Welding power supply device

Abstract

To appropriately image a monitoring target of a welded portion with a camera.SOLUTION: A welding power supply device comprises: a power supply that supplies power to an electrode for welding; and an imaging control unit that outputs, to a camera, an imaging signal on the basis of a waveform of a welding voltage and / or a welding current output by the power supply. The imaging control unit generates a waveform of a voltage prediction value that is obtained by shifting a phase of a measured value of a welding voltage forward by a prescribed time, and outputs, to the camera, an imaging signal when the voltage prediction value becomes lower than a voltage reference value.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a welding power supply. [Background technology]

[0002] For example, Japanese Patent No. 3165599 (Patent Document 1) discloses a control device that uses a camera to capture images of the molten pool that occurs during arc welding. This control device is located separately from the welding power supply that supplies power to the welding electrode, and monitors the welding voltage sent from the welding power supply during arc welding by performing signal processing such as A / D conversion (analog / digital conversion), and outputs a signal to the camera to capture an image of the molten pool when a predetermined change occurs in the monitored welding voltage value. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 3165599 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, the control device disclosed in Japanese Patent No. 3165599 outputs an image capture signal to the camera when a predetermined change occurs in the monitored welding voltage value. Therefore, the image capture timing can only be determined after the predetermined change occurs in the monitored welding voltage value, potentially resulting in inappropriate capture of the weld pool. Specifically, the timing at which the control device recognizes the welding voltage value is delayed from the actual change in the welding voltage due to factors such as the time required for signal processing, such as A / D conversion. Therefore, the timing at which the control device recognizes the change in the welding voltage value is delayed from the actual change in the welding voltage, which raises concerns that a large arc may be generated during the camera's capture time, preventing the weld pool from being captured appropriately.

[0005] The present disclosure has been made to solve the above-mentioned problems, and its purpose is to enable a monitoring target for a welded portion to be properly photographed with a camera. [Means for solving the problem]

[0006] The welding power supply according to the present disclosure is a welding power supply capable of controlling the timing of photographing an object to be monitored at a welding section with a camera, and includes a power supply that supplies power to a welding electrode, and an imaging control unit that generates an imaging signal that instructs the camera to take an image based on at least one of the welding voltage and welding current output by the power supply and outputs the imaging signal to the camera.

[0007] According to the above configuration, the imaging control unit provided in the welding power supply outputs the imaging signal to the camera, rather than a control device installed separately from the welding power supply. Therefore, compared to when a control device installed separately from the welding power supply outputs the imaging signal to the camera, the time required for signal processing within the control device is not required, and the delay in the timing of the camera imaging relative to actual changes in the welding voltage or welding current can be reduced. As a result, the object to be monitored at the welding zone can be properly captured by the camera. [Effects of the Invention]

[0008] According to the above welding power supply, the monitoring target of the welding portion can be properly photographed by the camera. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of the configuration of a welding system including a welding power supply; [Figure 2] FIG. 2 is a diagram schematically illustrating an example of an image captured by a camera. [Figure 3] 5 is a diagram showing an example of a correspondence relationship between a welding voltage waveform and an output timing of an imaging signal. FIG. [Figure 4] 10 is a flowchart (part 1) illustrating an example of a procedure of an imaging process executed by an imaging control unit. [Figure 5]5 is a diagram showing an example of a correspondence relationship between a welding current waveform and an output timing of an imaging signal; FIG. [Figure 6] 10 is a flowchart (part 2) illustrating an example of the procedure of the photographing process executed by the photographing control unit. [Figure 7] 5A and 5B are diagrams illustrating an example of a correspondence relationship between a waveform of a welding voltage, a waveform of a welding current, and an output timing of an imaging signal. [Figure 8] 10 is a flowchart (part 3) illustrating an example of the procedure of the photographing process executed by the photographing control unit. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0011] 1 is a diagram schematically illustrating an example of the configuration of a welding system 1 including a welding power supply 10 according to the present embodiment. Welding system 1 includes welding power supply 10, welding torch 20, robot arm 40, wire feeder 50, camera 61, and control device 30. Note that, although the following describes a case where welding system 1 is used to manufacture an additively manufactured object, the use of welding system 1 is not limited to manufacturing additively manufactured objects.

[0012] Robot arm 40 is a multi-joint arm, for example a six-axis multi-joint arm. Welding torch 20 is fixed to the tip of robot arm 40. Robot arm 40 functions as a drive device that moves welding torch 20 at a set welding speed. As robot arm 40 moves welding torch 20, a weld bead 70 formed by melting consumable electrode wire 51 is deposited. Robot arm 40 is controlled by control device 30 so that a molded object is formed by depositing weld beads 70.

