Welding inspection device

Abstract

Even if the actual shape of the object being inspected deviates from the initially assumed shape, the decrease in the accuracy of detecting internal defects is suppressed. [Solution] The welding inspection apparatus comprises a first irradiation device that irradiates a transmitting laser beam onto a transmitting point on the upper surface of the object to be inspected, a second irradiation device that irradiates a receiving laser beam onto a receiving point on the upper surface of the object to be inspected, a laser interferometer that performs interferometric measurement of the reflected light of the receiving laser beam irradiated from the second irradiation device, reflected at the receiving point and received by the second irradiation device, a control device that performs an internal inspection to determine whether or not there are internal defects inside the weld based on the measurement results of the laser interferometer, and a first adjustment device that can adjust the receiving angle, which is the angle at which the second irradiation device receives the reflected light. Before performing the internal inspection, the control device searches for the receiving angle at which the amount of reflected light received is maximum as the optimal receiving angle, and corrects the receiving angle to the optimal receiving angle.

Description

Technical Field

[0001] The present disclosure relates to a welding inspection apparatus that inspects a welded portion included in an inspection object using a laser ultrasonic method.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2023-20336 discloses a welding inspection apparatus that inspects a welded portion included in an inspection object using a laser ultrasonic method. This welding inspection apparatus irradiates a transmission point on the upper surface of the inspection object with a transmission laser beam to generate ultrasonic waves at the transmission point, and irradiates a reception point on the upper surface of the inspection object with a reception laser beam to perform interference measurement of the reflected light from the reception point of the reception laser beam using a laser interferometer. Ultrasonic waves generated at the transmission point and reaching the reception point are detected based on the measurement result of the laser interferometer, a reflected wave reflected from the lower surface of the inspection object is extracted from the detected ultrasonic waves, and internal defects of the welded portion are detected based on the extracted reflected wave.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the detection of internal defects using the laser ultrasonic method, measurement of vibration at the reception point on the upper surface of the inspection object is performed non-contact using the reflected light from the reception point of the reception laser beam. Therefore, in order to sufficiently collect the reflected light from the reception point of the reception laser beam and increase the measurement sensitivity, it is desirable to appropriately adjust the irradiation direction of the reception laser beam based on the shape of the inspection object so that the detection intensity of the reflected light becomes as large as possible.

[0005] However, due to dimensional errors, installation errors, and deformation caused by thermal distortion during welding, the actual shape of the object being inspected may deviate from the initially assumed shape. This discrepancy between the actual shape and the assumed shape can affect the direction of the receiving laser beam, potentially leading to a decrease in the accuracy of internal defect detection.

[0006] Therefore, the purpose of this disclosure is to suppress a decrease in the accuracy of detecting internal defects, even when the actual shape of the object being inspected deviates from the initially assumed shape. [Means for solving the problem]

[0007] The welding inspection apparatus according to this disclosure is a welding inspection apparatus for inspecting a welded part included in an object to be inspected, and comprises: a first irradiation device that irradiates a transmitting laser beam onto a transmitting point on the upper surface of the object to be inspected; a second irradiation device that irradiates a receiving laser beam onto a receiving point on the upper surface of the object to be inspected; a laser interferometer that interferometrically measures the reflected light of the receiving laser beam that is irradiated from the second irradiation device, reflected at the receiving point, and received by the second irradiation device; a control device that detects ultrasonic waves generated at the transmitting point by the irradiation of the transmitting laser beam and reaching the receiving point based on the measurement results of the laser interferometer, extracts reflected waves reflected from the lower surface of the object to be inspected from among the detected ultrasonic waves, and performs an internal inspection to determine whether or not there are internal defects inside the welded part based on the extracted reflected waves; and a first adjustment device that can adjust the receiving angle, which is the angle at which the second irradiation device receives the reflected light. Before performing internal inspection, the control device controls the second irradiation device and the first adjustment device to irradiate the receiving laser light while changing the receiving angle, monitors the amount of reflected light received, and performs a first search process to find the receiving angle at which the amount of reflected light received is maximum as the optimal receiving angle, and controls the first adjustment device so that the receiving angle becomes the optimal receiving angle. [Effects of the Invention]

[0008] According to this disclosure, even if the actual shape of the object being inspected deviates from the initially assumed shape, a decrease in the accuracy of detecting internal defects can be suppressed. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows an example of the overall configuration of a welding inspection device. [Figure 2] This diagram shows the state of a weld bead when there are no internal defects. [Figure 3] This diagram shows the condition when there are internal defects in the weld bead. [Figure 4] This diagram schematically shows an example of a B-scope displayed on a display device. [Figure 5] This diagram shows the relationship between the transmission position and the detected intensity of the reflected wave from the bottom surface. [Figure 6] This diagram illustrates an example of a method for determining the presence or absence of internal defects. [Figure 7] This figure shows an example of a condition where the actual deformation of the object being inspected deviates from the standard shape. [Figure 8] This is a flowchart showing an example of the processing procedure for a control device. [Figure 9] This diagram schematically shows an example of the difference between the measured shape of the object being inspected and the initially assumed shape of the object being inspected. [Figure 10] This diagram shows a welding inspection system with a measuring device added to detect deformation in the YZ plane of the object being inspected. [Figure 11] This flowchart shows an example of the processing procedure when a control device corrects the receiving angle. [Figure 12] This is a diagram illustrating the method for finding the optimal reception angle. [Figure 13] This flowchart shows an example of the processing procedure when a control device corrects the reception distance. [Figure 14] This diagram illustrates the method for finding the optimal reception distance. [Figure 15] This diagram schematically shows an example of the internal structure of the second irradiation device. [Figure 16] This flowchart shows an example of the processing procedure when a control device corrects the transmission distance. [Figure 17] This figure shows an example of a configuration for detecting the light intensity of ablation light. [Figure 18]This is a diagram for explaining a method of searching for an optimal transmission distance. [Figure 19] This is a diagram showing an example in which a positioner corrects a reception angle.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and their descriptions are not repeated.

