Laser welding method and laser welding device

Abstract

To provide a laser welding method that can equalize an amount of heat input in a laser beam scanning pattern and acquire a well-shaped weld bead.SOLUTION: A laser welding method comprises a welding step of welding a workpiece 200 by two-dimensionally scanning a laser beam LB and irradiating the surface of the workpiece 200 with the laser beam while advancing the laser beam LB in an X direction. In the welding step, the laser beam LB is scanned so as to draw a prescribed pattern on the surface of the workpiece 200. Furthermore, a drawing velocity V and an output P of the laser beam LB are controlled so that an amount of heat input per unit drawing length in a prescribed pattern is constant over the whole length of the prescribed pattern, and satisfies P / V=C (C is a constant). The prescribed pattern is such that two annular patterns are continuous while being in contact with each other at one point.SELECTED DRAWING: Figure 5

Description

[Technical Field]

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

[0002] Laser welding allows for high-speed, high-quality welding due to the high power density of the laser beam irradiated onto the workpiece. In particular, scanning welding, in which welding is performed while scanning the surface of the workpiece with a laser beam 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). Regarding laser beam scanning methods, methods have been proposed in which the laser beam is scanned so as to draw a Lissajous pattern on the surface of the workpiece (see, for example, Patent Document 2 and Patent Document 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-095934 [Patent Document 2] Japanese Patent Application Publication No. 177983 / 1983 [Patent Document 3] Japanese Patent Application Publication No. 11-104877 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional methods disclosed in Patent Documents 2 and 3, when drawing a Lissajous pattern on the surface of a workpiece, the drawing speed, in other words, the welding speed, may not be constant in each part of the pattern. In particular, a large speed difference may occur between the linearly drawn part and the part where the pattern direction changes.

[0005] If a large speed difference occurs during drawing of a Lissajous pattern, the amount of heat input to the workpiece, specifically the amount of heat input per unit drawing length, will vary depending on the location of the pattern, or in other words, the molten pool. This means that the amount of heat input to the workpiece will be uneven within the Lissajous pattern (molten pool), potentially resulting in an unsatisfactory weld bead shape during welding. This problem also occurs when the laser beam scanning pattern is not a Lissajous pattern, for example, when two circular patterns are connected at a single point.

[0006] The present disclosure has been made in consideration of these points, and its purpose is to provide a laser welding method and laser welding apparatus that can make the heat input amount uniform within the scanning pattern of the laser light and obtain a weld bead with a good shape. [Means for solving the problem]

[0007] In order to achieve the above object, the laser welding method according to the present disclosure includes a welding step of welding the workpiece by two-dimensionally scanning the laser light while advancing in a first direction and irradiating the workpiece surface with the laser light, wherein in the welding step, the laser light is scanned to draw a predetermined pattern on the surface of the workpiece, and further, the drawing speed and output of the laser light are controlled so that the heat input per unit drawing length in the predetermined pattern is the same over the entire length of the predetermined pattern, wherein the predetermined pattern is a continuous pattern in which two annular patterns are in contact at one point, and where the output of the laser light is P and the drawing speed of the laser light is V, the output of the laser light P and the drawing speed of the laser light V are controlled so that the relationship between the output of the laser light P and the drawing speed of the laser light V satisfies the relationship expressed by the equation P / V=C, where C is a constant and has a value corresponding to at least the shape of the welded portion of the workpiece or the shape of the penetration at the welded portion.

[0008] A laser welding apparatus according to the present disclosure includes at least a laser oscillator that generates laser light, a laser head that receives the laser light and irradiates it toward a workpiece, and a controller that controls the operation of the laser head, wherein the laser head has a laser light scanner that scans the laser light in each of a first direction and a second direction intersecting the first direction, and the controller drives and controls the laser light scanner so that the laser light draws a predetermined pattern on the surface of the workpiece. The controller also controls the drawing speed and output of the laser light so that the heat input per unit drawing length in the predetermined pattern is constant over the entire length of the predetermined pattern, wherein the predetermined pattern is a continuous pattern in which two annular patterns contact each other at one point, and wherein the output of the laser light is P and the drawing speed of the laser light is V, and the controller controls the output P of the laser light and the drawing speed V of the laser light so that the relationship between the output P of the laser light and the drawing speed V of the laser light satisfies the relationship expressed by the equation P / V=C, where C is a constant and has a value that corresponds to at least the shape of the welded portion of the workpiece or the shape of the penetration at the welded portion. [Effects of the Invention]

