Laser welding method and laser welding device

Abstract

The laser welding method includes: a welding step of irradiating the surface of a workpiece by two-dimensionally scanning a laser to perform spot welding on the workpiece. In the first irradiation step of the welding step, the laser is scanned so that the first drawn pattern (SP1) rotates about the origin of the first drawn pattern (SP1), thereby irradiating the laser over the entire area within a circle of the first radius. The first radius is half the length of the first drawn pattern (SP1).

Description

Technical Field

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

[0002] Since the power density of the laser irradiated onto a workpiece as an object to be welded in laser welding is high, high-speed and high-quality welding can be performed. In particular, in scan welding in which a laser is scanned at high speed on the surface of a workpiece while welding, the laser beam can be moved at high speed to the next welding point during a period when welding is not performed, so that the total welding time can be shortened (for example, refer to Patent Document 1). In addition, regarding the laser scanning method, a method of scanning a laser so as to draw a Lissajous pattern on the surface of a workpiece has been proposed in the past (for example, refer to Patent Documents 2 and 3). In addition, scan welding is not only applied to ordinary steel materials, but also can be applied to welding of thin plates of steel materials that have been surface-treated such as galvanized (for example, refer to Patent Document 4).

[0003] Prior Art Documents

[0004] Patent Documents

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

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

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

[0008] Patent Document 4: Japanese Patent No. 4915315 Summary of the Invention

[0009] -Technical Problem to be Solved by the Invention-

[0010] However, the boiling point of zinc (906°C) is much lower than the melting point of iron (1535°C). Therefore, in lap welding in which two steel plates each having a zinc-based coating formed on each surface are overlapped without a gap and welded, the galvanized coating present on the overlapping surface of the steel plates reaches the evaporation temperature before the iron melts. There is a concern that the generated zinc vapor may make the keyhole or the molten pool unstable, or form gas holes inside the workpiece, or in an extreme case cause the molten pool to splash, resulting in welding defects.

[0011] However, in the existing structures disclosed in Patent Documents 1 to 3, there is no disclosure of any lap welding of steel plates formed with a zinc-based coating, nor is there any disclosure of the above technical problem.

[0012] On the other hand, the following method is disclosed in Patent Document 4: The laser beam is swung back and forth along the welding direction, and the output of the laser in the forward process of swinging forward is lower than the output of the laser in the backward process of swinging backward. By doing so, the steel plates can be welded to each other after removing the galvanized layer. However, the method disclosed in Patent Document 4 is difficult to apply to a joint shape such as spot welding.

[0013] In addition, in spot welding, in the case where a covering layer such as a galvanized layer is not formed on the surface, in order to obtain a weld seam with a good shape, it is also necessary to suppress the generation of welding defects.

[0014] The present disclosure is made in view of this aspect, and an object thereof is to provide a laser welding method and a laser welding apparatus that can suppress the generation of welding defects in spot welding and obtain a weld seam with a good shape.

[0015] -Means for Solving Technical Problems-

[0016] In order to achieve the above object, the laser welding method according to the present disclosure is characterized by including: a welding step of irradiating the surface of a workpiece by two-dimensionally scanning a laser to perform spot welding on the workpiece, the welding step at least having: a first irradiation step of scanning the laser so that the laser depicts a first depiction pattern on the surface of the workpiece, and rotating the first depiction pattern around the origin of the first depiction pattern to irradiate the laser as a whole within a circle having a first radius, the first depiction pattern being a pattern in which two annular patterns are joined and continuous at the origin, and the first radius being half of the length of the first depiction pattern.

[0017] The laser welding apparatus according to the present disclosure is characterized by at least including: a laser oscillator that generates a laser; a laser head that receives the laser and irradiates the workpiece; and a controller that controls the operation of the laser head and the output of the laser, the laser head having: a laser scanner that scans the laser in a first direction and a second direction intersecting the first direction, and the controller drives and controls the laser scanner so that the laser depicts a first depiction pattern on the surface of the workpiece, and rotates the first depiction pattern around the origin of the first depiction pattern to irradiate the laser as a whole within a circle having a first radius, the first depiction pattern being a pattern in which two annular patterns are joined and continuous at the origin, and the first radius being half of the length of the first depiction pattern.

[0018] -Advantages of the Invention-

[0019] According to the present disclosure, it is possible to suppress the generation of welding defects in spot welding and obtain a weld seam with a good shape. Description of the Drawings

[0020] Figure 1 It is a schematic structural diagram of the laser welding device related to Embodiment 1.

[0021] Figure 2 It is a schematic structural diagram of the laser scanner.

[0022] Figure 3 It is a schematic cross-sectional view of the workpiece.

[0023] Figure 4 It is a diagram showing the basic scanning pattern of the laser.

[0024] Figure 5 It is a diagram showing the scanning trajectory of the laser.

[0025] Figure 6 It is a diagram showing the relationship between the laser drawing period and the output.

[0026] Figure 7 It is a schematic diagram showing the state change of the workpiece during laser irradiation.

[0027] Figure 8 It is a diagram showing the relationship between the output of the laser and the depth of the small hole.

[0028] Figure 9 It is a schematic diagram showing the state change of the workpiece during laser irradiation related to Modification 1.

[0029] Figure 10 It is a diagram showing the basic scanning pattern of the laser.

[0030] Figure 11 It is a diagram showing the scanning trajectory of the laser.

[0031] Figure 12A It is a diagram showing the first example of the second drawing pattern related to Modification 3.

[0032] Figure 12B It is a diagram showing the second example of the second drawing pattern.

[0033] Figure 12C It is a diagram showing the third example of the second drawing pattern.

[0034] Figure 12D It is a diagram showing the fourth example of the second drawing pattern.

[0035] Figure 12E It is a diagram showing the fifth example of the second drawing pattern.

[0036] Figure 12F It is a diagram showing the sixth example of the second drawing pattern.

[0037] Figure 12G It is a diagram showing the seventh example of the second drawing pattern.

[0038] Figure 12H It is a diagram showing the eighth example of the second drawing pattern.

[0039] Figure 12I It is a diagram showing the ninth example of the second drawing pattern.

[0040] Figure 12J It is a diagram showing the tenth example of the second drawing pattern.

[0041] Figure 12K It is a diagram showing the eleventh example of the second drawing pattern.

[0042] Figure 12L It is a diagram showing the twelfth example of the second drawing pattern.

[0043] Figure 12M It is a diagram showing the thirteenth example of the second drawing pattern.

[0044] Figure 12N It is a diagram showing the fourteenth example of the second drawing pattern.

[0045] Figure 12O It is a diagram showing the fifteenth example of the second drawing pattern.

[0046] Figure 13 It is a diagram showing the basic scanning pattern of the laser related to Embodiment 2.

[0047] Figure 14 It is a diagram showing the scanning trajectory of the laser.

[0048] Figure 15A It is a diagram showing the first scanning pattern of the laser related to Modification 3.

[0049] Figure 15B It is a diagram showing the second scanning pattern of the laser related to Modification 3.

[0050] Figure 15C It is a diagram showing the third scanning pattern of the laser related to Modification 3.

[0051] Figure 15D It is a diagram showing the fourth scanning pattern of the laser related to Modification 3.

[0052] Figure 15E It is a diagram showing the fifth scanning pattern of the laser related to Modification 3.

[0053] Figure 15F It is a diagram showing the sixth scanning pattern of the laser related to Modification 3. Detailed implementation mode

[0054] Hereinafter, embodiments of the present disclosure will be described based on the accompanying drawings. In addition, the description of the following preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0055] (Embodiment 1)

[0056] [Structure of Laser Welding Device and Laser Scanner]

[0057] Figure 1 A schematic diagram showing the structure of the laser welding device according to the present embodiment, Figure 2 A schematic diagram showing the general structure of the laser scanner. Figure 3 A schematic cross-sectional view of the workpiece.

[0058] In addition, in the following description, the direction parallel to the traveling direction of the laser LB from the mirror 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 direction orthogonal to the X direction and the Z direction may be referred to as the Y direction. When the XY plane including the X direction and the Y direction is a flat surface on the surface of the workpiece 200, it may be substantially parallel to the surface or may form a certain angle with the surface.

[0059] As Figure 1 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.

[0060] The laser oscillator 10 is a laser source that generates the laser LB by receiving power from a power supply (not shown). In addition, the laser oscillator 10 may include a single laser source or may include a plurality of laser modules. In the latter case, the lasers emitted from the plurality of laser modules are coupled and emitted as the laser LB. In addition, the laser source or laser modules used in the laser oscillator 10 are appropriately selected according to the material of the workpiece 200, the shape of the welding part, etc.

