Laser welding method and laser welding device

Abstract

A laser welding method provided with a welding step in which a surface of a workpiece is scanned two-dimensionally with a laser light while the laser light advances in the X direction, thereby forming on the workpiece a weld bead that includes a starting-end section, a main weld section, and a terminal-end section in the stated order. In the welding step, the laser light is made to oscillate along the X direction in a sinusoidal shape having a first frequency, and is made to oscillate along the Y direction in a sinusoidal shape having a second frequency. The laser light is scanned so as to draw one Lissajous figure in the main weld section and so as to draw another Lissajous figure in the starting-end section and the terminal-end section respectively.

Description

[Technical field]

[0001] The present disclosure relates to a laser welding method and a laser welding apparatus. [Background technology]

[0002] Laser welding can perform high-speed, high-quality welding because the power density of the laser light irradiated onto the workpiece to be welded is high. In particular, in scanning welding, in which welding is performed while scanning the surface of the workpiece with the laser light at high speed, the laser beam can be moved quickly to the next welding point during periods when welding is not being performed, so the total welding time can be shortened (see, for example, Patent Document 1). Regarding the method of scanning laser light, a method of scanning the surface of the workpiece with the laser light so as to draw a Lissajous figure has been proposed (see, for example, Patent Document 2 and Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-095934 A [Patent Document 2] Japanese Patent Application Publication No. 177983 / 1983 [Patent Document 3] Japanese Patent Application Publication No. 11-104877 Summary of the Invention [Problem to be solved by the invention]

[0004] When forming a weld bead on a workpiece by laser welding, the heat input at the start and end may differ from that at other parts. In such a case, there is a risk that the bead shape at the start and end may deteriorate. In addition, in welding using a Lissajous waveform, the bead shape at the start and end is affected by the shape of the Lissajous waveform, and there are cases where improvements are required from the viewpoint of, for example, the static mechanical strength or dynamic fatigue strength of the welded joint.

[0005] However, the conventional configurations disclosed in Patent Documents 2 and 3 do not disclose any adjustment of the heat input or bead shape at the start or end of the weld bead. In other words, no improvement method for improving the bead shape at the start or end of the weld bead is disclosed.

[0006] The present disclosure has been made in consideration of the above-mentioned points, and has an object to provide a laser welding method and laser welding apparatus that can obtain a weld bead with a good shape, including the starting end and the ending end. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, the laser welding method of the present disclosure includes at least a welding step of two-dimensionally scanning the laser light on a surface of a workpiece while advancing the laser light in a first direction to form a weld bead on the workpiece including a starting point, a main welded portion, and a terminal end portion in that order, the welding step including a first scanning step of scanning the laser light to draw a Lissajous figure at the main welded portion by vibrating the laser light in a sinusoidal manner having a first frequency along the first direction and in a sinusoidal manner having a second frequency along a second direction intersecting the first direction, and a second scanning step of scanning the laser light to draw another Lissajous figure different from the first Lissajous figure at the starting point and the terminal end portion.

[0008] The laser welding apparatus according to the present disclosure includes at least a laser oscillator that generates laser light, a laser head that receives the laser light and irradiates it toward a workpiece, and a controller that controls the operation of the laser head, wherein the laser head has a laser light scanner that scans the laser light in each of a first direction and a second direction intersecting the first direction, and the controller drives and controls the laser light scanner so that the laser light draws a Lissajous figure on a surface of the workpiece by vibrating the laser light in a sine wave shape having a first frequency along the first direction and in a sine wave shape having a second frequency along the second direction, and further drives and controls the laser light scanner so that the laser light draws another Lissajous figure different from the one Lissajous figure at a starting end and an ending end of a weld bead formed on the workpiece. Effect of the Invention

[0009] According to the laser welding method and laser welding apparatus of the present disclosure, a weld bead having a good shape can be formed, including the starting end and the terminal end. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic configuration diagram of a laser welding device according to the first embodiment. [Diagram 2] FIG. 2 is a schematic diagram of a laser beam scanner. [Figure 3A] FIG. 3A is a schematic diagram of a workpiece. [Figure 3B] FIG. 3B is a schematic diagram of another workpiece. [Figure 4] FIG. 4 is a schematic plan view of a weld bead. [Figure 5A] FIG. 5A is an example of a scanning pattern of a laser beam irradiated onto a main welded portion of a weld bead. [Figure 5B] FIG. 5B is an example of a scanning pattern of the laser light irradiated onto the starting end of the weld bead. [Figure 5C]FIG. 5C is an example of a scanning pattern of the laser light irradiated to the end portion of the weld bead. [Figure 5D] FIG. 5D is a schematic diagram illustrating a method for changing the phase of a Lissajous waveform. [Figure 6] FIG. 6 is a diagram showing a scanning pattern of the laser light when the phase of the rotational motion of the second mirror is changed stepwise. [Figure 7A] FIG. 7A is a schematic plan view of a weld bead according to a comparative example. [Figure 7B] FIG. 7B is a schematic plan view of the starting end portion of a weld bead according to a comparative example. [Figure 7C] FIG. 7C is a schematic plan view of an end portion of a weld bead according to a comparative example. [Figure 8] FIG. 8 is a schematic plan view of a weld bead according to a modified example. [Figure 9A] FIG. 9A is an example of a scanning pattern of the laser light irradiated onto the main welded portion of the weld bead shown in FIG. [Figure 9B] FIG. 9B is an example of a scanning pattern of the laser light irradiated onto the starting end of the weld bead shown in FIG. [Figure 9C] FIG. 9C is an example of a scanning pattern of the laser light irradiated to the end portion of the weld bead shown in FIG. [Figure 10] FIG. 10 is a schematic plan view of another weld bead according to a modified example. [Figure 11A] FIG. 11A is an example of a scanning pattern of a laser beam irradiated onto the main welded portion of the weld bead shown in FIG. [Figure 11B] FIG. 11B is an example of a scanning pattern of the laser light irradiated onto the starting end of the weld bead shown in FIG. [Figure 11C] FIG. 11C is an example of a scanning pattern of the laser light irradiated onto the end portion of the weld bead shown in FIG. [Figure 12] FIG. 12 is a diagram showing a scanning pattern of the laser light when the amplitude of the first mirror is changed. [Figure 13] FIG. 13 is a schematic plan view of a weld bead according to the second embodiment. [Figure 14A]FIG. 14A is an example of a scanning pattern of a laser beam irradiated onto a main welded portion of a weld bead. [Figure 14B] FIG. 14B is an example of a scanning pattern of the laser light irradiated onto the starting end of the weld bead. [Figure 14C] FIG. 14C is an example of a scanning pattern of the laser light irradiated to the end portion of the weld bead. [Figure 15] FIG. 15 is a diagram showing a scanning pattern of the laser light when the rotational frequency ratio between the first mirror and the second mirror is changed. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0012] [Configuration of laser welding device and laser light scanner] Fig. 1 shows a schematic diagram of the configuration of a laser welding device according to this embodiment, Fig. 2 shows a schematic diagram of a laser beam scanner, Fig. 3A shows a schematic diagram of a workpiece, and Fig. 3B shows a schematic diagram of another workpiece.