[0009] According to the present disclosure, it is possible to make the amount of heat input within the scanning pattern of the laser light uniform and obtain a weld bead with a good shape. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a laser welding device according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram of the laser beam scanner. [Figure 3] FIG. 3 is a schematic diagram illustrating the drawing distance in a Lissajous pattern. [Figure 4] FIG. 4 is a diagram showing a scanning pattern of the laser light according to this embodiment. [Figure 5] FIG. 5 is a diagram showing the relationship between the drawing speed and output of the laser beam relative to the drawing position of the laser beam. [Figure 6A] FIG. 6A is a diagram showing a first scanning pattern of a laser beam according to Modification 1. FIG. [Figure 6B] FIG. 6B is a diagram showing a second scanning pattern of the laser light according to the first modification. [Figure 7A] FIG. 7A is a diagram showing a third scanning pattern of the laser light according to the first modification. [Figure 7B] FIG. 7B is a diagram showing a fourth scanning pattern of the laser light according to the first modification. [Figure 7C] FIG. 7C is a diagram showing a fifth scanning pattern of the laser light according to the first modification. [Figure 8] FIG. 8 is a diagram showing an example of a combination of parameters when drawing a Lissajous pattern. [Figure 9] FIG. 9 is a diagram showing the relationship between the drawing position of the laser beam and the drawing speed of the laser beam according to the second embodiment. [Figure 10A] FIG. 10A is a diagram showing a first scanning pattern of a laser beam according to Modification 2. FIG. [Figure 10B] FIG. 10B is a diagram showing a second scanning pattern of the laser light according to the second modification. [Figure 10C] FIG. 10C is a diagram showing a third scanning pattern of the laser light according to the second modification. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses.

[0012] (Embodiment 1) [Configuration of laser welding device and laser beam scanner] FIG. 1 is a schematic diagram showing the configuration of a laser welding device according to this embodiment, and FIG. 2 is a schematic diagram showing the configuration of a laser beam scanner.

[0013] In the following description, the direction parallel to the traveling direction of the laser light LB from the reflecting mirror 33 toward the laser light 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 laser head 30 as the Z direction, and the direction perpendicular to the X direction and the Z direction as the Y direction. When the surface of the workpiece 200 is flat, the XY plane including the X direction and the Y direction within the plane may be approximately parallel to the surface or may form a certain angle with the surface.

[0014] As shown in FIG. 1, the laser welding apparatus 100 includes a laser oscillator 10, an optical fiber 20, a laser head 30, a controller 50, and a manipulator 60.

[0015] The laser oscillator 10 is a laser light source that receives power from a power source (not shown) and generates laser light LB. The laser oscillator 10 may be configured with a single laser light source or multiple laser modules. In the latter case, laser light emitted from the multiple laser modules is combined and emitted as laser light LB. The laser light source or laser module used in the laser oscillator 10 is selected appropriately depending on the material of the workpiece 200, the shape of the welding portion, etc.

[0016] For example, a fiber laser, a disk laser, or a YAG (Yttrium Aluminum Garnet) 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 400 nm to 600 nm.

[0017] The optical fiber 20 is optically coupled to the laser oscillator 10 , and the laser light LB generated by the laser oscillator 10 is incident on the optical fiber 20 and transmitted through the optical fiber 20 toward the laser head 30 .

[0018] The laser head 30 is attached to the end of the optical fiber 20 and irradiates the laser light LB transmitted from the optical fiber 20 toward the workpiece 200 .

[0019] The laser head 30 also has optical components, such as a collimation lens 32, a reflecting mirror 33, a focusing lens 34, and a laser light scanner 40, and these optical components are housed inside the housing 31 while maintaining a predetermined arrangement relationship.

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

[0021] The reflecting mirror 33 reflects the laser light LB that has passed through the collimation lens 32 and makes it incident on the laser light 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 collimation lens 32.

[0022] The condenser lens 34 condenses the laser light LB, which has been reflected by the reflecting mirror 33 and scanned by the laser light scanner 40, onto the surface of the workpiece 200.

[0023] 2, the laser beam scanner 40 is a known galvanometer scanner having a first galvanometer mirror 41 and a second galvanometer mirror 42. The first galvanometer mirror 41 has a first mirror 41a, a first rotation shaft 41b, and a first driver 41c, and the second galvanometer mirror 42 has a second mirror 42a, a second rotation shaft 42b, and a second driver 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.

[0024] For example, the first driver 41c and the second driver 42c are galvanometer motors, and 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.

[0025] The first mirror 41a rotates around the axis of the first rotation shaft 41b to a predetermined angle, causing the laser light LB to scan in the X direction. The second mirror 42a rotates around the axis of the second rotation shaft 42b to a predetermined angle, causing the laser light LB to scan in the Y direction. In other words, the laser light scanner 40 is configured to two-dimensionally scan the laser light LB within the XY plane and irradiate it toward the workpiece 200.

