JP6376963B2 - Laser welding apparatus having groove monitoring device and groove monitoring method for laser welding device - Google Patents

Description

  The present invention relates to a laser welding apparatus that has a groove monitoring device that directly monitors a groove portion to be laser-welded and performs welding with high accuracy and a groove portion monitoring method for the laser welding device.

Patent Document 1 proposes a laser welding apparatus that welds a laser beam by weaving, and includes error detection means for detecting a groove portion. This error detection means is arranged in front of the irradiation position of the laser beam and is composed of an optical system sensor such as a laser sensor.

JP 2003-170284 A

  For example, when butt welding welding materials (thick plates) with a thickness exceeding 50 mm up to 200 mm, the narrow groove width is several mm, but the beam spot of laser welding is small, so the beam spot is high speed. And weaving with high accuracy is required. In Patent Document 1, the groove portion is detected by a laser sensor in front of the irradiation position of the laser beam. However, since the beam spot is small, it is affected by slight fluctuations and displacements of the laser welding apparatus and the base material. Cheap. Further, when welding is performed by weaving the laser beam, the base material may be slightly deformed by heat, and the groove width may be slightly reduced or expanded from a normal value. For this reason, the conventional laser welding apparatus has a problem that it is difficult to increase the detection accuracy when detecting the position of the groove wall.

  An object of this invention is to provide the laser welding apparatus which has a groove part monitoring apparatus which can detect the position of a groove wall with high precision, and the groove part monitoring method of a laser welding apparatus.

A laser welding apparatus having a groove part monitoring device according to claim 1, wherein the laser welding apparatus welds along the welding line of the groove weld part while monitoring the groove weld part,
A weaving mirror disposed on the optical axis of the laser beam so as to freely swing;
A weaving driving device that swings the weaving mirror to weave the beam spot into a shape having a peak and a valley; and
An imaging device that captures an image of the groove weld;
A control device having an operation output unit and an image processing / determination unit that outputs a weaving waveform signal to the weaving driving device and outputs an imaging trigger signal to the imaging device;
The imaging device operated based on the imaging trigger signal has a beam spot in the vicinity of the peak or valley, and plasma light extending forward from the beam spot along the groove wall of the groove weld. Image
The image processing / determination unit determines a groove width and a groove center by determining a position of a groove wall of the groove welded part from the image including the plasma light.

  The laser welding apparatus having the groove portion monitoring device according to claim 2, wherein the operation output portion is 7% to 15% of the amplitude of the weaving from the position where the beam spot passes through the turning point of the peak portion or the valley portion. An imaging trigger signal is output so that the shutter of the imaging device is driven when moving within the range.

  In the laser welding apparatus having the groove portion monitoring device according to claim 3, the image processing / determination unit selects an image region that is ahead of the beam spot of the captured image and does not include the beam spot but includes plasma light, The position of the groove wall is determined based on the image area.

  The laser welding apparatus having the groove portion monitoring device according to claim 4, wherein the image processing / determination unit determines that a pixel column having a high luminous intensity among the pixel columns along the welding line is plasma light, and the plasma light welding line A pixel row having a large gradient of luminous intensity between adjacent pixel rows outside the area is determined as a groove wall.

The groove monitoring method for a laser welding apparatus according to claim 5, wherein the laser beam irradiated along the optical axis is irradiated to the groove weld through the weaving mirror, and the weaving mirror is swung. The beam spot irradiated to the groove welded part is weaved into a shape having a peak and a valley,
A beam spot is imaged in the vicinity of the peak or valley and the plasma light extending forward from the beam spot along the groove wall of the groove weld,
The groove width and the groove center are obtained by determining the position of the groove wall of the groove weld from the image containing the plasma light.

  The groove monitoring method for a laser welding apparatus according to claim 6, wherein the beam spot moves within a range of 7% to 15% of the amplitude of the weaving from the position where the beam spot passes through the turning point of the peak or valley. It is characterized in that the plasma light is imaged during the operation.

