Laser welding device and laser welding method

Abstract

This laser welding device comprises: a laser oscillator; a processing head that performs two-dimensional scanning while advancing laser light along a welding line having a curved portion and irradiates the surface of the workpiece with the laser light so as to periodically draw a predetermined pattern; and a controller that controls the movement of the processing head and the two-dimensional scanning of the laser light. The laser welding device controls the two-dimensional scanning of the laser light in the curved portion such that the first overlapping ratio indicating the overlapping rate of the pattern on one side based on the periodic drawing of the pattern in the curved portion and the second overlapping ratio indicating the overlapping rate of the pattern on the other side based on the periodic drawing of the pattern in the curved portion are identical.

Description

Laser welding device and laser welding method

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

[0002] Patent Document 1 discloses a laser welding method in which a plurality of metal plates, including a metal plate plated with a low-boiling-point metal having a boiling point lower than the melting point of the base material, are overlapped, and a laser beam is irradiated onto the overlapping portions of the metal plates to weld the plurality of metal plates. The laser beam transmitted from a laser oscillator is irradiated onto the overlapping portions by a scanner processing head while adjusting the focus.

[0003] Japanese Patent No. 4915315

[0004] The present disclosure has been devised in view of the conventional circumstances, and provides a laser welding device and a laser welding method that, in laser welding along a curved weld line, equalizes the heat input balance inside and outside the laser beam and suppresses deterioration of the quality of the weld bead.

[0005] The present disclosure provides a laser welding device comprising: a laser oscillator that generates laser light; a processing head that scans the laser light two-dimensionally while moving it along a welding line having at least a curved portion, and irradiates the workpiece surface so as to periodically draw a predetermined pattern; and a controller that controls the movement of the processing head along the welding line and the two-dimensional scanning of the laser light, wherein the controller controls the two-dimensional scanning of the laser light at the curved portion so that a first overlap rate indicating an overlap rate of the pattern on one side based on the periodic drawing of the pattern at the curved portion and a second overlap rate indicating an overlap rate of the pattern on the other side based on the periodic drawing of the pattern at the curved portion are equal.

[0006] The present disclosure also provides a laser welding method that is performed by a laser welding device that includes at least a laser oscillator that generates laser light, a processing head, and a controller, and includes the steps of: irradiating the laser light so that the laser light travels along a weld line having at least a curved portion while scanning it two-dimensionally to periodically draw a predetermined pattern on the surface of a workpiece; and controlling the movement of the processing head along the weld line and the two-dimensional scanning of the laser light, wherein in the step of controlling the two-dimensional scanning of the laser light, the two-dimensional scanning of the laser light is controlled at the curved portion so that a first overlap rate indicating an overlap rate of the pattern on one side based on the periodic drawing of the pattern at the curved portion and a second overlap rate indicating an overlap rate of the pattern on the other side based on the periodic drawing of the pattern at the curved portion are equal.

[0007] According to the present disclosure, in laser welding along a curved weld line, the heat input balance between the inside and outside of the laser beam can be made uniform, and deterioration of the quality of the weld bead can be suppressed.

[0008] FIG. 1 is a diagram showing an example of a schematic configuration of a laser welding device according to this embodiment; FIG. 2 is a diagram showing an example of a configuration of a galvanometer head; FIG. 3 is a diagram showing an example of a Lissajous pattern, which is an example of a scanning pattern of laser light; FIG. 4 is a diagram showing the overlap rate of the upper and lower weld lines during linear welding; FIG. 5 is a diagram showing the overlap rate of the conventional upper and lower weld lines during curved welding; FIG. 6 is a diagram showing the overlap rate of the upper and lower weld lines according to this embodiment during curved welding; FIG. 7 is a diagram showing an example of a laser welding pattern according to this embodiment;

[0009] (Background to the present disclosure) Laser light has a high power density and can perform high-speed, high-quality welding, and is applied to welding a variety of workpieces. In particular, scanning welding, in which welding is performed while scanning the surface of the workpiece with laser light at high speed, allows the laser beam to be moved quickly to the next welding point during periods when welding is not being performed, thereby shortening the total welding time (see, for example, Patent Document 1). Furthermore, with regard to laser light scanning welding, a method has been proposed in which the laser light is scanned so as to draw a Lissajous pattern on the surface of the workpiece (see, for example, Patent Document 1).

[0010] The conventional scanning welding proposed in Patent Document 1 focuses on high-speed welding by moving the laser beam, and can play a major role in improving productivity. However, in actual laser welding sites, laser welding is sometimes performed by periodically drawing a predetermined pattern while moving the processing head along a curved shape, such as to join two straight sections. In such cases, as the processing head moves along the curved section, unevenness (in other words, imbalance) in the amount of heat input of the laser light (laser beam) into the workpiece can occur between the inside and outside of the predetermined pattern, resulting in a problem of not being able to obtain a good weld bead.

[0011] Therefore, in the following embodiments, examples of a laser welding device and a laser welding method are described that, in laser welding along a curved weld line, achieve a uniform heat input balance inside and outside the laser beam and suppress deterioration in the quality of the weld bead.

[0012] Hereinafter, with reference to the drawings as appropriate, detailed descriptions of embodiments specifically disclosing a laser welding apparatus and a laser welding method according to the present disclosure will be provided. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters or redundant descriptions of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure and are not intended to limit the subject matter recited in the claims.

[0013] (Embodiment 1) 1. Configuration of Laser Welding Apparatus Fig. 1 is a diagram showing a schematic configuration example of a laser welding apparatus 100 according to this embodiment. The laser welding apparatus 100 includes a laser oscillator 10, an optical fiber 20, a galvanometer head 30 including a galvanometer scanner 40, a controller 50, and a manipulator 60. A display DP1 may be connected to the controller 50 so as to be able to display various data (e.g., screen data, etc.) from the controller 50.

[0014] In the following description, the direction parallel to the traveling direction of the laser light LB from the reflecting mirror 33 toward the galvanometer scanner 40 may be referred to as the X direction, the direction parallel to the optical axis of the laser light LB emitted from the galvanometer head 30 may be referred to as the Z direction, and the direction perpendicular to both the X direction and the Z direction may be referred to as the Y direction. When the surface of the workpiece 200 is flat, the XY plane including the X direction and the Y direction within the plane may be approximately parallel to the surface of the workpiece 200 or may form a certain angle with the surface of the workpiece 200.

[0015] The laser oscillator 10 is a laser light source that receives power from a laser drive power supply (not shown) and generates laser light LB. The laser oscillator 10 may be composed of a single laser light source or may be composed of multiple laser modules.

