Laser welding method and laser welding device

Abstract

The laser welding method includes a welding step of welding a workpiece by irradiating a surface of the workpiece with a laser while two-dimensionally scanning the laser in an X direction. In the welding step, the laser is scanned so that a prescribed pattern is drawn on the surface of the workpiece. Further, the laser is scanned so that the prescribed pattern is an asymmetric shape with respect to the X direction. The prescribed pattern is a pattern in which two annular patterns of mutually asymmetric shapes are continuous at one point.

Description

Technical Field

[0001] This disclosure relates to laser welding methods and laser welding apparatus. Background Technology

[0002] Because laser welding uses a high power density of laser light irradiating the workpiece, high-speed and high-quality welding is possible. In particular, in scanning welding, where welding is performed while the laser is rapidly scanning the workpiece surface, the laser beam can be moved at high speed to the next welding point during periods when welding is not in progress, thus shortening the overall welding time (see, for example, Patent Document 1). Furthermore, regarding laser scanning methods, methods for scanning the laser to depict Lissajous patterns on the workpiece surface have been proposed in the past (see, for example, Patent Documents 2 and 3).

[0003] Prior art literature

[0004] Patent documents

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

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

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

[0008] -The technical problem the invention aims to solve-

[0009] However, in the existing structures shown in patent documents 2 and 3, the Lissajous pattern is usually depicted as a shape that is symmetrical about its center point (hereinafter also referred to as the origin).

[0010] However, the workpieces actually welded have various shapes. For example, when butt-welding plates of different thicknesses, the heat capacity of the workpiece is asymmetrical on both sides of the weld line corresponding to the butt joint of the plates. Furthermore, depending on the joint shape of the workpiece, the heat capacity of the workpiece may also be asymmetrical on both sides of the weld line.

[0011] In this case, if the laser is used to create a Lissajous pattern depicting the aforementioned symmetrical shape for welding, there is a concern that the asymmetry of the workpiece's heat capacity may lead to different weld shapes on both sides of the weld line. For example, if the laser output is adjusted to match the side with smaller heat capacity in the welding area of ​​the workpiece, insufficient heat will be input on the opposite side with larger heat capacity, making it difficult to obtain a weld with a good shape. Furthermore, if the laser output is adjusted to match the side with larger heat capacity, excessive heat will be input on the opposite side with smaller heat capacity, raising concerns about weld defects such as burn-through. Moreover, such problems also occur when the laser scanning pattern is not a Lissajous pattern, such as when two circular patterns meet at a single point and are continuous.

[0012] This disclosure is made in view of this, and its object is to provide a laser welding method and a laser welding apparatus that irradiates a laser to draw a prescribed pattern on the surface of a workpiece, thereby enabling the weld formed on the workpiece to have a good shape.

[0013] -Methods for solving technical problems-

[0014] To achieve the above objectives, the laser welding method disclosed herein is characterized by comprising: a welding step in which the laser is scanned two-dimensionally to irradiate the surface of a workpiece while traveling in a first direction, thereby welding the workpiece; wherein, in the welding step, the laser is scanned to depict a predetermined pattern on the surface of the workpiece; further, the laser is scanned to make the predetermined pattern asymmetrical about the first direction or a second direction intersecting the first direction, wherein the predetermined pattern is a pattern in which two asymmetrical annular patterns meet at a point and are continuous.

[0015] The laser welding apparatus disclosed herein is characterized by comprising at least: a laser oscillator for generating laser light; a laser head for receiving the laser light and irradiating a workpiece; and a controller for controlling 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 the laser scanner to depict a predetermined pattern on the surface of the workpiece; further, the controller drives the laser scanner to make the predetermined pattern asymmetrical about the first direction or the second direction intersecting the first direction, wherein the predetermined pattern is a pattern of two asymmetrical annular patterns joined and continuous at a point.

[0016] -Invention Effects-

[0017] According to this disclosure, it is possible to make the weld formed on the workpiece have a good shape. Attached Figure Description

[0018] Figure 1 This is a schematic structural diagram of the laser welding apparatus according to Embodiment 1.

[0019] Figure 2 This is a schematic diagram of the laser scanner.

[0020] Figure 3A This is a schematic diagram of the workpiece.

[0021] Figure 3B yes Figure 3A A cross-sectional view at line IIIB-IIIB.

[0022] Figure 4 This is a cross-sectional schematic diagram of another workpiece.

[0023] Figure 5 It is a diagram representing the scanning pattern of a laser.

[0024] Figure 6 This is a diagram showing the typical scanning pattern of the laser used for comparison.

[0025] Figure 7 This is a diagram showing the relationship between the laser's position and output in Modified Example 1.

[0026] Figure 8 This is a diagram showing the scanning pattern of the laser involved in Variation Example 2.

[0027] Figure 9 It is a graph showing the relationship between the laser's position and its output.

[0028] Figure 10 This is a diagram showing the scanning pattern of the laser involved in Embodiment 2.

[0029] Figure 11 It is a graph showing the relationship between the laser's position and its output.

[0030] Figure 12 This is a diagram showing the positional relationship between the laser and the molten pool formed on the workpiece in Embodiment 3.

[0031] Figure 13 It is a diagram representing the scanning pattern of a laser.

[0032] Figure 14 It is a graph showing the relationship between the laser's position and its output.

[0033] Figure 15 This is a graph showing the relationship between the laser drawing speed and the laser drawing position according to Embodiment 4.

[0034] Figure 16A This is a graph showing another relationship between the laser's drawing speed and the laser's drawing position.

[0035] Figure 16B This is another graph showing the relationship between the laser's drawing speed and the laser's drawing position.

[0036] Figure 17A This is a diagram showing the first scan pattern of the laser involved in Modification Example 3.

[0037] Figure 17B This is a diagram showing the second scan pattern of the laser involved in Modified Example 3.

[0038] Figure 18A This is a diagram showing the third scan pattern of the laser involved in Modification Example 3.

[0039] Figure 18B This is a diagram showing the fourth scan pattern of the laser involved in Modification Example 3.

[0040] Figure 18C This is a diagram showing the fifth scan pattern of the laser involved in Modified Example 3.

[0041] Figure 19 This is a diagram illustrating an example of the combination of parameters used to depict a Lissajous pattern.

[0042] Figure 20A This is a diagram showing the first scan pattern of the laser involved in Variation Example 4.

[0043] Figure 20B This is a diagram showing the second scan pattern of the laser involved in Modification Example 4.

[0044] Figure 20C This is a diagram showing the third scan pattern of the laser involved in Variation Example 4. Detailed Implementation

[0045] The embodiments of this disclosure are described below with reference to the accompanying drawings. Furthermore, the following description of preferred embodiments is merely illustrative and is not intended to limit this disclosure, its applications, or its uses.

[0046] (Implementation Method 1)

[0047] [Structure of laser welding equipment and laser scanner]

[0048] Figure 1 A schematic diagram showing the structure of the laser welding apparatus according to this embodiment. Figure 2 This is a schematic diagram showing the basic structure of a laser scanner. Figure 3A A schematic diagram showing the workpiece. Figure 3B express Figure 3AA cross-sectional view at line IIIB-IIIB. Figure 4 A schematic diagram showing the cross-section of another workpiece.

[0049] Furthermore, in the following description, the direction parallel to the travel direction of the laser LB from the reflector 33 to the laser scanner 40 may be referred to as the X direction, the direction parallel to the optical axis of the laser LB emitted from the laser head 30 may be referred to as the Z direction, and the directions orthogonal to the X and Z directions may be referred to as the Y direction. When the surface of the workpiece 200 is flat, the XY plane encompassing the X and Y directions can be approximately parallel to the surface or at a certain angle to it.

