JP7553010B2 - Laser welding defect detection device and laser welding defect detection method - Google Patents

Description

This disclosure relates to a laser welding defect detection device and a laser welding defect detection method.

A laser welding defect detection device that inspects for defects in welding while welding is being performed with a laser beam is disclosed, for example, in JP 2000-334587 A (Patent Document 1).

In Patent Document 1, the welding light (reflected light, plasma light) emitted from the workpiece during laser welding is acquired optically coaxially with the laser irradiation light through an optical system inside the laser torch (processing head). The acquired welding light is photoelectrically converted, and the welding condition, such as the presence or absence of defects, is detected based on the electrical signal obtained by the photoelectric conversion.

JP 2000-334587 A

When welding parts for work machines and the like, large, thick materials are used as the workpieces. For this reason, when laser welding such materials, it is necessary to fix the workpieces and move the processing head of the laser welding machine.

In addition, with laser welding, if the focal position of the laser light on the workpiece changes, accurate welding cannot be performed. For this reason, it is important to maintain a constant distance between the processing head and the workpiece. If both the processing head and the workpiece are moved during laser welding, it becomes difficult to control the focal position of the laser light on the workpiece. For this reason, it is necessary to fix the workpiece and move the processing head of the laser welding machine during laser welding.

In addition, the weld shapes of parts for work machines and the like are often complex. For this reason, laser welding must be performed while moving the processing head three-dimensionally up and down, left and right, and back and forth relative to the workpiece.

According to the laser welding defect detection device described in Patent Document 1, a sensor that photoelectrically converts the welding light is connected to the processing head. This places many restrictions on the movement of the processing head, making it difficult to handle complex welding shapes.

The objective of the present disclosure is to provide a laser welding defect detection device and a laser welding defect detection method that can detect welding defects and can easily handle complex welding shapes.

The laser welding defect detection device disclosed herein includes a laser beam oscillator, a laser beam irradiator, a thermal radiation light sensor, a laser beam transmission path, and a thermal radiation light transmission path. The laser beam oscillator oscillates a laser beam. The laser beam irradiator irradiates the welded portion with the laser beam oscillated by the laser beam oscillator. The thermal radiation light sensor detects the intensity of the thermal radiation light generated from the welded portion by the irradiation of the laser beam. The laser beam transmission path has an optical fiber connected to the laser beam oscillator, and transmits the laser beam from the laser beam oscillator to the laser beam irradiator. The thermal radiation light transmission path transmits the thermal radiation light from the laser beam irradiator to the thermal radiation light sensor, and shares the optical fiber with the laser beam transmission path.

The laser welding defect detection method disclosed herein has the following steps:

A laser beam is oscillated. The oscillated laser beam is transmitted to the laser beam irradiating device via a laser beam transmission path having an optical fiber connected to the laser beam irradiating device. The laser beam is irradiated from the laser beam irradiating device to the welding point. Thermal radiation light generated from the welding point by the irradiation of the laser beam is transmitted to a thermal radiation light sensor via a thermal radiation light transmission path that shares the optical fiber with the laser beam transmission path. The intensity of the thermal radiation light is detected by the thermal radiation light sensor.

The present disclosure makes it possible to realize a laser welding defect detection device and a laser welding defect detection method that can detect welding defects and easily handle complex welding shapes.

1 is a perspective view showing a configuration of a laser welding defect detection device according to an embodiment; FIG. 2 is a diagram showing functional blocks of a controller included in the laser welding defect detection device shown in FIG. 1 . FIG. 1 is a flow diagram showing a laser welding defect detection method according to an embodiment. FIG. 11 is a flow chart showing a modified example of the laser welding defect detection method according to the embodiment. FIG. 2 is a schematic diagram showing a configuration of a laser welding defect detection device according to a comparative example. FIG. 1 is a diagram showing cross sections of welded portions of a plurality of samples produced by lap joint welding using laser light. FIG. 11 is a diagram showing the relationship between a bead width and a joint width. FIG. 13 is a diagram showing the relationship between thermal radiation light intensity and bead width. FIG. 13 is a diagram showing changes in thermal radiation light intensity and bead width when welding conditions are changed midway when welding is performed from left to right along the horizontal axis in the figure.

