Welding monitoring device

Abstract

In the observation of a molten zone (270) during welding, two optical paths are prepared for reflected light (205) and for visible light (206) and thermal radiation light (207), respectively, the optical paths being separated from each other by a wavelength-separating mirror (211) to allow light to enter each of the optical paths, and then combined by a wavelength-combining mirror (221) . After the reflected light (205) is coaxially combined with the visible light (206) and the thermal radiation light (207) by the wavelength-combining mirror, the combined light is incident on an end face (252) of an optical fiber (13) connected to a spectral device (40), which is connected to a determination device (50) that determines welding conditions. A collimator (290) modifies the beam diameter of at least the reflected light on the basis of the core diameter of the end face of the optical fiber so that the beam diameter of the reflected light is different from the respective beam diameters of the visible light and the thermal radiation light.

Description

Welding Monitoring Device

[0001] The present disclosure relates to a welding monitoring device that determines the welding state in laser welding processing, and particularly to the structure of a laser processing device among such devices.

[0002] In conventional laser welding, a welding condition determination unit determines the welding condition and occurrence of welding defects by observing the reflected light of the laser beam used for laser welding that is reflected from the processing portion and the plasma light and thermal radiation light that are emitted when the portion irradiated with the laser beam is heated (see, for example, Patent Document 1). Figure 9 is a diagram showing the configuration of a conventional laser processing device described in Patent Document 1.

[0003] 9 , a laser oscillator 101 generates laser light, which is transmitted to a lens barrel 103 through a laser transmission fiber 102, collimated into a parallel laser beam 106 by a collimating lens 104, reflected by a first mirror 107, and focused at a molten portion 27 of a workpiece 70 through a condenser lens 105. At the processing point of the molten portion 27, a portion of the irradiated laser beam 106 returns in the direction of irradiation as reflected light. Furthermore, as the workpiece 70 melts, plasma light and thermal radiation light are generated, which return to the condenser lens 105 in the same manner as the reflected light. Portions of the reflected light, plasma light, and thermal radiation light pass through the first mirror 107, are reflected by a second mirror 108, are incident on an optical fiber 113 by a condenser lens 111, and are sent to a spectrometer 140, where the light is converted into a signal and sent to a determination device (not shown).

[0004] International Publication No. 2022 / 181359

[0005] The configuration of a laser processing device in a conventional judgment unit is based on the assumption that the optical system is a fixed lens barrel, and when attempting to apply it to an optical system equipped with a galvanometer scanner, there are concerns about the following problems.

[0006] FIG. 10 is a diagram showing an overview of a conventional lens barrel combined with a galvanometer scanner unit. Explanation of portions overlapping with FIG. 9 will be omitted. In FIG. 10 , the optical system located between the condenser lens 105 and the workpiece 70 on the optical path of the conventional lens barrel shown in FIG. 9 is a galvanometer scanner unit 1240. By oscillating a galvanometer mirror 1241, laser light 106 can be irradiated at any position on the workpiece 260. When the scan position is the center of the scan lens 242, the reflected light, plasma light, and thermal radiation light emerging from the molten zone 261 at the center of the scan position enter the optical fiber 113 and are sent to the spectrometer 140, just as in the conventional lens barrel. On the other hand, when the scan position is at the end of the scan lens 1242, the plasma light and thermal radiation light emerging from the molten zone 262 at the end of the scan position experience chromatic aberration during transmission because the scan lens 1242 is designed to match the wavelength of the laser light 106. As a result, the positions of the plasma light and thermal radiation light are shifted relative to the positions of the reflected light when entering the optical fiber 113. Therefore, the size of the measurement area must be relatively larger than when a fixed lens barrel is used.

[0007] In recent years, laser oscillators consisting of a core and a ring have come into use to preheat the periphery of the molten zone in order to stabilize the molten zone of a weld.When such a laser oscillator is used while keeping the measurement area large, the surface of the workpiece is not melted in the preheating area of ​​the ring, so the influence of reflected light is large, and the information of the reflected light from the molten zone by the core is buried, resulting in a poor signal-to-noise ratio of the reflected light from the molten zone and a poor accuracy in determining the welding condition.Therefore, there is a problem in that the influence of the reflected light from the ring, which does not contain information reflecting the state of the molten zone, must be reduced.

[0008] An object of the present disclosure is to provide a welding monitoring device that can make stable judgments without deteriorating the signal-to-noise ratio of reflected light signals in an optical system equipped with a laser scanning unit.

[0009] The fixed lens barrel refers to an optical system that does not include a movable optical component such as a galvanometer mirror in the optical path of the laser light.

[0010] A welding monitoring device according to one aspect of the present disclosure is a welding monitoring device that determines a welding condition based on thermal radiation light, visible light, and reflected light generated at a molten zone formed on a surface of a workpiece when the workpiece is irradiated with laser light from a laser oscillator, and includes: a wavelength separation mirror that separates at least one of the thermal radiation light, the visible light, and the reflected light from the remaining light; a first lens barrel through which the at least one light passes; a second lens barrel through which the remaining light passes; a collimator that is provided within the first lens barrel and changes the beam diameter of the at least one light to be different from the beam diameters of each of the remaining light; and a wavelength combination mirror that coaxially combines the at least one light that has been separated by the wavelength separation mirror and passed through the first lens barrel and the collimator with the remaining light that has passed through the second lens barrel.