[0011] <Overall Configuration> FIG. 1 is a diagram showing an example of the overall configuration of a welding inspection apparatus 1 according to the present embodiment. The welding inspection apparatus 1 includes a transmission laser source 10, a first irradiation device (transmission laser beam irradiation device) 12, a reception laser source 16, a second irradiation device (reception laser beam probe) 18, a control device 22, a display device 24, and a measurement device 50.

[0012] This welding inspection apparatus 1 is used, for example, for inspecting a weld bead (weld portion) 6 in welding of thin plate-shaped base materials 2 and 4. The base materials 2 and 4 are, for example, galvanized steel plates having a plate thickness of about 1 to 2 mm. Hereinafter, the base materials 2 and 4 including the weld bead 6 are also referred to as "inspection targets". In the figure, the Y direction indicates the welding progress direction (the extending direction of the weld bead 6), the Z direction indicates the normal direction of the base materials 2 and 4, and the X direction indicates the direction orthogonal to the Y direction and the Z direction. The first irradiation device 12 and the second irradiation device 18 are fixed to a robot (not shown) movable in the Y direction (welding progress direction), and by moving the robot in the Y direction, the first irradiation device 12 and the second irradiation device 18 can be integrally moved relative to the base materials 2 and 4 in the Y direction.

[0013] The transmission laser source 10 generates excitation light for generating transmission laser light 14 in the first irradiation device 12 and outputs it to the first irradiation device 12. The transmission laser source 10 is constituted by, for example, an LD (Laser Diode) power source. <​The first irradiation device 12 receives excitation light from the transmitting laser source 10, generates a pulsed laser beam, the transmitting laser beam 14, and irradiates the upper surface (irradiation surface) of the object to be inspected. The point of intersection between the transmitting laser beam 14 and the upper surface of the object to be inspected is the transmission point 32.

[0015] The first irradiation device 12 includes a transmitting lens 12a for irradiating the transmitting laser beam 14 toward the object to be inspected. Furthermore, the first irradiation device 12 is configured to include a scanning mechanism (not shown) capable of scanning the transmitting laser beam 14 in the X direction. The scanning mechanism is configured, for example, to include an angle-adjustable galvanometer mirror and a drive mechanism for driving the galvanometer mirror. By controlling the scanning mechanism, the position of the transmission point 32 in the X direction (hereinafter also referred to as the "transmission position") can be changed.

[0016] The receiving laser source 16 includes a laser interferometer. The receiving laser source 16 generates a receiving laser beam 20 (reference beam) and outputs it to the second irradiation device 18.

[0017] The second irradiation device 18 irradiates the receiving laser beam 20 from the receiving laser source 16 onto a receiving point 36 located on the upper surface of the object to be inspected (the upper surface of the base material 4 of the lower plate). The receiving point 36 is the intersection of the receiving laser beam 20 and the upper surface of the object to be inspected. The second irradiation device 18 also receives the reflected light from the receiving point 36 of the receiving laser beam 20 and outputs it to the receiving laser source 16 (laser interferometer). The second irradiation device 18 includes a receiving lens 18a for irradiating the receiving laser beam 20 and receiving the reflected light.

[0018] The receiving laser source 16 receives reflected light from the second irradiation device 18, detects interference light including the reference light and the reflected light, and outputs it to the control device 22.

[0019] Furthermore, the welding inspection apparatus 1 according to this embodiment includes first to third adjustment devices 70, 80, and 90.

[0020] The first adjustment device 70 is configured to include a drive mechanism that allows the second irradiation device 18 to rotate, which is controlled by the control device 22. The first adjustment device 70 is configured to allow adjustment of the angle at which the second irradiation device 18 irradiates and receives the receiving laser light 20 (hereinafter also referred to as the "receiving angle") by rotating the second irradiation device 18.

[0021] The second adjustment device 80 is configured to include a drive mechanism that allows the receiving lens 18a of the second irradiation device 18 to move in the optical axis direction, which is controlled by the control device 22. The second adjustment device 80 is configured to allow adjustment of the distance from the receiving lens 18a to the receiving point 36 (hereinafter also referred to as the "receiving distance") by moving the receiving lens 18a in the optical axis direction.

[0022] The third adjustment device 90 is controlled by the control device 22 and includes a drive mechanism that allows the transmitting lens 12a to move in the optical axis direction. The third adjustment device 90 is configured to adjust the distance from the transmitting lens 12a to the transmitting point 32 (hereinafter also referred to as the "transmission distance") by moving the transmitting lens 12a in the optical axis direction.

[0023] The measuring device 50 consists of a laser line scanner that measures the shape of the top surface of an object to be inspected by irradiating the top surface of the object with a laser beam 52 separate from the transmitting laser beam 14 and the receiving laser beam 20. The measuring device 50 measures the top surface profile of the object to be inspected in at least the XZ plane. The measuring device 50 outputs a signal indicating the measurement result to the control device 22.

[0024] The control unit 22 consists of a CPU (Central Processing Unit), memory (RAM (Random Access Memory) and ROM (Read Only Memory)), and input / output ports for inputting and outputting various signals (none of which are shown). The CPU loads the program stored in ROM into RAM and executes it. The program stored in ROM describes the various processes to be executed by the control unit 22.

[0025] The control device 22 according to this embodiment performs an internal defect inspection to determine the presence or absence of internal defects in the weld bead 6 using the laser ultrasonic method. Specifically, the control device 22 irradiates a transmitting laser beam 14 onto a transmitting point 32 on the upper surface of the object to be inspected to generate ultrasonic waves at the transmitting point 32, and detects surface vibrations corresponding to the intensity of the ultrasonic waves at a receiving point 36 irradiated by a receiving laser beam 20, using interference light between the reference light and reflected light of the receiving laser beam 20. The control device 22 then determines the presence or absence of internal defects in the weld bead 6 based on the detection difference between when internal defects are present and when they are present. The internal defect inspection will be described in more detail below.