[0050] like Figure 1 As shown, the laser welding device 100 includes: a laser oscillator 10, an optical fiber 20, a laser head 30, a controller 50, and a robotic arm 60.

[0051] The laser oscillator 10 is a laser source that is powered by a power source not shown and generates laser LB. Alternatively, the laser oscillator 10 may comprise a single laser source or multiple laser modules. In the latter case, lasers emitted separately from the multiple laser modules are coupled and emitted as laser LB. Furthermore, the laser source or laser module used in the laser oscillator 10 can be appropriately selected based on the material of the workpiece 200, the shape of the welding area, etc.

[0052] For example, fiber lasers, disk lasers, or YAG (Yttrium Aluminum Garnet) lasers can also be used as laser sources. In this case, the wavelength of the laser LB is set in the range of 1000 nm to 1100 nm. Alternatively, semiconductor lasers can be used as laser sources or laser modules. In this case, the wavelength of the laser LB is set in the range of 800 nm to 1000 nm. Furthermore, visible light lasers can also be used as laser sources or laser modules. In this case, the wavelength of the laser LB is set in the range of 400 nm to 600 nm.

[0053] The optical fiber 20 is optically coupled to the laser oscillator 10. The laser LB generated in the laser oscillator 10 is incident on the optical fiber 20 and transmitted to the laser head 30 inside it.

[0054] The laser head 30 is mounted at the end of the optical fiber 20 and irradiates the workpiece 200 with the laser LB transmitted from the optical fiber 20.

[0055] In addition, the laser head 30, as an optical component, includes a collimating lens 32, a reflector 33, a condenser lens 34, and a laser scanner 40. These optical components are housed inside the housing 31 in a prescribed configuration.

[0056] The collimating lens 32 receives the laser beam LB emitted from the optical fiber 20, converts it into parallel light, and directs it onto the reflecting mirror 33. Furthermore, the collimating lens 32 is connected to a drive 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 beam LB is changed, allowing the laser beam LB to appropriately illuminate the workpiece 200 according to its shape. In other words, the collimating lens 32, in combination with the drive unit (not shown), also functions as a focal position adjustment mechanism for the laser beam LB. Alternatively, the focal position of the laser beam LB can also be changed by displacing the condenser lens 34 via the drive unit.

[0057] The reflector 33 reflects the laser LB from the transmission collimating lens 32, causing it to be incident on the laser scanner 40. The surface of the reflector 33 is set at approximately 45 degrees to the optical axis of the laser LB from the transmission collimating lens 32.

[0058] The focusing lens 34 is reflected by the reflecting mirror 33, causing the laser LB scanned by the laser scanner 40 to focus onto the surface of the workpiece 200.

[0059] like Figure 2 As shown, the laser scanner 40 is a known galvanometer scanner having a first galvanometer lens 41 and a second galvanometer lens 42. The first galvanometer lens 41 has a first reflector 41a, a first rotation axis 41b, and a first drive unit 41c, and the second galvanometer lens 42 has a second reflector 42a, a second rotation axis 42b, and a second drive unit 42c. The laser LB from the transmission focusing lens 34 is reflected by the first reflector 41a and further reflected by the second reflector 42a, irradiating the surface of the workpiece 200.

[0060] For example, the first drive unit 41c and the second drive unit 42c are galvanometer motors, and the first rotating shaft 41b and the second rotating shaft 42b are the output shafts of the motors. Although not shown, the first reflector 41a mounted on the first rotating shaft 41b is rotated around the axis of the first rotating shaft 41b by the first drive unit 41c using a driver that operates according to a control signal from the controller 50. Similarly, the second reflector 42a mounted on the second rotating shaft 42b is rotated around the axis of the second rotating shaft 42b by the second drive unit 42c using a driver that operates according to a control signal from the controller 50.

[0061] The laser LB is scanned in the X direction by rotating the first reflector 41a around the axis of the first rotation axis 41b to a predetermined angle. Similarly, the laser LB is scanned in the Y direction by rotating the second reflector 42a around the axis of the second rotation axis 42b to a predetermined angle. In other words, the laser scanner 40 is configured to scan the laser LB two-dimensionally in the XY plane and irradiate the workpiece 200.

[0062] The controller 50 controls the laser oscillation of the laser oscillator 10. Specifically, it controls the laser oscillation by providing control signals such as output current and on / off time to a power supply (not shown) connected to the laser oscillator 10.

[0063] Furthermore, the controller 50 controls the movement of the laser head 30 according to the selected laser welding program. Specifically, it controls the drive of the laser scanner 40 and the collimating lens 32 (not shown) located on the laser head 30. Further, the controller 50 controls the movement of the robot arm 60. Additionally, the laser welding program is stored in a storage unit (not shown) located inside the controller 50 or elsewhere, and can be retrieved by commands from the controller 50.

[0064] The controller 50 has an integrated circuit such as an LSI (not shown) or a microcomputer, and the functions of the controller 50 can be realized by executing a laser welding program as software on the integrated circuit. Alternatively, a separate controller 50 can be provided to control the movement of the laser head 30 and a separate controller 50 to control the output of the laser LB.

[0065] The robotic arm 60 is a multi-jointed robot mounted on the housing 31 of the laser head 30. Furthermore, the robotic arm 60 is interactively connected to the controller 50 to move the laser head 30, thereby tracing a predetermined trajectory according to the laser welding procedure. Alternatively, a separate controller (not shown) may be provided to control the movements of the robotic arm 60.

[0066] Figure 1 The laser welding apparatus 100 shown is capable of laser welding workpieces 200 of various shapes. For example, such as Figure 3A , 3B As shown, laser LB can also be used to irradiate the joint of workpieces 200, where first plate 210 and second plate 220 of the same material but different thicknesses are butted together at their end faces, to perform butt welding. Furthermore, as... Figure 3B As shown, laser LB can also be used to perform lap fillet welding by irradiating the corner of the joint of the workpiece 200, where the end faces of the third plate 230 and the fourth plate 240 are staggered and overlapped. However, it can also be said that the shape of the laser-welded workpiece 200 is not limited to... Figure 3A , 3B , Figure 4 The example shown.

[0067] [Mathematical representation of the Lissajous pattern]

[0068] Figure 5 The laser scanning pattern is represented by the laser LB being scanned to depict a Lissajous pattern (hereinafter also referred to as a Lissajous graphic) on the surface of workpiece 200 in the XY plane.

[0069] Figure 5 The Lissajous pattern shown can be obtained by vibrating the laser LB in the X direction at a predetermined frequency as a sine wave and in the Y direction at a frequency different from that in the X direction (half the frequency in the X direction) as a sine wave. Furthermore, as described, the scanning patterns in the X and Y directions of the laser LB 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 pattern obtained by driving the first reflector 41a are set as X1 and the position coordinates of the Lissajous pattern obtained by driving the second reflector 42a are set as Y1, the position coordinates X1 and Y1 are represented by the following equations (1) and (2), respectively.

[0070] X1=a×sin(nt)···(1)

[0071]

[0072] here,

[0073] a: Amplitude in the X direction of the Lissajous pattern

[0074] b: Amplitude in the Y direction of the Lissajous pattern

[0075] n: Frequency of the first reflecting mirror 41a

[0076] m: Frequency of the second reflecting mirror 42a

[0077] t: time

[0078] The phase difference when the first reflector 41a or the second reflector 42a is driven, specifically, the angular deviation set when the first reflector 41a and the second reflector 42a rotate.

