Patent Description:
Ultrasonic testing (UT) is known as a method for nondestructively detecting an internal defect such as a blow hole generated in a weld. However, because an object has a high temperature during welding, it is difficult to apply the method for directly accessing an inspection target surface with a probe in an in-process during welding.

Accordingly, an internal defect detection technique by what is called a "laser ultrasonic technique" is known, in which the inspection target surface is irradiated with laser (generation laser) to generate an ultrasonic wave inside an inspection target and the inspection target is separately irradiated with laser (detection laser) to detect the internal defect of the inspection target in a nondestructive method.

For example, Patent No. <CIT>discloses a weld inspection method for detecting the internal defect of the weld in-process using the laser ultrasonic technique in groove welding of a thick plate. In this weld inspection method, a bead surface is irradiated with the generation laser from above the weld bead, and an ultrasonic wave (scattered wave) reflected by the defect is detected using the detection laser, thereby detecting the internal defect of the weld.

In welding (lap fillet joint) of a thin plate for an automobile, it is difficult to detect the ultrasonic wave (scattered wave) reflected by the internal defect such as a blow hole because of a thin plate thickness (for example, about <NUM> to about <NUM>), and the weld inspection method described in Patent No.<CIT> also targets a groove welding of a thick plate. In addition, regarding UT as well, in JIS (Japanese Industrial Standards) Z <NUM> "Method for ultrasonic testing for welds of ferritic steel", the Architectural Institute of Japan, "Standard of ultrasonic testing for welded part in steel structural building" and the like, the applied plate thickness is defined to be greater than or equal to <NUM>, and welding (lap fillet joint) of a thin plate for an automobile is not applied.

European patent application <CIT> discloses a welding system with a welding mechanism, a reception laser light source, a reception optical mechanism, an interferometer and a data recording/ analysis mechanism. The reception laser light source generates reception laser light so as to irradiate the object to be welded with the reception laser light for the purpose of detecting a reflected ultrasonic wave obtained as a result of reflection of a transmission ultrasonic wave. The reception optical mechanism transmits, during or after welding operation, the reception laser light generated from the reception laser light source to the surface of the object to be welded for irradiation while moving, together with the welding mechanism, relative to the object to be welded and collects laser light scattered reflected at the surface of the object to be welded.

An object of the present disclosure is to provide a weld inspection device according to claim <NUM>, a welding system according to claim <NUM>, and a weld inspection method according to claim <NUM> capable of detecting the internal defect of the weld of the lap fillet joint used for the welding of the thin plate in the in-process method during the welding.

A weld inspection device according to one aspect of the present disclosure is a weld inspection device that inspects a weld of lap fillet joint, and includes first and second laser irradiation devices, a laser interferometer, and a determination device. The first laser irradiation device irradiates the weld of the inspection target after welding with generation laser exciting an ultrasonic wave inside the inspection target. The second laser irradiation device irradiates a predetermined position on the inspection target where the ultrasonic wave, which passes through the weld and is reflected on the lower surface of the base material of the inspection target, is to be detected with detection laser for detecting the ultrasonic wave. The laser interferometer measures interference of reflected light of the detection laser. The determination device determines existence of internal defect of the weld based on the measurement result of the laser interferometer. The first laser irradiation device includes a scanning mechanism that scans the irradiation position of the generation laser in a direction intersecting the welding direction.

In this weld inspection device, the scanning mechanism scans the irradiation position of the generation laser in the direction intersecting the welding direction. Then, the internal defect is detected using not the ultrasonic wave (scattered wave) reflected by the internal defect generated in the weld, but the ultrasonic wave that passes through the weld and is reflected by the lower surface of the base material of the inspection target. Accordingly, the internal defect of the weld of the lap fillet joint used for the welding of a thin plate can be detected.

The determination device may determine that the internal defect is generated in the weld when the attenuation degree of the intensity of the ultrasonic wave detected with the detection laser and the laser interferometer exceeds the threshold.

The welding system according to another aspect of the present disclosure includes an arc welding device including a welding torch, the weld inspection device that inspects the weld of the lap fillet joint formed by the arc welding device, and a welding robot. The welding torch and the first and second laser irradiation devices of the weld inspection device are mounted on a manipulator of the welding robot. The first and second laser irradiation devices are disposed behind the welding torch in the welding direction.

According to the above welding system, the internal defect of the weld of the lap fillet joint by the arc welding device can be detected in-process during the welding with the above weld inspection device mounted on the manipulator of the robot together with the arc welding device.

The welding robot includes a controller that controls the manipulator, and the controller controls the manipulator such that the first and second laser irradiation devices are positioned behind the welding torch in the welding direction during welding by the arc welding device.

The controller may stop the welding by the arc welding device and the operation of the manipulator when the weld inspection device detects the internal defect of the weld.

The controller may execute at least one of the following first processing and second processing when the internal defect of the weld is detected by the weld inspection device. The first processing includes processing of changing a welding condition of the arc welding device. The second processing includes processing of controlling the manipulator such that a welding speed is decreased as compared with a case where the internal defect is not detected.

The welding system may further include an adjustment mechanism and a deformation measurement device. The adjustment mechanism adjusts at least one of the position and the angle of the second laser irradiation device on the manipulator. The deformation measurement device is mounted on the manipulator and measures deformation at a predetermined position of an inspection target due to welding. The adjustment mechanism may adjust at least one of the position and the angle based on the measurement result of the deformation measurement device such that the relative positional relationship between the predetermined position and the second laser irradiation device becomes a predetermined relationship.

The welding system may further include a surface treatment device. The surface treatment device removes an oxide film generated on the inspection target surface by welding by the arc welding device ahead of a predetermined position in the welding direction.

The first laser irradiation device may include a plurality of pulsed laser irradiation devices each of which irradiates the weld with generation pulsed laser. The plurality of pulsed laser irradiation devices may emit the pulsed laser such that the laser irradiation timings are shifted from each other.

A weld inspection method according to still another aspect of the present disclosure is a weld inspection method for inspecting a weld of lap fillet joint, the weld inspection method includes: irradiating the weld of an inspection target after welding with generation laser exciting an ultrasonic wave inside the inspection target; irradiating a predetermined position on the inspection target where the ultrasonic wave is to be detected with detection laser for detecting the ultrasonic wave, the ultrasonic wave passing through the weld and being reflected by a base material lower surface of the inspection target; measuring interference of reflected light of the detection laser with a laser interferometer; and determining existence of an internal defect of the weld based on a measurement result of the laser interferometer. The irradiating the generation laser includes scanning an irradiation position of the generation laser in a direction intersecting a welding direction.

