Welding methods, welding systems, and adjustment methods.

Abstract

DEPCT68 The welding method disclosed here includes a procedure for applying laser light for... Inspect the workpiece at an angle while varying the amount of light dispersion. The process of determining the correction value for the amount of light scattering based on intensity. Laser backlight for inspection and workpiece welding process. Laser light is applied to the workpiece so that the amount of light scattering is adjusted. The correction value is zero in the welding method as disclosed, laser light for inspection. It is scanned in a direction approaching the laser emission point for time-based monitoring. The amount of light scattering will be zero during the laser application process for... Inspect the workpiece. From the results, determine the welding method, welding system, and possible adjustments. Improvements to the accuracy of laser beam focusing control for welding were provided;

Description

Welding method, welding system, and correction method

[0001] The present disclosure relates to a welding method, a welding system, and a method for correcting a defocus amount.

[0002] Patent Document 1 describes an inspection method for inspecting the focus deviation of a laser used for welding. In the inspection method described in Patent Document 1, an inspection laser is irradiated perpendicularly onto a workpiece and the inspection laser is scanned. Then, the laser focus deviation is inspected based on the intensity of the reflected light of the inspection laser.

[0003] Japanese Patent Application Laid-Open No. 2018-140426

[0004] The inspection method described in Patent Document 1 is used to inspect the defocusing of a laser used in laser welding, in which the laser is irradiated perpendicularly to a workpiece. Meanwhile, in recent years, laser welding devices capable of irradiating a laser while scanning from a fixed point have begun to be introduced. In such laser welding devices, when inspecting the defocusing of a laser, it is sometimes necessary to irradiate the inspection laser obliquely onto the workpiece.

[0005] The present inventors have discovered that when an inspection laser is irradiated at an oblique angle onto a workpiece and laser focus deviation is inspected while scanning the inspection laser, the inspection accuracy varies depending on the scanning direction of the inspection laser. In other words, the present inventors have discovered a problem in that when the inspection laser must be irradiated at an oblique angle onto the workpiece, the accuracy of laser focus control is insufficient depending on the scanning direction of the inspection laser. Patent Document 1 does not disclose a technology that can solve this problem.

[0006] The present disclosure has been made to solve such problems, and aims to provide a welding method, a welding system, and a correction method that can improve the accuracy of focus control of a welding laser.

[0007] A welding method according to one aspect of the present disclosure includes the steps of: irradiating an inspection laser obliquely onto a workpiece while changing a defocus amount; determining a correction value for the defocus amount based on the intensity of return light from the inspection laser; and irradiating the welding laser onto the workpiece and welding the workpiece so that the defocus amount corrected by the correction value becomes 0, wherein, during the step of irradiating the workpiece with the inspection laser, the inspection laser is scanned in a direction approaching the emission point of the inspection laser at a timing when the defocus amount becomes 0.

[0008] This configuration increases the amount of change in the return light of the inspection laser, thereby improving the accuracy of focus control of the welding laser in the welding method according to one aspect of the present disclosure.

[0009] In a welding method according to one aspect of the present disclosure, in the step of determining a correction value for the defocus amount, the defocus amount of the inspection laser at the timing when the intensity of the return light of the inspection laser takes an extreme value may be determined as the correction value for the defocus amount.

[0010] In a welding method according to an aspect of the present disclosure, in the step of determining a correction value for the defocus amount, the defocus amount of the laser at the timing when the intensity of the return light of the inspection laser takes on a minimum value may be determined as the correction value for the defocus amount.

[0011] In a welding method according to an aspect of the present disclosure, in the step of determining a correction value for the defocus amount, the defocus amount of the laser at the timing when the intensity of the return light of the inspection laser reaches a maximum value may be determined as the correction value for the defocus amount.

[0012] In the welding method according to one aspect of the present disclosure, in the step of irradiating the workpiece with an inspection laser, the scanning trajectory of the inspection laser may be substantially circular.

[0013] In a welding method according to an aspect of the present disclosure, the steps of irradiating the workpiece with an inspection laser, determining a correction value for the defocus amount, and welding the workpiece may be performed at a plurality of points. In the step of irradiating the workpiece with the inspection laser for the second or subsequent times, the inspection laser may be scanned in a direction approaching the emission point of the inspection laser at a timing when the defocus amount of the inspection laser corrected by the correction value for the defocus amount becomes zero.