[0026] The controller 50 controls the laser oscillation of the laser oscillator 10. Specifically, the controller 50 controls the laser oscillation by supplying control signals such as output current and on / off time to a power supply (not shown) connected to the laser oscillator 10.

[0027] Furthermore, the controller 50 controls the operation of the laser head 30 in accordance with the contents of the selected laser welding program. Specifically, the controller 50 controls the driving of a driving unit (not shown) of the laser beam scanner 40 and the collimation lens 32 provided in the laser head 30. Furthermore, the controller 50 controls the operation of the manipulator 60. The laser welding program is stored in a storage unit (not shown) provided inside the controller 50 or in a separate location, and is called by the controller 50 in response to a command from the controller 50.

[0028] The controller 50 has an integrated circuit such as an LSI or a microcomputer (not shown), and the integrated circuit executes a laser welding program, which is software, to realize the functions of the controller 50. Note that the controller 50 that controls the operation of the laser head 30 and the controller 50 that controls the output of the laser light LB may be provided separately.

[0029] The manipulator 60 is an articulated robot, and is attached to the housing 31 of the laser head 30. The manipulator 60 is connected to the controller 50 so as to be able to exchange signals, and moves the laser head 30 so as to trace a predetermined trajectory in accordance with the laser welding program described above. A separate controller (not shown) for controlling the operation of the manipulator 60 may be provided.

[0030] [About the drawing speed of Lissajous patterns] 3 is a schematic diagram illustrating the drawing distance of a Lissajous pattern. As shown in FIG. 3, laser light LB is scanned in an XY plane, in this case, on the surface of workpiece 200, so as to draw a Lissajous pattern (hereinafter also referred to as a Lissajous figure).

[0031] The width in the X direction of the Lissajous pattern shown in FIG. 3 is equal to the width in the Y direction, and when the welding speed is very fast, the width in the Y direction is approximately equal to the width W of the weld bead (not shown) in the Y direction. On the other hand, when the welding speed is slow, the width of the weld bead increases due to the influence of heat conduction, so the width in the Y direction of the Lissajous pattern is slightly narrower than the width of the weld bead in the Y direction. Note that in this specification, "substantially equal" or "substantially 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, "substantially equal" or "substantially the same" is also used to mean the same or identical, including manufacturing tolerances and assembly tolerances of each part, etc.

[0032] The Lissajous pattern shown in Fig. 3 is obtained by oscillating the laser light LB in the X direction in a sinusoidal manner at a predetermined frequency and in the Y direction in a sinusoidal manner at a frequency different from that in the X direction (half the frequency in the X direction). As described above, the scanning patterns of the laser light LB in the X and Y directions are determined based on the rotational motion of the first mirror 41a and the second mirror 42a. Generally, when the position coordinate of the Lissajous pattern shown in Fig. 3 obtained by driving the first mirror 41a is set to X1 and the position coordinate of the Lissajous pattern shown in Fig. 3 obtained by driving the second mirror 42a is set to Y1, the position coordinates X1 and Y1 are expressed by the following equations (1) and (2), respectively.

[0033] X1=a×sin(nt) (1) Y1=b×sin(mt+φ) (2) where: a: Amplitude in the X direction of the Lissajous pattern shown in Figure 3 b: Amplitude in the Y direction of the Lissajous pattern shown in Figure 3 n: frequency of the first mirror 41a m: frequency of the second mirror 42a t: time φ: the phase difference when the first mirror 41a or the second mirror 42a is driven, and more specifically, the amount of angular deviation provided when the first mirror 41a and the second mirror 42a are rotated.

[0034] The position coordinates X1 and Y1 shown in equations (1) and (2) are expressed in a stationary coordinate system of the Lissajous waveform with the position of the laser head 30 fixed.

[0035] Furthermore, frequencies n and m correspond to the drive frequencies of first mirror 41a and second mirror 42a, respectively.

[0036] The Lissajous pattern shown in Fig. 3 is an eight-shaped Lissajous pattern that corresponds to the case where a = 1, b = 1, n = 2, m = 1, and φ = 0 in equations (1) and (2). a and b are normalized to 1. Note that the phase difference φ in equations (1) and (2) can be either 0 degrees or 180 degrees.

[0037] As shown in FIG. 3, when the drawing distance of the Lissajous pattern in the X direction at a given time variation Δt is ΔX, the drawing distance in the Y direction is ΔY, and the drawing distance of the Lissajous pattern at the time variation Δt is ΔL, ΔX, ΔY, and ΔL are respectively expressed by the following equations (3) to (5).

