Laser welding method and laser welding device

Abstract

The laser welding method includes a welding step in which a laser beam is directed in the X-direction and scanned two-dimensionally across the workpiece surface to form a weld bead sequentially comprising a starting portion, a main weld portion, and a terminal portion. In the welding step, the laser beam is vibrated in the X-direction as a sinusoidal wave with a first frequency and in the Y-direction as a sinusoidal wave with a second frequency. The laser beam is scanned to form a single Lissajous figure at the main weld portion, and separate Lissajous figures are formed at the starting portion and the terminal portion.

Description

Technical Field

[0001] The present disclosure relates to a laser welding method and a laser welding device. Background Art

[0002] Laser welding enables high-speed, high-quality welding due to the high power density of the laser beam irradiated onto the workpiece. In particular, in scanning welding, where the laser beam is scanned at high speed across the workpiece surface to perform welding, the laser beam can be moved at high speed to the next weld point during periods of inactivity, thereby shortening the overall welding time (see, for example, Patent Document 1). Furthermore, regarding laser scanning methods, methods have been proposed in which the laser beam is scanned to create a Lissajous pattern on the workpiece surface (see, for example, Patent Documents 2 and 3).

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2005-095934

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 60-177983

[0007] Patent Document 3: Japanese Patent Application Laid-Open No. 11-104877 Summary of the Invention

[0008] -Problems to be solved by the invention-

[0009] However, when laser welding forms a weld bead on a workpiece, the heat input at the starting and ending points may differ from that at other parts. In this case, there is a concern that the weld bead shape at the starting and ending points may deteriorate. Furthermore, in welding using a Lissajous waveform, the weld bead shape at the starting and ending points is affected by the shape of the Lissajous waveform, which may require improvement from the perspective of, for example, the static mechanical strength or dynamic fatigue strength of the weld joint.

[0010] However, the conventional structures disclosed in Patent Documents 2 and 3 do not disclose adjusting the heat input or bead shape at the start or end of the weld bead. In other words, they do not disclose an improvement method for improving the bead shape at the start or end of the weld bead.

[0011] The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a laser welding method and a laser welding device for obtaining a weld bead having a good shape including a starting end portion and an ending end portion.

[0012] -Methods for solving the problem-

[0013] In order to achieve the above-mentioned purpose, the laser welding method involved in the present disclosure comprises at least a welding step, in which a laser is caused to travel in a first direction and scanned two-dimensionally on the surface of a workpiece to form a weld bead on the workpiece that sequentially includes a starting end portion, a main welding portion, and a terminal portion. The welding step comprises: a first scanning step of vibrating the laser along the first direction as a sinusoidal wave having a first frequency, and vibrating the laser along a second direction intersecting the first direction as a sinusoidal wave having a second frequency, scanning the laser so as to depict a Lissajous figure at the main welding portion; and a second scanning step of scanning the laser at the starting end portion and the terminal portion so as to depict other Lissajous figures different from the one Lissajous figure.

[0014] The laser welding device involved in the present disclosure comprises at least: a laser oscillator for generating laser light; a laser head for receiving the laser light and irradiating the workpiece with the laser light; and a controller for controlling the operation of the laser head, wherein the laser head has a laser scanner for scanning the laser light in a first direction and a second direction intersecting the first direction, respectively. The controller drives and controls the laser scanner by causing the laser light to vibrate in a sinusoidal wave shape having a first frequency along the first direction and in a sinusoidal wave shape having a second frequency along the second direction, so that the laser light draws a Lissajous figure on the surface of the workpiece. Furthermore, the laser scanner is driven and controlled so that the laser light draws other Lissajous figures different from the one Lissajous figure at the starting end and the ending end of the weld bead formed on the workpiece.

[0015] -Effects of the Invention-

[0016] The laser welding method and laser welding device disclosed herein can form a weld bead having a good shape including a starting end portion and an ending end portion. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic configuration diagram of a laser welding device according to the first embodiment.

[0018] Figure 2 This is a schematic diagram of the laser scanner structure.

[0019] Figure 3A is a schematic diagram of the workpiece.

[0020] Figure 3B is a schematic diagram of another workpiece.

[0021] Figure 4 It is a plan view of the weld bead.

[0022] Figure 5AThis is an example of a scanning pattern of the laser beam irradiated onto the main weld portion of the weld bead.

[0023] Figure 5B This is an example of a scanning pattern of the laser beam irradiated onto the starting end of the weld bead.

[0024] Figure 5C This is an example of a scanning pattern of the laser beam irradiated toward the terminal end of the weld bead.

[0025] Figure 5D This is a schematic diagram explaining a method of changing the phase of a Lissajous waveform.

[0026] Figure 6 This figure shows a scanning pattern of the laser beam when the phase of the rotational motion of the second reflecting mirror is changed stepwise.

[0027] Figure 7A is a schematic plan view of the weld beads involved in the comparison.

[0028] Figure 7B It is a schematic plan view of the starting end portion of the weld bead involved in the comparison.

[0029] Figure 7C 1 is a schematic plan view of the terminal end of the weld bead involved in the comparison.

[0030] Figure 8 It is a schematic plan view of a weld bead according to a modification.

[0031] Figure 9A It is Figure 8 The figure shows an example of a scanning pattern of a laser beam irradiated on the main weld portion of the weld bead.

[0032] Figure 9B It is Figure 8 An example of a scanning pattern of a laser beam irradiated at the starting end of a weld bead is shown.

[0033] Figure 9C It is Figure 8 An example of a scanning pattern of a laser beam irradiated at the terminal end of a weld bead is shown.

[0034] Figure 10 It is a schematic plan view of another weld bead according to a modification.

[0035] Figure 11A It is Figure 10 The figure shows an example of a scanning pattern of a laser beam irradiated on the main weld portion of the weld bead.

[0036] Figure 11B It is Figure 10 An example of a scanning pattern of a laser beam irradiated at the starting end of a weld bead is shown.