[0013] The welding torch 20 supplies a welding current to a consumable electrode wire 51 at the tip of a nozzle 21. The consumable electrode wire 51 melts due to an arc 22 generated between the consumable electrode wire 51 and the base material 80 or an already deposited weld bead 70. The melting of the consumable electrode wire 51 forms a molten pool 23, which cools and solidifies to form the weld bead 70. The welding torch 20 deposits the weld bead 70 using the consumable electrode wire 51. A shielding gas is supplied to the welding torch 20 by a shielding gas supply unit (not shown).

[0014] Welding power supply 10 includes welding power supply 11, which supplies a welding current to consumable electrode wire 51. The welding current output from welding power supply 11 may be DC or AC. When the welding current is AC, the magnitude of the welding current and the EN ratio may be set by control device 30. The EN ratio is the ratio of the time-integrated value of the negative polarity current during one AC cycle to the time-integrated value of the current during one AC cycle (the sum of the time-integrated value of the positive polarity current and the time-integrated value of the negative polarity current).

[0015] Wire feeder 50 includes a roller and a motor (not shown). Wire feeder 50 drives the motor to rotate the roller, thereby feeding consumable electrode wire 51 to welding torch 20.

[0016] Camera 61 photographs molten pool 23, which is the object of monitoring the weld zone, and outputs data indicating the photographing results to control device 30. Camera 61, like welding torch 20, is fixed to the tip of robot arm 40. This fixes the position of welding torch 20 in the image photographed by camera 61. Camera 61 is configured as a high-speed camera that includes an image sensor, such as a CCD (Charge Coupled Device) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor, and an electronic shutter, and that can adjust the time (photographing time) for capturing light into the image sensor by adjusting the shutter speed.

[0017] The control device 30 includes a CPU (Central Processing Unit), a memory, and an input / output port for inputting and outputting various signals (none of which are shown). These elements are connected via a bus.

[0018] Controller 30 controls the operation of robot arm 40 and wire supply device 50, as well as the output of welding power supply 10, so that welding is performed under set welding conditions (welding speed, wire feed speed, welding current, welding voltage, etc.). During this operation, controller 30 continuously monitors the state of molten pool 23 based on the photographic data sent from camera 61. Note that while FIG. 1 illustrates an example in which commands to wire supply device 50 are output from controller 30, commands to wire supply device 50 may alternatively be output from welding power supply 10 rather than from controller 30.

[0019] Control device 30 also includes signal processing circuits such as an A / D (analog / digital) conversion circuit, etc. Control device 30 performs signal processing such as A / D conversion on the measured values ​​of the welding current and welding voltage sent from welding power supply 10, and monitors the welding current and welding voltage.

[0020] <Timing of photographing the molten pool 23 by the camera 61> Fig. 2 is a diagram schematically illustrating an example of an image captured by camera 61. The left side of Fig. 2 shows an image captured during a period in which the size of arc 22 is smaller than a predetermined value (hereinafter also referred to as a "small arc period"), and the right side of Fig. 2 shows an image captured during a period in which the size of arc 22 is larger than a predetermined value (hereinafter also referred to as a "large arc period"). Note that the small arc period is a period that also includes a period in which no arc 22 is generated (a short-circuit period).

[0021] As shown on the left side of Figure 2, the image captured during the small arc period captures almost the entire outer shape of the weld pool 23. On the other hand, as shown on the right side of Figure 2, the image captured during the large arc period shows that the arc 22 overlaps most of the weld pool 23, and the outer shape of the weld pool 23 is almost completely hidden. Therefore, in order for the camera 61 to properly capture images of the weld pool 23 without being obstructed by the light of the arc 22, it is important to set the capture time of the camera 61 to the small arc period.

[0022] Generally, the size of arc 22 becomes smaller when the welding current or welding voltage is lower than the corresponding reference value. The light from arc 22 also becomes smaller when the welding current is lower than the reference value. Therefore, it is desirable to capture images with camera 61 while the welding current is lower than the reference value.

[0023] However, if control device 30 were to control the timing of camera 61's image capture, the arc period would be included in the image capture time of camera 61, which could result in an inability to properly capture an image of weld pool 23. Specifically, control device 30 is located separately from welding power supply 10, and the timing at which control device 30 recognizes the welding voltage is delayed by delay time d1 from the timing at which the welding current actually changes, due to factors such as the time required for signal processing such as A / D conversion. Due to the influence of delay time d1, the timing at which control device 30 recognizes a change in the welding current value is delayed from the timing at which the welding current actually changes, which raises the concern that the arc period will be included in the image capture time of camera 61.