[0016] The laser light source or laser module used in the laser oscillator 10 is appropriately selected depending on the material of the workpiece 200 to be welded, the shape of the welded portion, etc. For example, a fiber laser, a disk laser, or a Yttria-Aluminum-Garnet (YAG) laser can be used as the laser light source. In this case, the wavelength of the laser light LB is set in the range of 1000 nm to 1100 nm. A semiconductor laser can also be used as the laser light source or laser module. In this case, the wavelength of the laser light LB is set in the range of 800 nm to 1000 nm. A visible light laser can also be used as the laser light source or laser module. In this case, the wavelength of the laser light LB is set in the range of the blue wavelength band of 420 nm to 500 nm and the green wavelength band of 480 nm to 560 nm.

[0017] The optical fiber 20 has one end (incoming end) optically coupled to the laser oscillator 10 and the other end (outgoing end) optically coupled to the galvanometer head 30. The optical fiber 20 has a core (not shown) at its center, and a cladding (not shown) that is in contact with the outer circumferential surface of the core and is coaxial with the core. The core and cladding are each primarily composed of quartz, and the refractive index of the core is higher than the refractive index of the cladding. Therefore, the laser light LB generated by the laser oscillator 10 is incident on the incoming end of the optical fiber 20 and is transmitted through the core toward the outgoing end while repeatedly reflecting, etc. In addition, a coating (not shown) or a resin-based protective layer (not shown) that mechanically protects the optical fiber 20 is provided on the outer circumferential surface of the cladding.

[0018] The galvanometer head 30 is attached to the output end of the optical fiber 20, and contains at least a collimator lens 32 (an example of an optical component), a reflecting mirror 33 (an example of an optical component), a condenser lens 34 (an example of an optical component), and a galvanometer scanner 40 (an example of an optical component) in a housing 31. These optical components are housed inside the housing 31 while maintaining a predetermined arrangement relationship. An example configuration of the galvanometer scanner 40 will be described in detail with reference to FIG. 2.

[0019] The galvanometer head 30 first collimates the laser light (in other words, a laser beam) transmitted through the optical fiber 20 and expanded into parallel light, then reflects the collimated parallel light with a reflecting mirror 33 and focuses it with a focusing lens 34. Furthermore, the galvanometer head 30 two-dimensionally scans the laser light focused by the focusing lens 34 toward a welding point on the surface of the workpiece 200 using a galvanometer scanner 40 to periodically draw a predetermined pattern (see below) along a desired weld line. This enables the workpiece 200 to be welded by laser welding. The two-dimensional scanning of the laser light LB by the galvanometer scanner 40 in the galvanometer head 30 is controlled by a controller 50 controlling drivers (not shown) of an X-axis mirror (see below) and a Y-axis mirror (see below) of the galvanometer scanner 40.

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

[0021] The reflecting mirror 33 reflects the laser light LB that has passed through the collimating lens 32, and causes the light to pass through the condensing lens 34 and enter the galvano scanner 40. The surface of the reflecting mirror 33 is disposed so as to form an angle of approximately 45 degrees with the optical axis of the laser light LB that has passed through the collimating lens 32.

[0022] The condenser lens 34 condenses the laser light LB, which is reflected by the reflecting mirror 33 and scanned by the galvanometer scanner 40, onto the surface of the workpiece 200. In the drawing, the condenser lens 34 is placed in front of the galvanometer scanner 40 (on the collimator lens 32 side), but the condenser lens 34 may also be placed behind the galvanometer scanner 40 (on the workpiece 200 side).

[0023] The controller 50 has a control unit 51 including a processor and the like, and a memory 52 including a memory and the like. The controller 50 controls the timing, output, start, end, etc. of laser oscillation of the laser oscillator 10. Specifically, the controller 50 controls the laser oscillation and laser output in the control unit 51 by supplying control signals such as output current and on / off time to a laser drive power supply (not shown) connected to the laser oscillator 10. The controller 50 also controls the irradiation position of the laser light by the galvano head 30 in accordance with the contents of a processing program for laser welding (processing) the workpiece 200, which is stored in the memory 52. ​​The controller 50 also generates command signals for controlling the operation of the manipulator 60 and sends them to the manipulator 60.

[0024] The memory 52 stores a processing program for laser welding. The memory 52 may be provided inside the controller 50 as shown in Fig. 1, or may be provided outside the controller 50 and configured to be able to exchange data with the controller 50.

[0025] The manipulator 60 is, for example, a known vertical six-axis robot having six joint axes. The sixth joint axis is provided at the tip of a robot arm included in the manipulator 60. The manipulator 60 can grasp the galvanometer head 30 via a gripping part (not shown) attached to the sixth joint axis, and controls the position of the galvanometer head 30 so that it can be moved in response to a command signal from the controller 50.

[0026] The display DP1 is configured using, for example, a Liquid Crystal Display (LCD) or an organic electroluminescence (EL) display, and is connected to the controller 50 so as to allow input and output of data signals. The display DP1 displays a screen showing the processing results of the control unit 51 (for example, messages showing the start, interruption, resumption, and end of laser welding (processing)).

[0027] 2, the configuration and operation of the galvano scanner 40 housed in the galvano head 30 will be described. FIG. 2 is a diagram schematically illustrating an example of the configuration of the galvano head 30.

[0028] 2, the galvanometer scanner 40 is a known laser beam scanner having a first galvanometer mirror 41 (also referred to as an X-axis mirror) and a second galvanometer mirror 42 (also referred to as a Y-axis mirror). The first galvanometer mirror 41 has a first mirror 41a, a first rotation shaft 41b, and a first drive unit 41c. The second galvanometer mirror 42 has a second mirror 42a, a second rotation shaft 42b, and a second drive unit 42c. The laser beam LB transmitted through the condenser lens 34 is reflected by the first mirror 41a and then by the second mirror 42a, and is irradiated onto the surface of the workpiece 200.

[0029] For example, the first driver 41c and the second driver 42c are galvanometer motors. The first rotation shaft 41b and the second rotation shaft 42b are output shafts of the motors. Although not shown, the first driver 41c is rotationally driven by a driver that operates in response to a control signal from the controller 50, causing the first mirror 41a attached to the first rotation shaft 41b to rotate about the axis of the first rotation shaft 41b. Similarly, the second driver 42c is rotationally driven by a driver that operates in response to a control signal from the controller 50, causing the second mirror 42a attached to the second rotation shaft 42b to rotate about the axis of the second rotation shaft 42b.

[0030] The first mirror 41a rotates around the axis of the first rotation shaft 41b to a predetermined angle, thereby scanning the laser beam LB in the X direction. The second mirror 42a rotates around the axis of the second rotation shaft 42b to a predetermined angle, thereby scanning the laser beam LB in the Y direction. In other words, the galvano scanner 40 is configured to two-dimensionally scan the laser beam LB within the XY plane and irradiate it toward the workpiece 200.

[0031] The controller 50 controls the laser oscillation of the laser oscillator 10. Specifically, the controller 50 controls the laser oscillation by supplying control signals such as an output current and an on / off time to a laser drive power supply (not shown) connected to the laser oscillator 10. The controller 50 also controls the output of the laser light LB.