[0038] ΔX= a×n×cos(nt)×Δt (3) ΔY= b×m×cos(mt+φ)×Δt (4) ΔL= Δt×{(ΔX) 2 +(ΔY) 2} 1 / 2 ···(5) Therefore, the drawing speed V of the Lissajous pattern is expressed by the following equation (6).

[0039] V= ΔL / Δt (6) [Laser welding method] Fig. 4 shows a scanning pattern of the laser beam according to this embodiment, and Fig. 5 shows the relationship between the drawing speed and output of the laser beam relative to the drawing position of the laser beam. The scanning pattern shown in Fig. 4 has the same shape as the Lissajous pattern shown in Fig. 3. That is, the scanning pattern shown in Fig. 4 is an eight-shaped Lissajous pattern corresponding to the above-mentioned formulas (1) and (2) where a = 1, b = 1, n = 2, m = 1, and φ = 0. The size of the actual Lissajous pattern, that is, the amplitude in the X and Y directions, varies depending on the workpiece to be welded, but is approximately 1 mm to 10 mm each.

[0040] 5 is a value calculated based on the above-mentioned formula (6). The drawing speed V of the laser beam LB is normalized by setting the drawing speed of the laser beam LB when it passes through the origin O to 1. Similarly, the output power P of the laser beam LB is normalized by setting the output power of the laser beam LB when it passes through the origin O to 1.

[0041] In this embodiment, the laser head 30 is moved in the X direction at a predetermined speed by the manipulator 60, while the laser beam LB is irradiated onto the surface of the workpiece 200. Furthermore, an example will be described in which the laser beam LB is two-dimensionally scanned using a laser beam scanner 40 to draw a Lissajous pattern on the surface of the workpiece 200 as shown in Fig. 4, thereby laser welding the workpiece 200. The pattern shown in Fig. 4 is obtained by scanning the laser beam LB from the origin O through drawing positions A → B → C → O → D → E → F → O during one cycle.

[0042] In this embodiment, when the output of the laser light LB is P, the output P and the drawing speed V of the laser light LB are controlled so that the relationship between the drawing speed V and the output P when drawing the Lissajous pattern shown in FIG. 4 with the laser light LB satisfies the relationship shown in the following equation (7).

[0043] P / V=C (7) Here, C is a constant, and is a value that depends on the shape of the welded portion of the workpiece 200, which is the object to be welded, the penetration shape at the welded portion, and the like.

[0044] Normally, when scanning the laser light LB to draw the Lissajous pattern shown in Figure 4 on the surface of the workpiece 200, the drawing speed V decreases at each of the direction change parts in the Lissajous pattern, i.e., near the drawing positions A, C, D, and F, as shown in Figure 5.

[0045] In this case, if the output power P of the laser beam LB is the same at each drawing position, the heat input per unit drawing length of the Lissajous pattern shown in Fig. 4 will differ depending on the drawing position, as shown by the dashed line in Fig. 5. For example, the heat input per unit drawing length near drawing position B will be smaller than the heat input per unit drawing length near origin O.

[0046] In this case, as mentioned above, the amount of heat input to each irradiated portion of the laser beam LB during welding is non-uniform, which may result in a poorly shaped weld bead and a stable keyhole depth and a constant penetration depth. Also, this may narrow the appropriate range of conditions for the drawing speed V and output power P of the laser beam LB during laser welding.

[0047] Therefore, in this embodiment, the laser beam LB is controlled so that the drawing speed V and output power P of the laser beam LB satisfy the relationship shown in the above-mentioned formula (7). In other words, the drawing speed V and output power P of the laser beam are controlled so that the heat input per unit drawing length in the Lissajous pattern is the same over the entire length of the Lissajous pattern.

[0048] Specifically, as shown by the solid lines in Fig. 5, the output power P of the laser light LB is controlled to increase as the laser light LB approaches the drawing positions A, C, D, and F where the drawing speed V decreases. Also, the output power P of the laser light LB is controlled to decrease as the laser light LB moves away from the drawing positions A, C, D, and F.

[0049] Furthermore, the output power P of the laser light LB is controlled to decrease as the laser light LB approaches the drawing positions O, B, and E where the drawing speed V increases. The output power P of the laser light LB is controlled to increase as the laser light LB moves away from the drawing positions O, B, and E. Both the drawing speed V and the output power P change continuously with respect to the drawing position.

[0050] [Effects, etc.] As described above, the laser welding method according to this embodiment includes a welding step in which the laser beam LB is caused to travel in the X direction (first direction) and is scanned two-dimensionally to irradiate the surface of the workpiece 200, thereby welding the workpiece 200.

