JP7656791B2 - Laser welding method and laser welding device - Google Patents

Description

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

Laser welding allows high-speed, high-quality welding because the power density of the laser light irradiated onto the workpiece to be welded is high. In particular, in scanning welding, in which welding is performed while scanning the surface of the workpiece with laser light at high speed, the laser beam can be moved quickly to the next welding point during periods when welding is not being performed, thereby shortening the total welding time (see, for example, Patent Document 1). Regarding laser light scanning methods, methods have 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 2 and Patent Document 3).

JP 2005-095934 A Japanese Patent Application Publication No. 177983/1983 Japanese Patent Application Publication No. 11-104877

However, in the conventional configurations shown in Patent Documents 2 and 3, the Lissajous pattern is typically drawn so that it has a symmetrical shape with respect to its center point (hereinafter also referred to as the origin).

However, the workpieces that are actually welded have a variety of shapes. For example, when butt welding plates of different thicknesses, the heat capacity of the workpieces becomes asymmetric on both sides of the weld line corresponding to the butt joint of the plates. Depending on the shape of the joint in the workpieces, the heat capacity of the workpieces may also become asymmetric on both sides of the weld line.

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

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 irradiates laser light to draw a predetermined pattern on the surface of a workpiece, and that can improve the shape of the weld bead formed on the workpiece.

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 laser light onto a surface of the workpiece, wherein in the welding step, the laser light is scanned so as to draw a predetermined pattern on the surface of the workpiece, and further, an amount of heat input to the workpiece is controlled according to a drawing position of the laser light in the predetermined pattern, wherein the drawing position of the laser light in the predetermined pattern has a first drawing area and a second drawing area that does not overlap with the first drawing area, and when transitioning from the first drawing area to the second drawing area, a drawing speed of the laser light is controlled to be constant and an output of the laser light is controlled to change from a first output to a second output different from the first output, or an output of the laser light is controlled to be constant and the drawing speed of the laser light is controlled to change from a first speed to a second speed different from the first speed, and the predetermined pattern is a continuous pattern in which two annular patterns are in contact at one point.

A laser welding apparatus according to the present disclosure includes at least a laser oscillator that generates a laser beam, a laser head that receives the laser beam and irradiates the laser beam toward a workpiece, and a controller that controls the operation of the laser head and the output of the laser beam, the laser head having a laser beam scanner that scans the laser beam in a first direction and a second direction intersecting the first direction, the controller drives and controls the laser beam scanner so that the laser beam draws a predetermined pattern on a surface of the workpiece, and the controller controls at least one of a drawing speed and an output of the laser beam according to a drawing position of the laser beam on the surface of the workpiece, The drawing position of the laser light in the specified pattern has a first drawing area and a second drawing area that does not overlap with the first drawing area, and when transitioning from the first drawing area to the second drawing area, the controller controls the drawing speed of the laser light to be constant and controls the output of the laser light to change from a first output to a second output different from the first output, or the controller controls the output of the laser light to be constant and controls the drawing speed of the laser light to change from a first speed to a second speed different from the first speed, and the specified pattern is characterized in that two annular patterns are continuous and touch each other at one point.

According to the present disclosure, the shape of the weld bead formed on the workpiece can be made good.

