JP4861738B2 - Laser welding equipment - Google Patents

Description

  The present invention relates to a laser welding apparatus that welds an object to be welded by cooperation of a laser and an assist gas.

  Conventionally, a laser welding apparatus that injects an assist gas toward a laser irradiation portion is known. As this type of laser welding apparatus, the assist gas is injected from the tip of the gas supply nozzle toward the laser irradiation unit, and the irradiation unit is imaged by a camera fixed to the base end of the gas supply nozzle, and the captured image Is displayed on a display device, and an assist gas spraying position is manually adjusted to an appropriate position of an irradiation unit (see Patent Document 1).

Japanese Patent No. 2624033

  In a conventional laser welding apparatus, an operator who has confirmed the captured image projected on the display device manually adjusts the assist gas spray position, and the assist gas spray position deviates from the target during laser scanning. It was difficult to correct accurately. As a result, the quality of the welded portion tends to become unstable.

  It is an object of the present invention to provide a laser welding apparatus that enables automatic correction when assist gas injected from a gas supply nozzle is displaced from a target position and facilitates maintaining stable quality of a welded portion. To do.

A laser welding apparatus according to the present invention includes a laser head that irradiates a workpiece with a laser, a gas supply nozzle that is attached to the laser head and injects an assist gas obliquely toward a molten pool caused by laser irradiation, and a gas A nozzle actuator that moves the supply nozzle, a camera that images the molten pool, a detection unit that detects a molten pool center position based on image information captured by the camera, and a molten pool center position detected by the detection unit; A nozzle controller that calculates a distance deviation from the tube axis of the gas supply nozzle and outputs a control signal for moving the gas supply nozzle to the nozzle actuator so that the distance deviation is reduced; , based on the luminance distribution image data of the molten pool that has been captured by the camera, the molten pool center position of the highest position the brightness of the molten pool It is preferable to detect by. The position where the luminance of the molten pool is highest is a position where the temperature of the molten pool is highest.

  In this laser welding apparatus, the detection unit detects the molten pool center position based on the image information of the molten pool imaged by the camera, and the nozzle control unit detects the molten pool center position and the tube axis of the gas supply nozzle. A distance deviation is calculated, and a control signal for moving the gas supply nozzle so as to reduce the distance deviation is output to the nozzle actuator. The nozzle actuator moves the gas supply nozzle based on the input control signal. As a result, the position where the assist gas sprayed from the gas supply nozzle is hardly displaced from the molten pool center position, and stable quality of the welded portion is easily maintained.

Furthermore, closely related to the luminance distribution of the molten pool in a molten state of the molten pool (e.g., temperature of the molten pool), since it is possible to recognize the molten state of the molten pool by the luminance distribution image information, using the luminance distribution image information By detecting the molten pool center position, the assist gas can be sprayed to the optimum position corresponding to the molten state of the molten pool, and the quality of the welded portion is improved.

Furthermore, the highest position is the brightness of the molten pool, the temperature of the molten pool is highest position. Then, by blowing the assist gas with the position where the luminance of the molten pool is the highest as the molten pool center position, it is possible to enhance the shielding effect of effectively preventing the molten pool from being oxidized.

  ADVANTAGE OF THE INVENTION According to this invention, the automatic correction | amendment when the assist gas injected from a gas supply nozzle has shifted | deviated from the target position is enabled, and it becomes easy to maintain the stable quality of a welding part.

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

(Laser welding equipment)
As shown in FIG.1 and FIG.2, the laser welding apparatus 1 is a welding apparatus which uses a YAG laser as a heat source for welding. A laser welding apparatus 1 includes a laser head 2 that irradiates a laser plate L toward a stainless steel plate W as an object to be welded, and an assist gas (common name) obliquely toward a molten pool M generated on the surface of the plate material W by the laser L. And a gas supply nozzle 3 for injecting G). The laser head 2 and the gas supply nozzle 3 move along a straight line to be joined SS at the place where the two plate materials W overlap.

  The laser head 2 includes a laser oscillation unit 2b in a case 2a. The YAG laser is an optically excited solid laser, and the laser oscillation unit 2b emits a laser L having an oscillation wavelength of 1.06 μm. A condensing lens 2c made of optical glass is disposed on the optical axis LS of the laser L, and the laser L transmitted through the condensing lens 2c is condensed at an extremely small point.

  In the following description, the direction orthogonal to the optical axis LS of the laser L and along the moving direction of the laser head 2 is the X-axis direction, and the direction orthogonal to the X-axis and the optical axis LS of the laser L is the Y-axis direction. The direction along the optical axis LS of the laser L will be described as the Z-axis direction.

