JP6728291B2 - Seam welding apparatus and seam welding method - Google Patents

Description

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

In Patent Document 1, a plurality of overlapped works are sandwiched by a pair of roller electrodes to which a voltage is applied, and the plurality of works are moved while rotating the pair of roller electrodes, thereby seam welding the plurality of works. A seam welding facility (seam welding apparatus) is disclosed.

The seam welding equipment disclosed in Patent Document 1 detects the positions of the edges of a plurality of workpieces with a sensor, and controls the orientations of the shafts of the pair of roller electrodes based on the detection results.

Patent No. 6250555

In the seam welding equipment described in Patent Document 1, even if the sensor makes an erroneous detection, the position information indicates a normal range, and therefore an abnormality cannot be detected. Further, even if the abnormality can be detected by adding some means, it takes time to specify the cause of the abnormality, and it takes a corresponding time to deal with the abnormality.

The present invention has been made in consideration of such a problem, and it is possible to monitor whether or not there is an abnormality in the detection result of the work position sensor, and to determine the cause of the abnormality when the abnormality occurs. An object of the present invention is to provide a new seam welding device and a seam welding method.

According to a first aspect of the present invention, by sandwiching a plurality of stacked works with a pair of roller electrodes to which a voltage is applied and moving the plurality of works while rotating the pair of roller electrodes, A seam welding apparatus for seam-welding a plurality of works, wherein an electrode holding mechanism for holding the pair of roller electrodes so that the directions of the axes of the pair of roller electrodes can be changed, and the positions of the edges of the plurality of works. A work position detection sensor for detecting, and a control unit for controlling energization to the pair of roller electrodes, and a control unit for controlling the electrode holding mechanism based on a detection result of the work position detection sensor, and the control unit, A first determination unit that determines whether or not there is an abnormality in the detection result of the work position detection sensor, and if the first determination unit determines that there is an abnormality in the detection result of the work position detection sensor, A seam welding apparatus including: a second determination unit that determines a cause of abnormality based on a variation state of a detection result of a work position detection sensor.

A second aspect of the present invention is to start seam welding in which a plurality of stacked works are sandwiched by a pair of roller electrodes to which a voltage is applied and are moved while rotating the pair of roller electrodes. A step, a work position detecting step of detecting the positions of the edges of the plurality of works by a work position detecting sensor, and a first judging step of judging whether or not there is an abnormality in the detection result of the work position detecting sensor, A second determination step of determining a cause of abnormality based on a variation state of 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 is abnormal; And a seam welding method.

According to the present invention, the control unit can monitor whether or not there is an abnormality in the detection result of the work position detection sensor, determine the cause of the abnormality (defective) when the 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 problem.

It is a figure which shows the whole structure of the seam welding apparatus which concerns on this embodiment. FIG. 2A is a side view of a vehicle body including a welding target of the seam welding apparatus. FIG. 2B is a partial cross-sectional view showing a state where seam welding is performed on a welded portion (flange pair) of the vehicle body by the seam welding device. It is a figure for demonstrating the method of controlling the direction of the shaft of a roller electrode pair (method of correcting the welding trajectory of seam welding). It is a block diagram which shows the structure of control of a seam welding apparatus. It is a figure for explaining a method of judging whether or not there is an abnormality in the sensor output based on the average value of the control amount of the axis direction of the roller electrode pair. FIG. 6A is a diagram showing a sensor output and a variance value when the sensor output has an abnormality due to abnormality cause 1. FIG. 6B is a diagram showing a sensor output and a variance value when the sensor output has an abnormality due to abnormality cause 2. FIG. 6C is a diagram showing a sensor output and a variance value when the sensor output has an abnormality due to abnormality cause 3. It is a figure which shows the cause of abnormality according to the dispersion value of a sensor output, when there is an abnormality in a 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, with reference to preferred embodiments.

FIG. 1 is a diagram showing 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 overlapped works with a pair of roller electrodes 12A and 12B to which a voltage (pulse voltage) is applied, and rotates the pair of roller electrodes 12A and 12B. It is an apparatus for continuously spot welding a plurality of works by moving the works.

FIG. 2A is a diagram showing 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 apparatus 10 are, for example, the flange 13 of the inner member and the flange 15 of the outer member in the center pillar 11 of the vehicle body B, as shown in FIGS. 2A and 2B. FIG. 2B shows a cross section taken along line IIB-IIB of the center pillar 11 of FIG. 2A. Hereinafter, the flange 13 and the flange 15 are 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, and an operation unit, in addition to the pair of roller electrodes 12A and 12B. 21 and 21.

