Laser welding monitoring device and laser welding monitoring method

Abstract

When the laser beam emitted by the processing head (20) is irradiated on the butt joint (120) of the materials to be welded, i.e., the metal plates (W1) and the metal plates (W2), the light receiving units (30a-30c) receive the radiated light including the reflected light of the laser beam and the light having a wavelength different from the reflected light, i.e., the monitoring light generated by thermal radiation. The spectroscopic unit (40) spectroscopically separates the reflected light and the monitoring light and converts the monitoring light into a first electrical signal. The trigger unit (60) converts the reflected light into a second electrical signal and outputs a trigger signal when the level of the second electrical signal is above a predetermined threshold value. When the trigger signal is input, the laser welding monitor (80) starts to determine whether the laser welding of the materials to be welded is proceeding normally based on the first electrical signal.

Description

Technical Field

[0001] The present disclosure relates to a laser welding monitoring device and a laser welding monitoring method for monitoring whether laser welding is normally performed. Background Art

[0002] As described in Patent Documents 1 or 2, when a laser welding machine welds materials to be welded, a laser welding monitoring device monitors whether the laser welding is progressing normally.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2010-110796

[0006] Patent Document 2: Japanese Patent Application Laid-Open No. 2017-24046 Summary of the Invention

[0007] A laser welding monitoring device preferably begins monitoring when the laser welder begins welding the materials to be welded. For example, the laser welding monitoring device can simply begin monitoring at the same time as the laser oscillator begins emitting a laser beam. However, some laser oscillators do not output a signal indicating the start of laser beam emission at the same time. Therefore, a structure is required to accurately detect the timing when the laser welder begins welding the materials to be welded, thereby enabling the laser welding monitoring device to begin monitoring.

[0008] An object of one or more embodiments is to provide a laser welding monitoring device and a laser welding monitoring method that can accurately detect the timing at which a laser welding machine starts welding of materials to be welded, thereby starting monitoring of laser welding.

[0009] According to a first mode of one or more embodiments, a laser welding monitoring device is provided, comprising: a light receiving unit, which receives radiated light including reflected light of the laser beam generated at an irradiation position of the laser beam and monitoring light generated by thermal radiation, which has a wavelength different from that of the reflected light, when a material to be welded is irradiated with a laser beam emitted from a processing head of a laser welding machine; a spectroscopic unit, which spectroscopically separates the reflected light and the monitoring light included in the radiated light and converts the spectroscopically separated monitoring light into a first electrical signal; a triggering unit, which converts the reflected light into a second electrical signal and outputs a trigger signal when the level of the second electrical signal is above a predetermined threshold value; and a laser welding monitor, which, when the trigger signal is input, starts to determine whether the laser welding of the material to be welded is proceeding normally based on the first electrical signal.

[0010] According to a second mode of one or more embodiments, a laser welding monitoring method is provided, wherein when a material to be welded is irradiated with a laser beam emitted from a processing head of a laser welding machine, a light receiving unit receives radiated light including reflected light of the laser beam generated at an irradiation position of the laser beam and light having a wavelength different from that of the reflected light, i.e., monitoring light generated by thermal radiation, and the reflected light and the monitoring light contained in the radiated light are spectroscopically separated, the spectroscopically separated monitoring light is converted into a first electrical signal, and the reflected light is converted into a second electrical signal, a trigger signal is generated when the level of the second electrical signal is above a predetermined threshold value, the input of the trigger signal is used as a trigger, and it is determined whether the laser welding of the material to be welded is proceeding normally based on the first electrical signal.

[0011] According to the laser welding monitoring device and the laser welding monitoring method of the above embodiment, it is possible to accurately detect the timing at which the laser welding machine starts welding the materials to be welded, thereby starting monitoring of the laser welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 It is a perspective view showing a laser welding monitoring device according to one or more embodiments.

[0013] Figure 2 It is a perspective view showing a configuration example of a processing head included in a laser welding machine.

[0014] Figure 3 It is a diagram showing a configuration example of a spectroscopic unit included in a laser welding monitoring device according to one or more embodiments.

[0015] Figure 4 This is a block diagram showing a configuration example of a trigger unit included in a laser welding monitoring device according to one or more embodiments.

[0016] Figure 5 This is a characteristic diagram showing changes in the intensity of reflected light of the laser beam and radiated light of near-infrared light generated at the irradiation position of the laser beam when the laser welding machine starts irradiating the laser beam and ends irradiation.

