JP4777856B2 - Laser welding equipment - Google Patents

Description

  The present invention relates to a laser welding apparatus for performing welding on an object to be welded by cooperation of a laser beam and an assist gas.

  There is known a laser welding apparatus that injects an assist gas toward a portion to be irradiated with laser light. For example, the laser welding apparatus described in Patent Document 1 includes a movable gas supply nozzle. In this laser welding apparatus, a target value of the assist gas injection angle is set in accordance with welding conditions such as the material of the workpiece, the plate thickness, and the welded surface shape. In the laser welding apparatus, the deviation from the target value is calculated based on the injection angle detected by the sensor, and the gas supply nozzle is tilted so that the deviation is eliminated by feedback control of an actuator such as a servo motor.

JP-A-5-208291

  However, if feedback control is continuously performed from the start to the end of welding, the injection angle of the gas supply nozzle does not settle at the target value, and there is a possibility that the control of the divergent system is performed. In particular, when the positioning performance of the actuator having the servo motor is inferior to the position detection performance of the sensor, a slight vibration occurs in the gas supply nozzle when the control is a divergent system. Furthermore, the servo motor is more likely to deteriorate with age than the sensor, and the gas supply nozzle is likely to vibrate as it continues to be used.

  An object of the present invention is to provide a laser welding apparatus in which misalignment of an assist gas is less likely to occur while reliably preventing misalignment of a gas supply nozzle.

The present invention relates to a laser welding apparatus comprising: a laser head that irradiates an object to be welded with laser light; and a gas supply nozzle that injects an assist gas obliquely toward the irradiated portion of the laser light. A movable nozzle actuator , and a welding state detection unit that detects at least one change in light intensity of plasma and plume indicating a melting state of the irradiated portion, light intensity of laser light reflected on the surface, and temperature of the molten pool The gas supply nozzle only when it is determined that there is a welding abnormality by the welding abnormality determination unit and the welding abnormality determination unit that determines whether there is a welding abnormality due to the assist gas based on the output signal from the welding state detection unit and outputs a drive signal to the actuators so as to return to the set state of the initial position so that the temperature of the pre-molten pool becomes highest point activator Characterized in that a mediator controller.

According to this laser welding apparatus, the assist gas is based on at least one change in the light intensity of the plasma and plume indicating the molten state of the irradiated portion, the light intensity of the laser light reflected on the surface, and the temperature of the molten pool. Whether or not there is a welding abnormality due to this is determined. The laser welding apparatus returns the gas supply nozzle to the preset initial position only when it is determined that there is a welding abnormality, and when it is not determined that there is a welding abnormality, the gas supply nozzle is in the initial position. Even if it is deviated from the initial position, it does not return to the initial position where the temperature of the molten pool is the highest . As a result, compared with the case where the gas supply nozzle is moved so as to eliminate the deviation from the initial position by feedback control, it becomes difficult to control the diverging system, and the gas supply nozzle is hardly vibrated.

  Further, it is preferable that the initial position is set in advance by the front / rear / left / right positions of the gas supply nozzle. When the gas supply nozzle is shifted back and forth or left and right from the initial position as the laser beam is scanned, control is performed to return the gas supply nozzle to the initial position by front and rear and right and left operations.

  Furthermore, an image sensor that captures the intersection between the tube axis of the gas supply nozzle and the object to be welded, and a displacement from the reference intersection of the tube axis of the gas supply nozzle at the initial position and the object to be welded to the intersection imaged by the image sensor A displacement calculating unit for determining the position of the nozzle actuator, wherein the nozzle actuator supports the gas supply nozzle movably back and forth and right and left, translates the gas supply nozzle, and the actuator control unit returns to the initial position. It is preferable to output a drive signal that translates the gas supply nozzle by a correction amount that returns the displacement obtained by the displacement calculation unit. The intersection of the tube axis of the gas supply nozzle and the welded body is a position where the assist gas is actually injected on the welded body. Only when it is determined that there is a welding abnormality, in this laser welding apparatus, the gas supply nozzle returns to the state where the assist gas is injected toward the reference intersection, and the welding abnormality is resolved.

