JP7464430B2 - Method and device for determining the quality of welded joints - Google Patents

Description

The present invention relates to a method and device for determining the quality of a weld, and to a method and device for determining the quality of a weld that uses measurements obtained by irradiating a laser onto the weld and a workpiece in the vicinity of the weld to determine the quality of the weld.

The device shown in FIG. 8 is known as a conventional weld bead quality control device 100 (hereinafter referred to as "quality control device 100"). FIG. 8 is a schematic diagram illustrating the conventional quality control device 100.

As shown in FIG. 8, the quality control device 100 has a quality inspection device 102 that performs visual quality inspection of the weld bead 101. The quality inspection device 102 mainly includes a light projection means 103, an image capture means 104, a display means 105, an image preprocessing means 106, a determination means 107 that includes a shape feature value calculation means, and a control means 108. The light projection means 103 includes a semiconductor laser 109, a collimator lens 110, and a cylindrical lens 111.

As shown in the figure, the weld bead 101 is formed at the butt joint of thin steel plates 112, 113, and the laser light irradiated from the semiconductor laser 109 passes through a collimator lens 110 and a cylindrical lens 111, and irradiates the weld bead 101 as a slit-shaped laser light L1. The shape of the laser light L1 irradiated to the weld bead 101 is curved in the part corresponding to the weld bead 101, and the external shape of the weld bead 101 can be grasped.

In addition, in the quality control device 100, the image pre-processing means 106 generates a shape specific value from the two-dimensional image of the weld bead 101 captured by the imaging means 104. Then, the judgment means 107 judges the quality of the weld bead 101 by comparing the shape specific value with a predetermined quality judgment standard value (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 05-71932

As described above, in the conventional quality control device 100 quality determination method, the image pre-processing means 106 generates a shape specific value from the two-dimensional image of the weld bead 101 captured by the imaging means 104, and the determination means 107 compares the shape specific value with a predetermined quality determination standard value, thereby automating the quality determination of the weld bead 101.

However, the above pass/fail judgment method focuses only on the shape of the weld bead 101 and does not use the surfaces of the thin steel plates 112, 113 to be welded as the reference surface. In other words, because the butt joints of the thin steel plates 112, 113 each have a tolerance, the welded surfaces of the thin steel plates 112, 113 are not necessarily the same surface. Therefore, even if the shape of the weld bead 101 is pass/fail based on the pass/fail judgment criteria, there may be cases where the thin steel plates 112, 113 at the butt joints of the welded parts are misaligned in the height direction, causing undercuts or the like, and the weld must be judged as failing.

In other words, the method for determining whether the weld bead 101 is good or bad also takes into account the misalignment within the tolerance range in the height direction of the butt joint between the thin steel plates 112, 113. The above method for determining whether the weld bead is good or bad does not take into account the misalignment within the tolerance range, and there are problems with the accuracy of the determination.

In addition, for reasons such as worker safety, a chamfer is usually formed at the top corner of the groove where the thin steel plates 112, 113 butt together. However, the above-mentioned quality determination method does not disclose or suggest anything about how to determine whether or not a chamfer is provided. In particular, the standard values for undercuts as welds are strict, and there are issues with the accuracy of quality determination.

The present invention was made in consideration of the above circumstances, and aims to provide a method and device for determining the quality of a welded portion, which uses measurements obtained by irradiating a laser onto the welded portion and the workpiece in the vicinity of the welded portion to determine whether the welded portion is good or bad.

In the method for determining the quality of a weld according to the present invention, a laser is irradiated to a workpiece and the weld, which are welded and fixed to a groove between a first weld material and a second weld material, to measure the workpiece and the weld and determine the quality of the weld. Using measurements obtained by the irradiation of the laser, a surface of the first weld material near the groove is set as a first measurement reference plane, and a surface of the second weld material near the groove is set as a second measurement reference plane, and a measurement value of the weld is calculated based on the first measurement reference plane and the second measurement reference plane. The present invention is characterized in that a judgment height distance for judging the welding shape of the undercut portion is set, a first recess near the first measurement reference surface and a second recess near the second measurement reference surface are detected from the measurement values, a first height direction distance from the first measurement reference surface to the lowest point of the first recess and a second height direction distance from the second measurement reference surface to the lowest point of the second recess are calculated from the measurement values, and if the first height direction distance and the second height direction distance are less than the judgment height distance, the welding shape of the welded portion is judged to be good .