[0011] With this configuration, even when a laser scanning unit such as a galvanometer scanner unit uses laser light that has a preheating effect, such as the ring portion of a ring mode laser, the reflected light from the ring portion is prevented from entering the optical fiber, and the signal-to-noise ratio of the reflected light is improved, making it easier to obtain information about the molten portion and improving the accuracy of the determination.

[0012] As described above, according to the welding monitoring device of the above aspect of the present disclosure, by appropriately changing the beam diameter of the at least one light beam so that it is different from the beam diameters of the remaining light beams, it is possible to stably determine the welding condition without deteriorating the signal-to-noise ratio of the reflected light signal in an optical system equipped with a laser scanning unit. Therefore, it is possible to reduce or eliminate the influence of reflected light from, for example, a ring portion of a ring-mode laser, which has high reflectivity and does not contain information about the molten metal because the metal is not melted. As a result, it is possible to obtain information about the reflected light from the molten metal only or mostly from the molten metal. Furthermore, it is possible to maintain a relatively large measurement area for visible light and thermal radiation light, which have weaker light intensities than the reflected light, thereby preventing a decrease in the accuracy of determining the welding condition.

[0013] 1 is a diagram illustrating an overview of a determination system according to a first embodiment of the present disclosure. FIG. 2 is a diagram illustrating a configuration of a laser processing device according to a first embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a configuration of a spectroscopic device in the determination system. FIG. 4 is a block diagram illustrating an example of a configuration of a determination device in the determination system. FIG. 5 is a diagram illustrating the relationship between a measurement range and an optical system. FIG. 6 is a schematic diagram illustrating a focused spot of light on an incident end face of an optical fiber. (a) is a diagram of a conventional laser processing device described in Patent Document 1. (b) is a diagram of a case where a galvanometer scanner unit is combined with a conventional laser processing device. (c) is a diagram of a case where a ring laser oscillator is combined with (b). (d) is a diagram of a case according to the first embodiment of the present disclosure. FIG. 7 is a diagram illustrating a signal from an optical sensor according to the first embodiment of the present disclosure. FIG. 8 is a flowchart illustrating a determination process in a determination device. FIG. 9 is a diagram illustrating the configuration of a conventional laser processing device described in Patent Document 1. FIG. 10 is a diagram illustrating an overview of a case where a conventional lens barrel is combined with a galvanometer scanner unit.

[0014] Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the inventors provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and the subject matter described in the claims is not limited by them.

[0015] (First Embodiment) 1. Configuration A determination system according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing an overview of a determination system 100, which is an example of a welding monitoring device according to the first embodiment.

[0016] 1-1. System Overview The judgment system 100 includes, as an example, a laser processing device 30 that performs laser processing for lap welding, a spectrometer 40 that detects light components, and a judgment device 50, and irradiates a workpiece 70 with laser light 6 from a laser oscillator 1, and judges the welding condition based on thermal radiation light 207, visible light 206, and reflected light 205 generated in a molten zone 27 formed on the surface of the workpiece 70.

[0017] The laser processing device 30, the spectroscopic device 40, and the determination device 50 are examples of the laser processing device, the spectroscopic device, and the determination device according to the above aspects of the present disclosure, respectively.

[0018] The laser processing device 30 includes at least a laser scanning unit, a wavelength separation mirror 211 , a first lens barrel 210 , a second lens barrel 220 , a collimator 290 ( 212 , 213 ), and a wavelength coupling mirror 221 .

[0019] The galvanometer scanner unit 240 is an example of a laser scanning unit, and oscillates a galvanometer mirror 241 to irradiate the workpiece 70 with the laser light 6 while scanning it.

[0020] The wavelength separation mirror 211 separates at least one of the thermal radiation light 207 , the visible light 206 , and the reflected light 205 , for example, the reflected light 205 , from the remaining light, for example, the thermal radiation light 207 and the visible light 206 .

[0021] The first lens barrel 210 passes reflected light 205, which is an example of at least one type of light.

[0022] The second lens barrel 220 transmits the remaining light, ie, thermal radiation light 207 and visible light 206 .

[0023] The collimator 290 changes the beam diameter of the reflected light 205 inside the first lens barrel 210 so that the beam diameter of the reflected light 205 differs from the beam diameters of the thermal radiation light 207 and the visible light 206 .

[0024] The wavelength combining mirror 221 coaxially combines the reflected light 205 that has been separated by the wavelength separating mirror 211 and passed through the first lens barrel 210 and collimator 290, and the thermal radiation light 207 and visible light 206 that have passed through the second lens barrel 220.

[0025] The reflected light 205, the thermal radiation light 207, and the visible light 206 are coaxially combined by the wavelength combining mirror 221 and then incident on the end face 252 of the optical fiber 13 connected to the spectrometer 40 which is connected to the determination device 50 for determining the welding condition.

[0026] The collimator 290 changes the beam diameter of the reflected light 205 so that it is different from the beam diameters of the remaining light beams based on the core diameter of the end face 252 of the optical fiber 13. For example, in the case of a ring mode laser as an example of the laser oscillator 1, the beam diameter of the reflected light 205 is changed so that the ring portion 205b of the reflected light 205 is larger than the core diameter of the end face 252 of the optical fiber 13 and the core portion 205a of the reflected light 205 is smaller than the core diameter of the end face 252 of the optical fiber 13.

[0027] These configurations are described in more detail below.

[0028] The workpiece 70 for lap welding is made of, for example, metal, and when the laser light 6 is irradiated onto the workpiece 70, thermal radiation light 207 in the near-infrared region due to a temperature rise and visible light 206, i.e., light emission specific to metal or plasma light emission which is mainly a visible light component, are generated.