[0051] In the welding step, the laser beam LB is oscillated along the X direction in a sinusoidal manner having a first frequency corresponding to frequency n, and along the Y direction in a sinusoidal manner having a second frequency corresponding to frequency m, thereby scanning the laser beam LB so as to trace a Lissajous pattern on the surface of the workpiece 200.

[0052] The drawing speed V and output P of the laser beam LB are controlled so that the heat input per unit drawing length in the Lissajous pattern is the same over the entire length of the Lissajous pattern. Furthermore, the output P of the laser beam LB and the drawing speed V of the laser beam LB are controlled so that the relationship between the output P of the laser beam LB and the drawing speed V of the laser beam LB satisfies the relationship expressed by the formula P / V=C. C is a constant, and is a value that corresponds at least to the shape of the welded portion of the workpiece 200 or the shape of the penetration in the welded portion.

[0053] According to the laser welding method of this embodiment, the heat input per unit drawing length in the Lissajous pattern can be made the same over the entire length of the Lissajous pattern, thereby stabilizing the depth of a keyhole (not shown) in the welded portion and maintaining a constant penetration depth in the welded portion. This also makes it possible to improve the shape of the weld bead. Furthermore, the process margin for laser welding can be ensured without narrowing the appropriate condition ranges for the drawing speed V and output P of the laser beam LB.

[0054] The laser welding apparatus 100 of this embodiment includes at least a laser oscillator 10 that generates laser light LB, a laser head 30 that receives the laser light LB and irradiates it toward the workpiece 200, and a controller 50 that controls the operation of the laser head 30.

[0055] The laser head 30 has a laser beam scanner 40 that scans the laser beam LB in both an X direction (first direction) and a Y direction (second direction) that intersects with the X direction.

[0056] The controller 50 vibrates the laser beam LB in a sinusoidal wave shape having a first frequency along the X direction, and vibrates the laser beam LB in a sinusoidal wave shape having a second frequency along the Y direction. In this way, the controller 50 drives and controls the laser beam scanner 40 so that the laser beam LB draws a Lissajous pattern on the surface of the workpiece 200.

[0057] The controller 50 controls the drawing speed V and output power P of the laser beam LB so that the heat input per unit drawing length in the Lissajous pattern is constant over the entire length of the Lissajous pattern. Furthermore, the controller 50 controls the output power P of the laser beam LB and the drawing speed V of the laser beam LB so that the relationship between the output power P of the laser beam LB and the drawing speed V of the laser beam LB satisfies the relationship expressed by the formula P / V=C. C is a constant, and is a value that corresponds at least to the shape of the welded portion of the workpiece 200 or the shape of the penetration at the welded portion.

[0058] The laser welding apparatus 100 of this embodiment can stabilize the keyhole depth and maintain a constant penetration depth. It can also improve the shape of the weld bead. It can also ensure the process margin of laser welding without narrowing the appropriate range of conditions for the drawing speed V and output P of the laser beam LB.

[0059] The laser welding apparatus 100 further includes a manipulator 60 to which the laser head 30 is attached, and the controller 50 controls the operation of the manipulator 60. The manipulator 60 moves the laser head 30 in a predetermined direction relative to the surface of the workpiece 200.

[0060] In this way, the welding direction of the laser beam LB can be changed by providing the manipulator 60. Furthermore, laser welding can be easily performed on the workpiece 200 having a complex shape, for example, a three-dimensional shape.

[0061] The laser oscillator 10 and the laser head 30 are connected by an optical fiber 20 , and the laser light LB is transmitted from the laser oscillator 10 to the laser head 30 through the optical fiber 20 .

[0062] By providing the optical fiber 20 in this manner, it becomes possible to perform laser welding on the workpiece 200 that is placed at a position distant from the laser oscillator 10. This increases the degree of freedom in arranging each part of the laser welding apparatus 100.

[0063] The laser light scanner 40 is composed of a first galvanometer mirror 41 that scans the laser light LB in the X direction, and a second galvanometer mirror 42 that scans the laser light LB in the Y direction.

[0064] By configuring the laser beam scanner 40 in this manner, it is possible to easily perform two-dimensional scanning with the laser beam LB. Furthermore, since a known galvanometer scanner is used as the laser beam scanner 40, an increase in the cost of the laser welding apparatus 100 can be suppressed.

[0065] The laser head 30 further includes a collimation lens 32, which is configured to change the focal position of the laser light LB along the Z direction intersecting both the X direction and the Y direction. In other words, the collimation lens 32, in combination with a drive unit (not shown), also functions as a focal position adjustment mechanism for the laser light LB.