  According to the present invention, misalignment of the gas supply nozzle is reliably prevented, and welding abnormality due to the assist gas is less likely to occur.

  Hereinafter, preferred embodiments of a laser welding apparatus according to the present invention will be described in detail with reference to the drawings.

[ First Embodiment]
(Laser welding equipment)
As shown in FIGS. 1 to 3 , the laser welding device 50 is a welding device that uses a YAG (Yttrium Aluminum Garnet) laser as a heat source for welding, and laser light L toward a stainless steel plate W as a body to be welded. And a gas supply nozzle 53 for injecting the assist gas G obliquely toward the irradiated portion S near the focal point of the laser beam L. The laser head 52 and the gas supply nozzle 53 move along a straight joining line SS at a place where the two plate materials W overlap. In the following description, the front, rear, left, and right will be described with reference to the traveling direction of the laser head 2, and the irradiation direction of the laser light L will be described below, and vice versa.

  The laser head 52 includes a laser oscillation unit 52b in a case 52a. The YAG laser is an optically pumped solid laser, and the laser oscillation unit 52b emits a laser beam L having an oscillation wavelength of 1.06 μm. A condensing lens 52c made of optical glass is disposed on the optical axis LS of the laser light L, and the laser light L transmitted through the condensing lens 52c is condensed at an extremely small point.

  Further, a reflecting mirror 2d (see FIG. 3) is provided in the case 52a, and a photosensor unit 54 is provided in the vicinity of the reflecting mirror 2d. The photo sensor unit 54 includes a first photo sensor (welding state detection unit) 54a that detects light intensity of plasma and plume generated on the surface of the plate material W by irradiation of laser light, and a laser that reflects on the surface of the plate material W. A second photosensor (welding state detection unit) 54b for detecting the light intensity of the light L, and a third photosensor (welding state detection unit) 54c for detecting the temperature of the molten pool M generated by the irradiation of the laser light L; It has.

  The first photosensor 54a detects light having a wavelength of about 300 nm to about 800 nm, excluding the wavelength of the laser light L. The first photosensor 54a outputs an output signal corresponding to the light intensity of the plasma and an output signal corresponding to the light intensity of the plume. The output signal corresponding to the light intensity of the plasma and the output signal corresponding to the light intensity of the plume may be output together, or may be output separately by a band pass filter or the like. The output signal from the first photosensor 54a is input to the CPU 64 of the main control processing unit 68 described in detail later.

  The second photosensor 54b outputs an output signal corresponding to the intensity of light having the same wavelength as the laser light L, and the third photosensor 54c outputs an output signal corresponding to the light intensity of light in the infrared region excluding the wavelength of the laser light L. Is output. Each of these output signals is input to the CPU 64 of the main control processing unit 68 described in detail later.

  The intensity of light having a wavelength of about 300 nm to about 800 nm detected by the first photosensor 54a, the intensity of light having the same wavelength as the laser light L detected by the second photosensor 54b, and the third photosensor 54c. The light intensity in the infrared region is a physical quantity that changes according to the state of the molten pool M generated in the irradiated portion S of the laser light L, and these physical quantities indicate the molten state of the irradiated portion S.

  The case 52a of the laser head 52 is provided with a bracket 52e protruding rearward with respect to the traveling direction of the laser head 2, and the first linear actuator 55 is attached to the bracket 52e. The first linear actuator 55 has a servo motor and a ball screw formed on the output shaft of the servo motor, and linearly moves to the left and right with respect to the bracket 52e by the rotation of the ball screw. A second linear actuator 56 is attached to the first linear actuator 55. The second linear actuator 56 also has the same servo motor and ball screw as the first linear actuator 55, and linearly moves back and forth with respect to the first linear actuator 55 by the rotation of the ball screw. A rod 56b protruding downward is provided at the end 56a of the second linear actuator 56. The first and second linear actuators 55 and 56 constitute a nozzle actuator 59.