In this weld inspection method, the irradiation position of the generation laser is scanned in a direction intersecting the welding direction. Then, the internal defect is detected using not the ultrasonic wave (scattered wave) reflected by the internal defect generated in the weld, but the ultrasonic wave that passes through the weld and is reflected by the lower surface of the base material of the inspection target. Accordingly, the internal defect of the weld of the lap fillet joint used for the welding of a thin plate can be detected.

The determining may include determining that the internal defect is generated in the weld when the attenuation degree of the intensity of the ultrasonic wave detected with the detection laser and the laser interferometer exceeds a threshold.

The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

With reference to the drawings, embodiments of the present disclosure will be described in detail below. In the drawings, the same or corresponding portion is denoted by the same reference numeral, and the description thereof will not be repeated.

<FIG> is a view illustrating a configuration of a weld inspection device according to a first embodiment of the present disclosure. With reference to <FIG>, a weld inspection device <NUM> includes a generation laser source <NUM>, a generation laser irradiation device <NUM>, a detection laser source <NUM>, a detection laser probe <NUM>, a control device <NUM>, and a display device <NUM>.

Weld inspection device <NUM> is used for inspecting a weld <NUM> in lap fillet joint of a thin plate (base materials <NUM>, <NUM>) such as an automobile steel plate. For example, base materials <NUM>, <NUM> are galvanized steel plates having a plate thickness of about <NUM> to about <NUM>. In <FIG>, a Y-direction indicates a welding direction, an X-direction indicates a direction parallel to the base material and orthogonal to the welding direction (Y-direction), and a Z-direction indicates a normal direction of the base material.

Generation laser source <NUM> generates excitation light generating generation laser <NUM> in the generation laser irradiation device <NUM>, and outputs the excitation light to generation laser irradiation device <NUM>. For example, generation laser source <NUM> includes an LD (Laser Diode) power supply.

Generation laser irradiation device <NUM> receives the excitation light from generation laser source <NUM>, generates generation laser <NUM> that is the pulse laser, and irradiates weld <NUM> of the inspection target with the generation laser <NUM>. For example, generation laser irradiation device <NUM> includes a microchip laser that generates YAG (Yttrium Aluminum Garnet) pulsed laser and a scanning mechanism that can scan the irradiation position of generation laser <NUM> in the X-direction. For example, the scanning mechanism includes a galvano mirror in which an angle is adjustable and a drive mechanism that drives the galvano mirror.

Detection laser source <NUM> includes a laser interferometer. Detection laser source <NUM> generates detection laser <NUM> (reference light) irradiating base material <NUM> of the lower plate, and outputs detection laser <NUM> to detection laser probe <NUM>. In addition, detection laser source <NUM> receives reflected light from base material <NUM> of the detection laser <NUM> with which base material <NUM> is irradiated from detection laser probe <NUM>, detects interference light including the reference light and the reflected light, and outputs the interference light to control device <NUM>.

Detection laser probe <NUM> irradiates a predetermined position (ultrasonic detection point) of base material <NUM> of the lower plate with detection laser <NUM>. In addition, detection laser probe <NUM> receives the reflected light from base material <NUM> of detection laser <NUM> with which base material <NUM> is irradiated, and outputs the reflected light to detection laser source <NUM> (laser interferometer).

Weld inspection device <NUM> detects the internal defect of weld <NUM> using the laser ultrasonic technique. That is, weld <NUM> of the inspection target is irradiated with the laser (generation laser <NUM>) to generate the ultrasonic wave in the inspection target, and surface vibration corresponding to intensity of the ultrasonic wave at the position (ultrasonic detection point) on base material <NUM> irradiated with detection laser <NUM> is detected by the interference light between the reference light of detection laser <NUM> and the reflected light. The existence of the internal defect of weld <NUM> is determined based on detection difference between the case where the internal defect does not exist and the case where the internal defect exists in weld <NUM>. A detection principle of the internal defect of the weld by the weld inspection device <NUM> will be described in detail later with reference to <FIG> and <FIG>.

Control device <NUM> includes a central processing unit (CPU), a memory (random access memory (RAM) and read only memory (ROM)), and an input and output port inputting and outputting various signals (none of which are illustrated). The CPU expands a program stored in the ROM into the RAM, and executes the program. Various pieces of processing executed by control device <NUM> are described in the program stored in the ROM.

Control device <NUM> controls generation laser source <NUM> so as to generate the excitation light generating generation laser <NUM> in generation laser irradiation device <NUM>. In addition, control device <NUM> controls generation laser irradiation device <NUM> such that the irradiation position of generation laser <NUM> is scanned in the X-direction. In addition, control device <NUM> receives oscillation timing (timing of pulse irradiation) of generation laser <NUM> in generation laser irradiation device <NUM> from generation laser irradiation device <NUM>.

Then, control device <NUM> receives the interference measurement result of detection laser <NUM> by the laser interferometer of detection laser source <NUM> from detection laser source <NUM>, and determines the existence of the internal defect of weld <NUM> based on the intensity of the ultrasonic wave (the intensity of the surface vibration) at the irradiation position (ultrasonic detection point) of detection laser <NUM>. A method for determining the existence of the internal defect will be described in detail later.

Display device <NUM> is a display that displays various processing results of control device <NUM>. For example, a measurement screen called a B-scope indicating a measurement result of the ultrasonic wave in the inspection target by the weld inspection device <NUM> is displayed on display device <NUM>. The B-scope indicates an arrival time and intensity of the ultrasonic wave at the irradiation position (ultrasonic detection point) of the detection laser <NUM> according to the irradiation position (ultrasonic generation point) of the generation laser <NUM> scanned in the X-direction. For example, control device <NUM> and display device <NUM> are configured of a personal computer (PC). The method for detecting the internal defect of the weld by weld inspection device <NUM> will be described in detail below.

<FIG> and <FIG> are views illustrating the detection principle of the internal defect of the weld by weld inspection device <NUM>. <FIG> illustrates a state where there is no defect in weld <NUM>, and <FIG> illustrates a state where the internal defect (such as the blow hole) is generated in weld <NUM>.

