Laser welding apparatus and laser welding method

Abstract

A laser welding device is provided with: a laser oscillator to which the incidence end of a fiber is connected; a welding head connected to the emission end of the fiber, the welding head performing laser welding while condensing the laser light emitted by the laser oscillator through the emission end onto a workpiece and irradiating the workpiece; a sensing unit for sensing the presence / absence of a fault in laser welding; and a controller for controlling the operation of the laser oscillator and the welding head. Upon receiving, from the sensing unit, an output signal indicating a fault in a weld point on the workpiece during laser welding of the workpiece, the controller performs auxiliary laser welding at a prescribed position in the vicinity of the weld point.

Description

Technical Field

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

Background Art

[0002] Laser welding can perform high-speed and high-quality welding because the power density of the laser beam irradiated on the workpiece, which is the object to be welded, is high. In particular, in scanning welding in which welding is performed while scanning the laser beam at high speed on the surface of the workpiece, the laser beam can be moved at high speed to the next welding point during the period when welding is not performed, so that the total welding time can be shortened.

[0003] For example, Patent Document 1 discloses a method of laser welding two stacked workpieces. In this method, in order to form a keyhole that penetrates the entire workpiece in which the first workpiece and the second workpiece are stacked, a laser beam is irradiated on the surface of the first workpiece. When irradiating the laser beam, a scanning mirror that can be tilted in the X direction and the Y direction is built in the laser head of the laser welding apparatus, and the laser beam is reflected through this scanning mirror and irradiated on the surface of the workpiece. By driving the scanning mirror, the laser beam can be moved at high speed, so high-speed welding can be performed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, when forming a weld bead on a workpiece by laser welding, welding defects may occur due to various factors such as variations in the dimensions of the workpiece to be welded, variations in its surface condition, or variations in welding conditions. In particular, in scanning welding where high-speed welding is performed, since the welding speed is high, even a slight variation may lead to the occurrence of welding defects. In an actual production site, when unacceptable welding defects occur during laser welding, from the perspective of cost, instead of discarding the workpiece, means are taken to repair it after welding and reuse it. Since this work is carried out after welding is completed, time and labor are required for repair, which not only reduces the total production efficiency but also increases the production cost.

[0006] However, in the conventional configuration disclosed in Patent Document 1, although it is effective in reducing as much as possible the welding defects that may occur during welding, no disclosure is made regarding the countermeasures when unacceptable welding defects occur once.

[0007] The present disclosure has been made in view of such points, and its object is to provide a laser welding apparatus and a laser welding method that take measures to quickly and appropriately maintain the welding strength of the welding site where a welding defect is detected when an unacceptable welding defect is detected during laser welding.

Means for Solving the Problem

[0008] The present disclosure includes a laser oscillator to which the incident end of an optical fiber is connected, a welding head that is connected to the output end of the optical fiber and performs laser welding while condensing and irradiating laser light emitted from the laser oscillator through the output end onto a workpiece, a detection unit that detects the presence or absence of defects in the laser welding, and a controller that controls the operations of the laser oscillator and the welding head based on the output signal of the detection unit. When the controller receives an output signal indicating a defect at the weld point of the workpiece from the detection unit during laser welding of the workpiece, Different from the position of the welding point A laser welding apparatus that executes auxiliary laser welding at a predetermined position around the weld point is provided.

[0009] In addition, the present disclosure includes a step of performing laser welding while condensing and irradiating laser light emitted from a laser oscillator to which the incident end of a fiber is connected onto a workpiece through the output end of the fiber, a step of detecting the presence or absence of defects in the laser welding, a step of controlling the operations of the laser oscillator and the welding head based on the output signal of the detection unit, and when an output signal indicating a defect in the weld point of the workpiece is received during laser welding of the workpiece, Different from the position of the welding point a step of performing auxiliary laser welding at a predetermined position around the weld point, and provides a laser welding method.

Effects of the Invention

[0010] According to the present disclosure, when an unacceptable welding defect is detected during laser welding, means can be taken to quickly and appropriately maintain the welding strength of the welding site where the welding defect is detected.

Brief Description of the Drawings

[0011]

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Embodiments for Carrying Out the Invention

[0012] (Background Leading to the Present Disclosure) In Patent Document 1, detecting welding defects (welding failures) at the position to be welded (i.e., the welding point) during laser welding is not considered. For this reason, for example, a welding inspection process is required to confirm whether there are welding defects after the entire laser welding of the workpiece is completed. If welding defects that are unacceptable in the welding inspection process are found, it is necessary to perform corrective (auxiliary) laser welding or other welding methods such as arc welding again at the corresponding welding point. In other words, it has been difficult to reduce the tact time of the entire laser welding including the time required for corrective laser welding or other welding methods at the corresponding welding point.

[0013] Therefore, in the following embodiments, when a welding defect that cannot be tolerated is detected during laser welding, an example of a laser welding apparatus and a laser welding method that take measures to quickly and appropriately maintain the welding strength of the welded part where the welding defect is detected will be described.

[0014] Hereinafter, embodiments specifically disclosing the laser welding apparatus and the laser welding method according to the present disclosure will be described in detail with reference to the drawings as appropriate. However, a more detailed description than necessary may be omitted. For example, a detailed description of well-known matters and a redundant description of substantially the same configuration may be omitted. This is to avoid making the following description unnecessarily redundant and to facilitate the understanding of those skilled in the art. Note that the accompanying drawings and the following description are provided for those skilled in the art to fully understand the present disclosure, and it is not intended to limit the subject matter described in the claims thereby.

[0015] (Configuration of Laser Welding Apparatus) FIG. 1 is a diagram showing a schematic configuration example of a laser welding apparatus 100 according to Embodiment 1. The laser welding apparatus 100 includes a laser oscillator 80, a controller 70, an optical fiber 90, a welding head 30, a welding state detection mechanism 40, and a manipulator 60.

[0016] The laser oscillator 80 is a laser light source that generates laser light LB when power is supplied from a power source (not shown). The laser oscillator 80 may be composed of a single laser light source or a plurality of laser modules. In the latter case, the laser oscillator 80 combines the laser light emitted from each of the plurality of laser modules and emits it as laser light LB.