[0026] The control device 22 controls the transmitting laser source 10 to generate excitation light for generating the transmitting laser beam 14 in the first irradiation device 12. The control device 22 also controls the first irradiation device 12 to scan the irradiation position of the transmitting laser beam 14 (the position of the transmission point 32) in the X direction. As a result, the transmitting laser beam 14 is irradiated so as to straddle the weld bead 6. The control device 22 also receives the oscillation timing (pulse irradiation timing) of the transmitting laser beam 14 in the first irradiation device 12 from the first irradiation device 12.

[0027] The control device 22 then acquires from the receiving laser source 16 the interference measurement result of the receiving laser light 20 by the laser interferometer of the receiving laser source 16 as a signal indicating the detected intensity of the ultrasonic waves at the receiving point 36. Based on the detected intensity of the ultrasonic waves at the receiving point 36 acquired from the receiving laser source 16, the control device 22 determines whether or not there are internal defects in the weld bead 6. The method for determining the presence or absence of internal defects in the internal defect inspection will be explained in detail later.

[0028] The display device 24 is a display for showing various processing results of the control device 22. The display device 24 displays a measurement screen called a B-scope, which shows the measurement results of ultrasonic waves within the object being inspected by the welding inspection device 1.

[0029] The B-scope displays the distribution of the detected ultrasonic intensity at the receiving point 36, with the transmission position (the position of the transmission point 32 in the X direction) on the horizontal axis and the time it takes for the ultrasonic waves generated at the transmission position to reach the receiving point 36 (hereinafter also referred to as "ultrasonic arrival time" or simply "arrival time") on the vertical axis. On the B-scope, the distribution of the detected ultrasonic intensity is represented, for example, by a color map (changes in color or density).

[0030] The control device 22 and the display device 24 are configured, for example, by a PC (Personal Computer).

[0031] The control device 22 determines the presence or absence of internal defects in one XZ cross-section of the weld bead 6 by scanning the irradiation position of the transmitting laser beam 14 in the X direction. Then, the control device 22 determines the presence or absence of internal defects along the entire length of the weld bead 6 by performing the inspection by scanning the transmitting laser beam 14 in the X direction once (inspection of one XZ cross-section) multiple times while slightly shifting in the Y direction (the direction in which the weld bead 6 extends). This completes the inspection of the entire weld bead 6.

[0032] <Method for determining the presence or absence of internal defects> The method for determining the presence or absence of internal defects in internal defect inspection will be explained in detail below with reference to Figures 2 to 6.

[0033] Figure 2 shows the state when there are no internal defects in the weld bead 6. In this welding inspection device 1, a transmitting laser beam 14 (pulsed laser beam) is irradiated onto the upper surface of the base materials 2 and 4, including the weld bead 6, and ultrasonic waves are generated at the transmitting point 32. The ultrasonic waves generated at the transmitting point 32 pass through the inside of the weld bead 6, are reflected by the lower surface 5 of the base material 4, and then reach the receiving point 36 on the upper surface of the base material 4. The receiving laser beam 20 is used to measure the minute vibrations generated at the receiving point 36 on the upper surface of the base material 4 by the ultrasonic waves that are reflected by the lower surface 5 and reach the receiving point 36 (hereinafter also called "lower surface reflected waves" or simply "reflected waves"), thereby detecting the lower surface reflected waves at the receiving point 36.

[0034] The transmission points 32, indicated by the "x" mark, are scanned in the X direction using the scanning mechanism of the first irradiation device 12 (Figure 1). After measurement at a given transmission point 32 is completed, the irradiation position of the transmitting laser beam 14 is scanned in the X direction to become the next transmission point 32, and measurement is performed at the next transmission point 32.

[0035] The receiving point 36, indicated by the circle, is fixed in the X direction of the base material 4. The greater the distance in the X direction between the transmitting point 32 and the receiving point 36, the longer the propagation distance of the ultrasonic waves from the transmitting point 32 to the receiving point 36, and the intensity of the ultrasonic waves at the receiving point 36 (micro-vibrations on the surface) also decreases due to diffusion attenuation.

[0036] Figure 3 shows the state when there are internal defects 40 such as blowholes in the weld bead 6. When internal defects 40 such as blowholes are present in the weld bead 6, depending on the position of the transmission point 32, the ultrasonic waves generated at the transmission point 32 are divided into a non-passing component 41 that is scattered because its path is blocked by the internal defects 40 and does not reach the receiving point 36, and a passing component 44 that passes through the internal defects 40. In this case, the passing component 44 is reflected by the lower surface 5 of the base material 4 and reaches the receiving point 36, but the detection intensity of the lower surface ultrasonic waves at the receiving point 36 is smaller (attenuation is greater) than when there are no internal defects 40. Therefore, by capturing the degree of attenuation of the detection intensity of the lower surface ultrasonic waves at the receiving point 36, it is possible to determine whether or not there are internal defects 40 in the weld bead 6.

[0037] Figure 4 schematically shows an example of a B-scope displayed on the display device 24. Note that Figure 4 shows an example of a B-scope when there are no internal defects in the weld bead 6.

[0038] As described above, the B-scope displays the distribution of ultrasonic detection intensity at the receiving point 36, with the transmission position on the horizontal axis and the ultrasonic arrival time on the vertical axis. Therefore, the B-scope displays the transmission position, ultrasonic arrival time, and ultrasonic detection intensity on a single screen. In Figure 4, for ease of understanding, only the distribution of the maximum values ​​of the ultrasonic detection intensity at the receiving point 36 is shown as lines L1 and L2. Line L1 shows the distribution of surface waves that travel from the transmission point 32 through the surface layers of the weld bead 6 and base material 4 to the receiving point 36. Line L2 shows the distribution of bottom reflected waves.

[0039] The ultrasound detected at the receiving point 36 includes not only the bottom reflected wave (line L2) but also the surface wave (line L1). Since the propagation paths of the bottom reflected wave and the surface wave are different, the arrival times of the bottom reflected wave and the surface wave are also different. By utilizing this phenomenon, the bottom reflected wave (line L2) is extracted from the ultrasound (lines L1 and L2) that reaches the receiving point 36, excluding the surface wave (line L1). Specifically, the welding inspection device 1 sets the area indicated by the dotted line in Figure 4 as the "reflected wave extraction range," and extracts the ultrasound that reaches the set reflected wave extraction range as the bottom reflected wave.