With reference to <FIG>, in weld inspection device <NUM>, the region including weld <NUM> is irradiated with generation laser <NUM> (pulse laser) from above (Z-direction), and the ultrasonic wave is excited at the irradiation position of the laser. The generated ultrasonic wave passes through weld <NUM>, is reflected by a lower surface <NUM> of base material <NUM> on the lower side, and reaches the upper surface of base material <NUM>. The intensity of the ultrasonic wave at the irradiation position (ultrasonic detection point) of detection laser <NUM> is measured by measuring micro vibration generated on the surface of base material <NUM> by the reached ultrasonic wave using detection laser <NUM> (interference measurement using the laser interferometer).

The irradiation position of generation laser <NUM> is scanned in the X-direction using the scanning mechanism of generation laser irradiation device <NUM> (<FIG>). A point <NUM> indicated by a "×" mark indicates the irradiation position (ultrasonic generation point) of generation laser <NUM> that is the pulse laser. After the measurement at a certain irradiation position is completed, the irradiation position of generation laser <NUM> is scanned to the next position, and the measurement at the irradiation position is performed.

The irradiation position of detection laser <NUM> is fixed in the X-direction of base material <NUM>. A point <NUM> indicated by a "o" mark indicates the irradiation position (ultrasonic detection point) of detection laser <NUM>. As the distance between a detection point <NUM> and a generation point <NUM> in the X-direction increases, a propagation time of the ultrasonic wave from generation point <NUM> to detection point <NUM> increases, and the intensity of the ultrasonic wave (surface minute vibration) at detection point <NUM> also decreases due to diffusion attenuation.

With reference to <FIG>, when a defect <NUM> such as the blowhole exists in weld <NUM>, scattering attenuation is generated at defect <NUM> in addition to the diffusion attenuation. Therefore, the intensity of an ultrasonic wave <NUM> reaching detection point <NUM> is smaller (attenuation becomes large) than when defect <NUM> does not exist. Consequently, the existence of defect <NUM> in weld <NUM> can be determined by capturing an attenuation degree of the ultrasonic wave reaching detection point <NUM>.

<FIG> is a view illustrating a relationship between the irradiation position of generation laser <NUM> and the arrival time of the ultrasonic wave at the irradiation position of detection laser <NUM>. In <FIG>, the horizontal axis represents the irradiation position (the generation position of the ultrasonic wave) in the X-direction of generation laser <NUM>, and the larger the value, the farther from the irradiation position (ultrasonic detection point) of detection laser <NUM>. The vertical axis represents time from when generation laser <NUM> is emitted (after the ultrasonic wave is generated at the generation position) to when the ultrasonic wave reaches the irradiation position (ultrasonic detection point) of detection laser <NUM>.

With reference to <FIG>, a line L1 indicates the arrival time of the ultrasonic wave (surface wave) transmitted through weld <NUM> and the surface of base material <NUM>. A line L2 indicates the arrival time of the ultrasonic wave (reflected wave) that passes through weld <NUM> from the generation position of the ultrasonic wave and is reflected by lower surface <NUM> of base material <NUM>.

The arrival time of the reflected wave is not affected by the existence of defect <NUM>, so that whether the ultrasonic wave detected at the irradiation position (ultrasonic detection point) of detection laser <NUM> is a surface wave or an ultrasonic wave (reflected wave) reflected on lower surface <NUM> of base material <NUM> can be distinguished from the relationship between the generation position and the arrival time of the ultrasonic wave.

<FIG> is a view illustrating the relationship between the irradiation position of generation laser <NUM> and the intensity of the ultrasonic wave at the irradiation position of the detection laser <NUM>. In <FIG>, similarly to <FIG>, the horizontal axis represents the irradiation position (ultrasonic wave generation position) in the X-direction of generation laser <NUM>. The vertical axis indicates the intensity of the reflected wave (line L2) in <FIG> at the irradiation position (ultrasonic detection point) of detection laser <NUM>.

With reference to <FIG>, a line L3 indicates the intensity of the reflected wave (line L2) in <FIG> at the ultrasonic detection point when the internal defect does not exist in weld <NUM>. The larger the value of the generation position of the ultrasonic wave (the farther from the ultrasonic detection point), the more the signal intensity is attenuated by the diffusion attenuation.

A line L4 indicates the intensity of the reflected wave (line L2) in <FIG> at the ultrasonic detection point when the internal defect (such as the blow hole) exists in weld <NUM>. In a position where the generation position of the ultrasonic wave is larger than X1, the ultrasonic wave (reflected wave) reaching the ultrasonic detection point passes through the internal defect generated in weld <NUM>. At this point, because the scattering attenuation at the internal defect is generated in addition to the diffusion attenuation, the intensity of the ultrasonic wave at the ultrasonic detection point becomes smaller as compared with the case where the internal defect does not exist (line L3). That is, at the ultrasonic detection point, the attenuation degree of the ultrasonic wave when the internal defect is generated becomes larger as compared with the case where the internal defect does not exist.

The B-scope is displayed by changing the concentration according to the intensity of the ultrasonic wave at the ultrasonic detection point for each generation position of the ultrasonic wave for the lines L1, L2 in the graph of <FIG>. In the B-scope, the arrival time and intensity of the ultrasonic wave at the ultrasonic detection point are displayed on one screen for each generation position of the ultrasonic wave.

<FIG> is a view illustrating a method of determining the existence of the defect in weld <NUM>. With reference to <FIG>, the existence of the internal defect in weld <NUM> is determined by magnitude of the attenuation degree corresponding to the ultrasonic generation position with respect to the intensity of the ultrasonic wave (the intensity of the ultrasonic wave reflected on lower surface <NUM> of base material <NUM>) at the irradiation position (ultrasonic detection point) of detection laser <NUM>. That is, it is determined that the defect does not exist when the attenuation degree according to the generation position of the ultrasonic wave is smaller than a predetermined threshold, and it is determined that the internal defect is generated in weld <NUM> of the inspection target when the attenuation degree exceeds the threshold. The threshold is appropriately set to a value that can distinguish the existence of the internal defect by an evaluation test or the like in advance.

<FIG> is a flowchart illustrating a procedure of a series of processing in weld inspection device <NUM> of the first embodiment. With reference to <FIG>, first, control device <NUM> controls the scanning mechanism of generation laser irradiation device <NUM> so as to irradiate a predetermined position of the inspection target with generation laser <NUM> (step S10). Each irradiation position of generation laser <NUM> in one scan is previously determined in the X-direction (for example, <NUM> points in the region including weld <NUM>), and for example, the scanning mechanism is controlled such that generation laser <NUM> is first irradiated to a predetermined position closest to the irradiation position of detection laser <NUM>.