[0017] Figure 6 This is a flowchart illustrating a laser welding monitoring method according to one or more embodiments. DETAILED DESCRIPTION

[0018] Hereinafter, a laser welding monitoring device and a laser welding monitoring method according to one or more embodiments will be described with reference to the accompanying drawings. Figure 1The laser welding machine 50 includes an NC device 10, a laser oscillator 11, and a processing head 20. As an example, the laser oscillator 11 is a fiber laser oscillator that emits a laser beam with a wavelength of 1060 nm to 1080 nm. The laser beam emitted by the laser oscillator 11 is transmitted to the processing head 20 via an operating optical fiber 12.

[0019] like Figure 2 As shown, the machining head 20 includes a galvanometer scanner 21 and an fθ lens 22. The galvanometer scanner 21 includes galvanometer mirrors 211 and 213, and drive units 212 and 214 that rotate the galvanometer mirrors 211 and 213 to predetermined angles, respectively. A laser beam emitted from the process fiber 12 and incident on the galvanometer mirror 211 is reflected by the galvanometer mirror 211 and incident on the galvanometer mirror 213. It is then reflected by the galvanometer mirror 213 and incident on the fθ lens 22. The fθ lens 22 focuses the incident laser beam and irradiates it onto the material to be welded.

[0020] By varying the angles of galvanometer mirrors 211 and 213, the laser beam irradiating the material being welded can be displaced. By continuously moving galvanometer mirrors 211 and 213, the laser beam can be vibrated or rotated. Even when galvanometer scanner 21 is in operation, fθ lens 22 can focus the laser beam on a single plane of the material being welded.

[0021] return Figure 1 The NC device 10 controls the laser oscillator 11 and the drive units 212 and 214 of the galvanometer scanner 21. The NC device 10 also controls the movement of the processing head 20. The laser beam emitted from the processing head 20 irradiates the butting surfaces 120 of metal plates W1 and W2, which are an example of materials to be welded, thereby welding the metal plates W1 and W2.

[0022] The processing head 20 does not necessarily need to include the galvanometer scanner 21, but preferably includes the galvanometer scanner 21. When the processing head 20 does not include the galvanometer scanner 21, it only needs to include a bending mirror that reflects the laser beam toward the metal plates W1 and W2 and a normal focusing lens instead of the fθ lens 22.

[0023] exist Figure 1In the laser welding monitoring device 100, there are four light receiving units: light receiving units 30a to 30c, and a light receiving unit (not shown) located opposite the light receiving unit 30b across the processing head 20. A light receiving unit at any position is referred to as a light receiving unit 30. In a configuration where the processing head 20 includes a galvanometer scanner 21, there may be two or more light receiving units 30, and a plurality of light receiving units 30 may be arranged at equal intervals around the fθ lens 22. In a configuration where the processing head 20 does not include a galvanometer scanner 21, there may be a single light receiving unit 30. Even in a configuration where the processing head 20 does not include a galvanometer scanner 21, there may be two or more light receiving units 30.

[0024] Furthermore, the laser welding monitoring device 100 includes a spectroscopic unit 40 , a trigger unit 60 , and a laser welding monitor 80 .

[0025] When the laser beam is irradiated on the butt joint 120 of the metal plates W1 and W2, radiated light including reflected light of the laser beam and near-infrared light generated by thermal radiation is generated from the irradiation position of the laser beam. The radiated light is received by the four light receiving units 30, and the radiated light received by the four light receiving units 30 is incident on the spectroscopic unit 40 through the optical fiber bundle 31. Figure 1 In the figure, the solid arrow line from the abutting surface 120 toward the light receiving unit 30 represents the reflected light of the laser beam, and the dashed arrow line represents the near-infrared light. The wavelength of near-infrared light is 1300 nm to 2500 nm. Near-infrared light is a preferred example of monitoring light generated by thermal radiation, having a wavelength different from that of the reflected light of the laser beam.

[0026] The light receiving unit 30 has a protective glass on the incident surface of the radiated light, and the radiated light is incident on the end face of the core of the optical fiber. The structure of the light receiving unit 30 is not limited as long as it receives the radiated light including the reflected light of the laser beam and the near-infrared light generated by thermal radiation.