FIG. 1 is a schematic configuration diagram of a laser welding device according to a first embodiment. FIG. 2 is a schematic diagram of a laser beam scanner. FIG. 3A is a schematic diagram of a workpiece. FIG. 3B is a cross-sectional view taken along line IIIB-IIIB in FIG. 3A. FIG. 4 is a schematic cross-sectional view of another workpiece. FIG. 5 is a diagram showing a scanning pattern of the laser light. FIG. 6 is a diagram showing the relationship between the drawing position and the output of the laser light. FIG. 7 is a diagram showing a scanning pattern of laser light according to the first modification. FIG. 8 is a diagram showing the relationship between the drawing position and the output of the laser light. FIG. 9 is a diagram showing a scanning pattern of a laser beam according to the second embodiment. FIG. 10 is a diagram showing the relationship between the drawing position and the output of the laser light. FIG. 11 is a diagram showing the positional relationship between the laser beam and the molten pool formed on the workpiece according to the third embodiment. FIG. 12 is a diagram showing a scanning pattern of a laser beam. FIG. 13 is a diagram showing the relationship between the drawing position and the output of the laser light. FIG. 14 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 fourth embodiment. FIG. 15 is a diagram showing another relationship between the drawing position of the laser beam and the drawing speed of the laser beam. FIG. 16 is a diagram showing yet another relationship of the drawing speed of the laser beam to the drawing position of the laser beam. FIG. 17A is a diagram showing a first scanning pattern of a laser beam according to Modification 2. FIG. FIG. 17B is a diagram showing a second scanning pattern of the laser light according to the second modification. FIG. 18A is a diagram showing a third scanning pattern of the laser light according to the second modification. FIG. 18B is a diagram showing a fourth scanning pattern of the laser light according to the second modification. FIG. 18C is a diagram showing a fifth scanning pattern of the laser light according to the second modification. FIG. 19 is a diagram showing an example of a combination of parameters when drawing a Lissajous pattern. FIG. 20A is a diagram showing a first scanning pattern of a laser beam according to Modification 3. FIG. FIG. 20B is a diagram showing a second scanning pattern of the laser light according to the third modification. FIG. 20C is a diagram showing a third scanning pattern of the laser light according to the third modification example.

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

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

In the following description, the direction parallel to the traveling direction of the laser light LB from the reflection mirror 33 toward the laser light scanner 40 may be referred to as the X direction, 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.

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

The laser oscillator 10 is a laser light source that receives power from a power source (not shown) and generates laser light LB. The laser oscillator 10 may be composed of a single laser light source or multiple laser modules. In the latter case, the laser light emitted from each of 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 and the shape of the welded area, etc.

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.

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 therethrough toward the laser head 30.

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.

The laser head 30 also has optical components, including 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.

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

The reflecting mirror 33 reflects the laser light LB that has passed through the collimation lens 32 and causes it to enter the laser light scanner 40. The surface of the reflecting mirror 33 is arranged 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.

The focusing lens 34 focuses the laser light LB reflected by the reflecting mirror 33 and scanned by the laser light scanner 40 onto the surface of the workpiece 200.

2, the laser light scanner 40 is a known galvanometer scanner having a first galvanometer mirror 41 and a second galvanometer mirror 42. The first galvanometer mirror 41 has a first mirror 41a, a first rotation shaft 41b, and a first drive unit 41c, and the second galvanometer mirror 42 has a second mirror 42a, a second rotation shaft 42b, and a second drive unit 42c. The laser light LB transmitted through the focusing 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.

For example, the first drive unit 41c and the second drive unit 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 drive unit 41c is driven to rotate 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 around the axis of the first rotation shaft 41b. Similarly, the second drive unit 42c is driven to rotate 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 around the axis of the second rotation shaft 42b.

The first mirror 41a rotates around the axis of the first rotation shaft 41b to a predetermined angle, thereby scanning the laser light 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 light LB 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.

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.

The controller 50 also controls the operation of the laser head 30 according to the contents of the selected laser welding program. Specifically, it controls the drive of the laser light scanner 40 and the drive unit (not shown) of the collimation lens 32 provided in the laser head 30. Furthermore, the controller 50 controls the operation of the manipulator 60. The laser welding program is stored in a memory unit (not shown) provided inside the controller 50 or in a different location, and is called by the controller 50 in response to a command from the controller 50.

The controller 50 has an integrated circuit such as an LSI or microcomputer (not shown), and the functions of the controller 50 described above are realized by executing a laser welding program, which is software, on this integrated circuit. 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.

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

The laser welding device 100 shown in FIG. 1 can perform laser welding on workpieces 200 of various shapes. For example, as shown in FIGS. 3A and 3B, a laser beam LB is irradiated to the joint of the workpiece 200, in which a first plate material 210 and a second plate material 220, which are made of the same material but have different thicknesses, are butted together at their end faces, to perform butt welding. Also, as shown in FIG. 4, a laser beam LB is irradiated to the corner portion of the joint of the workpiece 200, in which a third plate material 230 and a fourth plate material 240 are overlapped with their end faces shifted, to perform lap fillet welding. However, it goes without saying that the shape of the workpiece 200 to be laser welded is not limited to the examples shown in FIGS. 3A, 3B, and 4.