[0024] Furthermore, the timing at which the camera 61 starts capturing images is delayed by a delay time d2 from the timing at which the camera 61 receives the capturing signal due to factors such as a delay in the control of opening the shutter of the camera 61. Due to the effect of this delay time d2, there is a concern that the arc period will be included in the capturing time of the camera 61.

[0025] Regardless of the cause, if the arc period is included in the photographing time of the camera 61, the molten pool 23 cannot be photographed properly.

[0026] Therefore, in welding system 1 according to the present embodiment, welding power supply 10 controls the timing of capturing images by camera 61, rather than control device 30 arranged separately from welding power supply 10. Specifically, welding power supply 10 includes, in addition to welding power source 11, imaging control unit 12. Imaging control unit 12 predicts the above-mentioned small arc period based on the welding current value output by welding power source 11, and outputs an imaging signal to camera 61 so that the imaging period of camera 61 falls within the small arc period. Note that the control performed by imaging control unit 12 may be processed by software or dedicated hardware (electronic circuitry).

[0027] 3 is a diagram showing an example of the correspondence relationship between the waveform of the welding current and the output timing of the imaging signal in this embodiment, where the waveform is shown when pulse welding is performed.

[0028] "(A) Comparative Example 1" on the left side of FIG. 3 shows an example in which control device 30 outputs an imaging signal based on a measured current value. "(B) Comparative Example 2" in the center of FIG. 3 shows an example in which imaging control unit 12 outputs an imaging signal based on a measured current value. "(C) This Disclosure" on the right side of FIG. 3 shows an example in which imaging control unit 12 outputs an imaging signal based on a predicted current value. The measured current is the value of the welding current measured by welding power supply 10. The predicted current value is a virtual value used by imaging control unit 12 for control, and is a value obtained by advancing the phase of the measured current by a time equivalent to delay time d2 (hereinafter also referred to as "lead time"). The measured voltage is the value of the welding voltage measured by welding power supply 10.

[0029] In all of Figures 3(A) to (C), the current is equal to the reference current value I thd The timing when the current falls below the current reference value I thd is higher than the current reference value I thd 3, an example is shown in which an image capturing signal is output to the camera 61 at the timing when the arc reference value A thdis the threshold value of the arc size at which the molten pool 23 can be photographed without being obstructed by the arc light.

[0030] In the case of Comparative Example 1 in FIG. 3(A), the measured current is equal to the reference current value I thd The timing at which the control device 30 recognizes that the measured current has fallen below the current reference value I thd , the timing at which the current measurement value actually falls below the reference current value I is delayed by the delay time d1 described above. Furthermore, the timing at which the camera 61 starts capturing images is delayed by the delay time d2 described above from the timing at which the camera 61 receives the capturing signal. Due to the influence of these delay times d1 and d2, thd The time from when the temperature actually falls below 0°C to when the camera 61 actually starts capturing images (hereinafter also referred to as the "capture delay time Di") is the sum of delay times d1 and d2. As a result, the capture time of the camera 61 includes a period during which capture is not possible (large arc period), and the molten pool 23 cannot be captured properly.

[0031] In the case of Comparative Example 2 in FIG. 3B, the measured current is equal to the reference current value I thd The timing at which the imaging control unit 12 recognizes that the measured current has fallen below the current reference value I thd 3B, however, there is still a period when photography is not possible (large arc period) at the end of the photography time, and the molten pool 23 cannot be photographed properly.

[0032] In contrast to these, in the case of the present disclosure shown in FIG. 3C, the imaging control unit 12 generates a waveform of a current prediction value in which the phase of the current measurement value is advanced by the above-mentioned leading time (the time corresponding to the delay time d2), and the current prediction value is set to the current reference value I thd When the welding current falls below the reference current value I, the image capturing signal is output to the camera 61. This eliminates not only the delay time d1 but also the delay time d2. thdTherefore, the camera 61 can be made to start photographing at a timing when the actual arc temperature falls below 100°C. As a result, the photographing period can be made to fall within the small arc period, and the molten pool 23 can be photographed appropriately.

[0033] The shooting control unit 12 can arbitrarily adjust the "leading time" corresponding to the delay time d2. As a result, even if there is a difference in the delay time d2 depending on the model or individual difference of the camera 61, the influence of the delay time d2 can be appropriately eliminated by adjusting the leading time.

[0034] 4 is a flowchart showing an example of the procedure of the photographing process executed by the photographing control unit 12 according to this embodiment. This flowchart is repeatedly executed every time a predetermined condition is met (for example, at predetermined intervals).

[0035] The imaging control unit 12 generates a waveform of a current prediction value in which the phase of the current measurement value is advanced by the aforementioned leading time (time corresponding to the delay time d2) (step S10).