  The case 2a of the laser head 2 is provided with a bracket 2d protruding rearward with respect to the traveling direction of the laser head 2, and the first linear actuator 4 is attached to the bracket 2d. The first linear actuator 4 has a servo motor and a ball screw formed on the output shaft of the servo motor, and linearly moves in the Y-axis direction with respect to the bracket 2d by the rotation of the ball screw. A second linear actuator 5 is attached to the first linear actuator 4. The second linear actuator 5 also has a servo motor and a ball screw similar to the first linear actuator 4, and linearly moves in the X-axis direction with respect to the first linear actuator 4 by the rotation of the ball screw. A rod 5b protruding in the Z-axis direction (downward) is provided at the end 5a of the second linear actuator 5. The first and second linear actuators 4 and 5 constitute a nozzle actuator 9.

  A U-shaped nozzle bracket 5c is provided at the tip of the rod 5b. The nozzle bracket 5c is provided with a pair of left and right side walls 5d and 5e so as to sandwich the gas supply nozzle 3, and a slit SL is formed in each of the side walls 5d and 5e. A pair of screw portions 3a and 3b protruding in the horizontal direction from the gas supply nozzle 3 are inserted into the pair of slits SL. The screw portions 3 a and 3 b are provided in the vicinity of the rear end 3 e of the gas supply nozzle 3 and extend orthogonal to the tube axis NS of the gas supply nozzle 3. Nuts 3c and 3d are screwed onto the tip portions of the screw portions 3a and 3b in a state of protruding from the side walls 5d and 5e. The gas supply nozzle 3 is fixed to the nozzle bracket 5c with the tube axis NS inclined with respect to the optical axis LS by tightening the nuts 3c and 3d.

  A hose 3h for supplying the assist gas G is fixed to a peripheral wall near the rear end 3e of the gas supply nozzle 3 via a pipe joint portion 3g. The assist gas G contains argon as an inert gas. The compressed assist gas G is supplied into the gas supply nozzle 3 through the hose 3h, and is injected toward the molten pool M from the tip 3f of the gas supply nozzle 3.

  A CCD camera 7 is fixed to the rear end 3 e of the gas supply nozzle 3. The CCD camera 7 is a camera including an electronic coupling element that sequentially outputs charges accumulated according to the amount of light in time series. The visual field of the CCD camera 7 is a range recognized through the inside of the gas supply nozzle 3, and the optical axis L of the CCD camera 7 and the tube axis NS of the gas supply nozzle 3 coincide with each other. The CCD camera 7 outputs two-dimensional image data for each sampling period as a digital 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. Further, an ND filter (not shown) is attached to the lens of the CCD camera 7. By attaching the ND filter, the amount of incident light from the molten pool M, which is at a high temperature, is suppressed, and the CCD camera 7 can accurately image information related to the luminance of the molten pool M.

  As shown in FIGS. 1 and 3, the movable arm portion 12 a of the manipulator 12 is fixed to the upper end portion of the laser head 2 via a support column portion 2 e. The manipulator 12 moves the laser arm 2 in the X-axis direction by moving the movable arm portion 12a. On the welding table 13 on which the plate material W is placed, the two plate materials W are placed in a state of being overlapped. The laser head 2 irradiates the laser L toward the linear joining line SS at the place where the two plate materials W overlap, and moves linearly on the welding table 13 by the operation of the manipulator 12. As the laser head 2 moves, the laser L is scanned along the planned joining line SS. The molten pool M is generated by the irradiation of the laser L, and after the laser L passes, the molten pool M is solidified to form the laser weld LJ.

  As shown in FIG. 3, the laser welding apparatus 1 includes a main control processing unit 18 configured by a CPU 14, a ROM 16, a RAM 17, and the like connected via a bus. The CPU 14 is connected to the manipulator 12, the laser oscillation unit 2b, the servo motors of the first and second linear actuators 4 and 5, and the CCD camera 7 so that signals can be transmitted and received by wire or wirelessly. The CPU 14 controls the operation of the entire laser welding apparatus 1. In particular, the two-dimensional image information of the molten pool M imaged by the laser scanning control unit 14 a that controls the irradiation intensity and laser scanning speed of the laser L and the CCD camera 7. (Luminance distribution image information) Detection unit 14b for detecting the center position (melt pool center position) CP (see FIGS. 6 to 8) of the weld pool M based on IM (see FIGS. 6 and 7), and a gas supply nozzle And a nozzle control unit 14c for controlling the movement of the three.

