Laser welding method and laser welding device

Abstract

A laser welding method, according to the present invention, is provided with a welding step for welding a workpiece by scanning a laser beam two dimensionally and irradiating the surface of the workpiece while moving the laser beam in the X direction. In the welding step, the laser beam is scanned so as to draw a prescribed pattern on the surface of the workpiece. Furthermore, the amount of heat input into the workpiece is controlled according to the drawing position of the laser beam in the prescribed pattern. The prescribed pattern is a continuous pattern in which two annular patterns touch at one point.

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 laser light so as to draw a Lissajous pattern on the surface of the workpiece 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] Incidentally, in the conventional configurations shown in Patent Documents 2 and 3, the Lissajous pattern is usually drawn so as to have a symmetrical shape with respect to its center point (hereinafter also referred to as the origin).

[0005] However, the workpieces to be welded in practice have various shapes. For example, when plate materials of different thicknesses are butt-welded, the heat capacity of the workpieces becomes asymmetric on both sides of the weld line corresponding to the butt joint of the plate materials. In addition, depending on the joint shape of the workpieces, the heat capacity of the workpieces may also become asymmetric on both sides of the weld line.

[0006] In this case, when welding is performed by irradiating the laser beam so as to draw the above-mentioned symmetrical Lissajous pattern, the shape of the weld bead may differ on both sides of the weld line due to the asymmetry of the heat capacity of the workpiece. For example, when the output of the laser beam is adjusted to match the side of the welded portion of the workpiece with a small heat capacity, the heat input to the opposite side with a large heat capacity is insufficient, making it difficult to obtain a weld bead with a good shape. Also, when the output of the laser beam is adjusted to match the side with a large heat capacity, the heat input to the opposite side with a small heat capacity is excessive, which may cause welding defects such as burn-through. In addition, such a problem also occurs when the scanning pattern of the laser beam is not a Lissajous pattern, for example, when two circular patterns are connected at one point to form a continuous pattern.

[0007] The present disclosure has been made in consideration of the above points, and its purpose is to provide a laser welding method and laser welding apparatus that irradiates laser light to draw a predetermined pattern on the surface of a workpiece, and that can improve the shape of the weld bead formed on the workpiece. [Means for solving the problem]

[0008] In order to achieve the above object, the laser welding method according to the present disclosure includes a welding step of welding a workpiece by two-dimensionally scanning the laser light while advancing in a first direction and irradiating the workpiece with the laser light, wherein in the welding step, the laser light is scanned so as to draw a predetermined pattern on the workpiece, and further, an amount of heat input to the workpiece is controlled according to a drawing position of the laser light in the predetermined pattern; the drawing position of the laser light in the predetermined pattern has a first drawing region and a second drawing region that does not overlap with the first drawing region, when transitioning from the first drawing region to the second drawing region, controlling a drawing speed of the laser beam to be constant and controlling an output of the laser beam to change from a first output to a second output different from the first output, or controlling an output of the laser beam to be constant and controlling a drawing speed of the laser beam to change from a first speed to a second speed different from the first speed;The predetermined pattern is characterized in that two circular patterns are continuous and in contact with each other at one point.

[0009] A laser welding apparatus according to the present disclosure includes at least a laser oscillator that generates a laser beam, a laser head that receives the laser beam and irradiates it toward a workpiece, and a controller that controls the operation of the laser head and the output of the laser beam, the laser head having a laser beam scanner that scans 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 predetermined pattern on a surface of the workpiece, and the controller controls at least one of a drawing speed and an output of the laser beam according to a drawing position of the laser beam on the surface of the workpiece, a drawing position of the laser beam in the predetermined pattern has a first drawing area and a second drawing area not overlapping with the first drawing area, and when transitioning from the first drawing area to the second drawing area, the controller controls the drawing speed of the laser beam to be constant and controls the output of the laser beam to change from a first output to a second output different from the first output, or the controller controls the output of the laser beam to be constant and controls the drawing speed of the laser beam to change from a first speed to a second speed different from the first speed, The predetermined pattern is characterized in that two circular patterns are continuous and in contact with each other at one point. Effect of the Invention

[0010] According to the present disclosure, the shape of the weld bead formed on the workpiece can be made good. [Brief description of the drawings]

[0011] [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 cross-sectional view taken along line IIIB-IIIB in FIG. 3A. [Figure 4] FIG. 4 is a schematic cross-sectional view of another workpiece. [Diagram 5] FIG. 5 is a diagram showing a scanning pattern of the laser light. [Figure 6] FIG. 6 is a diagram showing the relationship between the drawing position and the output of the laser light. [Figure 7]FIG. 7 is a diagram showing a scanning pattern of a laser beam according to the first modification. [Figure 8] FIG. 8 is a diagram showing the relationship between the drawing position and the output of the laser light. [Figure 9] FIG. 9 is a diagram showing a scanning pattern of a laser beam according to the second embodiment. [Figure 10] FIG. 10 is a diagram showing the relationship between the drawing position and the output of the laser light. [Figure 11] FIG. 11 is a diagram showing the positional relationship between the laser beam and the molten pool formed on the workpiece according to the third embodiment. [Figure 12] FIG. 12 is a diagram showing a scanning pattern of the laser light. [Figure 13] FIG. 13 is a diagram showing the relationship between the drawing position and the output of the laser light. [Figure 14] FIG. 14 is a diagram showing the relationship of the drawing speed of the laser beam to the drawing position of the laser beam according to the fourth embodiment. [Figure 15] FIG. 15 is a diagram showing another relationship of the drawing speed of the laser beam to the drawing position of the laser beam. [Figure 16] FIG. 16 is a diagram showing still another relationship of the drawing speed of the laser beam to the drawing position of the laser beam. [Figure 17A] FIG. 17A is a diagram showing a first scanning pattern of a laser beam according to Modification 2. FIG. [Figure 17B] FIG. 17B is a diagram showing a second scanning pattern of the laser light according to the second modification. [Figure 18A] FIG. 18A is a diagram showing a third scanning pattern of the laser light according to the second modification. [Figure 18B] FIG. 18B is a diagram showing a fourth scanning pattern of the laser light according to the second modification. [Figure 18C] FIG. 18C is a diagram showing a fifth scanning pattern of the laser light according to Modification Example 2. As shown in FIG. [Figure 19] FIG. 19 is a diagram showing an example of a combination of parameters when drawing a Lissajous pattern. [Figure 20A]FIG. 20A is a diagram showing a first scanning pattern of a laser beam according to Modification 3. FIG. [Figure 20B] FIG. 20B is a diagram showing a second scanning pattern of the laser light according to Modification Example 3. As shown in FIG. [Figure 20C] FIG. 20C is a diagram showing a third scanning pattern of the laser light according to Modification Example 3. As shown in FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] (Embodiment 1) [Configuration of laser welding device and laser light scanner] Fig. 1 shows a schematic diagram of the configuration of the laser welding device according to this embodiment, and Fig. 2 shows a schematic diagram of the laser beam scanner. Fig. 3A shows a schematic diagram of a workpiece, and Fig. 3B shows a cross-sectional view taken along line IIIB-IIIB in Fig. 3A. Fig. 4 shows a cross-sectional schematic diagram of another workpiece.