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

The electrode holding mechanism 14 is, for example, a multi-joint robot (here, six joint portions (first joint portion 14a, second joint portion 14b, third joint portion 14c, fourth joint portion 14d, fifth joint portion 14e and It is a 6-axis robot) having a sixth joint 14f). In the electrode holding mechanism 14, the first shaft portion 17A (relatively distal end side shaft portion) and the second shaft portion 17B (relatively proximal end side shaft portion) arranged coaxially with each other form a first joint. The portion 14a is 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 that is arranged in the longitudinal direction (the direction connecting the tip end and the base end) and that has three recesses 9a1, 9a2, and 9a3, each of which is open to the side surface. A motor 9b having a rotating shaft 9c on which the roller electrode 12A is coaxially fixed is fixed to the recess 9a1 on the front end side of the support member 9a. A motor 9d is provided in a recess 9a2 in the middle (between the front end and the base end) of the support member 9a so as to be slidable in the longitudinal direction of the support member 9a. The roller electrode 12B is coaxially fixed to the rotating 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 across a recess 9a3 on the base end side of the support member 9a and a recess 9a2 in the middle. An insertion hole, through which the cylinder 9f is inserted, is formed in the wall between the recess 9a3 on the base end side of the support member 9a and the recess 9a2 in the middle. The moving direction (sliding direction) of the motor 9d, that is, the extending/contracting direction of the cylinder 9f is substantially parallel to the arranging direction of the pair of roller electrodes 12A and 12B (longitudinal direction of the support member 9a). By the expansion/contraction operation of the cylinder 9f, the roller electrode 12B fixed to the rotating shaft 9e of the motor 9d is uniaxial 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. As a result, the flange pair FP having an arbitrary thickness within the predetermined range can be sandwiched between the pair of roller electrodes 12A and 12B. Further, it is possible to cope with a change in the thickness of the flange pair FP during seam welding. The motor 9b and the motor 9d are controlled by the control unit 18.

A drive unit including a motor is built in the first joint portion 14a. The driving force of this motor causes the support member 9a and the pair of roller electrodes 12A and 12B to integrally rotate around the axes of the first shaft portion 17A and the second shaft portion 17B. That is, the driving force of the motor causes the axial directions of the pair of roller electrodes 12A and 12B to change synchronously. As a result, by operating the first joint portion 14a, the axial directions of the pair of roller electrodes 12A and 12B can be changed. 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 configuration, and may be another configuration as long as the pair of roller electrodes 12A and 12B can be held so that the axial directions of the pair of roller electrodes 12A and 12B can be changed. 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 portion of the flange pair FP. Hereinafter, the end surface of the edge portion of the flange pair FP is also referred to as “detection surface DS”. The work position detection sensor 16 is attached to the wall between the recess 9a1 on the tip side of the support member 9a and the recess 9a2 in the middle so as to face the surface to be detected DS. That is, the work position detection sensor 16 is arranged between the rotating shaft 9c and the rotating shaft 9e. The detected surface DS is not limited to the end surface of the edge portion of the flange pair FP, and may be another surface of the edge portion 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 surface to be detected DS and its peripheral region (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 that deflects and scans light from the light emitting element. That is, the light irradiation unit 16a scans the surface to be detected DS and the peripheral region thereof with light. The light receiving unit 16b has a light receiving element such as a photodiode, and receives the light emitted from the light irradiation unit 16a and reflected by the surface to be detected DS and the peripheral region thereof.

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 scanning of the surface to be detected DS and the peripheral region thereof. 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 the distance to the detection surface DS (the detection result of the work position detection sensor 16) (control unit 18 ( Output to (Fig. 1). The surface to be detected DS is closest to the work position detection sensor 16 during scanning of the surface to be detected DS and its peripheral area.

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 the 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 arranged on the bottom surface of the package 16e. The light (emitted light) emitted from the light irradiation unit 16a enters the surface to be detected DS and the peripheral region thereof through the light transmission window 16d. The light (reflected light) reflected by the surface to be detected DS and the peripheral region thereof enters the light receiving portion 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 portion 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 value 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 irradiation unit 16a does not have to include the 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 the surface to be detected DS and its peripheral region with light. 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 so that the lens is exposed without providing the light transmission window 16d. The light receiving unit 16b may have a lens that collects light that enters the light receiving element. In this case, the lens may be provided in the package 16e so that the lens is exposed without providing the light transmission window 16d.