[0032] The controller 50 also controls the operation of the galvanometer head 30 in accordance with the contents of the selected machining program. Specifically, the controller 50 controls the driving of the galvanometer scanner 40 provided in the galvanometer head 30 and a driving unit (not shown) for the collimator lens 32. The controller 50 also controls the operation of the manipulator 60. The machining program is stored in a storage unit (not shown) provided inside the controller 50 or in another location, and is called by the controller 50 in response to a command from the controller 50.

[0033] The controller 50 has an integrated circuit such as an LSI or a microcomputer (not shown), and the above-mentioned functions of the controller 50 are realized by executing a processing program, which is software, on this integrated circuit. Note that the controller 50 that controls the operation of the galvano head 30 and the controller 50 that controls the output of the laser light LB may be provided separately.

[0034] The manipulator 60 is an articulated robot, and is attached with the housing 31 of the galvano head 30. The manipulator 60 is also connected to the controller 50 so as to be able to exchange signals, and moves the galvano head 30 so as to trace a predetermined trajectory in accordance with the above-mentioned processing program.

[0035] 2. Lissajous Pattern Next, a predetermined pattern, which is a scanning pattern that the galvanometer head 30 periodically draws along the welding line WL, will be described with reference to Fig. 3. The predetermined scanning pattern is, for example, a Lissajous pattern in the shape of a figure eight or a figure infinity. Fig. 3 is a diagram showing an example of a Lissajous pattern, which is an example of a scanning pattern of laser light. In the illustration, the welding line WL coincides with the X-axis.

[0036] The laser beam LB is scanned within the XY plane in Figure 3, in this case the surface of the workpiece 200, to trace a scan pattern SP. The width in the X direction of the scan pattern SP shown in Figure 3 is approximately equal to its width in the Y direction. In this specification, "approximately equal" or "approximately the same" means that the control results of the controlled object are the same or identical, including errors in the control system, and does not require that the two objects being compared be strictly the same or identical. Furthermore, "approximately equal" or "approximately the same" is also used to mean the same or identical, including manufacturing tolerances or assembly tolerances of each part, etc.

[0037] The scan pattern SP shown in FIG. 3 is a Lissajous pattern LJ0 obtained by oscillating the laser beam LB sinusoidally in the X direction at a predetermined frequency and in the Y direction at a frequency different from that in the X direction. The origin O1 of the scan pattern SP corresponds to the center point of the Lissajous pattern LJ0. The scan pattern SP shown in FIG. 3 is obtained by scanning the laser beam LB from the origin O1 in the direction of arrow AR1 shown in FIG. 3 during one period. That is, the Lissajous pattern LJ0 has a figure-eight shaped scan pattern from origin O1 → point A → point B → point C → origin O1 → point D → point E → point F → origin O1 as one period. Note that the laser beam LB may also be scanned from the origin O1 in the direction of arrow AR2 shown in FIG. 3 during one period. In this case, the Lissajous pattern LJ0 has one period of a figure-eight scanning pattern from origin O1 to point C to point B to point A to origin O1 to point F to point E to point D to origin O1.

[0038] As described above, the scanning patterns of the laser light LB in the X and Y directions are determined based on the rotational movements of the first mirror 41 a and the second mirror 42 a. Generally, when the position coordinate of the scanning pattern SP shown in Fig. 3 obtained by driving the first mirror 41 a is set to X and the position coordinate of the scanning pattern SP shown in Fig. 3 obtained by driving the second mirror 42 a is set to Y, the position coordinates X and Y are expressed by the following equations (1) and (2), respectively.

[0039] X=-a0×sin(2ωt)=-a0×sin(2・2πft) =-a0×sin(2・2πt / T)...(1) Y=-a0×sin(ωt)=-a0×sin(2πft)=-a0×sin(2πt / T)...(2)

[0040] Here, a0: amplitude in the X and Y directions of the scanning pattern SP1 shown in FIG. 3, ω: angular velocity, f: frequency, T: period (=1 / f), and t: time.

[0041] The position coordinates X and Y shown in equations (1) and (2) are expressed in a stationary coordinate system of the scan pattern SP when the position of the galvano head 30 is fixed. Furthermore, the frequency f corresponds to the drive frequencies of the first mirror 41a and the second mirror 42a, respectively. The scan pattern SP shown in FIG. 3 is a Lissajous pattern in the shape of a figure eight, which corresponds to the case where a0 = 1 in equations (1) and (2). Hereinafter, the length of the Lissajous pattern LJ0 is defined as the length of the line connecting points A and C, or the length of the line connecting points D and F. In equations (1) and (2), the same amplitude a0 is used in both the X and Y directions, but different amplitudes may be set in the X and Y directions.

[0042] 3. Overlap Ratios of the Inside and Outside During Laser Welding of a Straight Section Next, with reference to Fig. 4, the overlap ratios of the inside and outside when the weld line WL has a straight section and laser welding is performed in which the galvanometer head 30 periodically draws a Lissajous pattern along the straight section will be described. Fig. 4 is a diagram showing the overlap ratios of the upper weld line IN1 and the lower weld line OUT1 during straight welding.

[0043] As shown in Fig. 4, the weld line WL of the laser welding performed on the workpiece 200 by the laser welding apparatus 100 has a straight section (see straight sections LN1 and LN2 shown in Fig. 7). In the description of Fig. 4, the galvanometer head 30 is held by the manipulator 60 and moves the weld line WL in the welding direction WD, while two-dimensionally scanning the laser beam LB and irradiating the workpiece 200 with the laser beam LB so as to periodically trace a Lissajous pattern LJ1. To facilitate understanding of Fig. 4, the region of the weld line upper portion IN1 (e.g., the upper portion of the page in Fig. 4) on one side of the weld line WL is defined as the inner region of the weld line WL, and the region of the weld line lower portion OUT1 (e.g., the lower portion of the page in Fig. 4) on the other side of the weld line WL is defined as the outer region of the weld line WL.

[0044] 3 is a scanning pattern that is drawn by two-dimensionally scanning the laser beam LB while the galvanometer head 30 is not moving along the welding line WL (i.e., is stationary). That is, in one cycle of the Lissajous pattern LJ0, the start and end positions are the same, e.g., the origin O1.

[0045] However, when the galvanometer head 30 periodically draws Lissajous patterns while moving in the welding direction WD along the straight section of the weld line WL, a Lissajous pattern LJ1 as shown in FIG. 4 is drawn. The Lissajous pattern LJ1 has a configuration including multiple cycles, each cycle consisting of a roughly figure-8-shaped pattern connected by points G0 → G1 → G2 → G3 → G4 → G5 → G6 → G7 → G8. In this case, the start position (i.e., the position of point G0) and the end position (i.e., the position of point G8) of one cycle of the Lissajous pattern LJ1 are different. The distance between points G0 and G8 corresponds to the movement distance of the galvanometer head 30 in one cycle of drawing the Lissajous pattern LJ1 along the weld line WL in the welding direction WD. Note that FIG. 4 shows, for example, three cycles of the Lissajous pattern LJ1.