[0014] 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 form a certain angle with the surface.

[0015] 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.

[0016] 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.

[0017] 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 the 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 the laser module. In this case, the wavelength of the laser light LB is set in the range of 400 nm to 600 nm.

[0018] 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 .

[0019] 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 .

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The controller 50 has an integrated circuit such as an LSI or a microcomputer (not shown), and executes a laser welding program, which is software, on this integrated circuit to realize the above-mentioned functions of the controller 50. Note that the controller 50 that controls the operation of the laser head 30 and the controller 50 that controls the output of the laser light LB may be provided separately.

[0030] 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.

[0031] The laser welding device 100 shown in Fig. 1 can perform laser welding on workpieces 200 of various shapes. For example, as shown in Figs. 3A and 3B, 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, which are made of the same material but have different thicknesses, are butted together at their end faces, to perform butt welding. Also, as shown in Fig. 4, 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, 3B, and 4.

[0032] [Mathematical expression of Lissajous pattern] FIG. 5 shows a scanning pattern of the laser light, and the laser light LB is scanned within the XY plane, in this case the surface of the workpiece 200, so as to draw a Lissajous pattern (hereinafter also referred to as a Lissajous figure).

[0033] The width in the X direction of the Lissajous pattern shown in FIG. 5 is equal to the width in the Y direction, and the width in the Y direction is approximately equal to the width W of the weld bead (not shown) in the Y direction when the welding speed is very fast. 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 the Lissajous pattern in the Y direction is slightly narrower than the width of the weld bead 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.

[0034] The Lissajous pattern shown in Fig. 5 is obtained by vibrating the laser light LB in the X direction in a sinusoidal manner at a predetermined frequency and vibrating the laser light LB 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 direction and the Y direction 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 pattern shown in Fig. 5 obtained by driving the first mirror 41a is X1 and the position coordinate of the Lissajous pattern shown in Fig. 5 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.

[0035] X1 = a × sin(n) (1) Y1 = b × sin(mt + φ) (2) Where: a: Amplitude in the X direction of the Lissajous pattern shown in Figure 5 b: Amplitude in the Y direction of the Lissajous pattern shown in Figure 5 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.

[0036] The position coordinates X1, Y1 shown in equations (1) and (2) are expressed in a stationary coordinate system of the Lissajous pattern with the position of the laser head 30 fixed.

[0037] Moreover, frequencies n and m correspond to the drive frequencies of first mirror 41a and second mirror 42a, respectively.

[0038] The Lissajous pattern shown in FIG. 5 is an eight-shaped Lissajous pattern that corresponds to a=1, b=1, n=2, m=1, and φ=0 in equations (1) and (2). a and b are normalized to 1. The phase difference φ in equations (1) and (2) may be either 0 degrees or 180 degrees. The size of the actual Lissajous pattern, that is, the amplitude in the X and Y directions, is about 1 mm to 10 mm, respectively.

[0039] Here, as shown in FIG. 5, when the drawing distance of the Lissajous pattern in the X direction at a given time variation Δt is ΔX, the drawing distance in the Y direction is ΔY, and the drawing distance of the Lissajous pattern at the time variation Δt is ΔL, ΔX, ΔY, and ΔL are respectively expressed by the following equations (3) to (5).

[0040] ΔX= a×n×cos(nt)×Δt (3) ΔY= b×m×cos(mt+φ)×Δt (4) ΔL = Δt × {(ΔX) 2 +(ΔY) 2} 1 / 2 (5) Therefore, the drawing speed V of the Lissajous pattern is expressed by the following formula (6).

[0041] V = ΔL / Δt (6) [Laser welding method] FIG. 6 shows the relationship between the drawing position and output of the laser beam.

[0042] In this embodiment, the laser head 30 is moved in the X direction at a predetermined speed by the manipulator 60, while the laser beam LB is irradiated onto the surface of the workpiece 200. Furthermore, the laser beam LB is two-dimensionally scanned by the laser beam scanner 40 so as to draw a Lissajous pattern shown in Fig. 5 on the surface of the workpiece 200. In this embodiment, the case of butt welding the workpieces 200 shown in Figs. 3A and 3B will be described as an example.

[0043] The Lissajous pattern shown in Fig. 5 can be obtained by scanning the laser light LB from the origin O in the directions of the arrows AR1 and AR2 shown in Fig. 5 during one period. Specifically, the laser light LB is scanned from the origin O through the drawing positions A→B→C→O→D→E→F→O during one period.

[0044] Laser light LB is irradiated along the butt portion of the first plate material 210 and the second plate material 220, which corresponds to the welding portion of the workpiece 200, to perform laser welding. As shown in FIG. 3A, the butt portion extends along the X direction and corresponds to the above-mentioned welding line. On the other hand, as shown in FIG. 3B, the thickness of the first plate material 210 in the Z direction is larger than the thickness of the second plate material 220 in the Z direction. In addition, the first plate material 210 is made of the same material as the second plate material 220. Therefore, the heat capacity of the first plate material 210 is larger than the heat capacity of the second plate material 220. In other words, the heat capacity of the workpiece 200 is asymmetric with respect to the welding line corresponding to the abutting surface between the end face of the first plate material 210 and the end face of the second plate material 220.