[0037] Figure 11C It is Figure 10 An example of a scanning pattern of a laser beam irradiated at the terminal end of a weld bead is shown.

[0038] Figure 12 It is a diagram showing a scanning pattern of the laser beam when the amplitude of the first reflecting mirror is changed.

[0039] Figure 13 This is a schematic plan view of a weld bead according to the second embodiment.

[0040] Figure 14A This is an example of a scanning pattern of the laser beam irradiated onto the main weld portion of the weld bead.

[0041] Figure 14B This is an example of a scanning pattern of the laser beam irradiated onto the starting end of the weld bead.

[0042] Figure 14C This is an example of a scanning pattern of the laser beam irradiated toward the terminal end of the weld bead.

[0043] Figure 15 It is a diagram showing a scanning pattern of a laser beam when the rotation frequency ratio of the first reflecting mirror and the second reflecting mirror is changed. DETAILED DESCRIPTION

[0044] Hereinafter, embodiments of the present disclosure will be described based on the accompanying 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 applications, or its uses.

[0045] [Structure of Laser Welding Device and Laser Scanner]

[0046] Figure 1 A schematic diagram showing the structure of a laser welding device according to this embodiment, Figure 2 A diagram showing the schematic structure of a laser scanner. Figure 3A A schematic diagram representing the workpiece, Figure 3B A schematic diagram representing another workpiece.

[0047] In the following description, the direction parallel to the direction of travel of the laser beam LB from the reflector 33 to the laser scanner 40 is sometimes referred to as the X direction, the direction parallel to the optical axis of the laser beam LB emitted from the laser head 30 is sometimes referred to as the Z direction, and the direction perpendicular to the X and Z directions is sometimes referred to as the Y direction. When the surface of the workpiece 200 is a flat surface, the XY plane containing the X and Y directions may be substantially parallel to the surface or may have a certain angle therewith.

[0048] like Figure 1As shown, the laser welding device 100 includes a laser oscillator 10 , an optical fiber 20 , a laser head 30 , a controller 50 , and a robot 60 .

[0049] The laser oscillator 10 is a laser source that generates laser light LB, supplied with power from a power supply (not shown). The laser oscillator 10 may comprise a single laser source or multiple laser modules. In the latter case, the laser beams emitted from the multiple laser modules are coupled and emitted as laser light LB. The laser source or laser module used in the laser oscillator 10 is appropriately selected based on the material of the workpiece 200, the shape of the weld, and other factors.

[0050] For example, a fiber laser, a disk laser, or a YAG (Yttrium Aluminum Garnet) laser can also be used as a laser source. In this case, the wavelength of the laser LB is set to a range of 1000nm to 1100nm. In addition, a semiconductor laser can also be used as a laser source or a laser module. In this case, the wavelength of the laser LB is set to a range of 800nm ​​to 1000nm. In addition, a visible light laser can also be used as a laser source or a laser module. In this case, the wavelength of the laser LB is set to a range of 400nm to 600nm.

[0051] The optical fiber 20 is optically coupled to the laser oscillator 10 . The laser light LB generated by the laser oscillator 10 is incident on the optical fiber 20 and is transmitted inside the optical fiber 20 toward the laser head 30 .

[0052] The laser head 30 is attached to the end of the optical fiber 20 and irradiates the workpiece 200 with the laser beam LB transmitted from the optical fiber 20 .

[0053] The laser head 30 includes a collimator lens 32 , a reflective mirror 33 , a condenser lens 34 , and a laser scanner 40 as optical components. These optical components are housed in a predetermined arrangement relationship within the housing 31 .

[0054] The collimating lens 32 receives the laser light LB emitted from the optical fiber 20, converts it into parallel light, and makes it incident on the reflector 33. In addition, the collimating lens 32 is connected to a driving unit (not shown) and is configured to be displaceable in the Z direction according to a control signal from the controller 50. By displacing the collimating lens 32 in the Z direction, the focal position of the laser light LB is changed, and the laser light LB can be appropriately irradiated according to the shape of the workpiece 200. In other words, the collimating lens 32, in combination with the driving unit (not shown), also functions as a focal position adjustment mechanism for the laser light LB. In addition, the focusing lens 34 can also be displaced by the driving unit to change the focal position of the laser light LB.

[0055] The reflecting mirror 33 reflects the laser light LB transmitted through the collimating lens 32 and makes it incident on the laser scanner 40. The surface of the reflecting mirror 33 is provided so as to make an angle of about 45 degrees with respect to the optical axis of the laser light LB transmitted through the collimating lens 32.

[0056] The condenser lens 34 condenses the laser light LB reflected by the reflection mirror 33 and scanned by the laser scanner 40 onto the surface of the workpiece 200 .

[0057] like Figure 2 As shown, the laser scanner 40 is a well-known galvano scanner having a first galvano mirror 41 and a second galvano mirror 42. The first galvano mirror 41 includes a first reflector 41a, a first rotating shaft 41b, and a first drive unit 41c. The second galvano mirror 42 includes a second reflector 42a, a second rotating shaft 42b, and a second drive unit 42c. Laser light LB transmitted through the condenser lens 34 is reflected by the first reflector 41a, further reflected by the second reflector 42a, and irradiated onto the surface of the workpiece 200.

[0058] For example, the first drive unit 41c and the second drive unit 42c are electric motors, and the first rotating shaft 41b and the second rotating shaft 42b are output shafts of the motors. Although not shown, the first drive unit 41c is driven to rotate by a driver activated by a control signal from the controller 50, thereby rotating the first reflector 41a attached to the first rotating shaft 41b about the axis of the first rotating shaft 41b. Similarly, the second drive unit 42c is driven to rotate by a driver activated by a control signal from the controller 50, thereby rotating the second reflector 42a attached to the second rotating shaft 42b about the axis of the second rotating shaft 42b.