[0061] For example, a fiber laser, a disk laser, or a YAG (Yttrium Aluminum Garnet) laser can also be used as the laser source. In this case, the wavelength of the laser LB is set in the range of 1000 nm to 1100 nm. In addition, a semiconductor laser can also be used as the laser source or laser module. In this case, the wavelength of the laser LB is set in the range of 800 nm to 1000 nm. In addition, a visible light laser can also be used as the laser source or laser module. In this case, the wavelength of the laser LB is set in the range of 400 nm to 600 nm.

[0062] The optical fiber 20 is optically coupled to the laser oscillator 10, and the laser LB generated in the laser oscillator 10 is incident on the optical fiber 20 and transmitted inside it to the laser head 30.

[0063] 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.

[0064] In addition, as an optical component, the laser head 30 includes a collimator lens 32, a mirror 33, a condenser lens 34, and a laser scanner 40. Inside the housing 31, these optical components are accommodated while maintaining a specified configuration relationship.

[0065] The collimator lens 32 receives the laser LB emitted from the optical fiber 20, converts it into parallel light, and makes it incident on the mirror 33. In addition, the collimator 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 collimator lens 32 in the Z direction, the focal position of the laser LB can be changed, and the laser LB can be appropriately irradiated according to the shape of the workpiece 200. In other words, the collimator lens 32 also functions as a focal position adjustment mechanism for the laser LB in combination with a drive unit (not shown). Alternatively, the focal position of the laser LB can be changed by displacing the condenser lens 34 with the drive unit.

[0066] The mirror 33 reflects the laser LB that has passed through the collimator lens 32 and makes it incident on the laser scanner 40. The surface of the mirror 33 is set at approximately 45 degrees to the optical axis of the laser LB that has passed through the collimator lens 32.

[0067] The condenser lens 34 condenses the laser LB that has been reflected by the mirror 33 and scanned by the laser scanner 40 onto the surface of the workpiece 200.

[0068] As Figure 2 shown, the laser scanner 40 is a known galvanometer scanner having a first galvanometer mirror 41 and a second galvanometer mirror 42. The first galvanometer mirror 41 includes a first mirror 41a, a first rotation axis 41b, and a first drive unit 41c, and the second galvanometer mirror 42 includes a second mirror 42a, a second rotation axis 42b, and a second drive unit 42c. The laser LB that has passed through the condenser lens 34 is reflected by the first mirror 41a and further reflected by the second mirror 42a, and is irradiated onto the surface of the workpiece 200.

[0069] 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 drive unit 41c is rotationally driven by a driver that operates according to a control signal from the controller 50, so that the first mirror 41a mounted on the first rotating shaft 41b rotates about the axis of the first rotating shaft 41b. Similarly, the second drive unit 42c is rotationally driven by a driver that operates according to a control signal from the controller 50, so that the second mirror 42a mounted on the second rotating shaft 42b rotates about the axis of the second rotating shaft 42b.

[0070] The first mirror 41a rotates about the axis of the first rotating shaft 41b until a specified angle, so that the laser beam LB is scanned in the X direction. In addition, the second mirror 42a rotates about the axis of the second rotating shaft 42b until a specified angle, so that the laser beam LB is scanned in the Y direction. In other words, the laser scanner 40 is configured to two-dimensionally scan the laser beam LB in the XY plane and irradiate the workpiece 200.

[0071] The controller 50 controls the laser oscillation of the laser oscillator 10. Specifically, laser oscillation control is performed by providing control signals such as output current, on-off time, etc. to a power supply (not shown) connected to the laser oscillator 10. In addition, the controller 50 controls the output of the laser beam LB.

[0072] In addition, the controller 50 controls the operation of the laser head 30 according to the content of the selected laser welding program. Specifically, drive control is performed on drive units (not shown) of the laser scanner 40 and the collimating lens 32 provided in the laser head 30. Further, the controller 50 controls the operation of the robot arm 60. In addition, the laser welding program is stored in a storage unit (not shown) provided inside the controller 50 or other places, and is retrieved to the controller 50 by a command from the controller 50.

[0073] The controller 50 has an integrated circuit such as an LSI or a microcomputer (not shown), and the functions of the controller 50 can be realized by executing the laser welding program as software on this integrated circuit. In addition, a controller 50 for controlling the operation of the laser head 30 and a controller 50 for controlling the output of the laser beam LB can be provided independently.

[0074] The robot arm 60 is a multi-joint robot and is mounted on the housing 31 of the laser head 30. In addition, the robot arm 60 is connected to the controller 50 so as to be able to exchange signals, and moves the laser head 30 so as to draw a specified trajectory according to the laser welding program. In addition, another controller (not shown) for controlling the operation of the robot arm 60 can be provided.

[0075] Figure 1 The laser welding apparatus 100 shown is capable of laser-welding workpieces 200 of various shapes. For example, as Figure 3 shown, laser LB is irradiated onto a workpiece 200 in which a first plate 210 and a second plate 220, which have galvanized layers 211 and 221 mainly composed of zinc formed on their surfaces and include steel plates, are closely adhered and overlapped without a gap, and fillet welding is performed. By forming the galvanized layers 211 and 221 on the surfaces of the first plate 210 and the second plate 220 respectively, rusting of the steel plates can be prevented. In addition, of course, the structure and material of the workpiece 200 to be laser-welded are not limited to Figure 3 the example shown.

[0076] [Mathematical expression of Lissajous pattern]

[0077] Figure 4 It represents the scanning pattern of the laser. The laser LB is scanned so that a Lissajous pattern (hereinafter, also referred to as a Lissajous figure) is drawn on the surface of the workpiece 200 in the XY plane in this case.

[0078] Figure 4 The Lissajous pattern shown is obtained by causing the laser LB to vibrate in a sine wave shape with a prescribed frequency in the X direction and in a sine wave shape with a frequency different from that in the X direction (1 / 2 of the frequency in the X direction) in the Y direction. In addition, as described above, based on the rotational movements of the first mirror 41a and the second mirror 42a, the scanning patterns of the laser LB in the X direction and the Y direction are determined. When the position coordinates of the Lissajous pattern obtained by driving the first mirror 41a are set as X and the position coordinates of the Lissajous pattern obtained by driving the second mirror 42a are set as Y, the position coordinates X and Y are respectively represented by the following equations (1) to (4).

[0079] X = a1 × sin(nt) ··· (1)

[0080]

[0081] X = a2 × sin(nt) ··· (3)

[0082]

[0083] Here,

[0084] a1: Amplitude width in the X direction of the Lissajous pattern SP1

[0085] b1: Amplitude width in the Y direction of the Lissajous pattern SP1

[0086] a2: Amplitude width in the X direction of the Lissajous pattern SP2

[0087] b2: Amplitude width in the Y direction of the Lissajous pattern SP2

[0088] n: Frequency of the first mirror 41a

[0089] m: Frequency of the second mirror 42a

[0090] t: Time

[0091] Phase difference when the first mirror 41a or the second mirror 42a is driven. Specifically, the amount of angular deviation set during the rotational motion of the first mirror 41a and the second mirror 42a.

[0092] The Lissajous pattern SP1 (hereinafter, also referred to as the first drawing pattern SP1) is the Lissajous pattern in the first irradiation step described later, and the Lissajous pattern SP2 (hereinafter, also referred to as the second drawing pattern SP2) is the Lissajous pattern in the second irradiation step described later.

[0093] In addition, the position coordinates X and Y shown in formulas (1) to (4) are represented by the stationary coordinate system of the Lissajous pattern in a state where the position of the laser head 30 is fixed.

[0094] In addition, the frequency n and the frequency m correspond to the driving frequencies of the first mirror 41a and the second mirror 42a, respectively.

[0095] The first drawing pattern SP1 corresponds to the case where a1 = 0.5, b1 = 1, n = 1, m = 2 are set in formulas (1) and (2). On the other hand, the second drawing pattern SP2 corresponds to the case where a2 = 0.25, b2 = 0.5, n = 1, m = 2 are set in formulas (3) and (4). That is to say, in the Y direction, the first drawing pattern SP1 is a larger pattern than the second drawing pattern SP2. In addition, the parameters a1, a2, b1, and b2 are normalized by 1 based on the size of the first drawing pattern SP1. In addition, the phase difference in formulas (1) to (4). Can also be either 0 degrees or 180 degrees.

[0096] In addition, the actual sizes of the Lissajous patterns SP1 and SP2, that is to say, the amplitude widths in the X direction and the Y direction are respectively in the range of about 1 mm to 10 mm.

[0097] Here, as Figure 4 Shown, when the drawing distance in the X direction of the Lissajous pattern at a specified time variable Δt is set to ΔX, the drawing distance in the Y direction is set to ΔY, and the drawing distance of the Lissajous pattern at the time variable Δt is set to ΔL, ΔX, ΔY, and ΔL are respectively represented by the following formulas (5) to (7).