[0045] When laser welding is performed on such a workpiece 200 while drawing a Lissajous pattern shown in FIG. 5 on the surface of the workpiece 200 with the laser beam LB, the above-mentioned problem may occur if the output P of the laser beam LB is constant.

[0046] 5 is symmetrical with respect to the X and Y directions. Therefore, when the laser beam LB is caused to travel in the X direction and irradiated onto the butted portion of the first plate material 210 and the second plate material 220, the amount of heat input to the workpiece 200 is also symmetrical with respect to the weld line.

[0047] On the other hand, as described above, in the butted portion of the first plate material 210 and the second plate material 220, the heat capacity is asymmetric with respect to the weld line. Therefore, when attempting to form a weld bead along the butted portion, there is a risk that the shape of the weld bead will be deformed. For example, when laser welding is performed by matching the amount of heat input to the workpiece 200 by the laser light LB with the second plate material 220 with a small heat capacity, the heat input to the first plate material 210 with a large heat capacity is insufficient, and the shape of the weld bead may be deformed. On the other hand, when laser welding is performed by matching the amount of heat input to the workpiece 200 by the laser light LB with the first plate material 210 with a large heat capacity, the heat input to the second plate material 220 with a small heat capacity becomes excessive, and there is a risk that a weld defect such as burn-through will occur.

[0048] Therefore, in this embodiment, when drawing a Lissajous pattern, the output P of the laser light LB is controlled so that the output P1 of the laser light LB irradiated to the first plate material 210 is higher than the output P2 of the laser light LB irradiated to the second plate material 220. In other words, the output P of the laser light LB is controlled so that the output P1 of the laser light LB along the path O→A→B→C→O shown in FIG. 5 is higher than the output P2 of the laser light LB along the path O→D→E→F→O.

[0049] In this way, different amounts of heat can be input to both sides of the weld line at the butt joint between the first plate material 210 and the second plate material 220, which is the welded portion of the workpiece 200 where the heat capacity is asymmetrical with respect to the weld line. This makes it possible to improve the shape of the weld bead. Also, it is possible to prevent the occurrence of welding defects such as burn-through.

[0050] In addition, when changing the output P of the laser light LB, as shown by the dashed line in FIG. 6, the rising portion and the falling portion of the output P of the laser light LB may be controlled separately.

[0051] For example, when the drawing position of the laser light LB moves from the origin O to D, the output P of the laser light LB may be reduced from P1 to P2 during a period t1 from the time when the laser light LB passed the origin O. In this case, the control curve S1 of the output P may be linear or curved. Also, when the drawing position of the laser light LB moves from the origin O to A, the output P of the laser light LB may be increased from P2 to P1 during a period t2 from the time when the laser light LB passed the origin O. In this case, the control curve S2 of the output P may be linear or curved.

[0052] By controlling the output P of the laser beam LB as shown by the control curves S1 and S2, it becomes easy to make the output P reach the target value stably.

[0053] [Effects, etc.] As described above, the laser welding method according to this embodiment includes a welding step of welding the workpiece 200 by two-dimensionally scanning the laser light LB and irradiating the surface of the workpiece 200 with the laser light LB while traveling in the X direction (first direction).

[0054] In the welding step, the laser beam LB is oscillated in a sinusoidal manner having a first frequency corresponding to a frequency n along the X direction, and is oscillated in a sinusoidal manner having a second frequency corresponding to a frequency m along the Y direction. This causes the laser beam LB to scan the surface of the workpiece 200 so as to draw a Lissajous pattern.

[0055] Furthermore, the amount of heat input to the workpiece 200, specifically, the output P of the laser light LB, is controlled according to the drawing position of the laser light LB in the Lissajous pattern.

[0056] In this way, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity, on both sides of the weld line, thereby achieving a good weld bead shape.

[0057] In this embodiment, the butted portion of the first plate material 210 and the second plate material 220, which are the welded portions of the workpiece 200, has asymmetric heat capacity in the X direction, which is the direction in which the weld line extends. In this case, during drawing of the Lissajous pattern, the output P of the laser light LB irradiated to the first portion of the welded portions, which has a large heat capacity, i.e., the first plate material 210, is set to be higher than that of the second portion of the welded portions, which has a small heat capacity, i.e., the second plate material 220.

[0058] In this way, different amounts of heat can be input to both sides of the weld line to the welded portion of the workpiece 200, which has asymmetrical heat capacity. This makes it possible to improve the shape of the weld bead. Also, it is possible to prevent welding defects such as burn-through.

[0059] 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 and the output P of the laser light LB.

[0060] 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.

[0061] The controller 50 vibrates the laser light LB in a sinusoidal shape having a first frequency along the X direction, and vibrates the laser light LB in a sinusoidal shape having a second frequency along the Y direction. In this way, the controller 50 drives and controls the laser light scanner 40 so that the laser light LB draws a Lissajous pattern on the surface of the workpiece 200.

[0062] Furthermore, the controller 50 controls the amount of heat input to the workpiece 200, specifically, the output P of the laser light LB, depending on the drawing position of the laser light LB in the Lissajous pattern.

[0063] According to the laser welding apparatus 100 of this embodiment, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity relative to the weld line, on both sides of the weld line, thereby making it possible to obtain a good shape of the weld bead.

[0064] 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.

[0065] 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.

[0066] 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 .

[0067] 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.

[0068] 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.

[0069] 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.

[0070] The laser head 30 further includes a collimation lens 32, which is configured to change the focal position of the laser light LB along the Z direction intersecting with each of the X direction and the Y direction. 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).

[0071] In this way, the focal position of the laser light LB can be easily changed, and the laser light LB can be appropriately irradiated according to the shape of the workpiece 200.