[0059] The first reflector 41a rotates around the first rotation axis 41b at a predetermined angle, thereby scanning the laser beam LB in the X direction. Furthermore, the second reflector 42a rotates around the second rotation axis 42b at a predetermined angle, thereby scanning the laser beam LB in the Y direction. In other words, the laser scanner 40 is configured to scan the laser beam LB two-dimensionally within the XY plane and irradiate the workpiece 200.

[0060] 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 output current and on / off timing to a power supply (not shown) connected to the laser oscillator 10.

[0061] Furthermore, the controller 50 controls the operation of the laser head 30 based on the contents of the selected laser welding program. Specifically, it controls the driving of the laser scanner 40 and the collimating lens 32 (not shown) provided in the laser head 30. Furthermore, the controller 50 controls the operation of the robot 60. The laser welding program is stored in a storage unit (not shown) within the controller 50 or elsewhere and is retrieved by a command from the controller 50.

[0062] The controller 50 includes an integrated circuit such as an LSI or a microcomputer (not shown), and the functions of the controller 50 are realized by executing a laser welding program as software on the integrated circuit.

[0063] The robot 60 is a multi-jointed robot mounted on the housing 31 of the laser head 30. The robot 60 is connected to the controller 50 for signal transmission and reception, and moves the laser head 30 so that it traces a predetermined trajectory according to the laser welding program. Alternatively, another controller (not shown) may be provided to control the movement of the robot 60.

[0064] Figure 1 The laser welding device 100 shown in FIG. 1 is capable of laser welding workpieces 200 of various shapes. Figure 3A As shown in FIG, a joint of a workpiece 200 in which a first plate 210 and a second plate 220 are butt-welded by irradiating laser beam LB. Figure 3B As shown, the corner of the joint of the workpiece 200 in which the third plate 230 and the fourth plate 240 are overlapped with each other with their end faces offset can be irradiated with laser LB to perform lap fillet welding. However, it can be said that the shape of the workpiece 200 to be laser welded is not limited to Figure 3A 、 Figure 3B Example shown.

[0065] [Laser welding method]

[0066] Figure 4 A schematic plan view showing a weld bead. Figure 5A This shows an example of a scanning pattern of a laser beam irradiated onto the main weld portion of a weld bead. Figure 5B An example of a scanning pattern of a laser beam irradiated to the starting end of a weld bead is shown. Figure 5C An example of a scanning pattern of a laser beam irradiated onto the terminal end of a weld bead is shown.

[0067] like Figure 4As shown, a weld bead 300 sequentially comprises a starting portion 301, a main weld portion 302, and a terminal portion 303. For example, a robot 60 moves a laser head 30 linearly in the X direction at a constant speed on a plate workpiece 200 while irradiating the workpiece 200 with laser light LB, thereby forming the weld bead 300. Furthermore, during irradiation with laser light LB, a laser scanner 40 scans the surface of the workpiece 200 two-dimensionally. The length of the starting portion 301 in the X direction is denoted by L1, the length of the terminal portion 303 in the X direction is denoted by L2, and the width of the main weld portion 302 in the Y direction is denoted by W. Width W corresponds to the width of the weld bead 300 in the Y direction.

[0068] like Figure 5A As shown, laser light LB is scanned to draw a Lissajous figure in the XY plane, in this case, on the surface of the workpiece 200. In the following description, a plurality of Lissajous figures of different shapes may be referred to as patterns i (i=1, 2, 3, etc.). Figure 5A The Lissajous figure shown is called pattern 4.

[0069] The width of pattern 4 in the X direction is equal to the width in the Y direction. When the welding speed is very high, 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, the terms "approximately equal" or "approximately the same" refer to the control results of the controlled objects being the same or identical, including errors in the control system. It does not strictly require that the two objects being compared be the same or identical. Furthermore, the terms "approximately equal" or "approximately the same" are also used to mean that the manufacturing tolerances and assembly tolerances of various components are the same or identical.

[0070] Pattern 4 can be obtained by vibrating the laser light LB in the X direction as a sinusoidal wave of a predetermined frequency, and in the Y direction as a sinusoidal wave of a frequency different from that in the X direction (1 / 2 of the frequency in the X direction). Furthermore, 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 reflector 41a and the second reflector 42a. Generally, when the position coordinates of the Lissajous waveform obtained by driving the first reflector 41a are X1 and the position coordinates of the Lissajous waveform obtained by driving the second reflector 42a are Y1, the position coordinates X1 and Y1 are expressed by the following equations (1) and (2), respectively.

[0071] X1=a×sin(nt)···(1)

[0072]

[0073] Here,

[0074] a: Amplitude of the Lissajous waveform in the X direction

[0075] b: Amplitude of the Lissajous waveform in the Y direction

[0076] n: frequency of the first reflecting mirror 41a

[0077] m: frequency of the second reflecting mirror 42a

[0078] t: time

[0079] The phase difference when the first reflecting mirror 41 a or the second reflecting mirror 42 a is driven is, specifically, the angular deviation amount provided during the rotational motion of the first reflecting mirror 41 a and the second reflecting mirror 42 a .

[0080] The position coordinates X1 and Y1 shown in equations (1) and (2) can be expressed by a stationary coordinate system of a Lissajous waveform in a state where the position of the laser head 30 is fixed.

[0081] The amplitude a of the first reflecting mirror 41a and the amplitude b of the second reflecting mirror 42a correspond to the scanning amplitudes in the X and Y directions of the laser beam LB, respectively. The frequency n and the frequency m correspond to the driving frequencies of the first reflecting mirror 41a and the second reflecting mirror 42a, respectively.