  A U-shaped nozzle bracket 56c is provided at the tip of the rod 56b. The nozzle bracket 56c is provided with a pair of left and right side walls 56d and 56e so as to sandwich the gas supply nozzle 53, and a slit SL is formed in each of the side walls 56d and 56e. In the pair of slits SL, a pair of screw portions 53a and 53b protruding in the horizontal direction from the gas supply nozzle 53 are inserted. The screw parts 53 a and 53 b are provided in the vicinity of the rear end 53 e of the gas supply nozzle 53 and extend orthogonal to the tube axis NS of the gas supply nozzle 53. Nuts 53c and 53d are screwed onto the tip portions of the screw portions 53a and 53b in a state of protruding from the side walls 56d and 56e. The gas supply nozzle 53 is fixed to the nozzle bracket 55c with the tube axis NS inclined with respect to the optical axis LS by tightening the nuts 53c and 53d.

  A hose 53h for supplying the assist gas G is fixed to the peripheral wall near the rear end 53e of the gas supply nozzle 53 via a pipe joint portion 53g. The compressed assist gas G is supplied into the gas supply nozzle 53 through the hose 53h, and is injected toward the molten pool M from the tip 53f of the gas supply nozzle 53.

  A CCD camera (imaging device) 57 is fixed to the rear end 53 e of the gas supply nozzle 53. The CCD camera 57 is a camera including an electronic coupling element that sequentially outputs charges accumulated according to the amount of light in time series. The field of view of the CCD camera 57 is a range recognized through the inside of the gas supply nozzle 53, and the optical axis of the CCD camera 57 and the tube axis NS of the gas supply nozzle 53 coincide. The CCD camera 57 outputs two-dimensional image data for each sampling period as an output signal. The two-dimensional image data is determined by the number of output pixels in a plurality of rows and a plurality of columns each having a luminance of a predetermined number of gradations. A predetermined range including the intersection of the tube axis NS and the plate material W is imaged by the CCD camera 57.

Further, the lens of the CCD camera 57, ND filter (FIGS shown omitted) is attached. By attaching the ND filter, the amount of incident light from the molten pool M that is at a high temperature can be suppressed, and the CCD camera 57 can accurately image information relating to the light intensity of the molten pool M.

The gas supply nozzle 53 is supported by a nozzle actuator 59 so as to be movable in the front-rear and left-right directions. The gas supply nozzle 53 has an initial position set in advance based on the front, rear, left, and right positions based on the irradiated portion S of the laser light L.

  The laser head 52 irradiates the laser beam L toward the linear joining line SS where the two plates W on the welding table 13 overlap, and moves linearly on the welding table 13 by the operation of the manipulator 62. To do. As the laser head 2 moves, the irradiated portion S of the laser light L is scanned along the planned joining line SS. A molten pool M is generated in the irradiated portion S of the laser light L, and after the irradiated portion S has passed, a laser welded portion LJ is formed.

As shown in FIG. 3 , the laser welding apparatus 50 includes a main control processing unit 68 configured by a CPU 64, a ROM 66, a RAM 67, and the like connected via a bus. The CPU 64 is connected to the manipulator 62, the laser oscillator 62b, the servo motors of the first and second linear actuators 55 and 56, and the CCD camera 57 so that signals can be transmitted and received by wire or wirelessly.