Moreover, the device for determining the quality of a welded portion of the present invention includes a mounting table, a workpiece support section disposed on the mounting table and supporting a workpiece having a welded portion formed along its outer circumferential surface, a laser measurement section disposed on the mounting table and irradiating a laser with the workpiece and the welded portion to measure the welded portion and the workpiece in the vicinity thereof, and a welding condition determination section that determines the quality of the welded portion from measurement values obtained by the laser measurement section, wherein either the workpiece support section or the laser measurement section is movable so that the laser measurement section obtains the measurement values, and the welding condition determination section sets a first measurement reference surface and a second measurement reference surface for the workpiece from the measurement values. a judgment height distance is set for judging a weld shape of an undercut portion of the weld with respect to the first measurement reference surface and the second measurement reference surface; a first recess near the first measurement reference surface and a second recess near the second measurement reference surface are detected from the measurement values; a first height distance from the first measurement reference surface to a lowest point of the first recess and a second height distance from the second measurement reference surface to a lowest point of the second recess are calculated from the measurement values; and if the first height distance and the second height distance are equal to or less than the judgment height distance, the weld shape of the weld is judged to be good .

In the method for determining the quality of a weld of the present invention, first and second measurement reference surfaces are set for the workpieces at both ends of the weld, and the quality of the weld is determined using the first and second measurement reference surfaces, which makes it possible to take into account tolerances when assembling the workpieces and improves the accuracy of determining the quality of the weld.

In addition, in the method for determining the quality of a weld of the present invention, when determining the quality of an undercut portion of a weld, the accuracy of determining the quality of the undercut portion can be improved by using first and second measurement reference surfaces set on the workpiece.

In addition, in the device for determining the quality of a weld according to the present invention, the work support unit that supports the work or the laser measurement unit is movable, so that the weld on the outer peripheral surface of the work can be measured over the entire length. Furthermore, by setting the first and second measurement reference planes for the work in the vicinity of the weld, the tolerance when assembling the work can be taken into consideration, and the accuracy of determining the quality of the weld can be improved.

1A is a schematic diagram and FIG. 1B is a block diagram illustrating a device for determining the quality of a welded portion according to an embodiment of the present invention. 1A and 1B are a side view and a cross-sectional view illustrating a workpiece to be judged as being defective by a weld defect judgment device according to an embodiment of the present invention. 4 is a flowchart illustrating a method for determining the quality of a welded portion according to an embodiment of the present invention. 1A, 1B, and 1C are cross-sectional views illustrating a method for determining the quality of a welded portion according to an embodiment of the present invention. 4 is a flowchart illustrating a method for determining the quality of a welded portion according to an embodiment of the present invention. 4 is a flowchart illustrating a method for determining the quality of a welded portion according to an embodiment of the present invention. 1 is a cross-sectional view illustrating a method for determining the quality of a welded portion according to an embodiment of the present invention. FIG. 1 is a schematic diagram illustrating a conventional quality control device.

First, a device for determining the quality of a weld according to one embodiment of the present invention will be described in detail with reference to the drawings. In describing this embodiment, the same reference numbers will be used for the same components as a general rule, and repeated descriptions will be omitted.

Figure 1 (A) is a schematic diagram illustrating a weld quality determination device 10 (hereinafter referred to as "quality determination device 10") of this embodiment. Figure 1 (B) is a block diagram illustrating the quality determination device 10 of this embodiment. Figure 2 (A) is a side view illustrating a workpiece 17 for which quality determination is performed by the quality determination device 10 of this embodiment. Figure 2 (B) is an enlarged cross-sectional view illustrating a workpiece 17 for which quality determination is performed by the quality determination device 10 of this embodiment.