The embodiments of the present disclosure will be described in detail below with reference to the drawings. In the specification and drawings, the same or corresponding components are given the same reference numerals, and redundant explanations will not be repeated. In the drawings, configurations may be omitted or simplified for the sake of convenience. Furthermore, the embodiments and the modified examples may be combined with each other in any desired manner.

<Configuration of Laser Welding Defect Detection Device>
First, the configuration of a laser welding defect detection device according to the present embodiment will be described with reference to FIG.

Figure 1 is a perspective view showing the configuration of a laser welding defect detection device according to one embodiment. As shown in Figure 1, the laser welding defect detection device 10 is a device that performs laser welding and detects the presence or absence of defects in the welded portion.

The laser welding defect detection device 10 has a laser light oscillator 1, laser light transmission paths 2a, 2b, and 5, a processing head 3 (laser light irradiation device), thermal radiation light transmission paths 2a, 2c, and 5, a thermal radiation light sensor 4, a housing 6, and a controller 20.

The laser light oscillator 1 oscillates a laser light. The laser light may be any laser light that can propagate through an optical fiber. The laser light may be, for example, a YAG (Yttrium Aluminum Garnet) laser light, a semiconductor laser light, or a fiber laser light.

The processing head 3 is a part that irradiates the welding point with the laser light oscillated by the laser light oscillator 1. The processing head 3 has an optical system such as a lens inside. The laser light is focused by the optical system of the processing head 3 and irradiated to the welding point. The processing head 3 irradiates the laser light, for example, perpendicularly to the welding point.

The processing head 3 is configured to be able to move three-dimensionally up and down, left and right, and front and back relative to the objects to be welded 11, 12. The processing head 3 is attached, for example, to a multi-joint robot arm. The processing head 3 may be attached to a member other than a multi-joint robot arm (for example, a guide rail) as long as it is able to move up and down, left and right, and front and back relative to the objects to be welded 11, 12.

The processing head 3 is a part that acquires the thermal radiation light generated from the welding point and transmits it to the thermal radiation light transmission paths 2a, 2c, and 5. In the processing head 3, the thermal radiation light is transmitted coaxially through the same optical system as the laser light. The direction in which the thermal radiation light is transmitted through the optical system of the processing head 3 is opposite to the direction in which the laser light is transmitted through the optical system of the processing head 3.

The thermal radiation light sensor 4 is a part that detects the intensity of the thermal radiation light generated from the welding point by irradiation with laser light. The thermal radiation light sensor 4 is a photoelectric conversion element that photoelectrically converts the received thermal radiation light to obtain an electrical signal. The thermal radiation light sensor 4 is, for example, a photodiode.

The laser light transmission paths 2a, 2b, and 5 connect the laser light oscillator 1 and the processing head 3. The laser light transmission paths 2a, 2b, and 5 are sections that transmit the laser light oscillated from the laser light oscillator 1 to the laser light irradiation device 3.

The laser light transmission paths 2a, 2b, and 5 each have an optical fiber 2a, an optical fiber 2b, and an optical splitter 5. One end of the optical fiber 2a is connected to the processing head 3. One end of the optical fiber 2b is connected to the laser light oscillator 1. The other end of the optical fiber 2a and the other end of the optical fiber 2b are each connected to the optical splitter 5.

The thermal radiation light transmission paths 2a, 2c, and 5 connect the laser light oscillator 1 and the thermal radiation light sensor 4. The thermal radiation light transmission paths 2a, 2c, and 5 are the parts that transmit the thermal radiation light from the laser light irradiation device 3 to the thermal radiation light sensor 4.

The thermal radiation light transmission paths 2a, 2c, and 5 each include an optical fiber 2a, an optical fiber 2c, and an optical splitter 5. One end of the optical fiber 2c is connected to the thermal radiation light sensor 4. The other end of the optical fiber 2c is connected to the optical splitter 5.

The laser light transmission paths 2a, 2b, and 5 and the thermal radiation light transmission paths 2a, 2c, and 5 share the optical branching device 5 and the optical fiber 2a connected to the laser light oscillator 1. The optical fiber 2b and the optical fiber 2c are branched from the optical fiber 2a via the optical branching device 5.