In addition, control device <NUM> controls detection laser source <NUM> such that a predetermined detection point of the inspection target is irradiated with detection laser <NUM> (step S20). The irradiation position (ultrasonic detection point) of detection laser <NUM> is determined at a predetermined position in the X-direction. The irradiation with detection laser <NUM> may be performed before the irradiation with generation laser <NUM>, or may be started simultaneously with the start of the irradiation with generation laser <NUM>.

Then, detection laser source <NUM> receives the reflected light of detection laser <NUM> emitted to base material <NUM> from detection laser probe <NUM>, and measures interference between the reflected light and detection laser <NUM> (reference light) emitted to base material <NUM> using the laser interferometer (step S20).

Subsequently, control device <NUM> determines whether the scanning of generation laser <NUM> is completed (step S25). Specifically, it is determined whether the measurement is completed at all predetermined irradiation positions in the X-direction. When the scanning is not completed (NO in step S25), control device <NUM> updates the irradiation position of generation laser <NUM> to the next position (step S30). Then, the processing returns to step S10.

When it is determined in step S25 that the scanning for one line is completed (YES in step S25), control device <NUM> produces the B-scope and executes waveform processing (step S35). Specifically, control device <NUM> produces the B-scope indicating the relationship between each irradiation position (generation position) in the X-direction of generation laser <NUM> and the arrival time and intensity of the ultrasonic wave (the ultrasonic wave having passed through weld <NUM> from the generation position and reflected by lower surface <NUM> of base material <NUM>) at the irradiation position (detection point) of detection laser <NUM> for the measurement signal for one scan obtained in the processing of steps S10 to S30.

In producing the B-scope, frequency processing using an appropriate band-pass filter or the like may be performed on the measurement signal obtained in step S20 in order to remove a noise.

Subsequently, the signal of the ultrasonic wave that is reflected by lower surface <NUM> of the lower plate (base material <NUM>) to reach the ultrasonic detection point is extracted from the produced B-scope (step S40). As described with reference to <FIG>, in the B-scope, the ultrasonic wave (reflected wave) reflected by lower surface <NUM> of base material <NUM> can be distinguished from the surface wave or the like and easily extracted. This extraction work may be performed manually or automatically extracted by control device <NUM>.

When the signal of the ultrasonic wave that is reflected by lower surface <NUM> of the lower plate (base material <NUM>) to reach the ultrasonic detection point is extracted in step S40, control device <NUM> calculates the attenuation degree of the ultrasonic wave corresponding to the irradiation position (generation position) of generation laser <NUM> for the extracted signal (step S45). Specifically, control device <NUM> calculates a degree of decrease in intensity of the ultrasonic wave according to the generation position. Control device <NUM> may calculate a root mean square (RMS) value of signal strength for the measurement signal obtained at each generation position, and calculate a degree of decrease in the RMS value according to the generation position.

Then, control device <NUM> determines whether the attenuation degree calculated in step S45 is larger than the threshold (step S50). As described above, the threshold is appropriately set to a value that can distinguish the existence of the internal defect by the evaluation test in advance. When it is determined that the attenuation degree is larger than the threshold (YES in step S50), control device <NUM> outputs a signal indicating that the internal defect is detected in weld <NUM> to display device <NUM> (step S55).

As described above, in the first embodiment, the internal defect is detected using the ultrasonic wave that passes through weld <NUM> and is reflected by lower surface <NUM> of base material <NUM> of the inspection target, instead of the ultrasonic wave (scattered wave) reflected by the internal defect generated in weld <NUM>. Specifically, when the irradiation position of generation laser <NUM> is scanned in the X-direction, and the attenuation degree of the ultrasonic wave at the ultrasonic detection point according to the scanning of the irradiation position exceeds the threshold, it is determined that the internal defect is generated in the weld. According to the first embodiment, with such the configuration, the internal defect of weld <NUM> of the lap fillet joint used for welding of the thin plate can be detected in-process.

In a second embodiment, a welding system in which a welding device and the weld inspection device are mounted on an automatic welding robot will be described.

<FIG> is an overall configuration diagram illustrating the welding system of the second embodiment. With reference to <FIG>, a welding system <NUM> includes a robot manipulator <NUM>, a welding torch <NUM>, a wire <NUM>, a welding power supply <NUM>, and a controller <NUM>.

Robot manipulator <NUM> is an articulated manipulator, for example, is a six-axis articulated manipulator. Robot manipulator <NUM> is controlled by controller <NUM> so as to perform the lap fillet joint of base materials <NUM>, <NUM> by welding torch <NUM> at a set welding speed.

Welding torch <NUM> supplies a welding wire and a shielding gas such as argon gas and carbon dioxide gas) (not illustrated) toward the weld of base materials <NUM>, <NUM>. Welding torch <NUM> receives supply of a welding current from welding power supply <NUM> through wire <NUM>, and generates an arc <NUM> between the tip of the welding wire and the weld of base materials <NUM>, <NUM>.

Instead of the welding wire, a non-consumable electrode (tungsten or the like) may be used while adding a filler (filler material) forming a weld metal. That is, the arc welding by welding torch <NUM> may be a welding electrode type (such as mag welding or MIG welding) using the welding wire, or may be a non-welding electrode type (such as TIG welding) with addition of the filler.

Welding power supply <NUM> generates a welding voltage and a welding current in order to perform the arc welding, and outputs the generated welding voltage and welding current to welding torch <NUM>.

Controller <NUM> controls the operation of robot manipulator <NUM> and the output of welding power supply <NUM> such that the lap fillet joint of base materials <NUM>, <NUM> is performed by welding torch <NUM> at a set welding speed. At this time, controller <NUM> controls robot manipulator <NUM> such that a position of a weld inspection head <NUM> (described later) constituting the weld inspection device is behind welding torch <NUM> in the welding direction.

In addition, controller <NUM> communicates with control device <NUM> that controls the weld inspection device, and exchanges various signals with a control device <NUM>. For example, controller <NUM> notifies control device <NUM> of start, stop, and continuation of welding by welding torch <NUM>. When receiving a defect detection signal indicating that the internal defect of the weld is detected from control device <NUM>, controller <NUM> stops welding by welding torch <NUM> or changes a welding condition.

Controller <NUM> also includes a CPU, memories (RAM and ROM), and an input and output port inputting and outputting various signals (none of them are illustrated). The CPU expands a program stored in the ROM into the RAM, and executes the program. Various pieces of processing executed by controller <NUM> are described in the program stored in the ROM.