As shown in FIG. 1(A), the quality determination device 10 mainly comprises a mounting table 11 on which the quality determination work is performed, a work support unit 12 that supports a work 17 on which a weld 25 (see FIG. 2(A)) is formed, a laser measurement unit 13 that measures the weld shape of the weld 25 of the work 17, a barcode reader 14 that reads the product number engraved on the work 17, and a control unit 15 (see FIG. 1(B)) that controls the quality determination device 10 and determines the quality of the weld 25. Note that FIG. 1(A) shows the quality determination device 10 as seen from above.

The mounting table 11 is a work table on which the worker 16 performs the work of determining whether the workpiece 17 is good or bad, and the mounting table 11 is provided with a workpiece support unit 12, a laser measurement unit 13, a barcode reader 14, a work indicator lamp 18, etc. The worker 16 then places the workpiece 17 before the quality determination on the rotating support shaft 12A of the workpiece support unit 12, and removes the workpiece 17 after the quality determination from the rotating support shaft 12A of the workpiece support unit 12.

The workpiece support unit 12 is a member that supports the workpiece 17 on which the quality judgment is performed, and has a rotating support shaft 12A that rotates intermittently by a drive unit 22 (see FIG. 1(B)). The rotating support shaft 12A is disposed approximately at the center of the mounting table 11, and the workpiece 17 is inserted into the rotating support shaft 12A to fix the workpiece 17 on the mounting table 11. The rotating support shaft 12A rotates counterclockwise together with the workpiece 17 as shown by arrow 19, and the laser measurement unit 13 can measure the entire circumference of the weld 25 that is formed in a ring shape on the outer peripheral surface of the workpiece 17.

The laser measurement unit 13 is, for example, a non-contact laser displacement meter, and is fixed to the upper surface of the mounting table 11 in an area around the rotating support shaft 12A that faces the welded portion 25 of the workpiece 17 over the entire circumference. The welded portion 25 is formed in a ring shape in the circumferential direction on the outer peripheral surface of the workpiece 17, and the laser measurement unit 13 irradiates a line laser in a direction intersecting the circumferential direction of the welded portion 25, for example, in a perpendicular direction, and measures the weld shape of the welded portion 25 for each cross section all at once.

The barcode reader 14 is fixed to the top surface of the mounting table 11 around the rotating support shaft 12A in a position where it can read the barcode 28 (see FIG. 2(A)) engraved on the workpiece 17. A barcode 28 containing product number information is engraved on the outer peripheral surface of the workpiece 17. The barcode reader 14 reads the barcode 28, and the memory unit 20 (see FIG. 1(B)) links the measurement value measured by the laser measurement unit 13 with the product number and stores it.

In addition, a work indicator lamp 18 is installed on the mounting table 11, and displays the pass/fail status of the workpiece 17 so that it can be visually confirmed.

As shown in FIG. 1B, the control unit 15 is an electronic control unit (ECU) that includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), etc., and performs various calculations to control the quality determination device 10.

The memory unit 20 of the control unit 15 is composed of a non-volatile memory such as an EEPROM (Electrically Erasable Programmable Read-only Memory). The memory unit 20 stores the measurement values measured by the laser measurement unit 13 and the product number read by the barcode reader 14, as well as various thresholds used by the welding condition judgment unit 21 to judge the quality of the welding.

The welding condition determination unit 21 of the control unit 15 calculates the height direction distance of the welded portion 25 and the workpiece 17 in its vicinity from the measured value measured by the laser measurement unit 13, and judges the quality of the welded portion 25 by comparing the height direction distance with a preset threshold value. The welding condition determination unit 21 then inputs the height direction distance and the quality judgment result into the memory unit 20, which stores them in linkage with the product number and measured value.

The drive unit 22 is, for example, a stepping motor, which is connected to the rotating support shaft 12A of the work support unit 12 and intermittently rotates the rotating support shaft 12A as shown by arrow 19 (see FIG. 1(A)). The drive unit 22 rotates at 0.1 mm intervals under the control of an encoder, so that the laser measurement unit 13 measures the welded portion 25 at each cross section at 0.1 mm intervals in accordance with the timing of the stopping of the rotating support shaft 12A.