[0029] Furthermore, a portion of the laser beam 6 that does not contribute to processing is reflected as return light, i.e., reflected light 205. In this manner, when the laser beam 6 is irradiated onto the workpiece 70 from the laser processing device 30, thermal radiation light 207, visible light 206, and reflected light 205 are generated in the molten zone 27, which is an example of a welded zone formed in the workpiece 70.

[0030] The generated light is collected in the laser processing device 30 and transmitted to the spectroscopic device 40 through the optical fiber 13 connecting the laser processing device 30 and the spectroscopic device 40 .

[0031] The light transmitted to the spectroscopic device 40 is split into thermal radiation light 207, visible light 206, and reflected light 205, which are each detected by the optical sensor 22 of the spectroscopic device 40 and converted into a signal.

[0032] When the determination device 50 receives a signal from the spectrometer 40, it determines the welding condition such as abnormal combustion due to focal position deviation and / or contamination at the focal position F1 of the laser light 6, and outputs the determination result.

[0033] The deviation of the focal position F1 is determined by a numerical value including the distance (- or +) in the irradiation direction from the reference value "0," where the position where the spot diameter of the laser beam 6 is smallest near the surface of the workpiece 70 when the laser beam 6 is irradiated onto the workpiece 70 is set as the reference value. Furthermore, abnormal combustion is determined by observing a change in the intensity of the reflected light 205 due to the disturbance of the molten pool in the molten part 27, or an increase in the visible light 206 and the thermal radiation light 207 due to combustion, since combustion gas is generated due to contamination or the like.

[0034] Although lap welding has been described as an example here, the present disclosure may be applied to other welding methods such as butt welding.

[0035] 2 is a diagram illustrating the configuration of the laser processing apparatus 30 according to the present embodiment 1. The laser processing apparatus 30 includes, as an example, a laser oscillator 1, a laser transmission fiber 2, a lens barrel 3, a collimating lens 4, a galvanometer scanner unit 240, a galvanometer mirror 241, a scan lens 242, a first mirror 7, a first lens barrel 210, a wavelength separation mirror 211, a lens 212, a lens 213, a mirror 214, a second lens barrel 220, a wavelength coupling mirror 221, a mirror 222, a notch filter 223, an entrance lens barrel 250, and a lens 251.

[0036] A laser oscillator 1 supplies light for generating pulsed laser light 6 having a wavelength of, for example, approximately 1070 nanometers (nm). The light supplied from the laser oscillator 1 is transmitted to a lens barrel 3 via a laser transmission fiber 2, passes through a collimating lens 4 for obtaining a parallel beam within the lens barrel 3, forms laser light 6, and travels straight through the lens barrel 3. In this case, the configuration of the laser oscillator 1 and the laser transmission fiber 2 may be a single-core configuration, or may be an oscillator configuration having a double-core or triple-core profile accompanied by a ring portion.

[0037] The laser beam 6 is reflected by the first mirror 7 except for a portion that passes through, reflected by the galvanometer mirror 241, and focused on the workpiece 260 by the scan lens 242. At this time, by changing the rotation angle of the galvanometer mirror 241, the position of the laser beam 6 on the workpiece 260 (corresponding to the workpiece 70 in FIG. 1) can be moved while being irradiated. In this way, laser processing for lap welding is performed on the workpiece 260.

[0038] The wavelength of the laser light 6 is not limited to 1070 nm, and it is preferable to use a wavelength that is highly absorbed by the material.

[0039] When the laser beam 6 is irradiated onto the workpiece 260, thermal radiation light 207 from the workpiece 260, visible light 206 due to plasma emission, and reflected light 205 of the laser beam 6 are generated in the molten zone 261. These light components pass through the scan lens 242, are reflected by the galvanometer mirror 241, and are transmitted through the first mirror 7 at one end of the first lens barrel 210, the thermal radiation light 207 and visible light 206 are reflected by the wavelength separation mirror 211 and proceed to one end of the second lens barrel 220, and the reflected light 205 is transmitted through the wavelength separation mirror 211 and proceeds to the other end of the first lens barrel 210. As an example, the first lens barrel 210 and the second lens barrel 220 are arranged with their optical axes parallel to each other.

[0040] In the first lens barrel 210, a reduction collimator 290 is formed by lenses 212 and 213, and the beam diameter of the reflected light 205 is reduced by passing through the reduction collimator 290, and the reflected light 205 is reflected by a mirror 214 at the other end of the first lens barrel 210 and enters the other end of the second lens barrel 220.

[0041] As will be described in detail later with reference to Figures 5 and 6, the magnification of the reduction collimator 290 indicates the measurement range of the reflected light 205, and changing the collimator magnification makes it possible to suppress the influence of light that becomes noise. In the case of an optical fiber consisting of a ring portion and a core portion, the outer diameter of the core portion, which is the signal source, is approximately several times to one-tenth of the outer diameter of the ring portion, which is the main noise source. Therefore, the collimator magnification is set to a range of 0.95 to 0.1 times accordingly. Here, the diameter of the reflected light 205 imaged on the optical fiber end face 252 by the reduction collimator 290 is proportional to the reciprocal of the collimator magnification. In other words, when the collimator magnification is 0.95 to 0.1 times, the diameter of the image of the reflected light 205 is 1.05 to 10 times. That is, when the ratio of the outer diameter of the core portion to the outer diameter of the ring portion is one-tenth, by setting the collimator magnification to 0.1, the imaging range of the reflected light 205 from the core portion becomes approximately equal to the diameter of the optical fiber end face 252, and it becomes possible to prevent the reflected light 205 from the ring portion from entering the optical fiber 13. A similar calculation is possible when the ratio of the outer diameters is one-tenth.