[0017] The laser light source or laser module used in the laser oscillator 80 is appropriately selected according to the material of the workpiece W to be welded or the shape of the welding site. For example, a fiber laser, a disk laser, or a YAG (Yttrium Aluminum Garnet) laser can be used as the laser light source. In this case, the wavelength of the laser light LB is set in the range of 1000 nm to 1100 nm. Also, a semiconductor laser may be used as the laser light source or laser module. In this case, the wavelength of the laser light LB is set in the range of 800 nm to 1000 nm. Further, a visible light laser may be used as the laser light source or laser module. In this case, the wavelength of the laser light LB is set in the range of 400 nm to 800 nm.

[0018] An optical fiber 90 as an example of a fiber has one end side (input end) optically coupled to the laser oscillator 80 and the other end side (output end) optically coupled to the welding head 30, has a core (not shown) on its axis, and a first cladding (not shown) is provided coaxially with the core in contact with the outer peripheral surface of the core. The core and the first cladding are mainly made of quartz, and the refractive index of the core is higher than that of the first cladding. For this reason, the laser light LB generated by the laser oscillator 80 is incident on the input end of the optical fiber 90 and is transmitted through the inside of the core toward the output end (see above). Also, a film or a resin-based protective layer (both not shown) for mechanically protecting the optical fiber 90 is provided on the outer peripheral surface of the first cladding.

[0019] The welding head 30 is attached to the output end of the optical fiber 90, collimates the laser beam that has been transmitted through the optical fiber 90 and spread into parallel light once, and then condenses the collimated parallel light and irradiates the workpiece W as the laser light LB. As a result, the workpiece W is laser welded.

[0020] Further, the welding head 30 may be configured to two-dimensionally scan the laser beam LB and irradiate the workpiece W therewith. In this case, it has an optical scanning mechanism (see, for example, FIG. 9 or FIG. 10) for scanning the laser beam LB. Note that the optical scanning mechanism does not necessarily have to be limited to the configurations illustrated in FIGS. 9 and 10. Further, the welding head 30 may have a focal position adjustment mechanism (not shown) for intentionally changing the focal position of the laser beam LB irradiated toward the workpiece W. Details of the structure and functions of the welding head 30 will be described later.

[0021] The welding state detection mechanism 40 as an example of the detection unit detects the presence or absence of welding defects (welding failures) in the laser welding of the workpiece W at the welding point (see FIGS. 8 to 10) by the welding head 30. The welding state detection mechanism 40 generates an output signal indicating the detection result of the presence or absence of welding defects in the laser welding and sends it to the controller 70. Although details will be described later, the welding state detection mechanism 40 of the first embodiment is configured using a plurality (for example, three types) of different sensors and a processor (not shown). Each sensor is, for example, a first optical sensor S1, a second optical sensor S2, and a third optical sensor S3. Details of the operations of these sensors will be described later. This processor (not shown) detects the presence or absence of welding defects (welding failures) in the laser welding of the workpiece W at the welding point (see FIGS. 8 to 10) by the welding head 30 based on the outputs of the respective sensors.

[0022] Note that in the welding state detection mechanism 40, the configuration of this processor (not shown) may be omitted. In this case, the determination of the presence or absence of welding defects (welding failures) in the laser welding of the workpiece W at the welding point (see FIGS. 8 to 10) by the welding head 30 may be made in the control unit 71 of the controller 70.

[0023] The controller 70 is configured to include a control unit 71, a storage unit 72, and a display unit 73. The controller 70 controls the laser oscillation of the laser oscillator 80. Specifically, the controller 70 controls the laser oscillation and the laser output by supplying control signals such as output current and on-off time to a power supply (not shown) connected to the laser oscillator 80. Further, the controller 70 performs drive control of an optical scanning mechanism (not shown) and a focus position adjustment mechanism (not shown) provided in the welding head 30 via a driver (not shown) according to the content of the selected laser welding program. Also, the controller 70 controls the operation of the manipulator 60.

[0024] The storage unit 72 stores laser welding programs. As shown in FIG. 1, the storage unit 72 may be provided inside the controller 70, or may be provided outside the controller 70 and configured to enable data exchange with the controller 70. Further, although details will be described later, the storage unit 72 stores data in which the focus position of the laser beam LB and the penetration depth of the workpiece W are associated with the material of the workpiece W (see FIG. 3).

[0025] FIGS. 2A and 2B are diagrams schematically showing the relationship between the molten pool and the keyhole formed in the workpiece W and the focus position of the laser beam LB. FIG. 3 is a diagram showing an example of a table indicating the correspondence between the focus position of the laser beam LB and the penetration depth of the workpiece W. FIG. 2A shows the case where the focus of the laser beam LB is located near the surface of the workpiece W. FIG. 2B shows the case where the focus of the laser beam LB is located inside the workpiece W. When performing laser welding, in order to obtain a stable welding result, the setting of the focus position with respect to the workpiece W often follows FIG. 2.

[0026] Generally, when laser-welding a workpiece W made of metal, as shown in FIG. 2A, the portion irradiated with the laser beam LB is heated and melted, and a molten pool 800 is formed. Also, intense evaporation of the material constituting the molten pool 800 occurs in the portion irradiated with the laser beam LB, and a keyhole 810 is formed inside the molten pool 800 by the reaction force.

[0027] When the keyhole 810 is formed, most of the laser beam LB enters the inside of the keyhole 810 while being reflected multiple times by the inner wall surface of the keyhole 810 and is absorbed by the molten pool 800. By repeating the reflection on the inner wall surface of the keyhole 810, the absorption rate at which the laser beam LB is absorbed by the molten pool 800 is improved, the amount of heat input to the workpiece W increases, and the penetration depth becomes deeper. Also, although it varies depending on the material of the workpiece W or the welding conditions and the amount is small (it varies depending on materials, welding conditions, etc., but is usually 10% or less), a part is reflected by the keyhole wall near the entrance of the keyhole 810, and the reflected laser beam LB is reflected outside without entering the keyhole 810 and becomes a loss.