[0013] In the following description, a direction parallel to the traveling direction of the laser light LB from the reflection mirror 33 toward the laser light scanner 40 may be referred to as the X direction, a direction parallel to the optical axis of the laser light LB emitted from the laser head 30 as the Z direction, and a direction perpendicular to the X direction and the Z direction as the Y direction. When the surface of the workpiece 200 is flat, the XY plane including the X direction and the Y direction within the plane may be approximately parallel to the surface or may have a certain angle.

[0014] As shown in FIG. 1, the laser welding apparatus 100 includes a laser oscillator 10, an optical fiber 20, a laser head 30, a controller 50, and a manipulator 60.

[0015] The laser oscillator 10 is a laser light source that receives power from a power source (not shown) and generates laser light LB. The laser oscillator 10 may be composed of a single laser light source, or may be composed of multiple laser modules. In the latter case, the laser light emitted from the multiple laser modules is combined and emitted as the laser light LB. The laser light source or laser module used in the laser oscillator 10 is appropriately selected depending on the material of the workpiece 200, the shape of the welding portion, etc.

[0016] For example, a fiber laser, a disk laser, or a YAG (Yttrium Aluminum Garnet) laser may be used as the laser light source. In this case, the wavelength of the laser light LB is set in the range of 1000 nm to 1100 nm. A semiconductor laser may be used as the laser light source or laser module. In this case, the wavelength of the laser light LB is set in the range of 800 nm to 1000 nm. A visible light laser may be used as the laser light source or laser module. In this case, the wavelength of the laser light LB is set in the range of 400 nm to 600 nm.

[0017] The optical fiber 20 is optically coupled to the laser oscillator 10 , and the laser light LB generated by the laser oscillator 10 is incident on the optical fiber 20 and transmitted through the inside thereof toward the laser head 30 .

[0018] The laser head 30 is attached to an end of the optical fiber 20 and irradiates the laser light LB transmitted from the optical fiber 20 toward the workpiece 200 .

[0019] The laser head 30 also has optical components, such as a collimation lens 32, a reflecting mirror 33, a focusing lens 34, and a laser light scanner 40, and these optical components are housed inside the housing 31 while maintaining a predetermined positional relationship.

[0020] The collimation lens 32 receives the laser light LB emitted from the optical fiber 20, converts it into parallel light, and makes it incident on the reflection mirror 33. The collimation lens 32 is connected to a drive unit (not shown) and is configured to be displaceable in the Z direction in response to a control signal from the controller 50. By displacing the collimation lens 32 in the Z direction, the focal position of the laser light LB can be changed, and the laser light LB can be appropriately irradiated according to the shape of the workpiece 200. In other words, the collimation lens 32 also functions as a focal position adjustment mechanism for the laser light LB in combination with a drive unit (not shown). The focusing lens 34 may be displaced by the drive unit to change the focal position of the laser light LB.

[0021] The reflecting mirror 33 reflects the laser light LB transmitted through the collimation lens 32 and makes it incident on the laser light scanner 40. The surface of the reflecting mirror 33 is provided so as to form an angle of approximately 45 degrees with the optical axis of the laser light LB transmitted through the collimation lens 32.

[0022] The condenser lens 34 condenses the laser light LB, which has been reflected by the reflecting mirror 33 and scanned by the laser light scanner 40, onto the surface of the workpiece 200.

[0023] 2, the laser light scanner 40 is a known galvanometer scanner having a first galvanometer mirror 41 and a second galvanometer mirror 42. The first galvanometer mirror 41 has a first mirror 41a, a first rotating shaft 41b, and a first driving unit 41c, and the second galvanometer mirror 42 has a second mirror 42a, a second rotating shaft 42b, and a second driving unit 42c. The laser light LB transmitted through the condenser lens 34 is reflected by the first mirror 41a and then by the second mirror 42a, and is irradiated onto the surface of the workpiece 200.

[0024] For example, the first driving unit 41c and the second driving unit 42c are galvano motors, and the first rotating shaft 41b and the second rotating shaft 42b are output shafts of the motors. Although not shown, the first driving unit 41c is driven to rotate by a driver that operates in response to a control signal from the controller 50, so that the first mirror 41a attached to the first rotating shaft 41b rotates around the axis of the first rotating shaft 41b. Similarly, the second driving unit 42c is driven to rotate by a driver that operates in response to a control signal from the controller 50, so that the second mirror 42a attached to the second rotating shaft 42b rotates around the axis of the second rotating shaft 42b.

[0025] The first mirror 41a rotates around the axis of the first rotation shaft 41b to a predetermined angle, whereby the laser light LB is scanned in the X direction. The second mirror 42a rotates around the axis of the second rotation shaft 42b to a predetermined angle, whereby the laser light LB is scanned in the Y direction. In other words, the laser light scanner 40 is configured to two-dimensionally scan the laser light LB within the XY plane and irradiate it toward the workpiece 200.