  The laser scanning control unit 14 a outputs an irradiation intensity setting signal for setting the irradiation intensity of the laser L to the laser oscillation unit 2 b and an ON / OFF signal regarding the start and stop of the irradiation of the laser L, and further to the manipulator 12. A speed setting signal for setting the laser scanning speed, a laser scanning start signal, and a laser scanning stop signal are output. Further, the detection unit 14b analyzes the position of the highest luminance from the two-dimensional image information IM of the molten pool M imaged by the CCD camera 7, and determines the position as the center position CP of the molten pool M (see FIGS. 6 to 8). ) To detect. Further, the nozzle control unit 14c is configured to determine the length of the perpendicular drawn from the center position CP of the molten pool M to the tube axis NS of the gas supply nozzle 3 based on the two-dimensional image information IM of the molten pool M captured by the CCD camera 7. The deviation distance d1 (see FIGS. 7 and 8) is calculated, and a correction control signal for moving the gas supply nozzle 3 in the horizontal direction so as to decrease the deviation distance d1 is output to the nozzle actuator 9. The CPU 14 is also connected to a control valve (not shown) that opens and closes the flow path of the assist gas G supplied to the gas supply nozzle 3 so that signals can be transmitted and received, and also outputs an open / close signal to the control valve.

  A touch panel 19 as an operation unit is connected to the CPU 14 so that signals can be transmitted and received. On the liquid crystal screen of the touch panel 19, a touch part is displayed for instructing the initial conditions of laser welding and the start of laser welding. The touch panel 19 detects a position touched by the operator's finger on the liquid crystal screen and outputs an initial setting signal based on the position information. The initial setting signal output from the touch panel 19 is input to the CPU 14, and the CPU 14 outputs various signals to the laser head 2, the manipulator 12, and the nozzle actuator 9 in order to execute control according to the initial setting signal. To do.

(Laser welding method)
A laser welding method using the laser welding apparatus 1 will be described. When performing laser welding, the focus of the laser L irradiated from the laser head 2 is adjusted to the joining line SS of the plate material W (see FIG. 4), and the laser L is moved along the joining line SS at a predetermined speed. Laser scanning is performed while moving (see FIG. 1). Simultaneously with the laser scanning, the assist gas G is injected from the gas supply nozzle 3 to form an oxidation preventing atmosphere around the molten pool M. By forming the oxidation-preventing atmosphere, the weld bead shape after the molten pool M is solidified is stabilized, and scorching is also prevented. In particular, in the laser welding apparatus 1A, the assist gas G is injected toward the center position CP where the brightness of the molten pool M is the highest. The center position CP where the brightness of the weld pool M is highest is the highest temperature, and the assist gas G is injected toward the center position CP, thereby effectively preventing the weld pool M from being oxidized and enhancing the shielding effect. be able to.

  As shown in FIG. 9B, the center position CP of the molten pool M during laser scanning is slightly shifted to the rear side in the traveling direction of the laser head 2 from the optical axis LS of the laser L. As shown in FIG. 9B, it is located at the approximate center in the left-right direction orthogonal to the traveling direction of the laser head 2. Since the laser welding apparatus 1 continues to detect the center position CP of the molten pool M during laser scanning, an accurate amount of misalignment can be detected. FIG. 9 is a diagram showing the luminance distribution of the molten pool M, and FIG. 9A is a diagram showing the luminance distribution when the molten pool M is viewed from above. FIG. 9B is a graph showing the luminance distribution along the line bb in FIG. 9A. The horizontal axis indicates the distance from the front end P1 to the rear end P2 along the line bb. The luminance is shown on the vertical axis. FIG. 9C is a graph showing the luminance distribution along the line cc in FIG. 9A, and the distance from one end P3 to the other end P4 along the line cc is the vertical axis. The luminance is indicated on the horizontal axis.

  Next, the procedure from the start to the end of laser welding will be described with reference to FIG. The operator uses the touch panel 19 to perform an operation for starting laser welding. Then, an initial setting signal for setting a welding condition is output from the touch panel 19, and the initial setting signal is input to the CPU 14 (S1). The CPU 14 outputs a control signal based on the initial setting signal to the nozzle actuator 9 (S2). Then, the nozzle actuator 9 operates to move the gas supply nozzle 3 to the initial setting position (see FIG. 4), and hold the gas supply nozzle 3 at the initial setting position (S3). It should be noted that the center position CP of the molten pool M during laser scanning is slightly shifted to the rear side in the traveling direction of the laser head 2 from the optical axis LS of the laser L, and the width of the shift is divided as an approximate value from the laser scanning speed. Is issued. The CPU 14, after calculating the approximate value of the deviation width from the laser scanning speed based on the initial setting signal, performs the initial setting such that the assist gas G is injected toward the position corresponding to the deviation width based on the approximate value. Based on the initial setting, the second linear actuator 5 is operated to move the gas supply nozzle 3 to a predetermined position.