[0098] ΔX = a1×n×cos(nt)×Δt ···(5)

[0099]

[0100] ΔL = Δt ×{(ΔX) 2 +(ΔY) 2} 1 / 2 ···(7)

[0101] Therefore, the drawing speed V of the Lissajous pattern is expressed by Equation (8) shown below.

[0102] V = ΔL / Δt ···(8)

[0103] Equations (5) to (8) are formulas related to the first drawing pattern SP1 created based on Equations (1) to (2). Similarly, formulas related to the second drawing pattern SP2 can be created based on Equations (3) to (4). Here, the details are omitted.

[0104] In addition,[[]] Figure 4 the first drawing pattern SP1 shown can be obtained by scanning the laser LB so that it passes through the drawing positions A → B → C → O → D → E → F → O from the origin O during one cycle. In addition, the second drawing pattern SP2 can be obtained by scanning the laser LB so that it passes through the drawing positions A' → B' → C' → O → D' → E' → F' → O from the origin O during one cycle.

[0105] [Laser welding method]

[0106] Figure 5 represents the scanning trajectory of the laser,[[]] Figure 6 represents the relationship between the drawing period of the laser and the output.[[]] Figure 7 Schematically represents the state change of the workpiece during laser irradiation.

[0107] In the present embodiment, the case of lap spot welding the workpiece 200 shown by irradiating the surface of the workpiece 200 with the laser LB is taken as an example for explanation. Figure 3 the workpiece 200 shown is taken as an example for explanation.

[0108] At this time, first, using the laser scanner 40, the laser LB is scanned two-dimensionally to draw on the surface of the workpiece 200 Figure 4The first drawn pattern SP1 shown. If the first drawn pattern SP1 is drawn once, the laser scanner 40 is used to draw the first drawn pattern SP1 again on the surface of the workpiece 200 while rotating it by a predetermined angle in the rotation direction RD with the origin O as the center. Rotating from the initial position to 180 degrees with the origin O as the center, this step is repeatedly executed, and the laser LB is irradiated into a circle with a predetermined radius (corresponding to the amplitude width b1 (= 1) in the Y direction of the first drawn pattern SP1) starting from the origin O (the first irradiation step). The execution period of the first irradiation step is referred to as the first drawing period T1. In addition, as Figure 6 shown, it is set that during the first drawing period T1, the output P of the laser LB is P1.

[0109] Following the first irradiation step, the laser scanner 40 is used to two-dimensionally scan the laser LB and draw on the surface of the workpiece 200 Figure 4 the second drawn pattern SP2 shown. If the second drawn pattern SP2 is drawn once, the laser scanner 40 is used to draw the second drawn pattern SP2 again on the surface of the workpiece 200 while rotating it by a predetermined angle in the rotation direction RD with the origin O as the center. Rotating from the initial position to 180 degrees with the origin O as the center, this step is repeatedly executed, and the laser LB is irradiated into a circle with a predetermined radius (corresponding to the amplitude width b2 (= 0.5) in the Y direction of the second drawn pattern SP2) starting from the origin O (the second irradiation step). The execution period of the second irradiation step is referred to as the second drawing period T2. In addition, as Figure 6 shown, it is set that during the second drawing period T2, the output P of the laser LB is P2 (P2 > P1).

[0110] In addition, the drive control of the laser scanner 40 in the first irradiation step and the second irradiation step is performed by the controller 50. In addition, the output P of the laser LB is controlled by the controller 50.

[0111] Regarding Figure 3 the workpiece 200 shown, in the prior art, when performing lap spot welding without gaps by the laser LB, as described above, there is a concern about welding defects caused by zinc vapor generated before iron melting. On the other hand, according to the present embodiment, it is possible to remove the coatings 211 and 221 mainly composed of zinc existing at the interface between the first plate 210 and the second plate 220, and it is possible to suppress the generation of welding defects accompanied by the generation of zinc vapor, and a weld with a good shape can be obtained. This will be further described.

[0112] In the first irradiation step, by setting the output of the laser LB to Figure 6 the output P1 shown, as Figure 7As shown, for example, at the drawing position B, a small hole 301 with a depth of LKl is formed by the laser LB1 indicated by b-b' along the optical axis, and a molten pool 311 is further formed around it. At this time, the depth LK1 of the small hole 301 does not reach the interface W-W' between the first plate 210 (plate thickness: th1) and the second plate 220 (plate thickness: th2). Similarly, the molten pool 311 also does not reach the interface W-W' between the first plate 210 and the second plate 220. In other words, the first plate 210 is not completely melted to the bottom by the laser LB1.

[0113] On the other hand, due to the input heat from the laser LB1 reaching the inside of the small hole 301 and the heat generated in the molten pool 311, the temperature of the interface W-W' between the first plate 210 and the second plate 220 rises and reaches the boiling point of the zinc mentioned above, and the galvanized layers 211 and 221 existing at this interface W-W' evaporate. In addition, as described above, in the first irradiation step, the first drawing pattern SP1 is rotated at a predetermined angle in the rotation direction RD around the origin O, and from the initial position until 180 degrees, the first drawing pattern SP1 is repeatedly drawn on the surface of the workpiece 200. As a result, the galvanized layers 211 and 221 are removed from this interface W-W' over a range with a radius of 0.5LZn centered on the origin O. Additionally, sometimes the Figure 7 LZn shown is referred to as the galvanized layer removal width LZn.

[0114] On the other hand, in the second irradiation step, by setting the output of the laser LB to Figure 6 the output P2 shown, as Figure 7 shown, for example, at the drawing position B', a small hole 302 with a depth of LK2 is formed by the laser LB2 indicated by b”-b”’ along the optical axis, and a molten pool 312 is further formed around it. At this time, the small hole 302 penetrates the first plate 210 and reaches the inside of the second plate 220. Similarly, the molten pool 312 is also formed from the surface of the first plate 210 to the inside of the second plate 220. In other words, near the interface W-W' between the first plate 210 and the second plate 220 where the galvanized layers 211 and 221 have evaporated and been removed, is melted by the laser LB2 to form the molten pool 312.

[0115] In addition, as described above, in the second irradiation step, the second drawing pattern SP2 is rotated at a predetermined angle in the rotation direction RD around the origin O, and from the initial position until 180 degrees, the second drawing pattern SP2 is repeatedly drawn on the surface of the workpiece 200. As a result, a molten pool 312 is formed from the first plate 210 to the second plate 220 over a range with a radius of 0.5LW centered on the origin O. The molten pool 312 solidifies, and the first plate 210 and the second plate 220 are spot-welded. Additionally, sometimes the Figure 7 LW shown is referred to as the weld spot diameter LW.

[0116] In addition, according to the above description, the width LZn of the galvanized layer removal corresponds to the amplitude width b1 (= 1) in the Y direction of the first drawing pattern SP1, and the solder joint diameter LW corresponds to the amplitude width b2 (= 0.5) in the Y direction of the second drawing pattern SP2. In other words, the solder joint diameter LW is shorter than the width LZn of the galvanized layer removal, and the area where the galvanized layers 211 and 221 are removed is wider than the area where the first plate 210 and the second plate 220 are spot welded.

[0117] Therefore, since laser welding is performed on the area where the galvanized layers 211 and 221 are reliably removed, the porosity 302 caused by zinc vapor and the instability of the molten pool 312 can be reduced. Similarly, the generation of welding defects such as pores formed inside the workpiece 200 due to zinc vapor, sputtering caused by the splash of the molten pool 312, and craters can be suppressed.

[0118] [Effects, etc.]

[0119] As described above, the laser welding method according to the present embodiment includes a welding step in which the laser LB is two-dimensionally scanned to irradiate the surface of the workpiece 200, thereby performing spot welding on the workpiece 200.

[0120] The workpiece 200 has a structure in which the first plate 210 having a galvanized layer 211 formed on its surface and the second plate 220 having a galvanized layer 221 formed on its surface are overlapped without a gap. Both the first plate 210 and the second plate 220 are steel plates.

[0121] The welding step at least includes the following first irradiation step and second irradiation step. In the first irradiation step, the laser LB is scanned so as to draw a Lissajous figure in the shape of an 8, i.e., the first drawing pattern SP1, on the surface of the workpiece 200 by vibrating the laser LB in a sine wave shape having a first frequency along the X direction (the first direction) and vibrating the laser LB in a sine wave shape having a second frequency along the Y direction (the second direction) intersecting the X direction. And the laser LB is drawn so that the first drawing pattern SP1 rotates by a predetermined angle around the origin O of the first drawing pattern SP1 and is repeatedly drawn.