[0028] Further, since the keyhole 810 is an open space extending from the opening 811 of the keyhole 810 formed on the surface of the molten pool 800 toward the inside of the molten pool 800, as shown in Fig. 2B, when the focal position of the laser beam LB is moved from the surface of the workpiece W to the inside, specifically, to reach the inside of the keyhole 810, the power density of the laser beam LB irradiated on the inner wall surface of the keyhole 810 increases and the amount of light absorbed by the molten pool 800 increases, and the penetration depth can be made deeper than in the case shown in Fig. 2A. Also, when the focal position of the laser beam LB is made to reach the inside of the keyhole 810, the opening 811 of the keyhole 810 can be expanded more than in the case shown in Fig. 2A, so that the laser beam LB can more easily reach the inside of the keyhole 810. When the focal position of the laser beam LB is inside from the surface of the workpiece W, since the laser beam LB enters the depth of the keyhole 810 in a converged form near the opening 811 of the keyhole 810, it becomes less likely to be reflected by the keyhole wall near the entrance of the keyhole 810, and the increase in the amount of light absorbed by the molten pool 800 also leads to an increase in the penetration depth.

[0029] With reference to the surface of the work W, as the focal position of the laser beam LB moves upward, that is, outside the work W, the penetration depth of the work W becomes shallower. On the other hand, with reference to the surface of the work W, as the focal position of the laser beam LB moves downward, that is, to a predetermined position inside the work W, the penetration depth of the work W becomes deeper. Note that when the focal position of the laser beam LB moves deeper inside the work W than the predetermined position, the power density of the laser beam LB on the surface of the work W decreases, and the heat input to the work W at the initial stage of the formation of the molten pool 800 decreases. For this reason, the penetration depth rather becomes shallower.

[0030] In this way, by moving the focal position of the laser beam LB from the surface of the work W to a predetermined position inside so as to reach inside the keyhole 810, the penetration depth of the work W can be increased.

[0031] Also, the shape of the curve shown in FIG. 3 changes depending on the material of the work W and the output of the laser beam LB. For this reason, in the storage unit 72, the penetration depth of the work W with respect to the focal position of the laser beam LB is stored as data in a table format, associated with the material of the work W, the output of the laser beam LB, and the wavelength of the laser beam LB. Note that, for easy understanding of the description of FIG. 3, the change in the penetration depth of the work W with respect to the focal position of the laser beam LB is shown in a graph format, but actually, each plot of the curve shown in FIG. 3 is associated with the material of the work W and the like in a data format.

[0032] When laser-welding the work W, by changing the focal position of the laser beam LB based on the shape of the welding portion in the work W and the data shown in FIG. 3, laser welding can be appropriately performed according to the shape of the welding portion, and the joining strength of the work W can be ensured.

[0033] The control unit 71 controls the output intensity (power density) of the laser beam LB of the laser oscillator 80 according to the laser welding program stored in the storage unit 72. The control unit 71 transmits a position command to the servo motor (not shown) provided in the manipulator 60 according to the laser welding program stored in the storage unit 72 and the feedback signal from the encoder (not shown) provided in the manipulator 60, and controls the rotation speed and rotation amount of the servo motor (not shown).

[0034] In addition, the control unit 71 controls the operations of the laser oscillator 80 and the welding head 30 based on the output signal (to be described later with reference) obtained from the welding state detection mechanism 40. Details of the operation of this control unit 71 will be described later.

[0035] The display unit 73 displays the output state of the laser oscillator 80, the operation state of the manipulator 60, and warnings, etc. under the control of the control unit 71.

[0036] The manipulator 60 has a servo motor (not shown) and an encoder (not shown) for each joint axis (for example, there are four joint axes in FIG. 1, but in the case of laser welding, six axes are often provided). The manipulator 60 is connected to the controller 70, and by operating the servo motor and encoder for each joint axis, the welding head 30 is moved to draw a predetermined locus according to the above-described laser welding program.

[0037] FIG. 4 is a diagram schematically showing an example of a first arrangement position of a first optical sensor S1, a second optical sensor S2, and a third optical sensor S3 that constitute the welding state detection mechanism 40. The first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 that constitute the welding state detection mechanism 40 may be appropriately arranged non-coaxially with the laser beam LB (in other words, laser beam) irradiated onto the workpiece W on the side (side surface) of the welding head 30 as shown in FIG. 4. In other words, the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 move in conjunction with the movement of the welding head 30. Further, when the welding head 30 has a substantially cylindrical or cylindrical housing, the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 may be appropriately arranged along the housing of the welding head 30, respectively.

[0038] Details will be described later with reference to FIGS. 5A and 5B. The first optical sensor S1 detects the amount of light (an example of sensor signal intensity) of specific wavelength light reflected from the welding point of the workpiece W when irradiating the workpiece W with the laser beam LB from the welding head 30 (that is, laser welding). This specific wavelength light is the same as the wavelength of the laser beam LB (in other words, laser beam) irradiated onto the workpiece W. Hereinafter, this specific wavelength light is referred to as reflected light L1.

[0039] Details will be described later with reference to FIGS. 6A and 6B. The second optical sensor S2 detects the amount of light (an example of sensor signal intensity) of plasma emission L2 (for example, light having a wavelength in the visible light region) generated by irradiating the workpiece W with the laser beam LB from the welding head 30 (that is, laser welding).

[0040] Details will be described later with reference to FIGS. 7A and 7B. The third optical sensor S3 detects the amount of light (an example of sensor signal intensity) of radiation light, particularly near-infrared light L3 (for example, light having a wavelength of 800 nm or more) generated by the temperature rise at the welding point of the workpiece W when irradiating the workpiece W with the laser beam LB from the welding head 30 (that is, laser welding).

[0041] FIG. 5A is a diagram showing an example of the distribution of the sensor signal intensity by the first optical sensor S1 when the laser welding is normal. FIG. 5B is a diagram showing an example of the distribution of the sensor signal intensity by the first optical sensor S1 when the laser welding is abnormal. In FIGS. 5A and 5B, the horizontal axis represents time, and the vertical axis represents the sensor signal intensity (that is, the amount of the reflected light L1 (refer to the above) detected by the first optical sensor S1). The first optical sensor S1 detects the reflected light L1 generated from the welding point during the laser welding.