According to claim 1, plasma light extending forward along the groove wall of the groove weld from the beam spot is imaged, and the position of the groove wall of the groove weld is determined from an image including the plasma light. Thus, the position of the groove wall can be detected with high accuracy, and the groove width and the groove center can be obtained with high accuracy. For this reason, even if the value of the groove width slightly changes due to a processing error or the influence of heat, the amplitude of the laser beam is controlled by controlling the weaving drive device based on the detected groove width. It can be accurately adjusted according to the change in width.
According to claim 2, when the beam spot is moving within the range of 7% to 15% of the amplitude of the weaving from the position where the beam spot passes through the turning point of the peak portion or the valley portion, Since plasma light extending forward along the groove wall is generated, the plasma light can be reliably imaged by the imaging device.

  According to claims 3 and 4, even if the beam spot protrudes from the groove wall to the outside in the amplitude direction due to some external factor, plasma light is generated along the groove wall. If it does, the influence of the light of a beam spot can be excluded, and the position of a groove wall can be detected with high precision based on the gradient of luminous intensity of only plasma light.

According to the fifth aspect, the plasma light extending forward along the groove wall of the groove welded portion from the beam spot is imaged, and the position of the groove wall of the groove welded portion is determined from the image including the plasma light. Thus, the position of the groove wall can be detected with high accuracy, and the groove width and the groove center can be obtained with high accuracy. For this reason, even if the value of the groove width slightly changes due to processing errors, the influence of heat, etc., the amplitude of the laser beam is accurately adjusted according to the change in the groove width based on the detected groove width. Can be adjusted.
According to claim 6, when the beam spot is moving within the range of 7% to 15% of the amplitude of the weaving from the position where the beam spot passes through the turning point of the peak portion or the valley portion, Since plasma light extending forward along the groove wall is generated, the plasma light can be reliably imaged by the imaging device.

It is a block diagram of the laser welding apparatus which has a groove part monitoring apparatus in the 1st Embodiment of this invention. It is a figure which shows the screen of the groove part by the imaging device of a laser welding apparatus similarly. It is a block diagram which shows the operation output part of the control apparatus of a laser welding apparatus equally. FIG. 4 is an output waveform diagram of the operation output unit of FIG. 3. It is a schematic diagram which shows the movement path | route of the beam spot at the time of weaving of a laser welding apparatus. FIG. 4 is an image of a groove welded portion, where (a) is an image when the distance A between one folding point and a beam spot that has passed through this folding point is 12.5% of the amplitude E of the laser beam. (B) is a graph showing the luminous intensity of the pixel row of the same image. FIG. 6 is an image of a groove welded portion, where (a) is an image when the distance A between the other folding point and the beam spot that has passed through this folding point is 12.5% of the amplitude E of the laser beam. (B) is a graph showing the luminous intensity of the pixel row of the same image. It is a flowchart which shows the groove part monitoring method by a laser welding apparatus similarly. It is a picked-up image of a groove weld as a reference example, (a) is an image when the beam spot moves to one folding point, (b) is a graph showing the luminous intensity of the pixel row of the image. . It is a picked-up image of a groove weld as a reference example, (a) is an image when the distance A is a value of 25% of the amplitude E, (b) shows the luminous intensity of the pixel row of the image. It is a graph. As a reference example, it is a captured image of a groove weld when the distance A is 5.9% of the amplitude E. As a reference example, it is a captured image of a groove weld when the distance A is 6.5% of the amplitude E. As a 1st embodiment of the present invention, it is a picked-up image of a groove welding part when the distance A is a value of 7.1% of the amplitude E. FIG. 6 is a captured image of a groove weld when the distance A is 7.8% of the amplitude E. FIG. 4 is a captured image of a groove weld when the distance A is 8.5% of the amplitude E. FIG. 3 is a captured image of a groove weld when the distance A is 9.2% of the amplitude E. FIG. 4 is a captured image of a groove weld when the distance A is 13.1% of the amplitude E. FIG. 4 is a captured image of a groove weld when the distance A is 14.9% of the amplitude E. FIG. As a reference example, it is a captured image of a groove weld when the distance A is 15.8% of the amplitude E. As a reference example, it is a captured image of a groove weld when the distance A is 16.7% of the amplitude E. As a reference example, it is a captured image of a groove weld when the distance A is 17.7% of the amplitude E. It is the picked-up image of the groove welding part imaged with the laser welding apparatus in the 2nd Embodiment of this invention, (a) is the distance A of one folding point and the beam spot which passed this folding point is a laser beam. (B) is a graph showing the luminous intensity of the pixel column of the same image. FIG. 6 is an image of a groove welded portion, where (a) is an image when the distance A between the other folding point and the beam spot that has passed through this folding point is 12.5% of the amplitude E of the laser beam. (B) is a graph showing the luminous intensity of the pixel row of the same image. It is a picked-up image of a groove weld as a reference example, (a) is an image when the beam spot moves to one folding point, (b) is a graph showing the luminous intensity of the pixel row of the image. . It is a picked-up image of a groove weld as a reference example, (a) is an image when the distance A is a value of 25% of the amplitude E, (b) shows the luminous intensity of the pixel row of the image. It is a graph.