Welding system <NUM> further includes weld inspection head <NUM>, optical fiber <NUM>, <NUM>, a link <NUM>, a generation laser source <NUM>, a detection laser source <NUM>, and control device <NUM>.

Weld inspection head <NUM> includes a generation laser irradiation device <NUM> and a detection laser probe <NUM>. Generation laser irradiation device <NUM> and detection laser probe <NUM> are attached to an attachment member <NUM>, and attachment member <NUM> is connected to robot manipulator <NUM> by a link <NUM>.

Generation laser irradiation device <NUM> includes a microchip laser <NUM>, a scanning mechanism <NUM>, and a photodetector <NUM>. For example, microchip laser <NUM> is a small solid-state laser using a YAG crystal, receives excitation light from generation laser source <NUM> through optical fiber <NUM>, and generates high-output pulsed laser.

Scanning mechanism <NUM> includes a mechanism that scans the irradiation position of the pulsed laser generated by microchip laser <NUM> in the X-direction (a welding width direction orthogonal to the welding direction (Y-direction)). For example, scanning mechanism <NUM> includes a galvano mirror in which an angle is adjustable and a drive mechanism that drives the galvano mirror. The drive mechanism of scanning mechanism <NUM> is controlled by control device <NUM> such that ultrasonic generation point group <NUM> irradiated with generation laser <NUM> (pulse laser) includes the entire region in the X-direction of a weld bead <NUM>.

Photodetector <NUM> detects oscillation of generation laser <NUM> (pulse laser), and outputs a trigger signal Tr to control device <NUM> every time the pulse laser is oscillated.

Detection laser probe <NUM> irradiates ultrasonic detection point <NUM>, which is a predetermined position in the X-direction on base material <NUM>, with detection laser <NUM> (reference light) received from detection laser source <NUM> through optical fiber <NUM>. In addition, detection laser probe <NUM> receives the reflected light from base material <NUM>, which is detection laser <NUM> with which base material <NUM> is irradiated, and outputs the reflected light to detection laser source <NUM> through optical fiber <NUM>.

Detection laser source <NUM> includes the laser interferometer, and outputs detection laser <NUM> (reference light) emitted to base material <NUM> to detection laser probe <NUM> through optical fiber <NUM>. Then, detection laser source <NUM> receives the reflected light of detection laser <NUM> from base material <NUM> received by detection laser probe <NUM> from detection laser probe <NUM>, and outputs a detection signal IS of the interference light including the reference light and the reflected light of detection laser <NUM> to control device <NUM>.

In consideration of in-process defect detection during the welding, the irradiation positions of generation laser <NUM> and detection laser <NUM> are desirably close to the welding position (molten pool <NUM>). For example, the irradiation positions of generation laser <NUM> and detection laser <NUM> can be set to <NUM> to <NUM> behind molten pool <NUM> in the welding direction.

Control device <NUM> measures detection signal IS of the interference light between the reference light and the reflected light of the detection laser <NUM> for a predetermined time (for example, <NUM>) based on trigger signal Tr from photodetector <NUM>, which indicates the timing at which generation laser <NUM> (pulse laser) is oscillated. Then, control device <NUM> measures the intensity of the ultrasonic wave at ultrasonic detection point <NUM> corresponding to trigger signal Tr from measured detection signal IS of the interference light.

Control device <NUM> measures the intensity of the ultrasonic wave at ultrasonic detection point <NUM> as described above while scanning the irradiation position (ultrasonic generation point) of generation laser <NUM>. When the measurement for one scan is completed, control device <NUM> determines whether the internal defect is generated in the weld (weld bead <NUM>) based on the attenuation degree of the ultrasonic wave (reflected wave) that is reflected by the lower surface of the lower plate (base material <NUM>) to reach detection point <NUM> by the same method as that in the first embodiment.

In welding system <NUM> of the second embodiment, when control device <NUM> determines that the internal defect is generated in the weld, the defect detection signal indicating that the internal defect of the weld is detected is notified from control device <NUM> to controller <NUM> on the robot manipulator side, and the welding using welding torch <NUM> is stopped or the welding condition is changed (such as a change in welding speed or welding current).

<FIG> is a view illustrating an image of weld defect detection in process in welding system <NUM> in <FIG>. With reference to <FIG>, the upper view is a plan view illustrating the inspection target including the weld. Weld bead <NUM> is formed behind molten pool <NUM>, and a defect <NUM> indicated by a dotted line is the blow hole or the like generated inside the weld (weld bead <NUM>).

At the position in the Y-direction (welding direction) where the defect is not generated in the weld, the attenuation degree of the ultrasonic wave at ultrasonic detection point <NUM> according to the scanning of the irradiation position of generation laser <NUM> (pulse laser) is smaller than the threshold. On the other hand, at the position in the Y-direction where the defect is generated in the weld, the attenuation degree of the ultrasonic wave at ultrasonic detection point <NUM> according to the scanning of the irradiation position of generation laser <NUM> is larger than the threshold. In this manner, at which position defect <NUM> is generated in the weld (weld bead <NUM>) in the welding direction (Y-direction) can be determined in-process during the welding.

<FIG> is a flowchart illustrating a procedure of a series of processing in the welding system of the second embodiment. With reference to <FIG> together with <FIG>, control device <NUM> controls scanning mechanism <NUM> so as to irradiate a predetermined position in the X-direction of the welding target with generation laser <NUM> (step S110). Each irradiation position of generation laser <NUM> in one scan is previously determined in the X-direction, and in this example, <NUM> irradiation positions are determined in the region including weld bead <NUM>.

Subsequently, the oscillation (irradiation) of the generation laser <NUM> (pulse laser) is detected by photodetector <NUM>, and trigger signal Tr indicating the start of the detection of the ultrasonic wave corresponding to the pulse irradiation is transmitted from photodetector <NUM> to control device <NUM> (step S115).

Based on trigger signal Tr, control device <NUM> measures the intensity of the ultrasonic wave at ultrasonic detection point <NUM> based on the interference light of detection laser <NUM> acquired by the laser interferometer for a predetermined time (for example, <NUM>) (step S120).

Subsequently, control device <NUM> determines whether the measurement for one scan of generation laser <NUM> is completed (step S125). Specifically, it is determined whether the measurement is completed at all predetermined irradiation positions (<NUM> points in this example) in the X-direction. When the measurement for one scan is not completed (NO in step S125), control device <NUM> updates the irradiation position of generation laser <NUM> to the next position (step S130). Then, the processing returns to step S110.