As shown in FIG. 2(A), an example of the workpiece 17 is a differential gear for a vehicle, and the figure shows a state in which its components, a crown gear 23 as a first welded material and a differential case 24 as a second welded material, are welded and fixed. The thick line indicates the welded portion 25, which is formed in a ring shape around the outer circumferential surface of the workpiece 17. A barcode 28 including product number information is also engraved on the outer circumferential surface of the workpiece 17.

As shown in the figure, the differential gear, which is the workpiece 17, is fixed to the mounting table 11 by being inserted into the rotating support shaft 12A. The welded portion 25 is disposed approximately parallel to the upper surface of the mounting table 11 and rotates intermittently at 0.1 mm pitches in a counterclockwise direction via the rotating support shaft 12A. As described above, the laser measurement unit 13 irradiates the line laser in a direction perpendicular to the circumferential direction of the welded portion 25, and measures the welded portion 25 and the adjacent workpieces 17 above and below it. In this embodiment, the laser measurement unit 13 measures approximately 4,600 cross sections around the entire circumference of the welded portion 25.

Figure 2 (B) shows an enlarged cross section of the area indicated by circle 26 in Figure 2 (A), where a weld 25 is formed by laser welding while supplying nickel-based filler wire to a groove 27 in the weld area between the crown gear 23 and the differential case 24. The cross-sectional length L1 of the weld 25 is, for example, about 1 to 2 mm, and the weld 25 is formed in an annular shape on the outer circumferential surface of the workpiece 17 as a weld bead.

As will be described in detail later, the outer peripheral surface 23A of the crown gear 23 and the outer peripheral surface 24A of the differential case 24 are welded and fixed so that they are positioned at approximately the same height, but each has a tolerance when assembled. Therefore, in the method for determining the quality of a weld in this embodiment, the laser measurement unit 13 measures not only the weld 25 but also the outer peripheral surfaces 23A, 24A above and below it, and uses the outer peripheral surfaces 23A, 24A as the measurement reference surfaces, thereby improving the accuracy of determining the quality of the weld.

Next, a method for determining the quality of a welded joint according to another embodiment of the present invention will be described in detail with reference to the drawings.

Figure 3 is a flow chart explaining the method of determining the quality of the welded portion 25 in this embodiment, and more specifically, the method of determining the quality of the undercut portion 31 of the welded portion 25. Figures 4(A) to 4(C) are cross-sectional views explaining the method of determining the quality of the undercut portion 31 explained in Figure 3. Note that while Figure 4(A) illustrates the first and second measurement reference surfaces 32, 33, Figures 4(B) and 4(C) illustrate and explain only the first measurement reference surface 32. In addition, when explaining Figures 3 and 4, the explanations of Figures 1 and 2 will be referred to as appropriate, and repeated explanations will be omitted.

As shown in FIG. 3, in step S10, the worker 16 places the workpiece 17, before its quality judgment, on the rotating support shaft 12A of the workpiece support unit 12. The driving unit 22 rotates the rotating support shaft 12A at a pitch of 0.1 mm, and the workpiece 17 rotates together with the rotating support shaft 12A. Then, the laser measurement unit 13 irradiates the welded portion 25 and the workpiece 17 in the vicinity thereof with a line laser in accordance with the timing at which the workpiece 17 stops, measures the weld shape of the welded portion 25 for each cross section, and obtains the measurement values.

In step S11, the welding condition determination unit 21 sets a first measurement reference surface 32 and a second measurement reference surface 33 for the workpiece 17 near both ends of the welded portion 25 of the measurement cross section based on the measurement values acquired by the laser measurement unit 13.