[0026] The controller 50 controls the laser oscillation of the laser oscillator 10. Specifically, the controller 50 controls the laser oscillation by supplying control signals such as an output current and an on / off time to a power supply (not shown) connected to the laser oscillator 10.

[0027] Moreover, the controller 50 controls the operation of the laser head 30 according to the contents of the selected laser welding program. Specifically, the controller 50 controls the driving of the laser light scanner 40 and the driving unit (not shown) of the collimation lens 32 provided in the laser head 30. Furthermore, the controller 50 controls the operation of the manipulator 60. The laser welding program is stored in a storage unit (not shown) provided inside the controller 50 or in a different location, and is called by the controller 50 in response to a command from the controller 50.

[0028] The controller 50 has an integrated circuit such as an LSI or a microcomputer (not shown), and the above-mentioned functions of the controller 50 are realized by executing a laser welding program, which is software, on this integrated circuit.

[0029] The manipulator 60 is an articulated robot, and is attached to the housing 31 of the laser head 30. The manipulator 60 is connected to the controller 50 so as to be able to exchange signals, and moves the laser head 30 so as to trace a predetermined trajectory in accordance with the above-mentioned laser welding program. A separate controller (not shown) for controlling the operation of the manipulator 60 may be provided.

[0030] The laser welding apparatus 100 shown in Fig. 1 can perform laser welding on workpieces 200 of various shapes. For example, as shown in Fig. 3A, a laser beam LB is irradiated to a joint of the workpiece 200 in which a first plate material 210 and a second plate material 220 are butted together at their end faces, to perform butt welding. Also, as shown in Fig. 3B, a laser beam LB is irradiated to a corner portion of a joint of the workpiece 200 in which a third plate material 230 and a fourth plate material 240 are overlapped with their end faces shifted, to perform lap fillet welding. However, it goes without saying that the shape of the workpiece 200 to be laser welded is not limited to the examples shown in Figs. 3A and 3B.

[0031] [Laser welding method] Fig. 4 shows a schematic plan view of a weld bead. Fig. 5A shows an example of a scanning pattern of a laser beam irradiated to a main welded portion of a weld bead. Fig. 5B shows an example of a scanning pattern of a laser beam irradiated to a starting end of a weld bead. Fig. 5C shows an example of a scanning pattern of a laser beam irradiated to a terminal end of a weld bead.

[0032] 4, weld bead 300 has a starting portion 301, a main welded portion 302, and a terminal end portion 303 in this order. For example, weld bead 300 is formed by irradiating laser light LB onto workpiece 200, which is a plate material, while moving laser head 30 linearly in the X direction at a constant speed using manipulator 60. During irradiation of laser light LB, laser light scanner 40 two-dimensionally scans the laser light LB onto the surface of workpiece 200. The length of starting portion 301 in the X direction is L1, the length of terminal end portion 303 in the X direction is L2, and the width of main welded portion 302 in the Y direction is W. Width W corresponds to the width of weld bead 300 in the Y direction.

[0033] As shown in Fig. 5A, the laser light LB is scanned so as to draw a Lissajous figure within the XY plane, in this case, on the surface of the workpiece 200. In the following description, different types of Lissajous figures may be referred to as pattern i (i = 1, 2, 3, ...). The Lissajous figure shown in Fig. 5A is referred to as pattern 4.

[0034] The width of pattern 4 in the X direction is equal to the width in the Y direction, and when the welding speed is very fast, the width of pattern 4 in the Y direction is approximately equal to the width W of weld bead 300 in the Y direction. On the other hand, when the welding speed is slow, the width of the weld bead increases due to the influence of heat conduction, so the width of pattern 4 in the Y direction is slightly narrower than the width W of weld bead 300 in the Y direction. In this specification, "approximately equal" or "approximately the same" means that the control results of the controlled object are the same or identical, including errors in the control system, and does not require that the two objects being compared are strictly the same or identical. In addition, "approximately equal" or "approximately the same" is also used to mean the same or identical, including manufacturing tolerances and assembly tolerances of each part, etc.

[0035] Pattern 4 is obtained by vibrating the laser light LB in the X direction in a sinusoidal manner at a predetermined frequency and vibrating it in the Y direction in a sinusoidal manner at a frequency different from that in the X direction (half the frequency in the X direction). As described above, the scanning patterns of the laser light LB in the X and Y directions are determined based on the rotational motion of the first mirror 41a and the second mirror 42a. In general, when the position coordinate of the Lissajous waveform obtained by driving the first mirror 41a is X1 and the position coordinate of the Lissajous waveform obtained by driving the second mirror 42a is Y1, the position coordinates X1 and Y1 are expressed by the following formulas (1) and (2), respectively.

[0036] X1 = a × sin(n) (1) Y1 = b × sin(mt + φ) (2) Where: a: Amplitude of the Lissajous waveform in the X direction b: Amplitude of the Lissajous waveform in the Y direction n: frequency of the first mirror 41a m: frequency of the second mirror 42a t: time φ: the phase difference when the first mirror 41a or the second mirror 42a is driven, and specifically, the amount of angular deviation provided when the first mirror 41a and the second mirror 42a are rotated.

[0037] The position coordinates X1, Y1 shown in equations (1) and (2) are expressed in a stationary coordinate system of the Lissajous waveform with the position of the laser head 30 fixed.

[0038] Furthermore, the amplitude a of the first mirror 41a and the amplitude b of the second mirror 42a correspond to the scanning amplitudes of the laser light LB in the X and Y directions, respectively. The frequencies n and m correspond to the drive frequencies of the first mirror 41a and the second mirror 42a, respectively.