[0042] In the second lens barrel 220, the thermal radiation light 207 and visible light 206 are reflected by the mirror 222 so as to be parallel to the reflected light 205 in the first lens barrel 210, pass through the notch filter 223, are reflected by the wavelength coupling mirror 221, and proceed to the input lens barrel 250.

[0043] The notch filter 223 is set to block the wavelength of the reflected light 205 .

[0044] The wavelength coupling mirror 221 transmits the reflected light 205 incident from the first lens barrel 210 side and guides it to the incident lens barrel 250. At this time, the positions and angles of the mirrors 214 and 222 are adjusted so that the reflected light 205, the thermal radiation light 207, and the visible light 206 traveling from the second lens barrel 220 to the incident lens barrel 250 are coaxial.

[0045] Although the reduction collimator 290 in FIG. 2 is of the Galilean type, which is a combination of concave and convex lenses, the lens 212 and the lens 213, it may be of the Keplerian type, which is a combination of convex and convex lenses.

[0046] In the incident lens barrel 250, the reflected light 205, visible light 206, and thermal radiation light 207 are focused onto a fiber end face 252 by a lens 251 and transmitted to the spectrometer 40 through the optical fiber 13. Here, by superimposing the reflected light 205, visible light 206, and thermal radiation light 207, only one optical fiber 13 is required to transmit light to the spectrometer 40, which is the same as in the conventional case, and therefore retrofitting to parts other than the optical system of the laser processing device is possible.

[0047] The laser light 204 that is a part of the laser light 6 that has passed through the first mirror 7 may be detected by the photodetector 233 or a camera.

[0048] 3 is a diagram illustrating the configuration of a spectroscopic device 40 according to the first embodiment. The spectroscopic device 40 includes, inside a housing 28, a collimating lens 15, a third mirror 16, a fourth mirror 17, a fifth mirror 18, condensing lenses 19, 20, and 21, optical sensors 22 (22a, 22b, and 22c), a transmission cable 23, and a controller 24.

[0049] The housing 28 prevents unwanted light from entering the spectroscopic device 40 from the outside and prevents light from leaking from the inside.

[0050] The collimating lens 15 converts the light transmitted from the laser processing device 30 through the optical fiber 13 back into parallel light.

[0051] The third mirror 16 transmits visible light 206 with a wavelength of 400 nm to 700 nm, for example, and reflects other components. The fourth mirror 17 reflects reflected light 205 of the laser light 6 with a wavelength of approximately 1070 nm, for example, and transmits other components. The fifth mirror 18 reflects thermal radiation light 207 with a wavelength of 1300 nm to 1550 nm, for example.

[0052] The light that has passed through the collimating lens 15 is split into visible light 206, reflected light 205, and thermal radiation light 207 by the third mirror 16, fourth mirror 17, and fifth mirror 18, and each of these components is condensed by condenser lenses 19 to 21. Note that bandpass filters for visible light 206, reflected light 205, and thermal radiation light 207 may be disposed in the optical path after the third mirror 16, fourth mirror 17, and fifth mirror 18, respectively, to enable selection of the wavelengths to be passed.

[0053] The optical sensor 22 includes, for example, optical sensors 22a, 22b, and 22c, each highly sensitive to a different wavelength. The optical sensors 22a, 22b, and 22c detect the components of visible light 206, reflected light 205, and thermal radiation light 207 collected by the respective collecting lenses 19 to 21, and generate electrical signals corresponding to the intensities of the detected light. Note that the optical sensor 22 may be configured as a single optical sensor capable of detecting the intensity for each wavelength.

[0054] The electrical signals generated by the optical sensors 22 are transmitted to a controller 24 via transmission cables 23, respectively.

[0055] The controller 24 is a hardware controller. The controller 24 includes a CPU, a communication circuit, etc., and transmits the electrical signal received from the optical sensor 22 to the determination device 50. The controller 24 is equipped with, for example, an A / D converter to convert the analog electrical signal into a digital signal (also simply referred to as a "signal"). Note that the sampling period for converting into a digital signal is preferably, for example, 1 / 100 or less of the time for controlling the output of the laser light 6, from the viewpoint of ensuring a sufficient number of samples for capturing the characteristics of the machining process and the trends in local values ​​of physical quantities in determining the welding state.

[0056] 4 is a block diagram illustrating the configuration of the determination device 50 according to the first embodiment. The determination device 50 is configured as an information processing device such as a computer. The determination device 50 includes a CPU 51 that performs calculation processing, a communication circuit 52 for communicating with other devices, and a storage device 53 that stores data and computer programs.

[0057] The CPU 51 is an example of an arithmetic circuit of the determination device in the present embodiment 1. The CPU 51 executes a control program 56 stored in the storage device 53 to realize predetermined functions including learning and executing a determination model 57. The determination device 50 realizes the function of the determination device in the present embodiment 1 by the CPU 51 executing the control program 56. Note that the arithmetic circuit configured as the CPU 51 in the present embodiment 1 may be realized by various processors such as an MPU or a GPU, and may be configured by one or more processors.