[0079] In addition, the position coordinates X1 and Y1 shown in equations (1) and (2) are represented by the static coordinate system of the Lissajous pattern when the position of the laser head 30 is fixed.

[0080] Furthermore, frequency n and frequency m correspond to the driving frequencies of the first reflector 41a and the second reflector 42a, respectively.

[0081] according to Figure 5 It can be seen that the Lissajous pattern in this embodiment is asymmetrical about the center line that passes through the origin O and extends in the X direction.

[0082] If located at Figure 5 If the scanning pattern of the laser LB on the + side in the Y direction is set as LS1, then the scanning pattern LS1 (hereinafter also referred to as the drawing pattern LS1) corresponds to a=1, b=1, n=2, m=1 in equations (1) and (2). In the case of LS2, the scanning pattern located on the - side is set as LS2. Then the scanning pattern LS2 (hereinafter also called the drawing pattern LS2) corresponds to a = 0.5, b = 0.5, n = 2, m = 1 in equations (1) and (2). In other words, in the X and Y directions respectively, the trajectories depicted by pattern LS2 are smaller than those depicted by pattern LS1. Therefore, the depiction length of pattern LS2 is shorter than that of pattern LS1. Furthermore, a and b are normalized to the size of pattern LS1 using 1 as a reference. Additionally, the phase difference in equations (1) and (2)... It can be either 0 degrees or 180 degrees.

[0083] Furthermore, the combined pattern of patterns LS1 and LS2 is a figure-eight Lissajous pattern. Additionally, the actual size of the Lissajous pattern, in other words, the amplitudes in the X and Y directions, are approximately 1 mm to 10 mm.

[0084] Here, as Figure 5 As shown, in the pattern LS1, when the drawing distance of the Lissajous pattern in the X direction in the specified time variable Δt is set as ΔX, the drawing distance in the Y direction is set as ΔY, and the drawing distance of the Lissajous pattern in the time variable Δt is set as ΔL, ΔX, ΔY, and ΔL are respectively represented by the following equations (3) to (5).

[0085] ΔX=a×n×cos(nt)×Δt···(3)

[0086]

[0087] ΔL=Δt×{(ΔX) 2 +(ΔY) 2} 1 / 2 ···(5)

[0088] Therefore, the drawing speed V of the Lissajous pattern is expressed by the following equation (6).

[0089] V=ΔL / Δt···(6)

[0090] On the other hand, in the depiction pattern LS2, ΔX and ΔY can be calculated in the same way by equations (3) and (4), but only the amplitude in the X direction and the amplitude in the Y direction are different from those in the depiction pattern LS1.

[0091] [Laser Welding Method]

[0092] In this embodiment, a robotic arm 60 moves the laser head 30 in the X direction at a predetermined speed and irradiates the surface of the workpiece 200 with the laser LB. Furthermore, a laser scanner 40 is used to scan the laser LB two-dimensionally, thereby drawing a pattern on the surface of the workpiece 200. Figure 5 The Lissajous pattern is shown. Furthermore, in this embodiment, [the pattern is] used to [address / determine / adjust / etc.]. Figure 3A , 3B The following explanation uses the example of butt welding of workpiece 200 as an example. Furthermore, in this embodiment, the output P of the laser LB is controlled to be uniform throughout the entire length of the Lissajous pattern.

[0093] in addition, Figure 5 The Lissajous pattern shown here starts from the origin O during a period of 1 cycle. Figure 5 The directions of arrows AR1 and AR2 shown are obtained by tracing the laser LB. Specifically, during one cycle, the laser LB is scanned such that it travels from the origin O through the tracing positions A→B→C→O→D→E→F→O.

[0094] Laser welding is performed by irradiating the mating portion of the first plate 210 and the second plate 220 at the welding point of workpiece 200 with laser LB. Figure 3A As shown, the mating portion extends along the X direction, corresponding to the welding line described above. On the other hand, as... Figure 3B As shown, the thickness of the first plate 210 in the Z direction is greater than the thickness of the second plate 220 in the Z direction. Furthermore, the first plate 210 is made of the same material as the second plate 220. Therefore, the heat capacity of the first plate 210 is greater than that of the second plate 220. In other words, the heat capacity of the workpiece 200 is asymmetrical about the weld line corresponding to the contact surface between the end faces of the first plate 210 and the second plate 220.

[0095] When laser welding is performed on the surface of such a workpiece 200 by drawing a typical Lissajous pattern using laser LB, the following technical problems may arise.

[0096] Figure 6The typical scanning pattern of the laser used for comparison, in equations (1) and (2), is equivalent to the case where parameters a = 1, b = 1, n = 2, and m = 1. In other words, Figure 6 The Lisajous pattern shown is a figure-eight Lisajous pattern that is symmetrical about the X and Y directions.

[0097] If the laser LB travels in the X direction and irradiates the mating portion of the first plate 210 and the second plate 220 to achieve the desired effect... Figure 6 As shown in the Lissajous pattern, the heat input to the workpiece 200 is also symmetrical about the welding line.

[0098] On the other hand, as described above, the heat capacity at the joint between the first plate 210 and the second plate 220 is asymmetrical with respect to the weld line. Therefore, if a weld is formed along the joint, there is a concern about damage to the weld shape. For example, if laser welding is performed with the heat input to the workpiece 200 based on laser LB matched to the second plate 220 with its smaller heat capacity, the heat input to the first plate 210 with its larger heat capacity will be insufficient, raising concerns about damage to the weld shape. Conversely, if laser welding is performed with the heat input to the workpiece 200 based on laser LB matched to the first plate 210 with its larger heat capacity, the heat input to the second plate 220 with its smaller heat capacity will become excessive, raising concerns about welding defects such as burn-through.

[0099] Therefore, in this embodiment, the laser LB is controlled such that the drawing length of the depiction pattern LS1 irradiated onto the first substrate 210 in the Lissajous pattern is longer than the drawing length of the depiction pattern LS2 irradiated onto the second substrate 220. Furthermore, the drawing pattern LS1 of the laser LB is... Figure 5 The path O→A→B→C→O shown shows the pattern LS2 drawn by laser LB. Figure 5 The path shown is O→D→E→F→O.

[0100] In this way, the heat input to the first plate 210 via laser LB is greater than the heat input to the second plate 220. Therefore, different amounts of heat can be applied to the welding area of ​​the workpiece 200, where the heat capacity is asymmetrical with respect to the weld line—that is, the butt joint between the first plate 210 and the second plate 220—on both sides of the weld line. This results in a better weld shape. Furthermore, it helps to suppress welding defects such as burn-through.

[0101] [Effects, etc.]

[0102] As explained above, the laser welding method according to this embodiment includes a welding step in which the laser LB is irradiated onto the surface of the workpiece 200 by causing the laser LB to travel in the X direction (first direction) and scan the laser LB in two dimensions, thereby welding the workpiece 200.

[0103] During the welding process, the laser LB is vibrated along the X direction as a sinusoidal wave with a first frequency n, and along the Y direction as a sinusoidal wave with a second frequency m. This scanning of the laser LB results in a Lissajous pattern being drawn on the surface of the workpiece 200.

[0104] Furthermore, the laser LB is scanned so that the Lissajous pattern has an asymmetrical shape with respect to the X direction. Specifically, the laser LB is scanned so that the depiction length of the Lissajous pattern is different with respect to the X direction. More specifically, the laser LB is scanned so that the depiction length of the Lissajous pattern, sandwiched between a center line passing through the origin O and extending with respect to the X direction, is different on one side and the other side.