The CPU 64 controls the operation of the entire laser welding apparatus 50, and in particular, a laser scanning control unit 64 a that controls the irradiation intensity and laser scanning speed of the laser light L and a welding abnormality based on an output signal from the photosensor unit 4. A welding abnormality determination unit 64b for determining presence or absence. Further, the CPU 64 specifies an intersection (hereinafter referred to as “measurement intersection”) X1 between the tube axis NS of the gas supply nozzle 53 and the plate material W based on an output signal from the CCD camera 57, and the gas supply nozzle 53 of the initial position. A displacement calculation unit 64c that obtains an intersection displacement from the reference intersection X2 between the tube axis NS and the plate material W to the measurement intersection X1 and a drive signal that translates the gas supply nozzle 53 so as to return the intersection displacement are output to the nozzle actuator 59. And an actuator controller 64d. Incidentally, CPU 64 is also connected signal can be transmitted and received on the touch panel 69 as a control valve for opening and closing a flow path of the assist gas G supplied to the gas supply nozzle 53 (Figure shown shown) and an operation unit.

  The laser scanning control unit 64 a outputs an irradiation intensity setting signal for setting the irradiation intensity of the laser beam L to the laser oscillation unit 52 b and an ON / OFF signal regarding the start and stop of the irradiation of the laser beam L, and further to the manipulator 62. A speed setting signal for setting the laser scanning speed, a laser scanning start signal, and a laser scanning stop signal are output.

The welding abnormality determination unit 64b determines whether there is a welding abnormality caused by the assist gas G. When a laser scanning start signal is output from the laser scanning control unit 64a, the welding abnormality determination unit 64b starts acquiring three types of output signals from the photosensor unit 4, and displays waveform patterns with respect to the time axis of each output signal. Generate and determine the presence or absence of welding abnormality from the waveform pattern.

The displacement calculation unit 64c is configured to measure the intersection X1 between the tube axis NS of the gas supply nozzle 53 and the plate material W (see FIGS . 11 to 13 ) based on an output signal related to the two-dimensional image data input from the CCD camera 57 to the CPU 64 . ). Further, the displacement calculator 64c obtains the approximate distance d1 and the direction of deviation between the reference intersection point X2 and the measurement intersection point X1 between the tube axis NS of the gas supply nozzle 53 at the initial position and the plate material W as the intersection displacement. Further, the displacement calculation unit 64c obtains the movement amount d2 and the movement direction in the front-rear and left-right directions for returning the intersection displacement d1 as correction values. The approximate distance d1 is the distance between the measurement intersection X1 on the two-dimensional image captured by the CCD camera 57 and the reference intersection X2, and the movement amount d2 takes into account the inclination of the gas supply nozzle 53, and In order to eliminate the approximate distance d1, this is a distance by which the gas supply nozzle 53 is translated in the forward / backward / left / right direction.

  The actuator control unit 64b outputs a drive signal corresponding to the correction value obtained by the displacement calculation unit 64c to return the gas supply nozzle 53 to the initial position, and inputs the drive signal to the nozzle actuator 59 to input the gas supply nozzle 53. Is translated.

(Laser welding method)
The laser welding method using the laser welding apparatus 50 according to the third embodiment is different in nozzle control from the laser welding method using the laser welding apparatus 1 according to the first embodiment. In the following description, nozzle control will be mainly described with reference to FIGS. 3, 5, and 10 to 13 .

First, initial setting (S21) according to the operation of the touch panel 69 by the operator is performed. In the initial setting, an initial setting signal corresponding to the front / rear / left / right positions as the initial position of the gas supply nozzle 53 , the intensity of the laser beam L, and the laser scanning speed is output from the touch panel 69 and input to the CPU 64. The actuator control unit 64b of the CPU 64 outputs an initial drive signal to the nozzle actuator 59 based on the initial setting signal. Then, the nozzle actuator 59 is actuated to translate the gas supply nozzle 53 to the initial position, and hold the gas supply nozzle 53 at the initial position (see FIG. 10 ). In addition, it is preferable that the assist gas G is injected in the location where the temperature of the molten pool M is the highest. And the temperature of the molten pool M becomes the highest a little behind the irradiated part S of the laser beam L. Therefore, the reference intersection X2 between the tube axis NS of the gas supply nozzle 53 at the initial position and the plate material W is set at a position shifted rearward from the irradiated portion S (see FIG. 11 ).