[0058] The communication circuit 52 is a communication circuit that performs communication in accordance with a standard such as IEEE 802.11, 4G, or 5G. The communication circuit 52 may perform wired communication in accordance with a standard such as Ethernet (registered trademark). The communication circuit 52 is connectable to a communication network such as the Internet. The determination device 50 may also communicate directly with other devices via the communication circuit 52 or may communicate via an access point. The communication circuit 52 may also be configured to be able to communicate with other devices without using a communication network. For example, the communication circuit 52 may include connection terminals such as a USB (registered trademark) terminal and an HDMI (registered trademark) terminal.

[0059] The storage device 53 is a storage medium that stores computer programs and data necessary to realize the functions of the determination system 100, and stores the control program 56 executed by the CPU 51 and various data. After the determination model 57 is constructed, the storage device 53 stores the determination model 57.

[0060] The storage device 53 is configured with, for example, a magnetic storage device such as a hard disk drive (HDD), an optical storage device such as an optical disk drive, or a semiconductor storage device such as an SSD. The storage device 53 may include a temporary storage element configured with, for example, a RAM such as a DRAM or an SRAM, and may function as an internal memory of the CPU 51.

[0061] 2. Operation In the determination system 100 configured as described above, as shown in FIG. 1 , the laser processing device 30 splits the components of reflected light 205, visible light 206, and thermal radiation light 207 generated in the molten zone 27 when the workpiece 70 is irradiated with the laser beam 6, and passes them through the first lens barrel 210 or the second lens barrel 220, thereby limiting the measurement area and selecting the light obtained from the molten zone 27 to send to the spectrometer 40. The spectrometer 40 detects the components of the thermal radiation light 207, visible light 206, and reflected light 205 transmitted from the laser processing device 30 via the optical fiber 13 using the optical sensor 22. The spectrometer 40 transmits a signal corresponding to the intensity of each detected component to the determination device 50.

[0062] The operations of the laser processing device 30 and the determination device 50 in the determination system 100 will be described below.

[0063] 2-1. Measurement Area Limiting Process The measurement area limiting process for limiting the measurement area of ​​the reflected light 205 in the laser processing device 30 to suppress a decrease in the information on the molten portion 27 will be described below with reference to FIGS. 5 and 6.

[0064] 5 is a diagram showing the relationship between the measurement range and the optical system in the laser processing device 30 of the present embodiment 1. The relationship between the core diameter of the optical fiber 13 and the measurement range in which the light emitted from the fusion zone 27 can be focused and incident on the core of the optical fiber 13 is, for example, expressed as follows: ｃｏｒｅ = 1.0 mm, measurement range is D ｍｅａｓｕｒｅ , the focal length of the lens 251 on the optical fiber 13 side is f ｆｉｂｅｒ = 80 mm, and the focal length of the lens 242 on the melting part side is f ｍｅａｓｕｒｅ = 163 mm, it can be expressed as follows: The above numerical values ​​are values ​​in the first embodiment.

[0065] D ｍｅａｓｕｒｅ = D ｃｏｒｅ × f ｍｅａｓｕｒｅ ÷ f ｆｉｂｅｒ= Φ1.0 mm × 163 mm ÷ 80 mm = Φ2.0 mm In other words, in the present embodiment 1, the measurement range is set to Φ2.0 mm and the light generated within the measurement range is measured. In Figure 2, the lens on the molten portion side corresponds to the scan lens 242, and the lens on the optical fiber side corresponds to the lens 251.

[0066] Next, it will be explained how the collimator magnification of the lenses 212 and 213 in the first lens barrel 210 affects the measurement range. In the first embodiment, if the collimator magnification is 0.5, the following relationship holds:

[0067] D ｍｅａｓｕｒｅ = D ｃｏｒｅ × f ｍｅａｓｕｒｅ ÷ f ｆｉｂｅｒ × Collimator magnification = Φ1.0 mm × 163 mm ÷ 80 mm × 0.5 times = Φ1.0 mm In other words, this relationship can be restricted so that if the size of the molten portion 27 does not change, for example if the molten portion 27 is Φ2.0 mm and the collimator magnification is 0.5, the light transmitted within a range of Φ2.0 mm is irradiated onto the end face 252 of the incident end of the optical fiber 13, and only the area of ​​Φ1.0 mm of the core diameter of the optical fiber 13 is incident.

[0068] FIG. 6 is a schematic diagram showing a focused spot of light on the end face 252 of the incident end of the optical fiber 13. As shown in FIG.

[0069] Figure 6(a) shows the optical system of the conventional laser processing device of Figure 9 and the focused spot positions on the optical fiber incident end face of the optical fiber of reflected light 205, visible light 206, and thermal radiation light 207 generated from the melted part at the scan center position of Figure 2. The reflected light 205, visible light 206, and thermal radiation light 207 are focused at approximately the same position relative to the core diameter of the optical fiber incident end face 252, showing that all of the light amounts are incident.

[0070] 6B shows the focused spot positions on the optical fiber incident end face 252 of the reflected light 205, visible light 206, and thermal radiation light 207 generated from the molten portion 261 at the scan center position in FIG. 2. When the visible light 206 and thermal radiation light 207 pass through the scan lens 242, which is designed depending on the wavelength of the laser light 6, chromatic aberration occurs, causing the focused spot positions on the optical fiber incident end face 252 to move to positions relative to the reflected light 205. Therefore, when using the scan lens 242, the focal length of the scan lens 242 is set to 163 mm and the focal length of the lens 251 is set to 80 mm so that the measurement range is Φ2.0 mm in order to efficiently acquire the visible light 206 and thermal radiation light 207.