The control unit 18 shown in FIG. 1 controls energization to the pair of roller electrodes 12A and 12B, and also 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 is configured to include, 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 with respect to a plurality of workpieces while rotating along a desired welding trajectory in a plurality of stacked workpieces (for example, flange pairs). It is carried out by However, at the time of actual seam welding, the distance between the seam welding device and a plurality of stacked workpieces slightly changes with the passage of time, so if the roller electrode pair is moved as it is (with the axis direction fixed), The roller electrode pair deviates from the target range centered on the 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 centered on the desired welding trajectory DWT. The axis direction (angle) of the pair of REPs, that is, the steering angle of the roller electrode pair REP is controlled.

FIG. 4 is a block diagram showing a control configuration of the control unit 18. 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 axis direction (steering angle) of the roller electrode pair REP using the input control amount CA. The control amount CA is a difference between the target value of the shaft angle (direction) of the roller electrode pair REP based on the sensor output and the shaft angle of the roller electrode pair REP at that time (during control). The control amount CA has positive or negative depending on the control direction of the axis direction of the roller electrode pair REP.

The first determination unit 18c determines whether or not the detection result (sensor output) of the work position detection sensor 16 is abnormal. The first determination unit 18c determines whether or not 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 (control amount of the axis direction of the roller electrode pair REP) of the electrode holding mechanism 14 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 this normal distribution ND is less than the 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 the sensor output is abnormal. Here, the threshold Th is, for example, the 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 the sensor output is abnormal 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 becomes equal to or larger than the threshold Th, for example, when foreign matter is attached to the light transmission window 16d of the work position detection sensor 16 shown in FIG. 2B. Further, although the mechanism control unit 18b is taught so that the roller electrode pair REP processes the target range TR, the teaching corresponding to the shape of the work is performed, but the teaching is deviated from the work due to the change of the work or the like. Cases are also included.

The energization controller 18a shown in FIG. 4 controls energization of the roller electrode pair REP. Specifically, the energization controller 18a controls energization to the roller electrode pair REP based on the determination result of the first determiner 18c.

Here, if the seam welding is continued when the sensor output is abnormal, the roller electrode pair REP may be largely deviated from the desired welding track DWT. Therefore, the energization control unit 18a stops energization to the roller electrode pair REP and stops seam welding when the first determination unit 18c determines that the sensor output is abnormal.

When the first determination unit 18c determines that the sensor output is abnormal, 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 the variance value DV of the sensor output. The variance value DV of the sensor output represents 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. The second determination unit 18d is not limited to the variance value DV indicating the variation state of the sensor output, and other values indicating the variation state of the sensor output such as the standard deviation of the sensor output (a positive square root of the variance value DV). The cause of the abnormality may be determined based on

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

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

In the example shown in FIG. 6A, for example, minute foreign matter adheres to the light transmission window 16d of the work position detection sensor 16 at a high density in a wide range (for example, soiled with dust or oil) (abnormality cause 1). .. In this case, the light emitted from the light irradiation unit 16a is scattered by the light transmitting window 16d, and the light reflected by the surface to be detected DS and the peripheral region thereof is scattered by the light transmitting window 16d. Therefore, the variance value DV of the sensor output becomes large (more specifically, becomes larger than the upper limit PRu of the predetermined range PR (see FIG. 7)). At this time, if the axis direction 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 dispersion value DV is larger than the upper limit PRu of the predetermined range PR, the second determination unit 18d determines that foreign matter has adhered to the work position detection sensor 16 in a wide range, and outputs the determination result to the display unit 19. .. The display unit 19 displays the input determination result on the screen (for example, “Work position detection sensor has dirt attached”).

In the example shown in FIG. 6B, for example, foreign matter (granular solid or liquid) locally adheres to the light transmission window 16d of the work position detection sensor 16 (abnormality cause 2). In this case, the light from the light irradiation unit 16a may be reflected by the foreign matter and may be 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 detected surface DS. In this case, since the axis direction 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 adhering to the light transmission window 16d located at a constant distance from the light irradiation unit 16a, the sensor output hardly changes (substantially constant value). Indicates). Therefore, the variance value DV of the sensor output is extremely small (specifically, it is smaller than the lower limit PR1 of the predetermined range PR (see FIG. 7)).