(First embodiment)
A first embodiment of the present invention will be described below with reference to FIGS.
[Laser welding equipment]
As shown in FIGS. 1 to 4, this laser welding apparatus introduces a laser beam (CO ₂ laser, YAG laser, etc.) LB emitted from a laser resonator 11 through a fiber cable 12 and a collimation lens 13. Then, the light is reflected by a reflection mirror (weaving mirror) 14 disposed on the horizontal optical axis Oh, refracted by 90 °, and introduced onto the vertical optical axis Ov. Then, the beam is condensed by the focus lens 15 and irradiated to the groove welding portion 16 with the beam spot BS. The reflection mirror 14 is swingably supported by a weaving drive device (electric motor or the like) 17, and the beam spot BS is moved to the welding line WL by swinging the reflection mirror 14 with a predetermined amplitude and frequency. Weaving into a wave shape having peaks and valleys in the intersecting (orthogonal) direction. Here, the amplitude of the weaving waveform is set corresponding to the groove width W of the groove weld portion 16. Corresponding to the output and size of the beam spot BS, the frequency (period) of the weaving waveform is set in the range of several tens to several hundreds Hz.

The laser welding apparatus can be used for a metal plate having a thickness of about 15 mm to about 150 mm as a base material, and can be used for a narrow groove having a groove width W of about 3 mm to about 15 mm.
[Groove part monitoring device]
An entrance-side dichroic mirror (detection mirror) 18 and an exit-side dichroic mirror (illumination mirror) 19 each including a dichroic mirror that transmits the wavelength of the laser light are disposed on the optical axis Ov. These dichroic mirrors 18 and 19 transmit the laser beam LB and reflect visible light and near-infrared light with a predetermined reflectance, and are arranged with an inclination of 45 ° with respect to the optical axis Ov.

  Corresponding to the exit side dichroic mirror 19, an illumination light source 20 that irradiates the groove welding portion 16 with illumination light is installed. In addition, one imaging device 21 and two photosensors 22 and 23 are arranged corresponding to the entrance-side dichroic mirror 18.

  That is, the imaging dichroic mirror 24, the sensing condensing lens 25, and the sensing dichroic mirror 26 are sequentially arranged on the branch optical axis Os1 incident from the entrance-side dichroic mirror 18. On the branched optical axis Os2 of the imaging dichroic mirror 24, the imaging device 21 is installed via a band cutoff filter 27 for cutting light having the same wavelength as the laser beam LB. The imaging device 21 captures an image of the groove welding portion 16 from the optical axis Ov, and includes a high-speed shutter capable of capturing 40 to 200 frames / second. Further, an optical filter that irradiates the groove welding portion 16 with illumination light having a single wavelength selected from the illumination light source 20 and passes the illumination light preferentially from the reflected light is used in combination with the band cutoff filter 27. By doing so, an image excellent in contrast can be obtained. The exit side dichroic mirror 19 can be set at an arbitrary position on the optical axes Oh and Ov, and the installation position of the illumination light source 20 is not limited to the position shown in FIG.

[Control device]
The control device 41 provided in the laser welding apparatus outputs a weaving waveform signal to the weaving control unit 17 a that controls the weaving drive device 17, the shutter control unit 21 a that controls the imaging device 21, and the weaving drive device 17. The operation output unit 42 to be controlled, the image processing / determination unit 51 to which imaging data is input from the image output unit 21b of the imaging device 21, and the detection data of the groove walls 32R, 32L from the image processing / determination unit 51 Each of them has a signal comparison / determination unit 54 to be inputted.