Here, FIG. 4(A) shows a cross section of the welded portion 25 measured by the laser measurement unit 13, and shows that the first and second recesses 34, 35 that may be determined as undercut portions 31 are formed on the crown gear 23 side and the differential case 24 side. The outer peripheral surface 23A of the crown gear 23 and the outer peripheral surface 24A of the differential case 24 are both flat surfaces, and there is almost no change in the height direction distance of the above measured value. Therefore, the welding condition determination unit 21 sets the outer peripheral surface 23A of the crown gear 23 near the end of the welded portion 25 as the first measurement reference surface 32, and sets the outer peripheral surface 24A of the differential case 24 as the second measurement reference surface 33.

In step S12, the welding condition determination unit 21 sets a determination height distance C for each of the first measurement reference surface 32 and the second measurement reference surface 33.

As shown in FIG. 4(A), a groove portion 27 where a weld 25 is formed is formed between the crown gear 23 and the differential case 24, and a chamfered portion 27A is formed at the open end of the groove portion 27 from the viewpoint of the safety of the worker 16 and the like. Even if the chamfered portion 27A of the groove portion 27 is exposed between the weld portion 25 and the crown gear 23, or between the weld portion 25 and the differential case 24, it is not treated as a weak portion according to the standard. Therefore, in this embodiment, in order to prevent unnecessary defective judgment of the undercut portion 31, a judgment height distance C is set for each of the first measurement reference surface 32 and the second measurement reference surface 33.

In step S13, the welding condition determination unit 21 detects the first recess 34 from the opening end of the groove portion 27 on the first measurement reference surface 32 side from the measured values acquired by the laser measurement unit 13, and also detects the first second recess 35 from the opening end of the groove portion 27 on the second measurement reference surface 33 side. After that, the welding condition determination unit 21 calculates the height direction distance B1 from the deepest part of the first recess 34 to the first measurement reference surface 32, and calculates the height direction distance B2 from the deepest part of the second recess 35 to the second measurement reference surface 33.

In step S14, the welding condition determination unit 21 determines whether the height direction distances B1 and B2 are equal to or less than the determination height distance C for each of the first and second recesses 34 and 35.

If the welding condition determination unit 21 determines in step S14 that the height direction distances B1 and B2 are equal to or less than the determination height distance C, then in step S15 the welding condition determination unit 21 determines that there is no undercut portion 31 on the crown gear 23 side and the differential case 24 side, and that the weld shape of the welded portion 25 is good. Note that the determination of the undercut portion 31 is performed on both the crown gear 23 side and the differential case 24 side, and it is acceptable for either one of them to be determined as good or bad.

If the welding condition determination unit 21 determines in step S14 that the height direction distances B1 and B2 are greater than the determination height distance C, then in step S16, the welding condition determination unit 21 calculates the inclination B/A from the vicinity of the opening end of the groove portion 27 to the deepest part of the first and second recesses 34 and 35 in each of the first and second recesses 34 and 35. Note that the following explanation will be given for the crown gear 23, but the quality of the undercut portion 31 is determined by a similar method on the differential case 24 side as well. Therefore, the height direction distances B1 and B2 are denoted as B.

Compared to FIG. 4(A), FIG. 4(B) and FIG. 4(C) show a case where the distance from the first measurement reference surface 32 to the deepest part of the first recess 34 is greater than the judgment height distance C. As shown in the figure, in the first recess 34, if the vertical distance from the position of the judgment height distance C to the deepest part of the first recess 34 is B and the horizontal distance is A, then the slope is B/A.

If the weld condition determination unit 21 determines in step S16 that the slope B/A is equal to or greater than the threshold value α for determining the undercut portion 31, as shown in FIG. 4(B), it determines that the inner surface of the groove portion 27 is largely exposed from the end of the weld portion 25, that the first recess 34 is the undercut portion 31, and that the weld shape of the weld portion 25 is poor.

If the welding condition determination unit 21 determines in NO at step S16 that the slope B/A is smaller than the threshold value α for determining the undercut portion 31, then in step S17, as shown in FIG. 4(C), the inner surface of the groove portion 27 is not significantly exposed from the end of the welded portion 25, and the first recess 34 is an underfill portion 41 (see FIG. 7), and the process returns to step S15, determining that the weld shape of the welded portion 25 is good.