[0040] Then, using the bottom surface reflected waves extracted as described above, the presence or absence of internal defects 40 in the weld bead 6 is determined.

[0041] Figure 5 shows the relationship between the transmission position and the detected intensity of the reflected wave from the bottom surface. In Figure 5, line L3 represents the detected intensity of the reflected wave from the bottom surface when there are no internal defects in the weld bead 6. The detected intensity of the reflected wave from the bottom surface decreases due to diffusion attenuation as the value of the transmission position increases (the further the transmission point is from the reception point).

[0042] Line L4 represents the detection intensity of the bottom reflected wave when there is an internal defect in the weld bead 6. When the ultrasonic transmission position is greater than X1, the bottom ultrasonic waves reaching the ultrasonic receiving point pass through the internal defect in the weld bead 6. In this case, in addition to diffusion attenuation, scattering attenuation occurs at the internal defect, so the detection intensity of the bottom ultrasonic waves when there is an internal defect (line L4) is lower than when there is no internal defect (line L3). In other words, the attenuation of the detection intensity of the bottom reflected wave when there is an internal defect is greater than when there is no internal defect.

[0043] Figure 6 illustrates an example of a method for determining the presence or absence of internal defects in a weld bead 6. The control device 22 determines the presence or absence of internal defects in the weld bead 6 based on the magnitude of the attenuation of the detected intensity of the reflected wave from the bottom surface. Specifically, the control device 22 determines that there are no internal defects in the weld bead 6 if the magnitude of the attenuation of the detected intensity of the reflected wave from the bottom surface is below a predetermined threshold, and determines that there are internal defects in the weld bead 6 if the magnitude of the attenuation of the detected intensity of the reflected wave from the bottom surface exceeds the threshold. The threshold is set appropriately to a value that can distinguish the presence or absence of internal defects based on prior evaluation tests, etc. The threshold is set for each transmission position, taking into account the degree of diffusion attenuation according to the transmission position.

[0044] <Correction for reception angle, reception distance, and transmission distance> In the internal defect inspection described above, vibration measurement at the receiving point 36 on the upper surface of the object under inspection is performed non-contact using the reflected light from the receiving point 36 of the receiving laser beam 20. Therefore, in order to sufficiently collect the reflected light from the object under inspection and improve the measurement sensitivity, it is desirable to appropriately adjust the receiving angle and receiving distance based on the position and shape of the object under inspection so that the detection intensity of the reflected light is maximized. Specifically, it is desirable to adjust the receiving angle so that the second irradiation device 18 faces directly toward the irradiation surface of the receiving laser beam 20, and to adjust the receiving distance so that the position of the receiving point 36 coincides with the focal position of the light receiving lens, based on the position and shape of the object under inspection.

[0045] However, due to dimensional errors, installation errors, and deformation caused by thermal distortion during welding, the actual shape of the object being inspected may deviate from the initially assumed shape. This deviation between the actual shape and the assumed shape of the object being inspected can affect the receiving angle and receiving distance, potentially leading to a decrease in the accuracy of detecting internal defects.

[0046] Figure 7 shows an example of a situation where the actual deformation of the object being inspected deviates from the reference shape (originally assumed deformation) due to deformation caused by thermal strain during welding. Figure 7 shows an example where the receiving point 36 has shifted from its original position due to the actual deformation of the object being inspected deviating from the reference shape. In this case, the receiving angle and receiving distance deviate from the angle and distance assumed based on the reference shape. If the receiving angle is shifted, the second irradiation device 18 will no longer be directly facing the irradiation surface of the receiving laser beam 20, and the receiving sensitivity will decrease. Also, if the receiving distance is shifted, the receiving point 36 will no longer coincide with the focal position of the receiving lens 18a, and the receiving sensitivity will decrease.

[0047] Although not shown in Figure 7, if the transmission point 32 deviates from its position based on the reference shape due to deformation caused by thermal strain during welding, the transmission point 32 will no longer coincide with the focal position of the transmission lens 12a, reducing the intensity of the ultrasonic waves generated at the transmission point 32, which in turn reduces the accuracy of defect detection.

[0048] In view of these points, the control device 22 according to this embodiment suppresses a decrease in reception sensitivity during internal defect inspection by correcting the reception angle, reception distance, and transmission distance using the method described below before performing internal defect inspection.

[0049] Figure 8 is a flowchart showing an example of the processing procedure when the control device 22 performs an internal defect inspection.

[0050] First, the control device 22 obtains the position and shape of the object to be inspected, which are the measurement results from the measuring device 50, from the measuring device 50 (step S10).

[0051] Next, the control device 22 determines whether the measurement result from the measuring device 50 deviates from a predetermined standard (initial assumption) (step S20).

[0052] Figure 9 schematically shows an example of the difference between the measured shape of the object to be inspected obtained in step S10 and the initially assumed shape (reference) of the object to be inspected. In the example shown in Figure 9, there is a difference between the measured shape and the assumed shape. In such a case, the control device 22 determines, for example, whether the difference between the measured shape and the assumed shape exceeds a predetermined tolerance range, and if the difference exceeds the tolerance range, it determines that the measurement result of the measuring device 50 deviates from the predetermined reference.

[0053] While the measuring device 50 can detect deformation in the XZ plane of the object being inspected, deformation in the YZ plane may also occur in the object being inspected. Therefore, it may be possible to enable the detection of deformation in the YZ plane as well as deformation in the XZ plane of the object being inspected.

[0054] Figure 10 shows the welding inspection apparatus 1 with an additional measuring device 54 for detecting deformation in the YZ plane of the object being inspected, in addition to the measuring device 50. The measuring device 54 measures the top surface profile of the object being inspected in the YZ plane by irradiating the top surface of the object being inspected with a planar laser beam 56 that follows the YZ plane, and outputs a signal indicating the measurement result to the control device 22. In this way, the control device 22 can use the measurement results of the two measuring devices 50 and 54 to detect deformation in the YZ plane as well as deformation in the XZ plane of the object being inspected.