Thereafter, the injection of the assist gas G, the irradiation of the laser light L, and the laser scanning are started, and nozzle control (S4) for correcting the deviation of the gas supply nozzle 53 from the initial position is executed. As shown in FIG. 14 , while laser welding is being performed, the photo sensor unit 64 detects the molten state (S21), and the CPU 64 outputs an output signal corresponding to the light intensity from the photo sensor unit 64. Have been entered. The welding abnormality determination unit 64b of the CPU 64 determines whether there is a welding abnormality due to the assist gas G based on the output signal from the photosensor unit 64 (S22).

(First aspect related to a method for determining whether there is a welding abnormality)
  With reference to FIG. 6 and FIG. 7, the 1st aspect which concerns on the determination method of the presence or absence of welding abnormality is demonstrated. FIG. 6 is a diagram illustrating an example of a waveform pattern of output signals from the first photosensor 64a and the third photosensor 64c. In the figure, the horizontal axis represents time, and the vertical axis represents output signal intensity. In the example shown in FIG. 6, the waveform pattern P1 of the light intensity of the plasma and the plume and the waveform pattern P2 of the molten pool temperature are each subjected to smoothing processing, for example, by taking a moving average value for every 100 data points. . The welding abnormality determination unit 14b monitors the waveform patterns P1 and P2, and when the light intensity of the plasma and the plume and the temperature of the molten pool M both exceed twice normal values, the “welding caused by the assist gas” It is determined that there is an abnormality.

  FIG. 7 is a diagram illustrating an example of a waveform pattern of an output signal from the second photosensor 64b. In the figure, the horizontal axis represents time, and the vertical axis represents output signal intensity. In the example shown in FIG. 7, the waveform pattern P3 of the reflected light intensity is subjected to a smoothing process, for example, by taking a moving average value for every 50 data points. In order to determine the threshold value of the waveform pattern P3, the waveform pattern P4 of the upper limit measurement value and the waveform pattern P5 of the lower limit measurement value of the reflected light intensity are measured in advance, and the minimum value of the waveform pattern P4 and the maximum value of the waveform pattern P5 are The upper limit threshold value L1 and the lower limit threshold value L2 of the waveform pattern P3 of the reflected light intensity are set. When the waveform pattern P3 exceeds the upper limit threshold L1, it is considered that the loss of the laser beam L at the irradiation position is large and the amount of penetration is insufficient. When the waveform pattern P3 is less than the lower limit threshold L2, the laser beam L It is conceivable that the loss is too small and the amount of penetration is excessive. The welding abnormality determination unit 64b monitors the waveform pattern P3, and when the reflected light intensity falls below the preset lower limit threshold L2 or exceeds the upper limit threshold L1, “there is a welding abnormality” caused by the assist gas G. to decide.

(Second aspect related to a method for determining whether or not there is a welding abnormality)
  With reference to FIG. 8 and FIG. 9, a second mode relating to a method for determining whether or not there is a welding abnormality will be described. FIG. 8 shows an example of the reference waveform pattern P10 of the light intensity of plasma / plume. In FIG. 8, the horizontal axis indicates the time from the start to the end of laser scanning, and the vertical axis indicates the intensity of the output signal. The reference waveform pattern P10 is, for example, an output signal when laser welding is normally completed as a result of performing trial laser scanning in a state of being kept constant without performing control to change the injection angle of the gas supply nozzle 53. Is a waveform pattern based on Each output value included in the reference waveform pattern P10 is normalized based on the standard deviation σ, and the standard normalized value “+ 2σ” is obtained by doubling the standard deviation σ. The welding abnormality determination unit 14b uses the reference normalized value “+ 2σ” in determining whether there is a welding abnormality. FIG. 9 is a diagram in which the measured waveform pattern P11 of the light intensity of the plasma / plume measured within a predetermined sampling time and the reference normalized value “+ 2σ” are plotted during laser welding. In FIG. 9, the horizontal axis indicates time, and the vertical axis indicates the intensity of the output signal. The welding abnormality determination unit 14b integrates the number of times that the measured waveform pattern P11 exceeds the reference normalized value “+ 2σ”, and when the number of integration exceeds a predetermined number (for example, three times) set in advance, the assist gas Judging by welding abnormality caused by The welding abnormality determination unit 14b periodically acquires and monitors the measurement waveform pattern P11. As shown in FIG. 9, for example, the number of integrations of the measurement waveform pattern P11 within a predetermined sampling time is four. In this case, it is determined that “there is a welding abnormality”.