[0014] A welding method according to one aspect of the present disclosure relates to a welding system including: a laser irradiation unit that irradiates an inspection laser and a welding laser onto a workpiece; and a correction value determination unit that determines a correction value for a defocus amount based on the intensity of returned light from the inspection laser, wherein the laser irradiation unit irradiates the workpiece with the inspection laser while changing the defocus amount, scans the inspection laser in a direction approaching the emission point of the inspection laser at a timing when the defocus amount becomes 0, and irradiates the workpiece with the welding laser so that the defocus amount corrected by the correction value determined by the correction value determination unit becomes 0.

[0015] The correction method according to the present disclosure comprises the steps of: irradiating an inspection laser onto a workpiece while changing the defocus amount; and determining a correction value for the defocus amount based on the intensity of the return light of the inspection laser, wherein in the step of irradiating the workpiece with the inspection laser, the inspection laser is scanned in a direction approaching the emission point of the inspection laser at the timing when the defocus amount becomes 0.

[0016] The present disclosure can provide a welding method, a welding system, and a correction method that can improve the accuracy of focus control of a welding laser.

[0017] FIG. 1 is a block diagram showing the configuration of a welding system according to a first embodiment. FIG. 2 is a schematic cross-sectional view for explaining return light according to the first embodiment. FIG. 3 is a block diagram showing the configuration of a control unit 2 according to the first embodiment. FIG. 4 is a schematic cross-sectional view for explaining the effect of the welding system according to the first embodiment. FIG. 5 is a graph showing the intensity of return light according to the first embodiment. FIG. 6 is a flowchart showing the operation of the welding system according to the first embodiment. FIG. 7 is a schematic plan view showing the scanning trajectory of an inspection laser according to another embodiment.

[0018] (First embodiment) <Configuration of welding system> A first embodiment according to the present disclosure will be described in detail below with reference to the drawings. First, the configuration of the welding system according to the present embodiment will be described in detail. Fig. 1 is a block diagram for explaining the configuration of the welding system according to the first embodiment.

[0019] The welding system 100 according to the present embodiment irradiates the workpiece with an inspection laser and determines a correction value for the defocus amount before welding the workpiece. Then, the welding system 100 according to the present embodiment irradiates the workpiece with a welding laser based on the defocus amount corrected by the determined correction value, and welds the workpiece.

[0020] The defocus amount here is a numerical value that represents the difference in position between the laser irradiation point and the laser focus. The larger the absolute value of the defocus amount, the larger the difference in position between the laser irradiation point and the laser focus. When the defocus amount is 0, it indicates that the laser irradiation point and the laser focus are aligned.

[0021] The welding system 100 according to this embodiment includes a laser irradiation unit 1 and a control unit 2. The laser irradiation unit 1 irradiates an inspection laser and a welding laser onto a workpiece. The laser irradiation unit 1 is controlled by the control unit 2. The laser irradiation unit 1 is typically a laser welding device, for example, a laser welding device capable of welding multiple locations from a fixed point. The laser irradiation unit 1 includes a laser oscillation unit 11, an optical system 12, and a return light detection unit 13.

[0022] The laser oscillator 11 oscillates an inspection laser and a welding laser. More specifically, the laser oscillator 11 oscillates the inspection laser and the welding laser based on the control of the control unit 2. Specifically, the wavelength, intensity, and timing of laser emission of the oscillated laser of the laser oscillator 11 are controlled by the control unit 2. The inspection laser and the welding laser emitted by the laser oscillator 11 are irradiated onto the workpiece via the optical system 12.

[0023] Here, the inspection laser and the welding laser are both laser beams with different intensities that are irradiated onto a workpiece. The welding laser has a higher laser intensity than the inspection laser and is irradiated onto the workpiece in the process of welding the workpiece. On the other hand, the inspection laser beam has a lower laser intensity than the welding laser and is irradiated to determine a correction value for the defocus amount before welding the workpiece.

[0024] The optical system 12 irradiates the workpiece with the laser oscillated by the laser oscillation unit 11. More specifically, the optical system 12 adjusts the irradiation position and defocus amount of the laser oscillated by the laser oscillation unit 11 based on the control of the control unit 2, and irradiates the workpiece with the laser. The optical system 12 also guides the return light of the inspection laser, which will be described later, to the return light detection unit 13. In other words, the return light of the inspection laser reaches the return light detection unit 13 via the optical system 12.