[0122] In the second irradiation step, the laser LB is scanned so that an 8-shaped Lissajous figure, i.e., the second drawing pattern SP2, rotates by a predetermined angle around the origin O of the first drawing pattern SP1 and is repeatedly drawn.

[0123] In the first irradiation step, the galvanized layers 211 and 221 present at the interface between the first plate 210 and the second plate 220 are removed. In the second irradiation step, the first plate 210 and the second plate 220 from which the galvanized layers 211 and 221 have been removed are spot welded to each other.

[0124] According to the present embodiment, it is possible to remove the galvanized layers 211 and 221 present at the interface between the first plate 210 and the second plate 220, and it is possible to suppress the generation of welding defects accompanying the generation of zinc vapor. In addition, it is possible to make the shape of the weld formed on the workpiece 200 good.

[0125] In particular, in the first irradiation step, by scanning the laser LB so that the first drawing pattern SP1 rotates at a predetermined angle around the origin O of the first drawing pattern SP1 and is repeatedly drawn, the scanning locus of the laser LB can be made close to a perfect circle, and the heat input into the inside of the scanning locus can be made close to uniform. Thereby, it is possible to reliably remove the galvanized layers 211 and 221 present at the interface between the first plate 210 and the second plate 220.

[0126] In addition, in the second irradiation step, by scanning the laser LB so that the second drawing pattern SP2 rotates at a predetermined angle around the origin O of the first drawing pattern SP1 and is repeatedly drawn, the scanning locus of the laser LB can be made close to a perfect circle, and the heat input into the inside of the scanning locus can be made close to uniform. Thereby, it is possible to perform precise shape control of the solder joint. In addition, the generation of welding defects can be suppressed, and the first plate 210 and the second plate 220 can be reliably welded.

[0127] In addition, in the laser welding method of the present embodiment, the output P of the laser LB is controlled so that the output P1 of the laser LB in the first irradiation step is lower than the output P2 of the laser LB in the second irradiation step. By doing so, it is possible to remove the galvanized layers 211 and 221 in the first irradiation step, and on the other hand, it is possible to weld the first plate 210 and the second plate 220 in the second irradiation step.

[0128] In addition, it is preferable that the output P1 of the laser LB is set such that the keyhole 301 and the molten pool 311 do not reach the interface W - W' between the first plate 210 and the second plate 220. By doing so, it is possible to suppress the generation of welding defects due to the sudden ejection of zinc vapor. In addition, it is preferable that the output P2 of the laser LB is set such that the keyhole 302 and the molten pool 312 reach the inside of the second plate 220. By doing so, the first plate 210 and the second plate 220 can be reliably and firmly welded. In addition, the molten pool 312 may reach the back surface of the second plate 220. In this case, a so-called back bead is formed. In addition, the output P2 of the laser LB needs to be set such that penetration of the welding position does not occur.

[0129] In addition, by making the length of the second drawn pattern SP2 (corresponding to the amplitude width b2 in the Y direction of the second drawn pattern SP2 (= 0.5)) shorter than the length in the long side direction of the first drawn pattern SP1 (corresponding to the amplitude width b1 in the Y direction of the first drawn pattern SP1 (= 1)), the welding area can be made narrower than the area where the galvanized layers 211 and 221 are removed. In other words, since laser welding is performed on the area where the galvanized layers 211 and 221 are reliably removed, the pores 302 and the instability of the molten pool 312 caused by zinc vapor can be reduced. Similarly, the generation of welding defects such as pores formed inside the workpiece 200 due to zinc vapor, sputtering caused by the splash of the molten pool 312, and craters can be suppressed. Here, although the amplitude width b1 = 1 and the amplitude width b2 = 0.5 are set, it is desirable to set the amplitude width b2 to a value close to the amplitude width b1 to such an extent that no instability or sputtering of pores occurs in the second irradiation step, so as to determine the length of the second drawn pattern SP2.

[0130] In addition, in the present embodiment, pores 301 and 302 are formed in the workpiece 200 in the first irradiation step and the second irradiation step, respectively. By doing so, in the first irradiation step, the heat required to evaporate zinc can be reliably provided to the interface W - W' between the first plate 210 and the second plate 220. In particular, when the thickness of the first plate 210 is relatively thick, it is preferable to form the pore 301 in the first plate 210. The thickness of the first plate 210 is generally about 0.5 mm to 6 mm. In addition, the so-called relatively thick thickness of the first plate 210 generally refers to the case where the thickness of the first plate 210 exceeds 1.0 mm to 2 mm. In addition, in the second irradiation step, the heat required to weld the first plate 210 and the second plate 220 to each other can be reliably provided.

[0131] In addition, in the present embodiment, the ratio of the frequency n of the first mirror 41a to the frequency m of the second mirror 42a, in other words, the ratio n:m of the vibration frequency in the X direction of the laser LB, which is the first frequency, to the vibration frequency in the Y direction, which is the second frequency, is set to 1:2. By doing so, in both the first irradiation step and the second irradiation step, the scanning trajectory of the laser LB can be set as a Lissajous figure in the shape of an 8. As a result, the galvanized layers 211 and 221 can be removed at high speed, and the workpiece 200 can be continuously welded at high speed. In other words, the generation of welding defects can be suppressed, and the workpiece 200 can be spot-welded at high speed.

[0132] In addition, in the first irradiation step, it is preferable to scan the laser LB so that the drawing speed of the first drawing pattern SP1 (refer to Equation (8)) is constant. In the second irradiation step, it is preferable to scan the laser LB so that the drawing speed of the second drawing pattern SP2 is constant. As described above, by driving the laser scanner 40 using the controller 50, the first drawing pattern SP1 and the second drawing pattern SP2 are respectively drawn on the surface of the workpiece 200. By making the drawing speeds of the first drawing pattern SP1 and the second drawing pattern SP2 constant respectively, the drive control of the laser scanner 40 based on the controller 50 becomes simple. In addition, if the drawing speed of the laser LB changes, the depths and diameters of the small holes 301 and 302 change, so the shape of the weld, especially the shape of the bottoms of the molten pools 311 and 312, may change greatly.

[0133] On the other hand, according to the present embodiment, by making the drawing speeds of the first drawing pattern SP1 and the second drawing pattern SP2 constant respectively, the depths, diameters of the small holes 301 and 302, and thus the shape of the weld can be stabilized. In addition, if the shape of the weld is within the allowable range, the laser LB during the drawing of the first drawing pattern SP1 may also change its speed within a specified range according to Equations (1) to (2). Similarly, the laser LB during the drawing of the second drawing pattern SP2 may also change its speed within a specified range according to Equations (3) to (4).

[0134] The laser welding apparatus 100 according to the present embodiment includes at least: a laser oscillator 10 that generates the laser LB; a laser head 30 that receives the laser LB and irradiates the workpiece 200; and a controller 50 that controls the operation of the laser head 30 and the output P of the laser LB.

[0135] The workpiece 200 has a structure in which a first plate 210 having a galvanized layer 211 formed on its surface and a second plate 220 having a galvanized layer 221 formed on its surface are overlapped without a gap. Both the first plate 210 and the second plate 220 are steel plates.

[0136] The laser head 30 has a laser scanner 40 that scans the laser LB in the X direction (the first direction) and the Y direction (the second direction) that intersects the X direction, respectively.

[0137] The controller 50 vibrates the laser LB in a sine wave shape with a first frequency along the X direction, and vibrates the laser LB in a sine wave shape with a second frequency along the Y direction. Thereby, the controller 50 drives and controls the laser scanner 40 so that the laser LB depicts a figure-eight Lissajous pattern, i.e., a first depicted pattern SP1, on the surface of the workpiece 200. In addition, the controller 50 drives and controls the laser scanner 40 so that the first depicted pattern SP1 rotates by a predetermined angle around the origin O of the first depicted pattern SP1 and is repeatedly depicted.

[0138] In addition, the controller 50 drives and controls the laser scanner 40 so that the laser LB depicts a figure-eight Lissajous pattern, i.e., a second depicted pattern SP2, on the surface of the workpiece 200. In addition, the controller 50 drives and controls the laser scanner 40 so that the second depicted pattern SP2 rotates by a predetermined angle around the origin O of the first depicted pattern SP1 and is repeatedly depicted.

[0139] The controller 50 controls the output P of the laser LB so that the output P1 of the laser LB during the depiction of the first depicted pattern SP1 is lower than the output P2 of the laser LB during the depiction of the second depicted pattern SP2.

[0140] According to the laser welding apparatus of the present embodiment, the galvanized layers 211 and 221 existing at the interface between the first plate 210 and the second plate 220 can be removed, and the generation of welding defects accompanied by the generation of zinc vapor can be suppressed. In addition, the shape of the weld formed on the workpiece 200 can be made good.