[0071] 6(c) shows an example in which a ring mode laser, which has been widely used in recent years to stabilize welding, is used as the laser oscillator 1. In this case, the reflected light 205 directly follows the ring mode shape of the laser oscillator 1. Therefore, the reflected light 252b from the ring portion used for preheating does not melt the workpiece 70, and is light with a stronger intensity than the reflected light 252a from the core portion corresponding to the molten portion 27. This reduces the accuracy of information on the welding state of the molten portion 27.

[0072] 7A and 7B are diagrams illustrating signals from optical sensor 22 according to the first embodiment of the present disclosure. (a) of Fig. 7 illustrates signals from core portion 205a and ring portion 205b of reflected light 205. The signal from core portion 205a includes a spire-like signal 291 indicating an abnormality in fusion zone 27. The signal voltage from ring portion 205b is at a higher level than the signal voltage from core portion 205a. A conventional laser processing device would produce a signal voltage waveform as shown in (b) of Fig. 7B, and the signal-to-noise ratio of the spire-like voltage change indicating an abnormality would be poor.

[0073] Figure 6(d) shows the focused spot positions of reflected light 205, visible light 206, and thermal radiation light 207 from the ring mode laser oscillator at the optical fiber incident end face 252 when the collimator magnification of the collimator 290, formed by the lenses 212 and 213 of the first lens barrel 210, is set to 0.3. In this case, the ring portion 205b of the reflected light 205 is larger than the core diameter of the optical fiber incident end face 252, so it does not enter the optical fiber 13. Therefore, melted portion information of only the core portion 252a of the reflected light 205 is obtained, resulting in an improved signal-to-noise ratio compared to the state shown in Figure 6(c). Figure 7(c) compares the normalized change in signal voltage when information of only the core portion 252a is obtained and when signals from the core and ring portions are mixed. It can be seen that the noise level for the peak-shaped signal 291 indicating an abnormality is clearly improved.

[0074] In this way, in order to clearly improve the noise level for the spiky signal 291 indicating an abnormality, the inner diameter of the ring portion 205b of the reflected light 205 may be made larger than the core diameter of the optical fiber incident end face 252 so that the ring portion 205b of the reflected light 205 does not enter the optical fiber incident end face 252. However, the present disclosure is not limited to this, and in order to be able to recognize that the noise level has been improved in practice, it is preferable to prevent a part or all of the ring portion 205b of the reflected light 205 from entering the optical fiber incident end face 252. In other words, including the above-mentioned cases in which the noise level can be clearly improved and cases in which the noise level can be recognized as having been improved in practice, the ring portion 205b of the reflected light 205 may be configured to be disposed relative to the optical fiber incident end face 252 so that the average signal strength of the ring portion 205b of the reflected light 205 is 20% or less of the average signal strength of the core portion 205a of the reflected light 205.

[0075] The configuration shown in Figure 6(d) makes it possible to remove light that becomes noise from around the molten part 27, making it possible to determine the welding condition even when using the galvanometer scanner unit 240 and ring mode laser.

[0076] In the first embodiment, the wavelength of the reflected light 205 is assumed to be the wavelength of the laser light 6 of approximately 1070 nm, the wavelength of the visible light 206 to be 400 nm to 700 nm, and the wavelength of the thermal radiation light 207 to be 1300 nm to 1550 nm. In particular, since the wavelength of the reflected light 205 depends on the laser used, a laser oscillator suitable for processing may be selected.

[0077] 2-2. Determination Process The determination process for determining the displacement of the focal position F1 as the welding state in the determination device 50 will be described below with reference to FIG.

[0078] 8 is a flowchart illustrating a determination process in the determination device 50 according to the first embodiment. Each process shown in the flowchart is executed by, for example, the CPU 51 of the determination device 50. This flowchart is started when, for example, a user of the determination system 100 inputs a predetermined operation for starting the determination process from an input device connected via the communication circuit 52.

[0079] First, the CPU 51 acquires signals corresponding to the components of thermal radiation light, visible light, and reflected light detected by the optical sensor 22 of the spectrometer 40 via the communication circuit 52 (step S1).

[0080] Next, the CPU 51 calculates, from the acquired signal, a feature amount to be input to the determination model 57 (step S2).

[0081] In particular, thermal radiation light and visible light are likely to reflect changes in the molten state of the material of the workpiece 260, and by using the slope of the signal waveforms of these components as a feature amount, it is possible to accurately determine the deviation of the focal position F1. The feature amount is not limited to the slope. By comparing the average signal strength at the time of measurement with the average signal strength measured in advance under normal conditions and defining the ratio as the amount of fluctuation in signal strength and using it as a feature amount, it can also be used to detect welding abnormalities such as the generation of spatter.

[0082] After calculating the feature amount (step S2), the CPU 51 inputs the feature amount into the determination model 57 and performs a process of determining a deviation of the focal position F1 (step S3). In this embodiment, in the process of the determination model (step S3), the CPU 51 determines a numerical value indicating the relative position of the focal position F1 with respect to a reference position as the deviation of the focal position F1.

[0083] The CPU 51 outputs the determination result of the deviation of the focal position F1 determined by the processing of the determination model (step S3) via the communication circuit 52 (step S4). The determination result may be received and displayed, for example, by an external information processing device or display device. Alternatively, the determination device 50 may include a display device (e.g., a display) that can communicate with the CPU 51, and the determination result may be displayed on the display device.

[0084] Thereafter, the CPU 51 ends the flowchart of Fig. 8. The flowchart of Fig. 8 is repeatedly executed, for example, every time welding is performed on each workpiece 260.