[0039] Pattern 4 is a Lissajous figure in the shape of a figure of eight, which corresponds to the case where a=1, b=1, n=2, m=1, and φ=0 in formulas (1) and (2). a and b are normalized to 1. In actual welding, the above-mentioned parameters a, b, n, and m are changed appropriately according to the material of the workpiece 200, the joint shape, the required bead shape width, and the like. To obtain pattern 4, a=b and |n|=|2m| are set. The signs of n and m (i.e., whether they are plus (+) or minus (-)) represent the driving directions of the first mirror 41a and the second mirror 42a, and the two may have the same direction (sign) or a combination of different directions (signs). The driving frequency of the first mirror 41a is always twice the driving frequency of the second mirror 42a. The phase difference φ in formulas (1) and (2) may be either 0 degrees or 180 degrees.

[0040] In weld bead 300 shown in FIG. 4, main weld portion 302 which is an intermediate portion between starting portion 301 and ending portion 303 is laser welded while scanning laser beam LB so as to trace pattern 4 shown in FIG. 5A.

[0041] On the other hand, when welding the starting end 301 of the weld bead 300, the laser head 30 is moved at a constant speed in the X direction, and the scanning pattern of the laser light LB is changed continuously from pattern 1 to pattern 2 to pattern 3 to pattern 4 as shown in FIG. 5B. When welding the end 303 of the weld bead 300, the laser head 30 is moved at a constant speed in the X direction, and the scanning pattern of the laser light LB is changed continuously from pattern 4 to pattern 5 to pattern 6 to pattern 7 as shown in FIG. 5C. Pattern 1 is a single-peaked parabolic figure in the XY plane, and as it progresses from pattern 2 to pattern 3, it changes to a continuous double-peaked figure, and finally becomes pattern 4. Similarly, as it progresses from pattern 4 to pattern 5 and further to pattern 6, the figure of eight is deformed to a continuous double-peaked figure. Finally, as shown in pattern 7, it becomes a single-peaked parabolic figure in the XY plane.

[0042] In pattern 4 and the other patterns 1 to 3 and 5 to 7, among the parameters shown in equations (1) and (2), the amplitudes a and b of the first mirror 41a and the second mirror 42a and the frequencies n and m of the first mirror 41a and the second mirror 42a are all the same (a=b=1, n=2, m=1). In other words, the difference in shape between pattern 4 and the other patterns occurs due to the difference in phase φ shown in equation (2).

[0043] Fig. 6 shows the scanning pattern of the laser light when the phase of the rotational motion of the second mirror is changed stepwise, and as is clear from Fig. 6, the phase φ is 0 degrees in pattern 4, whereas the phase φ is set to 45 degrees and 30 degrees in patterns 1 and 2. Although not shown, it goes without saying that the phase φ is a value between 0 degrees and 30 degrees in pattern 3 shown in Fig. 5B.

[0044] In other words, the laser beam scanner 40 is driven and controlled so that the phase φ of the rotational motion of the second mirror 42a, in other words, the phase of the Y-direction vibration of the laser beam LB, changes at predetermined intervals from 45 degrees to 0 degrees, and laser welding is performed to form the starting end 301 of the weld bead 300.

[0045] Although not shown, in pattern 5 shown in FIG. 5C, the phase φ is −15 degrees, in pattern 6, the phase φ is −30 degrees, and in pattern 7, the phase φ is −45 degrees.

[0046] In other words, laser welding is performed by controlling and driving laser beam scanner 40 so that the phase of the Y-direction vibration of laser beam LB changes at predetermined intervals from 0 degrees to −45 degrees, and terminal end 303 of weld bead 300 is formed.

[0047] A method of changing the phase φ in Fig. 5B and Fig. 5C at a predetermined interval will be described with reference to Fig. 5D. Fig. 5D is a schematic diagram for explaining a method of changing the phase of a Lissajous waveform. For simplicity, a method of changing from pattern 1 to pattern 2 will be described, and since other patterns can be changed in a similar manner, a description thereof will be omitted.

[0048] In FIG. 5D, the solid lines represent pattern 1 (phase φ=45 degrees) and the dashed lines represent pattern 2 (phase φ=30 degrees).

[0049] For ease of explanation, both are plotted on the same drawing. In pattern 1, the drawing start position is P10, and then, as shown by the arrows, one cycle of Lissajous pattern 1 is drawn in the order of P11, P10, P12, P13, P12, and P10. On the other hand, in pattern 2, the drawing start position is P20, and then, as shown by the arrows, one cycle of Lissajous pattern 2 is drawn in the order of P21, P22, P23, P24, P25, P23, and P20. Here, the drawing start points for each pattern are P10 and P20 in FIG. 5D, but they may be other points.

[0050] When welding, the phase is switched immediately after one Lissajous pattern is drawn. In the timing shown in the figure, the laser light LB is moved from point P10 after drawing pattern 1 is completed to the drawing start point P20 of the next drawing pattern 2, and then switched to pattern 2. Since the phase difference between pattern 1 and pattern 2 is 15 degrees, the distance between P10 and P20 appears long in FIG. 5D. At this time, a large beam movement step occurs when switching between pattern 1 and pattern 2, so a large trace is left on the bead. In actual welding, by making this step as small as possible, the laser light LB can be moved smoothly and a good bead can be formed.

[0051] The interval of this phase difference can be obtained in advance by a welding test. After the drawing of pattern 1 is completed, the difference between the phase of the next pattern to be drawn and the phase of pattern 1 may be a predetermined interval that is determined in advance by the above-mentioned welding test. That is, as shown in Fig. 5B, the laser beam scanner 40 is driven and controlled so that the phase of the vibration of the laser beam LB in the Y direction changes from 45 degrees to 0 degrees at this predetermined interval, thereby performing laser welding and forming a good starting portion 301.

[0052] Since a good termination portion 303 can be formed based on the same principle as described above, a detailed description thereof will be omitted here.

[0053] In this way, as shown in FIG. 4, it is possible to improve the bead shape at both starting portion 301 and terminal end portion 303 of weld bead 300.

[0054] [Effects, etc.] As described above, the laser welding method according to this embodiment includes at least a welding step of two-dimensionally scanning laser light LB on the surface of workpiece 200 while causing laser light LB to travel in the X direction (first direction) to form weld bead 300 on workpiece 200, the weld bead including starting portion 301, main weld portion 302, and ending portion 303, in this order.