[0036] Next, the imaging control unit 12 calculates the current prediction value based on the current reference value I thd It is determined whether the predicted current value is greater than the current reference value I (step S11). thd If it is not greater than (NO in step S11), the imaging control unit 12 ends the process.

[0037] The predicted current value is the current reference value I thd If the current prediction value is greater than the current reference value I (YES in step S11), the imaging control unit 12 thd Whether the predicted current value has changed to a value smaller than the current reference value I thd It is determined whether the predicted current value is lower than the current reference value I (step S12). thd If the current prediction value is not lower than the current reference value I (NO in step S12), the imaging control unit 12 repeats the process of step S12 and thd Wait until it drops below .

[0038] The predicted current value is the current reference value I thd If the value falls below (YES in step S12), the photographing control unit 12 outputs a photographing signal to the camera 61 (step S13).

[0039] As described above, in welding system 1 according to the present embodiment, it is not control device 30 that is disposed separately from welding power supply 10, but rather imaging control unit 12 provided in welding power supply 10 that outputs the imaging signal to camera 61. Therefore, compared to when control device 30 outputs the imaging signal to camera 61, delay time d1 due to signal processing within control device 30 does not occur, and it is possible to reduce the delay in the imaging timing of camera 61 relative to actual changes in welding voltage or welding current. As a result, the imaging period can be kept within the small arc period, allowing weld pool 23 to be properly imaged.

[0040] Furthermore, the imaging control unit 12 according to this embodiment generates a waveform of a current prediction value in which the phase of the current measurement value is advanced by a "leading time" corresponding to the delay time d2, and the current prediction value is set to the current reference value I thd When the welding current falls below the reference current value I, the image capturing signal is output to the camera 61. This eliminates not only the delay time d1 but also the delay time d2. thd Therefore, the camera 61 can be made to start photographing at a timing when the actual arc temperature falls below 100°C. As a result, the photographing period can be made to fall within the small arc period, and the molten pool 23 can be photographed appropriately.

[0041] As described above, the imaging control unit 12 according to the embodiment generates a waveform of the predicted current value and determines the output timing of the imaging signal using the predicted current value. However, the imaging control unit 12 may determine the output timing of the imaging signal directly from the measured current value without generating a waveform of the predicted current value. For example, during the pulse peak period (when the measured current value is equal to or exceeds the reference current value I) shown in FIG. thdWhen the pulse peak period (the period during which the image capture signal exceeds the pulse peak period) is constant, the image capture control unit 12 determines how long after the pulse peak period has started that the image capture signal should be output, and can determine the output timing of the image capture signal.

[0042] [Variation 1] In the above-described embodiment, in consideration of the fact that the size of the arc changes depending on the welding current, imaging control unit 12 of welding power supply 10 outputs an imaging signal based on the waveform of the welding current.

[0043] In contrast, in the present first modification, in consideration of the fact that the ignition period and extinction period of the arc change depending on the welding voltage, imaging control unit 12 of welding power supply 10 outputs an imaging signal based on the waveform of the welding voltage.

[0044] Fig. 5 is a diagram showing an example of the correspondence relationship between the waveform of the welding voltage and the output timing of the imaging signal in Modification 1. Fig. 5 shows the waveform when pulseless welding is performed.

[0045] "(A) Comparative Example 1" on the left side of FIG. 5 shows an example in which control device 30 outputs an imaging signal based on a voltage measurement value. "(B) Comparative Example 2" in the center of FIG. 5 shows an example in which imaging control unit 12 outputs an imaging signal based on a voltage measurement value. "(C) This Disclosure" on the right side of FIG. 5 shows an example in which imaging control unit 12 outputs an imaging signal based on a voltage prediction value. The voltage measurement value is the value of the welding voltage measured by welding power supply 10. The voltage prediction value is a virtual value used by imaging control unit 12 for control, and is a value obtained by advancing the phase of the voltage measurement value by the aforementioned lead time (a time equivalent to delay time d2).

[0046] When performing pulseless welding, as shown in Figure 5, the welding voltage is set to the reference voltage V thd The period when the welding voltage is greater than the reference voltage V thd In view of this, in any of Figs. 5(A) to (C), the period when the voltage is equal to or smaller than the voltage reference value V thd The timing when the voltage falls below the voltage reference value Vthd higher than the voltage reference value V thd In this example, a photographing signal is output to the camera 61 at the timing when the voltage Vcc changes to a state lower than the reference voltage Vcc.

[0047] In Comparative Example 1 of FIG. 5(A), the measured voltage is equal to the reference voltage V thd The time from when the temperature actually falls below 0°C to when the camera 61 actually starts capturing images (hereinafter also referred to as the "capture delay time Dv") is the sum of delay times d1 and d2. As a result, the capture time of the camera 61 includes a period during which capture is not possible (large arc period), and the molten pool 23 cannot be captured properly.