After that, in step S15 or step S17, the quality judgment of the weld shape of the welded portion 25 at that cross section is completed, and the process moves on to the quality judgment of the weld shape of the welded portion 25 at the next cross section.

In this embodiment, approximately 4600 cross sections are measured at 0.1 mm intervals for the welded portion 25 to determine the quality of the undercut portion 31 described above, but by combining the results of the determination of consecutive cross sections in the circumferential direction of the welded portion 25, it is also possible to determine the quality of the undercut portion 31 in the circumferential direction of the welded portion 25. For example, as shown in FIG. 4B, if there are five consecutive cross sections in which the first recess 34 is determined to be an undercut portion 31, it is determined that the undercut portion 31 exists at a length of 0.5 mm in the circumferential direction of the welded portion 25, and the quality of the welded portion 25 can be determined based on the standard value of the undercut portion 31.

Figure 5 is a flow chart explaining the method of determining the quality of the welded portion 25 in this embodiment, specifically, the method of determining the quality of the underfill portion 41 of the welded portion 25. Figure 6 is a flow chart explaining the method of determining the quality of the welded portion 25 in this embodiment, specifically, the method of determining the quality of the build-up portion 51 of the welded portion 25. Figure 7 is a cross-sectional view explaining the method of determining the quality of the underfill portion 41 and build-up portion 51 explained in Figures 5 and 6. Note that when explaining Figures 5 to 7, the explanations of Figures 1 to 4 will be referred to as appropriate, and repeated explanations will be omitted.

As shown in FIG. 5, in step S20, the worker 16 places the workpiece 17, before its quality judgment, on the rotating support shaft 12A of the workpiece support unit 12. The driving unit 22 rotates the rotating support shaft 12A at a pitch of 0.1 mm, and the workpiece 17 rotates together with the rotating support shaft 12A. Then, the laser measurement unit 13 irradiates the welded portion 25 and the workpiece 17 in the vicinity thereof with a line laser in accordance with the timing at which the workpiece 17 stops, measures the weld shape of the welded portion 25 for each cross section, and obtains the measurement values.

In step S21, the welding condition determination unit 21 sets a first measurement reference surface 32 and a second measurement reference surface 33 for the workpiece 17 near both ends of the welded portion 25 of the measurement cross section based on the measurement values acquired by the laser measurement unit 13. The first measurement reference surface 32 and the second measurement reference surface 33 are set by the method described using FIG. 4(A).

In step S22, the welding condition determination unit 21 compares the first measurement reference surface 32 with the second measurement reference surface 33, and sets the first measurement reference surface 32, which is the lower one in the height direction of the workpiece 17, as the determination measurement reference surface 42.

As shown in FIG. 7, the outer peripheral surface 23A of the crown gear 23 and the outer peripheral surface 24A of the differential case 24 are welded and fixed so that they are positioned at approximately the same height, but each has a tolerance during assembly, and the height varies appropriately for each cross section. In the method for determining whether the underfill portion 41 is good or bad, the lower of the first measurement reference surface 32 and the second measurement reference surface 33 is used as the judgment measurement reference surface 42, because the excessive recession of the welded portion 25 becomes a weak part, and the pass/fail determination is performed.

In step S23, the welding condition determination unit 21 detects the lowest point of the weld 25 from the measurement value acquired by the laser measurement unit 13, and calculates the height direction distance D from the determination measurement reference surface 42 to the lowest point.

In step S24, the welding condition determination unit 21 determines whether the height direction distance D is equal to or less than the threshold value β. If the welding condition determination unit 21 determines that the height direction distance D is equal to or less than the threshold value β in step S24 (YES), the welding condition determination unit 21 determines that the underfill portion 41 is good in step S25. As shown in FIG. 7, the underfill portion 41 is a deep recess relative to the second measurement reference surface 33, which is not the measurement reference surface 42 for determination, but this does not pose a quality problem for the welded portion 25.

On the other hand, if the welding condition determination unit 21 determines that the height direction distance D is greater than the threshold value β in step S24 (NO), then in step S26, the welding condition determination unit 21 determines that the underfill portion 41 is defective.