[0055] Returning to Figure 8, if the measurement result of the measuring device 50 deviates from a predetermined standard (YES in step S20), the control device 22 corrects the receiving angle (step S30), the receiving distance (step S40), and the transmission distance (step S50).

[0056] Figure 11 is a flowchart showing an example of the processing procedure when the control device 22 performs correction of the receiving angle (step S30).

[0057] First, the control device 22 performs a first search process to find the optimal receiving angle (step S31). The optimal receiving angle is the receiving angle when the second irradiation device 18 is directly facing the irradiation surface of the receiving laser beam 20 (the upper surface of the object to be inspected), that is, the receiving angle when the irradiation angle of the receiving laser beam 20 is in the direction of the normal to the irradiation surface of the receiving laser beam 20.

[0058] Figure 12 is a diagram illustrating the method for finding the optimal receiving angle using the first search process. In the first search process, the control device 22 controls the second irradiation device 18 and the first adjustment device 70 to irradiate the receiving laser light 20 while changing the receiving angle, monitors the amount of reflected light received by the second irradiation device 18, and searches for the optimal receiving angle when the amount of reflected light received is maximum.

[0059] The control device 22 sets the search range (search angle range) for changing the reception angle in the first search process based on the measurement results of the measuring device 50. For example, the control device 22 may determine the center of the search angle range based on the measuring device 50, and also narrow the width of the search angle range as the difference between the measurement results of the measuring device 50 and the reference becomes smaller. In this way, by determining a rough range of the optimal reception angle (search angle range) based on the measuring device 50 and fine-tuning the optimal reception angle using feedback of reflected light quantity, the time required for the first search process can be reduced while ensuring the search accuracy of the first search process.

[0060] Returning to Figure 11, the control device 22 controls the first adjustment device 70 to correct the receiving angle to the optimal receiving angle found in the first search process (step S32). As a result, the second irradiation device 18 faces directly toward the irradiation surface of the receiving laser beam 20, suppressing a decrease in the amount of reflected light received, and thus suppressing a decrease in receiving sensitivity.

[0061] Figure 13 is a flowchart showing an example of the processing procedure when the control device 22 performs correction of the reception distance (step S40).

[0062] First, the control device 22 performs a second search process to find the optimal reception distance (step S41). The optimal reception distance is the reception distance at which the position of the receiving point 36 coincides with the focal position of the receiving lens 18a.

[0063] Figure 14 is a diagram illustrating the method for finding the optimal reception distance using the second search process. In the second search process, the control device 22 controls the second irradiation device 18 and the second adjustment device 80 to irradiate the receiving laser light 20 while changing the reception distance, monitors the amount of reflected light received by the second irradiation device 18, and searches for the reception distance at which the amount of reflected light received is maximum as the optimal reception distance.

[0064] The control device 22 sets the search range (search reception distance range) for changing the reception distance in the second search process based on the measurement results of the measuring device 50. For example, the control device 22 may determine the center of the search reception distance range based on the measuring device 50, and may also narrow the width of the search reception distance range as the difference between the measurement results of the measuring device 50 and the reference becomes smaller. In this way, by determining the approximate range of the optimal reception distance (search reception distance range) based on the measuring device 50 and fine-tuning the optimal reception distance using feedback of reflected light quantity, it is possible to reduce the time required for the second search process while ensuring the search accuracy of the second search process.

[0065] Returning to Figure 13, the control device 22 controls the second adjustment device 80 to correct the reception distance to the optimal reception distance found in the second search process (step S42). As a result, the position of the reception point 36 coincides with the focal position of the receiving lens 18a, suppressing a decrease in the amount of reflected light received, and thus suppressing a decrease in reception sensitivity.

[0066] Furthermore, the control device 22 performs a first search process to correct the reception angle, and then performs a second search process to correct the reception distance. This allows for efficient correction of both the reception angle and the reception distance. In other words, if the reception angle is corrected after the reception distance has been corrected, the optimal reception distance will shift due to the correction of the reception angle, requiring the reception distance to be corrected again. However, in this embodiment, since the reception distance is corrected after the reception angle, the need to correct the reception distance again can be avoided.

[0067] Figure 15 is a schematic diagram showing an example of the internal structure of the second irradiation device 18. The second irradiation device 18 includes a receiving lens 18a and a cylindrical lens tube 18b that surrounds the receiving lens 18a. The receiving lens 18a focuses the laser 18d from the fiber 18c and irradiates the object to be inspected with receiving laser light 20. The second adjustment device 80 described above adjusts the receiving distance by moving the receiving lens 18a in the optical axis direction within the lens tube 18b. Alternatively, the second adjustment device 80 may adjust the receiving distance by moving the receiving lens 18a and the lens tube 18b together in the optical axis direction.

[0068] Figure 16 is a flowchart showing an example of the processing procedure when the control device 22 performs a correction of the transmission distance (step S50).

[0069] First, the control device 22 performs a third search process to find the optimal transmission distance (step S51). The optimal transmission distance is the transmission distance at which the position of the transmission point 32 coincides with the focal position of the transmission lens 12a.

[0070] In this embodiment, the control device 22 searches for the optimal transmission distance in the third search process based on the amount of ablation light generated by irradiation with the transmitting laser beam 14. Because the intensity of the transmitting laser beam 14 is quite high, when the transmitting laser beam 14 is irradiated onto the transmission point 32, not only is ultrasound excited at the transmission point 32, but ablation occurs and ablation light is generated. Ablation is a phenomenon in which a solid surface becomes instantaneously hot and evaporates (vaporizes). Immediately after ablation occurs, matter such as atoms, molecules, ions, and electrons is explosively released from the solid surface, creating a kind of plasma state, which is accompanied by light emission. Ablation light is light generated by ablation (a type of plasma light). The amount of ablation light increases as the intensity of the transmitting laser beam 14 irradiated onto the transmission point 32 increases.

[0071] Focusing on the characteristics of the ablation light intensity, the control device 22 according to this embodiment monitors the ablation light intensity by controlling the first irradiation device 12 and the third adjustment device 90 to irradiate the transmitting laser light 14 while changing the transmission distance during the third search process, and searches for the transmission distance at which the ablation light intensity is maximum as the optimal transmission distance corresponding to the focal length of the transmitting lens 12a.