[0048] In Comparative Example 2 in Figure 5(B), the imaging delay time Dv is delay time d2, which is shorter than that of Comparative Example 1. However, in the example shown in Figure 5(B), there is still a period when imaging is not possible (large arc period) at the end of the imaging time, and the molten pool 23 cannot be properly imaged.

[0049] In contrast to these, in the case of the present disclosure shown in FIG. 5C, the imaging control unit 12 generates a waveform of a voltage prediction value in which the phase of the voltage measurement value is advanced by the above-mentioned leading time (the time corresponding to the delay time d2), and the voltage prediction value is equal to the voltage reference value V thd , the image capturing signal is output to the camera 61 at the timing when the voltage measurement value falls below the voltage reference value V. This eliminates not only the delay time d1 but also the delay time d2. thd Therefore, the camera 61 can be made to start photographing at a timing when the actual arc time exceeds the short arc time. As a result, the photographing period can be made to fall within the short arc period, and the molten pool 23 can be photographed appropriately.

[0050] 6 is a flowchart showing an example of the procedure of the imaging process executed by imaging control unit 12 of welding power supply 10 according to Modification 1. This flowchart is repeatedly executed every time a predetermined condition is met (for example, at predetermined intervals).

[0051] The imaging control unit 12 generates a waveform of a predicted voltage value by advancing the phase of the measured voltage value by the aforementioned leading time (time equivalent to the delay time d2) (step S20).

[0052] Next, the imaging control unit 12 calculates the voltage prediction value based on the voltage reference value V thd It is determined whether the predicted voltage value is greater than the reference voltage value V (step S21). thd If it is not greater than (NO in step S21), the imaging control unit 12 ends the process.

[0053] The predicted voltage is the reference voltage V thd If the voltage prediction value is greater than the voltage reference value V (YES in step S21), the imaging control unit 12 thd Whether the predicted voltage value has changed to a value smaller than the reference voltage value V thd It is determined whether the predicted voltage value is lower than the reference voltage value V (step S22). thd If the voltage prediction value is not lower than the voltage reference value V (NO in step S22), the imaging control unit 12 repeats the process of step S22 and thd Wait until it drops below .

[0054] The predicted voltage is the reference voltage V thd If the value falls below (YES in step S22), the photographing control unit 12 outputs a photographing signal to the camera 61 (step S23).

[0055] As described above, the imaging control unit 12 of the welding power supply 10 according to the first modification generates a waveform of a predicted voltage value in which the phase of the measured voltage value is advanced by the “leading time” corresponding to the delay time d2, and the predicted voltage value is adjusted to the reference voltage value V thd , the image capturing signal is output to the camera 61 at the timing when the voltage measurement value falls below the voltage reference value V. This eliminates not only the delay time d1 but also the delay time d2. thd Therefore, the camera 61 can be made to start photographing at a timing when the actual arc time exceeds the short arc time. As a result, the photographing period can be made to fall within the short arc period, and the molten pool 23 can be photographed appropriately.

[0056] [Variation 2] In this second variant, the timing for outputting the imaging signal is determined using both the welding voltage and the welding current, in consideration of the fact that the arc size becomes so large that it is impossible to image the molten pool 23 during periods when both the welding voltage and the welding current are high.

[0057] FIG. 7 shows an example of the correspondence between the welding current waveform, welding voltage waveform, and the output timing of the imaging signal in this second variation. Note that FIG. 7 illustrates waveforms for pulseless welding, where multiple rising edges of the current waveform occur within one voltage pulse cycle. For example, this applies to welding in which the current is suddenly reduced just before the arc re-strikes and then increased after the arc re-strikes to reduce the amount of spatter generated upon arc re-strike. In this case, the current suddenly decreases during the short-circuit period when the arc is extinguished and imaging is possible. If the start of imaging is determined based on this sudden decrease, imaging will not be possible because an arc will re-occur immediately after. Therefore, by ignoring the sudden current decrease when the voltage is low, the appropriate start of imaging can be determined.

[0058] "(A) Comparative Example 1" on the left side of FIG. 7 shows an example in which the control device 30 outputs an imaging signal based on current measurement values ​​and voltage measurement values. "(B) Comparative Example 2" in the center of FIG. 7 shows an example in which the imaging control unit 12 outputs an imaging signal based on current measurement values ​​and voltage measurement values. "(C) This disclosure" on the right side of FIG. 7 shows an example in which the imaging control unit 12 outputs an imaging signal based on current measurement values ​​and voltage measurement values.