[0085] According to the above-described determination process, the determination device 50 of the first embodiment acquires a signal generated by the optical sensor 22 of the spectrometer 40 (step S1), calculates a feature value from the signal (step S2), and determines the deviation of the focal position F1 using the determination model 57 based on the feature value (step S3). This allows the determination device 50 to determine in detail the deviation of the focal position F1 of the laser light 6 as the welding state in laser processing for lap welding.

[0086] 3. Effects, etc. As described above, the first embodiment provides a welding monitoring device for determining the welding state during laser processing, which enables the introduction of a galvanometer scanner unit 240 for lap welding and butt welding using a laser processing apparatus and the application of a laser oscillator 1 with a preheating effect, such as a ring laser. This device provides two lens barrels 210, 220 in the optical system of the laser processing apparatus 30, and sets appropriate measurement regions for the reflected light 205, visible light 206, and thermal radiation light 207 (in other words, by setting the reflected light 205 so that part or all of the ring portion 205b does not enter the optical fiber incident end face 252), thereby eliminating or suppressing the influence of the reflected light 205 from the ring portion 205b, which has high reflectivity due to the metal not being molten. As a result, only or mainly reflected light information from the molten portion 27 can be obtained. Furthermore, it is possible to maintain a relatively large measurement area for the plasma light and thermal radiation light 207 of visible light 206, and it is possible to prevent a decrease in the S / N ratio of the measurement signal even with a light intensity that is weaker than that of reflected light 205. As a result, the S / N ratio of the light transmitted to spectrometer 40 is improved, and the accuracy of the welding condition determination result is improved.

[0087] It should be noted that any of the various embodiments or modifications described above can be appropriately combined to achieve the effects of each. In addition, combinations of embodiments, combinations of examples, or combinations of embodiments and examples are possible, and combinations of features from different embodiments or examples are also possible.

[0088] (Additional Notes) The above description of the embodiments discloses the following techniques.

[0089] (Technology 1) A welding monitoring device that determines a welding state based on thermal radiation light, visible light, and reflected light generated at a molten zone formed on a surface of a workpiece when the workpiece is irradiated with laser light from a laser oscillator, the welding monitoring device comprising: a wavelength separation mirror that separates at least one of the thermal radiation light, the visible light, and the reflected light from the remaining light; a first lens barrel through which the at least one light passes; a second lens barrel through which the remaining light passes; a collimator that is provided within the first lens barrel and changes the beam diameter of the at least one light to be different from the beam diameter of the remaining light; and a wavelength combining mirror that coaxially combines the at least one light that has been separated by the wavelength separation mirror and passed through the first lens barrel and the collimator with the remaining light that has passed through the second lens barrel.

[0090] (Technology 2) A welding monitoring device according to Technology 1, further comprising a galvano scanner unit that irradiates the workpiece with the laser light while scanning it, wherein the laser oscillator is a ring mode laser, the reflected light of the ring mode laser includes a core portion and a ring portion, the at least one light is the reflected light, the at least one light and the remaining light are coaxially coupled by the wavelength coupling mirror and then incident on an end face of an optical fiber connected to a spectrometer that is connected to a determination device that determines the welding state, and the beam diameter of the at least one light is changed so that the ring portion of the reflected light is larger than the core diameter of the end face of the optical fiber and the core portion of the reflected light is smaller than the core diameter of the end face of the optical fiber (in other words, the ring portion of the reflected light is configured to be positioned with respect to the end face of the optical fiber so that the average signal strength of the ring portion of the reflected light is 20% or less of the average signal strength of the core portion of the reflected light).

[0091] (Technology 3) The welding monitoring device according to Technology 1 or 2, wherein the at least one light includes the reflected light, and the remaining light includes the thermal radiation light and the visible light.

[0092] (Technology 4) The welding monitoring device according to any one of Technologies 1 to 3, wherein the wavelength range of the visible light is 400 nm to 700 nm, the wavelength of the thermal radiation light is 1300 nm to 1550 nm, and the wavelength of the reflected light is the oscillation wavelength of the laser oscillator used.

[0093] (Technology 5) The welding monitoring device according to any one of Technologies 1 to 4, wherein the at least one light includes the reflected light, the remaining light includes the thermal radiation light and the visible light, and the wavelength separation mirror reflects wavelengths of the visible light and the thermal radiation light and transmits wavelengths of the reflected light.

[0094] (Technology 6) The welding monitoring device according to any one of Technologies 1 to 5, wherein the at least one light includes the reflected light, and the remaining light includes the thermal radiation light and the visible light, and the wavelength coupling mirror coaxially couples the at least one light and the remaining light while reflecting wavelengths of the visible light and the thermal radiation light and transmitting wavelengths of the reflected light.

[0095] (Technology 7) The welding monitoring device according to any one of Technologies 1 to 6, wherein the at least one light includes the reflected light, and the remaining light includes the thermal radiation light and the visible light, and the welding monitoring device has an optical path for the at least one light that is separated by the wavelength separation mirror and passes through the first lens barrel and the collimator, and an optical path for the remaining light that is separated by the wavelength separation mirror and passes through the second lens barrel.

[0096] (Technology 8) The welding monitoring device according to any one of Technologies 1 to 7, wherein the collimator is a reduction collimator with a magnification in the range of 0.95 to 0.1 times.