[0105] In this way, different amounts of heat can be applied to the welding area of ​​the workpiece 200 with asymmetrical heat capacity on both sides of the welding line, resulting in a good weld shape.

[0106] In this embodiment, the heat capacity of the welding portion in the workpiece 200, namely the butt joint of the first plate 210 and the second plate 220, is asymmetrical with respect to the extension direction of the weld line, i.e., the X direction. In this case, in the depiction of the Lissajous pattern, the first portion, i.e., the first plate 210, which has a larger heat capacity among the welding portions, receives a longer laser LB pattern than the second portion, i.e., the second plate 220, which has a smaller heat capacity.

[0107] In this way, different amounts of heat can be reliably applied to the welding area of ​​the workpiece 200 with asymmetrical heat capacity, on both sides of the weld line. This results in a good weld shape and also helps to suppress welding defects such as burn-through.

[0108] The laser welding apparatus 100 according to this embodiment includes at least: a laser oscillator 10 that generates laser LB; a laser head 30 that receives laser LB and irradiates workpiece 200; and a controller 50 that controls the operation of laser head 30 and the output P of laser LB.

[0109] The laser head 30 has a laser scanner 40 that scans the laser LB in the X direction (first direction) and the Y direction (second direction) that intersects the X direction.

[0110] The controller 50 causes the laser LB to vibrate 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. Thus, the controller 50 drives the laser scanner 40 to draw a Lissajous pattern on the surface of the workpiece 200.

[0111] Furthermore, the controller 50 drives the laser scanner 40 to make the Lissajous pattern asymmetrical about the X direction. Specifically, the controller 50 drives the laser scanner 40 to make the drawing length of the Lissajous pattern different about the X direction. More specifically, the controller 50 drives the laser scanner 40 to make the center line passing through the origin O and extending about the X direction on one side and the other side, thus making the drawing length of the Lissajous pattern different.

[0112] According to the laser welding apparatus 100 of this embodiment, different heat is applied to the two sides of the welding line of a workpiece 200 whose heat capacity is asymmetrical with respect to the welding line, so that the weld has a good shape.

[0113] The laser welding apparatus 100 also includes a robotic arm 60 equipped with a laser head 30, and a controller 50 controls the movement of the robotic arm 60. The robotic arm 60 moves the laser head 30 relative to the surface of the workpiece 200 in a specified direction.

[0114] By setting up the robotic arm 60 in this way, the welding direction of the laser LB can be changed. Furthermore, it is easy to perform laser welding on workpieces 200 with complex shapes, such as three-dimensional shapes.

[0115] The laser oscillator 10 and the laser head 30 are connected by an optical fiber 20. The laser LB passes through the optical fiber 20 and is transmitted from the laser oscillator 10 to the laser head 30.

[0116] By arranging the optical fiber 20 in this way, laser welding can be performed on the workpiece 200 located separately from the laser oscillator 10. This increases the degree of freedom in configuring the various parts of the laser welding apparatus 100.

[0117] The laser scanner 40 includes a first galvanometer 41 that scans the laser LB in the X direction and a second galvanometer 42 that scans the laser LB in the Y direction.

[0118] By configuring the laser scanner 40 in this way, the laser LB can be scanned in two dimensions easily. Furthermore, since a known galvanometer scanner is used as the laser scanner 40, the cost increase of the laser welding apparatus 100 can be suppressed.

[0119] The laser head 30 also includes a collimating lens 32, which is configured to change the focal position of the laser LB along the Z direction, which intersects both the X and Y directions. In other words, the collimating lens 32, in combination with a drive unit (not shown), also functions as a focal position adjustment mechanism for the laser LB.

[0120] In this way, the focal position of the laser LB can be easily changed, and the laser LB can be appropriately irradiated according to the shape of the workpiece 200.

[0121] Furthermore, in this embodiment, the laser head 30 is moved in the X direction to cause the laser LB to travel in the X direction, but this is not particularly limited to this. For example, if the mating portion of the first plate 210 and the second plate 220 extends in the Y direction, the laser LB can also be made to travel in the Y direction by moving the laser head 30 in the Y direction. Along with this, the shape of the Lissajous pattern can also be changed. However, in this case, it is also necessary to control the shape and drawing length of the Lissajous pattern so that different amounts of heat are applied to the two sides of the weld line for the welding portion of the workpiece 200 where the heat capacity is asymmetrical with respect to the weld line.

[0122] Furthermore, the direction in which the Lissajous pattern is drawn is not particularly limited to the aforementioned. For example, the Lissajous pattern can also be drawn by scanning the laser LB during one cycle, so that the pattern travels from the origin O through the drawing positions C→B→A→O→F→E→D→O. Alternatively, the Lissajous pattern can be drawn by scanning the laser LB during one cycle, so that the pattern travels from the origin O through the drawing positions D→E→F→O→A→B→C→O. Furthermore, the Lissajous pattern can also be drawn by scanning the laser LB during one cycle, so that the pattern travels from the origin O through the drawing positions F→E→D→O→C→B→A→O.

[0123] Alternatively, it can also be done on Figure 4 When laser welding is performed on the workpiece 200 shown, the method described in this embodiment is applied. At the corner of the joint of the workpiece 200 where the end faces of the third plate 230 and the fourth plate 240 overlap, the heat capacity of the overlapping portion (first part) of the third plate 230 and the fourth plate 240 is greater than that of the portion consisting only of the third plate 230 (second part). Therefore, in this overlapping portion, the laser LB is controlled so that the drawing length of the laser LB is longer than that of the portion consisting only of the third plate 230.

[0124] In this way, the aforementioned effects can be achieved. In other words, by applying different amounts of heat to the two sides of the weld line at the welding area of ​​the workpiece 200 where the heat capacity is asymmetrical about the weld line, a good weld shape can be achieved. Furthermore, welding defects such as burn-through can be suppressed.

[0125] <Variation Example 1>

[0126] Figure 7 This indicates the scanning pattern of the laser involved in this variation.

[0127] The structure shown in this modified example differs from the structure shown in Embodiment 1 in that it varies the output P of the laser LB according to the position depicted by the laser LB. Furthermore, the structure of the workpiece 200 being laser-welded is different from that shown in Embodiment 1. Figure 3A , 3BThe same applies as shown. Furthermore, the scanning pattern of the laser LB is the same as... Figure 5 The same applies as shown.

[0128] In this modified example, when depicting a Lissajous pattern, the output P of the laser LB is controlled such that the output P1 of the laser LB irradiating the first plate 210 is higher than the output P2 of the laser LB irradiating the second plate 220. In other words, the output P of the laser LB is controlled such that the output P1 of the laser LB irradiating the first plate 210 is higher than the output P2 of the laser LB irradiating the second plate 220. Figure 5 The output P1 of the laser LB in the depicted pattern LS1 with the path O→A→B→C→O is higher than the output P2 of the laser LB in the depicted pattern LS2 with the path O→D→E→F→O. The control of the output P of such laser LB is performed by controller 50.

[0129] In this way, the difference between the heat input to the first plate 210 and the heat input to the second plate 220 can be greater than that shown in Embodiment 1. This will be explained further.

[0130] like Figure 5 As shown, by setting the Lissajous pattern to an asymmetrical shape in the X direction, and making the drawing length of the drawing pattern LS1 longer than that of the drawing pattern LS2, a difference in the amount of heat applied to the workpiece 200 can be imparted with respect to the welding line extending in the X direction.