[0059] In FIG. 7, the current prediction value is a value obtained by advancing the phase of the current measurement value by the aforementioned leading time (the time corresponding to the delay time d2), and the voltage prediction value is a value obtained by advancing the phase of the voltage measurement value by the aforementioned leading time (the time corresponding to the delay time d2). thd is the current threshold value, and the voltage reference value V thd is the voltage threshold. Arc reference value A thdAs mentioned above, is the threshold value of the arc size at which the molten pool 23 can be photographed without being obstructed by the arc light. thd When the current is higher than the current reference value I thd The timing when the current falls below the current reference value I thd is higher than the current reference value I thd In this example, a photographing signal is output to the camera 61 at the timing when the voltage Vcc changes to a state lower than the reference voltage Vcc.

[0060] In the comparative example 1 of FIG. 7(A), due to the influence of the delay times d1 and d2, the imaging time of the camera 61 includes a period during which imaging is not possible (large arc period).

[0061] In Comparative Example 2 in Figure 7(B), the imaging delay time Di is delay time d2, which is shorter than that of Comparative Example 1. However, in the example shown in Figure 7(B), there is still a period when imaging is not possible (large arc period) at the end of the imaging time, and the molten pool 23 cannot be properly imaged.

[0062] In contrast to these, the imaging control unit 12 according to the present modified example 2 generates waveforms of predicted current values ​​and predicted voltage values ​​in which the phases of the measured current values ​​and the measured voltage values ​​are advanced by a “leading time” corresponding to the delay time d2, as shown in FIG. 7C, and the predicted voltage values ​​are adjusted to the reference voltage value V thd When the predicted current value is higher than the current reference value I thd The imaging signal is output to the camera 61 when the current drops below d1. This eliminates not only the delay time d1 but also the delay time d2. Furthermore, since the imaging signal is not output during the current rapid decrease period when the voltage is low, an arc is prevented from occurring immediately after the imaging signal is output. As a result, the imaging period can be kept within the small arc period, allowing the molten pool 23 to be properly imaged.

[0063] 8 is a flowchart showing an example of the procedure of the imaging process executed by imaging control unit 12 of welding power supply 10 according to Modification 2. This flowchart is repeatedly executed every time a predetermined condition is met (for example, at predetermined intervals).

[0064] The imaging control unit 12 generates a waveform of a current prediction value in which the phase of the current measurement value is advanced by the aforementioned leading time (time corresponding to the delay time d2) delay time d2 (step S10).

[0065] Next, the imaging control unit 12 generates a waveform of a predicted voltage value by advancing the phase of the measured voltage value by the aforementioned leading time (time equivalent to the delay time d2) (step S20).

[0066] Next, the imaging control unit 12 calculates the voltage prediction value based on the voltage reference value V thd It is determined whether the predicted voltage value is greater than the reference voltage value V (step S30). thd If it is not greater than (NO in step S30), the imaging control unit 12 ends the process.

[0067] The predicted voltage is the reference voltage V thd If the current prediction value is greater than the current reference value I (YES in step S30), the imaging control unit 12 thd It is determined whether the predicted current value is greater than the current reference value I (step S31). thd If it is not greater than (NO in step S31), the imaging control unit 12 ends the process.

[0068] The predicted current value is the current reference value I thd If the current prediction value is greater than the current reference value I (YES in step S31), the imaging control unit 12 thd Whether the predicted current value has changed to a value smaller than the current reference value I thd It is determined whether the predicted current value is lower than the current reference value I (step S32). thd If the current prediction value is not lower than the current reference value I (NO in step S32), the imaging control unit 12 repeats the process of step S32 and thdWait until it drops below .

[0069] The predicted current value is the current reference value I thd If the value falls below (YES in step S32), the photography control unit 12 outputs a photography signal to the camera 61 (step S33).

[0070] As described above, the imaging control unit 12 of the welding power supply 10 according to the second modification generates waveforms of the predicted current value and the predicted voltage value by advancing the phases of the measured current value and the measured voltage value by the delay time d2, and the predicted voltage value is adjusted to the reference voltage value V thd When the predicted current value is higher than the current reference value I thd The imaging signal is output to the camera 61 at a timing below d1. This eliminates not only the delay time d1 but also the delay time d2. As a result, the imaging period can be kept within the small arc period, allowing the molten pool 23 to be properly imaged.

[0071] In the second modification, the predicted voltage value is equal to the reference voltage value V thd When the predicted current value is higher than the current reference value I thd , the example in which the imaging signal is output to the camera 61 at the timing when the predicted current value falls below the current reference value I thd When the predicted voltage is lower than the voltage reference value V thd Alternatively, the imaging signal may be output to the camera 61 at a timing below the predetermined value.