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

The width in the X direction of the Lissajous pattern shown in FIG. 5 is equal to the width in the Y direction, and the width in the Y direction is approximately equal to the width W of the weld bead (not shown) in the Y direction when the welding speed is very fast. On the other hand, when the welding speed is slow, the width of the weld bead increases due to the influence of heat conduction, so the width of the Lissajous pattern in the Y direction is slightly narrower than the width of the weld bead in the Y direction. In this specification, "approximately equal" or "approximately the same" means that the control results of the controlled object are the same or identical, including errors in the control system, and does not require that the two objects being compared are strictly the same or identical. In addition, "approximately equal" or "approximately the same" is also used to mean the same or identical, including manufacturing tolerances and assembly tolerances of each part, etc.

The Lissajous pattern shown in FIG. 5 is obtained by vibrating the laser light LB in the X direction in a sinusoidal manner at a predetermined frequency and in the Y direction in a sinusoidal manner at a frequency different from that in the X direction (1/2 the frequency in the X direction). Also, as described above, the scanning patterns of the laser light LB in the X direction and the Y direction are determined based on the rotational motion of the first mirror 41a and the second mirror 42a. In general, when the position coordinate of the Lissajous pattern shown in FIG. 5 obtained by driving the first mirror 41a is X1 and the position coordinate of the Lissajous pattern shown in FIG. 5 obtained by driving the second mirror 42a is Y1, the position coordinates X1 and Y1 are expressed by the following formulas (1) and (2), respectively.

X1=a×sin(nt)...(1)
Y1=b×sin(mt+φ)...(2)
Where:
a: amplitude in the X direction of the Lissajous pattern shown in FIG. 5 b: amplitude in the Y direction of the Lissajous pattern shown in FIG. 5 n: frequency of the first mirror 41a m: frequency of the second mirror 42a t: time φ: phase difference when the first mirror 41a or the second mirror 42a is driven, specifically, the amount of angular deviation provided when the first mirror 41a and the second mirror 42a are rotated.

Note that the position coordinates X1 and Y1 shown in equations (1) and (2) are expressed in the stationary coordinate system of the Lissajous pattern with the position of the laser head 30 fixed.

Furthermore, frequency n and frequency m correspond to the driving frequencies of the first mirror 41a and the second mirror 42a, respectively.

The Lissajous pattern shown in Figure 5 is an eight-shaped Lissajous pattern that corresponds to the cases 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. Note that the size of the actual Lissajous pattern, that is, the amplitude in the X and Y directions, is approximately 1 mm to 10 mm, respectively.

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

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).

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

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

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

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

When laser welding is performed on such a workpiece 200 while drawing the Lissajous pattern shown in Figure 5 on the surface of the workpiece 200 using laser light LB, the above-mentioned problem may occur if the output P of the laser light LB is constant.

5 is symmetrical in both the X and Y directions. Therefore, when the laser beam LB is irradiated onto the butt joint between the first plate material 210 and the second plate material 220 while traveling in the X direction, the amount of heat input to the workpiece 200 is also symmetrical with respect to the weld line.

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

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

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

In addition, when changing the output P of the laser light LB, the rising and falling portions of the output P of the laser light LB may be controlled separately, as shown by the dotted line in Figure 6.

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

By controlling the output P of the laser light LB as shown in the control curves S1 and S2, it becomes easier to ensure that the output P reaches the target value stably.

[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) while two-dimensionally scanning the laser beam LB to irradiate the surface of the workpiece 200, thereby welding the workpiece 200.

In the welding step, the laser light LB is vibrated sinusoidally along the X direction with a first frequency corresponding to frequency n, and along the Y direction with a second frequency corresponding to frequency m. This causes the laser light LB to scan the surface of the workpiece 200 so as to draw a Lissajous pattern.

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

By doing this, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity, on both sides of the weld line, resulting in a good weld bead shape.

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

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

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

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

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

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

According to the laser welding apparatus 100 of this embodiment, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, on both sides of the weld line, thereby achieving a good weld bead shape.

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.