[0131] However, for example, due to the difference in thickness between the first plate 210 and the second plate 220, only the following is described. Figure 5 The Lissajous pattern shown may not produce a good weld shape even with workpiece 200, even when different heat is applied to both sides of the weld line. For example, in Figure 3B In this example, simply expanding the drawing area on the side of workpiece 210 is insufficient; to obtain a good weld (in this case, a weld shape on the back side), workpiece 210 needs to be melted more deeply. Furthermore, the actual dimensions of the Lissajous pattern are constrained by the specifications required for welding, such as weld width. Therefore, the range of the difference between the drawing length of drawing pattern LS1 and the drawing length of drawing pattern LS2 is also limited; even if different heat is applied to both sides of the weld line within workpiece 200, it may not be possible to obtain a good weld shape simply by adjusting the sizes of drawing patterns LS1 and LS2.

[0132] On the other hand, according to this modified example, laser LB is used to draw on the surface of workpiece 200. Figure 5 The Lissajous pattern shown is then laser-welded. Simultaneously, the output P1 of the laser LB irradiating the first plate 210 is higher than the output P2 of the laser LB irradiating the second plate 220, which has a smaller heat capacity than the first plate 210.

[0133] In this way, for the welding portion of workpiece 200 where the heat capacity is asymmetrical with respect to the weld line, namely the butt joint of the first plate 210 and the second plate 220, different heat can be reliably applied to both sides of the weld line, while also controlling the weld shape. This results in a good weld shape. Furthermore, it suppresses welding defects such as burn-through and insufficient penetration.

[0134] Additionally, when changing the output P of the laser LB, it can also be done as follows: Figure 7 As shown by the dashed lines, the rising and falling portions of the output P of the laser LB are controlled respectively.

[0135] For example, when the laser LB's drawing position moves from the origin O to D, the output P of the laser LB can be decreased from P1 to P2 from the moment the laser LB crosses the origin O until the elapsed period t1. In this case, the control curve S1 for the output P can be either linear or curved. Furthermore, when the laser LB's drawing position moves from the origin O to A, the output P of the laser LB can be increased from P2 to P1 from the moment the laser LB crosses the origin O until the elapsed period t2. In this case, the control curve S2 for the output P can also be either linear or curved.

[0136] By controlling the output P of the laser LB as shown in control curves S1 and S2, it is easy to make the output P stably reach the target value.

[0137] <Variation Example 2>

[0138] Figure 8 This represents the scanning pattern of the laser involved in this variation. Figure 9 This indicates the relationship between the laser's depicted position and its output. Additionally, for ease of explanation, in... Figure 8 , 9 In the accompanying drawings shown below, the same reference numerals are used for the same parts as in Embodiment 1, and detailed descriptions are omitted.

[0139] The direction in which the Lissajous pattern is depicted in this variation is different from the structure shown in Embodiment 1. Figure 8 The Lissajous pattern shown is formed by moving from the origin O to the origin O during a period of 1 cycle. Figure 7 The direction of the arrows AR3 and AR4 shown is obtained by scanning the laser LB. Specifically, the laser LB is scanned such that, during one cycle, the path is drawn from the origin O through the positions C→B→A→O→F→E→D→O.

[0140] Furthermore, in this variant example, as... Figure 9As shown, the output P of the laser LB is controlled such that the output P1 of the laser LB irradiating the first plate 210 is higher than the output P2 of the laser LB irradiating the second plate 220. In other words, the output P of the laser LB is controlled such that the output P1 of the laser LB irradiating the first plate 210 is higher than the output P2 of the laser LB irradiating the second plate 220. Figure 8 The output P1 of laser LB in the depiction pattern LS1 with the path O→C→B→A→O is higher than the output P2 of laser LB in the depiction pattern LS2 with the path O→F→E→D→O.

[0141] In this modified example, the same effect as that achieved by the structure shown in Modified Example 1 can be achieved. In other words, for the welding portion of the workpiece 200 where the heat capacity is asymmetrical with respect to the weld line, different amounts of heat can be reliably applied to both sides of the weld line. Furthermore, by changing the output of the laser LB on both sides, the penetration depth on the back side of the workpiece can be achieved at a specified level, resulting in a good weld shape. In addition, welding defects such as burn-through and insufficient penetration can be suppressed.

[0142] (Implementation Method 2)

[0143] Figure 10 This represents the scanning pattern of the laser involved in this embodiment. Figure 11 This illustrates the relationship between the laser's depiction position and its output. Furthermore, although not shown in the diagram, in this embodiment, the welding area of ​​the workpiece 200 is configured such that the heat capacity is the same on both sides sandwiching the welding line.

[0144] In this embodiment, in the depiction of the Lissajous pattern, the output P of the laser LB is lower near the origin O of the Lissajous pattern than in other parts, which is different from the structure shown in Embodiment 1.

[0145] Specifically, such as Figure 10 , 11 As shown, between the origin O and each drawing position A', C', D', F', the output P of the laser LB is P3, and at other Lissajous pattern drawing positions, the output P of the laser LB is P1 (P1 > P3). The control of the output P of the laser LB is performed by the controller 50.

[0146] As described, when a Lissajous pattern is drawn on the surface of workpiece 200 using a laser LB, the laser LB passes once during one cycle, for example, at drawing position A, and twice at the origin O. Furthermore, the speed at which the laser head 30 travels in the X direction, i.e., the travel speed of the laser LB in the X direction, is typically much lower than the drawing speed V of the laser LB when drawing a Lissajous pattern.

[0147] Therefore, the heat input to the origin O in the depiction of the Lissajous pattern is greater than the heat input to other depiction locations, such as locations A, B, C, D, E, and F. Thus, because the heat input to the surface of workpiece 200 is uneven according to location, the weld shape deteriorates as described above.

[0148] Therefore, in this embodiment, by making the laser output P of LB lower near the origin O of the Lissajous pattern than elsewhere, the uneven distribution of heat input to the surface of the workpiece 200 according to location is suppressed. This results in a well-shaped weld. Furthermore, it suppresses welding defects such as burn-through.

[0149] Furthermore, the distances from the origin O to each depicted position A', C', D', F' can be appropriately varied depending on the shape of the welding part of the workpiece 200, the material of the workpiece 200, etc. For example, if one cycle of the Lissajous pattern is considered as 360 degrees, and this distance is replaced by an angle viewed from the origin O, it is preferable that the angle is greater than 0 degrees and less than 3 to 15 degrees.

[0150] (Implementation Method 3)

[0151] Figure 12 This indicates the positional relationship between the laser and the molten pool formed on the workpiece in this embodiment. Figure 13 The pattern represents a laser scan. Figure 14 This indicates the relationship between the laser's depicted position and its output.

[0152] like Figure 12 As shown, when laser LB irradiates workpiece 200, the metal constituting workpiece 200 is rapidly heated and melted, forming a molten pool 201 in and around the irradiated area of ​​laser LB. Furthermore, at the irradiated area of ​​laser LB, metal evaporates, forming a small hole 202 from the surface of workpiece 200 inwards. By allowing laser LB to reach the interior of the small hole 202, the metal melts until it reaches the interior of workpiece 200, ensuring the depth of penetration of workpiece 200. Additionally, Figure 12 The laser LB shown is irradiated at a position equivalent to Figure 5 The origin O of the Lissajous pattern shown.