[0082] Pattern 4 is a pattern in which a=1, b=1, n=2, m=1, The corresponding 8-shaped Lissajous figure in the case of . a and b are standardized by 1. In actual welding, the parameters a, b, n, and m are appropriately changed according to the material of the workpiece 200, the shape of the joint, the required weld bead shape width, etc. In order to obtain pattern 4, it is set to a=b, |n|=|2m|. Regarding n and m, the signs of the two (in other words, whether positive (+) or negative (-)) represent the driving directions of the first reflector 41a and the second reflector 42a. The two can be set to the same direction (sign) or a combination of different directions (signs). In addition, the driving frequency of the first reflector 41a is always set to twice the driving frequency of the second reflector 42a. The phase difference between formulas (1) and (2) It may be either 0 degrees or 180 degrees.

[0083] exist Figure 4 The weld bead 300 shown in FIG. 1 is a weld bead 300 in which the laser beam LB is scanned to draw a line when the laser beam LB is scanned to draw a line when the laser beam LB is scanned to draw a line when the laser beam LB is scanned to draw a line Figure 5A The pattern shown is 4 while proceeding.

[0084] On the other hand, when welding the starting end portion 301 of the weld bead 300, the laser head 30 is moved at a constant speed in the X direction, and Figure 5B As shown in FIG. 1 , the scanning pattern of the laser LB is continuously changed to pattern 1 → pattern 2 → pattern 3 → pattern 4. When welding the terminal portion 303 of the weld bead 300, the laser head 30 is moved at a constant speed in the X direction, and as shown in FIG. Figure 5C As shown, the scanning pattern of laser LB is continuously changed to Pattern 4 → Pattern 5 → Pattern 6 → Pattern 7. Pattern 1 is a single-peaked parabolic pattern in the XY plane. As it progresses from Pattern 2 to Pattern 3, it changes to a continuous double-peaked pattern, ultimately becoming Pattern 4. Similarly, as it progresses from Pattern 4 to Pattern 5 and then to Pattern 6, the figure-eight pattern changes to a continuous double-peaked pattern. Ultimately, as shown in Pattern 7, it becomes a single-peaked parabolic pattern in the XY plane.

[0085] In pattern 4 and the other patterns 1 to 3, 5 to 7, the parameters shown in equations (1) and (2) are the same values ​​for the amplitudes a and b of the first reflector 41a and the second reflector 42a, and the frequencies n and m of the first reflector 41a and the second reflector 42a (a = b = 1, n = 2, m = 1). In other words, the difference in shape between pattern 4 and the other patterns is expressed by the phase difference shown in equation (2). The difference is caused.

[0086] Figure 6 The scanning pattern of the laser beam when the phase of the rotational motion of the second reflecting mirror is changed stepwise is shown. Figure 6 It can be seen that in pattern 4, the phase is 0 degrees, whereas in Pattern 1 and Pattern 2, the phase They are set to 45 degrees and 30 degrees respectively. Figure 5B In the pattern 3 shown, the phase It is a value between 0 degrees and 30 degrees.

[0087] In other words, the laser scanner 40 is driven and controlled so that the phase of the rotational motion of the second reflecting mirror 42a is In other words, the phase of the Y-direction vibration of the laser beam LB is changed at predetermined intervals from 45 degrees to 0 degrees, thereby performing laser welding to form the starting end portion 301 of the weld bead 300.

[0088] In addition, although not shown in the figure, Figure 5C In the pattern 5 shown, the phase is -15 degrees, in pattern 6, the phase is -30 degrees, in pattern 7, the phase It's -45 degrees.

[0089] In other words, the laser scanner 40 is driven and controlled so that the phase of the Y-direction vibration of the laser beam LB changes from 0 degrees to -45 degrees at predetermined intervals, thereby performing laser welding and forming the terminal end portion 303 of the weld bead 300 .

[0090] use Figure 5D To illustrate the Figure 5B and Figure 5C Phase A method that changes at specified intervals. Figure 5D This is a schematic diagram illustrating a method for changing the phase of a Lissajous waveform. For simplicity, the method for changing from pattern 1 to pattern 2 is described. Since other patterns can also be changed using the same method, the description is omitted.

[0091] exist Figure 5D In the figure, the solid line represents pattern 1 (phase degrees), the dotted line represents pattern 2 (phase Spend).

[0092] For ease of explanation, both are depicted in the same figure. In pattern 1, the drawing start position is P10, and as indicated by the arrow, the Lissajous pattern 1 is drawn in the order of P11, P10, P12, P13, P12, and P10 for one cycle. On the other hand, in pattern 2, the drawing start position is P20, and as indicated by the arrow, the Lissajous pattern 2 is drawn in the order of P21, P22, P23, P24, P25, P23, and P20 for one cycle. Here, Figure 5D In the example, the drawing start points are set to P10 and P20, but they may be set to other points.

[0093] During welding, the phase is switched immediately after one cycle of a Lissajous pattern is drawn. At the timing shown in the figure, the laser LB is moved from point P10 after the drawing of pattern 1 is completed to point P20, the drawing start point of the next pattern 2, and switched to pattern 2. The phase difference between pattern 1 and pattern 2 is 15 degrees, so Figure 5D In the figure, the distance between P10 and P20 appears long. In this case, the switching between Pattern 1 and Pattern 2 results in a large step size for beam movement, leaving a large mark on the weld bead. In actual welding, keeping this step size as small as possible allows for smooth movement of the laser beam LB, resulting in a good weld bead.

[0094] In addition, the interval of the phase difference can be obtained in advance through welding tests. After the drawing of pattern 1 is completed, the phase difference between the next pattern to be drawn and the phase of pattern 1 can be set to a predetermined interval determined in advance through the welding test. Figure 5B As shown, the laser scanner 40 is driven and controlled so that the phase of the Y-direction vibration of the laser beam LB changes from 45 degrees to 0 degrees at the predetermined interval, thereby performing laser welding and forming a good starting end portion 301.

[0095] In addition, a good terminal portion 303 can be formed by the same principle as described above, so its detailed description is omitted here.

[0096] In this way, if Figure 4 As shown, the weld bead 300 can have a good shape at the starting end portion 301 and the ending end portion 303 .

