropriate determination according to each.

  In the second determination step, when the variance value DV is within the predetermined range PR, it is determined that the teaching of teaching the target range TR to the electrode holding mechanism 14 has shifted. Thereby, it is possible to prompt to cope with the deviation of the teaching.

  The first determination step determines whether or not the detection result of the work position detection sensor 16 is abnormal based on the control amount CA of the shaft of the pair of roller electrodes 12A and 12B based on the detection result of the work position detection sensor 16. I do. Thus, for example, it is possible to determine whether or not the detection result of the work position detection sensor 16 is abnormal by a simple method of comparing the average value Ave of the control amount CA with the threshold value Th.

  The second determination step stops the seam welding when the first determination step determines that the detection result of the work position detection sensor 16 is abnormal. Accordingly, it is possible to prevent the seam welding from being continued in a state where the pair of roller electrodes 12A and 12B is largely displaced from the desired welding trajectory DWT (a state where the pair of roller electrodes 12A and 12B deviate from the target range TR).

DESCRIPTION OF SYMBOLS 10 ... Seam welding apparatus 12A, 12B ... Roller electrodes 13, 15 ... Flange (work) 14 ... Electrode holding mechanism 16 ... Work position detection sensor 18 ... Control part 18a ... Electrification control part 18c ... First judgment part 18d ... Second judgment Part DS: Detected surface (edge of work)

Claims (16)

Seam welding for seam welding the plurality of workpieces by sandwiching the plurality of workpieces between the pair of roller electrodes to which a voltage is applied and moving the pair of roller electrodes with respect to the plurality of workpieces while rotating the pair of roller electrodes. A device,
An electrode holding mechanism that holds the pair of roller electrodes so that the directions of the axes of the pair of roller electrodes can be changed,
A work position detection sensor that detects a position of an edge of the plurality of works,
A control unit that controls energization of the pair of roller electrodes and controls the electrode holding mechanism based on a detection result of the work position detection sensor,
With
The control unit includes:
A first determination unit that determines whether there is an abnormality in the detection result of the work position detection sensor;
When the first determination unit determines that the detection result of the work position detection sensor has an abnormality, a second determination unit that determines an abnormality cause based on a variation state of the detection result of the work position detection sensor;
And seam welding equipment. The seam welding apparatus according to claim 1,
The seam welding device, wherein the second determination unit determines that a foreign object has adhered to the work position detection sensor when a numerical value indicating the fluctuation state is not within a predetermined range. The seam welding apparatus according to claim 2, wherein
The seam welding apparatus, wherein the second determination unit determines that a foreign object has adhered to the work position detection sensor in a wide range when a numerical value indicating the fluctuation state is larger than an upper limit of the predetermined range. The seam welding apparatus according to claim 2, wherein
The seam welding apparatus, wherein the second determination unit determines that a foreign substance has locally adhered to the work position detection sensor when a numerical value indicating the fluctuation state is smaller than a lower limit of the predetermined range. The seam welding apparatus according to claim 2, wherein
The second determination unit includes:
When the numerical value indicating the fluctuation state is larger than the upper limit of the predetermined range, it is determined that foreign matter has adhered to the work position detection sensor in a wide range,
A seam welding apparatus that determines that a foreign matter has locally adhered to the work position detection sensor when a numerical value indicating the fluctuation state is smaller than a lower limit of the predetermined range. It is a seam welding apparatus according to any one of claims 2 to 5,
The seam welding device, wherein the second determination unit determines that a deviation of teaching to the electrode holding mechanism has occurred when a numerical value indicating the fluctuation state is between an upper limit and a lower limit of a predetermined range. A seam welding apparatus according to any one of claims 1 to 6,
A first determination unit configured to determine, based on a control amount of the electrode holding mechanism based on a detection result of the work position detection sensor, whether there is an abnormality in a detection result of the work position detection sensor; . It is a seam welding apparatus according to any one of claims 1 to 7,
The seam welding device, wherein the control unit stops the seam welding when the first determination unit determines that the detection result of the work position detection sensor is abnormal. A seam welding start step of starting seam welding performed by moving the pair of roller electrodes while rotating the pair of roller electrodes with a plurality of stacked workpieces sandwiched between the pair of roller electrodes to which a voltage is applied;
A work position detection step of detecting the positions of the edges of the plurality of works with a work position detection sensor,
A first determination step of determining whether or not the detection result of the work position detection sensor is abnormal;
When the first determination step determines that the detection result of the work position detection sensor has an abnormality, a second determination step of determining an abnormality cause based on a variation state of the detection result of the work position detection sensor;
And a seam welding method. A seam welding method according to claim 9,
The second determining step is a seam welding method that determines that a foreign object has adhered to the work position detection sensor when the numerical value indicating the fluctuation state is not within a predetermined range. The seam welding method according to claim 10, wherein
The second determination step is a seam welding method, wherein when the numerical value indicating the fluctuation state is larger than an upper limit of a predetermined range, it is determined that foreign matter has adhered to the work position detection sensor in a wide range. The seam welding method according to claim 10, wherein
The second determination step is a seam welding method, wherein when the numerical value indicating the fluctuation state is smaller than a lower limit of a predetermined range, it is determined that a foreign matter is locally attached to the work position detection sensor. The seam welding method according to claim 10, wherein
The second determination step includes:
When the numerical value indicating the fluctuation state is larger than the upper limit of the predetermined range, it is determined that foreign matter has adhered to the work position detection sensor in a wide range,
A seam welding method, wherein when the numerical value indicating the fluctuating state is smaller than the lower limit of the predetermined range, it is determined that foreign matter has locally adhered to the work position detection sensor. The seam welding method according to claim 10, wherein
The second determining step is a seam welding method that determines that a teaching deviation has occurred when a numerical value indicating the fluctuation state is between an upper limit and a lower limit of a predetermined range. A seam welding method according to any one of claims 9 to 14,
The first determination step determines whether or not the detection result of the work position detection sensor is abnormal based on a control amount of the shaft of the pair of roller electrodes based on the detection result of the work position detection sensor. Seam welding method. A seam welding method according to any one of claims 9 to 15,
The second determining step is a seam welding method, wherein the seam welding is stopped when the first determining step determines that the detection result of the work position detection sensor is abnormal.

Images