[0027] like Figure 3 As shown, the spectroscopic unit 40 includes a dichroic mirror 41 that transmits light with a wavelength of 1300 nm or longer and reflects light with a wavelength of less than 1300 nm, and a photosensor 42. The reflected light of the laser beam, indicated by the solid arrow line, is reflected by the dichroic mirror 41, while the near-infrared light, indicated by the dashed arrow line, transmits the dichroic mirror 41 and enters the photosensor 42. The photosensor 42 converts the incident near-infrared light into an electrical signal (near-infrared monitoring signal) and outputs it. The near-infrared monitoring signal is an example of a first electrical signal. The first electrical signal may be a digital signal.

[0028] exist Figure 1The reflected light of the laser beam emitted from the spectroscopic unit 40 is transmitted through the reflected light transmission fiber 51 and enters the trigger unit 60. The near-infrared monitoring signal output from the spectroscopic unit 40 is transmitted through the monitoring signal transmission cable 52 and input to the laser welding monitor 80.

[0029] like Figure 4 As shown, the trigger unit 60 includes a photoelectric sensor 61, a level determination unit 62, and a trigger signal generating unit 63. The photoelectric sensor 61 converts the reflected light of the incident laser beam into an electrical signal (a second electrical signal). The level determination unit 62 determines whether the level of the input electrical signal is above a predetermined threshold. When the electrical signal input to the level determination unit 62 is above a predetermined threshold, the trigger signal generating unit 63 generates and outputs a trigger signal. The level determination unit 62 and the trigger signal generating unit 63 can be formed by a circuit. The level determination unit 62 and the trigger signal generating unit 63 can also be formed by a processor. The second electrical signal can be an analog signal or a digital signal. The trigger signal can be a digital signal.

[0030] exist Figure 1 In the embodiment, a trigger signal is transmitted via a trigger signal transmission cable 71 and input to a laser welding monitor 80. Upon receiving the trigger signal, the laser welding monitor 80 begins monitoring whether laser welding is proceeding normally based on the near-infrared monitoring signal, using the trigger signal input as a trigger. For example, the laser welding monitor 80 integrates the input near-infrared monitoring signal for a predetermined time. If the integrated value is between a preset upper and lower limit, the laser welding monitor 80 determines that the laser welding is proceeding normally. If the integrated value is not between the upper and lower limits, the laser welding monitor 80 determines that the laser welding is not proceeding normally and an abnormality has occurred. There is no limitation on how the laser welding monitor 80 determines whether laser welding is proceeding normally.

[0031] The laser welding monitor 80 has LEDs L1 to L4 on the front of its housing. When the laser welding monitor 80 determines that laser welding is proceeding normally, for example, the green LED L4 is illuminated. When it determines that an abnormality has occurred in the laser welding, for example, the red LED L3 is illuminated. For example, the green LED L1 illuminates when the laser welding monitor 80 is powered on. For example, the green LED L2 illuminates when a trigger signal is input.

[0032] use Figure 5 The characteristic diagram shown in FIG. 1 illustrates the timing at which the laser welding monitor 80 starts monitoring the laser welding. Figure 5In the example, the machining head 20 begins irradiating the butting surface 120 of the metal plates W1 and W2 with a laser beam at time t0 and ends irradiation at time t1. The intensity of the near-infrared light, indicated by the dashed line, gradually increases after the start of laser beam irradiation. Meanwhile, the intensity of the reflected light from the laser beam, indicated by the solid line, increases sharply immediately after the start of laser beam irradiation, then decreases sharply before remaining approximately constant.

[0033] When the threshold value set in the level determination unit 62 of the trigger unit 60 is equal to Figure 5 When the level of the electrical signal corresponding to the radiation intensity threshold TH1 shown in FIG. 1 is reached, the trigger unit 60 outputs a trigger signal immediately after time t0. Therefore, the laser welding monitoring device 100 can accurately detect the timing at which the laser welder 50 starts welding the metal sheets W1 and W2, and can begin monitoring the laser welding process with virtually no time delay from the start of welding.

[0034] exist Figure 5 If trigger unit 60 is configured to output a trigger signal when the near-infrared light intensity reaches a predetermined level, the near-infrared light intensity increases only gradually. Therefore, if laser welding is repeated under the same laser welding conditions, the timing of exceeding threshold value TH1 may vary. Consequently, the trigger signal cannot be output immediately after time t0, resulting in a time delay or variations in the timing of trigger signal output. In contrast, reflected light increases rapidly immediately after the start of processing. Therefore, even with repeated processing, variations in the timing of exceeding threshold value TH1 can be suppressed, allowing laser welding monitoring to begin with high repeatability.