Therefore, when the variance value DV is smaller than the lower limit PR1 of the predetermined range PR, the second determination unit 18d determines that the foreign matter locally adheres to the work position detection sensor 16 and outputs the determination result to the display unit 19. To do. The display unit 19 displays the input determination result on the screen (for example, “Dust adheres to the work position detection sensor”).

The second determination unit 18d determines that foreign matter has adhered to the work position detection sensor 16 in a wide range when the variance value DV is larger than the upper limit PRu of the predetermined range PR (see FIG. 7), and the variance value DV Is smaller than the lower limit PR1 of the predetermined range PR, it is determined that the foreign matter locally adheres to the work position detection sensor 16, but the invention is not limited to this. For example, the second determination unit 18d only determines whether or not the dispersion value DV is within the predetermined range PR (whether or not a foreign substance 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 or not the dispersion value DV is larger than the upper limit PRu of the predetermined range PR (whether or not foreign matter is attached to the work position detection sensor 16 in a wide range) and the dispersion 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 PR1 (whether or not a foreign matter locally adheres to the work position detection sensor 16) and notify the determination result (for example, displayed 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 proper teaching corresponding to the work shape is not performed) has occurred in the electrode holding mechanism 14 (cause 3 of abnormality). In this case, as shown in FIG. 6C, the sensor output deviates (monotonically decreases) from the target distance Ta (the target distance between the work position detection sensor 16 and the detected surface DS) over time. In this case, if the axis direction 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 so that the roller electrode pair REP follows the desired welding trajectory DWT has occurred. ..

Even if there is no problem in the teaching itself, it is conceivable that the electrode holding mechanism 14 has a poor followability with respect to the teaching and an abnormality occurs 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 following capability of the electrode holding mechanism 14 with respect to teaching is poor, or the teaching itself has a problem". However, 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 above will be described with reference to the flowchart of FIG.

In the first step S1, the operator causes the seam welding apparatus 10 to start seam welding. 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 at the same time, 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 hold the flange pair FP.

Upon receiving the welding start trigger signal, the control unit 18 applies a voltage to the roller electrode pair REP to control the electrode holding mechanism 14 to move the roller electrode pair REP along the desired welding track 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 mutually opposite directions, and at the same time, the first joint portion 14a, the second joint portion 14b, and the third joint portion 14b. By appropriately operating the joint portion 14c, the fourth joint portion 14d, the fifth joint portion 14e, and the sixth joint portion 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 axial direction 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 controlled variable CA is equal to or greater than the threshold Th, that is, whether or not there is an abnormality in the sensor output. If the determination here is denied, the process proceeds to step S5, and if the determination is affirmative, the process proceeds to step S8.

In step S5, the first determination unit 18c determines that the sensor output is normal (the sensor output is normal).

In the next step S6, the control unit 18 controls the axis direction 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 drive unit of the first joint unit 14a of the electrode holding mechanism 14. As a result, the axis direction of the roller electrode pair REP is controlled (changed) by the control amount CA.

In the next step S7, the control unit 18 determines whether or not the seam welding is completed. Specifically, the control unit 18 completes the seam welding when it 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. I judge that I did. If the determination here is affirmative, the flow ends, and if the determination is negative, 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 seam welding. Specifically, the energization controller 18a stops energizing the roller electrode pair REP.

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

In the next step S11, the second determination unit 18d determines whether the variance value DV is larger than the upper limit PRu of the predetermined range PR. If the determination here is affirmative, the process proceeds to step S12, and if the determination is negative, the process proceeds to step S13.

In step S12, the second determination unit 18d determines that the foreign matter is attached to the work position detection sensor 16 (for example, the light transmission window 16d) in a wide range, and notifies the determination result (displayed 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 replacement of 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 PR1 of the predetermined range PR. If the determination here is affirmative, the routine proceeds to step S14, and if negative, the routine proceeds to step S15.

In step S14, the second determination unit 18d determines that the foreign matter locally adheres to the work position detection sensor 16 (for example, the light transmission window 16d), and notifies the determination result (displayed 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 replacement of the work position detection sensor 16. When step S14 is executed, the flow ends.

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

Next, the effect of the seam welding device 10 configured as described above will be described.