[0042] In FIG. 5A, the distribution characteristics (for example, the center curve MD1) of the detected light amount of the first optical sensor S1 when normal laser welding is performed from the start point to the end point of the laser welding are shown, and it is shown that the sensor signal intensity takes values in the normal range from the lower limit curve LW1 to the upper limit curve UP1. The work W is made of metal and is in a solid state until the work W starts to melt at the start point of the laser welding. Therefore, at the start point of the laser welding, the reflectivity of the work W becomes high, and the sensor signal intensity tends to be relatively high. As the work W starts to melt, the reflectivity from the welding point gradually decreases with the formation of the keyhole, so the sensor signal intensity gradually decreases from the initial high value and changes stably.

[0043] However, as shown in FIG. 5B, when normal laser welding is not performed at any timing from the start point to the end point of the laser welding, the distribution characteristics MS1 of the detected light amount of the first optical sensor S1 will have values deviating from between the lower limit curve LW1 and the upper limit curve UP1, which is the normal range, like in parts A and B. When at least one characteristic of such parts A and B is detected, the welding state detection mechanism 40 detects a welding defect (welding failure) of the corresponding welding point as the detection result of the first optical sensor S1.

[0044] For example, in part A, the sensor signal intensity is even lower than the lower limit curve LW1. This may be because, for example, in laser welding of thin plates, fluctuations in the laser power or variations in the workpiece W cause fluctuations in the molten pool, and finally a hole is formed in the workpiece W, resulting in the reflected light L1 at the weld point being lower than the lower limit curve LW1. Also, in lap welding of thin plates, the reflected light L1 may decrease due to the gap between the upper and lower plates becoming too wide and the molten pool becoming too large.

[0045] For example, in part B, the sensor signal intensity is even higher than the upper limit curve UP1. This may be because the melting amount of the workpiece W due to fluctuations in the laser power during laser welding is insufficient, resulting in the reflected light L1 at the weld point being higher than the upper limit curve UP1.

[0046] FIG. 6A is a diagram showing an example of the distribution of the sensor signal intensity by the second optical sensor S2 when the laser welding is normal. FIG. 6B is a diagram showing an example of the distribution of the sensor signal intensity by the second optical sensor S2 when the laser welding is abnormal. In FIGS. 6A and 6B, the horizontal axis represents time, and the vertical axis represents the sensor signal intensity (that is, the amount of light of the plasma emission L2 (refer to the above) detected by the second optical sensor S2). The second optical sensor S2 detects the plasma emission L2 generated from the weld point during laser welding.

[0047] In FIG. 6A, the distribution characteristics (for example, the center curve MD2) of the detected light amount of the second optical sensor S2 when normal laser welding is performed from the start point to the end point of the laser welding are shown, and it is shown that the sensor signal intensity takes values within the normal range from the lower limit curve LW2 to the upper limit curve UP2. The plasma emission L2 changes almost stably from the start point to the end point of the laser welding.

[0048] However, as shown in FIG. 6B, if normal laser welding is not performed at any timing from the start to the end of laser welding, the distribution characteristic MS2 of the detected light quantity of the second optical sensor S2 will have a value deviating from between the lower limit curve LW2 and the upper limit curve UP2, which is the normal range such as in the C part and the D part. When the characteristics of at least one of such C part and D part are detected, the welding state detection mechanism 40 detects a welding defect (welding failure) of the corresponding welding point as the detection result of the second optical sensor S2.

[0049] For example, in the C part, the sensor signal intensity is even higher than the upper limit curve UP2. This is presumably because, due to fluctuations in the laser power of the laser welding or individual variations in the workpiece W, phenomena such as excessive melting of the workpiece W and generation of spatter occurred, temporarily increasing the plasma emission amount at the welding point above the upper limit curve UP2. Even without fluctuations in the laser power, if the keyhole swings greatly due to fluctuations in the molten pool, large plasma emission may occur.

[0050] For example, in the D part, the sensor signal intensity is even lower than the lower limit curve LW2. This is presumably because, similar to the A part (see FIG. 5B), for example, due to fluctuations in the molten pool during laser welding, holes were formed in the workpiece W or there were too many gaps to form a stable molten pool, resulting in the plasma emission amount at the welding point being lower than the lower limit curve LW2.

[0051] FIG. 7A is a diagram showing an example of the distribution of the sensor signal intensity by the third optical sensor S3 when the laser welding is normal. FIG. 7B is a diagram showing an example of the distribution of the sensor signal intensity by the third optical sensor S3 when the laser welding is abnormal. In FIGS. 7A and 7B, the horizontal axis represents time, and the vertical axis represents the sensor signal intensity (that is, the light quantity of the near-infrared light L3 (refer to the above) detected by the third optical sensor S3). The third optical sensor S3 detects the near-infrared light L3 generated from the welding point, which has a strong correlation with the temperature of the molten pool during laser welding.

[0052] In Fig. 7A, the distribution characteristics (e.g., the center curve MD3) of the detected light quantity of the third optical sensor S3 when normal laser welding is performed from the start point to the end point of laser welding are shown, and it is shown that the sensor signal intensity takes values within the normal range from the lower limit curve LW3 to the upper limit curve UP3. The workpiece W is made of metal and is in a solid state until the workpiece W starts to melt at the start point of laser welding. For this reason, since the temperature of the workpiece W is low at the start point of laser welding, the temperature of the molten pool is also relatively low, and the sensor signal intensity tends to be relatively low. As the workpiece W starts to melt and its temperature gradually rises and stabilizes, the near-infrared light L3 gradually increases toward the end point of laser welding. In the figure, the intensity of the near-infrared light L3 gradually increases toward the end point of welding, but depending on the combination of the workpiece W and the welding conditions, the near-infrared light L3 may be almost constant until the end point of welding.

[0053] However, as shown in Fig. 7B, when normal laser welding is not performed at any timing from the start point to the end point of laser welding, the distribution characteristics MS3 of the detected light quantity of the third optical sensor S3 will have values deviating from the normal range such as in parts E and F. When at least one of the characteristics of such parts E and F is detected, the welding state detection mechanism 40 detects a welding defect (welding failure) at the corresponding welding point as the detection result of the third optical sensor S3.