[0141] The laser welding apparatus 100 further includes a robotic arm 60 on which the laser head 30 is mounted, and the 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 predetermined direction.

[0142] By providing the robotic arm 60 in this way, the welding direction of the laser LB can be changed. In addition, laser welding can be easily performed on a workpiece 200 having a complex shape, such as a three-dimensional shape.

[0143] The laser oscillator 10 and the laser head 30 are connected by an optical fiber 20, and the laser LB is transmitted from the laser oscillator 10 to the laser head 30 through the optical fiber 20.

[0144] By providing the optical fiber 20 in this way, laser welding can be performed on a workpiece 200 provided at a position separated from the laser oscillator 10. Thereby, the degree of freedom in arranging the respective parts of the laser welding apparatus 100 is increased.

[0145] The laser scanner 40 includes: a first galvanometer mirror 41 that scans the laser LB in the X direction, and a second galvanometer mirror 42 that scans the laser LB in the Y direction.

[0146] By configuring the laser scanner 40 in this way, it is possible to simply scan the laser LB two-dimensionally. In addition, since a known galvanometer scanner is used as the laser scanner 40, an increase in the cost of the laser welding apparatus 100 can be suppressed.

[0147] The laser head 30 also has a collimating lens 32, and the collimating lens 32 is configured to change the focal position of the laser LB along the Z direction that intersects the X direction and the Y direction, respectively. In other words, the collimating lens 32 is configured to change the focal position of the laser LB along the Z direction that intersects the surface of the workpiece 200. In other words, the collimating lens 32 functions as a focal position adjustment mechanism for the laser LB in combination with a drive unit (not shown).

[0148] By doing so, the focal position of the laser LB can be simply changed, and the laser LB can be appropriately irradiated according to the shape of the workpiece 200.

[0149] Alternatively, the first drawing pattern SP1 and the second drawing pattern SP2 may be Lissajous patterns having the long side direction in the X direction, and in this case, Lissajous patterns in the shape of ∞. In this case, the frequency n is set to 2 and the frequency m is set to 1 to change the shape of the Lissajous pattern.

[0150] <Modification Example 1>

[0151] Figure 8 Shows the relationship between the output of the laser and the depth of the small hole. Figure 9 Schematically shows the state change of the workpiece during laser irradiation according to this modification example. In addition, for convenience of explanation, in Figure 8 、 Figure 9 and the following respective drawings, the same reference numerals are given to the same positions as those in the first embodiment, and detailed descriptions thereof are omitted.

[0152] As Figure 8 shown, in a region (heat conduction welding region Rc) where the output P of the laser LB is smaller than a specified value, although the workpiece 200 is melted due to the input heat based on the laser LB, no small hole is formed. If the output P is increased from this region, it reaches the keyhole welding region Rk via the transition region Rt. When it becomes this region, a small hole is formed in the workpiece 200, and the depth of the small hole becomes deeper as the output P increases.

[0153] In the example shown in the first embodiment, during the laser welding of the workpiece 200, in the first irradiation step, the output P1 of the laser LB is set so as to form a small hole 301 in the first plate 210.

[0154] However, when the plate thickness of the first plate 210 is thinner than the specified value, if the output P of the laser LB is increased until the small hole 301 is formed in the first plate 210, the small hole 301 may reach the interface W-W' between the first plate 210 and the second plate 220, and zinc vapor may be ejected suddenly to cause welding defects. In addition, sometimes it is preferable not to form the small hole 301 in the first plate 210 according to the shape, material, etc. of the workpiece 200. In this case, as shown in this modified example, in the first irradiation step, the output P1 of the laser LB is set within the range of the heat conduction welding region Rc described above.

[0155] By doing so, as Figure 9 shown on the left side, during the first irradiation period T1, no small hole is formed in the first plate 210 with a plate thickness th3 (th3 < th1). However, by irradiating the laser LB, a molten pool 313 is formed in the first plate 210 to a depth that does not reach the interface W-W' between the first plate 210 and the second plate 220. Thus, within a circle with a radius of 0.5LZn centered on the origin O, the galvanized layers 211 and 221 existing at the interface between the first plate 210 and the second plate 220 are appropriately heated and evaporated and removed.

[0156] During the subsequent second irradiation period T2, as Figure 9 shown on the right side, a small hole 303 with a depth LK3 and a molten pool 314 are formed from the first plate 210 to the second plate 220, and the first plate 210 and the second plate 220 are spot-welded to each other. This is the same as that shown in the first embodiment.

[0157] According to this modified example, for example, even when the plate thickness th3 of the first plate 210 is thinner than the specified value, it is possible to suppress the sudden ejection of zinc vapor and the generation of welding defects accompanying it. In addition, thereby, a weld with a good shape can be obtained.

[0158] <Modified Example 2>

[0159] Figure 10 Shows the basic scanning pattern of the laser related to this modified example, Figure 11 shows the scanning trajectory of the laser.

[0160] When spot-welding the workpiece 200 shown in Figure 3 , when irradiating the laser LB in the patterns shown in Figure 4 and Figure 5 , the galvanized layers 211 and 221 may not be sufficiently removed at the center portion of the butt joint surface between the first plate 210 and the second plate 220. For example, the weld size LW is large and the required galvanized removal width LZn is wide (refer to Figure 7) or the case where the galvanized layers 211 and 221 are relatively thick is equivalent to this case. In the former case, since the solder joint size is large, it takes time for the zinc vapor generated near the origin O to be discharged to the outside through the gap between the first plate 210 and the second plate 220. On the other hand, in the latter case, since the galvanized layers 211 and 221 are relatively thick, it also takes time to remove the galvanized layers 211 and 221 respectively. In either case, there is a concern that it cannot cope with the patterns shown in Figure 4 and Figure 5 .

[0161] In order to suppress the occurrence of such defects, in this modification, the first drawing pattern SP3 is set as a Lissajous pattern asymmetric with respect to the origin O. Specifically, in the part (drawing pattern SP3U) located on the + side in the Y direction among the first drawing patterns SP3 shown in Figure 10 , in Equation (2), a1 = 0.5 and b1 = 1 are set. On the other hand, in the part (drawing pattern SP3L) located on the - side in the Y direction, in Equation (2), a1 = 0.25 and b1 = 0.5 are set.

[0162] By doing so, when the first drawing pattern SP3 is repeatedly drawn around the origin O by rotating it at a predetermined angle in the rotation direction RD, in the irradiation area of the laser LB near the origin O, compared with the example shown in Embodiment 1, the heat input to the central part, that is, the part on the - side in the Y direction of the second irradiation pattern SP4 in this modification, which is the part irradiated by the drawing pattern SP4L, can be increased. Thus, a difference in the input heat is given to the peripheral part and the central part of the solder joint irradiated by the laser LB, and the galvanized layers 211 and 221 can be reliably removed from the central part of the butt joint surface between the first plate 210 and the second plate 220.

[0163] In addition, in this modification, the second drawing pattern SP4 is also set as a Lissajous pattern asymmetric with respect to the origin O. Specifically, in the part (drawing pattern SP4U) located on the + side in the Y direction among the second drawing patterns SP4 shown in Figure 10 , in Equations (3) and (4), a2 = 0.25 and b2 = 0.5 are set. On the other hand, in the drawing pattern SP4L, in Equations (3) and (4), a2 = 0.125 and b2 = 0.25 are set.

[0164] By doing so, when the second drawing pattern SP2 is repeatedly drawn once around the origin O by rotating it at a predetermined angle in the rotation direction RD, in the irradiation area of the laser LB near the origin O, compared with the example shown in Embodiment 1, more laser energy can be input, and in particular, the weld shape can be made good when the solder joint diameter is large.

[0165] In addition, in the first irradiation step and the second irradiation step in Embodiment 1, when the first drawing pattern SP1 and the second drawing pattern SP2 are each rotated 180 degrees from the initial position, the laser LB is evenly irradiated into a circle with a specified radius centered on the origin O. On the other hand, in this modification example, the first drawing pattern SP3 and the second drawing pattern SP4 are each asymmetric with respect to the origin O. Therefore, in order to evenly irradiate the laser LB into a circle with a specified radius centered on the origin O, it is necessary to rotate the first drawing pattern SP3 and the second drawing pattern SP4 360 degrees each from the initial position.

[0166] In addition, when the first drawing pattern SP1 and the second drawing pattern SP2 are patterns that are mutually asymmetric with respect to the origin O, the values of the parameters a1, b1, a2, and b2 in formulas (1) to (4) can be appropriately changed according to the material of the workpiece 200, the thickness of each layer, and the like.

[0167] <Modification Example 3>

[0168] Figures 12A to 12O Examples 1 to 15 of the second drawing pattern related to this modification example are respectively shown.