[0072] In this embodiment, the laser head 30 is moved in the X direction to cause the laser light LB to travel in the X direction, but this is not particularly limited. For example, if the butted portion of the first plate material 210 and the second plate material 220 extends in the Y direction, the laser head 30 may be moved in the Y direction to cause the laser light LB to travel in the Y direction. Accordingly, the shape of the Lissajous pattern may be changed. However, even in this case, it is necessary to control the output P so that different amounts of heat are input to the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, on both sides of the weld line.

[0073] In addition, the drawing direction of the Lissajous pattern is not particularly limited to the above. For example, the Lissajous pattern may be drawn by scanning the laser light LB from the origin O through drawing positions C→B→A→O→F→E→D→O during one period. The Lissajous pattern may be drawn by scanning the laser light LB from the origin O through drawing positions D→E→F→O→A→B→C→O during one period. The Lissajous pattern may be drawn by scanning the laser light LB from the origin O through drawing positions F→E→D→O→C→B→A→O during one period. It goes without saying that the timing of changing the output P of the laser light LB is changed according to the change in the order of the drawing positions.

[0074] The method shown in this embodiment may be applied to laser welding the workpiece 200 shown in Fig. 4. At the corner of the joint of the workpiece 200 in which the third plate material 230 and the fourth plate material 240 are overlapped with their end faces shifted, the overlapping portion (first portion) of the third plate material 230 and the fourth plate material 240 has a larger heat capacity than the portion (second portion) of only the third plate material 230. Therefore, the laser light LB is controlled so that the output P of the laser light LB is higher at the overlapping portion than the portion of only the third plate material 230.

[0075] In this way, the above-mentioned effects can be achieved. That is, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, on both sides of the weld line, and the shape of the weld bead can be improved. In addition, the occurrence of welding defects such as burn-through can be suppressed.

[0076] <Variation 1> Fig. 7 shows a scanning pattern of the laser light according to this modification, and Fig. 8 shows the relationship between the drawing position of the laser light and the output. For convenience of explanation, in Figs. 7 and 8 and the following drawings, the same reference numerals are used for the same parts as those in the first embodiment, and detailed explanations are omitted.

[0077] In this modified example, the drawing direction of the Lissajous pattern is different from that of the configuration shown in the first embodiment. The Lissajous pattern shown in Fig. 7 is obtained by scanning the laser light LB from the origin O in the directions of the arrows AR3 and AR4 shown in Fig. 7 during one period. Specifically, the laser light LB is scanned so as to pass from the origin O through drawing positions C→B→A→O→F→E→D→O during one period.

[0078] In this modification, similarly to the first embodiment, the output P of the laser light LB is controlled so that the output P1 of the laser light LB irradiated to the first plate material 210 is higher than the output P2 of the laser light LB irradiated to the second plate material 220. In this case, the output P of the laser light LB is controlled so that the output P1 of the laser light LB along the path O→C→B→A→O shown in FIG. 7 is higher than the output P2 of the laser light LB along the path O→F→E→D→O.

[0079] This modified example also has the same effects as those of the configuration shown in the first embodiment. That is, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, on both sides of the weld line, and the shape of the weld bead can be improved. In addition, the occurrence of welding defects such as burn-through can be suppressed.

[0080] (Embodiment 2) Fig. 9 shows a scanning pattern of the laser beam according to this embodiment, and Fig. 10 shows the relationship between the drawing position and the output of the laser beam. Although not shown, the welded portion of the workpiece 200 in this embodiment is set so that the heat capacity is the same on both sides of the weld line.

[0081] This embodiment differs from the configuration shown in the first embodiment in that, while drawing a Lissajous pattern, the output power P of the laser light LB is set lower in the vicinity of the origin O of the Lissajous pattern than in other portions.

[0082] 9 and 10, the output P of the laser light LB is set to P3 between the origin O and each of the drawing positions A', C', D', and F', and the output P of the laser light LB is set to P1 (P1>P3) at other drawing positions of the Lissajous pattern. Such control of the output P of the laser light LB is performed by the controller 50.

[0083] As described above, when drawing a Lissajous pattern on the surface of the workpiece 200 with the laser light LB, for example, during one period, the laser light LB passes once at the drawing position A, whereas the laser light LB passes twice at the origin O. Also, usually, the speed at which the laser head 30 is advanced in the X direction by the manipulator 60, that is, the advancement speed of the laser light LB in the X direction, is much slower than the drawing speed V of the laser light LB when drawing a Lissajous pattern.

[0084] For this reason, the amount of heat input to origin O during drawing of the Lissajous pattern becomes larger than the amount of heat input to other drawing positions, for example, drawing positions A, B, C, D, E, and F. As described above, the shape of the weld bead deteriorates due to the heat input to the surface of the workpiece 200 becoming uneven from place to place.

[0085] Therefore, in this embodiment, the output P of the laser light LB is set lower near the origin O of the Lissajous pattern than in other parts, thereby preventing the amount of heat input to the surface of the workpiece 200 from becoming uneven from place to place. This makes it possible to improve the shape of the weld bead. Also, it is possible to prevent the occurrence of welding defects such as burn-through.

[0086] The distance from the origin O to each of the drawing positions A', C', D', and F' can be changed as appropriate depending on the shape of the welded portion of the workpiece 200, the plate thickness, the material of the workpiece 200, etc. For example, when one period of the Lissajous pattern is viewed as 360 degrees, if the distance is replaced with an angle viewed from the origin O as the base, the angle is preferably greater than 0 degrees and is equal to or smaller than 3 degrees to 15 degrees.

[0087] (Embodiment 3) Fig. 11 shows the positional relationship between the laser beam according to this embodiment and the molten pool formed on the workpiece, Fig. 12 shows the scanning pattern of the laser beam, and Fig. 13 shows the relationship between the drawing position of the laser beam and the output.