[0025] The optical system 12 is typically a galvanometer scanner. The optical system 12 typically has an emission point fitted with a protective glass, and emits a laser beam from the emission point toward a workpiece. The optical system 12 also guides the return light incident on the emission point to the return light detection unit 13.

[0026] In particular, the optical system 12 according to this embodiment irradiates the workpiece with the inspection laser obliquely while changing the defocus amount based on the control of the control unit 2. Furthermore, the optical system 12 according to this embodiment irradiates the workpiece with the welding laser based on the control of the control unit 2 so that the defocus amount corrected by a correction value described later becomes 0, thereby welding the workpiece.

[0027] The optical system 12 is realized by, for example, a combination of a protective glass, a lens, a reflecting mirror, and a position adjustment mechanism that adjusts the positions of these components. The optical system 12 may control the irradiation position of the laser oscillated by the laser oscillation unit 11, for example, by controlling the position and angle of the reflecting mirror. The optical system 12 may also control the defocus amount of the laser oscillated by the laser oscillation unit 11, by controlling the position of the lens.

[0028] Fig. 2 is a schematic cross-sectional view for explaining the return light according to the first embodiment. Fig. 2 illustrates an optical system 12, an inspection laser L1, return light L2, and a workpiece W. The optical system 12 illustrated in Fig. 2 is connected to the laser oscillator 11 via an optical fiber OF1 and to the return light detector 13 via an optical fiber OF2. In addition, a protective glass 121 is provided at the emission point from which the optical system 12 emits the laser to protect the internal structure of the optical system 12 from spatter generated due to welding.

[0029] The inspection laser L1 is emitted from the optical system 12 and irradiated onto the workpiece W. When the inspection laser light L1 is irradiated onto the workpiece W, a portion of the surface melts, forming a molten region M. Furthermore, a portion of the molten region M is evaporated by the irradiation of the inspection laser light L1, forming a keyhole KH, which is a tiny hole. The inspection laser L1 is reflected and absorbed inside the keyhole KH. The deeper the keyhole KH, the greater the amount of inspection laser L1 absorbed inside the keyhole KH.

[0030] The return light L2 is light that is incident from the irradiation point of the inspection laser L1 on the workpiece W to the emission point of the inspection laser L1 in the optical system 12. Typically, the return light L2 is reflected light of the inspection laser L1 that has been reflected one or more times inside the keyhole KH. Alternatively, the return light L2 may be thermal radiation light that is generated as a result of the inspection laser L1 being absorbed inside the keyhole KH.

[0031] As described above, reflection and absorption of the inspection laser L1 occur inside the keyhole KH, and the deeper the keyhole KH, the greater the amount of absorption of the inspection laser L1. Therefore, if the return light L2 is reflected light of the inspection laser L1 reflected inside the keyhole KH, the deeper the keyhole KH, the lower the intensity of the return light L2. On the other hand, if the return light L2 is thermal radiation light generated as a result of absorption of the inspection laser L1 inside the keyhole KH, the deeper the keyhole KH, the higher the intensity of the return light L2.

[0032] Since the absorption amount of the inspection laser L1 also depends on the defocus amount, the intensity of the return light L2 also depends on the defocus amount. More specifically, the closer the defocus amount is to 0, that is, the closer the irradiation position of the inspection laser and the position of the focal point are, the greater the absorption amount of the inspection laser L1 becomes.

[0033] Therefore, when the return light L2 is reflected light of the inspection laser L1 reflected inside the keyhole KH, the intensity of the return light L2 decreases as the defocus amount approaches 0. On the other hand, when the return light L2 is thermal radiation light generated as a result of the inspection laser L1 being absorbed inside the keyhole KH, the intensity of the return light L2 increases as the defocus amount approaches 0.

[0034] In addition, the welding system 100 according to this embodiment may detect only the reflected light of the inspection laser L1 as the return light L2, or may detect only the thermal radiation light generated as a result of the absorption of the inspection laser L1 as the return light L2, or may detect both of these as the return light L2.

[0035] Furthermore, the welding system 100 according to this embodiment may detect light other than these as the returned light L2. In other words, the welding system 100 according to this embodiment may detect any light as the returned light as long as the light is incident from the irradiation point of the inspection laser L1 on the workpiece W to the emission point of the inspection laser L1 of the optical system 12.