[0169] As described above, in order to remove the galvanized layers 211 and 221 of the workpiece 200 at high speed and reliably, the first drawing pattern SP1 can be set as a figure-eight or ∞-shaped Lissajous pattern. On the other hand, for example, when welding the first plate 210 and the second plate 220, the second drawing pattern SP2 does not necessarily have to be set as a Lissajous pattern. It is sufficient to spot-weld the first plate 210 and the second plate 220.

[0170] Based on this view, the second drawing pattern SP2 can take various shapes. For example, as shown in Figure 12A , the second drawing pattern SP2 can be set as an arc shape, or as shown in Figure 12E , the second drawing pattern SP2 can be set as a spiral shape. In addition, as shown in Figure 12J , the second drawing pattern SP2 can be set as a linear shape, or as shown in Figure 12L , the second drawing pattern SP2 can be formed by drawing a plurality of arcs at equal angular intervals centered on the origin O.

[0171] In any case, it is preferable that the outer edge of the second drawing pattern SP2 is at a position equidistant from the origin O. By doing so, the input heat can be made close to uniform within the welding area of the solder joint shape. In addition, when the second drawing pattern SP2 is set as Figures 12B to 12H , Figures 12J to 12L , Figure 12N and Figure 12OIn the case of the pattern shown, as in Embodiment 1, the laser LB can be scanned so that the second drawing pattern SP2 rotates by a predetermined angle around the origin O of the first drawing pattern SP1 and is repeatedly drawn. By doing so, by changing the drawing pattern of the welding step, it is possible to suppress the occurrence of welding defects, and the first plate 210 and the second plate 220 can be reliably welded with a desired weld shape.

[0172] (Embodiment 2)

[0173] Figure 13 Shows the basic scanning pattern of the laser according to this embodiment, Figure 14 Indicates the scanning trajectory of the laser.

[0174] In this embodiment, when spot-welding the workpiece 200, it is different from the structure shown in Embodiment 1 in that only the second irradiation step is performed.

[0175] For example, consider the case where Figure 3 In the workpiece 200 shown, a galvanized layer 211 is not formed on the surface of the first plate 210, and a galvanized layer 221 is not formed on the surface of the second plate 220.

[0176] In this case, the workpiece 200 has a structure in which the first plate 210 and the second plate 220 each containing a steel plate are directly overlapped. When spot-welding such a workpiece 200, the laser LB is scanned so that Figure 13 The second drawing pattern SP5 shown rotates around the origin O by a predetermined angle and is repeatedly drawn. In this case, from the initial position to a 180-degree rotation, the second drawing pattern SP5 is repeatedly drawn on the surface of the workpiece 200.

[0177] By doing so, the heat input into the inside of the welding area of the weld shape can be made close to uniform. Therefore, a molten pool can be formed evenly in the workpiece 200, and the shape of the weld can be made good. In addition, the irradiation area of the laser LB can be made close to a perfect circle, and precise shape control of the solder joint can be performed.

[0178] In other words, the scanning method of the laser LB of the present disclosure is also useful for overlap spot welding of plates having no covering layer such as a galvanized layer formed on the surface.

[0179] <Modification 3>

[0180] Figures 15A to 15F Respectively show the first to sixth scanning patterns of the laser according to this modification. In addition, in Figures 15A to 15F , the arrows AR1 and AR3 indicate the scanning direction (drawing direction) of the laser LB. In addition, Figures 15A to 15FThe 1st to 6th scanning patterns shown correspond to the 1st drawing pattern described above. The 2nd drawing pattern is not shown, but has a similar shape or a similar form to the 1st to 6th scanning patterns shown in this modified example, and is set to be only a specified size smaller.

[0181] The 1st drawing patterns SP1 and SP3 of the laser LB of the present disclosure are not limited to the Lissajous patterns shown in Embodiment 1. For example, as Figure 15A shown, the 1st drawing pattern SP6 may also be a composite pattern of two circular patterns that are respectively joined at the origin O and arranged symmetrically with respect to the X axis. In addition, as Figure 15B and Figure 15C shown, the 1st drawing patterns SP7 and SP8 may also be composite patterns of two elliptical patterns that are respectively joined at the origin O and arranged symmetrically with respect to the X axis. In the 1st drawing pattern SP7, the major axes of the two ellipses are in the X direction and the minor axes are in the Y direction. In the 1st drawing pattern SP8, the major axes of the two ellipses are in the Y direction and the minor axes are in the X direction.

[0182] In addition, as Figure 15D shown, the 1st drawing pattern SP9 may also be a composite pattern in which two circular patterns SP9U and SP9L of asymmetric sizes are respectively joined at the origin O and arranged with the X axis in between. As Figure 15E shown, the 1st drawing pattern SP10 may also be a composite pattern in which two elliptical patterns SP10U and SP10L of asymmetric sizes are respectively joined at the origin O and arranged with the X axis in between. In the 1st drawing pattern SP10, the major axes of the two ellipses are in the X direction and the minor axes are in the Y direction. In addition, as Figure 15F shown, the 1st drawing pattern SP11 may also be a composite pattern in which two elliptical patterns SP11U and SP11L of asymmetric sizes are respectively joined at the origin O and arranged with the X axis in between. In the 1st drawing pattern SP11, the major axes of the two ellipses are in the Y direction and the minor axes are in the X direction. Additionally, although not shown, each of the scanning patterns as Figures 15A to 15F shown may also be a composite pattern of two annular patterns that are respectively joined at the origin O and arranged with the Y axis in between. In addition, in this case, the two annular patterns may respectively be patterns rotated 90 degrees from the Figures 15A to 15F shown example. Furthermore, the sizes of the two annular patterns can also be appropriately changed.

[0183] In other words, the 1st drawing patterns SP1, SP3, SP6 to SP11 of the laser LB in the present application specification only need to be patterns in which two annular patterns are joined at one point and are continuous, and are not limited to the Figures 15A to 15F shown example. Additionally, these patterns can be obtained by driving the 1st mirror 41a and the 2nd mirror 42a respectively according to a specified driving pattern.

[0184] In addition, although not shown, the second drawing patterns SP2 and SP4 may be replaced with shapes that are respectively similar to the Figures 15A to 15F scanning patterns shown. It is not limited to the Figures 15A to 15F example shown. Instead of the second drawing patterns SP2 and SP4, two circular patterns that meet at a point and are continuous may be used.

[0185] (Other embodiments)

[0186] It is also possible to appropriately combine the respective structural elements shown in Embodiments 1 and 2 and Variation Examples 1 to 3 to form a new embodiment. For example, when depicting the scanning pattern shown in Embodiment 2, it is possible to use a Lissajous pattern that is asymmetric with respect to the origin O as shown in Variation Example 2.

[0187] In addition, in the Figure 1 example shown, the condenser lens 34 is arranged in front of the laser scanner 40, but it may also be arranged behind the laser scanner 40, that is, between the laser scanner 40 and the light exit port of the laser head 30.

[0188] In addition, it is also possible to make the laser LB vibrate in a cosine wave shape with a first frequency along the X direction and vibrate in a cosine wave shape with a second frequency along the Y direction, so that the scanning pattern of the laser LB becomes a Lissajous pattern. In this case, of course, the parameters a1, b1, a2, b2, n, m, and .

[0189] In addition, the drawing directions of the first drawing patterns SP1, SP3, SP6 to SP11 and the second drawing patterns SP2, SP4, SP5 are not particularly limited to the directions described above. For example, when depicting the first drawing patterns SP1, SP3, SP6 to SP11, the laser LB may be scanned during one cycle so that it passes through the drawing positions C→B→A→O→F→E→D→O from the origin O. Similarly, when depicting the second drawing patterns SP2, SP4, SP5, the laser LB may be scanned during one cycle so that it passes through the drawing positions C’→B’→A’→O→F’→E’→D’→O from the origin O. In addition, the rotation directions RD of the first drawing patterns SP1, SP3, SP6 to SP11 and the second drawing patterns SP2, SP4, SP5 are not particularly limited to Figure 4 , Figure 10 , Figure 13 and Figures 15A to 15FThe directions shown. It is also possible to rotate the first drawn patterns SP1, SP3, SP6 to SP11 and the second drawn patterns SP2, SP4, SP5 in the opposite direction to these shown directions. In addition, regardless of any combination, as the second drawn pattern, a pattern having a similar shape or a similar shape to the first drawn patterns SP6 to SP11 shown and being smaller than the first drawn patterns SP6 to SP11 by a specified size can be used. Figures 15A to 15F A pattern having a similar shape or a similar shape to the first drawn patterns SP6 to SP11 shown and being smaller than the first drawn patterns SP6 to SP11 by a specified size.