[0054] For example, in part E, the sensor signal intensity is even higher than the upper limit curve UP3. This is presumably because, similar to Fig. 6A, a phenomenon such as excessive melting of the workpiece W due to fluctuations in the laser output during laser welding or variations in the individual workpieces W has occurred, causing the near-infrared light (in other words, temperature) at the welding point to temporarily become higher than the upper limit curve UP3.

[0055] For example, in the F section, the sensor signal intensity is even lower than the lower limit curve LW3. Similar to FIG. 6B, this is presumably because, for example, when laser welding, a hole is formed in the workpiece W, or the gap is large and the molten pool is deeply recessed, resulting in the amount of near-infrared light at the welding point being lower than the lower limit curve LW3.

[0056] Next, an internal configuration example of the welding head 30 incorporating the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 will be described with reference to FIGS. 8, 9, and 10 respectively.

[0057] FIG. 8 is a diagram schematically showing a second arrangement position example of the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 constituting the welding state detection mechanism 40. In FIG. 8, the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 are all incorporated in the welding head 30. The welding head 30 is connected to the emission end of the optical fiber 90. In the welding head 30 shown in FIG. 8, a collimating lens CLL1, a first mirror MRR1, a condenser lens FCL1, a protective glass PTG1, a second mirror MRR2, a condenser lens FCL2, the first optical sensor S1, a third mirror MRR3, a condenser lens FCL3, the second optical sensor S2, a condenser lens FCL4, and the third optical sensor S3 are arranged.

[0058] The collimating lens CLL1, the first mirror MRR1, the condenser lens FCL1, and the protective glass PTG1 are arranged on the incident light optical axis aa'. Also, the first mirror MRR1, the condenser lens FCL1, and the protective glass PTG1 are arranged on the reflected light optical axis a'b. The first mirror MRR1, the second mirror MRR2, the third mirror MRR3, and the condenser lens FCL4 are arranged on the reflected light optical axis bb'. The second mirror MRR2, the condenser lens FCL2, and the first optical sensor S1 are arranged on the reflected light optical axis cc'. Note that c is located on the reflected light optical axis bb'. The third mirror MRR3, the condenser lens FCL3, and the second optical sensor S2 are arranged on the reflected light optical axis dd'. Note that d is located on the reflected light optical axis bb'.

[0059] Specifically, the laser beam LB (i.e., the output beam BM1) incident from the output end of the optical fiber 90 into the welding head 30 travels along the incident light optical axis aa', and is formed into a parallel collimated beam CLLBM1 through the collimating lens CLL1. This collimated beam CLLBM1 travels along the incident light optical axis aa', passes through the first mirror MRR1, and is focused by the focusing lens FCL1. The focused incident beam ICB1 is irradiated onto the welding point of the workpiece W through the protective glass PTG1 along the incident light optical axis aa'. Note that the first mirror MRR1 is pre-coated to transmit light in the direction of the incident light optical axis aa' and reflect light in the direction of the reflected light optical axis a'b by approximately 90 degrees clockwise as shown in the figure.

[0060] Light including various wavelength bands generated from the welding point of the workpiece W (e.g., reflected light L1, plasma emission L2, near-infrared light L3) travels along the reflected light optical axis a'b as the reflected beam RFB1, passes through the protective glass PTG1 and the focusing lens FCL1, and is reflected by the first mirror MRR1.

[0061] After this reflection, the reflected beam RFB1 travels along the reflected light optical axis bb'. Among the reflected beam RFB1, the reflected light L1 is reflected by the second mirror MRR2, and the light of the remaining wavelength bands (specifically, plasma emission L2 and near-infrared light L3) passes through the second mirror MRR2. The second mirror MRR2 is pre-coated to reflect the reflected light L1 and transmit the light of the remaining wavelength bands (specifically, plasma emission L2 and near-infrared light L3). The reflected light L1 travels along the reflected light optical axis cc', is focused through the focusing lens FCL2, and received by the first optical sensor S1, and its light quantity is detected as the sensor signal intensity (see Fig. 5A or Fig. 5B).

[0062] Of the plasma emission L2 and the near-infrared light L3 that have passed through the second mirror MRR2, the plasma emission L2 is reflected by the third mirror MRR3, and the light in the remaining wavelength band (specifically, the near-infrared light L3) passes through the third mirror MRR3. The third mirror MRR3 is pre-coated to reflect the plasma emission L2 and transmit the light in the remaining wavelength band (specifically, the near-infrared light L3). The plasma emission L2 travels along the reflected light optical axis dd', is condensed through the condenser lens FCL3, and is received by the second optical sensor S2, and the amount of the light is detected as the sensor signal intensity (see FIG. 6A or FIG. 6B).

[0063] The near-infrared light L3 that has passed through the third mirror MRR3 is condensed through the condenser lens FCL4 and received by the third optical sensor S3, and the amount of the light is detected as the sensor signal intensity (see FIG. 7A or FIG. 7B).

[0064] FIG. 9 is a diagram schematically showing a third example of the arrangement positions of the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 that constitute the welding state detection mechanism 40. Similar to FIG. 8 in FIG. 9, the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 are all built in the welding head 30. In the description of FIG. 9, the same elements as those in FIG. 8 are given the same reference numerals to simplify or omit the description, and the different contents will be described.

[0065] In the welding head 30 shown in FIG. 9, a collimating lens CLL1, a first mirror MRR1, a bend mirror BMRR1, a galvanometer scanner mechanism GLVU1, a condenser lens FCL1, a protective glass PTG1, a second mirror MRR2, a condenser lens FCL2, a first optical sensor S1, a third mirror MRR3, a condenser lens FCL3, a second optical sensor S2, a condenser lens FCL4, and a third optical sensor S3 are arranged. Since the configuration of the welding state detection mechanism 40 shown in FIG. 9 is the same as the configuration of the welding state detection mechanism 40 shown in FIG. 8, the description is omitted.