  As shown in FIG. 3, the operation output unit 42 includes a transmitter 43, a frequency divider 44, an address counter 45, a waveform table 46 (Sin table), a DA converter 47, an R position comparator 48R, and an L position comparator 48L. A shutter position setting unit 49 and an OR calculator 50 are provided. The transmitter 43 is, for example, a voltage control type transmitter that sets the weaving frequency, and can adjust the transmission frequency from the outside. The frequency divider 44 sets the frequency transmitted from the transmitter 43 to 1 / n. For example, the address counter 45 divides one cycle of the Sin waveform into m and writes the calculated value to the memory of the waveform table 46. The address (address) for repeating one cycle is stored in the memory value of the waveform table 46. ) Is specified. Then, the Sin waveform is output as a weaving waveform signal to the weaving control unit 17a of the weaving drive device 17 via the DA converter 47 every cycle in which this address is repeated.

Therefore, the weaving frequency (period) can be changed by changing the transmission frequency of the transmitter 43 or changing the number of divisions in the frequency divider 44.
Although the weaving waveform in the waveform table 46 is a Sin waveform here, a triangular waveform or a trapezoidal waveform can be output as a weaving waveform by controlling the weaving drive device 17 using a galvanometer capable of controlling current. it can.

The operation output unit 42 outputs an imaging trigger signal to the shutter control unit 21a, whereby the shutter of the imaging device 21 is operated at high speed.
The signal comparison / determination unit 54 compares the detection data of the groove walls 32R and 32L input from the image processing / determination unit 51, and outputs a warning signal when the displacement amount of each position is larger than a predetermined threshold. Can be output.

Further, a display device 55 for displaying the positions of the groove walls 32R and 32L, the groove width W, and the groove center C based on the input data, and an alarm device 56 for issuing an alarm are provided.
(Imaging trigger signal)
The operation output unit 42 is an imaging device when the beam spot BS is moving within a range of 7% to 15% of the amplitude E of the weaving from a position where the beam spot BS has passed the turning points 57R and 57L of the weaving peaks or valleys. An imaging trigger signal is output to the shutter control unit 21a so that the shutter 21 is driven.

  In other words, when the beam spot BS moves within the range of 7% to 15% of the amplitude E of the weaving from the position where the turning points 57R and 57L of the weaving peaks or troughs pass. As shown in FIG. 5, the distance A in the amplitude direction between the turning points 57R and 57L and the beam spot BS passing through the turning points 57R and 57L is within the range of 7% to 15% of the amplitude E of the laser beam LB. It is when it is included.

  That is, as shown in FIG. 3, the R-side position comparator 48R and the L-side position comparator 48L provided in the operation output unit 42 each have a counter address value corresponding to the angle of the Sin signal as a comparison value. When the accumulated value of the Sin signal output from the address counter 45 matches the L-side shutter setting value or the R-side shutter setting value, it is determined as the imaging position. The L-side shutter setting value and the R-side shutter setting value are such that the distance A between the turning points 57R, 57L and the beam spot BS passing through the turning points 57R, 57L is in the range of 7% to 15% of the amplitude E of the laser beam LB. When included, the imaging trigger signal is set to be output to the shutter control unit 21a of the imaging device 21 via the OR calculator 50.

(Imaging device and image processing / determination unit)
FIG. 2 shows a screen when the imaging device 21 is not welded, and a groove weld portion 16 having groove walls 32R, 32L is formed between the left and right base materials 31R, 31L. Reference numeral 33 denotes a shielding gas nozzle, and 34 denotes a filler filled in the groove weld portion 16.

  The image processing / determination unit 51 obtains the average value of the luminous intensity of the pixels j1 to j2 of the pixel rows i1 to i2 in a predetermined range along the welding direction from the image photographed by the imaging device 21. Then, the pixel columns L (i) and R (i) having a large gradient of light intensity with respect to the light intensity of the pixels in the adjacent pixel columns are determined as the positions of the groove walls 32R and 32L of the welding groove portion 16. It is configured.