[0036] Returning to the explanation of Fig. 1, the return light detection unit 13 detects the return light of the inspection laser via the optical system 12. The return light detection unit 13 is typically a light receiving element, and outputs the detected intensity of the return light as an electrical signal. The return light detection unit 13 outputs the detected intensity of the return light to the control unit 2.

[0037] The control unit 2 controls the operation of the laser irradiation unit 1. Fig. 3 is a block diagram showing the configuration of the control unit 2 according to the first embodiment. The control unit 2 includes an arithmetic unit 25 such as a CPU (Central Processing Unit) as shown in Fig. 3, and a storage unit 26 such as a RAM (Random Access Memory) or a ROM (Read Only Memory) that stores programs and data for controlling the laser irradiation unit 1. In other words, the control unit 2 functions as a computer, and controls the laser irradiation unit 1 based on the programs.

[0038] 1 can be configured in hardware by the CPU, memory unit, other circuits, etc., and can be realized in software by a program for controlling the laser irradiation unit 1 stored in the memory unit 26. In other words, the control unit 2 can be realized in various forms by hardware, software, or a combination of both.

[0039] The program includes instructions (or software code) that, when loaded into a computer, cause the computer to perform one or more functions described in the embodiments. The program may be stored in a non-transitory computer-readable medium or a tangible storage medium. By way of example and not limitation, computer-readable media or tangible storage media include random-access memory (RAM), read-only memory (ROM), flash memory, solid-state drive (SSD) or other memory technologies, CD-ROM, digital versatile disc (DVD), Blu-ray (registered trademark) disc or other optical disk storage, magnetic cassette, magnetic tape, magnetic disk storage or other magnetic storage device. The program may also be transmitted on a transitory computer-readable medium or communication medium. By way of example and not limitation, transitory computer-readable media or communication media include electrical, optical, acoustic, or other forms of propagated signals.

[0040] Returning to the explanation of Fig. 1, the control unit 2 includes a laser intensity control unit 21, a correction value determination unit 22, a DF amount control unit 23, and an irradiation position control unit 24.

[0041] The laser intensity control unit 21 controls the laser oscillation unit 11. More specifically, the laser intensity control unit 21 controls the wavelength and intensity of the laser oscillated by the laser oscillation unit 11, the timing at which the laser oscillation unit 11 oscillates the laser, and the like.

[0042] The correction value determination unit 22 acquires the intensity of the detected return light from the return light detection unit 13. The correction value determination unit 22 determines a correction value for the defocus amount based on the acquired intensity of the return light of the inspection laser. The correction value determination unit 22 outputs the determined correction value to the DF amount control unit 23.

[0043] Specifically, the correction value determiner 22 identifies the timing at which the intensity of the returned light detected by the returned light detector 13 takes on an extreme value. Then, the correction value determiner 22 acquires the defocus amount of the inspection laser at the timing at which the intensity of the returned light detected by the returned light detector 13 takes on an extreme value from the DF amount controller 23. The correction value determiner 22 determines the acquired defocus amount as the correction value for the defocus amount.

[0044] More specifically, when the returned light is reflected light of the inspection laser, the correction value determiner 22 determines the defocus amount of the inspection laser at the timing when the intensity of the returned light of the inspection laser reaches a minimum value as the correction value for the defocus amount. Also, when the returned light is thermal radiation light generated as a result of absorption of the inspection laser, the correction value determiner 22 determines the defocus amount of the inspection laser at the timing when the intensity of the returned light of the inspection laser reaches a maximum value as the correction value for the defocus amount.

[0045] That is, the correction value determination unit 22 according to this embodiment determines the defocus amount of the inspection laser at the timing when the intensity of the return light of the inspection laser takes an extreme value as the correction value for the defocus amount.

[0046] Here, as described above, if the returned light is reflected light of the inspection laser, the intensity of the returned light decreases as the defocus amount approaches 0. Also, if the returned light is thermal radiation light generated as a result of absorption of the inspection laser, the intensity of the returned light L2 increases as the defocus amount approaches 0.

[0047] Therefore, the timing when the intensity of the return light detected by the return light detection unit 13 reaches an extreme value corresponds to the timing when the defocus amount is 0, i.e., the timing when the irradiation point of the inspection laser and the focus coincide.