The optical splitter 5 is configured to transmit the laser light oscillated from the laser light oscillator 1 from optical fiber 2b to optical fiber 2a, but not to optical fiber 2c. The optical splitter 5 is also configured to transmit the thermal radiation light received by the processing head 3 from optical fiber 2a to optical fiber 2c, but not to optical fiber 2b. The optical splitter 5 is, for example, an optical circulator, a spectral filter, an optical coupler, a splitter, etc.

The housing 6 has an internal space. At least the laser light oscillator 1, the thermal radiation light sensor 4, the optical fibers 2b and 2c, and the optical splitter 5 are arranged in the internal space of the housing 6. A part of the optical fiber 2a may also be arranged in the internal space of the housing 6. The housing 6 is not attached to the processing head 3 and is separated from the processing head 3.

The controller 20 is connected to the thermal radiation light sensor 4 by wire or wirelessly. The controller 20 is, for example, a processor, and may be a CPU (Central Processing Unit). The controller 20 determines whether or not there is a defect in the welded portion based on the intensity of the thermal radiation light detected by the thermal radiation light sensor 4.

<Functional blocks of the controller 20>
Next, the functional blocks of the controller 20 included in the laser welding defect detection device 10 shown in FIG. 1 will be described with reference to FIG.

Figure 2 is a diagram showing the functional blocks of the controller included in the laser welding defect detection device shown in Figure 1. As shown in Figure 2, the controller 20 has at least a thermal radiation light intensity acquisition unit 20a, a defect determination unit 20c, and a memory unit 20d.

The thermal radiation light intensity acquisition unit 20a acquires an electrical signal representing the intensity of the thermal radiation light from the thermal radiation light sensor 4. The thermal radiation light intensity acquisition unit 20a outputs the acquired electrical signal representing the intensity of the thermal radiation light to the defect determination unit 20c.

The defect determination unit 20c determines whether or not there is a defect in the welded portion based on the acquired electrical signal representing the intensity of the thermal radiation light. The defect determination unit 20c determines whether or not there is a defect in the welded portion, for example, based on whether or not the intensity of the thermal radiation light is less than a threshold value. Specifically, the defect determination unit 20c determines that there is a defect in the welded portion when the intensity of the thermal radiation light is less than the threshold value, and determines that there is no defect in the welded portion when the intensity of the thermal radiation light is equal to or greater than the threshold value.

The threshold value used in the above judgment is stored, for example, in the memory unit 20d. The defect judgment unit 20c obtains the threshold value from the memory unit 20d when judging whether or not there is a defect in the welded portion.

The defect determination unit 20c outputs the determination result as to whether or not there is a defect in the welded portion to the display unit 8. The display unit 8 is disposed outside the controller 20. The display unit 8 displays the acquired determination result as to whether or not there is a defect in the welded portion.

Although the above describes a case where defects in a welded portion are directly determined from the intensity of the thermal radiation light, it is also possible to calculate the bead width from the thermal radiation light and determine defects in a welded portion based on the bead width. In this case, the controller 20 has a bead width calculation unit 20b.

The bead width calculation unit 20b acquires an electrical signal representing the intensity of the thermal radiation light from the thermal radiation light intensity acquisition unit 20a. The bead width calculation unit 20b calculates the bead width based on the acquired electrical signal representing the intensity of the thermal radiation light.

Specifically, the bead width calculation unit 20b refers to a table showing the relationship between the intensity of thermal radiation light and the bead width, and calculates the bead width from the acquired intensity of thermal radiation light. The table showing the relationship between the intensity of thermal radiation light and the bead width is stored, for example, in the memory unit 20d. When calculating the bead width, the bead width calculation unit 20b acquires the table showing the relationship between the intensity of thermal radiation light and the bead width from the memory unit 20d.

The bead width calculation unit 20b outputs the calculated bead width to the defect determination unit 20c. The defect determination unit 20c determines whether or not there is a defect in the welded portion based on the acquired bead width. For example, the defect determination unit 20c determines whether or not there is a defect in the welded portion based on whether or not the bead width is less than a threshold value. Specifically, the defect determination unit 20c determines that there is a defect in the welded portion if the bead width is less than the threshold value, and determines that there is no defect in the welded portion if the bead width is equal to or greater than the threshold value.