[0072] [Other variations] (A) The voltage reference value V thd may be dynamically changed depending on the results of measuring the arc 22.

[0073] For example, the welding voltage value when the size of the arc 22 in the captured image becomes smaller is set to the voltage reference value V thd For example, the welding voltage value when the size of the arc 22 and the size of the molten pool 23 become equal may be set as the voltage reference value V thd For example, the voltage reference value V thdThe voltage reference value V is set to the value when the photographed result of the molten pool 23 stops changing. thd The arc 22 may be measured using a camera 61 or other sensor.

[0074] Current reference value I thd Also, the voltage reference value V thd Similarly, the value may be dynamically changed depending on the result of measuring the arc 22.

[0075] (B) The voltage reference value V thd and the current reference value I thd may be set in accordance with the shutter speed (photographing time) of the camera 61. Conversely, the above-mentioned voltage reference value V thd and the current reference value I thd may be changed.

[0076] (C) The shutter speed (photographing time) of the camera 61 may also be dynamically changed. For example, if the molten pool 23 cannot be photographed properly, the shutter speed of the camera 61 may be increased to shorten the photographing time.

[0077] (D) A variable delay may be set when transmitting the imaging signal to adjust the imaging timing.

[0078] (E) The delay times d1 and d2 may be measured in advance, and the output timing of the imaging signal may be adjusted based on the results.

[0079] (F) The start of welding itself may be changed in response to the image capture signal. For example, if the shutter of camera 61 has not yet been closed, the start of the welding voltage may be delayed.

[0080] (G) The imaging signal may be output multiple times in one period.

[0081] (H) A signal to start shooting and a signal to end shooting may be sent separately, and shooting may continue in between.

[0082] (I) The timing and shutter speed of photographing welding elements other than the molten pool 23 (for example, the arc 22, the groove, and the weld bead 70) may also be changed.

[0083] (J) Whether to use the timing when the welding voltage or welding current exceeds the reference value or the timing when it falls below the reference value can be changed as appropriate.

[0084] (K) The standard to be compared with the welding voltage or welding current is not limited to a single value, but may have a predetermined range.

[0085] (L) In the above-described second modification, in order to adjust the amount of light, the image may be taken excluding the short-circuit period in which no arc 22 occurs. For example, since it may be impossible to take an image in a state in which there is no light from the arc 22, the image may be taken during a low-current arc period, for example.

[0086] (M) If the imaging control unit 12 of the welding power supply 10 can properly image the weld pool 23 simply by using the measured voltage or current value to determine the output timing of the imaging signal, it is not necessary to use the predicted voltage or current value described above. In other words, even if the imaging control unit 12 of the welding power supply 10 simply uses the measured voltage or current value to determine the output timing of the imaging signal, at least the delay time d1 described above is eliminated, and thus, by eliminating the delay time d1, it becomes easier to properly image the weld pool 23.

[0087] [Aspect] It will be understood by those skilled in the art that the above-described embodiments and their modifications are specific examples of the following aspects.

[0088] (Item 1) A welding power supply according to the present disclosure is a welding power supply capable of controlling the timing of photographing an object to be monitored at a welding section with a camera, and includes a power supply that supplies power to a welding electrode, and an imaging control unit that outputs an imaging signal to the camera to instruct the camera to take an image based on at least one of the welding voltage and welding current output by the power supply.

[0089] According to the configuration of paragraph 1, the imaging control unit provided in the welding power supply outputs the imaging signal to the camera, rather than a control device disposed separately from the welding power supply. Therefore, compared to when a control device disposed separately from the welding power supply outputs the imaging signal to the camera, no time is required for signal processing within the control device, and delays in the timing of the camera's imaging relative to actual changes in the welding voltage or welding current can be reduced. As a result, the object to be monitored at the welding point can be properly captured by the camera.

[0090] (Item 2) In the welding power supply described in item 1, the monitored object is a molten pool generated during arc welding. The imaging control unit predicts a small arc period, during which the size of the arc generated during arc welding becomes smaller than a predetermined value, based on at least one of the welding voltage and the welding current, and outputs an imaging signal to the camera so that the imaging period of the monitored object falls within the small arc period.

[0091] According to the welding power supply of paragraph 2, the camera's image capturing time can be within the small arc period, so that the molten pool, which is the object of monitoring, can be properly captured by the camera.

[0092] (Item 3) In the welding power supply device described in Item 2, the photography control unit generates a waveform of a predicted current value by advancing the phase of the measured welding current value by a predetermined time, and outputs a photography signal to the camera at the timing when the predicted current value changes from a state higher than the current reference value to a state lower than the current reference value.