[0055] In the welding step, the laser light LB is vibrated in a sinusoidal manner having a first frequency corresponding to a frequency n along the X direction, and is also vibrated in a sinusoidal manner having a second frequency corresponding to a frequency m along the Y direction. This causes the laser light LB to scan the main welded portion 302 so as to draw one Lissajous figure (pattern 4) (first scanning step).

[0056] Moreover, the laser light LB is scanned at the starting end 301 and the ending end 303 so as to draw a Lissajous figure (patterns 1 to 3 and patterns 5 to 7) different from pattern 4 (second scanning step).

[0057] By using this laser welding method, it is possible to obtain a good bead shape not only in the main welded portion 302 but also in each of the starting portion 301 and the ending portion 303. This will be further explained.

[0058] FIG. 7A shows a schematic plan view of a weld bead according to a comparison, FIG. 7B shows a schematic plan view of a starting end portion of the weld bead, and FIG. 7C shows a schematic plan view of an ending end portion of the weld bead.

[0059] 7A is formed by two-dimensionally scanning the surface of workpiece 200 with laser beam LB by laser beam scanner 40 while manipulator 60 moves laser head 30 linearly in the X direction at a constant speed. This is the same as the method of forming weld bead 300 shown in FIG.

[0060] On the other hand, when forming weld bead 310 shown in FIG. 7A, the scanning pattern of laser light LB is only one type, pattern 4, which is different from the method disclosed above.

[0061] 7A to 7C, the scanning pattern of laser light LB is reflected in the bead shape at each of starting end 311 and terminal end 313 of weld bead 310. In other words, depressions 314 that are recessed in the X direction are formed at each of starting end 311 and terminal end 313 of weld bead 310, and the appearance of weld bead 310 is impaired.

[0062] Furthermore, in the recesses 314, the workpiece 200 does not penetrate sufficiently, which may result in defective welding. For example, in lap fillet welding as shown in Fig. 3B, if the recesses 314 shown in Figs. 7A to 7C are formed at the ends of the third plate material 230 and the fourth plate material 240 in the direction perpendicular to the paper surface, the joining of the third plate material 230 and the fourth plate material 240 becomes insufficient, which may result in defective welding.

[0063] On the other hand, according to the laser welding method of the present embodiment, by performing the above-mentioned second scanning step in the welding step, it is possible to suppress the formation of recesses 314 shown in Figures 7A to 7C at starting end 301 and terminal end 303 of weld bead 300. This makes it possible to improve the shape of weld bead 300 from the starting end to the terminal end. In addition, it is possible to improve the aesthetic appearance of weld bead 300.

[0064] Furthermore, when forming weld bead 300, by scanning laser light LB so as to draw a Lissajous figure, uneven heat input in the irradiation area of ​​laser light LB can be reduced, and a good bead shape can be obtained.

[0065] For example, the manipulator 60 may be moved while controlling the amplitude a of the first mirror 41a and the second mirror 42a so that the laser beam LB forms a circular pattern, and laser welding may be performed so that the laser beam LB traces a spiral trajectory on the surface of the workpiece 200. In this case, the amount of heat input to the left and right sides of the workpiece 200 during welding differs depending on whether the trajectory rotates clockwise or counterclockwise. As shown in this embodiment, by scanning the laser beam LB, such an imbalance in heat input can be eliminated, and a good bead shape can be obtained.

[0066] In the second scanning step, it is preferable to scan the laser light LB so as to continuously change the phase of the sine wave along the Y direction.

[0067] More preferably, in the second scanning step, when forming the starting end 301, the laser light LB is scanned so as to change the phase of the sine wave along the Y direction from 45 degrees to 0 degrees at predetermined intervals, and when forming the ending end 303, the laser light LB is scanned so as to change the phase of the sine wave along the Y direction from 0 degrees to -45 degrees at predetermined intervals.

[0068] In this way, the width of weld bead 300 in the Y direction can be changed continuously from the start of weld bead 300 to main welded portion 302, and from main welded portion 302 to the end of weld bead 300. This makes it possible to improve the bead shape not only at main welded portion 302, but also at start portion 301 and end portion 303. In addition, the aesthetic appearance of weld bead 300 can be improved.

[0069] Lengths L1, L2 of starting end 301 and ending end 303 in the X direction may be approximately equal to or greater than the sum of half the width of pattern 4 in the X direction and width W of weld bead 300 in the Y direction.

[0070] By setting lengths L1 and L2 in this manner, it is possible to reliably prevent recesses 314 from being formed at starting end 301 and terminal end 303 of weld bead 300, respectively.

[0071] The laser welding apparatus 100 of this embodiment includes at least a laser oscillator 10 that generates laser light LB, a laser head 30 that receives the laser light LB and irradiates it toward the workpiece 200, and a controller 50 that controls the operation of the laser head 30.

[0072] The laser head 30 has a laser beam scanner 40 that scans the laser beam LB in both an X direction (first direction) and a Y direction (second direction) that intersects with the X direction.

[0073] The controller 50 vibrates the laser beam LB in a sinusoidal manner having a first frequency along the X direction, and vibrates the laser beam LB in a sinusoidal manner having a second frequency along the Y direction. In this way, the controller 50 drives and controls the laser beam scanner 40 so that the laser beam LB draws one Lissajous figure (pattern 4) on the surface of the workpiece 200.

[0074] Furthermore, the controller 50 drives and controls the laser light scanner 40 so that the laser light LB draws another Lissajous figure (patterns 1 to 3 and patterns 5 to 7) different from the one Lissajous figure at the starting end 301 and the ending end 303 of the weld bead 300 formed on the workpiece 200.

[0075] According to the laser welding apparatus 100 of this embodiment, it is possible to obtain a good bead shape not only at the main welded portion 302 but also at the starting portion 301 and the ending portion 303 .

[0076] It is preferable that controller 50 drives and controls laser beam scanner 40 so as to continuously change the phase of the sine wave along the Y direction at starting end 301 and terminal end 303 of weld bead 300.