  For example, in FIG. 6A, the distance A in the amplitude direction between one folding point 57R and the beam spot BS that has passed through the folding point 57R is about 12.5% of the amplitude E of the laser beam LB. Sometimes it is an image of the groove welded portion 16 imaged by the imaging device 21, and is imaged in the area of pixels i1 to i2 in the amplitude direction (left-right direction) and pixels j1 to j2 in the height direction (weld line direction). Yes.

  Further, as shown in FIG. 6B, if P (i, j) is the brightness of the pixel (i, j),

The average value f (i) of the brightness of the pixels j1 to j2 in each pixel column i1 to i2 is expressed by the expression (1).

In adjacent pixels i + 2 to i-2 columns,
R (i) = {f (i−2) + f (i−1)} − {f (i + 1) + f (i + 2)} (iR in which R (i) represented by the equation (2) is the maximum value) It is determined that there is a right groove wall 32R.

In FIG. 7A, the distance A in the amplitude direction between the other turning point 57L and the beam spot BS that has passed through the turning point 57L is about 12.5% of the amplitude E of the laser beam LB. In the same manner as described above, the average value f (i) of the brightness of the pixels j1 to j2 in each of the pixel columns i1 to i2 is obtained (FIG. 7). (See (b)),
L (i) = {f (i + 2) + f (i + 1)} − {f (i−1) + f (i−2)} (iL in which L (i) expressed by the equation (3) is the maximum value. It is determined that there is a left groove wall 32L.

Further, the groove width W = iR−iL and the center C of the groove welded portion 16 = (iR + iL) / 2.
In the image processing / determination unit 51, the position of the groove walls 32R and 32L of the groove welding part 16, the groove width W, and the groove center C of the groove welding part 16 are obtained by the above image processing.

Hereinafter, the operation of the above configuration will be described.
The control device 41 performs the following control.
As shown in FIGS. 5 and 8, first, weaving of the laser beam LB is started with a normal amplitude E corresponding to a normal groove width W that does not include an error of the groove weld portion 16 (S-1). Then, after the beam spot BS has passed through one folding point 57R and folded, the distance A in the amplitude direction between the folding point 57R and the beam spot BS is within a range of 7% to 15% of the amplitude E of the laser beam LB. Whether it is included is determined as follows (S-2). That is, the determination in S-2 is made based on whether or not the address counter setting value and the R-side shutter setting value match, and if the address counter setting value and the R-side shutter setting value match, the distance It is determined that A is included in the range of 7% to 15% of the amplitude E, and the groove welding portion 16 is imaged by the imaging device 21 (S-3).

  At this time, since the gap between the one groove wall 32R and the beam spot BS is larger than the gap between the one groove wall 32R and the one folding point 57R, the one groove wall 32R is emitted while the plasma emits light. And the beam spot BS flow along the one groove wall 32R to the front F in the longitudinal direction of the welding line WL. Due to such a phenomenon, as shown in FIG. 6A, plasma light 60 transmitted from the beam spot BS along the one groove wall 32 </ b> R to the front F in the longitudinal direction is generated. A region including 16 beam spots BS and plasma light 60 is imaged.

  Then, as described above, the image processing / determination unit 51 obtains the average value f (i) of the luminous intensity from the captured image, and as shown in FIG. 6B, among the pixel columns along the welding line WL. The pixel row having a large luminous intensity is determined as the plasma light 60, and the pixel row R (i) having a large luminous intensity gradient of the adjacent pixel row outside the welding line WL of the plasma light 60 is opened on one side of the welding groove portion 16. The position of the front wall 32R is determined (S-4).

  Thereafter, similarly to S-2 to S-4, when the beam spot BS turns back through the other groove wall 32L on the opposite side, the distance A in the amplitude direction between the turning point 57L and the beam spot BS is Whether it is included in the range of 7% to 15% of the amplitude E of the laser beam LB is determined as follows. That is, this determination is made based on whether or not the address counter setting value matches the L-side shutter setting value. If the address counter setting value and the L-side shutter setting value match, the distance A is It is determined that it is included in the range of 7% to 15% of the amplitude E, and the groove welding portion 16 is imaged by the imaging device 21.