[0046] The length of the inner Lissajous pattern of the Lissajous pattern LJ1 is, for example, the length of the straight line connecting points G1 and G3 of the Lissajous pattern of the first cycle, and similarly, the length of the straight line connecting points G9 and G11 of the Lissajous pattern of the second cycle, which is indicated by "L4" in Fig. 4. In addition, in three cycles of Lissajous pattern LJ1, the length of overlap between the Lissajous pattern on the inside of the first cycle (top IN1 of the weld line) and the Lissajous pattern on the inside of the following second cycle (top IN1 of the weld line) is the length of the straight line connecting point G3 of the first cycle and point G9 of the second cycle, which is indicated by "L3" in Fig. 4.

[0047] That is, in the straight section of the weld line WL, if the overlap rate of the Lissajous pattern on the inside (upper part IN1 of the weld line) is defined as α2, then α2 is calculated as α2=L3 / L4.

[0048] Similarly, the length of the outer Lissajous pattern of the Lissajous pattern LJ1 is, for example, the length of the straight line connecting points G5 and G7 of the Lissajous pattern of the first cycle, and similarly, the length of the straight line connecting points G13 and G15 of the Lissajous pattern of the second cycle, which is indicated by "L2" in Fig. 4. Furthermore, in three cycles of the Lissajous pattern LJ1, the length of overlap between the Lissajous pattern on the outside of the first cycle (below OUT1 of the weld line) and the Lissajous pattern on the outside of the following second cycle (below OUT1 of the weld line) is the length of the straight line connecting point G7 of the first cycle and point G13 of the second cycle, which is indicated by "L1" in Fig. 4.

[0049] That is, in the straight section of the weld line WL, if the overlap rate of the Lissajous pattern on the outside (bottom part OUT1 of the weld line) is defined as α1, then α1 is calculated as α1=L1 / L2.

[0050] In the straight section of the weld line WL, the inner Lissajous pattern and the outer Lissajous pattern are symmetrical across the weld line WL. Therefore, L1 = L3 and L2 = L4. In other words, the overlap rate α1 = the overlap rate α2.

[0051] Therefore, the control unit 51 calculates the positions X and Y at which the laser beam LB from the galvanometer head 30 is irradiated in the straight section of the weld line WL using equations (3) and (4), respectively, and the overlap ratios α1 and α2 using equations (5) and (6), respectively. The relationship α1 = α2 can be seen from equations (5) and (6). It can also be seen that unless the welding speed v is 0, the overlap ratios α1 and α2 are always 1 or less. The control unit 51 uses the calculation results of equations (3) and (4) to control the two-dimensional scanning of the laser beam LB. As a result, results such as those shown in equations (5) and (6) are obtained. The various parameters are, for example, three: a0, f, and v. Equation (4) is the same as equation (2) described above.

[0052] X=vt-a0×sin(2・2πft) =vt-a0×sin(2・2πt / T)...(3) Y=-a0×sin(2πft)=-a0×sin(2πt / T)...(4)

[0053] where a0: amplitude in the X and Y directions of the Lissajous pattern LJ1 shown in FIG. 4; ω: angular velocity; f: frequency; T: period; v: moving speed of the center of the Lissajous pattern in the welding direction WD (in other words, welding speed); t: time

[0054] α1 = L1 / L2 = (X coordinate of point G7 in the (7 / 8) cycle - X coordinate of point G13 in the (13 / 8) cycle)) / (X coordinate of point G15 in the (15 / 8) cycle - X coordinate of point G13 in the (13 / 8) cycle)) = (X(7T / 8) - X(13T / 8)) / (X(15T / 8) - X(13T / 8)) = (-a0 x sin(4π x 7 / 8) + v x (7T / 8) + a0 x sin(4π x 13 / 8) - v x (13T / 8)) / (-a0 x sin(4π x 15 / 8) + v x (15T / 8) + a0 x sin(4π x 13 / 8) - v x (13T / 8)) = (8 x a0 - 3 x vT) / (8 x a0 + vt) ...(5)

[0055] α2 = L3 / L4 = (X coordinate of point G3 in the (3 / 8) period - X coordinate of point G9 in the (9 / 8) period)) / (X coordinate of point G11 in the (11 / 8) period - X coordinate of point G9 in the (9 / 8) period)) = (X(3T / 8) - X(9T / 8)) / (X(11T / 8) - X(9T / 8)) = (-a0 x sin(4π x 3 / 8) + v x (3T / 8) + a0 x sin(4π x 9 / 8) - v x (9T / 8)) / (-a0 x sin(4π x 11 / 8) + v x (11T / 8) + a0 x sin(4π x 9 / 8) - v x (9T / 8)) = (8 x a0 - 3 x vT) / (8 x a0 + vt) ... (6)

[0056] 4. Issues with Laser Welding Curved Sections: Heat Input Imbalance Between the Inside and Outside of the Laser Beam Next, with reference to FIG. 5 , we will describe issues that arise when laser welding is performed in which a weld line WL has a curved section and a conventional galvanometer head periodically traces a Lissajous pattern along the curved section. FIG. 5 is a diagram showing the overlap ratios of the upper and lower weld lines in conventional curved welding. In the description of FIG. 5 , as in the description of FIG. 4 , the region of the upper weld line IN2 (e.g., the upper part of the page in FIG. 5 ), which is on one side of the weld line WL, is defined as the region inside the weld line WL, and the region of the lower weld line OUT2 (e.g., the lower part of the page in FIG. 5 ), which is on the other side of the weld line WL, is defined as the region outside the weld line WL.

[0057] The weld line WL shown in FIG. 5 has a curved portion with a curvature radius R. When the galvanometer head periodically traces Lissajous patterns while moving in the welding direction WD along the curved portion of the weld line WL, a Lissajous pattern LJ2 as shown in FIG. 5 is traced. The Lissajous pattern LJ2 has a configuration including multiple one-cycle patterns, each of which is a roughly figure-8-shaped pattern connected by points H0 → H1 → H2 → H3 → H4 → H5 → H6 → H7 → H8. In this case, the starting position (i.e., the position of point H0) and the ending position (i.e., the position of point H8) of one cycle of the Lissajous pattern LJ2 are different. Note that FIG. 5 shows, for example, three cycles of the Lissajous pattern LJ2.

[0058] The length of the inner Lissajous pattern LJ2 is, for example, the length of the arc connected by points H9 and H11 of the Lissajous pattern of the second cycle (which forms a concentric circle with the arc of the curved portion having the same radius of curvature R as the weld line WL. Below, L5 to L7 and L9 to L12 are also arcs, and therefore will not be described), and is indicated by "L8" in Fig. 5. Furthermore, in three cycles of Lissajous pattern LJ2, the length of overlap between the Lissajous pattern on the inside of the first cycle (upper part IN2 of the weld line) and the Lissajous pattern on the inside of the next second cycle (upper part IN2 of the weld line) is the length of the arc of the curved portion having the same radius of curvature R as the weld line WL (see above) connecting point H3 of the first cycle and point H9 of the second cycle, and is indicated by "L7" in Fig. 5.