[0077] More preferably, when forming the starting end 301, the controller 50 controls the driving of the laser light scanner 40 so as to change the phase of the sine wave along the Y direction from 45 degrees to 0 degrees at predetermined intervals.

[0078] Furthermore, when forming the terminal end 303, the laser light scanner 40 is driven and controlled so that the phase of the sine wave along the Y direction is changed at predetermined intervals from 0 degrees to −45 degrees.

[0079] By configuring controller 50 in this manner, it is possible to improve the bead shape not only at main weld portion 302 but also at starting portion 301 and ending portion 303. In addition, it is possible to improve the aesthetic appearance of weld bead 300.

[0080] The laser welding apparatus 100 further includes a manipulator 60 to which the laser head 30 is attached, and the controller 50 controls the operation of the manipulator 60. The manipulator 60 moves the laser head 30 in a predetermined direction relative to the surface of the workpiece 200.

[0081] In this manner, the welding direction of the laser beam LB can be changed by providing the manipulator 60. Furthermore, laser welding can be easily performed on the workpiece 200 having a complex shape, for example, a three-dimensional shape.

[0082] The laser oscillator 10 and the laser head 30 are connected by an optical fiber 20 , and the laser light LB is transmitted from the laser oscillator 10 to the laser head 30 through the optical fiber 20 .

[0083] By providing the optical fiber 20 in this manner, it becomes possible to perform laser welding on the workpiece 200 that is placed at a position away from the laser oscillator 10. This increases the degree of freedom in arranging each part of the laser welding apparatus 100.

[0084] The laser light scanner 40 is composed of a first galvanometer mirror 41 that scans the laser light LB in the X direction, and a second galvanometer mirror 42 that scans the laser light LB in the Y direction.

[0085] By configuring the laser beam scanner 40 in this way, it is possible to easily perform two-dimensional scanning with the laser beam LB. In addition, since a known galvano scanner is used as the laser beam scanner 40, an increase in the cost of the laser welding apparatus 100 can be suppressed.

[0086] <Modification> Fig. 8 shows a schematic plan view of a weld bead according to this modification. Fig. 9A shows an example of a scanning pattern of a laser beam irradiated to a main welded portion of the weld bead shown in Fig. 8, Fig. 9B shows an example of a scanning pattern of a laser beam irradiated to a starting end of the weld bead shown in Fig. 8, and Fig. 9C shows an example of a scanning pattern of a laser beam irradiated to a terminal end of the weld bead shown in Fig. 8.

[0087] Fig. 10 shows a schematic plan view of another weld bead according to this modification. Fig. 11A shows an example of a scanning pattern of a laser beam irradiated to a main welded portion of the weld bead shown in Fig. 10, Fig. 11B shows an example of a scanning pattern of a laser beam irradiated to a starting end of the weld bead shown in Fig. 10, and Fig. 11C shows an example of a scanning pattern of a laser beam irradiated to a terminal end of the weld bead shown in Fig. 10.

[0088] FIG. 12 shows the scanning pattern of the laser light when the amplitude of the first mirror is changed.

[0089] In the laser welding method shown in the embodiment 1, the amplitude a of the first mirror 41a and the amplitude b of the second mirror 42a are set to the same value (normalized to 1). Moreover, the laser welding device 100 drives and controls the laser beam scanner 40 so as to satisfy this condition. As a result, the laser beam LB is scanned so that the scanning amplitude in the X direction and the scanning amplitude in the Y direction are substantially equal.

[0090] However, from the viewpoint of aesthetic appearance, there is a demand to make the change in width in the X direction gentler and to make the weld bead 300 rounded at the start end 301 and the end end 303 of the weld bead 300 shown in Fig. 4. Also, depending on the shape of the workpiece 200, a similar demand may arise from the viewpoint of welding quality.

[0091] In order to meet such a demand, in this modification, the amplitude a of the first mirror 41a is set to be smaller than 1, and the scanning amplitude of the laser light LB in the X direction is set to be smaller than the scanning amplitude in the Y direction. In the example (pattern 8) shown in FIG. 12(b), a=0.5, and in the example (pattern 9) shown in FIG. 12(c), a=0.25. Here, the amplitude in the Y direction is normalized to 1.

[0092] By moving laser head 30 at a constant speed along the X direction and scanning laser light LB as shown in FIGS. 9A to 9C, the change in width in the X direction at starting end 321 and ending end 323 of weld bead 320 can be made gentler and rounded as shown in FIG. 8.

[0093] As shown in Fig. 9B, the scanning pattern of the laser light LB at the starting portion 321 is changed continuously from pattern 11 to pattern 12 to pattern 13 to pattern 8. As shown in Fig. 9C, the scanning pattern of the laser light LB at the terminal portion 323 is changed continuously from pattern 8 to pattern 14 to pattern 15 to pattern 16. As shown in Fig. 9A, the scanning pattern of the laser light LB at the main welded portion 322 is fixed to pattern 8.

[0094] In this case, the change in phase φ of the second mirror 42a is similar to that shown in Figures 5B and 5C. That is, in pattern 8, the phase φ is 0 degrees, and in pattern 11, the phase φ is 45 degrees. In pattern 12, the phase φ is 15 degrees, and in pattern 13, the phase φ is 30 degrees. In pattern 14, the phase φ is -15 degrees, in pattern 15, the phase φ is -30 degrees, and in pattern 16, the phase φ is -45 degrees.

[0095] It goes without saying that in any of the patterns 8 and 11 to 16, the amplitude a of the first mirror 41a is 0.5.

[0096] Furthermore, by moving laser head 30 at a constant speed along the X direction and scanning laser light LB as shown in FIGS. 11A to 11C, as shown in FIG. 10, starting end 331 and ending end 333 of weld bead 330 can have a more gradual change in width in the X direction than weld bead 320 shown in FIG. 8, and can be made even more rounded.