The seam welding apparatus 10 of the present embodiment rotates the pair of roller electrodes 12A and 12B by sandwiching the two overlapped flanges 13 and 15 (plural works) with the pair of roller electrodes 12A and 12B to which a voltage is applied. However, the seam welding device performs seam welding on the two flanges 13 and 15 by moving the two flanges 13 and 15 with respect to each 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 axial directions of the pair of roller electrodes 12A and 12B can be changed, and the positions of the edges of the two flanges 13 and 15 ( The work position detection sensor 16 that detects the position of the surface to be detected DS and the energization of the pair of roller electrodes 12A and 12B are controlled, and the electrode holding mechanism 14 is controlled based on the detection result of the work position detection sensor 16. And a control unit 18. The control unit 18 determines that the detection result of the work position detection sensor 16 is abnormal, and the first determination unit 18c determines that the detection result of the work position detection sensor 16 is abnormal. In this case, the 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 is included.

As a result, the control unit 18 can determine the cause of abnormality (defective) in the detection result of the work position detection sensor 16 and take appropriate action according to each case. As a result, it is possible to reduce the time required to deal with the problem.

The second determination unit 18d determines that foreign matter has adhered to the work position detection sensor 16 when the variance value DV is not within the predetermined range PR. Accordingly, the cause (defective) of 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 foreign matter has adhered to the work position detection sensor 16 in a wide range. Thereby, 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 in a wide range, and the edge portions of the two flanges 13 and 15 which are the detection targets of the work position detection sensor 16. Is considered to have not been detected, such an appropriate judgment can be made.

The second determination unit 18d determines that the foreign matter locally adheres to the work position detection sensor 16 when the dispersion value DV is smaller than the lower limit PR1 of the predetermined range PR. As a result, when the variance value DV is smaller than the lower limit PR1 of the predetermined range PR, the work position detection sensor 16 locally adheres 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 substance is detected, such an appropriate judgment can be made.

When the dispersion value DV is larger than the upper limit PRu of the predetermined range PR, the second determination unit 18d determines that foreign matter has adhered to the work position detection sensor 16 in a wide range, and the dispersion value DV is smaller than the lower limit PR1 of the predetermined range PR. In this case, it is determined that the foreign matter locally adheres to the work position detection sensor 16. When the dispersion value DV is larger than the upper limit PRu of the predetermined range PR and when the dispersion value DV is smaller than the lower limit PRl of the predetermined range PR, it is possible to make appropriate judgments according to the respective cases.

The second determination unit 18d determines that the teaching deviation that teaches the target range TR to the electrode holding mechanism 14 has occurred when the dispersion value DV is within the predetermined range PR. As a result, it is possible to prompt the user to deal with the teaching deviation.

The first determination unit 18c determines whether or not the detection result of the work position detection sensor 16 is abnormal based on the control amount CA of the electrode holding mechanism 14 based on the detection result of the work position detection sensor 16. Accordingly, it is possible to determine whether or not there is an abnormality in the detection result of the work position detection sensor 16 by a simple method such as comparing the average value Ave of the control amount CA with the threshold 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. As a result, it is possible to prevent the seam welding from continuing in a state where the pair of roller electrodes 12A and 12B are largely displaced from the desired welding trajectory DWT (a state where the pair of roller electrodes 12A and 12B deviates from the target range TR).

In the seam welding method of the present embodiment, the two overlapped flanges 13 and 15 (a plurality of works) are sandwiched by a pair of roller electrodes 12A and 12B to which a voltage is applied while rotating the pair of roller electrodes 12A and 12B. Seam welding start step for starting seam welding performed by moving, work position detecting step for detecting the positions of the edges of the two flanges 13 and 15 by the work position detecting sensor 16, and detection result of the work position detecting sensor 16. 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 determination step of determining the cause of the abnormality based on the DV.

As a result, in the second determination step, the cause of abnormality (deficiency) in the detection result of the work position detection sensor 16 can be determined, and appropriate measures can be taken. As a result, it is possible to reduce the time required to deal with the problem.

The second determination step determines that foreign matter has adhered to the work position detection sensor 16 when the variance value DV is not within the predetermined range PR. Thus, the cause (defective) of the detection result of the work position detection sensor 16 can be notified separately for the case where the foreign matter adheres to the work position detection sensor 16 and for other cases.

In the second determination step, when the dispersion 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 in a wide range. Thereby, 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 in a wide range, and the edge portions of the two flanges 13 and 15 which are the detection targets of the work position detection sensor 16. Is considered to have not been detected, such an appropriate judgment can be made.