The threshold value used in the above judgment is stored, for example, in the memory unit 20d. When judging whether or not there is a defect in the welded portion, the defect judgment unit 20c obtains the threshold value from the memory unit 20d. Information such as the threshold value is input to the memory unit 20d, for example, from the input unit 7.

The defect determination unit 20c outputs the determination result as to whether or not there is a defect in the welded portion to the display unit 8. The display unit 8 displays the acquired determination result as to whether or not there is a defect in the welded portion.

The memory unit 20d may not be included in the controller 20 and may be located outside the controller 20. The memory unit 20d may also store information, such as a threshold value and a table showing the relationship between the intensity of the thermal radiation light and the bead width, from an input unit 7 outside the controller 20.

<Laser welding defect detection method>
Next, a laser welding defect detection method using the laser welding defect detection device shown in FIGS. 1 and 2 will be described with reference to FIGS.

Figure 3 is a flow diagram showing a laser welding defect detection method according to one embodiment. As shown in Figures 1 and 3, first, a laser beam is emitted from the laser beam oscillator 1 (step S1: Figure 3).

The laser light emitted from the laser light oscillator 1 is transmitted to the processing head 3 via the laser light transmission paths 2a, 2b, and 5 (step S2: Figure 3). Specifically, the laser light emitted from the laser light oscillator 1 is transmitted to the processing head 3 via the optical fiber 2b, the optical splitter 5, and the optical fiber 2a in that order. At this time, the laser light emitted from the laser light oscillator 1 is not transmitted from the optical fiber 2b to the optical fiber 2c due to the function of the optical splitter 5.

The laser light transmitted to the processing head 3 is focused by an optical system in the processing head 3 and irradiated from the processing head 3 to the welding point (step S3: Figure 3). This allows the welding objects 11 and 12 to be joined by laser welding.

Specifically, the laser welding defect detection device 10 uses a laser beam to perform, for example, lap joint welding. In lap joint welding, for example, laser welding is performed with the lower plate 11 and the upper plate 12, which are the objects to be welded, overlapping each other. The laser beam focused by the processing head 3 is irradiated onto the upper plate 12. By irradiating the upper plate 12 with the laser beam, a keyhole is formed from the upper plate 12 toward the lower plate 11, and not only the upper plate 12 but also the lower plate 11 melts. As a result, both the lower plate 11 and the upper plate 12 melt and become integrated. The melted portion solidifies, and a bead 13 is formed as a weld mark.

The irradiation of the laser light causes thermal radiation light to be generated from the welded area. The thermal radiation light generated from the welded area is transmitted to the thermal radiation light sensor 4 via the optical system of the processing head 3 and the thermal radiation light transmission paths 2a, 2c, and 5 (step S4: Figure 3). Specifically, the thermal radiation light generated from the welded area is transmitted to the thermal radiation light sensor 4 via the optical system of the processing head 3, the optical fiber 2a, the optical splitter 5, and the optical fiber 2c in that order. At this time, the thermal radiation light that has passed through the optical system of the processing head 3 is not transmitted from the optical fiber 2a to the optical fiber 2b due to the function of the optical splitter 5.

The thermal radiation light transmitted through the optical fiber 2c is received by the thermal radiation light sensor 4. The thermal radiation light sensor 4 detects the intensity of the received thermal radiation light (step S5: FIG. 3). Specifically, the thermal radiation light sensor 4 converts the received thermal radiation light into an electrical signal indicating the intensity of the thermal radiation light by photoelectric conversion.

As shown in Figures 2 and 3, the thermal radiation light intensity acquisition unit 20a of the controller 20 acquires an electrical signal representing the intensity of the thermal radiation light from the thermal radiation light sensor 4 and outputs it to the defect determination unit 20c. The defect determination unit 20c determines whether or not there is a defect in the welded portion based on whether or not the intensity of the thermal radiation light obtained by the thermal radiation light sensor 4 is less than a threshold value (step S6: Figure 3).