[0097] As shown in Fig. 11B, the scanning pattern of the laser light LB at the starting portion 331 is changed continuously from pattern 17 to pattern 18 to pattern 19 to pattern 9. As shown in Fig. 11C, the scanning pattern of the laser light LB at the terminal portion 333 is changed continuously from pattern 9 to pattern 20 to pattern 21 to pattern 22. As shown in Fig. 11A, the scanning pattern of the laser light LB at the main welded portion 332 is fixed to pattern 9.

[0098] The change in phase φ of the second mirror 42a in this case is similar to that shown in Figures 5B and 5C. That is, in pattern 9, the phase φ is 0 degrees, and in pattern 17, the phase φ is 45 degrees. In pattern 18, the phase φ is 30 degrees, and in pattern 19, the phase φ is 15 degrees. In pattern 20, the phase φ is -15 degrees, in pattern 21, the phase φ is -30 degrees, and in pattern 22, the phase φ is -45 degrees.

[0099] It goes without saying that in any of Pattern 9 and Patterns 17 to 22, the amplitude a of the first mirror 41a is 0.25.

[0100] (Embodiment 2) Fig. 13 shows a schematic plan view of a weld bead according to this embodiment. Fig. 14A shows an example of a scanning pattern of a laser beam irradiated to a main welded portion of a weld bead, Fig. 14B shows an example of a scanning pattern of a laser beam irradiated to a starting end of a weld bead, and Fig. 14C shows an example of a scanning pattern of a laser beam irradiated to a terminal end of a weld bead.

[0101] FIG. 15 shows a scanning pattern of the laser light when the ratio of the rotational frequencies of the first mirror and the second mirror is changed.

[0102] In this embodiment, the weld bead 340 is formed extending in the Y direction. That is, in the laser welding direction shown in this embodiment, the laser head 30 is moved at a constant speed along the Y direction (first direction) to perform two-dimensional scanning with the laser light LB. Also, the laser welding device 100 drives and controls the laser light scanner 40 so as to satisfy this condition.

[0103] In addition, the scanning pattern of the laser light LB needs to be changed from pattern 4 shown in Fig. 15(a) to pattern 10 shown in Fig. 15(b). Specifically, the frequencies n and m of the first mirror 41a and the second mirror 42a are changed from n=2, m=1 to n=1, m=2. In other words, the drive frequency ratio of the first mirror 41a and the second mirror 42a is changed from 2:1 to 1:2. Although not shown, as long as this drive frequency ratio is maintained, the drive frequencies of both mirrors may be appropriately changed according to the shape of the workpiece 200 or the required bead shape.

[0104] By moving laser head 30 at a constant speed along the Y direction and scanning laser light LB as shown in Figures 14A to 14C, weld bead 340 shown in Figure 13 can be formed. In this case, good bead shapes can be obtained at starting end 341, terminal end 343, and main weld 342. Furthermore, the aesthetic appearance of weld bead 340 can be improved.

[0105] As shown in Fig. 14B, the scanning pattern of the laser light LB at the starting portion 341 is changed continuously from pattern 23 to pattern 24 to pattern 25 to pattern 10. As shown in Fig. 14C, the scanning pattern of the laser light LB at the terminal portion 343 is changed continuously from pattern 10 to pattern 26 to pattern 27 to pattern 28. As shown in Fig. 14A, the scanning pattern of the laser light LB at the main welded portion 342 is fixed to pattern 10.

[0106] In this case, the change in phase φ of the second mirror 42a is similar to that shown in Figures 5B and 5C. That is, in pattern 10, the phase φ is 0 degrees, and in pattern 23, the phase φ is -90 degrees. In pattern 24, the phase φ is -60 degrees, and in pattern 25, the phase φ is -30 degrees. In pattern 26, the phase φ is 30 degrees, in pattern 27, the phase φ is 60 degrees, and in pattern 28, the phase φ is 90 degrees.

[0107] Needless to say, the relationships a=b=1, n=1, and m=2 hold in all of pattern 10 and patterns 21 to 26. Note that here, a=b is a value normalized to 1, and n=1 and m=2 are values ​​obtained by normalizing the frequency relationship (1:2).

[0108] (Other embodiments) The components shown in the first and second embodiments and the modified examples can be appropriately combined to form new embodiments.

[0109] For example, in the configuration shown in the second embodiment, by making amplitude b of second mirror 42a smaller than 1, as shown in the modified example, the change in width in the Y direction at starting end 341 and terminal end 343 of weld bead 340 can be made gentler and rounded. This improves the aesthetic appearance of weld bead 340. Also, depending on the shape of workpiece 200, the welding quality can be improved.

[0110] In the example shown in FIG. 1, the focusing lens 34 is disposed in front of the laser light scanner 40, but it may be disposed in the rear of the laser light scanner 40, that is, between the laser light scanner 40 and the light emission port of the laser head 30.

[0111] Furthermore, the laser light LB may be oscillated in a cosine wave shape having a first frequency along the X direction and in a cosine wave shape having a second frequency along the Y direction, so that the scanning pattern of the laser light LB becomes a Lissajous figure. In this case, it goes without saying that the amplitudes a and b of the first mirror 41a and the second mirror 42a, the frequencies n and m of the first mirror 41a and the second mirror 42a, and further the phase φ are appropriately changed. [Industrial Applicability]

[0112] The laser welding method and the laser welding method disclosed herein are useful because they can produce a good shape of the weld bead, including the starting end and the ending end. [Explanation of symbols]

[0113] 10 Laser Oscillator 20 Optical Fiber 30 Laser Head 31 Case 32 Collimation Lens 33 Reflective Mirror 34 Condenser Lens 40 Laser light scanner 41 First Galvanometer Mirror 41a 1st mirror 41b First rotation axis 41c First Drive Unit 42 Second Galvanometer Mirror 42a 2nd mirror 42b Second rotation axis 42c Second Drive Unit 200 Work 300,310,320,330,340 Weld Bead 301,311,321,331,341 Starting end 302,312,322,332,342 Main weld 303,313,323,333,343 End 314 Recess

Claims

1. The method includes at least a welding step of two-dimensionally scanning the laser light on a surface of a workpiece while advancing the laser light in a first direction to form a weld bead including a starting portion, a main weld portion, and a terminal end portion in this order on the workpiece, The welding step includes: a first scanning step of scanning the laser light so as to draw a Lissajous figure at the main welded portion by vibrating the laser light in a sinusoidal manner having a first frequency along the first direction and vibrating the laser light in a sinusoidal manner having a second frequency along a second direction intersecting the first direction; and a second scanning step of scanning the starting end and the ending end with the laser light so as to draw another Lissajous figure different from the one Lissajous figure.