When it is determined in step S125 that the measurement for one scan of generation laser <NUM> is completed (YES in step S125), control device <NUM> produces the B-scope and executes the waveform processing (step S135). Furthermore, the signal of the ultrasonic wave (reflected wave) that is reflected by the lower surface of the lower plate (base material <NUM>) to reach detection point <NUM> is extracted from the produced B-scope (step S140). Furthermore, the control device <NUM> calculates the attenuation degree of the ultrasonic wave corresponding to the irradiation position (generation position) of generation laser <NUM> for the extracted signal (step S145). Because the pieces of processing in steps S135 to S145 described above are similar to the pieces of processing in steps S35 to S45 in <FIG> described in the first embodiment, detailed description will not be repeated.

Subsequently, control device <NUM> determines whether the attenuation degree calculated in step S145 is larger than the threshold (step S150). This threshold is appropriately set to a value with which the existence of the internal defect can be distinguished by the evaluation test in advance. When it is determined that the attenuation degree is larger than the threshold (YES in step S150), control device <NUM> outputs the defect detection signal indicating that the defect is detected in the weld (weld bead <NUM>) to controller <NUM> on the robot manipulator side (step S155). When the attenuation degree is less than or equal to the threshold (NO in step S150), control device <NUM> transfers the processing to step S160 without executing the processing in step S155.

Subsequently, control device <NUM> determines whether the welding is continued based on the signal from controller <NUM> indicating continuation necessity of the welding (step S160). When the welding is continued (YES in step S160), control device <NUM> transfers to the measurement in the next measurement line (step S165), and returns the processing to step S110.

On the other hand, when it is determined in step S160 that the welding is stopped based on the signal from controller <NUM> (NO in step S160), control device <NUM> transfers the processing to the end and ends the series of processing.

<FIG> is a flowchart illustrating a processing example of controller <NUM> when controller <NUM> receives the defect detection signal from control device <NUM>. With reference to <FIG>, controller <NUM> determines whether the defect detection signal is received from control device <NUM> (step S210). When the defect detection signal is not received (NO in step S210), controller <NUM> transfers to the return processing without executing the following series of processing.

When it is determined in step S210 that the defect detection signal is received from control device <NUM> (YES in step S210), controller <NUM> stops the welding using welding torch <NUM> (step S220). Furthermore, controller <NUM> stops the operation of robot manipulator <NUM> (step S230).

Then, controller <NUM> notifies control device <NUM> (weld inspection device) that the welding is stopped (step S240). That is, in this example, when the inspection of the weld (weld bead <NUM>) is performed in-process during the welding to detect the defect of the weld, the welding is stopped according to the defect detection signal output from control device <NUM> to controller <NUM> of the robot manipulator. Then, controller <NUM> notifies weld inspection device-side control device <NUM> that the welding is stopped.

As described above, according to the second embodiment, the weld inspection device (weld inspection head <NUM>) mounted on robot manipulator <NUM> together with welding torch <NUM> can detect the internal defect of the weld (weld bead <NUM>) by welding torch <NUM> in-process during the welding. According to the second embodiment, the welding by the welding robot can be stopped when the weld inspection device and the welding robot (robot manipulator <NUM> and welding torch <NUM>) are linked with each other, and when the internal defect is detected in the weld by the weld inspection device.

In the second embodiment, the welding is stopped when the weld defect is detected. However, the welding may be continued by changing the welding condition.

<FIG> is a flowchart illustrating a processing example of controller <NUM> when controller <NUM> receives the defect detection signal from control device <NUM> in the modification. This flowchart corresponds to <FIG> described above.

With reference to <FIG>, controller <NUM> determines whether the defect detection signal is received from control device <NUM> (step S310). When the defect detection signal is not received (NO in step S310), controller <NUM> transfers to the return processing without executing the following series of processing.

When it is determined in step S310 that the defect detection signal is received from control device <NUM> (YES in step S310), controller <NUM> changes the welding condition using welding torch <NUM> (step S320). The change of the welding condition is previously determined, and for example, the welding current is changed.

In addition, controller <NUM> decreases the welding speed (step S330). The degree of decrease in welding speed is also previously determined, and the welding speed after the decrease may be defined, or a rate of decrease in welding speed may be defined. Only the processing in any of steps S320 and S330 may be executed.

When the processing in step S320 and/or step S330 is performed, controller <NUM> notifies control device <NUM> (weld inspection device) that the welding is continued (step S340). That is, also in this example, when the inspection of the weld (weld bead <NUM>) is performed in-process during the welding to detect the defect of the weld, the welding condition and the welding speed are changed according to the defect detection signal output from control device <NUM> to controller <NUM> of the robot manipulator, and the welding is continued. Then, controller <NUM> notifies weld inspection device-side control device <NUM> that the welding is continued.

As described above, according to this modification, when the internal defect is detected in the weld by the weld inspection device, the welding condition can be changed or the welding speed can be lowered such that the defect is prevented in the subsequent welding.

In the defect detection using the laser ultrasonic technique, non-contact vibration measurement is performed using the reflected light from the irradiation surface of detection laser <NUM>. In order to sufficiently capture the reflected light from the inspection target to increase the measurement sensitivity, detection laser probe <NUM> needs to be disposed at the focal position while facing the irradiation surface of detection laser <NUM>.

<FIG> is a view illustrating a relationship between a deviation amount in the height direction from the focal position and the detection sensitivity of detection laser probe <NUM>. <FIG> illustrates the detection sensitivity when detection laser probe <NUM> faces a stainless mirror surface and when the height of detection laser probe <NUM> with respect to the stainless mirror surface is changed from the focal position.

As illustrated in <FIG>, when the deviation in the height direction from the focal position is generated, the detection sensitivity of detection laser probe <NUM> decreases. That is, when the distance between detection laser probe <NUM> and the irradiation surface of detection laser <NUM> (the surface of base material <NUM>) changes, the detection sensitivity of detection laser <NUM> by detection laser probe <NUM> decreases.

<FIG> is a view illustrating a relationship between an angular deviation with respect to the irradiation surface of detection laser <NUM> and the detection sensitivity of detection laser probe <NUM>. <FIG> illustrates the detection sensitivity when detection laser probe <NUM> faces the stainless mirror surface and when the angle of detection laser probe <NUM> with respect to the stainless mirror surface is changed.