[0048] Here, if there is no error in the optical system 12, the defocus amount of the inspection laser that the correction value determination unit 22 acquires from the DF amount control unit 23 should be 0. However, since there is some error in the actual optical system 12, the defocus amount that the correction value determination unit 22 acquires from the DF amount control unit 23 is not 0.

[0049] That is, the defocus amount that the correction value determination unit 22 acquires from the DF amount control unit 23 corresponds to an error in the defocus amount caused by an error in the optical system 12. Therefore, by using the defocus amount of the inspection laser at the timing when the intensity of the returned light takes an extreme value as the correction value for the defocus amount, the welding system according to this embodiment can appropriately correct the error in the defocus amount caused by an error in the optical system 12. Note that the error in the optical system 12 described above occurs due to various causes, for example, it occurs due to expansion of a protective lens provided at the emission point of the laser.

[0050] The DF amount control unit 23 controls the optical system 12. More specifically, the DF amount control unit 23 controls the optical system 12 to control the defocus amount of the laser irradiated by the laser irradiation unit 1. For example, the DF amount control unit 23 may control the position of a movable lens provided in the optical system 12 to control the defocus amount of the laser irradiated by the laser irradiation unit 1.

[0051] In order to control the defocus amount, the DF amount control unit 23 may acquire position information of the laser irradiation point from the irradiation position control unit 24. Then, the DF amount control unit 23 may calculate the distance between the laser emission point and the irradiation point, and control the laser defocus amount based on the calculated distance.

[0052] When the laser irradiation unit 1 is irradiating the inspection laser, the DF amount control unit 23 controls the optical system 12 so as to change the defocus amount while the laser is being irradiated. That is, the DF amount control unit 23 controls the laser irradiation unit 1 so as to irradiate the workpiece with the inspection laser while changing the defocus amount. In this case, the DF amount control unit 23 may change the defocus amount so that the focal position moves from in front of the workpiece to behind the workpiece, or may change the defocus amount so that the focal position moves from behind the workpiece to in front of the workpiece.

[0053] Here, the DF amount control unit 23 changes the defocus amount of the inspection laser so that the defocus amount becomes 0 while the irradiation point of the inspection laser is being scanned in a direction approaching the emission point of the inspection laser.

[0054] The DF amount control unit 23 outputs the defocus amount of the inspection laser at the timing when the intensity of the returned light takes an extreme value to the correction value determination unit 22. In addition, the DF amount control unit 23 acquires the correction value of the defocus amount from the correction value determination unit 22.

[0055] When the laser irradiation unit 1 is irradiating a welding laser, the DF amount control unit 23 controls the optical system 12 so that the defocus amount corrected by the correction value obtained from the correction value determination unit 22 becomes 0 while the laser is being irradiated.

[0056] The irradiation position control unit 24 controls the optical system 12. More specifically, the irradiation position control unit 24 controls the optical system 12 to control the position of the irradiation point of the laser irradiated by the laser irradiation unit 1. For example, the DF amount control unit 23 may control the angle of a reflecting mirror provided in the optical system 12 to control the position of the irradiation point of the laser irradiated by the laser irradiation unit 1.

[0057] When the laser irradiation unit 1 is irradiating the inspection laser, the irradiation position control unit 24 controls the optical system 12 so that the inspection laser is scanned in a direction approaching the emission point of the inspection laser at the timing when the defocus amount of the inspection laser becomes 0.

[0058] <Effects of the Welding System> With the above configuration, it is believed that the accuracy of the focus control of the welding laser is improved based on the following hypothesis, although the present disclosure is not limited to the following hypothesis.

[0059] 4 and 5 are schematic cross-sectional views for explaining the effects of the welding system according to the first embodiment. More specifically, Fig. 4 is a schematic cross-sectional view showing the optical system 12, the inspection laser L1, the return light L2, and the workpiece W when the laser irradiation unit 1 scans the inspection laser in a direction approaching the emission point of the inspection laser.

[0060] FIG. 5 is a schematic cross-sectional view showing the optical system 12, the inspection laser L1, the return light L2, and the workpiece W when the laser irradiation unit 1 is scanning the inspection laser in a direction away from the emission point of the inspection laser.

[0061] As shown in Fig. 4, when the laser irradiation unit 1 scans the inspection laser in a direction approaching the emission point of the inspection laser, the inspection laser L1 is incident in a direction where the molten pool M is formed. On the other hand, as shown in Fig. 5, when the laser irradiation unit 1 scans the inspection laser in a direction away from the emission point of the inspection laser, the inspection laser L1 is incident in a direction where the molten pool M is not formed.