[0035] use Figure 6 The flowchart shown in FIG. 1 illustrates a laser welding monitoring method executed by the laser welding monitoring device 100 . Figure 6 Also included is the processing performed by the laser welding machine 50. Figure 6 In step S1, the NC device 10 determines whether an instruction to start welding has been issued. If no instruction to start welding has been issued (No), the NC device 10 repeats the process of step S1. If an instruction to start welding has been issued (Yes), the NC device 10 starts laser oscillation of the laser oscillator 11 in step S2, thereby starting laser welding.

[0036] In step S3, the four light-receiving units 30 receive the radiated light from the laser beam irradiation position, and the optical fiber bundle 31 transmits the received radiated light to the spectroscopic unit 40. In step S4, the spectroscopic unit 40 separates the reflected light of the laser beam and the near-infrared light contained in the radiated light. In step S5, the photoelectric sensor 42 of the spectroscopic unit 40 converts the near-infrared light into an electrical signal and provides it to the laser welding monitor 80.

[0037] In parallel with step S5 , the trigger unit 60 converts the reflected light transmitted by the reflected light transmission optical fiber 51 into an electrical signal in step S6 , and outputs a trigger signal if the level of the electrical signal exceeds a threshold.

[0038] In step S7, the laser welding monitor 80 determines whether a trigger signal has been received from the trigger unit 60. If no trigger signal has been received (No), the laser welding monitor 80 repeats the process of step S7. If a trigger signal has been received (Yes), the laser welding monitor 80 starts monitoring the laser welding in step S8.

[0039] In step S9, the laser welding monitor 80 determines whether the preset measurement time has elapsed. If the measurement time has not elapsed (No), the laser welding monitor 80 repeats the process of step S9. Laser welding monitoring continues while the process of step S9 is repeated. If the measurement time has elapsed (Yes), the laser welding monitor 80 ends laser welding monitoring.

[0040] Even after the laser welding monitor 80 has finished monitoring the laser welding, welding by the laser welder 50 may not have finished. Welding by the laser welder 50 may also finish before the laser welding monitor 80 finishes monitoring the laser welding. Furthermore, even if a trigger signal is input to the laser welding monitor 80 again within the measurement time, the trigger signal within the measurement time is ignored.

[0041] The timing at which the laser welding monitor 80 ends monitoring the laser welding is not limited to the time when the measurement time has elapsed. The laser welding monitor 80 may end monitoring the laser welding when the welding performed by the laser welding machine 50 ends.

[0042] As described above, according to the laser welding monitoring device and the laser welding monitoring method of one or more embodiments, it is possible to accurately detect the timing at which the laser welding machine 50 starts welding the materials to be welded, thereby starting monitoring of the laser welding.

[0043] The present invention is not limited to the one or more embodiments described above, and various modifications are possible without departing from the spirit of the present invention. In one or more embodiments, the laser welding monitor 80 uses a near-infrared monitoring signal obtained by converting near-infrared light into an electrical signal to determine whether laser welding is proceeding normally. However, plasma light or visible light may also be converted into an electrical signal. It suffices to convert light of a wavelength different from that of the laser beam emitted by the laser oscillator 11 into an electrical signal.

[0044] A direct diode laser oscillator (DDL oscillator) may be used instead of a fiber laser oscillator as the laser oscillator 11. The DDL oscillator emits a laser beam with a wavelength of 910 nm to 950 nm. The wavelength of the laser beam emitted from the laser oscillator 11 may be in the 1 μm band of 900 nm to 1100 nm.

[0045] Figure 1 The laser welding monitoring device 100 shown has separate housings for the spectroscopic unit 40, trigger unit 60, and laser welding monitor 80. However, the trigger unit 60 may be disposed within the housing of the laser welding monitor 80. Alternatively, the spectroscopic unit 40 and trigger unit 60 may be disposed within a single housing. Alternatively, the spectroscopic unit 40 and trigger unit 60 may be disposed within the housing of the laser welding monitor 80. The placement of the spectroscopic unit 40 or trigger unit 60 is not limited.

[0046] The method of starting laser welding monitoring by inputting a trigger signal to the laser welding monitor 80 described above can also be applied when starting monitoring arc welding or laser cutting. In particular, in laser cutting of metal plates, the methods of one or more embodiments can be generally used as is, and a laser processing monitoring device and a laser processing monitoring method for laser welding or laser cutting can be provided.

[0047] This application claims priority from Japanese Patent Application No. 2020-039761, filed with the Japan Patent Office on March 9, 2020, the entire disclosure of which is incorporated herein by reference.