Specifically, if the intensity of the thermal radiation light is less than the threshold value, it is determined that there is a defect in the welded area (step S7: Figure 3). If the intensity of the thermal radiation light is equal to or greater than the threshold value, it is determined that there is no defect in the welded area (step S8: Figure 3).

As a result, the controller 20 detects welding defects by determining whether or not there is a defect in the welded area based on the intensity of the thermal radiation light detected by the thermal radiation light sensor 4.

Although the above describes a case where the presence or absence of a defect in a welded portion is determined based on the intensity of the thermal radiation light, the presence or absence of a defect in a welded portion may also be determined based on the bead width calculated from the thermal radiation light. A method for detecting laser weld defects in this case is described below with reference to FIG. 4.

Figure 4 is a flow diagram showing a modified example of the laser welding defect detection method according to one embodiment. As shown in Figure 4, the laser welding defect detection method in this modified example goes through steps similar to steps S1 to S5 shown in Figure 3. After this, the bead width of the welded area is calculated from the intensity of the detected thermal radiation light (step S11: Figure 4).

As shown in Figures 2 and 4, the thermal radiation light intensity acquisition unit 20a of the controller 20 acquires an electrical signal representing the intensity of the thermal radiation light from the thermal radiation light sensor 4 and outputs it to the bead width calculation unit 20b.

The bead width calculation unit 20b refers to a table showing the relationship between the intensity of the thermal radiation light and the bead width, and calculates the bead width from the acquired intensity of the thermal radiation light. The bead width calculation unit 20b outputs the calculated bead width to the defect determination unit 20c. The defect determination unit 20c determines whether or not there is a defect in the welded portion based on whether or not the bead width is less than a threshold value (step S12: Figure 4).

Specifically, if the bead width is less than the threshold value, it is determined that the welded portion has a defect (step S7: Figure 4). If the bead width is equal to or greater than the threshold value, it is determined that the welded portion does not have a defect (step S8: Figure 4).

As a result, the controller 20 detects welding defects by determining whether or not there is a defect in the weld based on the bead width.

＜Effects＞
Next, the effects of the above embodiment will be described in comparison with a comparative example shown in FIG.

Figure 5 is a schematic diagram showing the configuration of a laser welding defect detection device according to a comparative example. As shown in Figure 5, in the laser welding defect detection device 10A of the comparative example, no optical fiber is shared between the optical transmission path 2b between the laser light oscillator 1 and the processing head 3 and the optical transmission path 2c between the processing head 3 and the optical sensor 4a.

Specifically, the laser light oscillator 1 and the processing head 3 are connected by optical fiber 2b. The processing head 3 and the optical sensor 4a are connected by optical fiber 2c. Optical fiber 2b and optical fiber 2c form different optical transmission paths and do not share a single optical transmission path.

In the laser welding defect detection device of the comparative example, two different optical fibers 2b and 2c are connected to the processing head 3. This places many restrictions on the movement of the processing head 3 when it moves three-dimensionally up and down, left and right, and back and forth. This makes it difficult to handle complex welding shapes.

In contrast, according to the above embodiment and modified example, as shown in FIG. 1, the optical fiber 2a is shared between the laser light transmission path between the laser light oscillator 1 and the processing head 3, and the laser light transmission path between the processing head 3 and the optical sensor 4a. Therefore, only one optical fiber, the optical fiber 2a, is connected to the processing head 3. This reduces the restrictions on the movement of the processing head 3 when it moves three-dimensionally up and down, left and right, and back and forth. This makes it easier to accommodate complex weld shapes, for example, when laser welding parts such as the boom of a work machine.

In addition, according to this embodiment, as shown in FIG. 2, the controller 20 determines whether or not there is a defect in the welded portion based on the intensity of the thermal radiation light detected by the thermal radiation light sensor 4.

Here, the inventors discovered that when the bead width in laser welding becomes small, defects occur at the welded portion. This discovery is explained below.

The inventors performed lap joint welding using a laser beam to prepare several samples with different bead widths, and observed the cross sections of the welded parts of these samples. The results are shown in Figure 6.