  Thereafter, based on the initial setting signal output from the touch panel 19, the laser scanning control unit 14a of the CPU 14 applies an irradiation intensity setting signal for setting the irradiation intensity of the laser L and the irradiation of the laser L to the laser oscillation unit 2b. An ON signal to be started is output, and a speed setting signal for setting a laser scanning speed and a laser scanning start signal are output to the manipulator 12. Further, the CPU 14 outputs an open signal to a control valve (not shown) in order to inject the assist gas G from the gas supply nozzle 3 (S4). When the irradiation intensity setting signal and the ON signal are input, the laser oscillating unit 2b of the laser head 2 irradiates the laser L with the irradiation intensity corresponding to the irradiation intensity setting signal (see FIG. 1). Further, when the speed setting signal and the laser scanning start signal are input, the manipulator 12 starts laser scanning at a constant speed based on the speed setting signal. Further, when the open signal is input, the control valve opens the assist gas flow path and causes the assist gas G to be injected from the gas supply nozzle 3.

  After starting the laser scanning, the CPU 14 determines whether or not the welding end condition is satisfied depending on whether or not the end point of the planned joining line SS of the plate material W has been reached (S5). When the welding end condition is not satisfied, the detection unit 14b of the CPU 14 acquires the two-dimensional image information IM (see FIGS. 6 and 7) of the molten pool M based on the output from the CCD camera 7 (S6). The luminance distribution of the molten pool M is analyzed from the two-dimensional image information IM, and the position having the highest luminance is detected as the center position CP of the molten pool M (S7). Thereafter, the nozzle controller 14c of the CPU 14 determines the distance deviation d1 from the center of the two-dimensional image information IM corresponding to the tube axis NS of the gas supply nozzle 3 to the center position CP of the molten pool M (see FIGS. 7 and 8). Is calculated (S8). 7 and 8 show a case where the center position CP of the molten pool M is shifted to the rear side in the traveling direction of the laser head 2 with reference to the tube axis NS of the gas supply nozzle. Yes.

  Thereafter, the nozzle control unit 16c of the CPU 14 determines whether or not the distance deviation d1 calculated in step 8 is included in the predetermined range. If the distance deviation d1 is outside the predetermined range, the nozzle control unit 16c determines that the distance deviation d1 exists, and the predetermined range. If it is within, it is determined that there is no distance deviation d1 (S9). As shown in FIG. 6, when determining that there is no distance deviation d1, the CPU 14 returns to step 5 and again determines whether or not the welding end condition is satisfied (S5). On the other hand, as shown in FIGS. 7 and 8, when determining that the distance deviation d1 is present, the nozzle control unit 14c of the CPU 14 moves the gas supply nozzle 3 so that the distance deviation d1 approaches “0”. A correction control signal is output to the second linear actuator 5 (S10). The second linear actuator 5 is driven based on the correction control signal to move the gas supply nozzle 3 (S11). As shown in FIGS. 7 and 8, when the center position CP of the molten pool M is shifted from the tube axis NS of the gas supply nozzle to the rear side in the traveling direction of the laser head 2, the second position is obtained. The linear actuator 5 translates the gas supply nozzle 3 to the rear side in the traveling direction of the laser head 2. When the center position CP of the molten pool M is shifted to the front side in the traveling direction of the laser head 2 with respect to the tube axis NS of the gas supply nozzle, the second linear actuator 5 moves the gas supply nozzle 3 to the laser. The head 2 is moved in parallel in the traveling direction.

  The laser welding apparatus 1 repeatedly executes each process from step 5 to step 11 during laser scanning, and if the tube axis NS of the gas supply nozzle 3 is displaced from the center position CP of the molten pool M, the CPU 14 Outputs a correction control signal to the second linear actuator 5, and moves the gas supply nozzle 3 to automatically correct it. Then, when the laser L reaches the end of the planned joining line SS of the plate W, the CPU 14 determines that the welding end condition is satisfied (S5), and the OFF signal for stopping the laser oscillation to the laser oscillation unit 2b. And a laser scanning stop signal is output to the manipulator 12. Further, in order to stop the injection of the assist gas G, a close signal is output to a control valve (not shown). The laser oscillating unit 2b stops the irradiation of the laser L when the OFF signal is input, and the manipulator 12 stops the laser scanning by stopping the movement of the laser head 2 when the laser scanning stop signal is input. Furthermore, when the close signal is input, the control valve closes the flow path of the assist gas G and stops the injection of the assist gas G (S12). Laser welding is completed by stopping the irradiation of the laser L, stopping the laser scanning, and stopping the injection of the assist gas G.