  At this time, since the distance between the other groove wall 32L and the beam spot BS is larger than the distance between the other groove wall 32L and the other folding point 57L, the other groove wall 32L while the plasma emits light. Between the beam spot BS and the beam spot BS along the other groove wall 32L to the front F in the longitudinal direction of the welding line WL. Due to such a phenomenon, as shown in FIG. 7A, plasma light 60 transmitted from the beam spot BS to the front F in the longitudinal direction along the other groove wall 32 </ b> L is generated, and the groove welding portion is formed in the imaging device 21. An area including the light of the 16 beam spots BS and the plasma light 60 is imaged.

  Then, the image processing / determination unit 51 obtains an average value f (i) of the luminous intensity from the photographed image, and, as shown in FIG. 7B, a pixel having a high luminous intensity in the pixel row along the welding line WL. The column is determined to be the plasma beam 60, and the pixel column L (i) having a large gradient of the luminous intensity of the adjacent pixel column outside the welding line WL of the plasma beam 60 is defined as the position of the other groove wall 32L of the weld groove 16. Judge.

  The groove width W and the groove center C of the groove welded part 16 are obtained based on the position of the one groove wall 32R and the position of the other groove wall 32L detected in this manner. The amplitude E of the laser beam LB is corrected according to the groove width W and the groove center C, the beam spot BS is swung with the corrected amplitude E, and the above steps S-2 to S-5 are repeated in order. The pre-welded part 16 is welded.

  As a result, the positions of the groove walls 32R and 32L can be detected with high accuracy, and the groove width W and the groove center C are accurately determined based on the detected positions of the groove walls 32R and 32L. Since it can be detected well, the weaving driving device 17 is controlled on the basis of the detected groove width W even if the actual groove width W slightly changes due to processing errors or the influence of heat. Thus, the amplitude E of the laser beam LB can be accurately corrected (adjusted) in accordance with the change in the groove width W.

  In FIG. 6, the distance A (see FIG. 5) between the one turning point 57R and the beam spot BS passing through the turning point 57R is a value of about 12.5% of the amplitude E of the laser beam LB. This is an image of the groove welded part 16 when it becomes, and the plasma light 60 is clearly projected.

  On the other hand, as a reference example, FIG. 9 is an image of the groove weld 16 when the distance A is 0, that is, when the beam spot BS moves to one folding point 57R. Therefore, it is difficult to detect the position of one groove wall 32R with high accuracy based on the plasma light 60.

  As another reference example, FIG. 10 is an image of the groove welded portion 16 when the distance A becomes a value of about 25% of the amplitude E of the laser beam LB. Therefore, it is difficult to detect the position of one groove wall 32R with high accuracy based on the plasma light 60.

  The welding conditions relating to the images shown in FIGS. 6, 7, 9, and 10 are laser output: 6000 W, welding speed: 200 mm / second, laser oscillation frequency: 20 Hz, and the imaging conditions are the camera used. : Photonfocus MV1-D1312-160-CL (monochrome CMOS camera), shooting speed: 13.3 frames / second, exposure time: 0.2 ms, no external illumination.

  Further, FIGS. 11 to 21 are images of the groove weld 16 when the distance A (see FIG. 5) is a value of 5.9% to 17.7% of the amplitude E of the laser beam LB. . According to this, in the images shown in FIGS. 13 to 18, the distance A is 7.1%, 7.8%, 8.5%, 9.2%, 13.1% of the amplitude E of the laser beam LB, This is a case where the value is 14.9%, and it is recognized that the plasma light 60 is generated along one groove wall 32R. In contrast, in the remaining images shown in FIGS. 11, 12, and 19 to 21, the distance A is 5.9%, 6.5%, 15.8%, 16 of the amplitude E of the laser beam LB. The values are 0.7% and 17.7%, and the generation of the plasma light 60 is not recognized. For this reason, it is considered that the plasma light 60 is generated when the distance A is included in the range of 7% to 15% of the amplitude E of the laser beam LB.