[0097] [Effects, etc.]

[0098] As described above, the laser welding method involved in this embodiment includes at least a welding step, in which the laser LB is caused to move in the X direction (first direction) and the laser LB is scanned two-dimensionally on the surface of the workpiece 200 to form a weld bead 300 on the workpiece 200, which sequentially includes a starting portion 301, a main welding portion 302 and an end portion 303.

[0099] During the welding step, laser light LB is vibrated in the X direction as a sinusoidal wave having a first frequency corresponding to frequency n, and in the Y direction as a sinusoidal wave having a second frequency corresponding to frequency m. Thus, laser light LB is scanned to form a Lissajous figure (pattern 4) on the main weld portion 302 (first scanning step).

[0100] Furthermore, the laser beam LB is scanned at the starting portion 301 and the ending portion 303 so as to draw other Lissajous figures (patterns 1 to 3 and patterns 5 to 7) different from the pattern 4 (second scanning step).

[0101] By adopting such a laser welding method, it is possible to achieve a good weld bead shape not only in the main weld portion 302 but also in the start end portion 301 and the end end portion 303. This will be described further.

[0102] Figure 7A A schematic plan view showing the welds involved in the comparison, Figure 7B A schematic plan view showing the start of a weld bead. Figure 7C A schematic plan view showing the terminal end of a weld bead.

[0103] Figure 7A The weld bead 310 shown is formed by moving the laser head 30 linearly in the X direction at a constant speed using the robot 60 and scanning the laser LB two-dimensionally on the surface of the workpiece 200 using the laser scanner 40. Figure 4 The weld beads 300 shown are formed in the same manner.

[0104] On the other hand, the difference from the method of the present disclosure is that, in forming Figure 7A In the weld bead 310 shown, the scanning pattern of the laser LB is only one type of pattern 4.

[0105] In this case, if Figures 7A to 7C As shown, the scanning pattern of laser LB is reflected as the weld bead shape at the starting end 311 and the ending end 313 of weld bead 310. In other words, recessed portions 314 are formed in the X direction at the starting end 311 and the ending end 313 of weld bead 310, respectively, impairing the appearance of weld bead 310.

[0106] In addition, the workpiece 200 may not penetrate deeply enough in the recess 314, which may result in welding defects. Figure 3B In the lap fillet weld shown, if the ends of the third plate 230 and the fourth plate 240 in the direction perpendicular to the paper are formed Figures 7A to 7C If the recess 314 is not shown, the joining between the third plate 230 and the fourth plate 240 may become insufficient, resulting in welding defects.

[0107] On the other hand, according to the laser welding method of this embodiment, in the welding step, by performing the second scanning step, it is possible to suppress the formation of the starting end portion 301 and the terminal end portion 303 of the weld bead 300. Figures 7A to 7C As shown in the concave portion 314. This makes it possible to improve the shape of the weld bead 300 from the start end to the end end. In addition, the aesthetic appearance of the weld bead 300 can be improved.

[0108] Furthermore, when forming the weld bead 300 , by scanning the laser light LB so as to draw a Lissajous figure, it is possible to reduce uneven heat input in the irradiation area of ​​the laser light LB, and to obtain a good weld bead shape.

[0109] For example, while controlling the amplitude a of the first reflector 41a and the second reflector 42a, the robot 60 may be moved so that the laser light LB forms a circular pattern, and laser welding may be performed so that the laser light 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 being welded differs depending on whether the trajectory rotates clockwise or counterclockwise. As shown in this embodiment, by scanning the laser light LB, this imbalance in heat input can be eliminated, resulting in a good weld bead shape.

[0110] In the second scanning step, the laser beam LB is preferably scanned so that the phase of the sinusoidal wave along the Y direction continuously changes.

[0111] More preferably, in the second scanning step, when forming the starting portion 301, the laser LB is scanned so that the phase of the sine wave along the Y direction changes from 45 degrees to 0 degrees at a prescribed interval, and when forming the terminal portion 303, the laser LB is scanned so that the phase of the sine wave along the Y direction changes from 0 degrees to -45 degrees at a prescribed interval.

[0112] In this manner, the width of the weld bead 300 in the Y direction can be continuously varied from the starting end of the weld bead 300 to the main weld portion 302, and also from the main weld portion 302 to the end of the weld bead 300. This improves the weld bead shape not only in the main weld portion 302 but also in the starting end portion 301 and the end portion 303. Furthermore, the aesthetic appearance of the weld bead 300 can be improved.

[0113] The lengths L1 and L2 of the start portion 301 and the end portion 303 in the X direction may be approximately equal to or greater than the sum of 1 / 2 of the width of the pattern 4 in the X direction and the width W of the weld bead 300 in the Y direction.

[0114] By setting the lengths L1 and L2 in this manner, it is possible to reliably suppress the formation of the recessed portion 314 at the starting end portion 301 and the terminal end portion 303 of the weld bead 300 .

[0115] The laser welding device 100 according to 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 the workpiece 200 , and a controller 50 that controls the operation of the laser head 30 .

[0116] The laser head 30 includes a laser scanner 40 that scans the laser beam LB in both the X direction (first direction) and the Y direction (second direction) intersecting the X direction.

[0117] The controller 50 causes the laser beam LB to vibrate in a sinusoidal manner with a first frequency in the X direction and in a sinusoidal manner with a second frequency in the Y direction. The controller 50 thereby controls the driving of the laser scanner 40 so that the laser beam LB draws a Lissajous figure (Pattern 4) on the surface of the workpiece 200.

[0118] Furthermore, the controller 50 drives and controls the laser 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 .

[0119] The laser welding apparatus 100 of this embodiment can improve the weld bead shape not only in the main weld portion 302 but also in the start end portion 301 and the terminal end portion 303 .

[0120] Preferably, the controller 50 controls the driving of the laser scanner 40 so that the phase of the sinusoidal wave along the Y direction is continuously changed at the starting end portion 301 and the ending end portion 303 of the weld bead 300 .