[0066] In this way, the focal position of the laser light LB can be easily changed, and the laser light LB can be appropriately irradiated according to the shape of the workpiece 200.

[0067] In this embodiment, the laser head 30 is moved in the X direction to cause the laser light LB to travel in the X direction, but this is not particularly limited. The laser head 30 may be moved in the Y direction to cause the laser light LB to travel in the Y direction.

[0068] Furthermore, the drawing direction of the Lissajous pattern is not particularly limited to the above. For example, a Lissajous pattern may be drawn by scanning the laser light LB from the origin O through drawing positions C → B → A → O → F → E → D → O during one cycle. A Lissajous pattern may be drawn by scanning the laser light LB from the origin O through drawing positions D → E → F → O → A → B → C → O during one cycle. A Lissajous pattern may be drawn by scanning the laser light LB from the origin O through drawing positions F → E → D → O → C → B → A → O during one cycle.

[0069] <Variation 1> Fig. 6A shows a first scanning pattern of the laser light according to this modification, and Fig. 6B shows a second scanning pattern. Fig. 7A shows a third scanning pattern of the laser light according to this modification, and Fig. 7B shows a fourth scanning pattern and Fig. 7B shows a fifth scanning pattern. Fig. 8 shows an example of a combination of parameters when drawing a Lissajous pattern. Note that in Fig. 6A and the following drawings, parts similar to those in embodiment 1 are designated by the same reference numerals, and detailed description thereof will be omitted.

[0070] In actual laser welding, the parameters a, b, n, and m shown in equations (1) and (2) can be changed as appropriate depending on the material of the workpiece 200, the joint shape, the desired bead shape width, etc. Therefore, the scanning pattern of the laser light LB is not particularly limited to the pattern shown in FIG.

[0071] For example, as shown in Figures 6A and 6B, the parameter a may be reduced to reduce the amplitude of the Lissajous pattern in the X direction. Alternatively, as shown in Figure 7A, by setting frequency n = 1 and frequency m = 2, a scanning pattern may be generated in which the Lissajous pattern shown in Figure 4 is rotated by 90 degrees. Alternatively, as shown in Figures 7B and 7C, the parameter b may be reduced to reduce the amplitude of the Lissajous pattern shown in Figure 7A in the Y direction.

[0072] Furthermore, the values ​​of the parameters a and b shown in equations (1) and (2) are not particularly limited to the examples shown in Figures 6A, 6B and 7A to 7C, and can take appropriate values ​​within the ranges shown in Figure 8. In Figure 8, the Lissajous patterns shown in Figures 4, 6A and 6B are classified as pattern group 1, and the Lissajous patterns shown in Figures 7A to 7C are classified as pattern group 2.

[0073] Furthermore, by setting 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 of the first frequency, which is the oscillation frequency in the X direction of the laser light LB, to the second frequency, which is the oscillation frequency in the Y direction, to 2:1 or 1:2, a Lissajous pattern in the shape of a figure eight can be obtained. Furthermore, as long as this frequency ratio is maintained, the drive frequencies of the first mirror 41a and the second mirror 42a may each be changed depending on the shape of the workpiece 200 or the required bead shape.

[0074] (Embodiment 2) FIG. 9 shows the relationship between the drawing position of the laser beam and the drawing speed of the laser beam.

[0075] 9, in this embodiment, the drawing speed of the laser beam LB is controlled to be constant regardless of the drawing position of the laser beam LB. That is, in the laser welding method according to this embodiment, the drawing speed V of the laser beam LB is controlled to be constant over the entire length of the Lissajous pattern in the welding step. Furthermore, in the laser welding apparatus 100 according to this embodiment, the controller 50 controls the drawing speed of the laser beam LB to be constant over the entire length of the Lissajous pattern.

[0076] Also in this embodiment, as in the first embodiment, the output P and drawing speed V of the laser beam LB are controlled so as to satisfy the relationship shown in equation (7). Therefore, in this embodiment, the drawing speed V of the laser beam LB is controlled to be constant and the output P is also controlled to be constant over the entire length of the Lissajous pattern. However, the drawing speed V in this case does not satisfy the relationship shown in equations (3) to (6).

[0077] This configuration can achieve the same effects as those achieved by the configuration shown in embodiment 1. In other words, the heat input per unit drawing length in the Lissajous pattern can be made the same over the entire length of the Lissajous pattern, stabilizing the keyhole depth and maintaining a constant penetration depth. This also improves the shape of the weld bead. Furthermore, by making the drawing speed V and output P of the laser beam LB constant over the entire length of the Lissajous pattern, scanning control of the laser beam LB is simplified. Furthermore, control of the heat input to the workpiece 200 becomes easier.