After that, in step S25 or step S26, the quality judgment of the weld shape of the welded portion 25 at that cross section is completed, and the process moves on to the quality judgment of the weld shape of the welded portion 25 at the next cross section.

In this embodiment, approximately 4600 cross sections are measured at 0.1 mm intervals for the welded portion 25 to determine the quality of the underfilled portion 41 described above, but by combining the results of the determination of consecutive cross sections in the circumferential direction of the welded portion 25, it is also possible to determine the quality of the underfilled portion 41 in the circumferential direction of the welded portion 25. For example, if there are five consecutive cross sections determined to be defective underfilled portions 41, it is determined that the defective underfilled portion 41 exists for a length of 0.5 mm in the circumferential direction of the welded portion 25, and the quality of the welded portion 25 can be determined based on the standard value of the underfilled portion 41.

As shown in FIG. 6, in step S30, the worker 16 places the workpiece 17, before its quality judgment, on the rotating support shaft 12A of the workpiece support unit 12. The driving unit 22 rotates the rotating support shaft 12A at a pitch of 0.1 mm, and the workpiece 17 rotates together with the rotating support shaft 12A. Then, the laser measurement unit 13 irradiates the welded portion 25 and the workpiece 17 in the vicinity thereof with a line laser in accordance with the timing at which the workpiece 17 stops, measures the weld shape of the welded portion 25 for each cross section, and obtains the measurement values.

In step S31, the welding condition determination unit 21 sets a first measurement reference surface 32 and a second measurement reference surface 33 for the workpiece 17 near both ends of the welded portion 25 of the measurement cross section based on the measurement values acquired by the laser measurement unit 13. The first measurement reference surface 32 and the second measurement reference surface 33 are set by the method described using FIG. 4(A).

In step S32, the welding condition determination unit 21 compares the first measurement reference surface 32 with the second measurement reference surface 33, and sets the second measurement reference surface 33, which is higher in the height direction of the workpiece 17, as the determination measurement reference surface 52.

As shown in FIG. 7, the outer peripheral surface 23A of the crown gear 23 and the outer peripheral surface 24A of the differential case 24 are welded and fixed so that they are positioned at approximately the same height, but each has a tolerance during assembly, and the height varies appropriately for each cross section. In the method for determining whether the buildup portion 51 is good or bad, the parts may interfere with each other, and if the buildup portion 51 of the welded portion 25 is too small, it may fall off. Therefore, the higher of the first measurement reference surface 32 and the second measurement reference surface 33 is used as the judgment measurement reference surface 52 to determine whether it is good or bad.

In step S33, the welding condition determination unit 21 detects the apex of the weld 25 from the measurement value acquired by the laser measurement unit 13, and calculates the height direction distance E from the determination measurement reference surface 52 to the apex.

In step S34, the welding condition determination unit 21 determines whether the height direction distance E is equal to or less than the threshold value γ. If the welding condition determination unit 21 determines that the height direction distance E is equal to or less than the threshold value γ in step S34 (YES), the welding condition determination unit 21 determines that the buildup portion 51 is good in step S35. As shown in FIG. 7, the buildup portion 51 is a large convex portion relative to the first measurement reference surface 32, which is not the measurement reference surface 52 for determination, but this does not pose a problem in terms of the quality of the welded portion 25.

On the other hand, if the welding condition determination unit 21 determines that the height direction distance E is greater than the threshold value γ in step S34 (NO), then in step S36, the welding condition determination unit 21 determines that the buildup portion 51 is defective.

After that, in step S35 or step S36, the quality judgment of the weld shape of the welded portion 25 at that cross section is completed, and the process moves on to the quality judgment of the weld shape of the welded portion 25 at the next cross section.

In this embodiment, approximately 4600 cross sections are measured at 0.1 mm intervals for the welded portion 25 to determine the quality of the buildup portion 51 described above, but by combining the results of the determination of consecutive cross sections in the circumferential direction of the welded portion 25, it is also possible to determine the quality of the buildup portion 51 in the circumferential direction of the welded portion 25. For example, if there are five consecutive cross sections determined to be defective buildup portions 51, it is determined that the defective buildup portion 51 exists for a length of 0.5 mm in the circumferential direction of the welded portion 25, and the quality of the welded portion 25 can be determined based on the standard value of the buildup portion 51.