The displacement calculation unit 64c specifies the measurement intersection X1 only when the welding abnormality determination unit 64b determines that “there is a welding abnormality” (S23), and supplies the gas at the initial position where the temperature of the molten pool is the highest. The intersection displacement of the nozzle 53 from the reference intersection X2 to the measurement intersection X1 is calculated (S24). Based on the output signal input from the CCD camera 57 to the CPU 64, the displacement calculator 64c sets the approximate distance d1 (see FIGS . 11 to 13 ) between the reference intersection X2 and the measurement intersection X1 and the shifted direction as the intersection displacement. Ask. Further, the displacement calculator 64c obtains the movement amount d2 and the movement direction for returning the intersection displacement as correction values.

  When the correction value is obtained by the displacement calculation unit 64c, the actuator control unit 64d outputs a drive signal corresponding to the correction value and inputs it to the nozzle actuator 59 in order to return the gas supply nozzle 53 to the initial position. The nozzle actuator 59 is driven based on the drive signal, and moves the gas supply nozzle 53 in parallel to return it to the initial position. As a result, the welding abnormality caused by the assist gas G is eliminated.

  According to the laser welding apparatus 50, the presence / absence of a welding abnormality caused by the assist gas G is determined based on the change in the physical quantity indicating the melted state of the irradiated portion S. The laser welding apparatus 50 returns the gas supply nozzle 53 to the preset initial position only when it is determined that “the welding abnormality is present”, and when it is not determined that “the welding abnormality is present”, the gas supply is performed. Even if the nozzle 53 deviates from the initial position, the nozzle 53 is not returned to the initial position. As a result, compared to a conventional laser welding apparatus that moves the gas supply nozzle so as to eliminate the deviation from the initial position by feedback control, it is difficult to control the divergence system, and the gas supply nozzle 53 is difficult to vibrate. Therefore, misalignment of the gas supply nozzle 53 is reliably prevented, and an abnormal welding due to the assist gas G is hardly caused.

  Furthermore, the initial position of the gas supply nozzle 53 can be set according to the front / rear / left / right positions with respect to the irradiated portion S, and the gas supply nozzle 53 is displaced forward / backward or left / right from the initial position as the laser light L is scanned. Then, control is performed so that the gas supply nozzle 53 is returned to the initial position by front / rear / right / left operations.

  Furthermore, the intersection of the tube axis NS of the gas supply nozzle 53 and the plate material W is a position where the assist gas G is actually injected on the plate material W. Then, only when it is determined that there is a welding abnormality, in this laser welding apparatus 50, the gas supply nozzle 53 returns to the state where the assist gas G is injected toward the reference intersection X2, and the welding abnormality is resolved.