[0062] Here, when comparing the part on the workpiece W where the molten metal M is formed with the part where the molten metal M is formed, the part where the molten metal M is formed has a higher temperature and metal evaporation is more likely to occur.

[0063] Therefore, when comparing the case where the laser is incident in the direction where the molten pool M is formed with the case where the laser is incident in the direction where the molten pool M is formed, a deeper keyhole KH is formed when the laser is incident in the direction where the molten pool M is formed.

[0064] In other words, when comparing the case where the inspection laser is scanned in a direction approaching the emission point of the inspection laser with the case where the inspection laser is scanned in a direction away from the emission point of the inspection laser, as shown in Figures 4 and 5, a deeper keyhole KH is formed when the inspection laser is scanned in a direction approaching the emission point of the inspection laser.

[0065] Fig. 6 is a graph showing the intensity of returned light according to the first embodiment. More specifically, Fig. 6 shows graphs G1 and G2 superimposed on each other. Graph G1 is a graph showing the case where the inspection laser is scanned in a direction approaching the emission point of the inspection laser at the timing when the defocus amount becomes 0. Graph G2 is a graph showing the case where the inspection laser is scanned in a direction away from the emission point of the inspection laser at the timing when the defocus amount becomes 0. In other words, graph G1 is an example of a graph showing the intensity of returned light observed by welding system 100 according to the present embodiment, and graph G2 is a comparative example.

[0066] More specifically, graphs G1 and G2 are both graphs in which the intensity of the returned light is plotted against the amount of defocus, and show the change in the intensity of the returned light when the amount of defocus is changed from a to d.

[0067] Here, in graph G1, in section AB where the defocus amount is changed from a to b, the inspection laser is scanned in a direction away from the emission point, in section BC where the defocus amount is changed from b to c, the inspection laser is scanned in a direction towards the emission point, and in section CD where the defocus amount is changed from c to d, the inspection laser is scanned in a direction away from the emission point.

[0068] On the other hand, in graph G2, in section AB where the defocus amount is changed from a to b, the inspection laser is scanned in a direction approaching the emission point, in section BC where the defocus amount is changed from b to c, the inspection laser is scanned in a direction away from the emission point, and in section CD where the defocus amount is changed from c to d, the inspection laser is scanned in a direction approaching the emission point.

[0069] As described above, when the return light L2 is reflected light of the inspection laser L1 reflected inside the keyhole KH, the intensity of the return light decreases as the keyhole becomes deeper. Therefore, when comparing the case where the inspection laser is scanned in a direction approaching the emission point of the inspection laser with the case where the inspection laser is scanned in a direction away from the emission point of the inspection laser, the intensity of the return light decreases more when the inspection laser is scanned in a direction approaching the emission point of the inspection laser.

[0070] 6, the intensity of the returned light is greater in graph G1 than in graph G2 in sections AB and CD, and is smaller in graph G1 than in graph G2 in section BC.

[0071] As a result, as shown in Fig. 6, graph G1 has a larger change in the vertical direction than graph G2. The larger the change in the vertical direction of the graph, the more accurate the identification of extreme values ​​becomes. Therefore, identifying extreme values ​​using graph G1 can identify extreme values ​​more accurately than using graph G2.

[0072] That is, the welding system according to this embodiment improves the accuracy of identifying extreme values ​​of the intensity of the returned light by scanning the inspection laser in a direction approaching the emission point at the timing when the defocus amount becomes 0. As a result, the welding system according to this embodiment can improve the accuracy of laser focus control.

[0073] <Operation of Welding System> Next, the operation of the welding system, that is, the welding method according to the first embodiment will be described in detail. Fig. 7 is a flowchart for explaining the operation of the welding system according to the first embodiment.

[0074] First, the laser irradiation unit 1 irradiates the workpiece with the inspection laser (step ST1). More specifically, the laser irradiation unit 1 irradiates the workpiece with the inspection laser obliquely while changing the defocus amount. Furthermore, in step ST1, at the timing when the defocus amount becomes 0, the laser irradiation unit 1 scans the inspection laser in a direction approaching the emission point of the inspection laser.

[0075] Next, the return light detector 13 detects the intensity of the return light of the inspection laser (step ST2). The intensity of the return light detected by the return light detector 13 is output to the correction value determiner 22.