[0059] That is, in the curved section of the weld line WL, if the overlap rate of the Lissajous pattern on the inside (upper part IN2 of the weld line) is defined as α4, then α4 is calculated as α4=L7 / L8.

[0060] Similarly, the length of the outer Lissajous pattern of the Lissajous pattern LJ2 is the length of the arc of the curved portion (see above) with the same radius of curvature R as the weld line WL that connects, for example, points H13 and H15 of the Lissajous pattern of the second cycle, and is indicated by "L6" in Fig. 5. Furthermore, in three cycles of the Lissajous pattern LJ2, the length of overlap between the Lissajous pattern on the outside of the first cycle (lower part OUT2 of the weld line) and the Lissajous pattern on the outside of the second cycle (lower part OUT2 of the weld line) is the length of the arc of the curved portion (see above) with the same radius of curvature R as the weld line WL that connects point H7 of the first cycle and point H13 of the second cycle, and is indicated by "L5" in Fig. 5.

[0061] That is, in the curved section of the weld line WL, if the overlap rate of the Lissajous pattern on the outside (bottom OUT2 of the weld line) is defined as α3, then α3 is calculated as α3=L5 / L6.

[0062] In the curved section of the weld line WL, the radius of curvature R causes the inner and outer Lissajous patterns to be asymmetric across the weld line WL. More specifically, L5 < L1, L6 > L2, L7 > L3, and L8 < L4. That is, the overlap ratios are also α3 < α1, α4 > α2, with α3 ≠ α4. Therefore, when the weld line WL has a curved section and laser welding is performed in which the galvanometer head periodically draws Lissajous patterns along the curved section, the radius of curvature R causes the overlap ratios of the inner and outer Lissajous patterns to differ. Therefore, the relationship between the arc lengths of L5, L6, L7, and L8 shown in FIG. 5 can result in uneven heat input (in other words, imbalance) of the laser light (laser beam) irradiated from the galvanometer head to the workpiece. In other words, there is a problem in that a good weld bead cannot be obtained by laser welding.

[0063] 5. Respective Overlap Ratios of the Inside and Outside During Laser Welding of Curved Portions Next, with reference to FIG. 6 , a method for controlling the respective overlap ratios of the inside and outside when laser welding is performed in this embodiment in which the weld line WL has a curved portion and the galvanometer head 30 periodically traces a Lissajous pattern along the curved portion will be described. FIG. 6 is a diagram showing the overlap ratios of the upper weld line IN2 and the lower weld line OUT2 during curved welding in this embodiment. In the description of FIG. 6 , as in the description of FIG. 4 or FIG. 5 , the region of the upper weld line IN2 on one side of the weld line WL (e.g., the upper part of the page in FIG. 6 ) is defined as the inner region of the weld line WL, and the region of the lower weld line OUT2 on the other side of the weld line WL (e.g., the lower part of the page in FIG. 6 ) is defined as the outer region of the weld line WL.

[0064] The weld line WL shown in FIG. 6 has a curved portion with a curvature radius R. In this embodiment, when the galvanometer head 30 periodically draws Lissajous patterns while moving in the welding direction WD along the curved portion of the weld line WL, a Lissajous pattern LJ3 as shown in FIG. 6 is drawn. The Lissajous pattern LJ3 has a configuration including multiple one-cycle patterns, with one cycle consisting of a roughly figure-8 pattern connected by points J0 → J1 → J2 → J3 → J4 → J5 → J6 → J7 → J8. In this case, the starting position (i.e., the position of point J0) and the ending position (i.e., the position of point J8) of one cycle of the Lissajous pattern LJ3 are different. Note that FIG. 6 shows, for example, three cycles of the Lissajous pattern LJ3.

[0065] Of the Lissajous patterns LJ3, the length of the inner Lissajous pattern is, for example, the length of the arc of the curved portion (see above) with the same radius of curvature R as the weld line WL that connects point J9 and point J11 of the Lissajous pattern of the second period, and is indicated by "L12" in Fig. 6. Furthermore, in three periods of Lissajous patterns LJ3, the length of overlap between the Lissajous pattern on the inside of the first period (upper portion IN2 of the weld line) and the Lissajous pattern on the inside of the second period (upper portion IN2 of the weld line) is the length of the arc of the curved portion (see above) with the same radius of curvature R as the weld line WL that connects point J3 of the first period and point J9 of the second period, and is indicated by "L11" in Fig. 6.

[0066] That is, in the curved section of the weld line WL according to this embodiment shown in FIG. 6, if the overlap rate of the Lissajous pattern on the inside (upper part IN2 of the weld line) is defined as α6, then α6 is calculated as α6=L11 / L12.

[0067] Similarly, the length of the outer Lissajous pattern of the Lissajous pattern LJ3 is the length of the arc of the curved portion (see above) with the same radius of curvature R as the weld line WL that connects point J13 and point J15 of the Lissajous pattern of the second cycle, and is indicated by "L10" in Fig. 6. Furthermore, in three cycles of the Lissajous pattern LJ3, the length of overlap between the Lissajous pattern on the outside of the first cycle (lower part OUT2 of the weld line) and the Lissajous pattern on the outside of the second cycle (lower part OUT2 of the weld line) is the length of the arc of the curved portion (see above) with the same radius of curvature R as the weld line WL that connects point J7 of the first cycle and point J13 of the second cycle, and is indicated by "L9" in Fig. 6.

[0068] That is, in the curved section of the weld line WL according to this embodiment shown in FIG. 6, if the overlap rate of the Lissajous patterns on the outside (lower part OUT2 of the weld line) is defined as α5, then α5 is calculated as L9 / L10.

[0069] That is, in this embodiment, the control unit 51 of the laser welding apparatus 100 controls L9 and L10, or L11 and L12, or both, depending on the magnitude of the radius of curvature R of the curved portion of the weld line WL so that the overlap rates of the Lissajous patterns satisfy the relationship α5 = α6. This satisfies the relationship in which the overlap rate (α5) of the inner Lissajous pattern in the curved portion section of the weld line WL is equal to the overlap rate (α6) of the outer Lissajous pattern in the same curved portion section. Therefore, the laser welding apparatus 100 can obtain a good weld bead on the workpiece 200 without causing unevenness (in other words, imbalance) in the amount of heat input to the workpiece 200 by the laser beam LB irradiated from the galvanometer head 30.