  The welding conditions relating to the images shown in FIGS. 11 to 21 are laser output: 6000 W, welding speed: 150 mm / sec, laser light oscillation frequency: 20 Hz, and the shooting conditions are: Camera used: NAC Image Technology GX -8 (high speed camera), photographing speed: 5000 frames / second, external illumination: 40 W semiconductor laser (wavelength 940 nm), and a bandpass filter having a transmission wavelength near 940 nm was used during photographing.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIGS.
In the first embodiment described above, as shown in FIGS. 6 and 7, the image processing / judgment unit 51 has groove walls 32 </ b> R and 32 </ b> L based on the captured images of the beam spot BS and the plasma light 60. However, in the second embodiment, as shown in FIGS. 22 and 23, the image processing / determination unit 51 sets the beam spot BS in the longitudinal direction F from the beam spot BS. An image region 63 that does not include the plasma light 60 is selected. Based on the image of the image region 63, the groove wall 32R of the groove weld 16 is determined from the gradient of the luminous intensity, as in the first embodiment. The position of 32L is determined. The image area 63 is a rectangular area surrounded by a white line shown in FIGS.

  According to this, the same effect as that of the first embodiment can be obtained, and in particular, as shown in FIGS. 22A and 23A, the image region 63 does not include the beam spot BS. As shown in FIG. 22B and FIG. 23B, the luminous intensity graph obtained from the image in the image area 63 hardly includes the luminous intensity of the beam spot BS, and most of the luminous intensity is only the plasma light 60. Therefore, the positions of the groove walls 32R and 32L can be determined with high accuracy.

  Even if the beam spot BS protrudes outward from one groove wall 32R due to some external factor or the like, the plasma light 60 is generated along the one groove wall 32R. The influence of the light of the beam spot BS is excluded, and the position of one groove wall 32R can be determined with high accuracy based on the gradient of the luminous intensity of the plasma light 60 in the image region 63. Similarly, the position of the other groove wall 32L can be determined with high accuracy.

  In the first embodiment, since the position of one groove wall 32R is detected based on the gradient of the luminous intensity of both the beam spot BS and the plasma light 60, the beam is caused by some external factor. When the spot BS protrudes outward from one of the groove walls 32R, the pixel position where the light intensity gradient increases may be shifted outward from the actual position of the one groove wall 32R. There is a possibility that the detection accuracy of the position of the wall 32R is lowered. This also applies to the case where the position of the other groove wall 32L is detected.

  In FIG. 22, the distance A (see FIG. 5) between the one turning point 57R and the beam spot BS passing through the turning point 57R is about 12.5% of the amplitude E of the laser beam LB. This is an image of the groove weld 16 at the time, and the plasma light 60 is clearly projected in the image region 63.

  On the other hand, as a reference example, FIG. 24 is an image of the groove weld 16 when the distance A is 0, that is, when the beam spot BS moves to one folding point 57R. The plasma light 60 is not clearly recognized.

  As another reference example, FIG. 25 is an image of the groove welded portion 16 when the distance A is about 25% of the amplitude E of the laser beam LB. However, the generation of the plasma light 60 is not clearly recognized.

  The welding conditions relating to the images shown in FIGS. 22 to 25 are laser output: 6000 W, welding speed: 200 mm / second, laser oscillation frequency: 20 Hz, and the shooting conditions are the camera used: MV1-D1312 manufactured by Photonfocus -160-CL (monochrome CMOS camera), shooting speed: 13.3 frames / second, exposure time: 0.2 ms, no external illumination.

  In each of the above-described embodiments, as shown in FIG. 5, after the beam spot BS passes through the folding points 57R and 57L, the distance A between the folding point 57R and the beam spot BS is used as an index, and this distance A is the laser beam LB. In the case of being included in the range of 7% to 15% of the amplitude E, the groove weld 16 is imaged by the imaging device 21, but the beam spot BS is turned back using time instead of the distance A as an index. The groove weld 16 may be imaged by the imaging device 21 when a predetermined time has elapsed after passing through the points 57R and 57L.