2. 2. The laser welding method according to claim 1, A laser welding method, characterized in that in the second scanning step, the laser light is scanned so that a phase of a sine wave along the second direction is changed at predetermined intervals.

3. 3. The laser welding method according to claim 1, A laser welding method, wherein a ratio of the first frequency to the second frequency is 2:1 or 1:

2.

4. The laser welding method according to claim 3, When the ratio of the first frequency to the second frequency is 2:1, In the second scanning step, when forming the starting end, the laser light is scanned so that a phase of a sine wave along the second direction is changed at predetermined intervals from 45 degrees to 0 degrees; When forming the end portion, the laser light is scanned so as to change a phase of a sine wave along the second direction at predetermined intervals from 0 degrees to −45 degrees; When the ratio of the first frequency to the second frequency is 1:2, In the second scanning step, when forming the starting end, the laser light is scanned so that a phase of a sine wave along the second direction is changed at predetermined intervals from −90 degrees to 0 degrees; A laser welding method characterized in that, when forming the terminal portion, the laser light is scanned so as to change the phase of a sine wave along the second direction at predetermined intervals from 0 degrees to 90 degrees.

5. The laser welding method according to any one of claims 1 to 4, A laser welding method, characterized in that, in the first scanning step and the second scanning step, a scanning amplitude of the laser light in the first direction is approximately equal to a scanning amplitude of the laser light in the second direction.

6. The laser welding method according to any one of claims 1 to 4, A laser welding method, characterized in that, in the first scanning step and the second scanning step, a scanning amplitude of the laser light in the first direction is different from a scanning amplitude of the laser light in the second direction.

7. 7. The laser welding method according to claim 1, a length in the first direction of the starting end and the ending end of the weld bead is approximately equal to or greater than a sum of half a width in the first direction of the one Lissajous figure and a width in the second direction of the weld bead.

8. A laser oscillator that generates a laser beam; a laser head that receives the laser light and irradiates it toward a workpiece; A controller for controlling the operation of the laser head; the laser head has a laser beam scanner configured to scan the laser beam in a first direction and a second direction intersecting the first direction, The controller drives and controls the laser beam scanner so that the laser beam draws a Lissajous figure on the surface of the workpiece by vibrating the laser beam in a sinusoidal shape having a first frequency along the first direction and vibrating the laser beam in a sinusoidal shape having a second frequency along the second direction; The laser welding apparatus further comprises controlling and driving the laser beam scanner so that the laser beam draws another Lissajous figure different from the one Lissajous figure at the starting and ending ends of the weld bead formed on the workpiece.

9. 9. The laser welding apparatus according to claim 8, The laser welding apparatus is characterized in that the controller drives and controls the laser light scanner so as to change the phase of a sine wave along the second direction at a predetermined interval at a starting end and an ending end of the weld bead.

10. 10. The laser welding apparatus according to claim 8, A laser welding apparatus, wherein a ratio of the first frequency to the second frequency is 2:1 or 1:

2.

11. 11. The laser welding apparatus according to claim 10, When the ratio of the first frequency to the second frequency is 2:1, The controller drives and controls the laser beam scanner so that the phase of the sine wave along the second direction is changed at predetermined intervals from 45 degrees to 0 degrees when forming the starting end, and drives and controls the laser beam scanner so that the phase of the sine wave along the second direction is changed at predetermined intervals from 0 degrees to -45 degrees when forming the ending end; When the ratio of the first frequency to the second frequency is 1:2, The laser welding device is characterized in that the controller drives and controls the laser beam scanner so as to change the phase of the sine wave along the second direction at a predetermined interval from -90 degrees to 0 degrees when forming the starting end, and drives and controls the laser beam scanner so as to change the phase of the sine wave along the second direction at a predetermined interval from 0 degrees to 90 degrees when forming the ending end.

12. 12. The laser welding apparatus according to claim 8, The laser welding apparatus, characterized in that the controller drives and controls the laser beam scanner so that a scanning amplitude of the laser beam in the first direction is approximately equal to a scanning amplitude of the laser beam in the second direction.

13. 12. The laser welding apparatus according to claim 8, The laser welding apparatus, characterized in that the controller drives and controls the laser beam scanner so as to make a scanning amplitude of the laser beam in the first direction different from a scanning amplitude of the laser beam in the second direction.

14. 14. The laser welding apparatus according to claim 8, The laser welding device is characterized in that the controller drives and controls the laser light scanner so that the lengths of the starting end and the ending end of the weld bead in the first direction are approximately equal to or greater than the sum of 1 / 2 the width of the one Lissajous figure in the first direction and the width of the weld bead in the second direction.

15. 15. The laser welding apparatus according to claim 8, a manipulator to which the laser head is attached; The controller controls the operation of the manipulator; The laser welding apparatus is characterized in that the manipulator moves the laser head in a predetermined direction relative to the surface of the workpiece.

16. 16. The laser welding apparatus according to claim 8, the laser oscillator and the laser head are connected by an optical fiber; A laser welding device, characterized in that the laser light is transmitted from the laser oscillator to the laser head through the optical fiber.

17. 17. The laser welding apparatus according to claim 8, The laser welding apparatus, characterized in that the laser light scanner is composed of a first galvanometer mirror that scans the laser light in the first direction and a second galvanometer mirror that scans the laser light in the second direction.

18. 18. The laser welding apparatus according to claim 8, The laser head further includes a focal position adjustment mechanism, The laser welding device, characterized in that the focal position adjustment mechanism is configured to change the focal position of the laser light along directions intersecting the first direction and the second direction.

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