[0078] <Variation 2> 10A to 10C respectively show first to third scanning patterns of the laser beam according to this modified example, in which the arrows indicate the drawing direction of the laser beam LB.

[0079] The scanning pattern of the laser light LB of the present disclosure is not limited to the Lissajous pattern shown in the first embodiment and the first modification. For example, as shown in FIG. 10A, the scanning pattern may be a composite pattern of two circular patterns that are symmetrically arranged with respect to the X axis and that are in contact with each other at the origin O. Alternatively, as shown in FIG. 10B, the scanning pattern may be a composite pattern of two elliptical patterns that are symmetrically arranged with respect to the X axis and that are in contact with each other at the origin O. In the example shown in FIG. 10B, 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 be in the X direction and the minor axis may be in the Y direction. As shown in FIG. 10C, the scanning pattern may be a composite pattern of two diamond patterns that are symmetrically arranged with respect to the X axis and that are in contact with each other at the origin O. Although not shown, each of the scanning patterns shown in FIGS. 10A to 10C may be a composite pattern of two annular patterns that are symmetrically arranged with respect to the Y axis. In this case, each of the two annular patterns may be rotated 90 degrees from the example shown in FIGS. 10A to 10C. Furthermore, the size of each of the two annular patterns may be changed as appropriate.

[0080] 10A to 10C and their modifications. These patterns can be obtained by driving the first mirror 41a and the second mirror 42a in accordance with predetermined driving patterns.

[0081] Therefore, in the welding step of the laser welding method of the present disclosure, the laser beam LB is scanned over the surface of the workpiece 200 so as to draw a predetermined pattern.

[0082] Furthermore, the drawing speed V and output power P of the laser light LB are controlled so that the heat input per unit drawing length in a predetermined pattern is the same over the entire length of the predetermined pattern.

[0083] Furthermore, the controller 50 in the laser welding apparatus 100 of the present disclosure controls the driving of the laser beam scanner 40 so that the laser beam LB draws a predetermined pattern on the surface of the workpiece 200.

[0084] Furthermore, the controller 50 controls the drawing speed V and output power P of the laser light LB so that the amount of heat input per unit drawing length in a predetermined pattern is the same over the entire length of the predetermined pattern.

[0085] The "predetermined pattern" that is the scanning pattern of the laser light LB is a pattern in which two circular patterns are continuous and contact each other at one point, in this case the origin O. Furthermore, the two circular patterns are the same pattern. It goes without saying that the "predetermined pattern" includes the Lissajous pattern disclosed in this specification.

[0086] By configuring the laser welding method and laser welding apparatus 100 in this way, it is possible to achieve the same effects as those achieved by the configurations shown in the first and second embodiments and the first modification.

[0087] (Other embodiments) The components shown in the first and second embodiments and the first and second modifications can be combined as appropriate to form new embodiments.

[0088] For example, when drawing each of the scanning patterns shown in Modifications 1 and 2, as shown in the second embodiment, the drawing speed V and output power P of the laser light LB can be controlled to be constant over the entire length of the predetermined pattern.

[0089] Furthermore, in the first and second modifications and the second embodiment, for example, a predetermined pattern may be drawn by scanning the laser light LB from the origin O through drawing positions C → B → A → O → F → E → D → O during one cycle. Alternatively, a predetermined pattern may be drawn by scanning the laser light LB from the origin O through drawing positions D → E → F → O → A → B → C → O during one cycle. Alternatively, a predetermined pattern may be drawn by scanning the laser light LB from the origin O through drawing positions F → E → D → O → C → B → A → O during one cycle.

[0090] In the example shown in FIG. 1, the focusing lens 34 is arranged in front of the laser light scanner 40, but it may also be arranged in the rear of the laser light scanner 40, that is, between the laser light scanner 40 and the light emission port of the laser head 30.