[0072] Figure 17 shows an example of a configuration for detecting the light intensity of ablation light. In the example shown in Figure 17, the ablation light 60 generated by the irradiation of the transmitting laser light 14 is captured by the camera 61. The control device 22 can detect (monitor) the light intensity of the ablation light 60 by analyzing the image captured by the camera 61.

[0073] Figure 18 is a diagram illustrating the method for finding the optimal transmission distance using the third search process. As described above, in the third search process, the control device 22 controls the first irradiation device 12 and the third adjustment device 90 to irradiate the transmission laser light 14 while changing the transmission distance, monitors the amount of ablation light, and searches for the transmission distance at which the amount of ablation light is maximum as the optimal transmission distance.

[0074] The control device 22 sets the search range (search transmission distance range) for changing the transmission distance in the third search process based on the measurement results of the measuring device 50. For example, the control device 22 may determine the center of the search transmission distance range based on the measuring device 50, and may also narrow the width of the search transmission distance range as the difference between the measurement results of the measuring device 50 and the reference becomes smaller. In this way, by determining the approximate range of the optimal transmission distance (search transmission distance range) based on the measuring device 50 and fine-tuning the optimal transmission distance using feedback of the ablation light intensity, it is possible to reduce the time required for the third search process while ensuring the search accuracy of the third search process.

[0075] Furthermore, a loud noise is also generated when ablation light is produced. The volume of the noise generated when ablation light is produced increases with the intensity of the transmitting laser light 14 irradiated onto the transmitting point 32. Focusing on this point, the control device 22 may monitor at least one of the light intensity and volume of the ablation light in the third search process and search for the optimal transmission distance when at least one of the light intensity and volume of the ablation light is at its maximum. The volume of the ablation light can be detected, for example, by placing a microphone near the transmitting point 32.

[0076] Returning to Figure 16, the control device 22 controls the third adjustment device 90 to correct the transmission distance to the optimal transmission distance found in the third search process (step S52). This causes the position of the transmission point 32 to coincide with the focal position of the transmission lens 12a, suppressing a decrease in the intensity of the transmission laser light 14 irradiated onto the transmission point 32. As a result, a decrease in reception sensitivity can be suppressed.

[0077] Returning to Figure 8, if the measurement result of the measuring device 50 does not deviate from a predetermined standard (NO in step S20), the control device 22 performs the internal defect inspection without executing the correction processes in steps S30, S40, and S50 (step S70). This prevents the first search process in step S30, the second search process in step S40, and the third search process in step S50 from being performed unnecessarily, even if the object to be inspected does not deviate from the initially assumed shape. As a result, it is possible to prevent the time required for the internal defect inspection from becoming unnecessarily long.

[0078] [Example 1] In the above-described embodiment, if the measurement result of the measuring device 50 deviates from a predetermined standard, the first to third search processes are performed to correct the reception angle, reception distance, and transmission distance.

[0079] However, regardless of whether the measurement results of the measuring device 50 deviate from a predetermined standard, the first to third search processes may be performed to correct the reception angle, reception distance, and transmission distance. In this case, the first to third search processes will be performed even if the shape of the object to be inspected does not deviate from the standard shape, but the reception angle, reception distance, and transmission distance can be corrected even in a welding inspection device that does not have the measuring device 50 installed.

[0080] [Differentiation 2] In the above-described embodiment, the optimal receiving angle, optimal receiving distance, and optimal transmission distance are set by the first to third search processes.

[0081] However, the optimal receiving angle, optimal receiving distance, and optimal transmission distance may be calculated geometrically and simply based on the measurement results of the measuring device 50 without performing the first to third search processes. In this case, although the accuracy of the optimal receiving angle, optimal receiving distance, and optimal transmission distance may be slightly reduced, the time required for the first to third search processes is eliminated, thus shortening the time required to set the optimal receiving angle, optimal receiving distance, and optimal transmission distance.

[0082] [Difference 3] In the above-described embodiment, the receiving angle, receiving distance, and transmission distance are corrected (adjusted) by the first to third adjustment devices 70, 80, and 90, respectively.

[0083] However, corrections to the receiving angle, receiving distance, and transmitting distance are not necessarily limited to being performed by the first to third adjustment devices 70, 80, and 90. For example, corrections to at least one of the receiving angle, receiving distance, and transmitting distance may be performed by moving the positioner on which the object being inspected is placed.

[0084] Figure 19 shows an example of correcting the receiving angle using the positioner 100. The positioner 100 is a machine used to adjust the object to be inspected to a position suitable for welding. In this way, the receiving angle may be corrected by moving the positioner 100.

[0085] [Aspect] Those skilled in the art will understand that the embodiments and their modifications described above are specific examples of the following embodiments.

[0086] (Section 1) The welding inspection apparatus according to the present disclosure is a welding inspection apparatus for inspecting a welded part included in an object to be inspected, comprising: a first irradiation device that irradiates a transmitting laser beam onto a transmitting point on the upper surface of the object to be inspected; a second irradiation device that irradiates a receiving laser beam onto a receiving point on the upper surface of the object to be inspected; a laser interferometer that interferometrically measures the reflected light of the receiving laser beam that is irradiated from the second irradiation device, reflected at the receiving point, and received by the second irradiation device; a control device that detects ultrasonic waves generated at the transmitting point by the irradiation of the transmitting laser beam and reaching the receiving point based on the measurement results of the laser interferometer, extracts reflected waves reflected from the lower surface of the object to be inspected from among the detected ultrasonic waves, and performs an internal inspection to determine whether or not there are internal defects inside the welded part based on the extracted reflected waves; and a first adjustment device that can adjust the receiving angle, which is the angle at which the second irradiation device receives the reflected light. Before performing internal inspection, the control device controls the second irradiation device and the first adjustment device to irradiate the receiving laser light while changing the receiving angle, monitors the amount of reflected light received, and performs a first search process to find the receiving angle at which the amount of reflected light received is maximum as the optimal receiving angle, and controls the first adjustment device so that the receiving angle becomes the optimal receiving angle.