[0076] Next, the correction value determination unit 22 determines a correction value for the defocus amount based on the intensity of the return light of the inspection laser (step ST3). More specifically, the correction value determination unit 22 determines the defocus amount of the inspection laser at the timing when the intensity of the return light of the inspection laser takes an extreme value as the correction value for the defocus amount.

[0077] Finally, the laser irradiation unit 1 welds the workpieces (step ST4), and the series of operations of the welding system 100 is completed. More specifically, the laser irradiation unit 1 irradiates the workpieces with the welding laser so that the defocus amount corrected by the correction value determined in step ST3 becomes 0, and welds the workpieces.

[0078] As described above, the welding system 100 according to this embodiment determines the correction value of the defocus amount based on the intensity of the returned light of the inspection laser irradiated while changing the defocus amount. Furthermore, the welding system 100 according to this embodiment scans the inspection laser in a direction approaching the emission point of the inspection laser at the timing when the defocus amount becomes 0.

[0079] With this configuration, the welding system 100 according to this embodiment increases the amount of change in the intensity of the return light of the inspection laser, thereby improving the accuracy of the focus control of the welding laser.

[0080] Other Embodiments In welding system 100 according to other embodiments, the scanning trajectory of the inspection laser may be substantially circular. With this configuration, in the vicinity of the irradiation point where the defocus amount of the inspection laser is zero, the inspection laser scans in a direction approaching the emission point, while in other sections, the inspection laser scans in a direction away from the emission point. As a result, the amount of change in the intensity of the return light of the inspection laser increases, further improving the accuracy of focus control of the welding laser.

[0081] 8 is a schematic plan view showing a scanning locus of an inspection laser according to another embodiment. In FIG. 8, a locus C is a scanning locus of the inspection laser, a point O is a center point of the locus C, a point P0 is an emission point of the inspection laser, a straight line L1 is a line connecting the points O and P0, a straight line L2 is a tangent drawn from the point P0 to the locus C, a point P1 is an irradiation start point of the inspection laser, a point P2 is an intersection point of the line L2 and the locus C, a point P3 is an intersection point of the line L2 and the locus C, a point P4 is an irradiation end point of the inspection laser, and a point P5 is a tangent point of the locus C and the line L2.

[0082] For example, a welding system 100 according to another embodiment starts irradiating the inspection laser from point P1 and irradiates the inspection laser counterclockwise along a trajectory C to point P4. In this case, the inspection laser scans in a direction away from the emission point P0 in the section from point P1 to point P2 and in the section from point P3 to point P4. Furthermore, the inspection laser scans in a direction approaching the emission point P0 in the section from point P2 to point P3.

[0083] Therefore, in the welding system 100 according to the other embodiments, it is sufficient that the defocus amount of the inspection laser becomes 0 while the inspection laser is irradiated to the section from point P2 to point P3.

[0084] The point at which the defocus amount of the inspection laser becomes 0 may be anywhere within the section from point P2 to point P3, but it is particularly preferable that it be near point P5, where the scanning direction of the inspection laser is most oriented toward the emission point P0.

[0085] Furthermore, welding system 100 according to other embodiments may perform the steps of irradiating the workpiece with the inspection laser, determining the defocus amount correction value, and welding the workpiece at multiple points. In other words, welding system 100 according to the present embodiment may perform welding at multiple points.

[0086] In this case, the welding system 100 according to other embodiments may correct the defocus amount of the inspection laser using the previously determined correction value in the process of irradiating the workpiece with the inspection laser for the second or subsequent times.

[0087] The welding system 100 according to other embodiments may change the laser irradiation start position when the position of the point where the defocus amount of the inspection laser is predicted to be 0 is changed by the correction.

[0088] In addition, in other embodiments of the welding system 100, when the position of the point where the defocus amount of the inspection laser is predicted to be 0 is changed by the correction, the scanning speed of the inspection laser, or the rate of change of the defocus amount, or both may be changed.

[0089] This configuration allows the step of irradiating the workpiece with the inspection laser to be more appropriately performed, and as a result, the welding system 100 according to this embodiment can further improve the accuracy of the focus control of the welding laser.

[0090] The present invention has been described above in accordance with the above-described embodiments, but the present invention is not limited to the configurations of the above-described embodiments, and naturally includes various modifications, alterations, and combinations that can be made by a person skilled in the art within the scope of the invention claimed in the claims of this application.