Claims

1. A laser welding monitoring device, characterized in that: have: a light receiving unit for receiving, when a material to be welded is irradiated with a laser beam emitted from a processing head provided in a laser welding machine, radiated light including reflected light of the laser beam generated at an irradiation position of the laser beam and monitor light generated by thermal radiation, which is light having a wavelength different from that of the reflected light; a spectroscopic unit for spectroscopically splitting the reflected light and the monitoring light contained in the radiated light, and converting the spectroscopically split monitoring light into a first electrical signal; a trigger unit that converts the reflected light into a second electrical signal, determines whether the level of the second electrical signal is above a predetermined threshold, and outputs a trigger signal when the level of the second electrical signal becomes above the predetermined threshold, the trigger signal indicating a timing at which the laser welding machine starts welding to the material to be welded; as well as The laser welding monitor starts determining whether the laser welding of the materials to be welded is progressing normally based on the first electrical signal when the trigger signal is input.

2. A laser welding monitoring device, characterized in that: have: a light receiving unit for receiving, when a material to be welded is irradiated with a laser beam emitted from a processing head provided in a laser welding machine, radiated light including reflected light of the laser beam generated at an irradiation position of the laser beam and monitor light generated by thermal radiation, which is light having a wavelength different from that of the reflected light; a spectroscopic unit for spectroscopically splitting the reflected light and the monitoring light contained in the radiated light, and converting the split monitoring light into a first electrical signal; a trigger unit, which converts the reflected light into a second electrical signal and outputs a trigger signal when the level of the second electrical signal is above a predetermined threshold; as well as The laser welding monitor, when the trigger signal is input, starts monitoring whether the laser welding of the materials to be welded is proceeding normally based on whether the integrated value obtained by integrating the first electrical signal for a predetermined time is between a preset upper limit and a preset lower limit.

3. The laser welding monitoring device according to claim 1 or 2, characterized in that: The wavelength of the laser beam is 900nm to 1100nm, and the wavelength of the monitoring light is near-infrared light of 1300nm to 2500nm.

4. The laser welding monitoring device according to claim 1 or 2, characterized in that: The processing head has: a galvanometer scanner that displaces, vibrates, or rotates the laser beam emitted from the processing head; and an fθ lens that focuses the laser beam on the material to be welded to irradiate the material to be welded, The laser welding monitoring device includes a plurality of light receiving units arranged around the fθ lens.

5. A laser welding monitoring method, characterized in that: When a laser beam emitted from a processing head of a laser welding machine is irradiated on a material to be welded, a light receiving unit receives radiated light including reflected light of the laser beam generated at the irradiation position of the laser beam and monitor light generated by thermal radiation, which is light with a wavelength different from that of the reflected light. splitting the reflected light and the monitor light contained in the radiated light, converting the split monitoring light into a first electrical signal, converting the reflected light into a second electrical signal, determining whether the level of the second electrical signal is above a predetermined threshold value, and generating a trigger signal when the level of the second electrical signal becomes above the predetermined threshold value, the trigger signal indicating the timing at which the laser welding machine starts welding to the material to be welded, The input of the trigger signal is used as a trigger to start determining whether the laser welding of the materials to be welded is progressing normally based on the first electrical signal.

6. A laser welding monitoring method, characterized in that: When a laser beam emitted from a processing head of a laser welding machine is irradiated on a material to be welded, a light receiving unit receives radiated light including reflected light of the laser beam generated at the irradiation position of the laser beam and monitor light generated by thermal radiation, which is light with a wavelength different from that of the reflected light. splitting the reflected light and the monitor light contained in the radiated light, converting the split monitoring light into a first electrical signal, converting the reflected light into a second electrical signal, generating a trigger signal when the level of the second electrical signal is above a predetermined threshold, The input of the trigger signal is used as a trigger to monitor whether the laser welding of the materials to be welded is proceeding normally based on whether the integrated value obtained by integrating the first electrical signal for a predetermined time is between a preset upper limit and a preset lower limit.

7. The laser welding monitoring method according to claim 5 or 6, characterized in that: The wavelength of the laser beam is 900nm to 1100nm, and the wavelength of the monitoring light is near-infrared light of 1300nm to 2500nm.

8. The laser welding monitoring method according to claim 5 or 6, characterized in that: The processing head has: a galvanometer scanner that displaces, vibrates, or rotates the laser beam emitted from the processing head; and an fθ lens that focuses the laser beam on the material to be welded to irradiate the material to be welded, The radiated light is received by a plurality of light receiving units arranged around the fθ lens.

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