[0087] According to the welding inspection apparatus of paragraph 1, before performing internal inspection, the optimal receiving angle that maximizes the amount of reflected light received is searched by the first search process, and the receiving angle is corrected to the optimal receiving angle. As a result, even if the actual shape of the object to be inspected deviates from the initially assumed shape, the second irradiation device can be directly aligned with the irradiation surface of the receiving laser beam during internal inspection, thereby suppressing a decrease in the amount of reflected light received. Consequently, a decrease in the detection accuracy of internal inspection can be suppressed.

[0088] (Section 2) In the welding inspection apparatus described in Section 1, the second irradiation device includes a receiving lens for receiving reflected light. The welding inspection apparatus further comprises a second adjustment device capable of adjusting the receiving distance, which is the distance from the receiving lens to the receiving point. Before performing an internal inspection, the control device monitors the amount of reflected light received by controlling the second irradiation device and the second adjustment device to irradiate the receiving laser light while changing the receiving distance, and performs a second search process to search for the optimal receiving distance at which the amount of reflected light received is maximum, and controls the second adjustment device so that the receiving distance becomes the optimal receiving distance.

[0089] According to the welding inspection apparatus in paragraph 2, before performing internal inspection, the optimal receiving distance at which the amount of reflected light received is maximized is searched by a second search process, and the receiving distance is corrected to the optimal receiving distance. As a result, even if the actual shape of the object to be inspected deviates from the initially assumed shape, the receiving point and the focal position of the receiving lens can be aligned during internal inspection, thereby suppressing a decrease in the amount of reflected light received. Consequently, the decrease in detection accuracy of internal inspection can be further suppressed.

[0090] (Article 3) In the welding inspection apparatus described in Article 2, the welding inspection apparatus further comprises a measuring device for measuring the position and shape of the upper surface of the object to be inspected. The control device executes a first search process and a second search process when the measurement result of the measuring device deviates from a predetermined standard.

[0091] According to the welding inspection device described in paragraph 3, the first and second search processes are executed when the actual shape of the object being inspected, as measured by the measuring device, deviates from a predetermined standard (the initially assumed shape). Therefore, the first and second search processes are prevented from being performed unnecessarily even when the actual shape of the object being inspected does not deviate from the initially assumed shape. As a result, the time required for internal inspection can be prevented from becoming unnecessarily prolonged.

[0092] (Article 4) In the welding inspection apparatus described in Article 3, the control device sets the search range for changing the receiving angle in the first search process and the search range for changing the receiving distance in the second search process based on the measurement results of the measuring device.

[0093] According to the welding inspection apparatus of paragraph 4, the search range for changing the receiving angle in the first search process and the search range for changing the receiving distance in the second search process can be appropriately set based on the measurement results of the measuring device. For example, the smaller the difference between the measurement results of the measuring device and a predetermined standard, the narrower the width of the search range in the first and second search processes can be. This makes it possible to reduce the time required for the first and second search processes while ensuring the search accuracy of the first and second search processes.

[0094] (Clause 5) In the welding inspection apparatus described in Clause 2, the control device performs a first search process to set the receiving angle to the optimal receiving angle, and then performs a second search process to set the receiving distance to the optimal receiving distance.

[0095] According to the welding inspection device in paragraph 5, a first search process is performed to correct the receiving angle, and then a second search process is performed to correct the receiving distance. Therefore, the correction of the receiving angle and receiving distance can be performed efficiently. In other words, if the receiving angle is corrected after the receiving distance has been corrected, the optimal receiving distance will shift due to the correction of the receiving angle, so it will be necessary to correct the receiving distance again. However, according to the welding inspection device in paragraph 5, the receiving distance is corrected after the receiving angle has been corrected, so it is possible to avoid correcting the receiving distance again.

[0096] (Section 6) In the welding inspection apparatus described in Section 1, the first irradiation device includes a transmitting lens for irradiating a transmitting laser beam. The welding inspection apparatus further comprises a third adjustment device capable of adjusting the transmission distance, which is the distance from the transmitting lens to the transmission point. Before performing an internal inspection, the control device controls the third adjustment device so that the transmission distance becomes an optimal transmission distance corresponding to the focal length of the transmitting lens.

[0097] According to the welding inspection apparatus in Section 6, before performing internal inspection, the transmission distance is corrected to the optimal transmission distance corresponding to the focal length of the transmitting lens. This makes it possible to align the transmission point and the focal position of the transmitting lens during internal inspection, even if the actual shape of the object being inspected deviates from the initially assumed shape, thereby suppressing a decrease in the intensity of the transmitting laser light irradiated onto the transmission point. As a result, a decrease in reception sensitivity can be suppressed.

[0098] (Section 7) In the welding inspection apparatus described in Section 6, ablation light is generated at the transmission point by irradiation with a transmitting laser beam. The control device controls the first irradiation device and the third adjustment device to irradiate the transmitting laser beam while changing the transmission distance, monitors at least one of the light intensity and volume of the ablation light, and performs a third search process to find the optimal transmission distance at which at least one of the light intensity and volume of the ablation light is maximized, and controls the third adjustment device so that the transmission distance becomes the optimal transmission distance.

[0099] According to the welding inspection apparatus of paragraph 7, in the third search process, the optimal transmission distance can be searched by utilizing at least one of the light intensity and volume of the ablation light generated at the transmission point.

[0100] (Clause 8) In the welding inspection apparatus described in paragraph 7, the welding inspection apparatus further comprises a measuring device for measuring the position and shape of the upper surface of the object to be inspected. The control device executes a third search process if the measurement result of the measuring device deviates from a predetermined standard.

[0101] According to the welding inspection device described in paragraph 8, the third search process is executed when the actual shape of the object being inspected, as measured by the measuring device, deviates from a predetermined standard (the initially assumed shape). Therefore, the unnecessary execution of the third search process is suppressed even when the actual shape of the object being inspected does not deviate from the initially assumed shape. As a result, the time required for internal inspection can be prevented from becoming unnecessarily prolonged.