[0066] The difference between Fig. 9 and Fig. 8 is that the galvanometer scanner mechanism GLVU1 is adopted in Fig. 9. The galvanometer scanner mechanism GLVU1 includes an X-axis mirror XMRR1 driven in the X-axis direction that defines one of the XY planes parallel to the surface of the workpiece W, a Y-axis mirror YMRR1 driven in the Y-axis direction that defines one of the XY planes parallel to the surface of the workpiece W, and a control driver (not shown) that controls the X-axis mirror XMRR1 and the Y-axis mirror YMRR1. By controlling the X-axis mirror XMRR1 and the Y-axis mirror YMRR1, the galvanometer scanner mechanism GLVU1 irradiates the welding point of the workpiece W with the light incident on the galvanometer scanner mechanism GLVU1 (specifically, the collimated beam CLLBM1 reflected by the bend mirror BMRR1) as the incident beam ICB1.

[0067] The collimating lens CLL1, the first mirror MRR1, and the bend mirror BMRR1 are arranged on the incident light optical axis aa'. The galvanometer scanner mechanism GLVU1 is arranged on the incident light optical axis a''a'''. Also, the galvanometer scanner mechanism GLVU1, the condenser lens FCL1, and the protective glass PTG1 are arranged on the incident light optical axis a''''a''''' Also, the bend mirror BMRR1 and the first mirror MRR1 are also arranged on the reflected light optical axis a'b. Since the elements arranged on the reflected light optical axes bb', cc', and dd' are the same as those in Fig. 8, detailed description is omitted. Therefore, according to the example shown in Fig. 9, by arranging the condenser lens FCL1 at a position close to the surface of the workpiece W and adopting the galvanometer scanner mechanism GLVU1, the irradiation position of the laser beam on the workpiece W can be freely controlled.

[0068] Specifically, the laser light LB (i.e., the output beam BM1) incident on the inside of the welding head 30 from the output end of the optical fiber 90 travels along the incident light optical axis aa', and is formed into a parallel collimated beam CLLBM1 through the collimating lens CLL1. This collimated beam CLLBM1 travels along the incident light optical axis aa' and is transmitted through the first mirror MRR1 and reflected by the bend mirror BMRR1. The collimated beam CLLBM1 reflected by the bend mirror BMRR1 is incident on the galvanometer scanner mechanism GLVU1 along the incident light optical axis a''a'''. The collimated beam CLLBM1 is appropriately reflected by the X-axis mirror XMRR1 and the Y-axis mirror YMRR1 of the galvanometer scanner mechanism GLVU1, and then irradiates the welding point of the workpiece W along the incident light optical axis a''''a''''' through the focusing lens FCL1 and the protective glass PTG1. Note that the bend mirror BMRR1 is pre-coated to reflect the light in the direction of the incident light optical axis aa' counterclockwise by 90 degrees in the figure and to reflect the light in the direction of the incident light optical axis a''a''' clockwise by 90 degrees.

[0069] The light (e.g., reflected light L1, plasma emission L2, near-infrared light L3) containing various wavelength bands generated from the welding point of the workpiece W travels along the incident light optical axis a''''a''''' as the reflected beam RFB1, passes through the protective glass PTG1 and the focusing lens FCL1, and is reflected by the galvanometer scanner mechanism GLVU1.

[0070] After this reflection, the reflected beam RFB1 travels along the reflected light optical axis a'''a'', and is reflected by the bend mirror BMRR1. After this reflection, the reflected beam RFB1 travels along the reflected light optical axis a'b, and is reflected by the first mirror MRR1. Since the optical path of the light after this reflection is the same as that in FIG. 8, the description is omitted.

[0071] FIG. 10 is a diagram schematically showing a fourth example of the arrangement positions of the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 that constitute the welding state detection mechanism 40. Similar to FIG. 8 in FIG. 10, the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3 are all built in the welding head 30. In the description of FIG. 10, the same reference numerals are given to the same elements as those in FIG. 9 to simplify or omit the description, and the different contents will be described.

[0072] In the welding head 30 shown in FIG. 10, a collimating lens CLL1, a first mirror MRR1, a condenser lens FCL1, a bend mirror BMRR1, a galvanometer scanner mechanism GLVU1, a protective glass PTG1, a second mirror MRR2, a condenser lens FCL2, a first optical sensor S1, a third mirror MRR3, a condenser lens FCL3, a second optical sensor S2, a condenser lens FCL4, and a third optical sensor S3 are arranged. Since the configuration of the welding state detection mechanism 40 shown in FIG. 10 is the same as the configuration of the welding state detection mechanism 40 shown in FIG. 9, the description is omitted.

[0073] The difference between FIG. 10 and FIG. 9 is that the position where the condenser lens FCL1 is arranged is different in FIG. 10. The galvanometer scanner mechanism GLVU1 receives the light condensed by the condenser lens FCL1, and by controlling the X-axis mirror XMRR1 and the Y-axis mirror YMRR1, the light incident on the galvanometer scanner mechanism GLVU1 (specifically, the light reflected by the bend mirror BMRR1) is irradiated as the incident beam ICB1 toward the welding point of the workpiece W.

[0074] The collimating lens CLL1, the first mirror MRR1, the focusing lens FCL1, and the bending mirror BMRR1 are arranged on the incident light optical axis aa'. The galvanometer scanner mechanism GLVU1 and the protective glass PTG1 are arranged on the incident light optical axis a''''a'''''’. Also, the bending mirror BMRR1, the focusing lens FCL1, and the first mirror MRR1 are also arranged on the reflected light optical axis a'b. Since the elements arranged on the reflected light optical axes bb', cc', and dd' are the same as those in FIG. 8, detailed description thereof is omitted. Therefore, according to the example shown in FIG. 10, by arranging the focusing lens FCL1 in front of the incident side to the galvanometer scanner mechanism GLVU1 and adopting the galvanometer scanner mechanism GLVU1, the irradiation position of the laser beam on the work W can be freely controlled in the same manner as in FIG. 9.

[0075] Next, the laser welding points, auxiliary welding points, and operation procedures of the laser welding apparatus 100 according to the first embodiment will be described with reference to FIGS. 11 and 12. FIG. 11 is a diagram schematically showing an example of the laser welding points and auxiliary welding points according to the first embodiment. FIG. 12 is a flowchart showing an example of the operation procedure of the laser welding apparatus according to the first embodiment.