  The present invention is not limited to the above embodiments, and for example, a semiconductor laser, a CO2 laser, or the like may be used as a heat source for welding. In addition, the photo sensor as the welding state detection unit is a photo sensor that detects the light intensity of plasma and plume generated on the surface of the welded body by laser light irradiation, and the light intensity of the laser light reflected on the surface of the plate material. Any two of the photosensor for detecting and the photosensor for detecting the temperature of the molten pool generated by the irradiation of the laser beam may be used in combination, or may be used alone. Furthermore, it is possible to change both the injection angle of the gas supply nozzle and the parallel movement in the front / rear / left / right direction. When there is a welding abnormality due to the assist gas, the change of the injection angle of the gas supply nozzle and the front / rear left / right Control may be performed so as to return to the initial position by performing parallel movement in the direction.

1 is a perspective view showing a first embodiment of a laser welding apparatus according to the present invention. It is sectional drawing along the II-II line of FIG. It is a block diagram of a laser welding apparatus. It is a flowchart which shows the operation | movement procedure of laser welding. It is a flowchart which shows the operation | movement procedure of nozzle control. It is a figure which shows an example of the waveform pattern of the output signal which concerns on the light intensity of plasma / plume, and the temperature of a molten pool. It is a figure which shows an example of the waveform pattern of the output signal which concerns on the light intensity of the reflected light of a laser beam. It is a figure which shows an example of the reference waveform pattern of the output signal which concerns on the light intensity of a plasma / plume. It is a figure which shows the measurement waveform pattern and reference | standard normalization value of the output signal which concern on the light intensity of the plasma / plume within sampling time. It is a perspective view of the laser welding apparatus which shows the state which sets an initial position. It is a two-dimensional image of the molten pool imaged with the CCD camera, and is a figure which shows the case where there is no intersection displacement. It is a two-dimensional image of the molten pool imaged with the CCD camera, and is a figure which shows the case where there exists an intersection displacement. It is an expanded sectional view of the tip of a gas supply nozzle and a molten pool.

DESCRIPTION OF SYMBOLS 50 ... Laser welding apparatus, 52 ... Laser head, 53 ... Gas supply nozzle, 54a ... 1st photosensor (welding state detection part), 54b ... 2nd photosensor (welding state detection part), 54c ... 3rd Photosensor (welding state detection unit) 59 ... Nozzle actuator, 64b ... Welding abnormality judgment unit, 64c ... Displacement calculation unit, 64d ... Actuator control unit, 57 ... CCD camera (imaging device), NS ... Pipe axis of gas supply nozzle , X1 ... measurement intersection, X2 ... reference intersection, C ... rotation axis, L ... laser beam, S ... irradiated part, G ... assist gas.

Claims (3)

In a laser welding apparatus comprising: a laser head for irradiating a body to be welded with a laser beam; and a gas supply nozzle for injecting an assist gas obliquely toward the irradiated portion of the laser light.
A nozzle actuator for moving the gas supply nozzle;
A welding state detection unit that detects at least one change in the light intensity of plasma and plume indicating the molten state of the irradiated part, the light intensity of laser light reflected on the surface, and the temperature of the molten pool ;
Based on an output signal from the welding state detection unit, a welding abnormality determination unit that determines whether there is a welding abnormality caused by the assist gas;
Only when it is determined by the welding abnormality determining section that there is a welding abnormality, the nozzle actuator is configured to return the gas supply nozzle to the initial position set in advance so that the temperature of the molten pool is the highest. And an actuator control unit for outputting a drive signal. The initial position, the laser welding apparatus according to claim 1, characterized in that it is preset by the longitudinal and lateral position of the gas supply nozzle. An image sensor for imaging an intersection of the tube axis of the gas supply nozzle and the welded body;
A displacement calculation unit for obtaining a displacement from a reference intersection between the tube axis of the gas supply nozzle at the initial position and the body to be welded to the intersection imaged by the imaging device;
The nozzle actuator supports the gas supply nozzle movably back and forth and left and right, and translates the gas supply nozzle,
The actuator control unit outputs the drive signal for translating the gas supply nozzle by a correction amount for returning the displacement obtained by the displacement calculation unit in order to return to the initial position state. The laser welding apparatus according to claim 2 .

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