[0093] According to the welding power supply of paragraph 3, the imaging signal can be output to the camera a predetermined time earlier than the timing at which the welding power supply recognizes that the measured welding current has fallen below the reference current value. Therefore, even if there is a control delay in the camera, for example, the delay can be reduced and the molten pool can be properly imaged by the camera.

[0094] (4) In the welding power supply apparatus described in paragraph 2, the imaging control unit generates a waveform of a predicted voltage value by advancing the phase of the waveform of the measured welding voltage by a predetermined time, and outputs an imaging signal to the camera at the timing when the predicted voltage value changes from a state higher than the voltage reference value to a state lower than the voltage reference value.

[0095] According to the welding power supply of paragraph 4, the imaging signal can be output to the camera a predetermined time earlier than the timing at which the welding power supply recognizes that the measured welding voltage has fallen below the voltage reference value. Therefore, even if there is a control delay in the camera, for example, the delay can be reduced and the molten pool can be properly imaged by the camera.

[0096] (Item 5) In the welding power supply apparatus described in Item 2, the photography control unit generates a waveform of a predicted current value by advancing the phase of the waveform of the measured value of the welding current by a predetermined time, generates a waveform of a predicted voltage value by advancing the phase of the waveform of the measured value of the welding voltage by a predetermined time, and outputs a photography signal to the camera at the timing when the predicted current value changes from higher to lower than the current reference value while the predicted voltage value is higher than the voltage reference value, or at the timing when the predicted voltage value changes from higher to lower than the voltage reference value while the predicted current value is lower than the current reference value.

[0097] According to the welding power supply of paragraph 5, the imaging signal can be output to the camera a predetermined time earlier than the timing at which the welding power supply recognizes that the measured value of the welding voltage or the measured value of the welding current has fallen below the respective reference value. Therefore, even if there is a control delay in the camera, for example, the delay can be reduced and the molten pool can be properly imaged by the camera.

[0098] (Item 6) In the welding power supply according to any one of Items 3 to 5, the predetermined time is a time equivalent to a delay time from when the camera receives the image capturing signal until when the camera starts capturing images.

[0099] According to the welding power supply device of paragraph 6, even if there is a delay between when the camera receives the photographing signal and when the camera starts photographing, the delay can be eliminated and the molten pool can be properly photographed by the camera.

[0100] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The technical scope of the present disclosure is defined by the claims, not by the description of the above embodiments, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0101] 1 Welding system, 10 welding power supply device, 11 welding power supply, 12 photography control unit, 20 welding torch, 21 nozzle, 22 arc, 23 molten pool, 30 control device, 40 robot arm, 50 wire feed device, 51 consumable electrode wire, 61 camera, 70 weld bead, 80 base material.

Claims

1. A welding power supply capable of controlling the timing of photographing a monitoring target of a welding portion with a camera, a power supply for supplying power to the welding electrode; a photography control unit that outputs a photography signal to the camera to instruct the camera to take a photograph based on at least one of a welding voltage and a welding current output by the power supply.

2. The monitoring target is a molten pool generated during arc welding, The imaging control unit predicting a small arc period during which the size of the arc generated during arc welding is smaller than a predetermined value based on at least one of the welding voltage and the welding current; The welding power supply according to claim 1 , wherein the imaging signal is output to the camera so that the imaging period of the monitored object falls within the small arc period.

3. The imaging control unit generating a waveform of a predicted current value by advancing the phase of the waveform of the measured value of the welding current by a predetermined time; 3. The welding power supply according to claim 2, wherein the imaging signal is output to the camera at a timing when the predicted current value changes from a state higher than a current reference value to a state lower than the current reference value.

4. The imaging control unit generating a waveform of a predicted voltage value by advancing the phase of the waveform of the measured value of the welding voltage by a predetermined time; 3. The welding power supply according to claim 2, wherein the imaging signal is output to the camera at a timing when the predicted voltage value changes from a state higher than a voltage reference value to a state lower than the voltage reference value.

5. The imaging control unit generating a waveform of a predicted current value by advancing the phase of the waveform of the measured value of the welding current by a predetermined time; generating a waveform of a predicted voltage value by advancing the phase of the waveform of the measured value of the welding voltage by the predetermined time; 3. The welding power supply according to claim 2, wherein the imaging signal is output to the camera at a timing when the predicted current value changes from higher to lower than the current reference value while the predicted voltage value is higher than the voltage reference value, or at a timing when the predicted voltage value changes from higher to lower than the voltage reference value while the predicted current value is lower than the current reference value.

6. 6. The welding power supply according to claim 3, wherein the predetermined time period corresponds to a delay time between when the camera receives the image capturing signal and when the camera starts capturing images.

Images