[0091] Furthermore, the scanning pattern of the laser light LB may be a Lissajous pattern by oscillating the laser light LB in a cosine wave shape having a first frequency along the X direction and in a cosine wave shape having a second frequency along the Y direction. In this case, it goes without saying that the amplitudes a and b of the first mirror 41 a and the second mirror 42 a, the frequencies n and m of the first mirror 41 a and the second mirror 42 a, and the phase φ are changed as appropriate. [Industrial Applicability]

[0092] The laser welding method and laser welding method of the present disclosure are useful because they can produce a good weld bead shape. [Explanation of symbols]

[0093] 10 Laser oscillator 20 Optical Fiber 30 laser head 31 Case 32 Collimation Lens 33 Reflective mirror 34 Condenser Lens 40 Laser light scanner 41 First Galvanometer Mirror 41a 1st mirror 41b First rotation axis 41c First drive unit 42 Second Galvanometer Mirror 42a 2nd mirror 42b Second rotation axis 42c Second drive unit 50 Controllers 60 Manipulator 200 Work

Claims

1. a welding step of welding the workpieces by two-dimensionally scanning the laser light onto a surface of the workpiece while causing the laser light to travel in a first direction, In the welding step, scanning the laser light so as to draw a predetermined pattern on the surface of the workpiece; Furthermore, the drawing speed and output of the laser beam are controlled so that the heat input per unit drawing length in the predetermined pattern is the same over the entire length of the predetermined pattern; the predetermined pattern is a continuous pattern in which two circular patterns are in contact with each other at one point, When the output of the laser beam is P and the drawing speed of the laser beam is V, The relationship between the output power P of the laser beam and the drawing speed V of the laser beam is P / V = C To satisfy the relationship shown in the formula, controlling the output power P of the laser beam and the drawing speed V of the laser beam; A laser welding method characterized in that C is a constant and has a value that corresponds to at least the shape of the welded portion of the workpiece or the shape of the penetration at the welded portion.

2. The laser welding method according to claim 1, the predetermined pattern is a Lissajous pattern in the shape of a figure eight or a figure infinity, In the welding step, the laser beam is vibrated sinusoidally with a first frequency along the first direction, and also vibrated sinusoidally with a second frequency along a second direction intersecting the first direction, thereby scanning the laser beam to trace the Lissajous pattern on the surface of the workpiece.

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

2.

4. 4. The laser welding method according to claim 1, A laser welding method, characterized in that the drawing speed of the laser beam is controlled to be constant over the entire length of the predetermined pattern.

5. a laser oscillator that generates laser light; a laser head that receives the laser light and irradiates it toward a workpiece; a controller for controlling the operation of the laser head; the laser head has a laser beam scanner that scans the laser beam in a first direction and a second direction intersecting the first direction, and the controller drives and controls the laser beam scanner so that the laser beam draws a predetermined pattern on the surface of the workpiece; Furthermore, the controller controls the drawing speed and output of the laser beam so that the amount of heat input per unit drawing length in the predetermined pattern is the same over the entire length of the predetermined pattern; the predetermined pattern is a continuous pattern in which two circular patterns are in contact with each other at one point, When the output of the laser beam is P and the drawing speed of the laser beam is V, The relationship between the output power P of the laser beam and the drawing speed V of the laser beam is P / V = C To satisfy the relationship shown in the formula, controlling the output power P of the laser beam and the drawing speed V of the laser beam; A laser welding device characterized in that C is a constant and has a value that corresponds to at least the shape of the welded portion of the workpiece or the shape of the penetration at the welded portion.

6. 6. The laser welding apparatus according to claim 5, the predetermined pattern is a Lissajous pattern in the shape of a figure eight or a figure infinity, The laser welding device is characterized in that the controller drives and controls the laser beam scanner so that the laser beam draws the Lissajous pattern on the surface of the workpiece by vibrating the laser beam in a sinusoidal wave shape having a first frequency along the first direction and in a sinusoidal wave shape having a second frequency along the second direction.

7. 7. The laser welding apparatus according to claim 6, A laser welding apparatus, characterized in that the ratio of the first frequency to the second frequency is 2:1 or 1:

2.

8. 8. The laser welding apparatus according to claim 5, The laser welding device is characterized in that the controller controls the drawing speed of the laser beam so as to be constant over the entire length of the predetermined pattern.

9. 9. The laser welding apparatus according to claim 5, Further comprising a manipulator to which the laser head is attached, the controller controls the operation of the manipulator; The laser welding device is characterized in that the manipulator moves the laser head in a predetermined direction relative to the surface of the workpiece.

10. 10. The laser welding apparatus according to claim 5, The laser oscillator and the laser head are connected by an optical fiber, The laser welding device is characterized in that the laser light is transmitted from the laser oscillator to the laser head through the optical fiber.

11. 11. The laser welding apparatus according to claim 5, a first galvanometer mirror that scans the laser beam in the first direction, and a second galvanometer mirror that scans the laser beam in a second direction that intersects with the first direction.

12. 12. The laser welding apparatus according to claim 5, the laser head further includes a focal position adjustment mechanism; The laser welding device is characterized in that the focal position adjustment mechanism is configured to change the focal position of the laser light along directions that intersect with each of the first direction and the second direction.

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