[0088] 11, when the laser beam LB is irradiated onto the workpiece 200, the metal constituting the workpiece 200 is rapidly heated and melted, and a molten pool 201 is formed at the site irradiated with the laser beam LB and in its vicinity. Furthermore, at the site irradiated with the laser beam LB, the metal evaporates and a keyhole 202 is formed from the surface of the workpiece 200 toward the inside. When the laser beam LB reaches the inside of the keyhole 202, the metal is melted all the way to the inside of the workpiece 200, and the penetration depth of the workpiece 200 is ensured. The irradiation position of the laser beam LB shown in FIG. 11 corresponds to the origin O of the Lissajous pattern shown in FIG. 5.

[0089] Furthermore, in the third portion 203 located forward of the irradiation position of the laser beam LB along the direction in which the welding proceeds, in this case the X direction, the workpiece 200 is not sufficiently heated, and the molten pool 201 is not formed. On the other hand, the fourth portion 204 located rearward of the irradiation position of the laser beam LB has already been sufficiently heated by the laser beam LB. Therefore, the fourth portion 204 is located inside the molten pool 201 or in a portion where the molten pool 201 has solidified. In other words, the fourth portion 204 includes the molten pool 201.

[0090] Thus, along the weld line, a large amount of heat input is required in front of the origin O of the Lissajous pattern, which corresponds to the irradiation position of the laser beam LB, to melt the workpiece 200. On the other hand, behind the origin O of the Lissajous pattern, a heat input sufficient to maintain the already formed molten pool 201 is sufficient.

[0091] In accordance with the rear of the origin O of the Lissajous pattern, consider the case of adjusting the input heat amount, in this case, the output P of the laser beam LB. As shown in FIG. 5, when the Lissajous pattern is symmetric, in front of the origin O, the input heat amount to the workpiece 200 is insufficient, and there is a risk that the shape of the weld bead, particularly the shape during beading, will become uneven. On the other hand, when adjusting the output P of the laser beam LB in accordance with the front of the origin O of the Lissajous pattern, there is a risk that the heat input to the molten pool 201 will be excessive behind the origin O and the molten pool 201 will become unstable. In this case, it was difficult to obtain a weld bead with a good shape. Also, such problems can occur both when the heat capacities of the workpiece 200 are equal and when they are asymmetric on both sides across the welding line.

[0092] Therefore, in the present embodiment, the output P of the laser beam LB irradiated at the aforementioned third part 203 and fourth part 204 is changed. Specifically, in the present embodiment, when laser-welding the workpiece 200 by advancing the laser beam LB in the X direction, it is different from the configuration shown in the first embodiment in the following points.

[0093] That is, during the drawing of the Lissajous pattern, at the third part 203 where the laser beam LB is irradiated forward along the X direction from the molten pool 201 formed on the workpiece 200, the output P of the laser beam LB is made higher than that of the fourth part 204 where the laser beam LB is irradiated behind the third part 203 including the molten pool 201.

[0094] Specifically, as shown in FIGS. 12 and 13, in the drawing trajectories O→A→B and O→D→E located forward along the X direction with the origin O as a reference, the output P of the laser beam LB is set as P1. On the other hand, in the drawing trajectories B→C→O and E→F→O located rearward along the X direction with the origin O as a reference, the output P of the laser beam LB is set as P4 (P4 < P1). Such control of the output P of the laser beam LB is performed by the controller 50.

[0095] According to this embodiment, by making the output P1 of the laser beam LB irradiated to the third portion 203 higher than the output P4 of the laser beam LB irradiated to the fourth portion 204, it is possible to promote the formation of the molten pool 201 in the third portion 203 that has not yet been heated or melted. In addition, by lowering the output P4 of the laser beam LB, it is possible to suppress the molten pool 201 from vibrating excessively. This not only prevents the laser energy from being applied to the fourth portion 204 more than necessary, thereby saving laser energy, but also prevents the weld bead from becoming wavy in the fourth portion 204. Furthermore, by preventing the penetration depth of the workpiece 200 from becoming deeper than a desired value, it is possible to reduce the occurrence of welding defects such as burn-through, thereby improving the welding quality.

[0096] In addition, when the welding proceeds in the Y direction, for example, the output P of the laser beam LB may be P1 along the trace O→A→B→C→O located forward along the Y direction with the origin O as a reference, and the output P of the laser beam LB may be P4 along the trace O→D→E→F→O located backward. In this case, the above-mentioned effects can be achieved, that is, the formation of the molten pool 201 in the third portion 203 can be promoted, and the weld bead can be prevented from becoming wavy. In addition, the occurrence of welding defects such as burn-through can be reduced, the welding quality can be improved, and the laser energy can be saved.

[0097] (Embodiment 4) Fig. 14 shows the relationship between the drawing position and the drawing speed of the laser beam according to this embodiment, Fig. 15 shows another relationship between the drawing position and the drawing speed of the laser beam, and Fig. 16 shows yet another relationship between the drawing position and the drawing speed of the laser beam.

[0098] In the first to third embodiments and the first modified example, the drawing speed V of the laser beam LB may be kept constant while drawing the Lissajous pattern, as shown in Fig. 14. In other words, the drawing speed V of the laser beam LB may be kept constant over the entire length of the Lissajous pattern. This makes it easier to control the amount of heat input to the molten pool 201 (see Fig. 11).

[0099] In addition, in the example shown in embodiment 1, by controlling the output P of the laser light LB according to the drawing position of the laser light LB in the Lissajous pattern, different amounts of heat were input to the welded portion of the workpiece 200, which has an asymmetric heat capacity with respect to the weld line, on both sides of the weld line.

[0100] However, the amount of heat input to the workpiece 200 can also be changed by changing the drawing speed V of the laser light LB according to the drawing position of the laser light LB. For example, by lowering the drawing speed V of the laser light LB, the amount of heat input per unit drawing length increases. In other words, the same effect as that of increasing the output P of the laser light LB can be obtained.

[0101] Therefore, instead of controlling the output power P of the laser light LB in accordance with the drawing position of the laser light LB in the Lissajous pattern as shown in Fig. 6, the drawing speed V of the laser light LB may be controlled as shown in Fig. 15. Such control of the drawing speed V of the laser light LB is performed by the controller 50.