[0070] Furthermore, when the welding line WL includes both straight and curved portions, the control unit 51 of the laser welding apparatus 100 may control L9 and L10, or L11 and L12, or both, so that the overlap rates of the Lissajous patterns satisfy the relationship α5 = α6 = α1 = α2, depending on the magnitude of the radius of curvature R of the curved portions. In other words, when the welding line WL includes straight and curved portions (see FIG. 7 ), the control unit 51 controls the two-dimensional scanning of the laser light LB so that the overlap rates of the Lissajous patterns on the inside and outside of the welding line WL are equal. As a result, even if the welding line WL has straight sections as well as curved sections, the laser welding device 100 can obtain good welding beads without unevenness (in other words, imbalance) in the amount of heat input to the workpiece 200 by the laser light LB irradiated from the galvanometer head 30 on the inside and outside of the welding line WL, nor in the straight and curved sections, and without bias on the inside and outside, and in the straight and curved sections throughout the entire range of the welding line WL of the workpiece 200.

[0071] For curved portions (see FIG. 6 ), the control unit 51 calculates the positions X and Y at which the laser beam LB from the galvanometer head 30 is irradiated using equations (7) and (8), respectively. However, equations (7) and (8) require the use of an amplitude a(R, c), which is determined by the radius of curvature R of the curved portion of the weld line WL and whether the curved portion is inside or outside the curved portion of the weld line WL. As described above, this amplitude a(R, c) must be calculated through complex calculations after calculating the arcs L9 to L12 and setting the overlap ratio α5 = α6 (if there are straight portions, α5 = α6 = α1 = α2). While complex calculations are not possible here, values ​​calculated in advance through numerical calculations may be used. The control unit 51 uses the calculation results to control the two-dimensional scanning of the laser beam LB. The various parameters are, for example, a0, a(R, c), f, and v. Equation (8) is the same as equation (4) described above.

[0072] X=vt-a(R,c)×sin(2・2πft) =vt-a(R,c)×sin(2・2πt / T)...(7) Y=-a0×sin(2πft)=-a0×sin(2πt / T)...(8)

[0073] where a0: amplitude in the Y direction of the Lissajous pattern LJ3 shown in FIG. 6; a(R, c): amplitude in the X direction of the Lissajous pattern LJ3, which is a function of the radius of curvature R of the weld line WL and a parameter c indicating whether the weld line WL is on the inside or outside of the curved portion thereof; f: frequency; T: period; v: moving speed of the center of the Lissajous pattern in the welding direction WD (in other words, welding speed); t: time

[0074] 6. Operational Procedure of Laser Welding Next, an operational procedure of laser welding by laser welding apparatus 100 according to this embodiment will be described with reference to Figures 7 and 8. Figure 7 is a diagram showing an example of a laser welding pattern according to this embodiment. Figure 8 is a flowchart showing an example of an operational procedure of laser welding by laser welding apparatus 100 according to this embodiment in chronological order. The various processes shown in Figure 8 are mainly executed by control unit 51 of controller 50 in cooperation with memory 52.

[0075] The laser welding pattern shown in FIG. 7 is obtained by periodically drawing a Lissajous pattern by two-dimensional scanning of laser light LB by the galvanometer head 30 while moving the galvanometer head 30 along a welding line WL having straight line portions LN1, LN2, ... and curved line portions CV1, CV2, ....

[0076] In the laser welding pattern of Fig. 7, the Lissajous patterns drawn in each section of the straight line portions LN1, LN2, ... correspond to the Lissajous pattern LJ1 shown in Fig. 4, and the Lissajous patterns drawn in each section of the curved line portions CV1, CV2, ... correspond to the Lissajous pattern LJ3 shown in Fig. 6. The number of periods of the Lissajous patterns drawn in each straight line portion and each curved line portion depends on the laser welding pattern that is determined in advance before laser welding is started by the laser welding apparatus 100. In the illustration, the Lissajous patterns are drawn so that they do not overlap in either the straight line portions or the curved line portions, but this is for ease of visual recognition, and it is necessary that they always overlap in actual welding.

[0077] 8, the control unit 51 sends a control signal to the manipulator 60 in accordance with a laser welding processing program stored in the memory 52, thereby causing the manipulator 60 to move the galvanometer head 30 toward a desired welding point that constitutes the weld line WL defined in the processing program (step St1). Based on the control signal to the manipulator 60, the control unit 51 determines whether the current position on the weld line WL is a straight line portion (e.g., straight line portions LN1, LN2, ...) (step St2).

[0078] If the control unit 51 determines that the current position is a straight portion (step St2, YES), it sets the overlap rates of the inner and outer sides of the entire straight portion (e.g., the entire length of the straight portion LN1) (step St3). Furthermore, the control unit 51 sets various parameters of the Lissajous pattern drawn by the galvanometer head 30 (e.g., amplitude a0 in the X and Y directions of the Lissajous pattern, frequency f, and moving speed (welding speed) v of the center of the Lissajous pattern in the welding direction WD) (step St3). In the processing of step St3, the results calculated in real time each time may be used as the setting values, or results calculated in advance based on the shapes of the weld line WL and the Lissajous pattern may be read from a database (e.g., memory 52) and used as the setting values.

[0079] The control unit 51 uses the setting values ​​set in step St3 to weld the workpiece 200 (i.e., irradiate the laser beam LB while two-dimensionally scanning it) (step St4). After the welding in step St4 is completed, it is determined whether the entire welding is completed (step St5). If it is determined that the current position is not the welding end point (step St5, NO), the control unit 51 returns to step St2.

[0080] On the other hand, if the control unit 51 determines that the current position is a curved portion (NO in step St2), it sets the overlap rates of the inner and outer sides of the entire curved portion (e.g., the entire length of the curved portion CV1) (step St6). Furthermore, the control unit 51 sets various parameters of the Lissajous pattern drawn by the galvanometer head 30 (e.g., the amplitude a0 of the Lissajous pattern in the Y direction, the amplitude a(R, c) of the Lissajous pattern LJ3 in the X direction, which is a function of the radius of curvature R of the weld line WL and a parameter c indicating whether the weld line WL is on the inside or outside of the curved portion), the frequency f, and the moving speed (welding speed) v of the center of the Lissajous pattern in the welding direction WD) (step St6). For the processing of step St6, the control unit 51 uses as setting values ​​results previously calculated based on the shapes of the weld line WL and the Lissajous pattern read from a database (e.g., memory 52).

[0081] The control unit 51 uses the setting values ​​set in step St6 to weld the workpiece 200 (i.e., irradiate the laser beam LB while two-dimensionally scanning) (step St7). After the welding in step St7 is completed, it is determined whether the entire welding is completed (step St8). If it is determined that the current position is not the welding end point (step St8, NO), the processing of the control unit 51 returns to step St2. The above steps are repeated to perform welding, and if the control unit 51 determines that the welding is completed (step St5, YES or step St8, YES), the processing of the control unit 51 shown in FIG. 8 ends.