[0153] Furthermore, at the third location 203, which is positioned further forward than the laser LB irradiation position along the welding travel direction (in this case, the Y direction), the workpiece 200 is not sufficiently heated, and a molten pool 201 is not formed. On the other hand, the fourth location 204, positioned further backward than the laser LB irradiation position, has been sufficiently heated by the laser LB. Therefore, the fourth location 204 is located inside the molten pool 201, or in the solidified portion of the molten pool 201. In other words, the fourth location 204 contains the molten pool 201.

[0154] Thus, in front of the origin O of the Lissajous pattern along the welding line, corresponding to the irradiation position of the laser LB, a larger input heat is required to melt the workpiece 200. On the other hand, behind the origin O of the Lissajous pattern, the input heat is sufficient to maintain the already formed molten pool 201.

[0155] Consider adjusting the input heat by incorporating the origin O of the Lissajous pattern; in this case, the output P of the laser LB is adjusted. For example... Figure 6 As shown, if the Lissajous pattern is symmetrical, there is a concern that insufficient heat input to the workpiece 200 in front of the origin O may cause misalignment of the weld shape, particularly the weld bead shape. On the other hand, if the laser output P of LB is adjusted in conjunction with the location in front of the origin O of the Lissajous pattern, there is a concern that excessive heat input to the molten pool 201 behind the origin O may cause instability of the molten pool 201. In this case, it is difficult to obtain a weld with a good shape. Furthermore, the aforementioned technical problems may occur on both sides of the weld line, whether the heat capacity of the workpiece 200 is equal or asymmetrical.

[0156] Therefore, in this embodiment, the output P of the irradiated laser LB is varied at the third portion 203 and the fourth portion 204. Specifically, the structure shown in this embodiment differs from the structure shown in Embodiment 1 in the following aspects.

[0157] In other words, in the depiction of the Lissajous pattern, the heat input is greater when the laser LB is irradiated at the third part 203, which is further forward than the molten pool 201 formed on the workpiece 200, along the Y direction, compared to the heat input when the laser LB is irradiated at the fourth part 204, which contains the molten pool 201 and is further backward than the third part 203.

[0158] Specifically, such as Figure 13 , 14 As shown, the laser LB is controlled such that the output of the laser LB in the Lissajous pattern along the Y direction, in the portion of the LS1 pattern drawn in front of the origin O, or in the portion of the LS2 pattern drawn in front of the origin O, is higher than that in the portion of the LS1 pattern drawn behind the origin O, or in the portion of the LS2 pattern drawn behind the origin O.

[0159] This promotes the formation of a molten pool 201 in the unheated and unmelted third region 203. Furthermore, it suppresses excessive vibration of the molten pool 201. This prevents the weld from becoming undulating. Moreover, it prevents the weld penetration from becoming deeper than desired, reducing welding defects such as burn-through and improving weld quality. Furthermore, by avoiding unnecessary heat input to the fourth region 204, laser energy is saved.

[0160] In this embodiment, the output P of the laser LB is controlled by the controller 50 during the drawing of the drawing pattern LS1 and the drawing pattern LS2.

[0161] In this way, a molten pool 201 can be reliably formed in the unheated and unmelted third region 203. Furthermore, excessive vibration of the molten pool 201 can be suppressed. This prevents the weld from becoming undulating. Moreover, it prevents the weld penetration from becoming deeper than desired, reducing welding defects such as burn-through, and improving weld quality. Furthermore, by avoiding unnecessary heat input to the fourth region 204, laser energy can be saved.

[0162] (Implementation Method 4)

[0163] Figure 15 This indicates the relationship between the laser drawing speed and the laser drawing position in this embodiment. Figure 16A This represents another relationship between the laser's drawing speed and its drawing position. Figure 16B This represents another relationship between the laser's drawing speed and its drawing position. Furthermore, the scanning pattern of the laser LB in this embodiment is related to... Figure 5 The same applies as shown.

[0164] In embodiments 1 to 3 and variation 1, such as Figure 15 As shown, the drawing speed V of the laser LB can also be constant in the depiction of the Lissajous pattern. In other words, the drawing speed V of the laser LB can also be constant throughout the entire length of the Lissajous pattern. In this way, it is easy to draw the laser into the molten pool 201 (refer to...). Figure 12 (Control of input heat)

[0165] Furthermore, in Modification 1, by controlling the output P of the laser LB according to the position of the laser LB in the Lissajous pattern, different heat is applied to the two sides of the welding line for the welding part of the workpiece 200, which has a heat capacity that is asymmetrical with respect to the welding line.

[0166] However, by varying the laser LB's drawing speed V according to the drawing position, the input heat to the workpiece 200 can also be varied. For example, by decreasing the laser LB's drawing speed V, the input heat per unit drawing length increases. In other words, the same effect as increasing the laser LB's output P can be obtained.

[0167] Therefore, replacing such as Figure 7As shown, the output P of the laser LB can be controlled according to the drawing position of the laser LB in the Lissajous pattern, and the drawing speed V of the laser LB can also be controlled as shown in Figure 16. This control of the drawing speed V of the laser LB is performed by the controller 50.

[0168] In other words, targeting Figure 3A , 3B The workpiece 200 shown has a longer drawing length for the drawing pattern LS1 irradiated onto the first plate (first part) 210 than the drawing length for the drawing pattern LS1 irradiated onto the second plate (second part) 220, which has a smaller heat capacity than the first plate 210. At the same time, the drawing speed V2 of the laser LB in drawing the drawing pattern LS1 is lower than the drawing speed V1 of the laser LB in drawing the drawing pattern LS2 (V1 > V2).

[0169] In this way, the same effect as that achieved by the structure shown in Modified Example 1 can be achieved. In other words, for the welding part of the workpiece 200 where the heat capacity is asymmetrical with respect to the weld line, different heat can be reliably applied to both sides of the weld line, resulting in a good weld shape. Furthermore, the occurrence of welding defects such as burn-through can be suppressed.

[0170] In addition, it can also replace Figure 14 As shown, the output P of laser LB is changed in front of and around the molten pool 201, and as... Figure 16B The drawing speed V of the laser LB is controlled as shown. This control of the laser LB drawing speed V is performed by the controller 50.

[0171] In this way, the same effect as that achieved by the structure shown in Embodiment 3 can be achieved. In other words, it can promote the formation of a molten pool 201 at the third location 203 and suppress the weld from becoming undulating. Furthermore, it can reduce the occurrence of welding defects such as burn-through and improve the weld quality. Moreover, since unnecessary heat is avoided in the fourth location 204, laser energy can be saved.

[0172] Additionally, although not illustrated, it can be used as a substitute for, for example... Figure 11 As shown, the output P of the laser LB is varied near the origin O of the Lissajous pattern, thereby controlling the drawing speed V of the laser LB.

[0173] The drawing speed V of such laser LB is controlled by controller 50.

[0174] For example, it is also possible to do so at the origin O and... Figure 11Between the shown drawing positions A', C', D', and F', the drawing speed V of the laser LB is V1. At other Lissajous pattern drawing positions, the drawing speed V of the laser LB is V2 (V1 > V2).

[0175] According to this embodiment, the structure has the same function as that shown in Embodiments 1 to 3 and Modifications 1 and 2, and can apply different heat to the two sides of the welding line for the welding part of the workpiece 200 where the heat capacity is asymmetrical with respect to the welding line, so that the weld shape is good.

[0176] Furthermore, it can promote the formation of a molten pool 201 in the unheated and unmelted third part 203. It can also suppress excessive vibration of the molten pool 201. Thus, it can prevent the weld from becoming undulating. Furthermore, it prevents the weld penetration depth of the workpiece 200 from being deeper than desired, reducing welding defects such as burn-through, and ultimately improving weld quality.