[0102] In other words, for the workpiece 200 shown in Figures 3A and 3B, while drawing a Lissajous pattern, the drawing speed V1 of the laser light LB at the first plate material (first portion) 210 is set to be lower than the drawing speed V2 of the laser light LB at the second plate material (second portion) 220, which has a smaller heat capacity than the first plate material 210 (V1>V2).

[0103] In this way, it is possible to achieve the same effects as those achieved by the configuration shown in the first embodiment. In other words, it is possible to input different amounts of heat to both sides of the weld line to the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, and it is possible to improve the shape of the weld bead. In addition, it is possible to suppress the occurrence of welding defects such as burn-through.

[0104] Further, instead of changing the output power P of the laser beam LB in front of the molten pool 201 and at the molten pool 201 as shown in Fig. 13, the drawing speed V of the laser beam LB may be controlled as shown in Fig. 16. Such control of the drawing speed V of the laser beam LB is performed by the controller 50.

[0105] That is, during drawing of the Lissajous pattern, the drawing speed V of the laser light LB is set to be lower in the third portion 203 (see FIG. 11) than in the fourth portion 204 (see FIG. 11).

[0106] 16, the drawing speed of the laser light LB is V1 for drawing trajectories O→A→B and O→D→E located forward along the X direction with the origin O as the reference point. On the other hand, the drawing speed V of the laser light LB is V2 (V1>V2) for drawing trajectories B→C→O and E→F→O located backward along the X direction with the origin O as the reference point.

[0107] This can provide the same effects as those provided by the configuration shown in the third embodiment. That is, it is possible to promote the formation of the molten pool 201 in the third portion 203 and prevent the weld bead from becoming wavy. It also reduces the occurrence of welding defects such as burn-through, improves the welding quality, and saves laser energy.

[0108] Although not shown, the drawing speed V of the laser light LB may be controlled instead of changing the output P of the laser light LB near the origin O of the Lissajous pattern as shown in Fig. 10. Such control of the drawing speed V of the laser light LB is performed by the controller 50.

[0109] For example, the drawing speed V of the laser light LB may be V1 between the origin O and each of the drawing positions A', C', D', and F' shown in Figure 10, and the drawing speed V of the laser light LB may be V2 (V1>V2) at other drawing positions of the Lissajous pattern.

[0110] Moreover, taking the configurations shown in this embodiment, embodiments 1 to 3, and modification 1 together, it can be said that the laser welding method and laser welding apparatus 100 according to the present disclosure have the following configuration.

[0111] Moreover, taking the configurations shown in this embodiment and embodiments 1 to 3 together, it can be said that the laser welding method and laser welding apparatus 100 according to the present disclosure have the following configuration.

[0112] That is, the laser welding method according to the present disclosure controls the amount of heat input to the workpiece 200 according to the drawing position of the laser beam LB in the Lissajous pattern. More specifically, at least one of the drawing speed V and the output P of the laser beam LB is controlled according to the drawing position of the laser beam LB in the Lissajous pattern.

[0113] In the laser welding apparatus 100 according to the present disclosure, the controller 50 controls the amount of heat input to the workpiece 200 according to the drawing position of the laser beam LB in the Lissajous pattern. More specifically, the controller 50 controls at least one of the drawing speed V and the output P of the laser beam LB according to the drawing position of the laser beam LB in the Lissajous pattern.

[0114] In this way, different amounts of heat can be input to the welded portion of the workpiece 200, which has an asymmetric heat capacity relative to the weld line, on both sides of the weld line, thereby achieving a good weld bead shape.

[0115] It also promotes the formation of the molten pool 201 in the third portion 203 that has not yet been heated or melted. It also suppresses excessive vibration of the molten pool 201. This prevents the weld bead from becoming wavy. It also prevents the penetration depth of the workpiece 200 from becoming deeper than desired, reducing the occurrence of welding defects such as burn-through and improving the welding quality.

[0116] In addition, when changing the drawing speed V of the laser light LB, the rising portion and the falling portion of the drawing speed V may be controlled separately as shown by the dashed lines in FIGS.

[0117] In the example shown in Fig. 15, when the drawing position of the laser light LB moves from the origin O to D, the drawing speed V of the laser light LB may be increased from V2 to V1 during a period t3 from the time when the laser light LB passes the origin O. In this case, the control curve S3 of the drawing speed V may be linear or curved. Also, when the drawing position of the laser light LB moves from the origin O to A, the drawing speed V of the laser light LB may be decreased from V2 to V1 during a period t4 from the time when the laser light LB passes the origin O. In this case, the control curve S4 of the drawing speed V may be linear or curved.

[0118] In the example shown in Fig. 16, when the drawing position of the laser light LB moves from B to C, the drawing speed V of the laser light LB may be increased from V2 to V1 during a period t3 from the time when the laser light LB passes through position B. In this case, the control curve S3 of the drawing speed V may be linear or curved. Also, when the drawing position of the laser light LB moves from the origin O to D, the drawing speed V of the laser light LB may be decreased from V2 to V1 during a period t4 from the time when the laser light LB passes through the origin O. In this case, the control curve S4 of the drawing speed V may be linear or curved.

[0119] By controlling the drawing speed V of the laser beam LB as shown by the control curves S3 and S4, it becomes easy to make the drawing speed V stably reach the target value.

[0120] <Variation 2> Fig. 17A shows a first scanning pattern of the laser light according to this modification, and Fig. 17B shows a second scanning pattern. Fig. 18A shows a third scanning pattern of the laser light according to this modification, and Fig. 18B shows a fourth scanning pattern and Fig. 18B shows a fifth scanning pattern. Fig. 19 shows an example of a combination of parameters when drawing a Lissajous pattern.

[0121] In actual laser welding, the parameters a, b, n, and m shown in formulas (1) and (2) can be appropriately changed depending on the material, joint shape, plate thickness, desired bead shape width, etc. of the workpiece 200. Therefore, the scanning pattern of the laser light LB is not particularly limited to the pattern shown in FIG.