[0190] In addition, in this specification of the present application, the case of laser welding the workpiece 200 shown has been described as an example, but it is not particularly limited thereto. For example, the workpiece 200 may also be at least two base materials each including a plate-shaped portion, that is, the plate-shaped portions overlap or abut against each other, and a galvanized layer is formed at least on the surfaces of the plate-shaped portions. The base material in this case may be iron, mild steel, or high-tensile steel. The melting points of these are all higher than the boiling point of zinc. In addition, a zinc alloy coating containing zinc and aluminum may also be formed on the surfaces of the two base materials. In other words, a coating mainly composed of zinc may be formed on the surfaces of the two base materials. Here, the so-called "coating mainly composed of zinc" means a coating containing 50% or more of zinc. In addition, a covering layer containing materials other than zinc may be formed on the surfaces of the two base materials respectively. In this case, the materials of the covering layer and the base material are set respectively so that the boiling point of the material constituting the covering layer is lower than the melting point of the material constituting the base material. Figure 3 When laser welding such a workpiece 200, in the process of drawing any one of the first drawn patterns SP1, SP3, SP6 to SP11, the covering layer between the plate-shaped portions is removed. In the process of drawing any one of the second drawn patterns SP2, SP4, SP5, the two plate-shaped portions from which the covering layer has been removed are welded to each other. In addition, as the second drawn pattern, a pattern having a similar shape or a similar shape to the first drawn patterns SP6 to SP11 shown and being smaller than the first drawn patterns SP6 to SP11 by a specified size can also be used.

[0191] When laser welding such a workpiece 200, in the process of drawing any one of the first drawn patterns SP1, SP3, SP6 to SP11, the covering layer between the plate-shaped portions is removed. In the process of drawing any one of the second drawn patterns SP2, SP4, SP5, the two plate-shaped portions from which the covering layer has been removed are welded to each other. In addition, as the second drawn pattern, a pattern having a similar shape or a similar shape to the first drawn patterns SP6 to SP11 shown and being smaller than the first drawn patterns SP6 to SP11 by a specified size can also be used. Figures 15A to 15F A pattern having a similar shape or a similar shape to the first drawn patterns SP6 to SP11 shown and being smaller than the first drawn patterns SP6 to SP11 by a specified size.

[0192] When laser welding a workpiece 200 having such a structure, by applying the laser welding method and the laser welding apparatus of the present disclosure, it is possible to suppress the generation of welding defects caused by vapor generated by evaporation of covering layers such as the galvanized layers 211 and 221, and of course, it is also possible to obtain a good weld shape.

[0193] In addition, in Embodiments 1 and 2 and Modification Examples 1 to 3, the following laser welding method and laser welding apparatus 100 were described, that is, the laser LB is scanned so as to draw any one of the first drawing patterns SP1, SP3, SP6 to SP11 on the surface of the workpiece 200, and with the origin O of the drawn first drawing pattern as the center, the first drawing pattern is repeatedly drawn by rotating it at every predetermined angle. Further, the following laser welding method and laser welding apparatus 100 were described, that is, the laser LB is scanned so as to draw any one of the second drawing patterns SP2, SP4, SP5 on the surface of the workpiece 200, and with the origin O of the drawn second drawing pattern as the center, the second drawing pattern is rotated and repeatedly drawn at every predetermined angle. Further, the following laser welding method and laser welding apparatus 100 were described, that is, as the second drawing pattern, a pattern having a similar shape or a similar shape to the first drawing patterns SP6 to SP11 and having a size smaller than the first drawing patterns SP6 to SP11 by a predetermined size may be used.

[0194] However, the laser welding method and the laser welding apparatus 100 of the present disclosure allow scanning of the laser LB other than this. For example, when drawing any one of the first drawing patterns SP1, SP3, SP6 to SP11 on the surface of the workpiece 200, the first drawing pattern may be continuously rotated so that the laser LB is irradiated as a whole into a circle with a first radius with the origin O of the drawn first drawing pattern as the center. Here, the so-called first radius corresponds to half of the length of the first drawing pattern. Similarly, when drawing any one of the second drawing patterns SP2, SP4, SP5 on the surface of the workpiece 200, the second drawing pattern may be continuously rotated so that the laser LB is irradiated as a whole into a circle with a second radius with the origin O of the drawn second drawing pattern as the center. Here, the so-called second radius corresponds to half of the length of the second drawing pattern and is shorter than the first radius. Further, as the second drawing pattern, a pattern having a similar shape or a similar shape to the first drawing patterns SP6 to SP11 and having a size smaller than the first drawing patterns SP6 to SP11 by a predetermined size may be used.

[0195] Based on the above, the laser welding method of the present disclosure includes the following configuration.

[0196] In the welding step of the laser welding method of the present disclosure, the laser LB is scanned so as to draw any one of the first drawing patterns SP1, SP3, SP6 to SP11 or any one of the second drawing patterns SP2, SP4, SP5 on the surface of the workpiece 200. Further, the laser beam LB may be scanned so that, as the second drawing pattern, a pattern having a similar shape or a similar shape to the first drawing patterns SP6 to SP11 and having a size smaller than the first drawing patterns SP6 to SP11 by a predetermined size is drawn.

[0197] In the first irradiation step of the welding step, the laser LB is scanned so that the laser LB depicts any one of the first depicted patterns SP1, SP3, SP6 to SP11 on the surface of the workpiece 200. In this case, the laser LB is scanned so that by rotating the first depicted pattern with the origin O of the depicted first depicted pattern as the center, the laser LB is irradiated as a whole into the circle with the first radius. The first depicted patterns SP1, SP3, SP6 to SP11 are each a pattern in which two annular patterns are joined and continuous at the origin O. The first radius is half the length of the depicted first depicted pattern. In addition, the so-called "irradiating as a whole into the circle" means irradiating the laser LB equally onto the circumference of the circle and the inside of the circle.

[0198] When rotating the first depicted pattern, the first depicted pattern may be rotated at each prescribed angle and repeatedly depicted. In addition, the first depicted pattern may be continuously rotated.

[0199] In the second irradiation step of the welding step, following the first irradiation step, the laser LB is scanned as follows. In other words, the laser LB is scanned so that the laser LB depicts the second depicted pattern SP2, SP4 or SP5 on the surface of the workpiece 200. In this case, the laser LB is scanned so that by rotating the second depicted pattern with the origin O of the first depicted pattern as the center, the laser LB is irradiated as a whole into the circle with the second radius. In addition, the second depicted patterns SP2, SP4 and SP5 may each be a pattern in which two annular patterns are joined and continuous at the origin O. The second radius is half the length of the depicted second depicted pattern and is shorter than the first radius. In addition, the laser LB may be scanned so that as the second depicted pattern, a pattern similar or similar in shape to the first depicted patterns SP6 to SP11 and smaller by a prescribed size than the first depicted patterns SP6 to SP11 is depicted.

[0200] When rotating the second depicted pattern, the second depicted pattern may be rotated at each prescribed angle and repeatedly depicted. In addition, the second depicted pattern may be continuously rotated.

[0201] In addition, the controller 50 in the laser welding apparatus 100 of the present disclosure drives and controls the laser scanner 40 so that the laser LB depicts any one of the first depicted patterns SP1, SP3, SP6 to SP11 on the surface of the workpiece 200. In this case, the controller 50 drives and controls the laser scanner 40 so that by rotating the first depicted pattern with the origin O of the depicted first depicted pattern as the center, the laser LB is irradiated as a whole into the circle with the first radius.

[0202] When rotating the first drawing pattern, the controller 50 can also drive and control the laser scanner 40 so that the first drawing pattern rotates at every specified angle and is repeatedly drawn. In addition, the laser scanner 40 can be driven and controlled so that the first drawing pattern rotates continuously.

[0203] In addition, the controller 50 can also drive and control the laser scanner 40 so as to draw any one of the second drawing patterns SP, SP4, and SP5. In this case, the controller 50 drives and controls the laser scanner 40 so that the second drawing pattern rotates around the origin O of the first drawing pattern, thereby irradiating the entire inside of the circle of the second radius with the laser LB. When rotating the second drawing pattern, the controller 50 can also drive and control the laser scanner 40 so that the second drawing pattern rotates at every specified angle and is repeatedly drawn. In addition, the laser scanner 40 can be driven and controlled so that the second drawing pattern rotates continuously. In addition, the laser scanner 40 can be driven and controlled so that, as the second drawing pattern, a pattern similar in shape or similar to the first drawing patterns SP6 to SP11 and smaller than the first drawing patterns SP6 to SP11 by a specified size is drawn.

[0204] By setting the laser welding method and the laser welding apparatus 100 in this way, the same effects as those of the structures shown in Embodiments 1 and 2 and Modification Examples 1 to 3 can be achieved.

[0205] Industrial Applicability

[0206] The laser welding method of the present disclosure can suppress the generation of welding defects and obtain a weld bead with a good shape, and thus is useful when applied to spot welding.