Figure 6 shows the cross-sections of the welded parts of several samples produced by lap joint welding using laser light. As shown in Figure 6, the bead widths a, b, c, and d of samples A, B, C, and D have the following relationship: a>b>c>d. In other words, the bead width of sample A is the largest, followed by samples B, C, and D in that order.

In sample A, which had the widest bead width, the joint width between the lower plate 11 and upper plate 12, which are the objects to be welded, was sufficient and no defects were found. In samples B and C, the joint width between the lower plate 11 and upper plate 12 was smaller than that of sample A, and although a gap 14 was generated between the lower plate 11 and upper plate 12, the joint width was sufficiently large.

In contrast, in sample D, which had the smallest bead width among the samples produced, the lower plate 11 and the upper plate 12 were not joined, and the gap 14 between the lower plate 11 and the upper plate 12 was also large.

From the above results, it was found that when the bead width becomes small, the joint width between the lower plate 11 and the upper plate 12 becomes small. It was also found that when the bead width becomes too small, the lower plate 11 and the upper plate 12 are not joined (the joint width becomes 0), and a welding defect occurs.

The inventors therefore investigated the relationship between bead width and joint width in more detail. The results are shown in Figure 7.

Figure 7 is a diagram showing the relationship between bead width and joint width. As shown in Figure 7, the inventors investigated the change in the ratio of joint width to upper plate thickness (joint width/upper plate thickness) when the ratio of bead width to the thickness of the upper plate 12 (bead width/upper plate thickness) was changed.

As a result, it was found that when the bead width/upper plate thickness is less than a predetermined value, the joint width/upper plate thickness becomes 0. Here, a joint width/upper plate thickness of 0 means that the joint width is 0 and the lower plate 11 and the upper plate 12 are not joined.

From the above results, it was found that there is a threshold value for bead width/upper plate thickness between samples where the joint width is 0 and samples where the joint width is not 0. It was also found that the threshold value for bead width/upper plate thickness is in the range of 0.7 to 1.0. For this reason, it is preferable that the threshold value for bead width/upper plate thickness is 0.7, and it is even more preferable that it is 1.0.

The inventors further investigated the relationship between the intensity of thermal radiation emitted from the welded area during laser welding and the bead width generated at the welded area. The results are shown in Figure 8.

Figure 8 shows the relationship between the intensity of thermal radiation light and bead width. From the results shown in Figure 8, it was found that the intensity of thermal radiation light and bead width/upper plate thickness are almost proportional to each other.

From the results in Figures 6 to 8, it was found that the bead width can be determined from the intensity of the thermal radiation light during laser welding, and whether or not there is a welding defect in the welded area can be determined based on whether or not the bead width is less than the above threshold value.

For this reason, in this embodiment, by providing a thermal radiation light sensor 4 that detects the intensity of thermal radiation light, it becomes possible to determine whether or not there is a welding defect in the welded area.

In addition, according to this embodiment, as shown in FIG. 2, the controller 20 calculates the bead width at the welded portion based on the intensity of the thermal radiation light detected by the thermal radiation light sensor 4. By calculating the bead width in this manner, it becomes possible to determine whether or not there is a welding defect based on the size of the bead width.

Furthermore, according to this embodiment, as shown in FIG. 2, the controller 20 determines whether or not there is a defect in the welded portion based on whether or not the calculated bead width is less than a threshold value. In this way, it becomes possible to determine whether or not there is a welding defect based on whether or not the bead width is less than a threshold value. Furthermore, because the presence or absence of a welding defect can be realized by a simple algorithm of whether or not the bead width is less than a threshold value, the time required to create the algorithm can be shortened.

In the above, the bead width is calculated from the intensity of the thermal radiation light, and the presence or absence of a welding defect is determined based on whether the bead width is less than a threshold value. However, the presence or absence of a welding defect may also be determined based on whether the intensity of the thermal radiation light is less than a threshold value.

In this regard, the inventors investigated the changes in thermal radiation light intensity and bead width when the welding conditions were changed in lap joint welding using a laser beam. Specifically, in the above joint welding, areas with small and large gaps between the lower plate 11 and the upper plate 12 were intentionally provided, and the differences in thermal radiation light intensity and bead width when each area was welded were investigated. The results are shown in Figure 9. The welding conditions when welding the areas with small and large gaps were the same except for the size of the gap.