Finally, in this embodiment, the case where the workpiece 17 rotates together with the rotary support shaft 12A has been described, but the present invention is not limited to this case. For example, the workpiece 17 may be fixed to the mounting table 11 by the workpiece support portion 12, and a laser measurement portion 13 installed on a rotating table may rotate relative to the workpiece 17 to measure the welded portion 25, etc.

In addition, in this embodiment, the welding condition determination unit 21 determines the undercut portion 31, underfill portion 41, and build-up portion 51 of the welded portion 25 individually based on the measured values acquired by the laser measurement unit 13, but this is not limited to this case. For example, the welding condition determination unit 21 may simultaneously determine the undercut portion 31, underfill portion 41, and build-up portion 51 of the welded portion 25 based on the measured values for each cross section.

In addition, in this embodiment, the welded portion 25 is formed in a ring shape on the outer peripheral surface of the workpiece 17, but the present invention is not limited to this case. For example, even if the welded portion 25 is formed on a part of the outer peripheral surface of the workpiece 17, or if steel plates are welded together in a line, the quality of the welded portion 25 can be determined in the same manner as in the above embodiment. In addition, various modifications are possible without departing from the scope of the present invention.

REFERENCE SIGNS LIST 10 Weld quality judgment device 11 Placement table 12 Work support section 12A Rotating support shaft 13 Laser measurement section 15 Control section 17 Work 21 Welding condition judgment section 25 Welded section 27 Groove section 27A Chamfered section 31 Undercut section 32 First measurement reference surface 33 Second measurement reference surface 34 First recess 35 Second recess 41 Underfill section 42, 52 Judgment measurement reference surface 51 Build-up section

Claims (2)

A method for determining the quality of a weld, comprising: forming a weld at a groove between a first weld material and a second weld material, irradiating a laser beam to the weld and a workpiece fixed by welding; measuring the workpiece and the weld; and determining the quality of the weld,
Using the measured values obtained by irradiating the laser, a surface of the first weld material in the vicinity of the groove is set as a first measurement reference surface, and a surface of the second weld material in the vicinity of the groove is set as a second measurement reference surface;
A judgment height distance is set for judging a weld shape of an undercut portion of the weld with respect to the first measurement reference plane and the second measurement reference plane;
Detecting a first recess near the first measurement reference surface and a second recess near the second measurement reference surface from the measurement values;
Calculating a first height direction distance from the first measurement reference surface to a lowest point of the first recess and a second height direction distance from the second measurement reference surface to a lowest point of the second recess from the measured values;
A method for determining the quality of a weld , characterized in that if the first height direction distance and the second height direction distance are less than the judgment height distance, the weld shape of the weld is determined to be good . A mounting table;
a work support portion disposed on the mounting table and supporting a work having a welded portion formed along an outer circumferential surface thereof;
a laser measurement unit disposed on the mounting table, irradiating a laser onto the workpiece and the welded portion, and measuring the welded portion and the workpiece in the vicinity thereof;
a welding condition determination unit that determines whether the weld is good or bad based on the measurement value acquired by the laser measurement unit,
When either the workpiece support unit or the laser measurement unit is movable, the laser measurement unit acquires the measurement value,
the welding condition determination unit sets a first measurement reference plane and a second measurement reference plane for the workpiece from the measurement values, sets a judgment height distance for determining a welding shape of an undercut portion of the weld for the first measurement reference plane and the second measurement reference plane, detects a first recess near the first measurement reference plane and a second recess near the second measurement reference plane from the measurement values, calculates a first height direction distance from the first measurement reference plane to the lowest point of the first recess and a second height direction distance from the second measurement reference plane to the lowest point of the second recess from the measurement values, and determines that the weld shape of the weld is good if the first height direction distance and the second height direction distance are equal to or less than the judgment height distance .

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