[0122] For example, as shown in Figures 17A and 17B, the parameter a may be reduced to reduce the amplitude of the Lissajous pattern in the X direction. Also, as shown in Figure 18A, a scanning pattern may be generated in which the Lissajous pattern shown in Figure 5 is rotated 90 degrees by setting frequency n=1 and frequency m=2. Also, as shown in Figures 18B and 18C, the parameter b may be reduced to reduce the amplitude of the Lissajous pattern shown in Figure 18A in the Y direction.

[0123] Moreover, the values ​​of the parameters a and b shown in the formulas (1) and (2) are not particularly limited to the examples shown in Figures 17A, 17B, and 18A to 18C, and may take appropriate values ​​within the ranges shown in Figure 19. In Figure 19, the Lissajous patterns shown in Figures 5, 17A, and 17B are classified as pattern group 1, and the Lissajous patterns shown in Figures 18A to 18C are classified as pattern group 2.

[0124] Furthermore, by setting the ratio of the frequency n of the first mirror 41a and the frequency m of the second mirror 42a, in other words, the ratio of the first frequency which is the vibration frequency in the X direction of the laser light LB to the second frequency which is the vibration frequency in the Y direction, to 2:1 or 1:2, a Lissajous pattern in the shape of a figure 8 can be obtained. As long as this frequency ratio is maintained, the drive frequencies of the first mirror 41a and the second mirror 42a may each be changed according to the shape of the workpiece 200 or the required bead shape.

[0125] <Variation 3> 20A to 20C respectively show first to third scanning patterns of the laser light according to this modified example. Note that in Figs. 20A to 20C, the arrows indicate the drawing direction of the laser light LB.

[0126] The scanning pattern of the laser light LB of the present disclosure is not limited to the Lissajous pattern shown in the first embodiment and the modified example. For example, as shown in FIG. 20A, it may be a composite pattern of two circular patterns arranged symmetrically with respect to the X axis, each of which is in contact with the origin O. Also, as shown in FIG. 20B, it may be a composite pattern of two elliptical patterns arranged symmetrically with respect to the X axis, each of which is in contact with the origin O. In the example shown in FIG. 20B, in each of the two elliptical patterns, the major axis is in the Y direction and the minor axis is in the X direction, but the major axis may be in the X direction and the minor axis may be in the Y direction. As shown in FIG. 20C, it may be a composite pattern of two rhombic patterns arranged symmetrically with respect to the X axis, each of which is in contact with the origin O. Although not shown, each of the scanning patterns shown in FIG. 20A to FIG. 20C may be a composite pattern of two annular patterns arranged symmetrically with respect to the Y axis. Also, in this case, each of the two annular patterns may be a pattern rotated 90 degrees from the example shown in FIG. 20A to FIG. 20C. Furthermore, the size of each of the two annular patterns may be appropriately changed.

[0127] In other words, the scanning pattern of the laser light LB in this specification may be any pattern in which two annular patterns are continuous and in contact at one point, and is not limited to the examples shown in Figures 20A to 20C and their modified examples. These patterns can be obtained by driving the first mirror 41a and the second mirror 42a according to respective predetermined driving patterns.

[0128] Therefore, in the welding step of the laser welding method of the present disclosure, the surface of the workpiece 200 is scanned with the laser light LB so as to draw a predetermined pattern.

[0129] Furthermore, the amount of heat input to the workpiece 200 is controlled according to the drawing position of the laser beam LB in a predetermined pattern.

[0130] Moreover, the controller 50 in the laser welding apparatus 100 of the present disclosure drives and controls the laser beam scanner 40 so that the laser beam LB draws a predetermined pattern on the surface of the workpiece 200.

[0131] Furthermore, the controller 50 controls the amount of heat input to the workpiece 200 according to the drawing position of the laser light LB in a predetermined pattern.

[0132] The "predetermined pattern" which is the scanning pattern of the laser light LB is a pattern in which two annular patterns are in contact with each other at one point, in this case the origin O, and are continuous. More specifically, the two annular patterns are the same pattern. It goes without saying that the "predetermined pattern" includes the Lissajous pattern disclosed in the present specification. In the case of the pattern shown in FIG. 20C, the drawing length is shortened at the end in the Y direction, so it is necessary to take care when controlling the amount of heat input to the workpiece 200 according to the drawing position of the laser light LB in the pattern. On the other hand, as shown in FIG. 20A and FIG. 20B, when the scanning pattern of the laser light LB is a pattern in which two circular or elliptical patterns are in contact with each other at the origin O, the drawing length at the end in the Y direction can be secured, and it becomes easy to control the amount of heat input to the workpiece 200 according to the drawing position of the laser light LB in the pattern.

[0133] By configuring the laser welding method and the laser welding apparatus 100 in this manner, it is possible to achieve the same effects as those achieved by the configurations shown in the first to fourth embodiments and the first and second modifications.

[0134] (Other embodiments) The components shown in the first to fourth embodiments and the first to third modifications can be appropriately combined to form new embodiments.

[0135] For example, when drawing each scanning pattern shown in Modification 2, the output power P of the laser light LB can be controlled as shown in the first to third embodiments. Also, as shown in the fourth embodiment, the drawing speed V of the laser light LB can be controlled.

[0136] In the second to fourth embodiments and the second and third modifications, for example, a predetermined pattern may be drawn by scanning the laser light LB from the origin O through drawing positions C→B→A→O→F→E→D→O during one period. A predetermined pattern may be drawn by scanning the laser light LB from the origin O through drawing positions D→E→F→O→A→B→C→O during one period. A predetermined pattern may be drawn by scanning the laser light LB from the origin O through drawing positions F→E→D→O→C→B→A→O during one period. Needless to say, the timing for changing the drawing speed V and output P of the laser light LB is changed according to the change in the order of the drawing positions.

[0137] 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.