[0177] Additionally, when varying the drawing speed V of the laser LB, such as Figure 16A or Figure 16B As shown by the dashed line, the rising and falling portions of the drawing speed V can also be controlled separately.

[0178] by Figure 16A or Figure 16B In the example shown, when the drawing position of the laser LB moves from the origin O to D, the drawing speed V of the laser LB can be increased from V2 to V1 from the moment the laser LB passes through the origin O until a period t3 has elapsed. In this case, the control curve S3 for the drawing speed V can be either a straight line or a curve. Furthermore, when the drawing position of the laser LB moves from the origin O to A, the drawing speed V of the laser LB can be decreased from V2 to V1 from the moment the laser LB passes through the origin O until a period t4 has elapsed. In this case, the control curve S4 for the drawing speed V can be either a straight line or a curve.

[0179] By controlling the drawing speed V of the laser LB as shown in control curves S3 and S4, it is easy to make the drawing speed V stably reach the target value.

[0180] <Variation Example 3>

[0181] Figure 17A This represents the first scan pattern of the laser involved in this variation. Figure 17B This indicates the second scan pattern. Figure 18A This indicates the third scan pattern of the laser involved in this variation. Figure 18B This indicates the 4th scan pattern. Figure 18C This indicates the 5th scan pattern. Figure 19This represents an example of the combination of parameters used when depicting a Lisajous pattern.

[0182] In actual laser welding, the parameters a, b, n, and m shown in equations (1) and (2) can be appropriately changed according to the material of the workpiece 200, the joint shape, and the required weld shape and width. Therefore, the scanning pattern of the laser LB is not particularly limited to... Figure 5 The pattern shown.

[0183] For example, such as Figure 17A , 17B As shown, in patterns LS1 and LS2 respectively, the parameter a can be reduced, thereby decreasing the amplitude of the Lissajous pattern in the X direction. Furthermore, as... Figure 18A As shown, it can also be generated by setting the frequency n=1 and the frequency m=2. Figure 5 The image shown is a scanned pattern of the Lissajous pattern rotated 90 degrees. Additionally, as shown... Figure 18B , 18C As shown, the parameter b can also be reduced in the depiction patterns LS1 and LS2 respectively, thereby... Figure 18A The amplitude in the Y direction of the Lissajous pattern shown decreases.

[0184] Furthermore, the values ​​of parameters a and b shown in equations (1) and (2) are not particularly limited to Figure 17A , 17B as well as Figures 18A-18C The example shown, for instance, is able to Figure 19 Take an appropriate value within the range shown. Additionally, within... Figure 19 In the middle, Figure 5 as well as Figure 17A , 17B The Lissajous pattern shown is set as pattern group 1, and... Figures 18A-18C The Lissajous pattern shown is designated as pattern group 2.

[0185] Furthermore, by setting the ratio of the frequency n of the first reflector 41a to the frequency m of the second reflector 42a—in other words, the ratio of the vibration frequency of the laser LB in the X direction (i.e., the first frequency) to the vibration frequency in the Y direction (i.e., the second frequency) to 2:1 or 1:2—a figure-eight Lissajous pattern can be obtained. Moreover, as long as this frequency ratio can be achieved, the driving frequencies of the first reflector 41a and the second reflector 42a can be changed according to the shape of the workpiece 200 or the required weld shape.

[0186] <Variation Example 4>

[0187] Figures 20A-20C These represent the first to third scan patterns of the laser involved in this modified example. Additionally, in Figures 20A-20C In the diagram, the arrow indicates the direction in which the laser LB is drawn.

[0188] The scanning pattern of the laser LB disclosed herein is not limited to the Lissajous pattern shown in Embodiment 1 and Modification 3. For example, such as Figure 20A As shown, it can also be a composite pattern of two circular patterns with mutually asymmetrical shapes, respectively connected at the origin O and sandwiched by the X-axis. Furthermore, as... Figure 20B As shown, it can also be a composite pattern of two elliptical patterns with mutually asymmetrical shapes, respectively connected at the origin O and sandwiched by the X-axis. Figure 20B In the example shown, the major axis is in the Y direction and the minor axis is in the X direction in both elliptical patterns. However, the major axis can also be set to the X direction and the minor axis to the Y direction. Figure 20C As shown, it can also be a composite pattern of two rhomboid patterns with mutually asymmetrical shapes, respectively connected at the origin O and sandwiched between the X-axis. Additionally, although not shown, Figures 20A to 20C The scanning patterns shown can also be composite patterns of two annular patterns arranged asymmetrically about the Y-axis. Furthermore, in this case, the two annular patterns can be respectively from... Figures 20A to 20C The example shown is a pattern rotated 90 degrees. Furthermore, the size of each of the two ring-shaped patterns can also be changed appropriately.

[0189] In other words, the scanning pattern of the laser LB in this application specification can be any pattern consisting of two ring-shaped patterns that meet at a single point and are continuous, and is not limited to... Figures 20A to 20C Examples shown, and variations thereof. Furthermore, these patterns are obtained by driving the first reflector 41a and the second reflector 42a according to predetermined driving patterns, respectively.

[0190] Furthermore, if we summarize the structures shown in this modified example, embodiments 1 to 4, and further modified examples 1 to 3, we can say that the laser welding method and laser welding apparatus 100 disclosed herein have the following structures.

[0191] In other words, the laser welding method disclosed herein scans the laser LB to create a predetermined pattern that is asymmetrical about the X or Y direction. Furthermore, the drawn length of the predetermined pattern differs about the X or Y direction. More specifically, the laser LB is scanned such that the drawn length of the predetermined pattern differs on one side and the other side, centered on a centerline passing through the origin O and extending in the X or Y direction. Thus, the heat input to the workpiece 200 is controlled according to the drawn position of the laser LB within the predetermined pattern.

[0192] Furthermore, in the laser welding apparatus 100 disclosed herein, the controller 50 drives the laser scanner 40 to make the prescribed pattern asymmetrical about the X or Y direction. Additionally, the controller 50 drives the laser scanner 40 to make the drawing length of the prescribed pattern different about the X or Y direction. Further, the controller 50 drives the laser scanner 40 to make the drawing length of the prescribed pattern different on one side and the other side, centered on a centerline passing through the origin O and extending in the X or Y direction. Thus, the heat input to the workpiece 200 is controlled according to the drawing position of the laser LB in the prescribed pattern.

[0193] By configuring the laser welding method and laser welding apparatus 100 in this way, different heat can be applied to the two sides of the welding line for the welding part of the workpiece 200 where the heat capacity is asymmetrical with respect to the welding line, so as to make the weld shape good.

[0194] Furthermore, it can promote the formation of a molten pool 201 in the unheated and unmelted third part 203. It can also suppress excessive vibration of the molten pool 201. Thus, it can prevent the weld from becoming undulating. Furthermore, it prevents the penetration depth of the workpiece 200 from being deeper than desired, reducing welding defects such as burn-through, and further improving weld quality.

[0195] Furthermore, the so-called "prescribed pattern" as the scanning pattern of laser LB refers to a pattern in which two asymmetrical ring patterns are connected and continuous at a point, in this case, the origin O. This "prescribed pattern" naturally includes the Lissajous pattern disclosed in this application specification.

[0196] (Other implementation methods)

[0197] It is also possible to appropriately combine the structural elements shown in Embodiments 1 to 4 and Modifications 1 to 4 to create new embodiments.