By providing the manipulator 60 in this manner, the welding direction of the laser light LB can be changed. In addition, laser welding can be easily performed on a workpiece 200 having a complex shape, for example, a three-dimensional shape.

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.

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

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.

By configuring the laser beam scanner 40 in this manner, the laser beam LB can be easily scanned two-dimensionally. In addition, because a known galvanometer scanner is used as the laser beam scanner 40, the cost of the laser welding device 100 can be prevented from increasing.

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

By doing this, 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.

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

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

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

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

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

In this modified example, the drawing direction of the Lissajous pattern is different from the configuration shown in embodiment 1. The Lissajous pattern shown in Fig. 7 is obtained by scanning the laser light LB from the origin O in the directions of the arrows AR3 and AR4 shown in Fig. 7 during one period. Specifically, the laser light LB is scanned from the origin O through drawing positions C → B → A → O → F → E → D → O during one period.

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

This modified example can also achieve the same effects as the configuration shown in embodiment 1. In other words, different amounts of heat can be input to the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, on both sides of the weld line, and the shape of the weld bead can be improved. In addition, the occurrence of welding defects such as burn-through can be suppressed.

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

This embodiment differs from the configuration shown in embodiment 1 in that, while drawing the Lissajous pattern, the output P of the laser light LB is made lower near the origin O of the Lissajous pattern than in other areas.

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

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

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

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

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

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

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

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

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

Consider the case where the heat input, in this case the output P of the laser light LB, is adjusted to match the rear of the origin O of the Lissajous pattern. As shown in FIG. 5, if the Lissajous pattern has a symmetrical shape, the heat input to the workpiece 200 is insufficient in front of the origin O, and the shape of the weld bead, especially the shape at the edge of the bead, may become uneven. On the other hand, if the output P of the laser light LB is adjusted to match the front of the origin O of the Lissajous pattern, the heat input to the molten pool 201 may become excessive behind the origin O, and the molten pool 201 may become unstable. In this case, it is difficult to obtain a weld bead with a good shape. In addition, such a problem may occur both when the heat capacity of the workpiece 200 is equal on both sides of the weld line and when it is asymmetric.

Therefore, in this embodiment, the output P of the irradiated laser light LB is changed between the aforementioned third portion 203 and fourth portion 204. Specifically, in this embodiment, when the laser light LB is advanced in the X direction to laser weld the workpiece 200, the configuration differs from that shown in embodiment 1 in the following respects.

In other words, during drawing of the Lissajous pattern, the output P of the laser light LB is set to be higher in the third portion 203, where the laser light LB is irradiated forward along the X direction from the molten pool 201 formed in the workpiece 200, than in the fourth portion 204, where the laser light LB is irradiated rearward from the third portion 203, including the molten pool 201.

Specifically, as shown in Figures 12 and 13, the output P of the laser light LB is set to P1 for the drawing trajectories O→A→B and O→D→E located forward along the X direction with the origin O as the reference point. On the other hand, the output P of the laser light LB is set to P4 (P4<P1) for the drawing trajectories B→C→O and E→F→O located backward along the X direction with the origin O as the reference point. Such control of the output P of the laser light LB is performed by the controller 50.

According to this embodiment, by making the output P1 of the laser light LB irradiated to the third portion 203 higher than the output P4 of the laser light LB irradiated to the fourth portion 204, it is possible to promote the formation of the molten pool 201 in the third portion 203 that has not yet been heated or melted. In addition, by lowering the output P4 of the laser light LB, it is possible to suppress excessive vibration of the molten pool 201. This not only saves laser energy by not inputting more laser energy than necessary into the fourth portion 204, but also suppresses the weld bead from becoming wavy in the fourth portion 204. Furthermore, by suppressing the penetration depth of the workpiece 200 from becoming deeper than the desired value, it is possible to reduce the occurrence of welding defects such as burn-through, and improve the welding quality.

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

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

In embodiments 1 to 3 and variant 1, as shown in Figure 14, the drawing speed V of the laser light LB may be constant while drawing the Lissajous pattern. In other words, the drawing speed V of the laser light LB may be constant over the entire length of the Lissajous pattern. In this way, it becomes easier to control the amount of heat input to the molten pool 201 (see Figure 11).