  According to the laser welding apparatus 1, based on the two-dimensional image information IM of the molten pool M captured by the CCD camera 7, the detection unit 14b detects the center position CP of the molten pool M, and the nozzle control unit 14c A distance deviation d1 between the center position CP of the molten pool M and the pipe axis NS of the gas supply nozzle is calculated, and a correction control signal for moving the gas supply nozzle 3 so as to reduce the distance deviation d1 is output to the nozzle actuator 9. The second linear actuator 5 moves the gas supply nozzle 3 in the horizontal direction based on the input correction control signal. Thus, automatic correction is performed when the spray position of the assist gas G deviates from the center position CP of the molten pool M, and the spray gas center position of the assist gas G injected from the gas supply nozzle 3 is always set to the molten pool. By controlling so that it may be on the center position CP of M, it becomes easy to maintain the stable quality of a laser welding part.

  In particular, the detection unit 14b analyzes the luminance distribution of the molten pool M based on the two-dimensional image information IM of the molten pool M, and detects the center position CP of the molten pool M from the luminance distribution. The luminance distribution of the molten pool M and the molten state of the molten pool M (for example, the temperature of the molten pool M) are closely related, and the molten state of the molten pool M can be recognized by the two-dimensional image information IM. Then, by detecting the center position CP of the molten pool M using the two-dimensional image information IM of the molten pool M, the assist gas G can be sprayed to the optimum position according to the molten state of the molten pool M, The quality of the laser welded portion LJ is improved.

  Furthermore, the center position CP of the molten pool M is a position where the luminance of the molten pool M is the highest, and the position where the luminance of the molten pool M is the highest is a position where the temperature of the molten pool M is the highest. Then, by spraying the assist gas G with the position where the luminance of the molten pool M is the highest as the center position CP of the molten pool M, the shielding effect of effectively preventing the oxidation of the molten pool M can be enhanced.

The present invention is not limited to the above embodiments, and for example, a semiconductor laser, a CO ₂ laser, or the like may be used as a heat source for welding.

It is a perspective view which shows 1st Embodiment of the laser welding apparatus which concerns on this invention, and is a perspective view which shows the state during laser scanning. It is sectional drawing along the II-II line of FIG. It is a block diagram of a laser welding apparatus. It is a perspective view of the laser welding apparatus which shows the state which match | combined the laser before the laser scanning start with the joining planned line, and has matched the spray position of the assist gas to the joining planned line. It is a flowchart which shows the procedure of laser welding. It is a figure which shows the case where it is the two-dimensional image information of the molten pool imaged with the CCD camera, and does not have a distance deviation. It is a figure which shows the case where it is two-dimensional image information of the molten pool imaged with the CCD camera, and has a distance deviation. It is an expanded sectional view of the tip of a gas supply nozzle and a molten pool. It is a figure which shows the luminance distribution of a molten pool, (a) A figure is a figure which shows a luminance distribution when a molten pool is seen from the top, (b) A figure is the bb line | wire of (a) figure. FIG. 5C is a graph showing the luminance distribution along the line cc in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Laser welding apparatus, 2 ... Laser head, 3 ... Gas supply nozzle, 7 ... CCD camera, 9 ... Nozzle actuator, 14b ... Detection part, 14c ... Nozzle control part, W ... Plate material (to-be-welded body), L ... Laser , M ... weld pool, G ... assist gas, CP ... center position (melt pool center position), NS ... pipe axis, d1 ... distance deviation, IM ... two-dimensional image information (luminance distribution image information).

Claims (1)

A laser head for irradiating a workpiece with a laser;
A gas supply nozzle that is attached to the laser head and injects an assist gas obliquely toward a molten pool generated by the laser irradiation;
A nozzle actuator for moving the gas supply nozzle;
A camera for imaging the molten pool;
Based on image information captured by the camera, a detection unit that detects a molten pool center position;
A control signal for calculating the distance deviation between the molten pool center position detected by the detection unit and the pipe axis of the gas supply nozzle and moving the gas supply nozzle so as to reduce the distance deviation is sent to the nozzle actuator. A nozzle control unit that outputs to
The detection part, based on the luminance distribution image data of the weld pool captured by the camera, laser welding apparatus and detects the highest position the luminance of the molten pool as the molten pool center position.

Images