The second determination step determines that the foreign matter locally adheres to the work position detection sensor 16 when the variance value DV is smaller than the lower limit PR1 of the predetermined range PR. As a result, when the variance value DV is smaller than the lower limit PR1 of the predetermined range PR, the work position detection sensor 16 locally adheres 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 substance is detected, such an appropriate judgment 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 in a wide range, and when the variance value DV is smaller than the lower limit PRl of the predetermined range PR. First, it is determined that the foreign matter locally adheres 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 appropriate judgments according to the respective cases.

In the second determination step, when the variance value DV is within the predetermined range PR, it is determined that teaching deviation for teaching the target range TR to the electrode holding mechanism 14 has occurred. As a result, it is possible to prompt the user to deal with the teaching deviation.

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

The second determination step stops seam welding when the first determination step determines that the detection result of the work position detection sensor 16 is abnormal. As a result, it is possible to prevent the seam welding from being continued in a state where the pair of roller electrodes 12A and 12B largely deviate from the desired welding track 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... Energization control part 18c... 1st determination part 18d... 2nd determination Part DS: Detected surface (workpiece edge)

Claims (16)

Seam welding in which the plurality of works are seam welded by sandwiching the plurality of works with a pair of roller electrodes to which a voltage is applied and moving the plurality of works while rotating the pair of roller electrodes. A device,
An electrode holding mechanism for holding the pair of roller electrodes so that the axes of the pair of roller electrodes can be changed in orientation;
A work position detection sensor that detects the positions of the edges of the plurality of works,
A control unit that controls energization to the pair of roller electrodes and controls the electrode holding mechanism based on a detection result of the work position detection sensor,
Equipped with
The control unit is
A first determination unit that determines whether or not 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 is abnormal, a second determination unit that determines the cause of the abnormality based on the variation state of the detection result of the work position detection sensor,
Including seam welding equipment. The seam welding apparatus according to claim 1, wherein
The seam welding apparatus, wherein the second determination unit determines that a foreign matter 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 apparatus according to claim 2, wherein
The seam welding apparatus, wherein the second determination unit determines that foreign matter has adhered to the work position detection sensor in a wide range when the numerical value indicating the fluctuation state is larger than the 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 the foreign matter locally adheres to the work position detection sensor when the numerical value indicating the fluctuation state is smaller than the lower limit of the predetermined range. The seam welding apparatus according to claim 2, wherein
The second determination unit,
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 locally adheres 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 any one of claims 2 to 5,
The seam welding device, wherein the second determination unit determines that a deviation in teaching to the electrode holding mechanism has occurred when a numerical value indicating the variation state is between an upper limit and a lower limit of a predetermined range. The seam welding device according to any one of claims 1 to 6,
The first determination unit determines whether or not the detection result of the work position detection sensor is abnormal based on the control amount of the electrode holding mechanism based on the detection result of the work position detection sensor. .. The seam welding device 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 starting step for starting seam welding performed by moving the pair of roller electrodes while rotating the pair of roller electrodes by sandwiching a plurality of overlapped works with a pair of roller electrodes to which a voltage is applied,
A work position detecting step of detecting the positions of the edges of the plurality of works with a work position detecting sensor;
A first determination step of determining whether or not there is an abnormality in the detection result of the work position detection sensor,
A second determination step of determining a cause of abnormality based on a variation state of 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 is abnormal;
Seam welding methods, including. The seam welding method according to claim 9,
The seam welding method, wherein the second determination step determines that a foreign matter 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 seam welding method, wherein the second determination step determines that foreign matter has adhered to the work position detection sensor in a wide range when the numerical value indicating the fluctuation state is larger than an upper limit of a predetermined range. The seam welding method according to claim 10, wherein
The seam welding method, wherein the second determination step determines that a foreign matter locally adheres to the work position detection sensor when a numerical value indicating the variation state is smaller than a lower limit of a predetermined range. The seam welding method according to claim 10, wherein
The second determination step,
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 fluctuation state is smaller than the lower limit of the predetermined range, it is determined that a foreign matter locally adheres to the work position detection sensor. The seam welding method according to claim 10, wherein
The seam welding method, wherein the second determination step determines that teaching deviation has occurred when the numerical value indicating the variation state is between an upper limit and a lower limit of a predetermined range. The seam welding method according to any one of claims 9 to 14,
The first determination step determines whether or not there is an abnormality in the detection result of the work position detection sensor based on the 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. The seam welding method according to any one of claims 9 to 15,
In the second determination step, the seam welding is stopped when the first determination step determines that the detection result of the work position detection sensor is abnormal.

Images