[0207] -Symbol Explanation-

[0208] 10 Laser oscillator

[0209] 20 Optical fiber

[0210] 30 Laser head

[0211] 31 Housing

[0212] 32 Collimating lens

[0213] 33 Mirror

[0214] 34 Condensing lens

[0215] 40 Laser scanner

[0216] 41 First galvanometer mirror

[0217] 41a First mirror

[0218] 41b First rotation axis

[0219] 41c First drive unit

[0220] 42 Second galvanometer mirror

[0221] 42a Second reflecting mirror

[0222] 42b Second rotation axis

[0223] 42c Second drive unit

[0224] 50 Controller

[0225] 60 Robot arm

[0226] 200 Workpiece

[0227] 210 First plate (base material)

[0228] 211 Galvanized layer (coating layer)

[0229] 220 Second plate (base material)

[0230] 221 Galvanized layer (coating layer)

[0231] 301, 302 Small holes

[0232] 311, 312 Molten pools.

Claims

1. A laser welding method, comprising: a welding step of irradiating the surface of a workpiece by two-dimensionally scanning a laser to perform spot welding on the workpiece, The welding step at least includes: a first irradiation step of scanning the laser so that the laser depicts a first depiction pattern on the surface of the workpiece, and by rotating the first depiction pattern about the origin of the first depiction pattern, the laser is irradiated as a whole within a circle of a first radius, The first depiction pattern is a pattern in which two annular patterns are joined and continuous at the origin, The first radius is half the length of the first depiction pattern.

2. The laser welding method according to claim 1, wherein, In the first irradiation step, the laser is scanned so that, with the origin of the first depiction pattern as the center, the first depiction pattern is repeatedly depicted each time it rotates by a predetermined angle.

3. The laser welding method according to claim 1, wherein, In the first irradiation step, the laser is scanned so that, with the origin of the first depiction pattern as the center, the first depiction pattern rotates continuously.

4. The laser welding method according to any one of claims 1 to 3, wherein, The first depiction pattern is a figure-eight or ∞-shaped Lissajous pattern, In the first irradiation step, the laser is scanned so that: by vibrating the laser along a first direction into a sine wave shape having a first frequency, and vibrating the laser along a second direction intersecting the first direction into a sine wave shape having a second frequency, the first depiction pattern is depicted on the surface of the workpiece.

5. The laser welding method according to any one of claims 1 to 3, wherein, Following the first irradiation step, the welding step further includes: a second irradiation step of scanning the laser so as to depict a second depiction pattern having a predetermined length centered on the origin of the first depiction pattern, The predetermined length of the second depiction pattern is shorter than twice the first radius.

6. The laser welding method according to claim 5, wherein, In the second irradiation step, the laser is scanned so that by rotating the second depiction pattern about the origin of the first depiction pattern, the laser is irradiated as a whole within a circle of a second radius, The second radius is half the length of the second depiction pattern and is shorter than the first radius.

7. The laser welding method according to claim 6, wherein, In the second irradiation step, the laser is scanned so that, with the origin of the first depiction pattern as the center, the second depiction pattern is repeatedly depicted each time it rotates by a predetermined angle.

8. The laser welding method according to claim 6, wherein, In the second irradiation step, the laser is scanned so that, with the origin of the first depiction pattern as the center, the second depiction pattern rotates continuously.

9. The laser welding method according to claim 6, wherein, The second depiction pattern is a pattern in which two annular patterns are joined and continuous at the origin of the first depiction pattern.

10. The laser welding method according to claim 9, wherein, the second drawn pattern is a figure-eight or ∞-shaped Lissajous pattern, in the second irradiation step, the laser is scanned such that: by vibrating the laser along a first direction in a sine wave shape having a first frequency and vibrating the laser along a second direction intersecting the first direction in a sine wave shape having a second frequency, the second drawn pattern is drawn on the surface of the workpiece.

11. The laser welding method according to claim 5, wherein, the workpiece has a structure in which plate-like portions in two base materials each including a plate-like portion overlap or abut against each other, and a covering layer is formed at least on the surface of the plate-like portion, and the boiling point of the covering layer is lower than the melting point of the base material, the output of the laser is controlled such that the output of the laser in the first irradiation step is lower than the output of the laser in the second irradiation step.

12. The laser welding method according to claim 11, wherein, in the first irradiation step, the covering layer between the plate-like portions is removed, in the second irradiation step, the two plate-like portions from which the covering layer has been removed are welded to each other.

13. The laser welding method according to claim 11, wherein, the covering layer is a plating layer mainly composed of zinc.

14. The laser welding method according to claim 5, wherein, in the second irradiation step, a small hole is formed in the workpiece.

15. The laser welding method according to any one of claims 1 to 3, wherein, in the first irradiation step, a small hole is formed in the workpiece.

16. The laser welding method according to claim 4, wherein, the ratio of the first frequency to the second frequency is 1:

2.

17. The laser welding method according to any one of claims 1 to 3, wherein, the laser is scanned such that at least the drawing speed of the first drawn pattern is constant.

18. A laser welding method, comprising: a welding step of irradiating the surface of a workpiece by two-dimensionally scanning a laser to perform spot welding on the workpiece, the welding step at least includes: a first irradiation step of scanning the laser such that the laser draws a first drawn pattern on the surface of the workpiece, and by rotating the first drawn pattern about the origin of the first drawn pattern, the laser is irradiated as a whole within a circle of a first radius; and a second irradiation step of scanning the laser such that a second drawn pattern having a specified length centered on the origin of the first drawn pattern is drawn, in a plan view, the first drawn pattern and the second drawn pattern are asymmetric shapes with respect to the origin of the first drawn pattern, the first radius corresponds to the length of the longer side of the first drawn pattern with respect to the origin, the second radius corresponds to the length of the longer side of the second drawn pattern with respect to the origin, the specified length of the second drawn pattern is shorter than twice the first radius.

19. A laser welding apparatus, at least comprising: A laser oscillator that generates laser light; A laser head that receives the laser light and irradiates a workpiece; and A controller that controls the operation of the laser head and the output of the laser light, The laser head includes: a laser scanner that scans the laser light in a first direction and a second direction intersecting the first direction, The controller drives and controls the laser scanner so that the laser light depicts a first depiction pattern on the surface of the workpiece, and by rotating the first depiction pattern about the origin of the first depiction pattern, the laser light is irradiated over the entire interior of a circle with a first radius, The first depiction pattern is a pattern in which two annular patterns meet and are continuous at the origin, The first radius is half the length of the first depiction pattern.

20. The laser welding apparatus according to claim 19, wherein, The controller drives and controls the laser scanner so that: after the laser light depicts the first depiction pattern on the surface of the workpiece, the laser light depicts a second depiction pattern having a specified length about the origin of the first depiction pattern, The specified length of the second depiction pattern is shorter than twice the length of the first radius.

21. The laser welding apparatus according to claim 20, wherein, The controller drives and controls the laser scanner so that by rotating the second depiction pattern about the origin of the first depiction pattern, the laser light is irradiated over the entire interior of a circle with a second radius, The second radius is half the length of the second depiction pattern and is shorter than the first radius.

22. The laser welding apparatus according to claim 20 or 21, wherein, The workpiece has a structure in which plate-like portions of two base materials each including a plate-like portion overlap or abut each other, and a covering layer is formed at least on the surface of the plate-like portion, and the boiling point of the covering layer is lower than the melting point of the base material, The controller controls the output of the laser light so that the output of the laser light during the depiction of the first depiction pattern is lower than the output of the laser light during the depiction of the second depiction pattern.

23. The laser welding apparatus according to any one of claims 19 to 21, wherein, The controller drives and controls the laser scanner so that at least the depiction speed of the first depiction pattern is constant.

24. The laser welding apparatus according to any one of claims 19 to 21, wherein, The laser welding apparatus further includes: a robot arm on which the laser head is mounted, The controller controls the operation of the robot arm, The robot arm moves the laser head relative to the surface of the workpiece in a specified direction.

25. The laser welding apparatus according to any one of claims 19 to 21, wherein, The laser oscillator is connected to the laser head by an optical fiber, The laser light passes through the optical fiber and is transmitted from the laser oscillator to the laser head.

26. The laser welding apparatus according to any one of claims 19 to 21, wherein, The laser scanner includes: a first galvanometer mirror that scans the laser in a first direction, and a second galvanometer mirror that scans the laser in a second direction intersecting the first direction.

27. The laser welding apparatus according to any one of claims 19 to 21, wherein the laser head further has a focal position adjustment mechanism, and the focal position adjustment mechanism is configured to change the focal position of the laser along a direction intersecting the surface of the workpiece.

Images