[0198] For example, when drawing the scanning patterns shown in Modifications 3 and 4, the output P of the laser LB can be controlled as shown in Modifications 1, 2, and 3. Furthermore, the drawing speed V of the laser LB can be controlled as shown in Embodiment 4.

[0199] Furthermore, in embodiments 2-4 and variations 1-4, for example, the laser LB can be scanned during one cycle to draw a Lissajous pattern from the origin O through the drawing positions C→B→A→O→F→E→D→O. Alternatively, the laser LB can be scanned during one cycle to draw a Lissajous pattern from the origin O through the drawing positions D→E→F→O→A→B→C→O. Alternatively, the laser LB can be scanned during one cycle to draw a Lissajous pattern from the origin O through the drawing positions F→E→D→O→C→B→A→O. Furthermore, the drawing speed V of the laser LB and the timing of the output P can be changed according to the order of the drawing positions.

[0200] In addition, Figure 1 In the example shown, the focusing lens 34 is positioned at the front of the laser scanner 40, but it can also be positioned at the rear of the laser scanner 40, i.e., between the laser scanner 40 and the light emission port of the laser head 30.

[0201] Furthermore, the scanning pattern of the laser LB can be a Lissajous pattern by vibrating the laser LB in the X direction as a cosine wave with a first frequency and in the Y direction as a cosine wave with a second frequency. In this case, the amplitudes a and b of the first reflector 41a and the second reflector 42a, the frequencies n and m of the first reflector 41a and the second reflector 42a, and consequently the phase... It can be changed appropriately.

[0202] Industrial availability

[0203] The laser welding method disclosed herein, and the laser welding method itself, can produce a good weld shape and are useful.

[0204] -Symbol Explanation-

[0205] 10 Laser Oscillators

[0206] 20 optical fibers

[0207] 30 laser heads

[0208] 31. Shell

[0209] 32 Collimating Lens

[0210] 33. Reflector

[0211] 34 Condensing Lens

[0212] 40 laser scanners

[0213] 41 First galvanometer mirror

[0214] 41a First reflecting mirror

[0215] 41b First Rotational Axis

[0216] 41c First Drive Unit

[0217] 42 Second galvanometer mirror

[0218] 42a Second reflecting mirror

[0219] 42b Second Rotation Axis

[0220] 42c Second Drive Unit

[0221] 50 controllers

[0222] 60 robotic arms

[0223] 200 workpieces

[0224] 201 Molten Pool

[0225] 202 small holes

[0226] Part 3 of 203

[0227] 204 Part 4

[0228] 210 Plate No. 1 (Part 1)

[0229] 220 Second sheet material (second part)

[0230] 230 Third board material

[0231] 240. The fourth type of board material.

Claims

1. A laser welding method comprising: a welding step of irradiating a workpiece surface by scanning the laser in two dimensions while the laser travels in a first direction, thereby welding the workpiece. In the welding step, The laser is scanned to draw a predetermined pattern on the surface of the workpiece. Furthermore, the laser is scanned such that the prescribed pattern is asymmetrical about the first direction or a second direction intersecting the first direction. The specified pattern is a pattern in which two asymmetrical ring-shaped patterns meet and continue at a single point. The workpiece has a welded portion sandwiched between weld lines, forming a first portion on one side and a second portion on the other side with a smaller heat capacity than the first portion. The length of the pattern drawn by the laser irradiating the first part is longer than the length of the pattern drawn by the laser irradiating the second part.

2. The laser welding method according to claim 1, wherein, The specified pattern is a figure-eight or infinity-shaped Lissajous pattern. In the welding step, the laser is scanned to depict the Lissajous pattern on the surface of the workpiece by vibrating the laser along the first direction as a sine wave with a first frequency and along the second direction intersecting the first direction as a sine wave with a second frequency.

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

2.

4. The laser welding method according to any one of claims 1 to 3, wherein, The drawing length of the prescribed pattern differs depending on whether it is the first direction or the second direction.

5. The laser welding method according to claim 4, wherein, In the depiction of the prescribed pattern, when the portion irradiated by the laser along the first direction, which is further forward than the molten pool formed on the workpiece, is designated as the third portion, and the portion containing the molten pool and irradiated by the laser further backward than the third portion is designated as the fourth portion, The output of the laser irradiating the third part is higher than the output of the laser irradiating the fourth part.

6. The laser welding method according to claim 1, wherein, In the depiction of the prescribed pattern, the laser output is higher at the first location than at the second location.

7. The laser welding method according to any one of claims 1 to 3, wherein, In the depiction of the prescribed pattern, the laser output is lower near the origin of the prescribed pattern than in other areas.

8. The laser welding method according to claim 1, wherein, In the depiction of the prescribed pattern, the laser's drawing speed is lower in the first location than in the second location.

9. The laser welding method according to claim 5, wherein, In the third location, the laser's drawing speed is lower than in the fourth location.

10. The laser welding method according to any one of claims 1 to 3, wherein, In the depiction of the prescribed pattern, the laser's drawing speed is higher near the origin of the prescribed pattern than in other areas.

11. The laser welding method according to any one of claims 1 to 3, wherein, The laser's drawing speed remains constant throughout the entire length of the defined pattern.

12. A laser welding apparatus, comprising at least: A laser oscillator generates laser light. A laser head receives the laser and irradiates the workpiece; and The controller controls the movement of the laser head. The laser head includes a laser scanner that scans the laser in a first direction and a second direction intersecting the first direction. The controller drives the laser scanner so that the laser draws a predetermined pattern on the surface of the workpiece. Furthermore, the controller drives the laser scanner so that the prescribed pattern is asymmetrical about the first direction or a second direction intersecting the first direction. The specified pattern is a pattern in which two asymmetrical ring-shaped patterns meet and continue at a single point. The workpiece has a welded portion sandwiched between weld lines, forming a first portion on one side and a second portion on the other side with a smaller heat capacity than the first portion. The length of the pattern drawn by the laser irradiating the first part is longer than the length of the pattern drawn by the laser irradiating the second part.

13. The laser welding apparatus according to claim 12, wherein, The specified pattern is a figure-eight or infinity-shaped Lissajous pattern. The controller drives the laser scanner to depict the Lisajous pattern on the surface of the workpiece by vibrating the laser along the first direction as a sine wave with a first frequency and along the second direction intersecting the first direction as a sine wave with a second frequency.

14. The laser welding apparatus according to claim 13, wherein, The ratio of the first frequency to the second frequency is 2:1 or 1:

2.

15. The laser welding apparatus according to any one of claims 12 to 14, wherein, The controller drives the laser scanner to make the drawing length of the prescribed pattern different with respect to the first direction or the second direction.

16. The laser welding apparatus according to any one of claims 12 to 14, wherein, The laser welding device also includes: a robotic arm equipped with the laser head. The controller controls the movements of the robotic arm. The robotic arm moves the laser head relative to the surface of the workpiece in a predetermined direction.

17. The laser welding apparatus according to any one of claims 12 to 14, wherein, The laser oscillator is connected to the laser head via an optical fiber. The laser beam passes through the optical fiber and is transmitted from the laser oscillator to the laser head.

18. The laser welding apparatus according to any one of claims 12 to 14, wherein, The laser scanner includes a first galvanometer lens that scans the laser in the first direction and a second galvanometer lens that scans the laser in a second direction that intersects the first direction.

19. The laser welding apparatus according to any one of claims 12 to 14, wherein, The laser head also has a focus position adjustment mechanism. The focal position adjustment mechanism is configured to change the focal position of the laser along directions that intersect the first direction and the second direction, respectively.

Images