[0097] Conventional laser welding welding condition assessment systems are based on a fixed-barrel optical system, which poses problems when applied to an optical system including a galvanometer scanner unit. In particular, chromatic aberration occurs when scanning at the edge of the scan lens, resulting in misalignment of the reflected light. Furthermore, when stabilizing the molten zone using a laser oscillator, the influence of reflected light increases, degrading the signal-to-noise ratio of the reflected light signal and reducing the accuracy of the weld condition assessment. Each of the above technologies solves these problems. That is, each of the above configurations appropriately changes the beam diameter of at least one light beam so that it is different from the beam diameters of the remaining light beams, enabling stable assessment without degrading the signal-to-noise ratio of the reflected light signal in an optical system equipped with a laser scanning unit. This reduces or eliminates the influence of reflected light from, for example, the ring portion of a ring-mode laser, which has high reflectivity and does not contain information about the molten zone because the metal is not melted. As a result, it is possible to obtain only or mostly reflected light information from the molten zone. Furthermore, it is possible to maintain a relatively large measurement area for visible light and thermal radiation, which are weaker than the reflected light, thereby preventing a decrease in the accuracy of the weld condition assessment.

[0098] The welding monitoring device according to the above aspect of the present disclosure has the effect of preventing a decrease in the signal-to-noise ratio of the measurement signal when a laser oscillator having a preheating effect, such as a galvanometer scanner unit or a ring laser, is introduced, and can also be used to monitor the welding condition of laser welding in the manufacture of batteries or electronic devices, etc.

[0099] REFERENCE SIGNS LIST 1 laser oscillator 2 laser transmission fiber 3 lens barrel 4 collimating lens 5, 11 condensing lens 6 laser light 7 first mirror 8 second mirror 13 optical fiber 15 collimating lens 16 third mirror 17 fourth mirror 18 fifth mirror 19, 20, 21 condensing lens 22 optical sensor 23 transmission cable 24 controller 26 holding jig 27 melting portion 30 laser processing device 40 spectroscope 50 judgment device 51 CPU 52 communication circuit 53 storage device 56 control program 57 judgment model 70 workpiece F1 focal position D1 training data 100 judgment system 201 laser oscillator 202 optical fiber 203 laser light 204 transmitted laser light 205 reflected light 205a core portion of reflected light 205b Ring portion of reflected light 206 Visible light 207 Thermal radiation light 210 First lens barrel 211 Wavelength separation mirror 212 Lens 213 Lens 214 Mirror 220 Second lens barrel 221 Wavelength coupling mirror 222 Mirror 223 Notch filter 233 Photodetector 240 Galvanometer scanner unit 241 Galvanometer mirror 242 Scan lens 250 Incident lens barrel 251 Lens 252 Fiber end face 260 Workpiece 261 Melted portion at center of scan position 262 Melted portion at end of scan position 290 Reduction collimator 291 Spire-like signal

Claims

1. In a welding monitoring device that determines a welding state based on thermal radiation light, visible light, and reflected light generated in a molten part formed on the surface of a workpiece by irradiating the workpiece with laser light from a laser oscillator, a wavelength separation mirror that separates at least one of the thermal radiation light, the visible light, and the reflected light from the remaining light; a first lens barrel through which the at least one light passes; a second lens barrel through which the remaining light passes; a collimator provided in the first lens barrel for changing the beam diameter of the at least one light to be different from the beam diameter of the remaining light; a wavelength combining mirror that coaxially combines the at least one light that has been separated by the wavelength separation mirror and passed through the first lens barrel and the collimator with the remaining light that has passed through the second lens barrel. A welding monitoring device.

2. Further comprising a galvanometer scanner unit that irradiates the workpiece while scanning the laser light, the laser oscillator is a ring mode laser, the reflected light of the ring mode laser includes a core part and a ring part, the at least one light is the reflected light, after the at least one light and the remaining light are coaxially combined by the wavelength combining mirror, they are incident on the end face of an optical fiber connected to a spectroscopic device connected to a determination device for determining the welding state, the collimator changes the beam diameter of the at least one light so that the ring part of the reflected light is larger than the core diameter of the end face of the optical fiber and the core part of the reflected light is smaller than the core diameter of the end face of the optical fiber. The welding monitoring device according to claim 1.

3. The welding monitoring device according to claim 1, wherein the at least one light includes the reflected light, and the remaining light includes the thermal radiation light and the visible light.

4. The welding monitoring device according to claim 1, wherein the wavelength range of the visible light is 400 nm to 700 nm, the wavelength of the thermal radiation light is 1300 nm to 1550 nm, and the wavelength of the reflected light is the oscillation wavelength of the laser oscillator used.

5. The welding monitoring device according to claim 4, wherein the at least one light includes the reflected light, the remaining light includes the thermal radiation light and the visible light, the wavelength separation mirror reflects the wavelengths of the visible light and the thermal radiation light and transmits the wavelength of the reflected light.

6. The at least one light includes the reflected light, the remaining light includes the thermal radiation light and the visible light, and the wavelength combining mirror reflects the wavelengths of the visible light and the thermal radiation light and transmits the wavelength of the reflected light, and coaxially combines the at least one light and the remaining light. The welding monitoring device according to claim 4.

7. The at least one light includes the reflected light, the remaining light includes the thermal radiation light and the visible light, and the optical path of the at least one light separated by the wavelength separation mirror and passing through the first lens barrel and the collimator, and the optical path of the remaining light separated by the wavelength separation mirror and passing through the second lens barrel. The welding monitoring device according to claim 1.

8. The collimator is a reducing collimator in which the magnification of the collimator ranges from 0.95 to 0.1 times. The welding monitoring device according to claim 1.

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