[0102] (Clause 9) In the welding inspection apparatus described in Clause 8, the control device sets the search range for which the transmission distance is changed in the third search process based on the measurement results of the measuring device.

[0103] According to the welding inspection apparatus of paragraph 9, the search range for changing the transmission distance in the third search process can be appropriately set based on the measurement results of the measuring device. For example, the smaller the difference between the measurement results of the measuring device and a predetermined standard, the narrower the width of the search range in the third search process can be. This makes it possible to reduce the time required for the third search process while ensuring the search accuracy of the third search process.

[0104] (Section 10) In the welding inspection apparatus described in Section 6, the welding inspection apparatus further comprises a measuring device for measuring the position and shape of the upper surface of the object to be inspected. The control device controls the third adjustment device so that the transmission distance becomes the optimal transmission distance based on the measurement results of the measuring device.

[0105] According to the welding inspection device described in paragraph 10, the transmission distance can be corrected to the optimal transmission distance based on the measurement results of the measuring device.

[0106] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The technical scope provided herein is defined by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope equivalent to the claims are intended to be included. [Explanation of Symbols]

[0107] 1 Welding inspection device, 2,4 Base material, 5 Bottom surface, 6 Weld bead, 10 Transmitting laser source, 12 First irradiation device, 12a Transmitting lens, 14 Transmitting laser beam, 16 Receiving laser source, 18 Second irradiation device, 18a Receiving lens, 18b Lens tube, 18c Fiber, 18d Laser, 20 Receiving laser beam, 22 Control device, 24 Display device, 32 Transmitting point, 36 Receiving point, 40 Internal defect, 41 Non-transmitting component, 44 Transmitting component, 50, 54 Measuring device, 52, 56 Laser beam, 60 Ablation light, 61 Camera, 70 First adjustment device, 80 Second adjustment device, 90 Third adjustment device, 100 Positioner.

Claims

1. A welding inspection device for inspecting welds included in the object to be inspected, A first irradiation device that irradiates a transmission laser beam onto a transmission point located on the upper surface of the object to be inspected, A second irradiation device that irradiates a receiving laser beam onto a receiving point on the upper surface of the object to be inspected, A laser interferometer that performs interferometric measurement of the reflected light of the receiving laser beam that is irradiated from the second irradiation device, reflected at the receiving point, and received by the second irradiation device, A control device for performing an internal inspection, which detects ultrasonic waves generated at the transmitting point and reaching the receiving point by irradiation with the transmitting laser light, based on the measurement results of the laser interferometer, extracts reflected waves reflected from the lower surface of the object to be inspected from among the detected ultrasonic waves, and determines whether or not there are internal defects inside the welded part based on the extracted reflected waves, The second irradiation device comprises a first adjustment device that can adjust the receiving angle, which is the angle at which the reflected light is received, Before performing the internal inspection, the control device The second irradiation device and the first adjustment device are controlled to irradiate the receiving laser light while changing the receiving angle, and the amount of reflected light received is monitored. A first search process is performed to search for the optimal receiving angle, which is the receiving angle at which the amount of reflected light received is maximized. A welding inspection apparatus that controls the first adjustment device so that the receiving angle becomes the optimal receiving angle.

2. The second irradiation device includes a receiving lens for receiving the reflected light, The welding inspection apparatus further comprises a second adjustment device capable of adjusting the receiving distance, which is the distance from the receiving lens to the receiving point. Before performing the internal inspection, the control device The second irradiation device and the second adjustment device are controlled to irradiate the receiving laser light while changing the receiving distance, the amount of reflected light received is monitored, and a second search process is executed to search for the optimal receiving distance at which the amount of reflected light received is maximized. The welding inspection apparatus according to claim 1, wherein the second adjustment device is controlled so that the reception distance becomes the optimal reception distance.

3. The welding inspection apparatus further comprises a measuring device for measuring the position and shape of the upper surface of the object to be inspected. The welding inspection apparatus according to claim 2, wherein the control device executes the first search process and the second search process when the measurement result of the measuring device deviates from a predetermined standard.

4. The welding inspection apparatus according to claim 3, wherein the control device sets a search range for changing the receiving angle in the first search process and a search range for changing the receiving distance in the second search process based on the measurement results of the measuring device.

5. The welding inspection apparatus according to claim 2, wherein the control device performs the first search process to set the receiving angle to the optimal receiving angle, and then performs the second search process to set the receiving distance to the optimal receiving distance.

6. The first irradiation device includes a transmitting lens for irradiating the transmitting laser light, The welding inspection apparatus further comprises a third adjustment device capable of adjusting the transmission distance, which is the distance from the transmitting lens to the transmitting point. The welding inspection apparatus according to claim 1, wherein the control device controls the third adjustment device so that the transmission distance becomes the optimal transmission distance corresponding to the focal length of the transmitting lens before performing the internal inspection.

7. At the transmission point, ablation light is generated by irradiation with the transmission laser light. The control device is The first irradiation device and the third adjustment device are controlled to irradiate the transmitting laser light while changing the transmission distance, and at least one of the light intensity and volume of the ablation light is monitored. A third search process is performed to find the transmission distance at which at least one of the light intensity and volume of the ablation light is maximized, which is defined as the optimal transmission distance. The welding inspection apparatus according to claim 6, wherein the third adjustment device is controlled so that the transmission distance becomes the optimal transmission distance.

8. The welding inspection apparatus further comprises a measuring device for measuring the position and shape of the upper surface of the object to be inspected. The welding inspection apparatus according to claim 7, wherein the control device executes the third search process when the measurement result of the measuring device deviates from a predetermined standard.

9. The welding inspection apparatus according to claim 8, wherein the control device sets the search range for changing the transmission distance in the third search process based on the measurement results of the measuring device.

10. The welding inspection apparatus further comprises a measuring device for measuring the position and shape of the upper surface of the object to be inspected. The welding inspection apparatus according to claim 6, wherein the control device controls the third adjustment device so that the transmission distance becomes the optimal transmission distance based on the measurement result of the measuring device.

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