Figure 9 is a diagram showing the change in thermal radiation light intensity and bead width when welding conditions (size of gap) are changed midway when welding is performed from left to right along the horizontal axis. As shown in Figure 9, it was found that the intensity of thermal radiation light is high in areas where the gap between the lower plate 11 and the upper plate 12 is small, and the intensity of thermal radiation light is low in areas where the gap is large. It was also found that the bead width is large in areas where the gap between the lower plate 11 and the upper plate 12 is small, and the bead width is small in areas where the gap is large. Furthermore, in areas where the gap between the lower plate 11 and the upper plate 12 is small, the welded state shown by sample A in Figure 6 was obtained, and in areas where the gap is large, the welded state shown by sample D in Figure 6 was obtained.

The above results show that the presence or absence of a welding defect can be determined based on whether the intensity of the thermal radiation light is below a threshold value. Specifically, if the intensity of the thermal radiation light is below the threshold value, it can be determined that there is a defect in the welded area, and if the intensity of the thermal radiation light is equal to or greater than the threshold value, it can be determined that there is no defect in the welded area.

In this way, by determining whether or not there is a welding defect based on whether or not the intensity of the thermal radiation light is below a threshold value, it is possible to determine whether or not there is a welding defect without calculating the bead width.

Furthermore, according to this embodiment, as shown in FIG. 1, the housing 6 houses both the laser light oscillator 1 and the thermal radiation light sensor 4 in its internal space. This makes it possible to handle the laser light oscillator 1 and the thermal radiation light sensor 4 as a single module.

The embodiments disclosed herein should be considered to be illustrative and not restrictive in all respects. The scope of the present invention is indicated by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope of the claims.

1 Laser light oscillator, 2a, 2b, 2c Optical fiber, 3 Processing head, 4 Thermal radiation light sensor, 5 Optical splitter, 6 Housing, 7 Input unit, 8 Display unit, 10 Laser welding defect detection device, 11, 12 Welding object, 13 Bead, 20 Controller, 20a Thermal radiation light intensity acquisition unit, 20b Bead width calculation unit, 20c Defect determination unit, 20d Memory unit.

Claims (5)

a laser oscillator that emits laser light;
a laser light irradiation device that irradiates a welding point with the laser light oscillated by the laser light oscillation device;
a thermal radiation sensor that detects the intensity of thermal radiation generated from a welding point by irradiation with a laser beam;
a laser light transmission path having an optical fiber connected to the laser light oscillator and transmitting a laser light from the laser light oscillator to the laser light irradiation device;
a thermal radiation light transmission path that transmits thermal radiation light from the laser light irradiating device to the thermal radiation light sensor and shares the optical fiber with the laser light transmission path ;
and a controller that calculates a bead width at the welded portion based on the intensity of the thermal radiation light detected by the thermal radiation light sensor, and determines whether or not there is a defect in the welded portion based on whether the calculated bead width is less than a threshold value . The laser welding defect detection device according to claim 1 , wherein the controller determines whether or not there is a defect in the welded portion based on whether or not the intensity of the thermal radiation light detected by the thermal radiation light sensor is less than a threshold value. 3. The laser welding defect detection device according to claim 1 , further comprising a housing having an internal space and housing both the laser beam oscillator and the thermal radiation light sensor in the internal space. A step of emitting a laser beam;
transmitting the oscillated laser light to the laser light emitting device via a laser light transmission path having an optical fiber connected to the laser light emitting device;
irradiating a welding point with laser light from the laser light irradiation device;
a step of transmitting thermal radiation light generated from a welding point by irradiation with a laser beam to a thermal radiation light sensor via a thermal radiation light transmission path shared between the optical fiber and the laser beam transmission path;
detecting an intensity of the thermal radiation light by the thermal radiation light sensor ;
Calculating a bead width at the welded portion based on the intensity of the detected thermal radiation light;
and determining whether or not there is a defect in the weld based on whether or not the calculated bead width is less than a threshold value . The method of claim 4 , further comprising the step of determining whether the weld has a defect based on whether the intensity of the detected thermal radiation is less than a threshold value.

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