[0121] More preferably, when forming the starting end portion 301 , the controller 50 controls the driving of the laser scanner 40 so that the phase of the sine wave along the Y direction changes from 45 degrees to 0 degrees at predetermined intervals.

[0122] When the terminal portion 303 is formed, the laser scanner 40 is driven and controlled so that the phase of the sine wave along the Y direction changes from 0 degrees to -45 degrees at predetermined intervals.

[0123] By configuring the controller 50 in this manner, the weld bead shape can be improved not only in the main weld portion 302 but also in the start end portion 301 and the end end portion 303. Furthermore, the appearance of the weld bead 300 can be improved.

[0124] The laser welding apparatus 100 further includes a robot 60 to which the laser head 30 is attached, and the controller 50 controls the operation of the robot 60. The robot 60 moves the laser head 30 in a predetermined direction relative to the surface of the workpiece 200.

[0125] By providing the robot 60 in this manner, the welding direction of the laser beam LB can be changed. Furthermore, laser welding can be easily performed on a workpiece 200 having a complicated shape, for example, a three-dimensional shape.

[0126] The laser oscillator 10 and the laser head 30 are connected via an optical fiber 20 , and the laser light LB is transmitted from the laser oscillator 10 to the laser head 30 via the optical fiber 20 .

[0127] By providing the optical fiber 20 in this manner, it is possible to perform laser welding on the workpiece 200 that is provided at a position away from the laser oscillator 10. This improves the degree of freedom in arranging the various components of the laser welding apparatus 100.

[0128] The laser scanner 40 includes a first galvano mirror 41 that scans the laser beam LB in the X direction and a second galvano mirror 42 that scans the laser beam LB in the Y direction.

[0129] By configuring the laser scanner 40 in this manner, it is possible to easily perform two-dimensional scanning of the laser beam LB. Furthermore, since a well-known current scanner is used as the laser scanner 40, it is possible to suppress an increase in the cost of the laser welding apparatus 100.

[0130] <Modification>

[0131] Figure 8 A schematic plan view of a weld bead according to this modification is shown. Figure 9A Indicates Figure 8 The following is an example of a scanning pattern of a laser beam irradiated on the main weld portion of a weld bead. Figure 9B Indicates Figure 8 The following is an example of a scanning pattern of a laser beam irradiated at the beginning of a weld bead. Figure 9C Indicates Figure 8 An example of a scanning pattern of a laser beam irradiated at the terminal end of a weld bead is shown.

[0132] Figure 10 A schematic plan view of another weld bead according to this modification is shown. Figure 11A Indicates Figure 10 The following is an example of a scanning pattern of a laser beam irradiated on the main weld portion of a weld bead. Figure 11B Indicates Figure 10 The following is an example of a scanning pattern of a laser beam irradiated at the beginning of a weld bead. Figure 11C Indicates Figure 10 An example of a scanning pattern of a laser beam irradiated at the terminal end of a weld bead is shown.

[0133] Figure 12 The scanning pattern of the laser beam when the amplitude of the first reflecting mirror is changed is shown.

[0134] In the laser welding method described in Embodiment 1, the amplitude a of the first reflector 41a and the amplitude b of the second reflector 42a are set to the same value (normalized to 1). Furthermore, the laser welding apparatus 100 controls the laser scanner 40 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 approximately equal.

[0135] However, from the viewpoint of aesthetics required for the appearance, Figure 4 The starting end 301 and the ending end 303 of the weld bead 300 shown in FIG. 3 preferably have a rounded shape so that the width in the X direction changes gradually.

[0136] In order to meet the above requirements, in this modification, the amplitude a of the first reflecting mirror 41a is made smaller than 1, and the scanning amplitude of the laser beam LB in the X direction is made smaller than the scanning amplitude in the Y direction. Figure 12 In the example (pattern 8) shown in (b), a=0.5, Figure 12 In the example shown in FIG. 9( c ) (pattern 9), a = 0.25. Here, the amplitude in the Y direction is normalized to 1.

[0137] The laser head 30 is moved along the X direction at a certain speed. Figures 9A to 9C The laser LB is scanned as shown, so that Figure 8 As shown, at the starting end portion 321 and the ending end portion 323 of the weld bead 320 , the change in the width in the X direction can be made gentle and rounded.

[0138] In addition, if Figure 9B As shown, at the starting end portion 321, the scanning pattern of the laser LB is continuously changed to pattern 11 → pattern 12 → pattern 13 → pattern 8. Figure 9C As shown, at the terminal portion 323, the scanning pattern of the laser LB is continuously changed to pattern 8 → pattern 14 → pattern 15 → pattern 16. Figure 9A As shown, the scanning pattern of the laser beam LB at the main welding portion 322 is fixed to pattern 8 .

[0139] In this case, the phase of the second reflector 42a is Changes and Figure 5B 、 5C In other words, in pattern 8, the phase is 0 degrees, in pattern 11, the phase is 45 degrees. In pattern 12, the phase is 15 degrees, in pattern 13, phase is 30 degrees. In addition, in pattern 14, the phase is -15 degrees, in pattern 15, phase is -30 degrees, in pattern 16, phase It's -45 degrees.

[0140] In addition, in any of pattern 8 and patterns 11 to 16, the amplitude a of the first reflecting mirror 41 a is naturally 0.5.

[0141] In addition, the laser head 30 is moved at a certain speed along the X direction. Figures 11A to 11C The laser LB is scanned as shown, so that Figure 10 As shown, at the starting end portion 331 and the terminal end portion 333 of the weld bead 330, the width change ratio in the X direction can be made Figure 8 The weld bead 320 shown is more gradual and further rounded.