[0076] In FIG. 11, the laser welding apparatus 100 laser-welds each of a plurality of welding points WLP1, WLP2, WLP3, WLP4, WLP5 along the welding line WLN1 of the work W defined in advance in the laser welding program. In the laser welding program, for example, it is assumed that laser welding is executed in the order of the welding points WLP1, WLP2, WLP3, WLP4, WLP5. In FIG. 11, for example, the laser welding at three locations, the welding points WLP1, WLP2, and WLP5, is executed normally, but it is detected that abnormalities (i.e., welding defects) have occurred in the laser welding at two locations, the welding points WLP3 and WLP4.

[0077] In this case, the laser welding apparatus 100 performs auxiliary laser welding (repair welding) on an auxiliary welding point SPWLP1 indicating a predetermined position near the welding point WLP3 where a welding defect has occurred. When this repair welding is executed, the laser welding apparatus 100 executes laser welding on the next welding point WLP4 of the welding point WLP3.

[0078] However, when it is detected that a welding defect has also occurred at the welding point WLP4 in the same manner, the laser welding apparatus 100 performs auxiliary laser welding (repair welding) on an auxiliary welding point SPWLP2 indicating a predetermined position near the welding point WLP4 where the welding defect has occurred. When this repair welding is executed, the laser welding apparatus 100 executes laser welding on the next welding point WLP5 of the welding point WLP4.

[0079] In FIG. 12, the laser welding apparatus 100 performs laser welding on the K-th welding point (St1). K may be 1 or an integer of 2 or more. The laser welding apparatus 100 determines whether the state of the K-th welding point is OK (that is, the output signal from the welding state detection mechanism 40 indicates that there is no welding defect) (St2). This determination may be executed by, for example, the control unit 71 of the controller 70, and the same applies hereinafter.

[0080] When the laser welding apparatus 100 determines that the state of the K-th welding point is not OK (St2, NO), it executes auxiliary laser welding at a predetermined position (auxiliary welding point) near the K-th welding point (St3). After step St3 or when it is determined that the state of the K-th welding point is OK (St2, YES), the laser welding apparatus 100 performs laser welding on the (K + 1)-th welding point (St4). The laser welding apparatus 100 determines whether the state of the (K + 1)-th welding point is OK (that is, the output signal from the welding state detection mechanism 40 indicates that there is no welding defect) (St5).

[0081] When it is determined that the state of the (K + 1)-th welding point is not OK (St5, NO), the laser welding apparatus 100 performs auxiliary laser welding at a predetermined position (auxiliary welding point) near the (K + 1)-th welding point (St6). After step St6 or when it is determined that the state of the (K + 1)-th welding point is OK (St5, YES), the laser welding apparatus 100 performs laser welding on the (K + 2)-th welding point (St7). Note that the processing after step St7 is repeated in the same manner for each set, for example, with the processing from step St2 to step St3 as one set, until the laser welding for all the welding points is completed.

[0082] The above has described the welding method (step St3) of the auxiliary welding point when a welding defect has occurred (determined as NO in step St2). Needless to say, in terms of design, for welding points where the auxiliary welding point is not required, it may be regarded as YES determination in step St2, and subsequent welding may be performed.

[0083] As described above, the laser welding apparatus 100 according to the first embodiment includes a laser oscillator 80 to which the incident end of the fiber is connected, a welding head 30 that is connected to the output end of the fiber and performs laser welding while condensing and irradiating the laser beam LB emitted from the laser oscillator 80 through the output end onto the workpiece W, a detection unit that detects the presence or absence of defects in the laser welding, and a controller 70 that controls the operations of the laser oscillator 80 and the welding head 30 based on the output signal of the detection unit. When the controller 70 receives an output signal indicating a defect in the welding point of the workpiece W from the detection unit during laser welding of the workpiece W, the controller 70 performs auxiliary laser welding at a predetermined position around the welding point.

[0084] As a result, even if a welding defect at the welding point is detected during laser welding, the laser welding apparatus 100 can quickly and appropriately maintain the welding strength of the welded part where the welding defect is detected. For example, compared with the case where after all the welding points (for example, welding points WLP1 to WLP5) prepared on the workpiece W are laser welded and the presence or absence of welding defects is individually detected, and then welding by auxiliary laser welding or other methods is performed only on the locations with welding defects, performing auxiliary laser welding immediately near the welding point where the welding defect is detected not only reduces the overall tact time, but also improves the quality of laser welding. In the first embodiment, after all the welding points (for example, welding points WLP1 to WLP5) prepared on the workpiece W are laser welded and the presence or absence of welding defects is individually detected, auxiliary laser welding may be performed only on the locations with welding defects.

[0085] Further, after executing the auxiliary laser welding, the controller 70 executes laser welding of a second welding point (for example, welding point WLP4) indicating the next welding point of the welding point (for example, welding point WLP3) where the welding defect is detected. Thereby, since the laser welding apparatus 100 can continuously perform repair welding for assisting the welding point where the welding defect is detected, the tact time of laser welding to the workpiece W can be reduced.

[0086] Further, the detection unit has a plurality of different sensors, and outputs an output signal indicating that there is a defect in laser welding when receiving a signal indicating an abnormality from at least one sensor. Thereby, the laser welding apparatus 100 can comprehensively detect the presence or absence of welding defects at the welding points by a plurality of sensors.

[0087] Further, the detection unit includes a first optical sensor S1 that receives specific wavelength light (e.g., reflected light L1) from the welding point generated by laser welding and detects the presence or absence of abnormalities based on the intensity of the reflected light L1, a second optical sensor S2 that receives plasma light emission L2 from the welding point generated by laser welding and detects the presence or absence of abnormalities based on the intensity of the plasma light emission L2, and a third optical sensor S3 that receives near-infrared light L3 from the welding point generated by laser welding and detects the presence or absence of abnormalities based on the intensity of the near-infrared light L3. Thereby, the laser welding apparatus 100 can appropriately and highly accurately detect the presence or absence of welding defects at the welding point in view of the characteristics of light having various wavelength bands generated during laser welding respectively.