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

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

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

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

In this way, it is possible to achieve the same effect as the configuration shown in embodiment 1. In other words, it is possible to input different amounts of heat to both sides of the weld line in the welded portion of the workpiece 200, which has asymmetric heat capacity with respect to the weld line, and to improve the shape of the weld bead. In addition, it is possible to suppress the occurrence of welding defects such as burn-through.

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

In other words, while drawing the Lissajous pattern, the drawing speed V of the laser light LB is made lower in the third portion 203 (see Figure 11) than in the fourth portion 204 (see Figure 11).

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

In this way, it is possible to achieve the same effect as the configuration shown in embodiment 3. That is, it is possible to promote the formation of the molten pool 201 in the third portion 203 and prevent the weld bead from becoming wavy. It is also possible to reduce the occurrence of welding defects such as burn-through, improve the welding quality, and further save laser energy.

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

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

Furthermore, taking into consideration the configurations shown in this embodiment, embodiments 1 to 3, and variant example 1 as a whole, it can be said that the laser welding method and laser welding apparatus 100 disclosed herein have the configuration shown below.

Furthermore, taking the configurations shown in this embodiment and embodiments 1 to 3 together, it can be said that the laser welding method and laser welding apparatus 100 disclosed herein have the configuration shown below.

In other words, the laser welding method according to the present disclosure controls the amount of heat input to the workpiece 200 according to the drawing position of the laser beam LB in the Lissajous pattern. Furthermore, at least one of the drawing speed V and the output P of the laser beam LB is controlled according to the drawing position of the laser beam LB in the Lissajous pattern.

In addition, in the laser welding apparatus 100 according to the present disclosure, the controller 50 controls the amount of heat input to the workpiece 200 according to the drawing position of the laser light LB in the Lissajous pattern. Furthermore, the controller 50 controls at least one of the drawing speed V and the output P of the laser light LB according to the drawing position of the laser light LB in the Lissajous pattern.

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

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

When changing the drawing speed V of the laser light LB, the rising and falling portions of the drawing speed V may be controlled separately, as shown by the dotted lines in Figures 15 and 16.

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

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

By controlling the drawing speed V of the laser light LB as shown in the control curves S3 and S4, it becomes easy to stably cause the drawing speed V to reach the target value.

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

In actual laser welding, the parameters a, b, n, and m shown in formulas (1) and (2) can be changed as appropriate depending on the material of the workpiece 200, the joint shape, the plate thickness, 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.

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

Furthermore, the values of parameters a and b shown in equations (1) and (2) are not particularly limited to the examples shown in Figures 17A, 17B, and 18A to 18C, and may take appropriate values within the range shown in Figure 19. In Figure 19, the Lissajous patterns shown in Figures 5, 17A, and 17B are pattern group 1, and the Lissajous patterns shown in Figures 18A to 18C are pattern group 2.

In addition, 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 vibration frequency in the X direction of the laser light LB, to 2:1 or 1:2, a Lissajous pattern in the shape of a figure eight can be obtained. As long as this frequency ratio is maintained, the driving frequencies of the first mirror 41a and the second mirror 42a may be changed according to the shape of the workpiece 200 or the required bead shape.

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

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

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

Therefore, in the welding step of the laser welding method disclosed herein, the laser light LB is scanned to draw a predetermined pattern on the surface of the workpiece 200.

Furthermore, the amount of heat input to the workpiece 200 is controlled according to the drawing position of the laser light LB in a specified pattern.

In addition, the controller 50 in the laser welding apparatus 100 disclosed herein drives and controls the laser light scanner 40 so that the laser light LB draws a predetermined pattern on the surface of the workpiece 200.

Furthermore, the controller 50 controls the amount of heat input to the workpiece 200 depending on the drawing position of the laser light LB in a specified pattern.

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

By configuring the laser welding method and laser welding apparatus 100 in this manner, it is possible to achieve the same effects as those achieved by the configurations shown in embodiments 1 to 4 and variants 1 and 2.

Other Embodiments
The components shown in the first to fourth embodiments and the first to third modifications can be appropriately combined to form new embodiments.

For example, when drawing each scanning pattern shown in Modification 2, the output P of the laser light LB can be controlled as shown in embodiments 1 to 3. Also, as shown in embodiment 4, the drawing speed V of the laser light LB can be controlled.