[0142] In addition, if Figure 11B As shown, at the starting end portion 331, the scanning pattern of the laser LB is continuously changed to pattern 17 → pattern 18 → pattern 19 → pattern 9. Figure 11C As shown, at the terminal portion 333, the scanning pattern of the laser LB is continuously changed to pattern 9 → pattern 20 → pattern 21 → pattern 22. Figure 11A As shown, the scanning pattern of the laser beam LB at the main welding portion 332 is fixed to pattern 9.

[0143] In this case, the phase of the second reflector 42a is The changes are also related to Figure 5B 、 5C In other words, in pattern 9, the phase is 0 degrees, in pattern 17, phase is 45 degrees. In pattern 18, the phase is 30 degrees, in pattern 19, phase is 15 degrees. In addition, in pattern 20, the phase is -15 degrees, in pattern 21, phase is -30 degrees, in pattern 22, phase It's -45 degrees.

[0144] In addition, in any of pattern 9 and patterns 17 to 22, the amplitude a of the first reflecting mirror 41 a is naturally 0.25.

[0145] (Implementation Method 2)

[0146] Figure 13 A schematic plan view of a weld bead according to this embodiment is shown. Figure 14A This shows an example of a scanning pattern of a laser beam irradiated onto the main weld portion of a weld bead. Figure 14B An example of a scanning pattern of a laser beam irradiated to the starting end of a weld bead is shown. Figure 14C An example of a scanning pattern of a laser beam irradiated onto the terminal end of a weld bead is shown.

[0147] Figure 15 The scanning pattern of the laser beam when the rotation frequency ratio of the first reflecting mirror and the second reflecting mirror is changed is shown.

[0148] In this embodiment, the weld bead 340 is formed along the Y direction. In other words, 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), scanning the laser beam LB two-dimensionally. Furthermore, the laser welding apparatus 100 controls the driving of the laser scanner 40 to satisfy this condition.

[0149] In addition, it is necessary to change the scanning pattern of the laser LB from Figure 15 The pattern 4 shown in FIG. (a) is changed to Figure 15 (b) shows pattern 10. Specifically, the frequencies n and m of the first reflector 41a and the second reflector 42a are changed from n = 2, m = 1 to n = 1, m = 2. In other words, the drive frequency ratio of the first reflector 41a and the second reflector 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 the first reflector 41a and the second reflector 42a can be appropriately changed according to the shape of the workpiece 200 or the desired weld bead shape.

[0150] The laser head 30 is moved along the Y direction at a certain speed. Figures 14A to 14C As shown, by scanning the laser LB, it is possible to form Figure 13 The weld bead 340 shown in FIG. Furthermore, in this case, a good weld bead shape can be obtained at the starting end portion 341, the terminal end portion 343, and the main weld portion 342. Furthermore, the aesthetic appearance of the weld bead 340 can be improved.

[0151] In addition, if Figure 14B As shown, at the starting end portion 341, the scanning pattern of the laser LB is continuously changed to pattern 23 → pattern 24 → pattern 25 → pattern 10. Figure 14C As shown, at the terminal portion 343, the scanning pattern of the laser LB is continuously changed to pattern 10 → pattern 26 → pattern 27 → pattern 28. Figure 14A As shown, the scanning pattern of the laser beam LB at the main welding portion 342 is fixed to pattern 10 .

[0152] In this case, the phase of the second reflector 42a is Changes and Figure 5B 、 5C In other words, in pattern 10, the phase is 0 degrees, in pattern 23, the phase is -90 degrees. In pattern 24, the phase is -60 degrees, in pattern 25, the phase is -30 degrees. In addition, in pattern 26, the phase is 30 degrees. In pattern 27, the phase is 60 degrees. In pattern 28, the phase It's 90 degrees.

[0153] In any of pattern 10 and patterns 21 to 26, the relationship a=b=1, n=1, and m=2 naturally holds. Note that a=b is a value normalized to 1, and n=1 and m=2 normalize the frequency relationship (1:2).

[0154] (Other embodiments)

[0155] It is also possible to appropriately combine the constituent elements described in the first and second embodiments and the modified examples to form new embodiments.

[0156] For example, in the configuration shown in Embodiment 2, by setting the amplitude b of the second reflector 42a to less than 1, as shown in a modified example, the width of the weld bead 340 can be made to change more gently in the Y direction, creating a rounded arc at the starting end 341 and the ending end 343. This improves the aesthetic appearance of the weld bead 340. Furthermore, the weld quality can be improved by adjusting the shape of the workpiece 200.

[0157] In addition, Figure 1 In the example shown, the condenser lens 34 is arranged in front of the laser scanner 40 , but may be arranged in the rear of the laser scanner 40 , in other words, between the laser scanner 40 and the light emission port of the laser head 30 .

[0158] Alternatively, the laser beam LB may be vibrated in a cosine wave shape having a first frequency in the X direction and in a cosine wave shape having a second frequency in the Y direction, so that the scanning pattern of the laser beam LB becomes a Lissajous figure. In this case, the amplitudes a and b of the first reflecting mirror 41a and the second reflecting mirror 42a, the frequencies n and m of the first reflecting mirror 41a and the second reflecting mirror 42a, and the phases Of course, it can be changed appropriately.

[0159] Industrial applicability

[0160] The laser welding method and the laser welding method disclosed herein can improve the shape of a weld bead including a starting end portion and an ending end portion, and are therefore useful.

[0161] -Explanation of symbols-

[0162] 10Laser oscillator

[0163] 20 optical fibers

[0164] 30 laser heads

[0165] 31 shell

[0166] 32 collimating lens

[0167] 33 reflectors

[0168] 34 focusing lens

[0169] 40 laser scanners

[0170] 41 1st current mirror

[0171] 41a 1st reflector

[0172] 41b 1st rotation axis

[0173] 41c 1st drive unit

[0174] 42 Second Current Mirror

[0175] 42a Second reflecting mirror

[0176] 42b Second rotation axis

[0177] 42c Second drive unit

[0178] 200 workpieces

[0179] 300, 310, 320, 330, 340 welds

[0180] 301, 311, 321, 331, 341 beginning and end

[0181] 302, 312, 322, 332, 342 main welding parts

[0182] 303, 313, 323, 333, 343 terminal units

[0183] 314 recess.