[0091] This application claims priority based on Japanese Patent Application No. 2023-018276, filed February 9, 2023, the disclosure of which is incorporated herein in its entirety.

[0092] The present disclosure is applicable to a variety of devices that require laser focusing.

[0093] REFERENCE SIGNS LIST 1 Laser irradiation unit 11 Laser oscillation unit 12 Optical system 13 Return light detection unit 2 Control unit 21 Laser intensity control unit 22 Correction value determination unit 23 DF amount control unit 24 Irradiation position control unit 100 Welding system

Claims

DEPCT681. The welding method comprises: a procedure for applying the inspection laser at an angle to the workpiece while altering the amount of light dispersion; a procedure for determining the correction value for the amount of light dispersion based on the backlight intensity of the inspection laser; and a procedure for welding the workpiece by applying the welding laser to the workpiece so that the amount of light dispersion corrected by the correction value is zero, where the inspection laser is scanned in a direction approaching the emission point of the inspection laser at the time when the amount of light dispersion is zero during the laser application procedure to the workpiece.

2. The welding method according to claim 1, where in the procedure for determining the correction value for the amount of light dispersion, the amount of light dispersion of the inspection laser obtained at the time when the backlight intensity of the inspection laser reaches its extreme value is determined as the correction value for the amount of light dispersion. 3.The welding method under claim 2, where in the procedure for determining the correction value for the amount of light scattering, the amount of laser light scattering obtained at the time at which the laser backlight intensity for inspection reaches a minimum value is determined as the correction value for the amount of light scattering.

4. The welding method under claim 2, where in the procedure for determining the correction value for the amount of light scattering, the amount of laser light scattering obtained at the time at which the laser backlight intensity for inspection reaches a maximum value is determined as the correction value for the amount of light scattering.

5. Any one of the welding methods under claims 1 through 4, where in the procedure for applying the laser for inspection to the workpiece, the scanning trajectory of the laser for inspection is roughly circular. 6.In any of the welding methods under Claims 1 through 4, where the laser application for inspection of the workpiece, the correction procedure for the amount of laser dispersion, and the welding procedure are performed at more than one point, and in the second or subsequent laser application for inspection of the workpiece, the amount of laser dispersion for inspection is corrected by applying the correction value for the amount of laser dispersion determined in the last correction procedure.7The welding system comprises: a laser projection unit configured to apply laser beams for inspection and welding at an angle to the workpiece; and a correction unit configured to correct the amount of laser scattering based on the backlight intensity of the inspection laser. In this system, the laser projection unit applies the inspection laser to the workpiece while altering the amount of scattering, scans the inspection laser beam in a direction toward the inspection laser emission point at a time when the amount of scattering is zero, and applies the welding laser to the workpiece so that the amount of scattering, corrected by the correction value determined by the correction unit, is zero.8.

9. Any welding system under one of the claims in Patent 7, where the determination unit quantifies the laser beam dispersion for inspection, which is obtained at the time when the laser beam back intensity for inspection reaches its extreme value, as a correction factor for the amount of dispersion.

10. Any welding system under one of the claims in Patent 8, where the determination unit quantifies the laser beam dispersion, which is obtained at the time when the laser beam back intensity for inspection reaches its minimum value, as a correction factor for the amount of dispersion.

11. Any welding system under one of the claims in Patent 8, where the determination unit quantifies the laser beam dispersion, which is obtained at the time when the laser beam back intensity for inspection reaches its maximum value, as a correction factor for the amount of dispersion.

12. Any welding system under one of the claims in Patents 7 through 10, where the scanning trajectory of the laser beam for inspection is a simplistic circular path.In any of the welding systems under claims 7 through 10, where the laser beam unit welds more than one point, and in a second or subsequent weld, the amount of laser dispersion for inspection is corrected by applying the correction value for the amount of dispersion determined in the last weld.

13. The methods for correcting the amount of dispersion include: a procedure for applying the laser beam for inspection at an angle to the workpiece while changing the amount of dispersion; and a procedure for determining the correction value for the amount of dispersion based on the backlight intensity of the laser beam for inspection, in which, in the procedure for applying the laser beam for inspection to the workpiece, the laser beam for inspection is scanned in the direction approaching the laser beam emission point at the time at which the amount of dispersion is zero;

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