In addition, in the second to fourth embodiments and the second and third modified examples, 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. 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. 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. Needless to say, the timing for changing the drawing speed V and output P of the laser light LB is changed according to the change in the order of the drawing positions.

In the example shown in Figure 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.

In addition, the laser light LB may be vibrated 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 so that the scanning pattern of the laser light LB becomes a Lissajous pattern. In this case, it goes without saying that the amplitudes a and b of the first mirror 41a and the second mirror 42a, the frequencies n and m of the first mirror 41a and the second mirror 42a, and the phase φ are appropriately changed.

The laser welding method and laser welding method disclosed herein are useful in that they can produce a good weld bead shape.

10 Laser oscillator 20 Optical fiber 30 Laser head 31 Housing 32 Collimation lens 33 Reflection mirror 34 Condenser lens 40 Laser light scanner 41 First galvanometer mirror 41a First mirror 41b First rotation shaft 41c First drive unit 42 Second galvanometer mirror 42a Second mirror 42b Second rotation shaft 42c Second drive unit 50 Controller 60 Manipulator 200 Workpiece 201 Molten pool 202 Keyhole 203 Third portion 204 Fourth portion 210 First plate material (first portion)
220 Second plate material (second part)
230 Third plate material 240 Fourth plate material

Claims (19)