[0088] Also, the first optical sensor S1 receives the reflected light L1 from the welding point as the specific wavelength light. The second optical sensor S2 receives light having a wavelength of 400 nm to 800 nm among the plasma light emissions. The third optical sensor S3 receives light having a wavelength of 800 nm to 2000 nm among the near-infrared lights. Thereby, the laser welding apparatus 100 can appropriately and highly accurately detect the presence or absence of welding defects at the welding point in view of the characteristics of light that each sensor (i.e., the first optical sensor S1, the second optical sensor S2, and the third optical sensor S3) is likely to receive.

[0089] Also, each of the plurality of different sensors is arranged around the welding head 30. Thereby, not only can the attachment of the plurality of different sensors to the welding head 30 be simplified, but also since each of the plurality of different sensors moves together with the welding head 30, the presence or absence of welding defects at the welding point can be easily detected during laser welding.

[0090] Also, each of the plurality of different sensors is arranged coaxially with the irradiation direction of the laser light to the workpiece W and inside the welding head 30. Thereby, not only can the laser welding apparatus 100 be prevented from becoming large-sized as a whole because a plurality of different sensors can be incorporated inside the welding head 30, but also each sensor can be arranged coaxially with the irradiation direction of the laser light LB to the workpiece W, so that the presence or absence of welding defects at the welding point can be highly accurately detected during laser welding.

[0091] Further, each of a plurality of different sensors is disposed within the welding head 30, and the welding head 30 incorporates a galvanometer scanner mechanism GLVU1 that irradiates a laser beam LB onto the welding point of the workpiece W. As a result, by adopting the galvanometer scanner mechanism GLVU1 within the welding head 30, the irradiation position of the laser beam LB (in other words, the laser beam) onto the workpiece W can be freely controlled, and the presence or absence of welding defects at the welding point can be detected with high precision during laser welding.

[0092] As described above, various embodiments have been described with reference to the drawings. Needless to say, the present disclosure is not limited to such examples. It is obvious that those skilled in the art can conceive of various modification examples, correction examples, substitution examples, addition examples, deletion examples, and equivalent examples within the scope described in the claims, and it is naturally understood that those also belong to the technical scope of the present disclosure. Further, within the scope not departing from the gist of the invention, the respective components in the above-described various embodiments may be arbitrarily combined.

[0093] This application is based on a Japanese patent application filed on June 29, 2020 (Japanese Patent Application No. 2020-111720), the content of which is incorporated herein by reference.

Industrial Applicability

[0094] The present disclosure is useful as a laser welding apparatus and a laser welding method that take measures to quickly and appropriately maintain the welding strength of a welding site where a welding defect has been detected when an unacceptable welding defect is detected during laser welding.

Explanation of Reference Numerals

[0095] 30 Welding head 40 Welding state detection mechanism 60 Manipulator 70 Controller 71 Control unit 72 Storage unit 73 Display unit 80 Laser oscillator 90 Optical fiber 100 Laser welding apparatus LB Laser beam S1 First optical sensor S2 Second optical sensor S3 Third optical sensor W Workpiece

Claims

1. A laser oscillator to which an incident end of an optical fiber is connected, A welding head connected to an output end of the optical fiber, for performing laser welding while condensing and irradiating laser light emitted from the laser oscillator through the output end onto a workpiece, A detection unit for detecting the presence or absence of defects in the laser welding, A controller for controlling the operations of the laser oscillator and the welding head based on an output signal of the detection unit, When the controller receives from the detection unit an output signal indicating a defect in a weld point of the workpiece during laser welding of the workpiece, the controller performs auxiliary laser welding at a predetermined position around the weld point different from the position of the weld point, A laser welding apparatus.

2. The controller performs laser welding at each of a plurality of weld points on the welding line along the welding line of the workpiece defined in a laser welding program in advance, When the controller receives from the detection unit an output signal indicating a defect in a weld point of the workpiece during laser welding of the workpiece, the controller performs auxiliary laser welding at a predetermined position around the weld point different from the welding line, The laser welding apparatus according to Claim 1.

3. After performing the auxiliary laser welding, the controller performs laser welding of a second weld point indicating the next weld point of the weld point, The laser welding apparatus according to Claim 1.

4. The detection unit has a plurality of different sensors, and outputs an output signal indicating that there is a defect in the laser welding when receiving a signal indicating an abnormality from at least one of the sensors, The laser welding apparatus according to Claim 1.

5. The detection unit A first optical sensor that receives specific wavelength light from the weld point generated by the laser welding and detects the presence or absence of the abnormality based on the intensity of the specific wavelength light, A second optical sensor that receives plasma light emission from the weld point generated by the laser welding and detects the presence or absence of the abnormality based on the intensity of the plasma light emission; A third optical sensor that receives near-infrared light from the weld point generated by the laser welding and detects the presence or absence of the abnormality based on the intensity of the near-infrared light, and has: The laser welding apparatus according to claim 4.

6. The first optical sensor receives reflected light from the weld point as the specific wavelength light. The second optical sensor receives light having a wavelength of 400 nm to 800 nm among the plasma light emission. The third optical sensor receives light having a wavelength of 800 nm to 2000 nm among the near-infrared light. The laser welding apparatus according to claim 5.

7. Each of the plurality of different sensors is arranged around the welding head. The laser welding apparatus according to claim 4.

8. Each of the plurality of different sensors is arranged coaxially with the irradiation direction of the laser light onto the workpiece and within the welding head. The laser welding apparatus according to claim 4.

9. Each of the plurality of different sensors is arranged within the welding head, The welding head incorporates a galvanometer scanner mechanism that irradiates the weld point of the workpiece with the laser light. The laser welding apparatus according to claim 4.

10. A step of performing laser welding while condensing and irradiating laser light emitted from a laser oscillator to which an incident end of an optical fiber is connected onto a workpiece through an emission end of the optical fiber; A step of detecting the presence or absence of a defect in the laser welding; A step of controlling operations of the laser oscillator and the welding head based on an output signal of a detection unit that detects the presence or absence of a defect in the laser welding; A step of performing auxiliary laser welding at a predetermined position around the weld point different from the position of the weld point when receiving an output signal indicating a defect in the weld point of the workpiece during laser welding of the workpiece. A laser welding method.

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