[0138] Furthermore, the scanning pattern of the laser light LB may be a Lissajous pattern by oscillating the laser light LB 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. In this case, it goes without saying that the amplitudes a, b of the first mirror 41a and the second mirror 42a, the frequencies n, m of the first mirror 41a and the second mirror 42a, and the phase φ are appropriately changed. [Industrial Applicability]

[0139] The laser welding method and the laser welding method disclosed herein are useful because they can produce a good weld bead shape. [Explanation of symbols]

[0140] 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 50 Controller 60 Manipulator 200 Work 201 Molten Pool 202 Keyhole 203 Part 3 204 Part 4 210 1st plate material (1st part) 220 2nd plate material (2nd part) 230 Third plate material 240 4th plate material

Claims

1. A welding step of welding the workpiece by two-dimensionally scanning the laser light and irradiating the laser light onto a surface of the workpiece while traveling in a first direction, In the welding step, Scanning the laser light so as to draw a predetermined pattern on the surface of the workpiece; Furthermore, the amount of heat input to the workpiece is controlled according to the drawing position of the laser light in the predetermined pattern. a drawing position of the laser light in the predetermined pattern has a first drawing region and a second drawing region that does not overlap with the first drawing region, When transitioning from the first drawing area to the second drawing area, A drawing speed of the laser beam is controlled to be constant, and an output of the laser beam is controlled to change from a first output to a second output different from the first output, or controlling an output of the laser beam to be constant, and controlling a drawing speed of the laser beam to change from a first speed to a second speed different from the first speed; A laser welding method, wherein the predetermined pattern is a continuous pattern in which two annular patterns are in contact with each other at one point.

2. In the laser welding method according to claim 1, When transitioning from the second drawing area to the first drawing area, A drawing speed of the laser light is controlled to be constant, and an output of the laser light is controlled to change from a second output to the first output, or controlling the output of the laser beam to be constant, and controlling the drawing speed of the laser beam to change from a second speed to the first speed; The laser welding method according to claim 1 .

3. 3. The laser welding method according to claim 1, the predetermined pattern is a Lissajous pattern in the shape of a figure of eight or a shape of an infinity, The laser welding method is characterized in that, in the welding step, the laser light is vibrated in a sinusoidal manner having a first frequency along the first direction, and also in a sinusoidal manner having a second frequency along a second direction intersecting the first direction, thereby scanning the laser light to trace the Lissajous pattern on the surface of the workpiece.

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

2.

5. The laser welding method according to any one of claims 1 to 4, The welded portion of the workpiece has a first portion on one side of a weld line and a second portion on the other side of the weld line, the second portion having a smaller heat capacity than the first portion, A laser welding method comprising the steps of: during drawing of the predetermined pattern, output of the laser light is made higher in the first region than in the second region.

6. The laser welding method according to any one of claims 1 to 4, During drawing of the predetermined pattern, a portion to which the laser light is irradiated in front of a molten pool formed on the workpiece along the first direction is defined as a third portion, and a portion to which the laser light is irradiated in rear of the third portion including the molten pool is defined as a fourth portion, A laser welding method comprising: setting an output of the laser light irradiated to the third portion to be higher than that of the fourth portion.

7. The laser welding method according to any one of claims 1 to 4, A laser welding method comprising the steps of: during drawing of the predetermined pattern, setting an output of the laser beam to be lower in the vicinity of an origin of the predetermined pattern than in other portions.

8. 8. The laser welding method according to claim 1, A laser welding method comprising: making the drawing speed of the laser beam constant over the entire length of the predetermined pattern.

9. The laser welding method according to any one of claims 1 to 4, The welded portion of the workpiece has a first portion on one side of a weld line and a second portion on the other side of the weld line, the second portion having a smaller heat capacity than the first portion, A laser welding method, comprising the steps of: drawing the predetermined pattern at a drawing speed of the laser beam at the first portion slower than at the second portion.

10. The laser welding method according to any one of claims 1 to 4, During drawing of the predetermined pattern, a portion to which the laser light is irradiated in front of a molten pool formed on the workpiece along the first direction is defined as a third portion, and a portion to which the laser light is irradiated in rear of the third portion including the molten pool is defined as a fourth portion, A laser welding method, comprising: setting a drawing speed of the laser beam to be slower in the third region than in the fourth region.

11. The laser welding method according to any one of claims 1 to 4, A laser welding method comprising the steps of: drawing the predetermined pattern at a drawing speed of the laser beam in the vicinity of an origin of the predetermined pattern, the drawing speed being faster than that of other portions.

12. 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 and the output of the laser light; 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 predetermined pattern on the surface of the workpiece; Furthermore, the controller controls at least one of a drawing speed and an output of the laser beam according to a drawing position of the laser beam on the surface of the workpiece, a drawing position of the laser light in the predetermined pattern has a first drawing region and a second drawing region that does not overlap with the first drawing region, When transitioning from the first drawing area to the second drawing area, The controller controls a drawing speed of the laser beam to be constant, and controls an output of the laser beam to be changed from a first output to a second output different from the first output, or the controller controls an output of the laser beam to be constant, and controls a drawing speed of the laser beam to be changed from a first speed to a second speed different from the first speed; A laser welding device according to claim 1, wherein the predetermined pattern is a continuous pattern in which two annular patterns are in contact with each other at one point.

13. The laser welding apparatus according to claim 12, When transitioning from the second drawing area to the first drawing area, The controller controls the drawing speed of the laser light to be constant, and controls the output of the laser light to be changed from the second output to the first output, or the controller controls the output of the laser beam to be constant, and controls the drawing speed of the laser beam to change from a second speed to the first speed; 13. The laser welding apparatus of claim 12.

14. 14. The laser welding apparatus according to claim 12, the predetermined pattern is a Lissajous pattern in the shape of a figure of eight or a shape of an infinity, The laser welding apparatus is characterized in that the controller drives and controls the laser beam scanner so that the laser beam draws the Lissajous pattern on the surface of the workpiece by vibrating the laser beam in a sinusoidal shape having a first frequency along the first direction and in a sinusoidal shape having a second frequency along the second direction.

15. 15. The laser welding apparatus according to claim 14, A laser welding apparatus, wherein a ratio of the first frequency to the second frequency is 2:1 or 1:

2.

16. 16. The laser welding apparatus according to claim 12, 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.

17. 17. The laser welding apparatus according to claim 12, 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.

18. 18. The laser welding apparatus according to claim 12, The laser welding apparatus is 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 a second direction intersecting the first direction.

19. 19. The laser welding apparatus according to claim 12, 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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