[0082] 7 illustrates a pattern obtained by periodically drawing a Lissajous pattern by two-dimensionally scanning the laser light LB by the galvanometer head 30 while moving the galvanometer head 30 along the weld line WL. However, it goes without saying that the laser welding pattern of the laser welding apparatus 100 according to this embodiment is not limited to the Lissajous pattern shown in FIG. 7. For example, the patterns shown in the shapes of FIGS. 9A, 9B, and 9C may also be used.

[0083] 9A is a diagram showing an example of a pattern according to a first modified example, FIG. 9B is a diagram showing an example of a pattern according to a second modified example, and FIG. 9C is a diagram showing an example of a pattern according to a third modified example.

[0084] As shown in FIG. 9A, the pattern may be a composite pattern of two circular patterns that are in contact with each other at the origin O1 and are arranged on either side of the Y axis.

[0085] As shown in Fig. 9B, the pattern may be a composite pattern of elliptical patterns that are in contact with each other at the origin O1 and are arranged on either side of the Y axis. In the example shown in Fig. 9B, the major axis of each of the two elliptical patterns is in the Y direction and the minor axis is in the X direction. However, the major axis may also be in the X direction and the minor axis may also be in the Y direction.

[0086] 9C, the pattern may be a composite pattern of two diamond-shaped patterns that are in contact with each other at the origin O1 and are arranged on either side of the Y axis. The sizes of the two annular patterns may also be changed as appropriate.

[0087] In other words, the scanning patterns of the laser beam LB according to the first to third modified examples (examples of predetermined patterns) are not limited to the examples shown in FIGS. 9A to 9C or their modifications, as long as they are continuous patterns in which two circular patterns meet at the origin O1. For example, in each of the scanning patterns SP4, SP5, and SP6, the amplitude during up / down operation may be changed so as to be asymmetrical in the up / down direction. These patterns can be obtained by driving the first mirror 41a and the second mirror 42a according to predetermined driving patterns.

[0088] <Technology of the Present Disclosure> As described above, the present disclosure discloses the following technical ideas.

[0089] <Technology 1> A laser welding device comprising: a laser oscillator (10) that generates laser light (LB); a processing head (galvano head 30) that scans the laser light two-dimensionally while traveling along a weld line (WL) having at least curved portions (CV1, CV2, ...) and irradiates the workpiece (200) so as to periodically draw a predetermined pattern (Lissajous pattern LJ3) on the surface of the workpiece; and a controller (50) that controls movement of the processing head along the weld line and the two-dimensional scanning of the laser light, wherein the controller controls the two-dimensional scanning of the laser light on the curved portion so that a first overlap rate (α6) indicating an overlap rate of the pattern on one side (upper portion IN2 of the weld line) based on the periodic drawing of the pattern on the curved portion is equal to a second overlap rate (α5) indicating an overlap rate of the pattern on the other side (lower portion OUT2 of the weld line) based on the periodic drawing of the pattern on the curved portion. As a result, in laser welding along a weld line WL that has at least a curved shape (e.g., a curved portion having a radius of curvature R, see FIG. 6 ), the laser welding apparatus 100 can achieve a uniform heat input balance on both the inside and outside of the laser beam LB irradiated from the galvanometer head 30. Therefore, the laser welding apparatus 100 can suppress deterioration in the quality of the weld bead formed by laser welding.

[0090] <Technology 2> The laser welding device according to Technology 1, wherein the pattern is a Lissajous pattern in the shape of a figure eight or an infinity, and the controller controls the two-dimensional scanning of the laser light so that a center position of the Lissajous pattern (origin O1 or the center of gravity position of one cycle of the Lissajous pattern in FIGS. 4 and 6 ) passes through the weld line and a start position (point J0) and an end position (point J8) of one cycle of the Lissajous pattern in the curved portion are different. As a result, when performing laser welding such that a Lissajous pattern is periodically drawn while moving the galvanometer head 30 along the weld line WL, the laser welding device 100 can uniformly balance the heat input of the laser light LB irradiated from the galvanometer head 30 on each of the inside (top IN2 side of the weld line) and outside (bottom OUT2 side of the weld line) of the weld line WL.

[0091] <Technology 3> The laser welding device according to Technology 1 or Technology 2, wherein the controller includes a memory (52) that stores one or more first parameters (e.g., L11 and L12 shown in FIG. 6 ) for defining the first overlap ratio and one or more second parameters (e.g., L9 and L10 shown in FIG. 6 ) for defining the second overlap ratio. In this way, the laser welding device 100 uses set values ​​stored in advance in the memory 52 without calculating the first parameters and the second parameters in real time during laser welding, thereby suppressing an increase in the processing load on the control unit 51 and enabling laser welding that produces a high-quality weld bead.

[0092] <Technology 4> The controller calculates the first overlap ratio based on a length (L11) of overlap between the Lissajous pattern on one side (the upper IN2 side of the weld line) of the mth period (m: integer greater than or equal to 1) of the curved portion and the Lissajous pattern on the one side (the upper IN2 side of the weld line) of the (m+1)th period of the curved portion, and a length (L12) of one period of the Lissajous pattern; and calculates the second overlap ratio based on a length (L9) of overlap between the Lissajous pattern on the other side (the lower OUT2 side of the weld line) of the mth period of the curved portion and the (m+1)th Lissajous pattern on the other side (the lower OUT2 side of the weld line) of the curved portion, and a length (L10) of one period of the Lissajous pattern. This allows the laser welding device 100 to set the overlap rate to be equal on both the inside and outside of the curved section, and when laser welding is performed in a manner that periodically traces a Lissajous pattern while moving the galvanometer head 30 with the manipulator 60 in the curved section, the heat input balance on both the inside and outside of the laser light LB can be made uniform.

[0093] <Technology 5> The laser welding device according to Technology 2 or Technology 4, wherein the weld line further has straight line portions (LN1, LN2, ...), and the controller: calculates a third overlap ratio (α2) indicating an overlap ratio of the Lissajous pattern on one side (an upper portion IN1 side of the weld line) based on the periodic drawing of the Lissajous pattern on the straight line portions, calculates a fourth overlap ratio (α1) indicating an overlap ratio of the Lissajous pattern on the other side (a lower portion OUT1 side of the weld line) based on the periodic drawing of the Lissajous pattern on the straight line portions, and controls the two-dimensional scanning of the laser light on the curved line portions so that the first overlap ratio, the second overlap ratio, the third overlap ratio, and the fourth overlap ratio are all equal. As a result, when performing laser welding in which the welding line WL has both curved and straight portions and the galvanometer head 30 is moved along the welding line WL to periodically trace a Lissajous pattern, the laser welding apparatus 100 can uniformly balance the heat input of the laser light LB irradiated from the galvanometer head 30 on both the inside (upper IN2 side of the welding line) and outside (lower OUT2 side of the welding line) of the welding line WL, regardless of the shape of the welding line WL.