Claims

1. A laser welding method comprising: a welding step of causing a laser to travel in a first direction and scanning the laser two-dimensionally on a surface of a workpiece, thereby forming a weld bead including, in sequence, a starting end portion, a main welding portion, and an ending portion on the workpiece; The welding step comprises: a first scanning step of vibrating the laser beam in a sinusoidal wave shape having a first frequency along the first direction and in a sinusoidal wave shape having a second frequency along a second direction intersecting the first direction, thereby scanning the laser beam so as to draw a Lissajous figure on the main weld portion; and The second scanning step is to scan the laser beam at the starting end portion and the ending portion so as to draw another Lissajous figure different from the one Lissajous figure.

2. The laser welding method according to claim 1, wherein: In the second scanning step, the laser beam is scanned so that the phase of the sinusoidal wave along the second direction changes at predetermined intervals.

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

2.

4. The laser welding method according to claim 3, wherein: When the ratio of the first frequency to the second frequency is 2:1, In the second scanning step, when forming the starting end portion, the laser beam is scanned so that the phase of the sine wave along the second direction changes from 45 degrees to 0 degrees at predetermined intervals. When forming the terminal portion, the laser beam is scanned so that the phase of the sine wave along the second direction changes from 0 degrees to -45 degrees at predetermined intervals. When the ratio of the first frequency to the second frequency is 1:2, In the second scanning step, when forming the starting end portion, the laser beam is scanned so that the phase of the sine wave along the second direction changes from -90 degrees to 0 degrees at predetermined intervals. When forming the terminal portion, the laser beam is scanned so that the phase of the sinusoidal wave along the second direction changes from 0 degrees to 90 degrees at predetermined intervals.

5. The laser welding method according to any one of claims 1 to 4, wherein: In the first scanning step and the second scanning step, the scanning amplitude of the laser beam in the first direction is substantially equal to the scanning amplitude of the laser beam in the second direction.

6. The laser welding method according to any one of claims 1 to 4, wherein: In the first scanning step and the second scanning step, a scanning amplitude of the laser beam in the first direction is different from a scanning amplitude of the laser beam in the second direction.

7. The laser welding method according to any one of claims 1 to 4, wherein: The lengths of the starting end portion and the terminal end portion of the weld bead in the first direction are respectively approximately equal to or greater than the sum of 1 / 2 of the width of the one Lissajous figure in the first direction and the width of the weld bead in the second direction.

8. A laser welding device comprising at least: Laser oscillator, which generates laser light; a laser head, receiving the laser and irradiating the laser to a workpiece; and A controller controls the movement of the laser head. The laser head includes a laser scanner for scanning the laser light in a first direction and a second direction intersecting the first direction. The controller drives and controls the laser scanner by vibrating the laser light in the first direction with a first frequency and in the second direction with a sine wave with a second frequency, so that the laser light draws a Lissajous figure on the surface of the workpiece. Furthermore, the laser scanner is driven and controlled so that the laser draws other Lissajous figures different from the one Lissajous figure at the starting end and the ending end of the weld bead formed on the workpiece.

9. The laser welding device according to claim 8, wherein: The controller drives and controls the laser scanner so that the phase of the sinusoidal wave along the second direction changes at predetermined intervals at the starting end and the ending end of the weld bead.

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

2.

11. The laser welding device according to claim 10, wherein: When the ratio of the first frequency to the second frequency is 2:1, The controller drives and controls the laser scanner so that the phase of the sine wave along the second direction changes from 45 degrees to 0 degrees at predetermined intervals when forming the starting portion, and drives and controls the laser scanner so that the phase of the sine wave along the second direction changes from 0 degrees to -45 degrees at predetermined intervals when forming the ending portion. When the ratio of the first frequency to the second frequency is 1:2, When forming the starting portion, the controller drives and controls the laser scanner so that the phase of the sine wave along the second direction changes from -90 degrees to 0 degrees at a prescribed interval. When forming the ending portion, the controller drives and controls the laser scanner so that the phase of the sine wave along the second direction changes from 0 degrees to 90 degrees at a prescribed interval.

12. The laser welding device according to any one of claims 8 to 11, wherein: The controller drives and controls the laser scanner so that a scanning amplitude of the laser beam in the first direction is substantially equal to a scanning amplitude of the laser beam in the second direction.

13. The laser welding device according to any one of claims 8 to 11, wherein: The controller drives and controls the laser scanner so that a scanning amplitude of the laser beam in the first direction is different from a scanning amplitude of the laser beam in the second direction.

14. The laser welding device according to any one of claims 8 to 11, wherein: The controller drives and controls the laser scanner so that the lengths of the starting end portion and the ending portion of the weld bead in the first direction are approximately equal to or greater than the sum of 1 / 2 of the width of the Lissajous figure in the first direction and the width of the weld bead in the second direction.

15. The laser welding device according to any one of claims 8 to 11, wherein: The laser welding device further comprises: a robot arm on which the laser head is mounted, The controller controls the movement of the manipulator. The robot moves the laser head in a predetermined direction relative to the surface of the workpiece.

16. The laser welding device according to any one of claims 8 to 11, wherein: The laser oscillator is connected to the laser head via an optical fiber. The laser light is transmitted from the laser oscillator to the laser head through the optical fiber.

17. The laser welding device according to any one of claims 8 to 11, wherein: The laser scanner includes a first galvano mirror configured to scan the laser light in the first direction and a second galvano mirror configured to scan the laser light in the second direction.

18. The laser welding device according to any one of claims 8 to 11, wherein: The laser head also has a focus position adjustment mechanism. The focus position adjustment mechanism is configured to change the focus position of the laser beam along directions intersecting the first direction and the second direction.

Images