As illustrated in <FIG>, when the angle deviation of detection laser <NUM> is generated, the detection sensitivity of detection laser probe <NUM> decreases. That is, when the deviation between the irradiation direction of detection laser <NUM> and the normal direction of the irradiation surface (surface of base material <NUM>) of detection laser <NUM> is generated, the detection sensitivity of detection laser <NUM> by detection laser probe <NUM> decreases.

In the welding, a welding object may be deformed due to thermal strain caused by the welding. In particular, in the welding of the thin plate, deformation of the base material due to the welding is assumed as illustrated in <FIG>. As illustrated in <FIG>, in the case of deformation of lower base material <NUM>, there is a possibility that the detection sensitivity of detection laser <NUM> by detection laser probe <NUM> when the disposition of detection laser probe <NUM> remains in the initial state.

Accordingly, in the third embodiment, the deformation of the irradiation surface of detection laser <NUM> is measured during the welding, and the position and angle of detection laser probe <NUM> are adjusted using the information. Thus, the decrease in the detection sensitivity of detection laser probe <NUM> is prevented.

The detection sensitivity of detection laser probe <NUM> also changes depending on the state of the irradiation surface of detection laser <NUM>.

<FIG> is a view exemplifying the relationship between the surface state of the inspection target and the detection sensitivity of detection laser probe <NUM>. With reference to <FIG>, when a smut (oxide film) after the welding adheres to the irradiation surface of detection laser <NUM>, the detection sensitivity of detection laser probe <NUM> decreases. On the other hand, the detection sensitivity of detection laser probe <NUM> is improved by polishing the irradiation surface of detection laser <NUM>.

Accordingly, in the third embodiment, a tool polishing ultrasonic detection point <NUM> irradiated with detection laser <NUM> is further provided. For example, a brush, laser irradiation, or the like can be used as the tool. Thus, the decrease in the detection sensitivity of detection laser probe <NUM> is further prevented.

<FIG> is an overall configuration diagram illustrating a welding system according to the third embodiment. With reference to <FIG>, a welding system 100A further includes a laser line scanner <NUM>, a drive mechanism <NUM>, and a surface treatment device <NUM> in the welding system <NUM> in <FIG>.

Laser line scanner <NUM> is attached to attachment member <NUM> and measures a surface profile of the welded member after the welding. More specifically, laser line scanner <NUM> measures the surface profile of base material <NUM> after the welding at least in an XZ-plane. A signal Pf indicating the measurement result of laser line scanner <NUM> is output to control device <NUM>.

Drive mechanism <NUM> is controlled by control device <NUM>, and is able to change the position (Z-direction) and angle (rotation angle on the XZ-plane) of detection laser probe <NUM> with respect to attachment member <NUM>.

Based on signal Pf from laser line scanner <NUM>, control device <NUM> controls drive mechanism <NUM> such that detection laser probe <NUM> faces base material <NUM> and such that the position of detection laser probe <NUM> with respect to base material <NUM> is the focal position.

Surface treatment device <NUM> is a tool polishing the surface of base material <NUM> in ahead the welding direction of ultrasonic detection point <NUM> irradiated with detection laser <NUM>. For example, a brush can be adopted as surface treatment device <NUM>. Alternatively, the surface treatment device <NUM> may be configured by a laser irradiation device in which the output is adjusted so as to remove the smut after the welding while leaving the plating layer on the surface of the base material <NUM>.

In the above description, drive mechanism <NUM> can change the position and angle of detection laser probe <NUM>. However, drive mechanism <NUM> may change only one of the position and angle of detection laser probe <NUM>. Even when only one of the position and the angle is changed, the decrease in the detection sensitivity of detection laser probe <NUM> can be prevented.

In the above description, drive mechanism <NUM> corresponds to the "adjustment mechanism" that adjusts at least one of the position and the angle of detection laser probe <NUM>. Laser line scanner <NUM> is mounted on robot manipulator <NUM> and corresponds to the "deformation measurement device" that measures the deformation of the inspection target at ultrasonic detection point <NUM> irradiated with detection laser <NUM>.

In the above description, welding system 100A includes drive mechanism <NUM> and laser line scanner <NUM>. However, welding system 100A may include only one of drive mechanism <NUM> and laser line scanner <NUM>.

As described above, according to the third embodiment, when drive mechanism <NUM> and/or laser line scanner <NUM> is provided, the deterioration of the detection sensitivity of detection laser probe <NUM> due to the deformation of the welding target after the welding or the formation of the smut can be prevented. As a result, the decrease in the detection accuracy of the internal defect of the weld can be prevented.

Because weld inspection head <NUM> is mounted on robot manipulator <NUM> together with welding torch <NUM>, weld inspection head <NUM> also moves in the welding direction together with welding torch <NUM> during the welding. For this reason, the scanning direction of the irradiation position of generation laser <NUM> is inclined from the direction (X-direction) orthogonal to the welding direction (Y-direction).

<FIG> is a plan view illustrating the irradiation position of the generation laser <NUM> during the welding. With reference to <FIG>, ultrasonic generation point group <NUM> irradiated with generation laser <NUM> has a width Δy in the welding direction (Y-direction) at the start point and the end point of the scanning. It can be said that Δy indicates the spatial resolution of the weld inspection in the welding direction.

The spatial resolution can be increased (Δy can be decreased) by (i) decreasing the moving speed of weld inspection head <NUM>, (ii) decreasing the number of irradiation points of generation laser <NUM> (pulse laser) in one scan, and (iii) increasing the irradiation frequency of generation laser <NUM>.

However, the moving speed of weld inspection head <NUM> is the welding speed and the welding speed is determined by the welding condition, so that lowering the moving speed of weld inspection head <NUM> is a change of the welding condition and is not easy. Furthermore, reducing the number of irradiation points of generation laser <NUM> in one scan may reduce the amount of acquired information, which leads to degradation of detection accuracy. Accordingly, desirably the irradiation frequency of generation laser <NUM> (pulse laser) is increased.

<FIG> is a view illustrating a relationship between the irradiation frequency of generation laser <NUM> and the spatial resolution in the welding direction. <FIG> illustrates the spatial resolution (Δy in <FIG>) when the irradiation frequency of generation laser <NUM> is changed in the case that the number of irradiation points of generation laser <NUM> in one scanning is <NUM> and in the case that the welding speed is <NUM>/min.

The spatial resolution is Δy = <NUM> when the irradiation frequency (pulse frequency) of generation laser <NUM> is <NUM>, and the spatial resolution is half thereof when the irradiation frequency is <NUM>. As described above, the spatial resolution can be increased (Δy can be reduced) by increasing the irradiation frequency of generation laser <NUM>.