A welding step of welding the workpiece by two-dimensionally scanning the laser light and irradiating the laser light onto a surface of the workpiece while traveling in a first direction,
In the welding step,
Scanning the laser light so as to draw a predetermined pattern on the surface of the workpiece;
Furthermore, the amount of heat input to the workpiece is controlled according to the drawing position of the laser light in the predetermined pattern.
a drawing position of the laser light in the predetermined pattern has a first drawing region and a second drawing region that does not overlap with the first drawing region,
When transitioning from the first drawing area to the second drawing area,
A drawing speed of the laser beam is controlled to be constant, and an output of the laser beam is controlled to change from a first output to a second output different from the first output, or
controlling an output of the laser beam to be constant, and controlling a drawing speed of the laser beam to change from a first speed to a second speed different from the first speed;
A laser welding method, wherein the predetermined pattern is a continuous pattern in which two annular patterns are in contact with each other at one point. 2. The laser welding method according to claim 1,
When transitioning from the second drawing area to the first drawing area,
A drawing speed of the laser light is controlled to be constant, and an output of the laser light is controlled to change from a second output to the first output, or
controlling the output of the laser beam to be constant, and controlling the drawing speed of the laser beam to change from a second speed to the first speed;
The laser welding method according to claim 1 . 3. The laser welding method according to claim 1,
the predetermined pattern is a Lissajous pattern in the shape of a figure of eight or a shape of an infinity,
The laser welding method is characterized in that, in the welding step, the laser light is vibrated in a sinusoidal manner having a first frequency along the first direction, and also in a sinusoidal manner having a second frequency along a second direction intersecting the first direction, thereby scanning the laser light to trace the Lissajous pattern on the surface of the workpiece. The laser welding method according to claim 3 ,
A laser welding method, wherein a ratio of the first frequency to the second frequency is 2:1 or 1:2. The laser welding method according to any one of claims 1 to 4 ,
The welded portion of the workpiece has a first portion on one side of a weld line and a second portion on the other side of the weld line, the second portion having a smaller heat capacity than the first portion,
A laser welding method comprising the steps of: during drawing of the predetermined pattern, output of the laser light is made higher in the first region than in the second region. The laser welding method according to any one of claims 1 to 4 ,
During drawing of the predetermined pattern, a portion to which the laser light is irradiated in front of a molten pool formed on the workpiece along the first direction is defined as a third portion, and a portion to which the laser light is irradiated in rear of the third portion including the molten pool is defined as a fourth portion,
A laser welding method comprising: setting an output of the laser light irradiated to the third portion to be higher than that of the fourth portion. The laser welding method according to any one of claims 1 to 4 ,
A laser welding method comprising the steps of: during drawing of the predetermined pattern, setting an output of the laser beam to be lower in the vicinity of an origin of the predetermined pattern than in other portions. The laser welding method according to any one of claims 1 to 7,
A laser welding method comprising: making the drawing speed of the laser beam constant over the entire length of the predetermined pattern. The laser welding method according to any one of claims 1 to 4 ,
The welded portion of the workpiece has a first portion on one side of a weld line and a second portion on the other side of the weld line, the second portion having a smaller heat capacity than the first portion,
A laser welding method, comprising the steps of: drawing the predetermined pattern at a drawing speed of the laser beam at the first portion slower than at the second portion. The laser welding method according to any one of claims 1 to 4 ,
During drawing of the predetermined pattern, a portion to which the laser light is irradiated in front of a molten pool formed on the workpiece along the first direction is defined as a third portion, and a portion to which the laser light is irradiated in rear of the third portion including the molten pool is defined as a fourth portion,
A laser welding method, comprising: setting a drawing speed of the laser beam to be slower in the third region than in the fourth region. The laser welding method according to any one of claims 1 to 4 ,
A laser welding method comprising the steps of: drawing the predetermined pattern at a drawing speed of the laser beam in the vicinity of an origin of the predetermined pattern, the drawing speed being faster than that of other portions. A laser oscillator that generates a laser beam;
a laser head that receives the laser light and irradiates it toward a workpiece;
a controller for controlling the operation of the laser head and the output of the laser light;
the laser head has a laser beam scanner configured to scan the laser beam in a first direction and a second direction intersecting the first direction,
The controller drives and controls the laser beam scanner so that the laser beam draws a predetermined pattern on the surface of the workpiece;
Furthermore, the controller controls at least one of a drawing speed and an output of the laser beam according to a drawing position of the laser beam on the surface of the workpiece,
a drawing position of the laser light in the predetermined pattern has a first drawing region and a second drawing region that does not overlap with the first drawing region,
When transitioning from the first drawing area to the second drawing area,
The controller controls a drawing speed of the laser beam to be constant, and controls an output of the laser beam to be changed from a first output to a second output different from the first output, or
the controller controls an output of the laser beam to be constant, and controls a drawing speed of the laser beam to be changed from a first speed to a second speed different from the first speed;
A laser welding device according to claim 1, wherein the predetermined pattern is a continuous pattern in which two annular patterns are in contact with each other at one point. 13. The laser welding apparatus according to claim 12,
When transitioning from the second drawing area to the first drawing area,
The controller controls the drawing speed of the laser light to be constant, and controls the output of the laser light to be changed from the second output to the first output, or
the controller controls the output of the laser beam to be constant, and controls the drawing speed of the laser beam to change from a second speed to the first speed;
13. The laser welding apparatus of claim 12. 14. The laser welding apparatus according to claim 12 ,
the predetermined pattern is a Lissajous pattern in the shape of a figure of eight or a shape of an infinity,
The laser welding apparatus is characterized in that the controller drives and controls the laser beam scanner so that the laser beam draws the Lissajous pattern on the surface of the workpiece by vibrating the laser beam in a sinusoidal shape having a first frequency along the first direction and in a sinusoidal shape having a second frequency along the second direction. The laser welding apparatus according to claim 14 ,
A laser welding apparatus, wherein a ratio of the first frequency to the second frequency is 2:1 or 1:2. 16. The laser welding apparatus according to claim 12 ,
a manipulator to which the laser head is attached;
The controller controls the operation of the manipulator;
The laser welding apparatus is characterized in that the manipulator moves the laser head in a predetermined direction relative to the surface of the workpiece. 17. The laser welding apparatus according to claim 12 ,
the laser oscillator and the laser head are connected by an optical fiber;
A laser welding device, characterized in that the laser light is transmitted from the laser oscillator to the laser head through the optical fiber. 18. The laser welding apparatus according to claim 12 ,
The laser welding apparatus is characterized in that the laser light scanner is composed of a first galvanometer mirror that scans the laser light in the first direction, and a second galvanometer mirror that scans the laser light in a second direction intersecting the first direction. 19. The laser welding apparatus according to claim 12 ,
The laser head further includes a focal position adjustment mechanism,
The laser welding device, characterized in that the focal position adjustment mechanism is configured to change the focal position of the laser light along directions intersecting the first direction and the second direction.

Images