  In addition, about the welding conditions and imaging | photography conditions regarding an image, not only the specific example described in said each embodiment but the plasma light 60 can be imaged clearly according to the performance of a laser welding apparatus or the imaging device 21, etc. What is necessary is just to select the optimal welding conditions and imaging | photography conditions which can be performed suitably. Further, the conditions for imaging when the distance A shown in FIG. 5 is included in the range of 7% to 15% of the amplitude E of the laser beam LB are the welding conditions shown in the first and second embodiments. In the imaging conditions, the plasma light 60 extending along the groove walls 32R and 32L is clearly imaged. If the plasma light 60 can be clearly imaged in other welding conditions and imaging conditions, Even when the distance A is not within the range of 7% to 15% of the amplitude E of the laser beam LB, or when the beam spot BS is at a position near the peak or valley of the weaving waveform, the distance A It is also possible to obtain the groove width W and the groove center C by imaging the plasma light 60 of the pre-welded part 16 and judging the positions of the groove walls 32R and 32L of the groove weld part 16 from the image.

  In each of the above-described embodiments, as shown in FIG. 1, the image of the groove welded portion 16 is captured from the optical axis Ov of the laser beam LB using the imaging device 21. Can be observed from other than the optical axis Ov.

  Further, in each of the above embodiments, as shown in FIG. 5, the beam spot BS is weaved into a wave shape having a peak and a valley in a direction orthogonal to the welding line. Even a weaving that moves to the front F or a weaving that moves to the front F while drawing an ∞ symbol can be monitored by appropriately setting imaging conditions.

  The image by the imaging device 21 may be selected as appropriate according to the welding conditions in the wavelength range from visible light to near-infrared region generated during laser welding, and can also be captured through a filter such as a deflection filter. .

14 Reflection mirror (mirror for weaving)
16 Groove welded portion 17 Weaving drive device 21 Imaging device 32R, 32L Groove wall 41 Control device 42 Operation output unit 51 Image processing / judgment unit 57R, 57L Turn-around point 60 Plasma light 63 Image region BS Beam spot C Groove center E Laser beam amplitude LB Laser beam Oh, Ov Optical axis W Groove width WL Welding line

Claims (6)

A laser welding apparatus for welding along a weld line of a groove weld while monitoring the groove weld,
A weaving mirror disposed on the optical axis of the laser beam so as to freely swing;
A weaving driving device that swings the weaving mirror to weave the beam spot into a shape having a peak and a valley; and
An imaging device that captures an image of the groove weld;
A control device having an operation output unit and an image processing / determination unit that outputs a weaving waveform signal to the weaving driving device and outputs an imaging trigger signal to the imaging device;
The imaging device operated based on the imaging trigger signal has a beam spot in the vicinity of the peak or valley, and plasma light extending forward from the beam spot along the groove wall of the groove weld. Image
The image processing / determination unit has a groove portion monitoring device that determines a groove width and a groove center by determining a position of a groove wall of a groove welding portion from the image including the plasma light. Laser welding equipment. The operation output unit drives the shutter of the imaging apparatus when the beam spot moves within the range of 7% to 15% of the amplitude of the weaving from the position where the beam spot passes through the turning point of the peak or valley. An imaging trigger signal is output to the laser welding apparatus having a groove portion monitoring device according to claim 1. The image processing / determination unit selects an image area that is ahead of the beam spot of the captured image and does not include the beam spot but includes plasma light, and determines the position of the groove wall based on the image area. A laser welding apparatus comprising the groove monitoring device according to claim 1. The image processing / determination unit determines that a pixel column having a high luminous intensity among the pixel columns along the welding line is plasma light, and opens a pixel column having a large luminous intensity gradient between adjacent pixel columns outside the plasma light welding line. It is judged that it is a front wall. The laser welding apparatus which has a groove part monitoring apparatus of Claim 3 characterized by the above-mentioned. A laser beam irradiated along the optical axis is irradiated to a groove welded portion through a weaving mirror, and a beam spot irradiated to the groove welded portion by swinging the weaving mirror is defined as a peak portion. Weaving into a shape with a valley,
A beam spot is imaged in the vicinity of the peak or valley and the plasma light extending forward from the beam spot along the groove wall of the groove weld,
A groove part monitoring method for a laser welding apparatus, wherein a groove width and a groove center are obtained by determining a position of a groove wall of a groove weld part from an image including the plasma light. 6. The plasma light is imaged when a beam spot is moving within a range of 7% to 15% of the amplitude of the weaving from a position where the beam spot passes through the turning point of the peak or valley. The groove part monitoring method of the laser welding apparatus of description.