It is not easy to increase the oscillation frequency of microchip laser <NUM> in order to increase the irradiation frequency of generation laser <NUM>. Accordingly, in a fourth embodiment, the irradiation frequency of generation laser <NUM> is increased using a plurality of microchip lasers by taking advantage of the small size of the microchip lasers.

<FIG> is a view illustrating a configuration example of the generation laser irradiation device of the fourth embodiment. With reference to <FIG>, in the illustrated example, generation laser sources <NUM>-<NUM>, <NUM>-<NUM> and generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> are provided as the generation device of generation laser <NUM>. The configuration of each of generation laser sources <NUM>-<NUM>, <NUM>-<NUM> is the same as that of generation laser source <NUM> described in <FIG>, and the configuration of each of the generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> is the same as that of generation laser irradiation device <NUM> described in <FIG>.

Each of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> receives the excitation light from generation laser sources <NUM>-<NUM>, <NUM>-<NUM> through an optical fiber. Each of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> generates high-output pulsed laser. While the galvano mirror is controlled such that the irradiation positions of the pulsed laser output from generation laser irradiation device <NUM>-<NUM> and the pulsed laser output from generation laser irradiation device <NUM>-<NUM> are the same, the oscillation timings are shifted from each other.

<FIG> is a view illustrating the oscillation timing of the pulsed laser output from each of the generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM>. With reference to <FIG>, the oscillation timing of the pulsed laser is adjusted in each of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> such that the oscillation timings of the pulsed laser output from each of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> are shifted from each other by a half period. Thus, the number of times of the ultrasonic wave generated at the irradiation position of generation laser <NUM> can be substantially doubled. For example, when the frequency of the pulsed laser output from each of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> is <NUM>, the frequency of generation laser <NUM> with which the target is irradiated can be set to <NUM>.

Other configurations of the welding system according to the fourth embodiment are the same as those of welding system <NUM> in <FIG> or welding system 100A in <FIG>.

As described above, according to the fourth embodiment, the detection accuracy of the internal defect of the weld can be enhanced by enhancing the spatial resolution of the weld inspection in the welding direction.

In the fourth embodiment, the number of times of the ultrasonic wave generated at the irradiation position of the generation laser <NUM> is doubled by the plurality of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM>, but the control of the scanning mechanism (galvanometer mirror) and the management of the trigger by the photodetector are required for a plurality of devices, and the configuration of the entire device may be complicated. Accordingly, the control of the scanning mechanism and the management of the trigger by the photodetector can be integrated into one by configuring the plurality of microchip lasers to share the optical system (scanning mechanism).

<FIG> is a view illustrating a configuration example of a generation laser irradiation device according to a modification of the fourth embodiment. With reference to <FIG>, in this modification, a generation laser irradiation device <NUM> is provided instead of generation laser irradiation devices <NUM>-<NUM>, <NUM>-<NUM> in <FIG>. Generation laser irradiation device <NUM> includes microchip lasers <NUM>-<NUM>, <NUM>-<NUM>, a condensing mechanism <NUM>, scanning mechanism <NUM>, and photodetector <NUM>. The configuration of each of microchip lasers <NUM>-<NUM>, <NUM>-<NUM> is the same as microchip laser <NUM> in <FIG>.

Microchip laser <NUM>-<NUM>, <NUM>-<NUM> receives the excitation light from generation laser sources <NUM>-<NUM>, <NUM>-<NUM> through the optical fiber. Then, each of the microchip lasers <NUM>-<NUM>, <NUM>-<NUM> generates high-output pulsed laser, and outputs the pulsed laser to condensing mechanism <NUM>. The oscillation timings of the pulsed laser output from the microchip laser <NUM>-<NUM> and the pulsed laser output from microchip laser <NUM>-<NUM> are shifted from each other. More specifically, as illustrated in <FIG>, the oscillation timing of the pulsed laser is adjusted in each of microchip lasers <NUM>-<NUM>, <NUM>-<NUM> such that the oscillation timings of the pulse laser output from each of microchip lasers <NUM>-<NUM>, <NUM>-<NUM> are shifted from each other by a half period.

Condensing mechanism <NUM> condenses the pulsed laser output from microchip laser <NUM>-<NUM> and the pulsed laser output from microchip laser <NUM>-<NUM>, and outputs the light to scanning mechanism <NUM>. Condensing mechanism <NUM> includes the galvanometer mirror in which the angle is adjusted so as to condense the pulsed laser output from each of microchip lasers <NUM>-<NUM>, <NUM>-<NUM> to output the light to scanning mechanism <NUM>.

Photodetector <NUM> detects the oscillation of generation laser <NUM> (pulsed laser) output from scanning mechanism <NUM>, and outputs trigger signal Tr to control device <NUM> every time the pulsed laser is oscillated. Because scanning mechanism <NUM> and photodetector <NUM> have been described with reference to <FIG>, the description thereof will not be repeated.

In this modification, when light condensing mechanism <NUM> is provided, scanning mechanism <NUM> and photodetector <NUM> are shared by the plurality of microchip lasers <NUM>-<NUM>, <NUM>-<NUM>, so that the configuration of the entire device can be simplified as compared with the fourth embodiment.

Claim 1:
A weld inspection device (<NUM>) for inspecting a weld (<NUM>) of lap fillet joint, the weld inspection device comprising:
a first laser irradiation device (<NUM>) configured to irradiate the weld of an inspection target after welding with generation laser beam (<NUM>) exciting an ultrasonic wave inside the inspection target, wherein the inspection target comprises two base materials (<NUM>, <NUM>) joint by the weld (<NUM>) of a lap fillet joint;
a second laser irradiation device (<NUM>) configured to irradiate a predetermined position on the inspection target where the ultrasonic wave is to be detected with detection laser beam (<NUM>) for detecting the ultrasonic wave, the ultrasonic wave passing through the weld and being reflected by a base material lower surface (<NUM>) of the inspection target, wherein the second laser irradiation device (<NUM>) is configured to irradiate one of the two base materials (<NUM>, <NUM>);
a laser interferometer (<NUM>) configured to measure interference of reflected light of the detection laser; and
a determination device (<NUM>) configured to determine existence of an internal defect of the weld based on a measurement result of the laser interferometer,
wherein the first laser irradiation device (<NUM>) includes a scanning mechanism configured to scan an irradiation position of the generation laser in a direction intersecting a welding direction.