[0094] <Technology 6> The controller calculates the third overlap ratio based on a length (L3) of overlap between the Lissajous pattern on one side (top IN1 side of the weld line) of the nth period (n: integer greater than or equal to 1) in the straight portion and the Lissajous pattern on the one side (top IN1 side of the weld line) of the (n+1)th period, and a length (L4) of one period of the Lissajous pattern; and calculates the fourth overlap ratio based on a length (L1) of overlap between the Lissajous pattern on the other side (bottom OUT1 side of the weld line) of the nth period in the straight portion and the Lissajous pattern on the other side (bottom OUT1 side of the weld line) of the (n+1)th period, and a length (L2) of one period of the Lissajous pattern. This allows the laser welding device 100 to set the overlap rate to be equal on both the inside and outside of the straight section, and when laser welding is performed in the straight section by moving the galvanometer head 30 with the manipulator 60 to periodically draw a Lissajous pattern, the heat input balance on both the inside and outside of the laser light LB can be made uniform.

[0095] <Technology 7> This method is performed by a laser welding device (100) including at least a laser oscillator (10) that generates laser light, a processing head (galvano head 30), and a controller (50), and includes the steps of: irradiating a surface of a workpiece (200) with the laser light by scanning it two-dimensionally while traveling along a weld line (WL) having at least curved portions (CV1, CV2, ...) to periodically draw a predetermined pattern (Lissajous pattern LJ3) on the surface of the workpiece (200); and controlling the movement of the processing head along the weld line and the two-dimensional scanning of the laser light, wherein in the step of controlling the two-dimensional scanning of the laser light, the two-dimensional scanning of the laser light is controlled so that a first overlap rate (α6) indicating an overlap rate of the pattern on one side (upper portion IN2 of the weld line) based on the periodic drawing of the pattern on the curved portion is equal to a second overlap rate (α5) indicating an overlap rate of the pattern on the other side (lower portion OUT2 of the weld line) based on the periodic drawing of the pattern on the curved portion. This allows the laser welding apparatus 100 to achieve a uniform heat input balance between the inside and outside of the laser beam LB irradiated from the galvanometer head 30 during laser welding along a weld line WL that has at least a curved shape (e.g., a curved portion having a radius of curvature R, see FIG. 6 ). Therefore, the laser welding apparatus 100 can suppress deterioration in the quality of the weld bead formed by laser welding.

[0096] Although various embodiments have been described above with reference to the drawings, it goes without saying that the present disclosure is not limited to such examples. It is clear that a person skilled in the art can conceive of various modifications, alterations, substitutions, additions, deletions, and equivalents within the scope of the claims, and it is understood that these also naturally fall within the technical scope of the present disclosure. Furthermore, the components of the various embodiments described above may be combined in any manner without departing from the spirit of the invention.

[0097] This application is based on a Japanese patent application (Patent Application No. 2023-121954) filed on July 26, 2023, the contents of which are incorporated herein by reference.

[0098] The present disclosure is useful as a laser welding device and a laser welding method that, in laser welding along a curved weld line, equalizes the heat input balance between the inside and outside of the laser beam and suppresses deterioration in the quality of the weld bead.

[0099] REFERENCE SIGNS LIST 10 Laser oscillator 20 Optical fiber 30 Galvano head 31 Housing 32 Collimating lens 33 Reflecting mirror 34 Condenser lens 40 Galvano scanner 50 Controller 51 Control unit 52 Memory 100 Laser welding device 200 Workpiece LB Laser light

Claims

1. A laser welding device comprising: a laser oscillator that generates a laser beam; a processing head that irradiates the laser beam so as to move along a weld line having at least a curved portion and scan it two-dimensionally to periodically draw a predetermined pattern on the surface of a workpiece; and a controller that controls the movement of the processing head along the weld line and the two-dimensional scanning of the laser beam, wherein the controller controls the two-dimensional scanning of the laser beam on the curved portion so that a first overlap rate indicating an overlap rate of the pattern on one side based on the periodic drawing of the pattern on the curved portion and a second overlap rate indicating an overlap rate of the pattern on the other side based on the periodic drawing of the pattern on the curved portion are equal.

2. The laser welding device according to claim 1, wherein the pattern is a Lissajous pattern in the shape of a figure eight or a figure infinity, and the controller controls the two-dimensional scanning of the laser light so that the center position of the Lissajous pattern passes through the weld line and the start and end positions of one period of the Lissajous pattern in the curved portion are different.

3. The laser welding apparatus of claim 1, wherein the controller includes a memory that stores one or more first parameters for defining the first overlap ratio and one or more second parameters for defining the second overlap ratio.

4. The laser welding device according to claim 2, wherein the controller calculates the first overlap rate based on a length of overlap between the Lissajous pattern on one side of the mth cycle (m: integer greater than or equal to 1) of the curved portion and the Lissajous pattern on the one side of the (m+1)th cycle of the curved portion, and a length of one cycle of the Lissajous pattern; and calculates the second overlap rate based on a length of overlap between the Lissajous pattern on the other side of the mth cycle of the curved portion and the Lissajous pattern on the other side of the (m+1)th cycle of the curved portion, and a length of one cycle of the Lissajous pattern.

5. The laser welding device according to claim 2, wherein the weld line further has a straight line portion, and the controller calculates a third overlap ratio indicating an overlap ratio of the Lissajous pattern on one side based on the periodic drawing of the Lissajous pattern on the straight line portion, calculates a fourth overlap ratio indicating an overlap ratio of the Lissajous pattern on the other side based on the periodic drawing of the Lissajous pattern on the straight line portion, and controls the two-dimensional scanning of the laser light on the curved portion so that the first overlap ratio, the second overlap ratio, the third overlap ratio, and the fourth overlap ratio are all equal.

6. The laser welding device according to claim 5, wherein the controller calculates the third overlap rate based on a length of overlap between the Lissajous pattern on one side of the nth cycle (n: integer equal to or greater than 1) in the straight line portion and the Lissajous pattern on the one side of the (n+1)th cycle, and a length of one cycle of the Lissajous pattern; and calculates the fourth overlap rate based on a length of overlap between the Lissajous pattern on the other side of the nth cycle in the straight line portion and the Lissajous pattern on the other side of the (n+1)th cycle, and a length of one cycle of the Lissajous pattern.

7. A laser welding method which is executed by a laser welding device having at least a laser oscillator which generates laser light, a processing head, and a controller, and which comprises the steps of: irradiating the laser light so as to move along a weld line having at least a curved portion while scanning it two-dimensionally to periodically draw a predetermined pattern on the surface of a workpiece; and controlling the movement of the processing head along the weld line and the two-dimensional scanning of the laser light, wherein in the step of controlling the two-dimensional scanning of the laser light, the two-dimensional scanning of the laser light is controlled at the curved portion so that a first overlap rate indicating an overlap rate of the pattern on one side based on the periodic drawing of the pattern at the curved portion and a second overlap rate indicating an overlap rate of the pattern on the other side based on the periodic drawing of the pattern at the curved portion are equal.

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